Cameo and intaglio surface stability and variability of additively, subtractively, and conventionally manufactured occlusal devices after long-term storage.

STATEMENT OF PROBLEM: Additive and subtractive manufacturing have become alternative technologies for fabricating occlusal devices. However, knowledge of the long-term stability of occlusal devices fabricated using these recent technologies is limited. PURPOSE: The purpose of this in vitro study was to evaluate the cameo and intaglio surface stability and variability of additively, subtractively, and conventionally manufactured occlusal devices after 18 months of storage. MATERIAL AND METHODS: A standard tessellation language (STL) file of a dentate maxillary typodont was used to design a master occlusal device. The STL file of this design was used to fabricate occlusal devices additively either with a digital light processing (AM-1) or a continuous liquid interface production (AM-2) printer, subtractively with 2 different 5-axis milling units (SM-1 and SM-2), and conventionally (TM-HP) (n=10). STL files of each device's cameo and intaglio surfaces were generated using a laboratory scanner after fabrication and after 18 months of storage in a moist environment. These generated files were imported into an analysis software program (Geomagic Control X) to analyze the dimensional stability of tested devices by using the root mean square method. The average deviation values defined the variability of measured changes over time. Cameo and intaglio surface deviations were analyzed using the Kruskal-Wallis and Dunn tests, while the variability of measured deviations was analyzed with 1-way analysis of variance and the Tukey HSD tests (α=.05). RESULTS: Significant differences were observed among tested devices when the intaglio surface deviations and the cameo surface variability were considered (P<.001). SM-2 had significantly higher intaglio surface deviations than AM-1, SM-1, and AM-2 (P≤.036). Among the test groups, AM-1 had the greatest cameo surface variability (P≤.004). CONCLUSIONS: SM-2 resulted in lower intaglio surface stability than the additive and the other subtractive manufacturing technologies, while AM-1 led to the highest cameo surface variability among the test groups.

Effect of thermal cycling on the flexure strength of CAD-CAM denture base materials: An in vitro study.

STATEMENT OF PROBLEM: The impact of thermal cycling on the flexure strength of contemporary denture base materials remains inadequately understood despite its crucial role in determining the long-term performance of complete dentures. PURPOSE: The purpose of this in vitro study was to evaluate the flexural strength of different CAD-CAM denture base materials and the effects of thermal cycling. MATERIAL AND METHODS: A total of 120 rectangular specimens were fabricated from 6 denture base materials according to the International Organization for Standardization (ISO) 20795-1:2013 standard: a heat-compressed PMMA ([Lucitone 199 [C-L199]), 2 brands of milled material (Ivotion Base [M-IB] and Lucitone Digital Fit [M-LDF]), and 3 types of 3- dimensionally (3D) printed material (Lucitone Digital Print [P-LDP], Flexcera Base [P-FB], and FotoDent Dentures [P-FD]). Specimens were divided into 2 subgroups of 10; half underwent thermocycling, half did not. Thermally cycled specimens were immersed in distilled water at 37 °C for 2 days, followed by 5000 thermal cycles at 5 and 55 ºC, with a dwell time of 30 seconds. They were then subjected to a 3-point flexural strength test. Two-way ANOVA, followed by post hoc Tukey multiple comparison tests were used to assess the effect of material type and the thermal cycling process on the flexural strength of denture base materials (α=.05). RESULTS: All materials met the ISO standard of 65 MPa flexural strength, except for thermal cycled P-FB. A significant difference (P<.05) in flexure strength value was found among various denture base materials without thermal cycling (M-LDF>M-IB≈P-FD≈P-LDP>C-L199≈ P-FB) and with thermal cycling (M-LDF> M-IB≈P-FD>P-LDP≈C-L199>P-FB). The flexural strength of tested materials was reduced significantly (P<.05) with thermal cycling. CONCLUSIONS: Three-dimensionally printed denture base materials have a flexural strength value similar to or less than that of milled denture base materials. Thermal cycling impacts the flexural strength of denture base materials.

