Computer-aided Design And Computer-aided Manufacturing Materials Research Articles

Impact of various aging treatments on the microhardness and surface roughness of CAD-CAM monolithic restorative materials.

Dental ceramics deteriorate as a result of thermal aging and exposure to acidic solutions, which change their microhardness and surface roughness. This study assessed the resistance of several computer-aided design and computer-aided manufacturing (CAD-CAM) restorative dental materials in terms of surface roughness and microhardness following exposure to acidic solutions and thermal aging. Five different monolithic CAD-CAM restorative materials, two leucite-reinforced glass ceramics (G-Ceram and CEREC Blocs), a zirconia-infiltrated lithium silicate (Celtra Duo), a resin nanoceramic (Grandio), and monolithic zirconia (inCoris TZI), were used to create 2-mm-thick rectangular specimens (n = 100). After being immersed in either acidic saliva (pH = 4.0) (ST) or gastric juice (pH = 1.2) (GT), each material was subjected to 10,000 cycles of thermal aging. The Vickers microhardness and average surface roughness of the specimens were assessed at baseline, following thermal aging and exposure to either gastric juice or acidic saliva. The surface properties were examined using an atomic force microscope. The Mann‒Whitney U test with Bonferroni correction and the Wilcoxon signed-rank test was used for statistical analysis (a = 0.05). The surface roughness of two leucite-reinforced glass ceramics (G-ceram and CEREC) significantly decreased with ST (p = 0.027 and p = 0.044). Only the CEREC was affected when the aging protocols were compared, and the ST group had a significant reduction in roughness (p = 0.009). The microhardness values significantly decreased after both aging protocols in all groups except for the ST subgroup of G-Ceram. Only inCoris was affected when the aging protocols were compared, and the GT group exhibited a significant reduction in microhardness (p = 0.002). The surface roughness of the tested materials was not affected by the GT. Only leucite ceramics exhibited a decrease in surface roughness in the ST stage. Both aging processes produced a significant decrease in the microhardness of the tested ceramics. Leucite-reinforced glass-ceramic materials may be advantageous for patients with gastroesophageal reflux disease and those with a diet high in acidic foods due to their lower values for changes in microhardness and surface roughness compared to those of other CAD-CAM materials.

Stainability and translucency of potassium aluminum sulfate applied computer-aided design and computer-aided manufacturing materials after coffee thermocycling.

The purpose of this in vitro study was to evaluate the effect of potassium aluminum sulfate (alum) application on the stainability and translucency of computer-aided design and computer-aided manufacturing (CAD-CAM) materials after coffee thermocycling (CTC). Disk-shaped specimens (Ø10 × 1 mm; N = 200) were fabricated by using additively (Crowntec [CT] and Varseo Smile Crown Plus [VS]) and subtractively manufactured (Brilliant Crios [RCR], CEREC Block [FC], and Vita Enamic [VE]) CAD-CAM materials and polished. All specimens were randomly divided into two groups as alum applied and control (n = 10). All specimens were then subjected to CTC (10,000 cycles at 5-55°C) and color coordinates were measured at each time interval. Color differences (ΔE00 ) and relative translucency parameters (RTPs) were calculated and the data were statistically analyzed (a = 0.05). Among tested time intervals, alum applied specimens had their lowest ΔE00 after alum application (p ≤ 0.006), except for FC (p = 0.177). In addition, alum applied RCR had lower ΔE00 values than its control specimens (p = 0.029). Alum applied specimens had their lowest RTP after CTC (p < 0.001) and alum application decreased the RTP of CT (p = 0.010). CTC reduced the RTP of all materials in control groups (p < 0.001). Alum applied CT had higher RTP than its control specimens (p = 0.049). Alum application's effect on color change varied depending on the material and alum mostly resulted in clinically acceptable changes in translucency. CTC led to unacceptable color and translucency changes based on previously reported threshold values. Optical properties of CAD-CAM materials and the sustainability of these properties over time is critical for longevity. Alum may improve the color stability of reinforced composite resin when subjected to long-term coffee consumption.

Effect of simulated gastric acid on aesthetical restorative CAD-CAM materials' microhardness and flexural strength.

Gastric acid, which is among erosive substances, gradually rises to the mouth in individuals with reflux and bulimia nervosa disorders, and this causes various effects on dental restorations. The objective of this study is in vitro investigation of gastric acid's effect on flexural strength and hardness on aesthetic restorative computer-aided design and computer-aided manufacturing (CAD-CAM) materials. For this study, four materials have been used, namely Enamic (Vita), Superfect Zir (Aidite) Zirconia, IPS e.max CAD (Ivoclar Vivadent), and Mark II (Vita). From these four different materials, 24 samples with 14 × 4 × 1 dimensions in rectangular prism form are used, which makes a total of 96 samples. One group was separated as the control group, while the rest was allowed to wait at 37°C, 5 ml gastric acid for 96 hours. Hardness value and flexural strengths were measured as pre-exposure and post-exposure to gastric acid. There is a statistically significant difference between the groups in terms of the amount of decrease in the mean hardness after exposure to gastric acid compared to pre-exposure values (p: 0,000; P < 0,05). There was no statistically significant difference between the groups in terms of the amount of decrease in the post-exposure average flexural strength compared to the pre-exposure value (p: 0.063; P > 0.05). There is a statistically significant difference between the groups in terms of the average flexural strength after exposure to the acid. According to the data obtained, it was concluded that exposure to gastric acid affects the hardness and flexural strength properties of dental restorative ceramic materials.

