Abstract
The aims of the study were to investigate the alteration of temporomandibular disorders (TMD) after correction of dentofacial deformities by orthodontic treatment in conjunction with orthognathic surgery; and to compare the frequency of TMD in patients with dentofacial deformities with an age and gender matched control group. TMD were evaluated in 121 consecutive patients (treatment group), referred for orthognathic surgery, by a questionnaire and a clinical examination. 18 months after treatment, 81% of the patients completed a follow-up examination. The control group comprised 56 age and gender matched subjects, of whom 68% presented for follow-up examination. TMD were diagnosed according to research diagnostic criteria for TMD. At baseline examination, the treatment group had a higher frequency of myofascial pain ( P = .035) and arthralgia ( P = .040) than the control group. At follow-up, the frequencies of myofascial pain, arthralgia and disc displacement had decreased in the treatment group ( P = .050, P = .004, P = .041, respectively). The frequency of TMD was comparable in the two groups at follow-up. Patients with dentofacial deformities, corrected by orthodontic treatment in conjunction with orthognathic surgery, seem to have a positive treatment outcome in respect of TMD pain.
In patients with dentofacial deformities, the major indications for undergoing orthodontic treatment in conjunction with orthognathic surgery are function improvement and aesthetic considerations. Motivation for treatment may be influenced by many different factors, such as psychosocial concerns, cultural values, treatment costs, age at treatment, expected treatment outcomes and gender. Orthodontic treatment in conjunction with orthognathic surgery is expensive, arduous and not without complications. It is therefore important that the treatment outcomes meet patient expectations.
The aetiology of temporomandibular disorders (TMD) is complex and today most researchers and clinicians agree that the aetiology is multifactorial. Some studies have shown that compared to those with normal occlusion, subjects with malocclusions have a significantly higher prevalence of signs and symptoms of TMD. It has also been suggested that alterations in facial morphology, such as a hyperdivergent facial profile may influence the development of TMD. On the other hand, there are studies that have shown the opposite and the relative importance of the occlusion in the onset or perpetuation of the condition has been discussed.
A number of studies have shown that orthodontic correction of different types of malocclusion does not increase the risk of developing TMD. On the contrary, in subjects with pre-treatment signs and symptoms, orthodontic treatment may have a beneficial effect on TMD. In cases of major skeletal jaw discrepancies (i.e. dentofacial deformities) orthognathic surgery is indicated in conjunction with orthodontic treatment to correct the dental relationship.
Two recent systematic reviews, of changes in TMD after orthodontic treatment in conjunction with orthognathic surgery, disclosed lack of uniformity in study design and ambiguous results in the selected studies. The review by Abrahamsson et al. was limited to controlled studies only.
A well-designed study by Rodrigues-Garcia et al., albeit without a control group, reported positive treatment outcomes with respect to signs and symptoms of TMD. TMD symptoms fluctuate over time and the frequencies of symptoms appear to be age dependent. The importance of a control group should, therefore, not be underestimated.
The aims of the present study were twofold: to investigate whether correction of dentofacial deformities by orthodontic treatment in conjunction with orthognathic surgery alters the frequency of TMD, and over the same period of time, to compare and monitor the frequency of TMD in an untreated normal group (control group).
The hypothesis was that the patients with dentofacial deformities would benefit from treatment, in respect of TMD, and that post-treatment, the frequency of TMD would be similar to that in the control group.
Materials and methods
The study sample comprised 121 consecutive patients (51 males and 70 females) with dentofacial deformities, referred to the Department of Oral Maxillofacial Surgery, Malmö University Hospital, Malmö, Sweden for orthodontic treatment in conjunction with orthognathic surgery (the treatment group). The mean age was 22.5 ± 7.4 years. All patients were recruited during two periods, between 1992–1995 and 2000–2002. Under the Swedish National Health Service, patients with such severe deformities are entitled to subsidized treatment. The exclusion criteria were craniofacial syndromes, systemic arthritic and muscular diseases, and a dentition of fewer than 24 teeth. 23 patients were excluded. 98 patients (81%) met the inclusion criteria and the final sample comprised 38 males and 60 females, mean age 22.4 ± 7.5 years ( Fig. 1 ).
The control group comprised 56 subjects, 23 males and 33 females, mean age 23.4 ± 7.4 years, age and gender matched with the subjects undergoing treatment. They were recruited from general dental patients at the Faculty of Odontology, Malmö University, Sweden, and the Public Dental Health Clinic in Oxie, County Skane, Sweden. The inclusion criteria were normal occlusion, or minor malocclusions for which neither orthodontic therapy nor orthognathic surgery was indicated. The same exclusion criteria applied to the control group as to the treatment group. Of the 56 recruits who underwent the initial clinical examination and completed the questionnaire, 38 (68%) presented for the follow-up clinical examination and 47 (84%) completed the follow-up questionnaire ( Fig. 1 ).
