Using artificial intelligence to predict the final color of leucite-reinforced ceramic restorations.

OBJECTIVES: The aim of this study was to evaluate the accuracy of machine learning regression models in predicting the final color of leucite-reinforced glass CAD/CAM ceramic veneer restorations based on substrate shade, ceramic shade, thickness and translucency. METHODS: Leucite-reinforced glass ceramics in four different shades were sectioned in thicknesses of 0.3, 0.5, 0.7, and 1.2 mm. The CIELab coordinates of each specimen were obtained over four different backgrounds (black, white, A1, and A3) interposed with an experimental translucent resin cement using a calibrated spectrophotometer. The color change (CIEDE2000) values, as well as all the CIELab values for each one of the experimental groups, were submitted to 28 different regression models. Each regression model was adjusted according to the weights of each dependent variable to achieve the best-fitting model. RESULTS: Different substrates, ceramic shades, and thicknesses influenced the L, a, and b of the final restoration. Of all variables, the substrate influenced the final ceramic shade most, followed by the ceramic thickness and the L, a, and b of the ceramic. The decision tree regression model had the lowest mean absolute error and highest accuracy to predict the shade of the ceramic restoration according to the substrate shade, ceramic shade and thickness. CLINICAL SIGNIFICANCE: The machine learning regression model developed in the study can help clinicians predict the final color of the ceramic veneers made with leucite-reinforced glass CAD/CAM ceramic HT and LT when cemented with translucent cements, based on the color of the substrate and ceramic thicknesses.

Progression of non-carious cervical lesions: 3D morphological analysis.

OBJECTIVES: This longitudinal study aimed to investigate morphologically and quantitatively the progression of non-carious cervical lesions (NCCLs) using a confocal laser scanning microscope (CLSM) and replica models. MATERIALS AND METHODS: The samples examined comprised sets of replicas annually obtained from 83 lesions in 16 participants over 3 to 5 years. All lesions were visually categorized as wedge-shaped, saucer-shaped, or mixed-shaped lesions. CLSM images of the replicas were analyzed in terms of axial depth, occlusogingival width (height) in the buccolingual cross-section, and estimated volume using a custom code of the image analysis software to estimate the progression of the NCCLs over time. The morphological characteristics of the NCCLs were also objectively divided into three groups according to the depth to height ratio (D/H ratio). Fisher's exact test and the Cochran-Armitage trend test were used for statistical analysis. RESULTS: Saucer-shaped lesions progressed mainly in height, whereas wedge-shaped lesions increased both in height and depth. Annual progression in depth and volume significantly increased as the D/H ratio increased. More than half of the NCCLs with a small D/H ratio progressed 50 µm or more in height, whereas none of them progressed more than 50 µm in depth. Annual progression in depth significantly increased as the lesion depth at baseline increased. CONCLUSIONS: Progression patterns significantly differed between NCCLs of different shapes. Most NCCLs progressed slowly in depth regardless of their shape. Moreover, NCCLs may progress through active and inactive stages.

Microshear bond strength of resin cement to glass-ceramics after intaglio surface staining.

