A Prospective Long-Term Study of Signs and Symptoms of Temporomandibular Disorders in Patients Who Received Orthodontic Treatment in Childhood

Opinions on the relationship between orthodontics and temporomandibular disorders (TMD) have differed between those who have emphasized that orthodontic treatment may imply an increased risk for TMD and those who maintain that it may decrease such a risk.1– 7 Some investigations have shown that both the signs and symptoms of TMD decrease during the active phase of orthodontic treatment. The reason might be that the orthodontically moved teeth are sensitive to contact, resulting in a decrease of oral parafunctions,8 or due to altered activity of the jaw muscles.9 

Several extensive reviews10–13 and more recent studies have concluded that orthodontic treatment neither increases nor decreases the risk of developing TMD later in life.14–16 However, the conflict has not been fully settled because some studies have reported less-prevalent TMD signs and symptoms in orthodontically treated compared with untreated subjects.1,2,17,18 It has even been claimed that “if we have the concept of building an occlusion to fit the jaw mechanism, the TMJ pain-dysfunction syndrome can be virtually eliminated in the post-orthodontic patient.”19 

The discussion on orthodontics and TMD is closely related to the old but continuing controversy about the role of occlusion in development and treatment of TMD.20–23 It may be prudent to say that the role of orthodontics in TMD development is not fully known and therefore deserves further investigation. Long-term studies may offer such a possibility.

The results of a study that examined 50 consecutive patients before, during, and after orthodontic treatment indicated a slight reduction of TMD signs and symptoms from before to after orthodontic treatment.8 A follow-up of these patients might give further knowledge of the long-term development concerning the remaining questions described above.

The purpose of the present study of this group of orthodontically treated patients, therefore, was to evaluate the development of signs and symptoms of TMD as well as the outcome of the orthodontic treatment in a long-term perspective. We hypothesized that an experience of orthodontic treatment early in life will not have any influence on the development of TMD in the long term.

The original sample consisted of 50 consecutive patients (27 girls and 23 boys), who underwent orthodontic treatment during the period 1981 to 1983. Their mean age at start of treatment was 12.9 years. The patients were investigated with a questionnaire and a standardized clinical examination with special focus on signs and symptoms of TMDs before, during (10–12 months after start of treatment), and after the active phase of the orthodontic treatment (about one month after insertion of the retention). All but three patients were treated with fixed appliances with (32 patients) or without (15 patients) extraction of premolars. The orthodontic treatment in the remaining three patients was carried out with activators. The design, the methods, and the results of the study have been presented earlier.8 

After a mean of 17 years (range 15 to 18 y depending on the time of the completion of the active phase of the orthodontic treatment), an attempt was made to find the addresses of the patients. Forty-five of them (90%) could be traced and were sent a questionnaire and an invitation to a clinical examination. Forty former patients, 24 women and 16 men (89% of the traced subjects), completed and returned the questionnaire, and 31, 17 women and 14 men (69%), appeared for the clinical examination. Of the nine subjects who did not appear, six had moved to places far away, and three announced that they did not want to participate.

All the 31 clinically examined subjects had undergone orthodontic treatment with fixed appliances with or without extraction of premolars. After the active phase of treatment, all of them received retainers for long-term use. Twelve subjects had interrupted the treatment before it was considered fully completed, and a few admitted some neglect with the retainer.

A primary tabulation of reported symptoms at the original examination comparing the 10 dropouts with the 40 who answered the follow-up questionnaire showed only small and nonsignificant differences. The same was true for clinical signs at first examination comparing the 19 nonparticipants with the 31 subjects examined at the follow-up.

The questionnaire focused on the function of the masticatory system and the presence of symptoms such as temporomandibular joint (TMJ) sounds, difficulties in mouth opening, pain and tiredness in jaws, as well as headaches and oral parafunctions. This part of the questionnaire was the same as used originally.8 At the follow-up, a few questions were added regarding the orthodontic treatment and also whether the subjects rated themselves as often stressed, worried, irritated, or depressed (or all).

