RESUMEN
OBJECTIVES: This study evaluated the effect of restoration occlusal design on the maximum fracture load and stress distribution of a feldspathic ceramic crown. MATERIALS AND METHODS: Twenty dentin analogues were used to simulate a full-crown preparation. Next, 20 feldspathic crowns were milled according to the occlusal design parameter available in the CAD database (Young or Adult). The crowns were cemented with dual cure resin-cement and loaded until fracture at 1 mm/min crosshead speed. Data were analyzed by using one-way ANOVA and Tukey tests (p < 0.05). The same geometry and experimental setup was modeled and exported to the computer aided engineering software and tensile stress concentration was calculated using the finite element method with 300 N occlusal load simulation. RESULTS: The occlusal anatomy significantly influenced the load-to-fracture (p < 0.05). Adult design showed higher mean values (1149 ± 201 N) than Young design (454 ± 77 N). The maximum principal stress criteria showed similar stress pattern for both designs, however, the highest stress concentration was calculated for Young design (91 MPa) in the occlusal surface. CONCLUSIONS: An anatomy design with reduced cusp angulation and less evident occlusal sulcus can reduce the stress concentration and increase the fracture load for feldspathic CAD/CAM posterior crowns.
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Coronas , Diseño de Prótesis Dental , Diseño Asistido por Computadora , Análisis del Estrés Dental , Ensayo de MaterialesRESUMEN
PURPOSE: To assess stress distribution in full-crowns with a composite buildup and endocrowns under axial or oblique loads, both with different ferrules (1 or 2 mm) and ceramic materials (glass ceramic or hybrid ceramic). MATERIALS AND METHODS: Sixteen models were analyzed with finite element analysis. No-separation contacts were considered between restoration/resin cement and resin cement/tooth. The contact between the fixation cylinder and the root was considered perfectly bonded. The axial load was applied to the occlusal surface and the oblique load was applied to the buccal cusp. The resulting tensile stresses were shown for the crown, the cement layer and the tooth. RESULTS: Almost all factors influenced the stress distribution significantly in the crown and the cement layer, as well as the tooth. The only exception was found under oblique loading by the restoration material and the type of crown that were of no significant influence on the stress distribution in the tooth. CONCLUSIONS: Under axial load, the endocrown showed the least tensile stresses in the tooth, but under oblique loads, the full-crown showed less tensile stresses than the endocrown. With the hybrid ceramic material, lower stresses were found in the crown, but higher stresses were present in the cement layer. The 2 mm ferrule is beneficial for reducing the resulting tensile stresses in all modalities.
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Coronas , Porcelana Dental , Materiales Dentales , Análisis del Estrés Dental , Análisis de Elementos Finitos , Ensayo de MaterialesRESUMEN
OBJECTIVES: This study evaluated the danger zone (DZ) in mesial roots of mandibular molars and the correlation between anatomical references of the DZ and some anatomical landmarks including tooth/root length, depth of mesial and distal grooves, and inter-canal orifices distance. MATERIAL AND METHODS: Twenty-eight mesial roots of mandibular molars with 2 independent canals were scanned and divided into 2 groups according to root length. The anatomical landmarks were correlated (Pearson or Spearman coefficients) with root level, thickness, and position of the DZ and also compared (independent samples t or Mann-Whitney tests) between the 2 groups at α = 5%. RESULTS: No statistical difference was observed between groups regarding DZ parameters and depth of mesial and distal grooves (P > 0.05). Orifice distance in group 2 (4.49 ± 0.75 mm) was significantly greater than group 1 (3.76 ± 0.89 mm) (P < 0.05). Significant correlations (P < 0.05) were found between (i) DZ level and root/tooth length (r = 0.54 and 0.49, respectively), (ii) DZ thickness and distal groove depth (r = - 0.45), and orifice distance (r = 0.38), and (iii) DZ position and depth of mesial (r = 0.39) and distal (r = 0.40) grooves. Other variables such as root length and distal groove depth (r = 0.28), and orifice distance and mesial groove depth (r = 0.36) were also correlated (P < 0.05). CONCLUSIONS: The length of tooth/root, the distance of canal orifices, and the depth of mesial/distal grooves of mesial roots of mandibular molars might be predictive factors for the root level, position, and thickness of the DZ. CLINICAL RELEVANCE: The length, distance of mesial canal orifices, and the depth of mesial and distal grooves of the mesial roots of mandibular molars might be moderate predictive factors for the root level, position, and thickness of the DZ.