Complete Digital Workflow for Fabricating an Occlusal Device Using Artificial Intelligence- Powered Design Software and Additive Manufacturing: A Dental Method.

Artificial intelligence (AI) has been expanding into areas that were thought to be reserved for human experts and has a tremendous potential to improve patient care and revolutionize the healthcare field. Recently launched AI-powered dental design solutions enable automated occlusal device design. This article describes a dental method for the complete digital workflow for occlusal device fabrication using two different AIpowered design software programs (Medit Splints and 3Shape Automate) and additive manufacturing. Additionally, the benefits and drawbacks of this workflow were reviewed and compared to conventional workflows.

Effect of Polymerization Unit, Polishing, and Coffee Thermocycling on the Color and Translucency of Additively Manufactured Resins Used for Definitive Prostheses.

PURPOSE: To evaluate the effect of polymerization unit, polishing, and coffee thermocycling on the color and translucency of additively manufactured polyurethane-based resins with different viscosities. In addition, their color behavior was compared with the color of the shade tab throughout the fabrication steps and aging. MATERIALS AND METHODS: Disk-shaped specimens (Ø10 × 2 mm) were fabricated from polyurethane-based resins with different viscosities (Tera Harz TC-80DP and C&B permanent; n = 30 per material). Baseline color coordinates were measured after cleaning. The specimens in each resin group were divided into three subgroups (n = 10 per subgroup) to be polymerized with different polymerization units (Otoflash G171 [FLN], Wash and Cure 2.0 [CLED1], and P Cure [CLED2]), polished, and subjected to coffee thermocycling. Color coordinates were remeasured after each process. Color differences (ΔE00) and relative translucency parameter (RTP) values were calculated. Data were statistically analyzed (α = .05). RESULTS: Time points and polymerization units affected the ΔE00 for each material (P ≤ .049). ΔE00 of each polymerization unit pair had significant differences within and among different time points within each material (P ≤ .024). ΔE00 (when compared with the shade tab) and RTP were mostly affected by polymerization units and time points within both materials (P ≤ .042). CONCLUSIONS: Tested polymerization units, polishing, and coffee thermocycling affected the color difference and translucency of tested resins. Color differences ranged from moderately unacceptable to extremely unacceptable, and the differences in translucency values mostly ranged from perceptible to unacceptable, according to previous thresholds. In addition, tested resin-polymerization unit pairs had unacceptable color differences when compared to the shade tab. CLED1 may enable higher color stability for tested resins.

Flexural strength, surface roughness, and biofilm formation of ceramic-reinforced PEEK: An in vitro comparative study.

PURPOSE: This in vitro study aimed to compare flexural strength, surface roughness, and biofilm formation of ceramic-reinforced polyetheretherketone (PEEK) with conventionally heat-compressed and milled polymethylmethacrylate (PMMA) denture base materials. MATERIALS AND METHODS: Thirty strips (6.4 mm × 10 mm × 3 mm) and 30 discs (10 mm × 1 mm) were fabricated from a heat-compressed PMMA, milled PMMA, and ceramic-reinforced PEEK, 10 each. One surface of each sample was polished to mimic the laboratory procedure for denture base materials. Strips were then subjected to a three-point bend test using a universal testing machine at a crosshead speed of 5.0 mm/min. An optical profilometer was used to assess the Ra value (mm) of the discs on polished and unpolished sides. Biofilm formation behavior was analyzed by measuring the colony-forming unit (CFU)/mL of Candida albicans on the unpolished surface of the discs. One-way ANOVA followed by Tukey multiple comparison tests were used to compare the flexural strength, Ra value, and biofilm formation of the studied materials (a = 0.05). RESULTS: Ceramic-reinforced PEEK showed significantly higher flexural strength (178.2 ± 3.2 MPa) than milled PMMA (89.6 ± 0.8 MPa; p < 0.001) and heat-compressed PMMA (67.3 ± 5.3 MPa; p < 0.001). Ceramic-reinforced PEEK exhibited a significantly higher Ra value than the other groups on unpolished sides; however, the polishing process significantly reduced the Ra values of all studied groups (p < 0.05). There was no significant difference in C. albicans adhesion among the groups (p < 0.05). CONCLUSION: The flexural strength of tested materials was within acceptable limits for clinical use as a denture base material. Ceramic-reinforced PEEK had the highest surface roughness; however, its similarity in biofilm formation to other groups indicates its clinical acceptability as denture base material.

