Apical Size and Root Canal Treatment Success Trial (AS-RCT Trial)
Condition: Root Canal Therapy
Study type: Interventional

Summary: 
      This study is looking into two different ways to perform a root canal treatment. The study
      will look at differences and compare the two different treatment options over a 2-year
      period.More specifically, this study evaluates a small "skinny" root canal shape compared to
      a larger "broad" root canal shape and if this affects the success of the root canal
      treatment. Both types of treatment are standard of care and aim to treat the infection inside
      your tooth. When a tooth is infected with bacteria, we can see a dark area on the radiograph
      around the roots of the infected tooth. If this dark area becomes smaller or goes away
      completely after root canal treatment and you do not feel any pain or other symptoms, then we
      know that the treatment was successful and there is no need for further treatment on this
      tooth. To measure the size of the dark area around the tooth (i.e. volume) before and after
      the treatment we will need to take two limited volume three-dimensional radiographs (cone
      beam computed tomography-CBCT), one prior to treatment and one at two years after the root
      canal treatment is completed. These radiographs are more accurate in detecting changes in
      lesion size than the regular periapical radiographs. We will assess the changes in lesion
      volume for all teeth included in the study and that will help us find differences in success
      between the two root canal treatment protocols, We are specifically looking for persons that
      have been diagnosed with a necrotic permanent mandibular molar with an evident radiographic
      lesion (i.e. dark area around the tooth) that can be retained in the mouth with root canal
      treatment and permanent restoration. This study place participants in different treatment
      groups after randomization. Randomization means that you are placed by chance (like flipping
      a coin) into a treatment group. For this study, there are two treatment groups (protocol) and
      they are listed below.

      Protocol 1: Group S: Root canal treatment will be performed in 2-visits using hand files and
      rotary instruments to a final canal shape of size #25.

      Protocol 2: Group L: Root canal treatment will be performed in 2-visits using hand files and
      rotary instruments to a final canal shape of size #35
    

Detailed description: 
      We will perform a randomized, blinded clinical trial with clinical, microbiological and
      volumetric outcomes. The study population will be selected from adult patients in need of
      endodontic treatment on mandibular molars diagnosed with pulp necrosis and presenting with a
      visible radiographic lesion associated with at least the mesial root. Patients will be
      randomized into one of the two arms (group S: apical size#25; group L: apical size#35) and
      followed for 2 years post-treatment.

      Treatment sequence Endodontic residents under the direct supervision of a study investigator
      will perform all treatments; all providers will be trained and calibrated for root canal
      treatment protocol and microbial sample collection. The calibration session will be repeated
      annually until completion of the study.

      Treatment protocol First Appointment

        1. Pre-operative CBCT will be obtained and baseline clinical signs and symptoms will be
           recorded. Pain level will be recorded on a 0-10 visual analog scale (VAS).

        2. After ascertaining adequate local anesthesia, rubber dam isolation will be obtained and
           the field will be disinfected with 3% hydrogen peroxide and 2.5% sodium hypochlorite
           (NaOCl) solution as previously described (37).

        3. Access will be performed and the operative field will be again disinfected with 2.5%
           NaOCl followed by 5% sodium thiosulphate. A microbiological sample (S0) of the field
           will be obtained with paper points. S0 will be used as a negative control (i.e.
           sterility sample).

        4. The mesial canal walls will then be touched lightly with hand files to disrupt bacterial
           biofilms and a microbiological specimen (S1) will be obtained (described in detail
           below).

        5. Orifice will be enlarged with a Protaper Universal SX rotary file (Dentsply, Tulsa, OK)
           Apical patency will be determined with a size #10 hand file and working length will be
           obtained with the use of Root ZX apex locator (J Morita USA, Irving, CA) and verified
           with a PA radiograph.

        6. Coronal 2/3 of mesial canal WL will be instrumented with Vortex Blue rotary file 25/06
           (Dentsply). First apical binding file (FABF) will be recorded at this stage to serve as
           a covariable in the analyses.

        7. Apical 1/3 instrumentation of mesial canals will be carried out according to assigned
           group as follows:

      1. Group S: Instrumentation technique to working length (WL) using the sequence 15/04 →20/04
      →25/04 →25/06 Vortex Blue rotary file system (Dentsply).

      2. Group L: Instrumentation technique to WL using the sequence 15/04 →20/04 →25/04 →25/06 →
      30/04 →35/04 Vortex Blue rotary file system (Dentsply).

      8. Distal(s) canal instrumentation will be standardized for both groups as follows:

      1. Coronal 2/3 of distal canal will be instrumented with Vortex Blue rotary file 25/06 2.
      Apical instrumentation to WL using the sequence 15/04 →20/04 →25/04 →25/06 → 30/04
      →35/04→40/04 Vortex Blue rotary file system (Dentsply) 9. The canals will be irrigated using
      a 30-gauge side-vented needle with 6% NaOCl (10ml/canal) followed by 17%
      ethylenediaminetetraacetic acid (EDTA; 5ml/canal) followed by a final rinse of 6% NaOCl
      (10ml/canal) and 5% sodium thiosulfate (2ml/canal).

      10. A microbiological specimen (S2) will be obtained from mesial canals, and then the canals
      will be dried with paper points.

      11. Calcium hydroxide [Ca(OH)2] will be placed as an interim intracanal medicament and a
      temporary restoration consisted of Fuji II LC (GC Corp, Tokyo, Japan) will be placed in the
      access. A post-op radiograph will be made.

      Second appointment (within 10-14 days)

        1. Clinical signs and symptoms will be recorded. Pain level will be recorded on a VAS.

        2. After ascertaining adequate local anesthesia, rubber dam isolation will be obtained and
           the field will be disinfected as described above.

        3. Root canal system will be accessed and a second sterility microbiological sample will be
           obtained (S00).

        4. Ca(OH)2 will be removed by irrigating with 6% NaOCl (10ml/canal) followed by 17% EDTA
           (5ml/canal) and a final rinse of 6% NaOCl (10ml/canal). This will be followed by
           irrigation with 5% sodium thiosulfate (2ml/canal).

        5. A microbiological specimen (S3) will be obtained from mesial canals, and then the canals
           will be dried with paper points.

        6. Final obturation will be performed with gutta-percha and AH+ sealer utilizing the
           continuous wave condensation technique.

        7. Access will be restored permanently and patient will be referred to their dentist for
           full coverage restoration. Adequate existing full coverage restorations will remain in
           place. A post-op radiograph will be made.
    

Intervention name(s): final apical size instrumentation
Intervention type(s): Procedure
Intervention description(s): root canal instrumentation to two different final preparation sizes
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: randomized clinical trial 2 arms
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Treatment
Keywords: apical size; root canal treatment success; micro biome analysis; pulp necrosis