Repair Bond Strength of Two Shadeless Resin Composites Bonded to Various CAD-CAM Substrates with Different Surface Treatments

This study compared the repair bond strength values of two single-shade composite resins bonded to different computer-aided design and computer-aided manufacturing (CAD-CAM) substrates with different surface treatments. A total of 80 slice-shaped specimens were fabricated using two CAD-CAM materials: Lava Ultimate and VitaEnamic. The substrates were thermocycled and then, based on the surface treatment, each substrate material was subdivided into four groups: the air abrasion group (APA), the hydrofluoric-acid-etched group (HF) and two silicon carbide ground groups (SiCr). All of the groups received silane followed by Single Bond Universal Adhesive application prior to being repaired with a resin composite of a smaller disc shape. All the specimens were thermocycled prior to shear bond strength testing and subsequent failure analyses. Statistical analyses were conducted, and the level of statistical significance was set at 0.05. A comparison of the mean values showed a highly statistically significant difference among the eight groups. The highest value of mean shear bond strength was associated with Lava Ultimate substrates repaired using the Charisma Diamond ONE composite after APA surface treatment (36.7 ± 1.99). Meanwhile, the lowest value was recorded for the Vita Enamic group repaired using the OMNICHROMA composite after SiCr surface treatment (17.8 ± 1.6). The failure analysis revealed that cohesive failure in the substrate was the most predominant. Within the limitations of this study, Charisma Diamond ONE showed better bond strength values compared to Omnichroma. Meanwhile, APA is recommended for improved bond strength in repairs of Lava Ultimate restorations.

Evaluation of marginal and internal fit of single crowns manufactured with an analog workflow and three CAD-CAM systems: A prospective clinical study.

This prospective clinical study evaluated and compared the marginal and internal fit of crowns fabricated with an analog workflow and three different computer-aided design and computer-aided manufacturing (CAD-CAM) systems. Twenty-five participants in need of a single complete-coverage molar or premolar crown were recruited in the study. Twenty-two completed the study, and three participants dropped out. Teeth were prepared according to a standardized protocol by one operator. For each participant, one final impression was made with polyether material (PP) and three intraoral scanners: CEREC Omnicam (C), Planmeca Planscan (PM), and True Definition (TR). For the PP group, crowns were fabricated with a pressable lithium disilicate ceramic, whereas for the other three groups (C, PM, and TR), crowns were designed and milled with dedicated CAD-CAM systems and materials. Marginal (vertical and horizontal) and internal discrepancies between the crowns and tooth preparation were measured at various locations with digital superimposition software. Data was analyzed for normality with Kolmogorov-Smirnov and Shapiro-Wilk tests and then compared with one-way ANOVA and Kruskal-Wallis tests. Mean vertical marginal gap values were 92.18±141.41μm (PP), 150.12±138.06μm (C), 129.07±109.96μm (PM), and 135.09±112.03μm (TR). PP group had statistically significantly smaller vertical marginal discrepancy (p=0.001) than all other groups, whereas no significant difference was detected among the three CAD-CAM systems (C, PM, and TR). Horizontal marginal discrepancies were 104.93±111.96μm (PP), 89.49±119.66μm (C), 113.36±128.49μm (PM), and 136.39±142.52μm (TR). A significant difference was detected only between C and TR (p<0.0001). Values for the internal fit were 128.40±49.31μm (PP), 190.70±69.79μm (C), 146.30±57.70μm (PM), and 168.20±86.67μm (TR). The PP group had a statistically significant smaller internal discrepancy than C (p<0.0001) and TR groups (p=0.001), whereas no significant difference was found compared to the PM group. Posterior crowns fabricated with CAD-CAM systems showed vertical margin discrepancy greater than 120μm. Only crowns fabricated with the conventional methodology had vertical margins below 100μm. Horizontal marginal discrepancy was different among all groups, and only CEREC CAD-CAM was below 100μm. Internal discrepancy was less for crowns fabricated with an analog workflow.

