Injury Risk Estimation in Mandible-Related Surgical Procedures: A CBCT Study Based on Vital Interforaminal Anatomical Structures.

The mandibular interforaminal region has been considered safe for surgical procedures; nevertheless, the risk of injury to neurovascular structures, such as the mental foramen (MF) and its related structures (anterior loop [AL] and lingual foramina [LF]) should not be overlooked. The study aimed to evaluate the relative risk of injury to these structures during surgical procedures in the anterior region of the mandible based on cone-beam computed tomography (CBCT) scans. A retrospective cross-sectional and observational study was performed on 250 CBCTs from adults (18-69 years) with dentate jaws. Linear measurements of the MF, AL, and LF were evaluated to estimate the risk of injury to these structures during chin-related surgical procedures. The most frequent distance between the base of the mandible (BM) and MF was 8 mm (30.2%). In addition, 20.4% of the CTs had 6 mm from the vestibular cortical bone to the LF. The commonly found measurement from LF to the apex of the nearest tooth was 7 mm (24.0%); 64.2% of the CTs showed a 2-mm distance between the most distal point of the dental implant site to the most anterior point of the AL. Safety distances for genioplasty techniques (MF to mandible base > 6 mm, 96.6% [CI 95%, 95.0%-98.2%]) were observed. Considering the 5-mm cut-off point between the lower limit of a hypothetical bone graft and the chin, 65.4% (CI 95%, 58.9%-71.9%) of CTs were within this distance. Regarding the safety margin of 8 mm, 85.6% (CI 95%, 80.8%-90.4%) were up to this value. This study found safety margins for genioplasty and chin bone grafting surgical techniques that adopt a 5-mm cut-off point. Further similar studies assessing other surgical methods and employing larger samples from different geographical origins may contribute to this field of investigation.

Morphometric aspects and proposal of a new classification of genial tubercles in cone-beam computed tomography in a Brazilian population.

Objective: This study evaluated epidemiological and morphological aspects of genial tubercles (GTs) using cone-beam computed tomography (CBCT). Methods: This retrospective, observational and cross-sectional study evaluated 276 tomographs of adult dentate individuals (18-69 years). The presence and absence of GTs were evaluated, and in cases in which this structure was observed, linear measurements (length, height, and width), and anatomical distances. In addition, a GT classification was proposed based on the presence, number, and location of the tubercles. Results: Of the 276 CT scans, 28 (10.14%) had absence of GTs and in 248 CT scans GTs were present, of which 42 (57.5%) were from females and 106 (42.5%) from males. Regarding the number of GTS, the most prevalent variant was the two-tubercle-variant (143, 57.7%), followed by the presence of a single tubercle (n = 62, 25.0%), 3 tubercles (n = 40, 16.1%) and 4 tubercles (n = 3, 1.2%). The most prevalent classification was IIIA (n = 96, 38.7%), followed by IIIB (n = 60, 36.3%), IIA (n = 53, 21.4%) and IIB (n = 9, 3.6%). Conclusion: A prevalence of GT of approximately 90% was observed, with two GTs per exam as the most frequent finding. Men had a longer mean GT length compared to women. Female individuals exhibited a shorter distance from the base of the GT to the base of the mandible.

Mandibular incisive canal-related prevalence, morphometric parameters, and implant placement implications: a multicenter study of 847 CBCT scans

BACKGROUND: This study evaluated the epidemiological and morphological features of the mandibular incisive canal (MIC) using cone beam computed tomography (CBCT) in a significant sample of subjects in Brazil. MATERIAL AND METHODS: This retrospective, multicenter study assessed 847 CBCT scans performed at four oral imaging centers. The sample comprised CBCT images acquired from dentate individuals who presented at least from tooth 35 to tooth 45 in the anterior mandible region. Data regarding patient sex and age, and MIC linear measurements (length and diameter in mm), anatomical distances (to the alveolar, buccal and lingual cortexes, inferior border of the mandible, and adjacent teeth apexes), and location were obtained. RESULTS: The MIC was more prevalent in women (76.3% [p < 0.001]) between the fourth and sixth decades of life (p < 0.001). It was present bilaterally (p < 0.001) and exhibited a mean length of 7.7 mm (standard deviation [SD]=3.7 mm). Spearman correlation and logistic regression analysis revealed collinearity between age and linear measurements (p < 0.05). The mean distances varied from the initial to the final portion of the MIC, respectively, in relation to the buccal cortex (mean = 2.6 mm, SD = 1.27; mean=3.96 mm; SD =1 .43), to lingual cortex (mean=5.13 mm; SD=1.7; mean = 4.61 mm, SD = 1.65), and to the inferior mandibular border (mean = 9.32 mm, SD = 1.92; mean=8.76 mm, SD = 2.07 mm). The difference in the proximity of the MIC to the apex of the inferior lateral incisor was statistically significant (p < 0.05). CONCLUSIONS: Results of this study revealed a high prevalence of MIC with a bilateral pattern in women who were between the fourth and sixth decades of life. Both the distance between the MIC and the lingual cortex of the mandibular alveolar bone, and the diameter of the MIC, decreased as its trajectory assumed a more anterior position

