Diagnostic Efficacy of Four Methods for Locating the Second Mesiobuccal Canal in Maxillary Molars.

INTRODUCTION: The major cause for failure of root canal therapy is the inability to recognize the presence of all canals of the root canal system. Auxiliary tools, such as magnifying loupe, operative microscope and computed tomography (CT) images are used to facilitate the location of canals. The objective of the present survey was to evaluate the diagnostic efficacy of four methods for detecting the second canal of mesiobuccal roots (MB2) of permanent maxillary molars. METHODS AND MATERIAL: A total of 147 extracted human maxillary molars were assessed. The floor of the pulp chamber was inspected by an endodontist to find MB2 canals. Analyses were performed without magnification (direct visual method), using a loupe (with 3.5× magnification), and using a microscope (with 16× magnification). A fourth analysis was conducted using cone-beam computed tomography (CBCT) images. Teeth were sectioned horizontally into three parts (cervical, medial and apical thirds) to confirm the presence of MB2 canals (reference standard method). Sensitivity, specificity, and positive/negative predictive values were calculated for each method. RESULTS: No statistically significant differences were observed in the frequency of MB2 found between the microscope and the reference standard or between CBCT and the reference standard. CBCT had higher sensitivity (0.88), specificity (0.88), positive (0.84) and negative (0.91) predictive value than the other three methods. CONCLUSION: CBCT was the most accurate method for detecting the MB2 and it had a diagnostic efficacy similar to that of the reference standard method.

Incidence of Dentinal Defects and Vertical Root Fractures after Endodontic Retreatment and Mechanical Cycling.

INTRODUCTION: The aim of this study was to evaluate the incidence of dentinal defects and vertical root fractures (VRFs) after endodontic retreatment and mechanical cycling (MC). METHODS AND MATERIALS: Two hundred mandibular premolars were selected. Forty teeth were left unprepared (control group). The remaining 160 root canals were prepared with ProTaper instruments and filled by using two different techniques [eighty with lateral compaction (LC) and eighty with single-cone (SC)]. Forty canals from each group (LC and SC) received no further treatment. The remaining eighty teeth were divided into two groups (LCR and SCR) (n=40) in order to undergo the removal of the root filling, re-preparation and refilling with lateral compaction and single-cone, respectively. All of the teeth were subjected to MC (1000000 cycles, 130 N, 2.2 Hz and 37°C). The roots were sectioned at 3, 6 and 9 mm from the apex and observed under 20× magnification. The defects were classified as: no defect, VRF and other defects. Statistical analysis was performed using the Fisher's Exact test and the Chi-Squared tests (α=0.05). RESULTS: MC alone did not promote any other defects or VRFs. Experimental groups presented higher dentinal defects than the control group (P=0.021). Retreatment groups did not present a higher amount of dentinal defects than the groups that were subjected to the first treatment (P>0.05). CONCLUSION: Endodontic treatment and retreatment, regardless of the filling technique and MC, did not influence the occurrence of dentinal defects or VRFs in the human premolars.

Influence of Endodontic Treatment and Retreatment on the Fatigue Failure Load, Numbers of Cycles for Failure, and Survival Rates of Human Canine Teeth.

INTRODUCTION: This study evaluated the effects of endodontic treatment and retreatment on the fatigue failure load, numbers of cycles for failure, and survival rates of canine teeth. METHODS: Sixty extracted canine teeth, each with a single root canal, were selected and randomly divided into 4 groups (n = 15): untreated, teeth without endodontic intervention; prepared, teeth subjected only to rotary instrumentation; filled, teeth receiving complete endodontic treatment; and retreated, teeth retreated endodontically. After the different endodontic interventions, the specimens were subjected to fatigue testing by the stepwise method: 200 N (× 5000 load pulses), 300 N, 400 N, 500 N, 600 N, 800 N, and 900 N at a maximum of 30,000 load pulses each or the occurrence of fracture. Data from load to failure and numbers of cycles for fracture were recorded and subjected to Kaplan-Meier and Log Rank tests (P < .05), in addition to Weibull analysis. The fractures of the specimens were classified as repairable or catastrophic. RESULTS: The retreated, filled, and untreated groups presented statistically significantly higher fatigue failure loads and numbers of cycles for failure than did the prepared group. Weibull analysis showed no statistically significant difference among the treatments for characteristic load to failure and characteristic number of cycles for failure, although, for number of cycles, a higher Weibull modulus was observed in filled and retreated conditions. The predominant mode of failure was catastrophic. CONCLUSION: Teeth subjected to complete endodontic treatment and retreatment behaved similarly in terms of fatigue failure load and number of cycles to failure when compared with untreated teeth.

