Effects of prolonged use of over-the-counter bleaching agents on enamel: An in vitro study.

This study evaluated the effects of four over-the-counter (OTC) bleaching products on the properties of enamel. Extracted human molars were randomly assigned into four groups (n = 5): PD: Poladay (SDI), WG: White Teeth Global (White Teeth Global), CW: Crest3DWhite (Procter & Gamble), and HS: HiSmile (HiSmile). The hydrogen peroxide (H2 O2 ) content in each product was analyzed via titration. Twenty teeth were sectioned into quarters, embedded in epoxy resin, and polished. Each quarter-tooth surface was treated with one of the four beaching times: T0: control/no-bleaching, T14: 14 days, T28: 28 days, and T56: 56 days. Materials were applied to enamel surfaces as recommended. Enamel surfaces were examined for ultramicrohardness (UMH), elastic modulus (EM), superficial roughness (Sa), and scanning electron microscopy (SEM). Ten additional teeth were used to evaluate color and degree of demineralization (DD) (n = 5). Data were statistically tested by two-way ANOVA and Tukey's tests (α = 5%). Enamel surfaces treated with PD and WG presented UMH values significantly lower than the controls (p < .05). Elastic modulus (E) was significantly reduced at T14 and T28 for PD, and at T14 for HS (p < .05). A significant increase in Sa was observed for CW at T14 (p < .05). Color changes were observed in the PD and WG groups. Additionally, DD analysis showed significant demineralization at T56 for CW. Overall, more evident morphological alterations were observed for bleaching products with higher concentrations of H2 O2 (p < .05), PD, and WG. Over-the-counter bleaching products containing H2 O2 can significantly alter enamel properties, especially when application time is extended.

Consensus on glass-ionomer cement thresholds for restorative indications.

OBJECTIVE: The aim of this paper is to present the results of a consensus meeting on the threshold property requirements for the clinical use of conventional glass-ionomer cements (GICs) for restorative indications. METHODS: Twenty-one experts on GICs evaluated the results of tests on mechanical and optical properties of 18 different brands of restorative GICs: Bioglass R [B], Chemfil Rock [CR], Equia Forte [EF], Gold Label 2 [GL2], Gold Label 9 [GL9], Glass Ionomer Cement II [GI], Ionglass [IG], Ion Z [IZ], Ionomaster [IM], Ionofil Plus [IP], Ionostar Plus [IS], Ketac Molar Easymix [KM], Magic Glass [MG], Maxxion R [MA], Riva Self Cure [R], Vidrion R [V], Vitro Fil [VF] and Vitro Molar [VM]. All experiments were carried out by a team of researchers from Brazil and England following strict protocols, under the same laboratory conditions throughout, and maintaining data integrity. RESULTS: There was consensus on: determining as primary properties of the material: compressive strength, microhardness, acid erosion and fluoride release, and as secondary properties: contrast ratio and translucency parameter, in order to rank the materials. Seven brands were below the thresholds for restorative indications: IZ, IM, IG, MA, VF, B and MG. CONCLUSIONS: Based on the primary properties adopted as being essential for restorative indications, the conventional restorative GICs that met the thresholds and could be considered suitable as long-term restorative materials were: EF, GI, GL9, KM, IP, GL2, IS, CR, V, VM and R. A decision-making process to select the best GIC must also include results from clinical trials. CLINICAL SIGNIFICANCE: This study provides a ranking of GICs that could be considered suitable as long-term restorative materials based on their main properties.

Methods used by dental practice-based research network dentists to diagnose dental caries.

OBJECTIVES: To (1) identify the methods that dentists in The Dental Practice-based Research Network (DPBRN) use to diagnose dental caries; (2) quantify their frequency of use, and (3) test the hypothesis that certain dentist and dental practice characteristics are significantly associated with their use. METHODS: A questionnaire about methods used for caries diagnosis was sent to DPBRN dentists who reported doing some restorative dentistry; 522 dentists participated. Questions included the use of dental radiographs, the dental explorer, laser fluorescence, air-drying and fiber-optic devices and magnification as used when diagnosing primary, secondary/recurrent or non-specific caries lesions. Variations on the frequency of their use were tested using multivariate analysis and Bonferroni tests. RESULTS: Overall, the dental explorer was the instrument most commonly used to detect primary occlusal caries and caries at the margins of existing restorations. In contrast, laser fluorescence was rarely used to help diagnose occlusal primary caries. For proximal caries, radiographs were used to help diagnose 75%-100% of lesions by 96% of the DPBRN dentists. Dentists who use radiographs most often to assess proximal surfaces of posterior teeth were significantly more likely to also report providing a higher percentage of patients with individualized caries prevention (p = .040) and seeing a higher percentage of pediatric patients (p = .001). CONCLUSION: The use of specific diagnostic methods varied substantially. The dental explorer and radiographs are still the most commonly used diagnostic methods.

