Wear and mechanical properties of nano-silica-fused whisker composites.

J Dent Res. 2004 Dec;83(12):930-5

Authors: Xu HH, Quinn JB, Giuseppetti AA

Resin composites must be improved if they are to overcome the high failure rates in large stress-bearing posterior restorations. This study aimed to improve wear resistance via nano-silica-fused whiskers. It was hypothesized that nano-silica-fused whiskers would significantly improve composite mechanical properties and wear resistance. Nano-silicas were fused onto whiskers and incorporated into a resin at mass fractions of 0%-74%. Fracture toughness (mean +/- SD; n = 6) was 2.92 +/- 0.14 MPa.m(1/2) for whisker composite with 74% fillers, higher than 1.13 +/- 0.19 MPa.m(1/2) for a prosthetic control, and 0.95 +/- 0.11 MPa.m(1/2) for an inlay/onlay control (Tukey's at 0.95). A whisker composite with 74% fillers had a wear depth of 77.7 +/- 6.9 mum, less than 118.0 +/- 23.8 microm of an inlay/onlay control, and 172.5 +/- 15.4 microm of a prosthetic control (p < 0.05). Linear correlations were established between wear and hardness, modulus, strength, and toughness, with R = 0.95-0.97. Novel nano-silica-fused whisker composites possessed high toughness and wear resistance with smooth worn surfaces, and may be useful in large stress-bearing restorations.

PMID: 15557400 [PubMed - indexed for MEDLINE]

[Effects of thickness and opaque resin on the color of Artglass]

Shanghai Kou Qiang Yi Xue. 2004 Feb;13(1):59-61

Authors: Zhang QL, Chen JH

PURPOSE: The purpose of this study was to measure the normal color value and the infinite optical thickness value of Artglass DA3,and evaluate the effect of different thickness and the use of opaque resin on the color values of Artglass. METHODS: A Minolta CS-321 portable colorimeter was used for color value measurement.The CIE L*a*b* color system was used to describe the color of specimens.Color difference,quantitated in deltaE units, were determined according to the following formula: DeltaE=[(DeltaL)(2)+(Deltaa)(2)+(Deltab)(2)](1/2). DeltaE values below 1.5 was used as being identical for human eyes. Artglass disks with a thickness of 4.0 mm were fabricated and the normal color value were obtained by two specimens pile up. Fifteen groups of specimens of 0.5 to 4.0 mm were made and the color of them were measured on the white and metal background color. The specimens used opaque resin with the thickness of 1.5 to 3.5 mm were determined by colorimeter. RESULTS: The normal color values of Artglass DA3 were L* 61.23,a* -1.18,b* 11.29.The infinite optical thickness value of Artglass DA3 was 2.75 mm. The opaque resin can increase the values of L*a*b* of Artglass. The effect will disappear until the thickness reaches 2.50 mm. CONCLUSIONS: From this study, we conclude that the color values of Artglass have a negative correlation between thickness when the background color is white. Thickness and opaque resin have significant effect on the color values of Artglass.

PMID: 15007485 [PubMed - indexed for MEDLINE]

Long-term water-aging of whisker-reinforced polymer-matrix composites.

J Dent Res. 2003 Jan;82(1):48-52

Authors: Xu HH

Long-term water exposure may degrade polymer-matrix composites. This study investigated the water-aging of whisker composites. It was hypothesized that whiskers would provide stable and substantial reinforcement, and that whisker type would affect water-aging resistance. Silica-fused Si(3)N(4) and SiC whiskers were incorporated into a resin. The specimens were tested by three-point flexure and nano-indentation vs. water-aging for 1 to 730 days. After 730 days, SiC composite had a strength (mean +/- SD; n = 6) of 185 +/- 33 MPa, similar to 146 +/- 44 MPa for Si(3)N(4) composite (p = 0.064); both were significantly higher than 67 +/- 23 MPa for an inlay/onlay control (p < 0.001). Compared with 1 day, the strength of the SiC composite showed no decrease, while that of the Si(3)N(4) composite decreased. The decrease was due to whisker weakening rather than to resin degradation or interface breakdown. Whisker composites also had higher moduli than the controls. In conclusion, silica-fused whiskers bonded to polymer matrix and resisted long-term water attack, resulting in much stronger composites than the controls after water-aging.

