Publication details

Cox proportional hazard model and its application to data analysis of failure of endodontic equipment


BENDOVÁ Veronika BUMBALEK Michal KATINA Stanislav

Year of publication 2017
Type Article in Periodical
MU Faculty or unit

Faculty of Science

Keywords Cox proportional hazards model; Mtwo; Ni-Ti endodontic equipment; ProTaper; R software; Revo-S; Wizard navigator
Description Background and Aims. A very common statistical method used in statistical analysis of medical data is the Cox proportional hazard model (Cox model). The aim of this paper is to describe statistical data analysis as a process beginning with data management, followed by statistical coding and statistical analysis, including survival analysis and the Cox model, and finishing with the interpretation of results. The methods are applied to the data from stomatology - the influence of selected variables on the fracture of endodontic equipment. Statistical analyses were performed in R. Methods. Exploratory analysis and visualization methods are firstly presented. The survival analysis methods of Kaplan- Meier's product limit estimate, estimate of the cumulative hazard function, and Nair's 95% confidence bands are then calculated. Finally, the conditional hazard is modelled with the Cox model where regression parameters are tested with the Wald test and the proportionality of hazard with the Schoenfeld test. Results. In the Cox model, covariates influencing the fracture of endodontic equipment, the radius of the dental canal, the size and brand of the endodontic equipment (Mtwo, ProTaper, Revo-S, and Wizard Navigator) were used. The regression parameters of the radius of the dental canal and endodontic equipment size proved to be statistically significant. Compared to the reference brand Mtwo endodontic equipment, the regression parameters of the ProTaper and Revo-S drills proved to be statistically significant. Conclusions. Fracturing endodontic equipment during a root canal treatment often leads to undesirable resting of the tool in the root canal of the patient's tooth, which can lead to less successful endodontic treatment and thus less satisfactory prognosis. The dentist's efforts should allow the use of endodontic equipment for sufficient root canal treatment with minimum risk of fracturing the equipment inside the root system. Removal of the equipment is often very difficult and sometimes fails, resulting in subsequent hermetic closure of the root canal by the root filling not being possible and thereby greatly reducing satisfactory prognosis for the tooth.
Related projects: