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Biomedical subjects

N M Jedynakiewicz

Publications and source records attributed to N M Jedynakiewicz.

12 recordsLinked to original sources
PubMed2001

Expansion behaviour of compomer restoratives.

This study measured the dimensional changes due to hygroscopic expansion that occur in five commercially available compomer restorative materials using a computer-controlled laser micrometer. The materials tested were; [C] = Compoglass-F (Vivadent); [D] = Dyract AP (Dentsply DeTrey); [E] = Elan (Kerr); [F] = F2000 (3M); [H] = Hytac (Espe). Twelve discs of each test material were prepared, 10 mm diameter x 1 mm thickness. All specimens were kept dry for 48 h during polymerisation. Two control specimens of each group were kept in a desiccating chamber; five specimens in deionized water at 37 degrees C and five specimens in artificial saliva (Salivace, Penn) at 37 degrees C. The diameter of each disc was measured automatically across 200 points by rotation through the laser beam. These measurements, together with weight measurements, were carried out at intervals over a 2 month period. At 2 months, the mean % changes in volume after water immersion were: [C] = 2.45% (SD = 0.10); [D] = 1.50% (SD = 0.12); [E] = 1.53% (SD = 0.09); [F] = 1.69% (SD = 0.12); [H] = 1.44% (SD = 0.18). Specimens immersed in artificial saliva showed expansion rates identical to those immersed in water with the exception of material [H] at 1.73% (SD = 0.02) (p = 0.01). All specimens immersed in saliva showed a greater weight gain than those in water. The time taken to reach 90% of the final expansion varied from 7 days [F] to 50 days [H].

Compomers↗
PubMed2001

The effect of surface coating on the bond strength of machinable ceramics.

This study examined the nature of the surface presented by a machinable feldspathic porcelain and by a machinable glass-ceramic for bonding to conventional composite luting agents and measured the bond strengths which may be achieved with various surface treatments. There was no significant difference between the bond strengths achieved to etched porcelain, Silicoated porcelain or etched glass-ceramic. Silicoated glass-ceramic specimens showed a significantly higher adhesive assembly strength (p = 0.02). Examination of the fractured specimens showed that in all cases the failure involved part cohesive failure of the ceramic surface and part failure at the cement-ceramic interface.

Acid Etching, Dental↗
PubMed2001

Posterior restorations--a clinical view.

This paper examines the state-of-the-art in the direct restoration of posterior teeth. The existing paradigms for the management of caries are questioned and some existing methods of cavity preparation are reviewed. Dental restorations need to be durable but able to adapt to a changing environment brought about by wear of the adjacent tooth substance and by fatigue processes within the tooth itself. The wear of restorative materials needs to be matched to that of the tooth, otherwise differential loss of either the restorative material or the enamel may destabilize the occlusion. Esthetic instability due to natural darkening of the tooth with age, punctuated by clinical intervention with bleaching procedures, adds a further dimension to the concept of a permanent restoration. Clinical methods that minimize the disruptive effects of dental restorations upon the remaining tooth structure are a continuing challenge.

Bicuspid↗
PubMed2001

CEREC: science, research, and clinical application.

Computer-aided design/computer-aided manufacture (CAD/CAM), as embodied in the CEREC system, enables the fabrication of high-quality esthetic ceramic restorations chairside. Resin cements are used to complete the clinical process, providing a high-strength, stress-free adhesive assembly. The current generation of CEREC technology can be used to create restorations with a repeatable 50-micron adhesive interface width. Systematic analysis of the literature on clinical trials of CEREC restorations indicates a high level of clinical success. CEREC technology is compatible with contemporary, conservative cavity preparation design and limits pulpal trauma by completing complex restorations in a single visit. The occlusal form of CEREC restorations can be machined with full regard to the patient's occlusion, using functionally generated pathway recordings.

Ceramics↗
PubMed2000

Interface dimensions of CEREC-2 MOD inlays.

OBJECTIVES: To quantify the width of the cement interface between ceramic inlays generated by the CEREC-2 CAD-CAM system and the tooth, and to determine the effect of cement viscosity on the interface width. METHODS: Standardised MOD cavities were cut in 15 human premolar teeth using a custom paralleling device. A ceramic inlay was made with a CEREC-2 CAD-CAM machine for each tooth. The inlays were cemented using one of three resin-based composite systems of varying viscosity; a hybrid microfilled posterior composite, a compomer restorative and a dual-cure luting composite. The teeth were subsequently sectioned and measurements were taken at 21 key points with the aid of an image-analysis light microscopy system. RESULTS: Statistical significance tests were applied to examine for difference in interface dimensions at specific points within each of the cement-groups and amongst groups. The interface space at the occlusal walls has a distinct wedge shape, being narrower at the external interface (50 microns, SD 15) than internally (211 microns, SD 38). There is no statistically significant difference in the interface dimensions of the gingival floor between the boxes that lie above and below the CEJ. There is no statistically significant difference in the width of the interface at any given point between the three cement groups. SIGNIFICANCE: There is a significant improvement in the fit of CEREC-2 restorations when compared with the original CEREC system. Cements of varying viscosity (within the measured range) may be used for cementation of these inlays, without adversely affecting the width of the interface. Caution must be exercised with light-activated composite cements to ensure adequate transmission of light through the ceramic and the underlying composite cement.

