The relationship of hydrogen peroxide exposure protocol to bleaching efficacy.

The purpose of this study was to compare two in-office bleaching methods with respect to tooth color change and level of hydrogen peroxide penetration into the pulp cavity and to evaluate relationships between penetration level and color change. Eighty extracted canines were exposed to two different bleaching regimens (conventional vs sealed bleaching technique). After exposure to 38% hydrogen peroxide gel for one hour, hydrogen peroxide amount was estimated spectrophotometrically. Color change was measured per Commission Internationale de l'Eclairage methodology. Linear regression was used to evaluate factors affecting color change, including bleaching technique. The conventional and sealed bleaching groups showed no difference for any color change parameters (ΔL, Δa, Δb, ΔE); however, there was significantly greater hydrogen peroxide penetration in the conventional bleaching group (p<0.05). Linear modeling of the change in lightness (ΔL) showed that the increase in lightness tended to be greater for teeth with lower initial L* values (r=-0.32, p<0.05). After adjustment for initial L*, there was no evidence that ΔL differed with hydrogen peroxide penetration levels (p>0.05) or bleaching technique (mean group difference in ΔL=0.36; p>0.05).

Analysis of debond rates of resin-bonded prostheses.

Debonding rates of 164 resin-bonded prostheses (RBP) placed from 1974 to 1985 were examined at recall. The yearly debond rates were calculated, the cumulative probability of failure was determined for the debonded RBPs, and Weibull distribution parameters were determined. For perforated prostheses, there was a high initial debond rate, followed by slowly decreasing rates for about 5 years. Increasing rates after 5 years indicated the beginning of wear-out. The Weibull parameters for the wear-out period of the perforated prostheses were: characteristic life = 128 (SE = 2) months, modulus = 1.27 (0.06), and threshold parameter = 0. Data were available for etched frameworks for 6 years and showed decreasing debond rates during this time. The characteristic life of the etched bridges was 318 (84) months. The cumulative failure data were also modeled with a cubic polynomial distribution that resulted in a U-shaped hazard function.

In vitro bond strengths and SEM evaluation of dentin bonding systems to different dentin substrates.

In comparison to enamel, bonding to normal dentin is a greater challenge because of its organic constituents, fluid-filed tubules, and variations in intrinsic composition. Bonding to sclerotic dentin is even more difficult. To evaluate the shear bond strengths of four adhesive systems to dentin substrates with different levels of mineralization, 120 extracted human teeth were randomly assigned to three groups (n = 40). After mid-coronal dentin was exposed, groups of specimens were artificially hypermineralized by immersion in a remineralizing solution, demineralized by means of an acetic acid demineralizing solution, or stored in distilled water to model sclerotic, carious, and normal dentin, respectively. Resin composite was bonded to dentin by use of commercial adhesive systems. After the specimens were thermocycled, shear bond strengths were determined in an Instron universal testing machine. Dentin substrates and resin/dentin interfaces were examined by SEM. For each adhesive system, the mean shear bond strength to normal dentin was significantly higher than that to either of the other substrates. Shear bond strengths to hypermineralized dentin were significantly higher than those to demineralized dentin with all adhesives except Prisma Universal Bond 3.

Bond strength and microleakage of current dentin adhesives.

OBJECTIVES: The purpose of this in vitro study was to evaluate shear bond strengths and microleakage of seven current-generation dentin adhesive systems. METHODS: Standard box-type Class V cavity preparations were made at the cemento-enamel junction on the buccal surfaces of eighty extracted human molars. These preparations were restored using a microfill composite following application of either All-Bond 2 (Bisco), Clearfil Liner Bond (Kuraray), Gluma 2000 (Miles), Imperva Bond (Shofu), OptiBond (Kerr), Prisma Universal Bond 3 (Caulk), Scotchbond Multi-Purpose (3M), or Scotchbond Dual-Cure (3M) (control). Lingual dentin of these same teeth was exposed and polished to 600-grit. Adhesives were applied and composite was bonded to the dentin using a gelatin capsule technique. Specimens were thermocycled 500 times. Shear bond strengths were determined using a universal testing machine, and microleakage was evaluated using a standard silver nitrate staining technique. RESULTS: Clearfill Liner Bond and OptiBond, adhesive systems that include low-viscosity, low-modulus intermediate resins, had the highest shear bond strengths (13.3 +/- 2.3 MPa and 12.9 +/- 1.5 MPa, respectively). Along with Prisma Universal Bond 3, they also had the least microleakage at dentin margins of Class V restorations. SIGNIFICANCE: No statistically significant correlation between shear bond strength and microleakage was observed in this study. Adhesive systems that include a low-viscosity intermediate resin produced the high bond strengths and low microleakage. Similarly, two materials with bond strengths in the intermediate range had significantly increased microleakage, and one material with a bond strength in the low end of the spectrum exhibited microleakage that was statistically greater. Thus, despite the lack of statistical correlation, there were observable trends.

