Evaluating the accuracy of CAD/CAM optimized stones compared to conventional type IV stones.

This study compared the accuracy (trueness and precision) of stone models fabricated using two brands of CAD/CAM optimized stones Cerec Stone (BC) and Elite Master (EM), and a conventional type IV stone Elite Rock Fast (ERF). 30 conventional Type IV and scannable stone complete-arch models were scanned with a blue LED extraoral scanner, and root mean square values were obtained. 6 abutments were used in complete-arch models. The digital models were compared with the master model to evaluate their trueness using model superimposition with Geomagic software. Precision was determined for each case by superimposing combinations of the 10 datasets in each group. The point cloud density of each model was calculated with MeshLab software. Kruskal-Wallis and Mann-Whitney non-parametric tests were used for the statistical analysis. The trueness of the stone models was 96 µm for the BC, 88.2 µm for the EM, and 87.6 µm for the ERF. There were no significant differences between the tested dental stones (p = .768). However, the EM models (35.6 µm) were more precise than the BC (46.9 µm) and ERF (56.4 µm) models (p = .001, p < .001). EM models also showed the highest point cloud density. There were significant differences in point cloud density (p = .003). The EM models showed significant differences in precision but no significant differences in terms of trueness. Although EM was more precise and had the highest point cloud density, all models were within the clinically acceptable limit.

Detecting the presence of taurodont teeth on panoramic radiographs using a deep learning-based convolutional neural network algorithm.

OBJECTIVES: Artificial intelligence (AI) techniques like convolutional neural network (CNN) are a promising breakthrough that can help clinicians analyze medical imaging, diagnose taurodontism, and make therapeutic decisions. The purpose of the study is to develop and evaluate the function of CNN-based AI model to diagnose teeth with taurodontism in panoramic radiography. METHODS: 434 anonymized, mixed-sized panoramic radiography images over the age of 13 years were used to develop automatic taurodont tooth segmentation models using a Pytorch implemented U-Net model. Datasets were split into train, validation, and test groups of both normal and masked images. The data augmentation method was applied to images of trainings and validation groups with vertical flip images, horizontal flip images, and both flip images. The Confusion Matrix was used to determine the model performance. RESULTS: Among the 43 test group images with 126 labels, there were 109 true positives, 29 false positives, and 17 false negatives. The sensitivity, precision, and F1-score values of taurodont tooth segmentation were 0.8650, 0.7898, and 0.8257, respectively. CONCLUSIONS: CNN's ability to identify taurodontism produced almost identical results to the labeled training data, and the CNN system achieved close to the expert level results in its ability to detect the taurodontism of teeth.

Effect of repeated millings on the surface integrity of diamond burs and roughness of different CAD/CAM materials.

OBJECTIVES: This study evaluated the surface integrity of two types of diamond burs and their effect on the roughness of different CAD/CAM materials. MATERIALS AND METHODS: CAD/CAM materials, Vita Mark II (VM), IPS e.max CAD (EM), Celtra Duo (CD), G-Ceram (GC), and Lava Ultimate (LU) blocks were milled with CEREC MCXL. Five pairs of pointed cylinder burs (CB) and step burs (SB) were used repeatedly. The wear rate of burs was analyzed before and after milling with a scanning electron microscope (SEM) and weighing the burs. The milling time of the blocks at different milling stages was recorded from 2 (M2) to 8 times (M8) of use. The surface roughness (Ra) of blocks was measured with a profilometer. Data from the differences in surface roughness were analyzed using univariate analyses of variance and Kruskal-Wallis tests (alpha = 0.05). RESULTS: For M2, the highest roughness (2.12 ± 0.1 µm) was observed with the VM block. EM blocks presented the highest roughness values (1.82 ± 0.3 µm, 1.85 ± 0.1 µm, and 1.86 ± 0.04 µm) at M4, M6, and M8, respectively. While the highest Ra values were observed for VM (2.12 to 1.43 µm), LU provided the lowest mean Ra (1.62 to 1.33 µm) among the tested materials. After the repeated use of burs up to 8 times, the surface roughness of all the tested materials decreased. Milling of LU resulted in chip deposits on the CB surface in SEM images. The duration of cutting was higher for CD and EM materials than those of other materials, but the milling duration for VM, GC, and LU blocks was similar. SB burs exhibited more wear than CB after repeated milling. CONCLUSIONS: A repeated number of millings more than 4 times decreased the surface integrity of the milling burs, increased the surface roughness of CAD/CAM blocks except for LU, and increased the milling duration. Increased material hardness was more detrimental on bur surface integrity. CLINICAL RELEVANCE: During milling CAD/CAM blocks, clinicians should note that the surface integrity of milling burs decreases after 4 times of use as a function of material hardness where step burs wear quicker than pointed cylinder burs.

