Computer-aided Design And Computer-aided Manufacturing Research Articles

Effect of CAD/CAM Position and Thickness of Ultra-Translucent Multilayered Zirconia on Color Aspects.

Ultra-translucent multilayered zirconia restorations fabricated using computer-aided design and computer-aided manufacturing (CAD/CAM) technology have recently gained popularity. Their esthetic appeal is crucially dependent on the color accuracy, influenced by prosthesis thickness and multilayer composition due to CAD/CAM milling positions. This study comprehensively investigated how these two factors impacted color accuracy, thereby enhancing our understanding of color outcomes. One hundred monolithic multilayer zirconia specimens with 10 × 10 mm square shape were milled in four different positions and five different thicknesses (1.0, 1.5, 2.0, 2.5, and 3.0 mm). The specimens were placed on an A3 shade resin composite substrate, and CIELAB values (L ∗, a ∗, and b ∗) were measured using a spectrophotometer. Delta E (ΔE) values were calculated to quantify the color differences between the specimens and the A3 VITA classical shade tab and compared with the perceptibility and acceptability thresholds of ΔE = 1.2 and 2.7, respectively. Pearson correlation, two-way ANOVA, and Tukey multiple comparisons (α = 0.05) were performed. The proportion of the dentin layer was positively correlated with the a ∗ and b ∗ values, while specimen thickness was positively correlated with the a ∗ value and negatively correlated with the L ∗ and b ∗ values. Significant difference in ΔE value due to different CAD/CAM positions was not observed within the same specimen thickness. Perceptible color differences were observed in specimens with thicknesses greater than 1 mm, while specimens with 1 mm thickness fell within the clinically acceptable range. Highest ΔE value was found in the specimen with 1 mm thickness. Different compositions of multilayers in the final restoration due to different CAD/CAM positions do not significantly affect the color appearance of ultra-translucent multilayer zirconia, with color only influenced by specimen thickness.

Assessment Methods for Marginal and Internal Fit of Partial Crown Restorations: A Systematic Review.

Different methods are used for the analysis of marginal and internal fit of partial crowns, but not all of them are applicable for in vivo studies. The aim of this review is to search the available methods, described in the current literature, to assess marginal and internal fit in partial crowns. an electronic search was performed on Pubmed and Web of Science databases to find studies published from 1 January 2017 up to 2 March 2023, following PRISMA guidelines and Cochrane handbook for systematic reviews. The search strategy applied was: "(marginal) AND (fit OR gap OR adaptation OR discrepancy) AND (inlay OR onlay OR partial crown)". In vitro studies which evaluated marginal and internal fit on CAD CAM or 3D printed partial crowns were included in this review. Quality of the studies was assessed by using Quality Assessment Tool For In Vitro Studies (QUIN tool). 22 studies were included. Among conventional methods, direct view with microscope, indirect view on resin replicas, and silicone replica technique (SRT) were used. Considering new digital methods, micro-CT, SRT 3D and triple scan technique (TST) were applied. Among 2D methods, direct view technique is the most used marginal fit analysis. For a more comprehensive evaluation, a 3D digital analysis is suggested. SRT and indirect view are the only 2D methods available for in vivo analysis. A protocol for the application of TST for assessment in vivo is now available, but no studies are reported in literature yet.

TO COMPARE THE MARGINAL FIT, INTERNAL GAP AND FIRING SHRINKAGE OF METAL CERAMIC CROWN FABRICATED BY CAD-CAM AND CONVENTIONAL METHOD:AN INVITRO STUDY

