Biomedical subjects

R J Smales

Publications and source records attributed to R J Smales.

At least 37 records · Page 2Linked to original sources

PubMed2000

In vitro fluoride release from aesthetic restorative materials following recharging with APF gel.

In this in vitro study, the fluoride ion release from three more-viscous conventional glass ionomer cements (GICs)--ChemFlex, Fuji IX GP, Ionofil Molar--four polyacid-modified resin composites (compomers)--Dyract AP, Compoglass F, Freedom, F2000--and a hybrid resin composite--Ariston pHc--were compared. The amounts of fluoride release from 3 x 2.7 mm specimens were measured over six weeks using a fluoride ion-selective electrode. After six weeks, the specimens were recharged with 2 ml of 1.23 per cent acidulated phosphate fluoride (APF) gel for four minutes. The recharged specimens were then assessed for the amounts of fluoride release over another six weeks. Statistical analyses were performed using one-way and repeated measures ANOVA. The GICs and Compoglass F showed significantly higher initial fluoride release rates during the first two days (p < 0.05). After the first two days, fluoride release rates from all materials dropped quickly and became essentially stabilized within three-five weeks, in an exponential mode. The recharging of the specimens with APF gel caused a brief, but significant, increase in fluoride release for all materials (p < 0.05), before decreasing to previous comparable rates. Compoglass F released relatively more fluoride, and Ariston pHc relatively less, after APF gel application than before. The lowest total amounts over the study were released by Dyract AP and Freedom. The newer compomers, as well as the newer more-viscous GICs, appear to act as fluoride reservoirs to varying extents.

Acidulated Phosphate Fluoride↗

PubMed2000

Demineralisation and remineralisation of dentine caries, and the role of glass-ionomer cements.

In accordance with the principles of modern operative dentistry, to conserve tooth structure and to use therapeutic restorative materials, an understanding of the carious process in dentine and the biological properties of glass-ionomer cements (GICs) are necessary. Delineation of the outer necrotic from the inner vital and remineralisable carious dentine allows for the preservation of tooth structure. This delineation is not possible when relying on visual and tactile perceptions, but requires the use of a caries detecting dye. GICs are ideal dentine substitutes because of their anticariogenic properties, stable long-term ionic bonding, and ability to assist the process of remineralization. The range of usage of these restorative materials continues to expand with the development of improved products.

Apatites↗

PubMed2000

Effects of surface treatments on shear bond strengths between a resin cement and an alumina core.

STATEMENT OF PROBLEM: Although bonding to all-ceramic restorations is desirable, there is little information on the use of resin cements containing a phosphate monomer, and the importance of different surface treatments on their adhesion to high-strength core materials. PURPOSE: This study attempted to determine the shear bond strength values between Panavia 21 resin cement (Kuraray) and an alumina core material (In-Ceram) after 3 surface treatments and the application of a silane coupling agent. MATERIAL AND METHODS: Forty-five In-Ceram cylindrical rods were fabricated and assigned to 3 groups. Group I specimens were treated with a 9.5% hydrofluoric (HF) acid, group II with a 5% HF acid, and group III were sandblasted. All specimens were coated with a silane coupling agent (Cavex Clearfil Photobond and Activator) before cementation with Panavia 21 to sandblasted nickel-chromium rods. As a control, group IV consisted of 8 porcelain (Vitadur Alpha) rods treated with a 5% HF acid and silane. All specimens were subjected to a load of 1.2 kg during cementation, then stored under water for 36 hours. A jig mounted on a Hounsfield Universal Testing machine was used at a crosshead speed of 0.5 mm/min to test the shear bond strengths. RESULTS: The results were 14.65 +/- 4.64 MPa for group I, 18.03 +/- 6.13 MPa for group II, and 22.35 +/- 5.98 MPa for group III In-Ceram specimens; and 18.05 +/- 8.46 MPa for control (group IV). CONCLUSION: The use of Panavia 21 resin cement and a silane coupling agent can achieve a successful bond between either sandblasted or 5% HF acid-etched In-Ceram core material.

Aluminum Oxide↗

PubMed2000

Fluoride release from a polyacid-modified resin composite and 3 resin-modified glass-ionomer materials.

