Effect of different rotary instrument designs (protaper ultimate and protaper gold) on postoperative pain and bacterial reduction: a randomized clinical trial.

backgroundProTaper Ultimate (PTU) is one of the recently introduced nickel–titanium rotary endodontic systems and possesses distinctive instrument design features characterized by a parallelogram cross-sectional geometry. This design is produced through an alternating offset machining process, resulting in a file whose center of mass is not aligned with its center of rotation. Such configuration is claimed to create increased space for debris removal during instrumentation while simultaneously reducing stress concentration on the instrument during cutting. Despite the manufacturer’s claims regarding the novel geometry and expected advantages of ProTaper Ultimate files, independent clinical scientific evaluation of these features remains limited. Understanding whether the parallelogram cross-section and offset center of mass truly translate into improved clinical performance and enhanced debris elimination is essential for evidence-based endodontic practice. Therefore, this study aimed to objectively assess these claimed advantages, providing clinicians with reliable data regarding the bacterial reduction and postoperative pain of PTU. The findings will contribute to informed decision-making when selecting rotary systems and may clarify the clinical relevance of this new design concept.

aimThis prospective randomized double-blinded trial clinically compared postoperative pain and bacterial reduction after using two rotary systems; ProTaper Ultimate (PTU) versus ProTaper Gold (PTG) in necrotic maxillary premolars. METHODOLOGY: Fifty-six patients with necrotic maxillary first premolars with normal periapical condition were randomly assigned to PTU (n=28) or PTG (n=28). Root canal preparation was performed using the allocated file system. The primary clinical outcome was postoperative pain and was recorded preoperatively and at 6, 12, 24, and 48 hours using a modified visual analogue scale (mVAS). The secondary outcome was intracanal bacterial load and bacterial reduction percentage, quantified as aerobic and anaerobic colony-forming units per milliliter (CFU/ml). Samples were collected pre-instrumentation (S1), post-instrumentation (S2), and after final irrigation with 2.5% sodium hypochlorite (NaOCl) (S3). Incidence and number of analgesic intakes was also documented. Data were analyzed using Student’s t-test, chi-square, Mann-Whitney U test, Friedman’s test, frequencies (n), percentages (%), Fisher exact test, repeated measures ANOVA, and Spearman’s correlation coefficient (ρ).

resultsPostoperative pain was significantly higher with PTU than PTG immediately (p=0.004) and at 12 hours (p=0.035), 24 hours (p=0.002), and 48 hours (p=0.005), with no significant difference at 6 hours (p=0.055). Analgesic intake was significantly greater in the PTU group, which was 3.45-fold more prone to require medication. PTU showed significantly lower bacterial reduction than PTG after instrumentation (S1–S2: aerobic p=0.0014; anaerobic p=0.0326) and after final irrigation (S1–S3: aerobic p=0.0183; anaerobic p=0.0276). Spearman’s correlation analysis revealed no significant association between bacterial reduction and pain scores in either group (PTU: ρ = 0.06, p = 0.760; PTG: ρ = 0.03, p = 0.896).

conclusionPTG, with its convex triangle cross-section and lower rotational speed and torque, resulted in lower postoperative pain intensity, less need for analgesics and statistically higher bacterial reduction compared to the parallelogram cross-section of PTU.

trial registrationThe study protocol was listed on www.clinicaltrials.gov (ClinicalTrials.gov identifier: NCT05305742) https://clinicaltrials.gov/study/NCT05305742?cond=Necrosis&viewType=Table&term=GOLD&rank=5 . ClinicalTrials.gov identifier NCT05305742 registration date (30/03/2022).