The effect of interocclusal appliances on temporomandibular joints as assessed by 3D reconstruction of MRI scans

Abstract

Magnetic resonance imaging (MRI) enables simultaneous visualization of hard and soft tissues. The aims of the present study were to computer generate three-dimensional (3D) images, reconstructed from MRI scans of normal temporomandibular joints (TMJ), to assess the relative positions of the disc, condyle and articular surface of the temporal bone and to study the effect of two mandibular group function interocclusal appliances (IOAs). Bilateral MRI scans of 2mm slice thickness were generated for the TMJs of 12 asymptomatic subjects with the image acquisition coils orientated in a corrected oblique sagittal plane. MRI scans were generated for all subjects with 3mm interincisal distance IOAs, while a subgroup (n=4) was also scanned with a 5mm interincisal IOA in situ. An average of 10 slices through each TMJ were generated for the closed mouth and IOA positions. Three-dimensional reconstruction was performed on a 486 IBM compatible computer using a suite of nine programs not commercially available. Threedimensional images allowed visualization of composite images of joint relationships. Subjective assessment indicated that joint relations in 3D were more informative than multiple separate 2D MRI scans. With the 3mm IOA in situ, the disc was positioned posteriorly and superiorly to the condyle in three of 12 cases. In four of 12 cases the condyle, and in two of 12 cases both the disc and condyle, were positioned anteriorly and inferiorly. With the 5mm IOA changes in condyle/disc and condyle/fossa relationships were more variable. It was concluded that 3D images of TMJs enabled the assessment of the positional changes of the condyle/disc and condyle/fossa relationships as altered by IOAs. However, the role of IOAs on the internal arrangements within the TMJ remains variable and is deserving of further study.

Position of Mandibular Condyles during Stabilization Splint Wearing

“…Although the results of the present investigation (Figs. 2 and 3) are contrary to previous studies of the condylar position with occlusal splints 10,11,16,19 , the present study results can be interpreted as similar to the studies of condylar position at the centric relation occlusion [20][21][22][23][24] . Investigations of the centric relation occlusion [20][21][22][23][24] confi rmed superior condylar position with anterior or posterior component in most participants compared to the habitual occlusion.…”

“…Insertion of stabilization appliance caused a mean 0.2±0.5 mm sagittal and 0.8±0.5 mm vertical condylar movement, with average anterior and inferior direction. Chu et al 11 using magnetic resonance imaging scans investigated the eff ect of interocclusal appliances on the mandibular position. Most of the participants had anterior and inferior condylar position with acrylic splint (3-mm interincisal distance) compared to habitual occlusion.…”

“…Th e main function of the interocclusal appliance therapy is considered to be reduction in temporomandibular joint loading and reduction in muscle activity 11 . Casares et al 25 studied intra-articular pressure of the temporomandibular joint during function of the lower jaw using a pressure transducer.…”

“…Mandibular position during occlusal splint wearing was studied with diff erent approaches: cast analysis in the articulator 9 , magnetic resonance imaging 10,11 , transcranial radiography 12 , computed tomography 13 , and with jaw tracking devices 14 . Obrez and Gallo 15 state that only since the development of three-dimensional tracking systems supplemented with sophisticated mathematical transformation of the data obtained, it has been possible to estimate condylar movements relatively accurately.…”

The effect of an interocclusal appliance on bite force and masseter electromyography in asymptomatic subjects and patients with temporomandibular pain and dysfunction

“…A mandibular group function IOA was fabricated for each subject in both control and patient groups. The IOA was constructed by pressure forming a laminate base and adding acrylic bite blocks to approximate the required vertical dimension (15, 16). The occlusal surfaces were meticulously adjusted for group function at the insert visit.…”