Experimental validation of finite element simulation of a new custom-designed fixation plate to treat mandibular angle fracture.

BACKGROUND: The objective of the study was to validate biomechanical characteristics of a 3D-printed, novel-designated fixation plate for treating mandibular angle fracture, and compare it with two commonly used fixation plates by finite element (FE) simulations and experimental testing. METHODS: A 3D virtual mandible was created from a patient's CT images as the master model. A custom-designed plate and two commonly used fixation plates were reconstructed onto the master model for FE simulations. Modeling of angle fracture, simulation of muscles of mastication, and defining of boundary conditions were integrated into the theoretical model. Strain levels during different loading conditions were analyzed using a finite element method (FEM). For mechanical test design, samples of the virtual mandible with angle fracture and the custom-designed fixation plates were printed using selective laser sintering (SLS) and selective laser melting (SLM) printing methods. Experimental data were collected from a testing platform with attached strain gauges to the mandible and the plates at different 10 locations during mechanical tests. Simulation of muscle forces and temporomandibular joint conditions were built into the physical models to improve the accuracy of clinical conditions. The experimental vs the theoretical data collected at the 10 locations were compared, and the correlation coefficient was calculated. RESULTS: The results show that use of the novel-designated fixation plate has significant mechanical advantages compared to the two commonly used fixation plates. The results of measured strains at each location show a very high correlation between the physical model and the virtual mandible of their biomechanical behaviors under simulated occlusal loading conditions when treating angle fracture of the mandible. CONCLUSIONS: Based on the results from our study, we validate the accuracy of our computational model which allows us to use it for future clinical applications under more sophisticated biomechanical simulations and testing.

Identification of Body Dysmorphic Disorder in Patients Seeking Corrective Procedures From Oral and Maxillofacial Surgeons.

INTRODUCTION: Body dysmorphic disorder (BDD) is an obsessive-compulsive related disorder characterized by an individual's preoccupation with the appearance of at least 1 perceived physical flaw. The bodily concerns held by individuals with BDD are largely unnoticeable, if at all, to other individuals. Those living with BDD are compelled to engage in repetitive behaviors or cognitive acts that interfere with daily function and activities. Despite the high prevalence of BDD in patients who seek cosmetic procedures (ie, as high as 1 in 5 such patients) and the availability of validated screening tools for this disorder, implementing a protocol of regularly screening for BDD is only rarely practiced by surgeons. Few studies have investigated its prevalence in the setting of elective dentoalveolar and orthognathic procedures. With the scope of practice of maxillofacial surgeons expanding in recent years to include facial cosmetic procedures, it is becoming increasingly important to screen for such disorders so that patients and physicians can appropriately weigh the risks and benefits of surgical intervention. METHODS: We conducted a cross-sectional cohort study (n = 46) consisting of 3 groups of patients, who were seeking either facial cosmetic, orthognathic, or dentoalveolar procedures. All patients in the study were screened for BDD using the Body Dysmorphic Disorder Questionnaire (BDDQ) and assessed for severity of disorder using the BDDQ severity scale. Additional patient variables included age, sex, history of psychiatric diagnosis, primary diagnosis, and type of operation/procedure being sought. RESULTS: Among the 3 groups, patients seeking dentoalveolar surgery were the most represented (67%) in this sample, followed by cosmetic surgery (27%) and orthognathic surgery (6%). Twenty-six female participants and 20 male participants were included, with an overall mean age of 38 years. Two percent of participants carried a previous psychiatric diagnosis and 10.8% of the sample were classified as high-risk for BDD. The group containing the highest proportion of patients at high-risk for BDD were those seeking facial cosmetic procedures (16.7%), followed by those seeking dentoalveolar procedures (10%); none of the patients seeking orthognathic procedures were found to be at high-risk for BDD (0%). CONCLUSIONS: The BDDQ is an efficient way to screen for BDD in patients who are seeking orthognathic or facial cosmetic surgery. In our sample, patients presenting to maxillofacial surgeons for facial cosmetic surgery were found to score significantly higher on the BDDQ than those presenting for dentoalveolar surgery. In contrast to results of previous literature, patients seeking orthognathic surgery in our sample demonstrated no elevated risk for BDD, a finding which may be attributable to our small sample size. Ultimately, the data obtained from this study can aid surgeons in identifying patients with BDD in their own surgical practice, so that they may appropriately triage patients who may, or may not, benefit from surgical intervention.