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Mandíbula , Raíz del Diente , Cavidad Pulpar/diagnóstico por imagen , Mandíbula/diagnóstico por imagen , Diente Molar/diagnóstico por imagen , Raíz del Diente/diagnóstico por imagenRESUMEN
AIM: To evaluate the influence of various endodontic access cavity designs and the use of an operating microscope (OM) with or without ultrasonic troughing to detect middle mesial canals (MMCs) in extracted mandibular first molars. METHODOLOGY: Sixty extracted mandibular first molars were evaluated by cone beam computed tomography (CBCT) in order to detect the presence of MMCs and then divided into two groups (n = 30) with an equal proportion of 1 molar with MMC for each 3 molars. A specific access cavity design was performed for each group, either a conservative access cavity (CAC) or a traditional access cavity (TAC). Root canals were detected in three assessment stages: (i) no magnification, (ii) using an OM and (iii) using an OM together with ultrasonic troughing. Evaluations were performed on a mannequin head in an ergonomic working position. The confidence obtained in the assessment stages was portrayed by sensitivity, specificity and accuracy, calculated by the area under the ROC curve. The difference in the proportion of correct diagnoses in identifying the MMC using either CAC or TAC preparation, at each of the three stages, was checked using Cochran's Q tests. Binomial tests were performed at each stage to investigate whether there was a difference between the types of endodontic access designs to detect MMCs. Significance was set at P < 0.05. RESULTS: Accuracy increased at each assessment stage. At the third stage, both groups provided perfect accuracy (1.00). Cochran's Q tests indicated that the confidence of MMC detection for both TAC and CAC groups (P < 0.05) increased significantly at each stage. Binomial tests demonstrated that there was no significant difference between the TAC and CAC groups, when evaluation was performed without magnification (P > 0.05), with OM (P > 0.05), or with OM associated with ultrasonic troughing (P > 0.05). CONCLUSION: The access cavity design did not significantly affect detection of middle mesial canals in extracted mandibular first molars placed in a mannequin. However, the use of OM increased the accuracy of the MMC identification, especially when associated with ultrasonic troughing.
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Cavidad Pulpar , Ultrasonido , Tomografía Computarizada de Haz Cónico , Cavidad Pulpar/diagnóstico por imagen , Mandíbula , Diente Molar/diagnóstico por imagen , Raíz del DienteRESUMEN
BACKGROUND: The aim of the study was to assess the number and anatomical classification of roots and root canals of first and second mandibular molars using cone-beam computed tomography (CBCT) in a Chilean population. MATERIALS AND METHODS: This study evaluated the CBCT scans of 289 patients aged between 14 and 86 years, obtaining a sample of 1022 mandibular first and second molars. The number of roots and root canals was evaluated according to the anatomical classification proposed by Ahmed in 2016. Data were analysed using Pearson's chi-squared test and ANOVA. RESULTS: Nine hundred fifty-one (93.05%) molars had two roots, while the remaining 71 (6.95%) molars had one root. The most frequent root and root canal morphologies found were: ²MM M² D¹ (29.65%), ²MM M²â»¹ D¹ (22.3%) and ²MM M¹ D¹ (13.4%) (M - mesial, D - distal), with a total of 32 different anatomical distributions. C-shaped canals were present in 56 molars and were more frequently found in women than in men (7.1% vs. 3.88%; p = 0.024). CONCLUSIONS: The analysis of internal anatomy using CBCT revealed a highly variable distribution of root canals. The most frequent morphology found in mandibular molars in a Chilean population was two roots and three canals.
