PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “DENTAL RESTORATION, PERMANENT”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources
PubMed1995

Fatigue resistance of composite restorations: effect of filler content.

OBJECTIVES: The purpose of this study was to evaluate the effects of filler level on the fatigue impact resistance of resin composite. METHODS: A series of experimental composite materials was prepared by incorporating a silanized quartz filler (3-5 microns in size) into a light-cured resin matrix of Bis-GMA/TEGDMA. The filler contents in the experimental composites varied from 40 to 85 wt%. The composites were placed in standardized Class I cavities prepared in bovine teeth. The specimens were stressed with a repetitive impact load (1.6 x 10(2) joule) with loading cycles ranging from 50,000 to 150,000 times. The cracks induced by cyclic loading were observed on the sectioned surfaces of the tested specimens. RESULTS: The composites with considerably low or high filler content (< 60% or > 80% by weight) were significantly low in fatigue resistance. The results revealed that an inverse linear relationship tended to exist between filler level and fatigue resistance of the composite materials beyond a certain level of filler content. SIGNIFICANCE: Increased filler level does not necessarily improve the fatigue resistance of a resin composite as determined by applying a repetitive impact load.

Animals↗
PubMed1995

Fracture toughness of water-aged resin composite restorative materials.

OBJECTIVES: The purpose of this study was to assess the effects of aging experimental dimethacrylate resin composites in water at 37 degrees C for periods up to 6 wk by measuring the variations in fracture toughness (K(c)), elastic modulus (E), fracture energy (G(c)), and water sorption. METHODS: Six experimental resins were formulated from dimethacrylate resins, and were filled to 86 wt% (ca. 70 vol%) with treated inorganic filler to form six experimental composites. The fracture toughness was determined using a double torsion technique, the elastic modulus was measured in flexure, and the fracture energy was calculated from the fracture toughness and elastic modulus. RESULTS: As a result of aging in water, K(c) and the G(c) increased, and the elastic modulus decreased, but all values approached a plateau near 6 wk. Water sorption also occurred during this period, mainly during the first 2 wk. SIGNIFICANCE: Variations in the mechanical properties are interpreted as being due to plasticization of the resin matrix by water, which appears to lower the yield stress and increase in the size of the plastic zone ahead of the crack, thereby causing the observed increase in G(c) and K(c). After approximately 6 wk, no further changes in properties occurred.

Absorption↗
PubMed1995

A new technology for direct restorative alloys.

OBJECTIVES: The purpose of this study was to develop a new technology for preparing mercury-free metallic dental restorative materials. METHODS: The novel approach relies on the cold welding of surface treated silver particles. At ambient temperature, intermetallic compound formation takes place spontaneously at the silver-tin interface. The ability of a loose powder to consolidate at ambient temperature under moderate pressure and within a short time duration was investigated for various mixtures of elemental silver, tin, and pre-alloyed silver-coated powders. Surface treatment aimed at removing silver surface oxide layers is done with a dilute acid. The compressive and the transverse rupture strengths of several of the consolidated powder mixtures were determined. RESULTS: Cold-welding of surface-treated powder particles takes place across the silver-silver interface and is promoted by exposure to a mild acid. Powder mixtures containing approximately 50% silver powder, 40% silver-coated silver-tin intermetallic compound particles, and a small silver-tin fraction deposited from an aqueous solution display very good condensability, depending on the amount of silver-silver interface area available. The attained rupture strength values (200 Mpa) were higher than those of amalgams; the compressive strengths (120 MPa) and hardness values (100 KHN), however, were lower than those found for amalgams. SIGNIFICANCE: Mercury-free silver-tin powder mixtures can be processed for use as metallic composite dental restorative materials.

Analysis of Variance↗
PubMed1995

Mechanical longevity estimation model for post-and-core restorations.

OBJECTIVES: The aim of this study was to integrate existing knowledge of in vitro strength of post-and-cores and masticatory loading to arrive at longevity estimates for post-and-core restorations when subjected to clinically relevant loads. METHODS: A biomechanical model was developed to predict the in vivo longevity. This method was applied to direct post-and-core restorations with amalgam or composite cores. Both experimental laboratory strength values and theoretical clinical strength values were used in the model. The restorations made in the laboratory were assumed to be of a higher quality than clinically made restorations, due to factors such as ease of manipulation, absence of saliva, etc. Both a high and low level of average masticatory loading were considered. The model was used to estimate the probability of mechanical failure before 5 X 10(6) load cycles (5 to 15 years) for all combinations of load range and manufacturing quality. RESULTS: The calculated failure probability was effectively zero for most combinations except for a clinical quality core subjected to loads in the high range. There the probability of mechanical failure before 5 X 10(6) cycles was estimated to be 2 X 10(-5) for amalgam and 5 X 10(-5) for composite cores. These results agree with the overall observed clinical failure rate of about 1% per year for post-and-core restorations. SIGNIFICANCE: The mechanical properties of the post-and-core restorations were adequate for clinically relevant loading conditions.