In vitro accuracies of 3D printed models manufactured by two different printing technologies.

PURPOSE: This study aims to compare the accuracies of full-arch models printed by two different 3D printing technologies. MATERIALS AND METHODS: A mandibular horseshoe-shaped master model was designed with RapidForm XOR2 software The master model was printed 10 times with 3D printers using direct light processing (DLP) and PolyJet technology (n=20). The printed models were then scanned with an industrial scanner and saved in STL file. All digital models superimposed with the master model STL file and comparison of the trueness was performed using Geomagic Control 3D analysis software. The precision was calculated by superimposing combinations of the 10 data sets in each group. RESULTS: The trueness of printed models was 46 µm for the DLP printer and 51 µm for PolyJet printer; however, this difference was not statistically significant (p=0.155). The precision of printed models was 43 µm for the DLP printer and 54 µm for PolyJet printer. DLP printed models were more precise than the PolyJet printed models (p<0.001). CONCLUSION: The 3D printing technologies showed significant differences in the trueness of full-arch measurements. Although DLP printed models had better trueness than PolyJet printed models, all of the 3D printed models were clinically acceptable and might be used for the production of fixed restorations.

Accuracy evaluation of complete-arch models manufactured by three different 3D printing technologies: a three-dimensional analysis.

Purpose This study aimed to evaluate the trueness and precision of complete-arch models printed with three-dimensional printers via three different printing technologies.Methods An arch-shaped master model was designed using software (RapidForm XOR2, 3D Systems Inc., USA), and the digital master model was printed 10 times with three-dimensional printers using stereolithography (SLA), direct light processing (DLP), and Polyjet technology (n = 30). The printed models were then scanned with an industrial scanner to create the respective digital models. All digital models were compared with the master model, and an evaluation of the trueness was performed by model superimposition with Geomagic Control software (3D Systems, Rock Hill, SC, USA). Precision was determined for each case by superimposing some combination of the 10 datasets in each group.Results The trueness of the printed models was 46.2 µm for the DLP printer, 51.6 µm for the SLA printer, and 58.6 µm for the Polyjet printer. The DLP models were significantly better than the Polyjet models (p = .005). However, the Polyjet models (30.4 µm) were more precise than the SLA (37.6 µm) and DLP (43.6 µm) models (p < .001, p = .016). Furthermore, the SLA (11.8 µm) was the most accurate printer in the Z-direction (p = .016, p = .002).Conclusions The 3D printing technologies showed significant differences in the precision and trueness of complete-arch measurements. Although DLP was more accurate other tested 3D printers, the accuracy of all 3D printed models was within clinical tolerance, and they were clinically acceptable and could be used for the production of fixed restorations.

Effect of Denture Cleansing Solutions on the Retention of Locator Attachments Over Time.

