Mastication: Clinical Protocols

 

-D-  CLINICAL PROCEDURES (Le Gall et Lauret, 2002 ; Le Gall et Lauret, 2008, 2011)

Fig. D 5 Video: test of adjunction

Note:  The final balancing is very acute and is only finished, when the patient says ”I am well”, or “It feels comfortable”. The perception of the patient is very acute, it’s  why his feeling is so important. Often, the breadth of the cycle is finally restored by a very thin last alteration, in the range of 30µm….

In Occlusion of Class 1 (Le Gall and Lauret, 2002, 2008, 2011)

When the occlusal relationships are optimal in class 1, all we need, is to restore the cusps of the first maxillary and/or mandibular molar with the composite-up method (similar to the wax-up), in the same place and according to occlusal curves.Fig. D 6a: Occlusion relationship class 1, without loss of VDO

The surface of composite additions must be coated with a bonding liquid, in order to avoid salivary contamination, and the sticking, with opposite teeth, during closure. It is generally not necessary to already ask the patient to simulate chewing, because as long as the material is not polymerized, chewing is reduced to a vertical shearing movement (fig. D7ab).
The hardening of the composite sets new marks and cancels the protective reflexes.A chewing simulation and the patient’s perception, then allow the progressive coordination of the guides, up to the cycle and comfortable feelings are restored. This stage, must be carefully completed -sometimes it is long- (Video D5, D8). The restoration of the main guiding rail must be favored. It is performed without any difficulty, if the opposite anatomy is optimal . This procedure can be also applied to ceramic, with a specific primer.
When finished, an impression of the tooth can be taken Video D5), to realize a new identical crown. Which may be obtained either by means of a conventional impression, or using an optical impression, which will allow the realization of a clone by CADCAM.

Fig. D 6b Summary: occlusal optimization of the mandibular first molar by carving in the composite and building up one cusp, mesio-buccal. It will be followed by the opposite rebuilding of maxilla first molar.This dual restoration has two objectives: to align the teeth along occlusal curves and restore the occlusal functional anatomy, the couple first molars.

Fig. D 7: Now the under-guiding upper first molar will be rebuilt. Before the composite hardens, the cycle keeps the initial vertical cutting shape. After polymerization, the protective reflexes are instantly canceled, and the cycle tries to expand. The composite additions appear to be excessive. An adjustment by subtraction must be performed with great care up to the functional balance and the optimal shape of the cycle are reached, in according with the patient TMJ kinetics. It’s why the patient’s feedback must guide the practitioner and is so important. See the movie below.

Fig. D 8: Video of the clinical case developed on figure D6b, D7

In Occlusion of Class 2 and related (Le Gall and Lauret, 2002, 2008, 2011)

In class2, a sagittal shift in the occlusal relationships can provoke a significant loss of transverse guides, during Cycle-In and especially during Cycle-Out (fig. D9, D10). They are even more important in partial class 2, with cusp tips in opposition, when there is an important gap between the opposite occlusal faces and when the chewing cycle is often reduced to a simple vertical shearing. The rehabilitation principle (fig. D9, D10) generally consists in modifying one part of the occlusal face of the mandibular first molar, by creating an artificial cusp, antagonist to the maxillary cusp disto-buccal, on the internal slope. This cusp, has a buccal cycle-in support and a cycle-out table, internal slope there. These guides are generally sufficient to restore the breadth of chewing cycle. In optimal conditions the hand rail can be also restored (like in Class 1). This rail has a significantant role in child, during growth, but a reduced role in adult, when the function is shared by several teeth.

Fig. D 9a: When the teeth can’t be moved, the solution consist to modify the occlusal anatomy by addition to restore optimal class 1 cycles. 

