Accuracy of full-arch digitalization for partially edentulous jaws — a laboratory study on basis of coordinate-based data analysis

Objectives To compare the accuracy (trueness and precision) of direct digitization of four different dental gap situation with two IOS (intraoral scanner). Materials and methods Four partially edentulous polyurethane mandible models were used: (1) A (46, 45, 44 missing), (2) B (45, 44, 34, 35 missing), (3) C (42, 41, 31, 32 missing), and (4) D (full dentition). On each model, the same reference object was fixed between the second molars of both quadrants. A dataset (REF) of the reference object was generated by a coordinate measuring machine. Each model situation was scanned by (1) OMN (Cerec AC Omnicam) and (2) PRI (Cerec Primescan AC) (n = 30). Datasets of all 8 test groups (N = 240) were analyzed using inspection software to determine the linear aberrations in the X-, Y-, Z-axes and angular deviations. Mann–Whitney U and two-sample Kolmogorov–Smirnov tests were used to detect differences for trueness and precision. Results PRI revealed higher trueness and precision in most of the measured parameters ($${\overrightarrow{V}}_{E}$$ V → E 120.95 to 175.01 μm, $$\overrightarrow{V}_{E}$$ V → E (x) − 58.50 to − 9.40 μm, $$\overrightarrow{V}_{E}$$ V → E (z) − 70.35 to 63.50 μm), while OMN showed higher trueness for $$\overrightarrow{V}_{E}$$ V → E (y) regardless of model situation (− 104.90 to 34.55 μm). Model D revealed the highest trueness and precision in most of the measured parameters regardless of IOS ($$\overrightarrow{V}_{E}$$ V → E 120.95 to 195.74 μm, $$\overrightarrow{V}_{E}$$ V → E (x) − 9.40 to 66.75 μm,$$\overrightarrow{V}_{E}$$ V → E (y) − 14.55 to 51.50 μm, $$\overrightarrow{V}_{E}$$ V → E (z) 63.50 to 120.75 μm). Conclusions PRI demonstrated higher accuracy in the X- and Z-axes, while OMN depicted higher trueness in the Y-axis. For PRI, Model A revealed the highest distortion, while for OMN, Model B produced the largest aberrations in most parameters. Clinical relevance Current results suggest that both investigated IOS are sufficiently accurate for the manufacturing of tooth-borne restorations and orthodontic appliances. However, both hardware specifications of IOS and the presence of edentulous gaps in the dental model have an influence on the accuracy of the virtual model dataset.

Myofunctional parameters in patients using full removable dentures with progenic and prognathic ratio of the anterior segments of the edentulous jaws

The aim study was to construct artificial dentitions based on the method of mathematical modeling with the progenic and prognatic ratios of toothless frontal segments and to analyze the functional activity of the masticatory muscles in patients using dentures made in this way, compared with standard prosthetic structures. To compare and interpret the data obtained, electromyographic studies were performed in the control group (16 people), whose teeth were made using the traditional method, and the main group (22 people), whose artificial teeth were formed according to individual mathematical calculations, taking into account the size of the sagittal gap of the frontal segments of the progenic and prognatic ratio of toothless jaws. Statistical processing of the results of the electro-myographic study was carried out using the Statistica application software package. The digital data were processed by the method of variational statistics using the Student's t-test. The analysis of the obtained data showed the advantages of using individual mathematical calculations when solving the issue of tactics for constructing dentitions in the frontal segment of toothless jaws, taking into account the degree of the sagittal gap in the progenic and prognatic correlation of the jaws and their possible combinations.

Variants of the design of the dentition of the anterior segments with a progenic and prognathic ratio of edentulous jaws

Objective: To improve the prosthetic and aesthetic treatment of patients with complete absence of teeth, taking into account the development of an algorithm for determining the size of the sagittal gap of the frontal segments against the background of a progenic or prognathic ratio of the jaws and their combinations. Methods: A method of mathematical modeling based on digital data of the distance between the tops of the alveolar ridges of the frontal areas of the edentulous jaws has been developed using a designed measuring device. Results: The results of digital calculations based on the determination of the root-mean-square deviation of the interalveolar lines revealed a different amount of bends and configurations of the interalveolar gaps and median arches common to both parts of the frontal segments. Five main variants of the interalveolar fissure and 26 cases of symmetric or asymmetric arrangement of the tops of the alveolar ridges of the right and left sides were obtained. Accordingly, the divergence angles for each pair in the projection of the missing teeth had their own characteristics, which must be taken into account when deciding on the choice of tooth placement in each specific case. Conclusions: Based on the obtained digital interpolation ratios of the interalveolar lines and the angles of their inclination in relation to the midline, the anterior teeth are placed taking into account the level of the sagittal gap, the parameters of which have different levels of symmetry or asymmetry on the right and left sides.

