The effects of bonding system and light curing method on reducing stress of different C-factor cavities

Purpose: The effect of the slow-start curing method on the marginal sealing and cavity wall adaptation on resin composite restorations with different C-factors was evaluated. Methods: Cylindrical cavities, 1 mm deep and 3 mm in diameter (C-factor = 2.3) or 2 mm in diameter (Cfactor = 3) were prepared on flat superficial bovine dentin surfaces. The teeth were restored with Clearfil Photo Bond, Clearfil Liner Bond 2 or Super-Bond D Liner adhesive systems followed by Photo Clearfil Bright composite. The resins were cured with a conventional method using 600 mW/cm2 (tip-to-resin distance 0 mm) for 60 s, or the slow-start curing method of 270 mW/cm2 (tip-to-resin distance 10 mm) for 10 s, followed by a 5-s interval, then 50 s at 600 mW/cm2. After thermocycling, a dye penetration test was carried out. The dye penetration length was calculated as a percentage of the total cavity wall length. Results: Cavity-wall gap formation increased when the C-factor increased from 2.3 to 3, except in one material, Super-Bond D Liner, which showed good marginal sealing and resin composite adaptation to the cavity wall regardless of light curing method and C-factor. Conclusion: It is necessary to take care when a cavity with a high C-factor is to be restored with resin composite. The combination of a flexible adhesive and the slow-start curing method would seem to be effective in reducing polymerization contraction stress for large C-factor cavities.link_to_subscribed_fulltex

A light curing method for improving marginal sealing and cavity wall adaptation of resin composite restorations

Objective: The aim of this study was to evaluate whether the method of light curing could influence: (a) marginal sealing and resin composite adaptation to the cavity wall; (b) polymerization contraction rate; and (c) the hardness at the top and bottom surfaces of a body of resin composite. Methods: Standard cylindrical cavities, 1 mm deep and 3 mm in diameter were prepared on flat superficial dentin surfaces in bovine teeth. The teeth were bonded with one of two adhesive systems (Clearfil Photo Bond, and Super-Bond D Liner) and filled with a hybrid resin composite. The resins were cured using three light intensities of 600, 270 and 20 mW/cm2, and various curing times. After thermal cycling, the specimens were subjected to a dye penetration test to evaluate marginal sealing and adaptation of the resin composite to the cavity walls. In addition, using the same curing conditions, the rate of polymerization contraction was measured. The difference of hardness over time of composite specimens was measured using Knoop hardness measurements taken at the top and bottom surfaces of resin specimens made in a Teflon mold the same dimensions as the cavity prepared in dentin. Results:When the composite was light cured with an initial light intensity of 270 mW/cm2 for 10 s, a 5 s interval then a light intensity of 600 mW/cm2 for 50 s, the best marginal sealing and cavity wall adaptation was observed compared with the other curing modes. Earlier hardening occurred at the resin composite base compared with the top surface of the composite, and most of the polymerization contraction was completed during the initial flowable stage of the resin composite. All other methods demonstrated results with some degree of marginal opening and cavity wall gap formation, the worst being 600 mW/s for 60 s. Significance: The use of a low initial light intensity (270 mW/cm2) for 10 s followed by high intensity light (600 mW/cm2) for 50 s provides the best adaptation of resin composite to cavity walls and possibly the least polymerization contraction stress. © 2001 Academy of Dental Materials. Published by Elsevier Science Ltd. All rights reserved.link_to_subscribed_fulltex

The effect of bonding system and composite type on adaptation of different C-factor restorations

This study evaluated the effect of two adhesive systems and four resin-based composites on the marginal sealing and cavity wall adaptation of restorations with different C-factors. Cylindrical cavities, 1 mm deep and 3 mm in diameter (C-factor = 2.3) or 2 mm in diameter (C-factor = 3), were prepared on superficial bovine dentin surfaces. The teeth were restored with Clearfil SE Bond or Single Bond adhesive system followed by hybrid (Photo Clearfil Bright or Z100) or flowable (Filtek Flow or Estelite LV) resin composite. After thermocycling, a dye penetration test was carried out to evaluate the degree of marginal leakage and cavity-wall gap formation. Cavity-wall gap formation increased when the C-factor increased from 2.3 to 3, except for Estelite LV resin composite. In terms of marginal sealing, Clearfil SE Bond showed better performance than Single Bond. When using Clearfil SE Bond, flowable composites improved resin composite adaptation to the cavity wall compared with hybrid composites.link_to_subscribed_fulltex

The effect of thermal stress on bonding durability of resin composite adaptation to the cavity wall

This study evaluated the effect of thermal stress on marginal sealing and cavity wall adaptation using two adhesive systems. Cylindrical cavities were prepared in superficial dentin of bovine incisors and bonded with Clearfil SE Bond or Single Bond adhesive. Cavities were bulk-filled with Photo Clearfil Bright or Filtek Flow resin composite and light-cured for 40 seconds. Specimens were thermocycled for 0, 500, or 5000 times. A dye penetration test was carried out to determine adaptation to the cavity wall. Dye penetration length was calculated as a percentage of the total cavity wall length. Clearfil SE Bond showed excellent marginal sealing and cavity wall adaptation regardless of composite type up to 500 cycles of thermal stress. As for the Single Bond groups, significantly greater marginal leakage occurred after 500 cycles. At 5000 cycles of thermal stress, both adhesive systems showed significantly decreased marginal integrity compared with the 0 cycle group.link_to_subscribed_fulltex

Effect of light-curing method and irradiation time on marginal sealing and cavity wall adaptation of resin composite restorations.

