ESTRATTO RUGA INGLESE

IX

Table of contents Chapter 1

Chapter 3

Overview of diode laser physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Laser safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

L. Zamprotta, E. Trevisiol

Laser physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

Laser beam characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3

Chapter 2

Diode laser overview: how it is done and how to manage it . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5

E. Ruga

Main unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Connection between main unit and means of transport-conduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8

27

E. Trevisiol, L. Zamprotta, M. Signorini

Risk assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Labeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Classification of lasers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Risk assessment for sensitive individuals . . . . . . . . . . . . . . . . . . . 30 Risks of exposure to laser radiation . . . . . . . . . . . . . . . . . . . . . . . . . 31 Distances for prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Prevention strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Prevention measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

33

Quality test on laser equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Safety checks on laser equipment . . . . . . . . . . . . . . . . . . . . . . . . . . .

33 33

Main types of accidents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

33

Radiation protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

35

10

Health surveillance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

37

Power supply system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11

Training and information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

37

Pedal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11

Microscopy, magnification systems and LASERS . . . . . . . . . .

37

Means of transport/conduction of the laser beam . . . . . . . . . .

11

Optical fibers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12

Suggestions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

37

Magnifying loupes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

38

Handpieces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15

CONTACT handpiece . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15

Handpiece with interchangeable inserts (MULTITIP silver) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16

Biostimulation handpiece . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16

Flat wave handpiece . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17

Intraoral biostimulation terminal for MULTITIP handpiece . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

18

Bell-shaped biostimulation terminal for MULTITIP handpiece . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

18

Introduction to dental laser applications . . . . . . . . . . . . . . . . . . .

Management, preparation, activation of optical fiber of diode laser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Whitening arch for MULTITIP handpiece . . . . . . . . . . . . . . . . . .

19

Optical fiber management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

51

Focused handpiece for sapphire inserts . . . . . . . . . . . . . . . . . . . .

19

Pre-use steps of the diode laser in the dental field . . . . . . . . .

52

Telescopic zoom terminal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

20

Connections between handpiece and inserts . . . . . . . . . . . . . . . 20 Inserts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

21

Cable inserts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

21

Chapter 4

Overview of laser history and introduction to current dental applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

41

R. Riversa, M. Garrone, E. Trevisiol, V. Partipilo, M. Maggioni, E. Ruga 42 51

Chapter 5

Photobiomodulation: actuality and future perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Interchangeable fiber optic inserts (MULTITIP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

22

M. Garrone, L. Barreiro, E. Ruga

Sapphire inserts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

22

Low Level Laser Therapy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

55

55

X

Table of contents

Periodontal plastic surgery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

History of the LLLT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

55

Advantages of the LLLT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

56

Mechanism of action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

56

Effects on tissue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

56

Irradiation parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

56

Diode laser in implant dentistry . . . . . . . . . . . . . .

Applications in dental procedures . . . . . . . . . . . . . . . . . . . . . . . . . .

57

E. Amerio, R.M. Calvi, M. Garrone, A. Etemadi, E. Ruga

Surgery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

57

Laser-assisted peri-implant soft-tissue management . . . . . 98

Bisphosphonate-related osteonecrosis . . . . . . . . . . . . . . . . . . . .

58

Implant uncovering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

Orthodontics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

58

Periodontology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

59

Aggressive periodontitis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

59

Laser assisted therapy of peri-implantitis

Gingivitis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

59

E. Amerio, E. Ruga

Peri-implantitis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

59

Dental reimplantation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

59

Peri-implantitis definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

Management of temporomandibular joint disorders . . . . . . .

60

Muscle alterations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

60

Dentin hypersensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

62

Endodontics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

62

Oral medicine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

63

Radio-induced mucositis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

63

Nerve repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

63

Chronic idiopathic orofacial pain . . . . . . . . . . . . . . . . . . . . . . . . .

64

Obstructive Sleep Apnea Syndrome . . . . . . . . . . . . . . . . . . . . . . .

66

Chapter 6

Dental whitening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

71

R.M. Calvi, H.S. Marjara, E. Ruga

Chapter 8

Surgical technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

97

98

Peri-implantitis risk factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 Introduction to treatment of peri-implantitis . . . . . . . . . . . . . . 107 Role of diode laser in the treatment of peri-implantitis . . . . . . 108 Safety and antimicrobial effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 Photobiomodulation effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 Photosensibilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 Clinical studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 Concluding remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 Clinical protocol according to the authors . . . . . . . . . . . . . . . . . 110

Chapter 9

Diode laser in restorative dentistry . . . . . . . . . .

119

E. Ruga, M. Garrone, R.M. Calvi, M. Amoroso, M. Pelliccia

Clinical procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Laser-assisted teeth whitening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

72

Internal and external whitening in case of non-vital teeth . .

76

Gingival whitening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Gingivoplasty and clinical crown lengthening

76

E. Ruga, M. Garrone, R.M. Calvi

Description of the operative technique . . . . . . . . . . . . . . . . . . . .

76

Laser-assisted clinical crown lengthening . . . . . . . . . . . . . . . . . . 120

72

81

Hard tissue decontamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Periodontitis: case definitions and phases of treatment . . 81 81

Definition of periodontal stability . . . . . . . . . . . . . . . . . . . . 82

Role of diode laser in the treatment of periodontitis . . . . . . .

123

E. Ruga, M. Garrone, R.M. Calvi

E. Amerio, A. Etemadi, E. Ruga

Phases of treatment of periodontitis . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . 120

Dental dam punching with diode laser . . . . . . . . . . . . . . . . . . .

Chapter 7

Diode laser in periodontology . . . . . . . . . . . . . . . . . .

Gingivectomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

125

E. Ruga, M. Garrone, R.M. Calvi

Pretreatment of adhesive systems E. Ruga, M. Garrone, R.M. Calvi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

82

PHASE 2: Causal related therapy . . . . . . . . . . . . . . . . . . . . . . . . . .

82

PHASE 3: Treatment of the residual pockets . . . . . . . . . . . . . . .

84

PHASE 4: Supportive periodontal care . . . . . . . . . . . . . . . . . . . .

85

Concluding remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Clinical protocols and laser setting in periodontal treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

Use of the diode laser in the clinical protocol of dentin desensitization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

126

M. Amoroso, M. Pelliccia, E. Ruga

Dentin hypersensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 Laser-assisted desensitization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 Recent clinical studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

Table of contents

Chapter 10

Diode laser in endodontics . . . . . . . . . . . . . . . . . . . . . . .

Chapter 13 131

R. Riversa, E. Ruga

Possible uses of endodontic diode laser . . . . . . . . . . . . . . . . . . . . . 134 Mode to use diode laser in endodontic therapy . . . . . . . . . . . . . 135 Photo-activated decontamination (PAD) . . . . . . . . . . . . . . . . . . . 142 PAD procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142

Diode laser in oral surgery . . . . . . . . . . . . . . . . . . . . . . .

175

E. Ruga, M. Garrone, H.S. Marjara, M. Pelliccia, A. Agnone, P. Nocentini, A. Simeone, R. Ruga, V. Carbone

Management of the postextractional alveolar socket . . . . . . .

Incision of abscess collections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Incision for the design of surgical flaps . . . . . . . . . . . . . . . . . . . . .

Surgical sutures and diode lasers . . . . . . . . . . . . . . . . . . . . . . . . . . . .

176 178 178 178

Sutures, when? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178

Chapter 11

Diode laser in prosthetic dentistry . . . . . . . . . . .

XI

Removal of sutures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 149

Oral soft tissue plastic surgery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183

D. Nocentini, A. Paccagnella, C. De Vito, M. Garrone, E. Ruga, H.S. Marjara

Frenectomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183

Preprosthetic management of soft tissues in fixed and removable prosthodontics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 Laser-assisted dental impression . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 Sinergy between laser and digital methods . . . . . . . . . . . . . . . . . 155

Lingual frenectomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184

Surgical exposure of teeth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198 Surgical exposure of deciduous and permanent teeth in the developmental age . . . . . . . . . . 198 Surgical exposure of third molars and other permanent teeth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

Chapter 12

Diode laser in oral medicine . . . . . . . . . . . . . . . . . . . . .

