Molar Intrusion in Open-bite Adults Using Zygomatic Miniplates

Area of Science:

• Orthodontics and Dentofacial Orthopedics
• Skeletal Biology
• Biomechanical Engineering

Background:

• Skeletal anterior open bite presents a complex orthodontic challenge, often involving posterior dentoalveolar excess.
• Traditional methods for correcting open bite may have limitations in achieving significant skeletal changes.
• Maxillary molar intrusion is a key strategy for managing open bite, but effective skeletal anchorage is crucial.

Purpose of the Study:

• To evaluate skeletal, dental, and soft tissue changes following maxillary molar intrusion using zygomatic miniplates in adult skeletal anterior open bite patients.
• To measure the amount and rate of molar intrusion and assess changes in molar axial inclination.
• To analyze the effects on mandibular position and facial convexity.

Main Methods:

• A study group of 13 adult skeletal anterior open bite patients with posterior dentoalveolar excess was selected.
• Zygomatic miniplates were placed bilaterally, and intrusive force was applied to maxillary molars using NiTi coil springs (450g per side).
• Lateral and posteroanterior cephalograms were taken before and after intrusion; data analyzed using Wilcoxon Signed Ranks test.

Main Results:

• Mean molar intrusion of 3.1mm was achieved at a rate of 0.36mm/month, resulting in a mean bite closure of 6.55mm.
• Significant increases in SNB and SN-Pog angles and decreases in ANB, MP-SN, and N-S-Gn angles indicated mandibular autorotation.
• No significant buccal tipping of the intruded molars was observed.

Conclusions:

• Zygomatic miniplate anchorage provides an effective method for correcting skeletal open bites through posterior dentoalveolar intrusion.
• Posterior tooth intrusion with skeletal anchorage induces counterclockwise mandibular rotation, improving the anteroposterior intermaxillary relationship.
• This technique leads to significant improvements in facial soft tissue convexity and bite depth.