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Scientific Section |
Malmö University, Sweden
T. Henrikson, Department of Orthodontics, Faculty of Odontology, Malmö University, Carl Gustafs väg 34, S-205 06 Malmö, Sweden. Email: thor.henrikson{at}od.mah.se
| Abstract |
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Design: Prospective observational cohort.
Subjects: Sixty-five girls with Class II malocclusion who received orthodontic treatment, 58 girls with no treatment, and 60 girls with normal occlusion.
Method: The girls were examined for symptoms and signs of TMD and re-examined 2 years later. Additional records were taken in the orthodontic group during active treatment and 1 year after treatment
Results: All three groups included subjects with more or less pronounced TMD, which showed individual fluctuation during the ongoing study. In the orthodontic group, the prevalence of muscular signs of TMD was significantly less common post-treatment. Temporomandibular joint clicking increased in all three groups over the 2 years, but was less common in the normal group. The normal group also had a lower overall prevalence of TMD than the orthodontic and the Class II group at both registrations. Functional occlusal interferences decreased in the orthodontic group, but remained the same in the other groups over the 2 years.
Conclusions: (i) Orthodontic treatment either with or without extractions did not increase the prevalence or worsen pre-treatment symptoms and signs of TMD. (ii) Individually, TMD fluctuated substantially over time with no predictable pattern. However, on a group basis, the type of occlusion may play a role as a contributing factor for the development of TMD. (iii) The large fluctuation of TMD over time leads us to suggest a conservative treatment approach when stomatognathic treatment in children and adolescents is considered.
Key words: Fixed appliance, occlusion, orthodontic treatment, temporomandibular disorders
| Introduction |
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Symptoms and signs of temporomandibular disorders (TMD) are relatively common in children and adolescents.4
These can appear, increase in frequency and severity during the second decade of life.5,
6
Importantly, about 30 per cent of the population of children and adolescents receive orthodontic treatment in most western European countries during this period. This has, arguably, led to claims that orthodontic treatment is a risk factor for the development of TMD have appeared in the literature.7
11
These claims have been questioned and discussed in recent literature reviews.12,
13
However, previous studies analysing the role of orthodontic treatment in relation to TMD have often included large age variations and different malocclusions, both in the orthodontic treatment group and, if present, in the control group. Therefore, there is a need for controlled studies to further investigate the relationship between orthodontic treatment and TMD, especially since this relationship still is under debate.
In view of the high prevalence of symptoms and signs of TMD in children and adolescents, it is likely that patients receiving orthodontic treatment could experience TMD before, during, or after their orthodontic treatment.
This encouraged us to carry out a series of prospective studies to study symptoms and signs of (TMD), and occlusal changes in girls with Class II malocclusion receiving orthodontic treatment in comparison with untreated Class II malocclusions and with normal occlusion subjects.
| Material and methods |
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Signs and symptoms of TMD, mandibular function, and the functional occlusion were registered at each examination by either one of two specialists in stomatognathic physiology.1
3,
14,
15
Anamnestic and clinical registrations were made at the start and after 2 years in all three groups. In the orthodontic group, additional registrations were made during orthodontic treatment (after 1 year) and 1 year post-treatment (3 years). One subject in the Class II group moved away from the region and was not able to participate in the second examination. One subject discontinued the orthodontic treatment and did not want to participate in the re-examination, and a further three subjects were impossible to reach at the follow-up after 3 years.
| Statistical methods |
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Differences between the groups were calculated as follows:
P-values below 0.05 were considered as statistically significant. The actual P values are given in the text.
| Results |
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When comparing the self-rated level of anxiousness on a VAS, no significant differences were found between the three groups at any of the two registrations.
Need of and demand for stomatognathic treatment. A total of 21 subjects at the first registration and 23 subjects after two years rated their overall symptoms of TMD as moderate, severe, or very severe (Figure 2
). These subjects were judged to be in need of some treatment of their TMD, and given a diagnosis/diagnoses of TMD and headaches. A noteworthy finding was, that among the 21 subjects with TMD diagnoses at the first registration, only four subjects rated their symptoms as moderate, severe, or very severe 2 years later. Three of these four subjects had unchanged TMD diagnoses.
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Anamnestic and clinical findings before, during and after orthodontic treatment
Both symptoms and signs of TMD showed considerable fluctuations over the 3-year period within the individuals. The general tendency was a decreased prevalence of symptoms and signs of TMD over the 3 years (Table 4
). The prevalence of pain on mandibular movement and tenderness to palpation of the masticatory muscles was significantly lower during, after active treatment, and 1 year post-treatment than before treatment (P < 0.01).
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| Discussion |
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All three groups in these studies included subjects with more or less pronounced symptoms and signs of TMD, which fluctuated substantially in the individuals over the course of time. This finding was in agreement with several previous studies of children and adolescents.5,
6,
16
20
It was not possible, on an individual basis, to predict the risk of TMD based on the presence of malocclusion or not, but the normal group had less symptoms and signs of TMD than both the orthodontic and the untreated Class II group. The relatively low prevalence of symptoms and signs of TMD in the normal group was one of the most striking results these studies. On a group basis, it seemed that the type of occlusion may play a role as a contributing factor for the development of TMD, although this influence is difficult to quantify and predict.
