Alteration of masticatory electromyographic activity and stability of orthognathic surgery in patients with skeletal class III malocclusion

Assessment of Masseter Volume and Postoperative Stability After Orthognathic Surgery in Patients With Skeletal Class III Malocclusion With Facial Asymmetry

OBJECTIVE

This study aimed to evaluate the effect of orthognathic surgery on masseter volume in patients with skeletal Class III malocclusion with facial asymmetry and the effect of masseter volume on stability in orthognathic surgery.

METHODS

This research studied 16 patients with Class III malocclusion with facial asymmetry who received combined orthodontic-orthognathic treatment and underwent craniofacial computed tomography (CT) before (T0), 2 weeks after (T1), and 6 months after (T2) surgery. Three-dimensional (3D) CT images were retrospectively analyzed, using 3D volume reconstruction to obtain the masseter volume and examine the impact of the masseter volume on stability in orthognathic surgery.

RESULTS

A statistically significant difference ( P < 0.05) in the volume of the masseter was found up to 6 months after orthognathic surgery compared with the preoperative period, and the reduction in the masticatory muscle volume on the lengthened side is greater than on the shortened side ( P < 0.05). The volume of both masseters differed according to facial asymmetry, and the difference was significantly reduced after orthognathic surgery ( P < 0.05). During the period time (T1-T2), cephalometric maxillary marker points were not significantly different ( P > 0.05), and mandibular marker points were significantly anteriorly shifted ( P < 0.05). There was an association between the masseter volume and anterior shift of point B (R > 0.5, P < 0.05), the upward and anterior shifts of the gonion point differed between the lengthened and shortened sides ( P < 0.05).

CONCLUSION

The size of the masseter becomes smaller 6 months after orthognathic surgery, and orthognathic surgery improves both bone and soft tissue symmetry. A larger sagittal relapse of mandibular setback occurred in patients with greater masseter volume. Considering these alterations may be helpful in planning orthognathic surgery.

Baseline masticatory muscles' performance may predict pain relief in temporomandibular disorders

OBJECTIVES

To compare masticatory muscles' recruitment in patients with temporomandibular disorders and asymptomatic control subjects. To evaluate if the masticatory muscles' recruitment pattern may predict symptoms' improvement after temporomandibular disorders treatment.

MATERIALS AND METHODS

Standardized surface electromyography of anterior temporalis and superficial masseters muscles were recorded and compared at baseline in 26 patients with arthrogenous temporomandibular disorders (study group) and 26 asymptomatic subjects (control group). The study group was treated pharmacologically and by means of five arthrocentesis sessions. Pre-, during-, and post-treatment pain and mandibular function were assessed and compared among timepoints. Clinical improvement in terms of pain and mandibular function was correlated with pre-treatment standardized surface electromyography values.

RESULTS

Temporomandibular disorders patients showed improved maximum mouth opening and pain during and after treatment with arthrocentesis compared to baseline (T-test p < 0.01). Standardized surface electromyography values were significantly different in temporomandibular disorders subjects compared to controls (T-test p < 0.05). Improvement in pain at rest after treatment was inversely correlated with pre-treatment masseters standardized surface electromyography symmetry (R-coefficient 0.3936; p < 0.05).

CONCLUSIONS

Temporomandibular disorders patients showed a different muscular recruitment pattern compared to controls. The lesser the pre-treatment masseters symmetry, the greater the improvement of pain at rest after treatment.

Assessment of Electromyographic Changes in Masseter and Temporalis Muscles for Patients Undergoing Lower Third Molar Surgery: A Prospective Study