Plastic and fornix exploitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192

159

Gingival hypertrophy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 Removal of oral neoformations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205

Potentially malignant disorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159

Surgical technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212

Leukoplakia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159

Surgical treatment of lymphoepithelial cysts of the oral cavity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212

M. Garrone, A. Etemadi, E. Ruga

Oral lichen planus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160

Pemphigus vulgaris . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Mucous membrane pemphigoid . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Recurrent aphthous stomatitis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Herpes simplex virus infection . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Medication-related osteonecrosis of the jaw . . . . . . . . . . . . . . .

Vascular anomalies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Burning mouth syndrome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Laser-assisted biopsy techniques . . . . . . . . . . . . . . . . . . . . . . . . . . .

162 162 162 163 164

Mucocele of the oral cavity and diode laser . . . . . . . . . . . . . . . . 216 Sialolithiasis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 Ranula . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224

165 166

Chapter 14

166

Introduction to laser applications in esthetic medicine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

Stages of a biopsy performed by diode laser . . . . . . . . . . . . . . . 169 Summary tables: 915 nm diode laser, parameters of use in oral medicine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Surgical treatment of HPV-related neoformations . . . . . . . . . 212

Surgical pathology of the salivary glands . . . . . . . . . . . . . . . . . . . 216

171

E. Ruga, M. Garrone, R.M. Calvi, R. Ruga

Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 Diagnostic pathways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 Dermoscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240

Esthetic surgical treatment of lesions and neoformations of the skin . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 Biostimulation of perioral tissues . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 Esthetic treatment of low-flow vascular anomalies and malformations of the face . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243 Laser-lifting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243

Subject index

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246

Chapter 1

1

Overview of diode laser physics L. Zamprotta, E. Trevisiol

Laser physics To describe the microscopic operation of a laser, let us consider a generic atom where E1 represents the “fundamental” state, of minimum energy, allowed for the atom. If the system is brought to the excited level E2, since E2 > E1, the atom will tend to return to the fundamental state, with the emission of corresponding energy difference ΔE = E2 – E1.

The energy will be released in the form of an electromagnetic wave. The process, called spontaneous or radiative emission, consists of the emission of a photon with energy hν = ΔE = E2 − E1.

Each photon is emitted independently, i.e. with a direction and phase (instant) that are independent from those of the other atoms, but with a frequency (ν) or wavelength λ (for an EM wave λ = c/ν, where c represents the speed of light) well defined and characteristic of the atom. In a system formed by many equal atoms, in which, at a certain instant, N2 atoms per unit volume are at the level E2, the probability of decay by spontaneous emission, per unit time and volume, i.e. how fast the photons are emitted per unit volume, is given by the relation: (dN2/dt)spont = –AN, where the coefficient A is called probability density of spontaneous emission or also “Einstein’s A” coefficient.

Let us consider the situation in which the atom is in the state E2, but is hit by an EM wave of frequency ν equal to the characteristic frequency of the spontaneous emission. It is observed that there is a certain probability that the wave “forces” the atom to make the transition E2 → E1, through the emission of an EM wave of the same frequency as the incident one.

In the stimulated or “forced” emission described above, the emission of photons from each atom occur “in phase” with the incident wave and in the same direction, i.e. the emitted photons are superimposable on the incident ones. Again, the probability of decay per unit of time and volume is given by the relation: (dN2/dt)stim = – W21N2 where W21 is called the probability density of stimulated transition ad depends on the intensity of the incident EM wave. If, on the other hand, we consider our atom still in the fundamental state E1, another type of process can occur, called absorption, in which it absorbs an incident photon of frequency ν equal to the characteristic frequency, and brings itself to the excited level E2. The probability of absorption per unit of time and volume will be dN1/dt = –W12N1, where W12 is the probability of absorption per time unit and N1 the numbers of atoms in the E1 state, per volume unit.

2

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Overview of diode laser physics

To understand the physics behind the laser, consider a plane wave, an ideal wave whose front is an infinite plane surface, travelling in a certain material along the z-direction, and let N1 and N2 be the population of atoms in levels 1 and 2 of the same material. Let the frequency ν of the plane wave be equal to the characteristic frequency of the material, i.e. ν = (E2 – E1)/h.

The intensity of the wave, i.e. the number of photons in it, will vary as it propagates through the material. In fact, stimulated emission processes will add, for each incident photon, another photon in the same direction, while absorption processes will eliminate an incident photon. The material behaves as an amplifier if N2 > N1 when passing through it, vice-versa it behaves an absorber if N2 < N1.

Therefore, if the material acts as an amplifier at frequency ν, the population of the two levels will reach a condition N2 > N1, called population inversion. This is a state of non-equilibrium, i.e. the opposite of the thermodynamic equilibrium that is obtained in a material in the absence of external stimuli. A material with a population inversion is called active. If the separation in energy E2 – E1 between the two levels under examination corresponds to a frequency ν in the microwave range, the amplifier obtained in this way is called a MASER (Microwave Amplification by Stimulated Emission of Radiation) amplifier. If, on the other hand, frequency ν falls in the optical frequency range, the resulting amplifiers are called a LASER (Light Amplification by Stimulated Emission of Radiation) amplifier.

To obtain a radiation source from an amplifying material that does not generate radiation but only amplifies it, it is necessary to introduce an element that makes other atoms available for amplification (positive gain or positive feedback).

In the case of lasers, this is usually achieved by placing the active material between two mirrors, in the simplest case flat and parallel, with high reflectivity. The plane wave of the previous paragraph, of frequency ν in the visible, will travel back and forth through the active material and will be amplified at each pass. Part of the produced photons (light) can be extracted if one of the mirrors transmits part of the incident radiation. Generation of radiation (oscillation) is achieved when the gain for each amplification in the active material compensate for “losses” through the semi-reflecting mirror 2. There is a threshold condition for laser operation which is reached when the population inversion N2 – N1 reaches a critical value, called critical inversion, where the corre-

sponding gain balances the losses. When the critical inversion is reached, oscillation begins due to spontaneous emission by the atoms of the active material.

Let us see how to generate a population inversion: the simplest solution would seem to be to investing the atoms with numerous EM waves of characteristic frequency, ν = (E2 – E1)/h, since, in the initial state, there are more atoms on the level E1 than on the level E2, the phenomenon of absorption (E1 → E2) will prevail over that of stimulated emission (E2 → E1), producing in time a population inversion. However, this type of system cannot work, at least in a continuous regime. In fact, once the equalization of the two populations is reached, N1 = N2, the phenomena of absorption and stimulated emission will be balanced and the material will become “transparent” (instantaneously the number of absorbed photons will be equal to the number of emitted photons for stimulated emission). In order to carry out the inversion, not only two levels (E1 and E2) will be sufficient, but it will be necessary to work with atomic or molecular systems that allow three or more levels to be used.

In the three-level laser, atoms are brought from the E1 level to the E3 level. The active material used has the characteristic of decaying rapidly on the E2 level, thus achieving a population inversion between the E1 and E2 levels. In this system, half of the N atoms must be brought to the E2 level, and any additional atoms brought from the E1 level to the E3 level will be useful for population inversion. The four-level laser is even more effective in achieving population inversion. As before, level E3 is empty, but in this case E1 will be empty as well, so the first atom brought to level E3 will immediately produce a population inversion between levels E1 and E2. In order for the four-level system to continue to function as such during laser action, the transition between E1 and E0 must also be very rapid if the E1 level is to continue to be depopulated, since, during the emission of laser radiation, the atoms move back from the E2 level to the E1 level. Good candidates for operation as laser active materials will therefore be those materials for which the condition imposed for the various transition are verified.

The process by which the atoms are brought from 1 to 3 (for three levels) and from 0 to 3 (for the four levels) is called pumping and it is usually carried out in one of the ways described below, each characterised by the efficiency with which the atoms are poured into the higher energy level: Ä Using a light source: this is known as optical pumping and it was the first to be employed. It used to use

Overview of diode laser physics

xenon, krypton or mercury lamps and, due to the considerable difficulty of implementation and size, is now generally abandoned in favour of a similar process, used in dye or YAG lasers, which uses another laser, either a semiconductor or nitrogen laser, as source. Ä Using an electrical discharge: a system known as electrical pumping and is widely used in gas and semiconductor lasers. Ä Through a chemical reaction: system used in chemical lasers. Ä Through a process of rapid expansion of a gas: system used in gas-dynamic lasers.

