Wear, strength, modulus and hardness of CAD/CAM restorative materials

Indirect composites have been undergoing an impressive evolution over the last few years. Specifically, recent developments in computer-aided design-computer-aided manufacturing (CAD-CAM) blocks have been associated with new polymerization modes, innovative microstructures, and different compositions. All these recent breakthroughs have introduced important gaps among the properties of the different materials. This critical state-of-the-art review analyzes the strengths and weaknesses of the different varieties of CAD-CAM composite materials, especially as compared with direct and artisanal indirect composites. Indeed, new polymerization modes used for CAD-CAM blocks-especially high temperature (HT) and, most of all, high temperature-high pressure (HT-HP)-are shown to significantly increase the degree of conversion in comparison with light-cured composites. Industrial processes also allow for the augmentation of the filler content and for the realization of more homogeneous structures with fewer flaws. In addition, due to their increased degree of conversion and their different monomer composition, some CAD-CAM blocks are more advantageous in terms of toxicity and monomer release. Finally, materials with a polymer-infiltrated ceramic network (PICN) microstructure exhibit higher flexural strength and a more favorable elasticity modulus than materials with a dispersed filler microstructure. Consequently, some high-performance composite CAD-CAM blocks-particularly experimental PICNs-can now rival glass-ceramics, such as lithium-disilicate glass-ceramics, for use as bonded partial restorations and crowns on natural teeth and implants. Being able to be manufactured in very low thicknesses, they offer the possibility of developing innovative minimally invasive treatment strategies, such as "no prep" treatment of worn dentition. Current issues are related to the study of bonding and wear properties of the different varieties of CAD-CAM composites. There is also a crucial need to conduct clinical studies. Last, manufacturers should provide more complete information regarding their product polymerization process, microstructure, and composition, which significantly influence CAD-CAM material properties.

From Artisanal to CAD-CAM Blocks: State of the Art of Indirect Composites.

Statement of problem Recent polymer-based computer-assisted design and computer-assisted manufacturing (CAD-CAM) materials have been commercialized for inlay restorations, a polymer-infiltrated ceramic-network (PICN) and composite resin nanoceramics Little independent evidence regarding their mechanical properties exists Internal adaptation is an important factor for the clinical success and longevity of a restoration, and data concerning this parameter for inlays made with these blocks are scarce Purpose The purpose of this in vitro study was to evaluate and compare the mechanical properties (flexural strength, flexural modulus, Vickers hardness, fracture toughness) and the internal adaptation of these recent polymer-based blocks with a lithium disilicate glass-ceramic block Material and methods The materials tested in this study were a PICN material (Vita Enamic), 2 composite resin nanoceramics (Lava Ultimate; 3M ESPE and Cerasmart; GCDental Products), and a lithium disilicate glass-ceramic (IPS emax CAD) Mechanical properties were evaluated according to ISO norm DIS 6872:2013 Bar-shaped specimens (18×3×3 mm) were prepared and submitted to a 3-point bend test using a universal testing machine at a cross-head speed of 05 mm/min In addition, identical cavities were prepared in 60 human mandibular extracted molars (n=15) and optically scanned to receive mesioocclusodistal inlays milled with the 4 materials tested in a CEREC Inlab milling machine The replica technique and a stereomicroscope (×20) were used to measure the internal fit of the inlays at 9 preselected locations All data were statistically analyzed using 1-way ANOVA and the post hoc Tukey multiple comparison or Games-Howell test (α=05) Results The mean flexural strength of the tested blocks ranged from 1487 ±95 MPa (Vita Enamic) to 2165 ±283 MPa (Cerasmart) The mean flexural modulus ranged from 233 ±64 GPa (Vita Enamic) to 528 ±105 GPa (IPS emax CAD) The mean Vickers hardness ranged from 066 ±002 GPa (Cerasmart) to 598 ±069 GPa (IPS emax CAD) The mean fracture toughness ranged from 12 ±017 MPam 1/2 (Cerasmart) to 18 ±029 MPam 1/2 (IPS emax CAD) The values for internal discrepancy ranged from 119 ±55 μm to 234 ±51 μm The mean internal discrepancy was significantly higher for Lava Ultimate ( P P 2 =0941; P Conclusions The mechanical properties of the CAD-CAM block materials tested were within the acceptable range for fabrication of single restorations according to the ISO standard for ceramics (ISO 6872:2008) IPS emax CAD and Cerasmart were observed to have superior flexural strength and better internal fit

