Surface Evaluation of Milled Chairside CAD/CAM Materials Based on Manufacturing Speed.

AIM: The aim is to record the surface roughness of monolithic chairside CAD/CAM zirconia materials to evaluate the influence of milling speed on the ability to achieve a clinically desirable surface. The null hypothesis is that there is no significant difference in the surface roughness of different zirconia materials based on the speed of subtractive milling. MATERIALS AND METHODS: All test samples were milled from four different monolithic CAD/CAM zirconia blocks including CEREC Zirconia (Dentsply Sirona), CEREC Zirconia+ (Dentsply Sirona), CEREC MTL Zirconia (Dentsply Sirona), and Katana Zirconia (Kuraray Noritake). Four different dry milling speeds, Super Fast/Good, Super Fast/Very Good, Fast, and Fine were used to dry mill the specimens in a CEREC Primemill (Dentsply Sirona). A 3D measuring laser microscope (OLS4100 LEXT by Olympus) was used to measure surface roughness. RESULTS: An Analysis of Variance (ANOVA) was used to analyze the surface roughness data for each material and milling speed. There was a significant difference for milling speed (p < 0.05) but not between zirconia materials (p > 0.05). CONCLUSION: Based on the limitations of this study, the milling speed influenced the surface roughness of dry milled and sintered zirconia with slower speeds resulting in smoother surfaces. The largest improvement in surface roughness occurred between Super Fast and Fast milling with a smaller incremental improvement in surface roughness with Fine milling for the Primemill. All recorded surface roughness values are within the expected range of values to be able to efficiently hand polish a clinically acceptable surface finish.

Virtual clinic: Applying technology to expand dental school walls.

Dental education traditionally requires the use of dedicated fixed preclinic facilities to provide clinically relevant experiences to support the development of dexterity, critical thinking, and self-assessment skills that are essential for excellent patient care. As a result of the social distancing guidelines instituted at the height of the COVID pandemic, dental education was severely affected when education pivoted to remote instruction and had significant restrictions on in-person training. This study evaluated a novel application of modern technology to allow students to perform clinically relevant hands-on exercises away from dental school and, most importantly, receive feedback on their performance as an aid in their development. Student surveys and a comparison of pre- and post-COVID grades were used to evaluate the effectiveness of the virtual clinic to support remote dental education.

Keys to Predictable Digital Impressions.

Conventional impressions are the benchmark for any new replication technique due to the demonstrated accuracy of PVS and polyether impression materials.1 However, it is well known that throughout the impression process there are potential risks to final accuracy, including setting of the impression material, removal of the impression, and fabrication of the stone model.2-4 Despite the documented accuracy of PVS and polyether impressions, studies have repeatedly shown that most impressions sent to dental laboratories have some sort of deficiency. One study evaluated 193 FPD impressions made by 41 dentists immediately after they arrived at 11 dental laboratories and reported that 50.7 percent of all the impressions had voids or tears in the finish line area, 40.4 percent had air bubbles at the margin line, and 26.9 percent had both.5 Thus, although impression material has documented accuracy, making an accurate impression involves more than just the precision of the material.

Tooth-cusp preservation with lithium disilicate onlay restorations: A fatigue resistance study.

