Effect of immediate dentin sealing on load-bearing capacity under accelerated fatigue of thin occlusal veneers made of CAD-CAM glass-ceramic and resin composite material.

OBJECTIVE: The objective of this study was to assess the influence of immediate dentin sealing (IDS) on the fatigue behavior of laminate occlusal veneers fabricated with CAD/CAM lithium disilicate ceramic and resin composite. METHODS: Forty sound human molars were prepared and randomly divided into 4 groups (n = 10): RC-IDS+ (IDS and resin composite occlusal laminate veneer); RC-IDS- (resin composite occlusal laminate veneer without IDS); LD-IDS+ (IDS and lithium disilicate laminate veneer); LD-IDS- (lithium disilicate occlusal laminate veneer without IDS). The restorations were obtained using a digital workflow. After surface conditioning and bonding, thermocycling and accelerated fatigue tests (20 Hz, 5000 cycles with an initial load of 300 N, step-size of 100 N for 10,000 cycles, up to 1000 N, and then a step-size of 50 N until failure) were conducted. Fatigue data were recorded for both outcomes (crack or fracture) and statistically analyzed. Fractographic and adhesive interface analysis were conducted. RESULTS: The indirect resin composite groups showed better fatigue behavior compared to lithium disilicate. IDS only had a positive effect for the survival of resin composite restorations for the 'fracture' outcome. Evident presence of micro-gaps at the adhesive interface in the LD-IDS- group could be noted. SIGNIFICANCE: Immediate dentin sealing improved fatigue resistance behavior of resin composite occlusal veneers. However, this effect was not observed in lithium disilicate veneers.

Pressable lithium disilicate ceramic versus CAD/CAM resin composite restorations in patients with moderate to severe tooth wear: Clinical observations up to 13 years.

OBJECTIVE: To report the long-term clinical survival and failure rates of single-tooth restorations made of pressable lithium disilicate ceramics (LS2 ) and CAD/CAM resin composite (RC) by two separate clinical observations. MATERIALS AND METHODS: Twenty-one patients (12 female, nine male) were treated with 436 minimally invasive single-tooth restorations made of 274 pressed LS2 (n = 12; posterior: monolithic IPS e.max Press; anterior: IPS e.max Ceram veneered, Ivoclar) or 162 milled from RC (n = 9; monolithic exp. CAD/CAM resin composite, Ivoclar). The mean age of patients was 44.1 ± 9.3 years and the mean observation time was 86.2 ± 13.5 months (7.7 ± 1.1 years), with 8.5 ± 2.7 years for LS2 and 6.7 ± 0.5 years for RC. All restorations were observed for technical/biological failures using the modified criteria of the United States Public Health Service (USPHS). Collected data were analyzed using Kaplan-Meier survival analysis and log-rank test (α < 0.025). RESULTS: The 274 LS2 restorations showed a survival of 100% and a total failure rate of 5.5%. The 162 RC restorations showed a survival of 100% and a total failure rate of 25.3%. RC restorations exhibited more material fractures (p = 0.020) and higher discoloration rates (p < 0.001). CONCLUSIONS: Pressed LS2 single-tooth restorations showed lower long-term failure rates than restorations made of RC. CLINICAL SIGNIFICANCE: Despite the limitations of the clinical observations, single-tooth restorations of both materials can be recommended for permanent use in patients with severe tooth wear.

Effects of Immediate and Delayed Cementations for CAD/CAM Resin Block after Alumina Air Abrasion on Adhesion to Newly Developed Resin Cement.

The purpose of this study was to evaluate the effect of one week of Computer-aided design/Computer-aided manufacturing (CAD/CAM) crown storage on the µTBS between resin cement and CAD/CAM resin composite blocks. The micro-tensile bond strength (µTBS) test groups were divided into 4 conditions. There are two types of CAD/CAM resin composite blocks, namely A block and P block (KATANA Avencia Block and KATANA Avencia P Block, Kuraray Noritake Dental, Tokyo, Japan) and two types of resin cements. Additionally, there are two curing methods (light cure and chemical cure) prior to the µTBS test-Immediate: cementation was performed immediately; Delay: cementation was conducted after one week of storage in air under laboratory conditions. The effect of Immediate and Delayed cementations were evaluated by a µTBS test, surface roughness measurements, light intensity measurements, water sorption measurements and Scanning electron microscope/Energy dispersive X-ray spectrometry (SEM/EDS) analysis. From the results of the µTBS test, we found that Delayed cementation showed significantly lower bond strength than that of Immediate cementation for both resin cements and both curing methods using A block. There was no significant difference between the two types of resin cements or two curing methods. Furthermore, water sorption of A block was significantly higher than that of P block. Within the limitations of this study, alumina air abrasion of CAD/CAM resin composite restorations should be performed immediately before bonding at the chairside to minimize the effect of humidity on bonding.

Data on bond strength of resin cement systems to CAD/CAM resin composite after aging.