Introduction Lower third molar impaction surgery is one of the most common minor oral surgical procedures done. Trismus has been one of the most common and disturbing postoperative sequelae for patients. The study aimed to evaluate the electrical activity of the masseter and temporalis muscles after mandibular third molar surgery. Materials and methods The research was conducted at Saveetha Dental College and hospitals in the Department of Oral and Maxillofacial Surgery. The study consisted of 20 individuals. The EMG (electromyography) activities of both masseter muscles in each patient were measured before the tooth extraction surgery, postoperatively after 72 hours, and after seven days. The inter-incisal distance was also measured at similar follow-up intervals. Data were analyzed using IBM Corp. Released 2015. IBM SPSS Statistics for Windows, Version 23.0. Armonk, NY: IBM Corp., with p-values less than 0.05 considered statistically significant. The Mann-Whitney U test was used for the comparison of electrical activity between masseter and temporalis on both the operated and non-operated sides during preoperative, postoperative, 72-hour, and postoperative seven-day periods. Results It has been found that the electrical activity of the temporalis is higher than that of the masseter muscle measured at all the intervals of the follow-up period, with statistically significant values (p=0.001). It was noted that all the patients have reduced mouth opening when compared with preoperative (mean mouth opening = 45.6 mm), postoperative 72 hours (mean mouth opening = 31.2 mm), and postoperative seven days (mean mouth opening =35.6 mm). When a comparison was done between temporalis and masseter, the masseter took longer to return to pre-operative electrical activity, which might also imply that for prolonged trismus seen in patients after lower third molar surgery, it is the masseter that is affected and needs recovery for trismus to be resolved.  Conclusion  Based on the results obtained, it can be concluded that there was a reduction in the electrical activity of both the masseter and temporalis post-third molar impaction surgery. It was also found that there was a reduction in mouth opening in patients who underwent lower third molar extraction surgery. Masseter muscle took longer to return to its preoperative electrical activity than temporalis muscle, implying that targeted therapies to accelerate the healing of masseter muscle may prevent prolonged trismus in patients who undergo lower third molar impaction surgery.

Skull Biomechanics and Simplified Cephalometric Lines for the Estimation of Muscular Lines of Action

Our study introduces a novel cephalometric analysis aimed at facilitating biomechanical simulations by elucidating the intricate relationship between craniofacial morphology and the size and inclination of the masseter muscle (MM) while incorporating muscle values. Our study analyzes the line of action of the MM drawn between the Gonion (Go) and Orbital (Or) points concerning dental and skeletal references (occlusal and Frankfort planes). A total of 510 pre-treatment lateral cephalometric tracings (217 males, 293 females, aged 6-50 years) and lateral Bolton standard tracings were examined. The key parameters investigated include (a) skeletal-cutaneous class (linear distance between projections of points A' and B' on the occlusal plane), (b) the angle between the perpendicular line to the occlusal plane and the Go-Or line at the molar occlusal point, and (c) the angle between the Go-Or line and the Frankfort plane. The assessment of anterior-posterior jaw discrepancy, measured as the skeletal-cutaneous class, ranged from -14.5 to 15.5 mm. Abnormal values were identified in two adolescents, showing no gender- or age-related patterns. The angle between the MM's line of action (Go-Or) and the normal to the occlusal plane averaged 39.3°, while the angle between Go-Or and Po-Or (Frankfort plane) averaged 41.99°. Age had an impact on these angles, with an average 3° decrease in adults and a 4° increase between ages 6 and 50. A weak relationship was observed between sagittal jaw discrepancy and the angle between Go-Or and the Frankfort plane, with about 20% of the variance explained by the anteroposterior maxillary-mandibular relationship. In conclusion, the study presents a cephalometric analysis of the relationship between craniofacial morphology and masseter muscle parameters. It finds that age influences the angles between key reference points, while the skeletal-cutaneous class does not exhibit age- or gender-specific trends. These findings can contribute to a better understanding of craniofacial biomechanics and aid in clinical orthodontic assessments and treatment planning.

Long-term evaluation of masseter muscle activity, dimensions, and elasticity after orthognathic surgery in skeletal class III patients

OBJECTIVE

To evaluate changes in the masseter muscle after orthognathic surgery using electromyography (EMG), ultrasonography (US), and ultrasound elastography (USE) in individuals with skeletal class III anomaly over long-term follow-up and compare with a control group.

