成人下颌第三磨牙与下前牙拥挤的相关性研究

[摘要] 目的 通过讲究成人下颌第三磨牙倾斜角及萌出间隙与下前牙不齐指数间的相关性,探讨下颌第三磨牙是否为导致下前牙拥挤的原因及下颌第三磨牙是否应在正畸治疗中拔除。方法 选择成人骨性Ⅰ类下颌前牙区拥挤的患者34例,在治疗前的下颌记存模型上测量下前牙不齐指数,在曲面断层片上测量下颌第三磨牙倾斜角及萌出间隙,分析下颌第三磨牙与下前牙拥挤的相关性。结果 下颌第三磨牙倾斜角及萌出间隙与下前牙不齐指数间无线性相关关系(P>0.05)。结论 不能证明下颌第三磨牙是下前牙拥挤的主要原因,应尽量避免预防性拔除没有临床症状的第三磨牙。     

Incisor crown shape and crowding.

The aim of this study was to investigate correlations between the shape of mandibular incisor crowns and crowding. Study models of 50 untreated white subjects (25 men and 25 women) with varying degrees of crowding were studied. The lower incisors were sectioned and imaged at the contact point and midpoint levels, and the mesiodistal width was measured. Crowding was quantified by using both Little's irregularity index and anterior tooth size-arch length discrepancy. The ratio of the 2 mesiodistal widths was correlated with Little's irregularity index and anterior tooth size-arch length discrepancy. In the women, the ratio showed correlations of 0.52 (P =.008) and 0.55 (P =.005) for central and lateral incisors, respectively, with anterior tooth size-arch length discrepancy. No predictors of lower incisor crowding could be established from mandibular incisor crown shape in this study.     

欧米加阻挡曲扩弓法排齐和整平下颌拥挤牙列效果的临床研究

目的 评价下颌非拔牙病例中,澳丝弯制的欧米加阻挡曲扩弓法在传统直丝弓托槽上排齐和整平下颌拥挤牙列方面的临床效果。方法 选择58例正畸患者,年龄19~24岁,随机均分成2组,各29例,一组接受传统矫治方法,另一组采用欧米加阻挡曲扩弓法矫治。每种矫正方法又分为轻-中度拥挤（5 > Ⅱ > 2）和重度拥挤（Ⅱ > 5）两个亚组。下颌治疗结束时间以下牙弓完全排齐和整平为准。头颅侧位片评价下牙弓排齐和整平前后下切牙位置的变化;模型上测量下尖牙间距和下第一恒磨牙间距以反映牙弓宽度的变化。结果 2种排齐和整平的方法获得了相同程度的前牙区和后牙区扩弓量;就重度拥挤病例而言,欧米加阻挡曲扩弓法要明显快于传统方法（P=0.017）;结论 2种方法无论在切牙的唇向移动程度还是尖牙间距和磨牙间距的扩大情况等各方面几乎获得了同样的效果,对于严重拥挤的牙列,欧米加阻挡曲扩弓装置显示出更高的效率,是非常值得推荐的一种矫正方法。     

A long-term study of the relationship of third molars to changes in the mandibular dental arch

The purpose of this study is to determine the relationship of third molars to changes in the mandibular dental arch. The sample for this study consisted of four groups and subgroups. The groups consisted of premolar extraction treated, nonextraction treated with initial generalized spacing, nonextraction treated, and serial extraction untreated subjects. The subgroups were divided into persons who had mandibular third molars that were either impacted, erupted into function, congenitally absent, or extracted at least 10 years before postretention records. The mean postretention time interval was 13 years, with a range of 10 to 28 years. The mean postretention age was 28 years 6 months, with a range of 18 years 6 months to 39 years 4 months. Two-way analysis of variance with repeated measures was used to compare the changes over time (before treatment, at end of active treatment, and after retention) of groups and third molar subgroups. With time, mandibular incisor irregularity increased while arch length and intercanine width decreased. The eruption patterns of mandibular incisors and first molars were similarly dispersed in all groups studied. The findings between the subgroups in which mandibular third molars were impacted, erupted into function, congenitally absent, or extracted 10 years before postretention records revealed no significant differences between any of the subgroups for the parameters studied. No significant differences in mandibular growth were found between the third molar subgroups; this suggests that persons with third molars erupted into satisfactory function do not have a significantly different mandibular growth pattern than those whose third molars are impacted or congenitally missing. In the majority of cases some degree of mandibular incisor crowding took place after retention, but this change was not significantly different between third molar subgroups. This finding suggests that the recommendation for mandibular third molar removal with the objective of alleviating or preventing mandibular incisor irregularity may not be justified.     