Purpose: The purpose of this in vitro study is to compare the marginal fit , internal gap and firing shrinkage of metal ceramic crown fabricated by cad-cam and conventional method. Materials And Methods: Atotalof30workingmodels,i.e.15modelseachgroup:conventionallost-waxandmillingwere used.Marginaldiscrepancywasevaluatedattheframeworkandporcelainstepsthroughscanningunder a stereomicroscope. Then, the crowns were cemented to the related die and the marginal gap was measuredundera stereomicroscopeandthensectioningwasdoneandinternalgapwasevaluatedusing scanning electron microscopy (SEM). The data was analyzed using the independent t test and the one- way analysis of variance (ANOVA). The significance level was set at0.05 Results: Among the experimental group, group 2 cad cam shows the better marginal gap in all aspect compare to group 1 conventional technique in both beffore after ceramic firing. Group 1 shows the better internal fit at 4 places out of 5 that is marginal opening area was better in group 2. Conclusion: Withinthelimitationofthisinvitrostudy,itwasconcludedthatforallthefeaturesCAD-CAM techniques gave better results except internal gap, when compared with the conventional methods and there was a significant statistical difference between the two comparisongroups.

Fracture strength and bonding interface morphology of CAD/CAM-fabricated ceramic laminate veneers on bleached enamel treated with two different antioxidants.

This study aimed to investigate the effects of two antioxidants and their application time on the fracture strength of computer-aided design and computer-aided manufacturing (CAD/CAM)-fabricated ceramic laminate veneers to bleached enamel, as well as their effects on the bonding interface micromorphology. Eight groups were set: Group NC (without bleaching and antioxidant treatment); Group NA (bleaching without antioxidant treatment); Group SA30, SA60, SA120 and Group PAC30, PAC60, PAC120 (bleaching and treating with sodium ascorbate or proanthocyanidins for 30, 60, and 120 min, respectively). After cementation of veneers, fracture strength values and failure modes were analyzed. The bonding interface morphology was observed by confocal laser scanning microscopy. The fracture strength was impaired when cementation procedure was performed immediately after bleaching. This reduction in fracture strength was reestablished with antioxidant treatment, and an extended treatment time contributed to better improvement. The resin tags at the bonding interfaces of the bleached enamel were impaired. Antioxidant treatments were able to reverse this unfavorable trend.

Influence of thermal aging on the marginal integrity of computer aided design/computer aided manufacturing fabricated crowns

Background/purposeThe adaptation and marginal integrity of computer-aided designed and computer-aided manufactured (CAD/CAM) crowns after exposure to thermal aging need to be investigated. The present in-vitro study was designed to investigate the marginal integrity of CAD/CAM fabricated crowns cemented on extracted teeth after thermocycling aging. Materials and methodsTwenty-six newly extracted human premolars were prepared for full-coverage CAD/CAM crowns and were divided into two groups (leucite-reinforced glass-ceramics and lithium disilicate glass-ceramics). Both crowns’ groups were cemented using dual curing resin cement. All specimen margins were measured for marginal integrity using an imaging system 24 h post cementation; then after 1, 3, and 5 estimated clinical years (10,000, 30,000, and 50,000 thermocycles). Two-way ANOVA analysis were used to determine whether the mean value difference is significantly different (ɑ = 0.05). ResultsThe average margin gaps recorded for leucite-reinforced glass-ceramic crowns were: 82.61 μm initial, and 91.02 μm after 5 estimated clinical year). For the lithium disilicate glass-ceramic crowns, the average margin gaps recorded were: 100.01 μm initial, and 120.21 μm after 5 estimated clinical year. During all measuring intervals, the leucite-reinforced glass-ceramic crown group had a lower marginal discrepancy. No statistically significant difference between the two groups was recorded. ConclusionAfter being subjected to thermocycling, both CAD/CAM ceramic crowns, exhibited an increase in their marginal discrepancy; the difference was within the accepted clinical range.