Abutment design for implant-supported indirect composite molar crowns: reliability and fractography.

PURPOSE: To investigate the reliability of titanium abutments veneered with indirect composites for implant-supported crowns and the possibility to trace back the fracture origin by qualitative fractographic analysis. MATERIALS AND METHODS: Large base (LB) (6.4-mm diameter base, with a 4-mm high cone in the center for composite retention), small base (SB-4) (5.2-mm base, 4-mm high cone), and small base with cone shortened to 2 mm (SB-2) Ti abutments were used. Each abutment received incremental layers of indirect resin composite until completing the anatomy of a maxillary molar crown. Step-stress accelerated-life fatigue testing (n = 18 each) was performed in water. Weibull curves with use stress of 200 N for 50,000 and 100,000 cycles were calculated. Probability Weibull plots examined the differences between groups. Specimens were inspected in light-polarized and scanning electron microscopes for fractographic analysis. RESULTS: Use level probability Weibull plots showed Beta values of 0.27 for LB, 0.32 for SB-4, and 0.26 for SB-2, indicating that failures were not influenced by fatigue and damage accumulation. The data replotted as Weibull distribution showed no significant difference in the characteristic strengths between LB (794 N) and SB-4 abutments (836 N), which were both significantly higher than SB-2 (601 N). Failure mode was cohesive within the composite for all groups. Fractographic markings showed that failures initiated at the indentation area and propagated toward the margins of cohesively failed composite. CONCLUSIONS: Reliability was not influenced by abutment design. Qualitative fractographic analysis of the failed indirect composite was feasible.

Effect of mode of application on the microtensile bond strength of a self-etch and etch-and-rinse adhesive system.

UNLABELLED: This study examined the 24-hour microtensile bond strength (microTBS) of a three-step etch-and-rinse (All Bond 3 [AB3]) and a two-step self-etch system (All Bond Self-Etch [ABSE]) to dentin and ground enamel, varying the application mode. METHODS: AB3 was applied according to the following procedures: A-phosphoric acid + adhesive application. The adhesive was then light-cured before resin buildup. B-similar to Procedure A, except that a thin layer of bonding resin was applied over the cured adhesive; C-similar to Procedure B, however, the adhesive was not light-cured before application of the bonding resin. ABSE was applied according to the following procedures: A--the acidic adhesive was applied and light-cured; B--after the acidic adhesive application and light-curing, a thin layer of ABSE Liner was applied and light cured; C--similar to B, however, the acidic adhesive was not light cured before application of the ABSE Liner. Resin composite buildups (Charisma) were bonded to teeth substrates after adhesive application. The bonded specimens were sectioned into beams 0.9 mm2 after storage in water (24 hours/37 degrees C) and subjected to microTBS with a crosshead speed of 0.5 mm/minute. The average values (MPa) obtained in each substrate were subjected to two-way repeated measures ANOVA and the Tukey's test (alpha=0.05). RESULTS: No significant difference was observed among the experimental groups either in ground enamel or dentin. CONCLUSIONS: The 24-hour microtensile bond strength of All Bond 3 and All Bond Self-Etch was similar, regardless the mode of application of the adhesive systems.

A randomized clinical evaluation of a one- and two-step self-etch adhesive over 24 months.

OBJECTIVE: To evaluate the performance of All Bond SE used in a one- or two-step protocol in a 24-month randomized clinical study. METHODS: Thirty-three patients with two similarly sized non-carious cervical lesions participated in this study. A total of 66 restorations were placed, half using the one-step All Bond SE protocol (SE-1) and the other half using the two-step All Bond SE protocol (SE-2). The restorations were evaluated at baseline and after 6, 12 and 24 months following the modified USPHS criteria and analyzed by the McNemar's test and Fisher's exact test (alpha = 0.05). RESULTS: After 24 months, six SE-1 and four SE-2 restorations were rated as Bravo in marginal discoloration The retention rates for SE-1 and SE-2 were 84.8% and 90.9%, respectively, after 24 months. Compared to baseline, the retention rate for SE-1 was statistically lower. CONCLUSIONS: All Bond SE used in the one- or two-step protocol resulted in high retention rates after 24 months.

Direct resin composite restorations versus indirect composite inlays: one-year results.

AIM: The aim of this study was to evaluate the clinical performance of direct resin composite restorations (Tetric Ceram-TC) and indirect composite inlays (Targis-TG) after 12 months. METHODS AND MATERIALS: Seventy-six Class I and II restorations (44 direct and 32 indirect) were inserted in premolars and molars with carious lesions or deficient restorations in 30 healthy patients according to the manufacturer's instructions. Each restoration was evaluated at baseline and after 12 months according to the modified USPHS criteria for color match (CM), marginal discoloration (MD), secondary caries (SC), anatomic form (AF), surface texture (ST), marginal integrity (MI), and pulp sensitivity (PS). Data were analyzed by Fisher and McNemar Chi-square tests. RESULTS: No secondary caries and no pulpal sensitivity were observed after 12 months. However, significant changes in marginal discoloration (MD) criteria could be detected between baseline and one-year results for both materials (p<0.05). For marginal integrity (MI) criteria, the differences between baseline and one-year recall were statistically significant (p<0.05). For marginal integrity (MI) criteria, Tetric Ceram (TC) showed results statistically superior to Targis (TG) in both observation periods (p<0.05). No statistically significant changes in color match (CM), anatomic form (AF), or surface texture (ST) appeared during the observation periods (p>0.05). CONCLUSIONS: BDirect resin composite restorations performed better than indirect composite inlays for marginal integrity, but all restorations were judged to be clinically acceptable. CLINICAL SIGNIFICANCE: Tetric Ceram direct restorations and Targis indirect inlays in posterior teeth provide satisfactory clinical performance and the comparison between them showed little difference after one year.

A 24-month randomized clinical trial of a two- and three-step etch-and-rinse technique.

PURPOSE: This 24-month randomized paired tooth clinical study evaluated the performance of All Bond 3 used in the simplified (2-step) and full (3-step) versions. METHODS: 33 patients, with at least two similar sized non-carious cervical lesions participated in this study. A total of 66 restorations were placed, half using the 2-step All Bond 3 (AB3-2) and the other half using 3-step All Bond 3 (AB3-3). The restorations were placed incrementally using the composite resin Aelite. The restorations were evaluated at baseline and after 6, 12 and 24 months following the modified USPHS criteria. Statistical differences between the adhesive were tested using with McNemar's test and clinical performance over time for each material with the Fisher's exact test (alpha = 0.05). RESULTS: After 24 months, six AB3-2 and four AB3-3 were rated as bravo for marginal discoloration but did not differ from each other significantly (P > 0.05). The retention rates at 24 months of AB3-2 and AB3-3 were 90.9% and 97.0%, respectively (P > 0.05).

Reaction kinetics of sodium ascorbate and dental bleaching gel.

OBJECTIVE: The aim of this study was to establish the reaction kinetics of 35% hydrogen peroxide and sodium ascorbate and to determine the mass of antioxidant required to neutralize the bleaching gel. METHODS: The method used to quantify sodium ascorbate was based on the United States Pharmacopeia (1995)(26). Oxidation-reduction titration was used to confirm the concentration of hydrogen peroxide and sodium ascorbate and to determine the reaction kinetics between them. RESULTS: The results indicated a direct correlation between the mass of hydrogen peroxide and that of the antioxidant agent. In addition, 5 min of contact was sufficient to neutralize the hydrogen peroxide used. CONCLUSION: This in vitro study showed that the amount of sodium ascorbate required for reduction of hydrogen peroxide is directly related to the concentration of the latter. In addition, the reaction kinetics between oxidant and antioxidant showed that a longer application time for sodium ascorbate does not influence the effectiveness of the reaction and that 5 min is sufficiently long for this antioxidant to exert an antioxidant effect.

