The use of CAD/CAM in dentistry

Complete mouth rehabilitation in a patient with condylar fracture malunion: A clinical report

Mandibular condyle fracture malunion and tooth loss can cause functional and esthetic problems. A patient with restricted mouth opening associated with muscle atrophy required prosthetic rehabilitation. Since the remaining teeth had a poor prognosis and the patient had difficulty adapting to the interim denture, complete mouth rehabilitation with implants was chosen. The implants were placed by using nerve lateralization and an autogenous bone graft. Prosthetic rehabilitation combines digital diagnosis and conventional prosthetic restorations. The definitive prosthesis was fabricated to ensure adequate oral hygiene and functional adaptation of the orofacial structures. Treatment resulted in stable masticatory function, occlusion, and esthetics and restored the function of the atrophied lips and restricted mouth opening.

Influence of microstructure on optical properties of CAD-CAM lithium disilicate glass-ceramics

OBJECTIVES

To evaluate the influence of microstructure and chemical composition on the optical properties of CAD-CAM lithium disilicate glass-ceramics.

METHODS

Samples (n = 5; 1.0 mm thickness) of shades A1, A2, and A3 were fabricated from CAD-CAM ceramic blocks (Ivoclar Vivadent): IPS e.max® CAD LT (emLT) and HT (emHT). Samples were polished to 1.0 ± 0.01 mm in thickness. The optical properties (R- reflectance; T- transmittance; μs'- reduced scattering and μa- absorption coefficients) from the post-crystallized samples were determined using the inverse adding-doubling (IAD) method based on integrating-sphere measurements. Additionally, scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were used to evaluate the microstructural properties. Energy-dispersive X-ray (EDX) was employed to analyze the chemical composition. The chemical and structural characterization were performed before and after crystallization of the ceramic samples.

RESULTS

emLT showed higher values of μs'and lower values of μa and T than emHT for each shade in all wavelengths (p < 0.003). Considering T for emHT, there were no statistical differences for shades A1 and A2 at 488 nm and 514.5 nm (p > 0.003) and shades A1 and A3 at 457.9 nm (p > 0.003). emLT showed particle length ranging from 0.74 to 2.78 µm (mean = 1.57 µm and RF-relative frequency = 28 %) and particle width ranging from 0.21 to 0.74 µm (mean = 0.30 µm and RF = 31 %). emHT showed particle length ranging from 0.83 to 3.08 µm (mean = 1.86 µm and RF = 21 %) and particle width ranging from 0.24 to 1.12 µm (mean = 0.56 µm and RF = 28 %). In comparison with emHT, emLT showed greater vol% for C, K, and Zr and lower vol% for O and Al.

SIGNIFICANCE

The optical properties of CAD-CAM lithium disilicate glass-ceramics are influenced by the chemical composition and, consequently, by the material microstructure.

Flexural Strength of Modern CAD/CAM Restoratives After Artificial Aging

Before clinical trials are initiated, studying the mechanical performance of modern CAD/CAM restorative materials exposed to aging conditions would provide insights on their performance in service. This study evaluated the impact of thermomechanical aging on various resin composite, ceramic, hybrid, and nano-filled resin composite materials after two polymerization modes. Specimens (3 × 4 × 14 mm3) were fabricated using (n = 12 per group) a universal composite (Filtek Supreme XTE photo-polymerized for either 40 s or 120 s per layer), hybrid ceramics (BRILLIANT Crios, GC Cerasmart, Lava Ultimate, VITA ENAMIC), glass ceramics (IPS e.max CAD, VITA Suprinity PC, Straumann n!ce), or feldspar ceramics (VITABLOCS Mark II, GC Initial LRF). In each group, half of the specimens underwent thermomechanical aging. A three-point bending test was applied to all specimens and the results were statistically analyzed (α = 0.05). Glass ceramics and hybrid ceramics presented higher flexural strength values than feldspar ceramics and the universal composite before and after aging (p < 0.05). Thermomechanical cycling affected the flexural strength of all materials (p < 0.05) except Lava Ultimate, Straumann n!ce, and GC Initial (p > 0.05). The highest decrease in flexural strength after aging was found in the universal composite (40 s polymerization) (p < 0.001) and Vita Enamic (p < 0.001), while the lowest decrease was in the hybrid ceramics, Cerasmart and Lava Ultimate (p < 0.05). Extending polymerization duration reduced the aging effect on the universal composite tested. Thermomechanical aging affected the flexural strength of most materials tested. Universal composites and feldspar ceramics presented similar flexural strength values.

Effect of mechanical and chemical surface treatments on the repairing of milled and 3D-printed denture bases

Ensuring a strong bond between chairside autopolymerized acrylic resin to denture base is essential for denture repair and reline procedures. However, there is no established protocol to enhance bond strength between autopolymerizing resin and computer-aided design and computer-aided manufacturing (CAD-CAM) denture base materials. The purpose of this study was to determine shear bond strength of CAD-CAM denture bases and autopolymerizing acrylic resin after mechanical and chemical surface treatments compared with heat-polymerized acrylic resin. Heat-polymerized, milled, and 3-dimensional (3D) printed denture bases were divided into 4 surface treatment protocols: none (control), airborne-particle abrasion (APA), tetrahydrofuran, and Vitacoll application. Autopolymerizing acrylic resin cylinders were bonded to denture surface. Shear bond strength and failure modes were determined after thermocycling. Denture base surfaces were assessed for surface roughness, surface morphology, and microhardness before and after surface treatment. Data was analyzed using two-way ANOVA and multiple comparison tests. The results showed that APA significantly increased shear bond strength and surface roughness of all denture base materials. Tetrahydrofuran and Vitacoll application improved shear bond strength of heat-polymerized acrylic resin, but did not reach the level achieved by APA. Conversely, tetrahydrofuran application improved bond strength of 3D-printed denture to the level of APA. Tetrahydrofuran and Vitacoll application significantly reduced denture base hardness, compared with control and APA. In conclusion, mechanical surface treatment using APA enhances the adhesion of autopolymerizing acrylic resin to heat-polymerized and CAD-CAM denture bases. Tetrahydrofuran and Vitacoll chemical surface treatment improved adhesion to heat-polymerized acrylic resin, with only tetrahydrofuran enhancing bond strength of 3D-printed denture to the level of APA. Without surface treatment, the highest bond strength was shown in 3D-printed denture base material.

Effect of scanning strategies on trueness and time efficiency of digital impression on paediatric models

BACKGROUND

Various scanning methods aim to reduce intraoral scanner errors, yet no specific approach targets paediatric patients.

AIM

Evaluate continuous (C) and noncontinuous (NC) scanning patterns' impact on the trueness and duration of paediatric digital impressions.

DESIGN

A standard pedodontic typodont model was scanned with a Trios 4 Move+ IOS using four scanning strategies. C1 and C2 followed continuous scanning from the right molars, with different directions. NC1 scanned noncontinuously from the right molar, with breaks every four teeth. NC2 began at the right primary incisor, with breaks after every three teeth. Each scan, performed five times by one researcher, was timed. Industrial scanning provided reference data. Deviations were analyzed using the MIXED procedure.

RESULTS

NC1 had higher deviations in the lower jaw, whereas C1 and NC1 showed higher deviations in the upper jaw (p < .001). C1 had significantly higher deviations in the upper jaw than the lower jaw (p = .041). NC2 had the longest scanning time in both upper and lower jaws (p = .002).

CONCLUSION

Paediatric digital impressions benefit from starting at the anterior and incorporating breaks, although this increases scanning time.

Could various angulated implant depths affect the positional accuracy of digital impressions? An in vitro study

PURPOSE

The purpose of this in vitro investigation was to assess how implant depth could affect the three-dimensional positional accuracy of digital impressions made from angulated implants.

MATERIALS AND METHODS

Four modified maxillary models were printed and divided into four study groups. In each model, two angulated implant analogs were placed at the sites of the first premolar and first molar at four different depths of 1 (G1), 2 (G2), 3 (G3), and 4 (G4) mm from the models' edentate area. Scan bodies were connected to the analogs, and one operator made 10 full-arch scans for each master model using an intraoral scanner. Afterward, the marginal gingival part of all models was removed, and digital scans were performed for each model using a laboratory scanner to achieve a reference STL file as the control group. One-way ANOVA and Leven's tests were used to measure and compare the 3D distance deviations across research groups after the superimposing test and control scans.

RESULTS

A significant difference between research groups was revealed by trueness and precision analysis (p < 0.001). The trueness and precision results obtained for G1 and G4 were significantly better than those for G2 and G3 (p < 0.05).

CONCLUSION

This study demonstrated that implant depth could affect the digital implant impressions' 3D positional accuracy.