Patient Satisfaction with Anterior Interim CAD-CAM Rehabilitations Designed by CAD Technician versus Trained Dentist—A Clinical Preliminary Study

The objective of this study was to assess the impact of digital waxing expertise on patient satisfaction with anterior interim computer-aided design and computer-aided manufacturing (CAD-CAM) prosthetic rehabilitations designed either by a CAD and dental technician or by a dental clinician with basic CAD-CAM training. This in vivo preliminary study was conducted on a total of 18 patients receiving anterior CAD-CAM rehabilitations (at least from canine to canine) with fixed bridges and/or single crowns. Only patients that had conventional chairside temporary restorations were enrolled. Three within-patient groups were defined at different time points: group CONTROL refers to all 18 patients at their first appointment, when they were using their initial temporary conventional prostheses; group DENT refers to all patients immediately after trying in a set of CAD-CAM prostheses designed by a dental clinician (with basic one-week CAD-CAM training); and group CAD refers to all patients after trying in a set of CAD-CAM prostheses for the same tooth elements but designed by an experienced CAD technician (who was also an experienced dental prosthetic technician). All CAD-CAM restorations were milled in polymethyl methacrylate (PMMA) with high translucency and strength properties (Prime, Zirkonzahn). Satisfaction with comfort and esthetics was assessed for all patients for the three different time points (groups CONTROL, DENT and CAD). Statistically significant differences among groups were assessed with the Friedmann’s test. Group CAD significantly outperformed the other groups in both assessed variables (p = 0.001). The group DENT, in turn, outperformed group CONTROL for satisfaction with esthetics (p = 0.006) but not for comfort (p > 0.05). In conclusion, CAD operator background and expertise level significantly affect patient self-reported outcomes for anterior CAD-CAM rehabilitations. Single crowns and fixed bridges digitally designed by an experienced professional trained in both CAD-CAM and dental technology will likely offer high satisfaction and comfort to patients receiving anterior prosthetic rehabilitations.

Detection of misfits at the abutment-prosthesis interface in the esthetic zone: Implications of the radiographic technique and the magnitude of the misfit

Misfits in the abutment-prosthesis interface represent a setback for implant-supported prostheses. Periapical radiographs have been used as an auxiliary method in the evaluation of prosthesis fit to the abutments; however, the evidence supporting the use of this method is still restricted to studies of low to moderate quality. Furthermore, studies on the diagnostic accuracy of different periapical techniques used to detect misfits in the abutment-prosthesis interface, especially in the esthetic zone, are lacking. The purpose of this in vitro study was to assess the discrimination power of 3 periapical radiographic techniques in detecting misfits at the abutment-prosthesis interface in the esthetic zone and evaluate whether the magnitude of the misfit influenced the diagnosis. A total of 15 implants with an internal conical connection were installed in the central incisor region in polyamide jaws. Custom ceramic copings for cemented crowns were made by using a computer-aided design and computer-aided manufacturing (CAD-CAM) system. Misfits of 50, 100, and 150µm were simulated by interposing 1, 2, or 3 50-μm-thick polyester strips at the abutment-prosthesis interface; the absence of the strip represented the control group. Digital radiographs were obtained by using film holders for the following periapical techniques: bisecting angle (PBA), standard paralleling (PSP), and modified paralleling (PMP). Two radiologists and 1 prosthodontist evaluated a total of 180 radiographs. The values of the area under the receiver operating characteristic curve (Az) were regarded as a measure of diagnostic accuracy and subjected to the Friedman test with post hoc Durbin-Conover (α=.05). The PSP (Az=0.873) had higher Az values than the PBA (Az=0.753) for the 50-μm misfits (P<.05). Larger misfits resulted in greater accuracy than smaller misfits (P<.05). Interactions between the factors radiographic technique and misfit magnitude resulted in statistically significant differences for all comparisons (P<.05), except between the PSP for the 100-μm misfits (Az=0.976) and the PMP for the 150-μm misfits (Az=0.998). The PSP was more accurate than the PBA in detecting the 50-µm misfits at the abutment-prosthesis interface; larger misfits resulted in more accurate diagnoses, regardless of the technique used.