Effect of an additional hydrophilic versus hydrophobic coat on the quality of dentinal sealing provided by two-step etch-and-rinse adhesives.

OBJECTIVE: To test the hypothesis that the quality of the dentinal sealing provided by two-step etch-and-rinse adhesives cannot be altered by the addition of an extra layer of the respective adhesive or the application of a more hydrophobic, non-solvated resin. MATERIAL AND METHODS: full-crown preparations were acid-etched with phosphoric acid for 15 s and bonded with Adper Single Bond (3M ESPE), Excite DSC (Ivoclar/Vivadent) or Prime & Bond NT (Dentsply). The adhesives were used according to the manufacturers' instructions (control groups) or after application to dentin they were a) covered with an extra coat of each respective system or b) coated with a non-solvated bonding agent (Adper Scotchbond Multi-Purpose Adhesive, 3M ESPE). Fluid flow rate was measured before and after dentin surfaces were acid-etched and bonded with adhesives. RESULTS: None of the adhesives or experimental treatments was capable to block completely the fluid transudation across the treated dentin. Application of an extra coat of the adhesive did not reduce the fluid flow rate of adhesive-bonded dentin (p>0.05). Conversely, the application of a more hydrophobic non-solvated resin resulted in significant reductions in the fluid flow rate (p<0.05) for all tested adhesives. CONCLUSIONS: The quality of the dentinal sealing provided by etch-and-rinse adhesives can be significantly improved by the application of a more hydrophobic, non-solvated bonding agent.

Correlation between margin fit and microleakage in complete crowns cemented with three luting agents.

UNLABELLED: Microleakage can be related to margin misfit. Also, traditional microleakage techniques are time-consuming. This study evaluated the existence of correlation between in vitro margin fit and a new microleakage technique for complete crowns cemented with 3 different luting agents. Thirty human premolars were prepared for full-coverage crowns with a convergence angle of 6 degrees, chamfer margin of 1.2 mm circumferentially, and occlusal reduction of 1.5 mm. Ni-Cr cast crowns were cemented with either zinc phosphate (ZP) (S.S. White), resin-modified glass-ionomer (RMGI) (Rely X Luting Cement) or a resin-based luting agent (RC) (Enforce). Margin fit (seating discrepancy and margin gap) was evaluated according to criteria in the literature under microscope with 0.001 mm accuracy. After thermal cycling, crowns were longitudinally sectioned and microleakage scores at tooth-cement interface were obtained and recorded at x100 magnification. Margin fit parameters were compared with the one-way ANOVA test and microleakage scores with Kruskal-Wallis and Dunn's tests (alpha=0.05). Correlation between margin fit and microleakage was analyzed with the Spearman's test (alpha=0.05). Seating discrepancy and marginal gap values ranged from 81.82 microm to 137.22 microm (p=0.117), and from 75.42 microm to 78.49 microm (p=0.940), respectively. Marginal microleakage scores were ZP=3.02, RMGI=0.35 and RC=0.12 (p<0.001), with no differences between RMGI and RC scores. The correlation coefficient values ranged from -0.27 to 0.30 (p>0.05). CONCLUSION: Margin fit parameters and microleakage showed no strong correlations; cast crowns cemented with RMGI and RC had lower microleakage scores than ZP cement.

One-year comparison of metallic and translucent matrices in Class II composite resin restorations.

PURPOSE: To evaluate the clinical performance of composite restorations performed with two matrix and wedge systems. METHODS: Each of 23 subjects received at least one pair of Class II restorations, one with metallic matrix and wooden wedge and the other with polyester matrix and reflexive wedge. One dentist placed 109 Class II restorations, 51 in premolars and 58 in molars, all in occlusion. Most of the cavities were surrounded by enamel. The restorations were evaluated at baseline, and after 12 months using the modified USPHS criteria. All cavities were restored using Single Bond and P-60, according to the manufacturer's indications. In the metal matrix group, polymerization was performed from occlusal, and in the polyester group, through the reflexive wedge. Statistical analysis was carried out with Chi-square and McNeumar tests. RESULTS: After 12 months, there was a significant increase in marginal staining, and marginal adaptation was affected by clinical service. There were no differences between matrix and wedge systems, neither considering dental groups nor cavity types.

