| Crowding is the most common malocclusion in clinical orthodontics,the incidence in our country was 60%-70%.The reasons for the formation of crowding is very complex,and it usually caused by genetic or environmental factors.The root of the crowding mechanism lies in the amount of teeth and bone mass to be not harmonious,so the clinical manifestations of crowding include arrangement of teeth,arch stenosis,ectopic eruption,impaction and so on.The core to correct crowding is to open space.So how to obtain and distribut space becomes the major problem of orthodontic clinical workers which need to be solved.The main clinical methods to open space are extraction and non-extraction treatment,and expansion is the most important treatment method in non-extraction.At present,for the treatment of patients with crowding,we usually use the method of extraction and expansion.With the improvement of people's life,more attention was paid to the fullness of surface type,the definition of beauty is no longer limited to tooth arrangement and occlusion relationship,coordination,stability and beautiful become the ultimate goal of orthodontic treatment.For some cases of class I dentition crowding,the treatment method is to extract four premolars to solve the discordance of the amount of teeth and bone,in most cases can get the maxillofacial coordination.We found that in the clinic,patients with crowded by tooth extraction can obtain well tooth arrangement and occlusion relationship,but the treatment time is long,and may affect surface coordination due to excessive adduction of anterior teeth.Expansion is an effective method to obtain the clearance in addition to tooth extraction,It can preserve the full dentition and avoid the risk of forming an orthodontic face.At present,the research on the expansion is mainly concentrated in the maxillary,Our professor has used the maxillomandibular expansion to correct class I dental crowding for ten years,and obtain satisfactory results.For some class I dental crowding,we have applied the method of expanding to increase the width of the transverse dental arch,In the case of insufficient gap,we can also distal the molar.The expansion also have relatively strict indications.Therefore,in the formulation of the program,we should grasp the scope of the application of the two methods strictly,and choose the treatment method flexibly.It is necessary to select the two main treatment methods for moderate or severe crowding cases,to discuss the indications for providing a reference in clinic.PAR index as the objective index was used to evaluate the severity of the deformities and the degree of improvement in the orthodontic treatment.Its reliability is high,the measurement is convenient,and it is used for orthodontic clinical treatment effect evaluation.X-ray measurement is commonly used in clinical evaluation method,can effectively record changes before and after treatment of maxilla and soft tissue.To evaluate the clinical curative effect of class I dental crowded with PAR index and X-ray measurement method from the occlusion and jaw.ObjectivesThis study investigated extraction group and maxillomandibular expansion group to correct class I dental crowded patients,to discuss the clinical efficacy,indication and precautions of the two treatment techniques by the before and after treatment PAR indexes of and the Cephalometric analysis for providing a reference in clinic.Methods40 adolescent patients with class I dental crowding were selected,which were finished form January 2004 to July 2014 in the Orthodontic department of Air Force General Hospital,PLA.Tooth extraction group were 20 cases,expansion group were 20 cases,12~14 years old,average course was 2 years and 8 months.Case inclusion criteria: Angle class Imarginal crowding;during or before growth spurt stage;early permanent dentition;nodentition deficience;no orthodontic treatment and cleft lip and palate history.To evaluate effect and comparison of two groups before and after treatment by PAR index and the cephalometrical lateral film.To make paired t test before and after treatment,and analyze the variance between the two groups with SPSS13.0 software.Result1.The difference between PAR index indicators(misalignment of teeth,buccal occlusion,overjet,overbite,midline)of extraction group and expansion group were statistically significant(P <0.01)before and after treatment.The weighted PAR score of extraction group decreased 12.77 ± 3.38 and the weighted PAR score reduction percentage was(86.2 ± 12.1)%.The weighted PAR score of expansion group decreased 11.95 ± 3.10 and the weighted PAR score reduction percentage was(91.2 ± 13.5)%.The two groups were greatly improved after treatment.2.In hard tissue measurements,U1 / SN,U1 / NA,U1 / NA(mm)L1 / MP,L1-NB(mm)of the extraction group reduced significantly(P <0.05).In expansion group,the changes of SNA,SNB,ANB,MP-SN,U1/SN,U1/NA,U1/NA(mm)were not statistically significant(P > 0.05).L1/MP increased 7.55°and L1-NB(mm)increased 1.79 mm,which showed that lower incisor became lip inclination after the treatment.The U1-SN and L1-MP of extraction group before treatment is larger than expansion group.The incisors of expansion group had more lingual inclination.3.After treatment,soft tissue on the upper and lower lips of the extraction group has an obvious adduction.The upper lip receded 2.27 mm relative to E line.The lower lip receded 1.90 mm relative to E line.In expansion group,the upper lip receded 0.57 mm relative to E line,the lower lip forwarded 0.62 mm relative to H line.The indexes of soft tissue in the two groups before treatment were analyzed by variance analysis.The results showed that the lip protrusion of extraction group were larger than maxillomandibular expansion group.ConclusionTooth extraction and arch expansion can solve dental crowding,improve the relationship,and obtain well teeth arrangement and occlusal relationship for Angle I class marginal dental crowed patients.The crowded patients with obvious lower incisor labial inclination tend to choose extraction,appropriate adduction can decrease the lip inclination.The crowded patients with erect lower incisors or slightly lingual inclination are suitable for arch expansion,to expand labially to obtain better overbite and over jet.The patients who have relatively convex facial are more suitable for extraction treatment to improve facial profile.Expansion treatment can avoid risks of damaging initial facial profile for patients who have erect or not full surface.Expansion treatment should be chosen carefully for the larger lower lip protrusion,extraction treatment can improve the lip protrusion well.Arch expansion treatment is suitable for patients who have receding lower lip to forward lower lip. |
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