Knowledge, Awareness, and Perception of Dental Students Regarding Digital Dentistry in Egypt: A Cross-Sectional Study

Introduction Dental students are the future of the dental profession, and since digital dentistry is becoming more prevalent, they must receive an education that incorporates digital workflows and practices. This study aimed to determine the level of dental students' knowledge, awareness, and perception (KAP) of digital dentistry, as well as the influence of the type of school funding and information source on these aspects. Methods A cross-sectional online survey was performed between September 2023 and March 2024. Dental students from Egyptian public and private universities constituted our study sample. A 22-item questionnaire with four sections was employed for data collection. The data were analyzed using IBM SPSS Statistics for Windows, Version 25, (Released 2017; IBM Corp., Armonk, NY, USA). Results Out of 390 responses, 213 (54.6%) were females, 218 (55.9%) were students, and 287 (73.6%) received computer-aided design/computer-aided manufacturing (CAD/CAM) training in their dental schools. Most of the participants had a moderate to high level of knowledge (48.50% and 43.60%, respectively); 73.10% showed a moderate level of awareness; and 73.60% had a high level of perception of digital dentistry. Additionally, it was shown that interns and participants who gained their knowledge from social media and attended hands-on workshops had significantly higher KAP scores (p ≤ 0.05). The knowledge and perception scores were also impacted by attending a private dental school (p ≤ 0.05). Furthermore, reading books or articles considerably raised participants' awareness, whereas sharing knowledge with peers greatly enhanced their knowledge (p ≤ 0.05). Conclusion Our study revealed a moderate to high level of knowledge, a moderate level of awareness, and a high level of perception about digital dentistry among the majority of participants. Moreover, it underscores the need for comprehensive digital dentistry educational courses, emphasizing practical hands-on training - especially in public dental schools - to equip future dentists with the necessary knowledge and skills.

Digital technology implementation in prosthodontics postgraduate programs in Saudi Arabia: a multi-institutional survey of program directors

OBJECTIVE

To assess the current status of digital technology (DT) implementation in prosthodontics post-graduate (PG) programs in Saudi Arabian dental institutions.

METHODOLOGY

A 19-item survey was created using Google forms and the link was emailed to the 29 prosthodontics PG program directors (advanced clinical training and joint program) in Saudi Arabia. The questionnaire contained five Sect. 1) didactic training and DT usage in PG preclinical, clinical and laboratory training, 2) incorporation of DT in PG program, 3) utilization of DT and the types of cases treated by PG students during their course, 4) information on the faculties involved in prosthodontics PG education, and 5) potential challenges encountered and program directors' satisfaction of the PG program. Descriptive statistics was used to present the frequencies and proportions, and Chi square inferential test was used to compare the participants' response based on the type of PG programs (α = 0.05).

RESULTS

Only 28 program directors responded to the survey, yielding a 95.5% response rate. Among the program directors, 24 (85.7%) and 4 (14.3%) directors supervised the advanced clinical training and joint programs, respectively. Among the DT, CAD/CAM was the most used technology (50-80%), followed by intra-oral scanning (28-96%). Digital technology implementation was largely limited by lack of resources or equipment (67%), cost (53%) and scarcity of PG teaching staff (46%). A significant difference was observed between the programs regarding the mandatory use of DT for their cases (p = 0.03).

CONCLUSIONS

This multi-institutional survey of program directors revealed that DT is continuously implemented in the last few years. Saudi dental institutions must prioritize implementing and utilizing DT in PG training to graduate competent prosthodontists in this fast-paced digital era. While DT is pivotal in dental education, its implementation is limited in many institutions due to resources or equipment, cost, and lack of trained faculty.

Knowledge structure and research hotspots on digital scanning for implant-supported complete-arch prosthesis: A bibliometric analysis

Background

Digital scanning is increasingly widely used for implant-supported complete-arch prosthese. However, a quantitative literature analysis is lacking for this field. This study aims to conduct a bibliometric analysis to summarize the knowledge structure and research hotspots of digital scanning for implant-supported complete-arch prosthesis.

Materials and methods

Relevant articles and reviews, published between 1994 and 2023, were obtained from the Web of Science Core Collection (WoSCC). Indicators such as publication count, annual growth, citation count, co-citation count, impact factor, Journal citation reports (JCR) division, H-index are used to assess the contribution of countries, journals, authors or the quality of articles. Visual maps, cluster analysis and keyword cloud are used to evaluate the cooperation pattern and topic trends.

Results

580 eligible publications, including 555 articles and 25 reviews, were analyzed. The United States is the leading country in this area, received the most citations. The Journal of Prosthetic Dentistry is the scientific journal with the highest impact. The analysis of keywords and ongoing trials shows that the accuracy of relevant techniques is a current hot topic in this field.

Conclusion

In recent years, digital scanning technique for implant-supported complete-arch prosthesis has made rapid progress. By reviewing the published literature, we found the United States is the global leader in the field of digital scanning for complete-arch implant prosthesis. Accuracy is the core word in this field, more scientific evidence is needed to support the clinical application of digital scanning in this field.

Transitioning from injectable resin composite restorations to resin composite CAD/CAM veneers: A clinical report

OBJECTIVE

To describe a shift from injectable resin composite technique to composite resin computer-aided design and computer-aided manufacturing (CAD/CAM) veneers in addressing esthetic concerns associated with diastemas between anterior lower teeth in a clinical case.

CLINICAL CONSIDERATIONS

Among several techniques proposed for direct resin composite restoration, the "Injectable resin composite technique" has gained popularity for its time-efficiency, reduced technique sensitivity, and diminished reliance on clinician skills. However, challenges such as staining and the need for frequent polishing follow-ups may prompt the consideration of more stable alternatives such as indirect veneer restorations. While ceramic veneers offer superior mechanical and optical properties, resin ceramic veneers, especially those milled from CAD/CAM resin ceramic blocks, offer advantages such as rapid, cost-effective production, simplified intra-oral repairs, less susceptibility to fracture, superior stress absorption, and requires minimal tooth preparation, making them an appealing option for many patients. Moreover, a fully-digital approach not only streamlines the process but also saves time and labor while ensuring the delivery of high-quality restorations to patients.

CONCLUSION

In addressing a patient's dissatisfaction with constant polishing of direct resin composite restorations, a shift to resin composite CAD/CAM veneers was implemented. Utilizing a fully-digital approach with CAD/CAM resin ceramic restorations successfully restored both esthetics and function.

CLINICAL SIGNIFICANCE

While the injectable resin composite technique achieves immediate esthetic results, its low color stability necessitates frequent polishing sessions. The replacement of direct resin composite restorations with CAD/CAM resin composite veneers becomes a viable option for patients seeking more stable restorations that require fewer follow-ups. This transition addresses both esthetic concerns and the need for enduring solutions in restorative dentistry.

Virtual sketching-based dental anatomy module improves learners' abilities to use computer-aided design to create dental restorations and prostheses

Dental anatomy education for dental technology students should be developed in alignment with digital dental laboratory practices. We hypothesized that a virtually assisted sketching-based dental anatomy teaching module could improve students' acquisition of skills essential for digital restoration design. The second-year dental technology curriculum included a novel virtual technology-assisted sketching-based module for dental anatomy education. Pre- and post-course assessments evaluated students' skill sets and knowledge bases. Computer-aided design (CAD) scores were analyzed after one year to assess how the skills students developed through this module impacted their subsequent CAD performance. Participants who undertook the dental sketching-based teaching module demonstrated significantly improved theoretical knowledge of dental anatomy, dental aesthetic perception, and spatial reasoning skills. A partial least squares structural equation model indicated that the positive effects of this module on subsequent CAD performance were indirectly mediated by dental aesthetic perception, spatial reasoning, and practice time. A virtually assisted sketching-based dental anatomy teaching module significantly improved students' acquisition of skills and knowledge and positively mediated dental technology students' CAD performance.

Zirconia Dental Implant Designs and Surface Modifications: A Narrative Review

Titanium currently has a well-established position as the gold standard for manufacturing dental implants; however, it is not free of flaws. Mentions of possible soft-tissue discoloration, corrosion, and possible allergic reactions have led to the development of zirconia dental implants. Various techniques for the surface modification of titanium have been applied to increase titanium implants' ability to osseointegrate. Similarly, to achieve the best possible results, zirconia dental implants have also had their surface modified to promote proper healing and satisfactory long-term results. Despite zirconium oxide being a ceramic material, not simply a metal, there have been mentions of it being susceptible to corrosion too. In this article, we aim to review the literature available on zirconia implants, the available techniques for the surface modification of zirconia, and the effects of these techniques on zirconia's biological properties. Zirconia's biocompatibility and ability to osseointegrate appears unquestionably good. Despite some of its mechanical properties being, factually, inferior to those of titanium, the benefits seem to outweigh the drawbacks. Zirconia implants show very good success rates in clinical research. This is partially due to available methods of surface treatment, including nanotopography alterations, which allow for improved wettability, bone-to-implant contact, and osteointegration in general.

Comparison of the flexural strength of printed and milled denture base materials

BACKGROUND

To evaluate the flexural strength of digitally milled and printed denture base materials.

METHODS

The materials tested were Lucitone 199 denture base disc (Dentsply Sirona), AvaDent denture base puck (AvaDent), KeyMill denture base disc (Keystone), Lucitone digital print denture base resin (Dentsply Sirona), Formlab denture base resin (Formlabs), and Dentca base resin II (Dentca). Sixty bar-shaped specimens of each material were prepared for flexural strength testing and were divided into five groups: control, thermocycled, fatigue cycled, and repair using two different materials. The flexural strength and modulus were tested using a 3-point bend test performed on an Instron Universal Testing Machine with a 1kN load cell. The specimens were centered under a loading apparatus with a perpendicular alignment. The loading rate was a crosshead speed of 0.5 mm/min. Each specimen was loaded with a force until failure occurred. A one-way ANOVA test was used to analyze the data, followed by Tukey's HSD test (α = 0.05).