Use of Intravenous Acetaminophen in Postoperative Pain Management After Partial and Full Bony Impacted Third Molar Extractions: A Randomized Double-Blind Controlled Trial.

PURPOSE: Currently, there is a concern at the national level of the overuse of both prescription and nonprescription opioid use. The purpose of this study was to identify whether the use of the intravenous (IV) formulation of acetaminophen (Ofirmev; Mallinckrodt Pharmaceuticals, Staines-upon-Thames, United Kingdom) is an effective tool in the reduction of postoperative pain, with a secondary goal of reduction of postoperative narcotic use. MATERIALS AND METHODS: A total of 72 patients with previously diagnosed either partial bony or complete bony impacted third molars were selected with care to avoid long-acting local anesthetics or dissociative anesthetic agents. The patients' postoperative pain scores at 4 and 24 hours were collected via a verbal rating scale by the primary investigator. The exclusion criteria included administration of bupivacaine or ketamine, hepatic or renal impairment, pregnancy, or allergy to any of the normally administered sedation medications. RESULTS: At all postoperative increments (immediately, 4 hours, and 24 hours), there was no significant difference at P < .05 between scores for either the IV acetaminophen or placebo group. Although there was a recorded difference in reduction of pain at both 4 and 24 hours postoperatively, these were not statistically significant variables. CONCLUSIONS: The use of IV acetaminophen showed no statistically significant decrease in patient pain at either 4 or 24 hours postoperatively. Although there are not representative data suggesting the routine use of IV acetaminophen, on the basis of the abundance of literature on the treatment of pain for other procedures, this medication should not be discarded as ineffective.

Does the Intake of Selective Serotonin Reuptake Inhibitors Negatively Affect Dental Implant Osseointegration? A Retrospective Study.

The success of osseointegration is influenced by several factors that affect bone metabolism and by certain systemic medications. Selective serotonin reuptake inhibitors (SSRIs) have been previously suggested to be among these medications. This study aims to investigate the association between systemic intake of SSRIs and failure of osseointegration in patients rehabilitated with dental implants. A retrospective cohort study was conducted, including a total of 2055 osseointegrated dental implants in 631 patients (109 implants in 36 SSRI \users and 1946 in 595 nonusers). Predictor and outcome variables were SSRI intake and osseointegration failure, respectively. The data were analyzed with Mann-Whitney test or Fisher exact test accordingly. Both patient-level and implant-level models were implemented to evaluate the effect of SSRI exposure on the success of osseointegration of dental implants. Median duration of follow-up was 21.5 months (range = 4-56 months) for SSRI users and 23 months (range -60 months) for nonusers ( P = .158). Two of 36 SSRI users had 1 failed implant each; thus, the failure rate was 5.6%. Eleven nonusers also had 1 failed implant each; thus, the failure rate was 1.85%. The difference between the 2 groups failed to reach statistical significance at patient and implant levels ( P = .166, P = .149, respectively). The odds of implant failure were 3.123 times greater for SSRI users compared with nonusers. Patients using SSRIs were found to be 3.005 times more likely to experience early implant failure than nonusers. The results of this study suggest that SSRIs may lead to increase in the rate of osseointegration failure, although not reaching statistical significance.

A customized fixation plate with novel structure designed by topological optimization for mandibular angle fracture based on finite element analysis.

