Comparison of 3D positional accuracy of implant analogs in printed resin models versus conventional stone casts: Effect of implant angulation.

PURPOSE: To study the effect of implant angulation on 3D linear and absolute angular distortions of implant analogs in printed resin models and conventional stone casts. MATERIALS AND METHODS: Three sectional master models with two implants with total inter-implant angulations of 0°, 10°, and 20° were fabricated. For each master model, five conventional stone casts (CS) and printed resin models (PM) were fabricated (n = 5). Test models were made with nonsplinted impression copings and open tray polyether impressions for the CS groups and scan bodies scanned using an intraoral scanner for the PM groups. The physical positions of the implants and implant analogs were measured with a coordinate measuring machine. 3D linear distortion (ΔR) and absolute angular distortion (Absdθ) defined the 3D positional accuracy of the analogs in the test models. Univariate ANOVA was used to analyze data followed by post hoc tests (Tukey HSD, α = 0.05). RESULTS: Mean ΔR was significantly greater for PM10 (73.5 ± 8.9 µm) and PM20 (65.5 ± 33.3 µm) compared to CS0 (16.8 ± 14.1 µm), CS10 (22.2 ± 13.0 µm), CS20 (15.6 ± 19.9 µm), and PM0 (23.9 ± 16.1 µm). For Absdθ, there were no significant differences between test groups. CONCLUSIONS: With conventional stone casts, implant angulation had no significant effect on 3D linear and absolute angular distortions. Amongst printed resin models test groups, angulated implants had significantly greater ΔR. Amongst angulated implants test groups, printed resin models had significantly greater ΔR than conventional stone casts. Compared to the master model, all test groups, regardless of inter-implant angulation, produced greater inter-analog distances.

A Fully Digital Auricular Splint Workflow for Post-Keloid Excision.

Ear keloids are challenging lesions to treat due to high recurrence rates postexcision. Conservative compression techniques as adjunct treatment have been reported to be effective. An innovative technique of using computer-aided design/computed-aided manufacturing to print a customized auricular splint improves efficiency and comfort level for patients compared with conventional methods. The ear is scanned using an intraoral scanning 2 weeks postsurgery. A two-piece auricular splint is designed on the digital model, incorporating perforated projections for three nylon screws for retention of the splint. The splint is printed with clear acrylic material, postprocessed, and finished. The patient is taught to assemble the components of the splint and instructed to wear for at least 8 hours daily. The surgery site reviewed for any ulceration, pain, or recurrence of keloid for 6 months. During the 6-month review, the excision scar remained flat and pink. The patient also reports unrestricted daily activities. The digital workflow increases comfort for the patient and reduces the number of hours required to produce a customized auricular splint compared with conventional methods. A fully digital workflow for a printed auricular splint should be considered for adjunctive treatment to excision of ear keloids.

Accuracy of Implant Analogs in 3D Printed Resin Models.

PURPOSE: To study the effect of implant analog system, print orientation, and analog holder radial offset on 3D linear and absolute angular distortions of implant analogs in 3D printed resin models. MATERIALS AND METHODS: A sectional master model simulating a 2-implant, 3-unit fixed prosthesis in a partially edentulous jaw was fabricated. Three implant analog systems for 3D printed resin models-Straumann (ST), Core3DCentres (CD) and Medentika (MD)-were tested. The corresponding scan bodies were secured onto the implants and scanned using an intraoral scanner. Models were obtained with a Digital Light Processing printer. Each implant analog system had 2 print orientations (transverse [X] and perpendicular [Y] to the printer door) and 2 analog holder radial offsets (0.04 mm and 0.06 mm), for a total of 60 models. The physical positions of the implants in the master model and the analogs in the printed resin models were directly measured with a Coordinate Measuring Machine (CMM). 3D linear distortion (ΔR) and absolute angular distortion (Absdθ) defined the 3D accuracy of the analogs in the printed models. Univariate ANOVA was used to analyse data followed by post hoc tests (Tukey HSD, α = 0.05). RESULTS: Mean ΔR for ST (-155.7 ± 60.6 µm), CD (124.9 ± 65.0 µm) and MD (-92.9 ± 48.0 µm) were significantly different (p < 0.01). Mean Absdθ was not significantly different between ST (0.57 ± 0.48°) and CD (0.41 ± 0.27°), but both were significantly different from MD (2.11 ± 1.14°) (p < 0.01). Print orientation had a significant effect on ΔR only but no discernible trend could be found. Analog holder radial offset had no significant effect on ΔR and Absdθ. CONCLUSIONS: Implant analog system had a significant effect on ΔR and Absdθ. Compared to the master model, CD produced greater mean interanalog distances, while ST and MD produced smaller mean interanalog distances. MD exhibited the greatest mean angular distortion which was significantly greater than ST and CD.