Orthodontics and masticatory dysfunction
In 1934, COSTEN was the first to describe a link between certain malocclusions, the loss of posterior dental alignment and vertical dimension, with temporomandibular disorders (TMD). These temporomandibular disorders are the main cause of pain of non-dental origin in the orofacial region. Their definition in the occlusodontics lexicon is as follows: “Symptomatic expression of a myoarthropathy of the masticatory system”. Their etiology and
Pathophysiology remains poorly understood. Currently, the etiology appears to be multifactorial, involving a large number of direct and indirect factors; occlusion is often cited as one of the main factors causing these TMDs. In various epidemiological studies, signs and symptoms of TMD are frequently found in children and adolescents and show an increased prevalence in subjects between 15 and 45 years of age.
- Roles of occlusion and condyle position in the occurrence of TMD
Occlusion and condylar position have long been seen as the main etiological agents
TMJ disorders were considered a separate disease, caused by
occlusion, or an overly eccentric position of the condyle.
II-1) Role given to occlusion in the appearance of TMD
II-1-a) Responsibility for occlusion
In 1988, GREENE and LASKIN published a list of 10 myths in this field which, surprisingly after 20 years, are still a subject of debate among orthodontists:
- People with certain untreated malocclusions (e.g., Class II, Division 2, deep overbite, crossbite) are more likely to develop TMD.
- Patients with an excessively large anterior guide, or those with a complete lack of incisal guide (open bite) are more likely to develop TMD.
- People with severe maxillomandibular disharmonies are more likely to develop TMD.
- X-rays taken before treatment of both TMJs should be performed. The position of each condyle in its socket should be assessed, and orthodontic treatment should result in a good position at the end, i.e., a concentric position of the condyle in the glenoid fossa.
- Orthodontic treatment, when performed correctly, reduces the later risk of developing TMD.
- Adherence to gnathological principles during treatment completion reduces the risk of TMD. 7-The use of certain traditional orthodontic procedures and/or appliances may increase the risk of TMD.
- Adult patients who present with occlusion disturbances with the presence of symptoms
of TTM, will probably require occlusal correction.
- A retrusive position of the mandible, whether constitutional or after a treatment procedure, is a major factor in the etiology of TMD/
- When the mandible is in this retrusive position, the articular disc can slide in front of the condyle.
II-1-b) Questioning the main role of occlusion in the appearance of TMD:
The opinions of authors, or series of cases from the 1970s and 1980s, incriminating occlusion as the main etiological factor of TMD, have been called into question due to the low scientific level they represent.
presented. The groups studied, the criteria used, and the analysis methods employed did not allow definitive conclusions to be drawn. The role of occlusion is now considered secondary in the multifactorial etiology of TMD.
II-2) Role given to the mandibular position in the appearance of TMD
Centric Relationship is a very controversial topic in orthodontics. Its definition has changed over the years.
century several times, its role in the development of TMD has long been highlighted. There is no meta-analysis on the subject, however, RINCHUSE and KANDASAMY, with the help of in-depth scientific research in a systematic review, try to refute some received dogmas, of non-scientific origin.
II-2-a) Responsibility of the condylar position
The position of the mandibular condyle in the glenoid fossa appears to play a predominant role in
the appearance of TTM for some authors.
Studies conducted in the 1970s and 1969 by PAMEIJER and GLICKMAN show that even if full mouth rehabilitations were performed in the ORC position, patients continued to have an occlusion functioning in OIM.
Thus, there is not a single position of the condyle in the fossa, but a number of acceptable positions, as concluded by RINCHUSE, JOHNSTON, MOHL and MAC NAMARA SELIGMAN and OKESON in their articles.
MAC NAMARA, SELIGMAN and OKESON in 1995 only found signs of TTM from a slippage greater than 4mm, and even added that this slippage is a result of TTM rather than a cause.
II-2-b) Recording of RC: the gnathological approach
-Different schools differ among themselves in the definition of RC, but also in its registration.
-The definition of RC has changed over the past half century, from a posterior retrusive position to an anterosuperior position.
-Data indicate that condyle position or condyle RC position is not a diagnostic indicator of TMD. Although an anterosuperior position is more favorable than a retrusive position, some patients may be found with a posterior position consistent with good TMJ health. Studies implicating condyle position had low specificity leading to false positives.
-Although RC recordings made by a dentist are more reliable than recordings in an unmanipulated patient, they are still less physiological.
