Premolar Area Research Articles

Dimensional changes of buccal bone plate in immediate implants inserted through open flap, open flap and bone grafting and flapless techniques: A cone-beam computed tomography randomized controlled clinical trial.

To assess through cone-beam computed tomography (CBCT) buccal alveolar bone alterations after immediate implant placement using the following techniques: open flap and grafting (flap-graft), open flap and no grafting (flap-nograft) and flapless and no grafting (noflap-nograft). This was a three-armed parallel group randomized clinical trial with allocation ratio 1:1:1. Patients were eligible in case they needed immediate implant replacing teeth in maxillary premolar area, with sufficient buccal bone support. CBCT was performed immediately after the intervention and 6months later. The main outcomes were CBCT measurements performed at apical (A-EA), medial (M-EM) and external and internal implant bevel level (B-EB, B-IB) and vertical defect depth (DP). Pain and discomfort, time of surgery and complications were recorded. Differences between groups were estimated through ANOVA tests and post-hoc Scheffe's analysis for pairwise comparisons. Multiple regressions were conducted to estimate influence of gingival biotype and baseline marginal gap dimension. Forty-five patients were recruited and randomized to treatments with one lost to follow-up. Analysis of variance showed that the effect of treatment technique was not relevant for all horizontal and vertical outcomes. The three techniques exhibited almost complete fill of marginal gap, with a mean residual vertical gap of 0.27mm and horizontal gap of 0.5mm. Regression models indicated a positive effect of thick biotype on gap filling and dimensional bone reduction. The noflap-nograft technique resulted less painful. The option of noflap-nograft surgery in post-extraction implants allows for minimal surgical intervention with comparable buccal bone changes and gap filling after a follow-up of 6months in sites with sufficient buccal bone support.

Vestibular incisional subperiosteal tunnel access versus coronally advanced flap with connective tissue graft for root coverage of Miller's class I and II gingival recession: A randomized clinical trial.

Background This study aimed to compare the clinical efficacy of vestibular incisional subperiosteal tunnel access (VISTA) with subepithelial connective tissue graft versus a coronally advanced flap (CAF) with subepithelial connective tissue graft for the treatment of gingival recession defects. Materials and Methods. This randomized clinical trial was performed on 24 recession defects that were bilaterally Miller’s class I or II in the maxillary canine and premolar area. One quadrant in each patient was selected randomly to receive VISTA (test group) or CAF (control group) with connective tissue graft. Clinical parameters measured at baseline and at 3- and 6- month postoperative intervals included recession width (RW), recession depth (RD), keratinized tissue width (KTW), clinical attachment level (CAL) and probing depth (PD). Results Healing was uneventful in both the test and control groups. At the 6-month follow-up, there was a significant decrease in RD, RW and CAL and an increase in KTW in both the test and control groups. The PD remained unchanged. At 3 and 6 months, no statistically significant differences were found between VISTA and CAF for root coverage and clinical attachment gain. Mean root coverage (MRC) was 70.69% and 67.22% in the test and control group, respectively. VISTA demonstrated higher frequency of complete root coverage (CRC) compared to CAF: 50% vs. 33% (P<0.05). The mean KTW was 2.4±0.7 mm at the test and 2.7±0.8 mm at the control sites (P>0.05) Conclusion VISTA, as a minimally invasive approach, can enhance root coverage, KTW and clinical attachment gain; therefore, it can be used as a substitute for CAF with connective tissue graft as a gold standard for root coverage.

