Orthodontics

– F –     CONSEQUENCES IN ORTHODONTICS   

Note the mesial axis orientation of the maxillary first molar and the low position of his disco-buccal cusp. In addition to its occlusal morphofunctional characteristics, this feature allows the couple first molars to impose its functional kinetics and TMJ shaping during growth. It also serves to guide the positioning of the teeth according to the following equilibrium curve of Spee sagittal and frontal Wilson. This is the coordinate chewing kinetics, the first molars and the articulation, which creates these functional curves during growth. They must be respected later, to maintain optimal functional balance.

axes dents Buff

Fig. F1: Orientation dental units. The distal-buccal cusp of the maxillary first molar excess of the curve of Spee. This position allows it to achieve with the mandibular first molar, early interception and guiding the dental cycles-in. It is a dynamic key chewing, exceeding the static definition that gave Andrew. This orientation buttress, of the first molars, is rarely reproduced in dental anatomy books (Picture Dr. Bufévant).

Swallowing: a neglected clinical data, in adults occlusion.  (Fontenelle, Woda 1993; Romette1976 Le Gall et al 2010, Le Gall, 2013)
Swallowing is also an essential act as breathing or blood circulation. It begins during fetal life and corresponds to all the muscle and joint movements that allow to pass the “bolus” (including saliva) in the oral cavity to the digestive tract.
It consists of three successive phases: oral, pharyngeal, esophageal. Oral phase of swallowing implements not only the lingual and masticatory muscles but also the facial muscles and the infra-hyoid muscles and sub-hyoid.

In the newborn, swallowing moved from birth through nutrition function. The tongue is then in a low position and interposed between the arcades during swallowing. Later, she will go up against the palate and the wedging of swallowing will occur on teeth. His daily frequency (between 1 000 and 3000 times per day) and constantly repeated functional stimulation it causes, among other at the TM joint level, allows the progressive installation during growth, of a direct anatomical correlation, between maximum occlusion and articular swallowing position.  The role and position of tongue are essential to a physiological swallowing. 

In children, in deciduous and mixed dentition (Fig 2), atypical or inaccurate lingual postures are consistently associated with facial deformities(Deffez 1995). Disorders of the position and volume lingual, dyskinesia, thus have a direct impact on facial growth and positioning of the teeth in occlusion and along occlusal curves (Wilson and Spee).

Impact of clinical concepts on facial growth and occlusal pattern

If they have not been treated before permanent teething, they can worsen, modify the facial growth and evolve toward facial insufficiency, with transverse, anterior or vertical  hypo- or hyper-development, themselves responsible for ventilation deficit, tooth-maxilla disharmony, with transverse or sagittal malocclusions, or anterior or lateral open-gap.

Diskin Tongue a          

 

Fig. F2a: Tongue in anterolateral and low position, anomalous

                                                             Dyskin tongue b          

 

Fig. F2b: Early Tongue Inaccurate ante-position

 

                                                                                                                                Dyskin tongue c

 

Fig. F2c: low and forward atypical posture of the tongue.

 

 

 

Their early treatment allows to redirect and get a physiological growth with bilateral establishment of the optimal occlusal scheme and the occlusal plane orientation.

The beginning and objectives of an early treatment differ according to the concepts:

  • For M.J. Deshayes and her school*, early treatment begins at age 3 and its goal is to prepare the emergence of first molars and their placement in class 1 occlusion, three years later, by a cranio-facial growth control. Because movements-rotations of cranial bones during growth have a direct impact on the orientation and shape of the glenoid cavity. The way in which the chewing function, in lacteal dentition, is set depends on the bone structure of the temporal bones. The objectives of this early treatment are to establish an early symmetrization of bone structures that simultaneously leads to that of chewing. The least asymmetry characteristics must be taken into account. In this context a well-balanced masticatory function, bilateral and alternating, is restored naturally, with a physiological growth. For MJ Deshayes and E Jaunet the correction of masticatory function before the age of 6 has become the rule. “Controlled condylar growth, between 3 and 6 years, is a key that leads to the positioning of M1 in class 1 relationship, with alternating, wide and symmetrical bilateral chewing” (Deshayes).
  • The stages of an early treatment: The early symmetrization of bone structures is achieved through the 24H24 port of the unlocking orthosis (USP).. Especially during chewing. the wearing of the unlocking orthosis and the  difference in thickness between the right and left side will change the chewing at the beginning of the early treatment, and will lead to a remodeling of the TMJ. The tilting of the upper occlusal plane will allow a symmetry of the chewing, without any apparatusl (Jaunet E. Poster 2018 Brescia).
  • The early treatment lasts 6-9 months and the growth of the dental arches is normalized over a period of 2 years without any apparatus. It is this approach, where possible, that presents the best functional coherence (Deshayes M.J. conf 14 April 2018 (Eurocclusion Italy Brescia www.eurocclusion.it). It requires collaboration with the practitioner, the parents and the child, which is not always easy at this age.                                                                                                       *Teaching and research group on cranio-facial bio-dynamics. Dr. Marie Joseph Deshayes Dr. Emmanuelle Jaunet (ejaunet@cranexplo.com)                                                                         
  • Fig. F2 d: Unlocking sliding device (E Jaunet poster, Brescia 2018)

 

 

 

 

  • For other authors (Bonnet 2010, Rollet 2013), early treatment begins with the change of teeth.

