Functional treatment of bilateral posterior crossbite improves mandibular kinematics during chewing.

OBJECTIVES: To evaluate the effects of treatment of bilateral posterior crossbite (BPXB) on mandibular kinematics by the percentage of reverse chewing cycles (RCCs) during soft and hard bolus chewing before and after the correction of the malocclusion with function-generating bite (FGB). MATERIALS AND METHODS: This prospective study included 71 subjects: 19 patients with occlusally symmetric BPXB (M = 9; F = 10; mean age 9.3 ± 2.2[yr.mo]), 32 patients with occlusally asymmetric BPXB (19 with more teeth in crossbite on the right side (right prevalent side), M = 7; F = 12; mean age 8.2 ± 1.6 [yr.mo] and 13 on the left side, M = 7; F = 6; mean age 9.6 ± 1.9 [yr.mo]) and 20 controls without malocclusion (M = 8; F = 12; mean age 10.2 ± 1.7 [yr.mo]). Masticatory patterns were recorded before (T0) and after (T1) the correction of the malocclusion with FGB, with the K7-I® kinesiograph using standardized soft and hard boluses. RESULTS: BPXB was corrected in all included patients. At T0, the percentage of RCCs in BPXB was significantly increased compared to controls (P < .0001); symmetric BPXB showed no difference in RCCs between the sides, whereas asymmetric BPXB showed significantly more RCCs on the side with more teeth in crossbite (prevalent side). After treatment with FGB (T1), the percentage of RCCs was significantly reduced in both symmetric BPXB patients (soft bolus, P = .003; hard bolus, P < .001) and asymmetric BPXB patients (prevalent side: soft and hard bolus, P < .00001; non-prevalent side: soft bolus, P = .01 and hard bolus, P = .0002). CONCLUSION: Functional correction of BPXB with FGB significantly improved mandibular kinematics during chewing.

Comparative analysis of myoelectric activity and mandibular movement in healthy and nonpainful articular temporomandibular disorder subjects.

OBJECTIVES: Temporomandibular disorders (TMDs) are one of the leading causes of craniofacial pain, and a high incidence of TMDs in young adults has been reported. Previous studies have used surface electromyography (sEMG) and mandibular kinematic analysis for TMDs diagnosis. This study aimed to provide normal reference values of sEMG and mandibular kinematics in Han Chinese adults, compare the sex differences and assess their diagnosis value on pain-free articular TMDs. MATERIALS AND METHODS: This observational study recruited healthy young adults with individual normal occlusion and nonpainful articular TMDs patients with disc displacement. The sEMG signals of the anterior temporalis (TA), masseter (MM), and sternocleidomastoid and digastric were recorded in the mandibular postural positions (MPP) and during maximal voluntary clenching (MVC) with K7 electromyograph. Mandibular kinematics, including maximum opening and opening/closing velocities, were assessed by K7 kinesiograph. RESULTS: The sEMG reference values ranged from 3.0 to 4.3 µV in the MPP (n = 90) in healthy subjects. The sEMG values during MVC, maximum opening, and opening velocity were significantly higher in males than in females. Also, these indices showed good diagnostic efficiency for pain-free articular TMDs (n = 26). CONCLUSIONS: Reference values and sex differences in sEMG and mandibular kinematics in healthy subjects were determined. Compared with them, articular TMDs patients showed significantly lower myoelectric activity during maximal biting and restricted mouth opening range and velocity, which may assist in TMDs diagnosis. CLINICAL RELEVANCE: By analyzing sEMG of masticatory muscle and mandibular kinematics data from healthy Han Chinese young adults and TMDs patients with disc displacement, this study evaluated the sex difference and their diagnosis value on nonpainful TMDs with disc displacement. CLINICAL TRIAL REGISTRATION ID: NCT06372769.

Is there a relationship between the presence of external root resorption in second molars adjacent to impacted mandibular third molars with awake bruxism and masticatory muscle activity?

