Physical and mechanical properties of some resin-based restorative materials after immersion in two different media

by Huang, Cui

Abstract of thesIs entItled "Physical and "lechanical Propertie .?of Some Resin-

Based Restorative Materials After Immersion In Two Different Media"

Submitted by Huang Cui

For the deglee of Master of Dental Surgery,

Faculty of DentlstIy, The Ul1lverstty of Hong Kong,

August, 200 I

Tim, study IS an u1VestIgatlOn of the physIcal and mechamcal plOperl1eS of

~evel

obJcctlves wcre to examIne the effect of hygroSCOpIc expansIon of several reSIn-based

Icstoratrve matenals on artIficIal mmgInal gap reductIon over a twelve week peIlod of

watel storage. 011 storage was usecl as control. TransmISSIon electron microscopy

(TEM) was used to examllle the eXistence of a glass lOnomer phase III reSIn-based

matcnah c"pecwlly In some hybnd matenals The mfluence of watel sorptIOn on the

ultlmatc tensIle stlength (UTS) of a compomer and a composIte was also studied

In total, two resm-modlfied glass IOnomer cements (lUvl-GICs). three

compol11crs, two glOmers and three composIte resms were used to Illvestlgate the

hygroscopIc expansIOn on artifiCIal gap reduCtlon 111 thIS study Ten specImens of each

matenal werc stored m de-lOl1lzed water (W) and ten 111 nonaqueous sll1cone flUId (0) at

3TC The chmenslOn of the maxImum gap was repeatedly measured at 0, 1, 2. 4, 6. 8,

10 and 12 wecks Gap WIdths m each of the groups were statIstIcally compared and

conclatlons between the mean gap WIdth reductIOn and the stOlage tunes wCle also

examll1ecl In Older to bettel explam the dlffelent changes among these matenals, one of

cach kmd of matellal was used for TEM observation to exam me the eXIstence of the

glas" lOnomel pha'ic Fmally, one composite (Spectrum TPH) and one compomer

Abstract

(Dytact f\P) were chmen to evaluate the CTS over 180 days aftet storage ll1 water and

011 An analysts of vanance was used to compare the results

There wcre no stgl1lticant dlffelences ll1 the margll1ul gaps for all groups 111

slhconc nUlcl The marg1l1al gap reductIOns ll1 the water groups were directly

altnbutable to water sorptIon and that the reductIOns were more extensIve and rapid 111

f

I

Rt\;l-GIC~, followed by compomers, whereas wIth composites they were relatIvely

stable One of the glOmers (Reactmet Paste), exhIbited rapId and extensIVe expansIOn

and should probably not be used 111 cavIties that ll1volve thll1 ancl unsupported enamel

TE,M study showed thll1 SIliceous hydrogel layers (80-100 nm) ll1 a Rc'Vl-GIC

(FuJI II LC) that became thicker upon water storage No glass IOnomer pha~e was

observed 1111tlally ll1 DYlact AP and Spectrum TPH A very thm SIliceous hydrogellayel

?200 nm) wa:> found on the glass fillers 111 Dyract AP aftel water storage fOJ 12 weeks

Water stOlage for 180 days had mllumal effect on the tensIle sttength of the

composite, Spectrum TPH However, the compomer, DYlact AP exhIbIted a delayed,

slight but slgl1lficant drop ll1 tensIle strength aftet 90 days that was dIrectly attnbutable

to watcr sorptIOn

In conclUSIOn. the undetstand111g of the phYSIcal and mechal11cal ptopertles of

rC:>1l1-bascd IcstOJatlve matenals should help the dentIst to predIct how a matellal w1l1

behave ll1 VIVO, and how they should be used clll11cally to the best advantage.

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