RESULTS

The milled materials exhibited higher flexural strength than the printed materials. Thermocycling and fatigue reduce the flexural strengths of printed and milled materials. The repaired groups exhibited flexural strengths of 32.80% and 30.67% of the original flexural strengths of printed and milled materials, respectively. Nevertheless, the type of repair material affected the flexural strength of the printed materials; the composite resin exhibited higher flexural strength values than the acrylic resin.

CONCLUSIONS

The milled denture base materials showed higher flexural strength than the printed ones.

Influence of sandblasting and bonding on the shear bond strength between differently pigmented polyetheretherketone (PEEK) and veneering composite after artificial aging

OBJECTIVE

Achieving a strong bond between Polyetheretherketone (PEEK) and veneering composites is challenging due to PEEKs low surface energy. This study examined the effects of sandblasting and bonding on the shear bond strength (SBS) between veneering composite and pigmented PEEK, considering artificial aging.

METHODS

Of three pigmented PEEK compounds (DC4420R, DC4450R, DC4470R; Evonic Operations GmbH, Marl, Germany), 40 specimens each were milled and polished up to 2500 grit. Prior to veneering, specimens were divided into 4 subgroups: Subgroup 1: Polishing; 2: Polishing + bonding; 3: Sandblasting; 4: Sandblasting + bonding. Sandblasting was performed using Al2O3. Adhesive was an agent containing MMA (Signum Universal Bond, Kulzer GmbH, Hanau, Germany). After veneering (Composite, Kulzer GmbH) the subgroups were divided into 2 subgroups. One subgroup was immersed in 37 °C warm distilled water for 24 h. The second subgroup was artificially aged by thermocycling (TCL) with 5000 cycles in distilled water (5 °C / 55 °C; 30 s). Surface roughness, water contact angles and failure modes were recorded. SBS was measured using a universal testing machine.

RESULTS

Results demonstrated that the combination of sandblasting and bonding significantly improved the SBS compared to polishing alone. PEEK color did not significantly influence the SBS. Aging by TCL had a negative effect on the SBS.

SIGNIFICANCE

Sandblasting and the use of an adhesive containing MMA were found to be effective in achieving satisfactory SBS between veneering composite and pigmented PEEK surfaces. These pretreatment methods demonstrate their potential for establishing durable and reliable bonding in clinical applications.

Comparison of the morphological accuracy of automatic crowns designed by multiple computer-aided design software programs with different levels of dentition information acquisition

STATEMENT OF PROBLEM

Information on the morphological accuracy of crowns automatically produced by different computer-aided design (CAD) software programs for multilevel dentition defects is limited.

PURPOSE

The purpose of this in vitro study was to compare the morphological accuracy of crowns fabricated using different CAD software programs with different design theories for multilevel dentition defects.

MATERIAL AND METHODS

Four dentition defect types (the standard group, the abrasion group, the adjacent-teeth-missing group, and the antagonist-tooth-missing group, n=10) were fabricated to represent different levels of missing dentition information. Two design modes (the library mode and correlation mode) of 3 common CAD software programs (3Shape [3Shape A/S], CEREC [Dentsply Sirona], and exocad DentalCAD [exocad GmbH]) were used to design crowns automatically, and the morphologies of the generated crowns and original teeth were recorded. The root mean square (RMS) value was calculated to evaluate the morphological deviations between the autogenerated crowns and original teeth using the 3D matching system (Geomagic GmbH). As each group in this study represented 3 factors, the mean differences between the treatment combinations and the interaction effects were analyzed by performing factorial analysis of variance (α=.05).

RESULTS

The RMS values of autogenerated crowns designed using the correlation method were significantly lower than those designed using the library method of each software program in the 4 groups (P<.05). The RMS values of crowns designed by the 3Shape and CEREC software programs in library mode under conditions with dentition information loss were lower than those of crowns designed by the exocad software program (P<.05). Changes in the acquisition of dental information did not decrease the CEREC design accuracy (P>.05), while they did decrease the 3Shape and exocad design accuracy (P<.05).

CONCLUSIONS

The correlation method showed higher accuracy in rebuilding the original morphology of the teeth than the library method. Both the 3Shape and CEREC software programs showed higher accuracy than the exocad software program in library mode under conditions with dentition information loss, while CEREC showed higher stability than the 3Shape and exocad software programs.

Advancements in guided surgical endodontics: A scoping review of case report and case series and research implications

This scoping review examined current case series and reports on guided surgical endodontic applications in order to provide a critical platform for future research. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) extension for scoping reviews guidelines were followed. A search on PubMed and Scopus yielded 611 articles, with 17 case reports and 1 series meeting inclusion criteria. Overall, guided surgery addressed anatomical complexities, with 15 articles employing static protocols and 3 dynamic. Results showed minimal iatrogenic errors and reduced chair time, with no postoperative issues reported. Within the cases described, guided endodontic surgery exhibited satisfactory results in management of anatomical complex cases. Cost-effectiveness, the need for adequate follow-up, procedure's reproducibility and accuracy, and objective measurement of the reduction in operative times and iatrogenic errors are some of the limitations in the current reports that need to be considered for planning of future experimental and cohort studies.

Influence of different designs of bulb support structures on the accuracy and weight of 3D printed maxillary obturators. An in vitro study

STATEMENT OF PROBLEM

Evidence is lacking on the influence of different designs of bulb support structures on the accuracy of 3-dimensional (3D) printed obturators.

PURPOSE

The purpose of this in vitro study was to evaluate the influence of various infill designs (hollow, honeycomb, and gyroid) for the bulb of an obturator on the accuracy and weight of digital light projection (DLP) 3D printed maxillary obturators.

MATERIAL AND METHODS

A maxillary obturator was virtually designed and used to obtain 3 digital reference files which were defined based on the design of the infill support structure within the bulb: hollow, honeycomb, and gyroid. The resultant standard tessellation language (STL) files were used to fabricate the obturators using a DLP 3D-printer in FREEPRINT denture resin material (n=10 per each group design). The fitting surfaces of all printed specimens (n=30) were digitized using a laboratory scanner, and the scan STL files were exported to the Geomagic control X program for dimensional accuracy analysis (trueness and precision) using the digital subtraction technique. One-way analysis of variance (ANOVA) was used for analysis (α=.05) RESULTS: Quantitative analysis revealed no significant difference in root mean square estimate (RMSE) values among the test groups for trueness (P=.326) and precision (P=.140). Hollow bulb design was significantly lighter in weight than both honeycomb and gyroid infill designs (P<.001). Colormaps revealed increased areas of negative deviation around the circumference of the bulb wall in the hollow design compared with both the gyroid and honeycomb groups and the close surface matching of fitting surfaces in the 3 groups.

CONCLUSIONS

The lack of significant difference in accuracy among the tested groups and the significantly lighter hollow design obturator compared with honeycomb and gyroid designs favors the selection of the hollow bulb design in the digital fabrication of maxillary obturators.

Aesthetic and Functional Rehabilitation for Dentogingival Asymmetry Using Zirconia Restorations

In an effort to improve dentogingival aesthetics, scientific research has been developing non-surgical techniques and dental restorative materials. A 45-year-old female reported to the hospital with a complaint of an unpleasant aesthetic in the anterior region of the maxilla. She has an irregular contour of the gingiva in her anterior region and no temporomandibular problems. There is a history of trauma, but she did not take any treatment for it, which caused discolouration. Plaque index was retained by the surface roughness. Due to this reason, the patient's appearance, self-esteem, and quality of life have decreased. The purpose of this case is to provide a system-based clinical example of oral rehabilitation for anterior teeth. The patient didn't like the way she looked, and hence aesthetic and functional rehabilitation was planned. Treating the dentogingival asymmetry was the first step in the therapeutic approach. An in-ceram zirconia permanent porcelain metal-free crown was positioned after the temporary crowns were cemented into place. It should be mentioned that in clinical situations, the integration of periodontal and prosthetic treatment is crucial. Additionally, it is stated that the in-ceram zirconia system can produce satisfactory results when applied appropriately. For the main anterior teeth, zirconia crowns have offered an alternate treatment option that addresses aesthetic concerns and facilitates the installation of extra-coronal restorations. This article describes a case involving the aesthetic and functional restoration of severely damaged maxillary incisors using zirconia crowns.

Evaluation of the effect of different core substrates on the accuracy of intraoral scanners

BACKGROUND

The aim of this study was to determine if different types of core substrates have any effect on the trueness and precision of digital intraoral impressions.

MATERIAL AND METHODS

A customized typodont with four similar cores of natural dentine, composite, metal (Ni-Cr), and zirconia in the position of premolars was fabricated. The study model was scanned five times with two types of intraoral scanners (Carestream 3600 and 3Shape Trios 3), and a reference standard scan was obtained using a laboratory scanner (3shape D1000). A metrology software (Geomagic X) was used to align the data of experimental scans and the reference scan to determine deviation values (trueness). Precision values were calculated with random superimposition in each intraoral scanner group. The Kruskal-Wallis test was used to compare differences between different substrates, and the Mann-Whitney test was used to compare the average values between the two scanners.

RESULTS

Trios 3 was found to be significantly truer and more precise than Carestream 3600 (p value = .005, <0.001). There were no significant differences in the trueness of different substrates when they were scanned by Trios 3, while different materials showed significantly different trueness values in the Carestream 3600 group (p value = .003). Dentin showed the best trueness, and zirconia performed worse than other substrates. Regarding the precision of the scanners, neither of the scanners was affected by the type of scanning substrate.

