Effect of Crown Preparation Height on Retention of a Prefabricated Primary Posterior Zirconia Crown.

Abstract

<b>Purpose:</b> The purpose of this study was to evaluate the retention strength of prefabricated zirconia crowns for primary teeth with various crown preparation heights. <b>Methods:</b> Seventy-five extracted human teeth were prepared to have remaining occluso-cervical heights (OCH) of one mm, two mm, three mm, and four mm. Prefabricated posterior zirconia crowns (EZCrown) were cemented with glass ionomer cement. All groups were thermocycled, except for the nonthermocycled control group, which had three mm OCH. Instron E3000 was used for the pullout test. One-way analysis of variance (ANOVA) with Least Significant Difference post hoc test (P<0.05) were performed. <b>Results:</b> The means for the one-mm, two-mm, three-mm, and four-mm thermocycled groups were 1.7±1.0 MPa, 2.9±1.4 MPa, 3.1±0.7 MPa, and 3.3.0±0.6 MPa, respectively. The mean for the nonthermocycled control three-mm group was 2.7±0.8MPa. A significant difference in retention within the four thermocycled groups was observed (one-way ANOVA, P<0.001). <b>Conclusions:</b> The zirconia crown retention force is closely related to occluso-cervical heights. Two millimeters OCH is crucial for prefabricated zirconia crown retention. (Pediatr Dent 2019;41(3):229-33) Received November 14, 2018 | Last Revision February 25, 2019 | Accepted March 5, 2019.