Fracture load of chairside CAD-CAM veneers fabricated with pre-and fully crystalized lithium disilicate ceramics.

PURPOSE: To evaluate the fracture load of chairside computer-aided design and computer-aided manufacturing (CAD-CAM) veneers fabricated with two conventional pre-crystallized and two fully crystallized lithium disilicate ceramic materials. MATERIALS AND METHODS: Seventy-five chairside CAD-CAM veneers (15 specimens/group) for maxillary right central incisors were fabricated with different lithium disilicate brands: (1) IPS e.max CAD; (2) Amber Mill; (3) Cerec Tessera; (4) n!ce Straumann; and (5) GC Initial LiSi Block. Restorations were cemented with resin luting cement (Variolink Esthetic, Ivoclar) to 3D-printed resin dies. Bonded restorations received 5000 thermal cycles and then were loaded until fracture. Statistical analysis included One-Way ANOVA. RESULTS: Conventional pre-crystallized e.max CAD displayed the highest fracture load value (640 N), followed by fully-crystallized n!ce Straumann (547 N), pre-crystallized Cerec Tessera (503 N), pre-crystallized Amber Mill (476 N), respectively; fully-crystallized GC Initial LiSi Block (431 N) displayed the lowest values. When comparing the fracture load of recent lithium disilicate ceramic material to the e.max group, which acted as the control, significant differences were noted. The LiSi Block GC group, in particular, had considerably higher mean difference values (208.867, p < 0.001, 95% CI [89.63, 328.10]), as did the Amber Mill group (164.200, p = 0.002, 95% CI [44.96, 283.44]) and CEREC Tessera group (137.533, p = 0.016, 95% CI [18.30, 256.77]). The e.max and n!ce Straumann groups had no statistically significant differences in mean scores (92.933, p = 0.198, 95% CI [-26.30, 212.17]). These findings imply that the clinical performance of recent lithium disilicate veneers varies when compared to the e.max CAD group. CONCLUSIONS: The fracture load of chairside CAD-CAM lithium disilicate veneers for maxillary central incisors varies according to the type of ceramic brands. Conventional pre-crystallized e.max CAD displayed higher fracture load than the recent pre- and fully-crystallized lithium disilicate materials, emphasizing the significance of choosing the right product based on the desired clinical outcome.

Automated scoring and augmented reality visualization software program for evaluating tooth preparations.

STATEMENT OF PROBLEM: Tooth preparation is an essential part of prosthetic dentistry; however, traditional evaluation methods involve subjective visual inspection that is prone to examiner variability. PURPOSE: The purpose of this study was to investigate a newly developed automated scoring and augmented reality (ASAR) visualization software program for evaluating tooth preparations. MATERIAL AND METHODS: A total of 122 tooth models (61 anterior and 61 posterior teeth) prepared by dental students were evaluated by using visual assessments that were conducted by students and an expert, and auto assessment that was performed with an ASAR software program by using a 3-dimensional (3D) point-cloud comparison method. The software program offered comprehensive functions, including generating detailed reports for individual test models, producing a simultaneous summary score report for all tested models, creating 3D color-coded deviation maps, and forming augmented reality quick-response (AR-QR) codes for online data storage with AR visualization. The reliability and efficiency of the evaluation methods were measured by comparing tooth preparation assessment scores and evaluation time. The data underwent statistical analysis using the Kruskal-Wallis test, followed by Mann-Whitney U tests for pairwise comparisons adjusted with the Benjamini-Hochberg method (α=.05). RESULTS: Significant differences were found across the evaluation methods and tooth types in terms of preparation scores and evaluation time (P<.001). A significant difference was observed between the auto- and student self-assessment methods (P<.001) in scoring both the anterior and posterior tooth preparations. However, no significant difference was found between the auto- and expert-assessment methods for the anterior (P=.085) or posterior (P=.14) tooth preparation scores. Notably, the auto-assessment method required significantly shorter time than the expert- and self-assessment methods (P<.001) for both tooth types. Additionally, significant differences in evaluation time between the anterior and posterior tooth were observed in both self- and expert-assessment methods (P<.001), whereas the evaluation times for both the tooth types with the auto-assessment method were statistically similar (P=.32). CONCLUSIONS: ASAR-based evaluation is comparable with expert-assessment while exhibiting significantly higher time efficiency. Moreover, AR-QR codes enhance learning and training experiences by facilitating online data storage and AR visualization.

