International Journal of Computerized Dentistry, 01/2022

Aim: The present narrative review aims to provide an overview of the in vivo accuracy of full-arch scans performed with currently used intraoral devices and to compare different methods for the determination of in vivo accuracy. Materials and methods: An electronic search was performed with the PubMed, Cochrane Central Register of Controlled Trials (CENTRAL), and Web of Science databases, including articles from 2015 to 2020. Specific search strategies were developed for each platform. Results: The final search resulted in five published articles. The mean values of trueness and precision of the examined scanners ranged from 12.9 to 80.01 µm for trueness and from 42.9 to 86.0 µm for precision in full-arch dentition. Not all studies evaluated both trueness and precision. Furthermore, the methods and references for determining the in vivo accuracy proved to be very different. Conclusion: To date, no scientific consensus on the required accuracy of in vivo full-arch scans has been reached and published. Due to the small number of studies on the in vivo accuracy of full-arch scans, further studies should be conducted in this area. In addition, a concept for a valid reference that can be scanned both extraorally and intraorally should be developed. Keywords: CAD/CAM, accuracy, in vivo accuracy, intraoral scanner, optical impressions, digital impression, digital dentistry

Aim: To determine the effect of intraoral conditions on the accuracy of digital full-arch scans. Materials and methods: A reference bar was used for the in vivo and in vitro parts of the present study. For the in vitro part (PAT-vitro), the bar was fixed to connect the maxillary second molars on the patient’s resin model. The same reference bar was fixed in a similar position intraorally for the in vivo testing (PAT-vivo). Model and patient were digitized using an intraoral scanner (Cerec Primescan AC, N = 40, n [PAT-vitro] = 20, n [PAT-vivo] = 20). Datasets were exported and metrically analyzed (Geomagic Control 2015) to determine the 3D linear and angular distortions in all three coordinate axes of the datasets with reference to the bar. Normality of the data distribution was tested using the Kolmogorov-Smirnov and Shapiro-Wilk tests. Homogeneity of the variances was tested using the Levené test. Statistically significant differences for all measured parameters in view of trueness were determined using the two-sample t test, and in view of precision using the two-sample Kolmogorov-Smirnov test. Results: The PAT-vivo group showed significantly higher trueness for most of the measured linear and angular distortion parameters than the PAT-vitro group. Regarding precision, the PAT-vitro group showed significantly better values for most of the measured linear and angular distortion parameters than the PAT-vivo group. Conclusions: Within the limitations of the present study, Cerec Primescan AC leads to comparable accuracy parameters when applied in vivo and in vitro. The reproducibility (precision) was higher when scans were performed in vitro. Due to the high trueness, the system seems to be a valid tool to obtain digital full-arch datasets in vivo with comparable accuracy to in vitro tests. coronalaxial Keywords: digital impression, full-arch accuracy, in vitro digitalization, in vivo digitalization

Aim: To compare the clinical outcomes of conventional and digital implant impressions in all-on-4 mandibular implant prostheses. Materials and methods: Fifty-six participants were randomly stratified into two control groups (Axial Conventional Impression Group [ACIG] and Tilted Conventional Impression Group [TCIG]), and two test groups (Axial Digital Impression Group [ADIG] and Tilted Digital Impression Group [TDIG]). Conventional pick-up and digital impressions were made for each group, respectively. Participants in ACIG and ADIG received four axial implants, and those in TCIG and TDIG received two anterior axial and two distal tilted implants. All participants received all-on-4 mandibular prostheses and maxillary complete dentures. Implant survival, prosthetic complications, and marginal bone loss were recorded at 6, 12, and 24 months. Data were statistically described in terms of mean ± standard deviation. Results: After 24 months, the implant survival rate was 100%. A significant difference in bone loss was shown between ACIG and ADIG at 6, 12, and 24 months, with P = 0.647, 0.821, and 0.505, respectively. An insignificant difference in bone loss was shown between TCIG and TDIG at 6 ,12, and 24 months, with P = 0.671, 0.935, and 0.687, respectively. No significant difference was shown in prosthodontic complications between all groups throughout the follow-up period. Conclusions: The digital impressions showed clinically better implant survival, stable peri-implant marginal bone level, and reasonable prosthodontic complications. The present study represents a steppingstone and proof of concept that supports the routine clinical use of digital impressions, especially in a post-COVID-19 world. Keywords: implant, digital impression, analog impression, implant survival, prosthetic complications, marginal bone loss

