[Bonding and enamel prisms: is the "bevel" still significant?]

Following a recall of the various preparations of the cavo-surface for posterior composites (straight, rounded, concave bevel, or without bevel), a study at the M.E.B. analysed the interface between the tooth and the filling in each case investigated. With the straight bevel with a slight angulation (40 degrees), the limit of the cavity-filling joint is clear. A disintegration of the material exists with the straight bevel having a 70 degrees angulation. The hiatus is even more marked with rounded or concave bevels. The absence of a bevel provides a clear occlusal joint without irregularity at the cavo-surface limit. In the light of this investigation and the results observed in the clinic in the medium and long term, it appears that the preparation of the cavo-surface margins of occlusal cavities of the pre-molars and molars for posterior composites may make do with a bevel which is not very extensive and not widely opened (40 degrees), or even the total absence of a bevel.