MATERIALS AND METHODS

The study group included 29 patients with class III dentofacial deformities scheduled to undergo orthodontic treatment and orthognathic surgery. The control group included 20 individuals with dental class I occlusion. Assessment of the masseter muscles using EMG, US, and USE was performed before orthognathic surgery (T1) and at postoperative 3 months (T2) and 1 year (T3) in the study group, and at a single time point in the control group. All assessments were performed at rest and during maximum clenching. Masseter muscle activity, dimension, and hardness were analyzed.

RESULTS

Electromyographic activity of the masseter muscle during maximum clenching was increased at postoperative 1 year but did not reach control group values. On ultrasonography, the masseter muscle showed minimal changes in dimension at postoperative 1 year compared to preoperative values and remained below control group values. The postoperative increase in masseter muscle hardness at rest and during maximum clenching persisted at postoperative 1 year.

CONCLUSION

The results of this study suggest that after orthognathic surgery, additional interventions and much longer follow-up are needed to ensure better muscle adaptation to the new occlusion and skeletal morphology.

CLINICAL RELEVANCE

All assessment methods are useful for comprehensively evaluating changes in the masticatory muscles after orthognathic surgery.

Occlusal function and electromyographic activity of masticatory muscles in skeletal Class III patients with different patterns of mandibular asymmetry

BACKGROUND

Although jaw asymmetry is commonly seen in skeletal Class III patients, its correlation with occlusal function and masticatory muscle activity has not been fully elucidated.

OBJECTIVES

The purpose of this study was to investigate the occlusal function and masticatory muscle activity in skeletal Class III patients with various patterns of mandibular asymmetry.

METHODS

Forty-two patients and 10 normal participants were examined. The patients were categorised into three groups. Groups 1 and 2 exhibited menton and ramus deviation to the same side. Menton deviation was larger than ramus deviation in Group 1, whereas Group 2 showed the inverse relation. Group 3 patients showed menton and ramus deviation in opposite directions. Occlusal contact area (OCA), relative bite force (RBF), and temporalis anterior (TA) and masseter muscle (MM) activity at maximum clenching were measured using T-Scan Novus system and Bio-EMG-III. Statistical analysis was performed using the t-test, one-way analysis of variance with Bonferroni correction and Spearman correlation (α = .05).

RESULTS

Compared with normal participants, the patients had smaller OCA and greater asymmetry in the distribution of masticatory muscle activity. Greater ramus deviation was associated with smaller OCA in Group 1 but with larger OCA in Group 3. In Group 1, greater menton deviation was related to stronger TA activity on the non-deviation side. In Group 2, greater ramus deviation was related to stronger MM activity on the deviation side.

CONCLUSION

Deviation of the menton and ramus was individually related to OCA and masticatory muscle activity, and this relationship varied according to the pattern of mandibular asymmetry.

Effects of class II intermaxillary elastics on masticatory muscle activity balance, occlusal contact area and masticatory performance: A multicenter randomised controlled trial

BACKGROUND

Bilateral Class II intermaxillary elastics (CII elastics) are commonly used in orthodontics; however, the effects of CII elastics on masticatory muscle activity and the occlusal contact area have not been studied.

OBJECTIVES

To evaluate the short-term effects of CII elastics on masticatory muscle activity balance, occlusal contact area and masticatory performance in a group of adult orthodontic patients after 3 months.

MATERIALS AND METHODS

Forty-three patients with a <3 mm Class II molar relationship receiving ongoing treatment with fixed appliances were recruited. The experimental group (n = 21) wore CII elastics (100-150 g/side) full time; the control group (n = 22) did not wear CII elastics. Surface electromyography, the areas of occlusal contact and near contact (ACNC) and the median particle size of a test food were assessed prior to (T0) and after one (T1) and 3 months (T2). Within- and between-group differences were analysed and the relationships between changes in dependent variables were examined (α = 0.05).

RESULTS

At T2, the experimental group showed better masticatory muscle activity balance (p < .001) and masticatory performance (p < .05) than controls. Both masticatory muscle activity balance (p < .001) and masticatory performance (p < .001) significantly improved in the experimental group between T0 and T2. The changes in masticatory muscle activity balance and masticatory performance were significantly related (p < .05). No significant changes in cumulative ACNC or ACNC balance were observed (p > .05).

