The Effect of Calcium Hydroxide Pastes on Isolated Vital Nerve Fibers.

INTRODUCTION: Calcium hydroxide pastes (CHPs), commonly used for disinfecting root canals during endodontic treatment, are generally considered safe. However, accidental extrusions result in minimal injuries and little to no discomfort, except when extruded pastes come into contact with nerve bundles, such as the inferior alveolar nerve. Currently, there is a lack of information about the possible role of specific paste vehicles on the extent of nerve injury. The purpose of this study was to compare the role that paste vehicles, such as water or methylcellulose, may play when nerve fibers are exposed to CHP. METHODS: Isolated sciatic nerves of Sprague-Dawley rats were exposed to either water-based or methylcellulose-based CHP for varying durations of time (30, 60, or 90 minutes). Histopathological changes, including axonal edema, myelin alterations, and loss of cellular outlines, were assessed, and the degrees of changes were compared using chi-square intraclass correlation coefficient tests. RESULTS: Both groups exposed to the pastes demonstrated varying degrees of histopathologic changes, including axonal edema, myelin changes, and loss of cellular outlines, at different exposure times. The water-based calcium hydroxide paste induced these changes more rapidly than the methylcellulose-based paste. Similar patterns were observed in the scanning electron microscopic findings. Exposure time emerged as an important difference in the effects of the 2 pastes. In each of these tests, all observations of water-based paste exposure were rated as moderate to severe, whereas the observed cellular changes (axonal, myelin, and intact cellular outline) were rated as mild to moderate after exposure to methylcellulose-based paste for the same exposure durations. The chi-square tests indicated a statistically significant association between the material and each of the outcomes (axonal changes: χ²15 = 81.0, P < .001; myelin changes: χ²15 = 81.0, P < .001; intact cellular outline, χ²15 = 81.0, P < .001). The intraclass correlation coefficient value was 0.93. CONCLUSIONS: The study demonstrates that axonal and myelin damage increase with longer exposure times, with water-based CHP causing more damage than methylcellulose-based CHP at each time point.

Effects of Apical Barriers and Root Filling Materials on Stress Distribution in Immature Teeth: Finite Element Analysis Study.

PURPOSE: A finite element analysis (FEA) study was performed to determine whether the material of apical barrier used for root apexification and/or the use of canal reinforcement affect the stress distribution in an endodontically treated immature permanent tooth in order to infer in which clinical scenarios a fracture is more likely to occur based on the ultimate tensile strength threshold of dentin. METHODS AND MATERIALS: An extracted human immature mandibular premolar was selected as the reference model and scanned by micro-computed tomography (micro-CT). The digital model was segmented and converted to STL (Standard Tessellation Language) using Simpleware Scan-IP and exported in IGES (Initial Graphics Exchange Specification) to Ansys 19. Six experimental models were designed with different combinations of composite, mineral trioxide aggregate (MTA), and Biodentine (BIO). Using FEA, a static 300 N load at a 135 angle with respect to the axis of the tooth was applied to each model and von Mises stress values (MPa) were measured at the sagittal, apical 8-mm, 5-mm, 2-mm, and 1-mm levels. RESULTS: In all regions examined, the control (NT model) had lower stress in the root compared WITH experimental models. At the mid-root level, models with composite, MTA, and BIO reinforcement exhibited lower stresses in the root dentin than those with pulp or gutta-percha. BIO models had equal or greater average von Mises stress values than those of MTA models in all regions. Both, MTA and BIO, caused increases in stress of surrounding root dentin, with BIO causing a greater increase than MTA. CONCLUSIONS: Stress distribution in immature permanent teeth treated by apexification is affected by the types of materials used. Root dentin's stress was lower when the mid-root canal was reinforced by composite, MTA, or BIO, which provided similar stress reduction to the root dentin. MTA is a more favorable apical barrier material from a mechanical standpoint because it induces less stress on apical root dentin than BIO.

Imaging of the upper airway: which method is best for orthodontic assessment?

