The Effect of Surface Treatments on the Mechanical and Optical Behaviors of CAD/CAM Restorative Materials

Effect of hydrofluoric acid and self-etch ceramic primers on the flexural strength and fatigue resistance of glass ceramics: A systematic review and meta-analysis of in vitro studies

This systematic review evaluated the effect of different hydrofluoric acid (HF) etching regimens and a self-etch ceramic primer (SECP) on the flexural strength (FS) and fatigue failure load (FFL) of glass-ceramic materials.The identification of relevant studies was conducted by two authors in five databases: PubMED, Scopus, Web Of Science, LILACS and Virtual Health Library (BVS) until July 2022 with no year limit. The analysis was conducted in RevMan 5.4.1 Software (Cochrane Collaboration) using Random effect model at 5 %. The risk of bias of the included studies were assessed. From the 5349 articles identified, 34 were included for quantitative analysis. Meta-analysis showed that for predominantly glassy ceramics, etching with HF 5 % had no significant impact on FS, however, HF acid etching with concentrations greater than 5 % negatively impacted FS. For lithium disilicate glass-ceramics (LDGC) HF acid etching, negatively influenced FS, while increasing the FFL. HF etching negatively affected FS of hybrid ceramics. The self-etch ceramic primer and HF acid etching showed a similar impact on FFL and FS. This meta-analysis indicates that the impact of SECP and HF acid etching on the mechanical behavior of glass ceramics is material-dependent.

Evaluation of the optical and surface properties of monolithic CAD-CAM ceramics after simulated tooth-brushing

STATEMENT OF PROBLEM

Monolithic computer-aided design and computer-aided manufacturing (CAD-CAM) ceramics have various microstructures, but studies on their optical and surface properties after tooth-brushing are lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the changes in the color, gloss, surface roughness, and surface topography of different monolithic CAD-CAM ceramics after simulated tooth-brushing and compare the tested parameters of the different ceramics.

MATERIAL AND METHODS

Ninety specimens were prepared with a 1.5-mm thickness from 9 different materials: monolithic zirconia (ZR), lithium disilicate ceramics (precrystallized and crystallized), zirconia reinforced lithium silicate ceramics (precrystallized and crystallized), interpenetrating network ceramic, leucite reinforced ceramic, feldspathic ceramic, and interpenetrating network nanoceramics (n=10). After mechanical polishing, the color parameters, gloss, and surface roughness values of each specimen were measured. Then, the specimens were subjected to 50 000 tooth-brushing cycles. After the brushing simulation, the color change (ΔE00) values were calculated, and the gloss and surface roughness values of the specimens were measured. Data were statistically analyzed with 2-way repeated measures of ANOVA and Bonferroni multiple comparison tests (α=.05).

RESULTS

The brushing simulation and ceramic type affected the gloss and surface roughness values of the tested ceramics (P<.001). The surface roughness values of the ceramics increased after 50 000 cycles of simulated brushing. The surface gloss of the ZR group significantly increased after 50 000 cycles of simulated brushing (P<.001). Only the ceramic type affected the color change values (P<.001). The color change value (ΔE00) of ZR was the highest among the tested materials, exceeding the perceptibility threshold after 50 000 cycles, while the ΔE00 of the other materials was lower.

CONCLUSIONS

Simulated tooth-brushing affected the surface gloss and surface roughness of the tested materials. The ceramic type affected the surface gloss, surface roughness, and color change values. Except for the monolithic zirconia, the color change values were below the perceptibility threshold (0.8) in the experimental groups.

A novel zwitterion incorporated Nano-crystalline ceramic and polymer for bacterial resistant dental CAD-CAM block

OBJECTIVES

To create bacteria-resistant dental CAD-CAM blocks with a biofilm-resistant effect by incorporating Nano-crystalline ceramic and polymer (NCP) with 2-methacryloyloxyethyl phosphorylcholine (MPC) and sulfobetaine methacrylate (SBMA) and at an equimolar ratio, referred to as MS.

METHODS

Experimental groups comprised NCP blocks containing zwitterions at 0.15wt% (MS015) and 0.45wt% (MS045). NCP blocks without MS served as control (CTRL). Flexural strength, surface hardness, water sorption and solubility, photometric properties, and cytotoxicity were assessed for all samples. Additionally, the resistance to single and multi-species bacterial adhesion was investigated.

RESULTS

MS045 showed significant reduction in flexural strength (P < 0.01) compared to both CTRL and MS015. Both MS015 and MS045 showed significantly increased water sorption and significant reduction in water solubility compared to CTRL. Light transmission remained consistent across all MS content levels, but the irradiance value decreased by 12 % in the MS045 group compared to the MS015 group. Notably, compared to the CTRL group, the MS015 group exhibited enhanced resistance to adhesion by Porphyromonas gingivalis and a multi-species salivary biofilm, with biofilm thickness and biomass reduced by 45 % and 56 %, respectively.

CONCLUSIONS

NCP containing 0.15 % MS can effectively reduce adhesion of multiple species of bacteria while maintaining physical and mechanical properties.

CLINICAL SIGNIFICANCE

NCP integrating zwitterions is clinically advantageous in resisting bacterial adhesion at internal and external margins of milled indirect restoration.

Does the internal surface treatment technique for enhanced bonding affect the color, transparency, and surface roughness of ultra-transparent zirconia?

PURPOSE

To investigate the effects of different surface treatments and thicknesses on the color, transparency, and surface roughness of ultra-transparent zirconia.

METHODS

A total of 120 Katana ultra-translucent multi-layered zirconia specimens were divided into 12 groups according to the thickness (0.3, 0.5, and 0.7 mm) and surface treatment (control, airborne particle abrasion [APA], lithium disilicate coating, and glaze on). Color difference (ΔE00) and relative translucency parameter (RTP00) were calculated using a digital spectrophotometer. The surface roughness (Ra, Rq, Sa, and Sq) was measured using a non-contact profile scanner. The surface morphologies and microstructures of the samples were observed using a tungsten filament scanning electron microscope. Statistical analyses were performed by one-way and two-way analysis of variance (ANOVA) followed by post hoc multiple comparisons and Pearson's correlation (α = 0.05).

RESULTS

The results showed that the surface treatment, ceramic thickness, and their interactions had significant effects on ΔE00 and RTP00 (p < 0.001). The surface treatment significantly altered the micromorphology and increased the surface roughness of the ceramic samples. APA exhibited the lowest transparency, largest color difference, and highest surface roughness. Zirconia with 0.3 mm and 0.7 mm thicknesses showed strong negative correlations between Sa and RTP00.

CONCLUSIONS

The three internal surface treatments significantly altered the surface roughness, color difference, and transparency of ultra-transparent zirconia. As the thickness increased, the influence of the inner surface treatment on the color difference and transparency of zirconia decreased.

CLINICAL IMPLICATIONS

For new zirconia internal surface treatment technologies, in addition to considering the enhancement effect on the bonding properties, the potential effects on the color and translucency of high-transparency zirconia should also be considered. Appropriately increasing the thickness of zirconia restorations helps minimize the effect of surface treatment on the optical properties.

Translucency and colour masking ability of hybrid CAD/CAM materials with different thicknesses: in vitro study

OBJECTIVE

To evaluate effect of material thickness and translucency of two different hybrid CAD/CAM materials on their masking ability.

MATERIALS AND METHODS

40 rectangular-shaped specimens (12 × 14 mm) were obtained from Vita Enamic and Grandio blocks at 0.5 and 1 mm-thick (n = 10/group). Colour parameters of specimens were measured on PMMA tooth-coloured replica backgrounds (A2, C4) and black, white backings using dental spectrophotometer. Translucency parameter (TP) and masking ability (∆E00) values of tested materials with 0.5, and 1 mm thicknesses were calculated. Quantitative variables were compared between groups using student t-test.

RESULTS

TP and ∆E00 significantly decreased as thickness of tested materials increased. Grandio showed significantly higher TP values. There were significantly lower ΔE00 values for Vita Enamic compared to Grandio at 1 mm thickness and inversely insignificant at 0.5 mm. The 0.5 mm-thick ∆E00 of tested materials was above clinical acceptability threshold, whereas, 1 mm-thick did not exceed showing better masking properties.

CONCLUSIONS

Thickness is more effective for colour masking than translucency. In thin thickness, the masking ability is less effective, irrespective of tested materials. Translucency of tested materials was affected by their composition. Both hybrid CAD/CAM materials are promising alternatives for masking dark discolouration at 1 mm-thick.

Effect of Er,Cr: YSGG laser debonding treatment on the optical properties and surface roughness of ceramic laminate veneers: An in vitro study

PURPOSE

The objective of this study was to evaluate the effect of (Er,Cr: YSGG) laser debonding treatment on optical properties and surface roughness of veneers made of different ceramic materials.