CONCLUSION

After 3 months, CII elastics improved masticatory muscle activity balance, which led to better masticatory performance.

Relapse patterns of two-jaw surgical correction in patients with skeletal Class III malocclusion and different vertical facial types

The aim of this study was to evaluate postoperative relapse after the surgical correction of skeletal Class III deformities of various facial patterns as a guide to surgical planning. A retrospective cohort study of 90 consecutive patients with skeletal Class III malocclusion who underwent bimaxillary surgery was performed. The surgical outcomes and postoperative stability were compared. The primary predictor variable was vertical facial type, which was classified into three groups according to the Frankfort mandibular plane angle (FMA). The primary outcome of angular and linear measurements was obtained using serial cone beam computed tomography scans obtained at time points of preoperative, 1 week after surgery, and orthodontic debonding. No significant difference in skeletal relapse was observed in patients with the different vertical facial types. The mandible displayed a forward and upward relapse in all three groups postoperatively. The patients with a low FMA exhibited a more consistent mandibular relapse pattern than those with a normal or high FMA. These findings suggest that bimaxillary surgery is clinically stable for mandibular prognathism regardless of the vertical facial pattern. However, 1-1.5 mm of overcorrection in the mandible setback should be considered in patients with a low FMA, because of the greater facial depth and consistent forward and upward mandibular relapse pattern.

Electromyographic, Ultrasonographic, and Ultrasound Elastographic Evaluation of the Masseter Muscle in Class III Patients Before and After Orthognathic Surgery

PURPOSE

The aim of this study was to examine changes in the electromyographic activity, thickness, width, and hardness of the masseter muscle from before to after orthognathic surgery.

MATERIAL AND METHODS

The study included 15 patients with Class III dentofacial deformities who were treated with combined orthodontic and orthognathic surgery. Fifteen individuals with normal occlusion and no signs or symptoms of temporomandibular joint dysfunction were used as controls. All records were obtained bilaterally in the study group before surgery (T1), at 3 months after surgery (T2), and in the control group (CG) while at rest and in maximum voluntary contraction (MVC).

RESULTS

There was no difference in resting masseter muscle activity between T1, T2, and CG. Resting thickness and width of the masseter muscle did not differ significantly between T1 and T2. MVC masseter muscle activity and thickness increased significantly and width decreased significantly from T1 to T2 but did not reach CG values. Muscle hardness increased from T1 to T2.

CONCLUSIONS

The authors' findings indicate that despite improved muscle activity and dimensions, postoperative 3 months is still early period for adaptation of the masseter muscles to the new occlusion and skeletal morphology.

Effects of Chewing Exerciser on the Recovery of Masticatory Function Recovery after Orthognathic Surgery: A Single-Center Randomized Clinical Trial, a Preliminary Study

Background and Objectives: The aim of this study was to evaluate the effects of the chewing exerciser (CE) on the functional recovery of the masticatory muscles after orthognathic surgery. Material and Methods: This randomized clinical trial was conducted in patients undergoing bimaxillary orthognathic surgery including bilateral sagittal split ramus osteotomy. Postoperative physiotherapy (PT) was performed for 3 weeks starting 3 weeks after the surgery. The patients were randomly divided into two groups: control (Con) (conventional PT) group and CE group (use of CE in addition to conventional PT). The masticatory function was evaluated based on three standards: bite force (BF), amount of mouth opening (MO), and surface electromyography (sEMG) of the anterior temporal muscle (TA), masseter muscle (MM), sternocleidomastoid muscle, and anterior belly of digastric muscle before, 3 weeks (before PT) and 6 weeks after the surgery (after PT). Results: Finally, 22 subjects participated in this study: 10 patients for Con group and 12 patients for CE group. In both groups, the BF, which was reduced significantly after the surgery, recovered after the PT similar to that before the surgery. In both groups, the MO was also significantly reduced by the surgery. However, it did not recover as much, as it was before the surgery after applying the PT. There was no difference in BF and MO between the two groups. All muscles did not show significant changes in sEMG by surgery and PT at both resting and clenching states. Conclusion: Applying CE as a PT after orthognathic surgery did not cause any harmful side effects. In both groups, the weakened muscle activity after orthognathic surgery (OGS) was adequately restored 6 weeks after the surgery. However, CE did not offer a statistically significant benefit to the masticatory function in the recovery process after OGS.