Long-Term Effect of Nanosized Boric Acid Powder on Optical Properties of Polymer Infiltrated Ceramic CAD-CAM Material

The current study investigated the effect of boric acid (H3BO3) nanosized powder on the optical properties of a Computer-Aided Design and Computer-Aided Manufacturing (CAD-CAM) polymer infiltrated ceramic material. Specimens (n = 60), (15 × 8 × 1.5 mm3) were fabricated from a polymer infiltrated ceramic network (PINC) (Vita Enamic, Vita Zahnfabrik, VITA-shade scale A2). Boric acid (B) nano powder was applied to Vita Enamic in half of the specimens (n = 30), while the other half was left untreated (NB) (n = 30). Aging for all specimens was performed for 5 h at 134 °C. Color coordinates (L*, a*, and b*) before and after aging were measured to calculate the color change (ΔE00) and the translucency parameter (TP) within and between the B and NB groups. One-way ANOVA was used to analyze the effect of boric acid on all color parameters (α = 0.05). Only L* increased in B after aging (p &lt; 0.001). L* and b* significantly changed after aging in NB (p &lt; 0.001). Boric acid application affected the color change within the ceramic after aging (p &lt; 0.001). The mean color change (ΔE00) in B after aging was significantly smaller than the color change in NB after aging (p &lt; 0.001). The color difference between B and NB increased after aging (p &lt; 0.001). No significant effect of aging was found on TP of B (p = 0.143). The TP of NB significantly decreased after aging (p &lt; 0.001). The use of boric acid provided color stability and translucency on aged tested material.

Effect of virtual cement space and restorative materials on the adaptation of CAD-CAM endocrowns.

This study aimed to evaluate the effect of virtual cement space and restorative materials on the fit of computer-aided design and computer-aided manufacturing (CAD-CAM) endocrowns. A mandibular first molar tooth model received a butt joint margin endocrown preparation with a 2-mm occlusal thickness. Then, using a 3D-printing system, 120 copies of this prepared die were printed and assigned equally to three groups with different cement space settings (30, 60, and 120μm) during the chairside CAD design. In the milling process, CAD-based models with a particular space setting were subdivided into four groups (n = 10) and fabricated from different CAD-CAM materials: Vita Suprinity (VS), Celtra Duo (CD), Lava Ultimate (LU), and Grandio blocs (GR). Finally, the endocrowns were stabilized over their corresponding models with siloxane and subjected to micro-computed tomography to measure the fit. The cement space that was predesigned at 30μm generated the largest marginal discrepancy (from 144.68 ± 22.43μm to 174.36 ± 22.78μm), which was significantly different from those at 60μm and 120μm (p < 0.001). The combination of VS or CD with a pre-setting cement space of 60μm and the combination of LU or GR with a cement space of 120μm showed better agreement between the predesigned and actual measured marginal gap widths. For internal adaptation, only the cement space set to 30μm exceeded the clinically acceptable threshold (200μm). The setting of the cement space and restorative material significantly affected the marginal adaptation of CAD-CAM endocrown restorations. Considering the discrepancy between design and reality, different virtual cement spaces should be applied to ceramic and resin composite materials.

Trueness of crowns fabricated by using additively and subtractively manufactured resin-based CAD-CAM materials

Statement of problemAdvancements in digital dental technologies have enabled the use of different resin-based materials that can be fabricated either additively or subtractively. However, knowledge on the fabrication trueness of these materials is scarce. PurposeThe purpose of this in vitro study was to investigate the trueness of crowns fabricated by using different resin-based computer-aided design and computer-aided manufacturing (CAD-CAM) materials. Material and methodsA complete crown for a mandibular right first molar with a 30-μm cement space was designed in standard tessellation language (STL) format. This master STL (MC-STL) was used to fabricate 40 complete crowns with 4 different resin-based CAD-CAM materials and either additive (Crowntec [MS]) or subtractive techniques (Brilliant Crios [BC], breCAM.monoCOM [PMMA], and G-CAM [GR]; n=10). All crowns were digitized with an intraoral scanner (CEREC Primescan SW 5.2) to generate their STL files (TC-STLs). MC-STL and TC-STLs were transferred into a 3-dimensional analysis software program (Medit Link v2.4.4), and a trueness (overall, external, occlusal, intaglio occlusal, and marginal) analysis was performed by using the root mean square (RMS) method. The Kruskal-Wallis and Dunn tests were performed to analyze data (α=.05). ResultsThe test groups had significantly different deviations on all surfaces (P≤.001). MS crowns had higher overall (P≤.007) and external surface (P≤.001) deviations than GR and PMMA crowns, while the differences between GR and PMMA crowns were not significant (P≥.441). BC crowns had higher external surface deviations than GR crowns (P=.005), higher occlusal deviations than GR and MS crowns (P≤.007), and higher intaglio occlusal deviations than GR and MS crowns (P≤.009). However, BC crowns had lower marginal deviations than MS and GR crowns (P≤.018). ConclusionsThe brand of resin-based CAD-CAM materials affected the trueness of crowns. Additively manufactured crowns (MS) mostly had lower overall and external surface trueness than the other groups. Nevertheless, the deviation values of occlusal, intaglio occlusal, and marginal trueness were generally small; thus, the effect of the tested materials on clinical crown fit may be negligible.