Long-term stability of combined rapid palatal expansion-lip bumper therapy followed by full fixed appliances.

INTRODUCTION: The purpose of this study was to evaluate the long-term postretention stability of rapid palatal expansion-lip bumper therapy followed by full fixed appliances. METHODS: The sample included 20 treated patients (11 women and 9 men) who were recalled to obtain postretention records. The subjects were out of retention for a minimum of 4 years and an average of 7.9 years. They had begun treatment in the late mixed dentition at a mean age of 11.1 with considerable incisor crowding but, on average, no tooth size-arch length discrepancies. Pretreatment, posttreatment (mean age, 13.6 years), and postretention (mean age, 24.3 years) models were digitized, and the computed measurements were compared with untreated reference data. RESULTS: The majority of treatment increases in maxillary and mandibular arch dimensions were statistically significant (P < .05) and greater than expected for untreated controls. Although many measurements decreased postretention, net gains were maintained for 21 of the 30 measurements evaluated. The notable exception was arch perimeter, which decreased to less than pretreatment values. Postretention incisor irregularity increased 0.5 +/- 1.2 mm in the maxillary arch and 1.1 +/- 1.5 mm in the mandibular arch. CONCLUSIONS: Based on the good long-term stability observed in this study, we concluded that use of rapid palatal expansion-lip bumper expansion therapy in the late mixed dentition followed by full fixed appliances is an effective form of treatment for patients with up to moderate tooth size-arch length discrepancies.     

Evaluation of the relationship between the anterior component of occlusal force and postretention crowding.

The aim of this study was to investigate whether a relationship exists between the anterior component of occlusal force (ACF) and postretention crowding in the mandibular incisor area. The study group comprised 32 adults who had undergone fixed orthodontic treatment in the department clinic at Marmara University in Istanbul, Turkey. In 13 subjects, the mandibular arch was treated without extractions; in 19, it was treated with bilateral first premolar extractions. The average postretention period was 3.5 years. The ACF created in the left side of the mandibular dentition was determined by measuring interdental frictional forces at each contact point mesial to the first molar and distal to the canine. Anatomic contact point displacements between the left mandibular anterior teeth (lateral incisor-canine, central incisor-lateral incisor, and central incisor-central incisor) were measured on plaster casts and summed to provide the irregularity index for these teeth. Correlation analysis was used to assess the relationship between the ACF values at each contact and the irregularity index. In the nonextraction group, statistically significant positive correlations were observed between the ACF and the irregularity index at the 3 contact points that were measured. The strongest correlation was found at the canine-first premolar contact (r = 0.65). In the extraction group, a positive correlation was found between the ACF and the irregularity index (r = 0.49, P <.05) at the second premolar-first molar contact, but no correlation was found at the canine-second premolar contact.     

No Correlation between Primary Mandibular Anterior Crowding and Vertical Craniofacial Configuration or Lower Incisor Inclination

The aim of the present study was to evaluate the correlation between primary mandibular anterior crowding and vertical craniofacial configuration or sagittal lower incisor inclination. The collective comprised 100 consecutive patients (50 males, 50 females) subject to 4 selection criteria: mandibular anterior crowding > or = 1.0 mm, no previous orthodontic therapy, completely preserved deciduous canines and molars, and lateral cephalograms of good diagnostic quality before initiation of orthodontic treatment. Study casts of all patients were used to measure the mesiodistal width of the incisors and deciduous canines as well as the anterior arch circumference. The difference between the 2 represented the amount of crowding. On all cephalograms 16 parameters of vertical craniofacial configuration and 9 parameters of lower incisor inclination were measured. For error evaluation all measurements were repeated independently on 10 randomly selected study casts and cephalograms. This error amounted for the combined tooth width to 0.51% +/- 0.81, for arch circumference to 0.03% +/- 0.68, and for all cephalometric parameters to 0.38% +/- 4.81. For all parameters, arithmetic means, standard deviations and ranges were calculated. Further, correlation coefficients were calculated between anterior crowding and all 25 cephalometric parameters. The arithmetic mean of crowding was m = 2.0 +/- 1.3 mm with a range of 1.0 to 6.6 mm. The values of all cephalometric parameters were close to well accepted norms in the literature. The correlation coefficients between crowding and all cephalometric parameters varied from r = 0.0 to 0.3. According to this study there is no correlation between primary mandibular anterior crowding and vertical craniofacial configuration or sagittal lower incisor inclination.     

