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Survival analysis of crown margin repair

by adminjay


Repairing crowns with defective margins is minimally invasive and cost-effective compared
with replacement. The authors’ objectives were to examine the survival trajectory
of crown margin repairs and to determine the factors associated with survival.


Records of adult patients from January 2008 through August 2019 were reviewed for
crown margin repairs completed at University of Iowa College of Dentistry. A total
of 1,002 crown margin repairs were found. Each repair was followed through the end
of study in 2019 or until an event (for example, additional repair, endodontic treatment,
crown replacement, or extraction). A Cox proportional hazards model was used to study
the relationship between selected covariates and time to event.


During the follow-up period, 32.8% of the repairs needed reintervention. In the final
model, repair material was the only significant covariate. No difference was found
between the survival of repairs done with resin-modified glass ionomer and amalgam.
However, the repairs done with resin-based composite and conventional glass ionomer
were more likely (1.5 times: 95% CI, 1.02 to 2.10 times; and 2 times: 95% CI, 1.40
to 2.73 times, respectively) to need reintervention than were those done with amalgam.


Median survival time of crown margin repairs was 5.1 years (95% CI, 4.48 to 5.72 years).
Median survival times for amalgam, resin-modified glass ionomer, resin-based composite,
and glass ionomer repair materials were 5.7 years (95% CI, 4.80 to 6.25 years), 5.3
years (95% CI, 4.73 to 6.34 years), 3.2 years (95% CI, 2.51 to 6.19 years), and 3.0
years (95% CI, 2.53 to 3.62 years), respectively.

Practical Implications

When considering crown margin repairs, resin-modified glass ionomer or amalgam is
preferable to resin-based composite or glass ionomer.

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