OBJECTIVES: The purposes of this study were to compare the fluoride ion release from a freshly mixed polyacid-modified resin composite, or "compomer" (Dyract), and 3 resin-modified glass-ionomer cements (Fuji II LC, Photac-Fil, and Vitremer) and to compare the use of 3 units for measuring fluoride release. METHOD AND MATERIALS: Five specimens (3.0 x 2.7 mm) of each material were prepared. The specimens were placed in polypropylene vials with 2 mL of deionized water and stored at 37 degrees C. The solutions were replaced weekly and the levels of fluoride ions were analyzed at days 1, 7, and 30 and subsequently every 28 days for 253 days. Fluoride measurements were carried out using a fluoride ion-selective electrode connected to a pH ion-selective electrode meter. Fluoride ion release was measured in parts per million, micrograms per square centimeter, and micrograms per cubic millimeter. RESULTS: Fuji II LC, Photac-Fil, and Vitremer showed high initial release values, which decreased exponentially and then showed a slow decline during the ensuing time. Dyract released significantly less fluoride ions during the first 84 days than did the 3 resin-modified glass-ionomer cements and maintained this low level of release throughout the study period. The amounts of fluoride ion release measured at any time interval varied with the units of measurement chosen, but the pattern of release remained the same. CONCLUSION: There was a wide variation in the amounts of fluoride ions released from related products, but the patterns of release were similar and unaffected by the units of measurement used.

Cariostatic Agents↗

PubMed2000

Fluoride release/uptake from newer glass-ionomer cements used with the ART approach.

PURPOSE: To determine the fluoride ion release/uptake of two conventional glass-ionomer cements (GICs) manufactured for use with the ART approach (Fuji IX GP, Ketac-Molar), as compared with that of a resin-modified GIC (Fuji II LC). MATERIALS AND METHODS: 15 specimens of each material were prepared and placed in vials with artificial saliva and stored at 37 degrees C. The solution was replaced weekly for 6 wks, and the fluoride ions released were measured in ppm each week. After 6 wks, the 15 specimens of each material were divided into three equal groups and placed into three fluoride recharging agents (1.23% APF gel, 1.1% neutral NaF and 0.001% CaF2) for 4 min at 23 degrees C. Fluoride ion measurements of the recharged specimens were carried out at 1 day, 2 days, then weekly for another 6 wks. RESULTS: All freshly-mixed specimens showed the highest fluoride ion release after 1 week, then the release rates dropped quickly to become largely stabilized after 3 wks. After one 4-min exposure to APF gel the initial fluoride ion release increased significantly for all materials. The highest rates were during the first day, but then dropped very quickly to again become largely stabilized after usually 3 wks. Exposure to NaF and CaF2 did not usually result in significantly sustained fluoride ion release by any material. The order of release/uptake for all three agents was Fuji II LC > Fuji IX GP > Ketac-Molar. The mechanism of fluoride ion release after the application of different fluoride recharging agents is not clear. It may occur partly by washout of recharge agents that are retained in the pores and cracks of the restorative materials, for APF gel is viscous and difficult to wash off completely with deionized water; by erosion of surfaces by low pH agents, or by the subsequent release of fluoride ions from within the cement matrix.

Acidulated Phosphate Fluoride↗

PubMed2000

Action research in the professional development of university staff: a case study from operative dentistry.

Action research has long been used in educational research and increasingly features in the professional development of university staff. A brief review of the historical development of action research is presented together with the range of approaches covered and their common characteristics. To illustrate the elements of action research, an example is drawn from operative dentistry. The steps taken by a lecturer to improve a pre-clinical course in operative dentistry are described in some detail and the outcomes of the action are reported and evaluated. The findings support the suitability of action research for professional development in dental education. The kinds of problems likely to be encountered by teachers using this methodology are reported. The ability of the participant investigators to reflect critically on the action taken was found to be a key component of action research.

Attitude↗

PubMed2000

A continuum from competency to proficiency through postgraduate general dentistry training.