PMID: 12508045 [PubMed - indexed for MEDLINE]

Thermal diffusivity of glass-ionomer cements.

J Dent Res. 1987 May;66(5):1040-3

Authors: Tay WM, Braden M

Thermal diffusivity, a property related to the thermal insulative efficiency of a material, was measured in nine glass-ionomer cements and compared with results from a silicate and a polycarboxylate cement. Each cement was mixed at various powder-liquid ratios (P/L) and moulded into a rectangular prism of approximate dimensions 2 cm cube with a thermocouple embedded in it. The prism was immersed in a constant-temperature bath at 1 degree C, and the fall in temperature was observed over a period of three min. Except for the initial and later stages, the plot of the logarithmic difference between external and internal temperatures of each block of cement against time showed a straight line in accord with theoretical prediction. From the slope, the thermal diffusivity of the material was calculated. The values for the silicate, polycarboxylate, and glass-ionomer-metal (cermet) showed a marked rise with increasing P/L, whereas at higher P/L, glass ionomer cements showed gradual change, with values being only slightly higher than the thermal diffusivity of dentin. Glass-ionomer cements are good thermal insulators over a wide range of P/L, and close agreement between experimental and theoretical data shows that glass-ionomer cements are homogenous isotropic materials.

PMID: 3475320 [PubMed - indexed for MEDLINE]

An erosion test for dental cements.

J Dent Res. 1985 Aug;64(8):1100-4

Authors: Walls AW, McCabe JF, Murray JJ

A new method for the in vitro measurement of the erosion of dental cements is described which allows repeated, gentle removal of loose surface debris and provides a direct quantitative measurement of material lost. A linear relationship for erosion against time is demonstrated for a glass polyalkenoate material under mildly acidic conditions. This test method is applicable to all acid/base-type cements and gives results comparable to those from in vivo tests.

PMID: 3860543 [PubMed - indexed for MEDLINE]

Prevention of in vitro secondary caries with an experimental fluoride-exchanging restorative resin.

J Dent Res. 1984 May;63(5):689-92

Authors: Zimmerman BF, Rawls HR, Querens AE

We investigated the development of artificial caries lesions adjacent to experimental composite resins which release fluoride by ion exchange. Overall, compared with both a commercial, non-fluoride composite and a restorative silicate cement, the cavity walls and tooth surfaces immediately adjacent to the experimental resins developed fewer and/or smaller lesions. When lesions did develop, they did not penetrate as far along the cavity walls adjacent to the experimental materials. In general, the degree of protection imparted by the fluoride composites increased with increasing fluoride content. These results demonstrate the potential of these adhesive resins for restorative and other dental applications in which an extended fluoride presence would be of benefit.

PMID: 6584474 [PubMed - indexed for MEDLINE]

Long-term F release from glass ionomer cements.

J Dent Res. 1984 Feb;63(2):158-60

Authors: Swartz ML, Phillips RW, Clark HE

Fluoride release from three commercial glass ionomer filling cements and three glass ionomer luting cements was measured in the laboratory over a 12-month period. Fluoride release from these glass ionomer cements was compared with that released from a silicate, silicophosphate, and a fluoride-containing polycarboxylate cement. The fluoride released from the glass ionomer cements throughout the one-year period was similar, both in quantity and pattern, to that released by the silicate cement. The silicophosphate cement tended to release fluoride in somewhat lesser amounts, while the amount of fluoride released by the polycarboxylate was negligible after the first few days. Analysis of these data indicates that these glass ionomer cements probably possess anticariogenic properties similar to those of silicate cement.

PMID: 6582098 [PubMed - indexed for MEDLINE]

Acinetobacter contamination of laboratory dental pumice.

J Dent Res. 1983 Oct;62(10):1073-5

Authors: Williams HN, Falkler WA, Hasler JF

Micro-organisms of the genus Acinetobacter, implicated as opportunistic pathogens, have been recovered from dentures after laboratory repair. A study was undertaken to determine if Acinetobacter could be isolated from used dental pumice. Cultural studies demonstrated that Acinetobacter calcoaceticus variety lwoffi was present in high numbers in used pumice and was a major gram-negative microbial contaminant.

