THE EVALUATION OF POST-OPERATIVE PAIN AFTER MULTIPLE-VISIT ROOT CANAL TREATMENTS WITH 2 DIFFERENT ROTARY NI-TI INSTRUMENT TYPES: A CLINICAL PROSPECTIVE STUDY

INTRODUCTION The post-operative pain (PP) of mild intensity is a common consequence of root canal preparation and is con- sidered a complex multifactorial process. Many factors inherent to patients, to the tooth and to the skills of the operator can influence the prevalence of PP. OBJECTIVES OF THE STUDY To investigate the incidence of and the factors influencing the PP after root canal treatments (RCT) associated to 2 different NiTi rotary instruments and to test the study method on a pilot sample. MATERIALS AND METHODS This observational prospective study was conducted in the Endodontic Department, University of Bologna. Thir- ty-three consecutive patients requiring management of endodontic disease and responding to the inclusion cri- teria were selected. Written informed consent was obtained from every involved patient. RCT were performed in multiple-visit, avoiding the risk that post-obturation pain could alter the results. Patients were given a ques- tionnaire to record the intensity and duration of post-endodontic pain, to be returned during the following set- ting. The enrolled clinicians were both endodontists (n=2) and postgraduate master’s students (n=14) operating under the supervision of trained tutors. The patient was questioned about the presence of preoperative pain in the previous 24 hours. The presence of Peri-Apical Lesion was assured by a value of Peri-Apical Index (PAI) ≥ 3, following Ørstavik et al. directives. The Curvature Radius was divided in 3 groups (straight, moderate or severe). After gaining straight access and removing interferences, the working length was electronically established and confirmed by an intraoperative radiograph. A manual glide path was then achieved using K-files up to 20 size. Mechanical preparation was performed using 2 different NiTi rotary systems with rotational speed and torque value adjusted according to manufacturer instructions. Used irrigant solutions were 5% NaOCl alternated with 1 to 3 mL of 10% EDTA. Obturation of the canal space with resin cement and carrier-based system was performed after 7 days and the PP was recorded as described. Both demographic and clinical variables were recorded in order to study their correlation in the aetiology of PP: patient, shaping and tooth-related factors were registered and statistically analysed. Distribution, intensity and duration of PP were evaluated with the aid of a 100 mm Visual Analogue Scale (VAS) at 24, 48, 72 hours and 7 days after initial appointment. Mean value or frequency distribution were carried out to describe quantitative or categorical parameters. Friedman test and Wilcoxon tests were used in comparison of VAS among time and between values (instrumentation and obturation at each time). Kruskal-Wallis test was performed aiming to compare VAS among curvature degree. level was set at 0.05. RESULTS Mean value of preoperative VAS was equal to 3.4±3.5 cm. Preoperative visual analogue scale measurements were always significantly different from Vas instrumentation and for obturation at each time (p=0.001), except at 24h. Significant differences were observed concerning the presence of pre-operative pain among the PP curvature (p=0.02). As for VAS relative to instrumentation in comparison with obturation, the only significant difference was observed at 24h, being the first higher than the second (p=0.024). Generally VAS mean values relative to instrumentation are higher than those of obturation. No significant differences were observed in VAS among dif- ferent curvature degrees. DISCUSSION The VAS is commonly used to represent pain intensity because of its reliability and validity. The use of more flex- ible NiTi instruments can be considered an important factor in determining a lower incidence and intensity of PP, by reducing apical transportation and by avoiding to push debris apically. CONCLUSION The prevalence of PP after RCT was significantly affected by the presence of pre-operative pain.