Clinical and SEM study of Tetric resin composite in posterior teeth: 12-month results

Thirty-nine conventional posterior composite fillings were placed according to the three-sited light curing technique using Tetric, a fine hybrid composite material, and Syntac, a dentin adhesive. Six and 12 months later, the restorations were clinically evaluated using macrophotographs. A quantitative marginal analysis was also done immediately after placing the restorations and at the two recall intervals using a replica technique and an SEM. Contour, secondary caries, postoperative sensitivity and bulk fractures all rated "A" at 12 months. Marginal discoloration and color match were scored as 97% "A" and 3% "B". The SEM evaluation of the marginal adaptation showed 95% "continuous margin" initially and 93% at 6 months and 89% at 12 months. No statistical difference was found between the initial findings and the 12-month recall between premolars and molars, nor between small and large restorations. The overall performance of the new composite material during the 12-month observation period was satisfactory.

Marginal castability of two different materials (a comparative study)

Achieving a clinically acceptable margin is a conspicuous objective to any practicing dentist. The main concern is the space existing between the margin of the prepared tooth and that of the final restoration. Marginal fit has been measured and evaluated in a variety of methods., and a gap of approximately 50 microns is usually considered acceptable. While inlay wax is the material commonly used in the wax-up stage when fabricating crowns and bridges, Duralay (methylmethacrylate) is a material widely used nowadays in the field of fixed prosthodontics. Due to the ease of using this material intra-orally to form margins, an attempt is made to compare the castability of margins made out of inlay wax to the ones made out of Duralay.

Confirmation of Leinfelder clinical wear standards

OBJECTIVES

Accuracy of composite wear studies based on Leinfelder standards has been disputed. There are differences with other well-calibrated systems such as the M-L and Vivadent wear standards. The objective of this study was to reevaluate the margin height at key regions along the restoration margins for each of the 6 Leinfelder standards using laser profiling techniques.

METHODS

The Leinfelder standards were profiled in parallel paths 100 microns apart and measured in x-y-z position every 20 microns along those paths using a laser profilometer.

RESULTS

Rounding of cavosurface enamel margins from intraoral wear greatly increased the uncertainty of the true enamel margin location and step height measurements, precluding unequivocal measurements for standards #2 and #3. Values for other standards for the original report, newly measured means and standard errors, and measured ranges were: #4 (322 microns, 333 +/- 34 microns, 171-507 microns), #5 (382 microns, 459 +/- 44 microns, 202-649 microns), and #6 (493 microns, 584 +/- 91 microns, 315-1022 microns). There were no statistically significant differences (p < or = 0.10) between these and original values. Large standard errors may have obscured small differences that may exist. The Leinfelder cast conversion scale seems to be the correct relative magnitude.

SIGNIFICANCE

Differences between Leinfelder casts and other standards may be due to differences in shadow production. Clinical wear may be systematically underestimated by other cast evaluation methods that have well-defined margins. This emphasizes the need for standard casts with margin morphology similar to the clinical casts being evaluated for wear.

Assessment of three different methods of tissue dilation for ceramometal restoration

Tissue dilation is one of the key factors in obtaining accurate duplication of subgingival finishing lines and hence excellent marginal adaptation of the restoration. Elastic impression materials do not displace the tissue. Therefore, the tissue must be displaced away from the prepared teeth or a small ribbon of the free gingiva must be removed to expose the finishing line before making the impression.

Adaptability and microleakage of indirect resin inlays: an in vivo investigation

The purpose of this in vivo study was to evaluate the microleakage of indirect composite resin inlays and to determine the thickness of composite resin luting material. Twenty periodontally involved posterior teeth scheduled for extraction were selected and Class II cavities were prepared. Ten cavities had gingival margins placed in enamel above the cementoenamel junction, and the other 10 were placed in dentin below the cementoenamel junction. Six months after cementation, the teeth were extracted and analyzed. The leakage was higher in inlays with gingival margins in dentin than in inlays with gingival margins in enamel. The cement thickness was between 15 and 40 microm, a clinically acceptable range.

Class II direct composite resin restorations with beta-quartz glass-ceramic inserts

With the increasing demand for esthetic posterior restorations, numerous techniques have been developed. The direct resin restoration has probably been used most extensively in Class II situations. Problems with Class II direct resin restorations include difficulty in developing proximal contact, occlusal wear, and polymerization shrinkage. Beta-quartz glass-ceramic inserts have been developed in an attempt to reduce the incidence of these potential problems. They can be placed in a one-appointment technique, are relatively inexpensive, and can readily be utilized by the clinician adept in placing Class II composite resin restorations.