PURPOSE: To evaluate and compare the alterations in retention of three Locator attachments after immersion in various denture cleansers at defined time intervals. MATERIALS AND METHODS: Two implants were embedded in an acrylic block. Pink, blue, and clear Locator attachments (n = 10 for each subgroup) were immersed into three different cleansing solutions (Corega, Protefix and NaOCl) and tap water (control) at different time intervals that simulate 1 (T1 ), 6 (T2 ), and 12 (T3 ) months of clinical use. Universal testing machine set at a crosshead speed of 50 mm/min was used for pull-out tests. After the immersion procedure, the peak force to dislodgement was recorded to demonstrate the changes in retention of Locator attachments. Data were analyzed using repeated-measures ANOVA followed by Tukey's Honestly Significant Difference (HSD) tests (α = .05). RESULTS: All denture cleansing solutions affected the retentive values of all Locator attachments at defined time intervals (F = 4.299, p = 0.001). NaOCl affected all groups significantly after 12-month immersion time (p = 0.001). The least retention loss at all subgroups was observed in Corega for clear Locator attachments (106.17 ± 5.21 N). The difference in retention values for pink attachments were not statistically significant for tap water, Protefix and Corega immersion at all time intervals (p > 0.05). Following NaOCl (blue; 33.31 ± 4.72 N, clear; 52.3 ± 8.5 N), tap water decreased the retention value of blue (41.14 ± 3.93 N) and clear (76.72 ± 8.42 N) Locator attachments at T3 . Corega caused the least retention loss to clear attachments at T1 (106.17 ± 3.55 N). CONCLUSION: The retention of Locator attachments decreases over time after exposure to various denture cleansing solutions. As NaOCl significantly decreased the retentive values of all attachments, patients must be informed about that disadvantage. Also, tap water remarkably decreased retentive ability of all attachments. Periodic addition of an effervescent tablet into tap water may be recommended to patients that wear implant retained overdentures with Locator attachments.

A comparative study of root canal shaping using protaper universal and protaper next rotary files in preclinical dental education.

BACKGROUND: Dentistry has undergone an evolution in endodontics practice caused by the advancement of rotary techniques for root canal preparation and their subsequent incorporation into the teaching of dentistry undergraduates. This research aimed to evaluate the shaping ability of third-year dental students as their first experience in rotary instrumentation using ProTaper Universal (PTU) and ProTaper Next (PTN) (Dentsply Maillefer) rotary instruments in simulated curved canals. METHODS: Forty students instrumented 200 simulated canals with a 40° curvature in resin blocks according to the manufacturer's instructions with PTU and 39 students and 195 canals with PTN files. The canals were prepared at a speed of 300 rpm using a 16:1 reduction hand-piece powered by an electric motor (Xsmart; Dentsply Maillefer). The final apical preparation was set to F2 for the PTU and X2 for the PTN group. The change in canal curvature was evaluated based on Schneider technique using the AutoCAD 2007 software on post-digital photographs. The incidence of instrument fracture and deformation, the incidence of ledge, the change in working length (WL), and the working time were noted. The data were analyzed with Student's t-test and Chi-Square test at a significance level of 0.05 using SPSS. RESULTS: PTN maintained the original canal curvature better, resulting in fewer fractures and ledges, and shaped the canals faster than the PTU (P < 0.05). The mean curves of the resin canals after the instrumentation for the PTU and PTN groups were 24.03° ± 3.14° and 25.64° ± 2.72°, respectively. Thirty-three (17.4%) PTU and 18 (9.3%) PTN files fractured (p < 0.05). Nine (4.5%) PTU and 2 (2.6%) PTN deformed (p > 0.05). The change in WL after instrumentation was 0.97 mm ± 0.95 mm in PTU and 0.96 mm ± 0.80 mm in PTN (p < 0.05). The mean times were 627 s ± 18 s for PTU and 379 s ± 18 s for PTN (p < 0.000). DISCUSSION: PTN can be recommended in severely curved root canals in terms of maintenance of the original canal curvature, superior instrument fracture and fewer ledges. Even if training before preparation provides an acceptable level of canal shaping for preclinical students, the use of NiTi rotary instruments should be included in the undergraduate dental curriculum, contributing to an increase in the quality of root canal shaping and, consequently, to an improvement of the clinical experience of students.