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Influence of abutment disconnection on peri-implant marginal bone loss: A randomized clinical trial.

OBJECTIVES: To evaluate the influence of abutment disconnections and reconnections on peri-implant marginal bone loss. MATERIAL AND METHODS: Twenty-four participants received single-unit implants and were randomly assigned into one of the two groups: the definitive abutment group (DEF), in which the definitive abutments were connected at the same time as the implant was inserted; and as a control, the healing abutment group (HEA), in which the healing abutments were disconnected and reconnected three times, at 8, 10, and 12 weeks after surgery. Peri-implant marginal bone level was measured through radiographic follow-up performed immediately after the surgery (baseline), at 8 weeks and after 6, 12, and 24 months. Implant stability and peri-implant health were assessed by resonance frequency analysis and peri-implant probing, respectively. RESULTS: At the end of 2 years, the mean bone level was -0.18 ± 0.12 mm for the DEF group and -0.13 ± 0.13 mm for the HEA group, resulting in a cumulative bone loss of -0.61 ± 0.10 mm and -0.81 ± 0.15 mm, respectively, with no statistical difference between groups. Bone level changes showed statistically significant differences only between 0 and 2 months (DEF: -0.70 ± 0.12 mm; HEA: -0.36 ± 0.10 mm) and between 2 and 6 months (DEF: -0.11 ± 0.11 mm; HEA: -0.65 ± 0.14 mm). No differences were observed between the groups for implant stability, probing depth, and bleeding on probing. CONCLUSION: Immediate connection of the prosthetic abutments did not reduce bone loss in comparison with three disconnections of the healing abutments.

Imaging Aspects of the Mandibular Incisive Canal: A PROSPERO-Registered Systematic Review and Meta-Analysis of Cone Beam Computed Tomography Studies

PURPOSE: This study aimed to perform a systematic review and meta-analysis of the literature on the mandibular incisive canal (MIC) studies using cone beam computed tomography (CBCT). MATERIALS AND METHODS: A PROSPERO-registered systematic review (#42017056619) was conducted following the PRISMA statements to summarize current knowledge on the CBCT aspects of the MIC. A search was performed in PubMed's Medline and Scopus databases, without date or language restrictions, using the algorithm {[(Interforaminal region) OR (mandibular incisive channel) OR (mandibular incisive nerve) OR (mental mandible) OR (anterior mandible) (cone beam computed tomography). Also, the references were crosschecked. The Meta-Analysis of Statistics Assessment and Review Instrument and meta-analysis was used to evaluate the selected studies. RESULTS: A total of 410 articles were found, and 25 studies were selected after a two-step selection process. The CBCT systems differed regarding field of view (FOV) (large, n = 3; medium, n = 2; small, n = 4; not informed, n = 16) and voxel size (0.15 to 0.4 mm). Geographically, the studies were distributed across four continents (South America, North America, Asia, and Europe), and there was a statistical significance of studies from the American and Asian continents (P < .0001). From 3,421 CBCT exams, the number of female patients was slightly higher than male, and the mean age ranged from 29.8 to 59.1 years. The overall mean prevalence of MIC was 89.6% ± 15.08%, and bilateral occurrence was statistically significant (P < .0001). The studies using a voxel size lower than 0.3 mm showed the highest mean prevalence (93.88%) in comparison with voxel size described as ≥ 0.3 mm (89.33%). Diameter (0.45 to 4.12 mm) and length (6.6 to 40.3 mm) showed great variability among the included studies. CONCLUSION: In summary, the results of this systematic review evidenced a high worldwide prevalence of MIC. There was no prevalence of MIC in relation to sex, and its presence was mainly related to adults between the fourth and sixth decades of life. In addition, great heterogeneity of methodologies was observed.