Effect of thickness and CAD-CAM material on fatigue resistance of endodontically treated molars restored with occlusal veneers.

To evaluate the influence of the thickness and type of computer-aided design and computer-aided manufacturing (CAD-CAM) material on the fatigue resistance and failure mode of endodontically treated teeth (ETT) restored with occlusal veneers (OV). Seventy-five (N = 75) ETT were restored with Herculite XRV in the endodontic access. Five experimental groups (n = 15) were tested. Four groups had two different thicknesses (0.6-0.7mm or 1.4-1.6mm) and two different CAD-CAM materials: zirconia-reinforced lithium-silicate (LS/Celtra Duo) and composite resin (RC/Cerasmart). The fifth group (control) did not have occlusal veneers. All the specimens were subjected to accelerated fatigue (5Hz frequency) with an occlusal load increasing up to 1800 N and 131,000 cycles. The number of cycles was recorded when the machine stopped or at the completion of the test. Fatigue resistance was analyzed using the Kaplan-Meier survival test (95% significance level, log-rank post hoc pairwise comparisons). The samples were categorized according to failure mode. The CAD-CAM materials were examined through scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). No differences were found between the thicknesses, regardless of the type of the CAD-CAM material. The thick LS OV outperformed the RC and control groups. The thin RC OV and control groups showed a higher percentage of repairable and possibly repairable failures than the other groups. LS was more homogeneous under SEM, and the EDS analysis detected Si and Zr, but not Li. A larger thickness did not improve the resistance of the CAD-CAM materials. Thick LS showed a higher cumulative survival rate to fatigue than the RC and control groups. The direct composite alone (control) survived similarly to the experimental groups, except for the thick LS.

Evaluation of the fracture resistance and failure types of different CAD-CAM ceramic crowns supported by angled titanium abutments.

To evaluate the fatigue resistance of computer-aided design and computer-aided manufacturing (CAD-CAM) single-ceramic crowns which were applied on angled implant abutments after thermomechanical aging. Titanium abutments (N = 72, MODE Medical Dental Implant, Turkey) with three different angles (0˚, 15°, and 25°) were restored using different materials (monolithic zirconia [Zir], lithium silicate ceramic reinforced by zirconia [VS], and hybrid ceramic [VE]). Crowns in the maxillary first premolar form were cemented to abutments using resin cement (Panavia 2.0 Introkit). Dynamic loading and thermomechanical aging were applied to the specimens (120,000 cycles, 49N, 5-55°C). Fracture resistance values were measured in the universal test machine and fracture types were determined. Two-way ANOVA and Tukey test were used for statistical analysis (Jamovi version 2.3.5). Both the abutment angle and the type of material had a significant effect on fracture resistance (F = 3.295, p<0.05). The highest fracture resistance was obtained in Group 0˚-Zir, and the lowest fracture resistance was obtained in Group 15˚-VE. Fracture resistance showed significant differences between Group 0˚ and Group 15˚ for the Zir and VE materials, and between Group 0˚ and Group 25˚ for VS (p<0.05); no statistical significance was determined between the other groups (p>0.05). When failure types were evaluated, they were seen to be full or partial crown fractures, and abutment deformation was found in some samples. Monolithic crowns may be preferred on angled abutments. The fracture resistance of CAD-CAM materials decreases as the angle of abutments increases. Monolithic zirconia has higher fracture resistance than other materials.

Fracture strength, pull-out bond strength, and volume of luting agent of tooth-colored CAD-CAM post-and-cores

Statement of problemLittle is known about the fracture strength, retention, and adaptation of post-and-cores fabricated with novel tooth-colored materials by computer-aided design and computer-aided manufacturing (CAD-CAM). PurposeThe purpose of this in vitro study was to investigate the fracture strength, pull-out bond strength (POBS), and volume of luting agent of endodontically treated premolars restored with post-and-cores milled from different CAD-CAM materials. Material and methodsPost spaces were prepared in 80 human premolars in which post-and-cores fabricated with polyetheretherketone (PK; Ceramill PEEK), nanohybrid composite resin (BB; Brava Block), polymer-infiltrated ceramic (EN; VITA Enamic), and fiber-reinforced epoxy resin (GF; Fiber Cad Post & Core) CAD-CAM materials were luted (n=20). All specimens were subjected to thermal aging (3000 cycles at 5 °C and 55 °C with a 20-second dwell time). Half of the specimens were subjected to mechanical fatigue (250 000 cycles at 5 Hz) before fracture strength testing, while the other half was submitted to POBS testing and volume of luting agent measurement. Fracture strength data were analyzed by 1-way ANOVA, while POBS and volume of luting agent data were submitted to Kruskal-Wallis followed by the Bonferroni-Dunn multiple comparison tests. The correlation between POBS and the volume of luting agent was determined by the Spearman test (α=.05). ResultsPOBS of GF was significantly higher than that for PK (P<.001); however, failure load (P=.160) and volume of luting agent (P=.390) values did not differ. EN showed the highest percentage of catastrophic failures (20%), while PK exhibited only core deformations. POBS and cement film volume were not significantly correlated (P>.05). ConclusionsDifferent CAD-CAM materials did not influence the fracture strength and volume of luting agent of post-and-cores. Post-and-cores made with PEEK blocks showed lower bond strength to intracanal dentin than those made with fiber-reinforced epoxy resin blocks. No significant correlation was found between bond strength and the volume of luting agent.