The objectives of the present study were to compare measurements of pharyngeal airway subregions on lateral cephalometric (LC) and cone beam computed tomographic (CBCT) images in relation to skeletal classes and discuss the advantages and disadvantages of these imaging formats for this type of assessment. The CBCT images were assessed via both multiplanar reconstruction (MPR) and 3-dimensional (3D) reconstruction. The LC and CBCT images from 107 patients were classified according to skeletal class: I, n = 35; II, n = 35; and III, n = 37. Linear measurements of the subdivisions of the upper airway were performed on the LC, MPR, and 3D images. In addition, area and volumetric measurements were performed on the MPR images. The relationships among imaging methods, skeletal class, and pharyngeal thirds were assessed by means of a 1-way analysis of variance (α = 0.05). No statistically significant differences in the linear, area, or volumetric measurements of the upper airway subregions were found among the skeletal classes (P > 0.05). For the linear measurements in the oropharynx and hypopharynx, greater values were observed for the LC images than for the MPR and 3D images (P ≤ 0.05). Based on the study findings, MPR images should be preferred for visualization of the pharyngeal airway subregions. However, LC imaging is preferable to 3D reconstruction.

Does the administration of meloxicam before head and neck radiotherapy reduce the risk of mandibular osteoradionecrosis? An animal model study.

OBJECTIVE: To assess whether the administration of meloxicam before head and neck radiotherapy reduces the risk of mandibular osteoradionecrosis in rats. MATERIAL AND METHODS: Sixty male Wistar rats were randomly divided into 6 groups (n = 10) according to the meloxicam administration and radiation therapy: control (C), irradiated (I), single dose of meloxicam (M1), single dose of meloxicam and irradiated (M1I), triple dose of meloxicam (M3), triple dose of meloxicam and irradiated (M3I). Meloxicam was administrated (20 mg/kg per dose) 1 h before the radiation therapy (single dose of 20 Gy) and 24 h and 48 h after the radiation therapy for groups with two additional doses. Ten days after the radiation therapy, the three right mandibular molars were extracted from all rats, who were euthanatized after 21 or 35 days (n = 5 per group). The mandibles were assessed by macroscopic evaluation and micro-CT analysis. RESULTS: The right hemimandibles of the irradiated groups revealed macroscopic signs of osteoradionecrosis, and those of the non-irradiated groups revealed complete gingival healing. A significant delay in alveolar socket healing in all irradiated groups was observed in the micro-CT assessment regardless meloxicam treatment. CONCLUSION: The administration of meloxicam before head and neck radiotherapy does not reduce the risk of mandibular osteoradionecrosis when associated to dental extractions. CLINICAL RELEVANCE: Since meloxicam has been shown to be a potential radiation-protective agent, and osteoradionecrosis physiopathology is believed to be related to an inflammatory process, possible interactions are relevant to be investigated.

Strategies and operational procedures in oral radiology to mitigate potential SARS-CoV-2 transmission / Estrategias y procedimientos operacionales en Radiología Oral para mitigar transmisión de SARS-CoV-2

SUMMARY Coronavirus disease (COVID-19) is highly transmissible through respiratory droplets, saliva, and aerosol particles. Infection can lead to severe acute respiratory syndrome and trigger multi-organ failure and death. Most clinical dental procedures involve contact with saliva or the generation of aerosols with saliva and blood. These airborne particles increase the risk of transmission by COVID-19 between dentists and patients. Thus, dentistry must adopt procedures to reduce transmission during dental procedures. Although these strategies may not be directly applicable to all institutions due to cultural, social, geographical, and economic differences, the underlying principles and implemented strategies remain relevant and can be adopted or modified by the institutions dealing with the current COVID-19 outbreak. The purpose of this article is to discuss one of the principal sources of COVID-19 transmission: saliva, the biofluid most frequently handled in a radiology environment. The authors also recommend strategies and operational procedures to decrease the spread of COVID-19 in a radiological routine.