Augmented reality for dental implantology: a pilot clinical report of two cases

BackgroundDespite the limited number of articles dedicated to its use, augmented reality (AR) is an emerging technology that has shown to have increasing applications in multiple different medical sectors. These include, but are not limited to, the Maxillo-facial and Dentistry disciplines of medicine. In these medical specialties, the focus of AR technology is to achieve a more visible surgical field during an operation. Currently, this goal is brought about by an accurate display of either static or dynamic diagnostic images via the use of a visor or specific glasses.The objective of this study is to evaluate the feasibility of using a virtual display for dynamic navigation via AR. The secondary outcome is to evaluate if the use of this technology could affect the accuracy of dynamic navigation.Case presentationTwo patients, both needing implant rehabilitation in the upper premolar area, were treated with flapless surgery. Prior to the procedure itself, the position of the implant was virtually planned and placed for each of the patients using their previous scans. This placement preparation contributed to a dynamic navigation system that was displayed on AR glasses. This, in turn, allowed for the use of a computer-aided/image-guided procedure to occur. Dedicated software for surface superimposition was then used to match the planned position of the implant and the real one obtained from the postoperative scan. Accuracies, using this procedure were evaluated by way of measuring the deviation between real and planned positions of the implants. For both surgeries it was possible to proceed using the AR technology as planned. The deviations for the first implant were 0.53 mm at the entry point and 0.50 mm at the apical point and for the second implant were 0.46 mm at the entry point and 0.48 mm at the apical point. The angular deviations were respectively 3.05° and 2.19°.ConclusionsFrom the results of this pilot study, it seems that AR can be useful in dental implantology for displaying dynamic navigation systems. While this technology did not seem to noticeably affect the accuracy of the procedure, specific software applications should further optimize the results.

Accuracy of Scanned Stock Abutments Using Different Intraoral Scanners: An In Vitro Study.

To determine the accuracy of a digital manufacturing method for dental implant restorations on stock abutments using intraoral scanners and prefabricated stock-abutment libraries. Two dental implants with internal hexagonal connections were placed in the mandibular second premolar and second molar areas of a partially edentulous dentoform model; stock abutments with a diameter of 5 mm, abutment height of 5.5 mm, and gingival cuff height of 2 mm were connected. The study model was scanned 10 times using a reference tabletop scanner and 5 types of intraoral scanners (IOSs). The data collected by 5 types of IOSs were divided into 3 groups, based on the type and matching of stock abutment library data: no library, optical library, and contact library groups. A total of 160 data files were analyzed, including reference data. The resulting data were used to evaluate trueness and precision. Trueness and precision values in the group in which library data of the stock abutment were not used were 42.0 to 76.3 µm and 30.5 to 99.7 µm; corresponding values when the library data using an optical scanner were matched were 51.2 to 73.4 µm and 26.3 to 62.8 µm, and those when contact scanner library data were used were 30.1 to 62.4 µm and 15.5 to 55.9 µm. Thus, the accuracy of the contact library group was significantly higher than the accuracies of the no library (p < 0.001) and optical library groups (p < 0.001). The application of prefabricated library data of stock abutments using a contact scanner improved the accuracy of scan data. Scan accuracy of the stock abutments differed significantly based on the type of scanner.

CLEAR CELLS TUMORS IN THE ORAL CAVITY: TWO CASES TO SHOW THE CHALLENGING DIAGNOSIS

Introduction Clear cell carcinomas in the jaws are very infrequent neoplasms. Differential diagnosis includes metastatic carcinomas, mucoepidermoid carcinoma, clear cell odontogenic carcinoma, and others. We present two cases of jaw tumors and focus on the diagnostic challenge of each. Case Reports The first case is a 65 year-old man without diagnosis of a systemic disease, with a gingival red tumor and a radiolucent image with irregular borders in the incisor area. Histopathology showed proliferation of clear cells with round hyperchromatic nuclei, some with atypia. These cells formed solid nests separated by thin connective tissue septa with marked vascular proliferation. The clear cells presented diastase–periodic acid–Schiff, anti-Vimentin, anti-CD-10 and anti-PAX-8, anti-human Ki-67 positivity (30% of the cells) and it was negative for S-100 and CK-7. The diagnosis was clear cell carcinoma suggestive of clear cell metastatic carcinoma (MRCC). The second case is a 36 year-old woman with an asymptomatic radiolucent lesion in the periapical area of maxillary premolars. Histopathology showed a cellular proliferation formed by nests of clear oval and polygonal cells, with mild atypia separated by fibrous connective tissue septa. The immunohistochemical staining showed positivity for cytokeratin AE1/AE3 and negative for both S-100 and-smooth muscle actin. Mucicarmin and Congo-red stains were negative. This case was diagnosed as suggestive of clear cell odontogenic carcinoma (CCOC); it was indicated to rule out metastasis. The imaging evaluation confirmed a renal neoplasm in the first case and rule out the presence of lesions in the rest of the body in the second case. Conclusions CCOC and MRCC are histologically similar and immunohistochemistry studies play an important role in diagnosing clear cell tumors. So it is vital for the pathologist to know histomorphology and histo and immuno-histochemistry staining should be considered.