Elution of Monomers From CAD-CAM Materials and Conventional Resin Composite in Distilled Water and Artificial Saliva.

The purpose of this study was to evaluate the leaching pattern of different types of polymer computer-aided design and computer-aided manufacturing (CAD-CAM) materials with a conventional resin composite. Specimens of three representatives by type of polymer CAD-CAM blocks and one conventional resin composite were suspended using a silk thread in distilled water and artificial saliva. After one day, seven days, 14 days, 30 days, and 60 days, the analysis of the eluates for the detection of bisphenol A (BPA), urethane dimethacrylate (UDMA), triethylene glycol dimethacrylate (TEGDMA) and bisphenol A-glycidyl dimethacrylate (Bis-GMA) was quantified by utilizing high-performance liquid chromatography (HPLC). TEGDMA was the main eluted monomer for the polymer CAD-CAM materials for both solutions. However, there was a decreasing pattern throughout the tested period. On the contrary, there was a constant release of monomers from the conventional resin composite. Bisphenol-A was released only by the conventional resin composite and in both solutions chosen. Different types of polymer CAD-CAM materials release minimal or no monomers compared to the conventional resin composite material. The methods of fabrication of polymer CAD-CAM materials produces better properties than the conventional resin composite with a dramatic decrease of monomer elution.

Effect of firing cycle and aging on long-term chemical degradation of monolithic CAD-CAM ceramics

Statement of problemPrevious studies have shown the susceptibility of dental ceramics to degradation when subjected to certain media. However, knowledge on the effect of repeated firings and thermocycling on the ion elution of computer-aided design and computer-aided manufacturing (CAD-CAM) ceramics is lacking. PurposeThe purpose of this in vitro study was to compare the effect of repeated firings on the ion elution of CAD-CAM materials before and after thermocycling. Material and methodsBar-shaped specimens were prepared from 4 different CAD-CAM materials (monolithic zirconia [Z], zirconia-reinforced lithium silicate glass-ceramic [S], lithium disilicate glass-ceramic [EX], and leucite-reinforced glass-ceramic [E]) and divided into 3 groups according to the number of repeated glaze firings (1 firing [1F], 2 firings [2F], and 4 firings [4F]). Specimens were placed into deionized water (pH 7.4) and stored at 37 °C for 168 hours. Inductively coupled plasma-optic emission spectrophotometry (ICP-OES) was used to measure the baseline values of the eluted ions in immersion. The specimens were then subjected to thermocycling. Then, surface roughness (Ra) and ion elution values were measured. The Kruskal-Wallis and Mann-Whitney U tests were used to analyze the ion elution data before and after thermocycling, and the effect of thermocycling on ion elution was assessed by the Wilcoxon signed rank test. Ra data were analyzed with 2-way analysis of variance (ANOVA) and the Tukey honestly significant difference tests (α=.05). ResultsElution of some ions varied depending on the material-firing pair before (Al, As, B, Ba, Cr, Cu, Li, Mg, Na, P, and Zn) and after (Al, As, B, Ba, Be, Ca, Cd, Co, Cr, Cu, K, Li, Mg, Na, P, Y, and Zn) thermocycling. Before thermocycling, all firing groups within each material showed a similar number of significantly higher eluted ions. After thermocycling, the number of significantly higher eluted ions decreased in all materials, except for EX. The effect of thermocycling on the ion elution of the 1F group of Z (Al, Be, Ca, Cd, Co, Cr, Cu, K, Li, P, Y, and Zn), S (As, Be, Cd, Co, Cr, K, P, and Y), EX (B, Cu, and P), and E (B and Ba); 2F group of Z (Al, Be, Ca, Co, Cr, Cu, K, Li, P, and Y), S (Be, Cd, Co, K, Li, and Y), EX (P), and E (P); 4F group of Z (Al, As, Ba, Be, Ca, Cd, Co, Cr, Cu, K, Li, P, and Y), S (Al, Be, Cd, Co, Cr, Li, Mg, and Y), EX (Be, Ca, Cd, Co, K, Y, and Zn), and E (Ca and P) was nonsignificant (P≥.051). The interaction between material and repeated firings (P<.001) had a significant effect on Ra. For 1F groups, E showed the highest Ra (P≤.003), while Z had higher Ra than S (P=.009). For 2F groups, Z had higher Ra than S (P=.01). The differences among 4F groups were nonsignificant (P≥.677). An increased number of repeated firings (2F and 4F) decreased the Ra of E (P<.001). ConclusionsThe effect of repeated firings and thermocycling on the chemical stability of the tested CAD-CAM materials varied. No clear trend was observed on the elution of different ions within material-firing pairs before thermocycling. However, thermocycling increased the number of significantly higher eluted ions for EX. The effect of thermocycling on the ion elution of materials varied depending on ions. Repeated firings decreased the surface roughness of E.

