Effect of radiotherapy on the microleakage of adhesive systems.

PURPOSE: The aim of this in vitro study was to evaluate the effect of radiotherapy on the microleakage of three adhesive systems: a one-step self-etching, a two-step self-etching, and an etch-and-rinse system. MATERIALS AND METHODS: Box-shaped Class V cavity preparations were prepared on the buccal surfaces of 84 extracted human molars. The molars were randomly assigned into 6 groups (n = 14) according to the irradiation and adhesive system as follows: G1, Clearfil S3 Bond (irradiated); G2, Clearfil SE Bond (irradiated); G3, Prime & Bond NT (irradiated); G4, Clearfil S3 Bond (nonirradiated); G5, Clearfil SE Bond (nonirradiated); and G6, Prime & Bond NT (nonirradiated). The cavities were restored with composite resin (Filtek Z 250). After restoration of the samples, a total dose of 60 Gy was delivered in 2 Gy/d fractions for 5 days per week for 6 weeks for the related groups. All specimens were thermocycled for 200 cycles between 5 degrees C and 55 degrees C using a dwell time of 60 s in each bath and then placed in 0.5% basic fuchsin solution for 24 h at room temperature. Specimens were then rinsed and sectioned; the dye penetration at the enamel and dentin margins was examined using a stereomicroscope, and a score of 0 to 3 was assigned. Data were analyzed using the Kruskal-Wallis and Mann-Whitney U-tests. RESULTS: No statistically significant difference existed between the irradiated and nonirradiated groups (p > 0.05). Significant differences in microleakage were observed between enamel and dentin (p < 0.01). The microleakage at the dentin margins was greater than at the enamel margins. Prime & Bond NT revealed statistically significantly (p < 0.05) higher leakage scores in dentin than did ClearfilS3 Bond and Clearfil SE Bond. CONCLUSION: Within the limitations of this study, irradiation application did not affect the microleakage of dental adhesive systems.

The effect of dentin-cleaning agents on resin cement bond strength to dentin.

BACKGROUND: Provisional cement remnants on dentin affect the bond strength of resin cements to dentin. The authors investigated the effects of dentin-cleaning agents and etching systems on the bond strength of adhesive resin cement. METHODS: The authors removed the provisional cement from the dentin surfaces of the specimens and then cleaned the surfaces with the dentin-cleaning agents Sikko Tim (VOCO GmbH, Cuxhaven, Germany), Cavity Cleanser (Bisco, Schaumburg, Ill.) or Consepsis Scrub (Ultradent, South Jordan, Utah). They used adhesive resin cement after applying the different etching adhesive systems. Then they examined the dentin surfaces by using scanning electron microscopy. RESULTS: The authors analyzed data by means of a two-way analysis of variance with Tukey honestly significant difference tests (alpha= .05). They found that specimens cleaned with Sikko Tim and Consepsis Scrub had higher shear bond strength values than did those in the no-treatment control group or the group cleaned with Cavity Cleanser. The specimens treated with the total-etching adhesive system had higher shear bond strength than did those treated with the self-etching adhesive systems. CONCLUSIONS: Sikko Tim and Consepsis Scrub were effective in removing provisional cement. Adhesive resin cement showed higher bond strength when used in conjunction with the total-etching adhesive system. CLINICAL IMPLICATIONS: The use of an effective dentin cleaner before cementation with resin cement can increase bond strength.

The effect of different light sources on microleakage of bleached enamel.

This study evaluated the immediate effects of halogen, LED (light-emitting diode), and plasma are curing units on microleakage of bleached enamel. The buccal and lingual enamel surfaces of experimental groups (n=30) were bleached with 16% carbamide peroxide for a period of 10 days, with a daily contact time of 90 minutes. Box-shaped Class V cavities were also prepared on 60 extracted molar teeth (n=30, control group). For all groups, a composite resin (Grandio) was bonded with one of the two employed adhesive systems, Single Bond 2 or Prime & Bond NT. After restoration, all specimens were thermocycled for 200 cycles between 5 degrees C and 55 degrees C with a dwell time of 60 seconds in each bath, and then exposed to a dye. In the control groups, microleakage was statistically lower than the bleached groups (p<0.01). Groups cured with QTH and PAC showed no statistical differences (p>0.05). However, groups cured with LED system showed statistically significant differences (p<0.01) in microleakage.

Bond strengths of two conventional glass-ionomer cements to irradiated and non-irradiated dentin.

This study evaluated the influence of irradiation on the dentin shear bond strength of two conventional glass ionomer cements (GICs). Thirty extracted molars were bisected in the mesio-distal direction. One-half of 20 teeth were irradiated with 60 Gy (5 days/week) for 6 weeks, and then GIC was placed on the irradiated dentin surface (Groups A1, B1). For the other halves of these tooth specimens, the GICs were first placed on their dentin surfaces and then the specimens irradiated (Groups A2, B2). The remaining 10 teeth were bisected and used as non-irradiated controls (Groups C1, C2). The GIC-dentin shear bond strengths were examined. Groups A2 and B2 had significantly lower bond strengths than groups A1, B1, C1, and C2 (p < 0.05). No significant differences were found among groups A1, B1, C1, and C2 (p > 0.05). In conclusion, irradiation may have an adverse effect on the bond strength of GICs depending on the application sequence.

