Do resin-based composite CAD/CAM blocks release monomers?

OBJECTIVE: The present study aimed to identify and quantify the elution of monomers of five different resin-based CAD/CAM blocks (RCBs) using HPLC. METHODS: Five different RCBs were used in the study: GC Cerasmart (CS), Voco Grandio blocs (GR), 3M Lava Ultimate (LU), Shofu Block (SB), and Vita Enamic (VE). Fifteen samples from each material were prepared using a low-speed precision diamond saw (ISOMET Buehler, Lake Bluff, IL, USA) at 5 × 5 × 4 mm size. After the preparation of samples, an extraction solution was mixed with %75/%25 ethanol/water. The samples were stored in the amber-colored bottles during three different immersed periods as 1 h, 24 h, and 90 days (n = 5). After immersion, 0.5 ml solutions were taken from each bottle and analyzed using HPLC. RESULTS: A total of 16.7 µg/ml of monomers from SB, 13.4 µg/ml of monomers from GR, 13.2 µg/ml of monomers from CS, and 6.7 µg/ml of monomers from LU were found after 3-m immersion. TEGDMA after 3-m of immersion was only released from the SB group, and also BisEMA was released from the CS group. Among the specimens immersed for 1 h, UDMA was released the least from the LU group and the most from the GR group (p < 0.05). Correspondingly, 24 h and 3 m after immersion, the highest release of monomers was found in the GR (p < 0.05). CONCLUSIONS: When the monomer release from RCBs was evaluated, it was shown that these materials released methacrylate-based monomers except VE, especially if they were kept in a solvent solution for a long time such as 3 m. CLINICAL SIGNIFICANCE: The novel resin-based CAD/CAM blocks might monomer release, which may cause cytotoxic effects. But, the detected amount of monomer release is below the estimated daily limit.

Discoloration and translucency changes of CAD-CAM materials after exposure to beverages.

STATEMENT OF PROBLEM: Color and translucency changes of recently introduced composite resin blocks after long-term exposure to various staining agents have not been fully investigated. PURPOSE: The purpose of this in vitro study was to evaluate the color stainability and translucency changes of computer-aided design and computer-aided manufacturing (CAD-CAM) materials immersed in beverages with staining potential. MATERIAL AND METHODS: Three types of CAD-CAM blocks were used: 3M Lava Ultimate (LU), GC Cerasmart (CS), and VITA Enamic (VE). Forty-five rectangular specimens (1.5-mm thickness) of each product were prepared. The specimens were divided into 3 subgroups (n=15 in each) according to the immersion beverage. The specimens were then immersed in distilled water, red wine, and coffee for 30 days. Color parameters (ΔE00), the translucency parameter, and the contrast ratio were determined after 24 hours and 1 month. The Kruskal-Wallis and Mann-Whitney U tests and the Wilcoxon, Freidman, and repeated measurement ANOVA tests were used for statistical analysis (α=.05). RESULTS: None of the materials showed clinically perceptible color changes except CS specimens immersed in coffee for 24 hours. The materials immersed in red wine and coffee for 1 month showed greater discoloration than those immersed in water (P<.05). The LU immersed in red wine showed the highest translucency changes, and VE was more resistant to translucency changes, as compared with the other materials tested. The contrast ratio values of the LU material were higher than those of the CS and VE materials in all the beverages. CONCLUSIONS: The red wine and coffee caused significant changes in the color and translucency of these novel CAD-CAM materials after a long immersion period.

Effect of Different Surface Treatments on Bond Strength of Resin Cement to a CAD/CAM Restorative Material.