Cone-beam CT assessment of implant-related anatomy landmarks of the anterior mandible in a Chinese population.

To investigate the prevalence, location, and morphology of the mandibular lingual foramen (MLF), mandibular incisive canal (MIC), and anterior loop of the inferior alveolar canal (ALC) in a Chinese population using cone-beam CT (CBCT). From 2014 to 2016, CBCT images from patients with various scanning purposes were obtained from the database of the Affiliated Stomatology Hospital of Kunming Medical University, China. Imaging analyses of the MLF, MIC, and ALC were performed via the NNT viewer software. The prevalence, location, length, classification of MLF, and its distances to the alveolar crest and the lower border of mandible were investigated, and the prevalence and length of MIC and the prevalence of ALC were also studied. This study examined 1008 subjects, 521 (51.7%) males, and 487 (48.3%) females. 916 (90.9%) subjects showed the medial lingual foramina (LF), a single medial LF with the supraspinous-type predominating. Lateral LF were observed in 547 (54.3%) subjects mostly located in the premolar areas. 876 (86.9%) subjects had the MIC on the left side, whereas 877 (87.0%) had the MIC on the right side. The ALC was present in 147 (14.6%) subjects. This study showed a high prevalence of LF and MIC in the Southwest Chinese population. Therefore, caution should be taken during the implant treatment at the anterior mandible region.

Relationship of gray values in cone beam computed tomography and bone mineral density obtained by dual energy X-ray absorptiometry

The aim of this study was to assess the correlation between bone mineral density (BMD) determined with cone beam computed tomography (CBCT) gray values and BMD determined by dual energy X-ray absorptiometry (DEXA). Women age greater than 50 years requiring CBCT for implant treatment were included in the study. BMD was determined by calculating the mean gray value of CBCT cross-sectional images of anterior, premolar, retromolar, and tuberosity areas of the mandible and maxilla. Patients were then subjected to DEXA of the femoral neck and lumbar spine. Independent t tests, analysis of variance (ANOVA), Pearson's correlation tests, and receiver operating characteristic (ROC) evaluation were used for data analysis. Of 61 asymptomatic patients (mean age 64 years), 47.5% and 55.7% had abnormal BMD, based on the T-scores of the femoral neck and lumbar spine, respectively. Significant correlations were noted between the T-scores of the femoral neck and lumbar spine and the gray values of the maxillary incisor and tuberosity areas. A strong correlation exists between the CBCT gray values at different sites in the maxilla and the results of DEXA. A gray value less than 298 at the maxillary tuberosity can help distinguish patients with osteoporosis from normal individuals, with 66% to 67% accuracy and suggests the need for DEXA analysis.

