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Posterior crossbite and temporomandibular disorders (TMDs): need for orthodontic treatment?

Birgit Thilander , Krister Bjerklin
DOI: http://dx.doi.org/10.1093/ejo/cjr095 667-673 First published online: 6 September 2011

Abstract

The aim of this work was to update the bibliography regarding the concept of ‘temporomandibular disorder (TMD)’ and ‘posterior crossbite’ and try to find out if there is any association between some special signs/symptoms of TMD and type of posterior crossbite. A literature search from 1970 to 2009, due to specified criterion, resulted in 14 publications that were found to be relevant for the present systematic review. An association between TMD and posterior crossbite (Yes-group) was reported as often as absence of such a relationship (No-group). The samples in the two groups showed similarities as well as differences with respect to number, gender, and age. Most articles reported only on ‘presence’ or ‘absence’ of crossbite and only few on type of crossbite opposite to a thorough account of clinical signs and symptoms of TMD. This review seems, however, to state that a functional posterior crossbite (mandibular guidance with midline deviation) is associated with headache, temporomandibular joint and muscular pain, and clicking. As evident from the discussion, such type needs orthodontic treatment to rehabilitate the asymmetric muscular activity between the crossbite and non-crossbite sides and the changed condyle/temporal relationship caused by mandibular deviation. Whether this treatment also will avoid future TMD problems can be answered only after clinical follow-up studies have been performed.

Introduction

A desire for aesthetic improvement of dental anomalies is the main reason for orthodontic treatment. Besides those aesthetic–psychological motives, there is a need for treatment of some malocclusions on prophylactic reasons, as for instance proclined maxillary incisors to avoid trauma. Moreover, any association between temporomandibular disorders (TMDs) and some malocclusions (e.g. posterior crossbite) should indicate need of orthodontic treatment to avoid future problems in joints and masticatory muscles.

As evident from previous reviews (Seligman and Pullinger, 1991; Dibbets et al., 1993; Vanderas, 1993; McNamara et al., 1995; Luther 1998), different opinions have been presented about an association between posterior crossbite and TMD, varying between ‘yes it is’, ‘no it is not’, and ‘maybe it is’. Differences as regards selection of subjects (age and number) and methods (examination or questionnaire) together with different and vague definitions of ‘TMD’ and ‘crossbite’ may account for these controversial opinions.

Many publications during the last 50 year period give a vague impression as regards the ‘concept of TMD’ as summarized by the American Academy of Orofacial Pain (de Leeuw, 2008). The original terminology ‘Costen syndrome’ [an isolated group of symptoms around the ear and temporomandibular joints (TMJs)] was changed to ‘TMJ dysfunction syndrome’ as well as ‘functional TMJ disturbances’. Because the symptoms are not restricted to the joints, those terms were considered to be too limited and that a broader term should be used, such as CMD (cranio-mandibular) or TMD (temporomandibular) or MPD (myofacial pain). The abbreviation D stands for either ‘dysfunction’ or ‘disorder’.

Anyhow, TMD is a generic term for a number of clinical signs and symptoms involving the masticatory muscles, the TMJs, and associated structures. Epidemiological studies have reported that functional disturbances of the masticatory system are common, usually of mild character, seem to exhibit a female preponderance, and seem to increase with age. Clinical signs (clicking, disk displacement, and tenderness of masticatory muscles on palpation) and symptoms (especially headache) are frequently reported, and significant associations exist between different signs. An uncertain relationship between signs and symptoms has been questioned as the subjects’ complaints might be seen as unreliable especially in children. Furthermore, difficulty exists in defining signs and symptoms qualitatively. Differences in degree between mild, moderate, and severe signs are very difficult to estimate, especially as regards symptoms.

Finally, the terms dysfunction and ‘parafunction’ (clenching, grinding, and dental wear) are often confused. Strictly defined dysfunction is a partial disturbance, impairment, or abnormality of the functioning of an organ, whereas parafunction is a disordered or perverted function, which can cause a dysfunction. This situation is made even more confusing by the fact that parafunctions are sometimes included in subjective symptoms and sometimes as clinical signs.

Thus, we agree with Luther (1998) in his critical review on orthodontics and TMJ that ‘more information with respect to etiologi, diagnosis, and assessment of TMD is still needed’. This request deserves attention for the diagnosis crossbite as well.

