Effects of exposure length, cortical and trabecular bone contact areas on primary stability of infrazygomatic crest mini-screws at different insertion angles.

BACKGROUND: The infrazygomatic crest mini-screw has been widely used, but the biomechanical performance of mini-screws at different insertion angles is still uncertain. The aim of this study was to analyse the primary stability of infrazygomatic crest mini-screws at different angles and to explore the effects of the exposure length (EL), screw-cortical bone contact area (SCA), and screw-trabecular bone contact area (STA) on this primary stability. METHODS: Ninety synthetic bones were assigned to nine groups to insert mini-screws at the cross-combined angles in the occlusogingival and mesiodistal directions. SCA, STA, EL, and lateral pull-out strength (LPS) were measured, and their relationships were analysed. Twelve mini-screws were then inserted at the optimal and poor angulations into the maxillae from six fresh cadaver heads, and the same biomechanical metrics were measured for validation. RESULTS: In the synthetic-bone test, the LPS, SCA, STA, and EL had significant correlations with the angle in the occlusogingival direction (rLPS = 0.886, rSCA = -0.946, rSTA = 0.911, and rEL= -0.731; all P < 0.001). In the cadaver-validation test, significant differences were noted in the LPS (P = 0.011), SCA (P = 0.020), STA (P = 0.004), and EL (P = 0.001) between the poor and optimal angulations in the occlusogingival direction. The STA had positive correlations with LPS (rs = 0.245 [synthetic-bone test] and r = 0.720 [cadaver-validation test]; both P < 0.05). CONCLUSIONS: The primary stability of the infrazygomatic crest mini-screw was correlated with occlusogingival angulations. The STA significantly affected the primary stability of the infrazygomatic crest mini-screw, but the SCA and EL did not.

Development of a continuously perfused ex vivo kidney training model for laparoscopic partial nephrectomy: validity and efficiency.

BACKGROUND: Suture hemostasis is essential for laparoscopic partial nephrectomy (LPN). This study aimed to develop, validate, and test the efficacy of a continuously perfused training model (CPTM) in LPN with high-level simulated bleeding. MATERIALS AND METHODS: The CPTM was constructed using fresh porcine kidneys with renal arteries continuously perfused with red-dyed liquid gelatin. Twenty-nine participants with expert, intermediate, or novice laparoscopic experience levels were recruited. The expert and intermediate participants evaluated the CPTM, and the novice participants were randomly assigned to one of two groups to complete training on a CPTM or dry box training model (DBTM). Messick's framework criteria were utilized to assess the validity and training efficacy of the model. The data were analyzed using the Mann-Whitney U , Kruskal-Wallis, and Friedman tests. A value of P< 0.05 was considered statistically significant. RESULTS: Positive comments were provided by all experts and intermediates for the Content . The Relationships with other variables demonstrated significant differences among novices, intermediates, and experts in all metrics ( P< 0.05). The Consequences showed that the CPTM helped novices acquire LPN skills. The training efficacy was significantly better than that of the DBTM ( P< 0.05). There were no significant differences between the final performances of the novices and the initial performances of the experts ( P >0.05). Synthesizing all metrics, the LPN skills learned using CPTMs were significantly improved in the 12th round of training. CONCLUSION: The CPTM offered a high-level simulation of bleeding with realistic tissue texture for acquiring LPN skills. Training of no fewer than 12 rounds is recommended for a novice's LPN training on the CPTM.

Endoscopic submucosal dissection training: evaluation of an ex vivo training model with continuous perfusion (ETM-CP) for hands-on teaching and training in China.

