Hydroxyapatite coating effect on the bond strength between CAD/CAM materials and a resin cement.

The purpose of this study was to evaluate the bond strength between CAD/CAM materials and a resin cement using hydroxyapatite coating as a surface treatment method. Different surface treatments (Control, no treatment-C; Sandblasting-SB; Hydrofluoric acid etching-HF; applying tooth desensitizer-TeM; applying topical crème-ToM, HAp coating with Pulse Laser Deposition technique-PLD) were applied to three different CAD/CAM materials (LAVA Ultimate, VITA Enamic, and Cerec Blocs). After surface treatments, a universal adhesive (Single Bond Universal, 3M ESPE) was applied and adhesive resin (Rely X Ultimate, 3M ESPE) were cemented on each material surface using plastic tubes (4 mm in diameter). The shear bond strength values were measured using a universal testing machine. Scanning electron microscope analysis were performed to evaluate failure modes and effects of surface treatments. Obtained data were statistically analyzed using two-way ANOVA and Tukey's post hoc test (p = 0.05). The bond strength of PLD groups were significantly higher than other groups in resin-ceramics (p < 0.05). In Cerec Blocs, HF resulted significantly higher bond strength than other groups (p < 0.05). SEM analysis of surface treatment methods (except TeM and ToM) revealed an increase in surface alterations compared to control groups. Failure modes were dominantly adhesive in groups C, TeM, and ToM, whereas mostly mix or cohesive failures were observed in PLD, HF, and SB. Hydroxyapatite coating with PLD technique exhibited promising bond strength results for CAD/CAM resin-ceramics. HAp coating can be used as a replacement for hydrofluoric acid etching and sandblasting in CAD/CAM resin-ceramic materials to obtain better bond strength values.

The Effect of Surface Treatments on the Bond Strength Between CAD/CAM Blocks and Composite Resin.

PURPOSE: The aim of this study was to evaluate the microtensile bond strength of three computer-aided design/computer-aided manufacturing (CAD/CAM) blocks repaired with composite resin using three surface treatment techniques. METHODS AND MATERIALS: Three different CAD/CAM blocks were used in this study: (1) Lithium disilicate, (2) feldspar ceramic, and (3) resin nano ceramic. All groups were further divided into four subgroups according to surface treatment: control, roughened with bur (B); roughened with bur and 5% Hydrofluoric acid (HF); roughened with bur and sandblasting (HF); and roughened with bur and CoJet (C). After surface treatments on each group, a silane and bonding agent were applied, and ceramics were repaired with a nano-hybrid composite. Then, the repaired ceramics were cut with a low-speed diamond saw for microtensile bond testing. Microtensile bond tests for 40 specimens per subgroup were carried out with a universal testing machine. The data were analyzed with ANOVA, Tukey's, and LSD at the 95% significance level. RESULTS: Mean bond strengths (MPa) of subgroups B, HF, S, and C were: 0, 29.8, 0, 23.3 for lithium disilicate ceramic; 26.4, 22.3, 22.4, 22 for feldspar ceramic; 54.8, 25.3, 42.1, 25.7 for resin nano ceramic. For subgroups B and S of lithium disilicate ceramics, bonding failed during specimen preparation. No significant differences were observed among all CoJet groups. In subgroups B and S, resin nano ceramics showed the highest bond strength. In feldspar groups, subgroup B showed higher bond strength than the other subgroups. CONCLUSION: This study demonstrates that lithium disilicate porcelain blocks required etching for repairing with composite material. Surface treatments did not increase the bond strength in feldspar ceramic groups and reduced the bond strength in resin nano ceramic groups.

The Effect Of Er,Cr:YSGG Laser Conditioning on Dentin Bond Strength and Nanoleakage of Universal Adhesive Systems: An In Vitro Study.

PURPOSE: To investigate the effect of erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser conditioning on dentin bond strength and nanoleakage of different universal and self-etch adhesives. MATERIALS AND METHODS: A total of 84 intact human third molar teeth were cut at the dentin level, and half of them were laser conditioned. The specimens were divided into three groups; two different universal resins and one self-etch adhesive resin were applied and composite resin restorations were created. For the microtensile bond strength (µTBS) test, 20 microspecimens were prepared from the laser and control group of each adhesive (n = 20) and tested with a universal device. For nanoleakage observation, 10 specimens were prepared from each group (n = 10) and stored in silver nitrate solution, and then the amount of nanoleakage was analyzed by field emission scanning electron microscopy (FESEM). Data were analyzed with two-way ANOVA, Tukey's honestly significant difference, and chi-square tests. RESULTS: The mean dentin bond strength of all adhesives in the laser groups was found to be statistically significantly lower than those of the control groups (P < .05). No difference was found between the mean bond strength of the adhesives in the laser and control groups (P > .05). Higher nanoleakage was observed in all adhesives in the laser groups compared to the control groups (P < .05). CONCLUSIONS: Irradiation of the dentin surface with Er,Cr:YSGG could adversely affect the µTBS and nanoleakage, likely by affecting the structure of the hybrid layer.

