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PubMed2003

Effect of sphered particles on the firing contraction of porcelain inlay processed by cold isostatic pressing.

The effect of the sphered particles on the contraction ratio of porcelain inlay processed by the cold isostatic pressure (CIP) method was investigated. The conventional lathe-cut porcelain powder was crushed to finer particles and the secondary particles with spherical shape by adding binders of acrylic resin, wax, and polyvinyl alcohol, respectively. Porcelain powder was molded as a disc-shaped green body in a refractory model and compressed at 200 MPa by CIP. From this green compact, the sintered porcelain was obtained by only one step of firing. The porcelain discs were then used for the measurements of contraction ratio, scanning microscopic observation, biaxial flexure strength, Vickers hardness, and density. Firing contraction was decreased to about 1% in the sphered particle groups, compared with 7% of the lathe-cut porcelain powder. Although biaxial flexure strength was about 85 MPa, which is lower than the 120 MPa of the control group, and the density was significantly decreased by about 10% from the 2.4 g/cm3 of the control substance, Vickers hardness, which ranged from 531 to 537, showed no significant differences among all of the groups. The CIP method could save labor in the process of making porcelain inlays, and sphered powders could contribute significantly to a decrease in the contraction ratio in the sintering process.

Biocompatible Materials↗
PubMed1989

Direct composite resin inlay.

Posterior composite resin restorations have several physical limitations. Polymerization shrinkage during curing and resistance to wear are two factors that can be alleviated by a composite resin inlay. Curing the restoration extraorally in a heat-and-light curing unit and cementing the restoration with a composite resin cement reduces the deleterious effects of polymerization shrinkage and increases wear resistance of the material. A method to make a direct composite resin inlay is detailed.

Chemical Phenomena↗
PubMed2003

Inlay fixed partial denture as a conservative approach for restoring posterior missing teeth: a clinical report.

Inlay fixed partial dentures luted by use of adhesive procedures offer a clinical alternative for the restoration of single missing posterior teeth. The introduction of ceromers and fiber-reinforced composites and the continuous improvement of adhesive systems and luting agents make this type of restoration possible, offering good aesthetic and functional results. The procedure is minimally invasive and conservative. This clinical report reviews the factors influencing the diagnosis and the clinical indications for an inlay fixed partial denture. In addition, a patient treatment is presented to illustrate the clinical procedures involved.

Adult↗
PubMed1991

Hardening of dual-cured cements under composite resin inlays.

This study was conducted to determine the extent of hardening of three dual-cured cements under composite resin inlays and to determine the effectiveness of a light-reflecting wedge in promoting curing of the cements in the proximal margin. The exposure times needed to optimally harden the cements were determined by directly exposing the cements to the curing light. Composite resin inlays were bonded in an extracted molar with Dual cement, Dicor light-activated cement, and Duo cement. Cure-Thru reflective wedges were placed in the gingival embrasure of half of the specimens. None of the cements hardened completely by 24 hours when we used an exposure time that met or exceeded that recommended by the manufacturers. The chemical-cure component did not completely cure the cements when light was attenuated by the tooth and restoration. The light-transmitting wedge had little effect on hardening of the cements.

Analysis of Variance↗
PubMed1996

Relative gap formation adjacent to ceramic inlays with combinations of resin cements and dentin bonding agents.

This study investigated the effect of combining dentin bonding agents (DBAs) with various resin cements on contraction gap formation at the cavity floor of resin-cemented ceramic inlays. Cylindrical dentin cavities were pretreated with one of five DBAs before luting of ceramic inlays with one of four dualcuring resin cements. Measurements of cross sections showed that mean gap widths were reduced from 46% to 93% compared with control specimens prepared without a DBA. The extent of the gap reduction was dependent on the type of bonding agent and resin cement. Although none of the resin cement-dentin bonding agent combinations tested were able to completely eliminate development of interfacial contraction gaps, some combinations produced considerable reductions in gap size.

