Effect of enamel and dentin surface wetness on shear bond strength of composites

Influence of surface wetness on bonding effectiveness of universal adhesives in etch-and-rinse mode

The purpose of this study was to evaluate whether surface wetness would influence the bonding effectiveness of universal adhesives in etch-and-rinse mode. All-Bond Universal (AB), G-Premio Bond (GP), Prime & Bond Active (PB), and Scotchbond Universal Adhesive (SU) were evaluated. Initial bond strengths and bond-fatigue strengths of universal adhesives to both wet and dry enamel and dentin in etch-and-rinse mode were determined. Scanning electron microscopy observations of the adhesive interfaces were also conducted. The bond-fatigue durability of universal adhesive to enamel in etch-and-rinse mode was influenced by the surface wetness, unlike that to dentin. The bond fatigue durability of AB and GP to dentin in etch-and-rinse mode was different depending on the surface wetness, unlike that of PB and SU. The thicknesses of the adhesive or hybrid layer of resin-dentin interfaces were not influenced by the surface wetness, but the length of resin tags in the wet group was longer than in the dry group. Some universal adhesives with the addition of specific components and optimization of water content can achieve stable bonds regardless of surface wetness, but the surface wetness of dentin is still a significant factor for universal adhesive bonding in etch-and rinse mode, unlike that of enamel.

Evaluation of the Shear Bond Strength of Composite Resin to Wet and Dry Enamel Using Dentin Bonding Agents Containing Various Solvents

INTRODUCTION

Bonding of composite resin to dentin mandates a wet substrate whereas, enamel should be dry. This may not be easily achievable in intracoronal preparations where enamel and dentin are closely placed to each other. Therefore, Dentin Bonding Agents (DBA) are recommended for enamel and dentinal bonding, where enamel is also left moist. A research question was raised if the "enamel-only" preparations will also benefit from wet enamel bonding and contemporary DBA.

AIM

The aim of this study was to compare the shear bond strengths of composite resin, bonded to dry and wet enamel using fifth generation DBA (etch and rinse system) containing various solvents such as ethanol/water, acetone and ethanol.

MATERIALS AND METHODS

The crowns of 120 maxillary premolars were split into buccal and lingual halves. They were randomly allocated into four groups of DBA: Group 1-water/ethanol based, Group 2-acetone based, Group 3-ethanol based, Group 4-universal bonding agent (control group). The buccal halves and lingual halves were bonded using the wet bonding and dry bonding technique respectively. After application of the DBAs and composite resin build up, shear bond strength testing was done.

RESULTS

Group 1 (ethanol/water based ESPE 3M, Adper Single Bond) showed highest bond strength of (23.15 MPa) in dry enamel. Group 2 (acetone based Denstply, Prime and Bond NT, showed equal bond strength in wet and dry enamel condition (18.87 MPa and 18.02 MPa respectively).

CONCLUSION

Dry enamel bonding and ethanol/water based etch and rinse DBA can be recommended for "enamel-only" tooth preparations.

Hydration and Dehydration Periods of Crown Fragments Prior to Reattachment

Introduction

Tooth fragment bonding is an excellent treatment option in dealing with traumatic injuries of the anterior teeth. Rewetting the tooth fragment has been shown to increase restoration durability. The present study examined the effect various dry and wet storage periods had on the reattached fragment's bond to the tooth.

Materials and Methods

One hundred and eight human mandibular incisors were fractured and assigned to undergo a dehydration period of 30 minutes, six hours, 24 hours, or three days before the rewetting procedure. After fracturing the teeth and drying the fragments, each of the specimens was assigned to one of the three main groups (A, B, or C) intended to evaluate the effect of different rehydration periods. Groups A and B underwent a 30-minute and a 24-hour rewetting period, respectively. Group C served as a control (without a rewetting stage). Tooth fragments were then reattached and prepared for the strength test. Force was applied on the lingual side of the tooth at a 1 mm/min rate until failure.

Results

The mean loads (N) required to fracture the restored teeth were as follows: 204.43 ± 33.48 N, 322.59 ± 34.62 N, and 253.25 ± 29.05 N for groups A, B, and C, respectively. Two-way analysis of variance (p<0.05) showed that rehydration and dehydration periods as well as their interaction caused significant differences in the strength of the final restoration. Multiple comparison tests showed that, in general, significant differences were not seen among different dehydration times prior to the rewetting stage (p>0.05), except in the case of the 30-minute dehydrated specimens (p<0.05).

Conclusion

Compared to a 30-minute period, a 24-hour rehydration of the tooth fragment before treatment seems to salvage enough moisture to result in an increase in reattachment strength.

Adhesive Bond Strengths to Enamel and Dentin Using Recommended and Extended Treatment Times

Self-etch adhesive systems are promoted as being more efficient for bonding procedures by using fewer treatment steps to condition tooth surfaces for bonding resin-based materials. Concern has been expressed regarding the ability of the newer self-etch adhesives to yield strong, durable bonds when compared to more traditional etch-and-rinse systems. Extending the treatment time of etch-and-rinse and self-etch adhesives does not appear to result in relevant increases in the bond strength of resin composites to enamel or dentin.

In vitro evaluation of the influence of repairing condition of denture base resin on the bonding of autopolymerizing resins

STATEMENT OF PROBLEM

Bonding failures of repair resin to denture base resin occurs when denture base resin is wet, however, little is known of how water relates to failures.

PURPOSE

This study evaluated the influence of water absorbed in denture base resin on the bond strength and resistance to cyclic thermal stresses of autopolymerizing resins bonded to denture base resin.