Interfacial micromorphology and shear bond strength of single-bottle primer/adhesives.

OBJECTIVES: This study was conducted 1) to characterize through SEM analysis the resin-dentin interface produced by single-bottle primer/adhesives and a three-component system [Scotchbond Multi-Purpose (3M Dental)] and 2) to evaluate the shear bond strength to dentin of these adhesive systems. METHODS: Single-bottle primer/adhesives [Bond 1 (Jeneric/Pentron), Single Bond, (3M Dental Products); One Step (Bisco Inc.), OptiBond Solo (Kerr Corp.), Prime & Bond 2.1 (L.D. Caulk-Dentsply), Syntac Single-Component (Ivoclar-Vivadent), Tenure Quilk with Fluoride (Den-Mat)] were used according to manufacturers' instructions to bond resin composite to flat dentinal surfaces of extracted human third molars (n = 15). All samples were thermocycled 300x. Twelve specimens per group were used to measure shear bond strength and three specimens were used to evaluate the interfacial morphology under SEM. A one-way ANOVA and Turkey's test were used to assess the results. RESULTS: Mean shear bond strengths in MPa +/- SD for the groups ranged from 22.27 +/- 4.5 MPa for Single Bond to 7.6 +/- 3.9 MPa for Syntac Single-Component. The statistical analysis indicated that Single Bond produced significantly higher (p < 0.001) bond strengths than Syntac Single-Component, Prime & Bond 2.1, Bond 1 and Tenure Quik With Fluoride. Bond strengths for Syntac Single-Component were significantly lower than One-Step, OptiBond Solo, Scotchbond Multi-Purpose Plus and Single Bond. SEM examination clearly revealed the formation of a distinct hybrid layer for all adhesive systems; however, minor variations in ultrastructure existed among products. SIGNIFICANCE: Some single-bottle primer/adhesive present in vitro bond strengths and hybrid layer formation similar to those found for the conventional three-component adhesive system tested.

Effects of polymerization techniques on uniformity of cure of large-diameter, photo-initiated composite resin restorations.

The polymerization effectiveness of various methods of exposing large-diameter, light-activated composite resin samples is reported. Results of Knoop hardness testing showed that highest mean hardness was achieved by using a wide tip (13 mm) with either the spot cure or overlap method for 60 seconds. More uniform hardness resulted from the wide-tip with scanning methods and 60-second cure than resulted from the narrow-tip (8 mm) with the spot or overlap method and 20-second cure.

Fracture resistance of endodontically prepared teeth using various restorative materials.

This study compares the fracture resistance of endodontically treated premolars with modified types of cavity preparations and restoration with either amalgam or composite resin. The greatest influence on fracture resistance was the remaining tooth structure. The effect of adequate wall support on tooth strength was compared with intact unprepared teeth.

Acid-etch retained cast metal prostheses: a seven-year retrospective study.

The results of this study showed: retention rate was good, caries on the retainer teeth was almost nonexistent, and the supporting tissue clinically did not appear to have a greater incidence of periodontal problems. We believe that these results indicate that the cast acid-etch retained anterior prosthesis should be considered a permanent restoration and a valuable aid for the dental patient.

The physical properties of packable and conventional posterior resin-based composites: a comparison.

BACKGROUND: The authors compared the physical properties of three packable hybrid resin-based composites with those of a conventional hybrid and a microfill composite material advocated for use as posterior restorative materials. They evaluated diametral tensile strength, or DTS; compressive strength, or CS; flexural strength, or FS; and depth of cure, or DC. METHODS: The authors studied the following resin-based restorative materials: three packable composites, Alert Condensable Composite (Jeneric Pentron), SureFil High Density Posterior Restorative (Dentsply Caulk) and Solitaire (Heraeus Kulzer); one conventional hybrid composite, TPH Spectrum (Dentsply Caulk); and one microfill, Heliomolar Radiopaque (Ivoclar-Vivadent). The authors evaluated DTS, CS, FS and DC, according to American National Standards Institute criteria. They made scanning electron micrographs of the packable resin-based composites. RESULTS: Results demonstrated that the conventional hybrid, TPH Spectrum, had significantly greater DTS and FS than other resin-based composites. Alert and SureFil had comparable DTS and FS, which were significantly greater than Heliomolar's DTS and FS. Solitaire had significantly lower DTS and FS than all other resin-based composites. SureFil had the highest CS, followed by TPH Spectrum, Solitaire and Alert, which were comparable and had significantly greater CS than Heliomolar. TPH Spectrum and Alert had significantly greater DC than all other resin-based composites, followed in decreasing order by SureFil, Solitaire and Heliomolar. CONCLUSION: While the packable composites tested in this study had physical properties superior to those of the microfill composite, they were no better suited for use as a posterior restorative material than was the conventional hybrid resin-based composite. CLINICAL IMPLICATIONS: Packable composites may be easier for clinicians to handle than conventional resin-based composites; however, their physical properties were not superior to those of the conventional small-particle hybrid resin-based composite. In addition, these materials may have the clinical drawback of increased wear and surface roughness that was seen with early, large-particle composite restorative materials.

