Interfacial Characteristics and Bond Durability of Universal Adhesive to Various Substrates.

OBJECTIVE: This study investigated the interfacial characteristics and bond durability of universal adhesives to various substrates. METHODS AND MATERIALS: Two universal adhesives were used: 1) Scotchbond Universal and 2) G-Premio Bond. The substrates used were bovine enamel and dentin with or without phosphoric acid etching, resin composite, lithium disilicate and leucite-reinforced glass ceramics, zirconia, and metal alloys. The surface free energy and the parameters of various substrates and of substrates treated by adhesive after light irradiation were determined by measuring the contact angles of three test liquids. Resin composite was bonded to the various substrates to determine shear bond strength after 24 hours water storage and 10,000 thermal cycles. A one-way analysis of variance (ANOVA) and the Tukey post hoc test were used for the surface free energy data, and a two-way ANOVA and the Tukey post hoc test were used for analysis of shear bond strength data (α=0.05). RESULTS: The interfacial characteristics of the various substrates show significant differences depending on the type of substrate, but the interfacial characteristics of substrate treated by adhesive after light irradiation did not show any significant differences regardless of the substrate used. The bond durability of two universal adhesives to various substrates differs depending on the type of substrate and the adhesive. CONCLUSIONS: The results of this study suggest that universal adhesives modify the interfacial characteristics of a wide range of substrates and create a consistent surface, but the bond durability of universal adhesive to various substrates differs depending on the type of substrate and the adhesive.

Wear rates of resin composites.

SUMMARY A laboratory study was conducted to examine the wear of resin composite materials using a generalized wear simulation model. Ten specimens each of five resin composites (Esthet•X [EX], Filtek Supreme Plus [SP], Filtek Z250 [Z2], Tetric EvoCeram [EC], and Z100 Restorative [Z1]) were subjected to wear challenges of 100,000, 400,000, 800,000, and 1,200,000 cycles. The materials were placed in cylinder-shaped stainless-steel fixtures, and wear was generated using a flat stainless-steel antagonist in a slurry of polymethylmethacrylate beads. Wear (mean facet depth [µm] and volume loss [mm(3)]) was determined using a noncontact profilometer (Proscan 2000) with Proscan and ProForm software. Statistical analysis of the laboratory data using analysis of variance and Tukey's post hoc test showed a significant difference (p<0.05) for mean wear facet depth and volume loss for both the number of cycles and resin composite material. Linear regression analysis was used to develop predictive wear rates and volume loss rates. Linear wear was demonstrated with correlation coefficients (R(2)) ranging from 0.914 to 0.995. Mean wear values (mean facet depth [µm]) and standard deviations (SD) for 1200K cycles were as follows: Z1 13.9 (2.0), Z2 26.7 (2.7), SP 30.1 (4.1), EC 31.8 (2.3), and EX 67.5 (8.2). Volume loss (mm(3)) and SDs for 1200K cycles were as follows: Z1 0.248 (0.036), Z2 0.477 (0.044), SP 0.541 (0.072), EC 0.584 (0.037), and EX 1.162 (0.139). The wear rate (µm) and volume loss rate (mm(3)) per 100,000 cycles for the five resin composites were as follows: wear rate Z1 0.58, EC 1.27, Z2 1.49, SP 1.62, and EX 4.35, and volume loss rate Z1 0.009, EC 0.024, Z2 0.028, SP 0.029, and EX 0.075. The generalized wear model appears to be an excellent method for measuring relative wear of resin composite materials.

Localized wear of compomer restorative materials.

