Biomedical subjects

R J Smales

Publications and source records attributed to R J Smales.

At least 19 recordsLinked to original sources

PubMed2005

Radiation-induced root surface caries restored with glass-ionomer cement placed in conventional and ART cavity preparations: results at two years.

BACKGROUND: There are no published studies comparing the clinical performances of more-viscous glass-ionomer cement (GIC) restorations when placed using conventional and atraumatic restorative treatment (ART) cavity preparation methods to restore root surface caries. METHODS: One dentist used encapsulated Fuji IX GP and Ketac-Molar to restore 72 conventional and 74 ART cavity preparations for 15 patients who had received cervicofacial radiation therapy. Two assessors evaluated the restorations at six, 12, and 24 months for retention, marginal defects and surface wear, and recurrent caries. RESULTS: After two years, the cumulative restoration successes were 65.2 per cent for the conventional and 66.2 per cent for the ART cavity preparations, without statistical or clinical significance (P > 0.50). Restoration dislodgement accounted for 82.8 per cent and marginal defects for 17.2 per cent of all failures. There were no instances of unsatisfactory restoration wear or recurrent caries observed. Teeth with three or more restored cervical surfaces accounted for 79.3 per cent of all failures (P < 0.0001). CONCLUSIONS: For root surface caries restored with GIC, the use of hand instruments only with the ART method was an equally effective alternative to conventional rotary instrumentation for cavity preparation. Larger restorations had higher failures, usually from dislodgement.

Adult↗

PubMed2004

Long-term cost-effectiveness of single indirect restorations in selected dental practices.

OBJECTIVE: To determine the relative cost-effectiveness of alternative methods for restoring large tooth substance loss in adults. METHODS: Long-term survival estimates and discounted costs for 245 large indirect restorations were used to calculate their incremental cost-effectiveness over 15 years when compared with direct placement Class II cusp-overlay amalgams and Class IV multisurface resin composites, placed in 100 patients from three private dental practices. RESULTS: The direct placement restorations were more cost-effective than the indirect restorations at all time intervals over the 15-year study period. The full gold crown and the ceramometal crown were the most cost-effective indirect posterior and anterior restorations respectively. The cast gold onlay and the porcelain jacket crown were the least cost-effective indirect posterior and anterior restorations respectively. CONCLUSIONS: When clinically practicable, large direct placement restorations should be placed initially in preference to indirect restorations.

Adult↗

PubMed2004

Longevity of a resin-modified glass ionomer cement and a polyacid-modified resin composite restoring non-carious cervical lesions in a general dental practice.

BACKGROUND: Long-term prospective survival studies of resin-modified glass ionomer cements (RMGICs) and polyacid-modified resin composites (compomers) placed in non-carious cervical lesions (NCCLs) are lacking from general dental practice. Short-term studies have shown an unsatisfactory clinical performance for several materials. METHODS: One practitioner placed 87 compomer (Compoglass, Vivadent-Ivoclar) and 73 encapsulated RMGIC (Fuji II LC, GC Int.) restorations in NCCLs for 61 adults. Compoglass was placed using SCA primer, and Fuji II LC using GC Dentin Conditioner. No cavity preparation was undertaken. The Kaplan-Meier method was used for estimating the cumulative survivals for those restorations that were replaced, with the probability level set at alpha = 0.05 for statistical significance. RESULTS: Restorations were judged unsatisfactory (by the practitioner and the subjects) because of surface and marginal loss of material (68.8 per cent), dislodgement (18.8 per cent) and discoloration (12.4 per cent), these modes being similar for both materials (P = 0.35). Unsatisfactory restorations were replaced in 121 (75.6 per cent) instances. After periods of up to five years, cumulative survival estimates were 14.9 (5.8 Standard Error) per cent for Compoglass and zero per cent for Fuji II LC (P = 0.74). Median survivals were 30 months for Compoglass and 42 months for Fuji II LC. CONCLUSION: Both materials had high long-term unsatisfactory performances when placed in non-prepared NCCLs in a general dental practice.