Biomechanical Phenomena↗
PubMed1993

An adaptive finite-element approach for the analysis of dental restorations.

The present paper deals with the problem of stresses generated during the setting process of polymer tooth fillings. A finite element procedure capable of accurately predicting the stresses along an interface between two different materials is presented. Adaptation of the finite element mesh is carried out based on a simple error estimator. The procedure is tested against benchmark problems and then applied to polymer tooth fillings. The results of the study are relevant in understanding and improving the behaviour of dental restorations.

Dental Cavity Preparation↗
PubMed1990

Effect of thermal stress on dentin adhesives used individually and in combination.

Polymerization shrinkage remains an inherent problem in composite restorations. Dentin adhesives generally improve bonding to dentin but do not consistently provide leak-free restorations. This study evaluated a dentin adhesive that bonds to dentinal calcium and another that bonds to dentinal collagen when used separately and in combination. The measurement of contraction gaps at the restoration-dentin interface was used as the means of testing the effectiveness of dentin adhesion. The effect of thermal stress on the dentin-polymer bond was also investigated. Results showed that the bisphenyl A glycidyl methacrylate (BISGMA)-based dentin adhesive was more effective when compared with the hydroxyethyl methacrylate (HEMA)-based adhesive. When used in combination, the mean contraction gaps of cavities were not found to be significantly better than those treated with only the BISGMA-based adhesive. Thermal stress reduced the effectiveness of dentin adhesives whether applied individually or in combination.

Composite Resins↗
PubMed1992

Dental anxiety and attendance in the north-west of England.

The aim of this study was to record the level of anxiety and last recorded visit for a dental check-up of a random sample of 300 workers at three sites in the North-west of England. All subjects were asked to complete a short written questionnaire and 255 (85 per cent) usable forms were returned. The mean level of anxiety using the Corah Dental Anxiety Scale (DAS) (N.L. Corah, 1969, J. Dent. Res. 48, 596) was 9.1. Females had a statistically higher mean DAS than males but there was no correlation between DAS and either age or occupational status. Those subjects who claimed not to have had a check-up in the past year had a significantly higher mean DAS than those who claimed to have been in the past year. Multiple regression analysis showed that the reported time interval since the last check-up was the most important predictor of the DAS score. The implications of the results are considered for the future of restorative dentistry.

Adolescent↗
PubMed1992

Effects of polymerization contraction in composite restorations.

Post-gel polymerization contraction of resin composite induces contraction stresses at the composite-tooth bond and in surrounding tooth structure. Strain gauges have been shown to be an effective method for measuring linear post-gel polymerization contraction of composites. A new model was developed in which the composite sample was bonded to and circumscribed by an acrylic ring. The model simulates a composite restoration surrounded by dentine. A strain gauge measured the deformation of the ring while a second strain gauge simultaneously recorded the dimensional change of the sample. Stresses placed on the acrylic ring as a result of polymerization contraction of the composite were calculated, based on the strains on the ring and the ring's material properties. Four composites (Heliomolar, Vivadent, Tonawanda, NY, USA; Herculite XR, Kerr Manufacturing Co., Romulus, MI, USA; P-50, 3M Co., St Paul, MN, USA; Silux Plus 3M Co.) were evaluated for polymerization contraction strain and stress on the surrounding acrylic ring during polymerization. At the end of the 60 s light application, Heliomolar demonstrated significantly lower post-gel contraction (0.12 per cent, P less than 0.05) when compared to the other materials. When the strain reached an equilibrium at the end of 14 min Heliomolar continued to demonstrate lower post-gel contraction, however this was not statistically significant at P less than 0.05. When the contraction stress on the surrounding acrylic ring was considered, P-50 rapidly developed and produced the largest stress values (1.7 MPa) at the end of the light application while Heliomolar produced the lowest stress values (0.3 MPa). These values, however, were not significantly different when evaluated statistically.(ABSTRACT TRUNCATED AT 250 WORDS)

Composite Resins↗
PubMed1992

Curing light performance and polymerization of composite restorative materials.