STATEMENT OF PROBLEM: Applying stains to the intaglio surface of computer-aided design and computer-aided manufacturing (CAD-CAM) monolithic ceramic restorations has been proposed as an option to help mask darkened substrates. However, little is known about the effects of this procedure on the adhesion between the resin cement and the ceramic. PURPOSE: The purpose of this in vitro study was to evaluate the effect of intaglio surface staining on the microshear bond strength between 2 CAD-CAM ceramics and a resin cement. MATERIAL AND METHODS: Lithium disilicate (Gmax) and leucite-reinforced (Gpress) ceramic blocks were sectioned, crystalized when indicated, and polished. They received either none, 1, or 2 layers of ceramic stains and a glaze liquid mixture followed by a firing cycle. The surfaces of groups Gmax0, Gmax1, and Gmax2 were etched with 9% hydrofluoric acid etching (HF) for 20 seconds, and those of groups Gpress0 and Gpress1 were etched for 60 seconds. After rinsing and drying, a ceramic primer was applied and air-dried. Resin cement rods (n=24 per group) were built from a silicone mold. Specimens were stored in distilled water for 24 hours before microshear bond testing. Failure mode was observed under a digital microscope. Data were analyzed by using the Kruskal-Wallis and Mann-Whitney nonparametric tests (α=.05). RESULTS: Intaglio staining negatively affected the microshear bond strength for both ceramics. A significant difference was observed between Gmax1 (3.5 ±1.73 MPa) and Gmax2 (3.7 ±2.1 MPa) when compared with Gmax0 (14.2 ±4.4 MPa) and also between GPress0 (25.7 ±5.1 MPa) and Gpress1 (1.8 ±2.7 MPa). No difference was observed between 1 and 2 stain layers for Gmax. Most failures were adhesive for Gmax0, mixed for Gpress, and cohesive within the stain layer for experimental groups. CONCLUSIONS: Intaglio surface staining with a stain and glaze mixture caused a significant reduction in bond strength between resin cement and both ceramics tested.

Moist vs over-dried etched dentin: FE-SEM/TEM and bond strength evaluation of resin-dentin interfaces produced by universal adhesives.

OBJECTIVE: To evaluate the influence of the degree of dentin moisture on interfacial ultramorphology and bond strength (µTBS) of universal adhesives. MATERIALS AND METHODS: Futurabond U (FBU), Scotchbond Universal (SBU), Adhese Universal (ADU), and Prime&Bond active (PBA) were used. After acid-etching, moist or over-dried dentin surfaces were tested. Teeth were restored for scanning and transmission electron microscopy (n = 3) and µTBS evaluation (n = 5). µTBS results were analyzed by two-way ANOVA and Tukey. RESULTS: For moist dentin, a well-formed hybrid layer (HL) was observed. However, when applied to over-dried dentin, remarkable differences were observed. Defects, gaps, and reduced HL thickness were observed mainly for ADU and FBU. When applied to wet dentin, µTBS values were similar for all adhesives, except for FBU, which was significantly lower. When applied to over-dried dentin, PBA presented the highest µTBS values, followed by SBU, ADU, and FBU. ADU presented significantly lower µTBS when applied to over-dried dentin. CONCLUSION: PBA, SBU, and FBU µTBS values were not sensitive to the degree of moisture. Even though application to over-dried dentin revealed defects, gaps and reduced HL thickness for SBU, ADU, and FBU, µTBS analysis only revealed a significant reduction for ADU. CLINICAL SIGNIFICANCE: Universal adhesives can be applied in either self-etching or etch-and-rinse mode. However, clinicians are not aware which universal adhesives should be strictly applied on a moist dentin for bonding in the etch-and-rinse mode.

Importance of the hybrid layer on the bond strength of restorations subjected to cyclic loading.

The present study evaluated the long-term microtensile bond strength of collagen-depleted dentin followed by cyclic loading. Bovine flat, midcoronal dentin received one of the following surface treatments: acid-etch or acid-etched + 5% NaOCl for 2 min. The teeth were restored with Single Bond, Scotchbond Multi-purpose, One-Step Plus, or All-Bond 2 adhesive systems. Half of the specimens were randomly assigned to receive 200,000 cycles (50 N force). Teeth were sectioned into 1 x 1 mm thick slices and stored for 24 h, 1 month, 3 months, or 6 months. Specimens were subjected to tensile testing after elapsed storage time. Samples were analyzed by three-way ANOVA and Fisher's PLSD (p < 0.05). The results showed that the deproteinized groups without cyclic loading presented lower bond strength when compared with the control group, but the difference was only statistically significant for Single Bond and All-Bond 2 (p < 0.05). All adhesives presented a decrease in bond strength over time, regardless of the dentin treatment. When cyclic loaded, the decrease in bond strength for the deproteinized group was even greater when compared with the control group (p < 0.05). The results suggest that the hybrid layer is important as a stress-buffering layer when loading is applied, and thus the presence of collagen is essential.