OBJECTIVES: This study aimed to assess whether awake bruxism and masticatory muscle activity could be related to external root resorption (ERR) in second molars adjacent to impacted mandibular third molars. MATERIALS AND METHODS: Sixty patients, with requests for a cone-beam, computed tomography, were divided into two groups: ERR (patients with ERR in the second molar, n = 30), and control group (n = 30). Awake bruxism was assessed through the Oral Behaviors Checklist (OBC) and an ecological momentary assessment (EMA). Surface electromyography (EMG) was used to assess the masseter and anterior temporal muscle function. Normality and homogeneity of variances were demonstrated. Descriptive analysis was performed, using the T-test and Chi-square test to compare the characteristics of the groups. A multiple regression model was performed. RESULTS: The ERR group presented more non-functional oral activities related to awake bruxism than the control group, according to OBC (p = 0.027) and EMA (p = 0.035). In addition, the ERR group had higher EMG activity than the control group in rest and isotonic protocols (p < 0.05). CONCLUSIONS: Awake bruxism and greater masticatory muscle activity seem to be related to the presence of ERR in second molars adjacent to impacted mandibular third molars. CLINICAL RELEVANCE: The results of the present study can reinforce the theory that triggering ERR in the second molars adjacent to impacted mandibular third molars may be related to mechanical forces coming from the masticatory function.

Prediction of jaw opening function after mandibular reconstruction using subject-specific musculoskeletal modelling.

BACKGROUND: Mandibular reconstruction patients often suffer abnormalities in the mandibular kinematics. In silico simulations, such as musculoskeletal modelling, can be used to predict post-operative mandibular kinematics. It is important to validate the mandibular musculoskeletal model and analyse the factors influencing its accuracy. OBJECTIVES: To investigate the jaw opening-closing movements after mandibular reconstruction, as predicted by the subject-specific musculoskeletal model, and the factors influencing its accuracy. METHODS: Ten mandibular reconstruction patients were enrolled in this study. Cone-beam computed tomography images, mandibular movements, and surface electromyogram signals were recorded preoperatively. A subject-specific mandibular musculoskeletal model was established to predict surgical outcomes using patient-averaged muscle parameter changes as model inputs. Jaw bone geometry was replaced by surgical planning results, and the muscle insertion sites were registered based on the non-rigid iterative closest point method. The predicted jaw kinematic data were validated based on 6-month post-operative measurements. Correlations between the prediction accuracy and patient characteristics (age, pathology and surgical scope) were further analysed. RESULTS: The root mean square error (RMSE) for lower incisor displacement was 31.4%, and the error for peak magnitude of jaw opening was 4.9 mm. Age, post-operative infection and radiotherapy influenced the prediction accuracy. The amount of masseter detachment showed little correlation with jaw opening. CONCLUSION: The mandibular musculoskeletal model successfully predicted short-range jaw opening functions after mandibular reconstruction. It provides a novel surgical planning method to predict the risk of developing trismus.

Rheumatoid Arthritis and Osteoarthritis in Adult Women: A Functional Approach to the Stomatognathic System.

Rheumatoid arthritis and osteoarthritis both affect the articular cartilage, and are characterized by signs and symptoms that can affect the functions of the human body. This cross-sectional observational study evaluated electromyographic activity in the masseter and temporalis muscles, molar bite force, and mandibular mobility in adult women with rheumatoid arthritis or osteoarthritis. A total of 42 women were distributed into 3 groups: rheumatoid arthritis group (ARG, n=14); osteoarthritis group (OAG, n=14); and a healthy control group (CG, n=14). Electromyography was used to evaluate mandibular tasks at rest, right and left laterality, protrusion, and dental clenching during maximum voluntary contraction, with and without parafilm, and a dynamometer was used to analyse the right and left molar bite forces. A digital caliper was used to measure the range of mandibular movement for maximum mouth opening, right and left laterality, and protrusion. Statistical analyses were performed, including analysis of variance and Tukey's test (P<0.05). Electromyography showed no significant differences between the groups when evaluating the masticatory muscles during the mandibular tasks. Significant difference was observed between the ARG and CG, however, in the maximum right (P=0.007) and left (P=0.02) molar bite forces. Significant difference was observed in the maximum mouth opening of the ARG and OAG groups compared with that of the CG (P=0.009), suggesting that adult women with rheumatoid arthritis or osteoarthritis experience functional alterations in the stomatognathic system, particularly in molar bite force and maximum mouth opening.