Influence of light-curing units on dentin bond strength after bleaching.

PURPOSE: The aim of this in vitro study was to comparatively evaluate the influence of three different light curing units (QTH Hilux, LED SmartLite, PAC Plasmaster) on shear bond strength of an adhesive system (Clearfil SE Bond ) after bleaching. MATERIALS AND METHODS: Sixty molars were used for this study. Carbamide peroxide was applied to the floor and wall of the dentin surfaces in bleached groups for 3 weeks. Each week the paste was renewed for the bleached group. Teeth were sectioned mesiodistally. The roots of the sectioned teeth were mounted in a cylindrical mold using chemically cured acrylic resin. Composite resin was added to the center of flattened dentin surfaces with an internal diameter of 3 mm and height of 3 mm. The bonding procedure was performed in the bleached test groups as follows: G1: immediately/QTH; G2: after 1 week/QTH; G3: after 2 weeks/QTH; G4: immediately/LED; G5: after 1 week/LED; G6: after 2 weeks/LED; G7: immediately/PAC; G8: after 1 week/PAC; G9: after 2 weeks/PAC. The non-bleached groups (control group) were G10: QTH; G11: LED; G12: PAC. Specimens were mounted in a universal testing machine and shear load was applied at a crosshead speed of 1 mm/min until failure. Bond strength values were calculated as MPa and the comparisons were made statistically using one-way ANOVA with light source and bleaching treatment) as the two factors. RESULTS: The mean values of shear bond strength in MPa were: G1 (12.23), G2 (19.18), G3 (23.08), G4 (13.07), G5 (21.01), G6 (25.27), G7 (12.55), G8 (19.06), G9 (25.41), G10 (24.54), G11 (26.99), G12 (25.97). No statistical difference was found between the control group and groups bonded two weeks later. The bond strength values of the control group and those bonded 2 weeks later were higher than other groups. Statistically significant differences were found between the immediate and 1-week groups (p < 0.01). Immediately bonded groups had the lowest bond strength compared to the others (p < 0.05). No significant differences in bond strength were observed among three lightcuring units (p > 0.05). CONCLUSION: It was concluded that different light-curing units had no effect on shear bond strength of bleached dentin. A 2-week delay in restoration after bleaching improved the reduced bond strength of resin composite.

Influence of radiation on bond strength.

PURPOSE: The aim of this in vitro study was to evaluate the shear bond strength of two adhesive systems--Prime & Bond NT (PBNT) and Clearfil SE Bond (CSEB)--to dentin irradiated before or after adhesive application. MATERIALS AND METHODS: Thirty extracted molars were sectioned mesiodistally with a diamond bur. The inner surface of each tooth's dentin was ground flat with SiC abrasive papers. The roots of the sectioned teeth were mounted in a cylindrical mold using chemically cured acrylic resin. In groups A1 and B1, a radiation dose of 60 Gy (R) was applied to the dentin surfaces at this point. In all groups, adhesives were applied according to the respective manufacturer's instructions. Cylindrical composite resin restorations (CRR; internal diameter 3 mm, height 4 mm) were then placed on the center of the flattened dentin surfaces. At this point, groups A2 and B2 received 60 Gy of radiation, and groups C1 and C2 remained as nonirradiated controls. Thus, the test groups were: A1: R + PBNT (Primed Bond NT) + CRR; A2: PBNT + CRR + R; B1: R + CSEB (Clearfil SE Bond) + CRR; B2: CSEB + CRR + R; C1: PBNT+ CRR; C2: CSEB+ CRR. Specimens were mounted in a universal testing machine and shear load was applied at a crosshead speed of 1 mm/min until failure. Bond strength values were calculated as MPa and the results were evaluated statistically using repeated measures of two-way ANOVA, with significance set at p < 0.05. RESULTS: Irradiation significantly affected adhesion of composite to dentin in groups A1 and A2 (p = 0.002). Group A1 showed statistically lower bond strength than group A2 (p < 0.05). No statistically significant differences were found among the other groups (p = 0.49). CONCLUSION: The time point of irradiation can have an adverse effect on bond strength, depending on the type of adhesive material.

Endodontic treatment of a taurodontic premolar with five canals.

Taurodontism is a morpho-anatomical abnormality in the shape of a tooth. An enlarged pulp chamber, apical displacement of the pulpal floor and no constriction at the level of the cemento-enamel junction are the characteristic features. Special care is required in all aspects of endodontic treatment of a taurodontal tooth, including identifying the orifice, canal exploration, cleaning, shaping and obturation of the root canal. This case report describes the successful endodontic treatment of a taurodontic mandibular second premolar with five root canals.

Multiple pulp stones: a case report.