The effect of load cycling on nanoleakage of deproteinized resin/dentin interfaces as a function of time.

OBJECTIVES: To evaluate the effects of cyclic loading on nanoleakage as a function of time at resin-dentin interfaces with and without removal of collagen. METHODS: Bovine flat mid-coronal dentin received one of the following surface treatments: (1) acid-etch or (2) acid etched+5% NaOCl for 2m. The teeth were then bonded with Single Bond (3M ESPE), Scotchbond Multi-Purpose (3M ESPE), One-Step Plus (Bisco) or All-Bond 2 (Bisco) adhesive systems and restored with Z250 composite. Half of the bonded teeth were randomly assigned to receive 200,000 cycles of loading at 50 N. Teeth were sectioned into 1 mm x 1 mm thick slices and stored in distilled water for 24h and 6 months. After water storage, beams were prepared for nanoleakage evaluation and observed under the SEM. Data were statistically analyzed using three-way ANOVA and Fisher's PLSD test (p<0.05). RESULTS: Use of NaOCl did not affect nanoleakage at the interface of all adhesive systems (p>0.05) when compared to their respective controls. After 6 months of immersion in water, except for One Step Plus, collagen-depleted groups and control groups presented similar leakage values. After cyclic loading, the deproteinized group revealed a higher degree of silver nitrate deposits when compared to the control group (p<0.05). All four adhesive systems presented a high degree of silver nitrate deposits after 6 months of water storage. SIGNIFICANCE: The hybrid layer is important as a stress-absorbing layer and it may not represent the weak link for initiation of the nanoleakage phenomenon.

Long-term bond strengths to dentin treated with different re-wetting solutions.

PURPOSE: To evaluate the microtensile bond strengths (microTBS) of two etch-and-rinse one-bottle adhesive systems to air-dried dentin re-wet with different agents. METHODS: 48 bovine teeth were ground flat to 600-grit and were assigned for treatment with either Single Bond or One-Step adhesives. Each group had three subgroups of re-wetting agents: water, Gluma Desensitizer and Aqua-Prep F. The teeth were acid-etched, air-dried for 5 seconds and re-wet with water, Gluma Desensitizer or Aqua-Prep F for 30 seconds and blot dried. Control specimens were prepared using a moist bonding technique. The adhesives were applied and the teeth were restored with Filtek Z250 or Renew composite. After 24 hours in distilled water at 37 degrees C, the teeth were sectioned into 0.7 mm-thick slabs, trimmed, and immediately tested for microTBS or stored for 6 months or 1 year prior to testing. Fracture sites were examined under scanning electron microscope (SEM). Data were evaluated by one- and three-way ANOVA, and Fisher's PLSD test (P<0.05). RESULTS: Except for Aqua-Prep F, the microTBS in the control, water and Gluma Desensitizer subgroups did not change significantly after 1-year for both Single Bond and One-Step groups. SEM analysis showed no specific pattern of fracture in the Single Bond specimens. One-Step had the majority of the fractures at the interface at baseline, and becoming a mixture of fractures at the interface and within the adhesive resin after 1 year.

Application of crosslinkers to dentin collagen enhances the ultimate tensile strength.