To obtain the operation of a laser, two essential conditions must be met. The first, as we have seen, is population inversion, in which most of the atoms in the active material are in an excited state rather than, as is normally the case, in the fundamental state. In order to achieve this, the atoms must first be supplied with energy by the process of pumping. The second is to maintain the population inversion for a spontaneous emission from the atom after excitation are very short, on the order of nanoseconds, but there are particular energy levels of the atom, called metastable, where an atom remains excited without decaying for much longer. Pumping must conveniently transport atoms to one of these metastable states, either directly or through intermediate decays.

Lasers in which the electrical discharge takes place continuously and the pumping continuously supplies the metastable state with excited atoms are called continuous wave laser. In pulsed lasers, on the other hand, the supply can be discontinuous: the phenomenon is triggered as soon as there is a population inversion, but is short-lived because it ends as soon as the metastable state is emptied. Continuous wave laser are characterised by the power of the beam, pulsed lasers by the energy of the pulse emitted.

In addition to lasers operating in the visible range, lasers emitting infrared radiation, particularly at a wavelength of 10 µm, are widely used, such as high-power lasers used in machining. There are also lasers operating in the ultraviolet and X-ray band.

Laser beam characteristics The main characteristics of the output beam of a laser are as follows: Ä Monochromaticity: this is a consequence of two con-

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3

comitant facts. Firstly, only an EM wave which has a characteristic atomic frequency can be amplified and, since the two mirrors constitute a resonant cavity, oscillation can occur at the characteristic resonant frequencies of the cavity. Secondly, the laser has a much smaller linewidth (up to 10 orders of magnitude) than the normal width of the E2 → E1 transition observed in spontaneous emission. Ä Coherence: understood as spatial and temporal coherence. > Spatial coherence: given two points on the wave front at time t0 of an EM wave, let E1 and E2 denote their respective electric fields. By definition of wave front, the phase difference between the two electric fields at time t0 will be zero. If this phase difference remains zero at any time t, the two points are said to be coherent. If this happens whatever the two points on the wave front are, the EM wave is said to have perfect spatial coherence. > Time coherence: consider the electric field on the EM wave at time t and time t' close to each another.

If the phase difference between E(t) and E(t') remains constant, the EM wave is said to have perfect temporal coherence. Ä Directionality: this is a consequence of the fact that the active material is essentially placed in a resonant cavity consisting of two mirrors. In fact, only an EM wave propagating in the direction orthogonal to the mirrors (or in direction very close to it) will be able to oscillate. The directionality of the light beam emerging from a laser cavity increases with the length of the cavity for geometrical reasons. Ä Brilliance: defined as the power emitted by an EM wave source per unit area and per unit solid angle.

A laser beam has a very high brilliance as a result of being collimated. Ä Short pulse duration: implies a concentration of energy in time. It can be seen as a complement to monochromaticity which, in turn, implies a concentration of energy in terms of wavelength. However, while all lasers can, in theory, be made monochromaticity by operating on the cavity, only laser with a large linewidth can produce pulses of very short duration.

For gas lasers, this means being able to produce light pulses of 0.1-1 ns duration (not particularly short).

For liquid and solid-state lasers, which have 105 – 106 times larger linewidths, light pulses of 10-100 fs duration can be generated.

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Diode laser overview: how it is done and how to manage it E. Ruga

Approaching the use of lasers in dentistry requires a preliminary discussion about the technical aspects of this “new” method.

The construction aspects of the recent diode lasers will be briefly described below, focusing attention on their functions and possible clinical implications, so as to guarantee the operator a more effective and aware use experience.

Each medical laser unit consists of several essential components (" 2.1), which are fundamental respectively for the production, emission and transmission of the laser beam.

According to the specific field of application, some units may differ in the type and specifications of the components. Units intended for intensive use and operating at high power ratings, for example, differ in shape, size and technical specifications compared to simpler and cheaper systems designed for applications requiring low power. Fixed systems with larger dimensions still differ in construction characteristics and technical specifications compared to portable and transportable systems.

The diode laser is a semiconductor laser, whose components, now increasingly miniaturized, frequently allow easy transport of the device.

A laser is essentially made up of an active medium, i.e. the element or substance that supplies the atoms, which, invested by energy emitted from an external source (pumping system), will absorb photons, which will transfer electrons from a given energy level to a higher one.1 The pumping system is represented, in the case of a diode laser, by the electric current. The active medium is confined to a structure, called “optical cavity” or “optical resonator”, which will allow the spontaneously emitted photons to trigger the stimulation mechanism and to generate the laser beam, once a certain threshold is exceeded (! 2.1). Each element will be characterized by specific energy levels and the photons emitted will, consequently, be characterized by specific energy, frequency and wavelength.2 " 2.1 Essential components of diode laser Main unit (including optical cavity and core) Remote control unit Energy source (pumping system) Means of conduction

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Diode laser overview: how it is done and how to manage it

The optical cavity is able, given its construction specifications, to select the desired wavelength, among the various possible ones, in relation to the element considered (! 2.2).

The diode is made up of several semiconductor elements arranged according to a specific layering.

Among the most used we have gallium-arsenic, suitably doped with aluminum atoms (AlGaAs).

A copper block with gold plating, for better electrical conductivity, is used as a support for mounting the diode (! 2.3). The diode is then joined to the block by the

interposition of a thin indium plate (! 2.4), a material with low resistivity, able to improve the behavior of the contact area and the conduction characteristics.

The diode support is, in turn, connected to a specific collimation device, used to align the beam coming out of the diode to the SMA 905 connector, where a connecting fiber capable of reaching an external connection will then be applied (! 2.5).

In the final assembly, a 200 μm fiber (patch cord) is often used to connect the collimated diode to the optical collimating device LIMO (! 2.6), which allows to coher-

Pumping system

Power

Optical cavity with EEL emitter MEANS OF CONDUCTION GaAs semiconductor

Optical cavity/Optical resonator

! 2.1 Constituents of a laser system: pumping system (orange), main unit (blue), means of conduction (yellow).

! 2.2 915 nm Multi-Mode diode in C-Mount format.

Direction adjustment SMA 905 connector and laser output

Adjustment gear

! 2.3 Support for the integration of the diode. An indium bonding plate (gray color) is visible.

! 2.4 Diode mounted and screwed on the support block.

Adjustment gear

! 2.5 Mounted diode solidarized with the collimator.

Diode laser overview: how it is done and how to manage it

ently join two laser sources: the 915 nm source (invisible) and the source at 630 nm (red, used as a pointing system).

This last aspect is very important: in infrared and near infrared lasers, the operator is unable to view the real laser beam emitted by the main diode, as it is invisible.

To overcome this drawback, the manufacturer usually applies a secondary (pointing) diode.

The function of the secondary diode is to allow the clinician to be able to correctly view the beam projection on the work area (! 2.7). Depending on your manufacturing choices, the pointer can be red, green, blue,

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or white. The secondary diode does not require high energy, not having a therapeutic function. The nominal power is therefore a few mW. The patch cord is generally 200 μm to allow you to connect fibers of the same or greater cross-section to the output available to the user.

The various components listed must then be connected to the motherboard (! 2.8 and 2.9), so that they can be suitably controlled by a microprocessor, capable of interfacing the entire architecture with the user through specific software.

200 µm patch cord

SMA 905 output available to the user

Optical collimation device LIMO

635 nm red diode laser pointer ! 2.6 Path of the laser beam inside the main unit: from the diode to the optical output.

! 2.7 Detail of the 915 nm C-mount diode and the SMA 905 optical output.

The secondary pointer diode that is inserted into the optical output is visible.

! 2.8 Motherboard of a modern portable diode system.

! 2.9 Motherboard with assembled diode, patch cord, secondary diode, optical output and cooling fan.

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Diode laser overview: how it is done and how to manage it

Chapter 2

Main unit The main unit contains all the technology necessary for the production of the laser beam and to be able to interface with external accessories. It differs in shape, weight, size and build quality depending on the active medium and the intended use of the device (" 2.2 and 2.3 and ! 2.10-2.12).

The chassis/case is the enclosure of the unit. It must first protect and isolate the internal components from the external environment, effectively behaving like a shell.

Among the most commonly used materials for the construction of the case, there are plastic and polymeric materials that can be printed and adapted according to the specific needs of the manufacturer. They can, for example, integrate display and control housings.

" 2.2 445 nm blu desktop diode laser (Zoetec, Padua, Italy) Specifications

Among metallic materials, aluminum is sometimes used, which acts as a Faraday cage, performing the function of isolating the internal environment from any electrostatic field present outside it.

Traditional units are static, typically removable, and require dedicated support and constant connection to the power source. Due to their size and heavy weight (sometimes over 10 kg), they are generally placed on special electrified carts.

