Sk. Sidhu et al., THE EFFECTS OF MATURITY AND DEHYDRATION SHRINKAGE ON RESIN MODIFIED GLASS-IONOMER RESTORATIONS, Journal of dental research, 76(8), 1997, pp. 1495-1501
The dimensional change, including hygroscopic change, of adhesive dent
al materials is a clinically important topic, since excessive changes
could cause debonding from tooth structure. The water balance of glass
-ionomer cements arises mainly from their sensitivity to the environme
nt; depending on the surroundings, they can gain or lose water, either
of which can be potentially damaging. These effects become less notic
eable as the cement ages. The effects of maturity of the newer resin-m
odified glass-ionomer materials and their responses to changes in mois
ture are unknown. Using confocal microscopy, we examined the effects o
f dehydration stress on the glass-ionomer/tooth interface in specimens
of various degrees of maturity. Wedge-shaped cervical cavities in ext
racted teeth were restored with one of three resin-modified glass-iono
mer restorative materials. The control specimens were restored with a
conventional glass ionomer. The samples were left to mature, then sect
ioned and examined at 1 day, 1 wk, 1 mo, 3 mos, 6 mos, and 1 yr. After
being sectioned, each specimen was examined immediately with a confoc
al microscope with water-immersion objectives so that the subsurface i
nterfacial characteristics could be studied. The specimen was then all
owed to dehydrate under the microscope, with further examinations at 1
5, 30, and 60 min. Generally, gap formation at the interface occurred
within 15 min of dehydration. All materials showed a different pattern
of gap change with maturity, probably due to the different setting me
chanisms involved. All of them were susceptible to dehydration shrinka
ge up to 3 mos of maturity. At 6 mos and 1 yr, Fuji IT and Fuji II LC
showed insensitivity to dehydration. Vitremer and Photac-Fil showed le
ss sensitivity to dehydration at 1 yr than at 6 mos. The results of th
is study of the maturing polymerized resin-modified cements have poten
tial clinical implications in the handling of these materials; the add
ition of resin has not significantly reduced the glass ionomer's susce
ptibility to dehydration problems.