Cementation↗
PubMed1996

Relative gap formation of resin-cemented ceramic inlays and dentin bonding agents.

The effect of dentin bonding agents (DBAs) on contraction gap formation at the cavity floor of resin-cemented ceramic inlays was investigated. Cylindrical dentin cavities were pretreated with one of 12 DBAs before luting of ceramic inlays with a dual-curing resin cement. Measurements of cross sections revealed that mean gap widths were reduced between 21% and 80% compared with control specimens prepared without a DBA. The extent of the gap reduction depended on the type of bonding agent. None of the dentin bonding agents tested were able to completely eliminate development of interfacial gaps.

Cementation↗
PubMed1997

Resin-bonded metal-ceramic inlays: a new approach.

With increasing demand for esthetics, dentists face the challenge of delivering definitive restorations that fulfill patients' expectations of esthetics, biocompatibility, and durability. Recent technical developments have encouraged fabrication of gold-reinforced porcelain inlays that meet these important criteria. This article describes a sequence to construct metal-reinforced porcelain inlay restorations.

Biocompatible Materials↗
PubMed2001

Current luting cements: marginal gap formation of composite inlay and their mechanical properties.

OBJECTIVE: The aims of this investigation were to investigate the effect of thermocycling on the marginal gap formation of composite inlays using three types of luting cements (Compolute, PermaCem, Fuji Plus, Panavia 21: as a control) and on mechanical properties of four luting cements. METHODS: The maximum marginal gap in the dentin cavity of each of ten resin inlay specimens in each group, was measured by a microscope before and after 10,000 thermocycles. The dimensional change, shear bond strength to dentin, and material and conditions for flexural strength and modulus testing were examined. RESULTS: Compolute and Panavia 21 showed marginal gaps of approximately 10 microm before thermocycling. In contrast, the gap widths after thermocycling was significantly wider. Although the gap widths of PermaCem and Fuji Plus were approximately 60-110 microm prior to thermocycling, they were significantly smaller in width after thermocycling. Statistical differences in the shear bond strength to dentin were not observed before or after thermocycling for all materials. The flexural strength and modulus were significantly increased after thermocycling compared with three products and with all four products, respectively. SIGNIFICANCE: The mechanical properties of all four luting cements were closely related to their marginal gap formations and these mechanical factors have important roles in determining their marginal gap formations.

Chi-Square Distribution↗
PubMed2002

Transformation-toughened zirconia for dental inlays, crowns and bridges: chemical stability and effect of low-temperature aging on flexural strength and surface structure.

OBJECTIVES: One concern, for transformation-toughened zirconia (Y-TZP) is their liability to low-temperature aging with accompanying alterations of properties such as strength. The loss in strength is attributed to the transformation of tetragonal grains to monoclinic. The transformation is related to loading of the dental inlays, crowns and bridges (reconstructions), temperature and time of exposure to surrounding media (aging) and the manufacturing process of Y-TZP. The purpose of this study was to determine chemical stability and effect of aging (4% acetic acid at 80 degrees C for 168 h) on flexural strength, surface and crystalline structures of two shades, P0 and P17, of a Y-TZP ceramic used for dental reconstructions. The hypotheses to be tested were that both shades of the dental Y-TZP ceramic have high flexural strength and chemical stability compared to other dental ceramics, and that the strength, surface and crystal structures of the ceramic were not affected by aging. METHODS: Forty specimens of Y-TZP, 20 of the shade P0 and 20 of the shade P17 were ground and polished. Ten specimens of each shade were exposed to low-temperature aging. The flexural strength of all 40 specimens was registered. Surfaces of the specimens were evaluated by using scanning electron microscopy (SEM), X-ray diffractometry and roughness recorder. The chemical solubility in 4% acetic acid was recorded by weight loss, and SEM was used to evaluate the surfaces of Y-TZP and dental feldspathic porcelain samples immersed in 8% SnF. Wilcoxon Signed Rank test was used for statistical analysis. RESULTS: As expected, the two shades, P0 and P17, of the studied dental Y-TZP had high strengths that were not affected by aging, and high chemical stability in the tested solutions. Contrary to what was assumed the crystal and surface structures of P0 and P17 were affected. Transformation from tetragonal to monoclinic structures occurred and small elevations on the ceramic surfaces were observed after aging. SIGNIFICANCE: The transformed-toughened Y-TZP ceramic used for dental inlays, crowns and bridges has high flexural strength compared to other dental ceramics and is chemically stable. The chemical solubility is well below the limit values of ISO 6872:1995 for dental ceramics.

