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Biomedical subjects

D J Setchell

Publications and source records attributed to D J Setchell.

14 recordsLinked to original sources
PubMed1992

Dentine-removing characteristics of K-files energized by the Piezon-Endo.

This in-vitro study evaluated the pattern of dentine removal when a size 25 K-file energized by the Piezon-Endo was applied to flat surfaces of dentine under standardized conditions. The effects of power setting, interfacial force between file and dentine, direction of file oscillation and operator-assisted movement were examined. Vinyl polysiloxane impressions of the instrumented surfaces revealed characteristic patterns consisting of a series of oblique crests, similar to those observed in a previous study using the Cavi-Endo. Each crest was parallel to the next and separated by a relatively constant distance. These crests were disposed along the line of contact with the file. The Reflex microscope was used to determine the height, width and separation of these crests. There were differences in the amount and pattern of dentine removal compared with the study on the Cavi-Endo. When the file was held against the dentine surface using the minimum power setting and an interfacial force of 30 g, the pattern of dentine removal was very similar to that produced by the Cavi-Endo. Increasing the power setting to the maximum recommended for endodontics produced a slight but statistically non-significant increase in dentine removal. Further increase of the power setting to the absolute maximum produced significantly deeper and wider areas of dentine removal by the apical part of the file.(ABSTRACT TRUNCATED AT 250 WORDS)

Dental Cavity Preparation↗
PubMed1991

Resistance to torsional forces of various post and core designs.

This in vitro study investigated the resistance of various post and core designs to torsional forces. Cast gold, parallel-sided, serrated post and cores were cemented in extracted teeth. The test groups were made up of the following designs: controls without an antirotational feature, keyway form, coronal flare form, auxiliary pin form, a cervical collar form, and included a tapered post group. The specimens were mounted on an Instron Universal testing machine and a torsional force was applied to the core using a lever arm until failure. All the antirotational features tested elevated resistance to torque. Failure occurred through fracture of the tooth, the cement, or an optional auxiliary pin. The cervical collar was the most favorable design, embracing resistance and reducing tooth fractures.

Dental Cavity Preparation↗
PubMed1991

Properties of the tray adhesive of an addition polymerizing silicone to impression tray materials.

Adhesive bond strength studies for the tray adhesive of an addition vinyl polysiloxane (President) impression material were conducted with an acrylic resin, chromium-plated brass, and plastic trays. Tensile and shear stress studies were performed on the Instron Universal testing machine. Acrylic resin specimens roughened with 80-grit silicon carbide paper exhibited appreciably higher bond strengths compared with different types of tray material and methods of surface preparation.

Acrylic Resins↗
PubMed1990

Relationship between contact angles of die stone on elastomeric impression materials and voids in stone casts.

Poor wettability of elastomeric impression materials results in surface defects on stone casts. This study examined the relationship between contact angles of die stone and voids in casts produced from five medium-viscosity impression materials. Contact angles of a die stone material formed against impression specimens made from polyether, addition and condensation silicones were measured by reflex microscope. The contact angle values achieved on the hydrophilic addition silicones were significantly higher than the polyether but lower than other silicone materials. Contact angle values correlated with the number of voids found at margins and line angles of stone casts but not with those on smooth surfaces.

Dental Impression Materials↗
PubMed1990

In vitro study to compare impact fracture resistance of intact root-treated teeth.

The aim of this in vitro study was to determine the effect on impact fracture resistance of three methods for restoration of root-treated lower incisor teeth with otherwise intact natural crowns. In a control group (Group I) laterally condensed gutta-percha filled the entire root canal, whereas part of the root filling was removed to enable insertion of a 1 mm diameter post in the other two groups. Stainless steel posts were placed in Group II and experimental carbon fibre reinforced carbon (CFRC) in Group III. A composite resin luting agent was used to lute the posts, and standardized composite resin restorations were placed in each access cavity. Fifteen specimens of each group were tested to failure with a single impact force applied at 90 degrees to the mid-point inciso-cervically on the labial surface. The peak force, peak energy, and first peak total energy required to fracture each specimen were recorded. The results showed no significant difference between the three groups, nor was a difference in the mode or site of fracture observed. The results suggested that there is no advantage from the point of view of fracture mechanics in 'restoring' intact root-treated teeth with either stainless steel or carbon fibre reinforced carbon rods.

