Temporomandibular disorders (TMD) are the most common source of orofacial pain of a non-dental origin. The subtypes of temporomandibular disorders (TMD) are myofascial pain, disc displacements, joint pain and degenerative and inflammatory joint disease (1, 2). Patients who seek professional help for these problems will commonly complain of pain located in the masticatory muscles, temporomandibular joint (TMJ) or both. Pain will usually increase during function. Patients also describe limited jaw movements and joint noise (3, 4).
Anterior disc displacement without reduction of the temporomandibular joint is a widespread disorder that clinically presents itself with restriction in jaw movements, in which the morphology of the disc is altered while the disc ligaments become elongated (5, 6). So far it has not been possible to identify a clear, single cause of disc displacement.
Functional imbalance of the TMJ could be related to trauma. This can be macro trauma – any sudden force to the joint resulting in structural alteration, or micro trauma -functional overloading associated with parafunctional activity (bruxism). Other potential risk factors related to derangement of condyle–disc complex include: increased laxity of the joints, changes in morphology and position of the condyle, osteoarthritis etc. (7, 8).
With the help of MRI, the position of the TMJ disc can be determined (9). However, MRI is a tool which aids the diagnosis, but on no account is it able to make a diagnosis by itself. It is the clinician's professional duty to correlate the patient's main complaint with the history of the symptoms and the signs during physical examination and make a final decision.
In the absence of clear knowledge of the etiological mechanisms that are underlying this disorder, main goal in the treatment of temporomandibular joint disc displacement without reduction is to relieve pain and to restore mandibular function despite the disturbed anatomical relationship between TMJ structures. Conservative treatments, including occlusal splint, medication, self-care strategies and physical therapy, are considered the first choice for TMJ treatment (10). Physical therapy seems to be effective in improving range of movement and reducing pain in TMD patients (11, 13).
Occlusal splint has been frequently used for internal derangement treatment. It is believed that wearing an occlusal splint alters the peripheral sensory input from receptors in the masticatory muscles, periodontal tissues and oral mucosa and decreases the intra-articular pressure in the TMJ (14, 15).
So far, numerous studies investigating either occlusal splint therapy or only physical therapy have been conducted. Studies comparing those two types of treatment are rare (16, 17). This study tested the hypothesis that the simultaneous use of occlusal splint and physical therapy is an effective method of treatment of anterior disc displacement without reduction in a 6-month period.
Materials and methods
The study was conducted at the Department of Prosthodontics, School of Dental Medicine, University of Zagreb. The subjects were selected from patients referred to the Department of Prosthodontics for reported pain and dysfunction of the temporomandibular region as the primary problem and they had not previously undergone any treatment protocols. Patients with anterior disc displacement without reduction (diagnostic category II of the RDC/TMD and confirmed by magnetic resonance imaging) were included in the study. The inclusion and exclusion criteria are shown in Table 1. Twelve patients (3 men and 9 women; age range 18-62 years; mean (standard deviation) age 30.5 (13.97) met the inclusion and exclusion criteria. They were informed about the study procedure and an informed consent was obtained. The study protocol was approved by the Ethics Committee of the School of Dental Medicine.
Patients were selected according to the following inclusion criteria: 18 years and above, both genders, patients with disc displacement (confirmed by magnetic resonance imaging) and spontaneous pain greater than 30 millimetres on a visual analogue scale (VAS). Exclusion criteria were symptoms related to disease in other parts of the masticatory system (e.g. toothache, neuralgia), history of arthritis or condylar trauma, degenerative changes of condylar head, pain due to systemic disease, fibromyalgia and history of psychiatric disorders.
Data on the participants' age, gender and marital status were obtained by a brief structured questionnaire. Subjects also filled in data related to the duration of pain. The patients underwent a routine clinical examination to detect signs and symptoms of TMD. The examination was based upon the Croatian version of RDC/TMD (Axis I), (18, 19).
Clinical sign evaluation
Spontaneous pain was evaluated by using a 100 mm-long VAS. The left endpoint of the scale indicated no pain at all, and the right endpoint indicated the worst pain imaginable.
Pain free opening and path of mouth opening
Pain-free opening e.g. maximum comfortable opening (MCO) was defined as the maximum distance the subject could open his/her mouth without experiencing any pain and discomfort. After the subject had opened this wide, the examiner measured the distance between the maxillary and mandibular incisal edges.
