Influence of operator experience, scanner type, and scan size on 3D scans.

STATEMENT OF PROBLEM: Intraoral scanners (IOSs) have some inherent distortions caused by optical and/or software imperfections. However, how other factors such as operator experience, scan time, scanner type, and scan size influence scan accuracy is not clear. PURPOSE: The purpose of this in vitro study was to evaluate the trueness and precision of scans performed by 3 professionals with different levels of experience by using 2 IOSs. MATERIAL AND METHODS: Three operators with low, medium, and high levels of experience scanned a master model 10 times by using 2 IOSs (CEREC Omnicam; Dentsply Sirona and TRIOS 3; 3Shape), resulting in 10 standard tessellation language files for each group (N=60). Each standard tessellation language file was divided into 2 areas (prepared teeth and complete arch). Precision was evaluated by comparing the 10 scans from each examiner for each system. Trueness was evaluated by comparing each scan file with a reference scan obtained from a laboratory scanner (D2000; 3Shape). A 3D analysis software program (Geomagic Control; 3D Systems) was used to perform all the comparisons and superimpositions. The 3-way ANOVA test followed by the Tukey HSD test were used to assess precision and trueness. The 2-way ANOVA followed by the Tukey HSD test was used to assess scan time. The Pearson correlation test was performed between scan time and trueness for both scanners. An additional correlation was performed between scan time and number of images, as well as between number of images and trueness for the TRIOS 3. RESULTS: Statistically significant influences of operator (P<.001), scanner (P<.001), scan size (P<.001), operator and scan size (P<.001), and scanner and scan size (P<.001) were observed. The TRIOS 3 group reported higher precision than the CEREC Omnicam group for complete-arch scans (P<.001), although no difference was observed for scans of the prepared tooth. Medium- (P=.002) and low-experience operators (P<.001) reported lower precision for complete-arch scans performed with CEREC Omnicam when compared with TRIOS 3. The low-experience operator reported significantly worse results for complete-arch scans in comparison with the medium- (P=.008 and P<.001) and high-experience operators (P<.001 and P=.001), by using TRIOS 3 and CEREC Omnicam, respectively. Medium- and high-experience operators reported similar results among themselves. The CEREC Omnicam scanner reported lower trueness for complete-arch scans when compared with the prepared tooth (P<.001); for TRIOS 3, a difference was only observed for the low-experience operator when compared with the high-experience operator (P<.001). The CEREC Omnicam reported lower trueness than the TRIOS 3, except for the medium-experience operator with the prepared tooth scan. Comparing the trueness between operators and considering the same scanner and scan size, all groups were similar. The low-experience operator had a longer scanning time than the medium- and high-experience operators. For TRIOS 3, the low-experience operator obtained the highest number of images during each scan. CONCLUSIONS: The accuracy of intraoral scans was influenced by operator experience, type of IOSs, and scan size. More experienced operators and smaller scan sizes made for more accurate scans. In addition, more experienced operators made faster scans, and the TRIOS 3 was more accurate than the CEREC Omnicam for complete-arch scans.

Use of a surgical template for minimally invasive second-stage surgery: A dental technique.

The introduction of new techniques and new technology has been directly related to successful outcomes in implant dentistry. Merging information from high-quality cone beam computed tomography images and detailed prosthetically driven digital planning translates into computer-guided surgery. A surgical template is a guide used to assist in the proper surgical placement and angulation of dental implants. However, a surgical guide not only facilitates implant placement but can also be used for other purposes, including diagnosis, treatment planning, and even second-stage surgery. In situations where multiple implants have been placed through computer-guided implant surgery, the preexisting surgical template can be used to perform the second-stage surgery with a flapless approach if the patient's soft tissue condition permits.

The Association Between Buccal Mucosa Thickness and Periimplant Bone Loss and Attachment Loss: A Cross-Sectional Study.