CONCLUSION

For Carestream 3600, substrate type did impact the trueness of intraoral scans, with dentin and zirconia showing the highest and lowest accuracy, respectively, while Trios 3 was similarly accurate across all substrates. Trios 3 had both higher trueness and precision than Carestream 3600.

Randomized clinical trial of zirconia laminate veneers sintered by using conventional versus speed process: 1-year follow-up

STATEMENT OF PROBLEM

The application of highly translucent multilayered zirconia ceramic in minimally invasive esthetic dentistry allows the achievement of both esthetics and strength with minimal thickness. Clinical studies that have assessed the performance of zirconia ultrathin veneers sintered with the conventional and speed procedure are lacking.

PURPOSE

The purpose of this clinical study was to evaluate the effect of speed sintering processes on the translucency and clinical performance of zirconia laminate veneers.

MATERIAL AND METHODS

Four participants had their teeth restored with 32 ultratranslucent zirconia laminate veneers. Based on the zirconia sintering procedure, the participants were randomly allocated into 2 groups. The teeth were prepared by selective reduction over trial restorations. Zirconia veneers were milled from multilayer zirconia blanks and sintered either by speed sintering or conventional sintering as specified by the manufacturer's recommendations. The intaglio surface of the veneers were airborne-particle abraded with 50-μm aluminum-oxide, and the veneers were then adhesively bonded to the teeth with translucent light-polymerizing resin cement. The modified California Dental Association (CDA)/Ryge criteria were used to assess participants at baseline and every 3 months for 12 months. The translucency and the color difference of the tooth before and after veneer restoration were evaluated. For statistical analysis, the Pearson chi squared test, independent t test, and paired t test were used (α=.05).

RESULTS

Translucency and color differences were significantly higher in the conventionally sintered group (P<.05). No restorations were lost. No significant differences were found between the 2 groups in the CDA/Ryge criteria or color parameter after follow-up intervals (P>.05). The primary qualitative changes observed at the final recall were marginal integrity and marginal discoloration. The color match and zirconia surface were rated Alfa.

CONCLUSIONS

After 1 year of follow-up, both conventional and speed sintered ultrathin zirconia laminates showed satisfactory functional, esthetic, and color stability outcomes.

Cellular responses to 3D printed dental resins produced using a manufacturer recommended printer versus a third party printer

PURPOSE

The aim of this study was to evaluate the influence of different 3D dental resins, using a manufacturer recommended printer and a third-party printer, on cellular responses of human gingival cells.

MATERIALS AND METHODS

Three NextDent resins (Denture 3D+, C&B MFH and Crowntec) were used to produce specimens on printers NextDent 5100 (groups ND, NC and NT, respectively) and Phrozen Sonic Mini 4K (groups PD, PC and PT, respectively). Human gingival fibroblasts were cultured and biocompatibility was evaluated on days 1, 3 and 7. IL-6 and IL-8 concentrations were evaluated at 3 days using ELISA. Surface roughness was evaluated by a contact profilometer. SEM and fluorescence micrographs were analyzed at days 1 and 7. Statistical analyses were performed using SPSS and mean differences were tested using ANOVA and post-hoc Tukey tests (P < .05).

RESULTS

There was an increase in cellular viability after 7 days in groups PC and PT, when compared to group PD. ND group resulted in higher concentration of IL-6 when compared to PT group. SEM and fluorescence micrographs showed less adhesion and thinner morphology of fibroblasts from group PD. No significant differences were found regarding surface roughness.

CONCLUSION

The use of different printers or resins did not seem to influence surface roughness. NextDent 5100 and Phrozen Sonic Mini 4K produced resins with similar cellular responses in human gingival fibroblasts. However, Denture 3D+ resin resulted in significantly lower biocompatibility, when compared to C&B MFH and Crowntec resins. Further testing is required to support its long-term use, required for complete dentures.

Stereomicroscope-Based in Vitro Study Evaluating the Marginal and Internal Fit of PEEK and PEKK Crowns

Purpose

The aim of the in vitro study was to compare the internal merge and marginal perfection of polyetheretherketone (PEEK) and polyetherketoneketone (PEKK) crowns under a stereomicroscope.

Methods

All-ceramic preparation is done on the maxillary first premolar which is mounted on the wax block which was scanned using 3Shape scanner and duplicated into 30 acrylic CAD/CAM dies (n = 15) for the placement of PEEK and PEKK crowns. The YENADENT milling system was used to fabricate 15 samples from Group A PEEK crowns and to fabricate 15 samples from Group B PEKK crowns. According to the manufacturer's instructions, an equal amount of the dual-cure resin luting agent (Rely X U200 Self-Adhesive resin, 3M, Germany) was dispensed on the mixing pad before being mixed with cement and painted on the internal surfaces of the copings with the finger pressure crowns which were luted. The values were then analyzed using one-way ANOVA (post hoc) followed by Dunnett's t-test.

Results

Among those two groups, PEEK group materials showed the lowest mean value of (28.73.3 ± 4.01) for marginal fit and (26.72 ± 2.53) for internal gap, whereas PEKK group showed a mean value of (32.85 ± 4.63) and (33.06 ± 4.14), respectively.

Conclusion

Among these two groups, comparatively less marginal fit and internal adaptation is seen in PEKK when compared to the PEEK crowns. While the marginal fit and internal adaptation of both PEEK and PEKK copings were in acceptable clinical range.

Comparing CBCT to model scanner for dental model scanning. An in vitro imaging accuracy study

OBJECTIVE

The aim of this study is to compare the accuracy of cone beam computed tomography (CBCT) for dental model scanning to the accuracy of model scanners.

METHODS

Subjects from private practice were collected and scanned according to specific selection criteria. A total of 10 STL files were produced and used as reference files. They were printed with a three-dimensional (3D) printer and then scanned with CBCT and model scanner. For trueness evaluation, all models were scanned once with both equipments. Each file derived from each scan was compared with the corresponding reference model file. For the precision measurements, the physical model from the first master reference model file was scanned 10 times with each equipment and compared with the reference STL file. A reverse engineering software was used for all 3D best-fit comparisons.

RESULTS

With regard to the measurement of trueness of each method, the calculated mean root mean square (RMS) value was 0.06±0.01mm for the CBCT, and 0.15±0.02mm for the model scanner. There was a significant difference between the two methods (P<0.01). For the evaluation of precision of each scanner, the mean RMS value was 0.0056±0.001mm for the CBCT, and 0.153±0.002mm for model scanner. There was a significant difference between the two methods (P<0.01).

CONCLUSIONS

Cone Beam Computed Tomography seems to be an accurate method for scanning dental models. CBCT performs better than model scanners to scan dental models in terms of trueness and precision.

Materials and Methods for All-Ceramic Dental Restorations Using Computer-Aided Design (CAD) and Computer-Aided Manufacturing (CAM) Technologies-A Brief Review

The materials used in dentistry for the fabrication of all-ceramic restorations have undergone great and rapid developments over the last two decades. Among the most common ceramic materials in dentistry are those based on zirconium and lithium disilicate. Due to the properties of these materials, they are in great demand in the field of dental restoration production. Thus, dental restorations that will use those materials are commonly machined in CAD/CAM systems, which offer the possibility of manufacturing all-ceramic dental restorations in a very short period of time. This article reviews the modern materials in the field of all-ceramic dental restorations, their manufacturing processes, as well as what determines which ceramic materials are used for the production of CAD/CAM blanks and their production technology.

Effect of various surface treatments on relining bond strength of CAD-CAM denture base materials

PURPOSE

The aim of this study was to analyze the impact of various surface treatments and production methods on the shear bond strength (SBS) between reline material and denture base resins.

MATERIALS AND METHODS

One-hundred-twenty specimens were produced using conventional heat-polymerization, subtractive, and additive techniques. Each group consisted of 40 specimens. The specimens were divided into four subgroups, each with 10 samples, for surface treatments. These subgroups were: (1) Control-only monomer application, (2) 50 μm airborne-particle abrasion, (3) 110 μm airborne-particle abrasion, and (4) Roughening with tungsten carbide bur. Representative specimens from each subgroup were examined under SEM. Then, auto-polymerized resin was condensed in the center of the specimens. Specimens were subjected to thermal aging (5000 cycles at 5-55°C). The SBS test was conducted and failure loads were recorded. The data were evaluated by two-way ANOVA and Tukey pairwise multiple comparisons method (p < 0.05).

RESULTS

The additively produced group showed significantly lower SBS than conventional and subtractive groups (p < 0.001), with no significant differences between the subtractive and conventional groups. Specimens that underwent monomer application only showed the lowest SBS among surface treatments, while 50 μm airborne-particle abrasion showed the highest SBS. Based on the partial eta-squared analysis results, the surface treatment mainly impacted SBS.

CONCLUSIONS

Among the surface treatment methods, treating denture bases with 50 μm airborne-particle abrasion is more effective for maintaining adhesion, especially in the additive technique.

Fully digital workflow for the fabrication of occlusal stabilization splints based on individual mandibular movement

OBJECTIVE

This study was conducted to present a completely digital workflow for the fabrication of occlusal stabilization splints using CAD/CAM systems and a digital face bow based on optical sensor technology.

METHODS

Digital scans of the maxillary and mandibular arches of 20 volunteers were obtained using an intraoral scanner. Jaw relation and mandibular movements were recorded with a digital face bow via optical sensors. The virtual increase of the vertical dimension of occlusion (VDO) was then performed, after which computer-aided design (CAD) of the occlusal stabilization splints was carried out. The corresponding splints were then manufactured using digitally controlled technology.