Ceramic-fused-to-metal restorations with a new CAD/CAM system

Experience has shown that a cast restoration will rarely have proper occlusal contacts. One possible solution could involve the application of a computerized design and fabrication system for restorations with accurately calculated and computer-milled occlusal surfaces. The Cicero system for the production of ceramic-fused-to-metal restorations makes use of optical scanning, nearly net-shaped metal and ceramic sintering, and computer-aided crown fabrication techniques to fabricate restorations with maximal static and dynamic occlusal contact relations. The Cicero system produces crowns, fixed partial dentures, and inlays with different layers, such as metal and dentin and incisal porcelains, for maximal strength and esthetics. Fabrication of a crown for a mandibular first molar is described to demonstrate the computer-based design system.

Evaluation of the porcelain laminate veneers as a new esthetic and reconstructive modality

Veneers are being used for the esthetic improvement of anterior teeth, and porcelain veneers are a recent development in this field. This article will described briefly the porcelain laminate technique and attempts to evaluate it as a new esthetic and treatment modality. Though there are some shortcomings yet the advantages afforded by this system are considerable enough to make the technique deserving of further investigation.

Microleakage of resin-modified glass ionomer cement restorations: an in vitro study

Microleakage of two resin-modified glass ionomer cement (GIC) restorative materials was compared with that of two conventional GIC restorative materials. Forty-five noncarious extracted human molars were prepared with standardized Class V cavity outlines on the buccal and lingual surfaces. The occlusal margin was in enamel and the gingival margin was in dentin/cementum. All were restored according to the manufacturers' instructions. After thermocycling, 30 teeth were placed in 2% basic fuchsin dye for 24 h, sectioned and viewed with a stereomicroscope to assess microleakage. The other 15 teeth were sectioned, replicated and prepared for marginal gap evaluation using a SEM. Differences in microleakage scores between materials were compared using Kruskal-Wallis and Mann-Whitney U tests. One resin-modified GIC restorative material showed significantly less microleakage against enamel and dentin/cementum compared to the conventional GIC restorative (p < 0.01). Marginal gap formation for both resin-modified GIC restorations was limited to the axial wall of the restorations.

Marginal distortion of metal-ceramic restorations during the porcelain firing procedure

The fit of a metal-ceramic casting deteriorates during the firing of a porcelain facing. Although many factors have been reported as the cause of these distortion phenomena, studies of marginal distortion associated with firing metal-ceramic restorations have yielded mixed results. The effect of firing cycles on distortion of a metal-ceramic coping was examined on 0.5 mm thick palladium-copper copings with shoulder marginal finish lines. It was found that the distortion produced in the first stage of firing was greater than at other stages. The marginal distortion seen on the porcelain veneered margin was not significantly different from the distortion on the non-veneered margin. These two results demonstrate that thermal contraction stresses due to porcelain contraction are probably not the primary cause of coping distortion. The internal surfaces of the copings were examined for contamination with porcelain particles and porcelain contamination was detected with an energy dispersive spectrometer analysis. The distortion produced during the porcelain veneering procedure was due to porcelain contamination on the internal surfaces of the copings. A convenient method is necessary to remove porcelain from the internal surfaces of completed restorations.

Shear bond strength, microleakage and scanning electron microscopy study of the Clearfil Liner Bond System

Various adhesive systems have been introduced for enamel and dentine bonding and one of the newer systems available recently is the Clearfil Liner Bond System. This investigation was to determine the shear bond strength, evaluate the microleakage and conduct SEM examinations of this new bond system. The results showed it was possible to obtain a mean shear bond strength of 17.45 MPa to human dentine. Microleakage was minimal at the cementum/dentine margin and no microleakage was observed at the enamel margin of resin restorations placed with the system. SEM examinations revealed minimal to significant resin penetration into dentinal tubules.

Effect of different types of finishing lines and etching methods of the enamel and dentin on the marginal integrity of Hi-ceram crowns

Porcelain is one of the oldest materials used in the dental field. It has the advantages of perfect shade reproduction, chemical and abrasion resistance and biologic compatibility to the oral tissue. The only drawback of dental compatibility to the oral tissue. The only drawback of dental porcelain is the occurrence of brittle fracture. Minute cracks formed on the outer surface of the porcelain crown are the cause of the fracture. These cracks are formed during cooling of the ceramic as a result of low thermal conductivity of the porcelain. Differential dimensional changes of the outside and the internal surface take place inducing the cracks. Tensile stresses on the internal surface of the porcelain lead to cracks propagation and fracture.

Microleakage of posterior composite resin restorations using beta quartz glass-ceramic inserts

The effectiveness of using beta quartz glass-ceramic inserts in Class II composite resin restorations to prevent microleakage at the gingival cementum margins was investigated. Class II cavities were prepared on both mesial and distal sides of ten extracted teeth with the gingival margins placed on cementum. Both cavities were then restored with a composite resin in exactly the same manner, except that one received a glass ceramic insert and the other did not. The specimens were then thermocycled in basic fuchsin solution, embedded in epoxy resin and sectioned. The extent of dye penetration at the gingival cementum margins was then assessed and scored. The result indicated that the use of a glass-ceramic insert substantially reduced the microleakage of gingival cementum margins of composite resin restorations.

