Biomedical subjects
Publications and source records attributed to C B Jenkins.
A case of a patient with multiple external root resorption affecting principally the molars and premolars is described. This case is unusual in that although both right and left molar and premolar teeth are involved, the resorption is worse on the left side and affects only the distal roots of the molars.
Although resin-bonded bridges should ideally be bonded to enamel, abutment teeth may present with dentine or restorations at the bonding sites. This study assessed the influence of bonding to such adherends on bridge retention by using tensile bond strength measurements as the criteria for judgement. An adhesive resin cement (Panavia Ex) was bonded to single adherends of enamel, dentine, composite resin, glass ionomer or amalgam, and to combined adherends of enamel/dentine or enamel/restorative material. The bond strength to enamel (28 MPa) was comparable with that to composite resin (25 MPa), but significantly higher than to dentine (8 MPa), amalgam (8 MPa) and glass ionomer (13 MPa). When the bonding area was half enamel and half restorative material, the bond strength was only equivalent to that obtained when the entire bonding area consisted of restorative material, the less favourable adherend. A similar trend was observed with specimens of enamel/dentine. This indicated that the magnitude of the bond between the resin cement and combined adherends was limited by the strength of the bond to the less favourable adherend. It appears that extending a bridge retainer to cover exposed dentine, a glass-ionomer filling or an amalgam filling, could adversely affect the bridge retention.
Perceptions of the requirements of cavity preparations have changed over the years. These have had a significant effect on undergraduate teaching at the University of Bristol Dental School, an explanation of which may help general dental practitioners in their quest for information on this important aspect of dental practice. A method is described for teaching undergraduate dental students cavity preparation in caries-free teeth, based upon the position, shape and extent of imaginary carious lesions. Scale diagrams of teeth are used, on which imaginary caries at the amelodentinal junction has been marked. The students are instructed to apply the principles of cavity preparation to equivalent, but caries-free, teeth in the laboratory. 'Outline forms' and other predetermined cavity shapes are not taught. Dental practitioners may find it appropriate to apply similar thinking to cavities they prepare in everyday practice, in an endeavour to avoid the unnecessary removal of tooth tissue that would be better retained.
Clinicians are frequently confronted with the problem of ditched amalgam restorations. Materials which develop strong bonds to amalgam and tooth substance appear to be suitable for repair of such restorations and eliminate the need for complete replacement. This study evaluated the bond strengths of three glass-ionomer cements to amalgam made from conventional and high copper alloys. It was found that the bond strength values to amalgam were comparable with those to enamel and significantly higher than those to dentine. All bonds to the high copper amalgam failed in a cohesive mode; for the conventional amalgam, failure was either of the adhesive or cohesive type.
This study evaluated the tensile strength of enamel-resin-metal joints formed with four adhesive systems for attaching resin-bonded FPDs. Groups of 10 cast alloy cylinders were blasted with 50 microns alumina, washed, and prepared for bonding according to the resin as follows: (1) Panavia Ex with no treatment, (2) Super-Bond oxidized for 2 minutes with potassium permanganate in sulphuric acid, (3) Conclude electrolytically etched, and (4) ABC conditioned with primer. The cylinders were bonded to etched human enamel and after 24 hours in water at 37 degrees C the tensile strengths of the joints were recorded. Joint failure was examined under a stereomicoscope and a scanning electron microscope. The results demonstrated that the adhesive system influenced the tensile strength and mode of failure of the joints.
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