Purpose: This study measured the microtensile bond strengths of 2 tooth-colored restorative materials with and without conditioning of primary teeth dentin, and examined the micromorphology of the ...debonded surfaces and material-dentin interfaces. Methods: Cylindrical
specimens of packable composite resin (PCR) and resin-modified glass ionomer cement (RMGIC) bonded to dentin of primary teeth were ground to an hourglass shape and tested for microtensile bond strength. The debonded surfaces and material-dentin interfaces were prepared and examined under a
scanning electron microscope (SEM). Results: The microtensile bond strength values (mean±SD, in MPa) of PCR (Filtek P60 with Single Bond) and RMGIC (Fuji II LC), with or without the application of Cavity Conditioner (14.8±5.36, 12.01±4.43, 11.94±4.60,
respectively), did not differ significantly (P>.05). Partial adhesive and partial cohesive failures within the restorative material predominated. The distributions of failure modes did not differ significantly between groups (P>.05). Under SEM, each material was seen to
be closely adapted to dentin. Dentinal tubules were enlarged with etching, and the depth of penetration of resin tags of PCR was greater than for RMGIC. Smear plugs were incompletely removed by cavity conditioning. Conclusions: The bond strength of the PCR, Filtek P60 with Single
Bond, to dentin of primary teeth was comparable to that of the RMGIC, Fuji II LC. Conditioning of the cavity preparation with Cavity Conditioner did not improve the bond strength of Fuji II LC. The distribution of failure modes did not differ between materials.
This in vitro study compared bond strength and fracture modes of tooth-colored restorations in 2 types of cavity preparations in human primary molars.
Standardized Class II cavities (40 dovetail and ...40 box-only preparations) in extracted human primary molars were restored with packable composite resin (PC), resin-modified glass ionomer cement (RMGIC), resin-modified glass ionomer/packable composite resin laminate (RMGIC/PC), or resin-modified glass ionomer/packable composite resin laminate with an experimental bonding agent, K-14 (RMGIC/K-14/PC). The ultimate load at fracture was measured on marginal ridges, and fractured surfaces were examined microscopically.
The mean (+/-SD) ultimate load at fracture (ULF, in Newtons) of PC and RMGIC/K-14/PC in box-only preparations (400+/-98; 386+/-82) did not differ significantly from that found in dovetail preparations (377+/-80; 317+/-92), and the mean ULF of RMGIC and RMGIC/PC in box-only preparations (307+/-44; 325+/-72) did not differ significantly from that in dovetail preparations (352+/-71; 353+/-70). No interactions were seen between materials and preparations (P=.09). Fracture modes for restorations in dovetail (predominantly mixed) and box-only preparations (predominantly mixed and adhesive) differed significantly (P=.003), but not between restorative procedures (P=.052).
Tooth-colored restorations placed in vitro in box-only preparations did not differ in fracture resistance from those placed in dovetail preparations. On fracture loading, resin-modified glass ionomer restorations placed in box-only preparations were more likely to show adhesive failure than those placed in dovetail preparations.
