BIOMECHANICS OF FIXED FUNCTIONAL APPLIANCE
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CONTENTS • • • • • • • • •
Introduction Classification Indications Contraindications Design of Appliances Fixed v/s Removable: The Biology Of Functional Appliances Mechanics Conclusion Bibliography www.indiandentalacademy.com
Introduction • Fixed functional appliances first appeared in the early 1900s, when Emil Herbst in 1905 presented his system at the Berlin International Dental Congress. • This device was one of the early attempts to produce mechanically a “jumping of the bite”; an idea that had earlier been advocated by Kingsley, among others. www.indiandentalacademy.com
• Since then and up to the seventies, very little was published on this appliance. It was at that time that Hans Pancherz brought the subject back into discussion with the publication of several articles on the Herbst. • It was only in the eighties that several systems derived from Herbst’s work started to appear. www.indiandentalacademy.com
• A number of fixed functional appliances have gained popularity in recent years to help achieve better results. • Talking about good results, it should be remembered that successful treatment always begins with good diagnosis for which an appropriate treatment plan is formulated . This is followed by mechanotherapy in order to attain the desired treatment objectives. www.indiandentalacademy.com
• In order that the latter part, viz. mechanotherapy can be executed without any hitches it is essential that a clinician be well versed with the biomechanics of the appliance that he/she chooses to employ. • Without this knowledge a clinician is akin to a person who is ‘lost in a maze’. He knows the ‘entrance’ and the ‘exit’ but he just does not know how to get there! www.indiandentalacademy.com
Classification
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a) Removable functional appliances –
Activator, Frankel
b) Semi-fixed functional appliances -
Denholtz, Bass
c) Fixed functional appliances – www.indiandentalacademy.com
Jasper Jumper, Herbst, MPA
According to theforceproduced (Jasper and McNamara, Am J Orthod 1995)
1)
Appliances producing pushing force. a) Temporarily fixed functional appliances Twin block. b) Permanently fixed functional appliances. Herbst & its family. Rick-a- nator. MPA Jasper jumper Churro jumper
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2) Appliances producing pull force eg. Severable Adjustable Intermaxillary Force (SAIF) spring
Classification Of Fixed Functional Appliances 1) Flexible fixed functional appliances. eg. Jasper jumper Churro jumper 2) Rigid fixed functional appliances eg. Herbst appliance 3) Hybrid fixed functional appliances eg. Eureka spring. www.indiandentalacademy.com
1. 2. 3. 4. 5. 6. 7. 8. 9.
Herbst Appliance Jasper Jumper Mandibular Protraction Appliance (MPA) Mandibular Advancing Repositioning Splint (MARS) Appliance Adjustable Bite Corrector Churro Jumper Eureka Spring Rick-e –Nator The Klapper Super Spring www.indiandentalacademy.com
10. 11. 12. 13. 14. 15. 16. 17. 18. 19.
Bite Fixer Magnetic Telescopic Device Amoric Torsion Coils Scandee Tubular Jumper Universal Bite Jumper BioPedic Appliance Mandibular Anterior Repositioning Appliance Intraoral Snoring-Therapy (IST) Appliance Ritto Appliance Twin Force Bite Corrector www.indiandentalacademy.com
Indications • It is used primarily in actively growing individuals with favorable facial growth patterns. • Cl . II skeletal pattern with mandibular deficiency • Lack of vertical development in lower face height
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• Cl. II molar relationship • True deep over bite, with infraocclusion of the posterior segments • The mandibular incisor teeth should be positioned upright over basal bone structures • The maxillary and mandibular teeth should be well aligned www.indiandentalacademy.com
Contraindications • Non-growing individuals • Cl . II skeletal pattern with maxillary excess • Increased lower anterior face height
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• Cl. I molar relationship • Shallow over bite • Pseudo deep bite due to supra eruption of the anterior teeth (“Gummy” smile) • Proclined mandibular anterior teeth • Decreased overjet/ Retroclined maxillary anterior teeth www.indiandentalacademy.com
Design Of The Appliances • Herbst Appliance • Jasper Jumper • Mandibular Protraction Appliance
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Herbst Appliance • The appliance can be compared to an artificial joint working between the maxilla and the mandible. • A bilateral telescope mechanism attached to orthodontic bands keeps the mandible mechanically in a continuous anterior jumped position
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Each telescopic device consists of 1. A tube ( upper) 2. A plunger ( lower) 3. Two pivots 4. Two screws. Pivots
Plunger Screws
Tube www.indiandentalacademy.com
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• The pivot for the tube is usually soldered to the maxillary permanent first molar band, and the pivot for the plunger to the mandibular first premolar band. • The screws prevent the telescoping parts from slipping off the pivots.
