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Biomedical subjects

A U Yap

Publications and source records attributed to A U Yap.

At least 37 records · Page 2Linked to original sources
PubMed1998

Influence of finishing time on marginal sealing ability of new generation composite bonding systems.

Although variation in finishing techniques has been shown to affect microleakage, little research has been published on the influence of finishing time on the marginal sealing ability of new generation composite bonding systems. The objective of the present study was to evaluate the influence of finishing time on the enamel and dentine marginal sealing ability of four new generation composite systems. Two class V preparations, which were solely in enamel or dentine, were made on the buccal surfaces of 96 freshly extracted molar teeth. The teeth were randomly divided into four groups of 24 and restored with composite resin (Silux Plus) utilizing the following bonding systems: Scotchbond Multi-purpose, Fuji Bond LC, Prime & Bond 2.0 and Bisco One-step. Half of the restorations in each group were finished immediately after light polymerization and stored for 1 week. For the remaining restorations, finishing was delayed for 1 week. The storage medium was isotonic saline at 37 degrees C throughout the experiment. All restorations were then thermocycled, subjected to dye penetration testing, sectioned and scored. The results suggest that the finishing of composite restorations, bonded with the bonding systems evaluated, should be carried out immediately after light polymerization. Delayed finishing does not improve but instead can be detrimental to the marginal seal of the restorations. The effects of delayed finishing are, however, both bonding system and tissue specific.

Analysis of Variance↗
PubMed1997

Post-irradiation hardness of resin-modified glass ionomer cements and a polyacid-modified composite resin.

This study examined the post-irradiation hardness of resin-modified glass ionomer cements and a polyacid-modified composite resin using a digital microhardness tester. Change in hardness of these materials over a period of 6 months was compared to that of conventional glass ionomer cements and a composite resin. With the exception of the composite resin, all materials showed a significant increase in hardness over 24 h after their initial set. Dual-cure resin-modified glass ionomer cements showed decreased hardness with increased storage time in saline at 37 degrees C. Results suggest that the addition of resins to glass ionomer cements does not improve initial hardness and does not negate the acid-base reaction of conventional cements. Resin addition may, however, lead to increased water sorption and decreased hardness.

Journal Article↗
PubMed1997

Reinforced glass-ionomer cements: the influence of conditioners on marginal leakage.

The purpose of this in vitro study was to evaluate the influence of conditioners on the enamel and dentine margin sealing ability of three different reinforced glass-ionomer cements. Two Class V preparations were made on the buccal and lingual surfaces of 36 freshly extracted molar teeth. Preparations were solely in enamel or dentine/cementum. The teeth were randomly divided into three groups of 12 and restored with either Ketac Silver (KS), Hi-Dense (HD) or Miracle-Mix (MM) with and without (-C) their respective conditioners. All materials were capsulated and were manipulated according to the manufacturers' instructions. The restorations were finished as recommended by the manufacturers and then stored in saline at 37 degrees C for 1 week, polished, thermally stressed, subjected to dye penetration, sectioned and scored. Rankings in the order of decreasing leakage were as follows: enamel margin KS > KS-C > HD-C > HD > MM > MM-C; dentine margin KS > HD-C > KS-C > HD > MM-C > MM. At the enamel margins, only HD showed a significant increase in leakage when conditioner was not used. At the dentine margin, however, KS had significantly more leakage than KS-C and HD-C had significantly more leakage than HD. There was no significant difference in leakage for MM both with and without conditioner. The influence of conditioners on marginal leakage appears to be both product and tissue specific.

Cermet Cements↗
PubMed1997

Comparative wear ranking of dental restorative materials utilizing different wear simulation modes.

The aim of this study was to compare the wear of seven different restorative materials using two different wear simulation modes. This included a non-impact sliding wear test (rotary pin and disc) and an impact-cum-sliding wear test (masticatory simulator). The difference in wear ranking between the two wear tests was compared as well as the correlation of wear to the hardness of the materials. Hardness ranking in the order of decreasing hardness was as follows: Dispersalloy (DA), P50 (P50), Hi-Dense (HD), TPH (TPH), Fuji II LC (FJ), Dyract (DR) and Vitremer (VM). For volumetric wear using the non-impact sliding test, the following ranking in the order of decreasing wear resistance was obtained: DA, TPH, DR, HD, VM, FJ, P50. The results for volumetric wear with impact-cum-sliding wear testing in the order of decreasing wear resistance were: TPH, DR, P50, AR, FJ, VM, HD. Results showed that there is no correlation between hardness and wear resistance. There is also no correlation between impact-cum-sliding wear and non-impact sliding wear. Impact wear should be considered in future two-body wear assessment of materials.