BACKGROUND: The purpose of this study was to design a customized fixation plate for mandibular angle fracture using topological optimization based on the biomechanical properties of the two conventional fixation systems, and compare the results of stress, strain and displacement distributions calculated by finite element analysis (FEA). METHODS: A three-dimensional (3D) virtual mandible was reconstructed from CT images with a mimic angle fracture and a 1 mm gap between two bone segments, and then a FEA model, including volume mesh with inhomogeneous bone material properties, three loading conditions and constraints (muscles and condyles), was created to design a customized plate using topological optimization method, then the shape of the plate was referenced from the stress concentrated area on an initial part created from thickened bone surface for optimal calculation, and then the plate was formulated as "V" pattern according to dimensions of standard mini-plate finally. To compare the biomechanical behavior of the "V" plate and other conventional mini-plates for angle fracture fixation, two conventional fixation systems were used: type A, one standard mini-plate, and type B, two standard mini-plates, and the stress, strain and displacement distributions within the three fixation systems were compared and discussed. RESULTS: The stress, strain and displacement distributions to the angle fractured mandible with three different fixation modalities were collected, respectively, and the maximum stress for each model emerged at the mandibular ramus or screw holes. Under the same loading conditions, the maximum stress on the customized fixation system decreased 74.3, 75.6 and 70.6% compared to type A, and 34.9, 34.1, and 39.6% compared to type B. All maximum von Mises stresses of mandible were well below the allowable stress of human bone, as well as maximum principal strain. And the displacement diagram of bony segments indicated the effect of treatment with different fixation systems. CONCLUSIONS: The customized fixation system with topological optimized structure has good biomechanical behavior for mandibular angle fracture because the stress, strain and displacement within the plate could be reduced significantly comparing to conventional "one mini-plate" or "two mini-plates" systems. The design methodology for customized fixation system could be used for other fractures in mandible or other bones to acquire better mechanical behavior of the system and improve stable environment for bone healing. And together with SLM, the customized plate with optimal structure could be designed and fabricated rapidly to satisfy the urgent time requirements for treatment.

Clinical relevance of the utilization of vital Lugol's iodine staining in detection and diagnosis of oral cancer and dysplasia.

OBJECTIVES: The aim of this study is to assess the clinical relevance of the utilization of vital Lugol's iodine staining in detection of oral cancer and dysplastic lesions as well as demarcation of the extent of these lesions. MATERIALS AND METHODS: A prospective, cross-sectional, hospital-based study was performed in Khartoum Teaching Dental Hospital, Sudan. Suspicious oral epithelial lesions indicating incisional biopsy were stained with 10 % Lugol's iodine solution and were clinically designated as "negative" for dysplasia or neoplasia when no unstained lesion (USL) area was observed, or as "positive" when a USL area is observed. Incisional biopsies involving both the unstained portion and the stained portion were obtained and histologically evaluated for definitive diagnosis. RESULTS: Forty-five biopsies were obtained from 28 patients. Histopathological examination of the specimens confirmed some degree of dysplasia or neoplasia in all clinically positive specimens with oral squamous cell carcinoma (OSCC) being the most common definitive diagnosis (17 patients, 60.7 %). Clinical relevance level of vital Lugol's iodine staining in detecting oral cancer and dysplasia was found to be 90.9 % (SE = 0.05, P = 0.05). CONCLUSION: The findings of this study showed that Lugol's iodine is an easy, safe, and effective method of visualizing oral epithelial lesions and differentiating epithelial carcinoma and dysplasia from other benign mucosal lesions. Despite certain limitations, its use is of great value in detection and diagnosis of oral cancer and dysplasia. CLINICAL RELEVANCE: Lugol's iodine staining can effectively be used in detection of the dysplastic and malignant superficial lesions of the oral epithelium.

Osteosarcoma of the Mandible Arising in Fibrous Dysplasia-A Case Report.

Fibrous dysplasia (FD) is a benign fibro-osseous lesion that typically behaves as a painless, slowly expanding tumor. On rare occasion, FD will undergo malignant transformation. When sarcomatous change occurs, osteosarcoma is the typical variant, followed by chondrosarcoma and fibrosarcoma. The incidence of malignant change varies from 1 to 4% depending on whether the disease is mono-ostotic or polyostotic and syndromic (McCune-Albright or Jaffe-Lichtenstein syndrome). Despite the low incidence of malignant change, the potential lethality of this disease behooves treating surgeons to be keenly aware of the signs and symptoms indicative of malignancy. This report documents a case of spontaneous transformation of FD into osteosarcoma in the setting of longstanding craniomaxillofacial FD in a 39-year-old woman.

