Effect of surface coating on water migration into resin-modified glass ionomer cements: A magnetic resonance micro-imaging study

Magnetic resonance micro-imaging was applied to study water diffusion into resin-modified glass ionomer cement restoration and to evaluate the effect of surface coating over restoration. Two cavities were prepared on the labi al surface of extracted teeth and restored with resin-modified glass ionome r cement; one was protected with surface coating and the other was not. Imm ediately after restoration, the teeth were immersed in water. Progress of w ater diffusion into restorations was monitored by T-1 weighted spin-echo MR I at one-day intervals after the start of immersion. To quantify the water diffusion, a model was developed and compared with imaging data. Best fit y ielded an effective water diffusion coefficient D = (2.3 +/- 0.4) 10(-12) m (2)/sec. Experimental results demonstrated that surface coating protects th e dental cement against water intrusion from the surface of the restoration which faces the oral cavity, Such coating, however, does not prevent water penetration from the dentine side. (C) 2000 Wiley-Liss, Inc.