Effect of polymerization unit, polishing, and coffee thermocycling on the color and translucency of additively manufactured resins used for definitive prostheses.

PURPOSE: To evaluate the effect of polymerization unit, polishing, and coffee thermocycling on the color and translucency of additively manufactured polyurethane-based resins with different viscosities. In addition, their color behavior was compared with the color of the shade tab throughout the fabrication steps and aging. MATERIALS AND METHODS: Disk-shaped specimens (Ø10x2 mm) were fabricated from polyurethane-based resins with different viscosities (Tera Harz TC-80DP and C&B permanent) (N=30). Baseline color coordinates were measured after cleaning. The specimens were divided into 3 to be polymerized with different polymerization units (Otoflash G171, FLN; Wash and Cure 2.0, CLED1; CARES P Cure, CLED2) (n=10), polished, and subjected to coffee thermocycling. Color coordinates were remeasured after each process. Color differences (ΔE00) and relative translucency parameter (RTP) values were calculated. Data were statistically analyzed (α=.05). RESULTS: Time points and polymerization units affected the ΔE00 for each material (P≤.049). ΔE00 of each polymerization unit pair had significant differences within and among different time points within each material (P≤.024). ΔE00, when compared with the shade tab, and RTP were mostly affected by polymerization units and time points within both materials (P≤.042). CONCLUSION: Tested polymerization units, polishing, and coffee thermocycling affected the color difference and translucency of tested resins. Color differences ranged from moderately unacceptable to extremely unacceptable and the differences in translucency values mostly ranged from perceptible to unacceptable according to previous thresholds. In addition, tested resin-polymerization unit pairs had unacceptable color differences when compared to the shade tab. CLED1 may enable higher color stability for tested resins.

The effects of manufacturing technologies on the surface accuracy of CAD-CAM occlusal splints.

PURPOSE: To investigate the effects of the manufacturing technologies on the surface (cameo and intaglio) accuracy (trueness and precision) of computer-aided design and computer-aided manufacturing (CAD-CAM) occlusal splints. MATERIALS AND METHODS: The digital design of the master occlusal splint was designed in a CAD software program. Six groups (n = 10) were tested in this study, including Group 1 - Milling (Wax), Group 2 - Heat-polymerizing, Group 3 - Milling (M series), Group 4 - Milling (DWX-51/52D), Group 5 - 3D-printing (Cares P30), and Group 6 - 3D-printing (M2). The study samples were placed in a scanning jig fabricated from putty silicone and Type III dental stone. The study samples were then scanned with a laboratory scanner at the intaglio and cameo surfaces, and the scanned files were exported in standard tessellation language (STL) file format. The master occlusal splint STL file, was used as a reference to compare with all scanned samples at the intaglio and cameo surfaces in a surface matching software program. Root mean square (RMS, measured in mm, absolute value) values were calculated by the software for accuracy comparisons. Group means were used as the representation of trueness, and the standard deviation for each group was calculated as a measure of precision. Color maps were recorded to visualize the areas of deviation between study samples and the master occlusal splint file. The data were normalized and transformed to rank scores, and one-way ANOVA was used to test for the differences between the groups. Pairwise comparisons were made between different groups. Fishers least square differences were used to account for the family-wise error rate. A 5% significance level was used for all the tests. RESULTS: The null hypotheses were rejected. The manufacturing technologies significantly affected the trueness of occlusal splints at both intaglio and cameo surfaces (p < 0.001). At the cameo surfaces, Group 1 - Milling (Wax) (0.03 ± 0.02 mm), Group 3 - Milling (M series) (0.04 ± 0.01 mm), and Group 4 - Milling (DWX-51/52D) (0.04 ± 0.01 mm) had the smallest mean RMS values and highest trueness. Group 3 had the smallest standard deviation and highest precision among all groups (p < 0.001, except p = 0.005 when compared with Group 2). Group 5 had the largest standard deviation and lowest precision among all groups (p < 0.001). At the intaglio surfaces, Group 1 - Milling (Wax) (0.06 ± 0.01 mm) had the smallest RMS values and highest trueness among all groups (p < 0.001), and Group 2 - Heat-polymerizing (0.20 ± 0.03 mm) and Group 5 - 3D-printing (Cares P30) (0.15 ± 0.05 mm) had significantly larger mean RMS and standard deviation values than all other groups (p < 0.001), with lowest trueness and precision. In the color maps, Group 2 - Heat-polymerizing and Group 5 - 3D-printing (Cares P30) showed the most discrepancies with yellow and red (positive discrepancies) in most areas, and Group 1 - Milling (Wax) showed the best and most uniform surface matching with the most area in green. CONCLUSION: The manufacturing technologies significantly affected the trueness and precision of occlusal splints at both intaglio and cameo surfaces. The 5-axis milling units and industrial-level CLIP 3D-printer could be considered to achieve surface accuracy of occlusal splints.