The Class II orthodontic group were treated with fixed appliance, as uniformly as possible, either with or without tooth extractions. The patients asked for orthodontic treatment of their malocclusion and not treatment of their TMD. No special attempts were made to individualize the orthodontic treatment in those subjects who had complaints of pre-treatment symptoms of TMD.
Orthodontic treatment with fixed appliance did not increase the prevalence of symptoms and signs, or worsen pre-existing symptoms and signs of TMD. On the contrary, subjects with Class II malocclusion and muscular signs of TMD seemed to benefit from orthodontic treatment in a 3-year perspective. The decreased prevalence of tenderness to palpation of the musculature in the orthodontic group has been the subject of discussion in earlier publications.21,
22
Whether this is a muscular response due to altered use of the masticatory muscles or due to occlusal changes has been difficult to say. Egermark-Eriksson and Rönnerman21
suggested that the decrease in muscle tenderness was due to a reduced activity of masticatory muscles during orthodontic tooth movement because of tender teeth. The present prospective study showed an early decrease of the prevalence of tender muscles, before the new occlusion had settled, which might indicate an explanation due to altered activity of the muscles. The prevalence of tenderness to palpation of the masticatory muscles seemed to be stable during the post-treatment year. The reason for the decreased prevalence of muscular signs of TMD is not well understood, but a better occlusal stability with less functional interferences and more occlusal contacts was found in the orthodontic group after treatment than before, might be one explanation. Psychological aspects of an improved dental appearance could be another explanation in some individuals.
Although individuals showed both improvement and impairment of clinically registered TMJ clicking, all three groups in this study showed a similar increase in the prevalence of TMJ clicking over the two years. Since this increase was seen in all three groups, it was concluded that the orthodontic treatment did not have any influence on TMJ clicking. The increased prevalence of TMJ clicking over the 2-year period in this study was in agreement with earlier studies, reporting that TMJ clicking increased from childhood to adolescence and to an even higher prevalence in adults.5,
6,
23
26
Substantial fluctuations of clinically registered TMJ clicking were found in the orthodontic group over the 3 years (Figure 6). This was in agreement with Sadowsky et al.,27
but differed from the findings of Egermark-Eriksson and Rönnerman,21
who reported that, among 50 subjects, aged 715 years, almost all of their patients with TMJ sounds before orthodontic treatment had these sound unchanged after treatment.
In the present studies, eight subjects at the start and 10 after 2 years had reciprocal TMJ clicking, which has been suggested to be a clinical sign of disc displacement.28,
29
It noteworthy is that only two subjects had reciprocal TMJ clicking at both registrations, which implies that natural fluctuations also exist in adolescents with reciprocal TMJ clicking. Sadowsky et al.27
found less reciprocal clicking after orthodontic treatment than before on a group basis, but reported individual fluctuations of reciprocal clicking similar to the findings in this study. Lundh et al.30
followed 70 adult patients with reciprocal clicking during a 3-year period, and found an unchanged status in 71 per cent and that 29 per cent of the reciprocal clicking disappeared.
It has been suggested that TMJ clicking is progressive.28,
31
Our finding of individual fluctuation over time and that none of the subjects in the three groups developed a closed lock of the TMJ during the observation period is more in line with those of Wänman and Agerberg32
and Könönen et al.24
The fluctuations over time of both TMJ clicking and reciprocal clicking found, in this and previous studies, is important knowledge for the orthodontist and the general dentist if a patient reports TMJ clicking during orthodontic treatment. Patient information that TMJ clicking may come and go spontaneously and a conservative treatment approach are recommended.
Comparison between the extraction and non-extraction group
About 50 per cent of the subjects were orthodontically treated in combination with tooth extraction. A numerically higher prevalence of registered symptoms and signs of TMD was found in the extraction group compared with the non-extraction group. The prevalence of tenderness to palpation of the masticatory muscles was significantly higher in the extraction group than in the non-extraction group both before treatment and 1 year post-treatment. Reported and clinically registered TMJ clicking, however, did not differ between the groups. These differences between the extraction and non-extraction groups concerning signs and symptoms of TMD in this study corroborate the findings of Janson and Hasund,33
but were unexpected since several other studies have not indicated differences between extraction and non-extraction groups.34
36
In this study, since the increased prevalences of symptoms and signs of TMD in the extraction group were found before the orthodontic treatment started, it appears to be the selection criteria for extraction, rather than the orthodontic extraction-treatment itself that contributes to the higher prevalences of symptoms and signs of TMD. The results from this study underline the importance of a prospective and longitudinal study design.
| Conclusions |
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Orthodontic treatment with fixed appliance either with or without tooth extractions did not increase the prevalence of symptoms and signs, or worsen pre-existing symptoms and signs of TMD. Subjects with Class II malocclusion and pre-existing signs of TMD of muscular origin seemed to benefit functionally from orthodontic treatment in a 3-year perspective.
One orthodontic treatment effect when normalizing Class II malocclusions with fixed appliances was a decreased prevalence of functional occlusal interferences, while the changes in subjects with untreated Class II malocclusion and normal occlusion were minor.
| References |
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Received April 15, 2002; accepted September 26, 2002
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