Composite Resins↗
PubMed1997

An in vitro microleakage study of the 'bonded-base' restorative technique.

Microleakage associated with a silver-reinforced restorative glass-ionomer cement (Hi-Dense) used with a composite resin (Z100) in a modified Class II bonded-base technique restoration was evaluated. The influence of long-term artificial saliva storage, thermal and load cycling was also determined. Class II composite (Z100) restorations used with a new dental adhesive system (Scotchbond Multi-Purpose Dental Adhesive) were used as controls. Results showed that the bonded-base technique can reduce the leakage observed with the direct composite technique. Thermocycling decreased the leakage at the composite-enamel interface but had no effect on the leakage at the composite-dentine interface or on the leakage patterns of bonded-base restorations. Load cycling had no significant influence on leakage patterns of either type of restorative mode. Storage in artificial saliva resulted in decreased leakage at the composite-enamel interface but had a minor adverse effect at the glass-ionomer-dentine interface.

Adhesives↗
PubMed1996

Resin-modified glass ionomer cements: a comparison of water sorption characteristics.

The purpose of this study was to quantify and compare the amount of water absorbed by six commercially available resin-modified glass ionomer cements and to investigate the possible influence of time and resin content on water sorption. The materials evaluated included Variglass used as a restoration, base and liner; Fuji II LC; Fuji Liner; Vitrebond; Vitremer and Photac-Bond. Z100, a composite resin, was used as control. All specimens were manipulated according to manufacturers' instructions and then subjected to a water sorption test based on the ISO 4049 requirements. Storage in water was further extended to 1 month to evaluate the effects of time and indirectly cement maturity on water sorption. Data were subjected to one-way ANOVA and Duncan's test at 0.05 significance level. Results show that the composite resin control had significantly less water sorption than all the resin-modified polyalkenoate cements evaluated. Variglass when used as a base or restorative had the least water sorption after both 1 week and 1 month storage in water. The degree of water sorption was product dependent and appeared to be influenced by the resin (HEMA) content. The results also reflect a potential relationship between time (cement maturity) and water sorption.

Absorption↗
PubMed1996

An in vitro microleakage study of three restorative techniques for Class II restorations in posterior teeth.

Microleakage associated with a silver reinforced restorative glass ionomer cement used alone and also as a laminate restoration with a composite resin and dentine adhesive in extracted premolar and molar teeth was evaluated. The influence of artificial saliva, thermal and load cycling was also determined. The composite and dentine adhesive alone were used for comparative purposes. The results showed that the composite resin/dentine adhesive restorations showed substantial microleakage at both the cervical and occlusal margins of the Class II restorations, whereas the glass ionomer alone showed little or no leakage after storage in water for seven days at 37 degrees C. These results were confirmed when the restorations were thermo-cycled and load stressed. The addition of glass ionomer as a base to the composite forming the laminate restoration reduced the leakage substantially and in certain conditions the leakage was less than that observed with glass ionomer restoratives alone.

Dental Leakage↗
PubMed1996

A cross-cultural comparison of perceived sources of stress in the dental school environment.

This study compared the perceived sources of stress in the dental school environment between an American and a South East Asian (Singapore) dental school across their entire curricula (D1-D4 years). The dental environmental stress (DES) questionnaire was administered to 137 (98 percent) Singapore dental students and results were compared to a previous study conducted at an American school. Significant differences were found for 12 questionnaire items across the four classes for the American cohort as compared to 13 in the Singapore cohort. While the greatest stressor for Singapore students was completing graduation requirements, American students were most stressed by examinations and grades. The overall perception of stress by Singapore students was higher than for their American counterparts. The primary concern for both cohorts was, however, related to the different areas of their academic courses.

Analysis of Variance↗
PubMed1996

An introduction to dental electronic anesthesia.

Dental electronic anesthesia, although still in its infancy, promises to be an increasingly effective adjunct for the management of dental pain. Electronic anesthesia is noninvasive, safe, and generally well accepted by patients. Electronic anesthesia can be used for a wide variety of operative, prosthodontic, and periodontal procedures and the management of some orofacial pain conditions including temporomandibular dysfunction. While it is unrealistic to expect electronic anesthesia to replace traditional local anesthetic, this method provides a feasible alternative in the dentist's pain control armamentarium in certain situations.

Anesthesia, Dental↗
PubMed1996

Electronic and local anesthesia: a clinical comparison for operative procedures.