RESULTS

A completely digital workflow for the manufacturing of occlusal stabilization splints was found to be clinically feasible. The corresponding data analysis revealed high congruence between virtual and physical occlusal contacts on the occlusal splint. Moreover, the appropriate guidance of the anterior teeth area was easily obtainable, and the time for adjusting the occlusion was less.

CONCLUSIONS

This study demonstrated that the fabrication of occlusal stabilization splints using a fully digital workflow is feasible. Compared to traditional impression-based manufacturing, several advantages of digital manufacturing include easy accessibility, time-efficient manufacturing, high-level accuracy in splint quality, and potential to manufacture duplicate splints.

CLINICAL SIGNIFICANCE

The proposed fully digital approach may help young dentists fabricating stable occlusal splints with beneficial curative effects. Meanwhile, it could also improve the production efficiency of stable occlusal splints, saving time for both doctors and patients while reducing labor costs.

Time efficiency and cost analysis between digital and conventional workflows for the fabrication of fixed dental prostheses: A systematic review

STATEMENT OF PROBLEM

Time and cost are factors that influence a patient's decision on dental prosthetic treatment. Evidence is needed to demonstrate that restoration using digital systems is more rapid and less costly than the conventional process.

PURPOSE

The purpose of this systematic review was to analyze and compare the duration and cost of fixed dental prostheses fabricated using digital and conventional methods from scanning or impression making to delivery of the prosthesis.

MATERIAL AND METHODS

A systematic review was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis Protocol (PRISMA-P 2015) guidelines. The analysis methods and inclusion criteria were documented in a protocol registered in the Prospective International Register of Systematic Reviews (PROSPERO) (CRD42023458734). The bibliographic search was carried out using PubMed, Cochrane, and PROSPERO databases. The main keywords used were (Prosthodontic OR restorative dentistry OR denture) AND (CAD CAM OR Digital workflow OR Computer Dentistry OR Digital Design) AND (Economic OR cost OR Financial OR time efficiency). Two investigators undertook the different steps of article selection.

RESULTS

A total of 8 articles published between 2010 and 2023 were found for the qualitative synthesis by using the search criteria. Two studies showed that conventional impressions took more time than digital scans for the fabrication of a single crown, and 1 study showed the opposite. One study found that a digital scan was faster than conventional impression making for the fabrication of a 3-unit fixed partial denture, and another study showed the opposite. The dental laboratory technician spent more time on the conventional workflow than the digital workflow for the 3-unit framework and veneering process. No difference was found between conventional and digital workflows for clinical evaluation and chairside adjustment for the fabrication of a single crown. No articles have compared the cost of fixed prostheses.

CONCLUSIONS

The digital pathway can shorten the laboratory process. However, the duration of the impression or scan may vary depending on the technique used. Studies are needed to analyze the cost-effectiveness of the fabrication of tooth-supported restorations.

A randomized clinical study evaluating the 30-month clinical performance of class II indirect restorations in endodontically treated teeth using ceramic, hybrid, and composite computer-aided design/computer-aided production blocks

Context Background

In the literature, the information about which indirect material is the most appropriate for the restoration of endodontically treated teeth is insufficient. Therefore, studies evaluating the clinical performance of root canal-treated teeth will shed light on this issue for clinicians.

Aim

This clinical study aimed to evaluate the clinical performances of class II indirect restorations using ceramic, hybrid, and composite blocks to endodontically treated teeth.

Materials and Methods

A total of 60 indirect class II restorations were performed in 51 patients using Cerasmart (GC Dental Products Europe, Leuven, Belgium) composite, IPS e.max computer-aided design CAD (Ivoclar Vivadent, Schaan, Liechtenstein) ceramic, and Vita Enamic (Vita Zahnfabrik, Bad Sackingen, Germany) hybrid blocks. All the restored teeth had root canal treatment. The restorations were evaluated using modified FDI criteria for 30 months.

Statistical Analysis Used

The data were analyzed using Kruskal-Wallis analysis and Friedman two-way analysis of variance.

Results

A total of 53 restorations of the 60 restorations could be followed up at the end of 30 months. No statistically significant difference was observed between the groups after 30 months in terms of all criteria evaluated (P > 0.05).

Conclusion

Composite, ceramic, and hybrid blocks showed successful clinical performance in endodontically treated posterior teeth with large material loss.

The Digital Era Heralds a Paradigm Shift in Dentistry: A Cross-Sectional Study

Background The transformation of dental practice from conventional methods to digital technology has been widely discussed. This study aimed to examine the awareness, understanding, and attitudes towards the use of digital technology in dentistry, with a particular focus on computer-aided design/computer-aided manufacturing (CAD/CAM) technology. Methods A cross-sectional study was conducted, involving a questionnaire distributed to a diverse group of participants from the dental field. The questionnaire covered aspects of digital technology in dentistry, including awareness, perceived usefulness, understanding of CAD/CAM technology, perceived benefits and shortcomings, system awareness, and the impact on clinical decision-making. Results Almost all participants (99.3%) reported being aware of digital technology in dentistry. The perceived utility of digital technology varied widely, but it was considered particularly useful for specific dental procedures. Most of the respondents (948 out of 953) were aware of CAD/CAM technology, and many acknowledged its benefits, including fewer appointments, less chairside time, and greater precision. However, high cost, lack of knowledge, and preference for traditional methods were identified as barriers to adoption. Most participants believed that CAD/CAM would influence clinical decision-making and expressed interest in integrating it into their regular workflow. A majority had attended CAD/CAM training programs and believed there was a need to increase education on CAD/CAM during undergraduate and postgraduate courses. While a significant majority agreed that digital technology was the future of dentistry, a substantial number also expressed reservations. Conclusion The study concluded that there is a high level of awareness and readiness to adopt digital technology in dentistry. However, its perceived utility varied among participants, and several barriers to adoption were identified, indicating the need for expanded education and training. Despite some resistance, there is a growing recognition of the potential benefits of CAD/CAM technology and a trend towards integrating it into regular practice.

Application of CAD/CAM technologies and materials for prosthetic restoration of severely damaged teeth-clinical cases

In cases of severely damaged teeth with limited coronal tooth structure and remaining hard dental tissues subgingivally, a custom-made post-and-core restoration is required. Teeth with non-circular canal space also require this type of restoration because the build-up with pre-fabricated posts could lead to thick cement layer. The development of CAD/CAM technologies widens the range of the materials that can be used for prosthetic restorations. Along with base dental alloys, newly developed materials may be applied. The aim of the article is to present four clinical cases of severely damaged teeth which utilize different materials and different production techniques for custom post-and-core fabrication. In the first clinical case, a metal post-and-core restoration was fabricated by direct metal laser sintering. In the second clinical case, digital technologies were used to produce a 3D-printed resin prototype for further investing and casting from base metal dental alloy. In the third clinical case, fibre-reinforced composite was used for fabrication of the custom post-and-core by milling. In the fourth clinical case, the restoration is produced by milling of lithium disilicate ceramics IPS emax CAD (Ivoclar Vivadent, Lichtenstein). The bond between the fibre-reinforced composite post-and-core and the hard dental tissues offered possibility to compensate-to some extent-the shape of the preparation which was not optimal. CAD/CAM technologies applied in these clinical cases provided combination of high accuracy of fitting with good stability and individual shape of the restorations. © 2023 Australian Dental Association.

Digital beading for a CAD-CAM framework for an implant-supported overdenture: A dental technique

The analog technique of making bead lines for a metal superstructure framework for the maxillary implant-supported overdenture is created by scribing shallow grooves on the surface of a definitive gypsum cast. This report describes a digital technique that uses computer-aided design and computer-aided manufacturing technology to make dental bead lines on an intraoral impression without using the gypsum cast.

Comparison of the weight of conventionally heat-processed hollow and solid obturators and 3D printed hollow obturators

STATEMENT OF PROBLEM

The weight of larger obturators places increased stress on the supportive teeth and bearing tissue and allows gravity to act as a dislodging factor affecting the stability and retention of the prosthesis. However, whether conventionally processed and 3-dimensionally (3D) printed hollow obturators have similar reduced weights compared with solid obturators is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate the weight difference between conventionally heat-processed complete denture obturators with and without hollowing and 3D printed obturators with a hollow bulb.

MATERIAL AND METHODS

Obturators were fabricated as conventionally heat-processed solid obturators, conventionally heat-processed with a hollow obturator bulb, and 3D printed with a hollow obturator bulb. Nine obturator prostheses were fabricated for each type of Aramany Class I, Class II, and Class III defect. The weights of each of the 27 obturator prostheses were measured, and a statistical analysis was performed with exact versions of the Kruskal-Wallis test or Wilcoxon Rank Sum test (α=.05).

RESULTS

Conventionally heat-processed solid obturators were significantly heavier than the conventionally heat-processed hollow (P<.001) or the 3D printed hollow obturators (P<.001). No significant difference (P=.222) was found between the conventionally heat-processed hollow and 3D printed hollow obturators. The decrease in weight was proportional to the size of the defect with the Aramany Class I defect having the largest differences in weight between the different fabrication methods, followed by Class II, and then Class III with a much smaller defect.

CONCLUSIONS

Additive manufacturing could be a suitable alternative to conventional techniques for the fabrication of a closed hollow obturator because of the comparable weights.