Acrylic Resins↗

PubMed2004

Survival of glass ionomer restorations placed in primary molars using atraumatic restorative treatment (ART) and conventional cavity preparations: 2-year results.

OBJECTIVE: To compare the survival of glass ionomer cement (GIC) restorations placed in a dental clinic setting using both the atraumatic restorative treatment (ART) approach with hand instruments, and conventional cavity preparation with rotary instruments. METHOD AND MATERIALS: Two encapsulated high-strength conventional GICs (Fuji IX GP, Ketac-Molar Aplicap) were placed in 82 Class I and 53 Class II preparations and one encapsulated non-gamma 2 amalgam alloy (GK-amalgam) was placed in 32 Class I preparations, in the primary molars of 60 Chinese children with a mean age of 7.40 +/- 1.24 (SD) years. Thus, 9 treatment groups were formed. RESULTS: After two years, there were no significant survival differences found among 7 of the 9 treatment groups (p = 0.99). However, two groups comprising Fuji IX GP and Ketac-Molar Aplicap placed in Class II cavities prepared using the ART approach showed significantly lower restoration survivals (p < 0.001). Only 3 of the 72 initially sealed fissures adjacent to the restorations appeared to retain any GIC material. CONCLUSIONS: In a clinic setting, both the ART hand instrument and conventional rotary instrument methods were equally suitable for high Class I restoration survival, but not for Class II restoration survival where the conventional cavity preparation method was preferable.

Child↗

PubMed2004

Placement and replacement of dental restorations.

OBJECTIVE: To determine the types of various dental restorative materials used, and the reasons for the placement and replacement of dental restorations in 10 randomly selected polyclinics in Riyadh, Saudi Arabia. DESIGN: A cross-sectional descriptive study. PLACE AND DURATION OF STUDY: Ten selected polyclinics in Riyadh metropolitan area, Saudi Arabia during a period of two weeks in January 2003. PATIENTS AND METHODS: Information was collected by using a specially-designed form that was distributed to one dentist in each selected polyclinic. The dentists were asked to record specific details for all restorations placed in adult patients. Chi-square tests were used to analyze the data. RESULTS: Data were collected for 326 restorations. Amalgam (52.5%) was the most commonly used restorative material followed by resin composite (31.3%) and temporary restorations (14.4%), with a minimal use of glass ionomer cement (1.8%, p<0.001). Most of the restorations (69.9%) were initial placements, while 30.1% were replacement restorations, (p<0.05). Caries was the major reason for the initial placement (92.1%), and for the subsequent replacement (96.9%) of restorations. CONCLUSION: Amalgam and resin composite were the most commonly used restorative materials. Caries was the major reason for the initial restoration placements and subsequent replacements.

Adolescent↗

PubMed2002

Micro-tensile bond strengths to sclerotic dentin using a self-etching and a total-etching technique.