PURPOSE: To investigate the effects of various surface treatment methods on the shear bond strength of self-adhesive resin cement to a novel CAD/CAM hybrid ceramic material. MATERIALS AND METHODS: A novel hybrid ceramic restorative material (Vita Enamic) was used in this study. Sixty resin block specimens were prepared and separated into six groups for each surface treatment method (n = 10); group 1: control group, no treatment applied; group 2: sandblasted by 30 µm silicate-coated alumina particles (CoJet Sandblasting); group 3: 50 µm Al2 O3 sandblasting; group 4: 10% hydrofluoric acid; group 5: no surface treatment + universal adhesive (3M Single Bond Universal); group 6: 200 mJ, 10 Hz 2W Er,Cr:YSGG laser treatment. For each specimen, surface roughness measurements in noncontact mode were taken after the surface treatments using a portable surface texture-measuring machine. A self-adhesive resin cement (3M U200) was applied on every surface treated with the help of a cylindrical mold (2 × 4 mm) and was filled gradually. Shear bond strength was measured using a universal test machine, and one-way ANOVA and a Duncan test (p = 0.05) were used to analyze the data. RESULTS: Mean values of the shear bond strength varied between 7.75 and 10.73 MPa. Bond strength values were enhanced by all surface treatment methods compared to the control group. The difference between group 5 and the control group (p < 0.05) was statistically significant, whereas there were no considerable differences between other treatment methods. CONCLUSION: Surface treatments of hybrid ceramic resin blocks could enhance the bond strength to resin cement; however, using Single Bond Universal without surface treatment showed a higher bond strength value.

Color of bulk-fill composite resin restorative materials.

OBJECTIVE: To evaluate the color stability of novel bulk-fill composite resins. MATERIALS AND METHODS: Color measurements of a nanohybrid composite resin (Z550) and 3 bulk-fill composite resins (BLK, AFX, XTF; n = 45) were performed before polymerization. After polymerization, color measurements were repeated and specimens were immersed in distilled water or red wine, or coffee. Color change [CIEDE2000 (ΔE00 )] was calculated after 24 h, 1 and 3 weeks. Data were analyzed with Kruskal-Wallis, Mann-Whitney U and Wilcoxon tests (α = 0.05). RESULTS: Color changes observed after polymerization were significant for all groups. Color changes observed in distilled water for Z550 and AFX were significant. Color changes after stored in red wine and coffee were significant for all groups. Bulk-fill composite resin color change increased over time for all groups in red wine and coffee (P < .05). CONCLUSION: Polymerization significantly changed the color of nanohybrid composite resin and bulk-fill composite resins. AFX had the highest color change in distilled water. The color of tested bulk-fill composite resins significantly changed after immersion in beverages and over time. Color change observed with the nanohybrid composite resin after 1 week was stable. CLINICAL SIGNIFICANCE: Clinicians should keep in mind that tested composite resins may change color when exposed to water and significantly change color immediately after they are polymerized. In addition, the color change continues over time should the patient is a coffee and/or red wine consumer.

The effect of thickness and translucency of polymer-infiltrated ceramic-network material on degree of conversion of resin cements.

PURPOSE: The aim of the present study was to determine the degree of conversion of light- and dual-cured resin cements used in the cementation of all-ceramic restorations under different thicknesses of translucent (T) and high-translucent (HT) polymer-infiltrated ceramic-network (PICN) material. MATERIALS AND METHODS: T and HT PICN blocks were prepared at 0.5, 1.0, 1.5, and 2.0 mm thicknesses (n=80). Resin cement samples were prepared with a diameter of 6 mm and a thickness of 100 µm. Light-cured resin cement was polymerized for 30 seconds, and dual-cure resin cement was polymerized for 20 seconds (n=180). Fourier transform infrared spectroscopy (FTIR) was used for degree of conversion measurements. The obtained data were analyzed with ANOVA and Tukey HSD, and independent t-test. RESULTS: As a result of FTIR analysis, the degree of conversion of the light-cured resin cement prepared under 1.5- and 2.0-mm-thick T and HT ceramics was found to be lower than that of the control group. Regarding the degree of conversion of the dual-cured resin cement group, there was no significant difference from the control group. CONCLUSION: Within the limitation of present study, it can be concluded that using of dual cure resin cement can be suggested for cementation of PICN material, especially for thicknesses of 1.5 mm and above.

