Dental Cement

Resin matrix dental materials undergo contraction and expansion changes due to polymerization and water absorption. Both phenomena deform resin-dentin bonding and influence the stress state in restored tooth structure in two opposite directions. The study tested three composite resin cements (Cement-It, NX3, Variolink Esthetic DC), three adhesive resin cements (Estecem, Multilink Automix, Panavia 2.0), and seven self-adhesive resin cements (Breeze, Calibra Universal, MaxCem Elite Chroma, Panavia SA Cement Plus, RelyX U200, SmartCem 2, and SpeedCEM Plus). The stress generated at the restoration-tooth interface during water immersion was evaluated. The shrinkage stress was measured immediately after curing and after 0.5 h, 24 h, 72 h, 96 h, 168 h, 240 h, 336 h, 504 h, 672 h, and 1344 h by means of photoelastic study. Water sorption and solubility were also studied. All tested materials during polymerization generated shrinkage stress ranging from 4.8 MPa up to 15.1 MPa. The decrease in shrinkage strain (not less than 57%) was observed after water storage (56 days). Self-adhesive cements, i.e., MaxCem Elite Chroma, SpeedCem Plus, Panavia SA Plus, and Breeze exhibited high values of water expansion stress (from 0 up to almost 7 MPa). Among other tested materials only composite resin cement Cement It and adhesive resin cement Panavia 2.0 showed water expansion stress (1.6 and 4.8, respectively). The changes in stress value (decrease in contraction stress or built up of hydroscopic expansion) in time were material-dependent.

Different techniques have been proposed for cementing crown restorations to implant abutments without excess cement extruding beyond difficult-to-access restoration margins. In one approach, a
copy abutment is fabricated onto which the cement-filled crown is fitted extraorally, allowing excess cement to be easily removed before intraoral transfer. This article presents a modification of this technique, wherein hot melt thermoplastic material is used for the copy abutment instead of
polyvinyl siloxane. This simplifies the technique, making it faster and more reliable. It involves injecting hot melt thermoplastic material into the wetted intaglio surface of the crown, fitting a dowel pin to serve as a removal handle, filling the crown with cement, fitting it onto the copy
abutment, and wiping the excess at the margins before intraoral transfer and definitive cementation.