Evaluation of the trueness and precision of eight extraoral laboratory scanners with a complete-arch model: a three-dimensional analysis.

PURPOSE: The purpose of this study was to evaluate the trueness and precision of eight different extraoral laboratory scanners using three-dimensional (3D) analysis method. METHOD: An arch-shaped master model was designed with a computer software (Rapidform XOR2) and manufactured with a 3D printer (Projet 3510 MP). Then the master model was digitized with an industrial 3D scanner (ATOS Core 200). With each scanner master model was scanned ten times and stereolithography (.stl) data were imported into 3D analysis software (Geomagic Control). Accuracy was determined with evaluating trueness and precision. RESULTS: Trueness of the scanners were 27.5 µm for 7 series; 30.9 µm for D640; 26.8 µm for D710; 33.3 µm for Activity 102; 32.4 µm for Tizian Smart-Scan; 21.6 µm for NeWay; 26.1 µm for inEOS X5 and 17,47 µm for D2000. 28.2 µm for laser; 32.9 µm for white light and 21.7 µm for blue light scanners. Significant differences were found between scanners (p < .001), (p < .001). Precision of the scanners were 30.1 µm for 7 series; 31.7 µm for D640; 26.3 µm for D710; 22.7 µm for Activity 102; 25.1 µm for Tizian Smart-Scan; 15.7 µm for NeWay; 26.1 µm for inEOS X5; 16.6 µm for D2000. 29.2 µm for laser; 24.4 µm for white light and 19.2 µm for blue light scanners. Significant differences were found between scanners (p < .001), (p = .027). CONCLUSIONS: The systems that had the best combination of trueness and precision for complete-arch scanning were D2000 and NeWay. Scanners using blue-light showed more accurate results than the white-light and laser scanners.

What is the changing frequency of diamond burs?

PURPOSE: The purpose of this study was to determine the changing frequency of a diamond bur after multiple usages on 3 different surfaces. MATERIALS AND METHODS: Human premolar teeth (N = 26), disc shaped direct metal laser sintered CoCr (N = 3) and zirconia specimens (N = 3) were used in this study. Groups named basically as Group T for teeth, Group M for CoCr, and Group Z for zirconia. Round tapered black-band diamond bur was used. The specimens were randomly divided into three groups and placed with a special assembly onto the surveyor. 1, 5, and 10 preparation protocols were performed to the first, second, and third sub-groups, respectively. The subgroups were named according to preparation numbers (1, 5, 10). The mentioned bur of each group was then used at another horizontal preparation on a new tooth sample. The same procedure was used for CoCr and zirconia disc specimens. All of the bur surfaces were evaluated using roughness analysis. Then, horizontal tooth preparation surfaces were examined under both stereomicroscope and SEM. The depth maps of tooth surfaces were also obtained from digital stereomicroscopic images. The results were statistically analyzed using One-Way ANOVA, and the Tukey HSD post-hoc tests (α=.05). RESULTS: All of the groups were significantly different from the control group (P<.001). There was no significant difference between groups Z5 and Z10 (P=.928). Significant differences were found among groups T5, M5, and Z5 (P<.001). CONCLUSION: Diamond burs wear after multiple use and they should be changed after 5 teeth preparations at most. A diamond bur should not be used for teeth preparation after try-in procedures of metal or zirconia substructures.

Effect of dental technician disparities on the 3-dimensional accuracy of definitive casts.

