Hardness testing of some fissure-sealing materials HARALD ULVESTAD Department of Pedodontics and Caries Prevention, Dental Faculty, University of Oslo, Oslo, Norway

AHSTKACr - The mechanical properties o f fissure-sealing materials are of significant importance for their durability, i.e. their wear resistance. One of the methods of evaluating a material's resistance to attrition is to apply a hardness test. In the present investigation, thr surface hardness of some fissure-sealing materials was tested. Sealants made from diluted composite materials and with inclusion of inorganic filler particles appeared to havr a considerable higher surface hardness than the other sealing materials tested.

(Accepted for publicalion I I June 1977)

The surface hardness of a material is often antagonist tooth) is much harder than the used as an index of its mechanical other material (e.g. a fissure sealant). strength and/or as an indication of its Thus, the relative surface hardness of resistance to wear (NIELSEN1962). Fissure softer materials, such as fissure sealants, sealing materials are placed directly on can be of practical value when comparing occlusal surfaces, thus creep and attrition their resistance to attrition. In most hardness tests, e.g. the Brine11 are two factors of special importance for the durability of the sealants. Attrition of test, the surface hardness of a polymer fully polymerized sealants is probably the material is generally measured in terms of most important factor in their long-time its resistance to indentation, and is primarily determined by the elastic elimination. Abrasion or attrition of a material is a modulus of the material. In the test mechanical property which is difficult to surface, the indenter will produce a define and measure adequately. Although complex state of stress, consisting both of test methods and instruments have been traction, and of elastic and plastic developed to measure abrasion, the deformation. Moreover, load time, results obtained with the different test temperature, and size of the indenter will methods generally d o not agree with each influence the hardness measurement LAUTENother or with practical experience (GREENER, HARCOURT& (NIELSEN 1962). Abrasion is related to SCHLAGER 1972). Nevertheless, it is friction as a frictional force is involved in possible to standardize most testing conany process of abrasion. This is especially ditions so that reproducible results can true if one material (e.g. the enamel of an be obtained, especially when comparing

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cliriiiically and mechanically related iii;iterials.. In an attempt to assess the relative resistance to attrition of fissuresealing inaterials, a hardness test was consitleretl adequate. Materialand methods 1'11~cotiiiiiercially available pit and fissure sr;ilatits tcstrtl i n tlie present investigation were Coticisr Etiatiiel Bond System' (Concise E.B., 3 M Cotiipaiiy), Delton' (Johnson & Johnson), lip)x yl i te 90'7 5 (Lee P har I naceuticals), Kerr

Pit ;itid Fissure Sealant' (Kerr Co.) and NuvaSeal' (L. D. Caulk Co.). In addition, sealants iiiitdc by diluting the universal and catalyst piistrs with equal volumes of universal and catiilyst resins of Adaptic' (Adaptic diluted, Joliiisoii 8c Johnson) and Concise' (Concise clilutetl, 3 M Company) were tested. The Coiicise E.B., Delton, Epoxylite 9075, and Nuva-seal consist of resins only, and form a glassy sealant. Adaptic diluted, Concise diluted, and Kerr contain inorganic filler pat.ticlcs, and form an opaque sealant: Tlie hardness of Adaptic and Concise composite materials without dilution was tested iiiitl used as control. I i i ail iron bar, 270 depressions were drilled, with a diaiiieter of 5 mm and a depth of 2 mm. Thirty 01' these depressions were filled with c*aclio f the inaterials listed above. The applicat i o n ol' the inaterials was performed with a plastic spatula. All depressions were slightly overfilled, and tlie iron bar with the specimens was polished i n a rotating wet disc 24 h after the application ol' the inaterials. By the polishing procedure, sirlootti test surfaces of all specimens were o1)taiiied. The specimens were conditioned for 7 days in saline at 37OC. They were tested in a Kcicherter Briviskop 187.5; the diameter of the itidenter was 0.625mtn; the applied load was 1.953 kp. The specimens were kept wet also at the testing at a test temperature of 37OC. The load time was 15s; the diameter of each indentation was measured in a microscope immediately after the release of the load. The hardness of each sealant material was calculated in kp/mm* (Brine11 Hardness Nuiiiber). Four ditterent points of each of the 30 specimens of the same material were tested;

t l i u s 120 observations were at hand for calculatiiig its BHN.

Resub The Brine11 Hardness Number and the standard deviation of each of the tested iiiaterials, obtained under the conditions ol'thc present study, are given in Fig. 1. When calculating the standard error of the diHi.rcnce between two means, the tlilli*rciices observed in BHN of the li)llowing inaterials were not found to be statistically significant: Iklton, Nuva-seal, Concise E.B.; Concise diluted, Adaptic diluted, Kerr; Adaptic, Concise. The hardness values (BHN) of the li)llowitig inaterials were found to differ I)y more than three times the standard error 01' the means: I)elton, Nuva-seal, and Concise E.B. dillbred from Epoxylite 9075; Coiicise diluted, Adaptic diluted, and Kerr dillered froin Delton, Nuva-seal, Coiicise E.B., and Epoxylite 9075. The coiiiposite materials Adaptic and Cotwise were found to have significantly higher liardness values than any of the sealants.

