Correlations Between The Palate-related Factors And The Effectiveness Of Microimplant-assisted Rapid Palatal Expansion

Objective:This study aimed to investigate the correlations between the effectiveness of microimplant-assisted rapid palatal expansion(MARPE)and various factors,such as age,sex,midpalatal suture maturation stage,palate morphology,midpalatal bone thickness,and the palatal bone thickness at each microimplant insertion site in late adolescents and adults,and then provide guidance for the treatment of maxillary transverse deficiency and the effective application of MARPE.Methods:This study included 50 patients(mean age 23.30±7.03 years)treated with MARPE therapy at the Department of Orthodontics,Stomatological Hospital of Shandong University.All patients were taken CBCT before treatment and three months after expansion.Then Mimics 21.0 software was utilized for measurement.The measurements included the midpalatal suture maturation stage,palate morphology(including palate length,width and height),midpalatal bone thickness,and the total palate bone thickness,the nasal cortical bone thickness,the cancellous bone thickness and palate cortical bone thickness at each microimplant insertion site.The maxillary expansion ratio was used to evaluate the MARPE effectiveness,which was the ratio of maxillary expansion width to MARPE jackscrew expansion width measured in CBCT images.Patients were then grouped into low and high effectiveness groups according to the mean of maxillary expansion ratio.SPSSAU 22.0 software was used to perform statistical analysis.Results:1.There were no significant differences in maxillary expansion ratio in relation to sex(P>0.05).There were significant differences in maxillary expansion ratio in relation to the midpalatal suture maturation stages(P<0.05).In patients with stage C the maxillary expansion ratio was highest,followed by stages D and E.There were significant differences in maxillary expansion ratio in relation to age(P<0.01).In late adolescents(aged 15-19 years)the maxillary expansion ratio was highest,followed by young adults(aged 20-24 years)and old adults(aged≥25 years).2.The mean age,midpalatal suture maturation stage,and midpalatal bone thickness in regions 18mm to 24mm behind the incisive foramen of the low effectiveness group were significantly greater than those of the high effectiveness group(P<0.05).The total palate bone thickness and nasal cortical bone thickness at anterior microimplant insertion sites were significantly thinner in the low effectiveness group than that in the high effectiveness group(P<0.05).3.Age,midpalatal suture maturation stages,and midpalatal bone thickness in regions 18mm and 21mm behind the incisive foramen correlated negatively with the maxillary expansion ratio(r=-0.340,r=-0.390,r=-0.386,r=-0.335,P<0.05).The total palate bone thickness and the nasal cortical bone thickness at the anterior microimplant insertion sites correlated positively with the maxillary expansion ratio(r=0.365,r=0.418,P<0.01).Conclusions:1.In late adolescents and adults,the effectiveness of MARPE decreased with increasing age and midpalatal suture maturation stages,respectively,but was not related to sex.2.Palate morphology did not significantly affect the effectiveness of MARPE.3.The effectiveness of MARPE was related to the midpalatal bone thickness.Excessive bone thickness may induce greater resistance to maxillary expansion,whereas insufficient thickness may compromise the stability of microimplants.4.The effectiveness of MARPE was related to the palate bone thickness at microimplant insertion sites.Adequate bone thickness promoted the stability of microimplants,thus the palate bone thickness should be evaluated prior to MARPE treatment.