Carbon↗
PubMed1990

An in vitro evaluation of a prototype CFRC prefabricated post developed for the restoration of pulpless teeth.

Carbon fibre reinforced carbon (CFRC) in the form of a prefabricated post has recently been developed and is theoretically acceptable for consideration in an endodontic post-retained crown system. This study compared four different types of postcore system cemented into 40 extracted anterior human teeth. The test groups consisted of CFRC posts cemented with a composite resin luting agent, and used with either a cast gold alloy core (Group B) or a composite resin core (Group C). Two existing post-core techniques were used as controls for comparison with the CFRC groups. One control was a prefabricated wrought precious alloy post having a cast gold alloy core, and cemented with zinc phosphate cement (Group A). The other was a prefabricated stainless steel post with a composite resin core, and cemented with a composite resin luting agent (Group D). All specimens were restored with a gold alloy crown and tested to failure with an obliquely applied compressive load at 130 degrees in an Instron using a cross-head speed of 5 cm min-1. The results showed that post-retained crowns using a prefabricated CFRC post exhibited properties comparable with, and in some cases better than, those of existing prefabricated posts. The mode of failure of specimens restored with a CFRC post was more favourable to the remaining tooth tissue than was that of specimens restored with a metallic post.

Carbon↗
PubMed1989

Dentine-removing characteristics of an ultrasonically energized K-file.

This in vitro study evaluated the pattern of dentine removal when an ultrasonically energized file (Cavi-Endo-size 25 file) was applied to flat surfaces of dentine under standardized conditions. The influences of power setting, interfacial force between file and dentine, direction of file oscillation and operator-assisted movement were examined. Impressions of the instrumented surfaces revealed characteristic patterns consisting of a series of oblique crests, each one parallel to the next and separated by a constant distance along the line of contact with the file. Determination of height, width and separation of these crests with a Reflex microscope aided objective assessment. The simplest pattern was formed when the energized file was held against the dentine (power setting = 1; interfacial force = 30 g). Increasing the power setting to 8 caused deeper troughs over the apical 5 mm. The width of the crests corresponded to the taper of the file except at the apical tip where the crests were relatively wider. However, increasing the interfacial force to 60 g reduced the efficiency of the apical part of the file. The superimposition of operator-induced movement greatly increased the extent of dentine removal, resulting in a tapering groove with a persistent crestal pattern. Oscillation of the file perpendicular to the dentine surface had a significantly greater influence on dentine removal, producing a deeper groove than was obtained with oscillation parallel to the surface. These findings may be of relevance in aiding controlled root canal preparation when using the Cavi-Endo instrument.

Dental Cavity Preparation↗
PubMed1989

Treatment of the worn dentition: 2.

This is the second of two articles concerning the practical techniques involved in reconstruction of the worn dentition. Part 1 discussed approaches to managing occlusion, and practical techniques for restoring worn anterior teeth. This second article will describe the procedures involved when both anterior and posterior teeth are worn, and then give a guide to the management of the short clinical crown.

Aged↗
PubMed1983

An investigation of the reproducibility of face-bow transfers.

An investigation was conducted to determine the reproducibility of the position of a maxillary cast in two widely-used semi-adjustable articulators when a face-bow transfer was repeated ten times for the same individual. The results obtained with the Dentatus AEB, Whipmix Quickmount and Almore transfer bows were compared. The variations in cast position rarely exceeded +/- 1.0 mm in any of three planes of space and although the results suggested a ranking in accuracy of the three instruments, all were considered clinically acceptable. On the basis of the results observed, face-bow transfer appears to be a reliable clinical procedure and accuracy in the determination of reference locations is unlikely to be negated by subsequent transfer errors, provided that appropriate care is employed.

Adolescent↗
PubMedDate not supplied

Treatment of the worn dentition. 1.

This is the first of two articles concerning the practical techniques involved in reconstruction of the worn dentition. The authors describe some of the procedures available and assess the appropriateness of 'conformative' versus 'reorganized' approaches to the occlusion. They continue by describing some practical aspects of reconstructive work. Part 2 will look at other practical techniques.

Crowns↗