The Association of Systemic and Mandibular Bone Mineral Density in Postmenopausal Females with Osteoporosis.

Background/Objectives: Osteoporosis is a common general disease that mostly affects the skeletal system, including the jawbone. There is a link between systemic and mandibular osteoporosis. This study aimed at assessing the association between systemic (lumbar spine L1-L4, femoral neck, total hip) bone mineral density (BMD) and mandible BMD sites in Romanian postmenopausal females. Methods: A total of 97 menopausal patients were studied, 62 with osteoporosis and 35 females with no osteoporosis. For each patient, dual-energy X-ray absorptiometry (DXA) assessments of BMD in the mandible, proximal femur, total hip, and lumbar spine (L1-L4) were performed. Mandibular measurements were performed using the distal forearm software, followed by manual analysis after the bone contour was defined in each case. Results: Comparing the osteoporosis and control groups, there were significant differences in BMD at each examined location. The mandibular BMD (1.125 ± 0.181506 g/cm2) in the osteoporosis group was considerably smaller than in the control group (1.35497 ± 0.244397 g/cm2). Correlations between the BMD at different sites were significant: lumbar spine and femoral neck (r = 0.738, p < 0.0001), lumbar spine and total hip (r = 0.735, p < 0.0001), lumbar spine and mandible (r = 0.506, p < 0.0001), femoral neck and total hip (r = 0.891, p < 0.0001), femoral neck and mandible (r = 0.482, p < 0.0001), and total hip and mandible (r = 0.466, p < 0.0001). Conclusions: There were correlations between mandible BMD and lumbar spine, femoral neck, and total hip BMD, suggesting that osteoporosis affects mandibular bone density. BMD assessments at common locations may help predict mandibular BMD and the probability of osteoporosis.

Mandibular biomechanical behavior of rats submitted to chronic intermittent or continuous hypoxia and periodontitis.

BACKGROUND: The aim of this study was to investigate the effects of exposure to continuous (CH) and intermittent (IH) hypoxia on biomechanical properties of the mandible and periodontal tissue of animals submitted to experimental periodontitis (EP) when applying loads in a hypoxic environment. METHODS: Adult female Wistar rats were exposed during 90 days to IH or CH (simulated high altitude of 4200 m above sea level). Fourteen days prior to the euthanasia, EP was induced to half of the animals of each group. RESULTS: Only in the rats with EP, IH decreased the maximum capacity of the mandible to withstand load and the limit of elastic load. Indicators of intrinsic properties of the bone material were significantly reduced by both types of hypoxia in rats with EP. Hypoxia enhanced the alveolar bone loss induced by EP in the buccal side of the mandible, without showing additional effects in lingual or interradicular bone. Hypoxia increased prostaglandin E2 content in gingival tissue of healthy animals and further elevated the E2 levels increased by EP. CONCLUSIONS: When periodontitis is present, hypoxic stress induces a decrease in mineral properties that ultimately affects the ability of the mandible to resist load, mainly during intermittent exposure to hypoxia. These effects on bone may be related to the higher levels of prostaglandin E2 reached in the surrounding gingival tissue. The findings of this study may stimulate strategies to prevent unwanted effects of hypoxia on periodontal tissues.

Morbidity of marginal mandibular nerve post vascularized submental lymph node flap transplantation.

