IMPLANT OCCLUSION AND FAILURES
INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
Contents •Introduction •Definition of implant failure •Signs and Symptoms •Criteria for successful Implants •Failing and Failed Implants •Peri implantitis •Classification of implant failures •Factors affecting Implant Failures a. surgical factors b. host factors c. implant factors d. prosthetic factors www.indiandentalacademy.com
• Force Delivery and Failure Mechanism - Moment arm - Fatigue Failure • Basic Considerations for Occlusion for Implants • Review of Occlusal Schemes • Factors Affecting Selection of Occlusal Scheme • Prescribed Occlusion a)Edentulous Situations b)Partially Edentulous situations • Important Guidelines to Follow • Conclusion • References www.indiandentalacademy.com
INTRODUCTION â€˘ Branemark defined osseointegration as â€œthe direct structural and functional connection between ordered living bone and the surface of a load carrying implant www.indiandentalacademy.com
Implant failure Definition:An implant failure may be defined as the first instance at which the performance of the implant, measured in some quantitative way falls below a specified acceptable level. Or can be defined as an implant that has a hopeless prognosis. www.indiandentalacademy.com
Signs and symptoms of implant failure 1) Horizontal mobility beyond 0.5mm or any clinically observed vertical movement under <500g force 2) rapid progressive bone loss regardless of the stress reduction and peri implant therapy 3) Pain during function or on percussion 4) Dull sound on percussion 5) Continued exudation inspite of surgical attempts at correction 6) Generalized radiolucency around an implant 7) >1/2 of the surrounding bone is lost 8) SLEEPERS -Implants inserted in poor position making them useless for prosthetic support 9) Pocket depth of 5mm and increasing www.indiandentalacademy.com 10) Bleeding on probing(BOP) Index of 2 or above
Failing and failed implants Failing Implant
Definition- Failure process is in early stages and is reversible Clinical featuresâ€˘ Progessive Marginal Bone loss(Saucerization) â€˘ absence of mobility â€˘ peri implant infection (peri implantitis
Failure process has reached the irreversible state Marginal bone loss reaching the apical 1/3 of implant mobility Thin peri fixtural radiolucency
Peri Implantitis Def-American Academy of Periodontology Defines Peri implantitis as â€œprogressive Peri implant bone loss in conjunction with a soft tissue inflammatory lesion.â€? Causes Bacterial Accumulation Overloading or Combination www.indiandentalacademy.com
Clinical SignsProgression of pocket depth Radiographically detectable bone loss Inflammatory Reaction of Mucosa
Classification of Implant Failures 1.According to Branemark et al • Loss of bone anchorage - Mucoperiosteal perforation - Surgical trauma • Gingival problems - Proliferative gingivitis - Fistula formation • Mechanical complications - Fixture fractures - Fracture of prostheses, gold screws, abutment screws www.indiandentalacademy.com
2. According to Misch Surgical failure
inability to place the abutment at the time of surgery
Osseous healing failure
period from implant placement to abutment connection,is related to healing ability of bone
Early loading failure
the first year the implant serves as a prosthetic abutment
Intermediate implant failure
time period after the 1st yr of loading upto following 5yrs of function
Late implant failure
after the implant and prosthesis have been loaded for >5yrs but <10yrs. www.indiandentalacademy.com
Long term failure
failures after 10 yrs.