Análise da intensidade de fluorescência em diferentes compósitos após exposição a agentes clareadores caseiros à base de peróxido de carbamida em diferentes concentrações / Analysis of fluorescence intensity in different composites after exposure to different concentrations of carbamide peroxide home bleaching agents

Objetivo: o objetivo neste estudo foi avaliar a influência de agentes clareadores à base de peróxido de carbamida (PC), em diferentes concentrações, sobre a fluorescência de três compósitos. Métodos: foram confeccionados 27 corpos de prova divididos em 9 grupos (n = 3), que foram armazenados em água deionizada, expostos ao PC 10% por 6 horas diárias e PC 22% por 1 hora diária, durante 14 dias. Após, foi realizada a leitura da fluorescência em um espectrofotômetro. Os valores de intensidade de fluorescência obtidos foram submetidos aos testes Shapiro-Wilk, Levene e Games-Howell (p < 0,05). Resultados: a média dos valores de intensidade de fluorescência para os grupos controle dos compósitos Esthet-X e Opallis não apresentou diferença estatisticamente significativa. Entretanto, o compósito Charisma apresentou intensidade de fluorescência estatisticamente diferente da dos demais. Após serem expostas aos diferentes agentes clareadores, apenas o compósito Charisma exposto ao PC 22% apresentou alterações estatisticamente significativas, aumentando a fluorescência. Conclusão: a intensidade de fluorescência pode ser afetada pela ação de agentes clareadores à base de PC, dependendo de sua concentração e das características do compósito.

Micromorphological evaluation of dentin treated with different desensitizing agents.

INTRODUCTION: The purpose of a desensitizing agent is a permanent coating or filling of dentin surface. Morphological analysis in vitro of this treated surface is essential to understand the interaction between desensitizing agent and hypersensitive dentin. The aim was to evaluate the morphology of four dentin surface treated with desensitizing agents. METHODS: This was an in vitro laboratory study, where fifteen specimens from extracted human premolars were obtained. The enamel was removed to expose the dentin surface, polished with silicon carbide abrasive papers and etched with 6% citric acid for 2 min.The specimens were randomly divided into 5 groups: G1 - without treatment (control) (C), G2 - fluoride varnish (FV), G3 - potassium oxalate (PO), G4 - 2-step self-etching adhesive system (AS), G5 - diode laser (DL). The specimens were cleaved in the lingual buccaldirection, prepared for analysis by Scanning Electron Microscope and the surface and interior of the dentinal tubules were observed at 1500× magnification. RESULTS: In the control group, the dentin etching promoted smear layer removal and exposure of dentinal tubules. In the group of fluoride varnish, a film was observed on the surface, with plugs of varnish into tubules. In the group of oxalate, partial obliteration of the tubular entrances was observed. In the group of the adhesive system, the tubules were obstructed through the formation of hybrid layer and a physical barrier on the surface. In the group of the diode laser, dentin melting and solidification with partial occlusion of dentinal tubules were observed. CONCLUSIONS: All desensitizing agents evaluated demonstrated ability to modify the surface of dentin, with partial or total occlusion of dentinal tubules. Thus, it is suggested to do more clinical studies to verify the effectiveness of the findings.