The effect of provisional cements on retention of cast dowels

Objectives: The purpose of this study was to investigate the effects of prior provisional cementation on the retention of cast dowels.

Methods: Thirty single-rooted premolars were collected and decoronated. The pulp was extirpated and a 10 mm post space was prepared using a 1mm-diameter Parapost drill. Thirty resin patterns were fabricated and casted with noble alloy. The prepared teeth were divided randomly into 3 groups (10 each). In two groups, temporary dowels were cemented with either TempBond® or TempBond® NE. After 24 hours, the temporary dowels were removed and cast dowels (type III) were cemented using zinc phosphate cement. In the third group (control), the cast dowels were cemented with zinc phosphate cement without prior cementation of temporary dowels. A vertical tensile force was applied at a crosshead speed of 1 mm/min until the dowel-dentin seal broke. The load to dislodgement (kg) for each cast dowel was recorded and data were analyzed using one-way ANOVA followed by Tukey HSD test. A p < 0.05 was considered significant. Data are presented as mean ±SD.

Results: There was a significant difference in the load to dislodgement between the three groups tested (F=6.54, p =0.005). Dowels in the control group exhibited the highest load to dislodgement (41.1 ± 13.4 kg), this was significantly higher than when temporary dowels were cemented provisionally with TempBond® NE (26.7 ± 7.1 kg, p =0.014) or TempBond® (27 ± 9, kg p =0.016). There was no significant difference between the two test groups (p=0.998).

Conclusion: Under the conditions of this study, the use of temporary cement before the final cementation of dowels significantly affects the retention values and thus it is not recommended.