PURPOSE: To determine and compare the localized wear of six compomer restorative materials. MATERIALS AND METHODS: Ten specimens of Dyract, Dyract AP, F2000, Compoglass F, Elan and Hytac were prepared in a custom fixture and polished. A pretest surface profile was generated using an MTS 3-D surface profilometer and the specimens were subjected to 400,000 cycles in a Leinfelder wear machine equipped with a conical stylus tip to simulate localized wear. A post-test profile was generated and the before and after profiles were fitted and analyzed using AnSur 3-D software. The total volume loss and depth of the wear facet on each specimen was calculated and statistical analysis was accomplished (ANOVA and Tukey's test). RESULTS: Volume loss (mm3) was as follows: F2000, 0.027 +/- 0.002; Hytac, 0.007 +/- 0.023; Elan, 0.054 +/- 0.013; Compoglass F, 0.135 +/- 0.006; Dyract AP, 0.135 +/- 0.023; Dyract, 0.185 +/- 0.032. Maximum depth of the wear facets (microm) was as follows: F2000, 112.2 +/- 10.2; Hytac, 132.8 +/- 9.3; Elan, 144.3 +/- 23. 1; Compoglass F, 168.3 +/- 13.0; Dyract AP, 194.0 +/- 19.7; Dyract, 220.6 +/- 15.8. There was not a difference (P > 0.05) in volumetric loss between F2000 and Hytac or between Hytac and Elan. The volume loss and maximum depth of the wear facets of F2000, Hytac and Elan was significantly less (P< 0.05) than Compoglass F, Dyract AP and Dyract The results of this study indicate that there are significant differences in the in vitro wear rates of compomer materials.

Use of electrosurgery and lasers in the presence of dental implants.

Use of electrosurgery or laser surgery in the presence of metallic implants has been implicated in generating heat-induced injury to peri-implant bone, with the subsequent loss of osseointegration. Studies involving lasers offer conflicting results, while in the case of the electrosurg, little research has been published supporting or refuting these claims. This study measured local heat effects created by use of a unipolar electrosurgical unit, a bipolar electrosurgical unit, and a neodymium:yttrium-aluminum-garnet (Nd:YAG) laser. Absolute temperature increase was measured during an in vitro uncovering surgical procedure performed with each unit. Analysis of variance for repeated measures was performed. Second, absolute temperature increase for each unit was compared with a theoretical clinical limit of a 10 degrees C increase. The findings suggest that use of the unipolar electrosurgical unit should be avoided, while judicious use of both the bipolar unit or the laser unit should produce temperature profiles well within clinical limits.

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.

4-year clinical study of castable ceramic crowns.

PURPOSE: To evaluate the 4-year clinical performance of castable glass ceramic crowns used to restore teeth in the posterior segments. MATERIALS AND METHODS: 101 castable ceramic (Dicor) full++ crown restorations were placed in 61 molar and 40 premolar teeth using a bonded resin cement. RESULTS: After 4 years of clinical performance, 15 of the original 101 restorations were known to have failed with 13 of those failures affecting molar restorations. All serviceable restorations were rated as excellent for color match, margin adaptation, proximal contact and gingival health. Cavosurface margin discoloration received a 93.5% alfa response. The results of this study show that Dicor crowns meet the esthetic and biological requirements for posterior restorations. The incidence of fracture of molar restorations in this study indicated that when used for restoring molars, careful case selection and caution must be employed.

Effect of porcelain surface treatments on bond strengths of composite resin bonded to porcelain.

A laboratory study was conducted to evaluate the bond strength of composite resin bonded to porcelain surfaces by use of a variety of treatment regimens with the All-Bond 2 adhesive system. There were significant differences in the 24-hour bond strengths between several of the surface treatment methods. The mean shear bond strength after 24 hours of water storage ranged from 10.6 +/- 2.3 MPa to 25.0 +/- 4.4 MPa. Nine of the surface treatment methods showed a significant decrease (p < 0.05) in bond strengths after 3 months of water storage and thermocycling. After 3 months, the bond strengths ranged 0.1 +/- 0.1 MPa to 17.4 +/- 2.0 MPa. Porcelain surface treatment with aluminum oxide air abrasion followed by hydrofluoric acid, a silane coupling agent, and an unfilled resin produced a bond strength after 3 months' water storage and thermocycling that was significantly greater (p < 0.05) than the other nine porcelain surface-treatment techniques. Visual examination of the debonded specimens generally showed cohesive failures in porcelain for the treatment groups with a mean bond strength above 13 MPa.

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.