-Recent data suggest that the concept of a “terminal hinge axis” cannot be valid, because there is an “instantaneous center of rotation,” in which the condyles perform simultaneous rotation and translation.
-There appears to be little benefit in analyzing patients’ articulator casts to compare differences between OIM and ORC, and it should be remembered that a large proportion of the population has this discrepancy without having TMD.
II-3) Role of articulators
Mounting casts on an articulator remains a subject of debate among practitioners since
about thirty years. Rinchuse in 1995 considered that articulators are very useful during major fixed or removable prosthetic restorations, or during surgical procedures, in order to maintain a certain DV. However, their usefulness in ODF remains equivocal. A review in the “journal of clinical orthodontics” published in 2001 estimates that 21% of practitioners surveyed mount their cases on articulators regularly, 44% occasionally, and finally 35% never mount.
Orthodontists are just as (or even more) involved in occlusion changes (static and functional) as other dental professionals, especially dental technicians, who also use an articulator.
The point of view against editing
-An articulator cannot accurately simulate human mandibular movements, being based on the now false theory of the terminal hinge axis. -There is no evidence that orthodontic treatment performed with model mounting improves the quality of results, whether in terms of TMJ health or TMD improvement. -There is no scientific evidence that the use of an articulator influences the diagnosis in any way. -RC records
prove reliable only under experimental conditions. -Errors during
Recording the RC or the assembly reduces the interest of the assembly. -The bite recordings used for articulator placement are static recordings and do not realize the actual movements of the mandible.
- ) Role of orthodontic treatments in the appearance of TMD
Gnathologists suggest that orthodontic treatments can cause TMD in two ways: – Directly through the orthodontic appliances used (uni or bi maxillary, fixed or functional) or through certain therapies (with or without extractions)
– Indirectly through poor occlusal finishing leading to interference and prematurity, or through an eccentric condylar position.
- ) Role of extractions in orthodontic treatments:
The use of dental extractions involves the responsibility of the dental surgeon and
the orthodontist. The act of extracting generally healthy teeth in order to achieve the objectives
desired therapeutic measures could have significant consequences on the mandibular joints.
Many authors have responded to this topic. We will first look at the authors who believe that extractions play a role in the development of TMD, due to the appearance of harmful effects found in the various articles:
- A modification of the occlusion with a retraction of the maxillary incisors, themselves responsible for a distal positioning of the mandible and the condyles in the glenoid fossa in a posterior position
- Joint noises
- Muscle pain
- A decrease in mouth opening
- A deviation of the inter-incisor line
Harmful consequences attributed to extraction therapies
O’Connor noted that the extraction rate declined significantly between 1988 and 1992, from 38% to 29%. This decrease was reportedly due to suspicions of harmful effects of extraction therapy on the TMJs. These findings have significantly influenced orthodontists’ treatment choices.
- Some authors have established that dental extractions lead to posterior displacement of the condyles and ultimately to joint dysfunction.
III-2) Role of different types of orthodontic appliances in temporomandibular disorders
Many studies have attempted to demonstrate the link between various types of orthodontic mechanics and the occurrence of TMD, but authors’ opinions on this subject differ.
III-2-a) Influence of certain processing aids:
TMD triggers are related to distal pressure on the condyles, resulting in disc compression. The disc will be brought forward, and the condyles will exert pressure against the highly vascularized and innervated part of the retrodiscal tissues, thus causing pain.
The use of Class II elastics and extra-oral force devices will pull the maxilla backward, the masticatory muscles will then tend to move the mandible back to compensate for the maxillary movement when the teeth close together, and thus exert distal pressure on the condyles.
III-2-b) Influence of single or double-maxillary treatments:
LARSSON and RONNËRMAN conducted a study in 1981 on 23 patients who had been treated 10 years previously. 18 were treated with fixed therapy and 5 received activator treatment.
Symptoms of moderate dysfunction were found in 8 patients, while only 1 patient presented severe signs of dysfunction.
The authors therefore conclude that orthodontic treatments do not create joint problems, however they note a slightly higher prevalence of symptoms in patients treated with fixed orthodontics in both arches, than only in the maxilla.