OBJECTIVES: This study examined the in vitro fatigue resistance of maxillary premolars with 2 mm or 3 mm preserved cusp thicknesses restored with lithium disilicate onlays. MATERIALS AND METHODS: Premolars(N = 48) were divided into six groups. Onlays for groups 1 to 4 preserved a 3 mm functional (G1), 2 mm functional (G2), 3 mm nonfunctional (G3), or 2 mm nonfunctional (G4) buccal-lingual cusp width. Onlays for group 5 (G5, control) replaced both cusps. Group 6 (G6) samples were identical to G1 with added retentive boxes. Lithium disilicate onlays were exposed to thermocycling (10 000 cycles, 5°C-55°C, 30s/cycle) and mechanical loading (1.2 million cycles at 1.4 Hz and 70 N). All samples were examined for onlay debonding or cusp or onlay fracture. RESULTS: Failure rates were 75%(G1), 0.0%(G2), 12.5%(G3), 0.0%(G4), 0.0%(G5), and 0.0%(G6). The difference in percent failure between the groups preserving the functional cusps (37.5%) and the groups preserving the nonfunctional cusps (6.3%) was statistically significant (P = .04; 95%CI:2.11-55.66). No cusp or restoration fractures were observed; all failures were due to debonding of the restoration. CONCLUSION: Teeth with thin remaining cusps that were restored with bonded lithium disilicate onlay restorations were not prone to fracture. Retentive preparation features that physically eliminated lateral displacement prevented onlay debonding even though the ceramic-enamel margin was directly at the occlusal contact. CLINICAL SIGNIFICANCE: The use of adhesively retained lithium disilicate ceramic onlays may be a viable alternative to full coverage restorations and may challenge traditionally accepted principals related to preparation resistance and retention form of ceramic partial coverage restorations.

Surface Evaluation of Resilient CAD/CAM ceramics after Contouring and Polishing.

OBJECTIVE: This in-vitro study measured the differences in surface roughness for computer assisted design/computer assisted manufacturing (CAD/CAM) resilient ceramic and CAD/CAM composite materials. MATERIALS AND METHODS: The materials included Lava Ultimate (3 M), Cerasmart (GC America), Vita Enamic (Vita Zahnfabrik), and Brilliant Crios (Coltene). One calibrated operator polished each material with three polishing sytems: spiral polishers (Diacomp FeatherLite/Brasseler), rubbercup polishers (Enhance/DentsplyCaulk), and brush-paste (Diashine/VH Technologies). Surface roughness was assessed using a confocal laser microscope (Lext OLS4000/Olympus). RESULTS: A two-way ANOVA revealed statistically significant differences in mean surface roughness values (Sa) among materials and polishers. Tukey multiple comparisons showed that mean Sa values for Lava Ultimate, Enamic, Cerasmart and Brilliant Crios polished with brush-paste as well as Lava Ultimate and Cerasmart values polished with spiral polishers were not significantly different from each other. CONCLUSIONS: The finished surfaces were significantly smoother than milled surfaces for all materials. The brush-paste polishing technique created the lowest surface roughness values for all CAD/CAM materials and values were comparable to what was achieved by spiral polishers for Lava Ultimate and Cerasmart. Rubber polishers did not provide a clinically smooth surface for CAD/CAM resilient ceramic/composite materials. CLINICAL SIGNIFICANCE: The results of the study indicate that polishing creates smooth surfaces for CAD/CAM resilient ceramic and CAD/CAM composite restorations.

Clinical evaluation of chairside Computer Assisted Design/Computer Assisted Machining nano-ceramic restorations: Five-year status.

OBJECTIVES: This investigation was a longitudinal, randomized clinical trial to measure the clinical performance of a nano-ceramic material (Lava Ultimate/3M) for chairside Computer Assisted Design/Computer Assisted Machining (CAD/CAM) fabricated restorations. MATERIALS AND METHODS: One hundred and twenty chairside CAD/CAM onlays were restored with a CEREC system randomly assigned to 60 leucite-reinforced ceramic (IPS EmpressCAD/Ivoclar Vivadent AGBendererstrasse 2FL-9494 SchaanLiechtenstein) onlays and 60 nano-ceramic (Lava Ultimate/3M) onlays. Equal groups of onlays were cemented using a self-etch and a total etch adhesive resin cement. The onlays were recalled for a period of 5 years. RESULTS: At 1 week postoperatively, 10% of the onlays cemented with both the self-etch and total etch adhesive resin cements were reported as slightly sensitive. However, all patients were asymptomatic by the 4th week without treatment. Four leucite-reinforced onlays and one nano-ceramic onlay fractured and required replacement. CONCLUSIONS: Adhesive retention with a self-etch or total etch cementation technique resulted in a similar clinical outcome with no reported debonds. The nano-ceramic onlays had a lower incidence of fracture compared to the leucite-reinforced ceramic onlays with both having a very low risk of fracture. Nano-ceramic onlays performed equally as well as glass ceramic onlays over 5 years of clinical service. CLINICAL SIGNIFICANCE: Ceramic materials have been a mainstay for chairside CAD/CAM restorations for the past 30 years and a new category of resilient ceramics with a resin matrix has been introduced reported to offer ceramic-like durability and esthetics with resin-like efficiency in handling. There are no long-term clinical studies on the performance of these materials. This is a 5-year randomized clinical trial on the performance of nano-ceramic onlays.

