Short- and long-term evaluation of mandibular dental arch dimensional changes in patients treated with a lip bumper during mixed dentition followed by fixed appliances

Objective:To evaluate short- and long-term mandibular dental arch changes in patients treated with a lip bumper during the mixed dentition followed by fixed appliances, compared with a matched control sample.Materials and Methods:Dental casts and lateral cephalograms obtained from 31 consecutively treated patients before (T₀) and after (T₁) lip bumper, after fixed appliances (T₂), and a minimum of 3 years after fixed appliances (T₃) were analyzed. The control group was matched as closely as possible. Arch width, arch perimeter, arch length, and incisor proclination were evaluated. Repeated measures ANOVA was used to analyze changes in measurements over all four time points between treatment and control groups.Results:Arch widths and crowding were always significantly different except at T₂−T₁. At T₁−T₀, only crowding decreased 3.2 mm while intercanine, interpremolar, and intermolar widths increased by 3.8, 3.3, and 3.9 mm, respectively. Changes at T₃−T₂ showed a significant decrease of 2.1 mm for crowding and an increase of 3.5, 2.9, 2.7, and 0.8 mm for intercanine, interpremolar, and intermolar widths and arch perimeter, respectively. Finally, at T₃−T₀, the reduction in crowding of 5.03 mm was significant and clinically important in the treated group. The differences between intercanine, interpremolar, and intermolar widths were also significant (2.1, 3.8, and 3.6 mm, respectively). All those differences favored the treated group.Conclusions:Mandibular dental arch dimensions were significantly changed after lip bumper treatment. At follow-up, all arch widths were slightly decreased, generating an increase of 0.4 mm in crowding, considered clinically irrelevant. Overall changes remained stable after an average 6.3-year follow-up.     

影响正畸治疗后牙弓稳定性的相关因素探讨

目的　探讨影响正畸治疗后牙弓稳定性的相关因素。方法　对正畸治疗后 2 4～ 97个月 (平均 5 0 .0 5个月 ) 74例错牙合畸形患者治疗前后及保持后模型进行牙弓测量。结果　保持后 ,大部分测量项目男性大于女性 ,但减少百分率无显著差异 ;不同的矫治器类型 (除上下尖牙宽度P <0 .0 5外 )、错牙合类型 (除上牙弓长P <0 .0 1外 )和保持时间组间牙弓测量项目差异无显著性 (P >0 .0 5 ) ;保持后下 3- 3长度减少百分率非拔牙组 (13.4 4 % )和青少年组 (8.93% )分别大于拔牙组 (7.2 2 % )和成年组 (4 .10 % )。结论　保持停止后 ,尖牙间长度、宽度随着年龄的增大不断减少 ;下颌骨的向前生长和过度扩弓是导致下前牙拥挤复发的主要原因之一。     

Twenty-year follow-up of functional treatment with a bionator appliance: A retrospective dental cast analysis

Objective:To investigate changes in dental arch configuration, relationship, and malocclusion directly after Class II malocclusion treatment with a Balters bionator modified by Ascher as well as 20 years after treatment.Materials and Methods:Orthodontic dental cast analysis of 18 patients with skeletal Class II treated with a bionator without any additional fixed therapy was performed with a digital caliper at three stages: before (T0), after (T1) and 20 years after (T2) treatment. Arch perimeter and depth, intermolar and intercanine distance, overjet, overbite, sagittal molar and canine relationship, mandibular incisor irregularity (Little''s index), and malocclusion (PAR index) were assessed.Results:During treatment (T0–T1), upper arch perimeter significantly increased with a significant decrease in the upper and lower arch perimeter long-term (T1–T2), whereas corresponding arch depths changed only slightly in both periods. Transverse intermolar width increased significantly during treatment, remaining almost constant from T1 to T2. Lower intercanine distance remained fairly unchanged during treatment, but decreased significantly during follow-up. Lower incisor irregularity improved slightly during treatment but increased significantly long-term. After treatment, sagittal molar relationships on both sides were improved, overjet and overbite reduced; these significant changes remained stable long-term. The peer assessment rating (PAR) index was significantly lower after treatment and increased insignificantly during follow-up.Conclusions:20 years after bionator treatment without additional fixed appliances, the improved sagittal relationship and the reduced overjet and PAR index remained fairly stable. Long-term changes are most likely due to physiological aging processes and are not associated with bionator treatment.     

