A Comparative Study of the Fitness and Trueness of a Three-Unit Fixed Dental Prosthesis Fabricated Using Two Digital Workflows

Comparing the accuracy of distinct scanning systems and their impact on marginal/internal adaptation of tooth-supported indirect restorations. A scoping review

OBJECTIVE

To summarize the existing scientific evidence on the effect of distinct intraoral (IOS) and extraoral (EOS) scanners in terms of their accuracy for image acquisition and the marginal/internal adaptation of indirect restorations.

METHODS

The protocol of this scoping review is available online (https://osf.io/cwua7/). A structured search, with no date restriction, was performed in LILACS, MEDLINE via Pubmed, EMBASE, Web of Science, and Scopus, for articles written in English. The inclusion criteria were studies that considered at least two scanners, regardless of method (intra or extraoral), for the production of tooth-supported restorations. Two independent and blinded researchers screened the studies, collected and analyzed the data descriptively.

RESULTS

103 studies were included (55 on marginal/internal adaptation, 33 on accuracy, 5 on both outcomes, and 10 reviews). Most of them, shown clinically acceptable adaptation (<120 μm). Factors commonly related to the performance of scanners are: use of anti-reflection powders, method of image acquisition, and restoration/tooth characteristics. The need of anti-reflection powders was controversial. Different scanning principles seems to result on similar performance; IOS that combine them could be promising. The most explored systems were Omnicam - IOS, and inEos X5 - EOS, which showed similar performance on marginal/internal adaptation. Scarce studies explored the performance of EOS systems, especially in terms of accuracy. Different restoration designs as single-unit seemed not to modify the performance of scanners. Limited information is available regarding the planned cement space, restorative material and design (multi-unit restorations), as also techniques to measure adaptation.

CONCLUSIONS

Digital scanners are valid approaches to obtain accurate impressions resulting in clinically acceptable restorations. Systems that uses combined principles of image acquisition seems promising for optimal performance. Based on high discrepancy, the quality of evaluated evidence is low, and well-designed studies are still encouraged, especially considering validated IOS/EOS as a control comparison condition.

Comparison of fit and trueness of zirconia crowns fabricated by different combinations of open CAD-CAM systems

PURPOSE

This study aims to clinically compare the fitness and trueness of zirconia crowns fabricated by different combinations of open CAD-CAM systems.

MATERIALS AND METHODS

Total of 40 patients were enrolled in this study, and 9 different zirconia crowns were prepared per patient. Each crown was made through the cross-application of 3 different design software (EZIS VR, 3Shape Dental System, Exocad) with 3 different processing devices (Aegis HM, Trione Z, Motion 2). The marginal gap, absolute marginal discrepancy, internal gap(axial, line angle, occlusal) by a silicone replica technique were measured to compare the fit of the crown. The scanned inner and outer surfaces of the crowns were compared to CAD data using 3D metrology software to evaluate trueness.

RESULTS

There were significant differences in the marginal gap, absolute marginal discrepancy, axial and line angle internal gap among the groups (P < .05) in the comparison of fit. There was no statistically significant difference among the groups in terms of occlusal internal gap. The trueness ranged from 36.19 to 43.78 µm but there was no statistically significant difference within the groups (P > .05).

CONCLUSION

All 9 groups showed clinically acceptable level of marginal gaps ranging from 74.26 to 112.20 µm in terms of fit comparison. In the comparison of trueness, no significant difference within each group was spotted. Within the limitation of this study, open CAD-CAM systems used in this study can be assembled properly to fabricate zirconia crown.

Digital Evaluation of Trueness and Fitting Accuracy of Co-Cr Crown Copings Fabricated by Different Manufacturing Technologies

INTRODUCTION

The dentistry industry has seen a number of exciting new advancements in recent years, many of which have been made possible by the introduction of automated technologies such as computer-aided design and computer-aided manufacturing (CAD/CAM). Despite the fact that these new approaches simplify the fabrication process in favor of decreased material consumption and improved time efficiency, it is possible that they may have an effect on the prosthesis's fitness, which in turn may affect how long they will last.

PURPOSE

The purpose of this in vitro study was to evaluate the trueness and fitness of cobalt-chromium (Co-Cr) crown copings fabricated by selective laser melting (SLM), milling, and conventional casting methods.

MATERIALS AND METHODS

A zirconium die was fabricated and scanned with a laboratory scanner to manufacture the Co-Cr metal copings for three groups (n = 12). In group A, the copings were fabricated by a 3D printing technique called SLM; in group B, the copings were fabricated by the milling technique; and in group C, the copings were fabricated by the conventional lost-wax method. After fabrication, the trueness and the internal fitness of the copings were evaluated using a metrology software program (Geomagic Control X, 3D Systems Inc., Rock Hill, SC). The one-way ANOVA and Tukey's honestly significant difference test were used to statistically analyze the data.