Acetic Acid↗
PubMed1998

Margin quality of titanium and high-gold inlays and onlays--a clinical study.

OBJECTIVES: Unalloyed titanium may be an economical substitute for gold alloys. The purpose of this study was to evaluate the suitability of unalloyed titanium as an alternative to gold alloys for posterior inlay and onlay restorations. METHODS: Fifty-four patients received 99 titanium restorations, 56 patients 96 gold alloy restorations. All titanium restorations were cast in a vacuum-pressure casting machine. Two weeks after insertion the clinical margin integrity was evaluated by replica technique. The maximum marginal gaps were assessed under the optical measuring microscope. The two tailed t-test for independent samples was used for statistical analysis. RESULTS: Accuracy of fit was significantly better in gold alloy than in titanium restorations. Mean maximum marginal gap between restoration margin and tooth structure were 72 +/- 18 microns (mean +/- S.D.) for titanium and 64 +/- 18 microns (mean +/- S.D.) for gold restorations. SIGNIFICANCE: Though marginal gap widths in titanium restorations did not yet match the gold standard, the data justify the use of titanium as an alternative to gold alloy for inlay and onlay restorations.

Adolescent↗
PubMed2000

A finite element analysis of the stress at the restoration-tooth interface, comparing inlays and bulk fillings.

A finite element investigation comparing bonded inlays and directly placed restorations is presented. The stress build-up due to the contraction of the restorative composite and the composite luting cement was computed using a finite element model accounting for the time-dependent, elasto-visco-plastic behaviour of the composite. In addition, the stresses generated in the restoration due to occlusal loading were computed. It was found that inlays, in general, generate higher stresses during curing, particularly along the interface between the cement and the dentine at the base of the cavity. This is probably due to a reduced capacity for stress relief through viscous flow during the early stages of the curing reaction. Under occlusal load, restorations placed using both techniques perform similarly, from a purely mechanical point of view.

Dental Caries↗
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↗
PubMed1993

A comparison of two in vitro methods for assessing the fitting accuracy of composite inlays.

Composite inlays were fabricated in standardised cavities cut into aluminum and perspex blocks using a computer controlled milling process. Four materials were used to construct the inlays. These were fabricated using an indirect technique following the manufacturers' recommendations, where applicable. In addition, for one of the composites, the fabrication procedures were modified. The fitting accuracy of the restorations was assessed by taking elastomeric impression wash replicas of the luting space and by examination of sectioned restored units using image analysis. The former method indicated significantly reduced fitting accuracy when either use of die spacer or secondary curing was omitted from restoration construction resulting in incomplete seating. The sectioning technique indicated that more factors appeared to significantly reduce fitting accuracy including bulk packing, alteration in curing time, omission to die spacer and the final polishing procedure. This method also provided more specific information concerning sites of premature contact. One material gave rise to significantly greater film thicknesses using both methods of assessment. No direct correlation was found between the two techniques of fit evaluation but both methods taken together provided complementary information.

Acrylic Resins↗
PubMed1994

A survey of current practice into the use of aesthetic inlays.