The relative frequency of odontogenic tumors: A study of 376 cases in a Brazilian population

BACKGROUND: Odontogenic tumors (OTs) are rare lesions, exclusive of the jaws, that are derived from epithelial and/or ectomesenchymal elements of the tooth-forming apparatus. Their biological behavior is heterogeneous, including hamartomatous tissue proliferation, benign nonaggressive and aggressive neoplasms, and malignant tumors with metastatic capacity. The aim of this study was to describe the relative frequency of odontogenic tumors in a Brazilian population. In addition, a review of the literature identified studies on odontogenic tumors that follow the 2005 World Health Organization. MATERIAL AND METHODS: A total of 376 cases of odontogenic tumors from an oral pathology service were reviewed about age, gender, anatomic site and histologic diagnosis. RESULTS: Keratocystic odontogenic tumors (31.6%) were the most common, followed by ameloblastoma (28.5%), and odontoma (22.6%). The mean age was 32.2 years, and more than half the patients (52.1%) were in the second and third decades of life. The male to female ratio was 1:1.37, with a maxilla to mandible ratio of 1:2.08. CONCLUSIONS: The variation in relative frequency of tumors observed among the several series, including the present study, is probably due in part to cultural differences between geographic areas but also to the study design

Analysis of the reproducibility of the gray values and noise of a direct digital radiography system.

The aim of this study was to evaluate the reproducibility of the gray values and noise of a direct digital radiography system (Visualix eHD) for various exposure times and analyzed regions. To obtain radiographic images in a standardized manner, the digital sensor of the system and a stepwedge were positioned in a phantom at a focus-film distance of 30 cm in a dental device at 70 kV, 7 mA and 2.2 mm filtration. Ten consecutive repetitions of X-ray imaging were performed at each exposure time (0.05, 0.07, 0.09 and 0.13 s). Gray values were analyzed using ImageJ software in five regions of interest (ROIs): alveolar bone (AB), soft tissue (ST) and three steps of the stepwedge (S1, S2 and S3). The results showed that both the variability of the gray values and the noise were statistically greater (p < 0.05) in the most radiolucent region (ST). Only the noise was affected by the exposure time. In conclusion, the reproducibility of the gray values and the noise of the Visualix eHD system can vary in specific areas with different radiolucency.

Analysis of the reproducibility of the gray values and noise of a direct digital radiography system

The aim of this study was to evaluate the reproducibility of the gray values and noise of a direct digital radiography system (Visualix eHD) for various exposure times and analyzed regions. To obtain radiographic images in a standardized manner, the digital sensor of the system and a stepwedge were positioned in a phantom at a focus-film distance of 30 cm in a dental device at 70 kV, 7 mA and 2.2 mm filtration. Ten consecutive repetitions of X-ray imaging were performed at each exposure time (0.05, 0.07, 0.09 and 0.13 s). Gray values were analyzed using ImageJ software in five regions of interest (ROIs): alveolar bone (AB), soft tissue (ST) and three steps of the stepwedge (S1, S2 and S3). The results showed that both the variability of the gray values and the noise were statistically greater (p < 0.05) in the most radiolucent region (ST). Only the noise was affected by the exposure time. In conclusion, the reproducibility of the gray values and the noise of the Visualix eHD system can vary in specific areas with different radiolucency.

Radiological and histopathological evaluation of experimentally-induced periapical lesion in rats

OBJECTIVE: This study evaluated experimentally-induced periapical bone loss sites using digital radiographic and histopathologic parameters. MATERIAL AND METHODS: Twenty-seven Wistar rats were submitted to coronal opening of their mandibular right first molars. They were radiographed at 2, 15 and 30 days after the operative procedure by two digital radiographic storage phosphor plates (Digora®). The images were analyzed by creating a region of interest at the periapical region of each tooth (ImageJ) and registering the corresponding pixel values. After the sacrifice, the specimens were submitted to microscopic analysis in order to confirm the pulpal and periapical status of the tooth. RESULTS: There was significant statistically difference between the control and test sides in all the experimental periods regarding the pixel values (two-way ANOVA; p<0.05). CONCLUSIONS: The microscopic analysis proved that a periapical disease development occurred during the experimental periods with an evolution from pulpal necrosis to periapical bone resorption.