Effectiveness of virtual reality interactive simulation practice in prosthodontic education: A systematic review and meta-analysis.

INTRODUCTION: Virtual reality-based interactive simulation (VRIS) provides a safe and controlled environment for dental students and professionals to develop skills and knowledge. This study aimed to investigate the effectiveness of using the VRIS for prosthodontic practice and to explore the trends, application areas, and users' attitudes towards VRIS. MATERIALS AND METHODS: This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines for searching studies published until 21 March 2023 that reported quantitative or qualitative learning outcomes related to the use of VRIS for dental prosthodontic practice and clinical training. The quality of the included studies was assessed using the Medical Education Research Study Quality Instrument (MERSQI) and Newcastle-Ottawa Scale-Education (NOS-E) tools. A random-effects meta-analysis was conducted to compare the intervention group (utilizing VRIS) and the control group (employing conventional prosthodontic training methods) based on performance skill scores and task completion time, with a significance level set at <.05. RESULTS: The meta-analysis revealed that the utilization of VRIS generally improves students' performance scores (SMD = 1.04; 95% CI, -0.35 to 2.44; I2 > 50%; p = .13) and reduces task completion time (SMD = -0.03; 95% CI, 1.39-7.72; I2 > 50%; p = .93). Notably, using VRIS significantly enhanced the performance scores in implant surgery practice (SMD = 0.26; 95% CI, 0.09-0.42; p < .05). Additionally, the VRIS method significantly reduced task completion time in the cavity restorative preparation task (SMD = -1.19; 95% CI, -1.85 to -0.53; p < .05). CONCLUSION: Engaging in practice with VRIS has the potential to enhance learning proficiency in prosthodontic education. The advantages associated with VRIS encompass the provision of immediate feedback, decreased task completion time, heightened confidence and motivation, accelerated skill acquisition, improved performance scores, and increased learning engagement.

A comparison study of pathological features and drug efficacy between Drosophila models of C9orf72 ALS/FTD.

Amyotrophic lateral sclerosis is a devastating neurodegenerative disease with a complex genetic basis, presenting both in familial and sporadic forms. The hexanucleotide (G4C2) repeat expansion in the C9orf72 gene, which triggers distinct pathogenic mechanisms, has been identified as a major contributor to familial and sporadic Amyotrophic lateral sclerosis cases. Animal models have proven pivotal in understanding these mechanisms; however, discrepancies between models due to variable transgene sequence, expression levels, and toxicity profiles complicate the translation of findings. Herein, we provide a systematic comparison of 7 publicly available Drosophila transgenes modeling the G4C2 expansion under uniform conditions, evaluating variations in their toxicity profiles. Further, we tested 3 previously characterized disease-modifying drugs in selected lines to uncover discrepancies among the tested strains. Our study not only deepens our understanding of the C9orf72 G4C2 mutations but also presents a framework for comparing constructs with minute structural differences. This work may be used to inform experimental designs to better model disease mechanisms and help guide the development of targeted interventions for neurodegenerative diseases, thus bridging the gap between model-based research and therapeutic application.

Impact of restoration thickness and tooth shade background on the translucency of zirconia laminate veneers: An in vitro comparative study.

Purpose: Our in vitro comparative study aimed to investigate the impact of thickness and tooth shade background on the translucency of highly translucent zirconia veneers. Materials and Methods: A total of 75 5Y-TZP zirconia veneers of shade A1 were fabricated with thicknesses of 0.50 mm (n = 25), 0.75 mm (n = 25), and 1.0 mm (n = 25). The translucencies were measured on composite resin teeth with shades A1, A2, A3, A3.5, and A4 using a digital color imaging spectrophotometer. Data were analyzed using ANOVA and post hoc Tukey's test (p < 0.05). Results: The translucency values were optimal for the veneers placed over the substrate teeth with shades A1 and A2, regardless of the veneer thickness. Additionally, veneers with a thickness of 0.50 mm exhibited significantly higher translucency than those with thicknesses of 0.75 mm and 1.0 mm. Conclusions: Our study demonstrated that the translucency of the highly translucent zirconia veneers was influenced by both veneer thickness and tooth shade background. The optimal veneer thickness for achieving the highest translucency was 0.50 for the veneers with A1 and A2 shades placed over the substrate teeth. Clinical Relevance: The optimal thickness for achieving the highest translucency of the highly translucent zirconia laminate veneers was 0.50 mm for the veneers with A1 and A2 shades placed over the substrate teeth. Clinicians and dental technicians could consider this when selecting materials for aesthetic restorations.

