The analysis of restoration survival data in split-mouth designs.
OBJECTIVE
To report methodological difficulties with restoration survival data in controlled clinical trials on Class II amalgam restorations using a split-mouth design. The advantages and disadvantages of different ways of handling these data are described.


METHODS
Three statistical methods (Kaplan-Meier estimation, logistic regression with random component and Friedman's statistic) are compared using data from a controlled clinical trial in which cavosurface angle (regular or non-standard) and cavity wall finish (applied or not applied) determine four treatment modalities of New True Dentalloy restorations.


RESULTS
In this study logistic regression with a random component yields the best interpretable results. Cavity wall finish in combination with a regular cavosurface angle is indicated as the worst and cavity wall finish in combination with a non-standard cavosurface angle as the best treatment when the criterion is replacement or not within 15 years.


CONCLUSIONS
The dependency between restorations within a patient needs to be taken into account. Logistic regression with a random component may be a valuable alternative to very advanced statistical survival modelling when restricting the research question to replacement within a certain time interval is not a major problem.
Tobi
H
H
Department of Paediatric Dentistry, Academic Centre for Dentistry Amsterdam, The Netherlands. H.Tobi@acta.nl
Kreulen
C M
CM
Gruythuysen
R J
RJ
van Amerongen
W E
WE
D003722:Dental Alloys / Q000737:chemistry; D003723:Dental Amalgam / Q000737:chemistry; D003737:Dental Cavity Preparation / Q000145:classification / Q000706:statistics & numerical data; D003793:Dental Restoration, Permanent / Q000145:classification / Q000706:statistics & numerical data*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016015:Logistic Models; D008297:Male; D015233:Models, Statistical; D016032:Randomized Controlled Trials as Topic / Q000706:statistics & numerical data; D012107:Research Design / Q000706:statistics & numerical data*; D019233:Retreatment; D013499:Surface Properties
D003722:Dental Alloys; C031359:New True Dentalloy; D003723:Dental Amalgam