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

Does the available interocclusal space influence the accuracy of the maxillomandibular relationship captured with an intraoral scanner?

STATEMENT OF PROBLEM

The accuracy of a maxillomandibular relationship acquired by intraoral scanners (IOSs) has been previously analyzed; however, the impact of the interocclusal space on the accuracy of the maxillomandibular relationship remains unknown.

PURPOSE

The purpose of this in vitro investigation was to evaluate the influence of the interocclusal space (0, 1, 2, 3, or 4 degrees of incisal opening in the articulator) on the accuracy of the maxillomandibular relationship captured with an IOS.

MATERIAL AND METHODS

Markers were attached to the first molars and canines of maxillary and mandibular diagnostic casts, which were mounted on a semi-adjustable articulator, and digital scans were acquired (TRIOS 4). Both digital scans were duplicated 100 times and distributed into 5 groups depending on the incisal pin opening in the articulator (n=20): 0 (Group 0), 1 (Group 1), 2 (Group 2), 3 (Group 3), and 4 degrees (Group 4). In Group 0 (control), the casts were maintained in maximum intercuspation (MIP) with the incisal pin of the articulator set at 0 degrees. Then, a bilateral virtual occlusal record was acquired and automatically processed by using the IOS software program. A laboratory scanner (Medit T500) was used to digitize the mounted casts. The same procedures were completed in Groups 1, 2, 3, and 4 but with the incisal pin set at 1, 2, 3, and 4 degrees respectively. The interlandmark distances were used to calculate the discrepancies between the control and groups tested. One-way analysis of variance (ANOVA) and pairwise comparison Tukey HSD tests were used to inspect the data (α=.05).

RESULTS

The interocclusal space available when capturing the occlusal records affected the trueness of the maxillomandibular virtual relationship measured (P<.001). Group 0 (135 μm) obtained the highest distortion, while Group 3 (73 μm) and Group 4 (71 μm) showed the lowest distortion. Additionally, the interocclusal space available (P<.001) impacted the precision of the maxillomandibular virtual relationship measured. Group 0 (111 μm) obtained the highest distortion, while Group 4 (precision mean value of 59 μm) had the lowest distortion among the groups tested.

CONCLUSIONS

The interocclusal space available when acquiring virtual bilateral occlusal records using the IOS tested impacted the accuracy of the maxillomandibular relationship. The smallest available interocclusal space tested (maximum intercuspation) showed the worst trueness and precision mean values, while the group with the largest interocclusal space available had the highest trueness and precision mean values among the groups studied.

Impact of different CAD software programs on marginal and internal fit of provisional crowns: An in vitro study

Statement of the problem

Different CAD software programs used for designing crowns show variations in marginal and internal fit. Marginal and internal discrepancies may cause poorly fitting crowns.

Purpose

The aim of this study was to compare the marginal and internal fit of single crown temporary restorations designed using three different CAD software programs.

Materials and methods

Dentbird, Exocad and Inlab 20 were used to design temporary single crowns using the same cement gap. Three experimental groups (n = 10/group) were formed based on the CAD software used. Geomagic Control X three-dimensional analysis software was used to compare the marginal and internal fit among the groups. Measurements were obtained at nine different thickness points. IBM SPSS Statistics, version 22 was used for all statistical analyses.

Results

Among the CAD software programs tested, Dentbird produced the best internal fit on the buccal surface and the best marginal fit on both buccal and mesial surfaces. Exocad achieved the best values on the distal surface for both internal and marginal fit, while Inlab showed the best values on the mesial surface for internal fit and on the palatal surface for marginal fit.

Conclusions

The Dentbird CAD software program provided the most accurate fit values that closely matched the design. The marginal and internal fit oftemporary crowns may vary depending on the CAD software used.

Evaluation of the virtual cement gap parameter of different CAD software programs in designing a single crown restoration: An in vitro study

STATEMENT OF PROBLEM

The accuracy of different virtual cement gap parameters in designing a single crown in a computer-aided design (CAD) software program is still unclear.

PURPOSE

The purpose of this in vitro study was to evaluate and compare the virtual cement gap settings of 3 different CAD software programs used to design a single crown restoration.

MATERIAL AND METHODS

Three different CAD software programs (exocad, Dental System, and B4D) were evaluated for designing single crowns with similar virtual cement gap settings. Three experimental groups were created based on the CAD software program used (n=10). Three-dimensional analysis software program was used to assess the virtual cement gap in the CAD restoration. The Shapiro-Wilk test of normality was used. Comparisons were carried out by using 1-way ANOVA and the Scheffé post hoc test (α=.05).

RESULTS

The Dental System software program had the lowest statistical mean error values at both tooth margin (4.6 μm) and axial wall (1.5 μm), followed by B4D then exocad. At the occlusal surface, the lowest statistical mean error value of 5 μm was achieved by the Dental System followed by exocad then B4D.

CONCLUSIONS

Accuracy of the virtual cement gap parameter in single crown design varies based on the CAD software used. The highest accuracy was attained by the Dental System software program at all tooth surfaces, followed by B4D at the tooth margin and axial wall and by exocad at the occlusal surface.

Evaluation of the marginal and internal fit of CAD/CAM crowns designed using three different dental CAD programs: a 3-dimensional digital analysis study

OBJECTIVES

The purpose of this in vitro study was to assess and compare the marginal and internal fit of machine-milled crowns designed using three different CAD software programs.

MATERIALS AND METHODS

Digital impressions of the master zirconia casts containing the prepared molar were obtained using an intraoral scanner. The obtained standard tessellation language (STL) files were imported into three CAD software programs (Multi-CAD, Blue-Sky CAD, and InLab), and crown designs were generated. Crown design digital STL files were used to mill crowns with a five-axis dental milling machine. The internal and marginal fits of the fabricated crowns over the master-prepared tooth were assessed using the triple-scan protocol and digital analysis techniques. The 3D marginal and internal fit values of the fabricated crowns from the designs generated by the three CAD programs were evaluated and statistically compared using one-way analysis of variance (ANOVA) and post hoc Tukey's tests (α = 0.05).

RESULTS

There were no significant differences in the internal fit of the crowns designed by the three CAD programs (p > 0.05). However, there were significant differences in the mean marginal fit (p = 0.009) of the crowns. The marginal fit values for the InLab-designed crowns were significantly better than those for Multi-CAD (p = 0.03) and Blue-Sky CAD (p = 0.012) groups.

CONCLUSIONS

All three CAD programs can design clinically acceptable crowns in terms of internal and marginal fit. InLab crowns outperformed the Multi-CAD and Blue-Sky CAD programs in terms of marginal fit.

CLINICAL RELEVANCE

It is critical to test the ability of newly released CAD programs to design acceptable virtual crowns that can be transformed into actual crowns with optimal marginal and internal fit to existing clinical tooth preparations/conditions to ensure the high technical quality and long-term success of fabricated crowns.