Clinical evaluation of four dental amalgams over a three year period

The aim of this study was to compare the clinical durability of four dental amalgams. In each of eighty-two patients one class 2 cavity was restored with Dispersalloy (Johnson and Johnson) which served as the control and all the other class 2 cavities were randomly restored with one of the following amalgams: Amalgaphase, Amalga 43 (Amalgam Alloys-South Africa) or Permite C (Southern Dental Industries). Matrix bands were placed and Kalzinol bases and Polyvar varnishes applied in all cavities. The amalgams were mixed according to the manufacturers' instructions, the cavities overpacked with amalgam, condensed by hand, carved and then burnished with a ball burnisher. Twenty-four hours later all restorations were polished and colour photographs taken. The restorations were evaluated using the Ryge and Snyder (1973) evaluation system, as well as comparison of the colour photographs. The Fisher's Exact Test was used for the statistical analysis. The two South African manufactured amalgams compared well with the two imported amalgams. However, at the end of the third year the score for the marginal integrity of Amalgaphase, one of the local products, was significantly different (p < 0.083) and inferior to that of the control, Dispersalloy. Evidence is produced to suggest that over a three year period Amalgaphase performed better than Dispersalloy, Amalga 43 and Permite C.

Effect of surface-penetrating sealant on composite wear

The wear resistance of posterior composites has improved dramatically over the last several years. Compared to the original formulations, many of the currently available composites exhibit wear rates of less than 10% of their early predecessors. Nevertheless, much research has been directed toward improving this property to a higher level. This investigation deals with a surface-penetrating sealant designed to increase the wear resistance and marginal integrity of posterior composites. In conjunction with a recently developed three-bodied wear testing device. it was shown that the effectiveness of this surface-penetrating sealant depends upon the mean particle size. Those composites in which the mean particle size is greater than 1 micrometer undergo nearly 40-50% reduction in wear. The wear of composites containing submicron-sized filler particles was not affected by the surface-penetrating sealant. Finally, regardless of the particle size of the composites, the surface-penetrating sealant enhanced marginal integrity.

The dimensional accuracy and stability of composite inlays

The dimensional accuracy and stability of two composite inlay materials was studied by assessing polymerisation shrinkage, thermal expansion and water sorption. Impression taking, die accuracy and stability and wear of the material were also considered. The mean coefficients of thermal expansion (20 to 65 degrees C) determined using a differential dilatometer were: Clearfil 21 X 10-6 and Isosit 31 X 10-6. A metal die similar to that used by Taylor in 1931 to assess casting shrinkage of gold inlays was used to assess polymerisation shrinkage. Isosit had a mean protrusion value of 0.321 mm providing a value for linear polymerisation shrinkage of 0.9%. In contrast Clearfil specimens had a mean protrusion of 0.108 mm providing a value for linear polymerisation shrinkage of 0.3%. The expansion due to water sorption at seven days was very small and did not offset the polymerisation shrinkage. However, these must be interpreted in light of the results of long term immersion studies. The total dimensional change of an Isosit specimen is -1.06%. For an inlay of 5 mm in diameter the linear dimensional change would be 54 micrometers, providing a cement space of 27 micrometers. The total dimensional change of a Clearfil specimen is -0.53%. For an inlay of 5 mm in diameter the linear dimensional change would be 27 micrometers, providing a cement space of 13.5 micrometers.

Clinical evaluation of four dental amalgams over a two year period

The aim of this study was to determine the clinical durability of two locally manufactured amalgams. In each of eighty-two patients one class II cavity was restored with Dispersalloy (Johnson and Johnson) which served as the control and all the other class II cavities were randomly restored with one of the following amalgams: Amalgaphase, Amalga 43 (Amalgam Alloys-South Africa) or Permite C (Southern Dental Industries). Matrix bands were placed. Kalzinol bases and Polyvar varnish were applied in all cavities. All amalgams were mixed according to the manufacturers' instructions. The cavities were overpacked with amalgam, and the amalgam condensed by hand, carved and then burnished with a ball burnisher. Twenty-four hours later all restorations were polished with a Shofu polishing system and colour photographs were taken. The restorations were evaluated using the Ryge and Snyder (1973) evaluation system, as well as comparison of the colour photos. The Fisher's Exact Test was used for the statistical analysis. During the second year there were no significant (p < 0.05) differences between the four brands of amalgam restorations except as regards the gloss category. The two South African manufactured amalgams compared well with the two imported amalgams. During the second year the marginal integrity and surface texture of Amalgaphase compared well with that of Permite C. Dispersalloy and Permite C showed more deterioration in anatomic form than the two South African amalgams. Amalgaphase was the only amalgam to show no bulk fracture within a period of two years. Amalgaphase performed better in the gloss category than the other three amalgams during the second year evaluation. According to the weighted product calculation Amalgaphase was the best amalgam followed by Dispersalloy, Amalga 43 and Permite C.