Wayne W. Barkmeier

Evaluation of porcelain surface treatments and agents for composite-to-porcelain repair

Intraoral repairs often involve bonding composite to fractured porcelain. Newer adhesive systems, currently referred to as multipurpose systems, include materials with recommended procedures for repair of porcelain. This laboratory study evaluated various treatment regimens with the ProBond adhesive system. Three different porcelain surface procedures were used: (1) air abrasion with aluminum oxide (50 microm), (2) 8% hydrofluoric acid, and (3) air abrasion and hydrofluoric acid. Eight different treatment procedures were then used to bond 10 composite cylinders to porcelain surfaces in each group. Shear bond strengths (in megapascals) were determined with an Instron testing machine after storage in water for 24 hours at 37 degrees C and after 3 months of storage and thermocycling. The combination of air abrasion and hydrofluoric acid on porcelain surfaces before bonding composite recorded the most consistently effective bond strengths. Four of the treatment regimens in the air abrasion groups yielded low bond strengths at 3 months. This study also indicated that silane treatment of porcelain is critical for development of suitable bond strengths for composite.

Quantitative wear measurement of posterior composite resins

A quantitative method for measuring the wear of posterior composite restorations has been developed. The system utilizes the comparison of die stone casts of restored teeth to a set of calibrated standards as a means of evaluating the wear on the restorations. The technique facilitates the determination of the actual rate of clinical wear. This method, therefore, can be used to relate quantitatively the performance of one material to another. Further advantages are that materials can be compared without being a part of the same study, and that direct comparisons can be made of a single restoration at two or more ages.

The role of etching in bonding to enamel: A comparison of self-etching and etch-and-rinse adhesive systems

OBJECTIVE Etch and resin infiltration morphologies were compared for three self-etch adhesive (SEA) systems and eleven model etch-and-rinse (ERA) systems using various phosphoric acid (PA) concentrations with Adper Single Bond Plus (SB) adhesive. Matches for the morphologies were made between each SEA system and one of the PA/SB systems and bond strength measurements were made for all the systems. The hypothesis was that similar morphology would result in similar bond strength assuming micro-mechanical bonding is the mechanism of adhesion. METHODS Three specimens were prepared on polished (4000 grit) human enamel for each adhesive system to examine etch and resin infiltration morphology by SEM. For the latter, the adhesive systems were bonded using recommended methods and the enamel was dissolved in acid to reveal the resin. The etch patterns for the SEA systems were determined by rinsing off the material with water and acetone. Polished (4000 grit) human enamel was used with each adhesive system to determine 24-h resin composite to enamel shear bond strengths (SBS). A minimum of 10 specimens were used for each group. Data were analyzed by a one factor ANOVA and Fishers PLSD post hoc test. RESULTS The SBS to polished enamel for two of the three SEA systems were statistically significantly greater (p<0.05) than the PA/SB matched systems, indicating that chemical bonding might be partly responsible for the measured bond strength. All three SEA systems provided statistically lower (p<0.05) SBS values than the PA/SB systems with PA concentrations between 2.5% and 40%. SIGNIFICANCE Although chemical bonding may be present for some SEA systems it does not provide enough increase in bond strength to compete with the bond produced by ERA systems using phosphoric acid etching of enamel.

Bond strength of self-etch adhesives to pre-etched enamel

OBJECTIVE Bond strengths of composite resin to enamel using four self-etch adhesive (SEA) systems were compared with the bond strength of an etch-and-rinse adhesive (ERA) system, for both polished enamel and enamel pre-etched with phosphoric acid. The objective was to determine if the pre-etching would increase the bond strengths of the SEA systems to match the ERA system. METHODS Ten specimens were used for each adhesive to determine 24-h resin composite to enamel shear bond strengths (SBS) to polished (4000 grit) human enamel and this was repeated for the SEA systems for enamel that was pre-etched with phosphoric acid for 15s. SEM analysis was made to assess the degree of etching and resin penetration into enamel for each of the adhesive systems. Data were analyzed by a two factor ANOVA with a Tukey HSD post hoc test. RESULTS The SBS to polished enamel for all four SEA systems were statistically significantly lower (p<0.05) than the ERA control, but with pre-etched enamel there were no statistically significant differences (p>0.05) between any of the adhesive systems. All four of the SEA systems demonstrated statistically significant increases in bond strength between bonding to polished and pre-etched enamel, ranging from 27% to 86%. The results of SEM analysis showed no differences in the resin penetration patterns of any of the adhesives for enamel that was etched with phosphoric acid. SIGNIFICANCE Pre-etching enamel may enhance the bond strength of SEA systems to values comparable with those found with ERA adhesive systems, which may improve their overall performance in clinical use.