Comparative Study between an Immediate Loading Protocol Using the Digital Workflow and a Conventional Protocol for Dental Implant Treatment: A Randomized Clinical Trial

Background: The purposes of this randomized clinical trial study was to compare the immediate loading of dental implants while employing digital workflow and conventional implants in terms of the success rate, marginal bone level, and patient satisfaction. Methods: Fifty patients who had edentulous area on the mandibular premolar or molar area were included in the study. Twenty-five patients were assigned to immediate loading implant treatment using the digital technique and 25 patients were assigned to conventional loading implant treatment. In the first group, the patients were received digital impression (Cerec Omnicam, Dentsply Sirona®, York, PA, USA), designed, producing zirconia crown, and inserted on the same surgery day. The second group, after a healing period of three months, was received analog impression following conventional impression for the zirconia crown. Clinical outcome and radiographic bone level were evaluated after three, six, and 12 months. Patient satisfaction was measured at 12 months after inserting the implant. Results: There was no implants and protheses failure in both groups. The mean resonance frequency analysis values at the day of surgery were 78.26 ± 4.09 in immediate loading using the digital group (ILD) and 73.74 ± 5.14 in the conventional loading group (CL), respectively. Insertion torque values at the day of surgery were 36.60 ± 12.64 in ILD and 38.8 ± 12.19 CL, respectively. The marginal bone level in CL at three, six, and 12 months were 0.14 ± 0.28 mm, 0.18 ± 0.30 mm, and 0.17 ± 0.29 mm, respectively, while in ILD at three, six, and 12 months were 0.18 ± 0.33 mm and 0.16 ± 0.27 mm and 0.15 ± 0.31, respectively. There was no statistically significant difference between the two groups. Only one question in patient satisfaction’s questionnaire was “Now, can your dental implant and crown be used well?” had been significantly different in favor to the conventional group. Conclusion: Within the limitation of this study, it may be concluded that, after one-year follow up, there were no statistically significant differences between the immediate loading of dental implants employed from the digital workflow and conventional implant treatment technique in the success rate and marginal bone level. In patient satisfaction, there was only statistic significant difference in question related to implant prosthetic function in favor of the CL group, whereas the question concerning speaking, cleansing, price, and expectation displayed no difference.

EVALUATION OF CLINICAL ASPECTS OF APPEARANCE OF TEETH NONCARIOUS DEFECTS IN BROXISM PATIENTS

Purpose - to study the etiology, prevalence, clinical course, functional examination and treatment of non-carious lesions located in the cervical area of patients with bruxism. Materials and methods. A prospective study of 200 outpatient cards of dental patients at the dental clinic of the Federal State Budgetary Educational Institution of Higher Medical Education of the KMGU of the Ministry of Health of Russia (Kursk) and Federal State Budgetary Educational Institution of Higher Medical Care of the Kuban State Medical University of the Ministry of Health of Russia (Krasnodar) in the age range from 18 to 55 years, whose average age was 38 ± 6.7 years. We studied the localization of cervical defects, etiological factors of occurrence, and also conducted an electromyographic study of the chewing muscles at rest, when the jaws were compressed and when chewing. Results. When studying the localization of cervical defects in different functional groups of teeth, defects in the cervical area of premolars were noted in 41 patients - 57%, in 18 - on canines (25%), in 10 - on incisors (13.8%), in 3 - on molars (4.2%). It was revealed that the trigger mechanism was a number of factors: partial loss of teeth (20 patients were diagnosed with partial absence of teeth of both jaws - Kennedy class III-IV without correct orthopedic treatment), 17 respondents had flattened occlusal surfaces of teeth after therapeutic treatment, 31 were diagnosed abrasion of varying severity and localization, in all patients - a violation of occlusal relationships. In 56 patients (77.77 %) a combination of several etiological factors was noted. A comparative analysis of EMG indices of paired masticatory muscles in the studied group showed that before the start of dental treatment, patients had uncontrolled bursts of bioelectric activity (BEA) in opposite muscles from opposite sides, an increase in the amplitude of muscle contractions during compression in both muscles (mostly in actually chewing ), decrease in the amplitude of muscle contractions during compression due to the rapid fatigability of muscles at rest. Conclusion. Thus, questions of etiology are still open and subject to further study. Of the many known causes, the most common are violation of occlusal relationships, muscular parafunctions, external traumatic factors, etc. The appearance of bruxism is associated with a significant risk of disturbing the occlusal relationship with a subsequent increase in the load on the tooth enamel. In this regard, a rational comprehensive dental treatment of patients with the studied combined pathology should be carried out after conducting electromyographic studies with samples of “rest”, “compression” and “chewing” strictly in accordance with the indications and timing of dynamic observation at least 1 time in 3 months.

