EVALUATION OF MASTICATORY EFFICIENCY IN MAXILLOFACIAL TRAUMA PATIENTS FOLLOWING OCCLUSAL REHABILITATION-A CLINICAL STUDY

Background: Some amount of occlusal discrepancies exist despite of the latest developments in the treatment of fractured jaw bones which may vary from mild to severe which inturn leads to decreased post operative muscle efciency. Occlusal rehabilitation has been carried out to reduce such discrepancies. This study is aimed to evaluate this post operative muscle efciency following occlusal rehabilitation with the help of surface electromyography. Materials and methods: Twenty patients who underwent surgical treatment for maxillofacial trauma and required correction for post operative occlusal discrepancies were selected. Pre and post occlusal rehabilitative masticatory efciency was compared with surface electromyography. Results: The study revealed a denite increase in masticatory efciency after post occlusal rehabilitative therapy both in right and left masseter muscle. The mean EMG record values for pre and post occlusal rehabilitation were found to be respectively 826.7 (SD – 179.48) and 1134.01 (SD219.02) in the right side, 775.66 (SD187.51) and 1067.45 (SD197.75) in the left side. Conclusion: Correction of post operative occlusal discrepancies denitely benets the patients to exert better masticatory efciency.


Introduction
Nothing inspires as humanitarian instincts like trauma. Maxillofacial trauma though is a vast eld in itself well studied and researched but still there are certain aspects, which are still in shadows.
In the era prior to the development of craniofacial surgery, the treatment of facial injuries was by necessity, signicantly more conservative than it is today. The bones were approached through limited incisions and manipulated into an approximately normal position where they were suspended with wires from the higher, non fractured bony structures. This approach required long periods of immobilization and frequently resulted in unstable results with residual deformity and functional discrepancies like occlusal discrepancies.
Over the years, surgical approach to facial injuries has radically changed. The fractured sites are widely dissected and exposed and under direct vision the bones are replaced in their normal anatomic position, where they are rmly xed by metal plates and screws. Inspite of all the various principles followed for treatment of fractures like Reduction, Immobilization and Fixation, there might be a result of occlusal discrepancy post operatively due to the following factors like poor patient compliance, inadequate immobilization, poor reduction, delayed healing and rigid xation.
Hence an adequate post-operative rehabilitation protocol has to be followed to obtain the objectives of reduction and xation of maxillofacial bone fractures. The protocols being are occlusal rehabilitation, prosthetic rehabilitation, orthodontic rehabilitation and surgical re-correction. The goal of occlusal rehabilitation is to remove the cause of dysfunction and functional restoration of the stomatognathic system.
The purpose of this study was to evaluate the masticatory efciency in trauma patients, compare the pre-rehabilitation and post-rehabilitation masticatory efciency by evaluating the masseter muscle activity by using surface electromyography and check the efcacy of multidisciplinary approach for the treatment of post-operative occlusal discrepancy.

Materials and methods
This clinical prospective study was done in Department of Prosthodontics. Twenty patients of age range 16 to 25 years who underwent surgical treatment for maxillofacial trauma and required correction for post-operative occlusal discrepancies were selected.
Following conrmation/detection of an occlusal discrepancy a preocclusal rehabilitative masseter muscle activity was recorded using surface electromyography as follows: Electromyography (EMG) activity was recorded from the supercial masseter muscle bilaterally by means of self adhesive, disposable, pregelled silver chloride surface electrodes. The patient was made to sit comfortably without any head supporting. The patients were instructed to perform maximum voluntary clenching without causing any discomfort and to maintain the same act for atleast one second while the EMG data were recorded (Fig 1). Same procedure was repeated for three times and average reading taken. The digitalized signals were monitored on a computer screen immediately following the test and stored and a mean EMG value for each masseter muscle was calculated. Table 1 shows the pre and post occlusal rehabilitation therapy EMG activities recorded from the right and left masseter muscle. Each phase of maximum clenching was recognized as burst of muscle activity. The patient was asked to bring his teeth into occlusion and bite to his maximum force. The masseter muscle activity was recorded. Sets of 3 recordings were made on each side/muscle and average amplitude was taken into considerations. The recordings were compared between the fractured side and non-fractured side before occlusal rehabilitation and after occlusal rehabilitation. This was done on twenty patients who revealed that a denite statistical difference between EMG recordings of the fractured and non-fractured side, and upon correction of occlusion and collateral physiotherapy, there was a denite masseter muscle activity increased on the fractured side which in turn would increase or aid in the improvement of masticatory efciency. The mean values are graphically represented in Fig 2. The EMG values of masseter muscle were used as a measure of muscle efciency in this study as done by Steven J. Lindauer1.

Discussion
Electromyographic systems measure the electrical potential of muscle

Santosh Kumar Yadav
Department of Oral and Maxillofacial Surgery College of Medical Sciences Teaching Hospital Bharatpur-10, Chitwan, Nepal -Corresponding Author units. Recordings from such systems have been used to evaluate muscle activity during mastication and command mandibular movements.
The masseter muscle has usually been selected for study although the other muscles of mastication have occasionally been used. The probable reason for a decrease in bite force after treatment of maxillofacial bone fractures is traumatic and surgical damage to the masseter and temporalis muscles. Placing xation hardware from an intra-oral approach necessitates the masseter muscle being stripped from their attachments. Further, a transfacial trochar used for instrumentation may also damage the masseter muscle. Hence, masseter muscle was taken into consideration for EMG studies. Lower bite forces occurred in patients with occlusal dysfunction in their 2 masticatory system when compared with healthy people and the bite force increased as the symptoms of masticatory dysfunction 3 decreased .
Size and mechanical advantage of the jaw adductor muscles, sensitivity of the teeth, muscles and TMJ and the patient's willingness to exert maximum effort have been found to inuence generation of maximum occlusal force.
Attempts have been made to measure masticatory force either directly, using various types of transducers in the mouth or indirectly from muscle activity levels. Ahlgren J et al4 and William R. Prot et al5 said that Electromyography can be a reliable index to estimate masticatory force and estimates of masticatory force was based on an indirect method using EMG levels during maximum voluntary clenching act which was used by Bakke M et al6. A more reliable estimate of masticatory force is achieved by averaging the EMG values7. There were signicant differences found between EMG mean values recorded on operated side before and after occlusal rehabilitation that vary the sequence contracting of muscle bers . 5. A difference in body build and general muscular strength certainly 5 would contribute to maximum occlusal force differences .

Conclusions
Within these limitations of the study, following conclusions could be drawn: 1. There is decrease in the masseter muscle activity in the postoperative period. 2. Statistically signicant increase in the masseter muscle activity is found after occlusal rehabilitation and co-lateral physiotherapy. 3. Multidisciplinary approach has proved benecial in increasing the masseter muscle activity in post rehabilitation patients and results are encouraging.