OBJECTIVES: To evaluate the in vitro regional micro-tensile bond strengths of a self-etching/self-priming adhesive system to sclerotic dentin, in the absence or presence of phosphoric acid conditioning. METHODS: Naturally-occurring, non-carious cervical lesions on extracted premolars were hand-cleaned with a slurry of pumice and chlorhexidine, then bonded without further cavity preparation. One group was bonded using Clearfil Liner Bond 2V (Kuraray Co. Ltd., Osaka, Japan). The other group was first conditioned with K-etchant; 40% phosphoric acid gel (Kuraray) prior to the application of the self-etching primer. Artificially prepared wedge-shaped cavities were also made in sound premolars and bonded with the two methods as controls. Resin composite build-ups were made using Clearfil Protect Liner F and AP-X resin composite (Kuraray). After storage in water for 24h, the teeth were sectioned into 0.7 x 0.7 mm composite-dentin beams along the occlusal and gingival walls, and at the apex of the lesions. The use of two conditioning methods, two substrate types, and three different locations yielded 10-14 beams for each of the 12 groups. After testing for the microTBS, representative beams that were stressed to failure were examined with SEM. Remaining fractured beams were demineralized and processed for TEM examination. Statistical analysis was performed using a three-way ANOVA and Student-Newman-Keuls tests. RESULTS: Regardless of the conditioning methods, bond strengths to sound dentin were significantly higher than to sclerotic dentin (P< 0.05). With sclerotic dentin, there was no significant difference for the conditioning methods used, except that K-etchant significantly improved the bond strength at the gingival aspect of the lesions. Fractographic analysis revealed that the self-etching primer could not etch beyond the surface hypermineralized layer of sclerotic dentin. Interfacial failure occurred along the surface of the mineralized intermicrobial matrix and/or hypermineralized layer. With the use of phosphoric acid, a hybrid layer was only seen when the surface layers were thin. Incompletely removed sclerotic casts were evident in both groups. SIGNIFICANCE: Removal of the surface layers of sclerotic dentin and/or conditioning with stronger acids may be beneficial to obtain stronger bonding to sclerotic dentin.

Acid Etching, Dental↗

PubMed2002

Glass ionomer cements used as fissure sealants with the atraumatic restorative treatment (ART) approach: review of literature.

AIM: To review the success of newer, more-viscous aesthetic conventional glass ionomer cements (GICs), that have been marketed specifically for the atraumatic restorative (ART) technique or approach, when used as pit and fissure sealants. As part of this approach, enamel fissures adjacent to the ART restorations are conditioned with poly (acrylic) acid (PAA) and then usually sealed with a GIC, using the finger-press method. RESULTS: The newer GICs appear in vitro to penetrate adequately and seal occlusal fissures in permanent molar teeth, and clinical studies of the ART approach over three years have found sealant retention (full and partial) to be approximately 70%, with fissure caries approximately 0-4%. In two studies, fissure caries was significantly reduced in sealed as compared with unsealed teeth over three years. CONCLUSIONS: Although the results appear to be better with the newer than with earlier conventional GIC products, the ART studies have generally involved populations at low-risk to caries, and further improvements in the mechanical properties of the cements are required for optimal long-term clinical success. Etching the enamel fissures with phosphoric acid, instead of conditioning with PAA, before GIC sealant placement warrants clinical investigation.

Acid Etching, Dental↗

PubMed2002

Restoration of teeth with more-viscous glass ionomer cements following radiation-induced caries.

OBJECTIVE: To assess the suitability of more-viscous conventional restorative glass ionomer cements (GICs) in a high-caries risk group of patients. METHODS: Fifteen adult patients with radiation-induced caries were treated at a dental hospital by one dentist. Two encapsulated aesthetic GICs were used in each patient to restore 146 carious lesions in the exposed dentine and cementum of 93 teeth. The restorations were assessed directly over two years for their retention, secondary caries, anatomic form, marginal integrity, marginal discolouration, and surface texture. RESULTS: Both GICs were placed in similar sized cavities (P = 0.63). After two years, although 30.0% of Ketac-Molar Aplicap and 12.5% of Fuji IX GP restorations had been lost (P = 0.01), there were no instances of secondary caries. The remaining GICs showed ongoing marginal deterioration, but there were very few instances where this required the repair or replacement of the restorations. No restorations failed from surface erosion. CONCLUSIONS: In these high-caries risk patients the placement of more-viscous GICs appeared to prevent secondary caries, even when the restorations were subsequently lost.

Adult↗

PubMed2001

Competency-based education in a clinical course in conservative dentistry.

