Temperature rise during photo-polymerization for onlay luting.

Purposes: (1) To measure the temperature rise during long-time irradiation needed to lute adhesive indirect restorations, with one halogen and five LED high-power lamps, in a simulated oral environment, and (2) to propose a technique to reduce heat.

Methods: Temperature within the pulp chamber of an extracted human molar in a 35 degrees C water bath, before and after restoration with a ceramic onlay, was continuously recorded during 3 x 120 seconds of irradiation for different curing regimens, with and without cooling by compressed air, water and water spray. Temperature rise in a thermo-insulated well was also measured during 120 seconds of irradiation with LEDemetron II and TuTu.

Influence of curing rate on softening in ethanol, degree of conversion, and wear of resin composite.

Purpose: To investigate the effect of curing rate on softening in ethanol, degree of conversion, and wear of resin composites.

Method: With a given energy density and for each of two different light-curing units (QTH or LED), the curing rate was reduced by modulating the curing mode. Thus, the irradiation of resin composite specimens (Filtek Z250, Tetric Ceram, Esthet-X) was performed in a continuous curing mode and in a pulse-delay curing mode.

Influence of curing protocol on selected properties of light-curing polymers: degree of conversion, volume contraction, elastic modulus, and glass transition temperature.

Objectives: The purpose of this study was to investigate the effect of light-curing protocol on degree of conversion (DC), volume contraction (C), elastic modulus (E), and glass transition temperature (T(g)) as measured on a model polymer. It was a further aim to correlate the measured values with each other.

Methods: Different light-curing protocols were used in order to investigate the influence of energy density (ED), power density (PD), and mode of cure on the properties.

Softening and elution of monomers in ethanol.

Objectives: The purpose of this study was to investigate the effect of light-curing protocol on softening and elution of monomers in ethanol as measured on a model polymer. It was a further aim to correlate the measured values with previously reported data on degree of conversion and glass transition temperature for the same polymer and curing protocols.

Methods: Different light-curing protocols were used in order to investigate the influence of energy density, power density, and mode of cure on the properties of a model polymer.

Effect of evaporation of solvents from one-step, self-etching adhesives.

Purpose: To investigate whether and to what extent the bonding capacity of one-step, self-etching adhesives is influenced by the degree to which solvent is evaporated.

Materials And Methods: Seven one-step, self-etching adhesives were tested (Adper Prompt L-Pop, Clearfil S3 Bond, Futurabond NR, G-Bond, Hybrid Bond, iBond, Xeno III). The variation in degree of evaporation was obtained by varying the duration of the air-blowing step.

Class I and Class II restorations of resin composite: an FE analysis of the influence of modulus of elasticity on stresses generated by occlusal loading.

Objectives: It was the aim of the study to analyze by the FE method stresses generated in tooth and restoration by occlusal loading of Class I and Class II restorations of resin composite. On the basis of available information on the influence of the modulus of elasticity, the research hypothesis was that the marginal stresses would decrease with increasing modulus of elasticity of the restoration.

Methods: A cylindrical tooth was modelled in enamel and dentin and fitted with a Class I or a Class II restoration of resin composite.

A survey of failed post-retained restorations.

Survival of endodontically treated, post-restored teeth depends on a multitude of factors, all of which are practically impossible to include in a randomized, controlled clinical study. The purpose of this survey was to characterize and analyze reported failures of post-retained restorations to identify factors critical to failure and to type of failure. A questionnaire was mailed to private practitioners in Denmark with a request to complete the questionnaire whenever a patient presented with a failed post-retained restoration.

Influence of curing rate of resin composite on the bond strength to dentin.

This study determined whether the strength with which resin composite bonds to dentin is influenced by variations in the curing rate of resin composites. Resin composites were bonded to the dentin of extracted human molars. Adhesive (AdheSE, Ivoclar Vivadent) was applied and cured (10 seconds @ 1000 mW/cm2) for all groups.

Class II restorations: influence of a liner with rubbery qualities on the occurrence and size of cervical gaps.