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• The length of the tube determines the amount of bite jumping. • Usually the mandible is retained in an incisal end-toend relationship.
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• The length of the plunger is kept at a maximum in order to prevent it from slipping out of the tube when the mouth is opened wide. • If the plunger is too long, however, it may protrude far behind the tube and injure the buccal mucosa distal to the maxillary permanent first molar.
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• The mechanism permits vertical opening movements and, when properly constructed, also lateral movements of the mandible. • The pivot openings for the tube and plunger should be wide enough to provide a loose fit of the telescoping parts at their points of attachment. This increases the lateral movement capacity of the lower jaw. www.indiandentalacademy.com
There are a number of modifications/ variations to the original Herbst design, which would include the following: • Cast splint Herbst • Stainless steel crown Herbst • Acrylic splint herbst • Cantilevered Bite Jumper • MALU – Mandibular Advancement Locking Unit • Flip-Lock Herbst Appliance • Ventral Telescope www.indiandentalacademy.com
Jasper Jumper The system is composed of two parts • The Force Module and • The Anchor Units.
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The force module
is constructed of a stainless steel coil or spring that is attached at both ends to stainless steel endcaps, in which holes have been drilled in the flanges to accommodate the anchoring unit.
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• This module is surrounded by an opaque polyurethane covering for hygiene and comfort. The modules are available in seven lengths, ranging from 26 mm to 38 mm in 2 mm increments.
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Anchor Units
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Attachment to the main arch wire
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Attachment To Auxiliary Arch Wires: The Use Of ''Outriggers''
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• When the force module is straight, it remains passive. As the teeth come into occlusion, the spring of the force module is curved axially as the muscles of mastication elevate the mandible, producing a range of forces from 1 to 16 ounces.
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Mandibular Protraction Appliance No. 2 (Carlos Martins Coelho Filho, JCO 1995 )
• The MPA No. 2 is fabricated by making right-angle circles in two pieces of 0.032" (0.8mm) stainless steel wire
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• A small piece of rigid coil, from 0.024" (0.6mm) stainless steel wire, or a stainless steel tubing is slipped over one of the wires.
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• One end of each wire is inserted through the other wire's loop, so that each wire passes through the other up to the limit of the wire coil . • The coil prevents the two wires from interfering with each other and ensures their correct relationship.
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• The maxillary archwire is made with occlusally directed circles against the molar tubes. • The mandibular archwire should have occlusally directed circles placed about 2-3mm distal to each cuspid.
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Fix ed v /s Remov able: The Biology Of Functional Appliances
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• Fixed functional appliances are normally known as "non-compliance Class II correctors" giving a false idea about the co-operation necessary during treatment.
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• When we compare them to removable appliances, we can clearly recognize fixed appliances as noncompliance devices. • However, for treatment to be successful, good cooperation is always necessary, especially if skeletal modifications instead of dentoalveolar compensations are desired.
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• According to Proffit, there are two mechanisms to protrusion: Active & Passive. • In PASSIVE protrusion, the mandible is held forward by the orthodontic appliance. This the case with fixed functional appliances.
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• In ACTIVE protrusion, the patient ‘responds’ to the appliance by using his or her muscles, especially the lateral pterygoid to hold the mandible forward. • Stimulating the muscles was thought to be important from the beginning of functional appliance therapy, hence both the generic functional name and the specific term activator. www.indiandentalacademy.com
• Whether the patient actively uses his musculature to posture the mandible forward or passively rests against the appliance may or may not affect the amount of mandibular growth. • But this definitely affects the amount of tooth movement that occurs and may determine the effect on the maxilla.