Effect of different surface treatments on the retention force of additively manufactured interim implant-supported crowns.

PURPOSE: To compare the effect of different pre-cementation surface treatments and bonding protocols on the retention force of additively manufactured (AM) implant-supported interim crowns. MATERIAL AND METHODS: A total of 50 AM interim crowns (Temporary CB resin) were cemented on implant abutments. Five groups (n = 10) were established based on the different surface pre-treatments performed in the intaglio surface of the specimens: no surface pre-treatment (Group C or control), air-abraded with 50-µm aluminium oxide particles (Group AP), air-abraded with 50-µm aluminium oxide particles followed by the application of silane (Group AMP), silane (Group MP), and air-abraded with 30 µm silica-coated aluminum oxide particles followed by the application of silane (Group CMP). Each specimen was cemented into an implant abutment using a composite resin cement (Rely X Unicem2). Afterward, the specimens underwent retention testing with a Universal Instron machine. Pull-off forces (N) and modes of failure were registered. Statistical analysis was performed using Mann-Whitney U tests with Bonferroni corrections for multiple tests (α = 0.05). RESULTS: The median retention force values were 233.27 ±79.28 N for Group Control, 398.59 ±68.59 N for Group MP, 303.21 ±116.80 N for Group AMP, 349.31 ±167.73 N for Group CMP, and 219.85 ± 55.88 N for Group AP. The pull-off forces were significantly greater for Group MP, while the differences between the remaining groups were not statistically significant (P > 0.05). Group AP showed the lowest retention force values among all the groups. Failure modes after the pull-off testing were predominantly adhesive and substrate failure of the AM interim material. CONCLUSIONS: The surface treatment of the intaglio AM crown tested significantly influenced the retention force values measured. Pre-treatment with an MDP-containing silane improved the retentive force values computed, whereas pre-treatment with 50-µm Al2 O3 air-particle abrasion alone is not recommended prior to cementation on a titanium-based implant abutment.

Effect of resin cement selection on fracture resistance of chairside CAD-CAM lithium disilicate crowns containing virgilite: A comparative in vitro study.

STATEMENT OF PROBLEM: Studies on the fracture performance of a recently introduced computer-aided design and computer-aided manufacturing (CAD-CAM) lithium disilicate ceramic containing virgilite with different cements are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the fracture resistance of crowns made of a recently introduced chairside CAD-CAM lithium disilicate containing virgilite cemented with different types of adhesive luting cement. MATERIAL AND METHODS: Sixty complete coverage crowns for a maxillary right central incisor were milled out of a lithium disilicate with virgilite (CEREC Tessera) (n=48) and a traditional lithium disilicate (e.max CAD) (n=12) using a chairside CAD-CAM system (Primescan). The central incisor tooth preparation included a 1.5-mm incisal reduction, a 1.0-mm axial reduction, and a 1.0-mm chamfer finish line. The restorations were bonded with different types of resin cement to 3D printed dies of the tooth preparation and were divided into 5 groups (n=12 per group): e.max CAD with Multilink Automix (E.Mu); Tessera with Multilink Automix (T.Mu); Tessera with Calibra (T.Ca); Tessera with Unicem (T.Un); and Tessera with Speedcem (T.Sp). The cemented restorations were stored in water for 30 days and then loaded until they were fractured in compression. The load at fracture was analyzed with a 1-way analysis of variance (ANOVA) and the honestly significant difference (HSD) Tukey test (α=.05). RESULTS: The mean fracture resistance of traditional lithium disilicate and virgilite lithium disilicate anterior crowns significantly differed depending on the type of resin cement used (P<.05). Group E.Mu displayed the highest values (946.35 ±155 N), followed by group T.Un (819.59 ±232 N), group T.Sp (675.52 ±153 N), and group T.Mu (656.95 ±193 N). The lowest values were displayed by group T.Ca (567.94 ±184 N). CONCLUSIONS: The fracture resistance of lithium disilicate containing virgilite and traditional lithium disilicate crowns cemented with the same cement displayed statistically similar values. However, significant differences were observed when the virgilite lithium disilicate crowns were cemented with different types of adhesive luting cement. The crowns in the T.Ca group displayed the lowest fracture resistance.