In vivo and in vitro evaluation of Class II composite resin restorations with different matrix systems.

PURPOSE: To investigate in vivo and in vitro Class II composite restorations performed with two matrix and wedge systems. MATERIALS AND METHODS: One hundred nine Class II restorations were performed in 23 patients, 59 with metallic matrices and wooden wedges (group 1) and 50 with polyester matrices and reflective wedges (group 2). All cavities were restored using Single Bond and P-60 (3M ESPE). In the metal matrix group, polymerization was performed from the occlusal, and in the polyester group through the reflective wedge. To assess microleakage, 40 proximal standard slot cavities were prepared in 20 noncarious human third molars. In the mesial cavity, the gingival margin was located at the enamel level, and in the distal cavity at the cementum/dentin. Specimens were randomly divided into two groups (n = 20) and restored with Single Bond, Z-250 (3M ESPE), and the same techniques used in the in vivo study: metal matrix/wooden wedge (group 1) and polyester matrix/reflective wedge (group 2). Specimens were thermocycled (500 times, 5 degrees C to 55 degrees C), then isolated with nail varnish and immersed in fuchsin for 8 h. Specimens were sectioned longitudinally and microleakage was assessed under magnification (40X) using a standard scoring system. RESULTS: Data were subjected to the chi-square test, Mann-Whitney U-test, and Kruskal-Wallis H-test. Matrix systems presented similar results in the clinical evaluation and the in vitro microleakage test of Class II composite restorations. Dye leakage was minimal at enamel margins, and statistically lower (p < 0.05) than at cementum/dentin margins. CONCLUSION: The different matrix systems had no influence on clinical performance or in vitro sealing ability of Class II composite restorations.

Effect of 2% iodine disinfecting solution on bond strength to dentin.

INTRODUCTION: Disinfection of dentin surfaces is desirable so long as it does not interfere with subsequent bonding of adhesive resins. OBJECTIVE: To test the null hypothesis that bond strengths to dentin are not affected by previous application of an iodine disinfecting solution. MATERIALS AND METHODS: Twenty-four extracted non-carious molars were selected. Occlusal enamel was removed producing a flat dentin substrate. Test teeth were all treated with 2% Iodine disclosing/disinfecting solution (I(2)DDS) for 20 sec and rinsed for 20 sec followed by the application of self- or total- etching bonding systems, generating five adhesive groups (n=3): Single Bond; Prime & Bond NT; Clearfil SE Bond; Opti-Bond Plus. The control groups (n=3 per adhesive) had no disclosing/disinfectant application prior to adhesive application. A 4-mm thick resin restoration was built up on each tooth for microtensile testing. Statistical analyses between experimental and control groups were performed by student's t-test (alpha= 0.05). RESULTS: In general, experimental groups (previously treated with I(2)DDS) showed significantly lower bond strength values when compared with their respective controls (p<0.05), except for group Prime & Bond I(2) that did not significantly differ from its control (p>0.05). CONCLUSION: Acetone-base adhesive systems seem not to be affected by the application of I(2)DDS prior to etching and bonding procedures.

Influence of carbamide peroxide-based bleaching agents on the bond strength of resin-enamel/dentin interfaces.

In this bond strength study, a bleaching agent containing 10% carbamide peroxide was applied over composite-teeth bonded interfaces of two adhesive systems applied to enamel and dentin. Sixteen human third molars were used for bonding procedures. Single Bond (SB) and Clearfil SE Bond (CB) were applied to enamel and dentin according to the manufacturers' instructions. A resin composite cube-like structure was incrementally built on the bonded surfaces. The restored teeth were sectioned into 0.7 mm thick slices that were trimmed at enamel or dentin bonded interfaces to an hourglass shape with a cross-sectional area of approximately 0.5 mm2. Specimens were assigned to 8 groups (n = 10) according to the following factors under study: dental substrate (enamel and dentin); adhesive system (SB and CB) and treatment (10% carbamide peroxide and not bleached/control). The bleaching gel (Opalescence) was applied at the bonded interfaces for 6 hours during 14 days and after daily treatment specimens were stored in artificial saliva. Unbleached specimens were stored in artificial saliva for 14 days. Specimens were tested for tension and the data were analyzed by three-way ANOVA and Tukey's test (p < 0.05). Enamel tensile bond strength of CB was reduced after carbamide peroxide application. The bleaching treatment did not alter dentin bond strength of both adhesives. The results suggest that bleaching significantly affects bond strength of CB to enamel, but no influence on bond strength to dentin was noted for both adhesive systems.