Predictors of postretention stability of mandibular dental arch dimensions in patients treated with a lip bumper during mixed dentition followed by fixed appliances

Objective:To identify which dental and/or cephalometric variables were predictors of postretention mandibular dental arch stability in patients who underwent treatment with transpalatal arch and lip bumper during mixed dentition followed by full fixed appliances in the permanent dentition.Materials and Methods:Thirty-one patients were divided into stable and relapse groups based on the postretention presence or absence of relapse. Intercuspid, interpremolar, and intermolar widths; arch length and perimeter; crowding; and lower incisor proclination were evaluated before treatment (T0), after lip bumper treatment (T1), after fixed appliance treatment (T2), and a minimum of 3 years after removal of the full fixed appliance (T3). Logistic regression analyses were performed to evaluate the effect of changes between T0 and T1, as predictive variables, on the occurrence of relapse at T3.Results:The model explained 53.5 % of the variance in treatment stability and correctly classified 80.6 % of the sample. Of the seven prediction variables, intermolar and interpremolar changes between T0 and T1 (P = .024 and P = .034, respectively) were statistically significant. For every millimeter of increase in intermolar and interpremolar widths there was a 1.52 and 2.70 times increase, respectively, in the odds of having stability. There was also weak evidence for the effect of sex (P = .047).Conclusions:The best predictors of an average 4-year postretention mandibular dental arch stability after treatment with a lip bumper followed by full fixed appliances were intermolar and interpremolar width increases during lip bumper therapy. The amount of relapse in this crowding could be considered clinically irrelevant.     

Stability of transverse expansion in the mandibular arch.

This was a retrospective, longitudinal cephalometric and cast study of 29 white patients at pretreatment, posttreatment, and an average of 6 years 3 months postretention. The goal was to assess changes with treatment and retention with the expanding mandibular lingual arch appliance in conjunction with fixed edgewise treatment. Seven mandibular cast measurements were assessed, including arch crowding, arch perimeter, arch length, and arch width at the permanent canines, first premolars, second premolars, and first molars. Cephalometric radiographs were digitized, and 16 cephalometric measurements were made. Repeated-measures analysis of variance and 2-sample t tests were used to determine statistically significant changes. It was found that the expanding lingual arch used for less than 6 months with the mandibular fixed edgewise appliance caused an increase in both the transverse and sagittal dimensions of the mandibular dental arch. Transverse expansion was more stable in the posterior region of the mandibular dental arch than in the anterior region. Mandibular intercanine width increase could be maintained only by fixed retention. Although the maxillary and mandibular incisors were advanced and proclined, lip protrusion did not occur.     

159例矫治前后牙弓测量结果分析

探讨和分析不同治疗方法不对病例矫治前后牙弓变化的规律。方法。对使用固定矫治器进行治疗的三组１５９例治疗前后研究模型进行牙弓测量。结果１治疗后,扩弓组６－６宽度增加;关隙组３－３长度,牙弓长度、３－３宽度减少;拔牙组３－３长度增加而牙弓长度,基骨长度减少,６－６宽度减少而基骨宽度增加。２治疗前基骨宽度关隙组〉扩弓组〉拔牙组;治疗后３－３长度关隙组〈扩弓组〈拔牙组和３－３宽度三组间无显著性差异。结论：     

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。     

应用Quick自锁托槽系统矫治上颌牙列拥挤的牙弓测量分析

目的 探讨Quick自锁托槽系统非拔牙矫治上颌牙列拥挤病例的牙弓变化特征。方法 选取37例上颌牙列轻到中度拥挤的正畸患者,使用Quick自锁托槽系统进行非拔牙矫治。对治疗前和上颌牙列排齐整平时的研究模型进行多项指标测量。应用SPSS 12.0统计软件分析治疗前后上颌牙弓宽度、牙弓长度及周长的变化。结果 上颌牙列排齐后与治疗前阶段相比,牙弓长度、周长、前磨牙间宽度和第一磨牙间宽度均显著增加,尖牙间宽度和第二磨牙间宽度无显著变化。结论 对于上颌牙列轻到中度拥挤的患者,在应用Quick自锁托槽系统排齐和整平牙列的初期,就可使上颌牙弓宽度、牙弓长度及周长均显著增大,扩大临床不拔牙矫治的范围。?     