In the treatment group, TMD was assessed by means of a questionnaire and a clinical examination before (baseline) and 18 months after surgery. The interval between the two examinations was approximately 3 years depending on length of orthodontic treatment. The questionnaire and the clinical examination were performed after treatment planning. The control group was similarly assessed, on two occasions, at an interval of at least 3 years.
The following issues were addressed in the baseline and follow-up questionnaires: frequency of TMD pain, jaw fatigue and temporomandibular joint (TMJ) clicking (never; once or twice a month; once a week; once or twice a week; daily); pain at rest (yes/no) and during mandibular movements (yes/no). The severity of discomfort associated with TMD was estimated on the following scale: 0, little or none; 1, slight; 2, moderate; 3, severe; 4, very severe. The subjects rated their anxiety levels on a visual analogue scale (VAS) with the endpoints calm and anxious/uneasy. The follow-up questionnaire also included questions about treatment satisfaction, such as whether the pre-treatment information had been adequate (yes/no), whether treatment met expectations (yes/no) and whether, post-treatment, the subjects had perceived any alterations in masticatory capacity, aesthetics and TMD symptoms (better, unchanged, worse).
The clinical examinations were conducted at the Department of Stomatognathic Physiology at the Faculty of Odontology, Malmö University, by one of two calibrated specialists in stomatognathic physiology. The extra oral examination preceded the intraoral examination. The examination included measurement of maximum mandibular opening capacity, registration of TMJ sounds (clicking and crepitation), and tenderness in the TMJs and related muscles. The clinical registrations were improved by calibrating the examination techniques of the two examiners before the start of the study. The calibration was performed by examining eight patients, not included in the study, and was achieved after discussion. Eight subjects not included in the study were examined regarding occlusal interferences with an observer error that was found to be acceptable. The specialists conducting the examinations were not informed whether the subject belonged to the test or control group at the follow-up.
Subdiagnoses for TMD pain followed the research diagnostic criteria (RDC) for TMD ( Table 1 ). Disc displacement was diagnosed if, upon opening and closing from maximum intercuspation, a click was noted audible or by palpation. Osteoarthrosis was diagnosed as registered crepitations by palpation of the TMJ.
| Diagnoses of TMD |
|---|
| Muscle disorders |
| Myofascial pain |
| 1. Report of pain or ache in the jaw, temples, face, preauricular area, or inside the ear at rest or during function; plus |
| 2. Pain reported by the subject in response to palpation of three or more of 20 muscle sites. At least one of the sites must be on the same site as the complaint of pain |
| Temporomandibular joint disorders |
| Arthralgia |
| 1. Pain in one or both joint sites (lateral pole and or posterior attachment) during palpation; plus |
| 2. One or more of the following self-reports of pain: pain in the region of the joint, pain in the joint during maximum unassisted opening, pain in the joint during assisted opening, pain in the joint during lateral excursion. |
| 3. For a diagnosis of simple arthralgia, coarse crepitus must be absent |
| Osteoarthritis |
| Arthralgia; plus coarse crepitus of the joint |
Functional occlusion was assessed by previously described methods and investigated for observer error. Mediotrusion interferences within a lateral excursion of 3 mm, laterotrusion interferences, protrusion interferences, and the distance and the direction of the slide between retruded contact position (RCP) and the intercuspal contact position (ICP) were registered.
Morphological occlusion according to Björk et al. was registered by intraoral examination. Further data were obtained from dental study casts, lateral cephalograms, and a cephalometric analysis. The diagnoses in the treatment group were also separated into sagittal and vertical discrepancies, according to a combination of morphological and cephalometric values ( Table 2 ).
| Skeletal diagnoses | n |
|---|---|
| Class II | 6 |
| Class III | 42 |
| Open bite in combination with: | |
| Normal sagittal relationship | 13 |
| Class II | 14 |
| Class III | 14 |
| Deep bite in combination with: | |
| Class II | 7 |
| Class III | 2 |
All subjects in the treatment group underwent pre- and postsurgical orthodontic treatment with fixed orthodontic appliances in both arches. Ten specialists carried out the orthodontic treatment; the duration varied between 18 and 24 months.