MATERIALS AND METHODS

Thirty bovine incisors were prepared to receive laminate veneers and divided into three groups (n = 10) according to ceramic material where group (E): IPS e.max CAD, group (S): Vita Suprinity, and group (C): Celtra Duo. Blocks were sectioned into 0.5 mm thickness plates and cemented on the labial surface of incisors using resin cement. The Er,Cr: YSGG laser was applied to each specimen at 4.5 W and 25 Hz for group E and at 6 W and 25 Hz for groups S and C. Color change (△E00), translucency parameter (TP) and surface roughness in µm (Ra) values were measured and calculated before and after laser treatment. Data were analyzed using two-way mixed model ANOVA at a significance level of p < 0.05.

RESULTS

The highest mean △E00 value was recorded in group E (1.35 ± 0.09) followed by group S (1.08 ± 0.16) and then group C (0.93 ± 0.10) with a significant difference between them (p < 0.001). All groups exceeded the perceptibility threshold but remained below the acceptability threshold. No statistically significant difference was found in TP except for group E (p = 0.019). Ra values after laser debonding showed significantly higher values than before laser treatment in all three groups (p < 0.001).

CONCLUSION

Er,Cr: YSGG laser can be safely used for debonding ceramic veneers without altering the optical properties but it does increase the roughness of debonded ceramic restorations.

The effect of repair protocols and chewing simulation on the microtensile bond strength of two resin matrix ceramics to composite resin

BACKGROUND

To assess the micro tensile bond strength (µTBS) of two resin matrix ceramic (RMC) blocks bonded to composite resin by using different repair protocols with and without chewing simulation (CS).

MATERIALS AND METHODS

Two resin matrix ceramic blocks (Vita Enamic and Lava Ultimate) were divided into 4 groups according to the surface treatments: Bur grinding (control), Bur grinding + silane, 9.5% HF acid etching, and 9.5% HF acid etching + silane. The single bond universal adhesive was applied on all specimens after the surface treatments according to the manufacturer's instructions, it was administered actively on the treated surface for 20 s and then light cured for 10 s, followed by incremental packing of composite resin to the treated surface. Each group was further divided into 2 subgroups (with/without chewing simulation for 500,000 cycles). A micro tensile bond strength test was performed for each group (n = 15). The effect of surface treatments on the materials was examined by using a scanning electron microscope (SEM). The micro tensile bond strength (MPa) data were analyzed with a three-way ANOVA, the independent t-test, and one-way ANOVA followed by the Tukey post-hoc test.

RESULTS

µTBS results were significantly higher for Lava Ultimate than Vita Enamic for all the surface treatment protocols with (p < 0.01). The chewing simulation significantly negatively affected the micro-tensile bond strength (p < 0.001). Bur grinding + saline exhibited the highest bond strength values for Lava Ultimate, both with and without chewing simulation. For Vita Enamic, bur grinding + saline and HF acid + saline showed significantly higher bond strength values compared to other surface treatments, both with and without chewing simulation (p ≤ 0.05).

CONCLUSION

Bur grinding + silane could be recommended as a durable repair protocol for indirect resin matrix ceramics blocks with composite resin material.

Evaluation of the Color Stability of Three Resin-Ceramic Materials Using a Spectrophotometer and a Digital Photography Software

Background

Computer-aided design/computer-aided manufacturing (CAD/CAM) resin ceramics allow easier milling than glass ceramics but are suspected to be more stainable. Although Photoshop® is widely used for picture analysis, its potential for shade selection has not been properly assessed.

Aim

Purpose primary: To evaluate the color stability of three CAD/CAM resin ceramics and Lithium Disilicate. Secondary: to compare the color evaluation between a spectrophotometer (Vita Easyshade compact) and Photoshop software.

Materials and Methods

Three CAD/CAM resin ceramic materials (n = 10) and a fourth group of lithium disilicate were used. Half of each group were thermocycled (5°C and 55°C; 3000 cycles). All samples were immersed in colored beverages (coffee, tea and red wine) for 30 days. Values were obtained by spectrophotometry and photographs analyzed using Photoshop software. The parameters measured were CIEL*a*b, and the color difference (ΔE) was analyzed. A mixed model test was used to compare the results through time and materials (α = 0.05). The comparison between the spectrophotometer and Photoshop results was performed using the bivariate Pearson's correlation test.

Results

Lithium disilicate glass ceramic exhibited less color change (ΔE = 14) than resin ceramics (15.7 < ΔE < 18.7). The least change was noted with GC Cerasmart (ΔE = 15.7) followed by Vita Enamic (ΔE = 17*) and Brilliant Crios (ΔE = 18.7*). Spectrophotometer and Photoshop values showed low correlations.

Conclusions

Resin ceramics may suffer from color change in clinical use. Photoshop is technique sensitive; pictures are easily affected by the light conditions and camera settings.

Influence of surface treatments and adhesive protocols on repair bond strength of glass-matrix and resin-matrix CAD/CAM ceramics

OBJECTIVE

To specify the effects of self-etching ceramic primer, Monobond Etch and Prime (MEP), and universal adhesive (UA) on repair bond strength between CAD/CAM blocks and resin composite.

MATERIALS AND METHODS

Vita Mark II (VM), IPS e.max CAD (EMAX), Shofu Block HC (SHC), and Tetric CAD (TET) blocks were sliced and thermocycled. They were divided into four groups according to surface treatments (n = 24): control, sandblasting (AL), hydrofluoric acid etching (HF), and MEP application. SEM analysis assessed surface topography. Subdivided, specimens followed distinct adhesive protocols (n = 12): control (silane + adhesive [SA] or adhesive [A] only for MEP group) and UA. Microshear bond strength (μSBS) was measured following resin composite repair. Data were analyzed using two-way ANOVA and Tukey tests (p < 0.05).

RESULTS

The μSBS of CAD/CAM blocks was significantly influenced by surface treatment type and adhesive protocol. The highest μSBS values for each block, considering surface treatment + adhesive protocol, were VM, HF + SA, or HF + UA; EMAX, MEP + A; and SHC and TET, AL + SA, or AL + UA.

CONCLUSIONS

Except for EMAX, it was not the adhesive protocol that made the significant difference in bond strength for each CAD/CAM block, but the surface treatment. MEP + UA application on glass ceramics lowered μSBS values significantly, so it is not recommended in clinical conditions.

CLINICAL SIGNIFICANCE

Repair is an essential therapeutic option, particularly in esthetic restorations, to swiftly repair the impaired esthetics caused by fracture. Repair protocol is dependent on the restorative material, and to have a reliable repair bond strength, the following surface treatment and adhesive protocol combinations are recommended for each CAD/CAM block: VM, HF + SA, or HF + UA; EMAX, MEP + A; and SHC and TET, AL + SA, or AL + UA.

Fatigue resistance of 3D printed anatomic post-and-core after mastication simulation

STATEMENT OF PROBLEM

Rigid post-and-core systems have traditionally been used in the restoration of endodontically treated teeth and are regarded by many as the standard treatment. Flexible materials, including nanoceramic resins, are being increasingly implemented as post-and-core systems, but data supporting their use are lacking.

PURPOSE

The purpose of this in vitro study was to compare the fatigue resistance of conventional cast metal and nanoceramic 3-dimensionally (3D) printed resin post-and-core systems with teeth without posts.

MATERIAL AND METHODS

Thirty freshly extracted human maxillary premolars were endodontically treated and divided into 3 subgroups (n=10) according to the restorative procedure: cast metal post-and-core (CM), nanoceramic 3D printed resin post-and-core (3DR), and without a post (0P). The CM post-and-core group was fabricated conventionally, while the 3DR group was printed using a 3D resin printing material. For the 0P group, the teeth were restored with a composite resin foundation after root canal obturation. Complete coverage 3-mol% monolithic zirconia restorations were cemented on all specimens. The specimens were exposed to simultaneous mastication simulation (1.2 million cycles) and thermocycling (10 000 cycles at 5 ºC to 55 ºC) and analyzed based on the failure of specimens. Data were analyzed using the Kruskal-Wallis survival analysis and the Wilcoxon rank sum test (α=.05).

RESULTS

The Kruskal-Wallis test indicated statistically significant differences among the cycles needed to reach failure for each of the 3 groups (P<.001). At 1.2 million cycles, there were no CM failures. The 3DR group failed at a median value of 950 000 cycles, while the 0P group failed at a median value of 222 500 cycles (P<.001).

CONCLUSIONS

All the endodontically treated teeth that received CM survived the 1 200 000 simulated mastication cycles. Both 3DR and 0P specimens fractured at the crown cervical third during mastication simulation.