First Bite Syndrome After Bilateral Temporomandibular Joint Replacement: Case Report.

First bite syndrome (FBS) refers to intense pain in the parotid region, which coincides with the first bite of every meal, gradually subsides over the next several bites, but returns with the first bite of the next meal. The definitive diagnosis can be readily established by the characteristic onset of pain after the first bite of every meal. Pain is typically most intense at the first meal of the day, although some patients experience symptoms when thinking of food or salivating. FBS is a recognized complication of surgery within the parapharyngeal space; however, other surgical procedures involving the upper neck have been associated with this syndrome. The extreme rarity of FBS complicates a thorough understanding of its pathophysiology. Various medical agents have been used, with variable success, for the management of patients with FBS. Although proved effective, more radical treatment modalities are commonly reserved for persistent or refractory cases, because there is potential of spontaneous decrease in the severity of symptoms with time. This report describes the case of a patient presenting with symptoms of FBS after bilateral temporomandibular joint replacement. To the authors' knowledge, this is the first case of FBS in the literature occurring after temporomandibular joint replacement.

Chronic osteomyelitis of the mandible: diagnosis and management--an institution's experience over 7 years.

PURPOSE: The objective of this study was to retrospectively evaluate and report the associated factors with the diagnosis and management of 24 patients with chronic osteomyelitis of the mandible seen at the authors' institution during the past several years. PATIENTS AND METHODS: Only cases of chronic osteomyelitis of the mandible not associated with antiresorptive medications or radiotherapy to the maxillofacial region were included in the study. After confirmation of the diagnosis, initial clinical and radiologic findings, treatment approach, and outcome were evaluated for each patient. Fourteen male and 10 female patients (average age, 53.75 yr; range, 22 to 83 yr) were included. RESULTS: The peak incidence of the disease was recorded in the fifth and sixth decades of life. An uneventful healing was observed in 20 patients (83.3%). One of 18 patients (5.5%) who underwent segmental resections developed a secondary infection and was managed with intravenously administered antibiotics. Three of 6 patients (50%) who were treated with marginal resections remained symptomatic after surgery. CONCLUSION: Independent of the cause and presentation of the disease, complete resolution of the infection should be the main focus of management in patients with chronic osteomyelitis of the mandible, and findings of this retrospective study indicate that a conservative surgical approach is more likely to result in a less than ideal outcome.

Anatomic study of the distance between the articular eminence and foramen spinosum and foramen spinosum and petrotympanic fissure.

PURPOSE: The middle meningeal artery is in close proximity to the medial aspect of the temporomandibular joint (TMJ). A major potential complication of surgery in the area of the TMJ is possible severance of the middle meningeal artery. An understanding of the relationship of the middle meningeal artery to easily identifiable landmarks lateral to the TMJ can help prevent the complications associated with TMJ surgery. The aim of the present study was to define the location of the middle meningeal artery by relating the distance between the easily identifiable bony landmarks of the articular eminence, petrotympanic fissure, and foramen spinosum. MATERIALS AND METHODS: Using a cross-sectional study design, we selected dried skulls from the Hamman-Todd skeleton collection at the Cleveland Museum of Natural History that were older than 20 years of age at death. The primary study variables were the distances between the articular eminence and foramen spinosum and the foramen spinosum and petrotympanic fissure. To appropriately analyze the variables, stratifications of age, gender, race, and anatomic location were applied. To measure the relationship between the stratifications and distances, a multivariate analysis of variance test was performed. The statistical results were deemed significant at P < .05. RESULTS: The sample consisted of 354 skulls or a total of 708 complexes. In analyzing the data, we noted that the only stratifications that bore any statistical significance were gender, with P < .0001, and the race-distance correlation, with a P value of .0007. CONCLUSIONS: The results of the present study suggest a definite difference in regard to gender on the distance between both sets of anatomic landmarks. Future studies could be tailored to further explore the effect of age on the distance, as a slight correlation was noted in our study.

The marginal mandibular nerve in relation to the inferior border of the mandible.