The conceptual difference between a competency-based education and an education based upon a conventional dental curriculum is, perhaps, the starting point for the development of new curricula. The two systems are not, in themselves, exclusive. There is common ground to be found, and the concept of combining instruction with competency-based learning experiences is emerging in recent publications. This paper describes a competency-based approach applied to a clinical course in conservative dentistry. The learning outcomes of the fourth-year dental students in the new course were assessed using methods that included continuous clinical assessments, student presentations and peer-group reflective evaluations, patient management reviews, a clinical progress examination, the range and amount of work completed, and a written examination and viva voce. Different weightings were given to various elements of the assessment. A formal student assessment of the course rated it as being satisfactory.

Clinical Competence↗

PubMed2001

Occlusal wear of a resin-modified glass ionomer cement following three surface treatments.

Unacceptable occlusal wear has been reported for resin-modified glass ionomer cements (RMGICs) placed in permanent molar teeth. Three different surface treatments of a RMGIC were evaluated over periods of up to 2 years for their effects on restoration wear behaviour: (a) sealing with a thin layer of low viscosity unfilled resin (sealed restoration), (b) sealing with a thicker layer of a lightly-filled pit and fissure sealant (sealant restoration), and (c) co-curing the RMGIC with a posterior resin composite (co-cured restoration). After 2 years the cumulative median (quartiles) wear was for (a) 100 (50-150) microns, (b) 25 (0-50) microns, and (c) 25 (25-38) microns. Although method (b) effectively reduced the surface wear of the RMGIC, this treatment required frequent re-sealing, involving 52% of the restorations. Sealing the surface of a RMGIC placed in permanent molars was not a satisfactory method for reducing occlusal wear. However, co-curing the RMGIC with a posterior resin composite reduced occlusal wear significantly (P < 0.0001), without the need for frequent reapplications of a pit and fissure sealant to the RMGIC.

Adolescent↗

PubMed2001

Bonding of contemporary glass ionomer cements to dentin.

OBJECTIVE: The objective of this study was to investigate the microtensile bond strength (microTBS) of contemporary glass ionomer cements (GIC) to sound coronal dentin. METHODS: Three specimen teeth were prepared for each material tested: Fuji IX GP (GC), ChemFlex (Dentsply) and Ketac-Molar Aplicap (ESPE). GIC buildups were made according to the manufacturers' instructions. After being stored at 37 degrees C, 100% humidity for 24h, the teeth were vertically sectioned into 1x1mm beams for microTBS evaluation. Representative fractured beams were prepared for scanning (SEM) and transmission electron microscopic (TEM) examination. RESULTS: Results of the microTBS test were: Fuji IX GP (12.4+/-8.6MPa), ChemFlex (15.0+/-9.3MPa) and Ketac-Molar Aplicap (11.4+/-7.7MPa). One-way ANOVA and a multiple comparison test showed that ChemFlex had a statistically higher microTBS (p<0.05). SEM fractographic analysis showed that the predominant failure modes were interfacial and mixed failures. The GIC side of the fractured beams revealed dehydration cracks, a high level of porosity, and voids with an eggshell-like crust. TEM analysis of the demineralized dentin sides of the fractured beams revealed the presence of an intermediate layer along the GIC-dentin interface. This zone was present on the fractured dentin surface in the case of interfacial failure, and beneath GIC remnants in specimens that exhibited a mixed failure mode. SIGNIFICANCE: The findings suggest that the bonding of GIC to dentin is not weak and that the microTBS values probably represent the weak yield strengths of GICs under tension.

Acid Etching, Dental↗

PubMed2001

Fluoride release/uptake of conventional and resin-modified glass ionomers, and compomers.

