Effect of varying levels of expertise on the reliability and reproducibility of the digital waxing of single crowns: A preliminary in vitro study

Can deep learning-designed anterior tooth-borne crown fulfill morphologic, aesthetic, and functional criteria in clinical practice?

OBJECTIVES

This study aimed to compare the design outcomes of anterior crowns generated using deep learning (DL)-based software with those fabricated by a technician using conventional dental computer-assisted design (CAD) software without DL support, with a focus on the evaluation of crown morphology, function, and aesthetics.

METHODS

Twenty-five in vivo datasets comprising maxillary and mandibular arch scans of prepared maxillary central incisors were utilized to design anterior crowns by using three methods: 1) a DL-based method resulting in as-generated outcome (DB), 2) a DL-based method further optimized by a technician (DM), and 3) a conventional CAD-based method (NC, control). Evaluations were conducted for crown morphology (total discrepancy volume (TDV), root mean square (RMS), positive average (PA) and negative average (NA) deviations), functional aspects (incisal path: deviations, length, and mean inclination), and aesthetics (crown width, height, width-to-height ratio, angular radius of mesioincisal line angle, proximal contact length, and tooth axis angle).

RESULTS

Significant differences in TDV ratio were noted between the DB-NC (32.3 ±8.5%) and DM-NC (26.5 ±5.4%) pairs (P = 0.006). No significant differences were observed in TDV between the DB-NC (65.3 ±24.4 mm3) and DM-NC (54.3 ±21.0 mm3) pairs (P = 0.095). For the entire palatal surface, significant differences in RMS and PA values were observed between the DB-NC and DM-NC pairs (P < 0.037). Significant differences in RMS values for the incisal half (P = 0.021) and in PA values for the cervical half (P = 0.047) of the palatal surface were also noted between these pairs. Significant differences in the deviation of the incisal path were observed between the DB-NC (290.4 ±212.4 μm) and DM-NC (132.0 ±122.3 μm) pairs (P<0.001). However, no significant differences were found among the groups (DB, DM, and NC) in terms of the length and mean inclination of incisal paths or in aesthetic outcomes.

CONCLUSIONS

A DL-based method can result in promising outcomes with clinically acceptable morphology and aesthetics for anterior crowns. Minor deviations in incisal path of the crowns may lead to anterior guidance discrepancies, which can be corrected by the dental technician at the design stage.

CLINICAL SIGNIFICANCE

With the potential of DL-based design methods in dental applications, integrating AI technology into dental CAD workflow can enhance the clinical efficiency and consistency of anterior crown design, although human intervention may be required to refine functional aspect.

Use of scanning electron microscope to evaluate the marginal fit of protocol bars obtained through benchtop or intraoral digital scanners

Aim: To evaluate the marginal fit of protocol bars milled from digital models obtained by conventional molding followed by bench scanning or digital molding with an intraoral scanner. Methods: Four morse-cone implants and the mini-pillars were installed in a 3D printed mandible model (master model). Digital models of the master model were obtained by (n=10): (Group A - Conventional) conventional (analog) molding of the master model followed by bench scanning or (Group B - Digital) molding of the master model with an intraoral scanner. All-on-four protocol bars were designed and milled from the digital models for both groups and screwed into the master model. Scanning electron microscopy (SEM) images from the distal, central, and mesial regions of each implant were obtained and the implant-protocol bar marginal fit was measured in an image software (Image J). The mean misfit of each region was analyzed by two-factor ANOVA, Tukey test, and Student’s t-test (0,05 = 0.05). Results: The digital approach (B) showed higher misadaptation than the conventional approach (A, p < 0.05), regardless of the region evaluated. In group A, the central region showed higher maladjustment than the mesial region (p<0.05), however, there were no differences among regions of group B (p>0.05). Conclusion: The conventional method of acquiring digital models using the bench scanner produced bars for the All-On-Four protocol with better marginal fit than the digital models obtained with an intraoral scanner.

Factors Affecting Trueness of Intraoral Scans: An Update

Background: Intraoral scanning (IOS) technologies have been constantly developed and improved. This systematic review aimed at assessing studies in the recent literature describing factors that influence the trueness of intraoral scans. Methods: Comparative in vitro and in vivo (i.e., interventional and observational) studies that quantitatively assessed the trueness of intraoral scans and that identified factors significantly affecting IOS trueness values were considered eligible for inclusion. The PUBMED and EMBASE databases were searched for articles published in the last two years (from February 2020 to February 2022). Data assessment and extraction were performed according to the guidelines of the PRISMA statement. Results: The present search strategy yielded 13 publications. An initial screening of the publications was performed using abstracts and key words, and after application of exclusion criteria, a total of nine studies were finally identified as eligible to be discussed. Several factors significantly affecting IOS were identified. Conclusions: Studies using current IOS technologies revealed that the device, scanning distance, operator experience, rescanning and post-processing scans, conditions of the preparations and presence of adjacent teeth are factors significantly affecting IOS trueness.

Digital versus Conventional Workflow in Oral Rehabilitations: Current Status

In recent years, computer-aided design and computer-aided manufacturing (CAD-CAM) technology has developed along with its applications in dentistry, including several new techniques that are used in oral rehabilitation applications [...]