Digital Gothic Arch Tracing Device with Open-Source Software for CAD/CAM Denture Fabrication.

Digital or CAD/CAM workflows and protocols are being increasingly utilized because of their improved efficiency and reproducibility. For the fabrication of complete dentures, digital workflows can reduce treatment time and clinical visits while enhancing the reliability and reproducibility of the laboratory phase and materials. However, establishing centric relation (CR) and vertical dimension of occlusion (VDO) in a reproducible way is still a challenging step for complete denture fabrication in both analog and digital workflows. This clinical report describes a digital workflow utilizing an individualized gothic arch tracing device (GATD) using open-source software for the fabrication of complete dentures. With this workflow, clinicians can offer customized solutions according to patient rehabilitation, with good reproducibility using gothic arch tracing to be implemented in the digital workflow.

Bead-anchored surgical templates for static computer-assisted implant surgery: A dental technique.

This technique report describes an alternative method to stabilize surgical templates throughout full-arch static computer-assisted implant surgery (FA s-CAIS). In FA s-CAIS, remaining teeth, mucosa, existing implants, custom occlusal device, bone, or any combination thereof, could be used as an initial positioning mechanism to position surgical templates. Different anchoring mechanisms are then used to stabilize the surgical templates during surgery. In this report, a novel design of surgical templates using remaining dentition and opposing occlusal surfaces as initial positioning mechanism followed by the combination of bone block fixation screw and stainless-steel beads as secondary anchoring mechanisms is described. The advantages, limitations, and comparisons with surgical templates using other anchoring mechanisms are also discussed.

Immediate Loading of Straumann® TLX Implant in Grafted Maxillary First Molar Site.

The patient treatment described in this case report demonstrates management of a failing maxillary first molar utilizing an immediate loading approach. Following extraction, the site was successfully managed with socket grafting (ridge preservation) and allowed to heal prior to implant placement. A Straumann® TLX implant was placed using a guided approach and restored using CAD/CAM.

Addition of an irrigation channel to a surgical template to facilitate cooling during implant osteotomy.

The increased precision and design of surgical templates for static computer-aided implant surgery has led to concerns of excessive heat generation from the friction between the twist drills, metal sleeves in the surgical template, and guide handles during osteotomy preparation. In addition, the presence of a surgical template can prevent proper cooling of the twist drill as it enters the osteotomy site, leading to greater heat generation. This excessive heat may result in bone necrosis and failure of osseointegration to the implant surface. This article describes a straightforward technique of incorporating an existing design feature in many virtual implant planning software programs to add an irrigation channel to the implant surgical template for effective cooling during osteotomy preparation.