Peri-operative second molar tube failure during orthognathic surgery: two case reports

With improvements in bonding techniques, bracket base design and bond strengths, molar tubes are becoming more popular in orthodontics. Molar tubes make an attractive alternative to conventional banding due to a reduction in clinical bonding time and ease of placement on partially erupted teeth. The use of molar tubes negates the need for orthodontic separation and subsequent cementation of bands, and offers improved periodontal health. Their use on terminal molars, however, should be limited to non-orthognathic cases. This paper presents two cases of peri-operative second molar tube failure during orthognathic surgery. They are presented in the hope that it will highlight the importance of banding the distal terminal molar in orthognathic cases to prevent loss of molar tubes and peri-operative contamination of the surgical wound site.

New iterative cone beam CT reconstruction software: parameter optimisation and convergence study

Cone beam computed tomography (CBCT) provides a volumetric image reconstruction from tomographic projection data. Image quality is the main concern for reconstruction in comparison to conventional CT. The reconstruction algorithm used is clearly important and should be carefully designed, developed and investigated before it can be applied clinically. The Multi-Instrument Data Analysis System (MIDAS) tomography software originally designed for geophysical applications has been modified to CBCT image reconstruction. In CBCT reconstruction algorithms, iterative methods offer the potential to generate high quality images and would be an advantage especially for down-sampling projection data. In this paper, studies of the CBCT iterative algorithms implemented in MIDAS are presented. Stability, convergence rate, quality of reconstructed image and edge recovery are suggested as the main criteria for monitoring reconstructive performance. Accordingly, the selection of relaxation parameter and number of iterations are studied in detail. Results are presented, where images are reconstructed from full and down-sampled cone beam CT projection data using iterative algorithms. Various iterative algorithms have been implemented and the best selection of the iteration number and relaxation parameters are investigated for ART. Optimal parameters are chosen where the errors in projected data as well as image errors are minimal.

High-latitude ionospheric response to co-rotating interaction region- and coronal mass ejection-driven geomagnetic storms revealed by GPS tomography and ionosondes

Positive ionospheric anomalies induced in the polar cap region by co-rotating interaction region (CIR)- and coronal mass ejection (CME)-driven geomagnetic storms are analysed using four-dimensional tomographic reconstructions of the ionospheric plasma density based on measurements of the total electron content along ray paths of GPS signals. The results of GPS tomography are compared with ground-based observations of F region plasma density by digital ionosondes located in the Canadian Arctic. It is demonstrated that CIR- and CME-driven storms can produce large-scale polar cap anomalies of similar morphology in the form of the tongue of ionization (TOI) that appears on the poleward edge of the mid-latitude dayside storm-enhanced densities in positive ionospheric storms. The CIR-driven event of 14–16 October 2002 was able to produce ionospheric anomalies (TOI) comparable to those produced by the CME-driven storms of greater Dst magnitude. From the comparison of tomographic reconstructions and ionosonde data with solar wind measurements, it appears that the formation of large-scale polar cap anomalies is controlled by the orientation of the interplanetary magnetic field (IMF) with the TOI forming during the periods of extended southward IMF under conditions of high solar wind velocity.

Current Products and Practice

This is a report on the use of a regional database of patients undergoing orthognathic treatment in the South West of England. The benefits and difficulties of using a regional database are discussed.

Maxillary incisor root resorption in relation to the ectopic canine: a review of 26 patients

A retrospective study of 26 patients with maxillary incisor root resorption relating to the presence of an ectopic canine was undertaken from case records. The group consisted of nine male and 17 female patients with a mean age of 12.5 years. There was a total of 35 resorbed teeth, 26 lateral and nine central incisors, and these were related to 32 ectopic canines. The resorption tended to be extensive, 30 teeth had pulpal involvement. In two-thirds of cases the pattern of resorption involved both apical and middle thirds of the root. Despite the extensive nature of the involvement there were few clinical signs and symptoms reported by patients. 43.8 per cent of canines were lying palatal to the arch, 18.7 per cent were in the line of the arch and 37.5 per cent were buccal. Significantly 15.6 per cent were buccal and erupted. The path of canine eruption was mesio-horizontal in 21 cases. No relationship could be found between resorption and the retention or loss of the deciduous canine. The canine root formation was virtually complete in 31 of the involved canines. The study indicated that the problem is often diagnosed late both in relation to the patient's age and the extent of resorption present. It is suggested that the problem may be underestimated by dental practitioners.