PMID: 6352756 [PubMed - indexed for MEDLINE]

Fluoride release from a silicophosphate cement with added fluoride.

J Dent Res. 1982 May;61(5):660-4

Authors: Derkson GD, Poon PJ, Richardson AS

PMID: 6953093 [PubMed - indexed for MEDLINE]

Dielectric properties of glass ionomer cements.

J Dent Res. 1981 Jul;60(7):1311-4

Authors: Tay WM, Braden M

PMID: 6940872 [PubMed - indexed for MEDLINE]

Fluoride distribution in teeth using a silicate model.

J Dent Res. 1980 Oct;59(10):1596-603

Authors: Swartz ML, Phillips RW, Clark HE, Norman RD, Potter R

The fluoride determinations were done on enamel biopsies taken before and after restoration of extracted teeth with silicate cement. Two sites, one near the restoration and one 3 mm or more away from the restoration, were assayed. No difference was noted in pre- and post-restoration biopsies when teeth were restored with a fluoride-free silicate. Post-restoration biopsies at sites near and away from the restoration were significantly higher in fluoride as compared to pre-restoration biopsies when the teeth were restored with a fluoride-containing silicate.

PMID: 6932416 [PubMed - indexed for MEDLINE]

Rheology of luting cements.

J Dent Res. 1980 Sep;59(9):1486-92

Authors: Lorton L, Moore BK, Swartz ML, Phillips RW

A rheometer has been developed to simulate the extrusion of luting cement from beneath a full crown during seating using clinically realistic shear rates. Five luting cements were studied, and differences in rheological behavior were illustrated. These measurements demonstrate the importance of consideration of the effects of shear rate on viscosity when evaluating a cement for optimal clinical utilization.

PMID: 6931125 [PubMed - indexed for MEDLINE]

The effect of various restorative materials on the microhardness of reparative dentin.

J Dent Res. 1980 Feb;59(2):109-15

Authors: Cox CF, Heys DR, Gibbons PK, Avery JK, Heys RJ

This study showed a statistically significant difference between the microhardness of reparative and primary dentin at both five-and eight-week intervals. Reparative dentin from occlusal trauma is harder than reparative dentin underlying a cavity preparation at the 99% level. No statistical difference was noted in the hardness of reparative dentin underlying different materials, but trends were observed.

PMID: 6766148 [PubMed - indexed for MEDLINE]

The quantitative measurement of the opacity of aesthetic dental filling materials.

J Dent Res. 1979 Jun;58(6):1585-96

Authors: Crisp S, Abel G, Wilson AD

A method is described for measuring the opacity of anesthetic dental filling materials using a goniophotometer. Procedures are given for converting measured opacity values to those referred to a 70% reflectance background (C0.7 values) as required by existing specifications. The conversion is involved, and, since most available white surfaces have reflectance of about 80%, it is recommended that in future specifications opacity be recorded as C0.8 values. Opacity values for 28 materials are reported. It was found that the opacity of dental cement decreases for several days following preparation and that powder/liquid ratio has little effect, while pigmentation has a marked effect on opacity.

PMID: 286705 [PubMed - indexed for MEDLINE]

Physical and chemical properties and wear.

J Dent Res. 1979 May;58(5):1535-43

Authors: Dickson G

PMID: 285965 [PubMed - indexed for MEDLINE]

A new type of hydraulic dental cement.

J Dent Res. 1979 May;58(5):1461-4

Authors: Kohmura TT, Ida K

A new type of hydraulic cement has been developed. This cement consists of a mixture of cement powder and setting agent powder and therefore has only to be kneaded with a little amount of water when being used.

PMID: 285960 [PubMed - indexed for MEDLINE]

The hydration of dental cements.

J Dent Res. 1979 Mar;58(3):1065-71

Authors: Wilson AD, Paddon JM, Crisp S

A study was made of the hydration of dental cements, water being classified as "non-evaporable" and "evaporable". The ratio of these two types of water was found to vary greatly among different cement types, being lesser in zinc oxide and ionic polymer cements and greater in ion-leachable glass and phosphoric acid cements. The cement with the least "non-evaporable" water, i.e., showing least hydration (the zinc polycarboxylate cement), had the lowest strength and modulus and the greatest deformation at failure. A linear relationship was found to exist between strength and the degree of hydration of dental cements. All the cements were found to become more highly hydrated and stronger as they aged.