With due caution, they can be moved short distances within the clinic.

In the case of transportable units, the overall dimensions are contained and the weight varies from 5 to 10 kg.

Technological advances nowadays allow the creation of miniaturized components, making it possible to assemble high-performance portable devices. Portable or even handheld units are able to reach a total weight of less than 1 kg.

In relation to type, model, manufacturer, the following components can be identified on the main unit by observing its chassis:

Laser class

4

Ä on/off button;

Laser source

Diode

Weight

2200 g

Ä security key;

Dimension (L×D×H)

28 × 26 × 28 cm

Wavelength

445 nm

Maximum power

4 W, CW

Pulse frequency

0-20,000

Emission mode

Single, repeated, pulse train

Ä pedal connector;

Software type

Preset, customizable and assisted

Ä service connector (for example serial/USB);

" 2.3 Portable diode laser (Pocket Laser®, 88Dent, Pero, Milan, Italy). Highlighted pocket dimensions and low weight, less than 1 kg Specifications Laser class

4

Laser source

Diodo

Weight

0,7 kg

Dimensions (L×D×H)

10.1 × 16.4 × 4.5 cm

Wavelength

915 nm

Maximum power

6 W, CW nominal power; 10 W max

Pulse frequency

20 Hz - 15 KHz

Emission mode

Single, repeated, pulse train

Software type

Preset, customizable and assisted

Ä key/button/emergency lever; Ä display; Ä commands (sometimes integrated into the display); Ä power connector; Ä connector for remote locking device; Ä cooling vents; Ä optical output-connection for means of conduction.

The power key allows the clinician to start the system making the device operative. It can be on the front or back of the unit. Some units additionally have an ignition/security key.

In the event of malfunction, emergency or necessity, the operator can immediately stop the activity of the diode. The key in charge is generally red and placed in a clearly visible and easily accessible position of the unit.

The display can be reduced to a simple LED panel with multiple digits or can be a real liquid crystal display, monochrome or color, with low or high resolution.

A simple control panel is usually sufficient to control the device settings. Configurations that provide touch-sensitive keys or in any case without continuity

Diode laser overview: how it is done and how to manage it

solutions are preferred, so as to favor the hygiene control and disinfection of the device.

Most modern units have color monitors with touch capabilities; therefore they perform the simultaneous function of display and control panel. The touchscreen can be resistive or capacitive. In this last case, touchscreen displays must be able to allow operation also

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through the use of gloves and through the interposition of protective films.

Depending on the presence of an internal or external power supply system, a different type of power connector is provided (! 2.12 and 2.13).

To interact with the diode, the operator communicates the instructions through the control panel and activates

! 2.10 Blue 445 nm desktop diode laser (Zoetec, Padua, Italy). The controls are integrated into the touchscreen display. The optical output connected to a MULTITIP handpiece is visible. The unit is equipped with an internal power supply.

! 2.11 810 nm diode laser (Ora-laser d-lux®, ORALIA, Konstanz, Germany). (1) Touchscreen display; (2) emergency button; (3) power button; (4) handpiece; (5) interlock connection; (6) remote pedal connection; (7) optical connection; (8) service serial port; (9) laser specifications; (10) integrated power cable.

! 2.12 915 nm portable/handheld diode laser. (1) optical connection; (2) touchscreen display; (3) status led; (4) emergency-stop button; (5) power button; (6) power/battery/charge led (Pocket Laser®, 88Dent, Pero, Milan, Italy).

! 2.13 915 nm portable diode laser. Left side portion: (7) mini-USB service port; (8) power/charging connector; (9) ventilation/cooling vent.

Upper portion: (1) optical connection; (10) ventilation grille and cooling fan; (11) laser specifications (Pocket Laser®, 88Dent, Pero, Milan, Italy).

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Diode laser overview: how it is done and how to manage it

the laser emission by pressing a button on the handpiece or by means of a foot pedal. A specific connection is therefore available, depending on the manufacturer’s choices. The physical connection with the unit is, however, absent in the case of systems with wireless pedals.

Some units have an auxiliary connection that can be used to connect a remote interlock type control.

Recently some devices have been equipped with auxiliary connections (serial/USB/MICRO-USB) to allow easier maintenance of the system by qualified personnel and, moreover, to allow the operator to update the software with new clinical programs and customized settings (! 2.13).

Inside the device is the active medium, the “beating heart” of the entire system. Since the present dissertation is focused on the diode laser, the active medium consists of a semiconductor.

The semiconductor is made up of several layers of materials of different nature (generally Ga, As, Al). The diode is connected to a specific collimator support, in turn interconnected with an optical fiber which has the function of bringing the beam to the interconnection device with the outside.

Connection between main unit and means of transport-conduction The manufacturer usually interfaces the medical laser to the conduction system by applying a special connector on the proximal side of the latter.

Through the connection interface, the beam emitted by the main unit is conveyed within the conduction medium (optical fibers, cords, articulated arms, etc.).

Sometimes the main device has a closed/“proprietary” connection, that is customized by the manufacturer; in this last case, the operator is bound in choosing only the components and accessories produced by the parent company, without the possibility of contacting third parties. Sometimes, there is not even the possibility for the user to be able to change the means of operation. In the latter case, it is impossible to use optical fibers, biostimulation handpieces and other accessories, resulting in a severely limited clinical operation.

More performing devices generally adopt “open” or universal connections, where the user is given the op-

! 2.14 SMA 905 connection. An SMA 905 universal female connection is present on the main laser unit. Note the black silicone hermetic protection device (Pocket Laser®, 88Dent, Pero, MI, Italy).

portunity to intervene on the connection between the main device and the means of conduction, so as to be able to choose the most appropriate one according to specific needs.

Compared to the standard ST and FC connectors, the SMA type appears to be the most frequently used solution in medical systems, even if no longer used in the telecommunications sector.3 In this type of connector it is possible to integrate a mechanical or electronic interlocking device for the authorized use of medical lasers and ocular safety.

The SMA 905 connection, located at the level of the main unit (female), is a universal type connection capable of hosting universal male SMA 905 connectors. The coupling of the two interfaces is guaranteed by a screw assembly (! 2.14). Once the connector is inserted, it is able to maintain its position with extreme precision, an essential requirement for the correct conduction of the laser beam.

It is essential to preserve the integrity of the connection area, protecting it with special seals or hermetic closing devices. The perfect coupling between the connectors allows the laser beam to be transmitted without alterations and power losses. The possible presence of impurities or residues in the interface structure is potentially capable of altering the conduction mechanism of the light beam. The occurrence of unwanted damage to this delicate interface is also possible. Damage can be reversible or irreversible and still require the intervention of a specialized technician.

Diode laser overview: how it is done and how to manage it

Power supply system Depending on the intended use and the characteristics of the laser compartment, each device is equipped with a specific power configuration. When the device is equipped with an internal power supply, we generally find, in the rear portion of the device, a three-pole connection similar to those used in desktop personal computers. In portable devices, conversely, the power supply unit is not located inside the chassis, so as to facilitate the portability of the instrument (! 2.15).

Portable systems are therefore equipped with an external power supply, which can be connected to the unit via a connector of varying specifications depending on the manufacturer, generally similar to that used in modern laptops.

Pedal Several diode lasers on the market today use a foot pedal as a remote control device. Having an operating command external to the handpiece guarantees the operator the ability to work hands-free, without hindrance.

There are basically two variants available: wired and wireless. The first remote control mode involves the use

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of a direct connection via a cable; it is universally widespread and offers a proven reliability. Some disadvantages, however, reside in the encumbrance of the communication cable, which is necessarily interconnected to the main unit. The presence of cables in the context of the dental clinic constitutes not only an obstacle to the operator’s movements, but a contrasting element with the hygiene and asepsis of the clinical area.

Wireless pedals have recently been introduced and adopted in the field of medical instruments (! 2.16 and 2.17). The wireless communication mode guarantees the operator the ability to easily move the pedal without hindrance. The pedal is therefore portable and, as such, does not require a permanent connection to the power system. Several units are equipped with lithium-ion batteries, with reduced memory effect.

Communication with the main unit generally requires the simple transmission of the ON/OFF operating data, without therefore affecting the available residual power capacity.

Means of transport/conduction of the laser beam In order for the radiant energy to reach the point of application on the target tissue, each laser has a specific

! 2.15 Power supply kit 30W 5V. The same power supply is able to serve the main unit and the control foot pedal (Pocket Laser ®, 88Dent, Pero, Milan, Italy).