Fracture resistance of zirconia surveyed crowns with four different occlusal rest seat designs.

PURPOSE: To determine the fracture resistance of chairside computer-aided design and computer-aided manufacturing (CAD-CAM) zirconia surveyed crowns for a mandibular first molar without occlusal rest and with four different rest seat designs. MATERIALS AND METHODS: Seventy CAD-CAM zirconia 4Y-PSZ (IPS e.max ZirCAD MT for CEREC A1, C15, Ivoclar Vivadent) crowns (14 specimens/group) were designed and fabricated with a dental chairside CAD-CAM system (CEREC PrimeScan, and CEREC MCXL Dentsply Sirona). The restorations were divided into groups according to the following rest seat designs: (1) Surveyed crown without rest seat, (2) surveyed crowns with disto-occlusal rest seat, (3) surveyed crowns with disto-occlusal extended rest seat, (4) surveyed crowns with interproximal rest seat, and (5) continuous rest seat. Crowns were treated with a primer system (Monobond Plus, Ivoclar Vivadent) and cemented using resin luting cement (Multilink Automix, Ivoclar Vivadent) to resin-printed dies (Grey Resin V4, FormLabs). Subsequently, the crowns were subjected to 200,000 load cycles at 1 Hz with 20 N force and then loaded with a steel indenter until fracture. The test results were analyzed with one-way Analysis of Variance (ANOVA) and HSD Tukey post-Hoc test. RESULTS: The mean fracture resistance of surveyed crowns without and with different rest seats was significantly different from each other. Surveyed crowns with no rest seat displayed the highest resistance (4238 N) followed by crowns with continuous rest seat (3601 N), crowns with disto-occlusal extended rest seat (3283 N), and crowns with disto-occlusal rest seat (3257 N). Crowns with interproximal rest seat displayed the lowest fracture resistance (2723 N). CONCLUSIONS: Surveyed crowns without rest seats had a higher fracture resistance than crowns with rest seats Surveyed crowns with interproximal rest seats presented the lowest fracture resistance among all rest seat designs. Crowns with disto-occlusal rest seats, disto-occlusal extended rest seats, and continuous rest seats displayed similar fracture resistance.

Accuracy of anterior denture tooth arrangements of CAD-CAM complete removable dental prostheses made with a tooth mold template.

STATEMENT OF PROBLEM: Research evaluating the accuracy of anterior tooth mold templates to computer-aided design and computer-aided manufacture (CAD-CAM) fabricated complete removable dental prostheses (CRDPs) is limited. PURPOSE: The purpose of this in vitro study was to investigate the accuracy of the anterior denture tooth arrangement on CAD-CAM complete removable dental prostheses made with the anterior tooth mold template. MATERIAL AND METHODS: A maxillary and mandibular edentulous model was mounted on a semiadjustable articulator to simulate a patient's maxillary arch. Definitive impressions and jaw relation records were made as per the manufacturer's protocol. A maxillary and mandibular anatomic measuring device was completely seated onto the edentulous models, centered on the edentulous model midline, and horizontally positioned parallel to the mandibular ridge. A medium-size anterior tooth mold template sticker was attached on the anatomic measuring device to identify the maxillary dental midline and incisal edge position and was sent to the manufacturer as the proposed tooth arrangement reference for the definitive complete removable dental prostheses. A total of 10 milled complete removable dental prostheses were generated for 2 groups by using 2 different tooth arrangement techniques. One group (n=5) used the monobloc milling technique without bonding of denture teeth, while the other group (n=5) used the bonding system for denture teeth on the milled denture base. For comparison, a camera mounted on a tripod was used for photographic documentation. Reference markers placed on the edentulous model were used to orient and measure the difference of 4 aspects of the anterior tooth arrangement: average incisal edge position, intercanine distance, midline, and clinical crown length of the left central incisor. The difference values between the tooth mold template and definitive complete removable dental prostheses were statistically analyzed by multivariate ANOVA (α=.05) and 1-sample t tests (adjusted α=.0125). RESULTS: Overall, statistically significant differences were found between the tooth mold template (control) and definitive complete removable dental prostheses at all measuring aspects except for the midline of the midline of the milled arrangement technique (P<.0125). In terms of the midline value, the value of the milled group did not show a significant difference compared with tooth mold template (-0.19 mm). However, the value of the bonded group indicated a significant difference of midline (0.44 mm toward to the left of the tooth mold template midline). When the complete removable dental prosthesis milled denture tooth and complete removable dental prosthesis bonded denture tooth techniques were compared, there was no difference in the tested variables between the milled and the bonded groups (P>.0125). CONCLUSIONS: The tooth mold template did not represent an accurate position for definitive complete removable dental prostheses for either the milled or bonded techniques. The largest differences were found at the average incisal edge of the anterior teeth and the intercanine distance for both groups. However, there was overall no clinical difference between the 2 groups (milled and bonded) of CAD-CAM complete removable dental prostheses.

