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At least 649 records · Page 36Linked to original sources
PubMed1999

Marginal gap formation of light-activated base/liner materials: effect of setting shrinkage and bond strength.

OBJECTIVES: The purpose of this study was to compare the effect of setting shrinkage and the shear bond strength on the marginal gap formation in dentin cavities of commercially available light-activated base/liner materials during the early stage of setting, with those of chemical-cured base/liner materials. METHODS: The maximum marginal gap width and the opposing width in the dentin cavity was measured 30 min after the start of mixing. The setting shrinkage and shear bond strength to dentin was measured as the same procedure. To estimate the setting shrinkage, the maximum marginal gap width and the opposing width that occurred with materials placed in a Teflon cavity was measured. RESULTS: The two light-activated base/liner materials produced a significantly wider marginal gap than the chemical-cured base/liner materials (p < 0.05). There were no significant differences in the width of the marginal gap between the remaining five light-activated base/liner and chemical-cured base/liner materials (p > 0.05). The material that produced the smaller marginal gap width in the dentin cavity had a smaller marginal gap width in the Teflon cavity. There was a highly significant correlation between the two findings (r = 0.93, p < 0.01). However, shear bond strength to dentin had no effect on the marginal gap in the dentin cavity (r = 0.04, p > 0.50). SIGNIFICANCE: It appeared that the setting shrinkage of light-activated base/liner materials in the early stage of setting had a greater effect on the marginal gap formation in the dentin cavity than the bond strength to the dentin structure.

Analysis of Variance↗
PubMed2001

Plaque, gingival health and post-operative sensitivity in titanium inlays and onlays: a randomized controlled clinical trial.

OBJECTIVES: Few clinical data on the use of titanium for restorative appliances are available. The aim of this study was to clinically evaluate titanium restorations compared to gold alloy restorations with regard to plaque, gingival health and post-operative sensitivity. METHODS: In 54 patients, 99 titanium restorations were placed. The control group comprised 56 patients with 96 high gold alloy restorations. The material was chosen by random. Each patient received one or two Class II restorations. Plaque Index (Silness and Löe, 0-3), Gingival Index (Löe and Silness, 0-3), and post-operative sensitivity (1-4, 1=none) were rated at 2 weeks, 3 months, 6 months, 12 months, and 18 months, post-operatively. RESULTS: The mean plaque scores ranged from 0.89 to 0.99 in the titanium group, and from 0.88 to 1.04 in the gold group. The mean gingival scores ranged from 0.91 to 1.07 in the titanium group, and from 0.82 to 0.99 in the gold group. The mean plaque and gingival scores of the titanium and gold group did not differ significantly at any visit (P>0.05). To evaluate post-operative sensitivity, patients with one MOD restoration each were included, resulting in 46 titanium and 44 high gold restored teeth. Mean values of the post-operative sensitivity scores in the titanium group were significantly higher than in the gold group (P<0.05). The restoration material was found to be the dominating variable with regard to post-operative sensitivity, which was not influenced by age, sex and the application of calcium hydroxide liner. CONCLUSIONS: It is concluded that neither higher plaque scores nor adverse effects on gingival health are to be expected in titanium restorations.

Adolescent↗
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↗
PubMed1998

Effect of composite basing on the resistance to bulk fracture of industrial porcelain inlays.