Effect of condensation techniques on amalgam bond strengths to dentin.

This in vitro study determined the shear bond strengths of Tytin amalgam to dentin using All-Bond 2, Amalgambond Plus, Amalgambond Plus with HPA powder, and OptiBond with hand and mechanical (Condensaire) condensation. The occlusal enamel surfaces were ground flat to expose the dentin surfaces, and polished with 600-grit SiC paper. The dentin surfaces were treated with one of the combinations of a dentin bonding agent and a condensation technique. All specimens were thermocycled 300 cycles in water between 5-55 degrees C, and shear bond strengths were determined with a Zwick Universal Testing Machine. Two-way ANOVA and Duncan's tests showed no significant differences (P > 0.05) in shear bond strength between hand and mechanical condensation of the paired groups, with the exception of Amalgambond Plus, where hand condensation was shown to be significantly better. For both condensation techniques, shear bond strength of Amalgambond Plus with HPA powder was significantly higher than the other materials. For mechanical condensation, OptiBond was significantly higher than either Amalgambond Plus or All-Bond 2, and no significant difference was found between Amalgambond Plus and All-Bond 2. For hand condensation, OptiBond was only significantly higher than All-Bond 2, while there was no significant difference between OptiBond and Amalgambond Plus or between Amalgambond Plus and All-Bond 2. In conclusion, for both condensation techniques, Amalgambond Plus with HPA powder performed the best in bonding amalgam to dentin. The two different condensation techniques did not significantly affect shear bond strength, except with Amalgambond Plus.

Amalgam shear bond strength to dentin using different bonding agents.

This study evaluated the shear bond strength of amalgam to dentin using five different bonding agents: Amalgambond Plus, Optibond, Imperva Dual, All-Bond 2, and Clearfil Liner Bond. Flat dentin surfaces obtained by grinding the occlusal portion of 50 human third molars were used for this study. To contain the amalgam on the tooth surface, cylindrical plastic molds were placed on the dentin and secured with sticky wax. The bonding agents were then applied according to the manufacturers' instructions or light activated and Tytin amalgam was condensed into the plastic molds. The samples were thermocycled and shear bond strengths were determined using an Instron Universal Testing Machine. Analysis by one-way ANOVA indicated significant difference between the five groups (P < 0.05). The bond strength of amalgam to dentin was significantly higher with Amalgambond Plus using the High-Performance Additive than with the other four bonding agents.

Effect of desiccation on microleakage of five Class 5 restorative materials.

Resin-modified glass ionomers, combinations of resin and glass-ionomer chemistry, have resulted in materials with longer working times and command set by visible light activation. These materials are easier to use and more resistant to early moisture contamination and fracture. A glass-ionomer or resin-modified glass-ionomer restoration may be inadvertently desiccated by isolation of the same quadrant for subsequent restorative procedures. The present study is an assessment of the effects of desiccation on microleakage of three resin-modified glass-ionomers: Vitremer, Photac-Fil, Fuji II LC; a glass-ionomer, Ketac-Fil; and a microfill resin, Silux Plus. Fifty extracted molars were prepared with class 5 preparations buccal and lingual and randomly assigned to 10 groups (n = 10). Restorations were placed according to the manufacturers' specifications and finished wet after the manufacturers' specified setting interval. All samples were thermocycled 300 cycles between 50 and 500 degrees C. Samples were stored in water at all times until the five groups to be desiccated were air dried and stored dry for 45 minutes. Desiccated groups were then rehydrated for 24 hours prior to AgNO3 staining. Teeth were sectioned mesiodistally and four buccolingual sections (0.6 mm thick) through each class 5 restoration were obtained with a Silverstone-Taylor hard tissue microtome. Each section was scored on a scale of 0-4 for microleakage, and the highest score for dye penetration was used as the score for that restoration. An increase in microleakage was observed in all desiccated groups. Three materials showed a statistically significant increase in microleakage (P < 0.05) following desiccation. Microleakage increases following a brief period of desiccation corresponding to typical treatment times indicate that clinicians need to protect previously placed restorations from undue drying during subsequent dental treatment.

Effect of retention grooves on fracture strength of Class 2 composite resin and amalgam restorations.