Prospective Analysis of the Swallowing Reflex After Sagittal Split Osteotomy: Comparison with Normal Volunteers

The aim of this study was electromyographic description of changes in swallowing before and after bilateral sagittal split ramus osteotomy. In this prospective study, twenty-eight patients were divided into 3 groups according to the occlusion pattern: Group I (Angle Class III), Group II (Angle Class II), and Control (Class I). Serial cone-beam computed tomography analyses and electromyographic data were collected preoperatively, 1st and 6th months after setback surgery in Group I, and advancement surgery in Group II. Swallowing reflex with 3-20 ml water bolus were studied. Patients were further divided into two subgroups according to the magnitude of relapse. The mean setback of the mandible was 4.62 ± 1.92 mm in Group I, and the mean advancement was 4.19 ± 2.00 mm in Group II. Mandibular relapse rate was 17.40%. Oral preparation phase shortened after surgery in both study groups. Two subjects in Group II and one in Group I had piecemeal deglutition, and two of them became normal postoperatively. Most of the swallowing durations of the relapsed cases were longer than those of stabilized patients. Important clinical considerations are as follows: the oral preparation period becomes shorter after surgery; piecemeal deglutition may disappear after treatment; and individuals with a longer oral period and piecemeal deglutition may have increased tendency to skeletal relapse. This multidisciplinary study enhances our understanding of the adaptive response to the swallowing reflex after orthognathic surgery and provides novel insight into the association between the submental muscle activity and relapse in orthognathic patients.

Electromyographic Changes in the Masseter and Temporalis Muscles Before and After Orthognathic Surgery in Patients With Mandibular Prognathism

OBJECTIVE

Evaluate the electromyographic changes in the Masseter (MM) and Temporalis (TM) muscles during voluntary clenching of the teeth both before and after orthognathic surgery in patients aged 18 years and older and diagnosed with mandibular prognathism.

METHODS

Eleven patients with prognathism were included in the study, in all of whom the initial phase of orthodontic treatment had been completed. The orthognathic procedure to reduce prognathism comprised intraoral oblique sliding (or subsigmoid) osteotomy, after which intermaxillary fixation with ligaments in the maxilla and mandible was undertaken in all patients for 6 weeks post-surgery. Electromyographic activity was recorded during the baseline maximum voluntary contraction of the teeth, with the same measurement taken 3 and then 6 months after orthognathic surgery.

RESULTS

Significant differences were found in the mean amplitude (17.0 vs 14.7, P = 0.020) and peak-to-peak amplitude (left [761.6 vs 457.0, P = 0.003] and right [676.9 vs 357.4, P = 0.007]) for the MM between the baseline score and 6 months after surgery. Likewise, significant differences were found in the mean amplitude (18.2 vs 25.6, P = 0.009) and peak-to-peak amplitude (left [856.4 vs 1594.2, P = 0.004] and right [804.4 vs 1813.4, P = 0.004]) for the TM between the baseline score and that taken 6 months post-surgery. Only 18.2% (2/11) presented orthodontic appliances problem in the 3 months post-surgery.

CONCLUSION

Electromyographic activity was restored 6 months after the orthognathic surgery. From a clinical perspective, the results obtained confirm that orthognathic surgery has not only an esthetic but also a functional objective in terms of achieving equilibrium and occlusal harmony.

Comparative study on long-term stability in mandibular sagittal split ramus osteotomy: hydroxyapatite/poly-l-lactide mesh versus titanium miniplate

Background

Resorbable devices have recently been adopted in the field of orthognathic surgery with controversies about their postoperative skeletal stability. Hence, we determined the long-term skeletal stability of unsintered hydroxyapatite/poly-l-lactic acid (HA/PLLA) mesh for osteofixation of mandibular sagittal split ramus osteotomy (SSRO), and compared it with that of titanium miniplate.