Maximum assisted opening
Maximum assisted opening (MAO) was defined as the maximum distance the subject could open the mouth, even if he/she felt pain or discomfort. After the subject had opened this wide, the examiner placed his fingers on the subject's maxillary and mandibular central incisors, and forced the subject's mouth to open wider. The interincisal distance between the maxillary and mandibular incisal edges was measured.
The examiner asked the patient to slowly open three times, observing from a position directly in front of the patient for movements of the mandible in the frontal plane that depart from a line parallel with a mid-sagittal plane. The presence of corrected or uncorrected deviation during mouth opening was evaluated. This was defined as deviation of the mandible of > 2mm to either the right or the left from the midline with maximum unassisted opening.
Training and calibration of the examiner
Standardization of the examiner and calibration of clinical examination was made on ten randomly selected subjects, different from the ones included in the investigation. There were no significant differences between the first and second measurement (p=0.85-0.89, paired t-test).
The patients were randomly allocated into 2 groups: 6 received stabilization splint only (SS) and 6 received both physical therapy and stabilization splint (SS&PT). All patients who enrolled in the study also completed the study.
Stabilization splint fabrication
Maxillary stabilization occlusal splint was fabricated on stone cast mounted on SAM-3 articulator in centric relation according to centric relation registration (20). It was a hard acrylic (Resilit-S, Erkodent) stabilization type of splint with full coverage of the occlusal surfaces and a thickness of about 1.5 mm at the level of the first molar. The same dental technician made all splints. The splint was adjusted to create uniform point contact of the centric cusps against the splint on all posterior teeth. Anterior teeth were in light point contact or were in slight disclusion. The splint also had canine guidance. Patients were instructed to wear the splint only during sleep. Comfort, patient acceptance and function of the appliance were checked within 2 weeks and the same procedure was repeated at all follow-up appointments by the same clinician.
Physical Therapy Technique
Patients in the SS&PT group received general information about self-care of jaw musculature. The clinician (M.G.) explained the normal jaw muscle function, emphasizing that excessive mandibular movements should be avoided. The clinician instructed the patients to pay attention to their jaw muscle activity and to keep muscles relaxed. The techniques comprised mobilizing the joint, passive traction and translation movement; these movements were performed in all directions (front, left and right). This mobilizing procedure was followed by massage exercise of masseter and temporal muscles (21). The patients were instructed to perform all the exercises at home, two to three times a day in front of a mirror.
Collection of data
An assessment of VAS (distance in millimetres from the lower anchor) was conducted at baseline before occlusal splint therapy (T0), and at follow-up appointments at 1 month (T1), 3 month (T2) and 6 month (T3) of the therapy. Treatment outcomes also included pain-free opening (MCO), maximum assisted opening (MAO) and path of mouth opening.
The clinician (I.A.), blind to a type of therapy and trained in TMD diagnosis, performed baseline assessment and all reassessments at 1st, 3rd, and 6th month after treatment initiation.
The SPSS (version 17) statistical package was used in all analyses. The baseline and 6-month follow-up data were analysed by chi-square (path of mouth opening) and t-test (pain free opening and maximum assisted opening). Univariate analysis of variance for repeated measurements was used to test the assessment (baseline-T0, T1, T2 and T3) differences in VAS scores. Statistical significance was assessed at the 0.05 level.
The mean age of 12 study participants was 30.5 (range 18 to 63) years. Table 2 summarizes participant baseline data (VAS scores, pain-free opening (MCO), maximum assisted opening (MAO)) in both treatment groups. According to the score on a 10-mm visual analogue scale, the mean values for the worst pain at baseline for SS&PT group and SS group were 74 and 65.3, respectively. The baseline mean pain free opening of SS&PT group and SS group were 32.43 mm and 31.33 mm, respectively. The baseline mean maximum assisted opening of SS&PT group and SS group were 35.25 mm and 38.17 mm, respectively. There were no statistical differences among the groups in terms of baseline pain (p>0.05) and mouth opening (p>0.05). Deviations in mouth opening were observed in all patients of both groups at the beginning of the treatment. The baseline scores for pre-treatment pain and range of mouth opening of each patient in the two groups are presented in Table 3.