Digital Denture Fabrication: A Technical Note

Fabricating a complete denture in a conventional manner may be complicated and difficult. The purpose of this article was to describe the benefits of a fully digital workflow and fabrication procedure of complete dentures based on digital impressions of edentulous jaws. The digital data for the workflow were acquired using an intraoral scanner and were then used to design the denture base and teeth. The resulting data were exported to a 3D printer or a milling machine for denture fabrication.

DIGITAL METHOD OF COMPARATIVE EVALUATION OF THE RIGIDITY BETWEEN THE CUSTOM MADE BY THE AUTHORS IMPLANT IMPRESSION TRAYS AND STOCK IMPLANT IMPRESSION TRAYS WITH REMOVABLE PARTS

Impression taking procedure from prosthetic area in case of constructing implant supported prostheses is one of the most important steps in the process of patient rehabilitation especially in producing long span structures. Quality of the impression could affect the precision and passive fit of the prosthesis to the implants therefore the overall quality of the work. Obtaining digital impressions of edentulous jaws with a different number of implants using intraoral devices is still an unresolved problem in full. The ergonomics of the process of obtaining an impression is not easy due to the need to place both scan abutments in the oral cavity and manipulate the working part of the intraoral scanner around them. The accuracy of digital impressions obtained from edentulous jaws for obtaining full-arch implant supported prostheses does not exceed that when obtaining a classic impression, and according to a number of researchers, it is even lower. The aim of this study was to construct implant impression convertible trays with increased to the optimum levels of rigidity, with simple disassemble process and having an easy access to the adapters, and also to digitally compare the rigidity of the author’s impression trays. The method of assessment was digital technology of analysing structural resistance and inherent stresses and deformations using SolidWorks software. We performed analysis of the resistance of the structure to external loads. We have developed and created the customised copyrighted versions of the upper and lower impression trays made of rigid titanium alloy by 3D printing using DMLM technology on a Concept Laser device made of titanium Ti6-Al4-V. Modeling was carried out in the Mimics Medical 21 program (Materialize, Germany) along the contours on the data of cone-beam computed tomography. Performed digital tests reveal the underlying advantages of the designed by authors impression trays.

Trueness and precision of digital implant impressions by intraoral scanners: a literature review

Background With the development of intraoral scanners, their trueness and precision have been evaluated in various studies. Through these studies, the amount of accuracy that can be expected from intraoral scanners has gradually been disclosed, at the same time, it was difficult to integrate the results of individual studies due to differences in evaluation methods between studies. The purpose of this article was to review the currently available evidence, summarise what is currently known about IOS, analyse the evaluation methods of each study, and list points to note when interpreting the results. Main text Most of the studies were conducted in vitro. The accuracy is evaluated in situations such as single missing teeth, partially edentulous ridges with multiple missing teeth, and fully edentulous jaws. To evaluate the accuracy, direct measurement of distance or angle by coordinate measuring machines and calculation of surface deviation by superimposing surface data were predominantly performed. The influence of parameters such as the number of implants, distance between implants, angle between implants, and experience of the operator was evaluated. Many studies have shown that trueness tends to decrease as the distance between the implants and the scan range increases. It was agreed that the implant angle did not affect either trueness or precision. Regarding other factors, the results varied among studies. Therefore, the effects of these parameters are not clear. Conclusions Heterogeneity in the research methodology was prevalent among the studies considered in this review. Therefore, we cannot make a decisive statement regarding the trueness and precision of digital implant impressions by IOSs. So far, the comparison of the numerical values of error between studies has yet to elucidate any clear answers, despite small methodological differences.

The use of laser welding in the immediate rehabilitation for dental patients with edentulou jaws

Necessary to take into account the effect of occlusal and non-axial loading in orthopedic treatment and rehabilitation of patients with edentulous jaws with implant-supported structures. Immediate stabilization, which achieved by intraoral welding, increases the posebility of success of implant osseointegration, and using immediate loading even in cases of bone atrophy for allows implants to be stabilized. The presented review of scientific literature on the use of laser welding in dentistry, the features of the application and the practical feasibility of immediate loading when splinting implants using intraoral welding. Many authors have investigated the use and effect of the parameters of a pulsed solid-state Nd:YAG laser for Ti and dental alloys. Scientists have proven the safety and effectiveness of using a dental Nd:YAG laser for welding metals directly in the oral cavity. The main risk for immediate loading implants is bone overload in the implants area during the first postoperative weeks, which can lead to their disintegration. Splinting prevent micro-displacement, distributes forces across multiple implants and shows highly effective immediate loading protocols. The expediency of immediate loading and the use of implant splinting with the intraoral welding prevents possible implant tilt and overload. The problem of using the method of immediate loading of implants with intraoral welding in dental orthopedic treatment has not been finally solved, and the well-known developments of the authors require further research and improvement.