Introduction: Several studies have evaluated the strengths and weaknesses of orthodonthic aligners however, the results are still uncertain. In the current study, we aimed to systematically review the literature and provide updates on the efficacy and effectivity of orthodontic therapy using aligners. Materials and Methods: PubMed, Web of Science and Cochrane Oral Health Group’s Trials Register databases were systematically searched for relevant literature up to December 2020. All studies reporting aligner therapy in management of dental misalignment were included. The quality was assessed using the methodological index for non-randomized studies (MINORS) criteria and Jadad scale for randomized controlled trials. Results: Of the initial 550 articles, 18 studies were ultimately included representing a total of 637 patients who were treated with clear aligners. Of the 18 studies, 15 had a retrospective design, one was an observational study, one was conducted as a prospective clinical trial, and one study was a randomized controlled trial. Due to the design and methodology of the studies the quality assessment revealed a high risk of bias. Significant diversity among the outcomes of the studies was observed; however, an underlying consistency was detected within the included studies with regards to the effectivity of aligner therapy in alignment of the anterior teeth, while the pretreatment predictive rates were not significantly different to treatment outcomes. In addition, despite comparable treatment outcomes between aligner therapy and conventional appliance technique, aligner therapy resulted in increased rates of patient satisfaction. Conclusion: Aligner therapy seems to be a viable alternative to conventional orthodontictherapy for correction of mild to moderate malocclusions in non-growing nonextraction patients. However, it should be taken into consideration that due to the high risk of bias, results should be interpreted with caution. Keywords: Orthodontics; Aligner; Tooth movement; Clinical effectivity.

Background and Aim: Mandibular setback surgery is one of the common treatments in patients with mandibular prognathism. In this surgery, the mandible is placed backward from its original position, and as a result, the soft tissue, tongue, and hyoid bone are slightly displaced, all of which can affect the dimensions of the airway. Given that these changes in the dimensions of the airway can lead to obstructive sleep apnea, it is important to examine these changes and their stability. In this regard, cephalometric radiography can be used, which haslowcost and dose in comparison to 3D radiographs, to examine changes in airway dimensions. The aim of this study was to evaluate the short-term and long-term changes in airway dimensions following mandibular steback surgery with the help of cephalometric radiography. Materials and Methods: The study was conducted by review method. Using the keywords ‘orthognathic surgery,’ ‘mandibular setback,’ ‘Malocclusion angle class III,’ ‘prognathism,’ ‘airway,’ ‘posterior airway space,’ ‘PAS,’ ‘pharyngeal space, ‘hypopharynx, a review of articles in PubMed and Embase databases, Google Scholar, and Cochrane databases was performed. The range of article searches was from 2000 to 2020. Conclusion: The results of studies showed that in the first 6 months after surgery, the dimensions of the airway decrease, but over time, due to the adaptation of the surrounding tissues and relapse after surgery, there is an improvement in the dimensions of the airway; Also, the study of index-related breathing disorders during sleep disorders during sleep showed that this surgery does not necessarily lead to obstructive sleep apnea. Keywords: Orthognathic surgery; Mandibular setback; Malocclusion angle class III; Prognathism;Airway; Posterior airway space; PAS; Pharyngeal space; Hypopharynx.

Background: Many studies have been performed on the effect of low level laser on wound healing which has been associated with different and sometimes contradictory results. On the other hand, considering that stress may affect the immune system the fact that it may delay wound healing has also been addressed. Therefore, the present study aimed to investigate the simultaneous effect of low level laser therapy and stress on wound healing at the three levels of histology (histological changes), biomechanics (stress and strain assessment) and macroscopic (wound size). Materials and Methods: In this interventional study, 72 male Wistar rats (8-10 weeks old, weight range: 240 to 330g) were randomly divided into three treatment groups and one control group. (18 per group). In all the rats, a 2.5cm full-thickness skin incision was made on the dorsal spine. Intervention was performed from day 1 to day 21 every other day with Kals-DX61 laser (cap s) with wavelength: 660nm, dose 3J/cm2, 100 sec and power density 30mW/cm2. Then, wound size was measured weekly until the third week (day 21). Then, tension metric tests were performed to evaluate the stress and strain of the restored tissue. At the end of each week, three animals from each group were sacrificed for histopathological evaluation. Results: There was a significant difference between the stress/no laser and laser/no stress groupsin all stages of evaluation. Mean and standard deviation of stress and strain were not significantlydifferent in the study groups. Conclusion: Stress can potentially slow the wound healing process, while receiving low level laser therapy speeds up the wound healing process, although in the end there was no significant difference in biomechanical characteristics between the groups. Keywords: Low level laser therapy; Rat; Stress; Wound healing.

Background: The customized prosthesis is a new method for the reconstruction of large mandibular defects. The ability of dental rehabilitation to improve masticatory functions while maintaining the aesthetics of the main anatomy of the patient’s jaw. But the most important problem with all custom prosthesis is the poor performance of screw fixation strength the connections at the bone-plate interface. Materials and Methods: This study was performed to investigate the effect of the number and layout of screws to improve the strength of the bone–prosthesis interface. Due to the inherent variability of input parameters, Analysis of the biomechanical performance of screw fixation strength, a probabilistic finite element method approach has been used. Random input parameters include mechanical properties of the cortical bone, cancellous bone, titanium alloy (Ti6Al4V), and bite force. The layout of the screws was designed in 6 models. Criteria for evaluating the biomechanical performance of screw fixation strength include maximum stress and strain of von Mises cortical bone around the screws. The Monte-Carlo method was used for finite element simulation. Results: The most critical screw in all models is screw No.1, which by increasing the number of screws and correcting the layout shape, the values of maximum stress and strain in the bone around screw No.1 has decreased by 26.7% and 46.3%, respectively, and increased the reliability of the screw connection performance by 25% and 28%, respectively. Conclusion: Finally, in the reconstruction of a large lateral mandibular defect by the customized prosthesis, the strength of the prosthesis to connect to the remaining mandible bone can be improved by increasing the number and modifying the layout of the screws. Keywords: Mandible reconstruction; Customized prosthesis; Probabilistic finite element method; Reliability.