PURPOSE: Injury to the marginal mandibular nerve (MMN) can occur in numerous surgeries involving incisions near the inferior border of the mandible. Injury to this nerve can cause considerable cosmetic and functional deformities. A thorough knowledge and understanding of the anatomic pathway of the MMN is important to avoid permanent nerve damage. The purpose of this study was to determine the position of the marginal mandibular nerve in relation to several key mandibular anatomic landmarks and to identify variations of the nerve as it approaches the inferior border of the mandible. MATERIALS AND METHODS: Human cadavers were dissected superficially from the parotid gland to the mental protuberance to expose the MMN. At complete exposure of the nerve, 5 anatomic landmarks on the inferior border of the mandible were identified and labeled. The distance between the MMN and these landmarks was recorded, and the average measurements were used to approximate the most common pathway of the MMN. RESULTS: It was found that the MMN runs, on average, 0.75 mm below the gonion, 0.08 mm superior to the posterior border of the antegonial notch, 0.06 mm superior to the arc of the antegonial notch, 1.29 mm superior to the anterior border of the antegonial notch, 3.6 mm superior to the point at which the facial artery reaches the inferior border of the mandible, and 10.9 mm superior to the vertical line that extends from the commissure of lip to the inferior border of the mandible. CONCLUSION: These data suggest 3 general pathways of the MMN in relation to the inferior border of the mandible.

The use of virtual reality and augmented reality in oral and maxillofacial surgery: A narrative review.

OBJECTIVE: The purpose of this article is to review the current uses of virtual reality (VR) and augmented reality (AR) in oral and maxillofacial surgery. We discuss the use of VR/AR in educational training, surgical planning, advances in hardware and software, and the implementation of VR/AR in this field. STUDY DESIGN: A retrospective comprehensive review search of PubMed, Web of Science, Embase, and Cochrane Library was conducted. The search resulted in finding 313 English articles in the last 10 years. RESULTS: A total of 38 articles were selected after a meticulous review of the aims, objectives, and methodology by 2 independent reviewers. CONCLUSIONS: Virtual reality/AR technology offers significant potential in various aspects, including student education, resident evaluation, surgical planning, and overall surgical implementation. However, its widespread adoption in practice is hindered by factors such as the need for further research, cost concerns, unfamiliarity among current educators, and the necessity for technological improvement. Furthermore, residency programs hold a unique position to influence the future of oral and maxillofacial surgery. As VR/AR has demonstrated substantial benefits in resident education and other applications, residency programs have much to gain by integrating these emerging technologies into their curricula.

Nonvascularized bone grafts: how successful are they in reconstruction of segmental mandibular defects?

OBJECTIVE: Segmental mandibular defects can occur due to various etiologies, including trauma and tumor resection. Reconstruction should provide adequate support for subsequent dental rehabilitation and allow for proper occlusion. Nonvascularized bone grafts have been used for reconstructing mandibular defects in cases where vascularized grafts were not feasible. The objective of this study was to assess the success rate of these grafts in reconstruction of segmental defects of various sizes in the mandible. STUDY DESIGN: Fifty patients were included in this retrospective chart review. Length of the grafts varied from 3 to 20 cm and patients were followed up from 4 to 80 months. Fifteen grafts were harvested from anterior iliac crest, 23 from posterior iliac crest, 9 grafts were a combination of either with costochondral graft, and 3 were solely allografts. Bone morphogenetic protein was utilized in 41 cases as an adjunct. RESULTS: Success was defined as continuity of bone clinically and radiographically at a 4-month follow-up. Nonvascularized bone grafting was successful in 90% of cases. Complications were observed in 34% of cases, of which the most common were infection followed by wound dehiscence. CONCLUSIONS: Our study demonstrated substantial success rate with nonvascularized bone grafts in reconstruction of segmental mandibular defects.

The use of clear aligners in orthognathic surgeries: a case series.