Radiological and histopathological evaluation of experimentally-induced periapical lesion in rats.

OBJECTIVE: This study evaluated experimentally-induced periapical bone loss sites using digital radiographic and histopathologic parameters. MATERIAL AND METHODS: Twenty-seven Wistar rats were submitted to coronal opening of their mandibular right first molars. They were radiographed at 2, 15 and 30 days after the operative procedure by two digital radiographic storage phosphor plates (Digora®). The images were analyzed by creating a region of interest at the periapical region of each tooth (ImageJ) and registering the corresponding pixel values. After the sacrifice, the specimens were submitted to microscopic analysis in order to confirm the pulpal and periapical status of the tooth. RESULTS: There was significant statistically difference between the control and test sides in all the experimental periods regarding the pixel values (two-way ANOVA; p<0.05). CONCLUSIONS: The microscopic analysis proved that a periapical disease development occurred during the experimental periods with an evolution from pulpal necrosis to periapical bone resorption.

Estudo microscópico morfométrico e genotípico de pacientes portadores de lesão central de células gigantes / Microscopic morphometric and genotypic assessment of patients with central giant cell lesions

A lesão central de células gigantes (LCCG) é uma afecção benigna dos maxilares, de comportamento biológico incerto, variando de discreta tumefação assintomática e de crescimento lento à uma forma agressiva, associada a dor, reabsorção radicular e óssea, com destruição cortical. Sua etiologia permanece desconhecida, havendo controvérsias entre processo reacional, neoplásico ou genético. Mutações no gene SH3BP2 foram identificadas em pacientes com querubismo, condição que compartilha várias características clínicas, radiográficas e histopatológicas com a LCCG. Para testar a hipótese de que tais mutações seriam responsáveis por, ou estariam associadas a LCCG e na tentativa de melhor entender a diferenciação microscópica/morfométrica das lesões agressivas e não agressivas, vinte e cinco pacientes portadores de LCCG foram selecionados para o estudo. O DNA foi obtido através do sangue e de espécimes em blocos de parafina, oriundos de biópsias e tratamento cirúrgico. Um estudo microscópico morfométrico foi paralelamente realizado, para avaliar o número de células gigantes e densidade de volume das mesmas nas lesões agressivas e não agressivas. O sequenciamento genético dos treze exons do gene SH3BP2 nos vinte e cinco pacientes estudados evidenciou uma alteração no códon do exon 4 em 10 pacientes. A densidade de volume de células gigantes foi maior nas lesões agressivas quando comparadas às não agressivas (p=0,013). Não houve diferença significante quanto ao número de células gigantes/mm2 em lesões agressivas e não agressivas (p =0,245).

Central giant cell lesion (CGCL) is a benign disease of the jaws, with uncertain behavior, ranging from mild asymptomatic slow-growing swelling to an aggressive form, with pain, radicular and bone resorption and cortical destruction. Its aetiology is still unknown and there is discussion whether it is a reactive, neoplastic or genetic disease. Mutations on gene SH3BP3 were identified in patients with cherubism, which shares several clinical, radiographic and histopathological features with CGCL. In order to test the hypothesis that such mutations would be responsible for or would be related to CGCL and also in order to better understand microscopic morphometric differentiation of the aggressive and non-aggressive lesions, 25 patients with CGCL were selected to this study. DNA was extracted from blood samples and from tissue samples, obtained by biopsy or surgical treatment. Microscopic morphometric assessment was also performed, in order to evaluate the number and the volume density of the giant cells in aggressive and in non-aggressive lesions. Gene sequencing of all 13 exons in gene SH3BP3, performed on each of the 25 patients, showed an alteration in one codon from exon 4, in ten patients. Volume density of giant cells was greater in aggressive lesions than in non-aggressive ones (p=0,013). There was no significant difference on the number of giant cells per mm2 when comparing aggressive and non-aggressive lesions.