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Cavidad Pulpar/anatomía & histología , Diente Molar/anatomía & histología , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Tomografía Computarizada de Haz Cónico , Femenino , Humanos , Masculino , Mandíbula , Persona de Mediana Edad , Adulto JovenRESUMEN
OBJECTIVES: To evaluate and compare irrigant distribution throughout the root canal system of mesial roots of mandibular molars after application of distinct adjunctive irrigant activation procedures. MATERIALS AND METHODS: Fifteen extracted mandibular molars presenting Fan's type II, III, or IV isthmus configurations were selected. The canals were initially enlarged and cleaned. The same specimens were subjected to conventional positive pressure irrigation (PPI) followed by adjunctive irrigation approaches: passive ultrasonic irrigation (PUI), mechanical activation with the XP-endo Finisher instrument, and a control group in which the irrigant remained in the canal with no activation. Retention time for the irrigant was the same for all groups. Sodium hypochlorite mixed with a contrast medium (Omnipaque 300) was used as the irrigant. Before and immediately after the adjunctive irrigation, micro-computed tomographic (micro-CT) scans were taken to evaluate the volume of the entire root canal system that was filled by the irrigant. An exclusive analysis was also done for the isthmus area. RESULTS: Analysis of the entire root canal system showed that the XP-endo Finisher instrument promoted better distribution of the irrigant than PUI and the control group (p < 0.01). PUI was not significantly different from the control group (p > 0.05). A separate analysis of the isthmus area showed no significant difference between the adjunctive irrigation methods and the control (p > 0.05). CONCLUSIONS: The XP-endo Finisher instrument promoted better distribution of irrigant throughout the root canal system, especially in the apical canal segment, when compared to PUI. However, the tested approaches did not differ as to the ability to drive irrigants into the isthmus area. CLINICAL RELEVANCE: This study highlighted that the XP-endo Finisher instrument presented a better performance to distribute irrigant throughout the root canal system, especially in the apical canal segment compared to positive pressure irrigation and PUI.
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Cavidad Pulpar , Diente Molar , Irrigantes del Conducto Radicular , Preparación del Conducto Radicular , Hipoclorito de Sodio , Irrigación TerapéuticaRESUMEN
Una de las variaciones anatómicas que pueden presentar los molares inferiores es una tercera raíz que ha sido denominada radix entomolaris o paramolaris dependiendo de su localización, ya sea lingual o vestibular respectivamente. Conocer las variaciones morfológicas de las piezas dentarias es un requisito fundamental para el éxito del tratamiento endodóntico. El objetivo de este artículo es la presentación de un caso clínico de una paciente con ambos primeros molares inferiores con presencia de radix entomolaris; en la pieza dentaria 4.6 se realizó tratamiento endodóntico y en 3.6 con una lesión endoperiodontal combinada verdadera se decidió su exodoncia (AU)
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Humanos , Femenino , Anciano de 80 o más Años , Cavidad Pulpar/anatomía & histología , Diente Molar/anatomía & histología , Tratamiento del Conducto Radicular , Extracción Dental , Raíz del Diente/anatomía & histología , Radiografía Panorámica , Factores Raciales , MandíbulaRESUMEN
AIM: To evaluate the efficacy of four final irrigation protocols on the reduction of hard-tissue debris accumulated within the mesial root canal system of mandibular first molars using micro-CT analysis. METHODOLOGY: Forty mesial roots of mandibular molars with a single and continuous isthmus connecting the mesiobuccal and mesiolingual canals (Vertucci's Type I configuration) were selected and scanned at a resolution of 8.6 µm. Canals were enlarged sequentially using WaveOne Small and Primary instruments activated in reciprocating motion without intracanal irrigation to allow debris to accumulate within the mesial root canal system. Then, specimens were anatomically matched and distributed into four groups (n = 10), according to the final irrigation protocol: apical positive pressure (APP), passive ultrasonic irrigation (PUI), Self-adjusting File (SAF) and XP-endo Finisher (XPF). The final irrigation procedures were performed over 2 min using a total of 5.5 mL of 2.5% NaOCl per canal. Reconstructed data sets were coregistered, and the mean percentage reduction of accumulated hard-tissue debris after the final irrigation procedures was compared statistically between groups using the anovapost hoc Tukey test with a significance level set at 5%. RESULTS: Reduction of accumulated hard-tissue debris was observed in all groups after the final irrigation protocol. Overall, PUI and XPF groups had higher mean percentage reductions of accumulated hard-tissue debris (94.1% and 89.7%, respectively) than APP and SAF groups (45.7% and 41.3%, respectively) (P < 0.05). No significant differences were found when comparing the results of PUI and XPF groups (P > 0.05) or APP and SAF groups (P > 0.05). CONCLUSIONS: The PUI technique and XP-endo Finisher instrument were associated with significantly lower levels of AHTD compared with conventional irrigation and the modified SAF system protocol in mesial root canals of mandibular molars.