Mechanical properties and internal fit of 4 CAD-CAM block materials

PURPOSE To evaluate the influence of different surface treatments of six novel CAD/CAM materials on the bonding effectiveness of two luting composites. MATERIALS AND METHODS Six different CAD/CAM materials were tested: four ceramics - Vita Mark II; IPS Empress CAD and IPS e.max CAD; Celtra Duo - one hybrid ceramic, Vita Enamic, and one composite CAD/CAM block, Lava Ultimate. A total of 60 blocks (10 per material) received various mechanical surface treatments: 1. 600-grit SiC paper; 2. sandblasting with 30-μm Al2O3; 3. tribochemical silica coating (CoJet). Subsequent chemical surface treatments involved either no further treatment (control), HF acid etching (HF), silanization (S, or HF acid etching followed by silanization (HF+S). Two specimens with the same surface treatment were bonded together using two dual-curing luting composites: Clearfil Esthetic Cement (self-etching) or Panavia SA Cement (self-adhesive). After 1 week of water storage, the microtensile bond strength of the sectioned microspecimens was measured and the failure mode was evaluated. RESULTS The bonding performance of the six CAD/CAM materials was significantly influenced by surface treatment (linear mixed models, p < 0.05). The luting cement had a significant influence on bond strength for Celtra Duo and Lava Ultimate (linear mixed models, p < 0.05). Mechanical surface treatment significantly influenced the bond strength for Celtra Duo (p = 0.0117), IPS e.max CAD (p = 0.0115), and Lava Ultimate (p < 0.0001). Different chemical surface treatments resulted in the highest bond strengths for the six CAD/CAM materials: Vita Mark II and IPS Empress CAD: S, HF+S; Celtra Duo: HF, HF+S; IPS e.max CAD: HF+S; Vita Enamic: HF+S, S. For Lava Ultimate, the highest bond strengths were obtained with HF, S, HF+S. Failure analysis showed a relation between bond strength and failure type: more mixed failures were observed with higher bond strengths. Mainly adhesive failures were noticed if no further surface treatment was done. The percentage of adhesive failures was higher for CAD/CAM materials with higher flexural strength (Celtra Duo, IPS e.max CAD, and Lava Ultimate). CONCLUSION The bond strength of luting composites to novel CAD/CAM materials is influenced by surface treatment. For each luting composite, an adhesive cementation protocol can be specified in order to obtain the highest bond to the individual CAD/CAM materials.

Bonding Effectiveness of Luting Composites to Different CAD/CAM Materials.

https://www.dental.theclinics.com/article/S0011-8532(18)30091-0/pdf

The Current State of Chairside Digital Dentistry and Materials.