New generation CAD-CAM materials for implant-supported definitive frameworks fabricated by using subtractive technologies.

Innovations in digital manufacturing enabled the fabrication of implant-supported fixed dental prostheses (ISFDPs) in a wide variety of recently introduced materials. Computer-aided design and computer-aided manufacturing (CAD-CAM) milling allows the fabrication of ISFDPs with high accuracy by reducing the fabrication steps of large-span frameworks. The longevity of ISFDPs depends on the overall mechanical properties of the framework material including its fit, and the physical properties of the veneering material and its bond with the framework. This comprehensive review summarizes the recent information on millable CAD-CAM framework materials such as pre-sintered soft alloys, fiber-reinforced composite resins, PEEK, and PEKK in high-performance polymer family, and 4Y-TZP. Even though promising results have been obtained with the use of new generation millable CAD-CAM materials for ISFDPs, clinical studies are lacking and future research should focus on the overall performance of these millable materials in both static and dynamic conditions.

Different surface treatment strategies on etchable CAD-CAM materials: Part II—Effect on the bond strength

Statement of problemBonding to recently launched polymer-based computer-aided design and computer-aided manufacturing (CAD-CAM) materials has been challenging. Evidence regarding etching strategies for dual-phase CAD-CAM materials is sparse, but adequate bonding is crucial for the clinical success and longevity of a restoration. PurposeThe purpose of this 2-part in vitro study was to evaluate and compare the effect of surface treatment strategies on the microshear bond strength and work of adhesion of polymer-based and ceramic materials. In addition, chemical elements present on the surface and the interface morphology after using those strategies were also assessed. Materials and methodsTwo CAD-CAM polymer and 1 CAD-CAM ceramic materials were selected for this in vitro study. The materials were subjected to different surface treatment strategies, including airborne-particle abrasion and the application of 9% hydrofluoric acid. Specimens were submitted to microshear bond strength before and after thermocycling, and the failure mode was classified. The work of adhesion was calculated based on the water-to-air surface tension of 72.8 mN.m-1 and the Young- Dupré equation. The surfaces were submitted to energy-dispersive X-ray spectroscopy, and the interfaces were analyzed using a scanning electron microscope. Data were subjected to 2-way ANOVA and the Tukey post hoc test (α=.05). ResultsThe highest microshear bond strength means were observed for the polymer-based materials when hydrofluoric acid or airborne-particle abrasion was applied. The 3 materials tested showed a decrease in microshear bond strength after thermocycling, except for applying airborne-particle abrasion to 1 of the polymer-based material tested. The ceramic material tested showed a high microshear bond strength with the application of airborne-particle abrasion and hydrofluoric acid combined. The work of adhesion varied across the materials and presented high means when hydrofluoric acid was used. ConclusionsA combination of airborne-particle abrasion plus hydrofluoric acid should be considered for polymer-based or feldspathic ceramic CAD-CAM materials. In this in vitro study, both etching procedures combined produced higher bonding values for all materials tested.

Different surface treatment strategies on etchable CAD-CAM materials: Part 1—Effect on the surface morphology

Statement of problemPolymer-based computer-aided design and computer-aided manufacturing (CAD-CAM) materials have either a high content of ceramic filler particles or a ceramic network structure. Proper etching of these materials is challenging. Therefore, it is relevant to assess different surface etching strategies and morphological alterations as a result of these techniques. PurposeThe purpose of this 2-part in vitro study was to evaluate different etching strategies on the surface roughness and its relationship to the surface contact angle with a subsequent morphological characterization of different CAD-CAM materials. Material and methodsTwo CAD-CAM polymer-based materials and 1 CAD-CAM ceramic material were selected for this study. The materials were treated with different strategies, including a combination of airborne-particle abrasion and an application of 9% hydrofluoric acid etching. After the surface treatment, roughness measurements (Sa) were assessed by using an optical profilometer on an area of 1.47 mm2. Subsequently, the contact angle on the surface was examined by means of the sessile drop technique and an optical contact angle meter. The data were analyzed by using a 2-way analysis of variance, the post hoc Tukey test (α=.05), and the Pearson correlation coefficient. ResultsThe 3 materials tested showed an increase in surface roughness when treated with surface airborne-particle abrasion. However, the materials with polymer in their composition concomitantly increased the contact angle. More hydrophilic surfaces were observed when hydrofluoric acid was applied, regardless of the composition of the materials. The surface roughness presented a strong positive linear tendency in the surface treatments used. ConclusionsThe application of airborne-particle abrasion on the surface of the polymer-based CAD-CAM materials increased the roughness and contact angle. However, the application of acid etching after the airborne-particle abrasion decreased the contact angle for polymer-based CAD-CAM materials, resulting in considerable enhancement of the surface quality for proper bonding.