The effect of approximal retention grooves on fracture strengths of class 2 composite resin and amalgam restorations was tested in vitro. Results indicated that retention grooves significantly improved (P less than 0.05) the compressive strength of amalgam restorations (38.6% stronger). For posterior composite resin restorations, there was no significant difference in mean compressive strength of restorations in preparations with and without retention grooves.

Evaluation of acidic primers in microleakage of Class 5 composite resin restorations.

The purpose of this in vitro study was to evaluate the marginal seal of two adhesive systems on class 5 composite resin restorations. Two adhesive systems that use acidic primers were used in this study: Clearfil Liner Bond 2 and Denthesive II. Scotchbond Multi-Purpose was used as a control. Class 5 cavity preparations were made at the CEJ (half of the preparation was in enamel and half in dentin/cementum) of 60 extracted human molars. Both systems were used with and without etching. The control group was used with etching only. Composite resin restorations were placed, light cured for 40 seconds, and polished. All specimens were thermocycled 500 times. The specimens were immersed in erythrosin B, tetra-iodo-fluorescent 2% solution, then sectioned to obtain 600 mm-thick sections. These were examined under X13.2 magnification, and the degree of dye penetration was measured in microns. A chi-square test demonstrated no significant differences in microleakage among groups for either dentin (P = 0.54) or enamel (P = 0.35).

Intraoral repair of cosmetic restorations.

The longevity of porcelain and composite resin restorations can often be prolonged by using sound principles, up-to-date materials, and judicious attention to repair when fracture problems arise. Careful case selection and correct usage of surface treatment agents, followed by the use of a quality bonding system and restorative materials, can result in a repair that exhibits excellent retention and natural color blending. This article outlines procedures and materials to repair both resin composite and porcelain intraorally.

A direct approach to restore anterior teeth.

When selecting the correct treatment for a patient with anterior esthetic problems, the dentist must choose between direct and indirect procedures. With situations allowing conservative treatment, direct resin restoration should be given strong consideration. Advances in materials and techniques that can positively affect this choice include pre-restorative bleaching procedures, new bonding agents, and new highly esthetic direct resin systems. A procedure is described to maximize esthetics and minimize finishing time during direct resin placement.

Microleakage of amalgam restorations using Amalgambond and Copalite.

This study compared the effect of using either Amalgambond as a cavity liner or Copalite in the reduction of microleakage in amalgam Class V restorations. Both retentive traditional and non-retentive cavity preparations were compared with gingival cavosurface margin locations both in enamel and in dentin. Cavity preparations were restored with their appropriate liner, thermocycled, and stored in erythrosin red stain for 10 days. The samples were then sectioned and degrees of microleakage determined. Statistical interpretation with the Wilcoxon test showed that microleakage was significantly greater (alpha = 0.05) with the non-traditional cavity design and with cavity margins located in dentin. The results also showed that Amalgambond as a cavity liner significantly reduced microleakage when compared to Copalite.

Effect of matrix systems and polymerization techniques on microleakage of Class II resin composite restorations.

This study investigated the effect of different sized light curing tips (2 mm and 11 mm) with curing techniques associated with different matrix systems (Mylar with reflective wedge and metal with wooden wedge) on microleakage of a posterior resin composite material (P-50) placed using a bonding agent (Scotchbond 2). Eighty Class II mesial and distal slot preparations (40 with enamel gingival margins and 40 with dentin gingival margins) were randomly divided into four equal groups: 1) metal matrix, large tip; 2) Mylar matrix, light emitting wedge, large tip; 3) Mylar matrix, light emitting wedge, small tip; 4) metal matrix, small tip. Three-way ANOVA indicated no statistical differences among groups using small and large curing tips. The results showed significantly more leakage (alpha = 0.05) in the dentin gingival cavosurface margin groups than the enamel cavosurface margin groups. The results also showed significantly greater leakage in the polymerization procedures associated with the metal matrix groups (alpha = 0.05) compared to polymerization procedures associated with the Mylar matrix groups.

Effects of chlorhexidine on dentin surfaces and shear bond strengths.

This in vitro study examined the effects of chlorhexidine on dentin surfaces and on the bond strengths of composite to dentin. Scanning electron microscopy revealed that the chlorhexidine solution deposited debris on the surface and within the tubules of etched dentin but chlorhexidine had no significant effect on the shear bond strengths of composite to dentin using the All-Bond 2 adhesive system.

Effects of dentin permeability and hydration on the bond strengths of dentin bonding systems.

This in vitro study evaluated the shear bond strengths of five adhesive systems bonded to dentin with and without simulated physiologic hydrostatic pressure. To simulate pulpal pressure, bonding procedures were done on extracted teeth connected to a hydration apparatus. Bond strengths were significantly less for each adhesive system under simulated physiologic conditions. Amalgambond had significantly higher bond strengths than Clearfil Photo Bond, Gluma, Scotchbond 2, or Tenure, either with or without simulated pulpal pressure.