Pre- and postoperative fixed orthodontic appliances are the customary and standard practice for patients with treatment planned for undergoing orthognathic surgery. Traditionally, most patients undergoing orthognathic surgeries are in their late teens. Although these patients still compose the greatest pool of the orthognathic surgery population, many patients seek orthognathic surgery later in life. This older patient population often has different concerns and goals than the younger patient population. One of these concerns is often the aesthetic appearance of fixed appliances and the time required to wear these appliances pre- and postoperatively. Today, removable orthodontic appliances consisting of a series of clear aligners have gained immense popularity due to their aesthetic appeal over traditional braces. Additional benefits of removable orthodontic appliances include improved oral hygiene leading to a decreased risk of gingivitis. Whereas clear aligner systems are commonly used in the nonsurgical orthodontic population, there has been limited use of Invisalign in the orthognathic surgery population. In this article, we present a case series of 5 patients who successfully underwent orthognathic surgery using clear aligners for pre- and postoperative orthodontic treatment.

Use of cone beam computed tomography to volumetrically assess alveolar cleft defects--preliminary results.

PURPOSE: The purpose of this study was to determine the utility of cone beam computed tomographic (CBCT) imaging in assessing the volume of alveolar cleft defects in patients undergoing secondary cleft repair. MATERIALS AND METHODS: Fourteen patients with unilateral clefts were analyzed in a retrospective study. Preoperative CBCT imaging of patients preparing to undergo secondary repair of alveolar clefts was reviewed. Using anatomic landmarks, 3 measurements were collected from CBCT images for each patient: facial width (FW), facial height (FH), and facial-palatal length (FL). These values were used to calculate the estimated volume (EV) of the cleft and thus the amount of bone graft material that would be needed to fill the defect. RESULTS: The overall mean values of FW, FH, and FL were 9.7 ± 3.1, 14.07 ± 2.7, and 5.6 ± 0.8 mm, respectively. Mean EV was 489.0 ± 151.6 mm(3). The single (0.879) and average (0.956) measurements of the intraclass correlation coefficient for FH were very good to excellent. Similar data were observed for FH (single, 0.827; average, 0.935). For FL, a decreasing trend in the mean and variability over the 3 measurement times was reflected in low single (0.305) and moderate average (0.569) intraclass correlation coefficients. CONCLUSIONS: CBCT imaging can be used to reliably measure FW, FH, and FL and to calculate the EV of the cleft. These data can be used by oral and maxillofacial surgeons to quantitatively assess the volume of an alveolar cleft and aid in preoperative determination of the amount of bone that will be needed to adequately graft the cleft space. This will also aid in appropriate selection of an autogenous graft donor site before surgery.

A 3-dimensional airway analysis of an obstructive sleep apnea surgical correction with cone beam computed tomography.

PURPOSE: The purpose of this case report is to present cephalometric changes in the craniofacial region and volumetric changes in the oropharyngeal region of a patient diagnosed with obstructive sleep apnea syndrome after maxillomandibular advancement and genial tubercle advancement surgeries. MATERIALS AND METHODS: Cone beam computed tomographic images were used to evaluate cephalometric changes in the craniofacial region and linear changes in the oropharyngeal region of the patient. RESULTS: A patient with obstructive sleep apnea was treated successfully with maxillomandibular advancement and genial tubercle advancement surgery. Airway analysis showed a significant increase in the volume of the patient's oropharynx after surgery. CONCLUSION: Cone beam computed tomographic images are recommended for 3-dimensional airway evaluation in the treatment of obstructive sleep apnea syndrome.

Utilization of the tympanomastoid fissure for intraoperative identification of the facial nerve: a cadaver study.

PURPOSE: Intraoperative identification of the facial nerve is an essential component of parotid gland surgery. Failure to visualize the facial nerve during the procedure can result in significant complications such as facial palsy. Several anatomic landmarks are used clinically to identify the facial nerve trunk; however, most of these structures have variable locations with respect to the nerve. The tympanomastoid fissure is the closest and least variable of the anatomic landmarks used in parotid gland surgery. The aim of this study was to evaluate the distance between the tympanomastoid fissure and the facial nerve trunk. MATERIALS AND METHODS: Thirty cadaver sides were dissected. A modified Blair incision exposed the facial nerve trunk, and the dissection was extended to the stylomastoid foramen and adjacent mastoid process. The distance between the most lateral aspect of the tympanomastoid fissure and facial nerve trunk was obtained using a digital caliper. RESULTS: The distance from the tympanomastoid fissure to the facial nerve trunk ranged from 3.3 to 9.2 mm with a mean of 4.9 mm. CONCLUSIONS: The results showed that the tympanomastoid fissure is a close and predictable anatomic landmark that can be used to identify the facial nerve trunk intraoperatively.