Evaluation of repair bond strength of a dental CAD/CAM resin composite after surface treatment with two Er,Cr:YSGG laser protocols following artificial aging

The aim of the present study was to evaluate the impact of two Er,Cr:YSGG laser surface treatments on the repair bond strength of a dental CAD/CAM resin composite (Brilliant Crios) after artificial aging. Twenty-four resin-based CAD/CAM blocks were cut and 48 rectangular slabs (3 x 12 x 14 mm) were prepared. Preliminary SEM observations indicated the most favorable laser settings regarding surface modification of the tested restorative material. The CAD/CAM specimens were then divided into 4 groups (n=12) based on their surface pretreatment: no treatment, air abraded with 50-μm Al2O3 particles, and laser irradiated with two different protocols using Er,Cr:YSGG laser with average power 3.5 and 4.5 W, pulse repetition rate 35 and 50 Hz, and pulse energy 100 and 90 mJ, respectively. After surface treatments each group followed a bonding protocol with silane and a flowable resin composite was used to prepare 48 microrods. Half of the microrods of each group were subjected on shear bond strength (SBS) test (chisel-shaped blade, load cell of 500 N, crosshead speed of 1 mm/min) after 24 h, while the other half underwent artificial aging (15,000 cycles, 5-55 °C) and then SBS test. The debonded specimens were examined under an optical microscope to determine the failure mode. All specimens were also evaluated using SEM to assess the surface topography after the treatments. The results showed that SBS significantly decreased after thermocycling in all the experimental groups (p<0.05). Control group presented much lower SBS values than the other groups after both 24 h and thermocycling (p<0.05). The highest values of SBS exhibited air-abrasion group (p<0.05), followed by the two laser groups, which did not differ to each other (p>0.05). The results of the current study indicated that Er,Cr:YSGG laser irradiation can be an alternative treatment for repairing the tested resin-based CAD/CAM restorative material.

Biaxial flexural strength and Weibull characteristics of a resin ceramic material after thermal-cycling

PURPOSE

The purpose of this in vitro study was to compare the flexural strength and Weibull characteristics of 3 different resin-ceramic materials with a zirconia-reinforced lithium silicate material after thermal-cycling.

MATERIAL AND METHODS

Four different computer-aided design and computer-aided manufacturing restorative materials (Vita Enamic, Lava Ultimate, Crystal Ultra, and Vita Suprinity) were tested. A total of 40 Ø12×1.2-mm disks were prepared and divided into 4 groups (n = 10). Their flexural strength was evaluated after 5000 thermal-cycles with a 4-point biaxial flexure test using a universal testing machine. The Weibull modulus and probability of failure were also determined from the biaxial flexural strength data. Data were analyzed with one-way ANOVA and the Tukey pairwise comparison test (α = 0.05).

RESULTS

Significant differences were found among the materials in terms of biaxial flexural strength (p < 0.05). Vita Suprinity had the highest mean ±standard deviation flexural strength (289.1 ± 15.1 MPa), and Vita Enamic had the lowest (100.0 ± 3.2 MPa). The highest Weibull modulus was calculated for Crystal Ultra, followed by Vita Enamic, Lava Ultimate, and Vita Suprinity.

CONCLUSION

Vita Suprinity had the highest flexural strength when compared with the other materials tested. Crystal Ultra had the highest flexural strength among the resin-ceramic materials. The highest Weibull modulus was calculated for Crystal Ultra and the lowest for Vita Suprinity.

Clinical Applications and Mechanical Properties of CAD-CAM Materials in Restorative and Prosthetic Dentistry: A Systematic Review

Clinical outcomes of dental restorations depend primarily on the choice of materials used, and nowadays, dental CAD-CAM (Computer-Aided Design Computer-Aided Manufacturing) materials have strongly changed daily clinical practice. The aim of this systematic review is to analyze CAD-CAM dental materials according to their mechanical properties and in relation to their clinical applications. A literature review was performed on PubMed, Scopus, Web of Knowledge, and the Cochrane Library. Articles addressing at least one of the following topics regarding dental materials for CAD-CAM systems: manufacturers, mechanical features, materials' composition, optical properties, clinical indications, and/or outcomes were included in the review. A flowchart was performed as described in the PRISMA guidelines. Among the 564 articles found, 63 were analyzed and evaluated. Within the limitations of this systematic review, it can be concluded that CAD-CAM materials present a wide range of clinical applications due to their improved mechanical properties. Specifically, in addition to materials that have been in use for a long time (such as feldspathic ceramics), resin block composites can also be used for permanent restorations.

Effect of plasma surface treatment of three different CAD/CAM materials on the micro shear bond strength with resin cement (A comparative in vitro study)

Objectives

This study aimed to evaluate and compare the effect of plasma treatment versus conventional treatment on the micro shear bond strength (μSBS), surface roughness, and wettability of three different CAD/CAM materials.

Materials and methods

Sixty cylindrical specimens (5 mm diameter × 3 mm height) were prepared from three different CAD/CAM materials: Group A: Zirconia, Group B: Lithium disilicate, and Group C: Resin nano-ceramic. Each group was subdivided into two subgroups according to surface treatment used: Subgroup I: Conventional treatment, zirconia was sandblasted with Al₂O₃, while lithium disilicate and resin nano-ceramic were etched with hydrofluoric acid. Subgroup II: Plasma treatment, the surface of each material was treated with a plasma device (PiezoBrush® PZ3 Handheld Device, Relyon Plasma, Regensburg, Germany). G-Multi PRIMER was applied, then self-adhesive cement (G-CEM ONE) was applied using a split mold (1 mm diameter × 3 mm height), and μSBS was tested in a universal testing machine. The surface roughness was measured using a profilometer. Nine additional specimens of each material for wettability test using an optical tensiometer.

Statistical analysis

The data were analyzed using ANOVA and Bonferroni test at a level of significance of 0.05.

Results

The highest mean of μSBS was recorded by AII (27.3 MPa), while the lowest was recorded by AI (17.9 MPa). One-way ANOVA test revealed a significant difference among groups. Bonferroni test showed each two subgroups significant difference except subgroups AI, CI and BII, CII, where there was a non-significant difference. For all CAD/CAM materials, conventional treatment increased the surface roughness compared to plasma treatment, while the contact angle decreased after plasma treatment.

Conclusion

Plasma treatment increased the μSBS of resin cement to zirconia significantly while not significantly affecting the μSBS of resin nano-ceramic. Conventional treatment of lithium disilicate provided significantly higher μSBS than plasma treatment.

Flexural Strength of CAD/CAM Lithium-Based Silicate Glass-Ceramics: A Narrative Review

Amongst chairside CAD/CAM materials, the use of lithium-based silicate glass-ceramics (LSGC) for indirect restorations has recently been increasing. Flexural strength is one of the most important parameters to consider in the clinical selection of materials. The aim of this paper is to review the flexural strength of LSGC and the methods used to measure it.

METHODS

The electronic search was completed within PubMed database from 2 June 2011 to 2 June 2022. English-language papers investigating the flexural strength of IPS e.max CAD, Celtra Duo, Suprinity PC, and n!ce CAD/CAM blocks were included in the search strategy.

RESULTS

From 211 potential articles, a total of 26 were identified for a comprehensive analysis. Categorization per material was carried out as follows: IPS e.max CAD (n = 27), Suprinity PC (n = 8), Celtra Duo (n = 6), and n!ce (n = 1). The three-point bending test (3-PBT) was used in 18 articles, followed by biaxial flexural test (BFT) in 10 articles, with one of these using the four-point bending test (4-PBT) as well. The most common specimen dimension was 14 × 4 × 1.2 mm (plates) for the 3-PBT and 12 × 1.2 mm (discs) for BFT. The flexural strength values for LSGC materials varied widely between the studies.

SIGNIFICANCE

As new LSGC materials are launched on the market, clinicians need to be aware of their flexural strength differences, which could influence the clinical performance of restorations.

The effect of sandblasting versus acid etching on the surface roughness and biaxial flexural strength of CAD/CAM resin-matrix ceramics (In vitro study)

BACKGROUND

CAD/CAM resin matrix ceramics are one of the materials used in dental offices. The long-term success of the restoration depends on the bond strength of the restoration to the tooth and other materials; thus, surface treatment of the restoration is necessary to achieve this. But such treatment may affect the restoration strength. The purpose of this study is to assess the impact of various surface treatments on the surface roughness (Ra) and the biaxial flexural strength of two CAD-CAM resin-matrix ceramics.

METHODS

Thirty-six-disc-shaped specimens, each measuring 1.2 mm in thickness and 12 mm in diameter, were machined from two resin-matrix ceramic blocks (Lava Ultimate and Cerasmart) (n = 18). Based on the surface treatments, each material was divided into 3 groups: control (no treatment), 50-μm Al₂O₃ sandblasting, or 9% hydrofluoric acid etching (n = 6). The surface roughness (Ra) was evaluated by the 3D laser scanning microscope. Then, specimens were aged by thermal cycling (5000 cycles) and tested for biaxial flexural strength using a universal testing machine at a crosshead speed of 1.0 mm/min.

RESULTS

No significant differences in flexural strength or Ra were found for Lava Ultimate among the surface treatment groups. For Cerasmart, only the sandblasting group showed significantly higher Ra values than the control group. Also, the Ra values for the sandblasting group were significantly higher than those for the acid etching group. The flexural strengths of the sandblasting and acid etching groups for Cerasmart were statistically similar, and both were significantly lower than the control group.

