Purpose: To assess oral sedation success using midazolam and hydroxyzine with and without meperidine, and to assess the relationship between child temperament and sedation outcomes. Methods: This study recruited children between the ages of 36 and 95 months who were randomly assigned to receive dental treatment with an oral sedation regimen of midazolam (0.5 mg/kg) and hydroxyzine (1.0 mg/kg) with or without meperidine (1.5 mg/kg). Data were collected from the treatment log and electronic health records. Parents completed the Child Behavior Questionnaire Short Form (CBQ-SF) to assess temperament. Results: The study included 37 participants. The overall treatment success rate was 54 percent. There were no significant differences in sedation outcome with age, sex, insurance status, sedation regimen, isolation method or duration of procedure. Children with high pre-operative Frankl behavioral ratings were more likely to have a successful sedation outcome (P <0.01). Children who displayed high soothability experienced higher rates of success (P =0.04), which was more pronounced in the non-opioid group (P <0.01). Conclusion: The study showed low rates of success for a relatively small sample size. There was no difference in sedation success between the opioid group and non-opioid group. However, pre-procedure behavior and temperament characteristic of sooth- ability may warrant more exploration as predictors of sedation success.