Three-Dimensional Digital Evaluation of the Fit of Endocrowns Fabricated from Different CAD/CAM Materials.

PURPOSE: A wide variety of CAD/CAM materials are available for single-tooth restorations. CAD/CAM material characteristics are different and may influence CAM fabrication accuracy. There is no study investigating the influence of different CAD/CAM materials on the final fit of the restoration. The aim of this study was to evaluate the fit of endocrowns fabricated from different CAD/CAM materials using a new 3D evaluation method with an intraoral scanning system. The null hypothesis was that there are no significant differences for the fitting accuracy of different CAD/CAM materials. MATERIALS AND METHODS: Preparation for an endocrown was performed on a maxillary right first molar on a typodont, and restorations were fabricated with a chairside CAD/CAM system (CEREC Omnicam, MCXL). Three groups using three different CAD/CAM materials were established (each n = 10): zirconia-reinforced lithium silicate ceramic (Celtra Duo; CD), leucite-reinforced silicate ceramic (Empress CAD; EM), resin nanoceramic (Lava Ultimate; LU). A 3D digital measurement technique (OraCheck, Cyfex AG) using an intraoral scanner (CEREC Omnicam) was used to measure the difference in fit between the three materials for a master endocrown preparation. The preparation scan and the endocrown fit scan were matched with special difference analysis software OraCheck. Three areas were selected for fitting accuracy measurements: margin (MA), axial (AX), occlusal (OC). Statistical analysis was performed using 80% percentile, one-way ANOVA, and post-hoc Scheffé test. Significance level was set to p = 0.05. RESULTS: Results varied from best 88.9 ± 7.7 µm for marginal fit of resin nanoceramic restorations (LU_MA) to worst 182.3 ± 24.0 µm for occlusal fit of zirconia-reinforced lithium silicate restorations (CD_OC). Statistically significant differences were found both within and among the test groups. Group CD performed statistically significantly different from group LU for marginal fit (MA) and axial fit (AX) (p < 0.05). For occlusal fit (OC), no statistically significant differences were found within all three test groups (p > 0.05). Deviation pattern for differences was visually analyzed with a color-coded scheme for each restoration. CONCLUSIONS: Statistically significant differences were found for different CAD/CAM materials if the CAM procedure was identical. Within the limitations of this study, the choice of CAD/CAM material may influence the fitting accuracy of CAD/CAM-fabricated restorations.

Digital evaluation of the fit of zirconia-reinforced lithium silicate crowns with a new three-dimensional approach.