BACKGROUND: This study investigated the morbidity of the marginal mandibular nerve (MMN) post vascularized submental lymph node (VSLN) harvest. METHODS: The VSLN with sacrifying or preserving the medial platysma was retrospectively classified as group I or II. Midline deviation and horizontal tilt were subjectively evaluated. Horizontal, vertical, and "area distribution" of the lower lip excursions of the surgical site were objectively compared with the nonsurgical site. RESULTS: Seventeen patients in group I and 12 patients in group II were included. At a median follow-up of 48.6 ± 16.8 months in group I and 14.8 ± 7.5 months in group II, no MMN palsy was found in both groups. Median midline deviation and horizontal tilt were 4.53 ± 0.52 and 5 ± 0 in group I and 4.67 ± 0.65 and 5 ± 0 in group II, respectively (P = .419 and 1.000). Median horizontal, vertical and area of distribution of lower lip excursions were 97.5 ± 12.3%, 98.8 ± 14.4% and 87.2 ± 14.7% in group I, and 99.3 ± 15.1%, 95.8 ± 8.2% and 84.2 ± 14.2% in group II, respectively (P = .679, .948 and .711). CONCLUSION: The VSLN flap was a safe procedure with minimal MMN morbidity.

Dose-dependent effects of mandibular advancement on optimal positive airway pressure requirements in obstructive sleep apnoea.

BACKGROUND: Implementation of mandibular advancement splint (MAS) therapy as first-line treatment for obstructive sleep apnoea (OSA) is hindered by inter-individual variability of treatment outcomes and lack of robust patient selection methods. Optimal continuous positive airway pressure (CPAP) requirement provides an estimate of airway collapsibility severity, and high CPAP requirements predict MAS therapy failure in retrospective studies. Thus, understanding the effects of mandibular advancement on optimal CPAP requirements may enhance optimisation of patient selection for MAS therapy. OBJECTIVE: This study aims to determine dose-dependent effects of mandibular advancement on optimal CPAP requirements in OSA. METHODS: Prior to MAS therapy initiation, participants with OSA (apnoea-hypopnea index (AHI) > 10 events/h) underwent a research polysomnogram in which a remotely controlled mandibular positioner (RCMP) was used to determine dose-response effects of varying mandibular advancement positions (0% 'habitual bite' and 25, 50, 75 and 100% of maximum mandibular advancement, in random order) on optimal CPAP requirements. A separate polysomnography determined treatment outcome. Data are presented as mean ± SD or median (1st-3rd quartiles). RESULTS: Seventeen participants (age = 47 ± 9 years, body mass index = 26 kg/m2 (23-27), apnoea-hypopnea index = 18 events/h (14-44) and minimal oxygen saturation = 84 ± 7%) were studied. Optimal CPAP requirements were reduced with mandibular advancement in a dose-dependent manner (8.9 ± 2.4 vs. 7.9 ± 2.8, 6.4 ± 1.8, 5.7 ± 1.9 and 4.9 ± 1.8 cmH2O; respectively, p < 0.0001). Compared with non-responders, responders to MAS therapy had lower AHI, lower arousal index and greater MinSaO2 at baseline. Optimal CPAP requirements at 0% mandibular advancement (or other positions) were not different between groups. CONCLUSIONS: Increasing mandibular advancement lowers optimal CPAP requirements in a dose-dependent manner. This supports prior work indicating a beneficial effect of MAS on upper airway collapsibility.

Intraoral photobiomodulation diminishes pain and improves functioning in women with temporomandibular disorder: a randomized, sham-controlled, double-blind clinical trial : Intraoral photobiomodulation diminishes pain in women with temporomandibular disorder.

