Influence of ultraconservative access cavities on instrumentation efficacy with XP-endo Shaper and Reciproc, filling ability and load capacity of mandibular molars subjected to thermomechanical cycling.

AIM: To evaluate the influence of ultraconservative access cavities (UltraAC) on canal shaping and filling ability and load capacity of mandibular molars after root canal preparation with XP-endo Shaper (XP) or Reciproc (RC), under simulated clinical conditions. Traditional access cavities (TradAC) were used for comparison. METHODOLOGY: Forty extracted mandibular molars were scanned by micro-computed tomographic and, based on similar anatomical features, were divided into four groups (n = 10), according to the type of access cavity and canal instrumentation protocol: TradAC/RC, TradAC/XP, UltraAC/RC and UltraAC/XP. All root canal procedures were performed with the teeth placed in a dental mannequin. Teeth were scanned after root canal instrumentation and filling. Unprepared canal area, dentine removed, accumulated hard tissue debris (AHTD), canal transportation, presence of voids and filling material remnants within the pulp chamber were analysed. After restorative procedures, the teeth were subjected to thermomechanical cycling and to a load capacity test. Statistical analyses were performed using two-way anova test, considering the randomized blocks design (P < 0.05). RESULTS: The percentage of unprepared canal area was significantly lower in TradAC groups when compared to UltraAC groups (P < 0.05), regardless of the instrument used. The UltraAC/XP group had significantly lower percentage of root dentine removed when compared to other groups (P < 0.05). UltraAC/XP and TradAC/XP groups had significantly lower percentages of AHTD than UltraAC/RC and TradAC/RC groups (P < 0.05). Regarding canal transportation, in the MB root canals, the TradAC/XP group had significantly lower values than other groups (P < 0.05). In general, in ML and distal root canals, TradAC/XP and UltraAC/XP groups had significantly lower values of canal transportation when compared to other groups (P < 0.05). Moreover, the UltraAC/RC had the greatest canal transportation values in MB and distal canals. The UltraAC groups had significantly greater percentages of voids and volume of remaining root filling material within the pulp chamber after cleaning procedures than TradAC groups (P < 0.05). There was no difference in the load capacity amongst groups (P < 0.05). CONCLUSION: The UltraAC/XP and UltraAC/RC groups had significantly greater areas of unprepared canal walls, significantly more voids and volume of root filling material remnants within the pulp chamber after canal filling. UltraAC/XP was associated with significantly less root dentine removal and significantly more AHTD whilst TradAC/XP had overall significantly less canal transportation. No differences were observed in the load capacity amongst groups.

Effect of Toothpaste Application Prior to Dental Bleaching on Whitening Effectiveness and Enamel Properties.

OBJECTIVE: The purpose of this study was to investigate the effects on the enamel properties and effectiveness of bleaching using 35% hydrogen peroxide (HP) when applying toothpastes with different active agents prior to dental bleaching. METHODS: Seventy enamel blocks (4 × 4 × 2 mm) were submitted to in vitro treatment protocols in a tooth-brushing machine (n=10): with distilled water and exposure to placebo gel (negative control [NC]) or HP bleaching (positive control [PC]); and brushing with differing toothpastes prior to HP bleaching, including potassium nitrate toothpaste (PN) containing NaF, conventional sodium monofluorophosphate toothpaste (FT), arginine-based toothpastes (PA and SAN), or a toothpaste containing bioactive glass (NM). Color changes were determined using the CIE L*a*b* system (ΔE, ΔL, Δa, and Δb), and a roughness (Ra) analysis was performed before and after treatments. Surface microhardness (SMH) and cross-sectional microhardness (CSMH) were analyzed after treatment. Data were analyzed with repeated measures ANOVA for Ra, one-way ANOVA (SMH, ΔE, ΔL, Δa, and Δb), split-plot ANOVA (CSMH), and Tukey post hoc test (α<0.05). The relationship between the physical surface properties and color properties was evaluated using a multivariate Canonical correlation analysis. RESULTS: Color changes were statistically similar in the bleached groups. After treatments, SMH and CSMH decreased in PC. SMH increased significantly in the toothpaste groups vs the negative and positive control (NM > PA = SAN > all other groups) or decreased HP effects (CSMH). Ra increased in all bleached groups, with the exception of NM, which did not differ from the NC. The variation in the color variables (ΔL, Δa, and Δb) explained 21% of the variation in the physical surface variables (Ra and SMH). CONCLUSION: The application of toothpaste prior to dental bleaching did not interfere with the effectiveness of treatment. The bioactive glass based toothpaste protected the enamel against the deleterious effects of dental bleaching.