Fig. D 9b: The antagonist area of the disto-buccal cusp is prepared by etching to receive the new cusp. The composite is put and shaped with a “microbrush” soaked with adhesive liquid. After one or two closures, it is polymerized. The closure shows a buccal and internal over guidance. They are gradually retouched with a fine-grained diamond bur. Firstly the contacts of swallowing have been balanced, chewing balancing, has followed. When the patient sensation is good and the cycle regained, the composite restoration is carefully polished with non abrasive silicone cups. In a later session, if necessary, the nearby teeth will be integrated into the new occlusal scheme.

Fig. D 10:  The patient is a dental practitioner. On right side, the breadth of the cycle is  almost acceptable, because second molar and second bicuspid partially compensate the missing guides on first molar couple. At the end of composite-up, the breadth of the cycle has been improved with better guides, and the patient feels more comfortable, He even notices that cycle-out is well guided, without any opposite touch, in the palatal concavities of upper incisors.

Various Malocclusions and Class 3

Clinical situations are very diverse, cross bites, reversed bites, class 3, open bites…

11a

11b

Fig. D 11a, b: A reflection must be done, based on the knowledge of the occlusal anatomy and functional kinetics. It allows to choose the best tooth or teeth positioned to support the guidances. It’s necessary to settle often relay functions, such as a cycle-in on one tooth and a cycle-out on its neighbor and distribute the guidances on several posterior teeth. When the case is complex, a multi-disciplinary diagnosis must be done, with a combined treatment possibly associated with orthodontics, orthognatic surgery and occlusion.
Class 3 occlusal relationships, reversed occlusions with cycles shaped like eight and cases of complex rehabilitation with cross bite, gap and others, like open bites, although obeying the same principles of treatment, won’t be completely call discussed here.

Sketchy Reminder : Clinical control of occlusion. Rational of the final functional adjustment of occlusal faces

Fig. D 12a: The colored film used is a waterproof one 15µm thickness. The Miller pliers are linked together by a silicon block, to be taken in one hand.

Fig. D 12b: Some advises for composite-up: privilege alterations in the bottom of a fossa (A), rather than on the top of a cusp, risking to flatten the cusp (D). You must maintain a personalized immediate side-shift, between cycle-out slopes (functional interplay, naturally present, allowing the cycle to pass through MIO without any stopping (C). The tripodic relationship of gnathology do not respects that rule. It’s why tripodism only exist on the schemes (B) of occlusal books, but not in the mouth of the patients…

Fig. D 13: On all video clips, we observe that there is a functional game at the passage of chewing cycles by Max Intercuspation. Similarly, when the anatomy is intact, the presence of rails can be observed on the occlusal surfaces of the M1.

Fig. D 14: The observations of the mandibular kinetics were made during the laterality movements, inverse of the chewing, without occlusal pressure of the elevating muscles. During centripetal chewing, under pressure of the elevator muscles, the tripodic relationship classically described in the manuals blocks chewing. The observations show the constant presence of a functional game at the moment of the passage of Maxi Intercuspation: the ISS (immediate side shift).

Fig.D 15: Same clinical case. It is observed that the ISS is mainly carried out in support of relatively flat marginal crests, with a small functional game between the cycle output tables.

Bibliography

  • Le Gall M.G., Lauret J.F. The Function of Mastication: Implications for Occlusal Therapy. Pract. Perio. Aest. Dent 1998; 10 (2): 225-229
  • Le Gall M. G., Lauret J. F. (†). Ouvrage : 3ème édition augmentée (2002, réédition 2004, 2008, 2011) “La Fonction occlusale : implications cliniques“ Editions CDP.2011 Paris www.editionscdp.fr/
  • Le Gall M. G., Lauret J. F. (†). Book : 3rd edition enriched (2002, reprinted 2004, 2008, 2011) “The occlusal function: clinical implications“ (French edition only) Editions CDP.2011 Paris www.editionscdp.fr/
  • Le Gall M. G. Physiologic balancing of Occlusion Part two : How to adjust posterior occlusal faces? Rev. Odont. Stomat. Nov. 2013; 42: 243-257 (English and French published article)