Over the last few decades, the increase in knowledge and advances in dental technology have raised oral health care to a new level, and dental educators and the profession have put increasing demands on the clinical competencies expected of new graduates. The medical profession has reformed radically with its evidence-based and problem-based curricula, and its extension of the post-qualification training of family practitioners has meant universities, colleges and postgraduate institutes developing new strategies. This paper reviews the development of general dentistry, with special emphasis on the global trend towards enhanced postgraduate training.

Competency-Based Education↗

PubMed1999

Fluoride release, weight loss and erosive wear of modern aesthetic restoratives.

OBJECTIVE: In this investigation, the in vitro sustained fluoride release, weight loss and erosive wear of three conventional glass ionomer cements (Fuji IX, ChemFil Superior, Ketac-Silver), three resin-modified glass ionomer cements (Fuji II LC, Vitremer, Photac-Fil), a polyacid-modified resin composite (Dyract), and a resin composite control material (Z100) were compared. METHODS: The amounts of fluoride released and weight changes were measured for 12 weeks using a fluoride electrode with TISAB III buffer. After 12 weeks, the specimens were recharged with fluoride using 2 mL of 1.23% APF gel. The recharged specimens were assessed for the amounts of fluoride released and weight changes over another 12 weeks. At the end of the experiment, the specimens were examined with SEM and surface profilometry. RESULTS: All materials, with the exception of Z100, showed the highest initial fluoride release rates during the first 2 days, dropping quickly over 2 weeks and becoming largely stabilised after 5 weeks, in an exponential mode. The recharging of the specimens with APF gel caused a large increase in the amounts of fluoride released during the first 2 days only. Analyses for all cements showed strong correlations between mean weight loss and cumulative fluoride release over a 5-week period following the application of the APF gel. SEM and surface profilometry found that roughness increased from the polyacid-modified resin composite to the conventional glass ionomer cements. CONCLUSIONS: APF gel caused erosive wear of the glass ionomer cements especially, and the wear correlated well with the weight losses. To minimise surface erosion, APF gel should not be used on these cements, especially as the recharging effects are transitory.

Analysis of Variance↗

PubMed1999

Assessment of tooth preparation designs for posterior resin-bonded porcelain restorations.

Tooth preparation designs advocated for posterior resin-bonded porcelain restorations were evaluated for clinical application. This study examined the design of tooth preparations from stone dies for individual posterior resin-bonded porcelain onlays and complete porcelain crowns placed in a specialist practice, and compared features that provided retentive and porcelain fracture-resistance with those in the dental literature. Stone dies of tooth preparations for 57 onlay and 46 crown preparations were provided. Measurements were recorded for the tooth preparations with the aid of interocclusal silicone impressions. Proximal boxes, grooves and occlusal steps resulting from removal of amalgam restorations were common. These retentive features were more evident with onlays, and appeared larger on the distal than the mesial surfaces. Internal tooth preparation tapers or convergence angles were frequently greater than 20 degrees, leading to relatively-wide occlusal isthmus widths, especially for onlays. There were wide variations in occlusal surface reductions for the central fossae and supporting cusps. Tapers for tooth preparations were frequently more extensive, and occlusal surface reductions were often less than recommended. The implications of these differences for long-term clinical success should be resolved.

Adult↗

PubMed1999

A 2-year clinical study of two glass ionomer cements used in the atraumatic restorative treatment (ART) technique.

The purpose of the study was to evaluate, in a clinical study over 2 years, the deterioration of two glass ionomer cements used with the atraumatic restorative treatment (ART) technique or approach. Fifty-five Fuji IX and 45 ChemFil Superior restorations were placed randomly in 23 adult patients, mainly in small occlusal preparations in molar teeth. The restorations were placed in a dental hospital by one dentist using the ART technique. Photographs, radiographs and replicas were obtained at baseline and subsequent recalls. Both cements were easy to mix and place, but the radiolucency of ChemFil Superior was a disadvantage. Both cements also showed early high losses of sealant and restorative material. After 2 years, 34.5% of the sealants appeared to be completely lost, with caries recorded in 5.3% of the exposed fissures. In some instances, these small lesions may have been present, but not detected clinically, at the time of sealing. Restoration failures of 7.0% were from wear and fracture of the cements and recurrent caries. Mean cumulative wear was 83.1 microm for Fuji IX and 104.0 microm for ChemFil Superior, which was not statistically significant. The cements became darker after their placement to more closely match the restored teeth, but there were few exact matches. There was no surface staining and only minor marginal discrepancies and staining associated with the restorations. Although the short-term clinical performance of the two glass ionomer cements was reasonable, the materials require further improvements in their mechanical properties, to reduce sealant losses and wear. The cements evaluated appear suitable for restricted use only, in posterior teeth.