RESULTS

The highest root mean square (RMS) value of trueness was for CAD/CAM milling, and the highest mean of horizontal gaps was for the casted (lost-wax technique) group. There were highly significant differences in the mean RMS value of trueness and the mean horizontal gaps between the three groups.

CONCLUSION

The fabrication method of Co-Cr crown copings has an effect on the trueness and fitness of the copings.

Three-Dimensional Modeling and 3D Printing of Biocompatible Orthodontic Power-Arm Design with Clinical Application

Three-dimensional (3D) printing with biocompatible resins offers new competition to its opposition—subtractive manufacturing, which currently dominates in dentistry. Removing dental material layer-by-layer with lathes, mills or grinders faces its limits when it comes to the fabrication of detailed complex structures. The aim of this original research was to design, materialize and clinically evaluate a functional and resilient shape of the orthodontic power-arm by means of biocompatible 3D printing. To improve power-arm resiliency, we have employed finite element modelling and analyzed stress distribution to improve the original design of the power-arm. After 3D printing, we have also evaluated both designs clinically. This multidisciplinary approach is described in this paper as a feasible workflow that might inspire application other individualized biomechanical appliances in orthodontics. The design is a biocompatible power-arm, a miniature device bonded to a tooth surface, translating significant bio-mechanical force vectors to move a tooth in the bone. Its design must be also resilient and fully individualized to patient oral anatomy. Clinical evaluation of the debonding rate in 50 randomized clinical applications for each power-arm-variant showed significantly less debonding incidents in the improved power-arm design (two failures = 4%) than in the original variant (nine failures = 18%).

3D Guided Dental Implant Placement: Impact on Surgical Accuracy and Collateral Damage to the Inferior Alveolar Nerve

An increase in the number of implants placed has led to a corresponding increase in the number of complications reported. The complications can vary from restorative complications due to poor placement to damage to collateral structures such as nerves and adjacent teeth. A large majority of these complications can be avoided if the implant has been placed accurately in the optimal position. Therefore, the aim of this in vitro pilot study was to investigate the effect of freehand (FH) and fully guided (FG) surgery on the accuracy of implants placed in close proximity to vital structures such as the inferior alveolar nerve (IAN). Cone-beam computed tomography (CBCT) and intraoral scans of six patients who have had previous dental implants in the posterior mandible were used in this study. The ideal implant position was planned. FG surgical guides were manufactured for each case. In this study, the three-dimensional 3D printed resin models of each of the cases were produced and the implants placed using FG and FH methods on the respective models. The outcome variables of the study, angular deviations were calculated and the distance to the IAN was measured. The mean deviations for the planned position observed were 1.10 mm coronally, 1.88 mm apically with up to 6.3 degrees’ angular deviation for FH surgery. For FG surgical technique the mean deviation was found to be at 0.35 mm coronally, 0.43 mm apically with 0.78 degrees angularly respectively. The maximum deviation from the planned position for the apex of the implant to the IAN was 2.55 mm using FH and 0.63 mm FG. This bench study, within its limitations, demonstrated surgically acceptable accuracy for both FH and FG techniques that would allow safe placement of implants to vital structures such as the IAN when a safety zone of 3 mm is allowed. Nevertheless, a better margin of error was observed for FG surgery with respect to the angular deviation and controlling the distance of the implant to the IAN using R2 Gate^® system.

Comparison of Intaglio Surface Trueness of Interim Dental Crowns Fabricated with SLA 3D Printing, DLP 3D Printing, and Milling Technologies

This study aimed to evaluate the intaglio surface trueness of interim dental crowns fabricated with three 3-dimensional (3D) printing and milling technologies. Dental crown was designated and assigned as a computer-aided design (CAD) reference model (CRM). Interim dental crowns were fabricated based on CRM using two types of 3D printer technologies (stereolithography apparatus and digital light processing) and one type of milling machine (n = 15 per technology). The fabricated interim dental crowns were obtained via 3D modeling of the intaglio surface using a laboratory scanner and designated as CAD test models (CTMs). The alignment and 3D comparison of CRM and CTM were performed based on the intaglio surface using a 3D inspection software program (Geomagic Control X). Statistical analysis was validated using one-way analysis of variance and Tukey HSD test (α = 0.05). There were significant differences in intaglio surface trueness between the three different fabrication technologies, and high trueness values were observed in the milling group (p < 0.05). In the milling group, there was a significant difference in trueness according to the location of the intaglio surface (p < 0.001). In the manufacturing process of interim dental crowns, 3D printing technologies showed superior and uniform manufacturing accuracy than milling technology.

