PubMed Health⌕ Search

Biomedical subjects

J A Sandham

Publications and source records attributed to J A Sandham.

10 recordsLinked to original sources

An investigation into the behavioural characteristics of orthodontic elastomeric modules.

The object of the study was to investigate the behavioural characteristics of orthodontic elastomeric modules with regard to their effect on frictional resistance and their failure load forces, and involved the use of an experimental laboratory-based study. Six cohorts were assembled employing five types of module and two bracket types. Straight lengths of 0.018 x 0.025-inch stainless steel were pulled through the ligated brackets and frictional resistance was measured using an Instron universal testing machine. Recordings were repeated over a 4-week period, during which time the cohorts were placed in a simulated oral environment. Failure load forces of new and used modules were also recorded, and frictional resistance and failure load forces. Analysis of variance revealed that the Minitwin cohort exhibited significantly higher frictional resistance and that the clear modules demonstrated the lowest levels of friction. Time soaked in a simulated oral environment had a variable effect on frictional resistance. A wide range of failure load forces was seen for the five types of module and all types showed a reduction in failure load force following their soaking in the simulated oral environment. There was variation in performance of the different modules both in friction testing and failure load testing.

Analysis of Variance↗

Electrothermal debonding of ceramic brackets: an ex vivo study.

The shear forces necessary to remove ceramic brackets from human premolar teeth using mechanical and electrothermal debonding techniques were compared and the post-debond enamel characteristics were evaluated. The temperature rise in the pulp cavity during electrothermal debonding was recorded. The samples were tested sequentially on a shear jig attached to an Instron Universal Testing Machine. The results indicate that removal of ceramic brackets with an electrothermal debonder requires less force than with a mechanical debonding technique. Furthermore, the associated pulp temperature rise appears to be within currently established biologically acceptable limits. However, the indices that are commonly used to define the condition of the enamel surface following debond may not be applicable to electrothermal debonding.

Adhesives↗

[The use of a computer to measure linear and angular variables for an assessment of symmetry of the base of the skull].

The use of a computer is described to make linear and angular measurements of the base of the skull. A group of 19 adult skulls from mediaeval Poland were chosen for this study. The cephalometric analysis defined 11 linear and 9 angular morphological variables. An assessment of method error due to point location by the cursor was made by duplicate determination, and an assessment of symmetry was carried out by comparing angular values derived from basion (ba) for right and left sides of the maxillary dental arch, zygomatic arch and cranial base. The results demonstrate that skull measurements could be recorded with a small method error of 0.2 mm for linear, and 0.2 degrees for angular recordings. Mean values for the 21 variables in the sample were recorded and statistically tested for point placement accuracy using measures of skewness and kurtosis to detect gross distribution errors.

Adult↗

Orthodontic treatment with lingually bonded brackets.

The direct bonding of orthodontic brackets to enamel has greatly improved the aesthetics of fixed appliance orthodontics. A recent development has been the lingual placement of the attachments which has resulted in none of the mechanics being visible on the anterior teeth. This article describes treatment with this technique and illustrates a treated case.

Dental Bonding↗