Bond strength of composite resin to porcelain with newer generation porcelain repair systems

A laboratory study was conducted to evaluate the mean shear bond strength of composite resin bonded to porcelain with the use of eight newer generation repair systems. The range of shear bond strength after 24 hours of water storage was 23.5 +/- 5.3 MPa to 12.0 +/- 2.3 MPa. After 3 months of water storage and thermocycling, the bond strength range was 20.7 +/- 1.7 MPa to 4.2 +/- 1.0 MPa. Three of eight systems evaluated did not exhibit a significant (p > 0.05) decrease in bond strength when the 24-hour bond strengths were compared with the 3-month bond strengths. Most specimens failed cohesively in the porcelain at 24 hours, but at 3 months only four of the eight systems showed consistent failures in the porcelain.

Effect of Enamel Etching Time on Roughness and Bond Strength

The current study examined the effect of different enamel conditioning times on surface roughness and bond strength using an etch-and-rinse system and four self-etch adhesives. Surface roughness (Ra) and composite to enamel shear bond strengths (SBS) were determined following the treatment of flat ground human enamel (4000 grit) with five adhesive systems: (1) Adper Single Bond Plus (SBP), (2) Adper Prompt L-Pop (PLP), (3) Clearfil SE Bond (CSE), (4) Clearfil S3 Bond (CS3) and (5) Xeno IV (X4), using recommended treatment times and an extended treatment time of 60 seconds (n = 10/group). Control groups were also included for Ra (4000 grit surface) and SBS (no enamel treatment and Adper Scotchbond Multi-Purpose Adhesive). For surface roughness measurements, the phosphoric acid conditioner of the SBP etch-and-rinse system was rinsed from the surface with an air-water spray, and the other four self-etch adhesive agents were removed with alternating rinses of water and acetone. A Proscan 2000 non-contact profilometer was used to determine Ra values. Composite (Z100) to enamel bond strengths (24 hours) were determined using Ultradent fixtures and they were debonded with a crosshead speed of 1 mm/minute. The data were analyzed with ANOVA and Fishers LSD post-hoc test. The etch-and- rinse system (SBP) produced the highest Ra (microm) and SBS (MPa) using both the recommended treatment time (0.352 +/- 0.028 microm and 40.5 +/- 6.1 MPa) and the extended treatment time (0.733 +/- 0.122 microm and 44.2 +/- 8.2 MPa). The Ra and SBS of the etch-and-rinse system were significantly greater (p < 0.05) than all the self-etch systems and controls. Increasing the treatment time with phosphoric acid (SBP) and PLP produced greater surface roughness (p < 0.05) but did not result in significantly higher bond strengths (p > 0.05).

Round robin test: Wear of nine dental restorative materials in six different wear simulators - Supplement to the round robin test of 2005

OBJECTIVE The purpose of the present study was to submit the same materials that were tested in the round robin wear test of 2002/2003 to the Alabama wear method. METHODS Nine restorative materials, seven composites (belleGlass, Chromasit, Estenia, Heliomolar, SureFil, Targis, Tetric Ceram) an amalgam (Amalcap) and a ceramic (IPS Empress) have been submitted to the Alabama wear method for localized and generalized wear. The test centre did not know which brand they were testing. Both volumetric and vertical loss had been determined with an optical sensor. After completion of the wear test, the raw data were sent to IVOCLAR for further analysis. The statistical analysis of the data included logarithmic transformation of the data, the calculation of relative ranks of each material within each test centre, measures of agreement between methods, the discrimination power and coefficient of variation of each method as well as measures of the consistency and global performance for each material. RESULTS Relative ranks of the materials varied tremendously between the test centres. When all materials were taken into account and the test methods compared with each other, only ACTA agreed reasonably well with two other methods, i.e. OHSU and ZURICH. On the other hand, MUNICH did not agree with the other methods at all. The ZURICH method showed the lowest discrimination power, ACTA, IVOCLAR and ALABAMA localized the highest. Material-wise, the best global performance was achieved by the leucite reinforced ceramic material Empress, which was clearly ahead of belleGlass, SureFil and Estenia. In contrast, Heliomolar, Tetric Ceram and especially Chromasit demonstrated a poor global performance. The best consistency was achieved by SureFil, Tetric Ceram and Chromasit, whereas the consistency of Amalcap and Heliomolar was poor. When comparing the laboratory data with clinical data, a significant agreement was found for the IVOCLAR and ALABAMA generalized wear method. SIGNIFICANCE As the different wear simulator settings measure different wear mechanisms, it seems reasonable to combine at least two different wear settings to assess the wear resistance of a new material.