A simplified method for measurement of palatal bone thickness to select the optimum length of orthodontic mini-implant

Introduction The palatal bone is a suitable site for mini-implant placement due to it being a “rootless area” with dense bone. This application has increased with mini-implant-assisted rapid palatal expansion becoming the preferred method of expansion. It is necessary to measure the vertical bone height with a reasonable accuracy, at the implant insertion site, to utilize the maximum available bone support, and to avoid the risk of perforations. As an accepted method, full-volume cone-beam computed tomography (CBCT) scan is advised for the same. This requires an additional procedure, further, radiation exposure, and cost to the patient. The aim of the study was to establish the utility of lateral cephalogram as a simple and reliable method to measure palatal bone thickness for placement of mini-implants in the 1st premolar and 1st molar region, which are the most common sites of mini-implant placement. Materials and Methods A total of 30 CBCT scans and digital lateral cephalograms of patients were selected and analyzed at the 1st premolar and molar region and were statistically evaluated using Student’s t-test and Wilcoxon rank-sum test. Results The results obtained indicated a highly significant correlation between the measurements obtained on lateral cephalograms at both the 1st premolar and 1st molar areas, P &lt; 0.001. Conclusion The data presented show that lateral cephalometry provides a reliable assessment of the quantity of vertical bone for paramedian insertion of a palatal implant.

Anterior open bite correction with hybrid FLOWJAC® system devices, patient with previous Chin bone resorption. Case report.

The orthodontic minitubes system (FLOWJAC ® System, Bogotá, Colombia) is an innovating system that blend the selfligating philosophy techniques and a lowprofile appliance. The FLOWJAC® System works with low orthodontic forces, same as selfligation devices. The system uses heat-treated wires with better physical properties such as hysteresis when is compare with traditional wires. However, the FLOWJAC® technique doesn´t use a wire sequence to get a “working wire”, just a 0,014 Copper NiTi. The clinician in each appointment must modify the minitube location to the clinical desire teeth position. The present report blend FLOWJAC® devices in the upper arch and clear selfligation in the lower arch. The patient treated has mandibular bone resorption due a alloplastic chin augmentation. The root apex from first right premolar to the first left premolar seen to be near to the resorption area using Cone Beam Computer Tomography. That´s the reason why we use a pre-adjust devices in the lower arch, to avoid pulpar and periodontal counter effects. This case was finished with proper functional and aesthetics objectives; such as molar and canine class I, anterior open bite closure with 20% of overbite, coincidence of dental smile arch with lower lip, and without root and pulpar counter effects. The porpoise of this report is to present an orthodontic case with bone resorption on right premolar and incisors area of the mandible. The case was treated with selfligation orthodontics system; FLOWJAC® System in the upper arch and Empower Clear® (American Orthodontics Shebboyiang, USA) in the lower arch and could be done with a precise diagnosis and adequate treatment planning.

Section Plane Effects on Morphometric Values of Microcomputed Tomography.