CAD/CAM resin composite crowns are inexpensive tooth-colored prostheses that have been widely used. However, bonding between CAD/CAM resin composites and resin cements could be difficult since the resin composite is highly cross-linked. There is limited existing data on the resin cements' bond strength with different monomers to CAD/CAM resin composites. In this study, CAD/CAM resin composite was bonded to an SUS rod with three different resin cements following treatment of the bonding surface using the manufacturer's recommended primer. After storing the specimens in water at 37 °C for 24 h, half of them were tested immediately and half were thermocycled for 10,000 cycles in water for a dwell time of 20 s at 5 and 55 °C. The means of the tensile bond strength and standard deviations were determined for each resin cement and testing condition. The data were compared using two-way ANOVA and Bonferroni's multiple comparison tests at 95% confidence level.

Flexural properties and wear behavior of computer-aided design/computer-aided manufacturing resin blocks.

This study investigates the flexural properties, Knoop hardness number (KHN), and wear behavior of computer-aided design and computer-aided manufacturing (CAD/CAM) resin blocks and compares these values with those of conventional resin composites for direct restoration (RCDs). Four CAD/CAM resin blocks and two RCDs are compared. Ten specimens per material are used to obtain the flexural properties according to ISO 6872 specifications, and five specimens per material are used for KHN measurement. For sliding impact wear testing, twelve specimens are prepared. Confocal laser scanning microscopy (LSM) is used to determine maximum facet depth and volume loss. Polished material surfaces and worn surfaces after wear testing are observed using scanning electron microscopy and LSM. While measured flexural properties and KHN are found to be material-dependent, CAD/CAM resin blocks exhibit higher wear resistance than RCDs. CAD/CAM resin blocks polymerized at high-pressure and high-temperature are found to exhibit wear behaviors far superior to those of RCDs.

Effect of surface treatment of CAD/CAM resin composites on the shear bond strength of self-adhesive resin cement.

This study examined the effects of sandblasting, hydrofluoric acid etching and priming on the shear bond strength of self-adhesive resin cement between seven different CAD/CAM resin composites and a resin composite core material at 24-h after cement mixing. Five surface treatments [control (C), sandblasting (S), priming (P), sandblasting with priming (SP), and 9% HF etching with priming (HFP)] were performed respectively for disc specimens of CAD/CAM blocks. There were no significant differences in bond strength among the C, S, and P, except for one block (p>0.05). SP showed a greater bond strength than S. Weibull moduli were not changed significantly among all treatments for all blocks, whereas the strengths with 5% and 95% failure probability of SP and HFP showed greater values than the others. The bond strengths of HFP were comparable to those of SP. Priming after sandblasting or HF etching could be effective to increase the bond strength of CAD/CAM blocks.

Clinical Evaluation of Three Types of CAD/CAM Inlay/ Onlay Materials After 1-Year Clinical Follow Up.

OBJECTIVE: To evaluate the clinical performance and the marginal adaptation of inlay/ onlay restorations made of lithium of a new lithium disilicate strengthened, lithium alumino-silicate glass-ceramic (LAS) material compared with a conventional lithium-disilicate glass-ceramic (LDS) and new-generation polymer-based CAD/CAM resin composite (CS) materials over one year. MATERIALS AND METHODS: Seventy-five inlay-onlay restorations were placed in 35 patients. The restorations were assigned and randomized to three groups as LDS, LAS, and CS. Clinical evaluations were performed after one week, six months, and one year after the cementation, according to the modified United States Public Health Services (USPHS) criteria. The marginal quality analyses of 21 samples (n=7) were assessed under a scanning electron microscope. The data were analyzed by using Friedman, Wilcoxon Signed Ranks, Chi-square and Paired t-tests (p⟨0.05). RESULTS: No statistically significant difference (p⟩0.05) was found between groups in the modified USPHS, gingival index, and plaque index evaluations, and the total success rate was 100% for three groups after one year. Following SEM evaluations in all groups, continuous margin percentages were decreased, but these results were not statistically significant (p⟩0.05). CONCLUSIONS: Lithium disilicate-strengthened lithium aluminosilicate glass-ceramics can be considered a reliable material for an option for posterior onlay/inlay restorations.

Mechanical properties of computer-aided design/computer-aided manufacturing resin composites assuming perfect silane coupling using in silico homogenization of cryo-electron microscopy images.