! 2.17 Wireless control pedal. Some LEDs provide information on the status of the remote control unit. The power/recharge connector is visible, identical to the one on the main unit (Pocket Laser®, 88Dent, Pero, Milan, Italy).

! 2.16 Wireless control pedal. Through the plantar pressure of a button it is possible to raise the pedal protection shield, which is free and operational. The same shield acts as a support for moving the pedal in "hands free" mode (Pocket Laser®, 88Dent, Pero, Milan, Italy).

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Diode laser overview: how it is done and how to manage it

transmission system. These systems must meet three basic needs: Ä preserve, at the point of application, a radiant power as close as possible to that of the emission source; Ä be manageable; Ä be replaceable and interchangeable.

In odontostomatology the handling and practicality of the means of conduction of the laser beam are fundamental.4 The different branches of the dental discipline require different and customized instruments; it is therefore essential for the clinician to have access to specific inserts, handpieces and tips. The operator must, therefore, be able to change the means of conduction in relation to specific clinical needs.

The ideal and most widespread instrument for laser transmission is, to date, the optical fiber. The optical fibers are of different types and shapes, responding to specific characteristics and requirements. Not all wavelengths cover this medium in an optimal manner.5 There are different construction materials, among which the most suitable for carrying the wavelengths of the diode are silica fibers.6 Then there are fluoride fibers, which are well suited to conveying the wavelengths typical of the erbium laser. The polycrystalline fibers are used to carry high frequency electromagnetic waves such as those of the CO2 laser.

The diameter of the fibers is of particular importance: decreasing the diameter, there is an increase in the intensity of energy due to the greater concentration of the beam, a useful feature for surgery.5,7 For whitening or biostimulation, for example, larger diameters and, generally unfocused are preferred.

There are also transmission tools currently in use (for CO2 erbium lasers), such as articulated arms equipped with mirrors and joints, which allow the various components to rotate so that the handpiece can be handled as freely as possible.

Finally, there are the most modern systems for transporting radiant energy consisting of hollow fibers (alternatives to optical fiber, but with the disadvantage of having higher production costs and being more perishable). Photons bounce off the hollow mirrored surface of the fibers.5 Optical fibers can be reduced to simple tips, similar in size to ultrasonic inserts. The use of disposable tips and interchangeable inserts offers undoubted advantages in terms of ease of use and safety for the patient. The adoption of specific handpieces, capable of hosting pre-

cision inserts of crystalline sapphire has recently been proposed. In these newly introduced instruments, the distal end is connected to the main system by optical fibers. The use of sapphire tips would entail significant ergonomic and clinical advantages both for the clinician and the patient.

Optical fibers In medical procedures, laser energy is transmitted through a group of optical fibers.

The use of optical fibers represents an advantage both for patients and clinicians: the fiber, being thin and flexible, can be suitably bent and adapted; the insertion of a fiber inside the tissues therefore requires only a small incision and the energy can be concentrated on the target without damaging the surrounding tissue. Therefore, medical procedures that use optical fibers are minimally invasive and, consequently, result in less traumatic experiences for patients.

The optical fibers consist of a silicate core covered with a protective sheath with a low reflectance index. Light travels inside the core and can travel long distances.

There are single-mode and multi-mode optical fibers.

The former are widely used in the telecommunications world, generally for long-distance data transport; the latter, used for short-distance data transport, are frequently used in the medical field.3 Single-mode fibers generally have a diameter of less than 20 µm. Multimode fibers instead exceed 50 µm.

While both the type of laser source and the conditions of activation of the optical fibers affect the laser power performance, other critical aspects are: proper fiber design, fiber termination, and end surface preparation.

Typical lasers used in these medical procedures are Nd:YAG lasers (1064 nm), dual frequency Nd:YAG lasers (532 nm), diode lasers (800 nm ~850 nm ~980 nm) and Ho:YAG lasers (2.1 μm). For these common lasers, index hopping multimode optical fibers with pure silicon core can be a good solution for laser energy transmission, as they transmit light well in the visible range and at IR lengths of up to 2.1 μm.

The CO2 laser (10.6 μm) and Er:YAG (2.9 μm) are establishing themselves in the medical field, but traditional optical fibers with silicon core do not work very well due to the high attenuation. As a replacement, it is possible to use hollow silica-based waveguides (silicon dioxide) optimized for these wavelengths.

Diode laser overview: how it is done and how to manage it

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13

The multimode optical fibers with pure silicon core have several advantages over simple telecommunication fibers (! 2.18).

First, the fiber is capable of handling high powers.

The large diameter of the core, often >0.1 mm, allows the fiber to transmit a greater amount of light. The high numerical aperture (NA) gives the fiber a wider angle of light acquisition, thus allowing a greater amount of light to be conveyed into the fiber. The high core/coating ratio allows the fiber to transmit maximum light power with the same core diameter, while maintaining the same flexibility. In addition, the fiber is capable of transmitting greater laser power, this happens because pure silicon-based material has a higher melting temperature and damage threshold than doped silicon. A second advantage is represented by the cost, thanks to the minimal amount of doping materials used in a fiber with a pure silicon core.

In addition, the fiber has greater mechanical strength and flexibility (normally the fibers are tested in line up to 150 kpsi and have a small bending radius).

Other benefits include ease of termination and the ability to sterilize fibers using standard methods including medical grade autoclave.

La fibra di silicio con guaina in poliimmide (PI) indurito e rivestimento o buffer in silicone è comune nelle applicazioni medicali.8 PIs are polymers (consisting of imide monomers) with very high performance, suitable for extremely critical

situations, which combine heat resistance, self-lubricating properties, dimensional stability and chemical resistance. Their mechanical, chemical and heat resistance is so high that these materials often replace glass and metals such as steel in many industrial applications.9,10 Polyimide works at temperatures up to 400° C. Since this coating is tough and thin, the polyimide-coated fiber is an excellent choice and sometimes does not require, in practice, additional buffers or sheaths.3 As material for the sheath, it is possible to use an optical polymer with a refractive index lower than that of silicon, this increases the mechanical strength of the fiber, as well as facilitating rapid sectioning and easy termination on site.8,11 Silicone has a high nominal temperature of up to 200° C. A rubber-based material, silicone is an excellent solution for applications requiring minimal losses in micro-creases. Secondary coatings are normally extruded onto the fiber to increase the mechanical protection. Commonly used materials are Tefzel, Nylon and Teflon. As fluoropolymers, Tefzel and Teflon are chemically inert, while Nylon is often used in cases where the sheath must be glued to the connector.

Hard polymer clad fibers (HPCF) are widely used in medical applications8,11 (! 2.19 and 2.20). From the point of view of the fiber configuration, there are single sheath HPCF and double sheath HPCF. Optical fibers transmit laser light. They consist of two specially prepared ends: the proximal and the distal termination (! 2.21-2.23).

The manufacturer usually interfaces the optical fiber with the medical laser by applying a special connector on the proximal side of the fiber itself. The SMA 905 type is the most frequently used solution in medical systems.

! 2.18 Standard optical fibers. (1) External silicone coating; (2) core of the optical fiber.

! 2.19 HPCF optical fibers. (1) External silicone coating; (2) core of the optical fiber; (3) cladding-coating, closely bonded to the fiber.

For the different types of lasers and specific applications it is therefore important to choose the right fiber.

CHARACTERISTICS OF MEDICAL OPTICAL FIBERS

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Both ends (proximal and distal) have peculiar characteristics.

In order to generate an emitting light beam suitable for specific applications, the distal portion of the fiber must be adequately “prepared”: sectioned, sculpted or polished.

The sectioning of the fiber, which is the subject of a specific discussion, is often performed by the operator and is one of the most important preliminary stages in the preparation of the laser before use. The correct execution of the cutting of the fiber is able to guarantee effectiveness in clinical performance, vice versa it can make the instrument inadequate. When done correctly, sectioning can provide a mirrored distal surface with minimal marginal alteration.3,12 The sculpting of the fiber, instead, is obtained during the production process to generate an emitting light beam (usually in an angled or lateral position) suitable

for specific applications. Today there are sculpted ends with a lateral beam and, also, with a spherical shape capable of emitting the beam at about 360°. A lateral beam end emits light at an angle close to 90° from the end of the fiber and finds application, for example, in prostate surgery, where laser energy is directed on the pro static tissue which is generally located lateral to the fiber. Fibers with a spherical terminal morphology are able to emit the 360° beam and are frequently used in intravenous therapy for the treatment of varicose veins of the lower limbs, for laser-assisted angioplasty and, again, for endodontic and periodontal applications.3,8,13,14 Mechanical polishing using specific microabrasive pastes is a typical process that produces a flat, possibly angled surface. The polishing process can be industrially automated by the manufacturer and, consequently, lead to a reduction in costs in the case of large productions.