Relationship between mandibular anterior crowding and lateral dentofacial morphology in the early mixed dentition

Mandibular anterior crowding is identified as the discrepancy between mesiodistal tooth widths of four permanent incisors and available space in the alveolar process. However, incisor crowding is not merely a tooth-arch size discrepancy. Many variables such as direction of mandibular growth, early loss of deciduous molars, the oral and perioral musculature and incisor and molar inclination can be associated with crowding. Only few studies evaluated the relationship between mandibular anterior crowding and cephalometric measurements in the early mixed dentition. It was the aim of this study to search for dentofacial factors that might be associated with mandibular crowding in the early mixed dentition. Lateral cephalograms and dental casts of 60 children (33 girls, 27 boys) were evaluated. It was determined that patients with crowding had smaller lower incisor to NB angles, maxillary skeletal lengths, mandibular skeletal length, and mandibular dental measurements. They also had greater interincisal angles, overjet, overbite, and Wits appraisal measurements. Significant inverse correlations were found between crowding and SNB, lower incisor to NB angle, anterior cranial length, mandibular length, maxillary length, mandibular dental measurement and direct correlations between crowding and interincisal angle, overjet, overbite, and FMIA. According to these results, we conclude that crowding of the mandibular incisors is not only a tooth-arch size discrepancy. Dentofacial characteristics also contribute to this misalignment.     

Evaluation of posttreatment stability after orthodontic treatment in the mixed and permanent dentitions

Objective:To investigate posttreatment changes in the maxillary and mandibular arches in patients who underwent orthodontic treatment during the mixed and permanent dentitions.Materials and Methods:The sample was collected retrospectively from three private practices and consisted of 42 patients who were at least 10 years out of orthodontic treatment. The longitudinal records of study casts and cephalometric radiographs were analyzed to quantify posttreatment changes.Results:Minimal changes in maxillary and mandibular irregularity occurred after an average of 16.98 years from completion of treatment. More than 10 years posttreatment, approximately 81% of the maxillary anterior teeth and 88% of the mandibular anterior teeth showed clinically acceptable incisor alignment (<3.5 mm). Mandibular fixed retainers greatly aided in maintaining the stability of the mandibular incisor alignment. However, posttreatment changes in maxillary incisor irregularity did not appear to be influenced by the presence of a mandibular fixed retainer. When compared with longitudinal changes observed in untreated subjects, the increase in incisor irregularity resembled a pattern similar to the regression line of untreated subjects and seems to be entirely age related. Arch width and arch depth was consistently decreased after treatment, but the magnitude of change was minimal at about 1 mm. No associations were found between any of the cephalometric measurements and changes in incisor irregularities.Conclusions:Orthodontic treatment stability can be achieved and mandibular fixed retention appears to be a valuable contributor, especially in patients with further growth expected.     

Postretention mandibular incisor stability after premolar serial extractions

The purpose of this study was to evaluate the mandibular incisor alignment in serial extraction cases, using the longitudinal dental cast records of the Burlington Growth Center as a control sample. Various parameters were investigated and the statistical differences determined between the treated and untreated groups. The results were also compared with data from serial extraction groups that subsequently had orthodontic treatment. Untreated subjects and subjects treated only with serial extractions showed similar longitudinal changes. However, the extraction group that also received orthodontic treatment appeared to show more lower incisor crowding long-term. No predictors for stability of clinical significance could be determined. Mechanotherapy influences the craniofacial and dentoalveolar dimensions, which appear to cause more long-term lower incisor crowding.     

Posttreatment and physiologic occlusal changes comparison

Objective:To compare posttreatment and postretention occlusal changes with the physiologic occlusal changes caused by natural development of untreated subjects.Materials and Methods:The sample was divided into three groups. Group 1 comprised 97 subjects treated with four premolar extractions at a mean pretreatment (T0) age of 13.03 years, a mean posttreatment (T1, first observation) age of 15.12 years, and a mean postretention (T2, second observation) age of 20.52 years. The mean observation period (T2-T1) was 5.39 years. Group 2 comprised 58 subjects treated nonextraction at a mean pretreatment age of 12.83 years, a mean posttreatment age of 14.99 years, a mean postretention age of 20.22 years, and a mean observation period of 5.22 years. Group 3 comprised 114 untreated subjects at a mean age at T1 of 14.91 years and at T2 of 20.48 years. The mean observation period was 5.56 years. Dental casts were evaluated using the Peer Assessment Rating (PAR) index and the Little irregularity index in maxillary and mandibular arches. Changes in PAR and Little indexes were compared among the three groups by analysis of variance and Tukey tests.Results:Intergroup comparison showed that at T1 and T2 the treated groups presented smaller PAR and Little indexes than the untreated group. In the observation period, the treated groups showed greater increase in PAR and Little maxillary indexes than the untreated group. The extraction group showed a greater increase of the Little mandibular index than the untreated group.Conclusions:The treated groups showed more changes according to PAR and Little maxillary indexes than the untreated group. The posttreatment change of the mandibular anterior crowding of the treated extraction group was greater than the mandibular crowding caused by physiologic changes in the untreated group.     