CONCLUSIONS

Although all of the applied surface conditioning techniques improved Ra, they had a negative impact on the flexural strength of resin-matrix ceramics. Thus, clinicians should utilize the appropriate surface treatment techniques, taking into account their effects on the surface roughness and mechanical properties of resin-matrix ceramics.

Effect of Adhesion Conditions on the Shear Bond Strength of 3D Printing Resins after Thermocycling Used for Definitive Prosthesis

Three-dimensional (3D) printing polymers such as urethane dimethacrylate (UDMA) and ethoxylated bisphenol A dimethacrylate (Bis-EMA) are typically used in definitive prosthesis and require surface treatments before bonding. However, surface treatment and adhesion conditions often affect long-term use. Herein, polymers were divided into Groups 1 and 2 for the UDMA and Bis-EMA components, respectively. The shear bond strength (SBS) between two types of 3D printing resins and resin cements was measured using Rely X Ultimate Cement and Rely X U200, according to adhesion conditions such as single bond universal (SBU) and airborne-particle abrasion (APA) treatments. Thermocycling was performed to evaluate the long-term stability. Sample surface changes were observed using a scanning electron microscope and surface roughness measuring instrument. The effect of interaction between the resin material and adhesion conditions on the SBS was analyzed via a two-way analysis of variance. The optimal adhesion condition for Group 1 was achieved when U200 was used after APA and SBU, whereas Group 2 was not significantly affected by the adhesion conditions. After thermocycling, the SBS significantly decreased in Group 1 without APA treatment and in the entire Group 2. Additionally, porosity, along with increased roughness, was observed on both material surfaces after APA.

Mechanical Properties, Wear Resistance, and Reliability of Two CAD-CAM Resin Matrix Ceramics

Background and Objectives: There are limited data regarding the behavior of resin matrix ceramics for current CAD-CAM materials. Further studies may be beneficial and can help clinicians planning to use these materials during prosthodontic rehabilitation. The aim of this study was to evaluate and compare the flexural strength and strain distributions, filler content, wear, and reliability of two resin matrix ceramic CAD-CAM materials. Materials and Methods: Two resin matrix ceramics, Ambarino High-Class (AH) and Vita Enamic (VE), were tested for flexural strength (n = 24), wear (n = 10), and reliability (n = 18). Thermogravimetric analysis was used to determine the percentage of filler by weight, and digital image correlation (DIC) was used for strain analysis in flexural strength test. Reliability of each resin matrix ceramic was compared after accelerated lifetime testing of crowns using a two-parameter Weibull distribution. Data of flexural strength, wear, and thermogravimetry were analyzed by independent t-tests with significance level at 5%. Results: The results of DIC analysis were analyzed by a qualitative comparison between the images obtained. The materials tested showed different flexural strength (p < 0.05) and strain distributions. The filler content was the same as informed by manufacturers. No difference was observed in the wear or reliability analysis (p > 0.05). The flexural strength of material AH was superior to VE, and the strain distribution was compatible with this finding. Conclusions: The two resin matrix ceramics tested showed similar behavior in wear and reliability analysis. Both can provide safe use for dental crowns.

Effect of Different Surface Treatments on Repair Bond Strength of CAD/CAM Resin-Matrix Ceramics

The purpose of this study was to investigate the influence of different surface treatment methods on the micro-tensile bond strength (μTBS) of resin-matrix ceramic (RMC) blocks repaired with resin composite. Three different prefabricated RMC blocks including Lava Ultimate (LU), Grandio Blocs (GB), and Shofu Block HC (HC) were thermo-cycled and divided into five surface treatment groups: Control (C), bur grinding (G), airborne particle abrasion (APA), Er,Cr:YSGG laser irritation (LI), and APA combined with LI (APA+LI). After surface treatments, topographic alterations were examined by scanning electron microscopy. Then, Universal Adhesive (Single Bond Universal) was applied and repair was simulated with nanohybrid composite (Grandio SO). Bonded specimens were cut into 1 mm2 sized beams (n = 16) and a μTBS test was conducted by using a universal test machine. Fracture types were evaluated by using a stereomicroscope. The bond- strength data was evaluated by two-way ANOVA and Tukey post-hoc test (α = 0.05). The μTBS values were significantly affected by the surface treatment variable and the interaction terms of the variables (p ≤ 0.001). However, no significant effect of RMC type was detected (p > 0.05). Among all materials, GBAPA+LI indicated the highest µTBS value. Except for the GBC, all surface treatments showed clinically acceptable bond-strength values. However, the surface treatments applied to GB and LU before the repair processes increased the repair bond-strength values while causing a negative effect for HC. In addition, LI and APA+LI can be applied as an alternative route compared to other procedures recommended by the manufacturer for surface preparation in intraoral RMC repair.

Effects of background color and thickness on the optical properties of CAD-CAM resin-matrix ceramics

STATEMENT OF PROBLEM

Information regarding the masking ability of computer-aided design and computer-aided manufacture (CAD-CAM) resin-matrix ceramic materials with different compositions is scarce.

PURPOSE

The purpose of this in vitro study was to evaluate the effects of background color and thickness on the optical properties (color and translucency) of CAD-CAM resin-matrix ceramics.

MATERIAL AND METHODS

Twelve rectangular specimens were fabricated at a different thickness (1, 1.5, and 2 mm) (n=12) from each of the resin-matrix ceramic materials: Shofu block (SB), Lava Ultimate (LU), CERASMART (CS), VITA ENAMIC (VE), Crystal Ultra (CU), and the VITABLOCS Mark II feldspathic ceramic (VB). The color of the specimens over amalgam, titanium, enamel, and dentin backgrounds was measured with a spectrophotometer, and the color differences (ΔE∗ab) were calculated by using the Commission Internationale de l'Eclairage (CIE) 76 formula. The difference in color of the specimen over the black and white backgrounds was used to calculate the translucency parameter (TP). ANOVA was used to statistically test whether material, background, and thicknesses influenced ΔE∗ab and TP values. Post hoc comparisons were performed to determine the significant difference among the groups (α=.05).

RESULTS

The interaction with 2 between factors demonstrated that the material was a factor that significantly influenced ΔE∗ab (P<.001). The highest mean ±standard deviation of ΔE∗ab was recorded in the combination of VB material and 2-mm thickness (1.84 ±0.37), and the lowest with CS material with 1.5-mm thickness (0.47 ±0.24). The type of material and specimen thickness significantly influenced TP (P<.001). The highest and lowest mean ±standard deviation of TP were recorded for the 1-mm-thick CS (14.20 ±0.90) and 2-mm-thick SB (4.91 ±0.42) specimens, respectively.

CONCLUSIONS

CERASMART resin-matrix ceramic and VITABLOCS Mark II feldspathic ceramic exhibited high and low masking abilities over the investigated background substrates, respectively. However, irrespective of the thickness, all study materials exhibited acceptable masking abilities.

Bonding of Clear Aligner Composite Attachments to Ceramic Materials: An In Vitro Study

Background: We aim to evaluate the effect of surface conditioning, bonding agents and composite types on surface roughness (SR) and shear bond strength (SBS) of clear aligner composite attachments bonded to ceramics. Methods: One hundred and eighty IPS e.max CAD specimens were prepared. For SR, 60 specimens were divided according to surface conditioning (n = 15) into four groups: control, 9.6% hydrofluoric acid (HFA), 37% phosphoric acid (PhA), air abrasion (AA). SR was measured using a Profilometer and Atomic Force Microscopy. For SBS, 120 specimens were divided according to conditioning methods (n = 40) (9.6% HFA and 37% PhA or AA), then according to bonding agents (n = 20) (Assure universal bond (AUB) or Single bond universal (SBU)) and then according to composite type (n = 10): Filtek™ Z350 and Filtek™ Z350 XT flowable composite. SBS was measured using Instron testing machine. Descriptive and group comparison were calculated (p < 0.05). Results: AA had the highest SR, while the control had the lowest SR (p < 0.05). HFA had the highest, but insignificant SBS, followed by AA (p > 0.05). AUB had higher SBS than SBU (p < 0.001). Filtek™ Z350 produced higher SBS than Filtek™ Z350 XT flowable composite (p < 0.01). Conclusion: The combination of AA, AUB, and Filtek Z350 produced the highest SBS, followed by HFA, AUB, and Filtek Z350.

Evaluation of surface characterization and mechanical features of resin-matrix ceramics before and after different surface treatments

STATEMENT OF PROBLEM

Surface treatments (STs) required for micromechanical interlocking can lead to alterations in the surface characterization and mechanical features of the resin-matrix ceramics (RMCs), which may jeopardize the long-term outcome of an indirect restoration. However, evidence on this issue is lacking.

PURPOSE

The purpose of this in vitro study was to assess the influence of different STs on the surface roughness (SR), water contact angle (WCA), and flexural strength (FS) of RMCs.

