Evaluation of crown discoloration induced by endodontic sealers and colour change ratio determination after bleaching.

The aim of this study was to evaluate tooth discoloration after the use of root canal sealers and the effect of internal bleaching on sealer discoloration. The crowns of 56 incisors were cut and randomly filled with four sealers (n = 14): Pulpispad, AH26, MTA Fillapex, EndoREZ. The colour measurement was taken with a spectrophotometer prior and after placement of sealers. Colour changes (ΔE) were recorded after 4 weeks then sealers were removed and an internal bleaching treatment was performed. After bleaching treatment colour changes (ΔE) were measured. Data were analysed using ANOVA and Tukey's test (α = 0.05). All tested sealers induced varying chromatic alterations. Pulpispad showed statistically more discoloration than other sealers (P < 0.05). After bleaching, EndoREZ showed statistically more bleaching ratio than MTA Fillapex and AH26 (P < 0.05). Internal bleaching was efficient in discoloured teeth induced by root canal sealers.

Effect of post-space treatments on the push-out bond strength and failure modes of glass fibre posts.

The aim of this study was to evaluate the effect of different post-space treatments on the push-out bond strength and failure modes of glass fibre posts. Forty mandibular premolar roots were cut and endodontically treated. Post spaces were prepared and roots were divided into four groups. In group 1 distilled water irrigation (control), in group 2 2.25% NaOCl irrigation, in group 3 2.25% NaOCl + 17% EDTA irrigation were done and in group 4 diode laser was applied to the prepared post spaces. Scanning electron microscope (SEM) analysis was made for each group. Fibre posts were then luted with resin cement. Each root was prepared for push-out test. Data were statistically analysed with anova (P = 0.05). After push-out test, the failure modes were observed but not statistically analysed. There were statistically significant differences between Group 3 and Group 2 in both regions (P < 0.05), also in the middle region of Group 4 and Group 2 (P < 0.05). Cervical root segments showed higher bond strengths than middle ones in all groups (P < 0.05). The highest bond strength values were obtained from NaOCl/EDTA and the lowest bond strength values were obtained from NaOCl for both regions.

Effect of light-activated bleaching on pulp chamber temperature rise: an in vitro study.

This study aimed to compare the pulp chamber temperature changes that occur with the use of different light sources during vital bleaching with and without application of bleaching agents. One hundred and forty-four mandibular incisor teeth were divided into four groups (n = 36) according to the use of halogen light, light-emitting diode, 3 W and 1.5 W diode laser. The teeth in the main groups were divided into three subgroups (n = 12). First subgroup had no bleaching gel application. By White and Whiteness HP were applied with a thickness of 2 mm to the other subgroups respectively. The labial surfaces of the teeth were irradiated with a total time of 20 s. Temperature changes in the pulp chamber were measured and analysed by using anova and Tukey test. The 3 W diode laser induced the highest pulp chamber temperature rise (P = 0.000). Bleaching gel application reduced the temperature changes in the diode laser groups (P < 0.05). Diode laser activation during vital bleaching induces pulp chamber temperature rise, which may cause thermal tissue damage.

Effect of different disinfectant methods on the initial microtensile bond strength of a self-etch adhesive to dentin.

The aim of this in vitro study was to evaluate the effect of different disinfection methods on the initial microtensile bond strength of a two-step, self-etch adhesive to dentin. Twenty mandibular molars were sectioned parallel to the occlusal plane to expose the mid-coronal dentin. All of the teeth were divided into four groups (n = 5 per group): (1) in group OZ, the dentin surfaces were exposed to ozone gas from the Ozonytron X delivery system (OzonyTron X-Bioozonix, Munich, Germany), (2) in group ND, the dentin surfaces were irradiated with an Nd:YAG laser (Pulsmaster 600 IQ, American Dental Technologies, U.S.), (3) in group CHX, the dentin surfaces were treated with a 2% chlorhexidine solution, and (4) in the control group, no treatment was applied. In all of the groups, the teeth were restored with Clearfil SE Bond (Kuraray, Tokyo, Japan) and Clearfil Majesty Posterior (Kuraray, Tokyo, Japan), according to the manufacturer's instructions. The teeth were sectioned perpendicular to the bonded surface (surface area of approximately 1 mm(2)). Thus, six to seven specimens were obtained from each tooth, and a total of 34 specimens were analyzed in each group. The specimens were attached to the microtensile test machine (Micro Tensile Tester, T-61010 K, Bisco, U.S.). The data was analyzed using the one-way analysis of variance (ANOVA) and Tukey test (p < 0.05). Fracture modes of each specimen were determined using a stereomicroscope (SZ-PT Olympus, Tokyo, Japan) and a scanning electron microscope (SEM). The lowest bond strength occurred in the OZ group. Significant differences were determined only between group OZ and the other groups (group ND, group CHX, and control group) (p < 0.05). In conclusion, although ozone decreased the microtensile bond strength of the self-etch adhesive system to dentin, the Nd:YAG laser and 2% chlorhexidine did not change the microtensile bond strength so in context of the present study it would appear that the Nd:YAG laser and 2% chlorhexidine may be used as pre-restorative sterilization procedures on the dentin prior to the application of a two-step, self-etch adhesive.

Fracture resistance of premolars with one remaining cavity wall restored using different techniques.