PURPOSE: The aim of this study was to determine the mechanical properties of computer-aided design/computer-aided manufacturing (CAD/CAM) resin composites for dental restoration assuming perfect silane coupling by in silico homogenization analysis using a three-dimensional model constructed from cryo-electron microscopy (cryo-EM) images. METHODS: Three-dimensional dataset of a commercial CAD/CAM resin composite block (RCB) was obtained using EM with cryo-stage and focused ion beam at -130°C. The region of inspection was 1.8µm×1.4µm×1.2µm, and 213 slices were obtained from this region. Each slice was processed (noise reduction, threshold setting, and segmentation) using image processing software to design an in silico model. From the processed image slices, a bulk three-dimensional object and stereolithography model were reconstructed using voxel modeling software. To evaluate the elastic modulus and Poisson's ratio of the CAD/CAM RCB, homogenization analysis was performed. RESULTS: The generated voxel model included 37,276,216 voxels, 42,472,040 patches of the surface, 2,123,672 nodes, a volume of 165,748,899, and a surface area of 175,206,723. The mean of the elastic moduli along each axis was 10.71±1.79GPa. The mean of the Poisson's ratios of each plane was 0.23±0.02. CONCLUSIONS: A CAD/CAM resin composite model was successfully reconstructed from cryo-EM images, suggesting that the established image processing method is useful for producing dental restorative materials containing nano-fillers and for predicting homogenized mechanical properties. The homogenized mechanical properties indicated that the mechanical properties of the CAD/CAM RCB assumed perfect silane coupling between the fillers and resin matrix.

Nine prophylactic polishing pastes: impact on discoloration, gloss, and surface properties of a CAD/CAM resin composite.

OBJECTIVES: To investigate discoloration reduction and changes of surface properties of a CAD/CAM resin composite after 14 days´ storage in red wine and polishing with nine different prophylactic polishing pastes (PPPs). MATERIALS AND METHODS: Rectangular discs (N = 172) were fabricated and polished (P4000) using GC Cerasmart (GC Europe) to investigate different polishing protocols with 1-4 related descending PPPs (22 in total): Cleanic/CLE-Kerr, CleanJoy/CLJ-Voco, Clean Polish/Super Polish/SPO-Kerr, Clinpro Prophy Paste/CPP-3M, Détartrine/DET-Septodont, Nupro/NUP-Dentsply Sirona, Prophy Paste CCS/CCS-Directa, Proxyt/PXT-Ivoclar Vivadent, and Zircate/ZIR Prophy Paste-Dentsply Sirona. Surface properties (roughness values (RV)/Ra, Rz, Rv, surface free energy (SFE), surface gloss (G), and discoloration (ΔE)) were analyzed before and after storage and additional polishing. Data were examined using Kolmogorov-Smirnov test, three-way ANOVA followed by Tukey-B post hoc, Mann-Whitney U, and Kruskal-Wallis H tests (α < 0.05). RESULTS: Regarding RV, CLE, followed by CCS, and CPP showed the highest values; the lowest presented SPO and DET (p < 0.001). No impact of PPP was observed on ΔE values (p = 0.160). The lowest SFE presented DET, followed by SPO; highest showed CCS followed by NUP and CPP (p < 0.001). Within G, lowest values were observed for CLE and NUP, followed by CCS, ZIP, and CLJ (p < 0.001); the highest presented SPO (p < 0.001). Polishing showed generally a positive impact on SFE values (p < 0.001-p = 0.007), except ZIP (p = 0.322) and CLE (p = 0.083). G increased and RV decreased after polishing (p < 0.001), except SPO, with no significant change for G (p = 0.786). CONCLUSIONS: Polishing with PPPs improves the surface properties and is generally recommended. The choice of PPP has a minor role in removing discolorations. Multi-step systems should be carried out conscientiously. CLINICAL RELEVANCE: The proper selection of PPP is essential for the clinical outcome of surface properties of prosthetic restorations. Not every polishing paste leads to the same final surface quality.

Fatigue behavior and crack initiation of CAD/CAM resin composite molar crowns.

OBJECTIVE: The aim of this study was to evaluate long-term fatigue behavior using an in vitro step-stress accelerated life test (SSALT), and to determine the crack initiation point using in silico finite element analysis for computer-aided designed and manufactured (CAD/CAM) molar crowns fabricated from three commercial CAD/CAM resin composite blocks: Cerasmart (CS; GC, Tokyo, Japan), Katana Avencia Block (KA; Kuraray Noritake Dental, Niigata, Japan), and Shofu Block HC (HC; Shofu, Kyoto, Japan). METHODS: Fifty-one mandibular first molar crowns luted on a resin core die were embedded in acrylic resin and covered with a polyvinyl chloride tube. Single compressive tests were performed for five crowns. SSALT was conducted for 36 crowns using three profiles and reliabilities at 120,000 cycles, and a Weibull analysis was conducted. The maximum principal strain of each CAD/CAM resin composite crown model was analyzed by three-dimensional finite element analysis. RESULTS: Fracture loads of CS and KA (3784±144N and 3915±313N) were significantly greater than that of HC (2767±227N) (p<0.05). Fracture probabilities at 120,000 cycles were 24.6% (CS), 13.7% (KA), and 14.0% (HC). Maximum principal strain was observed around the mesiolingual cusps of CS and KA and the distobuccal cusp of HC. SIGNIFICANCE: CAD/CAM resin composite molar crowns containing nano-fillers with a higher fraction of resin matrix exhibited higher fracture loads and greater longevity, suggesting that these crowns could be used as an alternative to ceramic crowns in terms of fatigue behavior.