PMID: 284040 [PubMed - indexed for MEDLINE]

Antibacterial activity of tooth-colored dental restorative materials.

J Dent Res. 1978 Feb;57(2):171-4

Authors: Orstavik D, Hensten-Pettersen A

The antibacterial activity of dental restorative materials (12 resin based and one silicate) was tested in vitro against 5 species of bacteria. When fresh, all materials inhibited growth in pour plates of at least one bacterial strain. After storage in saline for 24 hours, the antibacterial activity was markedly reduced. There was a wide variation among the materials in the extent of their antibacterial activity. The bacterial strains apparently differed in their susceptibility to the antibacterial activity of the materials.

PMID: 277508 [PubMed - indexed for MEDLINE]

Effects of alexidine.2HCL mouthwash on plaque and gingivitis after six months.

J Dent Res. 1977 Nov;56(11):1349-58

Authors: Spolsky VW, Forsythe AB

Two-hundred and fourteen subjects ranging in age from 22 to 63 years used either a mouthwash that contained 0.035% w/v alexidine.2HCL (2-ethylhexyl bisbiguanidine dihydrochloride) or a placebo twice daily on a doubleblind basis for six months in conjunction with routine oral hygiene procedures. The results indicated that alexidine.2HCL was safe and was statistically more effective in producing a clinically significant reduction in gingivitis than was the placebo.

PMID: 348734 [PubMed - indexed for MEDLINE]

Primate pulpal response to ultraviolet light-polymerized direct-bonding material systems.

J Dent Res. 1976 Nov-Dec;55(6):1118-24

Authors: Myers CL, Stanley HR, Heyde JB, Chamberlain J

The results of this study, plus those of a previous study, show that a layer of CaOH lining the floor of the tooth cavity will protect the dental pulp against toxic irritants inherent to an UV light-polymerized cavity liner and a UV light-polymerized composite restorative resin. This study also showed that a layer of CaOH lining the floor of the cavity will protect the dental pulp against acid irritants inherent in the enamel etching solution. It is recommended to restorative dentistry that all primary dentin within clinically accessible areas of the cavity preparation be covered with a layer of CaOH before the enamel is etched with the acid-conditioning solution. Precautionary protection of primary dentin in this manner affords a margin of safety should the conditioning solution inadvertently spill onto the primary dentin during the enamel-etching procedure. Second, if the conditioning solution does accidentally spill onto the previously placed protective layer of CaOH during the enamel-etching procedure, then it logically follows that this acid-contaminated layer of CaOH should be mechanically removed and a new layer of CaOH that completely lines at least the floor of the tooth cavity should be placed before the resins are applied.

PMID: 826551 [PubMed - indexed for MEDLINE]

Glass ionomer cements: chemistry of erosion.

J Dent Res. 1976 Nov-Dec;55(6):1032-41

Authors: Crisp S, Lewis BG, Wilson AD

A three-month study of the chemistry of the water erosion of two forms of ASPA cement has been made. The effect of varying cement consistency and cure time was investigated. The results are discussed in terms of the known chemistry and structure of the cement. The erosion behavior is compared to that of silicate, silicophosphate, and zinc polycarboxylate dental cements. The state of absorbed water and the mechanism of erosion is discussed.

PMID: 187630 [PubMed - indexed for MEDLINE]

Specification test for the solubility and disintegration of dental cements: a critical evaluation of its meaning.

