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Abstract Background The purpose of this study was to evaluate the accuracy of intraoral scanners by comparing the trueness and precision of several types of scanners in measuring the distance between the ball abutments on pairs of multiple implants. Methods Seven implants were placed on a fully edentulous upper jaw model. After ball abutments were attached to the implants on the master model, the three-dimensional (3D) shape of the model was evaluated using a computer numerical control 3D coordinate-measuring machine. Subsequently, the 3D shape-related data of the model were obtained using two types of intraoral scanners (3M True Definition Scanner [TDS] and 3Shape Trios3 [TR3]) and two types of laboratory scanners (KaVo ARCTICA Auto Scan [KA] and Identica Hybrid [IH]). Using the obtained 3D shape-related data, the trueness and precision in measuring the distance between the balls within seven pairs of ball abutments were compared among the scanners using 3D analysis software. Results Intraoral scanners produced significantly greater errors in trueness and precision than laboratory scanners in measuring the distances between the ball abutments in all the dental regions. Between the intraoral scanners, powder-requiring TDS produced significantly lower errors at inflection points than powder-free TR3. Conclusions These results indicate that an optical impression technique using an intraoral scanner is suitable for dental implant treatment in patients with a few missing teeth.

Purpose: This study aimed to clarify the effect of occlusal force on appropriate optical interocclusal registration in clinical practice, considering periodontal ligament and jawbone deformation. Methods: Forty participants with natural, healthy dentition were enrolled (19 men and 21 women; mean age, 27.7 ± 2.0 years). A TRIOS3 intraoral scanner was used to scan the right lateral first premolar to the second molar areas of the upper and lower jaws. During scanning for interocclusal registration, participants were instructed to "bite normally," "bite lightly," and "bite strongly" to obtain data for the three occlusal patterns. The standard triangulated language (STL) data for each occlusion condition were superimposed using the appropriate software, following which the tooth displacement was calculated. The conventional method was also used to record the occlusal contact area for a silicone model using a dental contact analyzer. Results: Tooth displacement was significantly lower for the strong-bite condition than for the weak-bite condition (0.018 mm vs. 0.028 mm, P<0.05). As the occlusal force increased, the occlusal contact area also increased, and significant differences were observed among the different occlusal conditions (P<0.05). Conclusions: Occlusal contact area changed depending on the bite force when using the silicone impression or optical intraoral scanning methods. Moreover, using optical impression methods in "strong bite force" may reduce the deviation and allow for stable interocclusal registration. [ABSTRACT FROM AUTHOR]

The recent literature on maxillary implant overdenture (IOD) was reviewed in order to clarify its predictability and establish treatment guidelines. Electronic searches were performed using PubMed, and articles about maxillary IOD written after 1990 were reviewed, focusing on the following items: I. implant survival rate, II. maxillary IOD survival rate, III. number of implants, IV. attachment type, V. follow-up period, VI. implant system, and VII. opposing dentition. The review revealed an implant survival rate of 61-100% and an overdenture survival rate of 72.4-100%. The attachments used included bars, balls, locators, and telescope crowns. The minimum and maximum observation periods were 12 months and 120 months, respectively, and the number of implants used for supporting IOD ranged from 2 to 8. At present, there is no strong evidence to indicate that maxillary IOD is clearly superior for all the items examined. However, the existing data indicate that maxillary IOD has almost the same therapeutic effect as fixed implant superstructures, and is a treatment option that can be actively adopted for patients in whom fixed superstructures cannot be applied for various reasons. [ABSTRACT FROM AUTHOR]

This narrative review aims to provide an overview of recent studies and case reports on three-dimensional (3D) printing, and to verify the applicability of 3D printers in the field of dental prostheses. This review was performed by conducting a search of PubMed. The clinical application of fabricating a prosthesis made with cobalt-chromium is considered possible depending on the material and hardware of the 3D printer. However, it is currently difficult to assess the clinical use of 3D-printed zirconia crowns. Further research is required, such as verification of materials used, margin morphology, and hardware. Clinically acceptable results have been reported for patterns using 3D printers. Interim restorations made using a 3D printer have been reported with good results that are considered clinically usable. Dentures made with 3D printers need further verification in terms of strength and deformation. Custom trays made with 3D printers are clinically useful, however, issues remain with design time and effort. Although several studies have reported the usefulness of 3D printers, further verification is required since 3D printers are still considered new technology. [ABSTRACT FROM AUTHOR]