Biometric Evaluation of Intracapsular Structures of the Temporomandibular Joint Before and After Orthesis Installation

Introduction

Temporomandibular disorders (TMD) are manifested by signs and symptoms that are attributed to occlusal, psychological and neuromuscular imbalances, in combination or separately. These consequently lead to changes in the oral motor sensory system and, more intensively, in stomatognathic functions: mastication, deglutition and even breathing [1]. Even though studied long ago, there are still many controversies in relation to etiology, diagnosis and treatment [1]. Among the most characteristic clinical signs of TMD is muscle and joint sensitivity to palpation and limitations on and/or difficulty in mandibular movement [2]. Diagnosis by means of imaging of the temporomandibular joint (TMJ) and other craniofacial structures is frequently an important phase in collecting data from patients with TMD. The technological advances in this area have established less invasive methods for showing the muscle abnormalities that result from TMD, although there are few studies in this field [3]. Magnetic resonance imaging (MRI) is the best method for noninvasive TMJ investigation. It clearly shows how the upper portion of the lateral pterygoid muscle is attached to the joint capsule and the anterior portion of the disc, and how the lower portion of this muscle is attached to the mandibular condyle [4]. Occlusal plates are widely used for treating TMD, in order to modify the occlusal relationship, redistribute the forces, avoid tooth wear, change the structural relationships between forces and TMJ, improve muscle and joint function and relieve associated pain. If TMD is diagnosed due to loss of vertical occlusal dimension (VOD), intraoral orthosis is indicated as a form of treatment, to increase or recover this measurement, thereby providing symptom improvement and proprioceptive pathological muscle memory for the patient [5, 6]. The aims of this study were to investigate, by means of MRI, whether installation of an intraoral orthosis of modified “Planas” type would increase the distance between the cortical points of the condyle head and the glenoid fossa, and to evaluate whether such increases would decrease the painful symptoms after 30 days [7].

Material and Methods

For this study developed in the Department of Imaging Diagnostics of UNIFESP, twelve patients of both genders and aged between 18 and 70 years were selected. They presented Angle class I, with a diagnosis of TMJ pain syndrome and complaints of localized pain for more than five years. This study was approved by the Research Ethics Committee of UNIFESP, and all patients were clearly informed about the aims and methodology of the study. They gave their consent for participating in the study, in accordance with a free and informed consent statement.

The patients underwent a clinical examination protocol, in which palpation was performed by means of pressure from the index finger for three to four seconds on the following muscles: posterior, medial and anterior portions of the temporal muscle on the right and left sides; superficial and deep portions of the masseter muscle on the right and left sides; upper, medial and lower portions of the sternocleidomastoid muscle on the right and left sides; and cervical and cervicoacromial portions of the trapezoid muscle on the right and left sides. The TMJ was also palpated with the mouth closed, functioning and open, on the right and left sides. Standard responses of “yes” and “no” were used to determine whether pain was present. The lab confection of the modified “Planas” appliance was made up in the laboratory, using chemically activated acrylic resin, with smooth neutral tracks over the upper and lower occlusals. The appliance raised the bite when installed and changed the vertical dimension of the occlusion. The patients were instructed to use the orthosis for 12 hours/day for 30 days, with reexamination after this period.

Results

Discussion

Many studies have sought to identify morphological changes in the TMJ through analyzing magnetic resonance imaging from patients with TMD. These studies have defined whether the disease was present or not, quantified the pathological tissue involved, quantified the magnitude of the degenerative process, and determined whether it was reversible or not, i.e. whether the process could be stabilized. Some studies have emphasized the importance of magnetic resonance imaging, with special attention to intra-joint pathological conditions of the TMJ, disc apposition, excursion, morphologic abnormalities, etc, thereby enabling diagnoses of internal TMJ disorders that are more specific [4, 5, 6, 7, 8, 9, 10]. The present study aimed to objectively show the clinical efficiency of an orthosis that the authors modified from the classic “Planas” model of functional orthopedic appliance [7]. This consisted of constructing two contact orthoses that were smooth on the occlusal faces and fitted onto the teeth, thus increasing the VOD and simulating a scenario of vertical increase. All of the dental fit or engagement represented by maximal centric intercuspation (MCI) was lost. This release of movement allowed the TMJ and related muscles to function and return to better spatial positioning without interference and without intracapsular compressive forces while at rest, in situations with the mouth closed, therefore justifying its nighttime use for 12 hours. In addition to presenting a significant clinical condition, the patients that showed chronic pain have led us to study the correlation between clinical diagnostic hypotheses and correlations by means of MRI examinations. This has become a field for many studies, which have affirmed that there is a connection between pain and MRI signs [11, 12]. In other words, the existence of morphological abnormalities is closely related to clinical pain. At the same time, disc positions and the morphological state, function, dislodgement and inflammation of such discs have been studied. Our study had precisely the aim of measuring the values of a new predictive intracapsular cephalometric tracing that would allow radiologists to evaluate whether installed orthoses confer intracapsular measurements that bring therapeutic efficacy. The clinical results showed that installing the “Planas” modified orthosis improved the muscle algic pattern, thereby confirming the results in the literature [7, 13, 14]. In analyzing our results in relation to localized pain in the TMJ, we found obtained pain in 75% and 83.3% of the right and left sides, respectively, with the mouth closed. After thirty days, our results showed pain in only 8.3% and 25%, which was a large decrease. Regarding the open mouth position, we found pain in 91.6% for both sides and, after thirty days, this decreased to 50% and 33%. Therefore, the present study concurs with previous affirmations with regard to investigating the tissue response to degenerative abnormalities in the TMJ [5, 13, 14, 15]. It also affirmed that, just like the joint disc, the joint cartilage that covers the condyle (joint eminence) could be affected by degenerative processes such as osteoarthrosis. These processes harm shape and function, thereby causing compensatory or pathological responses regarding the disc and adjacent tissues. The distance between the cortex of the condyle head and the mandibular fossa is a relevant factor in procedures relating to temporomandibular disorders, as also confirmed by other studies [16, 17, 18, 19]. In our study, we observed that an increase in the distance of the craniometric points led to a clinical improvement for the patients. The mean distance between U-GL and U-CO in closed mouth situations without appliance was 0.34 cm, and for this same measurement, we found a value of 0.56 cm with the appliance installed. In other words, the orthosis installation increased the distance between the mandibular fossa and the condyle head by an average of 0.22 cm. Associated with this result, there was an improvement in symptoms in all the cases studied. Moreover, this should also provide functional or compressive rest for intracapsular TMJ structures. This increase can also be measured during the first MRI examination for installing the orthosis. The TMJ can be measured with and without the orthosis installed, thereby confirming the views of authors who advocate the use of intraoral orthoses, which could be single or double, anterior, posterior or covering the whole occlusion. These authors affirm that the increase invertical occlusal dimension caused by these orthoses promotes intra-joint decompression in the TMJ, thus increasing or promoting better translation conditions for the condylar meniscus [6, 7, 13, 15, 19]. In the light of the methods used, our results showed that incremental installation of standardized orthoses and the acquisition of images from the first MRI examination brings new data for the radiological evaluation of TMJ, thus allowing radiologists and clinicians to analyze the intra-joint space situation. This turns MRI before and after the orthosis installation into a predictive examination with regard to the possibility of clinical improvement.

Conclusions

The installation of intraoral modified “Planas” orthoses increased the distance between the craniometrical points of the cortex of the condyle head and mandibular fossa. With this increased distance, we observed a clinical improvement in all cases, after thirty days.