Coefficient of thermal expansion of some anterior restorative materials by a new dilatometric technique.
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Composite Resins↗
Biomedical subjects
J F McCabe
Publications and source records attributed to J F McCabe.
The ball mill as a means of investigating the mechanical failure of dental materials.
OBJECTIVE: The main purpose of this paper is to present a new method of predicting clinical performance using mechanical loading in a ball mill. METHODS: A series of four experiments (two involving a hybrid composite and one each on orthodontic brackets and bands) is described in which the ball mill was used to subject specimens to mechanical fatigue. RESULTS: A reproducibility study using composite beam specimens showed no significant difference between the Mean Survival Time (MST) in all the three experimental runs (P = 0.42). When subjected to thermal cycling, the MST of the cycled group was 155.0 min compared to 247.0 min for the control group (P < 0.01). The MST of untreated and sandblasted brackets was 7.9 h and 14 h respectively (P < 0.01). There is also a significant difference (P < 0.001) in the MST of sandblasted bands when compared to the untreated bands. CONCLUSIONS: The ball mill proved to be a convenient and reproducible means of producing mechanical fatigue and may be useful in predicting the clinical performance of dental materials.
Bisphenol A-Glycidyl Methacrylate↗
Dental materials: 1995 literature review.
This critical review of the published literature on dental materials for the year 1995 has been compiled by the Dental Materials Panel of the United Kingdom. It continues the series of annual reviews started in 1973 and published in the Journal of Dentistry. Emphasis has been placed upon publications which report upon the materials science or clinical performance of the materials. The review has been divided by accepted materials classifications (fissure sealants, glass polyalkenoate cements, resin composites, dentine bonding, dental amalgam, endodontic materials, casting alloys, investment materials, resin-bonded bridges and ceramo-metallic restorations, all ceramic restorations, denture base and soft lining materials, impression materials, dental implants, orthodontic materials and biomechanics). Three hundred and thirty articles published in 68 titles have been reviewed.
Biomechanical Phenomena↗
A polyvinylsiloxane denture soft lining material.
A new denture soft lining material based on a polyvinylsiloxane system, similar to that used in addition-curing silicone impression materials, has recently been developed. The purpose of the work reported here was to compare certain key properties of the new material with those of other commercially available materials. Setting characteristics, resistance to penetration, elastic properties, water absorption, peel strength and contact angle with water were determined for five materials including the new product. In addition, the change in properties following water storage were determined. In many respects the properties of the new material were noted to be similar to those of a heat-cured silicone product. It is initially elastic and of "medium" softness as defined by ISO 10139-2. It was the only product which did not lose weight on storage in water and over 90 days of storage it gave only a small change in compliance as measured by surface penetration. Bond strength of the new material to an acrylic denture base appears only moderate. However, failure was cohesive within the soft material with no peeling, suggesting that peeling is unlikely to occur in practice. The affinity between the surface of the material and water, as determined by contact angle, is significantly better than for other silicone products. The properties of the polyvinylsiloxane denture soft lining material are in many respects similar to those of other silicone soft lining materials. However, the efficacy of the adhesive which prevents peeling combined with a convenient packaging, proportioning and mixing system suggests that the material may offer some advantages which warrant its clinical evaluation.
Absorption↗
The management of occlusal caries in permanent molars. A 5-year clinical trial comparing a minimal composite with an amalgam restoration.
A clinical trial comparing the efficacy of an occlusal amalgam restoration with a minimal composite restoration and fissure sealant in the management of occlusal caries in young patients has been performed. One hundred and fifty pairs of restorations were placed in 103 patients and assessed during the 5-year follow-up period. Nineteen restorations failed during this period: 11 amalgam and 8 minimal composite. There was some deterioration in anatomical form and marginal integrity of the remaining amalgam restorations. Of the remaining minimal composites, seven suffered clinically detectable wear and a further five had some marginal staining. Forty-nine of the minimal composites needed to have repairs to the fissure sealant. The amalgam restorations occupied, on average, 25% of the occlusal surface of the tooth, compared with 5% for the minimal composite resin. The results after a 5-year follow-up showed no significant difference in median survival times between the amalgam and the minimal composite restorations.
Adolescent↗
Treatment of dentin with polyacrylic acid--a retrospective observational study of the effect upon the durability of glass ionomer restorations.
This paper reports on the results of a material specific, retrospective observational study. It sought to determine the consequence of pretreatment of cavity margins with the conventional glass polyalkenoate Chemfil II prior to restoration with Tooth Cleanser on restoration durability. All restorations were placed and varnished by senior dental students under the supervision of a staff member. Manufacturer recommendations were followed. Data on each restoration was collected and entered into a relational computer database. Data included details of cavity morphology and the use or non-use of Tooth Cleanser. Six years following the study start a manual search of all records was carried out to determine, for those patients continuing to attend the Dental Hospital, the number of failed and surviving restorations. This yielded a dataset of 149 restorations, of which 41 had been placed with the aid of Tooth Cleanser and 108 without. The number of failed restorations was 20 and 62, respectively. Survival analysis by the Kaplan-Meier method revealed median survival times of 2,094 days, when Tooth Cleanser was used and 1,748 days when not. Although 80% survival times of 1111.0 (SE = 6.3) (With Tooth Cleanser) and 285.0 (SE = 3.8) (Without Tooth Cleanser) days were observed, together with a Hazard Ratio of 1.49 (95% Confidence Intervals 0.92 & 2.31), a Logrank test revealed no statistically significant difference between the survival curves (p = 0.12). It was concluded that although there was a trend for the application of Tooth Cleanser to improve the chances of obtaining a dependable restoration, this effect was not statistically significant.
Acrylic Resins↗
Salivary contamination and bond strength of glass-ionomers to dentin.
This study evaluated the effect of salivary contamination on the shear bond strength of two highly viscous glass ionomer cements (Fuji IX GP Fast and Ketac-Molar Maxicap) to conditioned dentin and assessed the effect of cleaning the contaminated field prior to bonding. The buccal surfaces of 90 human molars and premolars were ground to expose dentin and the teeth were then set in resin. The specimens were divided into two groups for each material, then further subdivided into three groups of 15 teeth each: Group 1--uncontaminated (control), Group 2--dentin contaminated with saliva, Group 3--dentin contaminated, washed and air dried. The specimens were made by bonding the test material to dentin using a 4 mm diameter gelatin capsule. All specimens were protected with varnish and placed in distilled water at 37 degrees C for seven days prior to measuring bond strength in shear. Fractured surfaces were examined visually and by using SEM to assess mode of failure. There were no significant differences in mean shear bond strength among the three test groups for either material (ANOVA). However, shear bond strength of Fuji IX to dentin was significantly greater than Ketac-Molar (p=0.019) for all groups. Weibull analysis showed that contaminated (Group 2) specimens had a greater probability of failure at low stresses. Modes of failure were mostly cohesive for Fuji IX and adhesive/cohesive for Ketac-Molar. In conclusion, salivary contamination did not affect the mean shear bond strength of Fuji IX GP Fast and Ketac-Molar Maxicap to conditioned dentin; however, it increased the probability of failure at low stresses.
Adhesiveness↗