Objective: To assess and compare the 2940 nm erbium:yttrium-aluminum-garnet (Er:YAG) laser versus a conventional rotary treatment during cavity preparation in children with regard to anxiety level, pain perception, restoration integrity, and bond interface quality.

Materials and Methods: In a randomized, blinded trial using a split-mouth design, forty (9-12-year-old) children with 80 carious deciduous molars were included. The cavity in one quadrant was treated conventionally using a bur, while the cavity in the other quadrant was prepared using an Er:YAG laser. Venham's dental anxiety scale and pulse rate measurement using a fingertip pulse oximeter were used to evaluate dental anxiety levels. The Wong-Baker facial pain rating scale and the number of local anesthesia required during both interventions were further applied to investigate pain perception. At the 1-year follow-up, clinical examinations was conducted and the integrity of the restorations was clinically assessed according to the Ryge criteria. Lastly, the restored teeth were extracted and histologically evaluated for bond interface quality using scanning electronic microscopy.

Study Design: A randomized, blinded split-mouth study was conducted with a sample of 40 healthy children aged 9 to 12 years (N=40 children) / (n=80 teeth). The children were divided into two groups randomly. The first group included 20 children who were assigned to receive the conventional treatment at the first visit and the laser treatment at the second visit (N=20 children) / (n=40 teeth). The second group was assigned to receive the laser treatment at the first visit and the conventional treatment at the second visit (N=20 children) / (n=40 teeth). Both groups received the laser and conventional treatment and were assessed for pain and anxiety during both interventions. After a follow -up period of 1 year, an analysis of the restorative integrity evaluation was performed using the Ryge criteria. The restored teeth were extracted according to the normal exfoliation schedule and analyzed for bond interface quality evaluation.

Study Sample: Study participants were recruited from the patient population at the pediatric dentistry clinics at King Abdulaziz University Dental Hospital in Jeddah, Saudi Arabia. Every patient in the appropriate age range has been examined for class I carious lesions of the molars, and in patients where these molars were present, the researcher was notified by the practitioner. The researcher was to make the final decision about the suitability of patients to be included in the study sample. The researcher explained the study procedures to the parents of potential subjects, and if they agreed to participate, consent to participate in the study has been obtained from the parents of the pediatric patients.

Sample Size Calculation: According to the authors' assumptions, a sample size of 31 pairs will have 80 percent power to detect a difference in proportions of restorations integrity of 0.2 when the proportion of discordant pairs is expected to be 0.21, and the analysis method is a McNemar's test of equality of paired proportions with a 5% two-sided significance level.

Randomization Procedure: Each patient has undergone conventional caries removal on one affected molar and laser caries removal on the other. The researcher prepared 80 sealed envelopes divided into two groups in 2 boxes, each containing 40 envelopes. The first group was for the treatment procedures randomization, 20 of which contained instructions to perform conventional caries removal on the first tooth and laser caries removal on the second, and other 20 contained instructions to use the laser on the first tooth and the rotary bur on the second. The second group for tooth randomization consisted of 40 envelopes, 20 of which contained instructions to treat the tooth in the right quadrant first, and 20 of which contained instructions to treat the tooth in the left quadrant first. The envelopes were identical from the outside, only the messages inside differed. The subjects, who did not know the contents of the envelopes, were asked to select two envelopes, one from each group. The researcher opened them and read the contents to be informed as to which treatment and which tooth would be performed first.

Treatment Procedure: The conventional treatment and the laser treatment took place at two separate visits, approximately one week apart, with the order of the treatments to be determined by the randomization process. The teeth were restored using Clearfil Universal Bond Quick self-etching primer, bonding resin and Clearfil APX composite resin.

One-Year-Follow-Up: Follow-up took place one year later, at which time clinical examination was conducted. The integrity of the restorations has been clinically examined. The examiner did not know which tooth had received which treatment. The restorations were evaluated according to Ryge criteria; the criteria published by the United States Public Health Service. The criteria that were measured included: anatomical form, axial contour, marginal contact, margin discoloration, secondary caries, and visible plaque. Each criterion received a numerical rating from zero to two (zero to three for some criteria) and a score of Alpha, Bravo, or Charlie (or Delta for marginal contact and axial contour.

Teeth Extractions: The restored teeth were followed up for two more years and were extracted whenever it was determined that the root of the successor's tooth was formed (according to the normal tooth shedding time of the patient). The extracted teeth were evaluated for bond interface quality.

Inclusion Criteria:

• Healthy patients between 9 and 12 years of age.
• Simple occlusal caries that is limited to enamel and dentine without proximal caries, or pulp involvement in at least two primary molars (pairs).
• Primary molars with 1/3rd of their root remained.
• Primary teeth have permanent successor teeth with 1/2 of the root formed.

Exclusion Criteria:

• Caries lesion that had reached or was approaching the pulp.
• Previous fillings.
• Periapical lesions, or dental abscess.
• No permanent successor teeth.
• Behavioral or medical problem.

The examiner who clinically evaluated the restorations using Ryge criteria did not know which tooth had received which treatment.