Changes in mandibular incisor position and arch form resulting from Invisalign correction of the crowded dentition treated nonextraction

Objective:To investigate changes in mandibular incisor position resulting from Invisalign correction of the crowded dentition without extraction.Materials and Methods:A retrospective chart review was completed on 61 adult White patients. Patients were categorized into three groups based on the value of pretreatment crowding of the lower dentition: 20 mild (2.0–3.9 mm), 22 moderate (4.0–5.9 mm), and 19 severe (>6.0 mm). Cephalometric radiographs were measured to determine lower incisor changes. Interproximal reduction and changes in arch width were also measured. Statistical evaluation of T₀ and T₁ values using paired t-tests and analysis of covariance were applied to evaluate mean value changes.Results:Lower incisor position and angulation changes were statistically significant in the severe crowding group. There were no statistically significant differences in lower incisor position between the mild and moderate crowding groups. There was a statistically significant increase in buccal expansion in each of the three groups.Conclusions:Invisalign^® treatment can successfully resolve mandibular arch crowding using a combination of buccal arch expansion, interproximal reduction, and lower incisor proclination. When there is <6 mm of crowding, lower incisor position remained relatively stable. The lower incisors proclined and protruded in the more severely crowded dentitions (>6 mm).     

Bolton tooth size ratio and its relation with arch widths,arch length and arch perimeter: A cone beam computed tomography (CBCT) study

Objective. The prime aim of the study was to measure and compare the 3D CBCT Bolton tooth size ratio in relation to the upper and lower arch widths, arch length and arch perimeter. Materials and methods. The data source was CBCT high volumetric data from the archives. Tooth size, arch widths, arch length and arch perimeter were measured in maxilla and mandibular arches. The independent t-test and ANOVA were used for statistical analyses. Results. The female Bolton anterior ratio (BAR) (78.373) and Bolton overall ratio (BOR) (93.231) show a greater tooth size ratio in comparison to male BAR (77.162) and BOR (93.124), respectively. However, no significant difference was found in the sexual comparison of all the measurements. Tooth size ratio in arch width groups also showed no significant difference. Significant discrepancies in the arch length (p < 0.05) groups and overall ratio and in the arch perimeter groups (p < 0.05 and p < 0.01) and anterior ratio were revealed. Conclusions. Tooth size ratios during orthodontic treatment for different arch length and arch perimeter groups need to be evaluated carefully.     

不同拔牙正畸模式牙弓形态变化的研究

目的 探讨不同拔牙正畸模式下,成人牙弓形态变化的规律.方法 选40例拔牙正畸病例,分为G1组20例:拔除四颗第一前磨牙,其中男13例,女7例,平均22岁;G2组20例:拔除四颗第二前磨牙,其中男8例,女12例,平均24岁.用模型测量观察矫治前后牙弓长度及尖牙区、前磨牙区和磨牙区宽度;用X线头影测量观察矫治前后切牙内收及...     

Short-term postorthodontic changes in the absence of retention

Objective:To evaluate short-term postorthodontic tooth movement without retention.Materials and Methods:Thirty consenting patients participated in the study. At the end of active treatment (T₁), final archwires were removed while leaving the fixed appliances on, and alginate impressions were taken. Four weeks later (T₂) a second set of impressions was taken. A clinical examination performed at T₂ determined if the fixed appliances could be removed or if additional treatment was required. Based on the examination, patients were divided into two groups. Patients in group I (n  =  13) had their fixed appliances removed, while those in group II (n  =  17) required additional treatment. The American Board of Orthodontics'' Objective Grading System scores and the following six variables were measured on plaster casts at T₁ and T₂: maxillary and mandibular crowding or spacing, overbite, overjet, and mandibular intercanine and intermolar widths. Data were analyzed to detect potential changes from T₁ to T₂ and to evaluate differences between the groups.Results:Mandibular crowding, overjet, and interproximal contacts worsened for the entire sample, while marginal ridges, occlusal contacts, and total American Board of Orthodontics scores improved. No statistically significant changes were found within group I from T₁ to T₂. Mandibular crowding, overbite, overjet, alignment/rotations, and interproximal contacts worsened within group II from T₁ to T₂, while marginal ridges and occlusal contacts improved. Significant differences were noted between the groups in terms of alignment/rotations, interproximal contacts, and mandibular intercanine width.Conclusion:Short-term postorthodontic tooth movement without retainers demonstrated improvement in specific characteristics of the occlusion but negatively affected alignment and interproximal contacts in the sample.     

Correlation between transverse expansion and increase in the upper arch perimeter after rapid maxillary expansion

The purpose of the present study was to assess the correlation between transverse expansion and the increase in upper arch perimeter, after maxillary expansion. Dental casts of eighteen patients were obtained before treatment and again five months after maxillary expansion. Measurements of intermolar width, intercanine width, arch length and arch perimeter were made with a digital caliper on photocopies taken from the dental casts. After assessment of the method error, a multiple regression model was developed following the identification of the best subset of variables. The resulting equation led to the conclusion that the increase in arch perimeter is approximately given by the addition of 0.54 times the intercanine expansion, and 0.87 times the arch length alteration.     