A literature search on ‘crossbite’ will result in a malocclusion with different localization such as ‘anterior’, ‘posterior’, ‘lateral’, and even ‘buccal’ crossbite, each of them often in combination with another dental anomaly. To classify these different malocclusion types in the same category, termed crossbite may explain the controversial opinions on its possible association with TMD. In the present paper, ‘posterior crossbite’ or its synonym ‘lateral crossbite’, defined as a section of teeth in crossbite position, is used,

The prevalence of posterior crossbite varies between 4 and 23 per cent in different populations. This wide range may be explained by differences in populations, but above all, that some studies focus on different age groups. Only few studies on the prevalence of malocclusion in large samples at different dental development periods have been published (Helm, 1970; Myllärniemi, 1970; Thilander et al., 2001). It is quite obvious from these studies that posterior crossbite is more frequent in the primary dentition, due to sucking habits (e.g. Larsson, 1978; øgaard et al., 1994), which may suggest that a crossbite in some young children is self-correcting (Leighton, 1966; Thilander et al., 1984; Kurol and Berglund, 1992). According to Helm (1970), the frequency increases in girls from mixed to permanent dentition.

The great majority of posterior crossbite are unilateral and are of three distinct types due to disproportion between the jaws in basal (skeletal) or dentoalveolar width or associated with a forced guidance of the mandible (functional type). A distinction between these different types and their possible association with TMD is generally neglected in previous publications.

The contradictory opinions discussed above are of no help to the clinician in making the decision to treat or not to treat children with posterior crossbite to avoid possible future TMD problems. The aim with the present study hence was to update the bibliography with special interest to analyse if those publications have focused on differential diagnosis of TMD as well as of posterior crossbite, which might answer the issue: is there any association between some special sign/symptom of TMD and the type of posterior crossbite, which will call for orthodontic treatment?

Material and methods

Literature search

A search in the MEDLINE database from January 1970 to August 2009 was made. Various combinations of the following MeSH terms were used: temporomandibular disorders OR dysfunction (TMD/CMD) AND malocclusions OR posterior crossbite. The inclusion criteria were studies in the English language, human studies, posterior crossbite, lateral crossbite, TMDs, randomized controlled trials (RCTs) or retrospective studies with controlled or reference group, controlled clinical trials, and prospective studies. Exclusion criteria were case reports, review studies, studies with unclear diagnosis or poorly defined patient material, cleft/lip and/or palate or other syndromes, diagnoses, treatment strategies, and treatment appliances.

In total, 210 articles were found. Among them, 116 focused on different treatment strategies in general or with various orthodontic appliances and their treatment results and were excluded. The abstracts of the remaining 94 articles were studied, but most of them did not fulfil the inclusion criteria and were excluded. Reading the remaining 26 full articles, no RCT study was found, which hardly is to be expected in such type of studies.

Half of the articles were found to be review papers or presentations of TMJ signs and symptoms but not related to crossbite. The literature search thus resulted in 14 articles, which fulfilled the criteria for the present systematic review (Table 1).

View this table:
Table 1

Temporomandibular disorder (TMD) signs and symptoms in patients with posterior crossbite.

Moreover, manual searching was carried out on the following journals for the same period: Journal of Orofacial Orthopedics / Fortschritte der Kieferorthopädie, European Journal of Orthodontics, Angle Orthodontics, American Journal of Orthodontics and Dentofacial Orthopedics, Orthodontics and Craniofacial Research, and International Journal of Jaw Functional Orthopedics. No additional information to the Medline database was found.

Results

As seen from Table 1, an association between TMD and posterior crossbite was reported in eight papers against five with absence of such a relationship. The samples in the two groups showed similarities as well as differences with respect to their structure. Thus, males and females were included in both groups. The number of subjects varied between rather few and many (a range of 27–4724 in the ‘Yes’-group and 337–3428 in the ‘No’-group). The ages 10–16 years were prevalent in both groups, while young children (5–8 years old) and adults (20–54 years of age) were found only in the Yes-group.

‘Presence’ or ‘absence’ of crossbite is in general simply given; a distinction between unilateral and bilateral type is unusual, and the difference between skeletal, dentoalveolar, and functional types is rare. Thus, we are informed that bilateral crossbite is reported in only 2 of the 14 articles, showing a tendency, not significant, to TMD (Mohlin et al., 2004) but did not differ from the unilateral type as regards mandibular dysfunction (Mohlin and Thilander, 1984). Unilateral crossbite with mandibular guidance including midline deviation is reported in three of the articles (de Boer and Steenks, 1997; Sonnesen et al., 1998; Thilander et al., 2002). Finally, in some papers, the prevalence of malocclusion was taken from the subjects’ dental record (school or private dentist).

Even if ‘clinical signs and symptoms’ were reported as often in the articles belonging to the Yes- and No-groups, more signs and symptoms were found in the former group. Moreover, differences as regards the type of sign and symptom existed between them.

Thus, ‘TMJ and muscle tenderness’ on palpation showed significant association with posterior crossbite according to some authors (de Boer and Steenks, 1997; Thilander et al., 2002; Vanderas and Papagiannoulis, 2002; Egermark et al., 2003) but not to others (Lieberman et al., 1985; Keeling et al., 1994; Demir et al., 2005; Farella et al., 2007).

