Relationship between the stability of micro-screw anchorage and vertical craniofacial pattern

Abstract

Objective To investigate the relationship between the vertical craniofacial pattern and the stability of micro-screw anchorage. Methods The failure rate of 286 self-drilling microscrews placed in the posterior region of the maxilla for anterior tooth retraction was analyzed. All 143 cases were sorted into high angle group and non-high angle group by FMA, as well as children group and adult group by age. The difference of failure rates was compared between high angle group and non-high angle group. Besides, the incidence of failure in both sides of one patient and the failure rates of re-implanted micro screws were also compared between high angle group and non-high angle group.The data were analyzed by chi-square or Fisher exact probability test with SPSS 15.0 software package. Results The average failure rate of 286 micro-implants was 17.5%. The failure rates were 30.6% in children high angle group, 16.7% in children non-high angle group, 21.1% in adult high angle group and 6.4% in adult non-high angle group, respectively. Both had significant difference between vertical craniofacial groups. The failure rates were 12.9% in both sides in children high angle group, 5.6% in children non-high angle group, 5.2% in adult high angle group and 0 in adult nonhigh angle group, respectively. No significant difference between vertical craniofacial groups was found. The failure rates of re-implanted micro screws were 47.4% in children high angle group and 38.9% in children non-high angle group, 50% in adult high angle group and 20% in adult non-high angle group, respectively. No significant difference between vertical craniofacial groups was found.Conclusions The average failure rate of 286 self-drilling micro-implants was 17.5%. There was significant relationship between the stability of micro-screw implants and vertical craniofacial pattern. Key words: Micro-screw anchorage; Self-drilling; Failure rate; Craniofacial pattern