Journal of Dental Research, Vol 75, 1396-1403, Copyright © 1996 by International & American Associations for Dental Research Online Journals
Dentin bonding: SEM comparison of the resin-dentin interface in primary and permanent teeth
J. E. Nor, R. J. Feigal, J. B. Dennison and C. A. Edwards
Department of Orthodontics and Pediatric Dentistry, University of Michigan, Ann Arbor 48109, USA.
Previous studies have suggested minor differences between primary and
permanent teeth in terms of dentin composition and morphology. Other
reports indicated lower bond strengths of resin composites to dentin of
primary teeth compared with dentin of permanent teeth; however, no
information is available regarding differences in the micromorphology of
the resin-dentin interface that may explain these lower bond strengths.
Therefore, the purpose of the present study was to compare primary and
permanent teeth in terms of the thickness of the hybrid layer developed
with two bonding systems. Our hypothesis was that bonding differences
previously reported between primary and permanent dentin would be reflected
in hybrid layer differences observable in SEM analyses. Twenty human
extracted and non-carious teeth were divided into 4 groups: 5 primary and 5
permanent teeth restored with All-Bond 2/Bisfil P system; and 5 primary and
5 permanent teeth restored with Scotchbond Multi-Purpose/Z100. The sample
area available on each tooth was divided for the two dentin conditioning
times (7 and 15 sec). Measurements of hybrid layer thickness were performed
by means of SEM at x13,000. The results of this study indicated that the
hybrid layer produced is significantly thicker in primary than in permanent
teeth (p = 0.0001), suggesting that primary tooth dentin is more reactive
to acid conditioning. No difference was observed in the hybrid layers
produced by the two adhesive systems (p = 0.7920). The increased thickness
of the hybrid layer in primary teeth (25 to 30%) and the subsequent lack of
complete penetration of adhesive resin into previously demineralized dentin
may contribute to the lower bond strengths to primary dentin reported in
the literature. If a narrower hybrid layer more uniformly infused with
resin is the goal of dentin bonding, it is concluded that a differentiated
protocol for bonding to primary dentin (with shorter time for dentin
conditioning) can be used as a means to reproduce the hybrid layer
thickness seen in permanent teeth.