Evaluation of marginal and internal fit of metal crowns made from wax patterns made by conventional technique and CAD CAM milling technique: An in vivo study

Introduction: Marginal and internal fit of a metal crown are very important for a successful metal crown prosthesis. This study will evaluate the marginal and internal fit of metal crowns produced from wax patterns that are formed by two different wax pattern fabrication procedures: conventional wax pattern fabrication and wax pattern milled using the computer-aided design and manufacture (CAD CAM) method. Objectives: To evaluate the marginal and internal fit of metal crowns over prepared tooth made from wax patterns made by conventional technique and CAD CAM technique. Methodology: A total of 21 participants with endodontically restored mandibular first molar will be selected. Two all-metal crowns will be made for each participant, thus 42 metal crowns in total will be made. These 42 metal crowns will be divided into two groups based on the method used to create wax patterns: metal crowns made using conventional hand-carved wax pattern technique (Group I, n=21) and metal crowns made using CAD CAM-milled wax pattern technique (Group II, n=21). Then, the marginal and internal fit of metal crowns from both groups will be compared. Expected results: It is expected that metal crowns made by CAD CAM milled wax pattern fabrication method will have better marginal and internal fit than those of conventional method. Conclusions: The clinical acceptability and success of the dental crown will be assessed by this study. Minimal marginal gap and better internal fit of all metal crown are key qualities.

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.

CAD-CAM and analog occlusal splints comparison based on the amount of occlusal adjustments. 3D analysis of the volumetric changes: A pilot study.

To evaluate the volumetric changes on occlusal surface of computer-aided design and computer-aided manufacturing (CAD-CAM) occlusal devices fabricated following a fully digital workflow after occlusal adjustment, compared to those fabricated with an analog workflow. Eight participants were included in this clinical pilot study, receiving two different occlusal devices fabricated with two different workflows, fully analog and fully digital. Every occlusal device was scanned before and after the occlusal adjustments to compare the volumetric changes using a reverse engineering software program. Moreover, three independent evaluators assessed a semi-quantitative and qualitative comparison using visual analog scale and dichotomous evaluation. The Shapiro-Wilk test was performed to validate normal distribution assumption, and a dependent t-Student test for paired variables was used to determine statistically significant differences (p-value < 0.05). The root mean square value was extracted from the 3-Dimensional (3D) analysis of the occlusal devices. The average values of the root mean square were higher for the analogic technique (0.23 ± 0.10 mm) than the digital technique (0.14 ± 0.07 mm) but the differences were not statistically significant (paired t-Student test; p = 0.106) between the two fabrication techniques. The semiquantitative visual analog scale values between the impression for the digital (5.08 ± 2.4 cm) and analog (3.80 ± 3.3 cm) technique were significant (p < 0.001), and statistically significant differences values were assessed for evaluator 3 compared to the other evaluators (p < 0.05). However, the three evaluators agreed on the qualitative dichotomous evaluation in 62% of the cases, and at least two evaluators agreed in 100% of the evaluations. Occlusal devices fabricated following a fully digital workflow resulted in fewer occlusal adjustments, as they could be a valid alternative to those fabricated following an analog workflow. Fabricated occlusal devices following a fully digital workflow could have some advantages over analog workflow such reduce occlusal adjustments at delivery appointment, which can result in reduced chair time and therefore increased comfort for the patient and clinician.

Risk factors associated with screw loosening in CAD-CAM custom abutments: A 6-year retrospective study