Complications/factors leading to implant failures . Surgical factors (early failures) Stage I surgery
1) Overheating of bone - necrosis,osteomyelitis 2) Lack of primary stability - bone loss 3) Infection 4) Lack of osseointegration 5) Poor placement or angulation, slips, eccentric drills 6) Damage to vital structures 7) Implant fracture 8) Inadequate no. of implants www.indiandentalacademy.com
Stage II surgery • Loose abutment • poor fixtures • early loading by prosthesis • poor abutments
Prosthetic factors (late failures) 1.Improper design, shape, contours 2.Poor fit of prostheses 3.Occlusal forces 4.Inaccurate framework 5.Cantilever extension 6.Framework fracture, prosthesis fracture 7.Functional problems eg speech www.indiandentalacademy.com
Implant related factors 1.Screw design:
conical screws - loosen flat head screws - better 2.Implant body design:
smooth cylinder implant - shear force at implant-bone interface threaded implant - can transform and change the direction of force through thread geometry
a) Shape of thread Square
Buttress thread www.indiandentalacademy.com
Standard v Thread
pitch: smaller the pitch more will be the surface
c) Thread depth: increases surface area
3. Implant length : area 4. Implant width :
increases surface increases surface area www.indiandentalacademy.com
Host factors • Patient dissatisfaction with the result. • Inadequate patient follow-up • Failure to maintain hygiene leading to periodontal breakdown • Parafunctional habits • Systemic health( medical complications) • Medications- alter tissue metabolism and repair • Social habits like smoking, stress,alcohol abuse affect wound healing • Poor bone quality and quantity - avascular bone,bone density, type of bone,etc.
Force delivery and failure mechanisms Moment loads (torque or torsional loads): is defined as a vector,the magnitude of which equals the product of force magnitude and the perpendicular distance from the implant to the line of action of force.
Possible rotations A total of six rotations may develop about three clinical co ordinate axes.
Clinical Moment Arms 1.OCCLUSAL HEIGHT MOMENT ARM 2.CANTILEVER LENGTH MOMENT ARM 3.OCCLUSAL WIDTH MOMENT ARM
Fatigue failure Four factors influence fatigue: 1. Biomaterial 2. Geometry of the structure -Twice thicker material have sixteen times more fatigue resistance . 3. Force magnitude 4. Number of loading cycles.
IMPLANT OCCLUSION BASIC CONSIDERATION – OCCLUSION CONCEPTS AND PHILOSOPHIES ARE NOT BASED UPON SCINTIFIC RESEARCH AND EVIDENCE. – THE CONCEPT THAT HAVE BEEN POPULAR FOR THE RESTORATION OF NATURAL TEETH HAVE BEEN JUSTIFIED BY PURELY EMPIRICAL METHODS AND HAVE HELD UP WELL TO THE TEST OF TIME. FOR IMPLANTS THE SAME CONCEPTS HAVE BEEN USED WHICH SERVE AS A GUIDE LINES TO ACHIEVE OPTIMUM OCCLUSION .
-TRULSSON AND GUNNE IN 1998 : CONCLUDED THAT THE RANGE OF “FOOD- HOLDING” FORCES FOR THE PATIENTS WITH IMPLANTS IS SIGNIFICANTLY HIGHER THAN THOSE FOR PATIENTS WITH NATURAL TEETH. THE KEY FEATURES OF AN OCCLUSION FOR IMPLANTS SHOULD DEPEND UPON THE TYPE OF PROSTHESIS GIVEN- SINGLE TOOTH IMPLANTS/FPD/CD/OVERDENTURE ,AS THE REQUIREMENT AND BIOMECHANICS OF EACH ARE DIFFERENT.
Review of occlusal scheme Flocken (1984) stated that to help alleviate the potential impact forces , the teeth should contact simultaneously when the mandible closes into maximum intercuspation.Natural teeth can function effectively from this position. Lundgren , Laurell (1984) suggested the need to minimize horizontal forces created by premature contacts or steep cusps. Albrektsson,et al., (1986) emphasized the need to distribute the load mainly over the areas supported directly by fixtures. Jemt (1986) described that when Osseo integrated implants are used in short span FPDs and single tooth replacements , the occlusion should be distributed in maximum intercuspation and all cusp interferences should be eliminated in eccentric positions. Lucia (1987) advocated the application of gnathological principles in development of occlusion www.indiandentalacademy.com in implants.