MATERIAL AND METHODS

Two hundred rectangular plates (12×14×1 mm) were prepared from 5 different RMC ingots, including a polymer-infiltrated ceramic network (Vita Enamic [VE]), 2 resin nanoceramics (Lava Ultimate [LU], Grandio Blocks [GB]), a flexible nanoparticle-filled resin (GC Cerasmart [GC]), and a reinforced composite resin (Brilliant Crios [BC]). Plates of each RMC group were further divided into 4 subgroups according to the ST applied: Control, no treatment (C); airborne-particle abrasion with aluminum oxide particles (APA); 2W- and 3W-Er,Cr:YSGG laser irradiations (LI^2W, LI^3W) (n=10 per ST). The SR (Ra) of each plate was recorded with a contact profilometer. WCAs (θ) of distilled water on the plates were determined by using the sessile-drop method. The FS (MPa) of each plate was measured with a universal testing machine. Data acquired for SR, WCA, and FS were statistically analyzed (α=.05). Weibull statistics were also conducted to determine the reliability of each material.

RESULTS

The 2-way ANOVA showed that SR, WCA, and FS values were significantly influenced not only by all tested variables but also by their interaction terms (P<.001). All STs significantly increased the SR values (P<.05). Maximum and minimum SR values were recorded in GC-LI^3W (7.06 ±0.16) and GC-C (0.07 ±0.02) groups. After STs, WCA values significantly diminished (P<.05). Maximum and minimum WCA values were recorded in LU-C (61.74 ±2.45) and VE-APA (40.38 ±1.56) groups. All STs significantly reduced the FS values (P<.05). The upper and lower FS bounds were 140.7 ±17.07 and 60.66 ±6.31, respectively, set by VG-C and GC-APA. Weibull distribution indicated that the untreated groups presented the highest m values. Among the treated groups, BC-LI^3W demonstrated superior reliability (m=14.04).

CONCLUSIONS

APA for LU, LI^2W for VG and BC, and LI^3W for GC and VE can be preferred. Although APA increased the SR and provided more wettable surfaces, it caused considerable loss of FS. Therefore, LI can be recommended as a safer ST for RMCs.

Effect of staining beverages and bleaching on optical properties of a CAD/CAM nanohybrid and nanoceramic restorative material

BACKGROUND

The purpose of this study was to evaluate the optical properties of nanohybrid Grandio (GR) and nanoceramic Lava Ultimate (LU) CAD/CAM restorative materials subjected to different beverage solutions and subsequently bleached.

METHODS

Five groups of each restorative material (n = 20/group, shade A2-high translucent) were immersed in distilled water, coffee, tea, cola, and ginger for one week. Changes in whiteness index, translucency parameter, and color changes of the specimens were evaluated. The data of color measurements after staining, bleaching, and the residual differences were statistically analyzed using Kruskal-Wallis and Mann-Whitney U tests at the significance level of P < 0.05.

RESULTS

LU and GR revealed the highest differences in whiteness index after coffee staining (P < 0.001). GR revealed lower translucency parameter differences after staining with coffee than LU (P = 0.007). There were no significant differences in translucency changes between LU and GR after staining with tea, cola, or ginger (P > 0.05). LU revealed significantly greater color changes than GR after staining (P < 0.001).

CONCLUSIONS

LU nanoceramic CAD/CAM restorative material revealed higher color changes than GR nanohybrid material. Staining beverage solutions had a distinct influence on the optical properties of the tested CAD/CAM restorative materials.

Masking Abilities of Dental Cad/Cam Resin Composite Materials Related to Substrate and Luting Material

An outstanding treatment challenge related to aesthetic monolithic materials is to mask discolored substrates in aesthetic areas. The purpose of the study is to evaluate the substrate masking ability of different resin composite materials and the influence of their association with luting agents and substrates. Five types of 2M2 HT (high translucency) resin composite materials were selected: Vita Enamic [E] and four types of nanoparticle-filled composites Lava Ultimate [L], Cerasmart [C], Shofu HC [S], and Hyramic [H]. Resin composite Vita VM LC with different shades was used for the substrates: 2M2, 3M2, and CP2. Variolink Esthetic Try-inpastes neutral, light+, and warm+ colors were chosen to simulate the luting agent color. Optical parameters (TP (translucency), CR (contrast ratio), and OP (opalesce)) and color differences ΔE (chromatic difference) were calculated. Statistical analyses were performed to evaluate the comparisons between the groups and establish correlations. TP average values for all materials were in the range of 21.49–24.53. OP average values were in the rage of 6.31–7.85. OP is moderate positive correlated to TP and CR is negative and strong correlated to TP. Related to materials, average color changes decrease as following: E > H > C > L > S. Referring to the tryin material, warm colors induce marked color changes of the restoration. The differences of the color changes determined by all studied substrates are significant. For the final aesthetic aspect of the restoration, it is essential to consider the underlying dental structure, luting agent, and restoration material as a whole unit. The masking ability of the investigated resin matrix ceramic materials materials shows differences, the best behavior demonstrated Shofu HC and Lava Ultimate. Marked color changes are related to high chroma substrates. For substrates with a darker color, the association with warm try-in pastes lead to marked color changes, but with neutral and light try-in pastes at most perceivable.

Is the Er:YAG laser affect the surface characteristics and bond strength of Y-TZP?

This study evaluated the surface characteristics and bond strength of Y-TZP treated with Er:YAG laser at different focal distances. 120 Y-TZP blocks were divided into five groups (n=24), according to the surface treatment: no treatment (C-); sandblasting with silica-coated aluminum oxide particles (C+); and Er:YAG laser application at focal distances of 1mm (Er:YAG-1), 4mm (Er:YAG-4), and 7mm (Er:YAG-7). Surface characteristics were analyzed using Vickers microhardness, confocal laser microscope, scanning electron microscopy (SEM), and X-ray diffractometer (XRD). For the bond strength test, 100 Y-TZP blocks were subdivided into two subgroups (n=10), according to the resin cement used: with (MDP+) or without 10-methacryloyloxydecyl dihydrogen phosphate (MDP-). The Vickers microhardness and surface roughness were analyzed by one-way ANOVA and bond strength by two-way ANOVA and Tukey's test for both (α=0.05). Vickers microhardness differences were not observed between the groups (p>0.05); C+ showed higher surface roughness values. SEM images showed micromorphological differences between the groups. The XRD data detected tetragonal crystals for C- and, for the other groups, tetragonal and monoclinic peaks. For bond strength, no statistically difference significance were observed among the cements with or without MDP (p>0.05) but showed significant difference between the surface treatments (C+ > C- = Er:YAG1 > Er:YAG4 = Er:YAG7) (p<0.05). Suggested that the Er:YAG laser cannot replace conventional treatment with aluminum oxide particles and the presence of MDP in the resin cement had no influence on the bond strength.

The effect of silane and universal adhesives on the micro-shear bond strength of current resin-matrix ceramics

PURPOSE

The aim of this in vitro study was to evaluate the effect of silane and universal adhesive applications on the micro-shear bond strength (µSBS) of different resin-matrix ceramics (RMCs).

MATERIALS AND METHODS

A total of 120 slides (14 × 12 × 1 mm) were produced from 5 different RMC materials (GC Cerasmart [GC]; Brilliant Crios [BC]; Grandio blocs [GB]; Katana Avencia [KA]; and KZR-CAD HR 2 [KZR]) and sandblasted using 50 µm Al₂O₃ particles. Each RMC material was divided into six groups according to the surface conditioning (SC) method as follows: control (G1), silane primer (G2), silane-free universal adhesive (G3), silane-containing universal adhesive (G4), silane primer and silane-free universal adhesive (G5), and silane primer and silane-containing universal adhesive (G6). Three cylindric specimens made from resin cement (Bifix QM) were polymerized over the treated surface of each slide (n = 12). After thermal cycling (10000 cycles, 5 – 55℃), µSBS test was performed and failure types were evaluated using a stereomicroscope. Data were analyzed using 2-way ANOVA and Tukey tests (α = .05).

RESULTS

µSBS values of specimens were significantly affected by the RMC type and SC protocols (P < .001) except the interaction (P = .119). Except for G2, all SC protocols showed a significant increase in µSBS values (P < .05). For all RMCs, the highest µSBS values were obtained in G4 and G6 groups.

CONCLUSION

Only silane application did not affect the µSBS values regardless of the RMC type. Moreover, the application of a separate silane in addition to the universal adhesives did not improve the µSBS values. Silane-containing universal adhesive was found to be the best conditioning method for RMCs.