Objectives Histomorphometry is the established gold standard for inspection of trabecular microstructures in biomaterial research. However, microcomputed tomography can provide images from the perspective of various section planes. The aim of the present study was to evaluate the effects of different section planes, which may cause bias in two-dimensional morphometry, on the morphometric values of microcomputed tomography. Methods A socket preservation technique was performed on the extracted premolar area of 4 beagle dogs. After an 8-week healing period, a total of 16 specimens were obtained and analyzed with conventional histomorphometry and microtomographic morphometry. Using the original images of the histologic specimens for comparison, the most similar tomographic image was selected by trial and error. Then, the section plane was then moved with ±79 μm parallel offsets and rotated ±10° around the center from the occlusal view. The images were compared in terms of bone, graft, and noncalcified area, and the concordance correlation coefficient (CCC) was calculated. Results There was a high CCC in the comparison between histomorphometric images and the most similar microtomographic images. However, the CCC value was low in the comparisons with both parallel movement and rotation. Our results demonstrate that the sectioning plane has a significant effect on measurements. Conclusion Two-dimensional morphometric values for biomaterial research should be interpreted with caution, and the simultaneous use of complementary 3-dimensional tools is recommended.

Comparison of WALA ridge and dental arch dimensions changes after orthodontic treatment using a passive self-ligating system or conventional fixed appliance.

To compare changes in WALA ridge and mandibular dental arch dimensions in orthodontic patients treated with a passive self-ligating system and conventional appliances. Original paper. Orthodontic department at Inga University Center, Maringá, PR, Brazil. Pretreatment (T1) and posttreatment (T2) dental casts of 60 patients with Class I malocclusion treated with slight to moderate crowding that were divided into two groups. Group 1: 30 patients treated with a passive self-ligating system, at a mean initial age of 17.68 years and mean treatment time of 2.31 years. Group 2: 30 patients treated with conventional appliances, at a mean initial age of 19.23 years and mean treatment time of 2.56 years. Measurements were taken using a digital caliper directly on pre and posttreatment dental casts to evaluate the transversal dimension behavior of the mandibular dental arch and the WALA ridge width. Self-ligating group presented an increase in WALA ridge width and mandibular transversal dimensions significantly greater than the conventional group, with the exception of intermolar cusp tip distance and intercanine WALA ridge. There was no statistically significant difference between the groups. There was also observed a significantly greater increase of the transversal buccal axis dimensions in the premolar area when compared to the WALA ridge increase in both groups. Treatment with a passive self-ligating system resulted in a significantly greater increase of the WALA ridge width and mandibular arch dimensions when compared to conventional appliance.

Digital Orthopantomography vs Cone Beam Computed Tomography—Part 1: Detection of Periapical Lesions

Digital orthopantomography (OPT) is usually the first examination step in supervising an incoming patient. Cone beam computed tomography (CBCT) is the most refined and affordable method to search for different dental lesions. The aim of this paper is to evaluate the effectiveness of OPT and CBCT in detecting periapical lesions in different dental groups. An OPT and a CBCT scan of the dental arches of 45 patients were examined. The presence of AP was pointed out for OPT and CBCT. Sensitivity, specificity, predictive values, and accuracy were calculated for OPT, using CBCT as the reference standard. OPT showed low sensitivity (40.0), positive predictive value (90.4), negative predictive value (90.0), accuracy (90.0), and high specificity (99.2). It was found to have higher sensitivity in the lower front and premolar areas, while the lowest was found in the upper molar area. OPT can be used for endodontic diagnosis in the lower central and premolar sections, but CBCT plays a decisive role in the evaluation of molar areas and in the endodontic treatment planning, when a close relationship between apex and important anatomical structures exists. CBCT exposes the patient to higher doses of radiations when compared with OPT, but CBCT, with its more selective sensitivity and the possibility to offer a three-dimensional (3D) rendering of dental and periodontal structures, is an elective choice for uncertain cases and for specific dental areas.

