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Biomedical subjects

A J Feilzer

Publications and source records attributed to A J Feilzer.

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

A radiographic and scanning electron microscopic study of approximal margins of Class II resin composite restorations placed in vivo.

INTRODUCTION: Clinical studies on the quality of Class II amalgam and resin composite restorations frequently report defective cervical margins. AIM: The aim of this study was to evaluate the quality of the approximal margins of Class II resin composite restorations placed in vivo using various application techniques and adhesive systems. MATERIALS AND METHODS: Class II restorations were placed in premolar teeth in vivo, using different adhesive systems and application techniques. After extraction of the teeth, the restorations were evaluated radiographically and by SEM. RESULTS: One-hundred and forty-four resin composite Class II restorations were evaluated. According to the radiographs, 4% of the restorations were overfilled and 33% were underfilled. SEM pictures revealed that 43% of the restorations were overfilled and 25% underfilled. Thirty-two per cent of the restored teeth showed a flash of bonding agent on the approximal surface. CONCLUSIONS: Class II resin composite restorations placed in vivo may be found frequently to show imperfect cervical margins. Overextended margins observed by SEM are difficult to detect on radiographs. When seen on a radiograph, a thick layer of bonding agent may be interpreted as an underfilled restoration.

Acid Etching, Dental↗
PubMed1998

Marginal integrity and postoperative sensitivity in Class 2 resin composite restorations in vivo.

INTRODUCTION: Problems that may arise in resin composite Class 2 restorations include microleakage and postoperative sensitivity. However, limited in-vivo research is conducted to evaluate these processes. AIM: The aim of this study was to assess postoperative sensitivity, microleakage and the pooling of adhesives in relation to Class 2 box-type composite restorations placed in vivo using various adhesive systems and application techniques. MATERIALS AND METHODS: One hundred and forty-four Class 2 box restorations were placed in the mesial and distal surfaces of 72 premolar teeth in-vivo using one of three combinations of adhesive systems and three filling techniques. After 6 weeks of clinical service postoperative sensitivity was recorded. The teeth were then extracted, immersed in a dye solution and sectioned. Microleakage and pooling of the adhesive was recorded. Statistical analysis involved logistic regression and chi2 tests to identify differences between groups at p < 0.05. RESULTS: Of the 144 restorations, 65 showed minimal cervical leakage in enamel, 5 suffered leakage into dentin and 74 were free of microleakage. No statistically significant differences were found in cervical microleakage between the adhesive systems or between filling procedures. Occlusal microleakage in the enamel was present in 16 of the 160 restorations. Liner Bond 2 restorations leaked significantly more at the occlusal surface (p < 0.05). Pooling of the adhesive was significantly less when PhotoBond was used. No spontaneous postoperative sensitivity was reported. Twenty-eight restorations were sensitive to loading. Postoperative sensitivity was significantly less in patients with Liner Bond 2 restorations. CONCLUSIONS: The adhesive systems used in this study showed minimal leakage into dentin in vivo. Using Liner Bond 2, restorations exhibited more occlusal leakage but were significantly less sensitive to loading.

Adhesives↗
PubMed1998

Class I occlusal composite resin restorations: in vivo post-operative sensitivity, wall adaptation, and microleakage.

PURPOSE: To investigate the effect of restoration technique and adhesive system on the post-operative sensitivity and marginal adaptation of Class I occlusal composite resin restorations placed in vivo. MATERIALS AND METHODS: 48 Class I cavities were restored in vivo according to one of three protocols: (1) Scotchbond Multi-Purpose/P50 placed in increments; (2) Scotchbond Multi-Purpose/P50 placed in bulk, and (3) Clearfil Liner Bond 2/Clearfil Ray Posterior placed in bulk. Post-operative sensitivity and sensitivity on loading were recorded 5-7 weeks after placement of the restorations; the teeth were cautiously extracted, immersed in a dye solution and sectioned. SEM observations were made from epoxy resin replicas. Microleakage and gap formation was assessed. RESULTS: No differences among adhesive systems or restoration procedures were found for microleakage. Post-operative sensitivity was reported in 14% of all teeth but was absent in the Clearfil Liner Bond 2 group. Sensitivity on loading was experienced by patients in 56% of the restorations. Group 1: nine teeth; Group 2: 15 teeth; Group 3: three teeth. Differences were statistically significant for all three groups. The SEM analysis showed that restorations placed in two layers showed less gaps than restorations placed in bulk.

