ANTEROPOSTERIOR DENTAL CHANGES RESULTING FROM POSTERIOR MINI-SCREW IMPLANT INTRUSION

Purpose To evaluate the anteroposterior dental changes (molars and incisors) resulting from posterior mini-screw implant intrusion treatment in mandibular retrognathic hyperdivergent patients. Materials and Methods The study sample included 17 (7 males, 10 females) previously treated subjects who were 13.2 ± 0.9 years old at initial records. Each subject was mandibular retrognathic and hyperdivergent. The orthopedic phase or intrusion phase of treatment was the focus of the study, which lasted approximately 2.4 ± 0.8 years. A rapid palatal expander was used to expand the maxillary teeth and serve as a rigid segmental appliance during posterior segmental intrusion. Two maxillary and two mandibular mini-screw implants were used for intrusion mechanics and for controlling the vertical dimension. A matched untreated control group was used in order to evaluate treatment effects. CBCT records were taken at the start of treatment and at the end of the orthopedic phase to determine dental and skeletal movements. Results The treated group showed significant (p<.05) relatively intruded nearly 4 mm, largely due to 2.5 mm of active maxillary molar intrusion relative to the palatal plane. Forward mandibular true rotation was over 3X greater in the treated group (2.01° vs 0.65°), with the chin moving anteriorly 4X more (3.1 mm vs 0.8 mm) than the controls (p.05), the chin also moved inferiorly approximately half as much as the control group (2.7 mm vs. 5.0 mm). Conclusions Posterior mini-screw implant intrusion in mandibular retrognathic hyperdivergent patients results in significant (approximately ½ step) class II molar and overjet correction, along with favorable orthopedic changes, mainly due to forward mandibular true rotation