Effect of peroxide-based bleaching agents on enamel ultimate tensile strength.

This study evaluated the effects of peroxide bleaching regimens on the ultimate tensile strength (UTS) of human enamel. A resin composite block was built-up on the bonded occlusal surface of 14 extracted, sound, erupted third molars to enable posterior preparation for the microtensile test. The bonded teeth were serially sectioned in a buccal-lingual direction into approximately 0.7-mm thick slices. Each slice was trimmed with a fine diamond bur to reduce the area of the buccal, internal slope of the cusps to a dumb-bell shape with a cross-sectional area of less than 1 mm2. The samples were randomly divided into seven groups (n = 10): unbleached control group and bleached groups treated with six bleaching regimens. The specimens were tested in tension at 0.5 mm/minute and the data were analyzed by ANOVA and Tukey test. Specimens from the control group presented 51.3 +/- 8.6 MPa, while the UTS of bleached enamel ranged from 22.0 +/- 5.6 to 36.3 +/- 9.1 MPa. All bleaching procedures significantly reduced enamel UTS (p < 0.05). Differences were also observed among treatments. The results suggested that bleaching regimens can significantly reduce enamel UTS.

Liner and light exposure: effect on in-vitro Class V microleakage.

This in vitro study evaluated the influence of different glass ionomer liners and curing methods on microleakage of resin composite restorations. Class V root preparations were made in 120 bovine incisors randomly divided into 12 groups according to liner and curing method. The resin composite system (Single Bond + Z100) was inserted and polymerized in one increment in all groups. Cavity preparations were either not lined (control), lined with a resin modified glass-ionomer cement (Vitrebond) or a conventional glass-ionomer cement (Ketac Bond). The restorations were light-cured using one of four curing methods. The teeth were thermocycled and immersed in 0.5% basic fuchsin, sectioned, and dye penetration was measured (Image Tool). No significant difference in leakage among conventional, ramp or pulse-delay methods was seen. High intensity light groups showed significantly greater penetration compared to other curing methods. No significant difference existed in marginal leakage between liners, but microleakage was significantly higher in groups restored using no liner. No relationship between lining technique and light curing method was observed. The use of glass ionomer liners reduced microleakage, while high intensity light curing produced the greatest dye penetration.

Effect of irradiation mode and filling technique on resin/dentin bonding strength in Class I cavities.

Factors such as light-curing mode, filling technique and cavity configuration may affect the bonding strength to dentin. This study evaluated the effect of irradiation mode and filling technique on resin/dentin bonding strength on the buccal wall of Class I cavities in human teeth. Occlusal enamel was removed to expose a flat dentin surface. Occlusal cavities (4 x 3 x 3 mm) were prepared in dentin. The adhesive Single Bond was applied according to the manufacturer's instructions and TPH Spectrum composite resin was placed using the following: oblique incremental, horizontal incremental or bulk filling techniques. The composite resin was light-cured either by continuous (600 mW/cm2 for 40 s) or Soft-Start (250 mW/cm2 for 10 s + 600 mW/cm2 for 30 s) modes. Specimens of the control group were obtained by bonding the material to the flat exposed buccal wall of the cavity (C-factor = 1). The teeth were stored in water at 37 degrees C for 24 h and prepared for microtensile testing. Bonded beams of approximately 0.8 mm2 were obtained from the buccal wall and tested with a tension of 0.5 mm/min. Results were analyzed by two-way ANOVA, Tukey's test and Dunnett's test (alpha = 0.05). Incremental placement techniques with both irradiation modes produced higher bonding strength values than the bulk technique (p < 0.05). Bonding strength tested in the cavities had lower values than those obtained in flat dentin surfaces (control group) (p < 0.05), except for incremental fillings using stepped irradiation. Bonding strength to the cavity walls depends on the filling technique and on the irradiation mode of composite resins.