The stabilization of dentin collagen with biocompatible crosslinking agents may be of clinical importance to improve dentin bond strength. The present study aimed to evaluate the effect of three collagen crosslinking agents on the ultimate tensile strength (UTS) of undemineralized and demineralized dentin. Ten freshly extracted sound molars were sectioned into 0.5 x 0.5 mm2 thick beams. The beams were either demineralized or kept undemineralized. Then, specimens were subdivided into four groups according to treatments--PBS solution (control), 5% glutaraldehyde (GD), 0.5% proanthocyanidin PBS solution (PA), and 0.625% genipin PBS solution (GE). Specimens were kept in their respective solutions for either 4 or 40 h. To assess UTS, specimens were subjected to tensile forces at a crosshead speed of 1 mm/min. Statistical analysis was performed using two-way ANOVA and Fisher's PLSD test (p < 0.05). Statistically significant increases in UTS were observed for demineralized dentin after PA and GE dentin treatment, when compared with those of the control group. Dentin treated with GD showed no statistically significant differences in UTS when compared with that the control. Undemineralized dentin revealed no significant differences as compared to that of the control, regardless of the collagen crosslinkers. The application of two naturally occurring crosslinkers, i.e., PA and GE, to dentin collagen significantly improves UTS, indicating its potential value in restorative dentistry.

Long-term TEM analysis of the nanoleakage patterns in resin-dentin interfaces produced by different bonding strategies.

OBJECTIVES: The aim of this study was to evaluate the ability of etch-and-rinse and self-etching adhesive systems to prevent time- and water-induced nanoleakage in resin-dentin interfaces over a 6-month storage period. METHODS: Five commercial adhesives were tested, which comprise three different strategies of bonding resins to tooth hard tissues: one single-step self-etching adhesive (One-up Bond F (OB), Tokuyama); two two-step self-etching primers (Clearfil SE Bond (SE) and an antibacterial fluoride-containing system, Clearfil Protect Bond (CP), Kuraray Inc.); two two-step etch-and-rinse adhesives (Single Bond (SB), 3M ESPE and Prime&Bond NT (PB), Dentsply). Restored teeth were sectioned into 0.9 mm thick slabs and stored in water or mineral oil for 24 h, 3 or 6 months. A silver tracer solution was used to reveal nanometer-sized water-filled spaces and changes that occurred over time within resin-dentin interfaces. Characterization of interfaces was performed with the TEM. RESULTS: The two two-step self-etching primers showed little silver uptake during the 6-month experiment. Etch-and-rinse adhesives exhibited silver deposits predominantly within the hybrid layer (HL), which significantly increased for SB after water-storage. The one-step self-etching adhesive OB presented massive silver accumulation within the HL and water-trees protruding into the adhesive layer, which increased in size and quantity after water-storage. After storage in oil, reduced silver deposition was observed at the interfaces for all groups. SIGNIFICANCE: Different levels of water-induced nanoleakage were observed for the different bonding strategies. The two-step self-etching primers, especially the antibacterial fluoride-containing system CP, showed the least nanoleakage after 6 months of storage in water.

Influence of water-storage time on the sorption and solubility behavior of current adhesives and primer/adhesive mixtures.

This study evaluated the effects of water-storage on the water sorption and solubility behavior of five commercially available dental adhesive systems and two primer/adhesive mixtures. The adhesives comprised three different approaches to bonding to hard tooth tissues: a one-step self-etching adhesive (One-up Bond F), two two-step self-etching primers (Clearfil SE Bond and Clearfil Protect Bond) and two etch-and-rinse systems: a water/ethanol-based (Single Bond) and an acetone-based filled adhesive (Prime&Bond NT). The bonding agents and primers of the two-step self-etching systems were mixed in a 1:1 volume ratio. Water sorption and solubility values were determined after 1, 7, 30, 90 and 180 days. The results showed that, except for SB, all adhesives presented increased water sorption with increased storage time. The one-step self-etching adhesive and self-etching primer/adhesive mixtures presented the highest water sorption and solubility values. Equilibrium in the water sorption values was observed for all adhesives after 90 days of water-storage. However, solubility values continued to increase for some materials until 180 days. The sorption and solubility behavior of the materials tested seem to be related to hydrophilicity of the adhesive resin solution and might influence the long-term performance of resin-based composite restorations.

In vitro inhibition of bacterial growth using different dental adhesive systems.