The standardized clinical examination24,25 comprised measurements of the range of movement of the mandible, presence of deflection during mouth opening, registration of TMJ sounds, joint locking or luxation, pain on movement of the mandible and TMJ, or muscle pain on palpation. From these clinical parameters, a clinical dysfunction index according to Helkimo26 was calculated.

The registration of morphological malocclusions, such as post- and prenormal occlusion, inverted incisors, crossbite, scissors bite, deep bite, anterior or lateral open bite, was made according to the definitions given by Björk et al.27 

The following findings were registered as functional malocclusions (occlusal interferences): unilateral contacts in retruded contact position (RCP) reported by the patient or visible by the naked eye, lateral forced bite (≥1 mm) between RCP and intercuspal position (ICP), anterior forced bite (≥2 mm) between RCP and ICP, occlusal interferences on the nonworking side preventing contact on the working side during lateral excursion.

A control group was taken from a 20-year follow-up of an epidemiological sample of 135 15-year-old subjects presented previously.24,28 The subjects of that sample who had not received any orthodontic treatment (n = 86 answered a questionnaire; n = 73 were also examined clinically)15 were used for comparison with the present study group.

The great majority of the previously orthodontically treated patients reported that they were satisfied with the treatment and would recommend it to others (Table 1). Many of them, however, had found the treatment sometimes inconvenient. Two (5%) of the 40 respondents to the questionnaire said that, in retrospect, they would have liked to have the treatment undone.

The orthodontic treatment had normalized the occlusion in practically all patients, and this situation was maintained in most individuals up to the follow-up after on average 17 years (Table 2A). Minor relapses had occurred in a few subjects. Four subjects (13%) were classified to have deep bites (three with an overbite of 5.0 mm, one with 5.5 mm). More than half of the patients had originally postnormal occlusion. One subject had postnormal occlusion after treatment and also at the follow-up. At the follow-up, there were six individuals with crossbites, five of them due to a buccally erupted mandibular third molar, whereas the last one had a bilateral crossbite. The prevalence of malocclusions at follow-up did not differ much from that of the control group (Table 2A).

At the follow-up, the mean overjet was 3.1 mm (range 2.0–5.5), and the mean overbite was 3.2 mm (range 0–5.5). After the active treatment on average 17 years earlier, the corresponding mean values were 3.1 and 2.5, respectively. The mean number of maxillary teeth in occlusal contact with the mandibular teeth was 12.7 (range 8–15, including the third molars).

The prevalence of most functional malocclusions (“occlusal interferences”) was reduced after treatment but increased somewhat during the follow-up period. At the final follow-up, the values were relatively similar to those of the control group (Table 2B). Most of the nonworking side interferences that had developed were on third molars erupted after the completion of the orthodontic treatment. Unilateral contact in RCP was recorded in a great majority of the subjects at all examinations as well as in the control subjects.

A slight increase of reported symptoms had occurred during the follow-up period after orthodontic treatment, and the prevalences at the follow-up were similar to those of the control group without earlier orthodontic treatment (Table 3). Twenty-three individuals (61%) reported that they had never had TMJ clicking, whereas two subjects had had clicking during the whole period. The remaining subjects had noticed a fluctuation in the TMJ clicking and in the other symptoms as well (Table 3).

A total of seven subjects (18%) reported that they had received an interocclusal appliance because of various problems related to the masticatory system during the follow-up period.

The great majority had no or mild clinical signs of dysfunction with only minor fluctuation between the three examinations (Helkimo Index 0+1, Table 4). The most frequent signs were muscle tenderness (15 subjects) and TMJ dysfunction (12 subjects; 11 with clicking and one with locking). Two subjects demonstrated pain at palpation of the TMJ. Only one individual was classified with severe dysfunction (Clinical Dysfunction Index 3); this individual had general joint problems affecting also the TMJ.