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Cavidad Pulpar/cirugía , Diente Molar/cirugía , Preparación del Conducto Radicular/métodos , Irrigación Terapéutica/métodos , Cavidad Pulpar/diagnóstico por imagen , Humanos , Mandíbula , Diente Molar/diagnóstico por imagen , Microtomografía por Rayos XRESUMEN
OBJECTIVE: To describe the morphological aspects of middle mesial canals (MMC) in mandibular first molars using micro-CT. DESIGN: Mandibular first molars collected from the Brazilian (n=136) and Turkish (n=122) populations were scanned (voxel size: 9.9µm) and mesial roots with MMC (n=48) evaluated regarding several morphological aspects. The incidence of MMC in each population was statistically compared using Chi-square test (α=0.05). RESULTS: Overall, the incidence of MMC was 18.6% (48 out of 258 molars) and was significantly higher in the Brazilian (n=30; 22.1%) than in the Turkish (n=18; 14.8%) population (p<0.05). In both populations, confluent configuration of the MMC was the most frequent anatomy. Most of the specimens with MMC had 3 independent orifices (n=26; 54.2%) and 3 apical foramina (n=21; 43.8%). The mean minor diameter of the MMC orifice (0.16mm) was 3 times less than the other orifices (â¼0.50mm). In mesial roots with independent configuration (n=3; 6.3%), the mean volumes (mm(3)) of the MMC, mesiobuccal (MBC) and mesiolingual (MLC) canals were 0.20±0.10, 0.75±0.28, and 0.88±0.19, respectively. In the specimens with canal confluence (n=26; 54.2%), MMC merged to the MBC (n=8; 16.7%), MLC (n=4; 8.3%), or to both MBC and MLC (n=14; 29.2%). Double mesial canal was observed in only 1 specimen. MMC with an independent foramen was observed mostly in Brazilian specimens. CONCLUSIONS: Incidence of MMC was higher in the Brazilian molars. Confluent configuration was the most prevalent anatomic variation, while independent and fin configurations, as well as, double MMC, were found only in a few specimens.
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Cavidad Pulpar/diagnóstico por imagen , Diente Molar/diagnóstico por imagen , Microtomografía por Rayos X , Brasil , Cavidad Pulpar/anatomía & histología , Humanos , Mandíbula , Diente Molar/anatomía & histología , TurquíaRESUMEN
AIM: To evaluate the removal of accumulated hard-tissue debris (AHTD) from the root canal system of mandibular molars by positive and negative pressure irrigation systems, using micro-CT imaging analysis. METHODOLOGY: Mandibular molars with a single canal in the distal root and 2 canals connected by an isthmus in the mesial root were matched based on similar morphological dimensions using micro-CT evaluation and assigned to 2 experimental groups (n = 20 mesial and 10 distal canals), according to the irrigation protocol: apical positive (conventional irrigation) or negative (EndoVac system) pressure. Changes in root canal volume and surface area as well as percentage of uninstrumented canal wall surface and accumulated hard-tissue debris (AHTD) after canal preparation were compared statistically using the independent sample t-test and Mann-Whitney U-test, with the significance level set at 5%. RESULTS: Volume, surface area and percentage of static voxels in either mesial or distal root canal systems were not significantly different between groups before or after root canal preparation (P > 0.05). After preparation, AHTD was not observed in the distal canal of both groups. However, in the mesial root canal system, the conventional irrigation group was associated with a significantly higher median percentage of AHTD (11.48%; IQR: 5.9-22.6; range: 1.86-41.98) than the EndoVac group (3.40%; IQR: 1.5-7.3; range: 0.82-12.84) (P < 0.05). CONCLUSIONS: Neither irrigation protocol succeeded in rendering the mesial canal system free of AHTD; however, apical negative pressure irrigation resulted in lower levels of AHTD than conventional irrigation.