Acid Etching, Dental↗
PubMed1997

The effect of curing light variations on bulk curing and wall-to-wall quality of two types and various shades of resin composites.

OBJECTIVES: This study evaluated the influence of light intensity and irradiation time variations on the curing efficacy of two types and various shades of resin composites and the effect of reduced light intensity on the preservation of wall-to-wall continuity. MATERIALS AND METHODS: Three microfilled composites (in three different shades) and one hybrid composite were used in this study. Polymerization shrinkage, and the hardness and adaptation of adhesive restorations in dentin cavities were determined at light intensities of 175 and 700 mW/cm2 and irradiation times of 10 and 60 s. Data were compared using in a general linear model analysis. RESULTS: Shrinkage measurements were the indication of conversion and conversion rate. Reduced intensity slowed down the rate of polymerization but did not reduce the conversion as long as an irradiation time of 60 s was employed. High-energy irradiation caused increased separation of the composite from the tooth structure. On the basis of obtaining optimal conversion and adaption, it was demonstrated that the irradiation time to be more effective than irradiation energy. SIGNIFICANCE: Light-cured composites require an understanding of their structure, pigmentation and irradiation parameters to obtain optimal performance. High intensity light-curing does not necessarily lead to optimal quality.

Analysis of Variance↗
PubMed1997

Sealing ability of eight resin bonding systems in a Class II restoration after mechanical fatiguing.

OBJECTIVE: The purpose of this in vitro study was to evaluate eight different adhesive systems to determine whether functional loading affects the marginal integrity of Class II restorations. METHODS: In 80 extracted upper human premolars, Class II cavities were prepared and restored with eight different commercially available adhesive resin restorative systems. The occlusal margins were located in enamel and the gingival margins in dentin. During immersion in a dye solution, half of the restored teeth were exposed to a load-cycling procedure, after which all the specimens were sectioned, and the extent of dye penetration was visually examined using a stereo microscope. The results were analyzed statistically using the Mann-Whitney U-test and Wilcoxons Rank test. RESULTS: Exposure of the restorations to load cycling significantly reduced the marginal integrity cervically. Perfect sealing was found practically at all occlusal margins. Significant differences (p < 0.05) were found in the cervical sealing quality of the various adhesive systems. SIGNIFICANCE: The results of this study show that functional loading damages the cervical marginal seal of adhesive Class II restorations. For many adhesive systems, the setting shrinkage stress alone was not able to damage the marginal integrity cervically. Therefore, mechanical fatiguing distinguishes the sealing quality of adhesive systems in a more expressive way. There is a substantial difference in sealing quality between the various resin restorative systems tested.

Bite Force↗
PubMed1997

Polymerization contraction stress in thin resin composite layers as a function of layer thickness.

OBJECTIVES: In the present study, the effect of layer thickness on the curing stress in thin resin composite layers was investigated. Since the value of the contraction stress is dependent on the compliance of the measuring equipment (especially for thin films), a method to determine the compliance of the test apparatus was tested. METHODS: A chemically initiated resin composite (Clearfil F2, Kuraray) was inserted between two sandblasted and silane-coated stainless steel discs in a tensilometer. The curing contraction of the cylindrical samples was continuously counteracted by feedback displacement of the tensilometer crosshead, and the curing stress development was registered. After 20 min, the samples were loaded in tension until fracture. The curing stress was determined for layer thicknesses of 50, 100, 200, 300, 400, 500, 600, 700 microns, 1.4 mm and 2.7 mm. The compliance of the apparatus was calculated with the aid of a non-linear regression analysis, using an equation derived from Hooke's Law as the model. RESULTS: None of the samples fractured due to contraction stress prior to tensile loading. The contraction stress after 20 min decreased from 23.3 +/- 5.3 MPa for the 50 microns layer to 5.5 +/- 0.6 MPa for the 2.7 mm layer. The compliance on the apparatus was 0.029 mm/MPa. SIGNIFICANCE: A measuring method was developed which was found to be suitable for the determination of axial polymerization contraction stress in this films of chemically initiated resin composites. The method makes it possible to estimate the stress levels that occur in resin composite films in the clinical situation.