OBJECTIVES: Bases are used in restorative dentistry for several reasons (i.e. isolation, elimination of undercuts, etc). Glass ionomers are the standard materials used as bases for porcelain inlays, despite the disadvantages of their mechanical properties. An alternative basing material is composite: a generous layer of posterior composite is cured and shaped in the cavity before an impression is taken. The composite basing technique has several clinical advantages. The aim of this study was to investigate the effect of the thickness of a composite base on the bulk fracture resistance of industrial porcelain, and to describe the procedure. METHODS: Fifteen porcelain (P) and 15 composite (C) bars, 1-, 2-, and 3-mm thick were joined to form 15 C/P bars, all 4-mm thick. Three groups were created: C 1 mm/P 3 mm (group 1), C 2 mm/P 2 mm (group 2), and C 3 mm/P 1 mm (group 3). The pairs were joined using Twinlook cement, subjected to a three-point bending test and loaded to fracture. The beam theory was used to support and explain the results. RESULTS: The fracture load means were: group 1, 197.7 +/- 18.7 N; group 2, 234.3 +/- 63.3 N, group 3, 336.3 +/- 31.3 N. Group 3 was significantly stronger than group 1 (P = 0.01) and group 2 (P = 0.03). Groups 1 and 2 were not statistically different. CONCLUSION: Composite basing is a tissue conserving method which may significantly increase the resistance to bulk fracture of adhesive porcelain inlays.

Acid Etching, Dental↗
PubMed1998

Decoloration of 1% methylene blue solution in contact with dental filling materials.

OBJECTIVES: Leakage studies have been performed frequently, since a tight seal provided by various dental fillings has been considered clinically important. The dye penetration experiment using a methylene blue solution as a tracer is one of the most common methods applied in these types of studies. The stability of the colour of methylene blue in contact with six dental filling materials was observed. METHODS: Silicon rubber tubes and human tooth roots of 10 mm in length and 1.5 mm inner diameter were filled with amalgam, calcium hydroxide, Cavit, Fuji II, mineral trioxide aggregate, or zinc oxide eugenol, 10 tubes or roots for each material. Groups of five tubes or roots filled with the same material were immersed in 0.8 ml 1% methylene blue dye solution. The optical density of the methylene blue solution before immersion and after 24, 48 and 72 h of immersion was measured in a spectrophotometer at 596 nm. RESULTS: The methylene blue solution was found to be decoloured over time by all the test materials (P < 0.01) except for Fuji II, in both silicone tubes and roots. At 24 h, the optical density value of methylene blue decreased by 73% for the Ca(OH)2/silicone group and 84% for the mineral trioxide aggregate/silicone group. CONCLUSION: Methylene blue is decoloured by some dental filling materials, which may result in unreliable results for these materials in dye leakage studies.

Aluminum Compounds↗
PubMed1998

Effect of a resin-modified glass ionomer liner on volumetric polymerization shrinkage of various composites.

OBJECTIVE: The aim of this study was to evaluate the volumetric polymerization shrinkage of a selection of composite resins alone, and in contact with a resin-modified glass ionomer (RMGI) liner. METHODS: Volumetric polymerization shrinkage was measured for five different composite resins by means of the Watts and Cash deflecting disk method. Shrinkage measurements were determined for 300 s for each composite alone, and when placed over pre-cured RMGI liner. Each sample was placed within a brass ring fixed to a glass microscope slide. A linear vertical displacement transducer (LVDT) was brought into contact with a flexible glass coverslip placed over the composite sample. On curing, the contraction of the setting composite sample caused distortion of the coverslip, the resulting deflection being recorded via the LVDT by means of data-logging software. All RMGI samples were prepared at 85% relative humidity (RH) and 35 degrees C. In all cases the composite was light-cured at ambient RH and 35 degrees C. RESULTS: Analysis of the data demonstrated statistically significantly less shrinkage for each composite when cured in contact with the set RMGI liner than when cured alone, at p < 0.001. SIGNIFICANCE: Use of an RMGI liner was found to significantly reduce volumetric polymerization contraction for all the light-curing composite resin restorative materials tested.

Analysis of Variance↗
PubMed1998

Cytotoxic effects of dental composites, adhesive substances, compomers and cements.