‘TMJ sounds and clicking’ were reported significant correlated with posterior crossbite (Pullinger et al., 1993; de Boer and Steenks, 1997; Thilander et al., 2002; Egermark et al., 2003) opposite to statement from other articles (Lieberman et al., 1985; Pahkala and Qvarnström, 2004). According to Pullinger et al. (1993), unilateral posterior crossbite occurred most frequently in subjects with disc displacement without reduction.

‘Headache’, above all, was reported as a factor in some articles as a factor with significant association with posterior crossbite (Sonnesen et al., 1998; Egermark et al., 2003; Lambourne et al., 2007).

Discussion

The present updated review, based on publications selected due to specified criterion, is in agreement with earlier reviews, i.e. positive as well as negative association between TMD and posterior crossbite were found. Of interest to note is the overall interest in the different TMD variables, whereas type of crossbite was ignored. However, functional crossbite (mandibular guidance including midline deviation; Figure 1) is mentioned in some articles (Pullinger et al., 1993; de Boer and Steeks, 1997; Thilander et al., 2002). In addition, joint sounds, clicking, muscle tenderness, and headache were significantly correlated to this type of posterior crossbite. Pullinger et al. (1993) also have reported that disk displacement without reduction is an important factor in this type. Thus, those findings indicate an association between functional unilateral posterior crossbite and some signs and symptoms of TMD (TMJ pain, muscular tenderness, clicking, and headache), which deserves attention in the orthodontic treatment plan, especially as the frequencies of TMD and posterior crossbite increase with age.

Figure 1

A 6-year-old boy with functional posterior crossbite. Arrow indicates mandibular sliding movement from retroposition (a) to intercuspal relationship and (b). The same boy 3 years later (not orthodontically treated) with increased midline deviation (c).

A forced guidance of the mandible will result in asymmetric activity of the masticatory muscles (Figure 2a and 2b), significantly lower on the non-crossbite side (Troelstrup and Möller, 1970; Ingervall and Thilander, 1975; Ferrario et al., 2002) probably due to differences in thickness of the muscles on the crossbite and non-crossbite sides (Rasheed et al., 1996). The asymmetric muscle activity was documented not only in intermaxillary position but even in rest position (Ingervall and Thilander, 1975), which suggests that the relaxed mandible was still displaced to the side of the forced bite caused by a neuromuscular adaptation to the intercuspal relationship (ICP). This hypothesis is based on the fact that treatment of the malocclusion will change growth and development of the muscles and hence eliminates their asymmetric activity (Pinto et al., 2001; Kecik et al., 2007).

Figure 2

The 9-year-old boy from Figure 1c showing facial asymmetry (a) and asymmetric activity of the temporal masseter muscles at the mandibular sliding to intercuspal relationship (b). Drawing illustrating the changed condylar position in relation to the temporal bony component (c).

Moreover, the maximum bite force in children with unilateral crossbite is significant lower than in controls (Troelstrup and Möller, 1970; Ingervall and Thilander, 1975; Sonnesen et al., 1998; Castelo et al., 2007). It has also been shown that treatment of the malocclusion will present symmetrical bite force and masticatory capacity between the crossbite and non-crossbite sides (Tsarapatsani et al., 1999). Thus, rehabilitation of the asymmetric muscle activity in the functional crossbite is of importance.

Finally, when the mandible is displaced into ICP, the condyle on the non-crossbite side will move in a downward, medial direction, and the one on the crossbite side in an upward, lateral direction (Figure 2a and 2c), resulting in a changed condylar position in the glenoid fossae and may cause TMJ pain and clicking. Moreover, such changed condylar/temporal relationship will have an influence on the remodelling processes in those areas (Thilander et al., 1976; Thilander, 1995; Hesse et al., 1997; Nerder et al., 1999; Pinto et al., 2001; Kecik et al., 2007). Thus, early treatment from growth-adaptive reason is indicated. Left untreated; there is a great risk that the functional crossbite in young ages will be transformed to a cranial skeletal malocclusion in later ages (Figure 3).

Figure 3

A functional crossbite transformed to a skeletal malocclusion in a 25-year-old woman. Facial asymmetry (a), midline deviation (b).

Conclusions

The present updated bibliography as regards the concept TMD and diagnosis posterior crossbite indicates an association between a unilateral posterior crossbite with mandibular deviation and some signs and symptoms of TMD (TMJ muscular pain, clicking, and headache). Should this indicate need for orthodontic treatment, as was questioned in the introduction? Need for orthodontic treatment of a functional unilateral posterior crossbite shall first of all focus on rehabilitation of the asymmetric muscular activity and the changed condylar position in the glenoid fossae due to the mandibular displacement. Whether this also should involve a prophylactic measure to avoid future problems in joints and masticatory muscles can only be answered after clinical follow-up studies have been performed.

References

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