OBJECTIVES: This study evaluated the antibacterial potential of four different adhesive systems. METHODS & MATERIALS: Gluma Comfort Bond + Desensitizer, Gluma Comfort Bond, iBond and One-Up Bond F were tested against Streptococcus mutans, Streptococcus sobrinus, Lactobacillus acidophilus and Actinomyces viscosus. The inhibition of growth by calibrated preparations was quantified by the measurement of zones of inhibition on bacterial lawns. Bactericidal activity was determined as reductions in recoverable colony-forming units in bacterial suspensions exposed to test preparations. RESULTS: All the preparations exhibited detectable zones of inhibition for all target bacteria through six months. When the bactericidal action was evaluated, all the materials were able to kill all the tested bacteria when tested immediately after polymerization. After one week of aging, iBond was the only material that continued to kill all of the test strains.

Microleakage evaluation of a new low-shrinkage composite restorative material.

PURPOSE: This study compared the microleakage of an experimental low-shrinkage resin composite (Hermes), a nanofilled resin composite material (Filtek Supreme) and a hybrid resin composite (Tetric Ceram) using a dye penetration method. METHODS AND MATERIALS: Class I cavities prepared in 60 human molars were randomly divided into 3 groups according to the restorative material used. The preparations were restored using a bulk or an incremental technique. Half of the specimens from each group were subjected to 200,000 cycles of loading at 50 N, while the other half were stored in distilled water for 24 hours at 37 degrees C. All specimens were immersed in 1% methylene blue (pH = 7.0) for 24 hours and sectioned into 3 slabs. The margins were evaluated for microleakage using an ordinal scoring system (0-4) under a stereomicroscope at 40x magnification. Data were subjected to the non-parametric Kruskal-Wallis analysis of variance and Mann-Whitney test (p<0.05). Data were expressed as median leakage scores and mean ranks. RESULTS: All of the restorative systems had microleakage, regardless of the insertion technique and mechanical load cycling. Incremental placement significantly reduced microleakage as compared to the bulk technique, regardless of the restorative system used. Load cycling significantly affected incrementally placed restorations, except for the Hermes system.

Bond strengths of a 1-step self-etching system to caries-affected and normal dentin.

This study was designed to evaluate the bond strengths of a 1-step self-etching system and a 2-step "etch and rinse" adhesive system to caries-affected dentin and normal dentin. In addition, the micromorphology of the adhesive interfaces was analyzed using scanning electron microscopy (SEM). Extracted human molars with occlusal caries that had been stored frozen were ground in order to expose the caries-affected dentin and surrounding normal dentin. The teeth were then bonded using either Adper Prompt L-Pop or Single Bond (3M ESPE) and restored with Filtek Z250 (3MESPE). After storage in water for 24 hours at 37 degrees C, the teeth were sectioned, prepared for microtensile bond strength test and tested in tension at a crosshead speed of 1-mm/minute. After debonding of the interfaces, microhardness of the dentin underlying the interface of all specimens was measured. The thickness of the hybrid layers was observed under SEM. The results of this study indicate that the bond strength of Adper Prompt L-Pop adhesive was significantly higher to normal dentin than to caries-affected dentin (p<0.05) and that the bond strength of Single Bond to both normal and caries-affected dentin was not significantly different (p>0.05). Additionally, the thickness of the hybrid layers produced by both adhesive systems was thicker for caries-affected dentin.

Prevention of artificial caries: effect of bonding agent, resin composite and topical fluoride application.