Misch (1991) developed IPO ‘Implant protective occlusion’ for implant supported restorations. IPO - Medial positioned lingualized occlusion is based on : - Narrow occlusal table. - occlusal table width similar to width of implant body. - Increasing surface area. - Design of occlusion in favour of weakest arch. - Decreasing force of occlusal contacts. - Eliminating or reducing all shear loads to implant to bone interface. - Posterior disocclusion by anterior components. - Initial contacts on only natural teeth and later on multiple contacts on both teeth and implants. Norton (1995) recommended an ideal occlusal scheme for fixed implant supported prostheses : - A centric occlusion ‘cusp to central fossa’ contact which is light. - An ideal anterior guidance : that is canine-guidance or group function; no posterior interferences. - Axial loading of the implants. www.indiandentalacademy.com
Factors affecting choice of occlusal scheme 1.Arch form: - Curve arch is favorable for less stresses - Influences no. of implants to be placed - Opposing arch form affects occlusion 2.Interarch distance and jaw relations : - May prevent development of particular occlusal scheme - May force to adapt a particular scheme - Affects biomechanical aspects 3. Orientation of the occlusal plane : - Arch in which is implant is placed becomes the dominant arch and opposing edentulous arch becomes weaker arch. - plane should favor weaker arch. www.indiandentalacademy.com
4. Abnormal mandibular movements
5. Bone support and bone mechanics : Sullivan (1990) stated that the final form of restoration should be development maintaining progressive loading. Good bone support - occlusal contacts can be increased.
6. Occlusal material : - affects the transmission of forces. - affects the maintenance of occlusal contacts. Acrylic has higher wear rate, so if acrylic is to be used then heavy occlusal contacts canâ€™t be given. www.indiandentalacademy.com
6. Zarb (1985): stated that acrylic teeth have shock absorbing effect and can be modified for use very easily.
They should be used to decrease overloading of implants.
However selection of occlusal material depends upon : - Opposing occlusion. - Remaining dentition. - Arch to be restored.
7. Attachment to natural teeth •Hobo in 1986 recommended a non rigid attachment and a Key and Key way type of attachment between teeth and implant. •Lundgren in 1986 recommended the use of Semi – precision attachment which detaches the teeth from the implant prosthesis allowing a tooth to move downward.
â€˘ The IMZ implant system uses a Intra mobile element [IME] to act as a shock absorber during function. It can act as a PDL analogue. However, Gracia in 1998 reported intrusion of the natural supporting teeth. â€˘Misch: stated that biomechanical concern and difference in Support should be understood and applied before attaching natural teeth to implants. He advocates initial occlusal contacts on the natural teeth.(Thin articulating paper of 25 ď m should be used for this. Once the equilibrium with a light bite force is completed, a heavier CR occlusal force is applied to have contacts on teeth as well as implant also, thus harmonizing the occlusal forces. www.indiandentalacademy.com
Heavy bite force is used because it depresses the natural teeth positioning them close to infra occluded or depressed implant position and equally sharing the load.
Only possible advantage is additional support to convert cantilever design to fixed one. 8. Quality of Osseo integration Its is the ability of implant to bear occlusal load . It depends upon: 1.
Implant length , width, design, surface coatings.
Number of implants, position of implants, orientation of implants.
Prescribed occlusion Edentulous situations 1.Implants opposing implants with cantilevers Onlight closure Ă˜Multiple even , simultaneous contact between all opposing restorations except the distal cantilever unit , where 100 microns clearance is required . On firm closure Ă˜Distal cantilever will remain out of contact .
FIXTURES SUPPORTING OVER DENTURES. • BALANCED OCCLUSION • LINGUALIZED OCCLUSION
FIXTURES SUPPORTED BRIDGES OPPOSING COMPLETE DENTURES.
• BALANCED / LINGUALIZED OCCLUSION.
FIXTURES SUPPORTED OVERDENTURES OPPOSING NATURAL TEETH WITH BRIDGE MUTUALLY PROTECTED OCCLUSION CANINE GUIDED OR ANTERIOR GROUP FUNCTION. BALANCED OCCLUSION.
PARTIAL EDENTULOUS CASES SINGLE TOOTH IMPLANT LIGHT LOAD ( INFRA- OCCLUSION BY 30 MICRONS ) UNDER HEAVY CLENCHING . AXIAL LOADING LIGHT OR NO ECCENTRIC CONTACTS NO GUIDANCE ON SINGLE IMPLANT
FIXTURES SUPPORTED BIDGE AGAINST NATURAL DENTITION. • CANINE PROTECTED / GROUP FUNCTION – LATERAL GUIDANCE.