OBJECTIVE: Several methods for the evaluation of fit of computer-aided design/computer-assisted manufacture (CAD/CAM)-fabricated restorations have been described. In the study, digital models were recorded with an intraoral scanning device and were measured using a new three-dimensional (3D) computer technique to evaluate restoration internal fit. The aim of the study was to evaluate the internal adaptation and fit of chairside CAD/CAM-fabricated zirconia-reinforced lithium silicate ceramic crowns fabricated with different post-milling protocols. The null hypothesis was that different post-milling protocols did not influence the fitting accuracy of zirconia-reinforced lithium silicate restorations. METHOD AND MATERIALS: A master all-ceramic crown preparation was completed on a maxillary right first molar on a typodont. Twenty zirconia-reinforced lithium silicate ceramic crowns (Celtra Duo, Dentsply Sirona) were designed and milled using a chairside CAD/CAM system (CEREC Omnicam, Dentsply Sirona). The 20 crowns were randomly divided into two groups based on post-milling protocols: no manipulation after milling (Group MI) and oven fired-glazing after milling (Group FG). A 3D computer method was used to evaluate the internal adaptation of the crowns. This was based on a subtractive analysis of a digital scan of the crown preparation and a digital scan of the thickness of the cement space over the crown preparation as recorded by a polyvinylsiloxane (PVS) impression material. The preparation scan and PVS scan were matched in 3D and a 3D difference analysis was performed with a software program (OraCheck, Cyfex). Three areas of internal adaptation and fit were selected for analysis: margin (MA), axial wall (AX), and occlusal surface (OC). Statistical analysis was performed using 80% percentile and one-way ANOVA with post-hoc Scheffé test (P = .05). RESULTS: The closest internal adaptation of the crowns was measured at the axial wall with 102.0 ± 11.7 µm for group MI-AX and 106.3 ± 29.3 µm for group FG-AX. The largest internal adaptation of the crowns was measured for the occlusal surface with 258.9 ± 39.2 µm for group MI-OC and 260.6 ± 55.0 µm for group FG-OC. No statistically significant differences were found for the post-milling protocols (P > .05). The 3D difference pattern was visually analyzed for each area with a color-coded scheme. CONCLUSION: Post-milling processing did not affect the internal adaptation of zirconia-reinforced lithium silicate crowns fabricated with a chairside CAD/CAM technique. The new 3D computer technique for the evaluation of fit of restorations may be highly promising and has the opportunity to be applied to clinical studies.

Full-Contour Zirconia Fixed Partial Dentures as Chairside Applications: A Case Report.

Clinical application of zirconia has been expanding due to the high strength properties it offers. Initial use of zirconia was as a coping or substructure material replacing cast metal. More recent formulations have been introduced for monolithic zirconia contour designs. New chairside computer-aided design and computeraided manufacturing (CAD/CAM) technology has made it possible for dentists to deliver 3-unit bridges in a single appointment. This case report will present such a clinical application.

Surface Evaluation of Polishing Techniques for New Resilient CAD/CAM Restorative Materials.

PURPOSE: The purpose of this study was to measure the surface roughness of milled chairside computer-assisted design/computer assisted machining (CAD/CAM) restorations using several contouring/polishing systems as to their effectiveness for creating a clinically acceptable surface. MATERIALS AND METHODS: One hundred onlays were milled from monolithic CAD/CAM blocks with an MCXL milling chamber (Sirona Dental) as follows: 30 resin nano-ceramic (Lava Ultimate, 3M ESPE), 30 hybrid ceramic (Enamic, Vita) and 40 leucite-reinforced ceramic (EmpressCAD, Ivoclar). A single group of EmpressCAD onlays was glazed-fired in a porcelain oven (Programat CS2, Ivoclar). Finishing and polishing systems consisted of either an abrasive-polish technique or a brush-polish technique. Roughness values were measured using a three-dimensional measuring laser microscope (OLS4000 LEXT by Olympus). RESULTS: There was a significant difference in the baseline surface roughness of the CAD/CAM materials (p ≤ 0.05), with the resin nano-ceramic (Lava Ultimate) being smoother than the hybrid ceramic (Enamic), and both being smoother than the leucite-reinforced ceramic (EmpressCAD). All polishing techniques resulted in a smoother surface compared with the baseline surface for the leucite-reinforced ceramic (p ≤ 0.05), with both techniques resulting in a significantly smoother surface than glazing in a porcelain oven (p ≤ 0.05). Both polishing techniques resulted in a smoother surface compared with the baseline surface for both the nano-ceramic and hybrid ceramic materials (p ≤ 0.05). CONCLUSIONS: It is possible to create an equally smooth surface for chairside CAD/CAM resilient materials compared with milled ceramics using several finishing and polishing techniques. In general, the polished ceramic surfaces were smoother than the glazed ceramic surfaces. CLINICAL SIGNIFICANCE: The results of the study indicate that it is possible to create an equally smooth surface for chairside CAD/CAM resilient materials compared with milled ceramics using several finishing and polishing techniques. In addition, both polishing techniques resulted in smoother ceramic surfaces when compared to glazed ceramic surfaces. The polished surface of the ceramic material was smoother than the glazed ceramic surface.