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• For example, with the Herbst appliance, the condyle is displaced anteriorly at all times. • Therefore this appliance should be considered, potentially, the most effective of the functional appliances in altering jaw growth. • But such is not the case!
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• Though with the Herbst appliance, the condyle is displaced anteriorly at all times, the amount of force against the teeth is very much under the patients control. • The patient can use his/her own muscles to hold the jaw forwards with the Herbst appliance serving only as a stimulus to do so. • Or the appliance can passively hold the jaw forward, with little or no contribution from the muscles. www.indiandentalacademy.com
• When there is no contribution from the muscles, i.e. when the muscles relax, the reaction force is distributed to the maxilla and also to the maxillary and mandibular teeth. • Thus, if the muscles hold the jaw forward, there is little or no reactive force against the teeth and minimal tooth movement occurs. • If the jaw repositioning is entirely passive, force against the teeth can displace the teeth quite significantly. www.indiandentalacademy.com
The “metabolic pump� www.indiandentalacademy.com
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Biomechanics
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Mf = F x d = F x 10
d = 10mm
= 10 F Mc should be equal to the Mf in order to get bodily movement i.e. Mc = Mf Mc = 10F
Mc : F = 10F: F = 10 : 1 www.indiandentalacademy.com
Mf = F x d = F x 10
d = 5mm
=5F Mc should be equal to the Mf in order to get bodily movement i.e. Mc = Mf Mc = 5F
Mc : F = 5F: F =5:1 www.indiandentalacademy.com
Mc > Mf Mc : F > 10 : 1 approx. 12 : 1
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Static Equilibrium
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Anchorage • “Resistance to unwanted tooth movement” • Reinforced anchorage eg. adding second molar to the anchor unit • Stationary anchorage eg. Pitting bodily movement of one tooth v/s tipping movement of another. www.indiandentalacademy.com
Mechanics of Fixed Functional Appliances
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• In terms of appliances and appliance design, there are numerous fixed functional appliances. • The mode of attachment does vary to a great extent. • However, the forces that they exert are very similar, i.e. a ‘push’ type of force to the maxillary and mandibular dentition and to their respective jaw bases. www.indiandentalacademy.com
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First Order View
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Mandibular Arch
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2 Order nd
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3rd Order View
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Conclusion Fixed functional appliances are, and will remain, an invaluable tool for every orthodontist. Having said so, it would not be inappropriate to say that knowing the mechanics of the same would be mandatory for every clinician. By knowing this the clinician can not only minimize the unwanted side effects but also optimise his treatment results. www.indiandentalacademy.com
In addition, ignoring the biology and the biological bases of these appliances would be an enormous error. Just keep both of these in mind, add just a little bit of common sense, and I assure you that you will get a sound Bio+Mechanical finish.
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Bibliography 1. Filho Carlos Martins Coelho. Mandibular Protraction Appliances for Class II Treatment .J Clin Orthod; 29:319 – 336, 1995. 2. Graber T M, Rakosi T, Petrovic A G. Dentofacial Orthopedics with Functional Appliances. St. Louis: Mosby; 2000. 3. Graber T M, Vanarsdall R L. Orthodontics Current Principles and Techniques. St. Louis: Mosby; 2000. 4. McNamara J A Jr., Orthodontics and Dentofacial Orthopedics. Ann Arbor: Needham Press; 2001. Jasper J J, McNamaraJ A Jr. The correction of interarch malocclusions using a fixed force module. Am J Orthod 108:6,641 – 650, 1995. www.indiandentalacademy.com
5. Pancherz H. The Herbst appliance— its biological effects and clinical use. Am J Orthod 1985;87:1-20. 6. Proffit W R, Contemporary Orthodontics. St. Loius: Mosby; 2000. 7. Ritto K A , The Orthodontic CYBERjournal Fixed Functional Appliances Classification. 8. Sachdeva R C L. Orthodontics for the next millenium. Dallas: Ormco; 1997. 9. Schwindling F P. Jasper Junper Colour atlas. Merzig: Edition Schwindling; 1997. 10. Williams P L. Gray’s Anatomy. Edinburgh: Churchill Livingstone; 1995. www.indiandentalacademy.com
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