PURPOSE: The aim of this study was to assess if there is an association between buccal mucosa thickness and periimplant attachment loss after 1 year of function. MATERIALS AND METHODS: A total of 28 patients (14 periimplantitis implants and 14 healthy implants) were included. The buccal mucosal thickness was assessed using K-files at 3 mm apical to the soft tissue margin of the implant. Probing depth, recession (REC), clinical attachment level (CAL), bleeding on probing, and radiographic bone loss on mesial and distal sites of the implant were recorded. RESULTS: The data showed that there was a statistically significant difference in midfacial REC between thin and thick buccal mucosa groups. However, the CAL was not statistically significant different between both groups. In addition, there was no statistically significant difference in mesial and distal bone loss between implants with thin and thick mucosa. CONCLUSION: When the midfacial soft tissue thickness was thin, the midfacial REC was greater and the CAL also tended to be higher. There was no association between buccal mucosa thickness and periimplant bone loss on mesial and distal sites of the implant after 1 year of function.

Marginal and internal adaptation of milled cobalt-chromium copings.

STATEMENT OF PROBLEM: The application of computer-aided design and computer-aided manufacturing (CAD/CAM) systems to produce complete coverage restorations with different materials continues to increase. To date, insufficient information is available regarding the adaptation of recently introduced milled cobalt-chromium (Co-Cr) copings for metal ceramic restorations. PURPOSE: The purpose of this in vitro study was to evaluate the marginal and internal fit of milled Co-Cr copings produced by CAD/CAM with 2 different marginal preparation designs. MATERIAL AND METHODS: Four master dies were developed from 2 ivorine central incisors and 2 ivorine maxillary molars, 1 of each prepared with a 0.8-mm chamfer and a 1.2-mm rounded shoulder. These 4 groups of teeth were replicated with polyvinyl siloxane and used as templates to fabricate epoxy dies (n=10) for each of the 4 groups; a total of 40 epoxy resin dies. Cobalt-chromium copings of standard thickness (0.4 mm) were fabricated for each die with CAD/CAM technology. Next, the working dies were scanned with a 5-axis laser scanner to produce a 3-dimensional model. A thin layer of low-viscosity polyvinyl siloxane material was placed inside each coping and seated on the die until the material set. Copings were removed from the dies, leaving the polyvinyl siloxane intact, and these silicone-coated dies were scanned. The software superimposed the 2 scans, and the marginal openings and internal fit were measured at multiple locations. The marginal opening was determined at 4 locations: mid-buccal (mB), mid-lingual (mL), mid-mesial (mM), and mid-distal (mD), and the mean of these 4 measurement locations was referred to as the group variable "edge." The internal occlusal adaptation was measured at the midpoint from buccal to lingual and mesial to distal locations and referred to as mid-occlusal (mO). Means and standard deviations for edge (marginal adaptation) and mO were calculated for each of the 4 groups. A 2-sample t test was performed to detect differences among groups. A regression analysis was done to evaluate the interaction between the variables mO and edge (α=.05). RESULTS: Significantly smaller mean marginal openings (P=.017) were observed overall for the chamfer marginal design (anterior chamfer: 61 ±41 µm; posterior chamfer: 52 ±27 µm) compared with the shoulder design (anterior shoulder 103 ±49 µm, posterior shoulder 113 ±110 µm). The anterior chamfer had a statistically significant (P=.055) smaller mean marginal opening (61 ±41 µm) than the anterior shoulder (103 ±49 µm). No statistically significant differences (P=.119) were found between the posterior chamfer and posterior shoulder. The internal adaptation at the mO location was not significantly different among all 4 groups (P>.05). However, a regression analysis demonstrated a strong correlation (R=.842; P<.001) between the occlusal seat (mO) and marginal opening, with the smaller mean marginal opening of the chamfer design coinciding with the smaller occlusal seat values (61µm; mO: 182 µm) anterior chamfer; (52 µm; mO: 172 µm) posterior chamfer versus (103 µm; mO: 235 µm) anterior shoulder; (113 µm; mO: 242 µm) posterior shoulder. CONCLUSIONS: The milled Co-Cr copings produced with a CAD/CAM system in this study demonstrated clinically acceptable marginal fit in the range of 52 to 113 µm before ceramic application.

Fabrication of a cast-based implant surgical guide using guide sleeves.

A unique method for fabricating cast-based surgical guides is presented. A proposed position and mesiodistal angulation of the implant are verified with periapical radiography and registered with a commercially available guide sleeve. The sleeve is attached to a surgical guide made of light-polymerized acrylic resin. The surgical guide can be used in a broad range of situations and allows for accurate implant placement in a prosthetically driven position with surgical access and visibility, simplicity, and cost efficiency.