The Effect of Cryotherapy on Treatment Outcomes for Pulpotomy in Permanent Mature Carious Posterior Teeth: A Randomized Controlled Trial

Materials and methods Study design and setting This study is a prospective, single-center, double-blinded, parallel-group, randomized controlled trial conducted at the Dental Department, Yala Hospital. All clinical procedures are performed by a single trained operator. Clinical outcome evaluations are carried out by the same operator, while radiographic outcome evaluations are conducted by an experienced endodontist. To maintain blinding during periapical evaluation, the crown of each tooth is masked.

Study participants Inclusion Criteria

• Healthy patients aged at least 18 years old with deep or extremely deep carious lesions in mature permanent posterior teeth diagnose with asymptomatic or symptomatic irreversible pulpitis. Diagnoses are confirmed using Electric Pulp Test(EPT) and cold test. Pulpal and periapical diagnoses are based on terminology from the American Association of Endodontists (AAE, 2013).
• Teeth are restorable with direct composite restoration. Exclusion Criteria
• Teeth with subgingival caries and/or clinical attachment loss more than 3 mm and probing depth more than 4 mm.
• Negative responses to pulp sensibility tests, presence of sinus tracts, swelling, non-restorable crowns, immature roots, or no pulp exposure following complete caries removal in case of pre-operative diagnosis as asymptomatic irreversible pulpitis.
• Patients with systemic diseases involving bleeding disorders such as hemophilia, Von Willebrand disease, platelet disorders. And patients under taking all kind of anticoagulant and anti-platelet.
• Known allergies to non-steroidal anti-inflammatory drugs (NSAIDs).
• Pregnant or lactating patients.
• Teeth with pulpal obliteration.
• Necrotic pulp is found after access opening.
• Bleed cannot be stopped within 8 minutes after full pulpotomy26,27 Treatment procedure A comprehensive medical and dental history is taken before treatment. Preoperative data, including age, sex and tooth number are recorded in a predesigned patient's chart. The treatment, the study design, alternative treatment modalities, potential benefits, risks, and follow-up protocol are explained to the qualifying patients and informed consent is obtained from the voluntary patients who are willing to participate in the study.

Sample size calculation The sample size was calculated based on a suspected difference of 25% in the success rate between the control and cryotherapy group in inferior alveolar nerve block35 using n4Studies with a 80% power, a 5% α error. The minimum sample size was calculated to be 122. Considering patients lost to follow-up, a total of 140 teeth from different patients are included in this study.

Randomization and masking Block randomization with variable 4 block sizes is used to generate a sequence of random numbers for allocating the patients equally into two study groups. Each random blocks are sealed in an opaque envelope which is opened at the beginning of the clinical trial by dental assistant who the one only know the intervention and prepare the intervention for operator. New block will be open after all the patient in the previous block was completed and repeat until the end of the clinical trials to ensure the equality of group distribution: The VTP with and without cryotherapy intervention groups.