In recent years there has been a concerted effort to produce an aesthetic restoration to replace amalgam, while retaining its qualities of strength and longevity. The use of porcelains and composite resins used indirectly as inlays and onlays has today improved the qualities of directly filled composites. A survey of 310 general dental practitioners in the UK known to use this type of restoration produced 162 responses to a questionnaire to evaluate their experiences to these techniques. The majority, 85%, had used a composite inlay system for about 2 years, with a 90% success rate over this period. Information collected provided details on variations in cavity design and cementing procedures.

Composite Resins↗
PubMed1999

Influence of polymerization initiator for base monomer on microwave curing of composite resin inlays.

Microwave polymerization was used to make composite resin inlays and the effect examined of the concentration of polymerization initiator for the base monomer. The monomers used were 2,2-bis [4-(3-methacriloxy-2-hydroxypropoxy) phenyl] propane (Bis-GMA) and triethyleneglycol dimethacrylate (TEGDMA). Bis-GMA and TEGDMA were mixed in a ratio of 6:4 by weight and were separated into five groups. To each group was added benzoyl peroxide (BPO) in the ratios of 0.1, 0.3, 0.5, 0.7 and 0.9 wt% as the polymerization initiator. These were used as the base monomers. The results showed that the degree of conversion of the cured sample increased with increasing concentration of BPO from 0.1 to 0.5 wt%, however there was no significant difference at 0.5, 0.7 and 0.9 wt% (P> 0.01). Compression strength, diametral tensile strength and the Knoop hardness showed a similar tendency as the degree of conversion. No significant difference was recorded in the Knoop hardness between the top and the bottom surfaces (P> 0.01), which suggested a uniform polymerization in the cured sample. Thus, microwave polymerization would be an efficacious method for making resin inlays with the addition of BPO to the base monomer (Bis-GMA:TEGDMA, 6:4). The maximum conversion was found at a concentration of 0.5 wt%.

Benzoyl Peroxide↗
PubMed2002

In vitro examination of the fracture strength of 3 different fiber-reinforced composite and 1 all-ceramic posterior inlay fixed partial denture systems.

PURPOSE: This in vitro study was carried out to examine the fracture strength of metal- free posterior inlay fixed partial dentures (IFPDs). The 3-unit IFPDs were made of either a polyethylene fiber-reinforced composite, 3 glass fiber-reinforced composites, or an all-ceramic material. MATERIALS AND METHODS: Eight IFPDs were fabricated of each material in accordance with the manufacturer's instructions and luted to extracted human molars with a dual-cure adhesive system. The molars were positioned in PMMA resin 10 mm apart mesiodistally. Inlay cavity preparations with enamel finishing lines were used. After thermal cycling and mechanical loading in an artificial oral environment, the cemented IFPDs were mechanically loaded until failure. Visual and radiologic examinations were done out to discern the different forms of fracture. Median and 25%/75% percentile values were calculated. Statistical analysis was performed using the Mann-Whitney U test and the Kruskal-Wallis test (p< or =0.05). RESULTS: With a median (and 25%/75% percentile) fracture strength of 368 N (234 N/424 N), the FibreKor/Conquest Sculpture showed significantly lower values than the Connect/BelleGlass [898 N (736 N/1033 N)], Vectris/Targis [723 N (692 N/806 N)], Everstick/Sinfony [634 N (532 N/673 N)], and Empress2 [520 N (385 N/706 N)]. CONCLUSIONS: Assuming maximum chewing forces of > or =500N in posterior areas, all systems showed sufficient fracture strength in most cases and warrant further investigation for potential clinical use.

Cementation↗
PubMed2001

The double-inlay technique: a new concept and improvement in design.

Gold and ceramic have long been used in prosthetic dentistry. In the posterior region, it is possible to use both materials with the double-inlay technique to add the strength of metal to the esthetics of ceramic. The problem, however, remains the volume of tooth reduction required to avoid ceramic fracture. This article describes a modification of the double-inlay technique that makes use of a pin system. This modified technique permits good retention while avoiding excessive tooth reduction.

Adult↗