OBJECTIVES: Although research interest in biocompatibility of dental materials has been increasing, findings are frequently controversial and non-harmonized experimental approaches often lead to the production of contradictory results. The aim of this study was to compare the cytotoxic effects of six different light-cured dental composites, one compomer, one advanced glass-ionomer, two glass-ionomer cements, two zinc phosphate cements, one calcium hydroxide liner, one composite cement and one carboxylate cement with the same standardized cell-culture system. Two composites, one compomer and one advanced glass-ionomer were also tested in combination with the appropriate bonding substances and surface primers. METHODS: Specimens were added to the cultures immediately after production or after preincubation for 1, 2 or 7 days or 6 weeks under cell-culture conditions. Specimens were incubated with L-929 fibroblasts for 72 h and cell numbers determined by flow cytometry. RESULTS: All freshly prepared composite materials were cytotoxic. These effects diminished with increased preincubation times and were not significant after 7 days. Combinations of composites and bonding substances were still cytotoxic after preincubation for 7 days, but not after 6 weeks. Combinations of compomers and bonding substances demonstrated stronger toxicity than composites, although these effects were reduced earlier during preincubation. Glass-ionomer and phosphate cements showed similar effects to the composites with the exception of carboxylate cement, which demonstrated severe and persistent effects even after 6 weeks' preincubation. Together, our data provide evidence that all dental materials tested are cytotoxic immediately after production and that these effects are reduced after different preincubation periods in most cases. SIGNIFICANCE: Tested with a standardized cell-culture system, differences in toxicological potency between various commonly used dental materials were observed. Cytotoxicity data from standardized protocols should form the basis of screening the cytotoxic effects of new materials.

Adhesives↗
PubMed1999

Effect of a fluoride varnish on demineralization adjacent to orthodontic brackets.

Home fluoride regimens have long been used to reduce the amount of demineralization adjacent to orthodontic appliances. In the absence of patient compliance, another method of applying the fluoride must be used. The purpose of this study was to evaluate, in vitro, the ability of a fluoride varnish, Duraflor, to directly inhibit demineralization of enamel surrounding orthodontic brackets. Brackets were bonded to 36 extracted human canines and premolars with a traditional composite resin and randomly assigned to three equal groups of twelve. Group 1 served as the control with no topical application after bonding. Group 2 was treated with a single application of a nonfluoridated placebo varnish. Group 3 was treated with a single application of Duraflor. All groups were cycled in an artificial caries challenge for 1 hour two times daily for 37 days and were brushed with a medium bristled toothbrush to simulate mechanical wear of the varnish. Demineralization of enamel was evaluated in longitudinal buccolingual tooth sections using polarized light microscopy. Both average depth and area of demineralization were measured with a sonic digitizer. ANOVA (P </=. 0001) and Duncan's test (P </=.05) indicated significant differences in depth and area of demineralized enamel. Those teeth treated with Duraflor exhibited 50% less demineralization than the control teeth and an even greater difference when compared to the placebo group. Fluoride varnishes should be considered for use as a preventive adjunct to reduce enamel demineralization adjacent to orthodontic brackets, particularly in patients who exhibit poor compliance with oral hygiene and home fluoride use.

Analysis of Variance↗
PubMed1996

Healing of apical periodontitis in dogs after apicoectomy and retrofilling with various filling materials.

OBJECTIVE: To histologically assess the efficacy of various retrofilling materials in apical surgery. STUDY DESIGN: The pulps of mandibular premolars in seven beagle dogs were infected; this resulted in periapical lesions. Apical surgery was performed without disinfection of the root canals. Super EBA (Harry J. Bosworth Co., Skokie, III.), two formulations of glass ionomer cement, amalgam with varnish, IRM,(Caulk Co., Ltd., Densply International, Milford, Del.) and a light-cured composite resin were the retrofilling materials used. Roots infected and apicoectomized without retrofilling were positive controls. After 6 months the dogs were killed. The experimental roots and surrounding apical tissues were prepared and histologically examined and relative percentages of bone and inflammation were calculated. RESULTS: Super EBA was consistently the best. In overall periapical condition, Super EBA was statistically superior to all materials except IRM. IRM was superior to the glass ionomer cements but not the other materials. As to percentage of bone, Super EBA was the best overall; it was superior to glass ionomer, composite resin, and the positive control but not different from amalgam or IRM. When comparing remaining numbers of inflammatory cells, Super EBA was superior with the lowest number of inflammatory cells present. CONCLUSION: Although not statistically different from IRM, Super EBA was consistently the best retrofilling material tested when compared with all retrofilling materials studied.