The aim of this study was to evaluate the ability of new rubbery liners, used as a cervical increment, to relieve contraction stress and thereby reduce the formation of cervical gaps in class II composite restorations. The investigated liners were made of polyester-acrylate (PE(1), PE(2) or PE(3)) or silicone-acrylate (S), mixed with UDMA, without (A, B, C, D) or with HEMA (AH, BH, CH, DH). A silanized filler was added to the mixture, DH, to give composites with 20, 40, 60, and 70% (w/w) of filler (DHF20, DHF40, DHF60, DHF70, respectively).

Bonding of dual-curing resin cements to dentin.

Purpose: The purpose of the study was three-fold: 1) to determine the strength of the bond between a number of dual-curing resin cements and dentin treated with corresponding adhesive systems, 2) to determine the effect on bond strength of not light curing the cements, and 3) to investigate whether application of a solution of sodium sulfinate or ascorbic acid would increase the bond strength in the cases where the manufacturer's version of an adhesive system resulted in low bond strength with chemically cured cement, ie, cement cured without light.

Materials And Methods: The adhesive systems comprised 5 simplified systems (Adper Scotchbond 1 XT, ED Primer II, Excite DSC, OptiBond Solo Plus, and Prime and Bond NT), and as controls, two three-step etch and rinse systems (Adper Scotchbond Multi-Purpose Plus and Gluma Solid Bond). The corresponding dual-curing resin cements were RelyX ARC, Panavia F 2.

Short- and long-term in vitro study of the bonding of eight commercial adhesives to normal and deproteinized dentin.

Objective: The aims of this study were to investigate the influence of deproteinization of dentin on the shear bond strength (SBS) mediated by eight dentin adhesives, and to evaluate the long-term durability of the SBSs. The hypotheses were that deproteinization of dentin would not affect the capacity for adherence, and that in contrast to the SBSs to collagen-rich surfaces, the SBSs to deproteinized surfaces would be stable during a 1-year period of storage in water.

Material And Methods: Ground surfaces of human dentin were either rinsed with water (normal dentin) or treated with sodium hypochlorite (deproteinized dentin).

Influence of eugenol-containing temporary cement on bonding of self-etching adhesives to dentin.

Purpose: To investigate the influence of eugenol-containing temporary cement on bonding of resin composite to dentin mediated by self-etching adhesives.

Materials And Methods: Flat dentin surfaces were produced by grinding of extracted human molars. The dentin surfaces were either used directly or after a one-week exposure to a zinc oxide-eugenol cement (IRM).

Bonding of resin cements to post materials: influence of surface energy characteristics.

Purpose: 1) To determine the surface energy characteristics of three variously treated post materials and two resin cements, and 2) to investigate if previously measured bond strengths between cements and treated posts could be related to the surface energy characteristics of the posts and cements.

Materials And Methods: The post materials were those of ParaPost XH, ParaPost Fiber White, and Cerapost, and the resin cements were ParaPost Cement and Panavia F. The post materials were surface treated by grinding, sandblasting, CoJet, or with Alloy Primer.

Polymerization contraction of resin composite vs. energy and power density of light-cure.

This study measured the polymerization contraction of a resin composite cured at three levels of energy density, each attained at six different levels of power density. The polymerization contraction of the composite was recorded by the method of the deflecting disc (n = 5) for 1 h following the start of irradiation. Power densities of 50, 100, 200, 400, 800 and 1,000 mW cm(-2), as measured on a dental radiometer, were obtained by variation of distance and supply voltage of a commercial light-curing unit.

Finite element analysis of stresses in endodontically treated, dowel-restored teeth.

Statement Of Problem: Endodontically-treated, dowel-restored teeth may experience fracture, but investigations of variables related to fracture are often inconclusive and occasionally contradictory.

Purpose: The finite element method was used to analyze the stresses in dowel-restored teeth. The variables studied were material, shape, bonding, modulus of elasticity, diameter, and length of the dowel.

Resin composite properties and energy density of light cure.

According to the "total energy concept", properties of light-cured resin composites are determined only by energy density because of reciprocity between power density and exposure duration. The kinetics of polymerization is complex, and it was hypothesized that degree of cure, flexural strength, and flexural modulus were influenced not only by energy density, but also by power density per se. A conventional resin composite was cured at 3 energy densities (4, 8, and 16 J/cm(2)) by 6 combinations of power density (50, 100, 200, 400, 800, and 1000 mW/cm(2)) and exposure durations.

