The Clinical Effects Of Rapid Maxillary And Mandibular Expansion With Fixed Orthodontic Appliances In Hyperdivergent Patients

Background:Arch constriction is particularly common in clinic, mainly for the narrow maxillary and mandibular transverse widths,posterior crossbite,crowding of the anterior teeth,lingual inclination of the posterior teeth,duck buccal corridors,etc.Haas proposed the fixed palatal expander to rapidly correct transverse maxillary deficiency,open space and solve anterior teeth crowding in children and adolescents in the 1960s.However,due to the special anatomical structure,the mandibular has been unable expanded the same as the palate of maxillary,morever,many scholars has been skeptical of the stability of the mandibular arch expansion in children, so the clinical application is little.Taking into account of profiles makes us have been actively exploring non-extraction treatment methods, especially to explore the technology of mandibular arch expansion.Learning the advantages and disadvantages of the removed mandibular arch expander, such as Bihelix, Schwarz, Crozat, etc. as well as special anatomical structure of the mandible, we have fixed mandibular arch expander,then used the technology of maxillary and concurrent mandibular expansion and achieved clinical application satisfactory results.At present,the vast majority of the literature has claimed rapid maxillary expansion will result in posterior rotation of the mandible and opening of the mandibular plane angle,which seemed to indicate that hyperdivergent patients would be affected negatively by rapid maxillary expansion in the vertical dimension.But for hyperdivergent patients with narrow arches,if you choose to extraction treatment,you could easily lead to the excessive retraction of anterior influencing the surface type of appearance,and we found that those who are on a short-term research study arch expansion, and not a long-term tracking.Most of the literature is all about rapid palatal expansion on dental and skeleton research, little has been reported mandibular expansion on the dental and skeleton changes, not to mention maxillary and concurrent mandibular expansion of the dental and skeleton research.Therefore, the purpose of this study was to assess evaluate the skeletal and dental changes in young patients treated with rapid maxillary and mandibular arch expansion with fixed orthodontic appliances, determine whether an hyperdivergent patient is a contraindication for rapid maxillary expansion and mandibular arch expansion therapy and aims to provide a reference for future clinical orthodontic work.Objective: ①The purpose of this study was to evaluate the skeletal and dental changes in young patients treated with rapid maxillary and mandibular arch expansion with fixed orthodontic appliances,and discuss the related problems of the improvement,the effect and stability of expansion. ② compare the skeletal and dental changes between hyperdivergent and normal vertical dimension patients treated with rapid maxillary and mandibular arch expansion with fixed orthodontic appliances,and appraise whether hyperdivergent patient can be a contraindication for rapid maxillary expansion and mandibular arch expansion therapy.From the research some references are provide for the clinical plan of orthodontic treatment.Methods:The sample consisted of 87 patients who (arch constriction) had rapid maxillary and mandibular expansion with fixed orthodontic appliances from the Department of Orthodontics of Air Force General Hospital in the past ten years. Two groups were established:a hyperdivergent group (SN-MP≥40°, N=36) and a normal vertical dimension group (29°<SN-MP<40°, N=51).Lateral cephalograms and plaster model were taken before treatment (average age,12.1 years in both groups) and after fixed appliance therapy (average age,14.3 years in both groups).The statistical analyses were performed by using the SPSS13.0.A paired-samples t test was used to evaluate the treatment change.Results: ①Significant difference in treatment effects of maxillary and mandibular arch widths was found in 36 cases of hyperdivergent group variables examined (P<0.05).The maxillary canine (13-23) width increased 2.92mm,the maxillary first premolar (14-24) width increased 6.49mm,the maxillary second premolar (15-25) width increased 6.14mm,the maxillary first molar (16-26) width increased 4.80mm,the most obvious change was the maxillary the the premolar width;The mandibular canine (33-43) width increased 2.40mm,the mandibular first premolar (34-44) width increased 5.36mm,the mandibular second premolar (35-45) width increased 6.04mm,the mandibular first molar (36-46) width increased 3.25mm,the most obvious change was the mandibular second premolar width.No significant differences in treatment effects were found in vertical skeletal (MP-SN、MP-FH) variables examined(P>0.05),which indicated the mandible didn’t back down clockwise.No significant differences in treatment effects were found in sagittal skeletal (SNA、SNB) variables examined(P<0.05).N-ANS、ANS-Me. Posterior Face Height significantly increased 2.11mm,3.23mm,4.63mm,respectively(P<0.05).Dentoalveolar effects (ANB、Wits、Overjet) significantly decreased 1.65,1.44mm,1.53° variables examined(P<0.05), respectively. L1-MP significantly increased 3.45 (P<0.05),no significant differences in treatment effects of U1-SN、 Overbite、U1-Ll(P>0.05).②Significant difference in treatment effects of maxillary and mandibular arch widths was found in 51 cases of normal vertical dimension group variables examined (P<0.05).The maxillary canine (13-23) width increased 2.73mm,the maxillary first premolar (14-24) width increased 5.92mm,the maxillary second premolar (15-25) width increased 6.23mm,the maxillary first molar (16-26) width increased 3.94mm,the most obvious change was the maxillary the second premolar width;The mandibular canine (33-43) width increased 2.64mm,the mandibular first premolar (34-44). width increased 4.96mm,the mandibular second premolar (35-45) width increased 5.42mm,the mandibular first molar (36-46) width increased 3.50mm,the most obvious change was the mandibular second premolar width.No significant differences in treatment effects were found in vertical skeletal (MP-SN、MP-FH) variables examined(P>0.05),No significant differences in treatment effects were found in sagittal skeletal (SNA) variables examined,but SNB significantly increased 0.76°,which indicated mandibular had a slight forward movement.N-ANS、 ANS-Me、Posterior Face Height significantly increased 2.7mm,3.13mm,3.21mm.Dentoalveolar effects (Overjet、Wits) significantly decreased 1.92°,0.52mm。 L1-MP significantly increased 4.31° (P<0.05),no significant differences in treatment effects of U1-SN、Overbite、U1-L1(P>0.05).③No significant differences in treatment effects were found in vertical skeletal (MP-SN、MP-FH) variables examined from T1 to T2 between two groups,which indicated the mandible didn’t back down clockwise comparing normal vertical dimension group(P>0.05).No significant differences in treatment effects were found in sagittal skeletal (SNA、SNB) variables examined(P<0.05).Conclusion: ①The rapid maxillary and mandibular expansion can effectively open space and solve maxillary transverse deficiency and crowding for adolescents.②The rapid maxillary expansion and mandibular arch expansion with fixed orthodontic can be carried out successfully in young patients without detrimental effects on the vertical skeletal sagittal direction relationships.Thus, an hyperdivergent patient is not a contraindication for rapid maxillary and mandibular expansion therapy absolutely.