J Dent Res. 1976 Sep-Oct;55(5):721-9

Authors: Wilson AD

The specification test for solubility and disintegration is an essential screening test for the quality control of certain cement types. No cement fails it can be considered for use; however, the test has only a limited clinical significance because it does not give an indication of the stability of the fully hardened cement matrix either in oral fluids or water. Instead, it gives a measure of the content of the soluble reaction intermediate present in cements that are still hardening and where the matrix has not fully formed. The test relates, therefore, to early vulnerability to aqueous attack and hardening rate. The period of test is, in fact, an atypical one and the true extent of the erosion of the cement matrix is obscured by the presence of soluble reaction intermediates. Long-term extrapolations cannot be made and so test results for broadly satisfactory cements within a category cannot be used for valid comparisons of clinical excellence, and they can be used even less to compare different cement types with different setting reactions. For example, in general, the dental silicate cement has a higher solubility and distinegration figure than the zinc phosphate cement because it contains soluble sodium salt and hardens more slowly. However, it is more stable under oral conditiont an indication of the vulnerability of the forming matrix to attack. The test is not valid when applied to zinc oxide-eugenol cements because the products of decomposition are either virtually water-insoluble or volatile and therefore not measured under the conditions of the test. A method is suggested for overcoming this deficiency. The test needs to be supplemented by other tests done on fully hardened cements for longer periods of time and in mediums that can represent oral conditions. One example would be to stimulate acid conditions developed in stagnation areas. A total estimation of decomposition products, both soluble and insoluble, is called for rather than the determination of soluble materials only.

PMID: 1067288 [PubMed - indexed for MEDLINE]

Short-term stress-relaxation behavior of nonmetallic restoratives.

J Dent Res. 1975 Nov-Dec;54(6):1149-53

Authors: Hertert RS, Huget EF, De Simon LB, Cosgrove JH

The rheological behavior of five nonmetallic dental materials was studied. Short-term stress relaxation was found to be strongly dependent on time and temperature. Relaxation behavior of the test materials conformed well to simple mathematical models.

PMID: 1059653 [PubMed - indexed for MEDLINE]

Assessment of microleakage using a conductimetric technique.

J Dent Res. 1975 Jan-Feb;54(1):41-8

Authors: Jacobsen PH, Von Fraunhofer JA

A new method enables the dimensional changes of a range of anterior restorative materials to be demonstrated in an artificial cavity. The cavity wall-restoration interspace was incorporated into an electrochemical cell and the changes in the current passing through this cell reflected changes in the dimensions of the interspace.

PMID: 1053773 [PubMed - indexed for MEDLINE]

Short-term bond strengths between adhesive cements and dental alloys.

J Dent Res. 1974 Nov-Dec;53(6):1377-86

Authors: Moser JB, Brown DB, Greener EH

PMID: 4610021 [PubMed - indexed for MEDLINE]

Setting characteristics of anterior restorative materials.

J Dent Res. 1974 Mar-Apr;53(2):461-7

Authors: Jacobsen PH, Von Fraunhofer JA

PMID: 4521909 [PubMed - indexed for MEDLINE]

Improved method of neutron activation analysis for microleakage studies.

J Dent Res. 1974 Mar-Apr;53(2):356-63

Authors: Meyer JM, Dennison JB, Craig RG

PMID: 4521895 [PubMed - indexed for MEDLINE]

Histopathological study of a quartz-filled composite dental restorative material.

J Dent Res. 1973 Mar-Apr;52(2):362-5

Authors: Adams RJ, Lord GH

PMID: 4347830 [PubMed - indexed for MEDLINE]

Effects of restorative materials on plaque composition.

J Dent Res. 1972 Nov-Dec;51(6):1596-601

Authors: Norman RD, Mehra RV, Swartz ML, Phillips RW

PMID: 4508969 [PubMed - indexed for MEDLINE]

Dental silicate cements. XV. Effect of particle size of the powder.

J Dent Res. 1971 Nov-Dec;50(6):1616-20

Authors: Kent BE, Wilson AD

PMID: 5288900 [PubMed - indexed for MEDLINE]

Dental silicate cements. XIV. Crazing, cement properties, and liquid composition.

J Dent Res. 1971 Mar-Apr;50(2):400-4

Authors: Kent BE, Lewis BG, Wilson AD

PMID: 5290877 [PubMed - indexed for MEDLINE]

Dental silicate cements. 13. Crazing and dulling of the surface.

J Dent Res. 1971 Mar-Apr;50(2):393-9

Authors: Kent BE, Lewis BG, Wilson AD

PMID: 5290876 [PubMed - indexed for MEDLINE]

Pulpal protection by a cavity liner applied as a thin film beneath deep silicate restorations.