MATERIAL AND METHODS

Denture base resin disks (n = 180; 12 mm diameter and 3 mm thick) were fabricated from heat-polymerized acrylic resin (Lucitone 199). The disks were divided into groups (n = 60) with 3 conditions of water content: (1) complete water saturation (control), (2) superficial desiccation by blowing air on the specimen, or (3) complete desiccation. Each denture base specimen received 1 of 3 surface treatments (n = 20) including: (1) no treatment, (2) airborne-particle abrasion, or (3) methylene chloride application. An autopolymerizing repair resin (Repair Material, n = 10) or reline resin (Tokuso Rebase Normal set, n = 10) was applied to the bonding area (5 mm diameter) and polymerized at 37 degrees C for 10 minutes. The resistance to cyclic thermal stress was determined after subjecting the specimens to 50,000 thermal cycles between 4 degrees C and 60 degrees C water baths with a 1-minute dwell time (n = 5 per group). Bond strength (MPa) was measured by shear bond testing at a 1.0 mm/min crosshead speed until the applied resin debonded from denture base resin. Data were statistically analyzed by 3-way analysis of variance and multiple comparisons among the groups were performed with Bonferroni test (alpha = .05).

RESULTS

The mean bond strengths of repair resin to airborne-particle-abraded denture base specimens were not significantly influenced by either thermal cycling or water content. The mean bond strengths of reline resin significantly decreased after thermal cycling (P < .0001) regardless of the conditions of surface treatment and water content. For methylene chloride treated specimens, bond strengths of both repair and reline resins to completely water saturated specimens were significantly higher than those of completely desiccated specimens (P = .0048 for repair resin, P < .0001 for reline resin) after thermal cycling.

CONCLUSIONS

Bond strengths of autopolymerizing resin to denture base resin were not significantly influenced by water content of denture base resin but were significantly influenced by resin type, thermal cycling, and surface treatment.

The effect of simulated intrapulpal pressure on bond strength to enamel and dentine

The purpose of this study was to evaluate the effect of simulated intrapulpal pressure on the shear bond strength (SBS) of a self-etching bonding system (Clearfil Liner Bond II) to both enamel and dentine surfaces. Forty-two caries-free human molar teeth were randomly assigned to two equal groups (n=21). One group of 21 teeth was connected to a special pulpal pressure machine, which is developed to simulate in vivo conditions. The buccal and lingual surfaces of the teeth were prepared with a diamond wheel to create flat dentine and enamel surfaces. A self-etching bonding system was then applied under pulpal pressure and 2.5 mm diameter composite cylinders were bonded to the prepared surfaces. The samples were then stored in distilled water at room temperature for 24 h under pulpal pressure before SBS was tested. The second restored group was used as a control and the teeth were not connected to the pulpal pressure apparatus during material application and test procedures. They were stored for 24 h in distilled water at room temperature before the SBS test. Fracture analysis of the enamel and dentinal surfaces was performed using a stereomicroscope. Shear bond strength values to dentine was significantly reduced with pulpal pressure (P < 0.001). However, in the enamel, SBS was increased (P < 0.001). In the control group, the SBS values to dentine and enamel did not show any significant difference (P > 0.05). Based on these results, it can be concluded that further analysis of enamel histology and bonding mechanisms are needed.

Penetration of an antibacterial dentine-bonding system into demineralized human root dentine in vitro

In this study, the penetration of three proprietary dentine-bonding agents (Prime & Bond 2.1, Single Bond, Liner Bond 2) and experimental dentine-bonding systems incorporating an antibacterial monomer, 12-methacryloyloxydodecylpyridinium bromide (MDPB), into artificial root caries lesions was evaluated, and the bactericidal activity of each material against Streptococcus mutans or Lactobacillus casei impregnated into demineralized dentine blocks was assessed. All of the commercial dentine-bonding agents were capable of penetrating into the artificial carious lesions to more than 150 microm. The depth of penetration of the experimental systems, which were based on Liner Bond 2, was not significantly different from that of their parent product. Liner Bond 2 primer exhibited the greatest bactericidal effects among the three proprietary dentine-bonding agents tested. Bactericidal activities of experimental primers containing MDPB were greater than those of any other products, and the application of 4% MDPB-containing primer resulted in complete killing of bacteria in demineralized dentine. The results indicate that the penetration of dentine-bonding agents into extensively demineralized root dentine is possible in vitro, and the experimental dentine-bonding systems containing the antibacterial monomer MDPB are capable of killing bacteria within demineralized dentine. This could be of benefit when managing root caries lesions.

Tensile bond strength of adhesive systems--effects of primer and thermocycling

The objective of this study was to evaluate the effects of primer and thermocycling on the bond strength of multi-purpose adhesive systems applied to enamel, under tensile stress. The following bonding systems were applied, according to the manufacturers' instructions, on unground enamel buccal surfaces of 96 premolars, with or without the application of primer: Scotchbond MP, OptiBond FL, Amalgambond Plus and OptiBond (dual-cure). A composite resin (Z100, 3M) was applied and light-cured in a cast metal hollow cone, which was previously fixed to the enamel surfaces. Half of the sample was subjected to 3,000 thermocycles (5-37 degrees C; 37-55 degrees C, dwell time of 60 s), and the other half was stored in water at 37 degrees C for the same period. The data were treated by means of ANOVA and no significant effects were detected, which indicates that tensile bond strength was not affected by the adhesive systems, application of primer or thermocycling.