The aim of the present study was to evaluate the effect of intraoral photobiomodulation involving super-pulsed laser (905 nm) combined with red (640 nm) and infrared (875 nm) light-emitting diodes on pain, mandibular range of motion, and functioning in women with myogenous temporomandibular disorder. A randomized, sham-controlled, double-blind clinical trial was conducted involving 30 women with myogenous temporomandibular disorder diagnosed using the Research Diagnostic Criteria for Temporomandibular Disorders. The participants were randomly allocated to two groups (active and sham photobiomodulation). The evaluations involved this use of the visual analog scale, digital calipers, and a functional scale. Photobiomodulation was administered intraorally in the region of the pterygoid muscles, bilaterally, in all participants for a total of six sessions. Evaluations were performed on five occasions: prior to the intervention, immediately after the first session, 24 h and 48 h after the first session, and after the six sessions. Significant differences between groups were found regarding pain (p ≤ 0.01) and functioning (p ≤ 0.04). However, no statistically significant difference was found regarding range of mandibular motion. The findings demonstrate that intraoral photobiomodulation involving super-pulsed laser (905 nm) combined with red (640 nm) and infrared (875 nm) light-emitting diodes diminishes pain and improves functioning but does not exert an influence on mandibular range of motion in women with temporomandibular disorder.Trial registration: NCT02839967.

A randomized clinical trial comparing the efficacy of low-level laser therapy (LLLT) and laser acupuncture therapy (LAT) in patients with temporomandibular disorders.

This study compared the efficacy of low-level laser therapy (LLLT) versus laser acupuncture therapy (LAT) in patients with temporomandibular disorders (TMDs). In this randomized, double-blind clinical trial, 45 TMD patients were randomly divided into three groups. In group 1 (LLLT), a GaAlAs laser was applied on painful masticatory muscles and TMJs (810 nm, 200 mW, 30 s per point, Gaussian beam, spot size 0.28 cm2, 21 J/cm2) two times a week for 5 weeks. In group 2 (LAT), the laser was emitted bilaterally on acupuncture points (ST6, ST7, LI4) with the same settings as the LLLT group. Group 3 (placebo) underwent treatment with sham laser. The patients were evaluated before treatment (T1), after 5 (T2) and 10 (T3) laser applications, and 1 month later (T4). The mandibular range of motion as well as pain intensity in masticatory system was recorded at each interval. There was no significant difference in mouth opening between the groups (p > 0.05), but the amount of lateral excursive and protrusive movements was significantly greater in LLLT and LAT groups than the placebo group at some intervals (p < 0.05). The overall pain intensity and pain degree at masticatory muscles (except temporal muscle) and TMJs were significantly lower in both experimental groups than the placebo group at most intervals after therapy (p < 0.05). Both LLLT and LAT were effective in reducing pain and increasing excursive and protrusive mandibular motion in TMD patients. LAT could be suggested as a suitable alternative to LLLT, as it provided effective results while taking less chair time.

Maxillomandibular Advancement for the Treatment of Obstructive Sleep Apnea in Patients With Normal or Class I Malocclusion.

BACKGROUND: Maxillomandibular advancement is an effective surgical option for obstructive sleep apnea (OSA) that achieves enlargement of the upper airway by physically expanding the facial skeleton. The authors sought to determine whether an advancement of 10 mm predicts surgical success and if any correlation existed between the magnitude of mandibular/maxillary advancement and improvement in polysomnography metrics using aggregated individual patient data from multiple studies. METHODS: A search of the PubMed database was performed to identify relevant articles that included preoperative and postoperative polysomnography data and measurements of the advancement of both the maxillary and mandibular portions of the face in patients with normal or class I malocclusion. Each patient was stratified into "Success" or "Failure" groups based on criteria defining a "Success" as a 50% preoperative to post-operative decrease in AHI or RDI and a post-operative AHI or RDI <20. RESULTS: A review of the PubMed database yielded 162 articles. Review of these resulted in 9 manuscripts and a total of 109 patients who met the inclusion criteria. There was no statistically significant difference in the amount of anterior advancement of either the mandible (P = 0.96) or the maxilla (P = 0.23) between the "Success" or "Failure" groups. CONCLUSIONS: While there is a paucity of individual data available, the current data does not support an ideal amount of maxillary or mandibular advancement that is required to obtain a surgical success in the treatment of OSA. Until a multicenter, prospective, randomized trial is performed, surgical planning should be tailored to patient-specific anatomy to achieve the desired result.