In orthodontics, functional schools (Bonnet, 1992.93, 2010) and oral function rehabilitation techniques (Fournier 1991. Deffez et al 1995) insist, when treating atypical swallowing in children, on the repositioning methods lingual to prevent pathological consequences, by a reorientation of growth. Their detection and early interception, often at the time of change of teeth is a key setting optimal occlusion of the first molars. B. Bonnet, uses the term occlusion “Linguo-Centered” to characterize the mandibular position, during the post-orthopedic phase of temporomandibular and dental, adaptation , when the mandible is then positioned and guided essentially by the tongue posture.

The placing of the tongue during closing in physiological swallowing situation leads to swallowing MIO, even without swallowing (consequently, compliance with this lingual posture, is essential to the search of a balanced swallowing in MIO).

In child, when first molars come in class 1 occlusion, they combine a sufficient wedging and guiding potential to support and canalize alone, transversal mastication dynamics, without any sideslip and to impose it, to next appearing teeth.
That occlusal relation must be bilateral to allow an breadth and alternated mastication and avoid asymmetrical growth risk.
Other types of occlusal relations are far away to have the same functional equilibrium and often show important underguidances area resulting in adaptative and/or incomplete cycles, even reduced to a vertical simple cutting (that is inefficient in transversal and postero-anterior facial growth stimulation).
These occlusal situations often result from tongue anomalous postures and can be  co-responsible for vertical, transversal and anterior anomalous growth, resulting in facial insufficiencies more or less evolutive and/or asymmetric, just like mandible mis-positioning.
Under these conditions, early reorientation of growth is an essential key to a physiologic growth.

It can be obtained, as appropriate, by associating functional education, mandible reposturation,  tongue repositioning and muscle rehabilitation. Several concepts using devices and different protocols are used to achieve these objectives, causing a disocclusion to enable a reposturation more or less active (rods, EF Splints, Planas tracks …) and / or the tongue repositioning, and muscular reeducation (Night Lingual Envelope, Lip bumper …).

Concept LROC, Linguo-Ramal and Occlusal Cortical, in case of hyper-divergence or biretrognathia (Bonnet 2010).
-1st Stage: vertical development of ramus (connecting rods) and tongue repositioning.
-2nd Stage: raising of lateral sectors mandible, then accompanied  by ascent of lateral sectors maxilla
-3rd Stage: occlusal overlapping, then increasing potency of chewing function, that is the true motor of transverse enlargement of maxilla and frontal-maxilla advancing.  Mandible simultaneously advancing to.

Bielle a    IMG_3416    Strech b

Fig. F3 In addition to functional education, three ares currently used devices: a- Connecting rods from Herbst modified by Bonnet. -Night lingual envelope.  b -Lip bumper for a stretching of the upper lip.  Courtesy Dr. Bruno Bonnet

LROC (Clinical case: courtesy Dr C. Le Crom)

moulagesFig. F4 Initial occlusal relationship on models: a- right partial class 2; b- class 2; c- buccal view: d- occlusal maxilla view

Vues vestFig. F5:Physiologic occlusal relationship at the end of treatment.
LROC procedure. Case Treated Without Any fixed device, by using modified connecting rods and night lingual envelope in addition to functional education.

OIM

Fig. F6a,b  Occlusal view of Maximum Interdental Occlusion (MIO), maxilla and mandible, without any alteration.

Lastic mandible

Fig. F7 a: well balanced chewing guidances on lower right side and not chewing side

b: well balanced mastication guidances on lower left side and not chewing side

Mast sup

Fig. F7 c: well balanced mastication guidances on upper right side and not chewing side

d: well balanced mastication guidances on upper left side and not chewing side    Courtesy Dr C. Le Crom

EF devices (Clinical case: courtesy Dr Daniel Rollet)

Another alternative is to combine functional education to the use of splints EF, allowing the repositioning of the mandible (Rollet D. 2013). The tracks introduced by Planas had a similar goal with a device and a protocol different.

Fig. F8: Tongue: Early abnormal posture, lower and forward. Consequences: crossbite in Class 3 seriously affecting growth. Clinical cases treated only with different types of splints EF with associated functional education.Clinical cases only treated with different types of unlocking and functional education splints (FE). Without any fixed devices.

Fig. F9 After treatment of mandibular anteposition, Class I occlusion reports were restored. Recovery cycles favored the transverse expansion, and advancing fronto-maxillary which allowed to redirect growth, now physiological.

 

Fig. F10: clinical control, over a year after the end of treatment …                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              

Class 2 clinical case treated by addition of composite

This chapter has still been developped in the chapter CLINICAL PROCEDURES. Go to this chapter, you will find  a clinical movie.
Below, an additional case:

Fig. F11: In class 2 and more in class 2 partial cycle-in guides are reduced and those cycle-out are generally absent.