A three-dimensional finite element analysis of the influence of varying implant crest module designs on the stress distribution to the bone

The aim of this study is the effect of stress distribution within the bone with varying implant crest module designs. Finite element models of a straight two-piece 4 mm × 13 mm screw-shaped threaded implant with divergent, straight, and convergent implant crest module with their surrounding suprastructure embedded in mandibular second premolar area were created with ANSYS software. Different implant crest module designs incorporated in D2 types of bone under 100N axial and 100N at 20° oblique load were created to evaluate stress distribution in the crestal bone around implant crest module. Maximum von Mises stress was observed at the crestal region of the bone and at crest module region of the implants in all the models. Divergent crest module design shows minimum von Mises stress at crestal bone during vertical loading within bone and at implant crest module. Straight crest module designs result in minimum stresses during oblique loading than vertical loading. Convergent crest module design shows maximum von Mises stress. Within limitations of the study, it was concluded that stress distribution in adjacent compact bone is greatly influenced by implant crest module design. Divergent crest module designs result in minimum stresses at crestal bone and in the implant crest module region, followed by straight and convergent crest module in ascending order of stress distribution.

Digital Orthopantomography vs Cone Beam Computed Tomography—Part 2: A CBCT Analysis of Factors Influencing the Prevalence of Periapical Lesions

Cone beam computed tomography (CBCT) is the most refined and affordable method available today for the examination of an incoming patient for different dental pathologies. The aim of this paper is to evaluate the significance of some factors influencing the prevalence of apical periodontitis. An ortopantomography (OPT) and CBCT scan of the dental arches were examined for each of the selected 45 patients. The presence of apical periodontitis (AP) was compared for CBCT and OPT examination. Sensitivity, specificity, predictive values, and accuracy were calculated for CBCT, using OPT as a reference. The impact of protective/risk factors on the development of AP was examined. CBCT showed higher sensitivity (250%), predictive values (111%), accuracy (111%), and specificity (101%) than OPT. It was found to have higher sensitivity in all the dentition areas, especially where empty anatomical spaces or more radiotransparent structures have a strict relationship with the tooth apex and periapical structures like upper front area, premolar areas, and, especially, in the upper molar area. The prevalence of AP increased from 16 to 17% in the case of insufficient conservative restoration or 25% in the case of microleakage, 35-42% in the case of prosthetic restoration, 56-67% for posts, and 60 and 85%, respectively, for inadequate endodontic treatment and missed canals. CBCT plays a decisive role in the evaluation of molar areas and in the endodontic treatment planning, when a close relationship between the apex and important anatomical structures exists. Different risk factors with different relevance are identified. As CBCT-examined results show, coronal restorations are moderate-risk factors, while insufficient endodontic treatments and posts are high-risk factors for the development of AP.

Relative frequency of dentigerous cyst in Iranian population: A 20-year retrospective study.

Dentigerous cyst (DC) is the most common type of developmental odontogenic cysts which apparently develops via accumulation of fluid between the reduced enamel epithelium and crown of the tooth. The aim of this study is to analyze the frequency of DC in Iranian population. The files of oral pathology, Shahid Beheshti University of Medical Sciences, served as the source of the materials from 1992 to 2012 for this study. All lesions diagnosed as DCs were subjected to microscopic reevaluation. Patient's age, sex, location, and microscopic characteristics were recorded. Based on these data, a descriptive statistical analysis was performed using SPSS 19 software (IBM SPSS Statistics 19, New York, United States) and the results with P < 0.05 were considered as significant. DC accounted for 34.37% of all odontogenic cysts of the jaws during the 20-year period. The mean age of patients was 24.72 years and most cases are diagnosed in the second and third decades of life. The male-to-female ratio was 1.52. About 73.89% of all lesions had occurred in the mandible and 26.11% in maxilla. DCs showed Vickers and Gorlin (ameloblastomatous) changes in 2.36% of cases. The mean age was significantly lower in the premolar area (P = 0.00). Age, sex, and location of DCs in Iranian population are similar to previous studies. In addition, the age of occurrence for this lesion in the premolar region was relatively lower than at other sites. Although the risk of ameloblastic change is low, it should be considered as an important issue.

