12/15/2010 Retention of Veneered SSCs on Replicated Typodont Primary Incisors: An In Vitro Study

Resident: J. Hencler
Date: 12/15/2010

Article title: Retention of Veneered SSCs on Replicated Typodont Primary Incisors: An In Vitro Study
Source: Pediatric Dentistry-25:3, 2003
Author: Guelmann et al.
Major topic: Retention of veneered SSCs
Type of Article: Scientific
Main Purpose: To determine the effect of crimping and cementation on retention veneered SSCs.

Overview of method of research:
120 crowns (90 nusmile) and (30 plain) were assessed for retention. An ortho wire was soldered perpendicular to the incisal edge and the crowns were fitted to acrylic replicas of ideal crown preps and were divided into 3 grps. Grp 1 crown crimp only, grp 2 crown cemented only, and grp 3 crowns crimped and cemented. An Instron machine recorded the amount of force necessary to dislodge the crowns.

Findings:
Grp 3 was statistically more retentive than grps 1 or 2 and Grp 2 was statistically more retentive than grp 1. In grp 1, Unitek crowns were more retentive than veneered crowns. In grp 2, NuSmile crowns showed less retention than all other brands, and in grp 3, Kinder Krowns showed better retention than all other brands.

Key points in the article discussion:
This study confirmed other reports that SSC retention is largely dependent on cement and demonstrated the beneficial effects of crimping in conjunction w/ cementation. Unitek crowns were more retentive in the “crimping only” grp as a direct result of the “snug fit” obtained from the internal walls of the crown being in direct contact w/ the tooth. The Dura Crown manufacturer clains crimping on both facial and lingual is possible w/out compromising the veneer integrity but this study found it was a challenge to crimp the facial margin w/out damaging the facings in some way. Kinder Krowns allowed crimping on the lingual surface only. These crowns are designed with an “incisal lock” technology to provide additional retention of the esthetic facings by mechanically forcing a portion of the facing material through openings on the incisofacial edge to the internal aspect of the crown. This prevented the Kinder Krowns from fully seating on the ideal tooth prep used in this study. Significant metal-cement bond failure for NuSmile primary crowns in the cementation only grp was difficult to explain. The use of natural teeth and a different luting cement may have a different impact on the results of this study.

Summary of conclusions:
Crimping does have a significant effect on retention of SSCs to acrylic replicas of primary teeth. The presence of cement significantly improved crown retention. Higher retention values were obtained for all brands tested when crimping and cement were combined. Crowns w/ veneer facings were significantly more retentive than the no-veneer (Unitek) crowns when cement and crimp were combined.

Assessment of article: Good article, nothing groundbreaking.