Effects of Artificial Tooth Brushing and Hydrothermal Aging on the Mechanical Properties and Color Stability of Dental 3D Printed and CAD/CAM Materials

This study analyzed the surface roughness and waviness, Vickers hardness (VHN), and color changes of six types of 3D printed resins and computer-aided design/computer-aided manufacturing (CAD/CAM) materials after artificial toothbrushing. The average surface roughness height (Ra) change of Formlabs denture teeth A2 resin (FMLB) was not significant between after artificial toothbrushing (0.17 ± 0.02 μm and 0.17 ± 0.05 μm, respectively; mean ± standard deviation). However, the Ra value increased significantly in all remaining groups. Regarding waviness, polymethylmethacrylate (PMMA) had the largest increases in average waviness height (Wa) and maximum surface waviness height (Wz) between, before (0.43 ± 0.23 μm and 0.08 ± 0.02 μm), and after (8.67 ± 4.03 μm, 1.30 ± 0.58 μm) toothbrushing. There were no significant changes in Wa for Formlabs denture teeth A2 resin (FMLB) and NextDent C&B (NXT). After artificial toothbrushing, the dispersed-filler composite (DFC) group had the largest color difference (ΔE, of 2.4 ± 0.9), and the remaining materials had smaller changes than the clinical acceptance threshold of ΔE = 2.25. The VHN of FMLB and NXT were 9.1 ± 0.4 and 15.5 ± 0.4, respectively, and were not affected by artificial toothbrushing. The flexural strengths of the 3D printed materials were 139.4 ± 40.5 MPa and 163.9 ± 14.0 MPa for FMLB and NXT, respectively, which were similar to those of the polycarbonate and PMMA groups (155.2 ± 23.6 MPa and 108.0 ± 8.1 MPa, respectively). This study found that the evaluated 3D printed materials had mechanical and optical properties comparable to those of CAD/CAM materials and were stable even after artificial toothbrushing and hydrothermal aging.

Color Stability and Translucency of Polymer-Infiltrated Ceramic-Network Materials—A Systematic Review of the Literature

This systematic review aimed to compile information and report the color stability and translucency of polymer-infiltrated ceramic-network (PICN) materials for suitable clinical applications in dentistry. Original peer-reviewed articles in electronic databases including PubMed, MEDLINE, Scopus, and Web of Science were searched to identify relevant papers published between January 2013 and August 2020. The published papers were only in the English language and limited to in vitro studies, and experimental reports were considered. The data from nine studies were considered when reviewing the color stability and translucency of PICN in comparison to other commonly used restorative materials. Among the included studies, color stability assessment was performed in five studies, and the other four studies were involved in the combined assessment of both color stability and translucency. PICN materials are a comparatively newer class of restorative materials and are recommended to overcome the drawbacks of ceramics and resin composites. The outcomes of previous laboratory studies still do not provide convincing results regarding the optical properties of PICN materials. However, with existing sources and evidence, PICN materials exhibit less color stability than ceramics do but better color stability compared to that of resin nanoceramics (RNC) and resin composites. The translucency of PICN materials is low compared to that of ceramics, nanoceramics, and resin composites.

A 3-dimensional finite element and in vitro analysis of endocrown restorations fabricated with different preparation designs and various restorative materials

STATEMENT OF PROBLEM

The preparation design and fabrication materials directly affect the clinical success of endocrown restorations, and yet, knowledge is lacking about the biomechanical impact of specific designs or materials on endocrown restorations.

PURPOSE

The purpose of this in vitro and finite element analysis study was to evaluate the biomechanical behavior of endocrown restorations.

MATERIAL AND METHODS

A total of 36 freshly extracted mandibular first molars were collected. The teeth were prepared as per 2 different preparation geometries: with the buccal wall intact (Class 2) and without the buccal wall (Class 3). Teeth were restored with endocrowns made from 3 different fabricating materials, Vita Enamic, GC Cerasmart, and Lava Ultimate. To analyze the in vitro fracture strength, cemented endocrowns were loaded in a universal test machine with a 200-N oblique force until the restoration fractured. Finite element analysis was used to evaluate the stress distribution on both the dentin tissue and the restorative materials. The data were analyzed with a 2-way ANOVA test and the Tukey post hoc test (α=.05).

RESULTS

No significant differences were found between the different preparation designs (Class 2 and Class 3) on fracture strength (P>.05). The highest mean ±standard deviation fracture strength values were found in the Lava Ultimate material (Class 2, 606.20 ±293; Class 3, 659.40 ±226 N) (P>.05), but the lowest fracture strength test values were obtained in the Vita Enamic material (Class 2, 439.60 ±136; Class 3, 340 ±98 N) (P>.05) for both preparation design test groups.

CONCLUSIONS

A statistically significant difference was not found between the 2 tooth preparation classifications. However, significant differences were observed among the test groups in the Class 2 preparation specimens. The Class 2 preparation design exhibited a higher number of irreparable failures.

Micro-shear bond strengths of resin-matrix ceramics subjected to different surface conditioning strategies with or without coupling agent application

PURPOSE

This study aimed to assess the influence of various micromechanical surface conditioning (MSC) strategies with or without coupling agent (silane) application on the micro-shear bond strength (µSBS) of resin- matrix ceramics (RMCs).

MATERIALS AND METHODS

GC Cerasmart (GC), Lava Ultimate (LU), Vita Enamic (VE), Voco Grandio (VG), and Brilliant Crios (BC) were cut into 1.0-mm-thick slices (n = 32 per RMC) and separated into four groups according to the MSC strategy applied: control-no conditioning (C), air-borne particle abrasion with aluminum oxide particles (APA), 2W- and 3W-Er,Cr:YSGG group coding is missing. The specimens in each group were further separated into silane-applied and silane-free subgroups. Each specimen received two resin cement microtubules (n = 8 per subgroup). A shear force was applied to the adhesive interface through a universal test machine and µSBS values were measured. Data were statistically analyzed by using 3-way ANOVA and Tukey HSD test. Failure patterns were scrutinized under stereomicroscope.

RESULTS

RMC material type, MSC strategy, and silanization influenced the µSBS values (P<.05). In comparison to the control group, µSBS values increased after all other MSC strategies (P<.05) while the differences among these strategies were insignificant (P>.05). For control and APA, there were insignificant differences between RMCs (P>.05). The silanization decreased µSBS values of RMCs except for VE. Considerable declines were observed in GC and BC (P<.05).

CONCLUSION

MSC strategies can enhance bond strength values at the RMC - cement interface. However, the choice of MSC strategy is dependent on RMC material type and each RMC can require a dedicated way of conditioning.

Effect of CAD-CAM ceramic materials on the color match of veneer restorations

STATEMENT OF PROBLEM

With the different translucency levels and types of computer-aided design and computer-aided manufacturing (CAD-CAM) ceramic materials, choosing the most appropriate CAD-CAM ceramic materials to better reproduce the color appearance of natural teeth can be challenging.

PURPOSE

The purpose of this in vitro study was to analyze the color differences between natural teeth and milled veneers fabricated with the different types of CAD-CAM ceramic materials.

MATERIAL AND METHODS

Ten extracted maxillary central incisor teeth with the A2 shade in the body region were prepared for ceramic veneers. The veneer restorations were designed by using the duplicating method and fabricated from 9 milling blocks (IPS e.max CAD HT/LT, Lava Ultimate CAD HT/LT, VITA SUPRINITY HT/T, IPS Empress CAD HT/LT/Multi) in a dental milling unit (n=10). The bonding surface of the abutment tooth was coated with a thin layer of a separating agent, and the veneer specimen with resin cement was then bonded to the corresponding abutment tooth. A clinical spectrophotometer was used to measure the Commission Internationale de l'Eclairage Lab values of natural teeth, abutment teeth, and milled veneers in the cervical, body, and incisal regions. Color differences between the natural tooth and A2 shade tab (ΔE₁) and between the milled veneer and natural tooth (ΔE₂) were calculated. The ΔE₂ values were compared with the perceptibility threshold (ΔE=2.6) and acceptability threshold (ΔE=5.5). The paired-samples t test, 1-way analysis of covariance, and 2-way ANOVA were used to analyze data (α=.05).

RESULTS

The results of 1-way analysis of covariance showed that ceramic materials significantly affected the a∗ and b∗ values of the milled veneers (P<.001) but did not affect the L∗ values of the milled veneers (P>.05). The results of 2-way ANOVA indicated that the ΔE₂ values were not significantly affected by different CAD-CAM ceramic materials (F=1.560, P=.138), while statistically significant differences were found in the veneer regions (F=6.588, P=.002). The ΔE₂ values ranged from 2.41 to 5.36, less than the clinically acceptable color threshold of 5.5.

CONCLUSIONS

The color parameters of milled veneers were affected by the different types of CAD-CAM ceramic materials. The color of the veneer restoration was able to match that of the natural tooth.

The effect of resin cement shade and restorative material type and thickness on the final color of resin-matrix ceramics

PURPOSE

This study aims to evaluate the effects of cement shade, restorative material type, and thickness on the final color of resin-matrix ceramics.

METHODS

Ninety A2 shade resin-matrix ceramic specimens were prepared from Vita Enamic, GC Cerasmart, and Lava Ultimate at 0.5 and 1.0 mm thicknesses. Sixty resin cement disks were fabricated from different shades (A1, A3O, B05, and TR) of RelyX Ultimate at 0.1 mm thickness. CIE color coordinates were measured using a spectrophotometer, and color differences (∆ E 00 ) were calculated. Data were statistically analyzed (P =0.05).

