Comparison of the soft and hard tissue effects of two different protraction mechanisms in class III patients: a randomized clinical trial

Abstract

Objective: The objective of the present study is to test the null hypotheses that there were no significant differences for hard and soft tissue changes induced by mini maxillary protractor (MMP) and face mask and rapid maxillary expansion (FM/RME).

Materials and methods: Thirty-two patients who met the criteria were randomly divided into two groups: 16 patients (males/females 7/9) in the MMP group and 16 patients (males/females 6/10) in the FM/RME group. The patients in both groups were instructed to wear the appliances for at least 20 h per day until a 2-mm positive overjet was achieved. Hard and soft tissue profile changes observed by MMP and FM/RME were compared using paired and Student's t tests.

Results: Class III malocclusion and negative overjet were improved by means of skeletal changes in conjunction with upper incisor proclination and lower incisor retroclination in both groups. Maxilla and surrounding soft tissues (SNA, Ls-E, and Ls-PMV) were significantly moved anteriorly with less rotation of the palatal plane in the MMP group. Mandibular incisors were found to be more retrusive in the FM/RME group (p = 0.024).

Conclusion: Both groups showed similar effects except more anterior movement of the maxilla and surrounding soft tissues with less rotation of the palatal plane and retrusion of lower incisors in the MMP group.

Clinical relevance: This is the first study to compare the soft and hard tissue changes induced by MMP appliance with a conventional FM /RME.

Keywords: Class III; Face mask; Maxillary deficiency; Maxillary protraction.