Here is the design of a clinical trial:

Official Title: Effectiveness of DentalVibe Comfort System in Reducing Injection Pain and Anxiety During Local Anaesthesia in Paediatric Patients

Included conditions:
- Pain Management
- Local Anaesthesia

Study Armgroups:
- {'label': 'Control group', 'type': 'ACTIVE_COMPARATOR', 'description': 'Local anaesthesia with conventional syringe', 'interventionNames': ['Procedure: Local anaesthesia with conventional syringe']}
- {'label': 'DentalVibe group', 'type': 'ACTIVE_COMPARATOR', 'description': 'Local anaesthesia with conventional syringe + DentalVibe', 'interventionNames': ['Device: Local anaesthesia with conventional syringe + Dentalvibe']}

Interventions:
- {'type': 'PROCEDURE', 'name': 'Local anaesthesia with conventional syringe', 'description': 'Buccal infiltration in posterior maxillary region with traditional technique. A 27 gauge short needle is inserted in the mucobuccal fold above the tooth to be anesthetized.\n\nLocal anaesthetic infiltration speed 1ml/min. Drug: Local anaesthetic - Ubistesin - 4% Articaine with adrenaline 1: 200 000 1.7 mL', 'armGroupLabels': ['Control group']}
- {'type': 'DEVICE', 'name': 'Local anaesthesia with conventional syringe + Dentalvibe', 'description': 'Buccal infiltration in posterior maxillary region. The tip of the DentalVibe device is placed in the mucobuccal fold above the tooth to be anesthetized. The device is activated for 5 s. A 27 gauge short needle is inserted as close as possible to the inner side of the prong while the vibration is still on.\n\nLocal anaesthetic infiltration speed 1ml/min. After injection the needle is withdrawn and vibration continues for another 5 s.\n\nDrug: Local anaesthetic - Ubistesin - 4% Articaine with adrenaline 1: 200 000 1.7 mL', 'armGroupLabels': ['DentalVibe group']}

Primary Outcomes:
- {'measure': 'Pain felt during injection using visual analogue scale', 'description': "Self-reported pain by the patient immediately after local anaesthesia infiltration using a VAS (visual analogue scale), containing a combination of Numeric Rating Scale (0-10, where 0 means no pain, 10 - worst possible pain) and Wong-Baker Faces Pain Scale, including pictures of facial expressions with correlating numbers of 0-10 (0 being 'no hurt' and 10 being 'hurts worst'). The combination allows children to pick a facial expression, that corresponds with their pain and see a number that matches it.", 'timeFrame': 'Immediately after local anaesthetic delivery'}

Please estimate the sample size based on the assumption: 
The error was set at 5% (significance level) and the power test at 95%. A dropout rate of 10% was anticipated.
Sample size calculation
        Given the lack of fully comparable research and the unknown population SD, we conducted a pretest with 20 subjects and considered the behaviour of this subgroup as population estimate. To estimate sample size for the primary outcomeâself-reported pain felt during injection, according to the VASâwe applied a t-test for paired groups (G* Power software V.3.1,6 since we have two groups (primary molar in theÂ right and left quadrants of upper jaw) on the same patient.
        The effect size was determined using the formula
        
ES=ControlâTreatedSDpooled=2.33â0.333.25=0.62,
        where SD is the pooled SD,Â an average of the SD of the experimental and control groups. The error was set at 5% and the power test at 95%. According to the calculation, a sample of 37 patients will be necessary to detect differences in pain. Since dropouts are unavoidable when collecting follow-up data, this number needs to be adjusted for the estimated dropout rate. During the pretest, we had a dropout rate of 5% for collecting the follow-up data, and if we anticipated a higher dropout rate for this study, we conservatively allowed for a 10% dropout rate. Adjusting the sample size for this dropout rate results in a sample of 41 patients needing to be recruited.