Reestablishing Biology, Function, and Esthetics for Fractured, Immature Incisors.

A seven-year-old boy with enamel-dentin fractures on both maxillary central incisors presented to the Piracicaba Dental School-UNICAMP seven days after the trauma. At the clinical evaluation, there were no clinical signs of pulp exposure, neither tooth was mobile, and both affected teeth presented a positive response to sensitivity tests and a negative response for percussion and palpation. The radiographic examination showed an undeveloped root and opened apex for both teeth. Indirect pulp capping was performed on the left maxillary central incisor, followed by a direct restoration. After one month, the patient complained of pain in the left central incisor, which responded negatively to sensitivity testing. Pulp revascularization was performed only on this tooth and was followed for 18 months. During this period, the left maxillary central incisor did not recover sensitivity, although radiographic examination showed apical closure, a slight increase in root length, and the formation of a mineralized barrier between the root canal and sealing material. The technique achieved its goal of restoring biological aspects, function, and esthetics of traumatized teeth when using this multidisciplinary approach.

Effect of diazepam on temporomandibular joints in rats with increased occlusal vertical dimension.

Anxiolytic agents, mainly benzodiazepines, have been used to treat symptomatic disorders of the temporomandibular joint (TMJ). Our aim was to evaluate the effect of diazepam on the TMJ of rats with increased occlusal vertical dimension (iOVD). Forty male rats were randomly assigned to 4 groups: control rats were given sham iOVD plus saline solution daily for 7 days. The first experimental group was given sham iOVD plus diazepam 2.5mg/kg/intramuscularly daily for 7 days (diazepam alone group); the second had iOVD induced in molars for 7 days plus saline daily for 7 days (iOVD alone group); and the third had iOVD induced in molars for 7 days plus diazepam 2.5mg/kg/intramuscularly daily for 7 days (iOVD plus diazepam group). At the end of each experiment the animals were killed and their bilateral TMJs were removed, randomly stained with haematoxylin and eosin and sirius-red, and immunoassayed. The thickness of condylar cartilage and of fibrous, proliferating, mature, and hypertrophic layers, number of collagen fibres, and the articular area were measured. Proinflammatory cytokines (interleukin (IL)-1α, IL-1ß, IL-6, and tumour necrosis factor (TNF)-α) were also measured. ANOVA and Tukey's tests or the Kruskal-Wallis test were used to compare data among groups (α=5%). Condylar cartilage was thicker in the control group than in the other groups, the diazepam alone group being thicker than the other 2 experimental groups. There were fewer collagen fibres in the 2 groups given diazepam than in the other 2 groups, and there were no significant differences in the area of cartilage among groups. The controls had lower concentrations of all cytokines (p<0.05) than the 3 experimental groups, except for IL-6. Both iOVD groups had higher concentrations of IL-1α, IL-1ß, and IL-6 than the diazepam alone group. Diazepam alone was associated with increased concentrations of all cytokines except IL-6. We conclude that both iOVD and diazepam induced significant changes in rats' articular cartilage.

Influence of an intermediary base on the microleakage of simulated class II composite resin restorations.