Surface trueness and precision of interim restorations fabricated by digital light processing and CAD-CAM milling systems

STATEMENT OF PROBLEM

The development of digital dental technologies has enabled clinicians to use additive and subtractive manufacturing techniques to fabricate interim restorations. However, knowledge of the trueness and precision of such restorations fabricated using digital light processing (DLP) and computer-aided design and computer-aided manufacturing (CAD-CAM) methods is limited.

PURPOSE

The purpose of this in vitro study was to assess and compare the accuracy of interim crowns fabricated using DLP and CAD-CAM methods.

MATERIAL AND METHODS

A typodont mandibular first molar was prepared for a ceramic crown, and a digital scan (Medit T500) was obtained to design interim crowns by using the CAD software program. The CAD data were designated as the reference data. A total of 20 crowns were fabricated by DLP and CAD-CAM technology. The fabricated interim crowns were further scanned using a laboratory scanner and were superimposed with the CAD data by using a 3-dimensional (3D) point cloud assessing software program (CloudCompare) for the evaluation of trueness and precision. Root mean square values (RMS) were obtained for the evaluation of discrepancies. The Student t test was used to compare data as the Shapiro-Wilk test confirmed the normal distribution.

RESULTS

RMS values for the trueness values of the external and intaglio surfaces of the 3D printed and milled interim crown displayed no statistically significant differences (P>.05). Precision for the external surface reported significance (P<.05), whereas that for the intaglio surface reported no significance (P>.05).

CONCLUSIONS

The accuracy of interim crowns fabricated by using DLP was comparable with that of milled crowns. Both manufacturing systems produced a true reproduction of the CAD. As for precision, the external surface of the DLP interim crown was statistically different from that of the milled group as it relates to the CAD.

Systematic review evaluating the influence of the prosthetic material and prosthetic design on the clinical outcomes of implant-supported multi-unit fixed dental prosthesis in the posterior area

OBJECTIVE

The objectives of the study were to assess the survival, failure, and technical complication rates of implant-supported fixed dental prosthesis (iFDPs) with pontic or splinted crown (iSp C) designs in the posterior area and compare the influence of prosthetic materials and prosthetic design on the outcomes.

METHODS

Electronic and manual searches were performed to identify randomized-, prospective-, and retrospective clinical trials with follow-up time of ≥12 months, evaluating the clinical outcomes of posterior iFDPs with pontic or iSp Cs. Survival and complication rates were analyzed using robust Poisson's regression models.

RESULTS

Thirty-two studies reporting on 42 study arms were included in the present systematic review. The meta-analysis of the included studies indicated estimated 3-year survival rates of 98.3% (95%CI: 95.6-99.3%) for porcelain-fused-to-metal (PFM) iFDPs, 97.5% (95%CI: 95.5-98.7%) for veneered zirconia (Zr) iFDPs with pontic, 98.9% (95%CI: 96.8-99.6%) for monolithic or micro-veneered zirconia iFDPs with pontic, and 97.0% (95%CI: 84.8-99.9%) for lithium disilicate iFDPs with pontics. The survival rates for different material combination showed no statistically significant differences. Veneered restorations, overall, showed significantly (p < .01) higher ceramic fracture and chipping rates compared with monolithic restorations. Furthermore, there was no significant difference in survival rates (98.3% [95%CI: 95.6-99.3%] vs. 99.1% [95%CI: 97.6-99.7%]) and overall complication rates between PFM iFDPs with pontic and PFM iSp Cs.

CONCLUSIONS

Based on the data identified by this systematic review, PFM, veneered Zr, and monolithic Zr iFDPs with pontic and iSp Cs showed similarly high short-term survival rates in the posterior area. Veneered restorations exhibit ceramic chipping more often than monolithic restorations, with the highest fracture rate reported for veneered Zr iFDPs.

A comparative study of CAD/CAM fabricated polyether ether ketone and fiber-glass reinforcement composites versus metal lingual retainers under vertical load (an in vitro study)

BACKGROUND

Retainer is a necessary procedure when orthodontic treatment complete to avoid relapse due to periodontal fiber elasticity and to allow for alveolar bone regeneration. Compare the influence of vertical force on the failure of three fixed retainers: CAD/CAM polyether ether ketone (PEEK), CAD/CAM fiber glass reinforced composites (FRCs), and lingual retainer wire "Bond-A-Braid™".

MATERIALS AND METHODS

One hundred and eight maxillary first premolars teeth were randomly allocated to three groups: Group A (CAD/CAM PEEK), Group B (CAD/CAM FRC), and Group C (lingual retainer wire " Bond-A-Braid™"). These retainers were bonded using Assure Plus Bonding Resin and GO TO Paste. For each specimen, a loading cycling and thermocycling machine was used. The failure debonding forces were measured on the interproximal segments using a universal testing machine with a cross-head speed of 1 mm/min. The adhesive remnant index (ARI) was calculated after identifying types of failure with a stereomicroscope at (X 20) magnification.

RESULTS

Group B and group C showed the highest failure bonding forces, with a mean of 209.67 ± 16.15 and 86.81 ± 4.59 N, respectively. However, Group A had a statistically significant lower bond failure force, with a mean value of 45.73 ± 4.48 N. At baseline, there was a statistically significant difference in connector retainer displacement between the three studied groups (p < .001). The ARI score was not statistically significant (p < .001) between the three study groups; for groups A and B, the ARI was predominantly score 3, and group C showed a mixed score of 2 and 3. The failure mode of retainers was investigated using an optical stereomicroscope. In group B, there was a cohesive breakdown in the retainer, and groups A and C exhibited failures primarily in the adhesive at the retainer interface.

CONCLUSION

All groups differed significantly, with group A having the lowest debonding force and group B having the highest. Furthermore, there was not a substantial variation in ARI, but there was a significant difference in connector retainer displacement and the types of failure amongst the three groups.

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

BACKGROUND

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.

METHODS

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).

RESULTS

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.

CONCLUSIONS

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.

Improving retention of dental veneers fabricated from an experimental enamel-based biopolymer compared with CAD/CAM hybrid materials

Objectives

CAD/CAM hybrid materials have become increasingly utilized in restorative dentistry. However, their low tensile bond strength (TBS) may lead to the detachment of minimally invasive restorations. When prepared, an experimental enamel-based biopolymer prosthesis provided a honeycomb-like interfacial layer with luting adhesives leading to a higher TBS than Ni-Cr-Be based alloy, lithium disilicate-based ceramic, and cured-resin-composite. This study aimed to compare TBSs of dental veneers fabricated from experimental biopolymer and commercial hybrid materials bonded to enamel using two different luting adhesives.

Methods

Laminate veneers (4 × 4 mm) 1 mm thick were prepared from commercial CAD/CAM blocks: VITA ENAMIC, SHOFU Block HC, KATANA AVENCIA, and an experimental biopolymer. The flat bonding surface of the veneers was ground to 600-grit, followed by 50-μm alumina air-abrading for standardization. Each veneer was fixed on flat ground bovine enamel using either Super-Bond C&B or RelyX™ U200 resin (n = 10). The surface treatment and bonding procedures were treated as recommended by the manufacturers. All bonded specimens were stored in water at 37 °C for 24 h before tensile testing with a universal testing machine at a cross-headed speed of 1.0 mm/min. The fractured surface was examined with a stereomicroscope and scanning electron microscope. TBS data were statistically analyzed using two-way ANOVA and Tukey's HSD test (α = 0.05).

Results

Experimental biopolymer veneers demonstrated the highest mean TBS with cohesive failure in the luting agents. Adhesive failure at the veneer side interface was found in other groups. There was no significant difference between the two luting agents.

Conclusion

The results indicate that the experimental biopolymer veneer bonded to enamel provided the best retention. The TBS at the enamel-resin interface is higher than at the veneer-resin interface for all commercial CAD/CAM hybrid materials.

Clinical significance

An experimental enamel-based biopolymer veneer can provide better retention than CAD/CAM hybrid materials in clinical treatment.

Effect of ceramic primers with different chemical contents on the shear bond strength of CAD/CAM ceramics with resin cement after thermal ageing

BACKGROUND

This study evaluated the effect of ceramic primers containing 10-methacryloyloxydecyl phosphate (10-MDP) and γ-methacryloxypropyl trimethoxysilane (γ-MPTS) agents on the shear bond strength (SBS) of CAD/CAM ceramics with different chemical structures and resin cement.

METHODS

A total of 640 CAD/CAM ceramic specimens were obtained from Vita Mark II (VM), IPS E.max CAD (EM), Vita Suprinity (VS) and Vita Enamic (VE). The specimens were divided into two groups: etched with hydrofluoric acid (HF) and unetched. Each group was treated with a different ceramic primer (Clearfil Ceramic Primer Plus, G-Multi Primer and Monobond S), except for an untreated group (n = 10). After ceramic primers and resin cement were applied to each ceramic surface, half of the specimens were thermally aged at 10,000 cycles, 5-55 ± 1 °C, with a dwell time of 30 s. The SBS was tested with a universal testing machine at a 0.5 mm/min crosshead speed. Data were analysed by using statistical software (SPSS 20). Normal data distribution was checked with the Shapiro‒Wilk test. Three-way ANOVA was used to analyse the difference between the numeric data of the HF etched and thermally aged groups. A post hoc Tukey test was applied in the paired comparison of significant difference. The statistical significance level was accepted as p < 0.05.