Assessment the Bond Strength of Ceramic Brackets to CAD/CAM Nanoceramic Composite and Interpenetrating Network Composite after Different Surface Treatments.

Adult orthodontics may confront problems related to the bonding performance of orthodontic brackets to new generation restorative materials used for crown or laminate restorations. The aim of the present study was to investigate the shear bond strength of ceramic brackets to two new generation CAD/CAM interpenetrating network composite and nanoceramic composite after different surface treatments. Er,Cr:YSGG Laser, hydrofluoric acid (9%), sandblasting (50 µm Al2O3), and silane were applied to the surfaces of 120 CAD/CAM specimens with 2 mm thickness and then ceramic brackets were bonded to the treated surfaces of the specimens. Bond strength was evaluated using the shear bond strength test. According to the results, CAD/CAM block types and surface treatment methods have significant effects on shear bond strength. The lowest bond strength values were found in the specimens treated with silane (3.35 ± 2.09 MPa) and highest values were found in the specimens treated with sandblast (8.92 ± 2.77 MPa). Sandblasting and hydrofluoric acid surface treatment led to the most durable bonds for the two types of CAD/CAM blocks in the present study. In conclusion, different surface treatments affect the shear bond strength of ceramic brackets to CAD/CAM interpenetrating network composite and nanoceramic composite. Among the evaluated treatments, sandblasting and hydrofluoric acid application resulted in sufficient bonding strength to ceramic brackets for both of the CAD/CAM materials.

Assessing staining resistance of a CAD/CAM interpenetrating network composite material.

BACKGROUND: Color change of dental materials over time because of staining agents has important effects on the long-term prognosis of dental esthetic treatments. In the present study, staining resistance of an interpenetrating network composite material with different translucency levels (translucent and high translucent) and various surface procedures for finishing were investigated. METHODS: Same shade CAD/CAM interpenetrating network composite specimens having two different translucency levels were prepared using by a water cooling cutting saw. Specimens were grouped and different finishing procedures were performed. Then, specimens were kept in distilled water, red wine and coffee for different periods. Color was evaluated before and after exposure to staining liquids using a clinical spectrophotometer. RESULTS: In the 7 days Glaze group (ΔE00 > 2.2), color difference was only perceivable in the specimens kept in red wine. In the 28 days red wine high translucent groups, only the high translucent Clinical group showed a clinically acceptable (ΔE00 < 2.2) color change. In the translucent groups kept in red wine, only the translucent Glaze group showed a clinically perceivable color change (ΔE00 > 2.2). In the 28 day measurements, all the translucent groups showed a clinically perceivable color change (ΔE00 > 2.2). Of the translucent groups kept in coffee for 28 days, it was observed that only the translucent Clinical group demonstrated a clinically non-perceivable color change (ΔE00 < 2.2). CONCLUSIONS: All the translucent groups kept in red wine showed a clinically perceivable color change after 28 days. Only the high translucent Clinical Kit group showed a clinically acceptable color change. Among high translucent and translucent specimens kept in coffee only the translucent Clinical group showed a clinically acceptable color change after 28 days.

Effects of staining liquids and finishing methods on translucency of a hybrid ceramic material having two different translucency levels.

PURPOSE: Beverages may affect the translucency of esthetic dental restorative materials. The aim of the present study was to investigate the effects of coffee and red wine on the translucency of a PICN material with two translucency levels, and finished with different methods. MATERIALS AND METHODS: 2M2 high translucent and translucent VITA Enamic hybrid ceramic blocks were investigated. Rectangular specimens with the dimensions of 12 mm × 14 mm × 2 mm were prepared. The specimens were finished and polished with different methods as suggested by the manufacturer. The translucency parameters of the specimens were evaluated before and after 24 hours, 7 days, and 28 days immersion in distilled water, coffee and red wine. Translucency parameters were measured using a portable spectrophotometer. RESULTS: At the end of 28 days, there was no statistically significant difference between the groups of specimens kept in coffee (P>.05). In the red wine groups, there was a statistically significant difference between the control group and all other groups (P<.05) at the end of 28 days. CONCLUSION: The translucency of hybrid ceramic for a restoration may not be important regarding the effects of coffee on translucency change because the specimens with different translucencies and finishing methods that were immersed to coffee had similar translucency parameters at the end of 28 days. The translucency of hybrid ceramic may be important in the case of red wine, however, since the results showed that highly translucent specimens exposed to red wine demonstrated better translucency parameters than specimens made from translucent blocks at the end of 28 days.

