Trueness of Digital Intraoral Impression in Reproducing Multiple Implant Position

The aim of this study was to evaluate the trueness of 5 intraoral scanners (IOSs) for digital impression of simulated implant scan bodies in a partially edentulous model. A 3D printed partially edentulous mandible model made of Co-Cr with a total of 6 bilaterally positioned cylinders in the canine, second premolar, and second molar area served as the study model. Digital scans of the model were made with a reference scanner (steroSCAN neo) and 5 IOSs (CEREC Omnicam, CS3600, i500, iTero Element, and TRIOS 3) (n = 10). For each IOS's dataset, the XYZ coordinates of the cylinders were obtained from the reference point and the deviations from the reference scanner were calculated using a 3D reverse engineering program (Rapidform). The trueness values were analyzed by Kruskal-Wallis test and Mann-Whitney post hoc test. Direction and amount of deviation differed among cylinder position and among IOSs. Regardless of the IOS type, the cylinders positioned on the left second molar, nearest to the scanning start point, showed the smallest deviation. The deviation generally increased further away from scanning start point towards the right second molar. TRIOS 3 and i500 outperformed the other IOSs for partially edentulous digital impression. The accuracy of the CEREC Omnicam, CS3600, and iTero Element were similar on the left side, but they showed more deviations on the right side of the arch when compared to the other IOSs. The accuracy of IOS is still an area that needs to be improved.ope

Use of an extraoral transfer jig and a handheld face scanner app for integrating face scan data into prosthesis design

This article demonstrates a case that successfully rehabilitated the maxillary anterior missing tooth area with a single-tooth implant prosthesis by integrating three-dimensional face scan data into the computer-aided design software. An extraoral transfer jig was self-invented to achieve this purpose, and a handheld face scanner app was used to accomplish economic benefits. Not only was the protocol convenient and efficient for both the patient and clinician, but it also resulted in a satisfactory outcome.ope

Use of Model-Free and Zero-Setup Computer-Guided Implant Surgical Template for Partial Edentulous Cases

This case report presents the cases of single anterior missing and posterior free-end edentulous ridge with computer-guided implant placement on the day of visit through a special tray containing fiducial markers without model scan or intraoral scan data. Cone beam CT was taken after fixing the marker embedded ready-made tray with a photopolymerized resin material by light-curing in the patient's mouth. The implant location was planned on the registered CT data in the planning software. The tool path calculation for the milling machine was conducted in the computer-aided manufacture (CAM) software. The guide was completed by milling the drill hole in the special tray as designed. Although the preparation for the conventional implant guide surgery takes considerable time, including data acquisition and 3D printing, it was possible to produce a guide on the day of the patient visit without a separate procedure other than a CT scan through this protocol. Also, the transfer of the implant surgery plan, the process of scanning and 3D printing, was omitted, thereby reducing the positional error between the CT data and the actual guide.ope

Comparison of Reproducibility of Milled Acrylic Resin and Zirconia Models for 3-unit bridge Using Three-dimensional Analysis

Purpose: The objective of this study was to investigate the reproducibility of milled acrylic resin and zirconia models using three-dimensional analysis. Material and Methods: Zirconia discs and acrylic resin blocks were milled to make models. Each model was scanned with a model scanner. The zirconia models were superimposed with other zirconia model, and the acrylic resin models were superimposed with other acrylic resin model threedimensionally. Root-mean-square (RMS) values were obtained. Distances between two superimposed models were measured. Statistical significances were tested using the Mann-Whitney U test and t-test. Results: The RMS values of the zirconia model and the acrylic resin model were not significantly different ( p ≥0.05). At the premolar site, distances between the zirconia models at the upper axial and at the lower axial wall were significantly smaller than for the acrylic resin models ( p <0.05). At the molar site, distance between the zirconia models at the lower axial wall was significantly smaller than for the acrylic resin models ( p <0.05). Conclusion: Although there is a difference in reproducibility between the milled acrylic resin model and the zirconia model in the localized region, no significant difference was found in the whole model.ope

Flexural Strength of 3D-Printing Resin Materials for Provisional Fixed Dental Prostheses

The clinical application of 3D-printed provisional restorations is increasing due to expansion of intraoral scanners, easy dental computer-aided design (CAD) software, and improved 3D printing speed. This study compared flexural strength of 3D-printed three-unit fixed dental prostheses with that of conventionally fabricated and milled restorations. A metal jig of two abutments and pontic space and an indenter for flexural strength measurement were fabricated. A three-unit fixed dental prosthesis was designed and manufactured using three additive manufacturing technologies, with subtractive manufacturing and a conventional method as controls. Digital light processing (DLP) group specimens were prepared from a polymethyl methacrylate (PMMA)-based resin and printed with a DLP printer. Stereolithography (SLA) group specimens were prepared from PMMA-based resin and printed with an SLA printer, and fused deposition modeling (FDM) group specimens were from a polylactic acid-based resin and printed with an FDM printer. Flexural strength was investigated using a universal testing machine, and the results were statistically analyzed. DLP and SLA groups had significantly higher flexural strength than the conventional group (p < 0.001). No significant difference was observed in flexural strength between DLP and SLA groups. The FDM group showed only dents but no fracture. The results of this study suggest that provisional restorations fabricated by DLP and SLA technologies provide adequate flexural strength for dental use.ope