Aim: To evaluate the survival of implant-retained restorations fabricated on CAD/CAM-derived zirconia abutments luted to a titanium base. Materials and methods: 153 patients who received a total of 310 dental implants (Camlog Promote plus or Xive S) and all-ceramic restorations on yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) abutments luted to a titanium base during the last 10 years were included. Patients were examined for technical complications during routine visits. Crestal bone level changes were randomly analyzed based on periapical radiographs of 75 implants. Results: Among the included 153 patients, 17 ceramic chippings (5.5%), 6 abutment loosenings (1.9%), and 2 abutment fractures (0.6%) were identified. The mean follow-up time was 4.7 years (standard deviation [SD]: 1.94), with a follow-up period of up to 10 years (maximum). Kaplan-Meier estimation resulted in a survival rate without complications of 91.6% for the restoration and 97.4% for the abutment. There was no statistically significant difference between the two implant systems, either between implant location or regarding the complication rate of the type of restoration. For the 75 implants included in the radiographic analysis, the mean bone level change was 0.384 mm (SD: 0.242, 95% CI: 0.315 to 0.452) for the Camlog implant system and 0.585 mm (SD: 0.366, 95% CI: 0.434 to 0.736) for the Xive system (P = 0.007). Conclusion: The results of the present retrospective study demonstrate acceptable clinical outcomes for zirconia abutments luted to a titanium base in combination with all-ceramic restorations. The assessed abutment design does not appear to have a negative impact on peri-implant hard tissue. Keywords: implant abutment, zirconia abutment, titanium base, two-piece abutment, implant restoration

Sufficient occlusion is a basic prerequisite for the functional efficiency of the occlusal surfaces. Exactly where and in what number the occlusal contacts in the posterior region should be present for this purpose is controversial. The present study investigated the number and location of occlusal contacts on posterior teeth without dental findings, ie, without caries or restorative restorations such as fillings, crowns, etc. Such natural posterior teeth were present in 709 subjects (males (m) = 446: 48.9 ± 13.04 years, females (f) = 283: 52.4 ± 14.23 years) of a subject collective of 1223 subjects (m = 648, f = 575) of the regional baseline study ‘Study of Health in Pomerania 1’ (SHIP-1). Silicone bite registrations in habitual intercuspation (IP) were evaluated, whereby the test persons were asked to fix the bite block with biting force without biting firmly. The registrations were scanned with a document scanner in incident and transmitted light; a calibration strip was used to determine the transparency threshold of a layer thickness of 20 μm, below and equal to which the transparent zone was considered as a contact or contact area. The Greifswald Digital Analyzing System 2 (GEDAS 2) software was used to determine the number and location of occlusal contact areas tooth by tooth. To define the localization of the contacts, a cross with two concentric circles symmetric to the longitudinal fissure was superimposed on the occlusal surface; this resulted in four inner and four outer quadrants. Thus, the number of pixels in occlusal contact areas per inner and outer quadrant could be determined. The image resolution was 300 dpi. On average (median), the premolars had two occlusal contacts each, the posterior teeth had four to five, and tooth 46 had six contacts. The right and left teeth did not differ in the frequency of occlusal contacts in the Mann-Whitney U test for independent samples. In the maxillary premolars, frequent contact areas were primarily located mesially on the inner and outer slopes of the palatal cusp. In the maxillary molars, the palatal slope of the distopalatal cusp and the inner slopes of the mesiopalatal and distopalatal cusps were frequently affected. On the mandibular premolars, the inner slopes of the buccal cusps and the buccal slope of the distobuccal cusp were particularly frequently addressed; in teeth 35 and 45, the buccal slope of the mesiobuccal cusp was also somewhat more frequently addressed. Teeth 36 and 46 frequently had contact areas on the buccal slope of the distobuccal cusp as well as on the inner slopes of the distal cusps (distobuccal and distolingual), whereas teeth 37 and 47 tended to behave similarly. Epidemiologically, the focus of the frequent contact areas on the respective supporting cusps of the maxillary and mandibular posterior teeth and a distribution of contacts stabilizing the tooth in its position in the dental arch through the interlocking were confirmed. It makes sense to take this into account when designing occlusal surfaces in the posterior region. Keywords: occlusion, occlusal contacts, posterior teeth, epidemiology

