Quantification of dental prostheses on cone-beam CT images by the Taguchi method.

The gray values accuracy of dental cone-beam computed tomography (CBCT) is affected by dental metal prostheses. The distortion of dental CBCT gray values could lead to inaccuracies of orthodontic and implant treatment. The aim of this study was to quantify the effect of scanning parameters and dental metal prostheses on the accuracy of dental cone-beam computed tomography (CBCT) gray values using the Taguchi method. Eight dental model casts of an upper jaw including prostheses, and a ninth prosthesis-free dental model cast, were scanned by two dental CBCT devices. The mean gray value of the selected circular regions of interest (ROIs) were measured using dental CBCT images of eight dental model casts and were compared with those measured from CBCT images of the prosthesis-free dental model cast. For each image set, four consecutive slices of gingiva were selected. The seven factors (CBCTs, occlusal plane canting, implant connection, prosthesis position, coping material, coping thickness, and types of dental restoration) were used to evaluate scanning parameter and dental prostheses effects. Statistical methods of signal to noise ratio (S/N) and analysis of variance (ANOVA) with 95% confidence were applied to quantify the effects of scanning parameters and dental prostheses on dental CBCT gray values accuracy. For ROIs surrounding dental prostheses, the accuracy of CBCT gray values were affected primarily by implant connection (42%), followed by type of restoration (29%), prostheses position (19%), coping material (4%), and coping thickness (4%). For a single crown prosthesis (without support of implants) placed in dental model casts, gray value differences for ROIs 1-9 were below 12% and gray value differences for ROIs 13-18 away from pros-theses were below 10%. We found the gray value differences set to be between 7% and 8% for regions next to a single implant-supported titanium prosthesis, and between 46% and 59% for regions between double implant-supported, nickel-chromium alloys (Ni-Cr) prostheses. Quantification of the effect of prostheses and scanning parameters on dental CBCT gray values was assessed.

Cervical Ripening Balloon for Induction of Labour in High Risk Pregnancies

Background: The Cervical Ripening Balloon (CRB) is a novel mechanical method for induction of labour (IOL), reducing the risks of hyperstimulation associated with pharmacological methods. However, there remains a paucity of literature on its application in high risk mothers, who have an elevated risk of uterine rupture, namely those with previous scars and grandmultiparity. Methodology: A retrospective study on IOL using the CRB in women with previous caesarean section or grandmultiparity between January 2014 and March 2015. All cases were identified from the Sarawak General Hospital CRB request registry. Individual admission notes were traced and data extracted using a standardised proforma. Results: The overall success rate of vaginal delivery after IOL was 50%, although this increases to about two-thirds when sub analysis was performed in women with previous tested scars and the unscarred, grandmultiparous woman. There was a significant change in Bishop score prior to insertion and after removal of the CRB. The Bishop score increased by a score of 3.2 (95% CI 2.8-3.6), which was statistically significant (p<0.01) and occurred across both subgroups, not limited to the grandmultipara. There were no cases of hyperstimulation but one case of intrapartum fever and scar dehiscence each (1.4%). Notably, there were two cases of change in lie/presentation after CRB insertion. Conclusion: CRB adds to the obstetricians’ armamentarium and appears to provide a reasonable alternative for the IOL in women at high risk of uterine rupture. Rates of hyperstimulation, maternal infection and scar dehiscence are low and hence appeals to the user.