Influence of Different Glide Path Techniques on Microcrack Formation after Two Different Root Canal Preparation Treatments: Micro Computed Tomography Analysis.

OBJECTIVE: This study aimed to evaluate the effect of WaveOne Glider (WOGG) with Waveone Gold (WOG) primary reciprocation systems on root dentine microcrack formation and to know the effect of TruNatomy Glider (TRNG) with TruNatomy (TRN) prime rotary systems on root dentine microcrack formation. METHODS: In this study, 40 extracted mandibular first molar roots were selected and divided randomly into four groups (n=10). Group MWOG: a manual glide path was performed + WOG primary. Group MTRN: manual glide path performed+TRN prime. Additionally, group WOGG: glide path preparation with WOGG+WOG primary. Finally, for group TRNG, the glide path preparation was performed with TRNG+TRN prime. Micro-CT was used for pre and post-instrumentation image analysis. Statistical analysis was performed using the Kruskal- Wallis test (p<0.05) with Two-way ANOVA. RESULTS: The Kruskal-Wallis test showed no significant differences among all groups in all thirds for pre and post-instrumentation regarding the crack formation. The Two-way ANOVA showed no significant difference or interaction between the ways of glide path preparation, whether manual or reciprocal WOGG, or between the rotary TRNG and the motion used in root canal preparation (rotary TRN or reciprocal WOG) regarding the crack formation and propagation. CONCLUSION: Microcrack formation and propagation occurred independently of using different glide path techniques (manual, rotary, or reciprocal).

Age and sex related change in tooth enamel thickness of maxillary incisors measured by cone beam computed tomography.

BACKGROUND: To measure adequate enamel thickness of maxillary incisors in planning enamel reduction for a porcelain laminate veneer restoration in relation to chronological age and sex by using cone beam computed tomography (CBCT) in an Iraqi subpopulation. METHODS: From 81 CBCT images, 324 maxillary incisors were examined. Enamel thickness was measured at both mesial and distal regions of the tooth in three different levels: cervical, middle, and incisal (occlusal) 1/3 at a sagittal section. Measurements were made for the following tooth areas using CBCT: facial enamel thickness at 1, 3, and 5 mm from the cementoenamel junction (CEJ), palatal enamel thickness at 5 mm from the CEJ (5 mm P), facial and palatal enamel thickness at the incisal edge (IFP), mid incisal enamel thickness (IET), and the incisal edge enamel-pulp distance (IEPD). Relationships of enamel thickness with age and sex were evaluated using Independent t-test, Mann-Whitney U-test and the Pearson correlation coefficient, a simple linear regression analysis used for statistical analysis. RESULTS: Significant differences (P < 0.05) were found in terms of an inverse association between enamel thickness and chronological age at all measurements above the CEJ and the regression model for the mid-incisal enamel thickness was (R2 of 0.4). In contrast, there was an increase in IFP, palatal, and IPED enamel thickness with age. Also, significant differences were found in enamel thickness between males and females, the enamel being thicker in females in relation to facial enamel thickness, enamel palatal thickness above CEJ and IET, while for IEPD, the enamel thickness was greater in males compared to females. CONCLUSION: The measurements for enamel thickness outcome variables in relation to chronological age revealed significant differences for each measured distance and there were statistically significant differences in enamel thickness between males and females at all measurements except at IFP. These results demonstrate that CBCT can be used for noninvasive, accurate measurements of enamel thickness in both sex.

Evaluation of video teaching on resident competency for all-ceramic crown tooth preparation.

PURPOSE: This study aimed to analyze the impact of live video instruction using digital evaluation of residents' performance in full ceramic crown preparation. METHODS: Digital evaluation using CEREC computer-aided design/computer-assisted manufacturing (CAD/CAM) 5.1.3 software was conducted of preparation on a typodont for all-ceramic crowns of mandibular first molars (MFMs) with a radial shoulder finish line, carried out by 30 residents. Each participant prepared two MFMs: group A prepared the right side without live video instruction, and group B prepared the left side after instruction. All prepared teeth were scanned by Dentsply Sirona chairside CAD/CAM system with Omnicom to assess the inter-occlusal space, undercut, the finish line of the preparation, and surface texture. The data were analyzed using Pearson Chi-square, Wilcoxon signed-rank test, and paired t-test. P-values less than 0.05 were considered to be statistically significant in all tests. RESULTS: Based on the Pearson Chi-square test, there were significant differences between the two groups in terms of inter-occlusal space on the buccal and lingual surface of the prepared tooth, in the presence of rough surfaces before and after the preparation, and difference in the type of finish line. The Wilcoxon signed-rank test revealed a significant difference in convergence angle buccolingually and the remaining height of the prepared teeth before and after the video instruction. CONCLUSIONS: The use of educational live video instruction can be helpful to residents in learning the principles of tooth preparation.