Ultimate tensile strength of tooth structures.

OBJECTIVE: This study determined the ultimate tensile strength (UTS) of enamel (E), dentin (D) and dentin-enamel junction (DEJ) using the microtensile technique. It was hypothesized that the UTS of dental structures varies according to location and nature. METHODS: Intact occlusal enamel surfaces from extracted human third molars were etched with 37% phosphoric acid and bonded with a one-bottle adhesive system. The bonded occlusal surfaces received a resin composite build-up and teeth were serially, vertically sectioned into several 0.7 mm thick slabs. Each slab was then trimmed to a dumbbell-shaped specimen with irrigated diamond burs to reduce the cross-sectional area to approximately 0.5 mm2 at E, D or DEJ. E was tested according to its prismatic orientation (parallel, EP; and transversally, ET) and D as function of depth (superficial, DS; middle, DM and deep, DD). Specimens were tested in tension in an Instron testing machine at 0.5 mm/min. Results were analyzed by one-way ANOVA and Duncan's Multiple Range test. RESULTS: UTS mean values (N = 20) were, MPa (SD): DEJ, 46.9 (13.7)b; EP, 42.1 (11.9)b; ET, 11.5 (4.7)d; DS, 61.6 (16.2)a; DM, 48.7 (16.6)b and DD, 33.9 (7.9)c. Enamel stressed transversally to its prismatic orientation was significantly weaker (p < 0.05) Dentin depth significantly affected its UTS (p < 0.05) DEJ presented UTS that was similar to EP and DM (p > 0.05) SIGNIFICANCE: The UTS of dental structures varies according to its nature and location.

Moisture spectrum of demineralized dentin for adhesive systems with different solvent bases.

PURPOSE: To determine the effects of different surface moisture on the bond strength of an ethanol/water-based (Single Bond [SB]), an acetone-based (One-Step [OS]), and a water-based (Syntac Single Component [SC]) adhesive system to dentin. MATERIALS AND METHODS: On 90 human third molars, a flat superficial dentin surface was exposed by abrasion with 600-grit SiC paper. The adhesives were applied to a delimited area of 52 mm2 according to the manufacturers' instructions on either dry (oil-free air/30 s) or rewetted surfaces (1.5, 2.5, 3.5, 4.0 or 4.5 microl of distilled water), and composite crowns were constructed incrementally. After storage in distilled water at 37 degrees C for 24 h, the teeth were longitudinally sectioned in the "x" and "y" directions to obtain bonded sticks with a cross-sectional area of 0.8 mm2. The specimens were tested in tension at 0.5 mm/min and the fracture mode analyzed. Resultant bond strength was expressed as an index that includes bond strength values of the different fracture patterns and the specimens that failed during preparation for the microtensile testing. The data was analyzed by two-way ANOVA, Tukey's multiple comparison, and regression analysis. RESULTS: Highly significant main effects and interaction (p < 0.0001) were detected. A quadratic relationship between the bond strength index and the surface moisture was identified (R2 = 0.95, p < 0.001). SB showed a maximum bond strength (42.2 +/- 6.7 MPa) that was statistically similar (p = 0.4996) to the maximum bond strength of OS (40.1 +/- 4.6 MPa), although obtained at a different degree of moisture (ca 1.5 microl for SB and 3.5 microl for OS). SC showed its maximum bond strength (27.7 +/- 3.9 MPa) with 1.5 microl moisture. SB presented its highest bond strength at 1.5 microl of water, which was significantly higher than the bond strength obtained at any other degree of moisture (p < 0.05). OS achieved its maximum bond strength at 3.5 microl of water; however, that value was not statistically different (p > 0.05) from the values obtained with 1.5 microl to 4.0 microl of water. Similarly, highest bond strengths obtained with SC were not different (p > 0.05) within the range of 0 microl to 3.5 microl of water. CONCLUSION: All adhesive systems tested had a different moisture spectrum in which higher bond strengths were obtained. SB and SC performed better on a drier substrate, while OS showed better performance on wetter substrates. OS and SC had a broader range of moisture within which maximal bond strength could be achieved.