A satisfactory solution is to change the occlusal anatomy of the mandibular first molar, creating a new cusp antagonist distobuccal cusp of the maxillary first molar, which lets you create a support buccal cycle-in and cycle-out table internal, on the maxilla molar, allowing the cycle to find the optimum kinetics, as class 1. This rational approach is applied to neutralize, not successful Orthodontics  processing (F12 below).

Fig. F12: Cycle-in and cycle-out guidances are now balanced and cycle pattern has found an optimal breadth like in class 1

Open bites and Overhangs

Guidelines for occlusal restoration, when the anterior guidance is absent

The open bite and overhangs, are usually the consequence of lingual apraxia during swallowing, appeared during growth.  When they occur early, they can be responsible for severe growth disorders that can evolve, toward severe mandible-maxillary facial dysmorphia, when growth is not redirected precociously. In the case of open bite, the tongue is situated in forward between the arcades, and disrupts more or less, occlusal contacts of the anterior and posterior teeth. The occlusal wedging during swallowing is sometimes provided by only one couple of teeth in occlusion, on each side: the most posterior. In other clinical situations, the support of deglutition is divided: one side is occluded, the other side is supported by tongue. Clinical situations are very diverse and personalized. They can be stabilized or progressing and sometimes reported to other etiologies or other aggravating factors, which may require, if orthodontic technics are inoperative, on the need for recourse to orthognathic surgery. But even in these extreme situations, the long term stability of these treatments will require the mastery of the tongue posture simultaneously with occlusion.

To thoroughly reduce an open bite, without any tongue reeducation is a certainty of recurrence. But reeducation alone is not a certitude of success. Particularly in adult, reeducation can fail if MIO is not simultaneouly balanced, because changing the tongue posture, changes immediately the mandible position and then maximum occlusion situation, which can become uncomfortable and unusable. Tongue reeducation and occlusion are the two keys of the treatment perenniality. Other etiologies can also be responsible for open bites: macroglossies, articular polyarthritis…Sometimes the occlusal contacts are  reduced to only one couple of teeth in occlusion on each side, the last one, responsible for vertical support and mastication. In these conditions, the therapeutic occlusal aim, is to put in occlusion at least one additional mesial couple on each side, sometimes more, it depends on the clinical case. In effect, to close wholly an open bite, without any certainty that the lingual reeducation has succeeded and is stabilized, always result in a recurrence of the open bite. Be cautious, because a deciding key of the success of the reeducation is the mastering of the occlusal wedging. During reeducation, the tip of the tongue is placed in a upper and more posterior position, just back upper incisors. Therefore the mandible also move back and MIO must be balanced in its new posture (Fig. F13).

Fig. F13 To insure the success of tongue reeducation It’s essential to fit maximum occlusion to the optimal new posture of the tongue and mandible (b) The patient must feel comfortable in the new MIO, otherwise the tongue will return in the previous disfunctional posture, that was comfortable.

14 a

14b

Fig. F14 a, b Following MIO balancing, the cycle kinetics must be balanced at least on an additional mesial couple (if possible)

Usual concepts in orthodontics
Conventional concepts in orthodontics, consist to tip back the posterior maxillary first molars, that are used later as a means of anchorage, for move the anterior teeth. Unfortunately when removing straight arch-wires, the maxillary first molars not spontaneously recover their angulation and functional relationship Fig. F14 and chewing cycles, their optimal breadth.

Retrait arc droit

Fig. F15  To anticipate, programming of the 2d order must be reconsidered and molar brackets positioned to “aim at” functional occlusion (Fig F15), or pre-angulated cases be preferred. It is complex, and evolutive, according to maturation (Buffévant). The tipping of first molars don’t allow them to alone found again their functional relation, especially their optimal angulation, compromising optimal mastication cycles.

Brackets inclinés

Fig. F16 The brackets positioning has allowed the molars to found again their physiologic  and occlusal relation, consequently the chewing cycles have reach their optimal extent. 

The anchorage necessities are to be reassessed, with using light forces, new computer datas, and above all, the replacement of molar anchorages by micro-implants.
But more important, if the arch-wires are really locks for growth, using these technics, in case of facial insufficiency, can result secondarily, in surgical indication, and in sleeping apnea syndrome (Bonnet 2010).
It seems that overtaking a too mechanistic approach, by early taking into account of growth, must become a priority aim in clinical orthodontics, when insufficiency growth is precociously diagnosed (i.e. in deciduous or mixed dentition, at the time of first molar couples appearance).
In Orthodontics, like in other domains, fast evolution of knowledges, techniques and protocols, suggest strongly, that one must not be captive of only one method or procedure.
It is suitable to establish firstly, the therapeutic aims and then to choose the optimal procedures to reach them in accordance with the progress of techniques and protocols.
The Ricketts Bioprogressive society is in this state of mind, with the famous three questions applied to orthodontics: What?, Why?, How?, and certainly represent a mode of reasoning and an example, to be followed.
It is in that orientation that we have proposed the new Organo-Functional theory of the occlusion (Le Gall 2010), provided as a conceptual frame, aiming at restoring or preserving the physiology of the manducatory tract.

 

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