The comfort on administration and effectiveness of electronic and local anesthesia for operative procedures, as perceived by clinicians and patients, were compared based on a 5-point Lickert scale, and a survey to solicit patient's feedback on the use of electronic anesthesia was conducted. Thirty patients, who required restorations on similar teeth bilaterally, and 10 clinicians were involved in the study. The two teeth in each patient were randomly restored under either electronic or local anesthesia. Administration of electronic anesthesia was perceived to be significantly more comfortable than that of local anesthesia, by both clinicians and patients. Local anesthesia was perceived to be significantly more effective by both evaluator groups, but 93.3% of the patients still preferred electronic anesthesia and would use it again. Minor after effects in some patients included redness of skin and briefly lingering sensation. All patients found electronic anesthesia easy to use, and most of the patients (93.3%) thought that the system was good to excellent.

Adult↗
PubMed1995

Resin-bonded prostheses.

This article reviews the uses, advantages, and disadvantages of the different types of resin-bonded prostheses. Resin-bonded prostheses can be used for tooth replacement as well as for occlusal, cosmetic, and orthodontic/periodontic therapy. Proper case selection is essential to their success. Although long-term clinical studies are not available for some of these types of prosthesis, they are generally promising and have become important elements in the provision of dental health care.

Dental Bonding↗
PubMed1995

Marginal sealing ability of three cervical restorative systems.

The purpose of this in vitro study was to evaluate the enamel and dentinal marginal sealing ability of three different cervical restorative systems. Class V preparations were made at the cementoenamel junction of 36 freshly extracted premolars. The teeth were randomly divided into three groups of 12 and restored with either a polyacid-modified resin composite ("compomer"), resin composite, or resin-modified glass-ionomer cement. The restored teeth were stored in saline at 37 degrees C for 1 week, thermally stressed for 500 cycles, and subjected to dye penetration testing. The results showed that there was no significant difference in dentinal margin sealing ability among the three materials evaluated. When the margins were in enamel, the resin composite restorations had significantly less leakage than did compomer or resin-modified glass-ionomer cement restorations. The marginal sealing ability of all three materials was significantly poorer in dentin than in enamel.

Analysis of Variance↗
PubMed1995

Shade match of tooth-colored restorative materials based on a commercial shade guide.

Many restorative materials are claimed by their manufacturers to match the Vita shade guide. To verify this claim, 40 dental personnel were asked to color match five different restorative materials to their respective Vita shade tabs according to a 5-point scale (1 = very poor color match; 5 = excellent color match). Three shades were chosen for each restorative material (a mid-Value shade as well as the highest Value shade and the lowest Value shade present in each system). Pooled scores indicated that the resin composite materials had significantly better overall shade match than did the other materials evaluated and that one resin-modified glass-ionomer cement had significantly better shade match than did the "compomer" and another resin-modified glass-ionomer cement. Only 11% of the scores for all material and shade combinations were given a good or excellent rating (score greater than 3). Shade match to the Vita shade guide was not material dependent but tended to differ among the different Value shades evaluated.

Analysis of Variance↗
PubMed1995

Cuspal coverage with resin-bonded metal onlays.

The use of resin-bonded onlays as a means of cuspal coverage is described with reference to two clinical cases. One distinct feature of this technique is the minimal tooth preparation required compared with that needed for a conventional crown or onlay. Conservation of the already compromised tooth tissue is thus achieved.

Bicuspid↗
PubMed1995

Non-carious cervical tooth loss: Part 1.

Non-carious cervical tooth loss is not always attributable to a single causative factor, as evidenced by the numerous terminologies used. In this, the first of two articles, the aetiology and prevalence of non-carious tooth loss are discussed. Guidelines are suggested as to how it may be diagnosed, prevented and monitored. A further article will cover the restorative management.

Adult↗
PubMed1995

Non-carious cervical tooth loss. Part 2: Management.

The aetiology, prevalence, diagnosis, prevention and monitoring of non-carious cervical tooth loss (NCTL) has been covered in the first article of this series. The aetiology of NCTL is usually multifactorial and may not be attributable to any single factor. Central to the successful management of NCTL is a correct diagnosis of the cause. This article will focus on the management of NCTL.

Composite Resins↗
PubMed1976

Pulmonary calcification in chronic renal failure: use of diphosphonate scintiscan as a diagnostic tool.

A patient with end-stage renal failure on maintenance hemodialysis for fifty-five months presented with signs and symptoms of cardiorespiratory failure and chest X-ray evidence of cardiomegaly and persistent bilateral nodular lung densities. A lung scan employing a bone seeking radionuclide, 99 Tc Diphosphonate, revealed active uptake in all areas corresponding to the X-ray densities. It was concluded that these densities represented active calcification. Thus, a diagnosis of pulmonary calcification was established without the need to resort to lung biopsy. It is suggested that bone-seeking radionuclides may be employed effectively to help establish an early diagnosis of pulmonary calcification especially in high risk dialysis patients.

Adult↗