Effects of different surface finishing procedures on the change in surface roughness and color of a polymer infiltrated ceramic network material.

PURPOSE: Polymer infiltrated ceramic network (PICN) materials, also called hybrid ceramics, are new materials in dental market. The manufacturer of the PICN material VITA Enamic suggests 3 different finishing procedures for this new material. In the present study, surface roughness and color differences caused from different finishing procedures of VITA Enamic were investigated. MATERIALS AND METHODS: 120 specimens were prepared in dimensions 2 × 10 × 12 mm from VITA Enamic hybrid ceramic blocks with 'high translucency' and 'translucency 2M2' shades. The specimens were divided into 8 groups. For each group, different finishing procedures suggested by the manufacturer were performed. Surface roughness values were determined by a tactile portable profilometer. Color changes were evaluated using a clinical spectrophotometer. The data were analyzed using one-way ANOVA and Tukey's post-hoc comparison. The significance level was set at α=0.05. RESULTS: The roughest surfaces were observed in Glaze Groups. Their surface roughness values were similar to that of the control group. Clinical Kit and Technical Kit groups did not show a statistically significant difference regarding surface roughness (P>.05). The largest color difference regarding ΔE00 was observed in Clinical Kit finishing groups. There were also statistically significant color changes between the groups (P<.05). However, all the groups showed clinically acceptable color change (ΔE00<2.25) except Clinical Kit Groups (ΔE00>2.25). CONCLUSION: Within the limitations of the present study, it may be suggested that finishing the VITA Enamic restorations by Technical Kit instead of Glaze and Clinical Kit gives better clinical performance in regard to surface roughness and shade matching.

Repair bond strength of composite resin to sandblasted and laser irradiated Y-TZP ceramic surfaces.

This study investigated the effects of different surface treatments on the repair bond strength of yttrium-stabilized tetragonal zirconia polycrystalline ceramic (Y-TZP) zirconia to a composite resin. Sixty Y-TZP zirconia specimens were prepared and randomly divided into six groups (n = 10) as follows: Group 1, surface grinding with Cimara grinding bur (control); Group 2, sandblasted with 30 µm silica-coated alumina particles; Group 3, Nd:YAG laser irradiation; Group 4, Er,Cr:YSGG laser irradiation; Group 5, sandblasted + Nd:YAG laser irradiation; and Group 6, sandblasted + Er,Cr:YSGG laser irradiation. After surface treatments, the Cimara(®) System was selected for the repair method and applied to all specimens. A composite resin was built-up on each zirconia surface using a cylindrical mold (5 × 3 mm) and incrementally filled. The repair bond strength was measured with a universal test machine. Data were analyzed using a one-way ANOVA and a Tukey HSD test (p = 0.05). Surface topography after treatments were evaluated by a scanning electron microscope (SEM). Shear bond strength mean values ranged from 15.896 to 18.875 MPa. There was a statistically significant difference between group 3 and the control group (p < 0.05). Also, a significant increase in bond strength values was noted in group 6 (p < 0.05). All surface treatment methods enhanced the repair bond strength of the composite to zirconia; however, there were no significant differences between treatment methods. The results revealed that Nd:YAG laser irradiation along with the combination of sandblasting and Er,Cr:YSGG laser irradiation provided a significant increase in bond strength between the zirconia and composite resin.