ABSTRACT
Objective: To evaluate the effect of adding a geometric feature on the accuracy of digital impressions obtained by intraoral scanners for implant restoration of edentulous jaw quantitatively. Methods: A dentiform model of the maxilla of completely edentulous arch with 6 implant analogs+scan bodies (No. 1-6) was selected as the reference model. Without geometric feature, the dentiform model was scanned by dental model scanner and repeated for 5 times as true value group. Before and after adding the geometric feature, the same operator used intraoral scanner A (Trios 3) and B (Aoralscan 2) to scan the dentiform model with the same scanning path. Each type of intraoral scanner scanned 10 times and ".stl " datas were obtained. The results were imported into reverse engineering software (Geomagic Studio 2015). The linear distances of center point of upper plane between sacn body 1 to 6 was calculated, denoted as D12, D13, D14, D15 and D16. Trueness was the absolute value subtracted from the measured value of the intraoral scanner groups and true value; precision was the absolute value of pairwise subtraction of the measured values in the intraoral scanner groups.The smaller the value, the better the accuracy or precision.With or without the feature, all scan data were statistically analyzed, and the effect of adding geometric feature on the trueness and precision of the two intraoral scanners were evaluated. Results: As for intraoral scanner A, with the feature in place, significant differences were found in D14, D15, D16 for tureness(t=2.66, 2.75, 2.95, P<0.05); the trueness for D16 decreased from (101.9±47.1) μm to (49.6±30.3) μm. On the other hand, with features on the edentulous area, the precision was significantly increased in D15 and D16 (U=378.00, 672.00, P<0.05); the precision for D15 decreased from 40.8 (45.1) μm to 13.1 (17.0) μm. As for intraoral scanner B, the trueness of D12, D13 and D14 after adding geometric features was significantly better than before (t=3.02, 2.66, U=22.00, P<0.05). With feature on the edentulous area, the trueness for D13 decreased from (116.6±41.2) μm to (70.8±35.5) μm. There was no statistical significance in the trueness of D15 and D16 with or without geometric feature (P>0.05), however, the precision of D15 and D16 after adding geometric feature was significantly better than before (U=702.00, 489.00,P<0.05). The precision of D16 decreased from 112.5 (124.7) μm to 35.9 (85.8) μm. Conclusions: The use of geometric feature in edentulous space improves the trueness and precision of the different principle intraoral scanners tested.
Subject(s)
Computer-Aided Design , Dental Implants , Dental Impression Technique , Imaging, Three-Dimensional , Models, DentalABSTRACT
OBJECTIVE@#To distinguish the endoscopic and clinical features of ampullary polyps, to investigate the endoscopic cancer risk factors of ampullary polyps based on the compared differences of benign lesions and adenocarcinoma, and to assess the accuracy of forceps biopsy.@*METHODS@#Authors retrospectively analyzed the data extracted from patients treated with endoscopic papillectomy (EP) from January 2009 to May 2019 in the Department of Gastroenterology, Peking University Third Hospital. Endoscopic pictures and pathology reports were reevaluated and analyzed. Differences between benign and cancer groups were conducted.@*RESULTS@#In the study, 42 cases were involved, 35 to 83 years old, containing 83.3% older than 50 years old patients. The histological types were as follows, 2 for inflammatory polyps (4.8%), 1 for neuroendocrine tumor (2.4%), 1 for hyperplastic polyp (2.4%), 5 for grade Ⅰ adenoma (11.9%), 10 for grade Ⅱ adenoma (23.8%), 4 for grade Ⅲ adenoma (9.5%) and 19 for adenocarcinoma (45.2%), and 90.5% were adenoma or adenocarcinoma. The average age of benign group (inflammatory polyps and adenomas) was (56.7±9.2), which was significantly younger than that of adenocarcinoma group [(66.0±9.8), P=0.004]. Tumor diameter in adenocarcinoma group[(2.3±0.8) cm] was significantly larger than that in benign group[(1.6±0.6) cm, P=0.002]. Benign lesions only showed Yamada type Ⅰ(57.1%)and type Ⅱ(42.9%). The percentage of Yamada type Ⅰ (36.8%)and type Ⅱ(31.6%) in adenocarcinoma group was lower than that in benign group. Moreover, Yamada type Ⅲ (31.5%) was only found in the adenocarcinoma group. Significant differences were observed between the two groups in Yamada types (P=0.046). Most of the benign lesions had clear boundary(18/21, 85.7%). The percentage of clear boundary in adenocarcinoma group (2/19, 10.5%) was significantly lower than that in the benign group (P < 0.001). No significant differences were investigated in color (P=0.353) and surface (P=0.324) between benign and adenocarcinoma lesions. Pooling age, lesion diameter, Yamada type and clear boundary into Logistic regression analysis, only age (OR=1.186, 95%CI 1.025-1.373, P=0.022) and clear boundary (OR=66.218, 95%CI 3.421-1 281.840, P=0.006) were the independent cancer risk factors. Only 2 (10.5%) in the 19 cancer patients had positive biopsy results before EP. As compared with post-EP, 55.3% (21/38) biopsies were under-estimated, including 17 (17/19, 89.5%) adenocarcinomas and 4 (4/10, 40%) grade Ⅱ adenomas.@*CONCLUSION@#adenoma and adenocarcinoma were the major histological type of ampullary po-lyps. Age and unclear boundary were the independent risk factors of ampullary adenocarcinoma. Forceps biopsy was not enough for ampullary polyp differentiation.