The aim of the study was to compare the fracture resistance of maxillary premolars with one remaining cavity wall restored using different post systems. Forty-eight maxillary premolars were endodontically treated and randomly assigned to four groups for postcore restoration. The first three test groups were restored with polyethylene woven fiber posts, custom-made glass fiber-reinforced composite posts, and titanium posts respectively. In the control Group 4, standardized cavities (3.5 x 1.5 mm) were prepared in the palatal canal entrance and filled with a resin composite. All the specimens were then restored with a resin composite crown seated on the post. Load was applied with a stainless steel ball (1 mm/min), and the failure modes of all specimens were evaluated. There were no significant differences in fracture resistance and failure mode among the different restorative materials (p>0.05). Within the limitations of this in vitro study, it was concluded that the presence and type of post did not influence the fracture load and failure mode of maxillary premolar teeth with one remaining cavity wall.

Fracture resistance of teeth restored with different post systems using new-generation adhesives.

AIM: The aim of this study was to investigate the fracture strength of three post systems cemented with a dual cure composite resin luting cement by using different adhesive systems. METHODS AND MATERIALS: In this study 63 extracted anterior teeth with single roots were endodontically prepared and filled. Teeth were randomly assigned to one of three post systems placed into the prepared canals: Group I - titanium posts (n=21) (Filpost); Group II - glass fiber posts (n=21) (Mirafit White); and Group III zirconia posts (n=21) (CosmoPost). Each group was again randomly divided into three subgroups according to the bonding materials used [Single Bond (n=7), Clearfil SE Bond (n=7), and Prompt L Pop (n=7)]. A dual cured resin cement (Rely X ARC) was used for bonding the posts into the root canals. Standard cores were made by a composite resin (Clearfil Photocore) using core build-ups. The samples were tested in the compression test machine for 1 mm/min and fracture resistance of the teeth were recorded. The data was analyzed by using two-way analysis of variance (ANOVA) and Duncan's New Multiple Range Tests. A significance level of p<.05 was used for all comparisons. RESULTS: There was a significant difference in fracture resistance between the post systems (p<0.05) and the interaction of adhesive resins and post systems (p<0.05). Mirafit White was more resistant to fracture than other groups; Filpost showed the least resistance to fracture. CosmoPost post system bonded with Single Bond recorded the lowest fracture resistance (p<0.05). CONCLUSION: Endodontically treated anterior teeth restored with glass fiber posts exhibited higher failure loads than teeth restored with zirconia and titanium posts. Self-etching adhesives are better alternatives to etch-and-rinse adhesive systems for luting post systems. CLINICAL SIGNIFICANCE: Under the condition of this study, glass fiber posts are preferable to restore endodontically treated anterior teeth.

Staining potential of calcium hydroxide and monochlorophenol following removal of AH26 root canal sealer.

AIM: The focus of this study was to examine the staining potential of calcium hydroxide (Ca(OH)2) on tooth structure following the removal of AH26 root canal sealer. METHODS AND MATERIALS: Fifty maxillary anterior teeth were prepared and obturated with AH26 and gutta percha. The sealers were then removed 24 hours later and the teeth were randomly divided into two groups. Ca(OH)2 was then placed in the root canals of the first group of teeth as a medicament and camphorated monochlorophenol (CMCP) was placed in the second group of teeth after the filling material was removed. The color of the external tooth surfaces was determined before tooth preparation and two weeks after the placement of the medicaments. The Z test was used for statistical analysis. RESULTS: All experimental teeth showed varying degrees of coronal discoloration with the Ca(OH)2 group showing more discoloration than the CMCP group (p<0.05). CONCLUSION: Using Ca(OH)2 as a medicament after removing AH26 caused progressive discoloration of the teeth, whereas using CMCP caused only slight discoloration. CLINICAL SIGNIFICANCE: To avoid staining of the treated tooth, AH26 root canal sealer must be completely removed from the dentin walls before using a medicament.

Effects of Er:YAG laser and Nd:YAG laser treatment on the root canal dentin of human teeth: a SEM study.

The objective of the study was to observe the morphological changes on root canal dentin after Er:YAG laser and Nd:YAG laser treatment. Twenty-one teeth biomechanically prepared were divided into three groups with seven teeth of each. Group A was unlased as a control. In group B, Er:YAG laser and in group C, Nd:YAG laser was applied to the root canal dentin. The roots were split longitudinally and examined using a scanning electron microscopy for the evaluation of debris, smear layer, and recrystallization. There was no statistically significant difference between the groups. This study indicates that laser beam is not effective in removing debris and smear layer.

Microhardness of packable composites used as posts condensed with different methods.

The purpose of this in vitro study was to evaluate the microhardness of packable composite compacted with hand or ultrasonic pluggers in post spaces. A total of 168 extracted human anterior teeth were prepared with Gates Glidden and ParaPost drills after obturation. A primer and a dentin-bonding agent were applied to the etched surface. Half of the specimens were compacted with an ultrasonic tip and the other half with a mechanical hand compactor and all specimens were polymerized for each increment. The roots were then sectioned horizontally from 0, 2.5, 3, 3.5, 4, 4.5, and 5 mm starting from the coronal and sliced 2.5-mm long. The microhardness test was applied to each specimen. There were statistically significant differences between ultrasonically and hand-condensed groups in whole specimens (p < 0.001). There were no significant differences between groups of 0, 2.5, and 3 mm until 3.5 mm was reached. After 3.5-mm depth, there were significant differences between the groups (p < 0.001). Ultrasonic condensation of packable composites provided mechanical advantage over hand condensation in root canals measuring microhardness in different depths. However, when microhardness was measured at different depths, values decreased after the depth of 3.5 mm in both condensation groups.