RESUMEN La enfermedad por coronavirus (COVID-19) se transmite fácilmente a través de gotitas respiratorias, saliva y partículas de aerosol. La infección puede desencadenar un síndrome respiratorio agudo severo, insuficiencia multiorgánica y, en algunos casos, la muerte. Los procedimientos clínicos dentales determinan el contacto con saliva o la generación de aerosoles con saliva y sangre, lo que implica un alto riesgo de transmisión por COVID-19 entre odontólogos y pacientes. Por ello, la práctica odontologica debe adoptar medidas para detener la propagación durante los procedimientos dentales. En este artículo se revisan las estrategias para mitigar el riesgo de transmisión de COVID-19. Si bien estas estrategias pueden no ser directamente aplicables a todas las instituciones debido a diferencias culturales, sociales, geográficas y económicas inherentes, los principios subyacentes y las estrategias implementadas siguen siendo relevantes y pueden ser adoptados o modificados por las instituciones que se ocupan del brote actual de COVID-19. El propósito de este artículo es discutir una de las principales fuentes de transmisión de COVID-19: la saliva, el biofluido que se maneja con mayor frecuencia en un entorno radiológico. Los autores también recomiendan estrategias y procedimientos operativos para disminuir la propagación de COVID-19 en una rutina radiológica.

Measurement of erosion depth using microcomputed tomography and light microscopy.

Tooth-erosion is the surface loss of dental hard tissue mostly associated with an acid attack. The aim was to compare dentin and enamel erosion depth measurements using micro-computed tomography (microCT) and light microscopy (LM). Enamel/dentin blocks were prepared from caries-free human molar-teeth (N = 12). Teeth were sectioned to a rectangular shape of 4 × 4 × 6 mm. Specimens were treated with water (NC) or 1.0% citric-acid solution (PC). After treatment, specimens were scanned with micro-computed tomography. On completion, specimens were sectioned and observed under a light-microscope. Lesion depth was observed with 10× magnification and images transferred to Simpleware software. Vertical distance from lesion surface to bottom was measured. Pearson correlation test was used to evaluate correlation and Wilcoxon Signed Rank test to evaluate differences in the two-analysis methods. Mean enamel erosion depth was 0.63 and 38.38 µm (microCT) and 0.54 and 39.43 µm (LM) for NC and PC, respectively. Dentin erosion depth was 0.72 and 48.05 µm (microCT) and 0.56 and 49.92 µm (LM) for NC and PC, respectively. There was a significant correlation between the two-analysis methods (r = 0.998; p < .001). No statistically significant difference in results were obtained when microCT and LM were compared (p = .584). This results obtained from the current study suggested that erosion depth measurements made using microCT and LM yielded comparable results. The microCT method is preferred if the conservation of specimens is desired.

A modified protocol of mandibular osteoradionecrosis induction in rats with external beam radiation therapy.

OBJECTIVE: To propose a modified protocol of mandibular osteoradionecrosis induction in rats with external beam radiation therapy. MATERIAL AND METHODS: A total of 45 male Wistar rats were used in this study. Firstly, 25 rats were divided into 5 groups (n = 5) according to the radiation dose protocol: without irradiation and irradiated with 15 Gy, 20 Gy, 25 Gy, or 30 Gy using a linear accelerator. Secondly, 15 other rats were divided into 3 groups (n = 5) according to the time of extraction of the three right mandibular molars: 7, 10, or 14 days after irradiation of 20 Gy. Lastly, dental extractions were performed in 5 other rats without irradiation (C-E10) for comparison with those of the group of dental extractions 10 days after irradiation (I-E10). RESULTS: The irradiated animals survived throughout the study period only at single doses of 15 Gy and 20 Gy. The suitable time for dental extractions after irradiation to induce mandibular osteoradionecrosis was defined as 10 days. Macroscopic evaluation of the right hemimandibles showed presence of osteoradionecrosis in I-E10 group and complete gingival healing in C-E10 group. CONCLUSION: A single radiation dose of 20 Gy focused on head and neck region combined with the extraction of the three mandibular molars 10 days after irradiation constitutes a feasible protocol of mandibular osteoradionecrosis induction in rats with external beam radiation therapy. CLINICAL RELEVANCE: Establishing a solid and widely available protocol of mandibular osteoradionecrosis induction is essential in the search for methods to prevent this complex disease.

The relationship of articular eminence and mandibular fossa morphology to facial profile and gender determined by cone beam computed tomography.