Comparison of tensile bond strength of denture reline materials on denture bases fabricated with CAD-CAM technology.

STATEMENT OF PROBLEM: Studies that have analyzed the bond strength of resilient denture liners to milled denture bases are sparse, and the authors are unaware of research that has investigated the tensile bond strength of denture relining materials to 3D-printed denture bases. PURPOSE: The purpose of this in vitro study was to evaluate the tensile bond strength of both hard and soft denture reline materials on denture bases fabricated by 3D printing and computer-aided design and computer-aided manufacture (CAD-CAM) milling technology. MATERIAL AND METHODS: Injected, milled, and printed denture base specimens were fabricated (n=30) and bonded to 5 different denture reline materials: soft chairside reline (Coe Soft and PermaSoft), hard chairside reline (Tokuyama Rebase ii and Kooliner), and hard laboratory reline (ProBase Cold). Specimens of each reline material were divided into 5 groups (n=10) and were placed in distilled water for 24 hours before tensile testing. Maximum tensile stress values before failure were recorded, and the failure mode was also determined. The type of failure was analyzed by a scanning electron microscope. Statistics were analyzed with 2-way ANOVA and multiple comparison tests (α=.05). RESULTS: Overall, no statistically significant difference in tensile bond strength was found in the injected, milled, and printed denture groups. However, the printed denture base group demonstrated significantly lower values of tensile bond strength (P<.05) with PermaSoft, Tokuyama Rebase ii, and ProBase Cold groups than other denture base groups (milled and injected). The milled denture bases had the highest mean value of tensile bond strength with 4 of the 5 denture relining materials tested (Coe Soft, PermaSoft, Tokuyama Rebase ii, and Kooliner). No statistically significant difference (P>.05) was found among the injected, milled, and printed denture bases when relined with Kooliner. When comparing the denture reline type, the lowest values were seen with the soft chairside relining materials, and highest values with the hard laboratory reline material. Among the modes of failure, adhesive failures were observed predominantly with the printed denture base materials relined with soft chairside relining materials, while cohesive and mixed modes of failure were found in the milled and injected denture base groups. CONCLUSIONS: The printed denture bases had significantly lower tensile bond strength values than the injection and milled denture bases with the PermaSoft, Tokuyama Rebase ii, and ProBase Cold denture relines, while milled denture bases demonstrated the highest values of tensile bond strength for all chairside relining groups. In addition, the soft chairside relining materials showed the lowest tensile bond strength values regardless of the denture processing method with respect to the denture base type (injected, printed, and milled) compared with the hard relining materials.

Effect of different storage conditions on the fit of 3D-printed occlusal devices used to treat temporomandibular disorders.