Methods

Patients were divided into resorbable mesh and titanium miniplate fixation groups. A comparative study of the change in the mandibular position was performed with preoperative, 1-day, 6-month, and 2-year postoperative lateral cephalograms.

Results

At postoperative 6 months—compared with postoperative 1 day, point B (supra-mentale) was significantly displaced anteriorly in the titanium-fixation group. Moreover, at postoperative 2 years—compared with postoperative 6 months, point B was significantly displaced inferiorly in the titanium-fixation. However, the HA/PLLA mesh-fixation group did not show any significant change with respect to point B postoperatively.

Conclusions

The HA/PLLA mesh-fixation group demonstrated superior long-term skeletal stability with respect to the position of mandible, when compared with the titanium-fixation group.

Overview of innovative advances in bioresorbable plate systems for oral and maxillofacial surgery

Maxillofacial osteosynthetic surgeries require stable fixation for uneventful boney healing and optimal remodeling. Although conventional titanium plates and screws for osteofixation are considered the gold standard for rigid fixation in maxillofacial surgeries, bioresorbable implants of plates and screw systems are commonly used for various maxillofacial osteosynthetic surgeries such as orthognathic surgery, maxillofacial fractures, and reconstructive surgery. Titanium plates are limited by their palpability, mutagenic effects, and interference with imaging, which may lead to the need for subsequent removal; the use of a biologically resorbable osteofixation system could potentially address these limitations. However, several problems remain including fundamental issues involving decreased mechanical strength and stability, slow biodegradation, complex procedures, and the available bioresorbable implant materials. Major advances in bioresorbable plate systems have been made with the use of bioactive/resorbable osteoconductive materials and an accelerator of bioresorption, such as polyglycolic acid. This report presents an overview of currently available resorbable implant materials and their applications, with a focus on recent innovative advances and new developments in this field.

Effect of the masseter muscle injection of botulinum toxin A on the mandibular bone growth of developmental rats

Background

The objective of this study was to evaluate the influence of masticatory muscle injection of botulinum toxin type A (BTX-A) on the growth of the mandibular bone in vivo.

Methods

Eleven Sprague-Dawley rats were used, and BTX-A (n = 6) or saline (n = 5) was injected at 13 days of age. All injections were given to the right masseter muscle, and the BTX-A dose was 0.5 units. All of the rats were euthanized at 60 days of age. The skulls of the rats were separated and fixed with 10% formalin for micro-computed tomography (micro-CT) analysis.

Results

The anthropometric analysis found that the ramus heights and bigonial widths of the BTX-A-injected group were significantly smaller than those of the saline-injected group (P < 0.05), and the mandibular plane angle of the BTX-A-injected group was significantly greater than in the saline-injected group (P < 0.001). In the BTX-A-injected group, the ramus heights II and III and the mandibular plane angles I and II showed significant differences between the injected and non-injected sides (P < 0.05). The BTX-A-injected side of the mandible in the masseter group showed significantly lower mandibular bone growth compared with the non-injected side.

Conclusion

BTX-A injection into the masseter muscle influences mandibular bone growth.

Correlation between change of tongue area and skeletal stability after correction of mandibular prognathism

The purpose of this study was to investigate the correlation between postoperative stability and a change in tongue area after treatment of mandibular prognathism. Twenty-six patients, who were treated for mandibular prognathism using intraoral vertical ramus osteotomy, were evaluated cephalometrically. A set of three standardized lateral cephalograms were obtained from each participant preoperatively (T1), immediately postoperatively (T2), and after 2 years postoperatively (T3). Student t test and Pearson correlation coefficient were used for statistical analysis. Immediately after the surgery (T12), the setback of the menton (Me) was 12.9 mm (p<0.001) and the tongue area had significantly increased to 105.8 mm² (p=0.047). At a 2-year follow-up to examine postsurgical stability (T23), the Me exhibited a forward movement of 0.6 mm (p=0.363) and the tongue area had significantly decreased to 124.3 mm² (p=0.004). Pearson correlation coefficient test revealed no statistical significance between postoperative stability and change in tongue area. The tongue area significantly increased during the T12 period and decreased during the T23 period. There is no significant correlation between postoperative skeletal relapse and a change in tongue area.