Adult↗

PubMed1999

Fluoride release and uptake by aged resin-modified glass ionomers and a polyacid-modified resin composite.

Little has been reported of the relationship of fluoride release and weight loss, and the effects of use of different fluoride agents on restorations, for the new generation of glass ionomer cements. The objectives of this study were to compare fluoride release of fresh and aged specimens of a polyacid-modified resin composite (Dyract), and of three resin-modified glass ionomer cements (Fuji II LC, Photac-Fil, Vitremer); and to correlate fluoride release and weight loss of aged specimens after recharging with three different fluoride agents. All materials showed high initial fluoride release immediately after uptake when using the agents. However, the levels of fluoride release dropped rapidly soon afterwards. Although initial fluoride release was significantly different between Dyract and the three resin-modified glass ionomers, when different fluoride agents were used on aged specimens after recharging, no significant differences were found after the first few hours. Linear regression analyses also showed no correlation between cumulative fluoride release and weight loss. Possible beneficial oral health effects may only be expected by frequent exposure of these materials to fluoride agents.

Acidulated Phosphate Fluoride↗

PubMed1999

2-year clinical performance of a resin-modified glass ionomer sealant.

PURPOSE: To compare the 2-year clinical performance of an experimental resin-modified glass ionomer cement sealant (K-512 = Fuji III LC) with that of a light-cured resin-based sealant (Delton Opaque) in young adults: MATERIALS AND METHODS: 14 subjects with 47 K-512 and 41 Delton sealants were recalled at 2 years for clinical examination, photographs after enamel etching, impressions and radiographs. RESULTS: K-512 showed 0% complete retention, 62% partial retention, and 38% nil retention. The corresponding percentages for Delton were 32%, 58% and 10%, respectively. There was one instance of fissure caries for K-512 and three for Delton. Sealants deemed to need retreatments because of retention failures were 62% for K-512 and 34% for Delton. The K-512 sealants continued to darken over the study, many becoming slightly darker than the sealed teeth.

Acid Etching, Dental↗

PubMed1999

Surface roughness and weight loss of esthetic restorative materials related to fluoride release and uptake.

The objective of this study was to assess the surface roughness of eight esthetic restorative materials and the relationship with weight changes during fluoride release and uptake. Five specimens each of ChemFil Superior, Fuji IX Dyract, Fuji II LC, Vitremer, Photac-Fil, Ketac-Silver, and Z100 (control) were prepared and immersed in 2 ml of artificial saliva at 37 degrees C. The changes in specimen weight and fluoride release were monitored for 12 weeks. This protocol was repeated after recharging the specimens with 1.23% APF gel for 12 more weeks. The immersed and fresh specimens for each material were then examined with SEM and surface profilometry. There was a significant weight loss for all glass ionomer cements following APF gel application (P < 0.01), which correlated with fluoride release (r = 0.89-0.98). Mean roughness (Ra) measurements and SEM showed that roughness increased from the resin composite to the conventional glass ionomer cements. The marked erosive effect of APF gel on glass ionomer restorations could increase surface colonization by plaque micro-organisms, and reduce the longevity of the restorations.

Acidulated Phosphate Fluoride↗

PubMed1997

Factors influencing long-term restoration survival in three private dental practices in Adelaide.

Very little is known of dentist and patient factors which may influence the survival or longevity of dental restorative materials placed in private practices. The present retrospective study investigated during 1992 the effects of six factors on the long-term survivals of five types of restorations placed by 20 male dentists in 100 adult patients, at 3 selected Adelaide dental practices. There were no significant effects on restoration survival from change, of dentist, and generally only one or two types of restorations had their survivals influenced significantly either by dental practice location, or by patient age, frequency of patient attendance, experience of dentist, and whether or not the restorations were replacements during the study period. Restoration survival was not influenced significantly by whether, or not, any replacements were made by the dentist who placed the initial restorations. The median survival times for amalgams were 22.52 years, resin composites 16.72 years, castings 13.75 years, and crowns an estimated 26 years. For glass-ionomers, 75 per cent were still present at 11.25 years.