This study investigated the effect of fluoride containing resin composites and bonding agents, as well as the topical fluoride (F) application on the inhibition of artificial caries progression by using a pH-cycling model with alternating demineralizing (pH:4.5) and remineralizing (pH:7.0) solutions. Two bonding systems (F-containing bonding system [Reactmer Bond: RB] and non-F containing bonding system [Clearfil SE Bond: SE]), two resin composites, (F-containing [Reactmer Paste: RP] and non-F containing [Clearfil AP-X: AP]) were used. A combination of each bonding agent and a resin composite, RB+RP, RB+AP, SE+RP and SE+AP, was placed in 2 x 3 x 1.5-mm cavities on root dentin of extracted molars (n=96). Specimens were subjected to pH-cycling for 6 or 12 weeks. Half of all specimens were immersed in 0.05% NaF solution for 1 minute once a day as a topical F application. After the pH cycling period, a microradiograph of each specimen was taken, and the outer lesion depth of the artificial caries was measured by means of image analyzing software. The depths of the outer lesions at different periods were analyzed by one-way ANOVA and Sheffe's test at p=0.05. The combination that received F treatment showed reduced lesion depth compared to the same combination without F application. Except for the F application group of 12 weeks, there was no significant difference in lesion depth among each bonding and composite combination (p>0.05). At week 12 with the F application, RB+RP showed the shallowest lesion compared to the other combinations (p<0.05). The results indicated that the F application reduced the progression of artificial caries. Moreover, the combination of fluoride containing bonding agent and restorative material was the most effective for the inhibition of artificial caries progression based on the 12-week experimental period with topical F application.

Fluoride release and uptake by various dental materials after fluoride application.

PURPOSE: To measure the amounts of fluoride released from fluoride-containing materials before and after daily topical fluoride applications. METHODS: A conventional glass-ionomer: Fuji Ionomer Type II (F2); a resin-modified glass-ionomer: Fuji Ionomer Type II LC (LC); two "giomer" materials: Reactmer Paste (RP), and Beautifil (BT); a fluoride-containing resin composite: Unifil F (UF); and a non-fluoride resin composite: AP-X (AP) were used in this study. Each material was filled into a plastic mold, with inner diameter of 9 mm wide x 3 mm high. The specimens were stored in vials filled with 8 ml distilled deionized water for 24 hours at 37 degrees C. The specimens were then removed from the vials and the amount of fluoride released into the water, over the 24-hour period, was measured. The amount of fluoride released was measured by using specific fluoride electrode and an ion-analyzer. These procedures were repeated at Days 2, 3, 7, 14, and 21. After 21 days, all specimens were exposed to 1000 ppm F NaF solution for 5 minutes once a day. This procedure and measurement of fluoride release were continued for 14 days. After 14 days, the specimens were placed in water for 7 days and fluoride release was measured. The results were statistically analyzed using Kruskal-Wallis and Mann-Whitney U-test (P< 0.05). RESULTS: At the 22nd day (1 day after starting fluoride exposure), there was no difference between the F2 and RP, though there were significant differences between the two GICs and the groups BT and UF. After that day, there were significant differences between GIC and the group RP, BT and UF. All materials showed a decrease in fluoride release 7 days after end of the fluoride immersion period. F2, LC, and UF showed no significant difference of fluoride release between Day 21 and 1 day after the end of the fluoride immersion period (P= 0.310: F2 and UF, 0.548: LC). On the other hand, RP and BT revealed lower fluoride release 1 day after the end of the fluoride immersion period as compared to Day 21 (P= 0.075: RP, 1.000: BT). For AP, fluoride release was not detected after the fluoride immersion period.

In vitro evaluation of caries inhibition promoted by self-etching adhesive systems containing antibacterial agents.

This study evaluated the cariostatic effect of antibacterial self-etching adhesive systems, by means of an in vitro bacterial caries model. Seventy-five prepared bovine slabs were randomly divided into groups (n=15): (1) unbonded composite, no carious challenge (UNB-NC); (2) unbonded composite, carious challenge (UNB-C); (3) Clearfil SE Bond, no antibacterial agent (CSE); (4) Protect Bond, containing MDPB and fluoride (PB); and (5) Reactmer Bond, fluoride-releasing (RB). All preparations were restored with Filtek Z-250. Groups (2)-(5) were submitted to a medium containing Streptococcus mutans (ATCC-- 25175) for 5 days, and Group (1) was kept in a noninoculated medium. Insoluble polysaccharides present in tooth biofilms were quantified, Knoop hardness (KHN) was measured on the enamel adjacent to restorations, and standard 35-mm polarized light photomicrographs were taken as illustrations. Polysaccharide and Knoop hardness results were analyzed with the use of ANOVA, with a split-split-plot statistical design for KHN. Except for Group (1), all groups showed similar caries formation. Biofilm over PB restorations showed the smallest amounts of polysaccharides (14.37 microg/mg), and CSE showed the highest amounts (20.87 microg/mg). All self-etching systems tested were unable to inhibit secondary caries in a bacterial model simulating a high caries challenge, even though there was reduced glucan synthesis provided by the adhesive system containing MDPB and fluoride.