RESULTS

The ΔE 00 values were influenced by the cement shade, restorative material type, thickness, and their interactions ( P < 0.05). A3O cement caused clinically unacceptable values for all groups at 0.5 mm thickness and GC at 1.0 mm thickness. A1 and TR cement shades demonstrated visually perceptible but clinically acceptable values, except for VE-A1 and LU-A1 at 0.5 mm thickness. The ∆E 00 values of the B05 cement shade were lower than the visually perceptible threshold for both thicknesses except for GC at 0.5 mm thickness.

CONCLUSIONS

The shade of the resin cement and the type and thickness of the resin-matrix ceramic material significantly affected the resulting final color. To provide a shade matching with natural dentition and to obtain esthetic restorations, especially for the anterior teeth, the resin cement shade and resin-matrix ceramic material should be carefully selected.

Review on Polymer, Ceramic and Composite Materials for CAD/CAM Indirect Restorations in Dentistry-Application, Mechanical Characteristics and Comparison

The aim of this review article is to present various material groups, including ceramics, composites and hybrid materials, currently utilized in the field of CAD/CAM. The described technology is amongst the most important in modern prosthetics. Materials that are applicable in this technique are constantly tested, evaluated and improved. Nowadays, research on dental materials is carried out in order to meet the increasing demand on highly aesthetic and functional indirect restorations. Recent studies present the long-term clinical success of restorations made with the help of both ceramic and composite materials in the CAD/CAM method. However, new materials are developed and introduced that do not have long-term in vivo observations. We can outline a monolithic polymer-infiltrated ceramic network and zirconia teeth support that show promising results to date but require further assessment. The materials will be compared with regard to their mechanical and clinical properties, purpose, advantages and limitations.

Effects of laser debonding treatment on the optical and mechanical properties of all-ceramic restorations

The objective of this study was to evaluate how erbium-doped yttrium aluminium garnet (Er:YAG) laser debonding treatment affects the optical and mechanical properties of dental ceramics. In total, 120 rectangular (22*5*1.2 mm) IPS E.max Press specimens were fabricated and divided into 4 groups: the control group, 3 W laser group, 4 W laser group, and 5 W laser group. For each group, 10 specimens were used for the colour test (colour difference (△E) and transparency parameter (TP)), 10 specimens were used for the flexural strength test, and 10 were used for the Vickers hardness test. One random sample from each colour test specimens was observed by scanning electron microscopy (SEM). The L*, a*, b*, △E, TP, flexural strength, and Vickers hardness values were measured and calculated. According to the Kruskal-Wallis test, the L*, a*, and b* values showed no significant variations (P > 0.05), except for the b* value in the 5 W laser group (P < 0.05). The △E, TP, flexural strength, and Vickers hardness values were analysed by one-way analysis of variance (ANOVA). The 5 W laser group exhibited a higher △E value, which exceeded the perceptible threshold and significantly lower TP values than the other groups (P < 0.05). The mean flexural strength and Vickers hardness values after Er:YAG laser debonding revealed no significant changes (P > 0.05). Microcracks were detected during the SEM analysis of the 5 W laser group. Er:YAG laser debonding treatment did not affect the mechanical properties, but changed the optical properties of dental ceramics.

Effect of color of the cement and the composite resin foundation on the resultant color of resin-matrix ceramics

STATEMENT OF PROBLEM

An improper restoration color match to the adjacent natural teeth can jeopardize esthetic success. The type of resin-matrix ceramic (RMC), the shade of the underlying foundation, and the shade of cement may affect the optical behavior of RMC materials, but studies on this issue are lacking.

PURPOSE

The purpose of this in vitro study was to assess the cumulative effect of different shades of composite resin foundation (CRF) and cement on the optical behaviors of 3 different RMCs.

MATERIAL AND METHODS

Forty-five rectangular RMC specimens (14×12×1 mm, shade A2) were prepared from 3 different blocks, including a polymer-infiltrated ceramic network (Vita Enamic [VE]), a resin nanoceramic (Lava Ultimate [LU]), and a flexible nanoparticle-filled resin (GC Cerasmart [GC]) (n=15 per RMC block). CRFs (14×12×4 mm) were fabricated in white and dentin shades (n=1 per composite resin shade). Cement specimens (G-CEM LinkForce) were prepared from 3 shades (A2, opaque [OP], and translucent [TR]) (n=15 per shade). For control groups, 3 rectangular RMC foundations (14×12×4 mm) were also milled from RMC blocks (n=1 per block). Color coordinates were recorded by using a digital spectrophotometer. The coordinates of 4-mm-thick RMC foundations served as the control groups. The coordinates of RMC specimens on each combination of CRF and cement served as test groups. The CIEDE2000 (ΔE₀₀) formula was used to assess color differences. Data were subjected to 3-way ANOVA and Tukey honestly significant difference (HSD) tests (α=.05).

RESULTS

ΔE₀₀ values of specimens were influenced by the CRF shade, cement shade, RMC type, as well as the interaction terms of the 3 variables (P<.001). Color differences in groups VE-A2-dentin, VE-OP-dentin, LU-OP-dentin, and GC-OP-dentin showed perceptible but clinically acceptable values (0.8<ΔE₀₀≤1.8). The highest and lowest ΔE₀₀ values were observed in the white-OP-LU (5.32 ±0.34) and dentin-OP-VE (0.94 ±0.31) groups.

CONCLUSIONS

Opaque cement on the white foundation led to the highest ΔE₀₀ values in the resultant colors of all RMC groups. When used with the same shade on the dentin foundation, this cement produced clinically acceptable results.

Shear bond strengths of aged and non-aged CAD/CAM materials after different surface treatments

PURPOSE

To assess shear bond strengths (SBS) of resin composites on aged and non-aged prosthetic materials with various surface treatments.

MATERIALS AND METHODS

Cerasmart (CE), Vita Enamic (VE), Vita Mark II (VM), and IPS e.max CAD (EC) blocks were sliced, and rectangular-shaped specimens (14 × 12 × 1.5 mm; N = 352) were obtained. Half of the specimens were aged (5000 thermal cycles) for each material. Non-aged and aged specimens were divided into 4 groups according to the surface treatments (control, air abrasion, etching, and laser irradiation; n = 11) and processed for scanning electron microscopy (SEM). The repair procedure was performed after the surface treatments. SBS values and failure types were determined. Obtained data were statistically analyzed (P≤.05).

RESULTS

The material type, surface treatment type, and their interactions were found significant with regard to SBS (P<.001). Aging also had a significant effect on prosthetic material-resin composite bonding (P<.001). SBS values of non-aged specimens ranged from 12.16 to 17.91 MPa, while SBS values of aged specimens ranged from 9.46 to 15.61 MPa. Non-aged VM in combination with acid etching presented the highest score while the control group of aged CE showed the lowest.

CONCLUSION

Etching was more effective in achieving durable SBS for VM and EC. Laser irradiation could be considered as an alternative surface treatment method to air abrasion for all tested materials. Aging had significant effect on SBS values generated between tested materials and resin composite.

How will surface conditioning methods influence the translucency and color properties of CAD-CAM resin-matrix ceramics with different thicknesses?

OBJECTIVE

It was aimed to evaluate the effect of various surface-conditioning methods on the translucency and color properties of resin-matrix ceramics (RMCs) with different types and thicknesses.

MATERIALS AND METHODS

Rectangle-shaped RMCs were prepared from Voco Grandio, Brilliant Crios, Lava Ultimate, GC Cerasmart, and Vita Enamic blocks at 0.5 and 1.0 mm thicknesses. Specimens were divided into four groups: control, airborne-particle abrasion (APA), 2 and 3 W Er, Cr:YSGG laser irradiations (L^2W , L^3W ) (n = 15). The color values of specimens were recorded before and after surface-conditioning using a spectrophotometer. The translucency parameter (RTP₀₀ ) and color difference (ΔE₀₀ ) values were calculated. Data were statistically analyzed using three-way ANOVA and Tukey post hoc tests.

RESULTS

The translucencies of RMCs decreased after all surface-conditioning procedures. L caused more decline in translucency of materials than APA. All ΔE₀₀ values were under the acceptability threshold except for APA-applied Voco Grandio at 0.5 mm. Differences in ΔE₀₀ values between APA and L^3W groups were significant (P˂0.05); while differences between L^2W and L^3W groups were insignificant (P > .05). In all experimental groups, ΔE₀₀ values decreased with increasing thickness of RMCs.

CONCLUSIONS

L and APA significantly affected the translucency and color properties of RMCs. APA was found more favorable than L.

CLINICAL SIGNIFICANCE

Clinicians should carefully use surface conditioning methods, considering their impact on the optical characteristics of RMCs, especially when the restoration is thin.