Correlations between lower incisor crowding and lower incisor position and lateral craniofacial morphology

Crowding of the lower incisors is a problem encountered frequently in orthodontic practice. Successful therapy may depend on the orthodontist's ability to evaluate factors contributing to the overall pattern. Two of these factors, vertical skeletal morphology and lower incisor position in the lateral cephalogram, were evaluated. Dental casts and cephalograms of 100 children with primary mandibular incisor crowding (that is, primary discrepancy between mesiodistal tooth width and available space of the dental alveolar process and apical base) were examined in this study. Results indicated the following: (1) all vertical skeletal and lower incisor position measurements closely duplicated published norms, (2) no correlation was found between lower incisor crowding and either skeletal morphology or lower incisor position, (3) a factor analysis did demonstrate, however, that other selected variables were interrelated, and (4) the cause of lower incisor crowding must be attributed to factors not examined in this study.     

Effect of serial extraction alone on crowding: Relationships between tooth width, arch length, and crowding

In this study, we examined the effect of serial extraction alone on crowding. We also investigated the relationships between tooth width, arch length, and irregularity index. Maxillary dental casts from 32 subjects who had undergone only serial extraction were analyzed at 3 stages: before deciduous canines extraction, after first premolars extraction, and at the end of the observation period. The mean of the irregularity index decreased significantly as serial extraction proceeded and further decreased during the observation period. In cases where the width of the incisor was more than 2 standard deviations above the means for the control subjects, there was a significant correlation between tooth width of the lateral incisors and irregularity index before extraction as well as a significant correlation between the summation of tooth widths of the central and lateral incisors and irregularity index at that time. There was a significant negative correlation between arch length discrepancy and irregularity index before extraction and also a significant correlation between arch length discrepancy and correction of the irregularity index from before deciduous canines extraction to after first premolars extraction. These results suggest that tooth width and arch length discrepancy might preferentially affect the degree of anterior crowding in cases of severe crowding. There was no aggravation of the average crowding level during the observation period in the present study. The present study quantitatively suggested that serial extraction was useful for the purpose of correcting crowding in most cases.     

Early extractions of premolars reduce age-related crowding of lower incisors: 50 years of follow-up

Objectives

To study the effects of extraction of four premolars, without subsequent orthodontic treatment, on the crowding of lower incisors in subjects between early adolescence and late adulthood, as compared to untreated subjects.

Materials and methods

A total of 45 subjects were included in this study. The extraction group comprised 24 subjects who had all the first premolars removed at a mean age of 11.5 years, to relieve crowding in a class I malocclusion without subsequent orthodontic treatment. The control group had 21 untreated subjects, having a normal occlusion at a mean age of 13.0 years. The participants were documented with dental casts and cephalograms at mean ages of 11.4 and 13.0 years, for the two groups respectively (T1), and at mean ages of 30.9 years (T2) and 61.7 years (T3). Changes in lower incisor crowding were described as changes in “irregularity” and “space deficiency.”

Results

The extraction group showed no changes in the irregularity of the lower incisors and significant improvement of the space deficiency of the lower teeth into late adulthood. While in the control group, both irregularity of the lower incisors and space deficiency of the lower teeth increased significantly into late adulthood.

Conclusion

Lower incisor alignment remains mainly unchanged into late adulthood in subjects who have all their first premolars removed in childhood, as the only treatment to relieve teeth crowding.

Clinical relevance

Severe crowding in a class I occlusion can be solved solely with premolar extraction, allowing for spontaneous adjustments with more stable incisor alignment up to late adulthood.

