Accuracy of implant height and width measurement with triaxial rotation method based on cone-beam CT.

Objective: To investigate the accuracy of implant height and width measurement in the mandibular and maxillary first molar region based on cone-beam CT (CBCT) data, and to establish an accurate method for bone measurement in the implant region. Materials and methods: CBCT images of 122 patients with implant in mandibular or maxillary first molar region were retrospectively collected. Two methods were used to measure sagittal height (SH), coronal height (CH), sagittal width (SW), and coronal width (CW) of implants. Method 1 (general method): the images were analyzed using the built-in software NNT 9.0 software. SHl, CHl, SWl, and CWl were measured on the reconstructed sagittal and coronal based on the radiologist's own experience. Method 2 (triaxial rotation method): the raw data were demonstrated in Expert mode of NNT 9.0 software, in which the coronal axis and sagittal axis were rotated paralleling to the long axis of the implant for reconstruction, and then SH2, CH2, SW2, and CW2 were measured on the reconstructed sagittal and coronal images. The results of two methods were compared with the actual implant size (H0, W0). Paired T-test was performed for statistical analysis. Dahlberg formula was used to check the measurement error. Results: For method 1, there was no significant differences between SHl and H0 (P > 0.05), but significant differences between CHl and H0, SWl and W0, and CWl and W0 (P < 0.05). For method 2, there were no significant differences between all measurements and actual size (P > 0.05). The random error range measured using Dahlberg formula was 0.157-1.171 mm for general method and 0.017-0.05 mm for triaxial rotation method. Conclusion: The triaxial rotation method is accurate for implant height and width measurements on CBCT images and could be used in pre-operatively bone height and width measurement of potential implant sites.

Clinical, radiographic features and prognosis of cemental tear: A retrospective study of 63 teeth.

Cemental tears are often misdiagnosed due to their scarcity. In this study, we reported the second largest cohort of cemental tears thus far. By reviewing the radiographic data and medical records of 63 cemental tear teeth, we found that periapical periodontitis was the most frequent diagnosis, followed by cracked tooth/root fracture and periodontitis. Most of the cemental tear teeth that did not have root canal treatment had vital pulp. The apical third of the root was the most prominent site of cemental tears. Cemental tears occurred more frequently in the palatal root of the maxillary molars and in the mesial root of the two-root mandibular molars. Uncontrollable bone loss and tooth mobility were the two main reasons for the extraction of teeth with cemental tears. We suggest that cemental tears should be included in the differential diagnosis of periapical periodontitis, cracked tooth, vertical root fracture and periodontitis, especially for teeth with periapical radiolucency and vital pulp. We believe our study could provide more insights into cemental tears, which will aid clinicians in the early diagnosis and proper treatment of cemental tears.