OBJECTIVE: The aim of this study was to evaluate the relationship of the morphology of the articular eminence and mandibular fossa to facial profile and sex by using cone beam computed tomography (CBCT) images. STUDY DESIGN: CBCT examinations of 76 patients were conducted, and the patients were classified according to facial profile as dolichocephalic, mesocephalic, or brachycephalic. The inclination and height of the articular eminence and the inclination of the mandibular fossa of 152 temporomandibular joints were measured. Comparisons between these measurements and facial profile and gender were performed by 2-way analysis of variance with Tukey's post hoc test. Significance was established at α = 0.05. RESULTS: Males with brachycephaly presented significantly greater values of eminence inclination compared with those with other facial types and greater values than patients with dolichocephaly for the measurements of eminence height and inclination of the fossa posterior wall (P ≤ .05). Females with brachycephaly presented significantly greater eminence height values compared with those with other facial profiles (P ≤ .05). No significant differences were observed between males and females. CONCLUSIONS: The morphology of the articular eminence and the mandibular fossa is associated with facial profile, with males with brachycephaly showing greater inclination of the eminence and mandibular fossa. Articular eminence height in brachycephaly was greater in both sexes.

Evaluation of the articular eminence and the occlusal surface of the molars by cone beam computed tomography.

The objective of this study was to utilize cone beam computed tomography (CBCT) to evaluate the posterior slope of the articular eminence and the lateral slope of the mandibular fossa in relation to the cusp-fossa angle of the first molars. The evaluation included 93 CBCT images from 93 patients aged 16-30 years. The angle of the posterior slope of the articular eminence was determined from the intersection of a line tangent to the uppermost point of the mandibular fossa and another line tangent to the slope of the anterior wall of the mandibular fossa. The angle of the mandibular fossa slope was determined from the intersection of a line tangent to the most superior point of the mandibular fossa and another line tangent to the slope of the lateral wall of the mandibular fossa. The cusp-fossa relationship of the maxillary and mandibular first molars was also verified on the CBCTs. There was a correlation between the angles of the mandibular left first molar fossa and the lateral slope of the left mandibular fossa. There was also a correlation between the cusp height of the mandibular left first molar and the angle of the lateral slope of the right mandibular fossa. Dentists should consider anatomical factors during restorative, prosthodontic, and orthodontic treatment planning, especially for treatment that will affect the molars, to prevent the development of occlusal interferences that can trigger temporomandibular disorders.

Correlation between midline deviation and condylar position in patients with Class II malocclusion: A cone-beam computed tomography evaluation.

INTRODUCTION: Midline deviation of the mandible and maxilla can affect craniofacial growth and occlusion and cause consequences to the temporomandibular joint. The aim of this study was to evaluate the lateral displacement of the skeletal and dental midlines in relation to the condyle head position in Class II patients with cone-beam computed tomography. METHODS: We used 82 cone-beam computed tomography images. The lateral displacement of the skeletal and dental midlines considering the 3-dimensional reference plane was analyzed with points in the maxillary and mandibular central incisors, anterior nasal spine, and menton. The condyle-fossa relationship, concentric position of the condyles, and dimensional and positional symmetries between the right and left condyles were evaluated. RESULTS: There was a statistically significant difference regarding anterior nasal spine with maxillary central incisor, menton, and mandibular central incisor points for both sides, and also for maxillary central incisor-menton for the displacement of the left side. We found differences in the temporomandibular joint for inclination and diameter measurements of the condylar process. Strong correlations were observed between the maxilla and the condylar process diameter (right side) and the distance between the geometric centers (left side), in addition to a strong correlation between the sagittal midline displacement and the geometric center differences on the right and left sides. CONCLUSIONS: In patients with Class II malocclusion, lateral displacement of skeletal and dental midlines in relation to the condyle head position has a significant correlation with the anteroposterior difference between the geometric center of the right and left condylar processes.

Simple bone cyst: rare incidental finding in the mandibular condyle by cone beam computed tomography.

The simple bone cyst (SBC) is a benign intraosseous lesion that is considered to be a pseudocyst because the cystic cavity does not present an epithelial lining. The most accepted theory regarding its etiology is that the SBC develops when the blood clot fails to organize subsequent to bleeding caused by trauma. The SBC is asymptomatic, and therefore the diagnosis is made through routine imaging examinations. In imaging examinations, the lesion is characterized by a radiolucent, unilocular, well-delimited appearance and an irregular or scalloped contour with or without a sclerotic halo. This case report describes an SBC in the mandibular condyle region, discovered incidentally on imaging examinations.