Length of Stay and Cost in Patients Undergoing Orthognathic Surgery: Does Surgeon Volume Matter?

PURPOSE

The relations among procedure-specific annual surgeon volume, hospital length of stay (LOS), and hospital costs for patients undergoing the 2 most common orthognathic surgical (OGS) procedures, segmental osteoplasty or osteotomy of the maxilla (SOM) or open osteoplasty or osteotomy of the mandibular ramus (SOMR), are not known. The authors hypothesized that treatment by high-volume surgeons would be associated with decreased LOS and costs.

MATERIALS AND METHODS

All patients 8 to 64 years old who underwent elective SOM or SOMR were selected from the 2001 to 2009 Nationwide Inpatient Sample. Patients with missing vital status or payment mode status or who underwent more than 1 OGS procedure during the index hospitalization were excluded. Based on year- and procedure-specific annual surgeon volumes, the highest (highest quartile) and lowest (lowest quartile) procedure volume surgeon groups were compared. Multivariable logistic regression was used to study the relation between surgeon volume and extended patient LOS (defined as LOS ≥ 75th percentile). Generalized linear models with a log-link and gamma distribution were used to examine the association between surgeon volume and hospital costs. Models were adjusted for patient- and hospital-level factors and type of procedure (SOM or SOMR). Analysis was weighted to represent national-level estimates and an α value of 0.05 was used for all comparisons.

RESULTS

After weighting to the population level, 8,062 patients were included for study. Most were white (80.6%), female (61.4%), and privately insured (84.6%). Mean age was 26 years (standard deviation, 0.38 yr). After adjusting for potential confounders, patients treated by high-volume surgeons showed 40% lower odds of extended LOS (odds ratio = 0.60; 95% confidence interval [CI], 0.38-0.95; P = .032) and incurred substantially lower costs (-$1,484.74; 95% CI, -2,782.76 to -185.58; P = .025) compared with patients treated by low-volume surgeons.

CONCLUSION

These findings suggest that regionalization of patients to high-volume surgeons for OGS procedures could decrease LOS and incurred costs.

Oral-motor and electromyographic characterization of patients submitted to open a nd closed reductions of mandibular condyle fracture

Purpose

To characterize the oral-motor system of adults with mandibular condyle facture comparing the performance of individuals submitted to open reduction with internal fixation (ORIF) and closed reduction with mandibulomaxillary fixation (CRMMF).

Methods

Study participants were 26 adults divided into three groups: G1 - eight individuals submitted to ORIF for correction of condyle fracture; G2 - nine individuals submitted to CRMMF for correction of condyle fracture; CG - nine healthy volunteers with no alterations of the orofacial myofunctional system. All participants underwent the same clinical protocol: assessment of the orofacial myofunctional system; evaluation of the mandibular range of motion; and surface electromyography (sEMG) of the masticatory muscles.

Results

Results indicated that patients with condyle fractures from both groups presented significant differences compared with those from the control group in terms of mobility of the oral-motor organs, mastication, and deglutition. Regarding the measures obtained for mandibular movements, participants with facial fractures from both groups showed significant differences compared with those from the control group, indicating greater restrictions in mandibular motion. As for the analysis of sEMG results, G1 patients presented more symmetrical masseter activation during the task of maximal voluntary teeth clenching.

Conclusion

Patients with mandibular condyle fractures present significant deficits in posture, mobility, and function of the oral-motor system. The type of medical treatment does not influence the results of muscle function during the first six months after fracture reduction. Individuals submitted to ORIF of the condyle fracture present more symmetrical activation of the masseter muscle.