Analysis of Variance↗
PubMed1997

Influence of compliance of the substrate materials on polymerization contraction stress in thin resin composite layers.

The present study determined in a laboratory set-up the influence of compliance of the substrate material on polymerisation contraction stress for various thicknesses of bonded dental resin composite films. When the compliance of the tensilometer set-up was increased from 0.029 micron MPa-1 to 0.150 micron MPa-1, the contraction stress in films with a thickness of 100 microns and a diameter of 5.35 mm decreased from 22 to 7 MPa. For the 700 microns samples the stress decreased from 12 to 11 MPa. It was concluded that if compliance from the substrate materials is possible, a thinner resin composite film may effect a more reliable bond.

Chemical Phenomena↗
PubMed1997

Polymerization shrinkage and polymerization shrinkage stress in polymer-based restoratives.

OBJECTIVES: This paper is intended to contribute to the recognition and understanding of problems related to polymerization shrinkage. DATA SOURCES: Scientific publications of relevance with regard to this subject were critically reviewed. STUDY SELECTION: The dimensional changes which develop during the curing of resin composites and glass polyalkenoate cements are studied, with special reference to methods of determining shrinkage, shrinkage stress and stress relief. CONCLUSIONS: As no method for handling the adhesive restorative materials has yet been described which guarantees a leakproof restoration, the practitioner has to accept the problem of polymerization shrinkage and destructive shrinkage stress. Only a proper understanding of the mechanisms that cause these problems and the techniques that may reduce their effects will enable the practitioner to derive maximum benefit from the application of resin composites and glass polyalkenoate cements in restorative dentistry.

Composite Resins↗
PubMed1995

The influence of water sorption on the development of setting shrinkage stress in traditional and resin-modified glass ionomer cements.

OBJECTIVES: The aim of this study was to determine the setting stress development for some traditional and resin-modified glass ionomer cements and to assess the effect of early water exposure to this stress. METHODS: The development of the setting stress of the glass ionomer cements was determined in a tensilometer set-up as described earlier by Feilzer et al. (1987). RESULTS: The results of this study show the influence of water sorption on the development of setting shrinkage stress in bonded glass ionomer cements. When curing took place under isolated conditions (no hydration or dehydration), all the traditional glass ionomer cements investigated fractured spontaneously, either adhesively and/or cohesively, due to the developing stress. Early exposure to water led to stress relief and prevented spontaneous fracturing. For the light-cured products, no spontaneous failures were observed under isolated conditions. Stress relief due to water sorption reversed the contraction stress into an expansion stress. SIGNIFICANCE: Exposure of traditional glass ionomer cements to water at an appropriate time by the use of permeable matrix systems is advised. Whether the conversion of contraction stresses into expansion stresses as observed for the resin-modified products, is beneficial for a restoration requires further study.

Absorption↗
PubMed1995

Influence of light intensity on polymerization shrinkage and integrity of restoration-cavity interface.

The results of this study showed that the use of high intensity curing light units negatively affected the integrity of the restoration-cavity interface in class V restorations This is explained by the high reaction rates of light curing resin composites. The interfacial integrity was better preserved with low light intensity as it extends the visco-elastic stage of the setting materials, thereby moderating the setting stress development. The ultimate polymerization shrinkages for both conditions were equal, which suggested equal degrees of conversion and thus equal material properties. The results may alleviate the trend in using higher intensity light curing units and in particular the development of units with laser beams in an attempt to further increase conversion rates.

Composite Resins↗
PubMed1995

Tensile strength of thin resin composite layers as a function of layer thickness.

As a rule, cast restorations do not allow for free curing contraction of the resin composite luting cement. In a rigid situation, the resulting contraction stress is inversely proportional to the resin layer thickness. Adhesive technology has demonstrated, however, that thin joints may be considerably stronger than thicker ones. To investigate the effects of layer thickness and contraction stress on the tensile strength of resin composite joints, we cured cylindrical samples of a chemically initiated resin composite (Clearfil F2) in restrained conditions and subsequently loaded them in tension. The samples had a diameter of 5.35 mm and thicknesses of 50, 100, 200, 300, 400, 500, 600, and 700 microns, 1.4 mm, or 2.7 mm. None of the samples fractured due to contraction stress prior to tensile loading. Tensile strength decreased gradually from 62 +/- 2 MPa for the 50-microns layer to 31 +/- 4 MPa for the 2.7-mm layer. The failures were exclusively cohesive in resin for layers between 50 and 400 microns thick. Between 500 and 700 microns, the failures were cohesive or mixed adhesive/cohesive, while the 1.4- and 2.7-mm layers always failed in a mixed adhesive/cohesive mode. For the resin composite tested, the contraction stress did not endanger the cohesive strength. It was concluded that if adhesion to tooth structure were improved, thinner adhesive joints might enhance the clinical success of luted restorations.