J Dent Res. 1971 Jan-Feb;50(1):90-5

Authors: Br&#xE4;nnstrom M, Nyborg H

PMID: 5275792 [PubMed - indexed for MEDLINE]

Solubility of a silicate cement.

J Dent Res. 1970 Nov-Dec;49(6):Suppl:1530-6

Authors: Pulver JC, Rossington DR

PMID: 5274384 [PubMed - indexed for MEDLINE]

Sequence of events after pulp exposure in monkeys.

J Dent Res. 1970 Sep-Oct;49(5):1181

Authors: el-Kafrawy A, Mitchell DF

PMID: 4989594 [PubMed - indexed for MEDLINE]

Dental silicate cements. XII. The role of water.

J Dent Res. 1970 Mar-Apr;49(2):307-14

Authors: Wilson AD, Kent BE, Batchelor RF, Scott BG, Lewis BG

PMID: 5264594 [PubMed - indexed for MEDLINE]

Dental silicate cements. XI. Electron probe studies.

J Dent Res. 1970 Jan-Feb;49(1):86-92

Authors: Kent BE, Fletcher KE, Wilson AD

PMID: 5262822 [PubMed - indexed for MEDLINE]

Dental silicate cements. IX. Decomposition of the powder.

J Dent Res. 1970 Jan-Feb;49(1):7-13

Authors: Wilson AD, Kent BE

PMID: 5262821 [PubMed - indexed for MEDLINE]

Dental silicate cements: X. The precipitation reaction.

J Dent Res. 1970 Jan-Feb;49(1):21-6

Authors: Wilson AD, Kent BE

PMID: 5262817 [PubMed - indexed for MEDLINE]

Punch-shear test for dental purposes.

J Dent Res. 1970 Jan-Feb;49(1):131-6

Authors: Roydhouse RH

PMID: 5262801 [PubMed - indexed for MEDLINE]

Dental silicate cements. 8. Acid-base aspect.

J Dent Res. 1969 May-Jun;48(3):412-8

Authors: Kent BE, Wilson AD

PMID: 5254481 [PubMed - indexed for MEDLINE]

Dental silicate cements: VII. Alternative liquid cement formers.

J Dent Res. 1968 Nov-Dec;47(6):1133-6

Authors: Wilson AD

PMID: 5249046 [PubMed - indexed for MEDLINE]

Quantitative method for studying microleakage in vivo and in vitro.

J Dent Res. 1968 Nov-Dec;47(6):1128-32

Authors: Going RE, Myers HM, Prussin SG

PMID: 5249045 [PubMed - indexed for MEDLINE]

Dental silicate cements. VI. Infrared studies.

J Dent Res. 1968 Jul-Aug;47(4):644-52

Authors: Wilson AD, Mesley RJ

PMID: 4298640 [PubMed - indexed for MEDLINE]

Dental silicate cements. V. Electrical conductivity.

J Dent Res. 1968 May-Jun;47(3):463-70

Authors: Wilson AD, Kent BE

PMID: 5240798 [PubMed - indexed for MEDLINE]

Investigation concerning the solubility of dental cements.

J Dent Res. 1968 Mar-Apr;47(2):280-5

Authors: Eichner K, Lautenschlager EP, Von Radnoth M

PMID: 5238762 [PubMed - indexed for MEDLINE]

Dental silicate cements. IV. Phosphoric acid modifiers.

J Dent Res. 1968 Mar-Apr;47(2):233-43

Authors: Wilson AD, Kent BE, Batchelor RF

PMID: 5238756 [PubMed - indexed for MEDLINE]

Dental silicate cements. II. Preparation and durability.

J Dent Res. 1967 Nov-Dec;46(6):1425-32

Authors: Wilson AD, Batchelor RF

PMID: 5234914 [PubMed - indexed for MEDLINE]

Heat of polymerization of certain new and conventional restorative materials.

J Dent Res. 1967 Sep-Oct;46(5):1106

Authors: Matsui A, Buonocore M, Yamaki M

PMID: 5248979 [PubMed - indexed for MEDLINE]

Comparisons of abrasion produced by a simulated manual versus a mechanical toothbrush.

J Dent Res. 1967 Sep-Oct;46(5):1022-7

Authors: Mc Connell D, Conroy CW

PMID: 5248963 [PubMed - indexed for MEDLINE]