This pilot study was performed to test the hypothesis that an orthodontic oral appliance (OA) that is designed to work against the backwardly directed forces on the upper incisors may counteract the reduction in overjet from these devices.Thirty patients with normal bites, good oral health, and milder sleep apnea were randomized to treatment with either OAs or orthodontic OAs. Bite changes were evaluated on plaster casts and radiographs and by questionnaires after a mean of 2.4 years in 19 frequent users.Four of nine patients in the orthodontic OA group increased their overjet by > or =0.4 mm, while none of the 10 patients in the OA group experienced that effect.Only the orthodontic OA increases the overjet; this design may therefore be beneficial to patients at risk of negative effects on their bite during OA treatment.