RESULTS

The highest SBS values were obtained in the HF etched G-Multi primer applied nonaged EM group (28.3 ± 2.62 MPa), while the lowest values were obtained in the nonetched and thermally aged EM group that received no treatment (2.86 ± 0.04 Mpa). The SBS significantly increased in all specimens on which the ceramic primer was applied (p < 0.001). Thermal ageing had a significant negative effect on the SBS values in all groups (p < 0.001).

CONCLUSION

The positive combined effects of the 10-MDP and γ-MPTS agents resulted in a significant increase in the bonding strength of the resin cement to the CAD/CAM ceramics. In addition, the increase in the amount of inorganic filler provided a favourable effect on durable adhesion.

Fracture Resistance Analysis of CAD/CAM Interim Fixed Prosthodontic Materials: PMMA, Graphene, Acetal Resin and Polysulfone

The aim of this study was to evaluate and compare the fracture resistance of temporary restorations made of polymethylmethacrylate (PMMA), graphene-modified PMMA (GRA), acetal resin (AR) and polysulfone (PS) obtained by a subtractive technique (milling) using a computer-aided design and manufacturing (CAD/CAM) system of a three-unit fixed dental prosthesis (FDP). Methods: Four groups of ten samples were fabricated for each material. Each specimen was characterized by a compression test on a universal testing machine, all specimens were loaded to fracture and the value in Newtons (N) was recorded by software connected to the testing machine. The fracture mode was evaluated on all samples using a stereomicroscope. Results: There were statistically significant differences (p value < 0.005) between PMMA and the other three materials (PMMA: 1302.71 N; GRA: 1990.02 N; RA: 1796.20 N; PS: 2234.97). PMMA presented a significantly lower value than the other materials, and PS showed the highest value. GRA and RA presented a similar range of values but they were still higher than those of PMMA. Conclusions: GRA, RA and PS are presented as valid options within the range of interim milled restorative materials and as alternatives to PMMA.

CAD-CAM complete denture resins: Effect of relining on the shear bond strength

OBJECTIVES

The aim of this study was to compare the shear bond strength of relined CAD-CAM complete removable dental prosthesis (CRDP) resins with conventional heat-polymerized polymethylmethacrylate (PMMA) resin.

METHODS

A total of 96 resin specimens in identical dimensions of 10 mm × 10 mm × 11 mm were fabricated for four study groups [#1- Conventional heat-polymerized group: n=24 (ProBase); #2- Milled#1: n=24 (Ivobase); #3- Milled#2: n=24 (Ivotion); #4- 3D-printed: n=24, (NextDent Denture 3D+)]. Twelve specimens in each group were sectioned in the middle to produce a 3 mm defect and then were relined using a conventional denture relining material. All specimens underwent thermocycling (5-55°C) for 10,000 cycles. The shear bond tests were carried out in a universal testing machine. One-way ANOVA and Tukey's test were used for statistical analysis (p<0.05). The two-parameter Weibull distribution values were calculated.

RESULTS

Relined 3D-printed specimens had a significantly lower shear bond strength when compared with conventional (p=0.0003) and milled groups (Milled#1: p=0.0004; Milled#2: p<0.0001). There were no differences in the shear bond strengths between the milled and conventional groups. Weibull distribution presented the highest shape value for the non-relined Milled#1 (22.83) group and the lowest values for the 3D-printed relined group (4.001).

CONCLUSION

The findings of this study conclude that the shear bond strength of the conventionally-relined 3D-printed resins used for fabricating CRDPs was inferior to the shear bond strength of conventionally-relined resins employed for manufacturing CRDPs using CAD-CAM milling and conventional heat-polymerization techniques.

CLINICAL SIGNIFICANCE

When considering 3D-printing for the fabrication of CRDPs, it is recommended to employ it in clinical situations where a frequent need for denture relining is not expected.

Flexural Strength Properties of Five Different Monolithic Computer-Aided Design/Computer-Aided Manufacturing Ceramic Materials: An In Vitro Study

Objective

The purpose of this in vitro study is to compare the flexural strength and Weibull modulus of 5 different monolithic computer-aided design/computer-aided manufacturing (CAD/CAM) ceramics.

Methods

A total of 50 specimens were fabricated, 10 from each of the following materials: lithium disilicate-based ceramic (IPS e.max CAD), zirconia -reinforced lithium-silicate ceramic (Vita Suprinity), leucite-based glass ceramic (IPS Empress CAD), and two zirconia-based ceramics (Zenostar and CopraSmile). The specimens were 4 mm wide, 2 mm thick, and 16 mm long. Flexural strength test was executed using a universal testing machine (Model 5980, Instron Industrial Products, Norwood, MA, USA). The two-parameter Weibull distribution function was used to analyze the variability of flexural strength values. Statistical analysis was performed on SPSS Version 23 (IBM Corp., Armonk, NY, USA) using one-way analysis of variance (ANOVA) and post-hoc Tukey’s test.

Results

Suprinity had the highest Weibull modulus value, while Empress CAD displayed the lowest value. One-way ANOVA showed significant difference in the flexural strength between the different materials tested (p<0.05). Post-hoc analysis revealed significant differences among all the test groups in terms of flexural strength. Zenostar presented the highest mean flexural strength value (1033.90 MPa), while Empress CAD had the lowest value.

Conclusion

High-translucency zirconia had superior flexural properties than translucent zirconia, lithium disilicate ceramics, zirconia-reinforced lithium silicate ceramics, and leucite-based glass ceramics.

Accuracy of Dental Models Fabricated Using Recycled Poly-Lactic Acid

Based on the hypothesis that the fabrication of dental models using fused deposition modeling and poly-lactic acid (PLA), followed by recycling and reusing, would reduce industrial waste, we aimed to compare the accuracies of virgin and recycled PLA models. The PLA models were recycled using a crusher and a filament-manufacturing machine. Virgin PLA was labeled R, and the first, second, and third recycles were labeled R1, R2, and R3, respectively. To determine the accuracies of the virgin and reused PLA models, identical provisional crowns were fitted, and marginal fits were obtained using micro-computed tomography. A marginal fit of 120 µm was deemed acceptable based on previous literature. The mesial, distal, buccal, and palatal centers were set at M, D, B, and P, respectively. The mean value of each measurement point was considered as the result. When comparing the accuracies of R and R1, R2, and R3, significant differences were noted between R and R3 at B, R and R2, R3 at P, and R and R3 at D (p < 0.05). No significant difference was observed at M. This study demonstrates that PLA can be recycled only once owing to accuracy limitations.

SEM Evaluation of the Marginal Accuracy of Zirconia, Lithium Disilicate, and Composite Single Crowns Created by CAD/CAM Method: Comparative Analysis of Different Materials

(1) Background: The objective of this in vitro study is to evaluate the marginal accuracy of crowns created by CAD/CAM. (2) Methods: A customized chrome-cobalt (Cr-Co) implant abutment simulating a maxillary right first molar was fixed in a hemi-maxillary stone model and scanned. In total, 27 crowns were fabricated, including 9 lithium disilicate crowns, 9 composite crowns, and 9 zirconia crowns. The measurements were determined by scanning electron microscopy. Descriptive analysis was performed using the mean and standard deviation, while the Kruskal-Wallis test was performed to determine whether the marginal discrepancies were significantly different between each group (p < 0.05). (3) Results: The lowest marginal gap value was reported for zirconia (21.45 ± 12.58 µm), followed by composite (44.7 ± 24.96 µm) and lithium disilicate (62.28 ± 51.8 µm). The Kruskal-Wallis tests revealed a statistically significant difference (p-value < 0.05) in the mean marginal gaps between different materials. (4) Conclusions: The proposed digital workflow can be a viable alternative for fixed prosthetic rehabilitations. The best performance in terms of marginal gap was achieved by zirconia crowns, but all three materials demonstrate marginal closure below the clinically accepted threshold value (120 µm). Clinical significance: although significant differences were reported, the investigated CAD/CAM materials showed clinically acceptable marginal gaps.

Microscopic Inspection of the Adhesive Interface of Composite Onlays after Cementation on Low Loading: An In Vitro Study

Purpose: This study aimed to assess the layer thickness and microstructure of traditional resin-matrix cements and flowable resin-matrix composites at dentin and enamel to composite onlay interfaces after cementation on low loading magnitude. Materials and Methods: Twenty teeth were prepared and conditioned with an adhesive system for restoration with resin-matrix composite onlays manufactured by CAD-CAM. On cementation, tooth-to-onlay assemblies were distributed into four groups, including two traditional resin-matrix cements (groups M and B), one flowable resin-matrix composite (group G), and one thermally induced flowable composite (group V). After the cementation procedure, assemblies were cross-sectioned for inspection by optical microscopy at different magnification up to ×1000. Results: The layer thickness of resin-matrix cementation showed the highest mean values at around 405 µm for a traditional resin-matrix cement (group B). The thermally induced flowable resin-matrix composites showed the lowest layer thickness values. The resin-matrix layer thickness revealed statistical differences between traditional resin cement (groups M and B) and flowable resin-matrix composites (groups V and G) (p < 0.05). However, the groups of flowable resin-matrix composites did not reveal statistical differences (p < 0.05). The thickness of the adhesive system layer at around 7 µm and 12 µm was lower at the interfaces with flowable resin-matrix composites when compared to the adhesive layer at resin-matrix cements, which ranged from 12 µm up to 40 µm. Conclusions: The flowable resin-matrix composites showed adequate flowing even though the loading on cementation was performed at low magnitude. Nevertheless, significant variation in thickness of the cementation layer was noticed for flowable resin-matrix composites and traditional resin-matrix cements that can occur in chair-side procedures due to the clinical sensitivity and differences in rheological properties of the materials.