STATEMENT OF PROBLEM: Studies that evaluated the effect of dental technician disparities on the accuracy of presectioned and postsectioned definitive casts are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the accuracy of presectioned and postsectioned definitive casts fabricated by different dental technicians by using a 3-dimensional computer-aided measurement method. MATERIAL AND METHODS: An arch-shaped metal master model consisting of 5 abutments resembling prepared mandibular incisors, canines, and first molars and with a 6-degree total angle of convergence was designed and fabricated by computer-aided design and computer-aided manufacturing (CAD-CAM) technology. Complete arch impressions were made (N=110) from the master model, using polyvinyl siloxane (PVS) and delivered to 11 dental technicians. Each technician fabricated 10 definitive casts with dental stone, and the obtained casts were numbered. All casts were sectioned, and removable dies were obtained. The master model and the presectioned and postsectioned definitive casts were digitized with an extraoral scanner, and the virtual master model and virtual presectioned and postsectioned definitive casts were obtained. All definitive casts were compared with the master model by using computer-aided measurements, and the 3-dimensional accuracy of the definitive casts was determined with best fit alignment and represented in color-coded maps. Differences were analyzed using univariate analyses of variance, and the Tukey honest significant differences post hoc tests were used for multiple comparisons (α=.05). RESULTS: The accuracy of presectioned and postsectioned definitive casts was significantly affected by dental technician disparities (P<.001). The largest dimensional changes were detected in the anterior abutments of both of the definitive casts. The changes mostly occurred in the mesiodistal dimension (P<.001). CONCLUSIONS: Within the limitations of this in vitro study, the accuracy of presectioned and postsectioned definitive casts is susceptible to dental technician differences.

Can Impression Procedures Affect Certain Vital Functions of Edentulous Patients? A Clinical Study.

PURPOSE: The most suitable treatment conditions and timing for medically unstable patients with severe systemic diseases about to undergo invasive dental treatment are well documented in the literature; however, no medical guides or recommendations identify these conditions for noninvasive dental treatments in such patients. The aim of this clinical study was to determine the effect of impression procedures on arterial oxygen saturation (AOS) and pulse rates (PRs) of edentulous subjects. MATERIALS AND METHODS: A total of 28 Caucasian edentulous participants (15 females, 13 males) were included in the study. Pulse oximetry recordings (150 seconds) were performed for each participant at three stages; recording at rest (CON), during mandibular impressions (MANIs), and maxillary impressions (MAXIs). The mean values of PR, AOS, and event scores (ESs) indicating desaturation were obtained from the records. The comparisons of mean PR and AOS values were performed with the Bonferroni-corrected Wilcoxon-signed ranks test. The ESs were analyzed with the McNemar Test. RESULTS: The mean AOS values of MANI and MAXI did not display significant changes when compared with CON; however, the ESs obtained in both MANI and MAXI were significantly higher than those of CON (p = 0.008, p = 0.004). In addition, mean PR values obtained in MAXI were significantly higher than CON (p = 0.009). CONCLUSIONS: According to the results of this clinical study, the impression procedures may affect the PR values and lead to desaturation events in edentulous patients; however, further studies evaluating blood gas levels, which indicate precise AOS values, are necessary to support the results of this study.

Evaluation of Low-Level Laser Therapy in TMD Patients.

Light amplification by stimulated emission of radiation (laser) is one of the most recent treatment modalities in dentistry. Low-level laser therapy (LLLT) is suggested to have biostimulating and analgesic effects through direct irradiation without causing thermal response. There are few studies that have investigated the efficacy of laser therapy in temporomandibular disorders (TMD), especially in reduced mouth opening. The case report here evaluates performance of LLLT with a diode laser for temporomandibular clicking and postoperative findings were evaluated in two cases of TMD patients. First patient had a history of limited mouth opening and pain in temporomandibular joint (TMJ) region since nine months. Second patient's main complaint was his restricted mouth opening, which was progressed in one year. LLLT was performed with a 685 nm red probed diode laser that has an energy density of 6.2 J/cm(2), three times a week for one month, and application time was 30 seconds (685 nm, 25 mW, 30 s, 0.02 Hz, and 6.2 J/cm(2)) (BTL-2000, Portative Laser Therapy Device). The treatment protocol was decided according to the literature. One year later patients were evaluated and there were no changes. This application suggested that LLLT is an appropriate treatment for TMD related pain and limited mouth opening and should be considered as an alternative to other methods.