Biomechanical and Mechanostat analysis of a titanium layered porous implant for mandibular reconstruction: The effect of the topology optimization design.

A porous scaffold/implant is considered a potential method to repair bone defects, but its mechanical stability and biomechanics during the repair process are not yet clear. A mandibular titanium implant was proposed and designed with layered porous structures similar to that of the bone tissue, both in structure and mechanical properties. Topology was used to optimize the design of the porous implant and fixed structure. The finite element analysis was combined with bone "Mechanostat" theory to evaluate the stress and osteogenic property of the layered porous implant with 3 different fixation layouts (Model I with 4 screws, Model II with 5 screws and Model III with 6 screws) for mandibular reconstruction. The results showed that Model III could effectively reduce the stress shielding effect, stress within the optimized implant, defective mandible, and screws were respectively dropped 48.18%, 44.23%, and 57.27% compared to Model I, and the porous implant had a significant stress transmission effect and maintained the same stress distribution as the intact mandible after the mandibular defect was repaired. The porous implant also showed a significant mechanical stimulation effect on the growth and healing of the bone tissue according to the bone "Mechanostat" theory. The combination of porous structure with the topology technique is a promising option to improve the mechanical stability and osteogenesis of the implant, and could provide a new solution for mandibular reconstruction.

Effect of intermittent systemic administration of recombinant parathyroid hormone (1-34) on mandibular fracture healing in rats.

PURPOSE: To establish a rat mandibular fracture model and investigate the short- and long-term effects of recombinant parathyroid hormone (PTH 1-34) on mandibular fracture healing in rats. MATERIALS AND METHODS: A controlled unilateral mandibular fracture was created surgically in 29 male Sprague-Dawley rats and then stabilized using an external fixation device. The rats were divided into 2 groups: 1 group received daily subcutaneous injections of 10 microg/kg of PTH(1-34) and 1 group served as the vehicle control. The rats were killed on postoperative days 7 and 21, and radiographic densitometry and histologic evaluation of new bone formation were performed. RESULTS: A novel unilateral mandibular fracture model was established that has significant differences from previously published models, both in the location of the osteotomy site and in the rigid external stabilization device. The PTH(1-34) treated rats showed a statistically significant difference (P < .05) in callous formation compared with the control animals. Radiographic densitometry evaluation of the injury site revealed an increase in bone density, apparent at day 7 in the experimental group. Visual inspection of the histologic sections stained with Masson's trichrome blue showed an apparent increase in new bone formation at 21 days in the PTH-treated group compared with the control group. CONCLUSIONS: Intermittent systemic administration of PTH(1-34) might enhance the healing of mandibular fractures in the early phase (7-day period). Long-term administration (21-day period) showed no statistically significant differences between the control and experimental group by radiographic densitometry.

Medication-related osteonecrosis of the jaw: An institution's experience.

OBJECTIVES: This study aimed to evaluate and report the outcomes associated with the management of patients who were treated surgically for medication-related osteonecrosis of the jaw (MRONJ).Methods: Demographic and medical profiles of patients with a diagnosis of MRONJ were created. The type of surgical treatment, complications, and treatment outcomes were identified.Results: Twenty-one patients with an average age of 68.42 years (range 40-90 years) were included. Nineteen patients had only mandible involvement, one patient had only maxilla involvement, and one patient had both mandible and maxilla involvement. Thirteen patients underwent marginal resections. Eight patients underwent segmental resection of the mandible with immediate reconstruction. Nineteen patients healed without any complications. Two patients who had undergone segmental resection of the mandible experienced postoperative complications and needed a second surgery to achieve primary closure.Discussion: Advanced MRONJ can effectively be treated with resective surgery in combination with medical treatment.