! 2.20 Detail under the 20× optical microscope. (1) JACKET (external silicone coating); (2) fiber core; (3) cladding/interior lining.

! 2.21 SMA 905 connection. The male pole is protected with an airtight silicone seal after use.

! 2.22 Magnified view of the connection area, obtained from a microscope for optical fibers (200×). It is possible to appreciate the presence of structural alterations and impurities at the interface of the optical fiber. In such conditions the quality of the transmission is compromised.

! 2.23 Magnified view of the connection obtained from a microscope for optical fibers (200×). We can appreciate the absence of structural alterations and impurities at the interface of the optical fiber. In such conditions the quality of the transmission is guaranteed.

Diode laser overview: how it is done and how to manage it

Laser polishing is an advanced technology that creates high efficiency flat end surfaces that can withstand high input power.3,8 The diameter of optical fibers used in dental lasers is generally in the size range of 200-400 µm 5 (" 2.4).

200 µm fibers offer greater fluency than 600 µm fibers, i.e., more energy per unit area. At the same time, the fragility of the fiber increases. Typically in oral surgery fibers with diameters between 300 and 400 µm are used.5,7,15 Other diameters used for medical applications are 100 µm,600 µm and 1000 µm.

In choosing the optical fiber for specific clinical applications, the operator must consider not only the diameter of the fiber, but also the type (! 2.24).

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" 2.4 Color codes of optical fibers. In bold to be preferred solutions for resistance, flexibility, safety Fiber diameter

Color code

Covering sheath

200 µm

Red

Single/Double

300 µm

Green

Double

330 µm

Yellow

Single

400 µm

Blue

Double

REQUIREMENTS AND FEATURES OF MEDICAL OPTICAL FIBERS

1

Biocompatibility certified by verification services as USP; CLASS VI optical fibers for medical applications.

2

Spectrum of transmittance and attenuation at the various wavelengths, allows to identify the optical fiber which, in addition to being effective in the photonic transmission of the source, is able to offer the least attenuation at the wavelengths of interest.

3

Optical core diameter (optically active material). It is that part of the fiber which is intended to transmit the beam from the source.

4

Numerical aperture angle of the fiber (n.a.): represents the apical angle of the cone receiving the laser radiation by the optical fiber.

5

Cladding: material of first covering of the core with a high refractive index, which allows to exploit the principle of the “total internal reflection” of the radiation, trapping it in the core.

6

Buffer: external coating of the fiber, which serves to protect the fiber itself from mechanical and environmental damage.

7

Jacketing: external covering to protect the fiber, which can be made of PVC tube, flexible steel or other depending on the work environment or the instrumentation to which the fiber is connected.

8

Connection: generally for medical fibers it is made through SMA 905 connectors.

9

Resistance to high temperatures. Prerequisite for sterilization procedures.

! 2.24 HCPF optical fiber with SMA 905 connector. The blue band encodes the diameter of the fiber (400 µm).

Handpieces CONTACT handpiece In order to be handled with precision and safety, the optical fiber can be inserted inside a specific handpiece.

The CONTACT multifunctional handpiece is one that can be dismantled into different subunits (! 2.25), all of which are autoclavable. The external surface is satin, so as to allow a reduction of reflections during clinical use.

The body of the handpiece has a terminal (replaceable) that allows the insertion of tips or inserts with Luer-Lock type attachment. The closing base of the handpiece allows the clinician to lock or slide the optical fiber inside the handpiece with a simple rotation of the ring.

The CONTACT handpiece is used, together with its interchangeable tips, to allow the laser beam to easily reach the target.

The use of disposable tips and interchangeable inserts offers undoubted advantages in terms of ease of use for the operator and safety for the patient.

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Having a universally widespread, quick and safe Luer-Lock tip connection system ensures use of a very wide variety of inserts, already available on the medical market.

Luer-type insertion terminals can be used for surgical, endodontic, periodontal and intralesional applications.

Inserts can be disposable or sterilizable and reusable.

The rotating coupling anchoring system allows the operator to avoid undesired accidental detachment of the insert, avoiding the risk of inhalation or swallowing by the patient.

Handpiece with interchangeable inserts (MULTITIP silver) The MULTITIP handpieces are versatile devices capable of hosting special interchangeable inserts made of preformed optical fibers on their distal end (! 2.26).

The conduction system consists of a cord that covers and protects, by means of special coatings, an optical fiber (generally with a section of 200 µm), which joins on one side with the universal connection SMA 905, ending on the other side with a quick connection for the inserts (! 2.27 and 2.28). The operator is therefore no longer required to replace the optical fiber in its entirety. If necessary, the desired insert can be easily replaced, with a considerable saving of time and ergonomic benefit.

Interacting on the handpiece, and not at the level of the connection on the main device, also protects the main SMA connection.

The handpiece contains some lenses inside, whose function is to collimate and focus the beam. The constructive characteristics therefore do not suggest the sterilization of the handpiece, which can, however, be lined with sterile disposable protections in case of surgical applications.

The inserts and the closure and protection devices can instead be sterylized by autoclave.

Biostimulation handpiece A specific cable with universal SMA 905 connection hosts an optical fiber inside, suitably protected by multiple cladding, buffering and jacketing. The cable ends in a special handpiece for defocused applications.

The base of the handpiece contains, inside, some lenses, whose function is to defocus the beam and distribute it over an area of variable diameter. The distal portion of the handpiece is empty inside and acts as a spacer with respect to the target tissue plane (! 2.29). The construction features therefore do not suggest the sterilization of the entire handpiece, which can however be lined with sterile disposable protections in case of need.

It is suitable for defocused applications (! 2.30): Ä Ä Ä Ä Ä Ä

biostimulation; LLLT; HLLT; photobiomodulation; dental whitening; dermo-esthetic applications.

! 2.25 Handpiece for contact applications. Features a Luer-Lock compatible insert connector (CONTACT®, 88Dent, Pero, Milan, Italy).

! 2.26 MULTITIP handpiece.

Diode laser overview: how it is done and how to manage it

Flat wave handpiece Designed by Prof. Alberico Benedicenti of the University of Genoa, father of laser therapy in the cranio-cervicofacial field, the flat wave handpiece (! 2.31) is a device capable of emitting a quantity of energy constantly distributed over a surface of 1 cm2, maintaining the same fluences up to a distance of about 100 cm from the area involved in the treatment.16 The handpiece uses a special system of lenses, which allow a constant focus of the laser beam, thus allowing to deliver the

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17

same energy density thanks to the constant focusing system. The resulting laser beam emission will therefore be flat and not conical, ensuring a more effective and uniform penetration into the tissues and a better result in therapies, completely eliminating possible operator errors.17 The uniform distribution of energy, made independent of the distance of application, makes it possible to make the biostimulation and photobiomodulation procedures predictable, repeatable and not operator-dependent (! 2.32-2.35).

! 2.27 MULTITIP handpiece. In evidence the protection terminal that is removed to allow the connection of the inserts.

! 2.28 Placement of a quick connection tip with integrated optical fiber. A locking ring ensures the tip in its correct position.

! 2.29 Handpiece defocused by biostimulation. The spacer tip can be separated and disassembled from the base and sterilized.

! 2.30 Unfocused laser beam.

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Intraoral biostimulation terminal for MULTITIP handpiece The terminal can be easily inserted on handpieces with interchangeable inserts, for example, MULTITIP. It allows you to perform unfocused laser applications, similar to the classic biostimulation handpieces. It is reminiscent, for shape and construction characteristics, of the classic tips for photopolymerization lamps. Its use is indicated for intraoral applications, where traditional (straight) biostimulation handpieces cannot easily

! 2.31 Flat wave handpiece. As always, the optical connection is adequately protected. A sophisticated set of optics inside the handpiece guarantees the production of an energetically equally distributed beam on the target.

! 2.33 Flat wave handpiece in contact with the target surface. The beam diameter is 10 mm.

reach the posterior sites (! 2.36). Its use is particularly appreciated in the post-extractive socket biostimulation procedures of the posterior dental elements.