The aim of this in vitro study was to qualitatively and quantitatively evaluate the microleakage of Class II cavities restored with a methacrylate-based composite (Filtek Z250, 3M ESPE) or silorane-based composite (Filtek LS, 3M ESPE), varying the application of an intermediary base, using a low-viscosity composite resin (Filtek Z350 Flow, 3M ESPE) or resin-modified glass ionomer cement (RMGIC) (Vitrebond, 3M ESPE) and no intermediary base (control groups). Sixty cavities were prepared on the proximal surfaces of bovine teeth and were randomly divided according to the experimental groups (n=10). Following the restorative procedures and thermocycling, the samples were immersed in methylene blue for two hours. The qualitative evaluation was made using a stereomicroscope, whereby two observers analyzed the infiltration level of the dye within the tooth/filling. Microleakage scores among the groups were compared using the Kruskal-Wallis test followed by the Mann-Whitney test (p≤0.05). The samples were then ground and the powder was prepared for quantitative analysis in an absorbance spectrophotometer. The results were statistically analyzed by analysis of variance and the Tukey test (p≤0.05). Results from the quantitative analysis showed that LS presented higher values of microleakage than did Z250. There was a significant difference between both composites concerning the intermediary materials, with the lowest values obtained using RMGIC as an intermediary base. Results from the qualitative analysis showed that there were no statistically significant differences between composites; however, there were significant differences for both composites concerning the intermediary materials, with the lowest values obtained using RMGIC as an intermediary. It is possible to conclude that using RMGIC as an intermediary base provided lower microleakage, indicating better sealing of the tooth-restoration interface.

Porcelain veneers as an alternative for esthetic treatment: clinical report.

This case report describes the restoration of the anterior dentition with porcelain laminate veneers. The advances in bonding of porcelain to tooth structure make this treatment a feasible alternative to restore teeth with alteration in shape and position in cases in which the esthetic demand is high. The rationale for various choices in this treatment protocol is detailed with reference to the pertinent literature. Thus, the clinical success of the technique depends on the correct identification of a case for which this treatment is appropriate and the successful execution of the clinical steps involved.

Influence of matrix metalloproteinase synthetic inhibitors on dentin microtensile bond strength of resin cements.

This study evaluated the effect of dentin pretreatment with 2% chlorhexidine (CHX) or 24% ethylenediamine tetra-acetic acid gel (EDTA) on the dentin microtensile bond strength (µTBS) of resin cements. Composite blocks were luted to superficial noncarious human dentin (n=10) using two resin cements (RelyX ARC [ARC] and RelyX U100 [U100]) and three dentin pretreatments (without pretreatment-control, CHX, and EDTA). CHX was applied for 60 seconds on the acid-etched dentin in the ARC/CHX group, and for the same time on smear layer-covered dentin in the U100/CHX group. EDTA was applied for 45 seconds on smear-covered dentin in the U100/EDTA group, and it replaced phosphoric acid conditioning in the ARC/EDTA group for 60 seconds. After storage in water for 24 hours, specimens were prepared for microtensile bond strength testing. The results were submitted to two-way analysis of variance (ANOVA) followed by Tukey test. ARC produced significantly higher µTBS (p<0.05) compared to the U100, except when EDTA was used. For ARC, no pretreatment and CHX produced higher µTBS than EDTA. For U100, EDTA produced higher µTBS; no statistical difference occurred between CHX pretreatment and when no pretreatment was performed. While CHX did not affect immediate dentin bond strength of both cements, EDTA improved bond strength of U100, but it reduced dentin bond strength of ARC.

Effect of tooth bleaching on bond strength of enamel-dentin cavities restored with silorane- and dimethacrylate-based materials.

The aim of this study was to evaluate the influence of tooth bleaching on the push-out bond strength of a composite resin based on dimethacrylates and silorane to cavities that involve both enamel and dentin. A total of 80 bovine incisors were sectioned on the buccal surface to obtain specimens (10 × 10 mm) presenting enamel and dentin (1-mm thick each substrate). The specimens were randomly distributed into eight groups (n=10), according to the bleaching protocol (1--none; 2--10% carbamide peroxide [CP] for 21 days, six hours each day; 3--three applications of 35% hydrogen peroxide [HP] in 15-minute sessions, one session every seven days for three weeks; 4--10% CP for 18 days, six hours each day + three applications of 35% HP in 15-minute sessions, one session every seven days for three weeks) and the restorative system applied (Adper Single Bond 2 + Filtek Supreme; Filtek Silorane adhesive and composite resin). After treatment, cavities were made (1.2-mm diameter on dentin; 1.5-mm diameter on enamel) with a diamond bur. At 24 hours after restoration, a push-out bond strength test was performed at a crosshead speed of 0.5 mm/min. The bleaching treatments did not significantly affect the bond strengths of either restorative system to enamel-dentin. Regardless of the bleaching treatment, the dimethacrylate-based resin system exhibited significantly higher bond strengths to enamel-dentin than did the silorane-based system.