Effects of 4-Week Diacutaneous Fibrolysis on Myalgia, Mouth Opening, and Level of Functional Severity in Women With Temporomandibular Disorders: A Randomized Controlled Trial.

OBJECTIVE: The purpose of this study was to assess the effects of 4-week protocol of diacutaneous fibrolysis (DF) compared with simulated DF (sham-DF) on myalgia and mouth opening. METHODS: In a sham randomized controlled trial, 34 women with temporomandibular disorders and myofascial pain were randomly divided as intervention group (IG) and sham-DF group (SG). The IG received 4 weeks of real DF, and the SG received sham. Pain was assessed through the visual analog scale and pressure pain thresholds (PPTs) on the temporomandibular joint (TMJ), and over the temporal and masseter muscles. The Mandibular Function Impairment Questionnaire was used to classify the participants regarding to the severity of the functional limitation related to TMD. RESULTS: Pain scores decreased for both groups, but the IG showed lower values at week 4, with between-group differences. Bilateral temporal PPT showed higher values at week 4, with between-group differences. The SG had lower PPTs but the IG had higher PPTs, both compared to baseline results. The time-by-group interaction and the frequency of participants above 40 mm of mouth opening showed a significant difference for the IG over time with higher results at the 4-week assessment compared to its own baseline. Both groups showed lower MFIQ scores from baseline to 4-week assessment. There was a lower frequency of a moderate level of severity for the IG. No differences were observed for TMJ or for the masseter muscles PPT. CONCLUSION: Improvements were observed for visual analog scale scores and PPTs on temporal muscles. There was a group-by-time interaction in the IG, suggesting a possible potential use of DF for mouth opening.

Elderly man with mandibular pain.

CLINICAL INTRODUCTION: A 77-year-old man presented to the ED with a history of fevers, purulent drainage and right mandibular pain. He had been diagnosed with multiple myeloma 2 years previously and was receiving treatment with pamidronate. On presentation, the lower right lip and chin were anaesthetic, tooth number 31 had grade 2 mobility and a 15 mm long ulceration was present on the lingual aspect of the mandible (figure 1). Antibiotics were administered, and a maxillofacial CT without contrast was performed (figure 2).emermed;36/1/17/F1F1F1Figure 1Clinical examination revealing a 15 mm long ulceration (arrow mark) associated with the lingual aspect of tooth number 31.emermed;36/1/17/F2F2F2Figure 2CT maxillofacial (coronal) demonstrating osseous destruction (arrow mark) of the right mandibular body. QUESTION: What is your diagnosis?Odontogenic abscessBenign fibro-osseous lesionMedication-related osteonecrosis of the jaw (MRONJ)Metastatic malignancy.

Painful temporomandibular disorders (TMD) and comorbidities in primary care: associations with pain-related disability.

Objective: We studied whether primary care temporomandibular disorder (TMD) patients reporting different levels of pain-related disability differ in terms of comorbid pains, general health conditions and quality of life.Material and methods: Consecutive TMD pain patients (n = 399) seeking treatment in primary care completed a questionnaire on comorbid pains and their interference and the Finnish version of the RAND-36-item quality of life questionnaire. Medical diagnoses confirmed by doctors were recorded. The patients were classified according to the Graded Chronic Pain Scale (GCPS) of the Research Diagnostic Criteria for TMD (RDC/TMD). The patients were classified: no disability group (0 disability points), low disability group (1-2 disability points) and high disability group (3-6 disability points).Results: Compared to patients in the no-disability group, patients in the high- and low-disability groups reported more comorbid pain conditions (p < .001), and experienced these as more intense and interfering more with daily life (p < .05). Patients in the high-disability group reported more general health-related medical diagnoses than patients in the no-disability group (p < .05). Furthermore, patients with low or high pain-related disability indicated poorer quality of life in all RAND-36 subscales than those with no disability (p < .05).Conclusions: The findings suggest that GCPS-related disability scoring can be used as a simple screening instrument to identify TMD patients with different degrees of health burdens.