A Comparative Study of the Accuracy of Dental CAD Programs in Designing a Fixed Partial Denture

PURPOSE

Error testing at each stage of prosthetic manufacturing remains relatively underdeveloped for computer-aided design/computer-aided manufacturing methods, and no experimental studies have validated the computer-aided design programs. This study aimed to test the accuracy and trueness of the computer-aided design of a three-unit fixed prosthesis.

MATERIALS AND METHODS

Three computer-aided design programs (Exocad, Dental System™, and inLab 16) were tested on the designs of a three-unit fixed partial denture, and a three-dimensional analysis program was used to calculate the internal clearance error for the computer-aided design prostheses. The Kruskal-Wallis and Dunn's post hoc tests were used to reveal significant differences in trueness between the three computer-aided design programs (α < 0.05).

RESULTS

Dental System™ showed the lowest mean error values for #24 and #26 at the mesial margin (both 0 µm), mesial wall (0.10, 0.12 µm, respectively), occlusal surface (-0.05, 0.10 µm), distal wall (0.23, -0.02 µm), and distal margin (both 0 µm). In sum, except for the mesial margin and distal margin site of tooth #26, the mean error value of Dental System™ was statistically the lowest, followed by those of Exocad and inLab 16 (p < 0.003).

CONCLUSIONS

The accuracy of computer-aided design differed according to the type of computer-aided design program. Dental System™ achieved the best trueness at the margins, axial walls, and occlusal surface, followed by Exocad and inLab 16.

Marginal and Internal Fit of Ceramic Restorations Fabricated Using Digital Scanning and Conventional Impressions: A Clinical Study

This clinical study was designed with the aim of fabricating four ceramic crowns using the conventional method and digital methods with three different intraoral scanners and evaluate the marginal and internal fit as well as clinician satisfaction. We enrolled 20 subjects who required ceramic crowns in the upper or lower molar or the premolar. Impressions were obtained using digital scans, with conventional impressions (polyvinyl siloxane and desktop scanner) and three different intraoral scanners (EZIS PO, i500, and CS3600). Four lithium disilicate glass-ceramic crowns were fabricated for each patient. In the oral cavity, the proximal and occlusal adjustments were performed, and the marginal fit and internal fit were evaluated using the silicone replica technique. The clinician satisfaction score of the four crowns was evaluated as per the evaluations of the proximal and occlusal contacts made during the adjustment process and the marginal and internal fit. For statistical analysis, the differences among the groups were analyzed with one-way analysis of variance and Tukey HSD test as a post-test; Pearson correlation analysis was used for analyzing the correlations (α = 0.05). There was a significant difference in the marginal and internal fit of the ceramic crowns fabricated using three intraoral scanner types and one desktop scanner type (p < 0.001); there was a significant difference in the clinician satisfaction scores (p = 0.04). The clinician satisfaction score and marginal fit were significantly correlated (absolute marginal discrepancy and marginal gap) (p < 0.05). An impression technique should be considered for fabricating a ceramic crown with excellent goodness-of-fit. Further, higher clinician satisfaction could be obtained by reproducing the excellent goodness-of-fit using the intraoral scanning method as compared to the conventional method.

Clinical evaluation of the fit of lithium disilicate crowns fabricated with three different CAD-CAM systems

STATEMENT OF PROBLEM

The fit and performance of prostheses fabricated using various computer-aided design and computer-aided manufacturing (CAD-CAM) systems have been evaluated. However, most studies were conducted in vitro, and relatively few have addressed gingival parameters and prosthesis fit under clinical conditions.

PURPOSE

This clinical study aimed to compare the fit of lithium disilicate crowns produced using 3 CAD-CAM systems and evaluate clinical results up to 6 months after delivery.

MATERIAL AND METHODS

Forty participants requiring a single crown were recruited. Three monolithic lithium disilicate crowns were fabricated per participant by using 3 different CAD-CAM systems (intraoral scanners, CAD software, and milling machines): CEREC group (CEREC Bluecam, CEREC AC, CEREC MC); EZIS group (EZIS PO, EZIS VR, EZIS HM); and TRIOS group (TRIOS 3, EXO-CAD, ARUM-4X). The fit of the prostheses was assessed via a silicone replica technique, and the most acceptable crown was delivered; 12 were selected from the CEREC group, 16 from the EZIS group, and 12 from the TRIOS group. Follow-up clinical examinations were performed at 1, 3, and 6 months after delivery. The Kruskal-Wallis test with the post hoc Mann-Whitney U test was conducted to analyze significant differences in crown fit and periodontal conditions among the groups (α=.05).

