PurposeThis study aimed to determine the most reliable scanning strategy and scanner type, using a new protocol for assessing the accuracy (trueness and precision) of intraoral scan data.Materials and MethodsFive different maxillary and mandibular typodont pairs (n = 10) and 2 intraoral scanners were used for the study. A reference scan for each arch was obtained with an industrial scanner. Scanning strategies were classified into 2 continuous methods—continuous scan in horizontal direction (CH group) and continuous scan with vertical rotation in anterior region (CV group)—and 1 segmental method (S group). In the CH group, the scanner head was maintained mostly in a horizontal position. In the CV group, the scanners were rotated 180° around the anterior tooth region to allow smooth scanning through the area. The intraoral scan data were individually superimposed over their corresponding reference scan data. Raw data of the distances between paired surface points were extracted from the superimposed pairs of datasets, with (original distance values) or without consideration (absolute distance values) of the value signs. Trueness values were calculated using absolute distance values, while precision values were obtained from original distance values. Data were analyzed with a 2‐way repeated‐measures analysis of variance using α = 0.05 as the level of significance.ResultsThe CV group produced significantly inferior outcomes compared to the CH and S groups in terms of trueness (p < 0.001, F = 24.67), whereas no significant differences were observed among the 3 scanning strategies with respect to precision (p = 0.451, F = 0.83). Scanner type did not produce significant differences in terms of either trueness (p = 0.058, F = 4.72) or precision (p = 0.742, F = 0.12).ConclusionsThe segmental approach for scanning the region of interest first and continuous scanning with the scanner head held mostly in a horizontal position are both acceptable as full‐arch scanning strategies. However, vertical rotation of intraoral scanners should be minimized.

Purpose To evaluate the accuracy of three digitization methods for the maxillary dental arch. Materials and Methods A maxillary typodont with various tooth preparation designs was used as the reference model. The scanned data were classified into direct scanning (DS), cast scanning (CS), and impression scanning (IS) groups according to the techniques applied for digitization (n = 10/group). An intraoral scanner was used for the DS group. Impressions obtained with polyether impression material were scanned with a tabletop scanner for the IS group. For the CS group, the definitive casts fabricated from the obtained impressions were scanned with the same tabletop scanner. The accuracy (trueness and precision) of the produced virtual dental casts was evaluated with specialized software. The full‐arch and individual abutment deviations were measured with regard to root mean square error (RMSE) values. Data were analyzed with statistical software with an α0.33em=0.33em0.05. Results The RMSE values for both trueness and precision were lowest in the IS group, followed by the CS and DS groups, with statistically significant differences among the groups (p < 0.05). The trueness of individual abutments was significantly higher in the IS group than in the DS group. In addition, the trueness of individual abutments was affected by the location of the abutments in the DS group, whereas it did not differ between individual abutments in the CS and IS groups. Conclusions These findings suggest that the IS method is an accurate digitization technique for the creation of a virtual dental cast.

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Background This study aimed to investigate the effects of ultraviolet (UV) photofunctionalization on the stability of implants during the early phase in the posterior region of the maxilla. The study was a randomized double-blinded clinical trial. Half of the participants received conventional commercial implants while the other half received UV-irradiated implants. The surgical sites were classified into three bone quality groups (II, III, IV) based on the grayscale value measured on cone-beam computed tomography. The values obtained from resonance frequency analysis were recorded immediately after implant placement and at 4 weeks and at 4 months postoperatively. The marginal bone level of the implants was evaluated using periapical radiographs at 4 weeks, 4 months, and 1 year postoperatively. Results Fifty-seven implants placed in 34 participants were analyzed in this study. In group III, significant differences were observed in terms of the differences of resonance frequency analysis values at 4 weeks (p = 0.004) and 4 months (p = 0.017) postoperatively. In group II, the UV-treated group showed significantly lesser bone loss at 4 weeks post-operatively (p = 0.037). Conclusions Within the limitation of the present study, we concluded that UV surface treatment on implants may increase the initial stability in the region of the maxilla with poor bone quality.

The present study aims to compare the accuracy of metal sleeve-free 3D-printed computer-assisted implant surgical guides (MSF group) (n = 10) with metal sleeve-incorporated 3D-printed computer-assisted implant surgical guides (MSI group) (n = 10). Implants of diameter 4.0 mm and 5.0 mm were placed in the left second premolars and bilateral first molars, respectively, using a fully guided system. Closed-form sleeves were used in teeth on the left and open-form sleeves on the right. The weight differences of the surgical guides before and after implant placement, and angular deviations before and after implant placement were measured. Weight differences were compared with Student’s t-tests and angular deviations with Mann–Whitney tests. Cross-sectional views of the insert parts were observed with a scanning electron microscope. Preoperative and postoperative weight differences between the two groups were not statistically significant (p = 0.821). In terms of angular deviations, those along the mesiodistal direction for the left second premolars were significantly lower in the MSF group (p = 0.006). However, those along the mesiodistal direction for the bilateral molars and those along the buccolingual direction for all teeth were not significantly different (p > 0.05). 3D-printed implant surgical guides without metal sleeve inserts enable accurate implant placement without exhausting the guide holes, rendering them feasible for fully guided implant placement.

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