Factors associated with spontaneous angular changes of impacted mandibular third molars as a result of second molar protraction.

INTRODUCTION: This study aimed to identify significant factors affecting the spontaneous angular changes of impacted mandibular third molars as a result of second molar protraction. Temporary skeletal anchorage devices in the missing mandibular first molar (ML-6) or missing deciduous mandibular second molar (ML-E) with missing succedaneous premolar spaces provided traction. METHODS: Forty-one mandibular third molars of 34 patients (10 male and 24 female; mean age 18.3 ± 3.7 years) that erupted after second molar protraction were included in this study. They were classified into upright (U) and tilted (T) groups. Linear and angular measurements were performed at the time of treatment initiation (T1) and of ML-6 or ML-E space closure (T2). Regression analyses were used to identify significant factors related to third molar uprighting. RESULTS: Nolla stage (odds ratio [OR] 4.1), sex (OR 0.003 for male), third molar angulation at T1 (OR 1.1), missing tooth space (OR 0.006), rate of third molar eruption (OR 23.3), and rate of second molar protraction (OR 0.2) significantly affected third molar uprighting. Age, third molar angulation at T1, rate of third molar eruption, and rate of second molar protraction were significant factors for predicting third molar angulation at T2. CONCLUSIONS: Available space for third molar eruption before and after second molar protraction is not associated with uprighting of erupting third molars. Older patients whose third molars are in greater Nolla stage, are in a more upright position at T1, and have a greater eruption rate have a greater chance for third molar uprighting. Alternatively, an increase in second molar protraction rate results in mesial tipping of the third molars.

Treatment of mandibular angle fracture: Revision of the basic principles.

Biodynamics of mandibular angle fractures has been extensively discussed in the literature in search for the best way to fixate and expedite recovery of trauma patients. Pioneers like Michelet and Champy had the greatest impact on evolving of osteosynthesis in maxillofacial traumatology; they introduced their basic principles frequently used to describe the biomechanics of mandibular fixation. Their concept states when a physiologic load is applied on mandibular teeth a negative tension will be created at superior border and a positive pressure will appear at inferior border. These simple definitions are the basis for the advent of fixation modalities in mandibular angle fracture. This article sought to reassess these principals based on load location via finite elements method.

Finite element analysis of occlusal splint therapy in patients with bruxism.

BACKGROUND: Bruxism is among the habits considered generally as contributory factors for temporomandibular joint (TMJ) disorders and its etiology is still controversial. METHODS: Three-dimensional models of maxilla and mandible and teeth of 37 patients and 36 control subjects were created using in-vivo image data. The maximum values of stress and deformation were calculated in 21 patients six months after using a splint and compared with those in the initial conditions. RESULTS: The maximum stresses in the jaw bone and head of mandible were respectively 4.4 and 4.1 times higher in patients than in control subjects. Similar values for deformation were 5.8 and 4.9, respectively. The maximum stress in the jaw bone and head of mandible decreased six months after splint application by up to 71.0 and 72.8%, respectively. Similar values for the maximum deformation were 80.7 and 78.7%, respectively. Following the occlusal splint therapy, the approximation of maximum deformation to the relevant values in control subjects was about 2.6 times the approximation of maximum stress to the relevant values in control subjects. The maximum stress and maximum deformation occurred in all cases in the head of the mandible and the splint had the highest effectiveness in jaw bone adjacent to the molar teeth. CONCLUSIONS: Splint acts as a stress relaxer and dissipates the extra stresses generated as well as the TMJ deformation and deviations due to bruxism. The splint also makes the bilateral and simultaneous loading possible and helps with the treatment of this disorder through regulation of bruxism by creating a biomechanical equilibrium between the physiological loading and the generated stress.