Bell-shaped biostimulation terminal for MULTITIP handpiece When using a handpiece with interchangeable inserts, for example MULTITIP, it is possible to easily switch from contact applications to non-contact applications by simply replacing the insert. In this case, the operator

! 2.32 Optics of the flat wave handpiece in detail.

! 2.34 Flat wave handpiece at a distance of 20 cm from the target surface. The diameter remains equal to 10 mm.

! 2.35 Flat wave handpiece 40 cm from the target surface. The beam diameter is unchanged.

Diode laser overview: how it is done and how to manage it

is not required to act at the level of the main connection with the machine body (one of the most delicate areas of the entire system).

It allows the user to perform defocused laser applications, similarly to the classic biostimulation handpieces.

The insert has a spacer with a characteristic “bell” shape (! 2.37). It is capable of delivering a cone-shaped defocused beam, the spot of which increases in diameter as a function of the distance from the target.

Whitening arch for MULTITIP handpiece It allows you to perform defocused laser applications, similar to what happens with biostimulation handpieces seen previously. The insert has a characteristic “arched” shape (! 2.38). It delivers a defocused beam, able to irradiate the dental arches individually or simultaneously during whitening procedures. For the specific use, see Chapter 6.

Focused handpiece for sapphire inserts Sapphire is a very hard material with quite peculiar mechanical and optical properties. It features high resistance and is capable of effectively transmitting laser radiation.

Recently some diode laser systems have been equipped with new conduction means: specific handpieces capable

! 2.36 Angled defocused tip for biostimulation. The terminal part can be separated from the MULTITIP base and sterilized.

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19

of using sapphire inserts in place of traditional optical fibers.

The innovative system consists of a cord containing an optical fiber of 400-600 µm (! 2.39), which is connected to a dedicated handpiece (! 2.40) consisting of different lenses with beam collimation function. At the head of the handpiece there is a threaded ring. On this area, specific polycrystalline sapphire inserts of varying shapes and sizes can be tightened with safety and precision.

During operation, the laser radiation travels through the handpiece that focuses the beam in the direction of the insert: while the handpiece and insert follow the operator in a movement very similar to the classic cold blade incision, the laser beam interacts with the tissues allowing to obtain a precise hemostatic incision with reduced carbonization phenomena.

Recent studies have confirmed how the handling and precision of this innovative instrument are similar to those obtainable with the traditional cold blade.18,19 The sapphire laser scalpel is a valid tool for oral surgery procedures, as it is innovative, minimally invasive, well tolerated by patients and ergonomic for the operator.

Applications: Ä oral surgery; Ä periodontal surgery; Ä implantology; Ä plastic/esthetic surgery.

! 2.37 “Bell” type unfocused insert for biostimulation. The spacer terminal can be removed from the MULTITIP base and subjected to sterilization procedures.

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! 2.38 Defocused whitening arch insert. It can be easily connected and disconnected from the MULTITIP handpiece in order to be sterilized.

! 2.39 Optic fiber cord with SMA 905 connection. Handpiece for sapphire inserts and conical inserts.

! 2.40 Focused handpiece for sapphire inserts.

As always, the free terminal is protected by a special silicone cover.

Telescopic zoom terminal It was created for non-contact applications. Its operation is based on the possibility of obtaining a telescopic movement by sliding its tubular components. It is thus possible to obtain an approach or a departure of suitable lenses inside it (! 2.41 and 2.42).

By rotating a ring, similar to what happens with the lens of a camera, the operator can select the focal diameter of the spot between 0.5 and 8 mm, depending on the construction characteristics. It is available with different focal lengths: variable spots from 0.5 mm to 8 mm on 400 µm fibers.

Applications: Ä transcutaneous and transmucosal treatment of intraoral and extraoral vascular anomalies; Ä treatment of dermatological lesions; Ä epilation by selective photothermolysis of the hair bulb.

Connections between handpiece and inserts Optical fibers are generally hosted inside specific handpieces; from here they can be further directed towards the target by means of special inserts or tips. The type of connection between handpieces and tips is a factor not to be underestimated not only in the choice of the handpiece, but also of the entire laser systems.

Having a universal connection allows the clinician not to be bound by the manufacturer in the choice of tips and inserts. It is also possible, over time, to resort to the use of specific tips or cannulas according to clinical needs.

The Luer-Lock connection is a standardized system of small-scale fluid fittings, used worldwide to make leakfree connections between a male conical fitting and its mating female part in medical and laboratory instruments, including syringe tips and hypodermic needles, needles and taps20 (Luer) (! 2.43).

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! 2.41 Telescopic zoom handpiece for dermatological and vascular applications.

! 2.42 Telescopic zoom handpiece for dermatological and vascular applications; detail.

! 2.43 Laser handpiece terminal with universal Luer-Lock connection.

This system was invented by Karl Schneider, who gave it the name of the 19th century German manufacturer of medical instruments Hermann Wülfing Luer.21 The main characteristics of Luer conical connectors are nowadays regulated by specific ISO, DIN, EN22 standards.

The 6% tapered Luer standard was developed in 1896.

The first standard for plastic applications was published and registered in 1955. Spread worldwide, it is used in thousands of medical devices.20 The Luer-Lock connection has proven over the years to be ergonomic and safe in medical applications.

When used in special handpieces, the Luer connection allows the connection of inserts and cannulas with varying technical specifications, according to clinical needs.

It is thus possible to accommodate the optical fiber and ensure the most ergonomic transport of the laser beam to the target site.

Inserts Cable inserts Handpieces equipped with universal Luer type connections can be equipped with universal hollow inserts, available in the dental materials market.

These inserts, being hollow, have the function of hosting the optical fiber inside them in order to direct it into the space.

To date, there are inserts that are able to convey the optical fibers and direct them towards the target tissue with different paths and angles. These devices must have dimensional specifications suitable for hosting the optical fiber in the required diameters (generally 200-400 µm) (" 2.5).

They can have different lengths depending on their intended use. They can be straight or angled, with vary-

Diode laser overview: how it is done and how to manage it

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22

" 2.5 Color codes of MULTITIP. 200 µm inserts , with high flexibility and resistance. 400 µm, Harder and non-­ deformable Fiber diameter

Color code

Covering sheath

200 µm

Yellow

Single

300 µm

Violet

Single

400 µm

Pink

Single

ing degrees of curvature. When they are angled, the morphology of the inserts must include gentle curves, such as to avoid the unwanted breakage of the fiber inside them.

Plastic polymer inserts can be of different quality, morphology and color (! 2.44). Dark colors are not recommended for use in combination with diode lasers as they risk interfering with the laser beam due to chromatic affinity. In this regard, the constituent material must also have adequate tolerance to high temperatures, in order not to incur in the unwanted melting of the insert during the procedures. White polymeric inserts (! 2.45) with reduced degree of flexibility are safe, effective and do not interfere with the near infrared laser beam.

Inserts with the metal terminal portion (! 2.46) offer a greater strength than those made of plastic or flexible polycarbonate. In this last case, the area of least resistance is located in the connection between the plastic portion and the metal one. They do not melt and do not undergo alterations when they come into contact with optical fibers.

! 2.44 Hollow inserts with connection with Luer-Lock compatible connections. The left (green) disposable insert features a metal terminal that can be bent by the operator. The right insert (white), autoclavable, is preformed with a 35° bend.

Interchangeable fiber optic inserts (MULTITIP) There are handpieces capable of hosting interchangeable optical microfibres in their distal portion.

In this case the optical microfiber is integrated in special inserts similar to those seen previously. The production process makes the two components inseparable, however, giving the operator the ability to change and replace the terminal optical fiber in a few seconds according to their needs. In the hypothetical transition from surgical activities to endodontic or periodontal activities, for example, the operator will simply have to replace the terminal optical fiber tip without having to replace the entire optical fiber (! 2.47-2.52).

Sapphire inserts Sapphire has long been a well-known component of some sophisticated laser systems with near infrared emission, more specifically in titanium sapphire (Ti: Al2O3) solid-state lasers, where the active medium consists of a sapphire crystal (Al 2O3) doped with titanium ions Ti3+.5 Sapphire has also been used for some time as a component of endoscopic systems, as a filter for laboratory tests and, again, for orthopedic and maxillofacial implants, due to its peculiar physical properties.5-7 Recently, the fields of application have been extended to neurosurgery, with the introduction of multichannel probes, and to microsurgery, where sophisticated and accurate micro scalpels have emerged.23-26 Sapphire, due to its optical properties (" 2.6, ! 2.53), constitutes

! 2.45 Interchangeable multi-purpose preformed hollow tip with Luer-Lock compatible connection.