III-2-c) Influence of the type of treatment; fixed or functional:
BROADBENT, BOWBEER, WITZIG, SPAHL, MEHTA and STACK emphasize the preventive role of orthodontic treatment in TMD in cases of therapies without 54 extractions, the use of functional appliances only, or in less common therapies involving the extraction of the second molar and its replacement by the 3rd. These publications published between 1971 and 1988 are not based on any statistical study, they only present the authors’ point of view.
JANSON and HASUND conducted a retrospective study in 1981 on 90 subjects with Class II malocclusion, 1, the results showed a statistically lower dysfunctional index of clinical examination and anamnesis for the group of subjects who did not benefit from extractions compared to the group whose malocclusion was not treated or treated with extractions of four premolars. Orthodontic treatments do not represent a risk factor for TMJ according to the authors, but activator treatments lead to a significant improvement in function, and thus this type of therapy should be used as often as necessary.
III-3) Do orthodontic treatments create occlusal conditions leading to ATM disorders?
The appearance of occlusal interferences occurring during orthodontic treatments can, during dental movements according to some authors, be the cause of dysfunctions of the temporomandibular joint.
Unfavorable role of orthodontic therapies in the appearance of occlusal interferences
Non-working occlusal contacts were found equally in treated and untreated patients. These types of occlusal contacts showed no relationship with the presence of signs and symptoms of temporomandibular dysfunction.
III-4) Role of orthodontic therapies in the position of the articular condyle:
According to some authors, the effect of certain orthodontic therapies would be to influence
distally the position of the condyle in the fossa, thus leading to joint disorders.
There is no statistically significant correlation between variations in the position of the condyle in the fossa and age, sex, skeleton or the presence of any dental treatment, with signs or symptoms of temporomandibular disorders, the use of FEO, certain types
elastics, or treatment with or without extractions. The fact of the change of the joint space during treatment can be explained by the growth and remodeling of the condyle, the fossa, and the
remodeling of one in relation to the other, in fact the joint adapts with the correction of the
malocclusion.
- Orthodontic treatments should not be considered responsible for the creation of TMD, regardless of the orthodontic technique used. These data also allow us to reject the hypothesis that orthodontic treatment is specific or necessary for the cure of TMD signs and symptoms. – Non-working occlusal contacts were found equally in treated and untreated patients. These types of occlusal contacts show no relationship with the presence of TMD signs and symptoms. Although a stable occlusion is a goal of orthodontic treatment, not achieving an occlusion that strictly follows gnathological principles does not increase the prevalence of TMD. – Signs and symptoms increase with age, especially during adolescence. Thus, TMDs that occur during orthodontic therapy cannot necessarily be associated with them. However, our assertions must be qualified; the association between malocclusions and TMD vary over time in some longitudinal studies and sometimes even disappear. Observations should be made before treatment as well as through long-term observation of treated and untreated subjects. An appropriate observation period would seem to be from late adolescence to adulthood (approximately 30 years). Differentiation of patients in the control group and in the group
study is a constant problem, and on the other hand, individual variations must be taken into account
taken into account when considering the results of the studies.
IV. Canine protection:
One of the most advocated principles of the gnathological school is the mutual protection of occlusion by the canines, or OPC. Only the canines, or sometimes the first premolars, should come into contact during diduction movements, thus protecting the rest of the dentition from occlusal shearing stresses. This occlusion should be achieved in patients treated in orthodontics or during prosthetic/conservative restorations (125). Gnathologists accuse the
practitioners who do not perform this functional occlusion, to generate TMD and recurrences
-The OPC is considered more as an established fact rather than an optimal functional occlusion model, and not based on the level of evidence. Balanced occlusion without interference, or group function are valid occlusions. -Each patient is different, their stomatognathic system is unique,
Other models may be equally acceptable, the most important point remains the absence of occlusal interference. The patient’s chewing pattern, craniofacial morphology , dental mesh, oral health status, and parafunctions provide important information, allowing the practitioner to be guided towards the best functional occlusion for the patient. -An improvement must be made in the recording of functional occlusion , taking into account the subject’s parafunctions. A recording that would be dynamic, rather than static.
Orthodontics and masticatory dysfunction
Wisdom teeth can cause pain if they erupt crooked.
Ceramic crowns offer a natural appearance and great strength.
Bleeding gums when brushing may indicate gingivitis.
Short orthodontic treatments quickly correct minor misalignments.
Composite dental fillings are discreet and long-lasting.
Interdental brushes are essential for cleaning narrow spaces.
A vitamin-rich diet strengthens teeth and gums.