The majority of modern composite restorative materials require light activation for polymerization. Variables affecting light energy absorption by the composite have been examined for their effect on the polymerization contraction. Since the polymerization contraction is closely associated in a complex way to the degree of cure of the restoration, this parameter served as an empirical indicator for the extent of polymerization. Variables included the composite shade, distance between the light source and composite sample, and light intensity. Three resin composites are evaluated. Post-gel polymerization contraction was evaluated using a strain gauge method. Curing light intensity diminished rapidly for distances greater than 2 mm between the tip of the light guide and material surface. A linear relationship was demonstrated between polymerization contraction and light intensity. The polymerization contraction of a microfilled composite and posterior composite, using a constant curing time and light intensity, decreased linearly with increasing sample thickness. Less than optimal light output of the curing light source can be compensated by increasing application time within reasonable limits.

Composite Resins↗
PubMed1993

Pins for direct restorations.

Self-threading dentine pins permit the retention of large complex direct restorations but there are problems associated with their placement. Strain and crazing of dentine following pin insertion and pulpal and lateral perforations are common. Perforations can be avoided by operator awareness of tooth morphology. Strain and crazing has been found to be minimized by unscrewing the pin slightly after insertion, by using pins with a tap thread, and by using the smallest pin possible. Twist drill form and dulling affects the pin channel shape which in turn influences pin seating. A lack of standardization of pin and twist drill diameter and length has been implicated as the cause of poor pin retention. Manufacturers, in an attempt to standardize the depth of penetration of pins, have incorporated shoulders at the midpoint of the pin, which has met with varying success. More research in the area of limiting pin penetration is necessary, as well as attempts to improve the quality control of pin and twist drill manufacture.

Dental Cavity Preparation↗
PubMed1995

Effect of food and oral simulating fluids on structure of adhesive composite systems.

This work evaluates the degradation of three adhesive/composite systems (Tenure/Marathon One. Scotchbond Multi-Purpose/Z100 and Optibond/Herculite XRV) upon immersion in 75% ethanol solution and in an artificial saliva (Moi-Stir). Shear bond strength (SBS) and diametral tensile strength (DTS) specimens were employed for this study. For the SBS specimens, the bonded interface and composite were exposed to food and oral simulating fluids at 37 degrees C for up to 30 days. A similar control series was stored in air. DTS specimens were stored in 75% ethanol at 37 degrees C for up to 30 days. The SBS specimens were sheared to failure. Small quantities of bonding resin were removed from the tooth side of the fractured surface and from the non-fractured fractured end of the composite for Fourier transform infrared microscopic evaluation. Similar scrapings were taken from DTS specimen surfaces. The infrared absorbance intensity (AI) of the major peaks was measured as a function of storage time and ratioed against the aromatic C = C (1609.4 cm-1) peak. The data were analysed using ANOVA and the Tukey LSD test. The AI of major peaks was similar for the materials stored either in air or in Moi-Stir for all testing periods. Storage in ethanol caused the AI of aliphatic C = C (1638 cm-1) and of O-H (approximately 3500 cm-1) bonds to significantly decrease (30-50%) for specimens of bonding resin while the AI of C = O bonds (1730 cm-1) increased (60-120%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adhesives↗
PubMed2004

Laser dentistry practice management.

Laser treatment in promoting dental care is present in many areas and disciplines. The public has an expectation that their dentist should be up to date with the most modern and advanced care possible. The future of lasers in dentistry is promising. New applications and procedures are constantly being developed. Dentists who position themselves to provide and manage these new technologies stand to be rewarded from clinical and financial aspects. Proper practice management strategies are key to achieving this success.

Dental Care↗
PubMed2006

Reconstructive materials and bone tissue engineering in implant dentistry.

Periodontal function for natural teeth and dental implants depends strongly on the mechanical integrity of the bone in the maxilla and mandible. Ongoing healthy bone remodeling around a natural tooth or implant is critical for longevity. Chemical factors that influence bone remodeling have been explored with the goal of enhancing the growth and maintenance of good quality bone. Less, but increasing, effort has been directed at understanding mechanical signals and factors, including those affected by implant/prosthesis materials that transmit loads directly to the surrounding bone. This article reviews research on the effects of synthetic materials and resulting mechanical stimuli on bone tissue engineering in dentistry.

Animals↗
PubMed2004

Temperature mediated coefficient of dimensional change of dental tooth-colored restorative materials.