     

Mandibular incisor alignment and dental arch changes 1 year after extraction of deciduous canines

This study investigated the early effects on mandibular incisor irregularity and rotation together with dental arch dimensions of the extraction of four deciduous canines. Children, during early mixed dentition, were randomized into one extraction (n = 32) and one control (n = 41) group. Dental casts from baseline (T0) and 1 year follow-up (T1) were used to evaluate changes in the irregularity index and in mandibular incisor rotation, dental arch dimensions, overjet, and overbite. Median mandibular incisor irregularity decreased over time, significantly more in the extraction than the control group (1.2 versus 0.7 mm; P < 0.01), with wide ranges in both groups. Rotational changes greater than 10 degrees for lateral incisors were twice as common in the extraction group (42 versus 20 per cent; P < 0.01). Central incisors displayed only minor changes in both groups. The correlation between changes in irregularity index and changes in incisor rotation was weak in both groups (r(s) < 0.3 not significant). According to professional assessment of overall alignment, 84 per cent in the extraction group versus 34 per cent in the control group (P < 0.001) improved from T0 to T1. A significant decrease in maxillary and mandibular arch length and circumference from T0 to T1 was recorded in the extraction group (1.3, 1.1 mm and 2.4, 2.0 mm, respectively; P < 0.001), while arch dimensions were preserved in the control group. To conclude, 1 year after extraction of the deciduous canines, small improvements in mandibular incisor alignment were seen, together with reduced arch dimensions. Little's index underestimated malalignment related to tooth rotation.     

The association of simple anterior dental crossbite to gingival margin discrepancy

The purpose of this study was to determine the severity of gingival margin discrepancy affecting the mandibular incisors in children with a single-tooth anterior crossbite. The response of the position of the gingival margin to correction of the crossbite also was investigated. Twenty-two subjects with a single central crossbite and 16 subjects with a single lateral crossbite were identified from two orthodontic practices. Seventeen of the 22 central incisor patients had immediate posttreatment records available; six patients had long-term follow-up records. An insufficient number of posttreatment records were available for the patients with lateral crossbites. The mean clinical crown length of crossbite mandibular incisors, measured on the study models, was compared with mean crown length of contralateral control incisors and the difference in clinical crown length was determined. A gingival margin discrepancy was identified when the gingival margin of the crossbite incisor was at least 1.0 mm apical to the gingival margin of the control incisor. The proportion of subjects with gingival margin discrepancy was significantly higher in subjects with central incisor crossbite (12/22 = 54%) than in those with lateral incisor crossbite (4/16 = 25%), P less than 0.05. While a gingival margin discrepancy persisted for eight of the 17 central incisor crossbites after discontinuing the appliance, 8.9 +/- 4.7 months, the severity of the discrepancy showed a significant reduction from 2.2 +/- 0.5 mm to 1.3 +/- 0.8 mm, P less than 0.05. True recession with exposure of cementum was not observed in any subjects.(ABSTRACT TRUNCATED AT 250 WORDS)     

A long-term evaluation of treated Class II division 2 malocclusions: a retrospective study model analysis.

Pre-treatment, end of treatment, and post-retention study models of 30 subjects with a Class II division 2 malocclusion were assessed, after a period of at least 3 years, in order to evaluate the long-term changes in occlusion, alignment, and arch dimensions. Molar relationship correction was found to be stable after retention. There were no variables which could be used to establish a prognosis of vertical stability. Over-correction of overbite was seen to relapse. Ten per cent of the cases showed unacceptable anterior maxillary irregularities after retention. Mandibular arch width and length usually showed a decrease after retention. An increase in lower intercanine width and arch length achieved by orthodontic treatment always relapsed. This relapse was associated with post-retention mandibular irregularity and crowding. Nine cases (30 per cent) showed an unacceptable degree of mandibular irregularity after retention. Pre-treatment crowding in the mandible showed a relationship with post-retention lower irregularity and crowding. There was a correlation between the number of years which had elapsed after retention, overbite relapse and post-retention mandibular irregularity.     