Statement of ProblemCustom abutments made by using computer-aided design and computer-aided manufacturing (CAD-CAM) are often used for implant-supported prostheses. However, studies on screw loosening of implant prostheses using custom abutments are lacking. PurposeThe purpose of this retrospective study was to investigate the risk factors of screw loosening in implant-supported prostheses using custom abutments made with CAD-CAM. Material and methodsClinical charts, radiographic images, and CAD custom abutment design file data were collected and analyzed retrospectively. The study included 255 patients with 401 dental implants, and the follow-up duration was 6 years. Age, sex (male/female), type of unit (single-unit or multiunit), location of the implant (maxilla or mandible and anterior, premolar, or molar tooth), type of antagonist, and experience of the prosthodontist were reviewed, and implant angulation (mesiodistal and buccolingual), location of the screw access hole (mesiodistal and buccolingual distances from center), and attrition status (none, localized, or generalized) were measured by using a CAD file. The frequencies and percentages of risk factors were evaluated with the Fisher exact test, and the Bonferroni correction was used as a post hoc test. Multiple logistic regression with the Firth method was performed to calculate the odds ratios and their confidence intervals (α=.05). ResultsScrew loosening showed a correlation with the severity of attrition (P<.001). Single-unit prostheses had a higher risk of screw loosening than multiunit prostheses (P<.001). Experience of the prosthodontist (P<.001). Buccolingual angulation of the implant and abutment significantly influenced the incidence of screw loosening (P<.05). Age, sex, location of the implant, type of antagonist, mesiodistal implant angulation, and buccolingual and mesiodistal location of the screw access hole did not significantly influence the incidence of screw loosening (P>.05). ConclusionsThe degree of attrition, buccolingual angulation of the implant and abutment, type of unit, and experience of the prosthodontist (>3 years or <3 years) were risk factors in the incidence of screw loosening.

Effect of Simulated Annual At-home Bleaching on Susceptibility to Staining, Translucency, and Whiteness Variations of Computer-aided Design and Computer-aided Manufacturing Monolithic Materials.

The effect of annual at-home bleaching on the color, translucency, and whiteness properties of computer-aided design and computer-aided manufacturing (CAD-CAM) monolithic materials requires investigation. The aim of the present in vitro study was to evaluate the effect of simulated annual at-home bleaching (consisting of daily applications for 10 hours a day for 14 days), for up to 3 years, on susceptibility to staining (ΔE00), translucency (ΔTP00), and whiteness (ΔWID) variations and on topography of CAD-CAM monolithic materials. Disks from the Lava Ultimate (LU), Vita Enamic (VE), IPS Empress CAD (EMP), and IPS e.max CAD (EMAX) were allocated as follows: 1) nonbleached or 2) bleached with 10% carbamide peroxide. After reading the CIE L*a*b* coordinates at baseline (R0), specimens were bleached or not and subsequently immersed for a 1-year simulated period in coffee before the next reading (R1). This process was repeated two more times, resulting in R2 and R3. The ΔE00, ΔTP00, and ΔWID between R1, R2, and R3 in relation to R0 were calculated. The surface topography was analyzed by scanning electron microscopy. In general, bleaching increased the staining susceptibility of all materials when compared to the nonbleached groups and that of the LU, VE, and EMAX over the years. Bleaching decreased the translucency of the VE in all years and over the years. When compared to the nonbleached groups, bleaching decreased the whiteness of the LU and EMAX and increased the whiteness of the EMP, while the VE was not affected. In the LU, the whiteness decreased over the years in both treatments, whereas the other materials were not affected with time. All materials showed progressive topographic changes over the years. The simulated annual at-home bleaching with 10% carbamide peroxide adversely affected the topography and the optical and/or colorimetric properties of the evaluated materials.

Fracture resistance of CAD CAM endocrowns bonded to teeth with different number of remaining walls :An In-Vitro Study.

Fracture resistance of CAD CAM endocrowns bonded to teeth with different number of remaining walls :An In-Vitro Study.