Evaluation of physical properties of enamel after microabrasion, polishing, and storage in artificial saliva.

This study evaluated the effect of microabrasion and polishing on the microhardness and roughness of bovine enamel, and the effect of artificial saliva on the hardness of enamel. Bovine enamel blocks were used, forming the groups (n = 48): GI-37% phosphoric acid and pumice, GII--Opalustre, and GIII--Whiteness RM. The groups were divided into different subgroups: (a) diamond paste, (b) fluoride prophylactic paste, and (c) without polishing. Hardness tests were carried out at the following set times: (T1) initial, (T2) after microabrasion and polishing, (T3) after immersion in artificial saliva for 24 h; and (T4) after seven days of immersion. Surface roughness tests were performed. The obtained data were analyzed by two-factor ANOVA and Tukey's test with significance of 5%. Microhardness increased in T2; without polishing, only groups GII and GIII showed an increased microhardness. T3 did not differ from T4; GI, GII and GIII did not provide surface roughness that differed from each other; and all microabrasive systems followed by polishing showed a higher surface smoothness compared with the control groups. It is concluded that microabrasion followed by polishing provided higher hardness and better surface smoothness of the enamel. However, immersion in artificial saliva was not able to increase the enamel hardness.

Effect of preheating resin composite and light-curing units on the microleakage of Class II restorations submitted to thermocycling.

This in vitro study evaluated microleakage in Class II cavities restored with dental composite and varying light-curing units and the temperature of the composite when subjected to a thermocycling test. Ninety cavities were prepared on the proximal surfaces of bovine teeth and randomly divided according to the light-curing mode (QTH-420 mW/cm2, LED 2nd generation-1100 mW/cm2, or LED 3rd generation-700 mW/cm2) and temperature of the resin composite (23°C, 54°C and 60°C). Following the restorative procedures and thermocycling, the samples were immersed in methylene blue for 12 hours. The samples were ground and the powder prepared for analysis in an absorbance spectrophotometer. All the results were statistically analyzed using the nonparametric tests of Kruskal-Wallis and Dunn (p ≤ 0.05). The results showed that there was no statistical difference between the light-curing modes at a temperature of 23°C. For 54°C, QTH showed a microleakage mean that was significantly lower than those of the LED groups, and for 60°C, QTH had a microleakage mean significantly lower than that of the LED 2nd generation group. There was no statistical difference between the temperatures of the resin composite when LEDs were used. For QTH, 54°C showed statistically lower microleakage than 23°C. The group preheated to 60°C showed no difference when compared to the group heated to 23°C. Preheating the resin composite (54°C and 60°C) did not improve the microleakage means when high-irradiance LED was used; however, it decreased the microleakage means when a QTH with low irradiance was used.

Quantitative evaluation of marginal leakage of two resin composite restorations using two filling techniques.

This in vitro study evaluated the marginal leakage of two light-cured resin composites used for posterior restorations using two filling techniques. Standardized Class V cavities were made on the enamel vestibular surface of 30 freshly extracted sound inferior bovine incisors. The teeth were randomly restored according to three experimental groups (Group 1--Z250 with 1 mm vertical increments; Group 2--Z250 with 1 mm horizontal increments; Group 3--SureFil with 1 mm horizontal increments). All samples were thermocycled (3000 cycles at 5 degrees C and 55 degrees C) with a dwell time of one minute at each temperature and immersed in a dye solution for 12 hours. After being ground into powder, the samples were individually immersed into glass tubes with absolute alcohol. The solution was centrifuged and the supernatant was analyzed using a spectrophotometer to quantify its dye concentration. Results showed that Group 2 exhibited the lowest leakage means, which was significantly different from Groups 1 and 3 (p<0.05). It was concluded that despite the lower leakage means exhibited by medium viscosity composites, no restorative material or filling technique was able to avoid leakage.