Here is the design of a clinical trial:

Official Title: A Split-mouth Clinical Study on the Effectiveness of Er:YAG Pulse Therapy for Achieving Pre-emptive Dental Analgesia in Children

Included conditions:
- Caries, Dental

Study Armgroups:
- {'label': 'Laser analgesia', 'type': 'EXPERIMENTAL', 'description': 'Procedure: Laser analgesic procedure Performing protocol for pre-emptive laser analgesia with Er:YAG laser (Litetouch, Syneron) switched on.', 'interventionNames': ['Procedure: Laser analgesic procedure']}
- {'label': 'Placebo analgesia', 'type': 'PLACEBO_COMPARATOR', 'description': 'Procedure: Placebo analgesic procedure Performing imitation of laser analgesic protocol with Er:YAG laser (Litetouch, Syneron) switched off - no pulse energy applied.', 'interventionNames': ['Procedure: Placebo analgesic procedure']}

Interventions:
- {'type': 'PROCEDURE', 'name': 'Laser analgesic procedure', 'description': 'Water mist spray set to "maximum", non-contact handpiece with sapphire tip. Tip-to-tissue distance 10 mm from the tooth neck, achieved by using a spacer. Energy is delivered to the enamel above the gingival margin adjacent to the cemento-enamel junction (perpendicularly towards the dental pulp) on each of the four line angles of the tooth for 30s, moving the laser handpiece in a sweeping action. Pulse energy - 0.2 W/ 10 Hz/ 20 mJ. Follows increase of energy and repetition of protocol - 0.6 W/ 15 Hz/ 40 mJ. Total duration of LA-induction - 240s.', 'armGroupLabels': ['Laser analgesia']}
- {'type': 'PROCEDURE', 'name': 'Placebo analgesic procedure', 'description': 'Performing imitation of laser analgesic procedure. No pulse energy applied, non-contact handpiece with sapphire tip. Moving the laser handpiece in a sweeping action towards the cemento-enamel junction (pointing perpendicularly towards the dental pulp) on each of the four line angles of the tooth. Total duration of placebo analgesia induction - 240s.', 'armGroupLabels': ['Placebo analgesia']}

Primary Outcomes:
- {'measure': 'Pain felt during treatment according to a visual analogue scale', 'description': "Reported by the patient at the end of the dental treatment session on a VAS (visual analogue scale), which contains a combination of Numeric Rating Scale (0-10, where 0 means no pain, 10 - worst possible pain) and Wong-Baker Faces Pain Scale, which includes 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': '1 hour'}

Please estimate the sample size based on the assumption: 
The error was set at 5%, the power test at 95%, and a 10% drop-out rate was conservatively allowed.
2.3.4
          Sample size calculation
          Given the lack of comparable research and the unknown population standard deviation we conducted a pretest with 20 subjects and considered the behavior of this subgroup as population estimate. To estimate sample size for the primary outcomeâpain felt during laser ablation of moderate carious lesion, according to the VAS scaleâwe applied a t test for paired groups (Gâ Power software version 3.1),[13] since we have 2 groups (first upper molar in right and left quadrant) on the same patient.
          The effect size was determined using the formulaÂ 
          Where SD is the pooled standard deviationâan average of the standard deviations 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 drop-outs are unavoidable when collecting follow-up data, this number needs to be adjusted for the estimated drop-out rate. During the pre-test, we had a drop-out rate of 5% for collecting the follow-up data and if we anticipated a higher drop-out rate for this study, we conservatively allowed for a 10% drop-out rate. Adjusting the sample size for this drop-out rate results in a sample of 41 patients needing to be recruited.