OBJECTIVES: To assess the levels of fluoride ions released from a range of freshly-prepared aesthetic restorative materials, and then the effects of a topical acidulated phosphate fluoride (APF) gel. METHODS: Five specimens each of four conventional GICs, two resin-modified GICs, two compomers, and a resin composite (control) were assessed for their fluoride ion release over 6 weeks, before being exposed to 1.23% APF gel for 4 min and then measuring their fluoride ion levels for another 6 weeks. RESULTS: Following an initial brief, variable burst of fluoride ion release, the rates then fell quickly for most materials and, although high rates of fluoride ion release were measured immediately following the application of APF gel, these rates also fell quickly for most materials. After 12 weeks, the mean fluoride ion levels were much lower than immediately before gel application. The APF gel treatment caused surface damage to all materials, especially to the conventional GICs. CONCLUSION: The results of this study suggested that much of the increased fluoride ion release found following topical exposure of the fluoridated restorative materials to APF gel was caused by surface effects rather than by chemical recharging.

Acidulated Phosphate Fluoride↗

PubMed2001

The glass-ionomer phase in resin-based restorative materials.

Glass-ionomer (GI) fillers are added to restorative materials, but it is unclear if they truly react with these materials. This TEM study evaluated the existence of the GI phase in a conventional GIC (ChemFlex), a resin-modified GIC (Fuji II LC), a giomer (Reactmer Paste), a compomer (Dyract AP), and a composite (SpectrumTPH), before and after water uptake. Wafers were stored at 100% RH for 24 hrs, or in water for 7 or 84 days. ChemFlex glass particles were surrounded by 300-nm-thick silica gel layers. In Fuji II LC, we found thinner hydrogel layers (100 nm) that became thicker upon water storage. No appreciable change occurred in Reactmer Paste. Only a very thin hydrogel layer occurred in Dyract AP, and none was seen in SpectrumTPH after water storage for 84 days. We conclude that the variable extent of the GI phase is determined by differences in the resin composition of the restoratives.

Biocompatible Materials↗

PubMed2001

Assessment of clinical preparations for single gold and ceramometal crowns.

OBJECTIVE: Single-crown preparations at a dental teaching hospital were compared with guidelines advocated in the dental literature. METHOD AND MATERIALS: Sixty-three single complete gold crown and 151 single ceramometal crown preparations were evaluated. Impression silhouettes were measured for occlusal and axial wall tooth reductions, shoulder widths, internal shoulder angles, and axial wall convergence angles. Marginal designs, the presence of retention grooves and undercuts, and the types of cores present were also recorded. RESULTS: Cuspal reduction was generally inadequate for the ceramometal crowns, and central fossa reduction was insufficient for both complete gold crowns and ceramometal crowns. The facial shoulder widths were also generally underprepared for the ceramometal crowns. Axial wall convergence angles for both complete gold crowns and ceramometal crowns were generally much greater than recommended. Large faciolingual convergence angles for anterior ceramometal crowns were associated with the absence of cingulum walls. Few preparations had retention grooves or undercut areas. CONCLUSION: Although strict guidelines for tooth preparations for complete crowns are available and well known to dentists, the preparations in this study did not always conform to these recommendations.

Analysis of Variance↗

PubMed2001

Effect of different conditioning protocols on adhesion of a GIC to dentin.

PURPOSE: This study examined the ultrastructure and microtensile bond strength (microTBS) of a restorative glass-ionomer cement (GIC; Dentsply) to sound dentin that was conditioned with various techniques. MATERIALS AND METHODS: Dentin surfaces from extracted human third molars were abraded with 180-grit SiC paper. Five groups of three teeth each were prepared: C - no acid pretreatment (control); P - 10% polyacrylic acid (PAA) for 10 s, no rinsing; R - 10% PAA for 20 s, rinsed; K - 25% PAA for 25 s, rinsed; and H -32% phosphoric acid for 15 s, rinsed. TEM was performed on a bonded specimen from each group, using unstained, undemineralized sections. GIC buildups were made on the remaining teeth, and after storage at 100% humidity for 24 h, the teeth were sectioned for microTBS and SEM evaluation. RESULTS: TEM revealed the presence of a structure known as the intermediate layer in all groups. This layer contains metallic salts contributed by both the GIC and dentin. In group C, this layer was restricted to the smear layer. In groups P and R, intermediate layers could be found above partially demineralized zones within the intertubular dentin. In groups conditioned with more aggressive protocols (K and H), the intermediate layers shifted downward to reside within the superficial portions of completely demineralized collagen. Group C had statistically lower microTBS (p < 0.05), while the other groups were not significantly different from each other. SEM revealed adhesive failures along the dentin surface in group C and mixed failures in the other groups. CONCLUSION: The lower microTBS observed in the control group reflects the weakness of the smear layer attachment to dentin. The higher microTBS in the other groups probably represent the cohesive strength of GIC under tension, rather than its true adhesive strength to dentin. Acid pretreatment dissolves the smear layer, creates a zone of partially demineralized dentin, and allows the PAA to interact with dentin via the intermediate layer. Overly aggressive conditioning renders the dentinal tubules patent, and leaves deeper demineralized dentin that does not form part of the intermediate layer.