Chemical degradation of dental CAD/CAM materials.

BACKGROUND: The chemical properties of the oral environment have an appreciable influence on the in vivo degradation of CAD/CAM materials. OBJECTIVE: The aim of the present study was to investigate the effect of organic acids, heptane and ethanol (the food-simulating liquids) on CAD/CAM restorative materials. METHODS: Four CAD/CAM materials were selected: (1) 3M ESPE LAVA Ultimate, (2) VITA Enamic, (3) IPS e.max CAD, (4) VITA Suprinity. Seven different samples were fabricated in 15 × 4 × 1.2 mm dimensions from each material (n = 7, N = 140). The materials were conditioned for 7 days at 37 °C as follows: artificial saliva, 75% ethanol, heptane, 0.02 N citric acid, 0.02 N lactic acid in aqueous solution and were tested to obtain flexural strength, surface micro-hardness and wear characteristics. After conditioning, the flexural strength values were assessed using a universal testing machine (1 mm/min crosshead speed) and the fractured samples were used for determination of Vickers hardness values using a digital micro-hardness tester (100 g/10 s) and determination of wear using a chewing simulator. Two factor analysis of variance with interaction model and Tukey's post hoc test were used for statistical analysis. RESULTS: The highest mechanical property values were found for IPS e.max and VITA Suprinity and the lowest values were found for LAVA Ultimate. Organic acids negatively affected the mechanical properties of e.max CAD and Suprinity. Ethanol and heptane were more effective on LAVA Ultimate and Enamic. There were significant differences among groups (p < 0.05). CONCLUSION: The mechanical properties of CAD/CAM restorative materials are influenced by food-simulating liquids.

The bond strength of highly filled flowable composites placed in two different configuration factors.

OBJECTIVE: The aim of this study was to evaluate the microtensile bond strength (µTBS) of different flowable composite resins placed in different configuration factors (C-factors) into Class I cavities. MATERIALS AND METHODS: Fifty freshly extracted human molars were divided into 10 groups. Five different composite resins; a universal flowable composite (AeliteFlo, BISCO), two highly filled flowable composites (GrandioSO Flow, VOCO; GrandioSO Heavy Flow, VOCO), a bulk-fill flowable composite (smart dentin replacement [SDR], Dentsply), and a conventional paste-like composite (Filtek Supreme XT, 3M ESPE) were placed into Class I cavities (4 mm deep) with 1 mm or 2 mm layers. Restored teeth were sectioned vertically with a slow-speed diamond saw (Isomet 1000, Buehler) and four micro-specimens (1 mm × 1 mm) were obtained from each tooth (n = 20). Specimens were subjected to µTBS test. Data were recorded and statistically analyzed with two-way analysis of variance and Tukey's post-hoc test. Fractured surfaces were examined using a scanning electron microscope. RESULTS: The µTBS in SDR-1 mm were higher than other groups, where Filtek Supreme XT-2 mm and GrandioSO Flow-2 mm were lower. No significant differences were found between C-factors for any composite resin (P > 0.05). CONCLUSION: Bulk-fill flowable composite provided more satisfactory µTBS than others. Different C-factors did not affect mean µTBS of the materials tested.

Temperature changes caused by light curing of fiber-reinforced composite resins.

OBJECTIVE: The aim of the study is to evaluate temperature change in fiber-reinforced composite (FRC) resin photopolymerized with a light-emitting diode (LED) light-curing unit (LCU). MATERIALS AND METHODS: Forty dentine disks (1 mm thick and 8 mm diameter) were prepared from human molars. The FRC specimens (2 mm thickness and 8 mm diameter) consisted of polyethylene fiber (Construct (CT)) products or glass fiber (ever Stick (ES)) and one hybrid composite bonded to the dentin disks and polymerized with an LED LCU. Control groups were prepared using the hybrid composite. Temperature rise in dentine samples under the FRC bonded disks was measured using a K-type thermocouple, and data were recorded. Temperature change data were subjected to analysis of variance (ANOVA) and Duncan's test. RESULTS: The results show that addition of fiber (one or two layers) did not change temperature rise values at any of the exposure times (P > 0.05). The CT fiber/two layer/40 s group exhibited the greatest temperature rise (5.49 ± 0.62) and the ES/one layer/10 s group the lowest rise (1.75 ± 0.32). A significant difference was observed in temperature rise measured during 10 and 20 s exposures (P < 0.05). CONCLUSION: Maximal temperature rise determined in all groups was not critical for pulpal health, although clinicians need to note temperature rises during polymerization.