|Group SS&PT (n=6)||Group SS (n=6)||t (p)|
|Age (years)||31.5±12.85||29.5±16.19||0.237 (0.817)|
|Initial pain||74.0±8.39||65.3±18.23||1.058 (0.315)|
|Initial MCO||32.43±6.12||31.33±13.18||0.183 (0.859)|
|Initial MAO||35.25±7.44||38.17±13.52||0.463 (0.653)|
(MCO= pain-free maximal mouth opening; MAO= assisted maximal mouth opening) t=t-test, Values are presented as mean±standard deviation. Group SS&PT: simultaneous application of physical therapy and occlusal splint Group SS: occlusal splint use only
Group SS&PT: simultaneous application of physical therapy and occlusal splint Group SS: occlusal splint use only MCO= pain-free maximal mouth opening MAO= assisted maximal mouth opening
The change patterns for pain in each group are shown in Figure 1. We checked the variable of pain at four points: baseline, 1 month, 3 months, and 6 months later. The levels of pain were found to decrease continuously across time; the difference was significant in group SS&PT (F=28.964, p=0.0001, effect size =0.853) and group SS (F=8.794, p=0.001, effect size =0.638).
We checked the variables of MCO and MAO at two points: baseline and 6 months later. Comparison of mouth opening at baseline and at the end of the therapy in both groups is shown in Figure 2. The pre-treatment and 6-month follow-up data were analysed by t-test for dependent samples. Pain free opening and maximum assisted opening improved significantly over time only in the SS&PT group (MCO: F=20.971, p=0.006; MAO: F=24.014, p=0.004) (Figure 2). The use of an occlusal splint did not lead to statistically significant changes in the amount of mouth opening (p>0.05).
We also checked the variable “path of mouth opening” at two points: baseline and 6 months later. The pre-treatment and 6-month follow-up data were analysed by chi-square. The changes in path of mouth opening differ significantly between the groups (p=0.040). Only one patient in SS&PT group still presented deviations in mouth opening after completed therapy while in the SS group deviations were present in 5 patients after completed therapy.
Anterior disc displacement without reduction has been reported to be a painful disorder (22). Most patients seek treatment when pain interferes with daily activities. Reduction or elimination of pain is an important parameter in evaluation of a therapeutic approach. The majority of patients with a diagnosed disc disorder can and should be treated with simple conservative means such as counselling, interocclusal device, medication and physical therapy. This approach has been proved to be very effective (23). A surgical approach to reposition the disc on the condyle is not recommended any longer.
Epidemiological studies revealed that female patients of reproductive age are mostly affected with TMD and seek more treatment than the males (24-26). This observation is confirmed in our study; the sample consisted of mainly female patients. Patients with anterior disc displacement without reduction were selected as the specific patient group. The study compared the treatment outcomes of the simultaneous use of occlusal splint and physical therapy (group SS&PT) and the use of occlusal splint alone (group SS).
At baseline of treatment there were no significant differences among the groups for VAS scores, as well as for the range of mandibular movement. As a result, both groups in this study showed reduction of pain.
Occlusal splint is often used for treatment of TMD. Lee et al. (27) showed that the adoption of occlusal splint in patients with anterior disc displacement without reduction significantly reduced TMJ pain. Major and Nebbe (28) reported that the application of occlusal splint resulted in significant reduction of headache and muscle pain, but its effect in the reduction of TMJ pain was limited.. According to Lundh et al. (29), occlusal splint had no results in the treatment of disc dislocation without reduction. In light of the results of our study, occlusal splint is beneficial to TMD patients.
Considering the improvement in the range of mouth opening and reducing deviations during mouth opening, the splint combined with physical therapy was more effective than the occlusal splint used alone. In the study of Nicolakis et al., exercise therapy seems to be useful in the treatment of anterior disc displacement without reduction. Furthermore, the anaesthetic blockade and physical therapy, when used together, are effective in the reduction of pain and increasing of mouth opening when used in patients with disc displacement without reduction (12, 30). In light of the results of our study, the simultaneous application of physical therapy and occlusal splint was more effective, improving the range of mouth opening and reducing deviations during mouth opening.
Our trial lacked a non-treatment or placebo control group, hence we cannot discard the possibility that natural reduction of pain occurred in some participants (31). Taking the limitations of this study into account, the results still show a significant restoration of physiological function in spite of objectively diagnosed disruption of functional temporomandibular anatomy. Our findings indicate that, for successful management of anterior disc displacement without reduction, simultaneous application of occlusal splint and physical therapy may be more effective than use of occlusal splint only.
This limited study provided evidence that during treatment period lasting for 6 months, simultaneous use of stabilization splint and physical therapy was more efficient in reducing deviations and improving range of mouth opening than stabilization splint used alone. Both treatment options were efficient in reducing pain in patients with anterior disc displacement without reduction. Despite of objectively diagnosed disruption of temporomandibular joint anatomy, physiological function was regained.