Orthodontic Retainers

To ensure that the results of fixed orthodontic therapy are maintained and do not relapse, it is crucial to retain and preserve the treatment outcomes. Retention is an essential aspect of orthodontics and can be viewed as the final stage of treatment. It is necessary to maintain an optimal esthetic and functional occlusion following orthodontic therapy.&#x0D; Aim : The objective of the article is to acknowledge the significance of maintaining the outcomes of orthodontic therapy and to assess the various techniques used to fabricate fixed and removable appliances for retention.&#x0D; Materials and Methods:&#x0D; The present article evaluates the different protocols for lingual fixed retainers, as well as removable retentive appliances such as Hawley, Begg, and vacuum-formed retainers (VFR). Removable appliances have been used for retentive purposes for a long period of time. Bonded fixed retainers were introduced in the 1970s, and they have several advantages over removable retentive appliances, such as better esthetics, the absence of patient cooperation, and suitability for lifelong retention. Fixed retainers can be of conventional or digital type. Conventional fixed retainers can be fabricated and attached directly or indirectly to the teeth using a transfer tray. Moreover, bonded retainers can now be digitally manufactured using computer-aided design and computer-aided manufacturing (CAD-CAM).

Defining challenging areas of the preparation finish line by using an open-source 3D modeling computer program: A tip to simplify margin identification by the dental laboratory technician

Intraoral data acquisition and computer-aided design and computer-aided manufacturing (CAD-CAM) systems have simplified and expedited the fabrication of dental prostheses. 1 Van Noort R. The future of dental devices is digital. Dent Mater. 2012; 28: 3-12 Crossref PubMed Scopus (801) Google Scholar ,2 Giuliodori G. Rappelli G. Aquilanti L. Intraoral scans of full dental arches: an in vitro measurement study of the accuracy of different intraoral scanners. Int J Environ Res Public Health. 2023; 20: 4776 Crossref Scopus (0) Google Scholar Contemporary dental CAD-CAM provides the freedom to design and fabricate diverse dental devices, including custom impression trays, surgical templates, and removable and fixed dental prostheses. 1 Van Noort R. The future of dental devices is digital. Dent Mater. 2012; 28: 3-12 Crossref PubMed Scopus (801) Google Scholar ,3 Revilla-León M. Özcan M. Additive manufacturing technologies used for processing polymers: current status and potential application in prosthetic dentistry. J Prosthodont. 2019; 28: 146-158 Crossref PubMed Scopus (217) Google Scholar ,4 Turkyilmaz I. Wilkins G.N. Varvara G. Tooth preparation, digital design and milling process considerations for CAD/CAM crowns: understanding the transition from analog to digital workflow. J Dent Sci. 2021; 16: 1312-1314 Crossref Scopus (8) Google Scholar These dental appliances are created from a digital file that recreates the surface geometry of the target object, typically a standard tessellation language (STL) file. 5 Grant G.T. Campbell S.D. Masri R.M. Andersen M.R. The American college of prosthodontist digital dentistry glossary development task force. Glossary of digital terms. J Prosthodont. 2016; 25: S2-S9 Crossref PubMed Scopus (27) Google Scholar A prerequisite for accurate manufacture is the exact capture and identification of the fine details in the target intraoral structures. An accurate capture can be challenging when the preparation finish line is subgingival, when abundant bleeding or salivation occurs, or when operator scanning skills and speed are still developing. 6 Mangano F. Gandolfi A. Luongo G. Logozzo S. Intraoral scanners in dentistry: a review of the current literature. BMC Oral Health. 2017; 17: 149 Crossref PubMed Scopus (308) Google Scholar Additionally, the location of fine details can be challenging for the dental laboratory technician to visualize when the CAD file is outsourced for the manufacture of the definitive restoration, since STL files lack attributes such as color and texture. 5 Grant G.T. Campbell S.D. Masri R.M. Andersen M.R. The American college of prosthodontist digital dentistry glossary development task force. Glossary of digital terms. J Prosthodont. 2016; 25: S2-S9 Crossref PubMed Scopus (27) Google Scholar These features help differentiate the tooth from its surrounding tissues when finish lines are subgingival or when displacement is limited. The present article presents a straightforward workflow that defines challenging areas of the preparation finish line by using an open-source 3D modeling computer program. This procedure can be used to communicate the finish line observed to the dental laboratory technician when STL files are used to design the definitive restoration and stops the technician guessing the finish line, since the hard-to-see areas are defined by the clinician. Additionally, this approach has advantages over the margin tracing and sculpting tools available in most 3-dimensional (3D) CAD computer programs since it allows selecting the critical areas around the finish line considering the mesh geometry of the 3D file. Visualizing the 3D mesh permits a more precise selection, which can minimize distortion as even the smallest changes in the mesh surface can be observed if transformation or sculpting procedures are used.