•M P O ( MUTUALLY PROTECTED OCCLUSION ) •ORGANIC OCCLUSION
FIXTURES SUPPORTED BRIDGE HAVING CANTILEVER EXTENSIONS OPPOSING COMPLETE DENTURES • BALANCED OCCLUSION • NO CONTACT ON CANTILEVER UNITS.
KENNEDY CLASS I • ANTERIOR GUIDANCE BY NATURAL TEETH AND POSTERIOR DISCLUSION. Canine guidance / anterior group function .
KENNEDY CLASS II • CONFIRM TO EXISTING OCCLUSION WITH 30 MICRONS CLEARANCE AT FREE END SADDLE • MPO
KENNEDY CLASS III • CONFIRM TO EXISTING OCCLUSION WITH INFRA OCCLUSION AT IMPLANT SITE. • MPO/ GROUP FUNCTION
KENNEDY CLASS IV • CONFIRM TO EXISTING OCCLUSION WITH INFRA OCCLUSION OF IMPLANT. • ANTERIOR GUIDANCE WHICH ACHEIVES POSTERIOR DISCLUSION. • GROUP FUNCTION
IMPORTANT GUIDELINES TO FOLLOW • INFRAOCCLUSION UPTO 30 MICRONS OF IMPLANT SUPPORTED RESTORATION • NO BALANCING CONTACTS ON CANTILEVERS. • NO GUIDANCE ON SINGLE IMPLANTS. • FREEDOM IN CENTRIC. • OCCLUSAL TABLE DIRECTLY PROPORTIONAL TO IMPLANT DIAMETER. • NARROW OCCLUSAL WIDTH. www.indiandentalacademy.com
•IMPLANT LENGTH – CROWN RATIO ideal – 1:2 acceptable – 1:1 for removable denture. •AVOIDANCE OF CANTILEVER LENGTH. maximum 10 and 20 mm is advised. 7 mm is optimum . •SHALLOW CENTRAL FOSSAE WITH TRIPODAL CUSPAL CONTACTS. •NO CONTACT IN LATERAL EXCURSION. •SLIGHT CONTACT IN CENTRIC OCCLUSION. www.indiandentalacademy.com
The surgeon’s tale ‘The implants were successfully integrated , but failed because of excess loads.’
or The Restorative Dentist’s tale ‘The implants were poorly integrated and so failed under normal masticatory loads.’
either way The Patient’s tale ‘My implants have failed!’
References 1.Carl.E.Misch : Implant Dentistry, 2nd ed.,pp 609-629,1999 2.Cury P.R.,Sendyk W.R.,Sallum A.W. Factors associated with early and late failure of osseointegrated implant.Braz J Oral Sci.2003;2 3. Davies S.J.,Gray R.J.M.,Young M.P.J.:Good occlusal practice in the provision of implant borne prosthes8es.BDJ 2002;192:79-88 4. Esposito M.,Hirsch J.M.,Lekholm U.,Thomsen P. Biological factors contributing to failures of osseointegrated oral implants.Euro.J.of Oral Sc.1998;106:527-551 5. Hobo, Ichida, Garcia: Osseointegration and Occlusal Rehabilitation,1st ed. pp.239-47,1988 6. Michael D.Wise : Failure in the Restored Dentition:Management and Treatment,1st ed. pp.489-564,1995 7. Palmer R,Palmer P,Howe L Dental implants: Part 10.Complications and maintenance. BDJ 1999 ; 187:653-658 8.Vincent Jimenez-Lopez : Implant-supported prostheses:Occlusion,Clinical Cases,and laboratory procedures, 1st ed.pp. 23-44,1995 9. Weinberg L A Reduction of implant loading using a modified centric occlusal anatomy. Int J Prosthodont 1998 ; 11:55-69www.indiandentalacademy.com
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