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.

Implant Angulation Effect on the Fracture Resistance of Monolithic Zirconia Custom Abutments: An In Vitro Study.

PURPOSE: To investigate the fracture resistance and performance of zirconia when employed for the fabrication of implant abutments with different angulations, simulating anterior maxillary oral rehabilitation. MATERIALS AND METHODS: Forty-five monolithic zirconia custom abutments of internal conical implant connection were CAD/CAM designed and fabricated. The specimens were divided into three groups (n = 15/group) according to implant-to-abutment angulation. The angulations used were; 0°, 15°, and 25°. The abutments were loaded until failure at 135° using the Universal Testing Machine (Instron, Canton, MA). Collected data were statistically analyzed using one-way ANOVA and post hoc Tukey test. RESULTS: Mean (±standard deviation) load at fracture of the zirconia abutments for the three groups were 962.37 ± 93.81 N (Gr15) > 718.25 ± 93.71 N (Gr25) > 534.05 ±133.77 N (Gr0). Statistically significant difference (p < 0.0001) was found between all groups; Gr0 vs. Gr15, Gr0 vs. Gr25, Gr15 vs. Gr25. CONCLUSIONS: Contrary to expectations, the non-angulated monolithic zirconia abutments presented the lowest fracture resistance values. Angulating the abutments 15 or 25 degrees, following the palatal resorption pattern of the premaxilla, significantly increased the in vitro fracture resistance.

A randomized controlled trial to compare aesthetic outcomes of immediately placed implants with and without immediate provisionalization.

INTRODUCTION: There are mixed results regarding the aesthetic advantage of immediate provisionalization of dental implants. Therefore, this study aimed to compare facial mucosal level of single immediately placed implants with and without immediate provisionalization. METHODS: Single implants were immediately placed to replace a hopeless maxillary anterior or premolar tooth in 40 subjects. Each implant was randomly assigned to receive a non-occluding temporary crown or a healing abutment after implant placement. At 4 months, these implants were permanently restored and followed up for 12 months. Clinical and radiographic parameters were measured and compared. RESULTS: The implant survival rate at 12 months in the test and control group was 90% and 100%, respectively. Mid-facial mucosal marginal level and papilla height changes were minimal within groups, and no significant differences were found between the two groups. The amount of marginal bone remodelling was modest, with no significant difference between the two groups. Radiographic bone changes were not statistically different between the groups, except for the vertical crestal bone resorption. CONCLUSION: Immediate implant placement with or without provisionalization can achieve stable vertical soft tissue level for 12 months as compared to pre-extraction level. However, immediate provisionalization was not able to improve the aesthetic outcome further.

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.

Prosthodontic treatment of a retrognathic edentulous maxilla demonstrating limited interarch distance: 3.5-year results with fixed and removable implant prostheses.

The prosthodontic treatment of patients with a retrognathic edentulous maxilla should consider the restoration of the lower facial profile and access for oral hygiene. This clinical report describes prosthodontic treatments of a patient with edentulism who presented with repeated fractures of the denture teeth of a maxillary implant-supported complete fixed dental prosthesis (ICFDP) and a mandibular implant-supported overdenture. Considerable plaque accumulation was noted on the ICFDP, which was replaced with an open palatal design implant-supported overdenture. However, the patient experienced difficulty managing the 2 removable prostheses. The patient's mandible was eventually restored with a milled titanium alloy framework ICFDP with metal occlusal surfaces. This combined approach of fixed and removable prostheses was stable at 3.5-year follow-up appointment, without compromising the patient's oral hygiene or comfort.

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.

Facial mucosal level of single immediately placed implants with either immediate provisionalization or delayed restoration: An intermediate-term study.

BACKGROUND: Immediately placed single implants with either immediate provisionalization (test) or delayed restoration (control) were followed for up to 1 year in our previous randomized clinical trial. Peri-implant tissues continue to remodel after implants are in function. Therefore, the primary aim of this study was to evaluate the facial mucosal level changes in the intermediate term between the two groups and to study potential factors influencing the mucosal level change. METHODS: Patients who had already completed the previous clinical trial by receiving a single immediately placed implant were re-invited to this study. The facial mucosal level as well as the other peri-implant hard and soft tissue dimensions and conditions were measured clinically, radiographically and with ultrasound. These data were compared between the test and control implants. The mucosal level change as the function of the final crown contour, measured as the abutment-crown angle (ACA), was estimated with a linear regression model. RESULTS: Twenty-eight patients (n of test/control = 16/12) with a mean 30-month follow-up were recruited. The mean mucosal level change was -0.38 mm (control) and 0.06 mm (test), without statistical difference between the two groups. The other clinical, radiographic, and ultrasound parameters were not statistically different. ACA was statistically significant associated with the recession (P = 0.02). The estimate effect was 0.25 mm per 10° increase (adjusted R2  = 0.18; 95% CI, 0.02 to 0.49 mm). After adjusting for vertical implant position, implant abutment angle and the group, the effect became borderline significant (P = 0.09). CONCLUSIONS: Peri-implant tissues, including the mucosal level change of immediately placed implants with either immediate provisionalization or delayed restoration remained stable and did not differ between the groups in the intermediate term. The final crown angle, influenced by implant position and abutment angle, might be associated with mucosal margin level change.