Resin composites: strength of the bond to dentin versus surface energy parameters.

Objectives: The strength of the bond to dentin treated with two adhesive systems was investigated. The bond was tested with six resin composites. It was hypothesized that the surface energy parameters of composite and adhesive-treated dentin would influence the bond strength.

Resistance to cyclic loading of teeth restored with posts.

This in vitro study evaluated the effect of presence of post, presence of core, and of shape, type, and surface treatment of posts on resistance to cyclic loading of crowned human teeth. For all teeth, crowns designed without ferrule were cast in sterling silver and luted with resin cement (Panavia F). Each tooth underwent cyclic loading of 600 N at two loads per second until failure.

Temperature rise induced by some light emitting diode and quartz-tungsten-halogen curing units.

Because of the risk of thermal damage to the pulp, the temperature rise induced by light-curing units should not be too high. LED (light emitting diode) curing units have the main part of their irradiation in the blue range and have been reported to generate less heat than QTH (quartz-tungsten-halogen) curing units. This study had two aims: first, to measure the temperature rise induced by ten LED and three QTH curing units; and, second, to relate the measured temperature rise to the power density of the curing units.

Retention and failure morphology of prefabricated posts.

Purpose: This study evaluated the effect of cement, post material, surface treatment, and shape (1) on the retention of posts luted in the root canals of extracted human teeth and (2) on the failure morphology.

Materials And Methods: Posts of titanium alloy (ParaPost XH), glass fiber (ParaPost Fiber White), and zirconia (Cerapost) received one of several surface treatments-sandblasting, CoJet treatment, application of Metalprimer II, or sandblasting followed by silane application-and were then luted in the prepared root canal of human incisors and canines (n = 10). Following water storage at 37 degrees C for 7 days, retention was determined by extraction of the posts.

Flexural strength and modulus of a step-cured resin composite.

In an attempt to reduce marginal contraction gaps, a step-curing mode of light polymerization of resin composite has been proposed. It was hypothesized that such an exposure mode, having an initial reduced curing rate, would result in composite having a lower modulus of elasticity than composite exposed in one step. The composite was initially exposed to power density levels of 50, 100, 150, or 200 mW/cm2 for durations of 10, 20, or 40 s.

Bond strength of resin cement to dentin and to surface-treated posts of titanium alloy, glass fiber, and zirconia.

Purpose: To determine the effect of surface treatments on bond strength of two resin cements (ParaPost Cement and Panavia F) to posts of titanium alloy (ParaPost XH), glass fiber (ParaPost Fiber White), and zirconia (Cerapost), and to dentin.

Materials And Methods: After embedding, planar surfaces of posts (n = 9 to 14) and human dentin (n = 10) were obtained by grinding. The posts received one of three surface treatments: 1.

Effect of surface treatment of prefabricated posts on bonding of resin cement.

This in vitro study evaluated the effect of various surface treatments of prefabricated posts of titanium alloy (ParaPost XH), glass fiber (ParaPost Fiber White) and zirconia (Cerapost) on the bonding of two resin cements: ParaPost Cement and Panavia F by a diametral tensile strength (DTS) test. The posts received surface treatments in three categories: 1) roughening by sandblasting and hydrofluoric acid etching; 2) application of primer by coating with Alloy Primer, Metalprimer II and Silane and 3) a combination treatment in the form of roughening (sandblasting or etching) supplemented by the application of a primer or in the form of the Cojet system. After surface treatment, the post was embedded in a cylinder of resin cement (diameter = 4.

Determinants of in vitro gap formation of resin composites.

Objectives: To investigate whether polymerization shrinkage, flow, modulus, and bond strength influence marginal gap formation of resin composite restorations in vitro.

Methods: Eleven proprietary resin composites were studied. Shrinkage was measured by the 'bonded-disk method' (n=3).

Influence of specimen diameter on the relationship between subsurface depth and hardness of a light-cured resin composite.

In pilot studies of the relationship between subsurface depth and hardness of a light-cured resin composite, it was found that the resin composite was softer at a depth of 0.5 mm than at, for example, a depth of 1.0 mm.