PURPOSE: To evaluate the effect of irradiation time on two light-curing methods on the marginal sealing and cavity wall adaptation of resin-based composite restorations. METHODS: Cylindrical cavities, 1 mm deep and 3 mm in diameter (C-factor = 2.3) were prepared on flat superficial bovine dentin surfaces. The teeth were restored with Clearfil Photo Bond, Clearfil Liner Bond 2 or Super-Bond D-Liner adhesive systems followed by Photo Clearfil Bright resin-based composite. The resins were cured using a conventional method at an output of 600 mW/cm2 for 60 s, or 600 mW/cm2 for 30 s, or the slow-start curing method at an output of 270 mW/cm2 for 10 s + 5 s (interval) + 600 mW/cm2 for 50 s or 270 mW/cm2 for 10 s + 5 s (interval) + 600 mW/cm2 for 20 s. After thermocycling, a dye penetration test was carried out. The dye penetration length was calculated as a percentage of the total cavity wall length. RESULTS: Slow-start curing method; 270 mW/cm2 10 s + 5 s (interval) + 600 mW/cm2 for 50 s showed the best marginal sealing and cavity wall adaptation. A shorter irradiation time increased cavity wall adaptation when the conventional curing method was used. Super-Bond D-Liner showed good marginal sealing and resin composite adaptation to the cavity wall regardless of the light-curing method.link_to_subscribed_fulltex

Effect of intrinsic wetness and regional difference on dentin bond strength

Objectives: The aim of this investigation was to determine the influence of intrinsic wetness on regional bond strengths of adhesive resins to dentin. Methods: Human caries-free third molars were randomly divided into three groups for bonding: Group 1 - no pulpal pressure; Group 2 -pulpal pressure of 15 cm H2O; and Group 3 - dentin dried overnight in a desiccator. Clearfil Liner Bond II (Kuraray) or One Step (Bisco) adhesive resins systems were applied to the flat dentin surfaces and the teeth were restored with APX resin composite (Kuraray). After 24 h in water at 37°C, the specimens were sectioned into 0.7 mm thick slabs and divided into three regional subgroups according to the remaining dentin thickness and visual criteria: pulp horn, center, and periphery. The slabs were then trimmed for the micro-tensile bond test and subjected to a tensile force and crosshead of 1 mm/min. The data were analyzed with ANOVA and Fisher's PLSD test at a confidence level of 95%. The fracture modes were determined under a scanning electron microscope (JXA-840, JEOL, Japan). Results: No significant regional difference was observed for the Group 1 and 2 specimens restored with Clearfil Liner Bond II (p > 0.05). However, bond strengths significantly decreased at the pulp horn region of the Group 1 and 2 specimens restored with One Step (p 0.05). Significance: The dentin adhesive system should be chosen according to the substrate and region to be bonded, since bond strengths can vary according to the intrinsic wetness, region, and the adhesive system. © 1999 Published by Elsevier Science Ltd on behalf of the Academy of Dental Materials. All rights reserved.link_to_subscribed_fulltex

Retrospective study of five-year clinical performance of direct composite restorations using a self-etching primer adhesive system

This study was conducted to assess the five-year clinical performance of composite restorations using a self-etching primer adhesive system, Clearfil Liner Bond II. Restorations were rated using the following scale: A - Good; B - Clinically accepable; C - Clinically unacceptable; or D - Already replaced. The ratings were analyzed using Freedman's test (p=0.01) and Steel-Dwass test (p=0.05). A total of 83 restorations from 36 patients were identified from treatment records. Twenty-six restorations (31.3%) presented A rating and 36 restorations (43.4%) were clinically acceptable (B rating), while five (6.0%) received C rating and 16 (19.3%) had already been replaced (D rating). The mean survival rate of serviceable restorations (i.e., combined A and B ratings) after five years was 74.7%. It was found that cavity form, including cavity size, and occlusal contact seemed to influence longevity.link_to_subscribed_fulltex

Retrospective study of the 10-year clinical performance of direct resin composite restorations placed with the acid-etch technique.

OBJECTIVE: To assess the 10-year clinical performance of resin composite restorations placed using the acid-etch technique. METHOD AND MATERIALS: Clinical evaluation of 58 resin composite restorations was performed by 9 operators of the Operative Dentistry Clinic of the Dental Hospital, Tokyo Medical and Dental University. Conservative preparations had been made and a total-etch adhesive system used for the resin composite restorations, which were placed in 1992 in the Operative Dentistry Clinic. Restorations were scored using the following scale: Alfa--good; Bravo--clinically acceptable; Charlie--clinically unacceptable; Delta-already replaced. The scores were analyzed using the chi-square test and the expected cell frequency (P = .05). RESULTS: The 58 restorations from 26 patients (13 men and 13 women) were identified in the treatment records and analyzed. Twenty-two restorations (37.9%) presented Alfa scores and 17 restorations (29.3%) were clinically acceptable (Bravo scores), while 3 restorations (5.2%) received Charlie scores and 16 restorations (27.6%) had already been replaced (Delta scores). The descending ranking of longevity by restoration type was Class 5 >Class 3 >Class 2 >Class 1 >Class 4 (P = .05). CONCLUSIONS: Of the restorations evaluated, 67.2% were ser-viceable (combined Alfa and Bravo scores) 10 years after placement. Longevity was significantly influenced by cavity type.link_to_subscribed_fulltex