Introduction - Materials and methods.
S. Huumonen, M. Lenander-Lumikari, A. Sigurdsson & D. Orstavik
NIOM, Scandinavian Institute of Dental Materials, Haslum, Norway. University of Turku, Finland.
University of North Carolina at Chapel Hill, USA.
Bacteria in dental root canals play a decisive role in the development of chronic apical periodontitis, and their elimination is the ultimate aim of endodontic treatment of infected teeth. The role of the root filling is to serve as a protection after biomechanical root-canal preparation by preventing bacterial ingress and activity and allowing the regenerative processes in the periapical tissues to proceed without harming them. Different methods and materials have been proposed for root-canal obturation. Most make use of gutta-percha cones in conjunction with a sealer. A sealer is required, because gutta-percha adheres poorly to root dentine and will not effectively seal off the root-canal system. Several types of sealers have been used with different physical and biological properties. Ideally, the root-canal sealer should be biocompatible and have satisfactory physical- chemical properties. Currently, root-canal sealers are available based on various formulas such as epoxy resin, calcium hydroxide and zinc oxide-eugenol (ZOE). The choice of sealer, however, may have an influence on the results of endodontic therapy (Orstavik et al.1987, Waltimo et al. 2001).
Silicone is inert and biocompatible and has been widely used in medicine as an implant material (Habal 1984, Deva et al.1998). Silicone-based root-canal sealers are also available. However, there are no data on the clinical performance of this type of material in endodontic treatment.
The main purpose of this multicentre, prospective clinical study was to assess the treatment results up to 1 year after endodontic treatment of apical periodontitis using a silicone-based sealer (Roeko Seal Automix, Roeko, Langenau, Germany) in comparison with a ZOE-based, Grossmanâ€™s type sealer. Moreover, the results at 3 months after treatment were comparedwiththe12- month follow-up to assess the prognostic value of a 3- month control.
Materials and methods.
A total of 199 teeth were treated. Roeko Seal Automix (RS) was used according to manufacturerâ€™s directions; and Grossmanâ€™s sealer (GS) was mixed according to Grossman (1978) (Table 1). Treatment was conducted by senior dental students, graduate students or clinic staff at the University of North Carolina at Chapel Hill, USA; University of Turku, Finland; or by endodontists in private practice in Oslo, Norway.
Table 1. Formula of the Grossman's root-canal sealer (from Grossman1978).
The study was approved by the Ethics Committees in Finland, Norway and the US, and the subjects gave written informed consent. The primary criterion for inclusion of subjects in the study was the presence of radiographically discernible apical periodontitis on a single-rooted tooth or on one root with a single canal in one root of a multirooted tooth. Patients were excluded if
- they had diagnosis of diabetes,
- they had diagnosis of HIV infection, or other immunocompromising disease,
- they were <20 or >80 years old.
Clinical and dental variables.
For each tooth, the following information was recorded at every examination: tooth type, soft tissue status, subjective pain, sensitivity to percussion and mobility, caries, restoration, dental arch support, antagonist, and occlusal interference.
The method of instrumentation was at the discretion of the operator or clinic, but with minimum ISO 35 for apical instrumentation. Calcium hydroxide was used as an interim dressing for a minimum of 7 days. When the root was ready for filling, the sealer was chosen by the flipping of a coin. A standardized gutta-percha master point was used with a sealer, and cold lateral condensation of accessory points completed the root filling of each root. The root filling was characterized with regard to the type of sealer, and the quality and extension of the root filling as assessed radiographically. The patients participated in a 3- and 12-month recall programme of clinical/radiological examination.
Radiographic technique and scoring .
Radiographs were taken with individual bite-blocks attached to beam-guiding device. The exposed films were processed in an automatic processor.
For each tooth the level of marginal bone, density and length of root-canal filling and periapical status were recorded. The periapical status was assessed by means of the periapical index (PAI) scoring system, as described previously (Orstavik et al.1986) (Table 2). â€˜Improvementâ€™ was calculated as a case showing lower PAI score at 3 or 12 months than at root filling. PAI scores were also pooled toâ€˜successâ€™ (PAI1and 2) at12 months. The scores were used for quantitative analyses of the treatment results.
One investigator (S.H.) analysed all the radiographs. Before scoring PAI, the investigator was calibrated by twice scoring a standard set of 100 cases of individual radiographs. After scoring the reference teeth, the scores were compared to the authoritative scores, and a Cohenâ€™s k=0.7 was obtained, indicating good reproducibility.
Table 2. Basic elements of the PAI scoring system (Orstavik et al. 1986).
The sealer was considered the dependent variable of the study. The other clinical and radiographical variables of known or possible influence on treatment prognosis were recorded for description of the material.
As PAI scores are noncontinuous data, nonparametric tests were used for the analyses. The Mann-Whitney U-test was used to compare sealer groups at different time points. For analysis of the process of healing between different time points, the Friedmanâ€™s test was used to determine whether an overall difference existed. If a difference was found, the Wilcoxonâ€™s test was used for paired comparisons. A level of a=0.01 was chosen for statistical significance.