RESULTS

The marginal gap of the CEREC group was significantly higher than that of the EZIS group, and the occlusal gap of the EZIS group was significantly lower than those of the CEREC and TRIOS groups (P<.05). Probing depth, bleeding index, and plaque index showed no intergroup differences at 6 months (P>.05).

CONCLUSIONS

The lithium disilicate crowns of all groups showed clinically acceptable fit. No significant differences were found among the groups in terms of periodontal conditions after 6 months.

Clinical Study of the Influence of Ambient Light Scanning Conditions on the Accuracy (Trueness and Precision) of an Intraoral Scanner

PURPOSE

To quantify the impact of ambient lighting conditions on the accuracy (trueness and precision) of an intraoral scanner (IOS) when maxillary complete-arch and maxillary right quadrant digital scans were performed in a patient.

MATERIAL AND METHODS

One complete dentate patient was selected. A complete maxillary arch vinyl polysiloxane impression was obtained and poured using Type IV dental stone. The working cast was digitized using a laboratory scanner (E4 Dental Scanner; 3Shape) and the reference standard tessellation language (STL file) was obtained. Two groups were created based on the extension of the maxillary digital scans performed namely complete-arch (CA group) and right quadrant (RQ) groups. The CA and RQ digital scans of the patient were performed using an IOS (TRIOS 3; 3Shape) with 4 lighting conditions chair light (CL), 10 000 lux, room light (RL), 1003 lux, natural light (NL), 500 lux, and no light (ZL), 0 lux. Ten digital scans per group at each ambient light settings (CL, RL, NL, and ZL) were consecutively obtained (n = 10). The STL_R file was used to analyze the discrepancy between the digitized working cast and digital scans using MeshLab software. Kruskal-Wallis, one-way ANOVA, and pair-wise comparison were used to analyze the data.

RESULTS

Significant difference in the trueness and precision values were found across different lighting conditions where RL condition obtained the lowest absolute error compared with the other lighting conditions tested followed by CL, NL, and ZL. On the CA group, RL condition also obtained the best accuracy values, CL and NL conditions performed closely and under ZL condition the mean error presented the highest values. On the RQ group, CL condition presented the lowest absolute error when compared with the other lighting conditions evaluated. A pair-wise multicomparison showed no significant difference between NL and ZL conditions. In all groups, the standard deviation was higher than the mean errors from the control mesh, indicating that the relative precision was low.

CONCLUSIONS

Light conditions significantly influenced on the scanning accuracy of the IOS evaluated. RL condition obtained the lowest absolute error value of the digital scans performed. The extension of the digital scan was a scanning accuracy influencing factor. The higher the extension of the digital scan performed, the lower the accuracy values obtained. Furthermore, ambient light scanning conditions influenced differently depending on the extension of the digital scans made.

Accuracy of Five Intraoral Scanners and Two Laboratory Scanners for a Complete Arch: A Comparative In Vitro Study

This study aims to evaluate the accuracy of five different intraoral scanners and two different laboratory scanners for a complete arch. A computer-aided design (CAD) reference model (CRM) was obtained using industrial scanners. A CAD test model (CTM) was obtained using five types of intraoral scanners (CS3500, CS3600, Trios2, Trios3, and i500) and two types of laboratory scanners (3shape E1 and DOF) (N = 20). In addition, the CRM and CTM were superimposed using a 3D inspection software (Geomagic control X; 3D Systems) and 3D analysis was performed. In the 3D analysis, the accuracy was measured by the type of tooth, the anterior and posterior region, and the overall region. As for the statistical analysis of the accuracy, the differences were confirmed using the Kruskal–Wallis H test (α = 0.05). Also, the differences between the groups were analyzed by post-hoc tests including Mann–Whitney U-test and Bonferroni correction method (α = 0.0017). There was a significant difference in the scanning accuracy of the complete arch according to the type of scanner (P < 0.001). The i500 Group showed the lowest accuracy (143 ± 69.6 µm), while the 3Shape E1 Group was the most accurate (14.3 ± 0.3 µm). Also, the accuracy was lower in the posterior region than in the anterior region in all types of scanners (P < 0.001). Scanning accuracy of the complete arch differed depending on the type of scanner. While three types of intraoral scanners (CS3500, CS3600, Trios3) can be recommended for scanning of a complete arch, the two remaining types of intraoral scanners (Trios2 and i500) cannot be recommended.