STATEMENT OF PROBLEM: Research-based storage guidelines for 3-dimensional (3D)-printed occlusal devices are lacking. PURPOSE: The purpose of this in vitro study was to investigate the dimensional stability of the internal surface of 3D-printed occlusal devices under different storage conditions. MATERIAL AND METHODS: Maxillary and mandibular dental casts were scanned and exported to a 3D printer to fabricate 30 occlusal devices. The specimens were stored under 3 different conditions (n=10): air dried and stored under natural light (group DL), stored in a dark container with water (group W), and air dried and stored in a dark container (group D). The intaglio surfaces of the occlusal devices were scanned by a laboratory scanner at 4 time points: immediately after polymerization (t0, control), after 1 day (t1), after 7 days (t2), and after 27 days (t3). The dimensional changes of the fitting surfaces between t0 and t1 (Δt1), t0 and t2 (Δt2), and t0 and t3 (Δt3) were measured by using best fit alignment in a surface analysis software program. In addition, comparisons were made between the posterior and anterior sections. Statistical analysis was completed with Kolmogorov-Smirnov, 1-way ANOVA, Friedman, Kruskal-Wallis, Mann-Whitney, and unpaired t tests. RESULTS: The root mean square (RMS) of group DL between Δt1 and Δt2 (P=.002) and between Δt1 and Δt3 (P=.002) showed a statistically significant difference. The RMS of group W between Δt1 and Δt3 (P=.008) showed a statistically significant difference. When the groups were compared with each other at the different time points, the DL group showed a statistically significant difference compared with groups W and D at Δt1. The examination of different areas of the occlusal device (right molar, incisor, and left molar sites) indicated no statistically significant differences in RMS among all groups (P>.05). CONCLUSIONS: The occlusal devices of group DL showed the least dimensional change of the fitting surface for Δt1 in comparison with group W and D, while no statistically significant differences were found among the groups for Δt2 and Δt3. In terms of the different locations, no statistically significant differences were found among the 3 locations for any given group after 27 days.

Influence of definitive and interim restorative materials and surface finishing on the scanning accuracy of an intraoral scanner.

PURPOSE: To analyze the influence of the restorative material type (definitive and interim) and its surface treatment (polished or glazed) on the scanning accuracy of an intraoral scanner. MATERIAL AND METHODS: A mandibular dental typodont containing 3 typodont teeth (left second premolar and left first and second molars) was used for testing. Ten groups were created based on the crown material: typodont tooth (control group), gold (G group), zirconia (Z group), lithium disilicate (LD group), hybrid ceramic (HC group), composite resin (CR group), conventional PMMA (CNV-PMMA group), bis-acryl composite resin (CNV-BA group), milled PMMA (M-PMMA group), and additively manufactured bis-acryl-based polymer (AM-BA group). Except the G group, groups were subdivided into polished (P subgroups) or glazed (G subgroups). Each specimen was digitized by using an extraoral scanner (D1000; 3Shape A/G) and an intraoral scanner (TRIOS 4; 3Shape). Each reference scan was used to measure the discrepancy with the corresponding 15 intraoral scans by calculating the root mean square (RMS) error (Geomagic; 3D Systems). The Welch ANOVA and Games-Howell tests were selected to examine trueness (α=0.05). The F-test with Bonferroni correction was used to evaluate precision. RESULTS: Significant trueness and precision differences were found (P<.001). The G-P subgroup had the lowest trueness values, while the CNV-PMMA-P, M-PMMA-P, and AM-BA-P subgroups had the highest trueness values. Significant RMS mean discrepancies were computed when comparing polished and glazed specimens fabricated with the same material (P<.001). The CNV-PMMA-G subgroup had the lowest precision values, while the CNV-BA-P subgroup had the highest precision values (P<.001). CONCLUSIONS: The type and surface finishing of the restorative materials tested influenced the scanning accuracy of the IOS tested. The lowest trueness values were found in the high noble alloy specimens, while the highest trueness values were measured in conventional and milled PMMA and additively manufactured bis-acryl-based polymer polished specimens. Except for zirconia crowns, higher trueness values were found in polished specimens when compared with glazed crowns. The CNV-PMMA-G subgroup had the lowest precision values, while the highest precision values were measured in the CNV-BA-P subgroup. CLINICAL SIGNIFICANCE: Definitive and interim materials tested decrease intraoral scanning accuracy. Furthermore, polishing instead of glazing definitive and interim material assessed might be preferable to maximize intraoral scanning accuracy.

Combined bone- and mucosa-supported 3D-printed guide for sinus slot preparation and prosthetically driven zygomatic implant placement.

The use of zygomatic implants to rehabilitate the severely atrophic maxilla has been well documented since first being introduced by Brånemark. Placement of zygomatic implants is technically complex, with catastrophic complications and numerous prosthetic challenges resulting from imprecise placement. The purpose of this report was to demonstrate a technique that allows transfer of the preoperatively planned sinus slot position to the surgical field by using cone beam computed tomography (CBCT) and an implant planning software program to fabricate a combined bone- and mucosa-supported 3D-printed surgical guide. This facilitates optimal zygomatic implant positioning and promotes favorable biomechanics with a predictable prosthetic outcome.