Composite Resins↗
PubMed1993

Setting stresses in composites for two different curing modes.

As a continuation of a study into the development of the polymerization shrinkage stress of chemically initiated composites (CC), the development of the polymerization shrinkage stress of light-initiated composites (LC) in relation to the configuration-factor was determined. During setting, the LC composites generated a higher polymerization shrinkage stress, developed higher cohesive strength to resist this stress and showed less flow than their CC analogues. Trying to find a comprehensive explanation for the differences in behavior of stress development in LC and CC composites, the effect of mixing-in of porosity was also investigated on LC composites. Mixing-in of porosity slowed down and decreased the shrinkage stress development. This was attributed to either oxygen inhibition due to admixed air or to an increase of free surface from the presence of pores within the bulk of the composite.

Composite Resins↗
PubMed1993

True linear polymerization shrinkage of unfilled resins and composites determined with a linometer.

A device, which was given the name "linometer", has been developed for measuring linear polymerization shrinkage of both unfilled resins and composites. The results were in agreement with those obtained with the mercury dilatometer. The present method is simple, fast, insensitive to temperature fluctuations, is operational at any temperature and, if desired, samples can be maintained in a 100% relative humidity environment. The linometer offers an easy means for routine polymerization shrinkage determinations and therefore may be useful in evaluating new monomer systems for dental composites. The linear polymerization shrinkage for several unfilled resins and composites was measured with this device.

Acrylic Resins↗
PubMed1992

The influence of polymerization shrinkage of resin cements on bonding to metal.

During the setting of a resin composite cement (RCC) used as an adhesive between a resin-bonded bridge and tooth structure, the adhesion may be disrupted by the development of shrinkage stress. The aim of this study was to investigate the influence of the shrinkage stress of three different RCCs on their adhesive and cohesive qualities when bonded to metal surfaces in a rigid set-up. Two opposing parallel NiCr discs (Wiron 77) were mounted in a tensilometer at a mutual distance of 200 microns and cemented with Panavia Ex, Clearfil F2, or Microfill Pontic C. The alloy surfaces were treated by either electrolytic etching, sand-blasting, silane-coating, or tin-plating. During setting, the discs were kept at their original mutual distance to simulate the extreme clinical situation of "complete" rigidity, where the casting and the tooth cannot move toward each other. The developing shrinkage stress was recorded continuously. During setting, the adhesive strength of the RCCs to silane-coated surfaces was always higher than their early cohesive strength. Electrolytically-etched surfaces as well as sand-blasted surfaces showed, in almost all cases, adhesive failure. The tin-plated samples showed mainly adhesive failure at the metal/resin interface. The highest bond strength values were found for silane-coated surfaces in combination with Clearfil F2.

Acid Etching, Dental↗
PubMed1992

The dependence of shrinkage stress reduction on porosity concentration in thin resin layers.

The development of polymerization contraction stress was determined as a function of the surface area of porosity, so that the contribution of voids in resin composite to stress relief could be investigated. Experiments were carried out on 200-microns-thick layers of resin bonded from wall to wall in a restrained condition. The resin samples were divided into three groups: Group A was without porosity, group B contained a small number of pores, and group C contained a large number of pores in comparison with group B. For each group, porosity area, maximal stress, and stress development rate were determined. The mean maximal stress and stress development rate were inversely proportional to the mean porosity surface. These characteristics differed significantly (p less than 0.01) between group A and C. For determination of whether shrinkage stress reduction has to be ascribed to flow from the outer surfaces of the voids or to inhibition of the setting reaction by oxygen in the voids, resin containing only nitrogen bubbles was also tested. The results indicated that both aspects contributed substantially to shrinkage stress relief. Incorporation of pores by the stirring of a luting cement contributes to stress reduction and can therefore be considered as a contribution to the maintenance of marginal integrity.

Analysis of Variance↗