Evaluation of Radix Entomolaris and Middle Mesial Canal in Mandibular Permanent First Molars in an Iraqi Subpopulation Using Cone-Beam Computed Tomography.

The aim of this study was to evaluate the radix entomolaris (RE) and middle mesial canal (MMC) in mandibular permanent first molars in an Iraqi subpopulation using cone-beam computed tomography (CBCT). Their prevalence and types were investigated in 201 patients (301 tooth subjects), among which 156 were of the right side, and 145 of the left side mandibular first molars (MFM), using CBCT scans. The effects of gender, age, and unilateral/bilateral on the presence of both RE and MMC were evaluated. Chi-square and Fisher's exact tests were used to determine the level of significance (p ≤ 0.05), and the kappa value was used to check reliability of results of the research. In MFM, the prevalence of right and left RE was 4.5% and 4.1%, respectively, and it was significantly higher in males than females (p = 0.006) based on the Chi-square test. No significant difference was identified in the prevalence of RE in relation to age and tooth position. MMC was found in 14.7% of teeth in the right side and 19.3% in the left side, with no significant differences for age or gender. MMC merged with mesiolingual canal presented with higher prevalence compared to other types of MMC (8.3% right side and 7.6% left side), again with no significant differences for age or gender. Within the limits of this study, no significant association was detected between the prevalence of MMC and RE in MFM.

Biomineralization of three calcium silicate-based cements after implantation in rat subcutaneous tissue.

OBJECTIVES: The aim of this study was to evaluate the dystrophic mineralization deposits from 3 calcium silicate-based cements (Micro-Mega mineral trioxide aggregate [MM-MTA], Biodentine [BD], and EndoSequence Root Repair Material [ESRRM] putty) over time after subcutaneous implantation into rats. MATERIALS AND METHODS: Forty-five silicon tubes containing the tested materials and 15 empty tubes (serving as a control group) were subcutaneously implanted into the backs of 15 Wistar rats. At 1, 4, and 8 weeks after implantation, the animals were euthanized (n = 5 animals/group), and the silicon tubes were removed with the surrounding tissues. Histopathological tissue sections were stained with von Kossa stain to assess mineralization. Scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDX) were also used to assess the chemical components of the surface precipitates deposited on the implant and the pattern of calcium and phosphorus distribution at the material-tissue interface. The calcium-to-phosphorus ratios were compared using the non-parametric Kruskal-Wallis test at a significance level of 5%. RESULTS: The von Kossa staining showed that both BD and ESRRM putty induced mineralization starting at week 1; this mineralization increased further until the end of the study. In contrast, MM-MTA induced dystrophic calcification later, from 4 weeks onward. SEM/EDX showed no statistically significant differences in the calcium- and phosphorus-rich areas among the 3 materials at any time point (p > 0.05). CONCLUSIONS: After subcutaneous implantation, biomineralization of the 3-calcium silicate-based cements started early and increased over time, and all 3 tested cements generated calcium- and phosphorus-containing surface precipitates.

Bioactivity and Physicochemical Properties of Three Calcium Silicate-Based Cements: An In Vitro Study.