A 3D-Printed Guide to Assist in Sinus Slot Preparation for the Optimization of Zygomatic Implant Axis Trajectory.

Zygomatic implants have become a predictable treatment modality for the rehabilitation of the severely atrophic maxilla. Due to differing anatomic variations, proximity to vital anatomic structures and limited intraoperative visibility, the placement of zygomatic implants can be a difficult task; compromised implant positioning may ultimately lead to postoperative surgical and prosthetic complications. The purpose of this report is to demonstrate a technique that allows for the transfer of the sinus slot position. Ultimately, this optimizes zygomatic implant axis trajectory from preoperative prosthetic planning by using cone beam computed tomography (CBCT) and 3-dimensional (3D) planning software to fabricate a stereolithographic 3D-printed surgical guide.

An accessory technique for the intraoral removal of a fractured implant abutment screw.

As the use of dental implants becomes more prevalent, mechanical complications become more common. When an implant abutment screw fractures, it can be difficult to retrieve the retained fragment. The purpose of this article is to describe a technique to remove the abutment screw fragments without damaging the implant body or its screw threads.

A method of locating the abutment screw access channel with cone-beam computed tomography and a 3D-printed drilling guide.

In managing loose abutment screws, locating precisely the position of the screw access channel is difficult. This technique describes the use of cone-beam computed tomography (CBCT) and surgical guide planning software to locate the screw access channel with the intention of retrieving a loosened cement-retained implant-supported prosthesis. The method minimizes damage to the abutment crown assembly.

Interproximal distance analysis of stereolithographic casts made by CAD-CAM technology: An in vitro study.

STATEMENT OF PROBLEM: The accuracy of interproximal distances of the definitive casts made by computer-aided design and computer-aided manufacturing (CAD-CAM) technology is not yet known. PURPOSE: The purpose of this in vitro study was to compare the interproximal distances of stereolithographic casts made by CAD-CAM technology with those of stone casts made by the conventional method. MATERIAL AND METHODS: Dentoform teeth were prepared for a single ceramic crown on the maxillary left central incisor, a 3-unit fixed dental prosthesis (FDP) on the second premolar for a metal-ceramic crown, and a maxillary right first molar for a metal crown. Twenty digital intraoral impressions were made on the dentoform with an intraoral digital impression scanner. The digital impression files were used to fabricate 20 sets of stereolithographic casts, 10 definitive casts for the single ceramic crown, and 10 definitive casts for the FDP. Furthermore, 20 stone casts were made by the conventional method using polyvinyl siloxane impression material with a custom tray. Each definitive cast for stereolithographic cast and stone cast consisted of removable die-sectioned casts (DC) and nonsectioned solid casts (SC). Measurements of interproximal distance of each cast were made using CAD software to provide mean ±standard deviation (SD) values. Data were first analyzed by repeated measures analysis of variance (ANOVA), using different methods of cast fabrication (stone and stereolithography) as one within subject factor and different cast types (DC and SC) as another within subject factor. Post hoc analyses were performed to investigate the differences between stone and stereolithographic casts depending upon the results from the repeated measures ANOVA (α=.05). RESULTS: Analysis of interproximal distances showed the mean ±SD value of the single ceramic crown group was 31.2 ±24.5 µm for stone casts and 261.0 ±116.1 µm for stereolithographic casts, whereas the mean ±SD value for the FDP group was 46.0 ±35.0 µm for stone casts and 292.8 ±216.6 µm for stereolithographic casts. For both the single ceramic crown and the FDP groups, there were significant differences in interproximal distances between stereolithographic casts and stone casts (P<.001). In addition, the comparisons of DC with SC of stone and stereolithographic casts for the single ceramic crown and FDP groups demonstrated there was statistically significant differences among interproximal distances between DC stereolithographic casts and SC stereolithographic casts only for the FDP group (P<.001). CONCLUSIONS: For both the single ceramic crown and the FDP groups, the stereolithographic cast group showed significantly larger interproximal distances than the stone cast group. In terms of the comparison between DC and SC, DC stereolithographic casts for the FDP group only showed significantly larger interproximal values than those of the SC stereolithographic casts for the FDP group.

Evaluation of die trim morphology made by CAD-CAM technology.

