Accuracy of 3D printing compared with milling - A multi-center analysis of try-in dentures.

OBJECTIVES: In recent years, computer-aided design/computer-aided manufacturing (CAD/CAM) has been used to produce removable complete dentures. Most workflows include fabrication of milled or 3D-printed try-in prostheses. 3D-printing accuracy is affected by laboratory-specific and operator-dependent factors. This international five-center study sought to compare the accuracy of 3D-printed and milled try-in dentures. METHODS: The construction file of a maxillary removable complete denture was selected as a reference. Eight try-in dentures were 3D printed at each of the five centers. Each center used their own printer (Objet260 Connex, Stratasys; MAX, Asiga; Anycubic Photon, Anycubic 3D; PRO2, Asiga and cara Print 4.0, Kulzer) along with their own material, printing settings, post-processing and light-curing parameters. At center 2, eight try-in dentures were milled to serve as a benchmark (PrograMill PM7, Ivoclar Vivadent). Dentures were scanned and aligned to the reference file using best-fit algorithms. Geometric accuracy was analyzed using the root mean square value (trueness) and standard deviation (precision) of the distributed absolute mesh deviations. Mean values of the five sets of printed dentures and the single set of milled dentures were compared. RESULTS: Milled dentures showed a mean trueness of 65 ±â€¯6 µm and a mean precision of 48 ±â€¯5 µm. Thus, they were significantly more accurate than the 3D-printed dentures in four out of five centers. In mean absolute numbers, 3D printing was less true than milling by 17-89 µm and less precise by 8-66 µm. CONCLUSIONS: Although milling remains the benchmark technique for accuracy, differences between milled and 3D-printed dentures were non-significant for one printing center. Furthermore, the overall performance of 3D printing at all centers was within a clinically acceptable range for try-in prostheses. CLINICAL SIGNIFICANCE: The accuracy of 3D printing varies widely between and within laboratories but nonetheless lies within the range of accuracy of conventional manufacturing methods.

Surgery-first approach in orthognathic surgery: Psychological and biological aspects - A prospective cohort study.

INTRODUCTION: The aim of this pilot study was to investigate psychological and biological changes after application of a surgery-first orthognathic treatment approach. METHODS: A prospective cohort study of 9 patients (6 women and 3 men; mean age 26.7 years) suffering from skeletal Class II and III deformities was conducted. Skeletal changes from pre-to post-treatment were analyzed based on data acquired by use of cone-beam computed tomography (CBCT). Psychological changes were analyzed using the orthognathic quality of life (OQLQ) questionnaire, Sense of Coherence 29-item scale (SOC-29) and longitudinal day-to-day questionnaire. For biological evaluation, concentrations of IL-1 ß, IL-6, TGF ß 1-3, MMP-2 and VEGF were assessed in crevicular fluid by bead-based multiplex assays at one preoperative and various postoperative time points. RESULTS: A significant improvement (P = 0.015) in quality of life, as measured with the OQLQ, was observed between baseline and 3 months post-surgery. The most affected dimensions were: facial aesthetics (p = 0.022), oral function (p = 0.051) and social aspects (p = 0.057). Sense of coherence (SOC) significantly improved after treatment by 9 points (P = 0.029). Despite the significant improvement in OQLQ and SOC during the course of the study, the personal experience of appearance varied distinctly in course and intensity. In accordance with the temporal pattern of fracture healing, the analysis of crevicular fluid revealed an increase in pro-resorptive factors (IL-1 ß, IL-6 and MMP-2) at early postoperative time points, while remodeling factors (members of the TGF-ß superfamily) were detected at later postoperative time points. CONCLUSIONS: Orthognathic treatment using the surgery-first approach has a positive impact on patient's psychosocial status. Accelerated tooth movement after surgery might, to a certain extent, be due to elevated levels of bone remodeling factors with overlapping functions during fracture healing and tooth movement.