Bicuspid↗
PubMed2000

The value of extended-setting-time amalgam in pre-clinical practice in undergraduate dental training.

This is a single-blind controlled study investigating the advantages of extended-setting time dental amalgam compared to a standard amalgam in the training of undergraduate dental students. 50 dental students were randomly assigned 1 of the 2 alloys for each restoration placed in the study. Each student placed class I and class II restorations in extracted human teeth mounted in typodont arches. 449 completed restorations were available for assessment, 228 restorations in the experimental group and 221 restorations in the control group. The test restorations were overall marginally inferior to those of the control group. There appears to be no advantage in using extended-setting time dental amalgam in undergraduate training.

Dental Amalgam↗
PubMed1999

Clinical performance of CEREC ceramic inlays: a systematic review.

OBJECTIVE: This systematic review of clinical trials seeks to identify the clinical performance of intra-coronal CEREC restorations luted with an adhesive composite technique. The focus of the review is to establish the survival rate of these restorations and to identify the factors that may cause them to fail. METHOD: A comprehensive literature search was undertaken, spanning from the year of introduction of the technology--1986 to 1997. This review identifies universal indicators of the clinical performance of intra-coronal CEREC restorations luted with an adhesive composite technique. Throughout the critical appraisal, each individual study was analysed identifying the aims, the methodology and materials used and the results obtained. RESULTS: 29 clinical reports were identified in the search. The systematic analysis reduced the focus of review to 15 studies. The data available establishes ceramic intra-coronal restorations machined by the CEREC system as a clinically successful restorative method with a mean survival rate of 97.4% over a period of 4.2 years. The review also highlights the reasons and the rates of failure for this type of restoration. The predominant reasons for failures are fracture of the ceramic, fracture of the supporting tooth, postoperative hypersensitivity and wear of the interface lute. SIGNIFICANCE: Machinable ceramics, as used by the CEREC system provide a useful restoration with a high success rate. These restorations are color stable and wear at a clinically acceptable rate. Wear of the luting composite on occlusal surfaces leads to the phenomenon of submargination. Ceramic fracture, wear at the interface and post-operative hypersensitivity remain a problem which require further investigation.

Ceramics↗
PubMed1999

Cuspal deflection during polymerisation of composite lutes of ceramic inlays.

OBJECTIVE: The purpose of this study was to measure the cuspal deflection that occurs in teeth as a result of the dimensional changes of resin-based lutes during polymerisation. METHODS: Standardised MOD cavities were cut in 15 intact human premolar teeth using a custom paralleling device. A ceramic inlay was machined by the CEREC 2 system for each tooth ensuring an interface width of 50 microns (SD = 17.5) at the cavity margin. The 15 teeth were divided into three groups of five according to the cementation system employed: a microfilled hybrid posterior composite; a compomer restorative; a dual-cure luting composite. The inter-cuspal tooth dimension was recorded continuously with a laser micrometer assembly during a 2 min photoactivation period and a further 30 min post-activation period. RESULTS: A clear overall reduction in tooth dimension was detectable for the first 10 min of polymerisation. The mean changes ranged from -0.02% to -0.06% depending on the nature of the luting material. In addition, all samples exhibited a slight expansion of 0.03% during the time of light-activation. CONCLUSIONS: The dimensional changes that teeth experience during the polymerisation of resin-based lutes are clearly detectable. It can be postulated that an increase in the dimensions of the teeth during photoactivation occurs as a result of expansion of the lute due to the thermal energy delivered.

Analysis of Variance↗
PubMed1992

A practical gloving and handwashing regimen for dental practice.

The debate concerning the re-use of gloves in dental practice continues, despite the fact that recent guidelines on cross-infection control recommend that a new pair of gloves should be used for each patient. Whichever policy for glove use is adopted, it is important to take the maximum possible precautions in hand care. This paper presents a practical regimen for hand/glove washing which is simple, quick and effective. The importance of establishing a hand-care regimen in dental practice is emphasised.

Cross Infection↗
PubMedDate not supplied

Practical gloving and handwashing regime for dental practice.

The debate concerning the re-use of gloves in dental practice continues, despite the fact that recent guidelines on cross-infection control recommend that a new pair of gloves should be used for each patient. Whichever policy for glove use is adopted, it is important to take the maximum possible precautions in hand care. This paper presents a practical regimen for hand/glove washing which is simple, quick and effective. The importance of establishing a hand-care regimen in dental practice is emphasised.

Cross Infection↗