Effect of Different Root Canal Preparation Sizes and Remaining Tooth Structure on the Survival of Endodontically Treated Mandibular Molars

NCT07583004 | Active Not Recruiting

• 2 other identifiers: SBU-GFOD-ENDO-SILANURUSTA-0032024/075
• Study Type: interventional
• Target: 60
• Locations: 1 country
• Sites: 1

Brief Summary

Teeth that have undergone endodontic treatment are biomechanically weakened compared to vital teeth due to factors such as extensive carious lesions, previous restorations, loss of marginal ridges and pericervical dentin, and hard tissue removal during access cavity preparation and root canal instrumentation. Additionally, the quantity and quality of the remaining coronal tooth structure, the presence of marginal ridges, the ferrule effect, and the integrity of pericervical dentin directly influence both fracture resistance and the long-term success of restorations. Following endodontic access cavity preparation, the fracture resistance of the tooth decreases by approximately 5%. This reduction increases to around 20-30% in the case of unilateral marginal ridge loss (mesio-occlusal \[MO\] or disto-occlusal \[DO\] cavities), and can reach up to 63% when both marginal ridges are lost (mesio-occluso-distal \[MOD\] cavities). This condition may lead to cusp deflection under occlusal forces and, particularly in the absence of appropriate post-endodontic restoration, may result in failures such as vertical root fractures. It has been reported that, after caries removal and access cavity preparation, the amount of remaining sound coronal tooth structure may play an important role in determining the extent of mechanical preparation during treatment. The goal of mechanical preparation of the root canal system is to remove infected dentin and biofilm as much as possible and to create a continuously tapered canal shape that allows effective delivery of irrigants to the apical region. Although conventional preparation principles may provide higher levels of disinfection, they have been associated with reduced tooth strength, particularly due to the loss of resistance in the pericervical area. This has led to the development of more conservative root canal preparation strategies using instruments with smaller apical sizes and tapers. Previous studies investigating the relationship between preparation size and fracture resistance have shown considerable heterogeneity. Moreover, the predominantly in vitro nature of these studies limits their ability to accurately simulate clinical conditions. In addition, factors such as the amount of remaining tooth structure after treatment and the effectiveness of the final restoration are often overlooked. Therefore, it is important to support in vitro findings with clinical studies. To date, there is no long-term clinical study in the literature evaluating the combined effects of conventional and conservative preparation strategies on clinical survival and periodontal health in teeth with varying degrees of coronal tissue loss. The aim of this study is to clinically and radiographically evaluate the survival of mandibular molars with different amounts of remaining tooth structure (O, MO/DO, and MOD) following conventional and conservative root canal preparation. The null hypothesis is that different preparation strategies and the amount of remaining tooth structure have a similar effect on tooth survival.

Conditions

Periapical Healing; Restoration Survival

Keywords

endodontics; restoration; preparation size; tooth survival

Outcome Measures

Primary Outcomes (1)

• Periapical healing

  Evaluation of the periapical healing based on the PAI score system. The system provides an ordinal scale of 5 scores ranging from 1 (healthy) to 5 (severe periodontitis with exacerbating features.

  at 6, 12 and 18 months

Secondary Outcomes (1)

• Restoration survival

  6, 12 and 18 months

Study Arms (2)

ProTaper Gold

EXPERIMENTAL

Mandibular molar teeth of patients will be treated using ProTaper Gold rotary file sytem.

Procedure: ProTaper Gold

TruNatomy

EXPERIMENTAL

Mandibular molar teeth of patients will be treated using TruNatomy rotary file sytem.

Procedure: TruNatomy file system

Interventions

ProTaper Gold PROCEDURE

Patients will be treated endodontically using Protaper Gold rotary file system

Also known as: File system

ProTaper Gold

TruNatomy file system PROCEDURE

TruNatomy file system

TruNatomy

Eligibility Criteria

• Age: 18 Years - 60 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• Patients with active caries in the relevant tooth that would create O, MO/OD, or MOD type cavitations.
• Patients with periodontally healthy teeth (Grade I mobility or \<4 mm pocket depth).
• Patients with no systemic diseases (ASA I or II).
• Patients between the ages of 18-60.
• Teeth where rubber dam isolation could be achieved.
• Cases where the remaining sound tooth structure allowed for a direct composite restoration.

You may not qualify if:

• Teeth that were not periodontally healthy (Grade II/III mobility or \>3 mm pocket depth).
• Teeth with complex root canal anatomy (curved canals, C-shaped canals, calcified/obstructed canals, etc.).
• Patients with systemic diseases, or those who were pregnant or breastfeeding.
• Patients with parafunctional habits such as bruxism.
• Teeth without an opposing tooth in the maxillary arch.
• Teeth that could not be restored due to advanced crown destruction or those with existing prosthetic restorations.
• Patients whose endodontic treatment had already been initiated elsewhere.
• Patients who experienced complications during the treatment procedure.

Sponsors & Collaborators

• Saglik Bilimleri Universitesi: lead

Study Sites (1)

Unişversity of Health Sciences

Ankara, 06120, Turkey (Türkiye)

Location

Related Publications (3)

• Usta SN, Silva EJNL, Falakaloglu S, Gundogar M. Does minimally invasive canal preparation provide higher fracture resistance of endodontically treated teeth? A systematic review of in vitro studies. Restor Dent Endod. 2023 Oct 17;48(4):e34. doi: 10.5395/rde.2023.48.e34. eCollection 2023 Nov.

  PMID: 38053776 RESULT

• Usta SN, Tekkanat H, Saglam Y, Aydin C. Exploring the impact of remaining tooth structure and preparation size on the fracture resistance of endodontically treated mandibular premolars. J Dent Res Dent Clin Dent Prospects. 2025 Mar 31;19(1):23-28. doi: 10.34172/joddd.025.42125. eCollection 2025 Mar.

  PMID: 40464029 RESULT

• Fransson H, Dawson V. Tooth survival after endodontic treatment. Int Endod J. 2023 Mar;56 Suppl 2:140-153. doi: 10.1111/iej.13835. Epub 2022 Oct 2.

  PMID: 36149887 RESULT

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: DOUBLE
• Who Masked: PARTICIPANT, OUTCOMES ASSESSOR
• Masking Details: Patients who will be treated and the assessor who will assess the periapical healing and restoration survival will be blinded regarding which file system was used.
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Associate Professor

Model Details: Patiens with different intact dentin walls will be divided into 2 groups based on the used file systems with different sizes.

Study Record Dates

• First Submitted: April 30, 2026
• First Posted: May 13, 2026
• Study Start: January 1, 2024
• Primary Completion: August 1, 2025
• Study Completion (Estimated): August 1, 2026
• Last Updated: May 13, 2026

Record last verified: 2026-04

Data Sharing

• IPD Sharing: Will not share

Locations

TU (1)