The orthognathic surgery was undertaken by four oral maxillofacial surgeons at the Department of Oral Maxillofacial Surgery, Malmö University Hospital, Malmö, Sweden. Vertical deformities was corrected in the maxilla with a one piece Le Fort I osteotomy or a segmental maxillary osteotomy. Sagittal adjustments were made either by sagittal split osteotomy, to advance the mandible, or by intraoral vertical ramus osteotomy, to correct mandibular prognathism. When bimaxillary surgery was indicated, in 27 patients, maxillary osteotomies were combined with either sagittal split or vertical ramus osteotomies. Maxillo-mandibular fixation was used for 4 weeks after intraoral vertical ramus osteotomies. In all other cases, rigid intra jaw fixation was used.
Statistical methods
One goal of the proposed study was to test the null hypothesis that the proportion of positive outcomes was identical in the two groups. Significance (alpha) was set at .05. The test was two-tailed (i.e. an effect in either direction was analysed). With the proposed sample size of 35 in each subgroup, the study had a power of 89.8% to yield a statistically significant result. This computation assumed that the difference in proportions in frequency of TMD pain was −.30 (specifically .05 vs .35). This was selected as the cut-off point for minimum detection; any effect below this level would not be of clinical relevance or of substantive significance.
A second goal of this study was to estimate the difference between the test and control groups and the precision in estimating the magnitude of the effect. Pearson’s χ 2 test with Yate’s correction for continuity was used when 2 × 2 cross tabulations were applicable. When the expected cell value in a 2 × 2 table was less than 5, Fisher’s exact test was used. The two-sample t -statistic was used to compare means in numerical variables. To estimate self-reported anxiety on the VAS, median values and percentiles ( Q ) were calculated.
To assess the differences within groups, McNemar exact test was used to analyse ordinal data before and after treatment. The paired t -test was used to compare the means of maximum mandibular opening capacity.
Results
Analysis of those who withdrew from the treatment and control groups, ( n = 23, 19%, and n = 18, 32%, respectively) showed no significant differences compared with the final study groups with respect to age, gender, self-rated level of anxiety on VAS, pain in the jaws and related muscles or diagnosed TMD reported at baseline. Thus, the participants who completed the study were considered to be representative of the initial study sample.
TMD diagnoses
At baseline, the most common diagnoses in both treatment and control groups were myofascial pain, disc displacement and arthralgia. At follow-up, the frequencies of these diagnoses were significantly reduced in the treatment group, but at the same time, the treatment group exhibited a significant increase in osteoarthrosis post-treatment ( Table 3 ). Compared with the control group, significantly more subjects in the treatment group had myofascial pain and arthralgia at baseline, but post-treatment these differences had been eliminated ( Table 3 ).
| Treatment group ( n = 98) | Control group ( n = 38) | Group differences * | ||||||
|---|---|---|---|---|---|---|---|---|
| Baseline (P1) | Follow up (P2) ∼3 years | Baseline (C1) | Follow up (C2) ∼3 years | Between groups | Within groups | |||
| TMD diagnoses | n (%) | n (%) | n (%) | n (%) | P1/C1 | P2/C2 | P1/P2 | C1/C2 |
| Myofascial pain | 29 (30) | 17 (17) | 4 (10) | 4 (10) | P = .035 | NS | P = .050 | NS |
| Disc displacement | 19 (19) | 9 (9) | 5 (13) | 8 (21) | NS | NS | P = .041 | NS |
| Arthralgia | 16 (16) | 4 (4) | 1 (3) | 2 (5) | P = .040 | NS | P = .004 | NS |
| Osteoarthritis | 1 (1) | 0 | 0 | 0 | NS | NS | NS | NS |
| Osteoarthrosis | 1 (1) | 9 (9) | 1 (3) | 0 | NS | NS | P = .008 | NS |
| At least one TMD diagnosis | 42 (43) | 32 (33) | 10 (26) | 11 (29) | NS | NS | NS | NS |
| At least one TMD pain diagnosis | 31 (32) | 18 (18) | 4 (10) | 4 (10) | P = .021 | NS | P = .029 | NS |
Myofascial pain was the only TMD diagnosis with a significant gender difference before treatment ( P = .015); it was more common in women (32%) than in men (12%), but at follow-up, no gender-related differences were found for any of the TMD diagnoses.
After stratifying the treatment group according to the type of dentofacial deformity ( Table 2 ), those with a Class III relationship combined with a normal vertical relationship of the jaws having myofascial pain ( n = 13) and/or arthralgia ( n = 8) had significantly decreased after treatment ( n = 4, P = .022 and n = 2, P = .031 respectively). None of the other subgroups showed significant differences in TMD diagnoses between baseline and follow-up.
Symptoms of TMD
In the treatment group, self-evaluated TMD discomfort, evaluated on a verbal scale, decreased significantly from baseline to follow-up ( Fig. 2 ).
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