At the follow-up, three subjects had TMD signs and symptoms that initiated some treatment (jaw exercises and minor occlusal adjustment).

The mean mandibular mobility was within normal values (maximal mouth opening = 55.2 mm, range 46–68 mm; excursion to the right 9.6, range 6–13 mm; to the left 9.7, range 6–14 mm; protrusion 8.6 mm, range 6–12 mm). None of the examined subjects exhibited pain on mandibular movements. However, three subjects had a reduced movement capacity according to the Helkimo index, all related to horizontal movements of less than six mm, resulting in a dysfunction score 1.

Only one individual reported that he was depressed (and had stomach problems as well), whereas 15 subjects answered affirmatively to one (n = 6) or more (n = 9) of the questions stressed, worried, irritated, and depressed (Table 5). There was a tendency that those who responded yes to one or more of the questions, more often had long-term subjective symptoms and clinical signs of TMD than those who answered no to the questions. However, the groups became too small for meaningful statistical comparisons.

In all long-term follow-up investigations, a loss of participants is inevitable. When considering the length of this follow-up investigation, 15 to 18 years, the present loss must be considered acceptable. Furthermore, the subjects who were lost did not differ from those who participated with respect to age, sex, or to any of the originally recorded signs or symptoms of TMD. All the clinical examinations followed the same methods and were performed by the same examiner. The questionnaires used were the same as from the first investigation, with the exception of a few added questions. These circumstances have probably minimized the errors, but, as always, results from questionnaires, as well as from clinical examinations based mainly on semiobjective parameters, should be interpreted with caution.

The results of this follow-up of subjects who had been treated orthodontically in childhood demonstrated in general a successful long-term outcome of the treatment, both as assessed by the patients and at clinical examination (Tables 1 and 2). A relapse of deep bite was noted in a few subjects and was limited to an overbite of maximum 5.5 mm. The greatest negative finding was the recurrence of crossbite, from 0% after treatment to 19% of the subjects at the long-term follow-up. These crossbites were, however, associated with buccal eruption of mandibular third molars, which occurred after the completion of the orthodontic treatment. These findings can therefore not be classified as relapse of the orthodontic treatment.

The functional malocclusions (occlusal interferences) had a tendency to come back after the reduction after orthodontic treatment. Unilateral contact in RCP was highly prevalent at all examinations and also in the control group. Such an occlusal contact seems to be almost omnipresent in healthy subjects29 and was registered in a great majority of the subjects in this study. It can be questioned whether it deserves to be classified as an occlusal interference. The relationship between the so-called occlusal interference and TMD development is still controversial but according to several reviews is considered very weak or nonexisting.21,30 No statistical analysis of this relationship was performed in this study, but primary tabulation did not suggest any correlation. In previous studies this has been discussed more extensively.15,28,31 

The prevalence of signs and symptoms of TMD also was low in comparison with epidemiological samples.32 When signs and symptoms of TMD were found in the subjects, they were in general occasional and of low intensity. Only one subject had severe dysfunction at the last follow-up, probably caused by a systemic joint disorder also affecting the TMJs. However, seven subjects (18%) had sought treatment for various TMD-associated problems during the observation period. In a 20-year follow-up study of an epidemiological sample, the same frequency (18%) of subjects who had received some TMD-related treatment was recorded.33 Both these studies thus indicated that the incidence per year of manifest TMD requiring treatment is approximately 1% in subjects followed from adolescence to young adult age. Only few studies of onset rates of TMD have been published previously, reporting rates of 2% to 3% per year.34 

• The vast majority of subjects who had undergone orthodontic treatment during childhood were satisfied with the result of the treatment.

• The results of the orthodontic treatment were in general stable during the follow-up period. A few subjects had developed a crossbite at the last follow-up because of buccal eruption of mandibular third molars after the completion of the orthodontic treatment.

• The low incidence rate of manifest TMD in the orthodontically treated subjects suggests that there is no elevated risk for developing TMD after orthodontic treatment thus corroborating several previous reviews and studies.