BACKGROUND: The existing ex vivo models of endoscopic submucosal dissection (ESD) cannot simulate intraoperative hemorrhage well. We aimed to establish an ESD training method by applying an ex vivo training model with continuous perfusion (ETM-CP). METHODS: Four training sessions were conducted for 25 novices under the guidance of 2 experts. Eventually, 10 novices completed ESD operations on a total of 89 patients after the training. The resection effectiveness, resection speed, complication rate, and novice performance before and after the training were compared. The data regarding the effects of the training and the model were gathered through a questionnaire survey. RESULTS: In terms of the simulation effect of the model, ETM-CP was evaluated as similar to the live pig in all aspects (P > 0.05). The questionnaire analysis revealed that the ESD theoretical knowledge, skill operation, and self-confidence of novices were improved after the training (P < 0.05). The resection time per unit area had a correlation with the number of training periods (rs = - 0.232). For novice performance, the resection time per unit area was shortened (P < 0.05). There was no difference in patient performance between the novice group and the expert group after the training in terms of en bloc resection, R0 resection, complication rate, endoscopic resection bleeding (ERB) score, muscularis propria injury (MPI) score, and resection time per unit area (P > 0.05). CONCLUSION: The ETM-CP is effective for ESD training.

Bone depth and thickness of different infrazygomatic crest miniscrew insertion paths between the first and second maxillary molars for distal tooth movement: A 3-dimensional assessment.

INTRODUCTION: This research aimed to measure the bone depth and thickness of different insertion paths for safe placement of infrazygomatic crest miniscrews between the first (U6) and second maxillary molars (U7) by 3-dimensional (3D) reconstruction and to explore their clinical significance. METHODS: Cone-beam computed tomography data from 36 adult orthodontic patients were obtained to generate 3D models (n = 72) of the infrazygomatic crest region. For each model, the bone depth and thickness of 27 different insertion paths were measured in the region between U6 and U7. The relationship between bone depth and thickness was statistically analyzed. The clinical risk for each insertion path was assessed according to the impacts of bone depth and thickness on insertion failure. RESULTS: Maximum bone depth (median, 7.41 mm; mean, 8.42 mm) was present at 13 mm insertion sites with a gingival tipping angle of 50° and a distal tipping angle of 30°. Maximum bone thickness (median, 3.73 mm; mean, 4.00 mm) was present at 17 mm insertion site with a gingival tipping angle of 70° and a distal tipping angle of 30°. There was a significant negative correlation between bone depth and bone thickness (rs = -0.569, P <0.001). Failure rates were significantly different among different insertion paths (P <0.001). CONCLUSIONS: Because the bone depth and thickness may affect the safe insertion of infrazygomatic crest miniscrews in the region between U6 and U7 and they are negatively related, a safe insertion protocol design for distal tooth movement should take both into consideration.

Is a patient-specific drill template via a cortical bone trajectory safe in cervical anterior transpedicular insertion?

BACKGROUND: This study aimed to develop patient-specific drill templates by computer numerical control or three-dimensional printing via two cortical bone trajectories (CBTs) and to evaluate their efficacies and accuracies in cervical anterior transpedicular insertion. METHODS: Preoperative CT images of 20 cadaveric cervical vertebrae (C3-C7) were obtained. After image processing, patient-specific drill templates were randomly assigned to be constructed via two CBTs (CBT0 and CBT0.7) and manufactured by two methods (computer numerical control and three-dimensional printing). Guided by patient-specific drill templates, 3.5-mm-diameter screws were inserted into the pedicles. Postoperative CT scans were performed to evaluate the screw deviation in the entry point and midpoint of the pedicle. The screw positions were also graded. RESULTS: Computer numerical control patient-specific drill templates had a significantly shorter manufacturing time compared to three-dimensional-printed patient-specific drill templates (p < 0.01). Absolute deviations at the entry point and midpoint of the pedicle had no significant differences on the transverse and sagittal planes (p > 0.05). There were no significant differences in screw positions (p = 0.3). However, three screw positions were in grade 3 in CBT0, while the others were in grade 1. CONCLUSIONS: CBT0.7 appears to be a safe and feasible trajectory for cervical anterior transpedicular insertion. Bio-safe computer numerical control patient-specific drill templates can facilitate cervical anterior transpedicular insertion with good feasibility and accuracy.