STATEMENT OF PROBLEM: The die contour can affect the emergence profile of prosthetic restorations. However, little information is available regarding the congruency between a stereolithographic (SLA) die and its corresponding natural tooth. PURPOSE: The purpose of this vitro study was to evaluate the shapes of SLA die in comparison with the subgingival contour of a prepared tooth to be restored with a ceramic crown. MATERIAL AND METHODS: Twenty extracted human teeth, 10 incisors, and 10 molars, were disinfected and mounted in a typodont model. The teeth were prepared for a ceramic restoration. Definitive impressions were made using an intraoral scanner from which 20 SLA casts with removable dies were fabricated. The removable dies and corresponding human teeth were digitized using a 3-dimensional desktop scanner and evaluated with computer-aided design software. The subgingival morphology with regard to angle, length, and volume at the buccolingual and mesiodistal surfaces and at zones A, B, C, and D were compared. Data were first analyzed with repeated measures analysis of variance (ANOVA), using locations (buccolingual and mesiodistal), zones (A, B, C, and D), and model type (SLA and Natural) as within-subject factors and tooth type (molar and incisor) as the between-subject factor. Post hoc analyses were performed to investigate the difference between natural teeth and corresponding SLA models, depending upon the interaction effect from the repeated measures ANOVA (α=.05). RESULTS: For angle analysis, the incisor group demonstrated a significant difference between the natural tooth and SLA die on the buccolingual surfaces (P<.05), whereas the molar group demonstrated a significant difference at the mesiodistal surfaces (P<.05). For the evaluation of length and volume, the incisor group showed significant differences in zone D on both the buccolingual (P<.05) and the mesiodistal (P<.05) surfaces. However, significant differences in zones C (P<.05) and D (P<.05) on the buccolingual surfaces and in all zones on the mesiodistal surfaces were observed in the molar group. CONCLUSIONS: For the comparison of angles, SLA dies did not replicate the subgingival contour of natural teeth on the buccolingual surfaces of the incisal groups. For the comparison of length and volume, SLA dies were more concave and did not replicate the subgingival contour of natural teeth in the incisal and molar groups.

A method of facilitating the fabrication of access openings for implant-supported complete fixed dental prostheses.

This report describes a method for fabricating access openings for implant-supported complete fixed dental prostheses (ICFP) by using a dental milling machine and silicone putty matrix. The method can help clinicians achieve the accurate and precise fabrication of access openings for ICFPs without excessive grinding.

Edge chipping resistance and flexural strength of polymer infiltrated ceramic network and resin nanoceramic restorative materials.

STATEMENT OF PROBLEM: Two novel restorative materials, a polymer infiltrated ceramic network (PICN) and a resin nanoceramic (RNC), for computer-assisted design and computer-assisted manufacturing (CAD-CAM) applications have recently become commercially available. Little independent evidence regarding their mechanical properties exists to facilitate material selection. PURPOSE: The purpose of this in vitro study was to measure the edge chipping resistance and flexural strength of the PICN and RNC materials and compare them with 2 commonly used feldspathic ceramic (FC) and leucite reinforced glass-ceramic (LRGC) CAD-CAM materials that share the same clinical indications. MATERIAL AND METHODS: PICN, RNC, FC, and LRGC material specimens were obtained by sectioning commercially available CAD-CAM blocks. Edge chipping test specimens (n=20/material) were adhesively attached to a resin substrate before testing. Edge chips were produced using a 120-degree, sharp, conical diamond indenter mounted on a universal testing machine and positioned 0.1 to 0.7 mm horizontally from the specimen's edge. The chipping force was plotted against distance to the edge, and the data were fitted to linear and quadratic equations. One-way ANOVA determined intergroup differences (α=.05) in edge chipping toughness. Beam specimens (n=22/material) were tested for determining flexural strength using a 3-point bend test. Weibull statistics determined intergroup differences (α=.05). Flexural modulus and work of fracture were also calculated, and 1-way ANOVA determined intergroup differences (α=.05) RESULTS: Significant (P<.05) differences were found among the 4 CAD-CAM materials for the 4 mechanical properties. Specifically, the material rankings were edge chipping toughness: RNC>LRGC=FC>PICN; flexural strength: RNC=LRGC>PICN>FC; flexural modulus: RNCLRGC=PICN>FC. CONCLUSIONS: The RNC material demonstrated superior performance for the mechanical properties tested compared with the other 3 materials.