Comparison of efficiency of hyaluronic acid and/or bone grafts in healing of bone defects.

BACKGROUND: Reconstruction of bone defects in oral and maxillofacial surgery has widespread uses. In recent years, the capacity of various biomaterials alone or in combination with bone graft materials to increase bone healing has been an intensive research topic. The aim of this study is to evaluate the efficacy of hyaluronic acid and/or bone graft material on bone healing in defects created in the rat mandible. Methods: In our study, rats were divided into 4 groups. Group 1 is designated to be treated with no materials, Group 2 with graft material, Group 3 with only hyaluronic acid, and Group with hyaluronic acid and graft material. A critical-size defect of 5 mm in diameter was created bilaterally in the rat mandibles and the rats were divided into the indicated groups accordingly. At the end of the postoperative 6th week, the experiment was terminated. The right halves of the mandibles were evaluated immunohistochemically and histopathologically in terms of bone healing, and the left in terms of mineralization level via microcomputed tomography. RESULTS: Histopathological evaluation showed that healing in the empty group was significantly lower than the other groups that were treated with materials (P < 0.05); but the difference between the material-treated groups was not significant. Immunohistochemical evaluation revealed that the staining was moderately positive/strongly positive in all groups, but the difference between the groups was not significant. The highest mineralization values observed in the defected areas that belonged to 2 groups using hyaluronic acid, and the difference between them was found to be statistically significant (P < 0.05). The lowest mineralization values observed in the defected areas was most frequent in the group where only the hyaluronic acid was used, and there was a statistically significant difference between the other groups (P < 0.05). CONCLUSION: In conclusion, the use of hyaluronic acid alone or in combination with bone grafting has been shown to contribute positively to the improvement of bone defects in the jaw area.

Disrupted mitochondrial function in the Opa3L122P mouse model for Costeff Syndrome impairs skeletal integrity.

Mitochondrial dysfunction connects metabolic disturbance with numerous pathologies, but the significance of mitochondrial activity in bone remains unclear. We have, therefore, characterized the skeletal phenotype in the Opa3L122P mouse model for Costeff syndrome, in which a missense mutation of the mitochondrial membrane protein, Opa3, impairs mitochondrial activity resulting in visual and metabolic dysfunction. Although widely expressed in the developing normal mouse head, Opa3 expression was restricted after E14.5 to the retina, brain, teeth and mandibular bone. Opa3 was also expressed in adult tibiae, including at the trabecular surfaces and in cortical osteocytes, epiphyseal chondrocytes, marrow adipocytes and mesenchymal stem cell rosettes. Opa3L122P mice displayed craniofacial abnormalities, including undergrowth of the lower mandible, accompanied in some individuals by cranial asymmetry and incisor malocclusion. Opa3L122P mice showed an 8-fold elevation in tibial marrow adiposity, due largely to increased adipogenesis. In addition, femoral length and cortical diameter and wall thickness were reduced, the weakening of the calcified tissue and the geometric component of strength reducing overall cortical strength in Opa3L122P mice by 65%. In lumbar vertebrae reduced vertebral body area and wall thickness were accompanied by a proportionate reduction in marrow adiposity. Although the total biomechanical strength of lumbar vertebrae was reduced by 35%, the strength of the calcified tissue (σmax) was proportionate to a 38% increase in trabecular number. Thus, mitochondrial function is important for the development and maintenance of skeletal integrity, impaired bone growth and strength, particularly in limb bones, representing a significant new feature of the Costeff syndrome phenotype.