Study on Users’ Responses to Facebook Messages from Dental Clinics

Purpose: Although many dental clinics have actively managed social network service (SNS), there are few studies on the effects of messages produced by SNS of dental clinics. The purpose of this study was, targeting Facebook messages of dental clinics, to examine the effects of messages on users by types, and learn various variables that influence the effects of messages. Methods: In order to measure the effects of messages produced by SNS of dental clinics, the types of Facebook messages of dental clinics were divided into interacting type, information providing type, and playing type, and users’ responses were divided into message attitude, image of dental clinics, and word-of-mouth effect. Considering that the main users of Facebook are young people aged 20-30 s, this study targeted Facebook users aged 20-30 s, performed a survey targeting 292 young people, and conducted two sample t-test, one-way ANOVA, and regression analysis by using SPSS 19.0. Results: It could be found that, among the types of Facebook messages of dental clinics, interacting type has a positive effect in the aspect of image of dental clinics, information providing type in the aspect of message attitude, and playing type in the aspect of word-of-mouth effect. Also, it could be found that, among users’ responses, message attitude of information providing type has the greatest effect on users’ Responses. Users having experience of seeing messages and having intention of receiving dental information show more positive effects in the aspects of message attitude, image of dental clinics, and word-of-mouth effect. And it was analyzed that as the rate of SNS use increases, users’ Responses turns out to be more positive. Conclusion: This study has a meaning in that it expanded the range of typical researches from the media characteristics of SNS to the effects of SNS messages. The information providing type, interacting type, and playing type messages have all had a positive effect on the user response. The users who have experienced the dental facebook message expressed more positive response than ones who have not. Frequent exposure of dental Facebook messages can be of interest to users.ope

Biomechanical Evaluation of Initial Stability of a Root Analogue Implant Design with Drilling Protocol: A 3D Finite Element Analysis

Background: The aim of this study was to biomechanically evaluate the initial stability of a patient-specific root analogue implant (RAI) design with drilling protocol by comparing it to designs without drilling protocol through a 3D finite element analysis (FEA). Methods: A 3D surface model of an RAI for the upper right incisor was constructed. To evaluate the effect of root apex drilling, four modified RAI shapes were designed with the press-fit implantation method: Non-modified, wedge added at root surface, lattice added at root surface, and apex-anchor added at root apex (AA). Each model was subjected to an oblique load of 100 N. To simulate the initial stability of implantation, contact conditions at the implant–bone interface were set to allow for the sliding phenomenon with low friction (frictional coefficient 0.1–0.5). Analysis was performed to evaluate micro-displacements of the implants and peak stress on the surrounding bones. Results: Under all low frictional coefficient conditions, the lowest von Mises stress level on the cortical bone and fewest micro-displacements of the implant were observed in the AA design. Conclusion: In view of these results, the AA design proved superior in reducing the stress concentration on the supporting cortical bone and the micro-displacement of RAI.ope

The use of implant surveyed fixed prosthesis for removable partial denture with a few unilateral remaining teeth : a case report

As implant can be covered by National Health Insurance Service (NHIS), it was increased the interest in the removable partial denture (RPD) with the surveyed fixed prosthesis supported by implant fixture. To achieve predictable result, it needs the prudent implant planning by basic principles of RPD and patient’s residual ridge. This 67 years old age male had a few unilateral remaining teeth, and hoped the treatment covered by NHIS. As using CAD software, the position of implant is planned with regarding to occlusal table of provisional denture, basic principles of RPD, and resorbed residual ridge. The definitive prostheses can ensure the stability and retention of removable prosthesis. When planning implant fixed prostheses, the digital technique was utilized to consider basic principle of RPD and resorbed residual ridge. As a result, it provided satisfactory prostheses.ope

3D Printing of Resin Material for Denture Artificial Teeth: Chipping and Indirect Tensile Fracture Resistance

3D printing of denture artificial teeth with resin materials is worthy of study in a novel way. This study evaluated chipping and indirect tensile fracture resistance of 3D printing resin material (Dentca 3D printing denture teeth resin) compared with conventionally prefabricated resin denture teeth (Premium-8, Surpass, SR-Orthosit-PE, and Preference). One hundred tooth specimens were prepared for testing. The 3D printed tooth specimens were printed at a 50 µm layer thickness with methacrylate-based photopolymerized resin by stereolithography 3D printing. Chipping and indirect tensile fracture tests were conducted at a speed of 1 mm/min until fracture. The indirect tensile fracture loads of the 3D printed resin teeth were higher than those of Premium-8, Surpass, and SR-Orthosit-PE, and lower than those of Preference teeth. Regarding chipping resistance, the 3D printed resin teeth were not different from Surpass and SR-Orthosit-PE, and were lower than Premium-8 and Preference teeth. The 3D printed resin teeth exhibited vertical fracture of the loaded cusp without deformation in chipping. The 3D printed resin teeth showed simultaneous fracture of two cusps in indirect tensile fracture, unlike other teeth. The results of this study suggest that 3D printing technology using resin materials provides adequate fracture resistance for denture artificial tooth use.ope

Wear Resistance of 3D Printing Resin Material Opposing Zirconia and Metal Antagonists

3D printing offers many advantages in dental prosthesis manufacturing. This study evaluated the wear resistance of 3D printing resin material compared with milling and conventional resin materials. Sixty substrate specimens were prepared with three types of resin materials: 3D printed resin, milled resin, and self-cured resin. The 3D printed specimens were printed at a build angle of 0° and 100 μm layer thickness by digital light processing 3D printing. Two kinds of abraders were made of zirconia and CoCr alloy. The specimens were loaded at 5 kg for 30,000 chewing cycles with vertical and horizontal movements under thermocycling condition. The 3D printed resin did not show significant difference in the maximal depth loss or the volume loss of wear compared to the milled and the self-cured resins. No significant difference was revealed depending on the abraders in the maximal depth loss or the volume loss of wear. In SEM views, the 3D printed resin showed cracks and separation of inter-layer bonds when opposing the metal abrader. The results suggest that the 3D printing using resin materials provides adequate wear resistance for dental use.ope