OBJECTIVES: Restorative materials are constantly subjected to thermal challenges in the oral environment. Such challenges, if significant, can have unfavorable effects on the margins of restorations in terms of the seal between the material and the tooth structure. This study aimed to assess the Coefficient of Dimensional Change (CDC) of tooth-colored restorative materials. METHODS: Five cylindrical specimens (6 mm x 4 mm) were made (using a stainless steel mold) of each of the following: the compomers Dyract AP (Dentsply), or F2000 Compomer (3M); a resin composite, Z100 MP (3M); a resin-modified glass-ionomer, Fuji II LC Capsule (GC); the conventional glass-ionomers Fuji IX GP Fast (GC) or Ketac Fil Aplicap (ESPE). The light-cured materials were cured for 40 s at each end and also around the 'waist' after removal from the mold. All specimens were stored in distilled water at 37 degrees C for 24 h, before testing. The CDC for each specimen was determined using a thermal mechanical analyser, by heating the sample from 25 to 70 degrees C at 10 degrees C min(-1). RESULTS: All materials except the glass-ionomers showed expansion on heating. The temperature response was non-linear in each case and values of CDC were therefore calculated between 25 and 50 degrees C and between 50 and 70 degrees C. The mean values of CDC (x 10(-6) degrees C(-1)) between 25 and 50 degrees C were Dyract: 83.4, F2000: 66.1, Z100: 64.5. The glass-ionomer materials showed contraction, which was non-linear in nature and was associated with a loss of water on heating. ANOVA and Tukey's pairwise comparisons of mean CDC values for the other materials indicated significant differences between all pairs of materials. SIGNIFICANCE: The compomers and resin composite tested had similar values of CDC. The conventional and resin-modified glass-ionomers contracted on heating. For one glass-ionomer the dimensional change on heating was minimal as thermal expansion appeared to be compensated by water loss.

Analysis of Variance↗
PubMed2004

Residual shrinkage stress distributions in molars after composite restoration.

OBJECTIVE: Experimental measurements on various restoration configurations have shown that restored teeth deform under the influence of polymerization shrinkage, but actual residual stresses could not be determined. The purpose of this study was to calculate and validate shrinkage stresses associated with the reported tooth deformations. METHODS: Three different restoration configurations were applied in a finite element model of a molar. The composite properties were based on experimentally determined composite behavior during polymerization. The occlusal deformation pattern and the residual stress states of the tooth, restoration, and tooth-restoration interface were calculated using a polymerization model based on the post-gel shrinkage concept. Reported strain gauge measurements and occlusal deformation patterns were used for validation. RESULTS: The shrinkage stresses depended on the configuration and size of the restorations. The tooth's resistance against polymerization shrinkage diminished with loss of dental hard tissue. Larger restorations resulted in lower stress levels in the restoration and tooth-restoration interface, but increased stresses in the tooth. The maximum stress values found for different configurations were not decisively different. SIGNIFICANCE: The validated model indicated that shrinkage stress cannot be based on composite properties or restoration configuration alone, but has to be approached as a distributed pattern that depends on the location and on the properties of tooth and restoration, geometry, constraints, and restoration procedures. Tooth deformation was indicative of stresses in the tooth rather than in the restoration or across the tooth-restoration interface.

Composite Resins↗
PubMed2004

Tooth deformation patterns in molars after composite restoration.

OBJECTIVE: Residual stresses from polymerization shrinkage in composite restorations deform a tooth. This may cause debonding, enamel crack propagation, and post-operative sensitivity. Deformation due to shrinkage has been measured previously at a few discrete points. The purpose of this study was to analyze cuspal deformation pattern of the occlusal portion of molars for various cavity types and sizes after restoration with a light-initiated composite. METHODS: Five extracted human molars were successively prepared as Class I, Class II OM, large Class II OM, and large Class II MOD. The cavities were filled with a light-curing composite using a dentin adhesive system. The occlusal portion of the unrestored cavity and the restoration were digitized with a profilometer. The digitized data of the unrestored and restored tooth were used to calculate the cuspal contour change with Cumulus software. Deformation was visualized as a color contour map. RESULTS: Cuspal deformation showed up in the contour map as a reduction of buccal and lingual contour perpendicular to the surface. Large Class II MODs exhibited the highest cuspal deformation, followed by large OM restorations. Cuspal deformations in Class I and small Class II OM restorations were not significantly different. SIGNIFICANCE: When a composite restoration was cured, the surrounding tooth deformed due to polymerization shrinkage. Cavity type and size affected how much cusps moved inward as a result of polymerization shrinkage. This study quantified and visualized the pattern of cuspal deformation.

Analysis of Variance↗