title: Frailty approach for the analysis of clustered failure time observations in dental research.
abstract: Because dental implant failure patterns tend to cluster within subjects, we hypothesized that the risk of implant failure varies among subjects. To address this hypothesis in the setting of clustered, correlated observations, we considered a retrospective cohort study where we identified a cohort having at least one implant placed. The cohort was composed of 677 patients who had 2349 implants placed. To test the hypothesis, we applied an innovative analytic method, i.e., the Cox proportional hazards model with frailty, to account for correlation within subjects and the heterogeneity of risk, i.e., frailty, among subjects for implant failure. Consistent with our hypothesis, risk for implant failure among subjects varied to a statistically significantly degree (p=0.041). In addition, the risk for implant failure is significantly associated with several factors, including tobacco use, implant length, immediate implant placement, staging, well size, and proximity of adjacent implants or teeth.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Massachusetts General Hospital and Harvard School of Dental Medicine, 55 Fruit Street, Warren 1201, Boston, MA 02114, USA. schuang@hsph.harvard.edu
authors.forename: S K
authors.initials: SK
authors.lastname: Chuang
authors.forename: T
authors.initials: T
authors.lastname: Cai
authors.forename: C W
authors.initials: CW
authors.lastname: Douglass
authors.forename: L J
authors.initials: LJ
authors.lastname: Wei
authors.forename: T B
authors.initials: TB
authors.lastname: Dodson
mesh_terms: D000704:Analysis of Variance; D016000:Cluster Analysis; D015331:Cohort Studies; D003758:Dental Implantation, Endosseous / Q000379:methods / Q000706:statistics & numerical data; D015921:Dental Implants / Q000706:statistics & numerical data*; D017267:Dental Prosthesis Design; D018865:Dental Research / Q000379:methods* / Q000706:statistics & numerical data; D019232:Dental Restoration Failure; D005260:Female; D006801:Humans; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D016016:Proportional Hazards Models; D012044:Regression Analysis; D012189:Retrospective Studies; D012307:Risk Factors; D012907:Smoking; D018709:Statistics, Nonparametric; D016019:Survival Analysis
chemical_list: D015921:Dental Implants