Fatigue of enamel bonds with self-etch adhesives

OBJECTIVE Fatigue testing of adhesive bonds to tooth structures in conjunction with bond strength testing can provide more useful information for examining the effectiveness of dental adhesives. The purpose of this study was to determine the shear bond strength (SBS) and shear fatigue limit (SFL) of composite to enamel bonds using modern adhesive systems. METHODS Twelve specimens each were used to determine 24-h resin composite (Z100-3M ESPE) to enamel shear bond strengths with an etch-and-rinse system (ERA), Adper Single Bond Plus (SB), and four self-etch adhesives (SEA)--Adper Prompt-L-Pop (PLP), Clearfil SE (CSE), Clearfil S(3) (CS3) and Xeno IV (X4). A staircase method of fatigue testing was used in a four-station fatigue cycler to determine the SFL of composite to enamel bonds with the adhesives (16-20 specimens for each adhesive) at 0.25 Hz for 40,000 cycles. ANOVA and Tukeys post hoc test were used for the SBS data and a modified t-test with Bonferroni correction was used for comparisons of the SFL. RESULTS The SBS and SFL of the etch-and-rinse system were significantly greater (p<0.05) than those of the four self-etch adhesives. The SBS and SFL of CSE were also significantly greater than for the other three self-etch systems. The ratio of SFL to SBS was highest with the etch-and-rinse system and the ratio became increasing smaller in the same order that the values for SBS decreased with the self-etch systems. SIGNIFICANCE The lower fatigue limits for composite to enamel bonds obtained with the self-etch adhesive systems may indicate that greater enamel margin breakdown will occur with restorations where these systems are used for bonding.

Bond strength of a resin cement to a composite inlay material

Abstract Although resin cements have been effectively bonded to mineralized tooth structures, bonding to a cured composite material has remained a challenge. This study evaluated the shear bond strength of a resin cement bonded to a cured composite inlay material by use of a variety of composite surface treatments: (1) hydrofluoric acid/60 seconds, (2) ammonium bifluoride/60 seconds, (3) resin adhesive, (4) microabrasion with 50 μm aluminum oxide, and (5) microabrasion with 50 μm aluminum oxide and application of a resin adhesive. The resin cement was also bonded to human enamel that was etched with phosphoric acid. Scanning electron microscopy examinations were completed to evaluate the effects of the composite surface treatments. The results indicated that microabrasion of a cured composite enhances bonding of a resin cement. The bond strength of a resin cement to a composite surface that was air abraded with aluminum oxide, with or without the application of a resin adhesive, was higher than surface treatments with hydrofluoric acid or ammonium bifluoride. Scanning electron microscopy indicated that an irregular surface on the composite was created with aluminum oxide air abrasion.

Influence of different etching modes on bond strength and fatigue strength to dentin using universal adhesive systems

OBJECTIVES The purpose of this study was to determine the dentin bonding ability of three new universal adhesive systems under different etching modes using fatigue testing. METHOD Prime & Bond elect [PE] (DENTSPLY Caulk), Scotchbond Universal [SU] (3M ESPE), and All Bond Universal [AU] (Bisco) were used in this study. A conventional single-step self-etch adhesive, Clearfil Bond SE ONE [CS] (Kuraray Noritake Dental) was also included as a control. Shear bond strengths (SBS) and shear fatigue strength (SFS) to human dentin were obtained in the total-etch mode and self-etch modes. For each test condition, 15 specimens were prepared for the SBS and 30 specimens for SFS. SEM was used to examine representative de-bonded specimens, treated dentin surfaces and the resin/dentin interface for each test condition. RESULTS Among the universal adhesives, PE in total-etch mode showed significantly higher SBS and SFS values than in self-etch mode. SU and AU did not show any significant difference in SBS and SFS between the total-etch mode and self-etch mode. However, the single-step self-etch adhesive CS showed significantly lower SBS and SFS values in the etch-and-rinse mode when compared to the self-etch mode. Examining the ratio of SFS/SBS, for PE and AU, the etch-and-rinse mode groups showed higher ratios than the self-etch mode groups. SIGNIFICANCE The influence of different etching modes on dentin bond quality of universal adhesives was dependent on the adhesive material. However, for the universal adhesives, using the total-etch mode did not have a negative impact on dentin bond quality.