The Light Reflection Changes of Monolithic Zirconia and Lithium Disilicate after Using Two External Staining Kits following by Thermocycling

BACKGROUND

The purpose of the study was to evaluate the changes of light reflection% on two materials (monolithic zirconia and lithium disilicate) after using two external staining kits following by thermocycling.

METHODS

Specimens were sectioned from monolithic zirconia (n = 60) and lithium disilicate (n = 60) then divided into six groups (n = 20). Two different types of external staining kits were used and applied to the specimens. The light reflection% was measured before staining, after staining and after thermocycling using a spectrophotometer.

RESULTS

The light reflection% of zirconia was significantly higher compared to lithium disilicate at the beginning of the study (p = 0.005), after staining with kit 1 (p = 0.005) and kit 2 (p = 0.005) and after thermocycling (p = 0.005). For both materials, the light reflection% was lower after staining with Kit 1 compared to kit 2 (p < 0.043). After thermocycling, the light reflection% of lithium disilicate increased (p = 0.027) and was unchanged with Zirconia (p = 0.527).

CONCLUSIONS

There is a difference between the materials regarding light reflection% as the monolithic zirconia showed higher light reflection% comparing lithium disilicate throughout the entire experiment. For lithium disilicate, we recommend using kit 1 as we found that, after thermocycling, the light reflection% of kit 2 was increased.

Analysing the effect of sodium bicarbonate and glycine air polishing on tooth surfaces with two different imaging methods

The aim of this study was to compare two different imaging methods by assessing changes caused by sodium bicarbonate and glycine air polishing on the tooth surfaces. Fourteen single root teeth with exposed root surfaces were included into the study. The teeth were randomly divided into two groups: sodium bicarbonate and glycine group. Samples were scanned in a micro-computed tomography (micro-CT) and CAD/CAM (computer-aided design/computer-aided manufacturing) at baseline and then after air-polishing powder applications, the defect volume values were evaluated. There was a statistically significant difference between mean defect volume values that occurred after glycine and sodium bicarbonate air polishing evaluated with micro-CT and CAD/CAM (p < 0.05). After sodium bicarbonate air polishing, defect volume on enamel surface at maximum power and defect volume on the exposed root surface at medium power values calculated with CAD/CAM were higher. After glycine air polishing, defect volume values on both surfaces at medium power setting calculated with CAD/CAM were lower. Defect volume values on enamel surface at maximum power setting calculated with CAD/CAM were higher than calculated with micro-CT. We concluded that CAD/CAM cannot provide as accurate results as micro-CT. Glycine-based powder is less abrasive than sodium bicarbonate, especially on enamel surface. Lay Description: Micro-CT is a non-destructive imaging method with high resolution and allows to examine all tooth structures individually. CAD/CAM are systems that are widely used in dentistry today. Access to the device is easier than micro-CT. Intraoral scanners in CAD/CAM systems also provide non-destructive image scanning. The aim of this study was to compare two different imaging methods by assessing changes caused by sodium bicarbonate and glycine air polishing on the tooth surfaces. The results showed that because of the analyses made with CAD/CAM, similar results could not be obtained with micro-CT and cannot be used to evaluate the changes that occur after air polishing.

Influence of thermo-mechanical aging on fracture resistance and wear of digitally standardized chairside computer-aided-designed/computer-assisted-manufactured restorations

OBJECTIVES

To investigate the influence of thermal cycling and mechanical loading (TCML) aging on fracture resistance and wear behavior of various chairside computer-aided-designed/computer-assisted-manufactured (CAD/CAM) premolar crowns cemented on standardized tooth abutments.

METHODS

Eighty chairside CAD/CAM crowns were prepared using lithium disilicate (IPS e.max CAD; EM), zirconia-infiltrated lithium silicate (Celtra Duo; CD), polymer-infiltrated ceramic network (Vita Enamic; VE), and resin nanoceramics (Cerasmart; CS) (n = 20). The specimens were divided into two groups (n = 10). In one group, they were subjected to TCML: thermocycling (6000 cycles in distilled water at 5-55 °C) and mechanical loading (50 N for 1.2 × 10⁶ cycles), while in control group they were stored in distilled water (37 °C for 24 h). The fracture load, height loss, and volume wear of the crowns were measured after TCML. Fractography was performed on fractured specimens. Data were analyzed using analysis of variance and multiple comparison tests (α=0.05).

RESULTS

The mean fracture loads of EM and CD were significantly higher than those of EC and CS (p<0.05). There was no significant change in the fracture load of any CAD/CAM crowns after TCML (p>0.05). CS exhibited a significantly higher volume wear than the other materials investigated. The wear tracts of all TCML crowns acted as failure origins during the fracture test.

CONCLUSIONS

The fracture resistance of glass-ceramic CAD/CAM crowns was significantly higher than that of resin composite crowns. A 5-year TCML aging did not affect the fracture resistance of CAD/CAM crowns investigated. However, TCML treatment produces a larger wear track in CS than in other materials.

CLINICAL SIGNIFICANCE

Appropriate chairside CAD/CAM restorative material should be selected for successful clinical practice after considering the fracture and wear resistance of the crowns.

Effect of Different Surface Treatments on the Shear Bond Strength of Metal Orthodontic Brackets Bonded to CAD/CAM Provisional Crowns

BACKGROUND

The aim of this study was to find the best surface treatment for CAD/CAM provisional crowns allowing the optimal bond strength of metal brackets.

METHODS

The sample consists of 30 lower bicuspids and 180 provisional crowns. The provisional crowns were randomly divided into six different groups. Orthophosphoric acid etching (37%) was applied to 30 lower bicuspids. The provisional crowns had undergone different surface treatments. Group 1: No treatment (Control Group). Group 2: Diamond bur. Group 3: Sandblasting. Group 4: Plastic Conditioner. Group 5: Diamond bur and Plastic Conditioner. Group 6: Sandblasting and Plastic Conditioner. The brackets in all groups were identically placed using Transbond XT^® Primer and Transbond XT^® Paste. Then, the entire sample underwent an artificial aging procedure, and a measurement of the bond strength was conducted. After debonding, the surface of the crowns was examined to determine the quantity of the adhesive remnant.

RESULTS

Bonding to natural crowns recorded the highest average, followed by the averages of groups 5 and 6. However, group 1 recorded the lowest average. Groups 2 and 4 had very close averages, as well as groups 5 and 6. A statistically significant difference between the averages of all groups was recorded (p < 0.001) except for groups 2 and 4 (p = 0.965) on the one hand, and groups 5 and 6 (p = 0.941) on the other hand.

DISCUSSION

The bonding of brackets on provisional crowns is considered a delicate clinical procedure. In fact, unlike natural crowns, the orthophosphoric acid usually used does not have any effect on the surface of provisional crowns.

CONCLUSIONS

Using a diamond bur combined with the plastic conditioner and sandblasting combined with that same product resulted in a bond strength close to natural crown.

Evaluation of the Translucency Properties for CAD/CAM Full Ceramic Crowns Fabricated From Glass Ceramics (E.max) or High Translucency Zirconia (Lava Plus): A Clinical Study

Introduction Nowadays, cosmetic demands are the first reason to visit dental clinic. However, most ceramic prostheses need an excessive removal of the dental structure, whether for full crowns or veneer preparation. With the innovation in ceramic materials, high translucent zirconia that demands minimal preparation with high aesthetic results was used for computer-aided design/computer-aided manufacturing (CAD/CAM) Full ceramic crown fabrication. The objective of this study was to compare the translucency properties of CAD/CAM full ceramic crowns fabricated from glass ceramics (E.max) and high translucency zirconia (Lava plus, 3M EPSE). Material and methods The sample consisted of 60 full ceramic crowns divided into two groups; the first group consisted of 30 IPS E.max CAD/CAM full ceramic crowns, while the second one consisted of 30 high translucent zirconia CAD/CAM full ceramic crowns. Translucency for both groups was evaluated directly after cementation by observing the blue light passing through the prostheses. Pearson Chi-Square test was used to study the difference in translucency between the two study groups. Results IPS E.max CAD showed a higher translucency compared to lava plus high translucency zirconia; in addition, this difference was statistically significant (p=0.028). Conclusion Within the limitation of this study, we found that the translucency of dental ceramic was affected by the ceramic material. As IPS E.max CAD was significantly higher in terms of translucency compared to High Translucent Zirconia.

Fracture strength and behavior of resin-faced CAD/CAM anterior crowns

The fracture strength and behavior of a novel resin-faced computer-aided design/computer-aided manufacturing (CAD/CAM) crown were investigated to evaluate application to the anterior teeth. Resin-faced CAD/CAM crowns were fabricated by arranging a resin composite on a frame prepared from a CAD/CAM resin block. The fracture strength was evaluated after 24 h of complete polymerization (day 0) and after water immersion for 30 days (day 30). Uniaxial loading was applied to the center point between the incisal edge and cingulum (loading point 1) or at 1.5 mm from the incisal edge (loading point 2). There was no significant difference in the fracture strength of the resin-faced CAD/CAM crowns between day 0 and 30 at loading point 1. At loading point 2, they exhibited decreased fracture strength after water immersion; however, the mean strength was still >1 kN. This novel crown showed good mechanical properties to serve as a prosthesis for the anterior teeth.