Analysis of the correlation between dental arch and articular eminence morphology: a cone beam computed tomography study.

OBJECTIVE: The aim of the study was to assess the correlation between the morphology of the dental arches (DAs) of patients with normal occlusion and of the articular eminence (AE) by using cone beam computed tomography (CBCT). STUDY DESIGN: CBCT scans of 60 patients were evaluated in terms of height and inclinations (angles α, ß, and δ) of the AE. DAs were classified according to their shapes (tapered, square, ovoid), and their perimeters, widths, and depths were measured. One-way analysis of variance, Pearson's correlation coefficients, and simple and multivariate linear regression models were used for the calculations. RESULTS: The ovoid arch was the most predominant shape (n = 66/120). Inclination of the AE (angle ß) had the greatest difference between DA shapes, with this angle usually being greater in the ovoid arch and smaller in the square arch (P < .05). The height of the AE presented greater correlation with DA measurements, with tapered arches having the most significant correlations (P < .05). DA depth had no influence on AE measurements (P > .05). The perimeter and width of the DAs had some influence (P < .05). CONCLUSIONS: Correlations were found between the DA and AE morphologies. The correlations should be taken into consideration, although the results do not prove absolute association between the variables. Whenever possible, the morphologic features of DAs should be preserved to avoid possible changes in AE.

Correlation between the position of hyoid bone and subregions of the pharyngeal airway space in lateral cephalometry and cone beam computed tomography.

OBJECTIVE: To correlate the pharyngeal airway subregions with the positioning of the hyoid bone. MATERIAL AND METHODS: The study examined 107 lateral cephalometric (LC) and cone beam computed tomography (CBCT) images. Linear and volumetric measurements of the pharyngeal subregions were made and correlated to linear measurements using hyoid triangle analysis on images of LC and multiplanar (MPR) and three-dimensional (3D) reconstructions of CBCT. RESULTS: There was significant correlation between linear measurements of the pharyngeal subregions and hyoid bone position in LC images and in MPR and 3D reconstructions of the CBCT. Correlations were more frequent in the oropharynx and hypopharynx, especially for LC images. No correlations were observed between LC images or CBCT reconstructions and the volumetric measurements of the pharyngeal subregions and the position of the hyoid bone. CONCLUSION: The hyoid bone position showed more correlations with oropharynx and hypopharynx airway measurements. The hyoid triangle method was not applicable to 3D images, since it showed a smaller number of measures correlated to the hyoid bone position.

Meloxicam as a Radiation-Protective Agent on Mandibles of Irradiated Rats.

This study evaluated the action of ionizing radiation and the possible radioprotective effect of the non-steroidal anti-inflammatory drug meloxicam on the bone physiology of rat mandibles by assessing the alveolar socket healing and bone strength. Forty male Wistar rats were divided in 4 groups (n=10): control (CG), irradiated (IG), meloxicam (MG), meloxicam irradiated (MIG). A dose of 0.2 mg/kg meloxicam was administered to MG and MIG. After this, IG and MIG were irradiated with 15 Gy radiation dose in the mandible. Forty days after the above procedures, the mandibular first molars were extracted and the animals were killed after 15 or 30 days (n=5). Micro-computed tomography and bending test were used to evaluate alveolar socket healing and bone strength, respectively. At 15 days, bone volume, bone volume fraction and trabecular thickness were higher in the CG and MG than in the IG and MIG; and trabecular separation was higher in the IG compared with the others. At 30 days, there was a difference only in trabecular separation, which was higher in IG than in CG and MG, and MIG did not differ from the others. Bone strength was lower in IG compared with CG and MG, and MIG did not differ from the others. In conclusion, the ionizing radiation affected the bone physiology of rat mandibles, delaying the alveolar socket healing and reducing the bone strength. Moreover, the meloxicam had a positive effect on the trabecular separation in alveolar socket healing and on the bone strength.