Computerized technology for restorative dentistry.

Computers have had a meaningful impact on the dental office and dental practice leading to significant changes in communication, financial accounting, and administrative functions. Computerized systems have more recently generated increasing diversity of application for the delivery of patient treatment. Digital impression systems and chairside CAD/CAM systems offer opportunities to integrate digital impressions and full contour restorations in the dental office. Systems rely on single image and video cameras to record the digital file that is the foundation for an accurate outcome. This article presents key aspects of computerized technology using the CAD/CAM process.

Using digital technology to enhance restorative dentistry.

While there are many benefits for dental practices that incorporate digital systems into their workflow, the dental team must first master the learning curve involved in order to maximize their advantages for creating well-fitting restorations. This article describes the current systems-both digital impression systems and chairside CAD/CAM systems-including software and digital cameras and scanners. The author emphasizes that to consistently capture accurate impressions with this technology, the dental team must continue to rely on traditional skills such as achieving optimal soft-tissue retraction and maintaining moisture control and isolation.

Chairside CAD/CAM: an overview of restorative material options.

A number of categories of materials are available for chairside CAD/CAM restorations that have demonstrated predictability and longevity. These materials include esthetic and high-strength ceramics, composite resins for both final and temporary restorations, and newer nanoceramics that offer ease of handling and a glossy surface finish. Each category of materials has unique features designed for specific clinical applications. This article will examine currently available materials designed for chairside CAD/CAM restorations and the various outcomes that are possible with this technologically advanced process.

Digital dentistry: innovation for restorative treatment.

The evolution of digital technology and computer-aided design/computer-aided manufacture (CAD/CAM) systems are creating exciting opportunities for improving the delivery of restorative dentistry. Digital systems now offer the opportunity to avoid traditional, analog impressions, including the usual impression materials, time, and handling limitations associated with them. Intraoral scanners have the potential to offer excellent accuracy with a more comfortable experience for the patient and more efficient workflow for the office.

A clinical evaluation of chairside lithium disilicate CAD/CAM crowns: a two-year report.

BACKGROUND: Developments in ceramic material science have led to improvements in the physical properties of modern ceramics, leading to a substantial increase in the clinical use of all-ceramic restorations. The authors evaluated the clinical performance of lithium disilicate (IPS e.max CAD, Ivoclar Vivadent, Amherst, N.Y.) all-ceramic crowns. METHODS: The authors fabricated 62 lithium disilicate crowns with a chairside computer-aided design/computer-aided manufacturing (CAD/CAM) system (CEREC 3, Sirona Dental Systems, Charlotte, N.C.) and cemented them with two types of adhesive resin cements. Two examiners used modified U.S. Public Health Service criteria to evaluate the crowns at baseline, six months, one year and two years. RESULTS: There were no clinically identified cases of crown fracture or surface chipping. There was no reported sensitivity at one or two years with either cement. For margin discoloration, the percentage Alfa score was 86.9 percent for crowns cemented with a self-etching, dual-curing cement. All other percentage Alfa scores were greater than 92.0 percent, indicating no appreciable change in the crowns during the two-year study. CONCLUSIONS: The results show that lithium disilicate crowns performed well after two years of clinical service. CLINICAL IMPLICATIONS: Early results indicate that monolithic lithium disilicate CAD/CAM crowns may be an effective option for all-ceramic crowns.