PubMed Health⌕ Search

Biomedical subjects

P R Walshaw

Publications and source records attributed to P R Walshaw.

6 recordsLinked to original sources
PubMed2003

Bond failure at dentin-composite interfaces with 'single-bottle' adhesives.

OBJECTIVES: Significant differences in interfacial fracture toughness (intK(1c)) among six dentinal adhesives have been reported. Resulting fractured test specimens were examined under SEM to determine differences in micromorphology, which might account for the respective intK(1c) results. METHODS: Interfacial fracture toughness specimens were assembled from bovine dentin and P50 resin composite under moist conditions, using one of five 'single-bottle' adhesives; either Single Bond, One Step, Optibond Solo, Prime & Bond 2.1, Bond 1 or a resin-modified glass ionomer, Fuji Bond LC. After fracture toughness testing, four fractured specimens from each group were sectioned transversely, critical-point dried and examined under SEM. RESULTS: Most bond failures occurred at the interface between adhesive resin and the top of the hybrid layer. Single Bond and One Step gave the highest intK(1c) results and showed good resin infiltration at this interface. Average film thickness of unfilled adhesives was 30 microm. When this intermediate adhesive layer was too thin, resin infiltration was poor and associated with low fracture toughness. Filled adhesives, Optibond Solo and Fuji Bond LC, formed thick films varying from 60 to 250 microm which failed cohesively, effectively sealing the dentin surface despite moderate fracture toughness results. CONCLUSIONS: Most bond failures occurred between the adhesive and hybrid layers. Good resin infiltration at the top of the hybrid layer combined with an intermediate adhesive layer of adequate width produced a fracture-resistant interface. Filled adhesives failed cohesively, providing a good dentin seal, despite material fracture.

Acetone↗
PubMed1998

Microscopic features of clinically successful dentine bonding.

Clinical success with resin-based bonding systems depends upon meticulous attention to detail at each stage of the bonding process. Cavity margins placed in enamel wherever possible and etched for at least 15 to 30 seconds will ensure a reliable peripheral seal. Dentine conditioning should be brief--a maximum of 15 seconds for surface demineralization only. Diffusion of primers into the full extent of dentinal demineralization is enhanced by application of multiple coats. Any solvent or moisture remaining on a primed dentine surface will prevent adaptation of bonding resin, resulting in non-attachment. Adhesive bonding resin provides a valuable elastic intermediate layer for absorption of stresses of polymerization shrinkage--but it should be of uniform thickness and not air-thinned. Incremental insertion of resin composite will reduce polymerization stresses and ensure a fully cured restoration.

Acid Etching, Dental↗
PubMed1996

Clinical considerations for optimal dentinal bonding.

A review of current clinical research has demonstrated that successful attachment with resin-based bonding systems is achieved through brief acidic conditions of dentin, followed by thorough coverage with resin priming and bonding agents. This article discusses factors of clinical relevance in achieving optimal results. Effective priming, using multiple coats to enhance resin penetration to the full depth of dentinal demineralization, is crucial. A thin, uniform layer of bonding resin is a critical, elastic intermediary for absorbing stresses of polymerization shrinkage. An air stream should be used only for evaporation of solvent and not for spreading bonding resin, because use of an air stream causes uneven thinning of this valuable intermediate layer. Contamination of the dentinal surface with excessive moisture or solvent or the presence of air voids will make bonding unpredictable under clinical conditions. Adequate etching of peripheral enamel continues to be an important factor in the long-term retention of adhesive restorations.

Acid Etching, Dental↗
PubMed1995

SEM characterization of the resin-dentine interface produced in vivo.

OBJECTIVES: A freeze-fracture technique with critical-point drying has been shown to preserve the structure of collagen in demineralized primed dentine in vitro (Titley K et al. Am J Dent 1994; 7: 22-26). This study utilized the technique to examine the attachment to dentine produced in vivo All-Bond 2 (AB2), Scotchbond Multi-Purpose (SBMP) and Prisma Universal Bond 3 (PUB3). METHODS: Eighteen medium-depth restorations were placed in buccal and/or lingual surfaces of premolar teeth (n = 7) scheduled for extraction for orthodontic purposes. After extraction, the restored teeth were split transversely by freeze-fracture, critical-point dried and examined under SEM. RESULTS: AB2 and SBMP produced significant gap-free attachment to dentine showing similar microscopic structural features. Resin interdiffusion with collagen fibrils of the intertubular matrix was clearly seen. Microspaces, observed at the periphery of the widened tubules and among the interdiffused collagen fibrils, suggested incomplete resin penetration. Fractures occurring parallel with the interface frequently showed detachment in the deepest layers of the hybrid zone. Adhesive gaps were seen at the resin-dentine interface, indicating some clinical technique failure. The PUB3 attachment was generally incomplete, with separation between the primed dentinal surface and the composite restoration. Where present, the bonded interface showed no evidence of true hybridization. CONCLUSION: Dentine conditioning, as a separate step, prior to priming, appears to be an important factor in successful resin-dentine attachment. Critical-point drying revealed variations in the degree of resin interdiffusion with intertubular collagen, suggesting potential sites for bond failure.

Acid Etching, Dental↗
PubMed1994

SEM evaluation of the resin-dentin interface with proprietary bonding agents in human subjects.

Laboratory studies on dentin bonding do not replicate physiological reality. This study examined with SEM the attachment produced in vivo under clinical conditions. Forty-four cavities were prepared in buccal/lingual surfaces of 16 premolar teeth scheduled for extraction and assigned randomly for treatment with: All-Bond 2 (Bisco) (A) with and (B) without dentin etch, (C) Scotchbond 2 (3M), (D) Scotchbond Multi-Purpose (3M), and (E) controls, using Enamel Bond (Kulzer) with dentin etch. After atraumatic extraction, restorations were split transversely by freeze-fracture and acid-treated. SEM examination of A revealed significant areas of gap-free attachment, with evidence of an acid-resistant hybrid layer (5-8 microns), often with resin tags of various lengths. Resin-reinforced collagen fibers were seen. Gap formation was coincident with lack of bonding resin layer over primed dentin. Attachment with B was less effective; a hybrid layer was infrequently seen and few resin tags. Pooled bonding resin at internal line angles appeared to favor an effective bond. Treatment C resulted in large areas of detachment, leaving an adherent primed dentin layer with short resin tags. Treatment D revealed significant areas of gap-free attachment and evidence of a hybrid layer. Controls (E) showed total bond failure. Attachment with A and D was secure, restorations remaining in situ even after freeze-fracture. This study confirmed that brief acid pre-treatment of dentin, allowing diffusion of resin-dentin primers, appeared conductive to development of an effective bond in vivo, similar to that reported in vitro.

Acid Etching, Dental↗