Cytotoxicity of universal, self-etching and etch-and-rinse adhesive systems according to the polymerization time.

This in vitro study evaluated in fibroblast cultures the direct cytotoxicity of universal, self-etching and etch-and-rinse adhesive systems according to the polymerization time. Paper discs were impregnated with adhesives and light-cured (10, 20 or 40 s). The discs were then immersed in culture medium to obtain the eluates for the experimental groups (A1-Single Bond 2; A2-Scotchbond Multi-purpose; A3-Clearfil SE Bond; A4 Scotchbond Universal). As a negative control, paper discs were immersed in culture medium only. After 24 h or 7 days, the eluate obtained was applied on fibroblast culture. Cell viability, cell morphology, membrane damage and the presence of residual monomers were evaluated by MTT assay, SEM, flow cytometry and high-performance liquid chromatography (HPLC), respectively. Data were analyzed by Kruskal-Wallis and Mann-Whitney tests (=0.05). All adhesive systems significantly reduced 33-51% cell metabolism when compared to the negative control, regardless of polymerization time, storage period and adhesive system. Moreover, the adhesives caused intense morphological alterations and cell membrane damage. Toxicity was directly related to the presence of residual monomers in the eluates. Residual monomers and additional components are capable of reducing mitochondrial activity, causing morphological alterations and disruption of the cell membrane in fibroblasts, regardless of the polymerization time. This study highlights that despite the more complex composition of the universal adhesive system, its biological response was not more toxic when compared with other systems, even when the shortest polymerization time was tested in cell culture.

Effects of saliva contamination on resin-resin bond strength.

OBJECTIVE: The purpose of this study is to evaluate the effects of saliva contamination on microtensile bond strength (microTBS) between resin interfaces and to determine which decontamination methods best re-established the original resin-resin bond strength. MATERIALS AND METHODS: Ninety-six light-cured resin composite cylinders of Z-250, Renew, Clearfil APX, and Pertac II were randomly divided into six groups. For each material, one group of specimens was not contaminated, serving as the control. For the other specimens, the top surface of each block was treated with saliva that was slowly dried (Treatment 1); dried forcefully (Treatment 2); slowly dried, rinsed, and dried (Treatment 3); slowly dried, rinsed, dried, and bonded with Single Bond, One-Step, Clearfil SE Bond, or Prompt L-Pop (Treatment 4); or slowly dried, but not rinsed, and bonded using the same adhesives (Treatment 5). Two 2-mm increments of resin composite were applied and light-cured. After 24 h, the assemblies were trimmed for microtensile bond testing and were loaded to failure at 1 mm/min. Data were analyzed using two-way and one-way ANOVA and Fisher's PLSD (p<0.05). RESULTS: Control values ranged from 45.1 MPa for Pertac II to 71.5 MPa for APX. Treatment 1 caused significant reduction in resin-resin bond strength for all materials tested but for two of the materials in treatment 2. Pertac II was the only material that did not show a statistical difference from control group for treatment 3. Treatment 4 re-established the control values for Z-250 and Renew and treatment 5 was the only one to show no statistical difference for all materials tested. SEM observation revealed a smooth surface in treatment 1, but treatment 3 showed a few craters. Treatment 4 and 5 showed a mixture of cohesive failure in the composite and adhesive. SIGNIFICANCE: The most reliable method for decontaminating saliva from resin surfaces involves the application of adhesives.