| Objective: Take an adolescent borderline case as an example, comparing thechanges of soft and hard chin position and morphology before and after treatment toevaluate the influence of non-extraction orthodontic treatment on chin position andmorphology. At the same time we would like to disscuss what effect does the delepmentfactor will do to chin, thus to provide a suggestion for clinical treatment.Methods: An adolescent male was choosed, who had been a patient ofStomatology Hospital of Shenyang City since July2010. This boy presented skeletalclass Ⅱ and Angle Ⅱ1smalocclusions. And his basic conditions were as followed:deep overbite Ⅲ°, deep cover Ⅲ°, diastema in maxillary dentition, mandibulardentition mild crowding, centric relationship of left side molar, far center tip to tiprelationship of right side molar, far center tip to tip relationship of canines from bothside, convex profile, genioglossal muscle tension. He was confirmed as a borderlinecase by5experts for Stomatology Hospital of Shenyang City and finally tooknon-extraction treatment. We use straight wire appliance combining with face bow toretract upper anterior teeth, which caused the changes of forerake of upper anterior teeth.During the treatment we stimulated the development of mandible with maxillaryinclined plate and closed diastemata and improve occlusal relationship with elastics inthe later stage. The patient took panoramic radiographs and lateral eephalometricradiographs before and after the treatment and cephalometrics were also performed for analyzing the changes of the hard and soft tissues and evaluating the improvements ofsoft tissue profile.Results: After non-extraction treatment, upper and lower dentition arranged inneat rows; Spee’s curve was flat; both overbite and overjet relationship of anterior teethwere normal; centric relationship of bilateral molars and canines. Dental arch lengthchanges before and after treatment: the front part and middle part of upper dental archlength decreases, and the back part of it increased. Dental Arch width changes beforeand after treatment are as followed: the front part and middle part of upper Dental archwidth decreased, and the back part of it increased. Tension of genioglossal muscle goteased, soft tissue profile was improved, the patient was satisfied with the results.Comparation of dental and craniofacial measuring items: SNA decreased, SNBincreased, ANB decreased. those transformations revealed that the maxilla developmentwas constrained and mandible developed and the difference between maxilla andmandible decreased; mandibular plane angle and Y-axis substantially unchanged,revealed the vertical control was successful; NP-FH, Po-NB, SL, Co-Po, ANS-Me andN-Me increased, which revealed mandible developed, chin protrusion improved,overall facial height and lower facial height increased; decreased UI-SN, UI-NP, UI-APand UI-LI revealed upper anterior teeth retracted and protrusion decreased; thedecreasing of ULP, LLP, Z angle, Ns-Sn-Pos and FCA revealed that lip protrusiondecreased and profile got better.Changes of the hard chin after the treatment are as followed: B-Me, C-C′, B-C,B-C′, B-C/B-C′and chin concave increased. B-Me/C-C′, B-B′/C-C′, and chinangle decreased, which revealed that chin grow forwardly and downwardly during thewhole development, caused the chin protrusion and volume increased, shape changed.The above diversity is conducive to the improve the profile.The soft chin after the treatment displayed: mentolabial sulcus shoaled, radian ofmentolabial sulcus increased, chin length decreased but radian increased, chinprotrusion increased, EP-UL, EP-LL decreased. All of above revealed that the softtissue of chin changed; with the forward and downward movement of mandible, the reduction of lip protrusion, the augment of chin protrusion and the reduction of softtissue profile protrusion, the soft tissue profile is improved..Conclusion:1. In order to get a better treatment outcome, the development ofchin should be considered in clinical orthodontic diagnosis and treatment. We shouldmake better use of growth and developoment, and promote chin grow forward to get abetter soft tissue profile.2. In this paper, after non-extraction treatment, the soft andhard chin’s morphology and position of the adolescent borderline case do change. Thecoordination of mentolabial relationships finally improved the soft tissue profile. |
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