Characterization of occlusal splint materials: CAD-CAM versus conventional resins

AimThe aim of this in vitro study was to assess the mechanical properties of five commercially available subtractive computer-aided design and computer-aided manufacturing (CAD-CAM) milled splint materials, as well as to compare them with conventional heat-polymerized and autopolymerizing resins used in the construction of conventional splints. Material and methodsFive CAD-CAM milled (ProArt CAD Splint, Therapon Transpa, Temp Premium Flexible Transpa, Cast, and Aqua), one autopolymerizing (Palapress), and one heat-polymerized (Paladon 65) resin materials were evaluated. Flexural strength, E-modulus, Vickers hardness, fracture toughness, fracture work, water sorption, and water solubility were measured. Samples were evaluated after dry and water storage for 30 days at 37 °C. Data were collected and statistically analyzed. ResultsUnder both storage circumstances, the flexural strength values of Paladon 65, Therapon Transpa, Temp Premium Flexible Transpa, and Aqua were statistically non-significant (P=0.055). The polycarbonate-based CAD-CAM material Temp Premium Flexible Transpa had the highest statistically significant values of the fracture toughness and fracture work (P<0.001). Moreover, it exhibited the lowest percentages of water sorption and water solubility among the investigated materials (P<0.001). All of the CAD-CAM materials exhibited dry elastic moduli greater than Palapress and lower than Paladon 65. One of the CAD-CAM materials, Cast, had the highest dry Vickers hardness value, which was non-significant when compared to Therapon Transpa (P=0.762). ConclusionCAD-CAM polycarbonate-based splint materials exhibit higher fracture toughness and fracture work as well as lower water sorption and solubility than polymethyl methacrylate-based ones. The mechanical characteristics of the assessed CAD-CAM milled splint materials were not typically superior to those of the conventional heat-polymerized resin. However, some of them outperformed the autopolymerizing acrylic resin in terms of flexural strength, surface microhardness, water sorption, and water solubility.

Effect of surface treatments on wear and surface properties of different CAD-CAM materials and their enamel antagonists

Statement of problemWhich surface treatment provides optimal surface roughness, microhardness, and wear behavior for computer-aided design and computer-aided manufacturing (CAD-CAM) materials and their enamel antagonists is unclear. PurposeThe purpose of this in vitro study was to evaluate the effect of surface treatment on the surface roughness, microhardness, and 2-body wear of different CAD-CAM materials and their enamel antagonists. Material and methodsMonolithic zirconia, polymer-infiltrated ceramic network, lithium disilicate, leucite-reinforced ceramic, zirconia-reinforced lithium silicate, and feldspathic ceramic specimens were sliced into 2-mm-thick rectangular plates and divided into polished or glazed subgroups (n=6). After surface roughness and microhardness measurements, the specimens were loaded at 49 N for 250 000 cycles and simultaneously thermocycled (5 °C and 55 °C). All specimens were scanned before and after the wear test by using a scanner. The volumetric loss and wear depth of the materials and the volumetric and height loss of the enamel were calculated, and scanning electron microscope images of the specimens were made. Multiple 2-way ANOVAs and Tukey honestly significant difference tests were used to assess the effect of material and surface treatment on surface roughness, microhardness, and wear behavior of materials and enamel (α=.05). ResultsMaterial and surface treatment interactions affected the surface roughness (P<.001), microhardness (P<.001), volumetric loss of materials (P=.044), and height loss of enamel (P<.001). ConclusionsPolishing resulted in higher surface roughness and microhardness than glazing. Volumetric loss depended on the material, which affected the height loss of the antagonists. Glazing and polishing had similar effects on the volumetric loss of materials and antagonists. No correlation was found between the wear of materials and the antagonists, nor between the surface roughness of materials and the volumetric loss of materials or antagonists.