! 2.46 Disposable cannula with metal terminal, compatible with the Luer-Lock connection.

Diode laser overview: how it is done and how to manage it

! 2.47 Solid 400 µm fiber optic insert (PINK color code). The insert is interchangeable and sterilizable. Compatible with MULTITIP handpieces.

10 mm of optical fiber, which extrude from the terminal metal folding of the insert, are available for use.

! 2.49 The protective cap is removed before inserting the microfibers into the MULTITIP handpiece.

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23

! 2.48 A special protective cap covers the coupling of the optical microfibers.

! 2.50 The microfibers are grafted onto the MULTITIP handpiece.

! 2.52 MULTITIP insert with integrated 200 µm optical fiber with 30 mm of active length. The fiber is specifically designed for endodontic applications. It has high flexibility and elevate fracture resistance. ! 2.51 A rotating bezel secures the microfiber to the handpiece.

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the final component of the conduction medium of some lasers including Er:Yag and, only recently, Nd:Yag and diode lasers.3 Sapphire is a transparent crystal formed by anisotropic aluminum oxide (Al2O3). The material can be constructed in different ways, so as to be able to exploit its peculiar properties, particularly the optical ones.

Polycrystalline sapphire is capable of effectively transmitting optical radiations, both visible and infrared, (! 2.53).

The wavelengths most commonly used by diode lasers in dentistry (808 nm, 810 nm and 980 nm) can be effectively applied to this new transmission medium. Recently introduced λ, such as the visible blue ones, 440-460 nm, can boast a transmission higher than 80%, close to 90% for λ 915 nm18,19 (! 2.54).

Characteristics of the sapphire include: Ä high hardness; Ä high resistance to chemical agents; Ä high resistance, preserved at high temperatures; Ä high maximum operating temperature; Ä excellent resistance to thermal shock.

The sapphire inserts currently available claim two distinct morphologies suitable for specific applications.

The base of the metal insert is provided with an internal thread in order to ensure a safe tightening with the

" 2.6 Physical properties of sapphire Mechanical

• Young module: 345 Gpa • Cutting Module: 145 GPa • Vickers hardness scale : 1570-1750 • Rupture Module: 420 MPa at 20° C

Thermal

• Melting point: 2030 °C • Thermal conductivity: 40 (W/m · °C) at 27° C

Optical

Transmission: >85% da 0.75 at 4.5 μm

handpiece. The stem of the insert protrudes from the base for a length of 10 mm.

The conical inserts have a conical morphology with a tip diameter of 500 µm (! 2.55). They are particularly suitable for soft tissue finishing, gingival recontouring, hooding and opercolectomy applications.18 The prismatic inserts attempt to reproduce the design of a micro-chisel or microsurgical blades (! 2.56 and 2.58).

They have a section of 400 µm × 1500 µm (! 2.57 and 2.58).

They are particularly suitable for the flap design, replacing the classic surgical carbon steel blade.

The inserts can be used in “activated” or not activated mode, contact or defocused mode. For further information, see the section in Chapter 4, Management, preparation, activation of optical fiber of diode laser.

Video Scan the QR code to access eight videos relating to the management, connection and disconnection phases of the optical fiber from the main unit: j Preparation. j Removal of the protective sheath of the optical fiber. j Fiber stripping. j Fiber connection to the main unit. j Insertion of the fiber in the handpiece. j Tip insertion and adjustment. j Quick fiber cutting. j Disconnection of the optical fiber from the main unit.

Diode laser overview: how it is done and how to manage it

Chapter 2

25

100

Transmission %

80

60

40

20

0

0.2

0.4

0.6 0.8 1

2

4

6

Wavelength µm

! 2.53 Optical transmission properties of polycrystalline sapphire. λ 915 nm highlighted.

! 2.54 Detail of a prismatic sapphire insert on a 915 nm diode laser (Pocket Laser®, 88Dent, Pero, Milan, Italy).

! 2.55 Conical shape sapphire tip.

! 2.57 Prismatic shape sapphire insert. The tip has a length of 10 mm.

The transmission area is 1500 µm × 400 µm.

! 2.56 Prismatic shape sapphire tip.

! 2.58 Dimensional comparison between 15C blade (left), prismatic sapphire inserts (center) and beaver blade (right).

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REFERENCES 1. Romagnoli E, Pecoraino P, Franchi GF, et al. Laser: complemento o strumento d’elezione? Il dentista moderno. Aprile 2008;36-55.

Tribology Applications. In: Nalwa HS, ed. Supramolecular Photosensitive and Electroactive Materials. San Diego: Academic Press; 2001. pp. 643–726.

18. Ruga E, Amerio E, Garrone M, et al.

Preliminar evaluation of a new surgical laser scalpel. J Osseointegr. Aprile 2017;9(1):234.

2. Pang P, Coluzzi D, Obeidi A, et al. Laser Energy in Oral Soft Tissue Applications.

J Laser Dent. 2010;18(3):123-31

11. Waynant RW. Lasers in Medicine. CRC Press; 2001. p. 354

3. Fibre ottiche per applicazioni medicali.

EO Med. Agosto 2015;8:8–11.

12. George R, Walsh LJ. Performance assessment of novel side firing flexible optical fibers for dental applications. Lasers Surg Med. 2009;41(3):214–21.

19. Ruga E, Garrone M, Amerio E, et al.

Valutazioni preliminari di inserti in Zaffiro e laser a diodi 915 nm in chirurgia implantare. Dent Tribune. Vol 2. 2018;

4. Jackson SD, Lauto A. Diode-pumped fiber lasers: a new clinical tool? Lasers Surg Med. 2002;30(3):184–90.

5. Stock K, Stegmayer T, Graser R, et al.

Comparison of different focusing fiber tips for improved oral diode laser surgery. Lasers Surg Med. 2012 December; 44(10):815–23.

6. Pang P, Coluzzi D, Rechmann P. Laser Energy in Oral Soft Tissue Applications.

J Laser Dent. 2010;18(3):123–31.

7. Romagnoli E. Laser: complemento o strumento d’elezione? ildentistamoderno. Aprile 2008;36–55.

8. Katzir A. Lasers and Optical Fibers in Medicine. Elsevier; 2012. p. 338.

9. McKeen L. The Effect of Sterilization on Plastics and Elastomers [Internet]. Elsevier; 2012.

10. Fahim M, Bijwe J, Nalwa HS. Chapter 8 - Polyimides for Microelectronics and

13. Garcez A, Fregnani E, Rodriguez H, et al. The use of optical fiber in endodontic photodynamic therapy. Is it really relevant? Lasers Med Sci. 8 marzo 2012;28.

14. Soukos NS, Chen PS-Y, Morris JT, et al. Photodynamic Therapy for Endodontic Disinfection. J Endod. 1 ottobre 2006;32(10):979–84.

15. Crippa R, Benedicenti S, Barone M. Laser a diodi in Odontoiatria. Milano: ediermes. 2008. pp. 1–186.

16. Amaroli A, Ravera S, Parker S, et al. An 808-nm Diode Laser with a Flat-Top Handpiece Positively Photobiomodulates Mitochondria Activities. Photomed Laser Surg. 2016 Nov;34(11):564-571 17. Benedicenti A, Amaroli A, Seting W, et al. Case Studies on the Use of a New Flattop Handpiec. Journal of the Laser and Health Academy. Journal of the Laser and Health Academy Vol. 2015.

20. Standards E. UNE EN 1707:1997 Conical fittings with a 6 % (Luer) taper for syringes, needles and certain other medical equipment.

21. The Life and Death of the Luer [Internet]. MDDI Online. 2012 22. ISO 594-1:1986 [Internet]. ISO. Disponibile su: https://www.iso.org/cms/ render/live/en/sites/isoorg/contents/ data/standard/00/46/4693.html 23. Kurlov VN, Shikunova IA, Ryabova AV, et al. Sapphire Smart Scalpel. Laser Florence 2009. 2010 American Institute of physics.

24. Dobrovinskaya ER, Lytvynov LA, Pishchik V. Sapphire: Material, Manufacturing, Applications. Springer Science.

2013;31-42.

25. Shikunova A, Kurlov VN. Sapphire shaped crystals for medicine. J Phys Conf Ser. 672 012018.

26. Lytvynov A. Peculiarity of sapphire application in medicine. Functional Materials. 2014;3(21):338-344.