Aim: The aim of the present study was to review the current development status of additive manufacturing (AM) technology for fabricating frameworks for removable partial dentures (RPDs) considering fit accuracy, surface condition, and mechanical strength. Methods: A search of the databases of MEDLINE, Cochrane Library, and Science Direct was conducted using definite keywords (“removable partial denture” or “framework” or “dental prosthesis design”) and (“additive manufacturing technology” or “rapid prototyping” or “3D-printing”). Result: A total of 23 articles were selected according to certain inclusion criteria. The direct AM techniques were applied to manufacture metal RPD frameworks consisting of selective laser melting (SLM), selective laser sintering (SLS), and metal binder jetting (MBJ). The SLM technique showed a good surface and mechanical strength, but low accuracy. The SLS technique showed higher accuracy than indirect AM, but further studies are required. The MBJ technique showed lower accuracy and a rougher surface than the conventional method. Conclusion: AM techniques can produce RPD frameworks within the acceptable range for clinical practice; however, more clinical studies are needed. Keywords: additive manufacturing, framework, removable partial denture, selective laser melting, selective laser sintering, metal binder jetting

Virtual planning has become part and parcel of digital dentistry to ensure more precise planning, better treatment outcomes, and more effective communication between dental practitioners, dental technicians, and patients. In dentistry, CAD software programs are one way to achieve virtual treatment planning. Among the most crucial and critical steps in treatment planning and execution are virtual articulation and occlusal analysis of the maxillary and mandibular arches. These steps have a great influence on the success of the final outcome. The present article proposes a detailed method for constructing a novel virtual articulator that can also be used for educational purposes to enable occlusal analysis and adjustment for a virtual tooth mock-up by simulating a virtual dynamic occlusion through the use of open-source Autodesk Meshmixer software. Keywords: virtual articulator, digital dentistry, Meshmixer, CAD, open-source, virtual education

Aim: The objective of the present case series was to evaluate the 4-year outcomes of implants placed in the esthetic area using static computer-assisted implant surgery (s-CAIS) and restored with a one-abutment one-time (OAOT) protocol using custom-made zirconia abutments and cemented provisional crowns manufactured prior to surgery. Materials and methods: Ten consecutive implants were placed in the esthetic area. Based on a digital implant and prosthodontic planning, surgical guides were ordered and used for the preparation of definitive custom-made zirconia abutments and polymethylmethacrylate provisional crowns. Implants were placed using the s-CAIS guide, and prosthetic components were placed immediately. Implant outcomes were evaluated at the time of surgery, after 4 months, and after 4 years. Results: All implants were successfully placed with s-CAIS and restored with final abutments and provisional crowns. No major prosthetic adverse events were observed. After 4 years, the implant survival rate was 100%, minor peri-implant bleeding on probing was reported, and very stable peri-implant bone levels were observed. The pink esthetic score showed that the prosthetic components were well integrated, and the peri-implant soft tissue was stable. Conclusions: Within the limitations of the present case series, these results suggest that emerging digital workflows allow the manufacture of final custom-made abutments and provisional crowns prior to surgery. This individualized OAOT procedure may reduce cement-related complications and improve esthetic outcomes by optimizing soft tissue healing with prosthetic components. However, such protocols have evolved toward fully digital workflows, and comparative clinical trials are needed. Keywords: s-CAIS surgery, digital workflow, one-abutment one-time (OAOT), custom-made abutment, bone remodeling, distance between the implant shoulder and first bone-to-implant contact (DBI), pink esthetic score (PES)