Clinical Study on Marginal Fidelity of Temporary Crown Systems

Objectives: A new temporary crown system made of a preformed self-supporting malleable composite (Protemp Crown™, 3M Espe [PTC]) facilitates rapid fabrication of temporary crowns. This study compared the clinical marginal fit of PTC to molded temporary crowns made with autopolymerized BisAcryl (Luxatemp™, Zenith, DMG [LUX]).

Material and Methods: Patients having posterior crowns made were randomly assigned to a temporary crown group: PTC- The appropriate size tooth form was selected, unwrapped, trimmed with scissors, pressed over the tooth preparation, and molded to margins with fingers and instruments while was patient biting. It was initially light-cured (LC), gently teased off of tooth and LC for 20 sec. LUX- Material was placed in a vinyl polysiloxane (VPS) mold with an automixing gun, seated on tooth and allowed to polymerize. The mold was removed and crown retrieved. Crowns were trimmed with temporary polishing system (Brasseler USA) and cemented with either Systemp Link (Ivoclar Vivadent) or Dycal (Caulk Dentsply). At crown delivery appointment a small impression was made of temporary crown with low and high viscosity VPS. Epoxy resin (Buehler) was poured in impressions. Epoxy crown replicas were sectioned faciolingually into halves for premolars yielding 4 measurements and thirds for molars yielding 8 measurements. Crowns evaluated: 13-LUX, 17-PTC. Measurement of marginal discrepancies was according to methodology described by Sorensen (J Prosthet Dent 1990;64:18). Vertical discrepancy = marginal gap size; horizontal discrepancy:+ = overcontoured, - = undercontoured.

Results: Mean(sd) Marginal Discrepancy [um]: Vertical: PTC=665(363), LUX=819(513), Horizontal: PTC=+352(434), LUX= +193(691). ANOVA, Tukey's test showed significant difference between PTC & LUX for vertical & horizontal discrepancies at p<0.05.

Conclusions: Significant differences existed for mean vertical and horizontal marginal discrepancies between temporary crown systems. Both systems had marginal overcontouring.

This study was partially sponsored by 3M Espe.