In vitro evaluation of material dependent force damping behavior of implant-supported restorations using different CAD-CAM materials and luting conditions

Statement of problemAlthough force-damping behavior that matches natural teeth may be unobtainable, an optimal combination of crown material and luting agent might have a beneficial effect on the force absorption capacity of implant-supported restorations. However, the force-absorbing behavior of various restorative materials has not yet been satisfactorily investigated. PurposeThe purpose of this in vitro study was to evaluate the material dependent force-damping behavior of implant-supported crowns fabricated from different computer-aided design and computer-aided manufacturing (CAD-CAM) materials luted to implant abutments under different conditions. Material and methodsTitanium inserts (N=84) were screwed to implant analogs, scanned to design zirconia abutments, and divided into 4 groups to receive CAD-CAM fabricated crowns in 4 materials: zirconia, polyetheretherketone (PEEK), polymer-infiltrated ceramics (VITA ENAMIC), and lithium disilicate (e.max). The crowns were subdivided as per the luting agent: none, interim cement, and adhesive resin cement. Measurements were performed by loading specimens in a universal testing machine with an increasing force and measuring the resulting force with a digital forcemeter, followed by image processing and data acquisition. Two-way multivariate analysis of variance (MANOVA) was used to assess all interactions with multiple pairwise comparisons (α=.05). ResultsThe curve progression of the applied and resulting forces varied significantly among the investigated materials, resulting in differently inclined slopes for each material (P<.001). With no cementation, the mean slope values of the resulting force curves ranged from 77.5 ±0.03 degrees for zirconia, followed by 71.8 ±0.03 degrees for lithium disilicate, 56.2 ±0.1 degrees for polymer-infiltrated ceramics, and 51.1 ±0.01 degrees for polyetheretherketone. With interim cementation, the mean slope values ranged from 75.4 ±0.01 degrees for zirconia, followed by 70.05 ±0.02 degrees for lithium disilicate, 56.1 ±0.02 degrees for polymer-infiltrated ceramics, and 52.2 ±0.1 degrees for polyetheretherketone. As with adhesive cementation, curve slopes ranged from 73.2 ±0.02 degrees for zirconia, followed by 70.5 ±0.2 degrees for lithium disilicate, 55.9 ±0.04 degrees for polymer-infiltrated ceramics, and 52.3 ±0.1 degrees for polyetheretherketone. Slope loss was significant after the cementation of zirconia and lithium disilicate crowns but less significant for polymer-infiltrated ceramics and polyetheretherketone. ConclusionsForce damping is generally material dependent, yet implant-supported crowns fabricated from resilient materials such as polymer-infiltrated ceramics and PEEK show better force absorption than rigid materials such as zirconia and lithium disilicate ceramics. Furthermore, cementation of rigid materials significantly increased slope loss, indicating enhancement in their force-damping behavior, whereas less-rigid materials benefit less from cementation. Further studies are essential to investigate the effect of prosthetic materials on the stress distribution to the peri-implant bone in the crown-abutment-implant complex.

Effect of mouth rinses on optical properties of CAD-CAM materials used for laminate veneers and crowns.

The purpose of this study was to investigate the effect of mouth rinses on the color and translucency of three computer-aided design and computer-aided manufacturing (CAD-CAM) restorative materials in laminate veneer and crown thicknesses. Specimens from two different 5Y-TZP zirconia (InCoris TZI (IT), and Zirkonzahn (ZH)) and lithium disilicate (IPS e.max CAD [IC]) in two different thicknesses (0.7 mm for laminate veneer, and 1.5 mm for crown) were sectioned. All specimens were colored with an A2-shade liquid, and the baseline color values were recorded according to the CIELab system with a spectrophotometer. Each group was divided into two subgroups (n=15) according to the immersion solution: two different mouth rinses, KL (Klorhex), and LI (Listerine, cool mint) for 180 hours. The color coordinates (L*, a*, b*) of the specimens were measured before and after immersion in a mouth rinse, and TP and ΔE00 color differences were calculated by using the CIEDE2000 color difference formula. A 3-way ANOVA, Bonferroni test, and 1-sample t tests were used to analyze the data (α=0.05). The 3-way ANOVA revealed a significant interaction of material, thickness, and mouth rinse for translucency parameter and color difference (ΔE00 ) data (p < 0.001). TP decreased for both zirconia materials in laminate veneer thickness when immersed in LI mouth rinse (p < 0.05). No difference was found among the TP mean values of three materials in crown thickness after immersed in mouth rinses (p > 0.826). Both zirconia materials immersed in LI showed greater discoloration than after immersed in KL (p < 0.05). A significant difference was found in color change values among three materials for the laminate veneer thickness after immersed in LI (p < 0.001). However, all color difference values were within the clinical acceptability threshold, except for when ZH in laminate veneer thickness was immersed in LI. The color change of ZH zirconia with LI mouth rinse in laminate veneer thickness was high. For both zirconia ceramics, translucency decreased and the color was less stable in laminate veneer thickness after immersed in LI compared to the crown thickness. The results of this in vitro study suggest that long-term use of alcohol-containing mouth rinse may alter the optical properties of tested CAD-CAM materials in tested laminate veneer thickness. For color stability with the long term use of tested mouth rinses, lithium disilicate may be preferred for both types of restorations.