Impact of midface and upper face fracture on bite force, mandibular mobility, and electromyographic activity

This study evaluated the bite force, electromyographic activity, and mandibular mobility in patients undergoing surgery for facial fracture treatment that required a coronal approach. Ten men were divided into two groups: group I, coronal approach with pre-auricular extension (n=4, average age 34.5 years); group II, coronal approach (n=6, average age 24.8 years). The maximum bite force was measured using a dynamometer and mandibular mobility using a calliper. The electromyographic activity of the right masseter (RM), left masseter (LM), right temporal (RT), and left temporal (LT) muscles was evaluated using a Myosystem-Br1 apparatus. Patients were evaluated at 1, 2, 3, and 6 months after surgery. Data were analysed using the repeated measures test (SPSS 21.0; P≤0.05). Statistically significant differences were found for electromyographic activity at rest (group II: LM P=0.00), left laterality (group I: RT P=0.02; group II: RT P=0.04), and maximum voluntary contraction (group I: RM P=0.04 and RT P=0.04; group II: RM P=0.05, LM P=0.00, and LT P=0.01 and for maximum molar bite force in the right (group I, P=0.00; group II, P=0.01) and left (group II, P=0.01) molar regions. The subjects regained electromyographic activity, maximum bite force, and mandibular mobility throughout the period evaluated.

Evaluation of the rigidity of sagittal split ramus osteotomy fixation using four designs of biodegradable and titanium plates--a numerical study

PURPOSE

This study was conducted to determine the best design of biodegradable plates for providing rigidity when used for fixation of sagittal split ramus osteotomy.

METHODS

A computerized tomography image of a patient was used to generate a 3D model of a hemi-mandible. Four plate designs were merged with the hemi-mandible. They were (1) straight plate, (2) double straight plate, (3) T-shaped plate, and (4) double Y-shaped plate. Four finite element models were analyzed using the properties of biodegradable materials for the plates, and four additional models were analyzed using titanium alloy properties.

RESULTS

The models predicted that rigidity of fixation would be noticeably less among biodegradable plates than titanium plates. They also predicted that the most rigid design among the titanium plates would be the straight plate, but among the biodegradable plates, it would be the double Y-shaped plate.

CONCLUSION

The double Y-shaped design is recommended when using biodegradable plates in fixation of sagittal split ramus osteotomy.

Does Prolonged Reconstruction of Disarticulation Defect With Bone Plate Affect the Electromyography Records of Masticatory Muscles?

OBJECTIVES

For medical or socioeconomic reasons, the primary reconstruction of disarticulation defects with bone plates stays for many years. This study was performed to assess the effect of this delay on electromyography (EMG) records of masticatory muscles.

MATERIALS AND METHODS

Twenty-five patients treated by insertion of reconstruction plates in disarticulation defects were prospectively included in this study. Electromyography records for masticatory muscles were obtained before surgery and 3 months, 6 months, 1 year, 2 years, and 3 years afterward. Paired t-test was used to determine whether there was significant difference between the EMG values.

RESULTS

At 3 years after surgery, the amplitude values of the masseter and temporalis muscles, on the resected side, have decreased by 39% and 60%, respectively, whereas on the nonoperated side, they have increased by 35% and 29%. The peak decrease, on the resected sides, has occurred at 3 months for the temporalis and 2 years for the masseter. On the nonoperated side, the peak increase has occurred at 6 months for both the temporalis and the masseter.

CONCLUSIONS

A prolonged use of bone plates to reconstruct disarticulation defects leads to alterations in EMG values of masticatory muscles. These alterations present clinically as muscle atrophy on the operated side and hypertrophy on the nonoperated side.

Bioabsorbable osteofixation for orthognathic surgery

Orthognathic surgery requires stable fixation for uneventful healing of osteotomized bony segments and optimal remodeling. Titanium plates and screws have been accepted as the gold standard for rigid fixation in orthognathic surgery. Although titanium osteofixation is the most widely used approach, the use of bioabsorbable devices has been increasing recently. Biodegradation of bioabsorbable devices eliminates the need for a second operation to remove metal plates and screws. However, long-term stability and relapse frequency in bioabsorbable osteofixation are still insufficiently studied, especially in cases of segmental movements of great magnitude or segmental movements to a position where bony resistance exists. This paper reviews the background, techniques, and complications of bioabsorbable osteofixation and compares bioabsorbable and titanium osteofixation in orthognathic surgery in terms of skeletal stability.