46例儿童矫治保存上颌前牙弓外牙的临床分析

目的 分析儿童上颌前牙弓外牙的临床特点,研究矫正治疗,探讨其矫治效果。方法 选择46例上颌前牙弓外牙的儿童患者,采用减数拔牙,使用方丝弓,直丝弓固定矫治,结合Ⅰ类、Ⅱ类牵引,方丝控根移动使12、22完全移至牙弓内,关闭牙弓间隙,调正上、下关系正中。治疗前、后经临床检查,X线头影测量分析,曲面断层片,头颅侧位片、以及治疗前后模型测量分析对照,评价治疗效果。结果 46例儿童固定矫治后,ANB角减小0.98°;UI/SN和UI/PP分别减小7.86°和9.82°;LI/MP减小了4.1°;UIA-PTV和UIE-PTV分别减小了2.73mm和5.12mm;LIE-PTV和LIA-PTV分别减小了3.38mm、1.31mm;UM-PTV和LM-PTV分别增加了3.56m和4.38,与矫治前相比,差异均在5%上,统计学显著,大部分在差异的P值小于1%。另外,患者面部左右对称,上、下牙弓排列整齐,磨牙中性关系,覆、覆盖关系正常。结论 儿童前牙弓外牙通过临床早期矫治或双期矫治可达到明显的临床效果。     

正畸治疗后牙弓稳定性的追踪研究

目的：探讨正畸治疗后牙弓的稳定性。方法：对正畸治疗后2－8年74例错He畸形患者治疗前后及保持后模型进行弓牙测量。结果：保持后，上基骨宽度较治疗后增加2．11％；上下6－6宽度、下基骨宽度没有显著性变化，其余均出现明显减少；减少百分率最大依次为上下3－3长度（7．79％，7．56％）、上下基骨长度（7．14％，5．12％）、上下牙弓长度（3．91％，3．37％）、上下3－3宽度（2．28％，3．30％）。结论：保持停止后，上下牙弓长度、基骨长度及3－3宽度有不断减少和3－3长度有回复治疗前水平的倾向，而6－6宽度较稳定。     

Extractions as a form of interception in the developing dentition: a randomized controlled trial

Abstract

Objective: To determine if the extractions of lower primary canines are an effective procedure to relieve crowding of the labial segment.

Study design: randomized controlled trial.

Subject sample: 83 cases were collected in clinics in Italy, Germany and Wales. The groups were followed over a 2-year period.

Method: Subjects were randomly allocated to a primary canine non-extraction or extraction group. Dental casts of the patients were collected at the start and at the recall period of the trial. The outcome measures recorded were lower incisor crowding, arch length, intermolar width, overbite, overjet, lower clinical crown heights and lower incisor inclinations.

Statistics: The Mann–Whitney test was used to compare the differences between the extraction and non-extraction groups.

Results: In both groups, crowding reduced 1.27 mm in the non-extraction group and 6.03 mm in the extraction group. The difference between the 2 groups was 4.76 mm (P<0.05). The arch perimeter decreased more in the extraction group by 2.73 mm (P<0.05). As the incisor inclination stayed essentially the same, the loss in arch length was attributed to the molars moving forward. The net gain from extracting deciduous canines was 2.03 mm.

Conclusions: There was a reduction in lower incisor crowding as a result of lower primary canine extraction. However, arch perimeter decreased more in the extraction group leaving less space for the eruption of the lower secondary canines.     

Is there a relationship between dental crowding and the size of the maxillary or mandibular apical base?

Objective:To determine whether apical base size is related to dental crowding.Materials and Methods:Digital scans of dental casts were taken of 75 untreated Class I adults to measure maxillary and mandibular tooth size, dental arch perimeters, intermolar widths, and intercanine widths. Cone beam computed tomography (CBCT) images were used to measure the apical base of the maxilla and mandible, including the total cross-sectional area, five basal arch perimeters and five basal arch widths. Principal components factor analyses were performed to evaluate the relationships between the apical base size and tooth-size-arch-length discrepancies (TSALD).Results:The dental arch and maxillary apical base measures were significantly larger in males than females. There were only limited sex differences in mandibular apical base size. The dental arch measurements were smaller in subjects with greater upper and lower TSALD. Maxillary and mandibular apical base dimensions were positively interrelated. Low-to-moderate correlations were found between the size of the maxillary apical base and TSALD. The size of the mandibular apical base was not related to upper or lower TSALD. Tooth size showed little to no relationship with TSALD.Conclusions:Although maxillary apical base size is related to maxillary and mandibular crowding in subjects with Class I malocclusion, mandibular apical base size is not.     

