Role of Orthodontic Tooth Movement on Temporomandibular Joint: An Original Research.

Introduction: Orthodontic treatment may bring about changes in the temporomandibular joint (TMJ) disc. Hence, we aim to assess the impact of the orthodontic tooth movement on the articular disc repositioning of TMJ. Materials and
Methods: We conducted an observational prospective study among 50 class IIdiv-I subjects. The magnetic resonance images were used to evaluate TMJ during the orthodontic treatments. The phases were T1-start of treatment, T2-thru phase I, T3-at the end of phase I, and T4-at the end of phase II. The qualitative values were compared for the disc changes.
Results: No significant changes in the disc position or the regression were seen with open or closed mouth between T1-T3, T3-T4, and T1-T4. Significant variation for the position of the disc was seen in the opened mouth between T3-T4. Significant variation for the form of the disc was seen when closed at T1-T2 and T2-T3. Conclusions: Disc of the TMJ maintained the form and position during the treatments. Copyright:

INTRODUCTION

The treatment for the proclined teeth is done with both the fixed and the orthopedic appliances. In class II div-I cases, the treatment starts with the “orthopedic functional appliances” and is continued in the second phase with a fixed appliance.[123] Herbst appliance is the most commonly used appliance in the correction of class II div-I cases. The temporomandibular joint (TMJ) is affected in the various orthodontic treatments that may or may not lead to a disorder during the treatment. Many studies have concluded a negative effect on the TMJ after the treatment.[456] Although the exact mechanism has not been elucidated, on the other hand, few studies report a positive effect on the disc positioning in the treatment for retrognathia. The recent advances in imaging help us to visualize the areas more clearly.[78] Hence, we aim to assess the impact of the orthodontic tooth movement on the articular disc repositioning of TMJ by the application of the magnetic resonance images (MRIs).

MATERIALS AND METHODS

We conducted an observational prospective study among 50 class II div-I subjects. The MRI was used to evaluate TMJ during the orthodontic treatments. The treatment was done with Herbst appliance for a year known as phase I, and later with the fixed orthodontic appliance till the normal occlusion is established that was for an average of 2 years. The phases were T1-start of treatment, T2-thru phase I, T3-at the end of phase I, and T4-at the end of phase II. The qualitative values were compared for the disc changes. MRI scans were taken in the coronal and parasagittal sections in the mouth closed and open positions to qualitatively study the disc at various stages of the treatment. The observations were analyzed for statistical significance.

RESULTS

We observed no significant difference between the genders or the age. There was no difference between the left and the right images. We observed that among the 50 subjects, who had bilaterally 100 disc images, for the disc position, no significant change was seen with open or closed mouth between T1-T3, T3-T4, and T1-T4. Significant variation for the position of the disc was seen in the opened mouth between T3-T4. Significant variation for the form of the disc was seen when closed at T1-T2 and T2-T3. We also observed that at the T2 phase, there was full or partial recapture of the disc [Table 1].

Table 1

Comparison of the various phases

Disc position	P	Disc form	P
MC - T1 3 T3	0.317	MC - T1 3 T2	**
MC - T3 3 T4	0.287	MC - T2 3 T3	**
MC - T1 3 T4	0.261	MC - T3 3 T4	0.5
MO - T1 3 T2	-	MC - T1 3 T3	1
MO - T2 3 T3	-	MC - T1 3 T4	0.25
MO - T3 3 T4	0.046*	MO - T1 3 T2	-
MO - T1 3 T3	0.223	MO - T2 3 T3	-
MO - T1 3 T4	0.082	MO - T3 3 T4	-

*Significance, ** Non significance. T1: Start of treatment, T2: Thru Phase I, T3: At the end of Phase I, T4: At the end of Phase II, MC: Mouth closed, MO: Mouth open

DISCUSSION

In the rapid expansion of the palate by the Herbst appliance, there may be a possibility of the impact on the TMJ. Hence, in our study, we aimed to find the same in class II div-I subjects by MRI of the TMJ for the disc position and the form.[16] In the study, we observed for both the coronal and the sagittal planes and for the disc position and the form. We observed for the disc position no significant change was seen with open or closed mouth between T1-T3, T3-T4, and T1-T4. Significant variation for the position of the disc was seen in opened mouth between T3 and T4. Significant variation for the form of the disc was seen when closed at T1-T2 and T2-T3. Our observations are in accordance with the study by Franco et al. and Kinzinger et al.[23] However, our study is in contradiction to the study of Gupta et al.[8] In our study, we observed that in few cases, there were disc displacements anterolaterally. This was similar to the study of Ruf and Pancherz.[1] In four cases, the disc was already displaced at T1; hence, the same was noted at T4. Further follow-up of these cases has to be done to know the impact on the TMJ. The malocclusion that is already presented by the patient may be corrected by the orthodontic treatment. However, the TMJ disorders may already be present by the time of the treatment that may decrease or persist after the treatment. During our study, random variations at T4 in the form and the position of the articular disc were seen. Hence, it may be advised to check for the TMJ images thoroughly for any changes before the start of the orthodontic therapy.

CONCLUSIONS

We can conclude that there was no significant difference at the various phases of the treatment for the form and the position of the TMJ. However, in a few cases, some changes were seen in the disc that may warn of future disorders of the TMJ.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.