Statement of problem The recent development of polymer-based computer-aided design and computer-aided manufactured (CAD/CAM) milling blocks and the limited availability of independent studies on these materials make it pertinent to evaluate their properties and identify potential strengths and limitations. Purpose The purpose of this in vitro study was to determine and compare mechanical properties (flexural strength, flexural modulus, modulus of resilience) and compare the margin edge quality of recently introduced polymer-based CAD/CAM materials with some of their commercially available composite resin and ceramic counterparts. Material and methods The materials studied were Lava Ultimate Restorative (LVU; 3M ESPE), Enamic (ENA; Vita Zahnfabrik), Cerasmart (CES; GC Dental Products), IPS Empress CAD (EMP; Ivoclar Vivadent AG), Vitablocs Mark II (VM2; Vita Zahnfabrik), and Paradigm MZ100 Block (MZ1; 3M ESPE). Polished 4×1×13.5 mm bars (n=25) were prepared from standard-sized milling blocks of each tested material. The bars were subjected to a 3-point flexural test on a 10-mm span with a crosshead speed of 0.5 mm/min. In addition, 42 conventional monolithic crowns (7 per material) were milled. Margin edge quality was observed by means of macrophotography and optical microscopy, providing a qualitative visual assessment and a measurement of existing roughness. The results were analyzed by ANOVA followed by the Tukey HSD test (α=.05). Results The mean flexural strength of the tested materials ranged from 105 ±9 MPa (VM2) to 219 ±20 MPa (CES). The mean flexural modulus ranged from 8 ±0.25 GPa (CES) to 32 ±1.9 GPa (EMP). The mean modulus of resilience ranged from 0.21 ±0.02 MPa (VM2) to 3.07 ±0.45 MPa (CES). The qualitative assessment of margin edge roughness revealed visible differences among the tested materials, with mean roughness measurements ranging from 60 ±16 μm (CES) to 190 ±15 μm (EMP). The material factor had a significant effect on the mean flexural strength ( P P P P Conclusions The new-generation polymer-based materials tested in this study exhibited significantly higher flexural strength and modulus of resilience, along with lower flexural modulus values compared with the tested ceramic or hybrid materials. Crowns milled from the new resin-based blocks seemed to exhibit visibly smoother margins compared with the ceramic materials studied.

Mechanical properties of resin-ceramic CAD/CAM restorative materials

Statement of problem The development of polymer-based computer-aided design and computer-aided manufacturing (CAD-CAM) milling bocks and the limited availability of independent studies on these materials make it pertinent to evaluate changes in their mechanical properties after simulated aging to identify strengths and limitations. Purpose The purpose of this in vitro study was to measure the effect of thermocycling on the flexural properties of ceramic, resin, and resin-ceramic CAD-CAM materials. Material and methods Studied materials included Lava Ultimate Restorative (LVU; 3M ESPE), Enamic (ENA; VITA Zahnfabrik), Vitablocs Mark II (VM2; VITA Zahnfabrik), and Paradigm MZ100 (MZ1; 3M ESPE). Polished 4×1.2×14 mm bars (n=45 per material) were prepared from standard-size milling blocks. The 2 distilled water baths of the thermocycling apparatus were set to 5°C and 55°C, with a specimen immersion time of 15 seconds and transfer time of 4 seconds. Fifteen specimens from each material group were subjected to a 3-point flexural test at 3 different thermocycling intervals: 0 (control), 5000, and 10 000 cycles. The flexural test was performed over a 12-mm span with a crosshead speed of 0.5 mm/min. Data were subjected to multiple analyses of variance and the Tukey HSD post hoc tests (α=.05). Results Mean flexural strength values for 0, 5000, and 10 000 cycles were 133, 130, and 128 MPa for VM2; 175, 139, and 134 MPa for LVU; 154, 144, and 138 MPa for MZ1; and 149, 136, and 132 MPa for ENA. Mean flexural modulus values were 51, 52, and 54 GPa for VM2; 14, 13, and 13 GPa for LVU; 16, 15, and 15 GPa for MZ1; and 31, 30, and 31 GPa for ENA. Mean modulus of resilience values were 0.17, 0.16, and 0.15 MPa for VM2; 10.1, 0.76, and 0.72 MPa for LVU; 0.77, 0.69, and 0.62 MPa for MZ1; and 0.42, 0.31, and 0.28 MPa for ENA. A significant difference was found among the materials in the mean change of flexural strength ( P P P =.113). Conclusions The mean flexural strength of resin-ceramics is significantly different from that of the feldspathic ceramic control at 0 and 5000 cycles, but not at 10 000 cycles. The mean modulus of resilience of resin-ceramics varies significantly after thermal cycling, unlike the feldspathic ceramic control. Conversely, the mean flexural modulus of tested materials did not vary significantly after thermocycling.

Abdallah Awada

Papers

Mechanical properties of resin-ceramic CAD/CAM restorative materials

Mechanical properties of resin-ceramic CAD-CAM materials after accelerated aging.