Relationship between dental arch width and vertical facial morphology in untreated adults

The objectives of this study were to investigate if a relationship exists between dental arch width and the vertical facial pattern determined by the steepness of the mandibular plane, and to examine the differences in dental arch widths between male and female untreated adults. Lateral cephalograms and dental casts were obtained from 185 untreated Caucasians (92 males, 93 females) between 18 and 68 years of age with no crossbite, minimal crowding, and spacing. The angle of the mandibular plane (MP) to the anterior cranial base (SN) was measured on cephalograms of each patient. Dental casts were used to obtain comprehensive dental measurements including maxillary and mandibular intercanine, interpremolar, and intermolar widths, as well as the amount of crowding or spacing. The arch widths of males and females were analysed and the differences between them were tested for significance using a Student's t-test. Regression analysis was used to determine the statistical significance of the relationships between MP-SN angle and dental arch width and crowding or spacing. The results showed that male arch widths were significantly larger than those of females (P < 0.05). For both males and females, there was a trend that as MP-SN angle increased, arch width decreased. It was concluded that dental arch width is associated with gender and facial vertical morphology. Thus, using individualized archwires according to each patient's pre-treatment arch form and width is suggested during orthodontic treatment.     

上颌中切牙内收与消耗牙弓间隙量的相关性研究

目的 探究上颌中切牙内收量与其消耗牙弓间隙量的比例关系。方法 选择拔除上颌第一前磨牙的前牙深覆盖成年正畸患者203例,对治疗前、后的锥形束CT进行三维重建,测量上颌中切牙内收量(X₁)、尖牙间宽度变化量(X₂)及尖牙远中移动量。数字化扫描仪扫描治疗前的上颌石膏模型,测量上颌前段牙弓拥挤度。将上颌中切牙内收量、尖牙间宽度变化量与消耗的总牙弓间隙量(Y)进行相关分析、线性回归分析。结果 上颌中切牙内收量与牙弓间隙的消耗量呈强正相关(r=0.726,P＜0.001),尖牙间宽度变化量与牙弓间隙消耗量呈负相关(r=-0.317,P<0.001),消耗的总牙弓间隙量(Y)与上颌中切牙内收量(X₁)、尖牙间宽度变化量(X₂)的回归方程为Y=1.25X₁-0.494X₂-2.299。结论 上颌中切牙每内收1 mm,消耗的牙弓间隙为1.250 mm;尖牙间宽度每缩减1 mm,消耗的牙弓间隙为0.494 mm。     

Dental arch changes following rapid maxillary expansion

The purpose of this research was to evaluate changes in upper arch dimension and form following rapid maxillary expansion (RME) using a modified Haas appliance in the primary dentition. The sample comprised 49 children [17 males, 32 females, mean age 7 years 5 months, standard deviation (SD) 1 year 1 month] with a crossbite or maxillary crowding. Twenty patients had a normal SN-GoGn angle (7 males, 13 females, mean 33.25 degrees, SD 2.10), three were low angle (1 male, 2 females, mean 27.67 degrees, SD 2.31), and 22 were high angle (8 males, 14 females, mean 39.95 degrees, SD 3.15). The vertical dimensions of four patients could not be measured, due to the unavailability of radiographs. Expansion was undertaken to either correct a crossbite or treat maxillary crowding. The upper dental casts were analysed using a computerized system: before treatment (T1), at appliance removal (T2), and 2 years 4 months after appliance removal (T3). Using bootstrap statistical analysis applied to distance ratio values [Euclidean distance matrix analysis (EDMA)], it was found that 48 patients showed a change in arch form. In 40.82 per cent (n = 20, group A), the arch form changed from T1 to T2, T1 to T3, and T2 to T3. In 32.65 per cent (n = 16, group B), it varied from T1 to T2 but relapsed at T3 to the form of T1. For 24.5 per cent (n = 12, group C), it changed from T1 to T2 but maintained the same form at T3. The favourable characteristics for obtaining expansion, identified by logistic regression analysis, were being male, of an immature stage of dental development (lateral incisor not fully erupted) and the presence of a lateral crossbite. Intercanine and intermolar widths, arch length, and the distance between the interincisive point and the line joining the canines (depth of the intercanine arch) at the different time points were analysed using a two-tailed t-test (P < 0.05). For the whole group, the increase in intercanine and intermolar width and in the depth of the intercanine arch was significant. Comparison between groups A, B, and C was undertaken using an analysis of variance, but there was no significant difference between the groups. This modified type of Haas appliance was able to increase the transverse dimension of the maxillary dental arch in the mixed dentition. The most appropriate timing for treatment appears to be before the eruption of the permanent lateral incisors.