Acid Etching, Dental↗

PubMed2001

Computer-assisted learning (CAL) in undergraduate clinical dentistry: a review.

OBJECTIVE: To review the effectiveness of computer-assisted learning (CAL) in undergraduate clinical dentistry. METHODS: A review of dental and related medical literature was conducted using a selective MEDLINE search and by manual search. RESULTS: An attempt was made to evaluate the results of computer-based teaching methods in clinical dentistry, and the future. Analysis of several controlled studies showed equivocal learning improvements for CAL when compared with other teaching methods in clinical dentistry. However, CAL technology and appreciation of the standards required for effective learning programmes have changed considerably since these early studies were published. CONCLUSIONS: There is considerable potential for effective computer-based education in undergraduate clinical dental programmes, and the Internet can provide better access to such material. However, using newer technologies, further controlled studies of the learning effectiveness and cost-effectiveness of CAL in clinical dentistry are required.

Computer-Assisted Instruction↗

PubMed2000

Review of competency-based education in dentistry.

Dental education was previously structured in such a way that students largely learned what teachers chose to teach them. The aim was to produce a dentist with prescribed packages of knowledge upon graduation. This traditional approach was mainly disciplined-based. Increasingly, the current trend is towards competency-based education, which provides a sequence of defined learning experiences to students so that on graduation they may be considered as qualified beginners in dental practice. The adoption of competency-based learning requires the re-assessment and revision of old curricula, but there remains some common ground between traditional and competency-based education.

Competency-Based Education↗

PubMed2000

In vitro caries inhibition at the enamel margins of glass ionomer restoratives developed for the ART approach.

OBJECTIVES: To assess the ability of conventional glass ionomer cements manufactured specifically for the atraumatic restorative treatment (ART) approach to inhibit the in vitro demineralization of enamel. METHODS: Twenty-four sound permanent premolar teeth, extracted for orthodontic reasons, had cervical cavities (4x2x1. 5mm(3)) prepared in enamel. These were restored with Fuji IX, Fuji IX GP, Ketac-Molar and Compoglass, and then thermocycled 300 times between 5-55 degrees C before being placed in a demineralizing solution (0.1M lactic acid with 1g/l dissolved hydroxyapatite at pH 4.7) for four weeks. Buccolingual planoparallel sections were cut axially through the restorations, and subsequently lapped to approximately 100 microm thickness. The sections were examined with a polarized light microscope, and lesion measurements made using image analysis software. ANOVA and coefficients of variance were used to compare the findings. RESULTS: Compoglass and Ketac-Molar showed significantly less surface erosion than did the other two cements (p<0.0001). Inhibition of enamel demineralization immediately adjacent to the restoration margins was more frequent with the glass ionomer cements (20.5-25.0%) than with Compoglass (13.0%). However, the widths of the inhibition zones varied between materials and sites. CONCLUSIONS: Fluoride ion release from the restorative materials afforded some degree of protection to the adjacent enamel against in vitro demineralization.

Analysis of Variance↗