Fit and fatigue behavior of CAD-CAM lithium disilicate crowns

Statement of problemNew computer-aided design and computer-aided manufacturing (CAD-CAM) lithium disilicate glass-ceramics have been marketed. However, information concerning their biomechanical behavior is lacking. PurposeThe purpose of this in vitro study was to compare the fit and fatigue behavior of two recently introduced CAD-CAM lithium disilicate materials with the standard IPS e.max CAD ceramic and to investigate the effect of the thermal treatment for crystallization on crown fit. Material and methodsMonolithic crowns (n=15) were milled from 3 CAD-CAM lithium disilicates: IPS e.max CAD (Ivoclar AG), Rosetta SM (Hass), and T-lithium (Shenzhen Upcera Dental Technology). Marginal and internal fit were evaluated using the replica technique before and after crystallization, and the fatigue behavior of the luted crowns was evaluated by the step-stress method. One-way ANOVA and the Tukey test were used to compare fit among the materials. Fatigue failure load was evaluated by the Kaplan-Meier and Mantel-Cox tests. The effect of crystallization on fit was evaluated with the paired t test (α=.05). ResultsMarginal fit was different between IPS e.max CAD (74 μm) and Rosetta SM (63 μm) (P=.02). T-lithium was similar to the other ceramics (68 μm) (P>.05). Occlusal internal space was similar among all materials (P=.69). Fatigue failure loads of Rosetta SM (1160 N) and T-lithium (1063 N) were similar to IPS e.max CAD (1082 N) (P>.05). The fatigue failure load of Rosetta SM was higher than that of T-lithium (P=.04). Crystallization reduced the axial internal space of all materials (P<.05) without significantly affecting marginal fit (P>.05). ConclusionsThe fit and fatigue behavior of Rosetta SM and T-lithium were similar to that of IPS e.max CAD. Crystallization reduced the internal space of the crowns.

Review article: CAD-CAM in removable dental prosthesis

Removable dentures are a treatment option for replacing missing teeth. Use digital technologies in manufacturing of removable dental prosthesis is recent with computer-aided design and computer-aided manufacturing (CAD-CAM). Additive or subtractive methods can be used for the fabrication of removable dentures. This review includes articles from the last 5 years on the use of CAD-CAM for manufacture of removable prostheses. The most frequent failures of the conventional system in the manufacture of removable dental prosthesis should avoid with digital workflow in clinical procedures, fabrication methods and materials used. Intraoral scans for removable dentures have been a lack of accuracy and difficulties in capturing soft tissues because. Manufacturing of removable dental prostheses with CAD-CAM has proven properties clinically acceptable, with milled, three-dimensional printer or laser‐sintered methods. CAD-CAM-milled and rapid-prototyped of removable denture are similar in terms of biocompatibility and surface roughness. This technology allows exploring the use of new materials such as polyetheretherketone for manufacture of frameworks for removable prostheses. Digital scanning, three-dimensional printing or milled method is more efficient and more comfortable, allowing advantages in terms of time and cost of prosthesis with predictable results. New studies are needed to show the benefits of CAD-CAM technology in removable dental prosthesis.

Digital Evaluation of Trueness and Fitting Accuracy of Co-Cr Crown Copings Fabricated by Different Manufacturing Technologies.