OBJECTIVE: This study evaluated the bioactivity and physicochemical properties of three commercial calcium silicate-based endodontic materials (MTA, EndoSequence Root Repair Material putty, and Biodentine™). Material and Methods. Horizontal sections of 3 mm thickness from 18 root canals of human teeth were subjected to biomechanical preparation with WaveOne Gold large rotary instruments. The twelve specimens were filled with three tested materials (MM-MTA, EndoSequence Root Repair Material putty, and Biodentine™) and immersed in phosphate-buffered saline for 7 and 30 days. After this period of time, each specimen of each material was processed for morphological observation, surface precipitates, and interfacial dentin using SEM. In addition, the surface morphology of the set materials, without soaking in phosphate-buffered solution after one day and after 28 days stored in phosphate-buffered saline, was evaluated using SEM; also, the pH of the soaking water and the amount of calcium ions released from the test materials were measured by using an inductively coupled plasma-optical emission spectroscopy test. Data obtained were analyzed using one-way analysis of variance and Tukey's honest significant difference test with a significance level of 5%. RESULT: The formation of precipitates was observed on the surfaces of all materials at 1 week and increased substantially over time. Interfacial layers in some areas of the dentin-cement interface were found from one week of immersion. All the analyzed materials showed alkaline pH and capacity to release calcium ions; however, the concentrations of released calcium ions were significantly more in Biodentine and ESRRM putty than MM-MTA (P < 0.05). ESRRM putty maintained a pH of around 11 after 28 days. CONCLUSION: Compared with MM-MTA, Biodentine and ESRRM putty showed significantly more calcium ion release. However, exposure of three tested cements to phosphate-buffered solution resulted in precipitation of apatite crystalline structures over both cement and dentin that increased over time. This suggests that the tested materials are bioactive.

Prevalence of impacted mandibular third molars and its association with distal caries in mandibular second molars using cone beam computed tomography / Prevalencia de terceros molares mandibulares impactados y su asociación con caries distales en segundos molares mandibulares mediante tomografía computarizada de haz cónico

This study evaluated the prevalence and eruption's pattern of impacted mandibular third molars (IMTM) and the influence of their eruption status on the distal caries of mandibular second molars (MSM) using cone-beam computed tomography (CBCT). Material and methods: CBCT images taken for different purposes in private dental practices were analyzed retrospectively. Radiographic assessment included: prevalence of IMTM, degree of angulation, level of impaction and type of IMTM. Furthermore, the distance between the cement-enamel junctions (CEJ) of second and third molars and the occurrence of caries lesion on the distal surface of MSM was also evaluated. Data were analyzed by chi square test and logistic regression was used to find the association between distal caries of MSM and eruption status of IMTM. Results: Three hundred and eight CBCTs were screened, the prevalence of IMTM was 36.88% and their angulation degree were mostly less than 90º (mesioangular). Amongst those with impaction, 58 subjects (43%) had distal caries on MSM, 29.6% in females and 30.4% in the age group 19-27 years. Caries on the distal side of MSM were significantly associated with age, level and type of impaction, angulation degree and CEJ distances (p<0.05). Conclusions: The prevalence of IMTM is high (36.88%) and there are significant relationships between angulation degree, level and type of impaction, and CEJ distances with caries on the distal side of MSM.

Introducción: Este estudio evaluó la prevalencia y el patrón de erupción de terceros molares mandibulares impactados (TMMI), y la influencia de su estado de erupción en la caries distal de los segundos molares mandibulares (SMM) mediante tomografía computarizada de haz cónico (TCHC). Material y métodos: se analizaron retrospectivamente las imágenes de TCHC tomadas para diferentes fines en prácticas dentales privadas. La evaluación radiográfica incluyó: prevalencia de TMMI, grado de angulación, nivel de impacto y tipo de TMMI. Además, también se evaluó la distancia entre la unión amelocementaria (UAC) de los segundos y terceros molares y la aparición de lesión de caries en la superficie distal de SMM. Los datos se analizaron mediante la prueba de chi cuadrado y se usó la regresión logística para evaluar asociaciones entre la caries distal de SMM y el estado de erupción de TMMI. Resultados: Se examinaron 308 TCHC, la prevalencia de TMMI fue de 36.88% y su grado de angulación fue mayoritariamente menor a 90º (mesioangular). Entre aquellos con impacto, 58 sujetos (43%) tenían caries distales en los SMM, 29.6% eran mujeres y 30.4% pertenecieron al grupo de edad de 19-27 años. Las caries en el lado distal de MSM se asociaron significativamente con la edad, el nivel y el tipo de impactación, el grado de angulación y las distancias UAC (p<0.05). Conclusiones: la prevalencia de TMMI es alta (36.88%) y existen relaciones significativas entre el grado de angulación, el nivel y el tipo de impacto, y las distancias UAC con presencia de caries en el lado distal de los SMM.