Alveolar Process↗
PubMed2002

Modified Class II open sandwich restorations: evaluation of interfacial adaptation and influence of different restorative techniques.

The sandwich technique with resin-modified glass ionomer cement (RMGIC) has been proposed to relieve the contraction stresses of direct resin composite (RC) restorations. The aim of this study was to evaluate the interfacial adaptation to enamel and dentin of modified Class II open RMGIC/RC sandwich restorations and the influence of different light curing techniques and matrix bands. Forty box-shaped Class II fillings were placed in vivo in premolars scheduled for extraction after one month. In groups I and II, a metal matrix was used; RC was inserted with horizontal (group I) and diagonal (group II) increments and cured with indirect/direct light. Group III was performed as group II, but a transparent matrix was used. Group IV was as group II, but with a separating liner between RMGIC and RC. Group V was a closed sandwich restoration. Interfacial quality was studied using SEM replica technique. Gap-free interfacial adaptation to enamel was observed for RMGIC in 70%, for RC in 70% and to dentin for RMGIC in 81%, for RC in 56%. No significant differences were seen between the experimental groups. At the cervical margins, RMGIC showed significantly better adaptation to enamel than RC, 74% and 42%, respectively. In conclusion, the investigated restorations showed a high percentage of gap-free interfacial adaptation in vivo. Interfacial adaptation to dentin and to cervical enamel was significantly better for RMGIC than for RC.

Adolescent↗
PubMed2003

In vitro evaluation of marginal and internal adaptation after occlusal stressing of indirect class II composite restorations with different resinous bases.

Composite inlays are indicated for large cavities, which frequently extend cervically into dentin. The purpose of this study was to compare in vitro the marginal and internal adaptation of class II fine hybrid composite inlays (Herculite, Kerr) made with or without composite bases, having different physical properties. Freshly extracted human molars were used for this study. The base extended up to the cervical margins on both sides and was made from Revolution (Kerr), Tetric flow (Vivadent), Dyract (Detrey-Dentsply) or Prodigy (Kerr), respectively. Before, during and after mechanical loading (1 million cycles, with a force varying from 50 to 100 N), the proximal margins of the inlay were assessed by scanning electron microscopy. Experimental data were analysed using non-parametric tests. The final percentages of marginal tooth fracture varied from 30.7% (no base) to 37.6% (Dyract). In dentin, percentages of marginal opening varied from 9.2% (Tetric Flow) to 30.1% (Prodigy), however, without significant difference between base products. Mean values of opened internal interface with dentin varied from 11.06% (Tetric Flow) to 28.15% (Prodigy). The present results regarding dentin adaptation confirmed that the physical properties of a base can influence composite inlay adaptation and that the medium-rigid flowable composite Tetric Flow is a potential material to displace, in a coronal position, proximal margins underneath composite inlays.

Compomers↗
PubMed1999

An evaluation of sealant restorations after 2 years.

AIM: To obtain evidence of the efficacy of sealant restoration used in the management of fissure caries. DESIGN: A controlled study in a UK dental hospital environment. METHODS: Suspect fissure lesions were investigated in 164 young adult patients attending for routine dental care. Only one test tooth per subject was included in the study. Patients were recalled after 6, 12 and 24 months at which time the fissure sealant retention and the performance of the restorative materials were noted. RESULTS: Successful recall was achieved with 91.5% of patients. Most teeth treated (92%) involved the preparation of an investigative cavity. The mean age of patients treated was 23.9 years and second permanent molar teeth were the most commonly affected teeth requiring treatment in this age group. The presence of small composite restorations did not adversely affect fissure sealant retention but after 2 years, significantly more sealant was lost from the surface of light cured glass-ionomer cement and larger composite restorations. CONCLUSIONS: Sealant restorations provide an effective method of management of fissure caries in young adult patients.

Adult↗