Adult↗

PubMed1997

In vitro evaluation of sealing pits and fissures with newer glass-ionomer cements developed for the ART technique.

Four conventional glass-ionomer cements specifically developed for use with the atraumatic restorative treatment (ART) technique were compared with a resin-based sealant for marginal and surface dye penetration, material voids, and completeness of enamel fissure penetration. Thirty sound permanent mandibular molar teeth were randomly divided into five groups. After delayed placement of the glass-ionomer cement sealants using standardized finger pressure, and conventional placement of the resin-based sealant using a dental probe, the teeth were first thermocycled then the crowns immersed in methylene blue dye before being sectioned. There were no statistically significant differences found between any of the five materials, apart from less marginal dye leakage being present for the resin-based sealant than for one of the glass-ionomer cements. The cements, however, showed better fissure penetration than did the sealant. Despite the delayed placement and higher viscosity, all of the glass-ionomer cements showed satisfactory penetration of the enamel fissures and minimal marginal and surface dye penetration, and material voids, when placed using firm finger pressure. The cements could prove to be useful in the dental treatment of apprehensive children.

Analysis of Variance↗

PubMed1996

Factors affecting the amount of long-term restorative dental treatment provided to 100 patients by 20 dentists in 3 Adelaide private practices.

Apart from the effects of the frequency of patient attendance for dental examination, and of a change of dentist, little is known of those factors which may influence the amount of treatment provided in dental practice. The present study investigated during 1992 the effects of seven factors on the amount of treatment provided for 100 adult patients treated by 20 male dentists over many years in three selected Adelaide private practices. The amounts of particular types of restorative treatments provided were significantly related to patient age, gender and frequency of attendance, and to practice location, change of dentist and number of changes of dentist, and to the experience or time since graduation of the dentist. These factors were of special significance for the number of crowns provided, most of which were placed in older patients by more experienced dentists. But, there was no evidence of increased numbers of direct placement restorations being received by patients who attended more frequently or who changed their dentists.

Adult↗

PubMed1996

Long-term survival and cost-effectiveness of five dental restorative materials used in various classes of cavity preparations.

This retrospective study examined the survival and cost-effectiveness of five different types of dental materials used to restore various classes of cavity preparations in permanent teeth. Information on the restorations was obtained from the casenote records of 100 long-term adult patients treated at various times by 20 dentists in three city practices. Patients attended for checkups and restorative treatments on a regular basis for around 25 years on average, ranging from 10 to 46 years. All of the restorative materials lasted well, despite the frequent patient checkups and changes of dentists. Cusp-covered amalgams were approximately 3.8 times more cost-effective than were either cast gold or ceramometal crowns, and resin composites were approximately 3.7 times more cost-effective than were cast gold inlays for restoring Class IV preparations. However, there were no significant differences found in the cost-effectiveness of using either resin composites or glass-ionomer cements to restore Class III preparations, or between using either of these two materials, or amalgams, to restore Class V preparations.

Adolescent↗

PubMed1996

Handling and clinical performance of a glass ionomer sealant.

PURPOSE: To compare the handling and 6-month clinical performance of an experimental resin-modified glass ionomer cement (K-512 = Fuji III LC) with that of a light-cured resin-based sealant (Delton Opaque) when used as a pit and fissure sealant in 15-27 year old subjects. MATERIALS AND METHODS: Seventeen patients with 65 cement and 55 resin-based sealants were recalled after 6 months for clinical examination and color photographs. RESULTS: Sealant retention failures requiring retreatment were 74% for the glass ionomer cement sealant and 11% for the resin-based sealant, with one instance of fissure caries being found for each material. The resin-modified glass ionomer cement sealant showed a slight darkening from its initial placement, and was also more difficult to handle than the resin-based sealant.

Adolescent↗