Background: The surgical guide enabled the surgeon to accurately perform osteotomy, minimize iatrogenic injury to vital structure in vicinity to osteotomy and moving the bony segments to desired position exactly as planned during computer simulation. The purpose of this study is assess the role of computer assisted designed and manufactured surgical guide in minimizing inferior alveolar nerve injury during sagittal split ramus osteotomy (SSRO). Materials and Methods: A prospective double blind, randomized controlled, clinical trial is designed to assess role of computer assisted designed and manufactured surgical guide in minimizing inferior alveolar nerve injury during sagittal split ramus osteotomy (SSRO). We had two study group, the side of mandibular ramus that were treated by conventional SSRO (can be right or left) and the side that was treated using the computer designed and manufactured surgical guide of same patient (can be right or left side). For every patient the side of mandibular and osteotomy technique was selected by simple random sampling technique (double coin tossing). The statistical analyses were performed using SPSS version 25 (statistics package for social sciences, Chicago. IL). Statistical significance threshold was set to 0.05 (p-value<0.05). Result: The study population consisted of 10 subjects undergoing SSRO (Sagittal split ramus osteotomy). Seven (70%) were female and three were male. Their mean (±SD) age was 22.4±3024 yrs., range 16 to 27. The mean (±SD) duration of osteotomy on surgical guide assisted SSRO side was 37.2±4.83 and for conventional SSRO side it was 28.2±4.10 and the difference is statistically significant. Conclusion: Using CAD/CAM surgical guide for SSRO has no significant difference with conventional osteotomy technique regarding minimizing the incidence of inferior alveolar nerve injuries that occurs intraoperatively. Keywords: Sagittal split ramus osteotomy; Surgical guide; Neurosensory disturbance; Computer.

Introduction: The etiology of TMD is complex and multifactorial, but it is thought that psychological factors contribute to the etiology and persistence of TMD. Therefore, the aim of this study was to investigate the role of anxiety and depression in the development of temporomandibular joint disorders in patients referred to Tehran University of Medical Sciences, School of Dentistry, International Campus. Materials and Methods: This cross-sectional study was performed on patients referred to Tehran University of Medical Sciences, School of Dentistry, International Campus who had temporomandibular joint disorder. Hence the number of 224 people easily selected at random. They were given 3 questionnaires to assess their anxiety and depression (9-PHQ, 4-PHQ7 and-GAD-7). After collecting data using SPSS software version 22 and considering the error level at 0.50% probability and one-way analysis of variance and frequency analysis were performed. Results: The rate of depression in patients with TMD was 8.83 according to the 9-PHQ questionnaire and 4.72 according to the 4-PHQ questionnaire, and the level of anxiety in patients withTMD according to the 7-GAD questionnaire was equal to 8.95 There was no significant relationship between patients’ gender and their level of anxiety (p<0.50), but there was a significant relationshipbetween patients’ age and their level of anxiety (p>0.50). Conclusion: Age and gender are not significantly associated with temporomandibular joint disorders.  Also, anxiety and depression are positively related and there is a significant value achieved with the incidence of TMD in the participants. A reduction in the level of anxiety and depression within people, can have a great impact on the treatment of TMDs in individuals. Keywords: Temporomandibular joint disorder; Anxiety; Depression.

Patients with tooth loss in the posterior mandible,requiring dental implantation, mayalso require other simultaneous surgical procedures due to severe atrophy, such as nerve lateralization. However, it is difficult to achieve the appropriate width and height in this area in patients with atrophic ridges. In the present case, we performed inferior alveolar nerve (IAN) repositioning and iliac bone grafting simultaneously to achieve satisfactory width and height in an edentulous adult patient with insufficient bone height and width in the posterior mandible. The follow-up did not indicateany nerve damage, anda significant increase was observed in the bone height, which facilitated successful implantation. This study showed the feasibility of IAN repositioning withsimultaneous iliac bone autogenous grafting for thetreatment of atrophic posterior mandibular ridges. However, further studies are required to confirm the safety and efficacy of this combinational method. Keywords: Alveolar bone loss; Mandibular nerve; Nerve repositioning; Iliac bone; Autografts.

Lipoma a benign mesenchymal tumor is a rare finding in the oral cavity. This paper reports a case of 75 years old male patient with a huge lipoma of the floor of the mouth, along with its management at the Department of Maxillofacial surgery at Abbasi Shaheed Hospital, Karachi Pakistan. Conclusion: Lipoma of the floor of the mouth is very rare. We endorse complete surgical excision as an optimal treatment of oral lipoma. Keywords: Lipoma; Mesenchymal tumor; Floor of the mouth (FOM).

Mesenchymal chondrosarcoma as an aggressive type of chondrosarcoma shows a characteristic biphasic histopathologic pattern. The head and neck region is included a high proportion of extra skeletal sites. Very rare examples of Mesenchymal Chondrosarcoma involving the mandible have been described. Based on fragmented or tiny specimens, the diagnosis of this lesion has been remained a challenge because the specimens may contain only one of the two neoplastic elements. We report a rare case of mesenchymal chondrosarcoma of the mandible in a 19 years old male with delaying in diagnosis due to massive extension of the tumor to the soft tissues. Keywords: Mesenchymal chondrosarcoma; Mandible; Neoplasm.