Evaluation of the Treatment Effects of Tooth Borne Versus Bone-anchored Protraction Procedures in Class III Patients With Maxillary Deficiency

Today, the treatment of class III malocclusion is becoming more important due to the increased awareness of people about their appearance and the impact of appearance on the psychosocial state.

Various studies have shown that 40% of class III malocclusions are clinically caused by maxillary deficiency, 42% by mandibular excess, and 18% by a combination of maxillary deficiency and mandibular excess.

The face mask is the most effective treatment modality for class III malocclusions caused by a maxillary deficiency. The rationale for using a face mask is to apply heavy forces to the midface to advance the maxilla forward. These forces cause disarticulation by initiating resorption and apposition in the sutural articulations. However, undesirable dental effects arise from the use of tooth-borne rapid maxillary expansion (RME) during these treatments. These include loss of anchorage and incisor proclination during the mesialization of the maxillary dentition, extrusion of the upper molars and posterior mandibular rotation, and insufficient anterior displacement of the maxilla (1-3 mm).

Studies have shown that increasing the skeletal effects can reduce post-treatment relapse, one of the most important problems in orthodontics.

To increase the amount of maxillary skeletal advancement and to minimize the side effects of tooth-borne maxillary expansion and protraction, a new bone-anchored hybrid hyrax appliance has been proposed. Hybrid hyrax treatment has the following advantages over tooth-borne mechanics:

• Since the force is applied close to the center of resistance of the maxilla, counterclockwise rotation of the maxilla and related posterior mandibular rotation are not observed.
• Transversal forces are applied to premolars or deciduous molars and mini implants without the risk of periodontal damage, fenestration, and dehiscence that may occur with tooth-borne appliances are avoided.
• Mesial migration of the dentition, proclination of the upper incisors, and occupation of the necessary place for the canines to erupt are avoided.
• Treatment is minimally invasive.
• Upper and lower arches remain completely accessible for orthodontic interventions.
• Only skeletal maxillary advancement is achieved. In our study, additionally, the Alternate Rapid Maxillary Expansion and Constriction (AltRamec) protocol, which increases the skeletal effects during maxillary protraction by providing more effective disarticulation of circummaxillary sutures than conventional rapid maxillary expansion was used.