Effect of Pressure and Particle Size During Aluminum Oxide Air Abrasion on the Flexural Strength of Disperse-Filled Composite and Polymer-Infiltrated Ceramic Network Materials

Esthetic dental computer-aided design/computer-aided manufacturing (CAD/CAM) polymers such as disperse-filled composites (DFC) and polymer-infiltrated ceramic networks (PICN) should be subjected to surface treatment before bonding. However, such treatment can lead to defect formation and a decrease in strength. Therefore, in this study, we compared the flexural strengths of DFC and PICN materials air-abraded with alumina particles of different sizes at different pressures. In addition to Weibull analysis, the samples (untreated and treated) were characterized by scanning electron microscopy and atomic force microscopy. Both DFC and PICN exhibited the lowest flexural strength at large particle sizes and high pressures. Therefore, we optimized the air abrasion parameters to maintain the flexural strength and significantly increase surface roughness. In the case of DFC, the optimal particle size and pressure conditions were 50 µm at 2 bar and 110 µm at 1 bar, while for PICN, the best performance was obtained using Al₂O₃ particles with a size of 50 µm at 1 bar. This study reveals that optimization of the surface treatment process is crucial in the fabrication of high-performance clinical materials for dental restorations.

Repair bond strength of resin composite to three aged CAD/CAM blocks using different repair systems

PURPOSE

The purpose of this study is to evaluate the repair bond strength of a nanohybrid resin composite to three CAD/CAM blocks using different intraoral ceramic repair systems.

MATERIALS AND METHODS

Three CAD/CAM blocks (Lava Ultimate, Cerasmart, and Vitablocks Mark II) were selected for the study. Thirty-two specimens were fabricated from each block. Specimens were randomly divided into eight groups for the following different intraoral repair systems: Group 1: control group (no treatment); Group 2: 34.5% phosphoric acid etching; Group 3: CoJet System; Group 4: Z-Prime Plus System; Group 5: GC Repair System; Group 6: Cimara System; Group 7: Porcelain Repair System; and Group 8: Clearfil Repair System. Then, nanohybrid resin composite (Tetric Evo Ceram) was packed onto treated blocks surfaces. The specimens were thermocycled before application of repair systems and after application of composite resin. After second thermal cycling, blocks were cut into bars (1 × 1 × 12 mm³) for microtensile bond strength tests. Data were analyzed using two-way ANOVA and Tukey's HSD test (α=.05).

RESULTS

Cimara System, Porcelain Repair, and Clearfil Repair systems significantly increased the bond strength of nanohybrid resin composite to all CAD/CAM blocks when compared with the other tested repair systems (P<.05). In terms of CAD/CAM blocks, the lowest values were observed in Vitablocks Mark II groups (P<.05).

CONCLUSION

All repair systems used in the study exhibited clinically acceptable bond strength and can be recommended for clinical use.

Durability of staining and glazing on a hybrid ceramics after the three-body wear

Hybrid ceramic is a promising material for monolithic restorations that could require an individualization through the extrinsic staining to improve aesthetics. Due to the possibilities to treat this ceramic prior to staining, this study evaluated the wear resistance of surface treatments prior to staining and glazing a hybrid ceramic. Thirty-two specimens (Vita Enamic) were divided into 8 groups according to the surface treatment prior to the staining (Polishing: Pol, Acid etching: Ac, Sandblasting with Al₂O₃: Sd or Self-etching silane: Ses) and glaze application (with: gl or without: gl). The specimens were submitted to the ACTA wear machine simulating the presence of food bolus and antagonist. The wear rate of the stain was determined after 7 intervals of 20,000 cycles, using a profilometer. The surface before and after staining, and after wear were inspected using Scanning Electron Microscopy (SEM). The rates were analyzed using three-way ANOVA and Tukey test. The wear was affected by surface treatment, glaze application and number of cycles (p < 0.001). 100% of the staining was removed after 20,000 cycles for Pol, 40,000 for Pol + gl, 60,000 for Ses + gl, 80,000 for Ac, 100,000 for Sd and Ses, 120,000 for Ac + gl and 140,000 for Sd + gl. SEM showed similar worn surfaces. Sandblasting followed by glaze application was the most durable treatment to maintain the external staining on the hybrid ceramic surface when subjected to three-body wear.

Does the application of surface treatments in different sintering stages affect flexural strength and optical properties of zirconia?

OBJECTIVE

To investigate the influence of surface treatments conducted in presintering and postsintering stages on flexural strength and optical properties of zirconia.

MATERIALS AND METHODS

Specimens were milled from partially sintered zirconia blocks in different geometries and divided into three main groups as presintered, postsintered, and control groups. Test groups were further divided into three subgroups (n = 10) according to the surface treatments conducted (grinding, Er,Cr:YSGG laser irradiation, air-borne particle abrasion [APA]). Four-point flexural strength (σ) test and Weibull analysis were conducted. Color differences (ΔE₀₀ ) and translucency parameter (TP_ab ) were calculated with a spectrophotometer. Surfaces of specimens were scrutinized under FESEM. Data were statistically analyzed.

RESULTS

Postsintered groups exhibited higher σ values (P < .05). Within all groups, highest and lowest σ values were detected at postsintered and presintered APA groups, respectively (P < .05). All ΔE₀₀ values were above the perceptibility threshold (ΔE₀₀  > 0.8). Higher TP_ab values were obtained and deeper scratches were observed in presintered groups.

CONCLUSIONS

Surface treatments performed at postsintering stage had a favorable effect on the flexural strength of all specimens. Surface treatments performed before sintering increased translucency and caused higher ΔE₀₀ values.

CLINICAL SIGNIFICANCE

Surface treatments performed at different sintering stages can alter mechanical and optical properties of zirconia.

Bonding to industrial indirect composite blocks: A systematic review and meta-analysis

OBJECTIVE

The aim of this systematic review and meta-analysis was to evaluate the effect of surface conditioning methods on the bond strength of industrial indirect composite blocks (ICs).

METHODS

Based on the PICOS strategy, the Medline via PubMed, Embase and Web of Science (ISI - Web of Knowledge) electronic databases were searched for peer-reviewed articles in both English and Chinese, with no publication year limit. In vitro studies evaluating the effects of surface conditioning on the bond strength of ICs were selected. The meta-analysis was conducted to calculate the mean difference between surface-conditioned ICs and unconditioned controls. Subgroup analysis was performed to evaluate the different surface conditioning methods, separately for polymer-infiltrated ceramic network (PICN) material and the ICs with dispersed fillers (ICDFs). Meta-analyses were performed with a random-effects model at a significance level of 0.05.

RESULTS AND SIGNIFICANCE

From 802 relevant studies, 25 were selected for full-text analysis. Nineteen studies were eligible for inclusion in this systematic review, whereas 9 studies were included in the meta-analysis. A manual search of the principal periodicals specific to the area resulted in no additional articles. The meta-analysis indicated a significant difference in bond strength between the surface-conditioned ICs and controls under both non-aged and aged conditions. The combination of mechanical and chemical conditioning yielded the highest bond strength of ICs. This meta-analysis suggests that chemical etching followed by a universal primer and alumina air abrasion followed by a silane coupling agent could be considered the best strategy for optimizing the bond strength of PICN materials and ICDFs under aged conditions, respectively.

Uniaxial/biaxial flexure strengths and elastic properties of resin-composite block materials for CAD/CAM

OBJECTIVE

Comparing strengths under different loading conditions provides useful information on the mechanical behaviour of restorative materials under multiaxial masticatory loading in the oral cavity. The aims of this study was to investigate the flexural strengths and the reliability of resin-composite blocks for CAD/CAM by uniaxial and biaxial flexure tests and to compare the elastic properties measured by different methods including digital image correlation (DIC).

METHODS

Four resin-composite blocks for CAD/CAM, namely, VE (Vita Enamic), LU (Lava Ultimate), MD (Mazic Duro), and CS (Cerasmart), were investigated. Beam specimens (4.0×1.4×18.0mm³) and disks (12-14mmϕ×1.5mm) were prepared to determine the uniaxial (three-point bending) and biaxial (ball-on-ring, BOR) flexural strengths and flexural moduli. A compression test (8×4×18mm³) with DIC analysis was utilized to measure the elastic modulus and Poisson's ratio. Data were analysed by a 2-parameter Weibull function and ANOVA with Scheffe's test.

RESULTS

The mean uniaxial and biaxial strengths and Weibull moduli of the specimen groups were as follows: uniaxial VE (140.1±7.0, 24.1), LU (159.1±6.3, 31.5), MD (144.9±13.3, 13.6), and CS (165.4±16.9, 11.2) and biaxial VE (153.6±10.4, 19.0), LU (231.0±29.3, 9.7), MD (148.9±23.8, 7.4), and CS (249.7±22.4, 13.8). Although the ranking of both sets of strength data remained unchanged, the strength reliability was significantly affected by the loading; the Weibull moduli of the specimens decreased when they were subjected to biaxial tests (except for that of CS). The elastic modulus values of the materials varied significantly under the different test loadings, although they were in the same order regardless of the test method: VE>>LU≈MD>CS. The DIC technique yielded elastic moduli that were in good agreement with those measured by the uniaxial flexure test.

SIGNIFICANCE

The flexural strength, reliability, and elastic modulus of resin-composite block materials differed with the uniaxial and biaxial flexural loading and the test method. The different behaviours under both loadings should be considered in the evaluation of the mechanical performance of those materials.