Comparing different bar materials for mandibular implant-supported overdenture: Finite-element analysis

<br><b>Aim:</b> This study was conducted aiming to optimize the selection of bar material that can minimize stresses on mandibular bone. <b>Subjects and Methods:</b> One finite-element model was created under ANSYS environment to evaluate the use of different materials as a bar-manufacturing material in mandibular implant-supported overdenture (OD). Model components were created on engineering computer-aided design software and then assembled under the finite-element package. A force of 200 N was unilaterally and vertically applied on the left second premolar area. <b>Results:</b> Within these study conditions, the polyether ether ketone bar produced the lowest Von Mises stress on OD and the maximum value of deformation. Stainless steel bar produced the maximum OD total deformation. <b>Conclusions:</b> Cortical and spongy bones are not sensitive to the bar material. Increasing bar material stiffness increases Von Mises stresses in the bar itself and reduces its total deformation, in what is called overconstrained system.<br>

Influence of Hyrax screw position on dental movement and cortical bone: A study of finite elements.

BackgroundRapid maxillary expansion (RME) has effects on the dental and periodontal structures of the parts involved, which vary according to the design and position of the expansion screw. The purpose of the study was to determine the optimal three-dimensional position of the Hyrax screw to obtain precise control of the dental movement and effect on the bone cortex using the finite element method (FEM).Material and MethodsRME was performed from the patient whom two Cone-Beam computerized tomography scans (CBCT) were obtained: T1 before expansion, and T2 three months after stabilization of RME. The FEM model was designed with T1 and of Hyrax photographs. FEM was obtained by comparing the simulation, T2, and clinical results. Three sagittal screw positions (anterior-middle-posterior) and vertical (upper-medium-low) were evaluated.ResultsA coronal- buccal displacement of premolars and first molars was found which decreased in the occlusal-apical direction, presenting different types of dental movement in the screw positions; besides, a tendency of translational movement in the posterior-high location was observed. In the posterior-high position a higher concentration of efforts and homogeneous deformations in the periodontal ligament and vestibular cortex of the cervical area of first molars, first and second premolars were observed, with variations according to the screw position and the distribution of stresses.ConclusionsThe ideal location of the expansion screw for controlling dental movement and periodontal side effects was the high-posterior position. Key words:Maxillary expansion, dental movement, finite element analysis, orthodontic appliances.

Dental implant displacement in the maxillary sinus: A case report

Case report informationThis case report describes clinical and radiographic features of a 30 years old female patient suffering from an accidental displacement of dental implant into the maxillary sinus. Clinical presentationShe started to feel dyspneic, voice changing, headache and nocturnal snoring. She went to see an otorhinolaryngologist to address those symptoms, a complete clinical and radiographic work up revealed; adenoid with unilateral nasal blockage that could be associated with displaced dental implant into the right maxillary sinus. Clinical examinationThe patient had poor oral hygiene and bad attitude toward dentistry. She presented with multiple missing teeth and many defective prosthesis. A panoramic film showed the horizontally displaced implant and the significance of the iatrogenic damage. Computerized tomography (CT) Report Computerized tomography (CT) sections in the coronal (A), sagittal (B), axial (C) and surface rendered view (D), of the paranasal sinuses showed that both extension of the maxillary sinus floor inferiorly and severe marginal alveolar bone loss have resulted in marked reduction in the dimensions of the residual alveolar ridge in the area of the missing posterior teeth in the upper right side. An unloaded dental implant was dislodged into the right maxillary sinus which is totally opacified with blockage of the ostium communication between the sinus and the nasal cavity. The wall of the right maxillary sinus in interrupted at the posterioinferiolateral corner (white arrow). ConclusionThe dental implant preoperative assessment of sites in the maxillary premolar and molar areas must include radiographic assessment of the residual maxillary alveolar ridge relation to the maxillary sinus in all dimension. Although the recommended post implant insertion radiographic examinations are intraoral radiographs and panoramic radiographs, when surgical complication are expected, the radiographic examination should include sectional images in all dimensions acquire. CBCT or CT that will help in the diagnosis, treatment planning and treatment.