Discussion Most polymer materials used in dentistry have a fairly low hardness, and their resistance to attrition is also rather low (VLACK1964, GREENER et al. 1972). This applies even to the pit and fissure sealants, chemically related to the resins in coniposite tilling materials. One of the problems in the sealing of fissures lies in the fact that it is often difficult to recognize the sealant after 2-4 years. This leaves the dentist in doubt of the presence of the polymer coating (KOPEL & GRENOBLE1973). A low

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FISSIJKE-SEALING MATERIALS BRINELL HARONESS NUMBER IN KP/MM*

55

-

50

-

45 -

t

35 -

40

30

f

-

25 20

-

15

-

t

10 -

5 -

-

CONCISE E.E.

T

t

11.2

M.3

DELTON

EPOXYKERR LITE 9075

NUVA-SEAL AOAPTIC OILUTEO

42.1

50.1

CONCISE OILUTEO

AMPTIC

CONCISE

Fzg. I. Brine11 Hardness Numbers of some lissurc sealing and composite materials.

attrition resistance of the sealant is property is to be obtained of such a protjably the main contributor to this pre- sealant. The wetting property, even for coinposite materials without dilution, dicanien t. Common composite materials in Class s e e m to be acceptable for obtaining a V, IV, and 111 restorations seem to resist good retention in the acid-etched enamel SHIMOKOBE 1975, normal wear for many years (XHONGA, ( J ~ K G E N S E N& W O L C O &~ SOCNNAES1972, KOCH & PAHLAVAN,DENNISON& CHARBENEAU PAULANDER 1976). In earlier 1976). The data from the present investigation investigations, based on clinical evaluation, it has been claimed that even cannot be interpreted directly as a consealants with inorganic filler particles firination of the clinical observations that appeared rather resistant to abrasion diluted composite sealants have a lower (MCLEAN 8c WILSON 1974, ULVESTAD attrition than unfilled sealants as surface 1976). As a sealant has to be floated onto hardness is a different property than occlusal surfaces and into pits and resistance to abrasion. Moreover, caution fissures, a dilution of composite materials must be exercised in transferring in uitm to clinical situations. seems necessary if an adequate floating lindings

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Nevertheless, the highly significant and conspicuous difference in surface hardness of sealants with and without inorganic tiller particles can be taken as a n indication of improved resistance to attrition of filled fissure-sealing materials. Reference8

1973: 63/11, 51-54.

MCLEAN,J. W. & WILSON,A. D.: Fissure sealing and filling with a n adhesive glassionomer cement. Br. Dent. J. 1974: 136: 269-276.

L. E. : Mechanical properties ofpobmers. Reinhold, New York - Amsterdam London 1962. p. 228. PAHLAVAN, A., DENNISON, J. B. & CHARBENEAU, G. T.: Penetration of restorative resins into acid-etched human enamel. J. Am. Dent. Assoc. 1976: 93: NIELSEN,

GREENER,E. H., HARCOURT, J. K. & 1 170-1 176. LAUTENSCHLAGER, E. P.: Materials science in ULVESrAD, H.: Evaluation of fissure sealing dentistry. The! Williams & Wilkins Co., with a diluted composite sealant and an Baltimore 1972, pp. 382, 383, 388, 389. UV-light polymerized sealant after 36 J ~ R G E N S E NK. , D. & SHIMOKOBE, H.: Adaptation of resinous restorative materials months’ observation. Scand. J. Dent. Res. 1976: 84: 401-403. to acid etched enamel surface. Scand. J. Dent. Res. 1975: 83: 31-36. VLACK,L. H.v.: Elements ofmalerials science, 2nd ed. Addison-Wesley, Reading, Mass. 1964, KOCH, G, & PAULANDER, J.: Klinisk p. 461. uppfoljning av composit-restaureringar XHONGA, F. A., WOLCOlT, R. B. & SOGNNAES, utforda med emaljetsningsmetodik. Swed. R. F.: Dental erosion 11. Clinical Dent. J . 1976: 69: 191-196. measurements of dental erosion progress. J. KOPEL,H. M. & GRENOBLE, D. E.: The pit and Am. Dent. Assoc. 1972: 84: 577-582. fissure sealants: a critical review. Oral Health

Address : Department of Pedodontics and Caries Prevention 7 1 Geitmyrsveien N-OSLO4 Norway

Hardness testing of some fissure-sealing materials.

Hardness testing of some fissure-sealing materials HARALD ULVESTAD Department of Pedodontics and Caries Prevention, Dental Faculty, University of Oslo...
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