Mandibular changes in persons with untreated and treated Class II Division 1 malocclusion

The growth potential of individuals with Class II malocclusions is of interest to the practicing orthodontist because such malocclusions constitute a significant percentage of cases. The purpose of this study was to evaluate on cross-sectional and longitudinal bases the changes in mandibular length and relationship and maxillary-mandibular relationships in untreated Class II subjects from deciduous to permanent dentition and also to evaluate the effects of orthodontic treatment, with and without the extraction of first premolars, on these relationships. Class II samples were compared with matched normal, untreated individuals. The Class II Division 1 (Class II/1) untreated sample comprised 30 subjects, 15 males and 15 females. Each subject had a complete set of data at three stages of dental development—namely, Stage I, after the completion of eruption of the deciduous dentition; Stage II, at the time when the permanent first molars and most of the incisors have erupted (i.e., in mixed dentition); and Stage III, at the completion of eruption of the permanent dentition, excluding third molars. The Class II treated sample comprised 44 subjects (21 males, 23 females) treated with four first-premolar extractions and 47 subjects (20 males, 27 females) treated without extraction. Treatment was accomplished with the use of an edgewise appliance, appropriate extraoral traction, and Class II elastics. The extraction decision was based mainly on the presence of crowding and profile consideration. Records on 35 normal subjects (20 males, 15 females) were available from the Iowa Longitudinal Facial Growth Study. Cephalograms for the normal individuals were matched to the corresponding ages of the Class II cases. With regard to these findings, few consistent differences were noted between the untreated Class II/1 and normal subjects on cross-sectional comparisons. The differences in mandibular length and position were more evident in the early stages of development than at later stages. Longitudinal comparisons of growth profiles indicated that the growth trends were essentially similar between the untreated Class II/1 and normal subjects in the various parameters compared. The comparisons of growth magnitude indicated the presence of greater skeletal facial convexity in the untreated Class II/1 subjects, accompanied by a tendency for a more retruded mandible. Initial comparisons between the Class II/1 treated groups and normal subjects indicated that the Class II/1 malocclusions were associated with a larger overjet, deeper overbite, and greater ANB angle. After a 5-year treatment and observation period, an overall “normalization” in the mandibular and maxillary-mandibular skeletal relationships was noted in the treated Class II/1 subjects in both the extraction and the nonextraction groups compared with normal subjects. The changes were more pronounced in the extraction group.(Am J Orthod Dentofacial Orthop 1998;113:661-73)     

Prediction of mandibular incisor and canine crowding changes in the mixed dentition

To test the hypothesis that preeruptive tooth positions and dental arch parameters might forecast crowding changes, a sample of 47 aboriginal children (26 males, 21 females) was selected stringently on the basis of Class 1 characteristics and an untreated dentition unaffected by caries or attrition. Crowding scores, radiographic relationships of 765E, and dental arch dimensions were evaluated for the mixed dentition (Stage 1, 8.91 +/- 1.05 years) and earliest emergence of the permanent dentition (Stage 2, 12.48 +/- 0.97 years). Changes between the stages were calculated and the sample was divided into two groups, according to an increase (Group 1) or decrease (Group 2) in incisor and canine crowding. Multivariate and multiple regression analyses were used to identify predictors (Stage 1 radiographic and dental arch parameters) of incisor and canine crowding behavior. Dental arch form and tooth size were important factors in measuring the amount of incisor or canine crowding at Stage 1 and Stage 2. Neither the radiographic nor the dental arch predictors proved useful in forecasting crowding changes. Group 2 dental arches tended to be initially narrower, shallower, and more crowded; however, they showed greater molar and canine width expansion and lessened arch depth reduction than Group 1 cases. Many cases showed a reduction in canine crowding from mixed to permanent dentition. This appeared to be largely independent of the observed incisor crowding. Sexual, racial, and individual variations in dentofacial pattern reinforce the need to carefully consider interceptive extraction or space-regaining therapy for each patient because of the unpredictability of crowding behavior during the transition from mixed to permanent dentition.     

Impaction of the central maxillary incisor associated with supernumerary teeth: initial position and spontaneous eruption timing

The aim of the retrospective study was to evaluate the influence of the initial vertical position of the impacted maxillary incisor on spontaneous eruption frequency and timing after surgical removal of the supernumerary tooth. Records of 33 patients with unilateral impaction of upper central incisor caused by supernumerary teeth with the average age 9.58+/-1.54 years were analyzed. Impacted teeth were distributed into 3 groups on the basis on their initial vertical position on the orthopantomograms. The results indicate that impacted maxillary central incisors spontaneously erupt in 63.6% of cases after removal of supernumerary teeth. The average time of the spontaneous eruption of impacted maxillary central incisors was 16.05+/-9.3 months (from 3 to 30 months). Statistically significant differences in the spontaneous eruption time were found between the groups with different initial vertical position of the impacted central maxillary incisor. Maxillary central incisor impacted at the projection level of the apical third of the contralateral completely erupted central maxillary incisor should be treated by the surgical-orthodontic approach, because spontaneous eruption is unlikely to expect.