The dentistry industry has seen a number of exciting new advancements in recent years, many of which have been made possible by the introduction of automated technologies such as computer-aided design and computer-aided manufacturing (CAD/CAM). Despite the fact that these new approaches simplify the fabrication process in favor of decreased material consumption and improved time efficiency, it is possible that they may have an effect on the prosthesis's fitness, which in turn may affect how long they will last. The purpose of this in vitro study was to evaluate the trueness and fitness of cobalt-chromium (Co-Cr) crown copings fabricated by selective laser melting (SLM), milling, and conventional casting methods. A zirconium die was fabricated and scanned with a laboratory scanner to manufacture the Co-Cr metal copings for three groups (n = 12). In group A, the copings were fabricated by a 3D printing technique called SLM; in group B, the copings were fabricated by the milling technique; and in group C, the copings were fabricated by the conventional lost-wax method. After fabrication, the trueness and the internal fitness of the copings were evaluated using a metrology software program (Geomagic Control X, 3D Systems Inc., Rock Hill, SC). The one-way ANOVA and Tukey's honestly significant difference test were used to statistically analyze the data. The highest root mean square (RMS) value of trueness was for CAD/CAM milling, and the highest mean of horizontal gaps was for the casted (lost-wax technique) group. There were highly significant differences in the mean RMS value of trueness and the mean horizontal gaps between the three groups. The fabrication method of Co-Cr crown copings has an effect on the trueness and fitness of the copings.

Digital working process in diagnosis, treatment planning and fabrication of personalized orthodontic appliances

ABSTRACT Until recently, the working process of personalized orthodontic appliances (POAs) is performed digitally with the use of virtual systems including diagnosis, treatment planning and remote monitoring. Based on the exponential development of digital technologies such as imaging systems, computer-aided design and computer-aided manufacturing (CAD/CAM) systems, three-dimensional (3D) printing and artificial intelligence (AI), orthodontists want to go further and create an almost automatic intelligent orthodontic procedure containing big data to assist orthodontists in clinical treatment and reduce therapy duration. Here, we review the latest studies illustrating the application of digital technologies during treatment and manufacturing process of POAs. In addition, we highlight the current challenges and future directions of digital technology in POAs to call for more attention to the (I) AI applications for image analysis and treatment designation, and (II) 3D printing technologies for precise fabrication of POAs like clear aligner, accessories of fixed orthodontic appliances.

Effect of the CAD-CAM and lost-wax framework fabrication techniques on the fracture strength of porcelain in metal-ceramic restorations.

Ceramic fracture is a common problem in metal-ceramic restorations (MCRs). The advent of computer-aided design and computer-aided manufacturing (CAD-CAM) technology eliminated the lost-wax technique, which was responsible for many of the problems associated with framework fabrication. However, the role of the CAD-CAM technology in decreasing porcelain fracture is not yet known. The aim of the present in vitro study was to compare the fracture strength of porcelain in MCRs with metal frameworks fabricated with the use of the lost-wax and CAD-CAM techniques. Twenty metal dies were prepared with a deep chamfer finish line, with a depth of 1.2 mm and the occlusal taper of the walls of 8°, a 2-millimeter occlusal reduction of the functional cusp, a 1.5-millimeter occlusal reduction of the nonfunctional cusp, and the functional cusp bevel. Ten frameworks were fabricated using the CAD-CAM system and 10 with the lost-wax technique. After porcelain veneering, the specimens underwent thermocycling and cyclic loading to simulate the aging process. The load test was then performed. The fracture strength of porcelain was compared between the 2 groups, and the mode of failure was also determined using a stereomicroscope. Two specimens were excluded from the CAD-CAM group. Thus, 18 specimens were statistically analyzed. The results revealed no significant difference in fracture strength between the 2 groups (p > 0.05). The mode of failure was mixed in all specimens from both groups. Our results indicated that the fracture strength of porcelain and the mode of failure did not depend on the metal framework fabrication technique (lost-wax or CAD-CAM).