Pulp stones are usually found in the pulp chamber. Radiographically, they appear as radiopaque structures in the pulp chambers or root canals of individual teeth. Generalized pulp stones throughout the dentition are usually associated with systemic or genetic disorders of the dentine. This report presents an unusual case of a 13-year-old girl with generalized pulp stones with clinically normal crowns. The patient's main complaint was a crossbite affecting all permanent canines. Radiographic examination revealed multiple pulp stones and several teeth with atypically shaped roots. Orthodontic treatment, gingivoplasty, and esthetic restorations were performed, thus using a multidisciplinary approach to establish functionally and esthetically sound dentition.

Effects of three canal sealers on bond strength of a fiber post.

INTRODUCTION: This study evaluated the effects of three different endodontic sealers on the bond strength of a fiber post cemented with adhesive resin cement. METHODS: Forty-eight extracted maxillary central incisors were prepared with the step-back technique and randomly divided into four groups (n=12 for each group): group 1, control group (gutta-percha points only, no sealer); group 2, resin-based sealer (AH plus; Dentsply De Trey GmbH, Konstanz, Germany); group 3, zinc oxide-eugenol-based sealer (Endofill; Produits Dentaires SA, Vevey, Switzerland); and group 4, calcium hydroxide-based sealer (Sealapex; Kerr, Romulus, MI). The roots were obturated with gutta-percha using the cold lateral compaction technique. Fiber posts were cemented into the prepared post spaces with the adhesive resin cement Panavia F 2.0 (Kuraray Medical, Okayama, Japan). A push-out test was performed in a universal machine, and failure modes were observed. Morphologic changes of the root canal dentin surfaces were examined with scanning electron microscopy (SEM). RESULTS: One-way analysis of variance revealed that sealers have significant effects on bond strength (p<0.05). The control group had the highest mean push-out bond strength. No statistical difference was detected between the eugenol-based sealer group and the resin-based sealer group (p>0.05). The root surfaces were covered with the smear layer and debris in all the groups after post space preparation in SEM analysis. However, some of the dentin tubules were partially open in the control and calcium hydroxide-based sealer groups after the application of the resin monomer. CONCLUSION: The results of this study showed that the type of canal sealer and chemomechanical preparation of the root canals affect the bond strength of a fiber post cemented with resin cement.

Effect of different surface treatments on the push-out bond strength of fiber post to root canal dentin.

OBJECTIVE: The purpose of this study was to evaluate the effects of different surface treatments on the bond strength of a fiber post to dentin. STUDY DESIGN: Sixty extracted human maxillary incisor teeth were manually shaped with K-files using the step-back technique. ISO size 45 files were used as master apical files. Post spaces were prepared and then the root canals were subjected to one of the following 5 surface treatments: irrigation with 5% sodium hypochlorite (NaOCl); treatment with ethanol, ethyl acetate, and acetone-based cleansing agent (Sikko Tim); irrigation with 17% EDTA; etching with 37% orthophosphoric acid for 15 seconds; and etching with 10% citric acid for 15 seconds. Fiber posts were luted using self-etching/self-priming dual polymerized resin cement. From the coronal part of each root, 3 slides of 0.6-mm thickness were obtained. A push-out bond strength test was performed by a universal testing machine at a crosshead speed of 0.5 mm/min. Dentin surfaces were examined under scanning electron microscopy (SEM) after different surface treatments. Data were analyzed with a one-way analysis of variance (ANOVA) and Tukey HSD test. RESULTS: ANOVA revealed that canal surface treatment affected the bond strength (P < .001). The highest bond strength was obtained in the Sikko Tim group. The results also showed that surface treatment methods increased the bond strength to dentin when compared with the control group. CONCLUSIONS: Sikko Tim group was the more effective surface treatment agent compared with EDTA, orthophosphoric acid, citric acid, and control groups; however, it could not remove the smear layer and sealer remnants effectively on radicular dentin surfaces. Removal of the smear layer and opening of dentinal tubules are not recommended when a self-etching/self-priming adhesive system is used.

Comparison of shaping ability of RaCe and Hero Shaper instruments in simulated curved canals.

OBJECTIVE: This study compared the shaping ability of Hero Shaper and RaCe instruments in simulated curved canals. STUDY DESIGN: Forty simulated canals in resin blocks were divided into 2 experimental groups, each comprising 20 resin blocks, and prepared with Hero Shaper and RaCe using the crown-down technique. Preoperative and postoperative photographs, recorded using a digital camera, were superimposed and aberrations were recorded. Material removal was measured at 10 points beginning 1 mm from the end point of the canal. Mean total widths, outer and inner width measurements, were determined on each central canal path and differences were statistically analyzed using Student t test. RESULTS: The Hero Shaper and RaCe instruments removed almost the same amount of material from the inner side of the simulated canals. On the outer canal wall, the RaCe instruments removed significantly more material from the first 3 mm (P < .05). However, Hero Shaper removed more material from the middle and coronal aspects of the canal and the differences were statistically significant (P < .01). CONCLUSION: RaCe instruments removed more resin from the outside of the curvature at the apical thirds, while Hero Shaper removed more material from the middle and coronal thirds on the outer canal wall. Hero Shaper instruments showed better centering ability and fewer aberrations. No instrument fractures but some deformations were observed for both systems.