An occlusal and cephalometric analysis of lower first and second premolar extraction effects.

This study was designed to examine lateral cephalometric and arch dimensional changes that occur in the mandibular arch during orthodontic treatment involving the extractions of various premolars. Pretreatment and posttreatment records of 73 patients were chosen at random from completed cases in the practice of one experienced orthodontist. Eighteen involved the extraction of lower first premolars, and 55 involved the extraction of lower second premolars. Of these 55, 29 involved the extraction of upper first premolars and 26 involved the extraction of upper second premolars. In the lower first premolar group, however, all 18 involved the extraction of upper first premolars. Males and females were evenly represented in the 3 subgroups. Pretreatment factors that suggested a basis for the extraction choice in this group of patients were found to include incisal overjet, molar relationship, and underlying vertical facial pattern. A wide variety of arch dimensional changes was found with different lower premolar extraction patterns. There was evidence, however, of more intermolar arch width reduction after the extraction of lower second premolars than lower first premolars. Orthodontic treatment with the extraction of premolars did not consistently cause a retrusive effect on the incisors. In fact, instances of proclination of the incisors occurred within all of the extraction groups. A large amount of individual variation in incisor and molar changes accompanied treatment involving all lower premolar extraction patterns.     

Growth and treatment changes distal to the mandibular first molar: a lateral cephalometric study

This study examined space changes occurring distal to the mandibular first molar in growing patients treated using two different approaches. Two groups of 50 patients were selected for the study. The patients in group I were treated with the extraction of mandibular second premolars, whereas those in group II were treated without mandibular premolar extractions, by holding E-spaces with utility arches. Lateral cephalograms taken before and after treatment were used to measure space changes within the mandible. Follow-up written treatment records and radiographs were also examined to ascertain whether the mandibular third molars were ultimately extracted or retained. A greater mean space increase between Xi point and the mandibular first molar was found in boys and girls treated with second premolar extractions. The mean space increase between Xi point and the mandibular first molar, as well as the average increase in total mandibular length, was greater in boys than in girls for both treatment modalities. This reflects a greater amount of growth in boys during the treatment period. The greater mean space increase in the groups treated with second premolar extractions could be attributed to the fact that the first molar generally moved further mesially during treatment in the extraction subjects, whereas in the E-space subjects, the first molars were perhaps held back. It was noted that the mandibular third molars were ultimately more likely to have been extracted in the E-space groups than in the second premolar extraction groups within this sample.     

Premolar and additional first molar extraction effects on soft tissue. Effects on high Angle Class II division 1 patients

OBJECTIVE: To determine the effects of premolar and additional first molar extractions (AFMEs) on soft tissue changes after four premolar extractions in high Angle Class II division 1 patients. MATERIALS AND METHODS: Thirty-three AFME patients, 24 of who had maxillary-only AFME and 9 of who had all-four AFME, were studied by cephalometric analysis and compared with 43 patients treated with four premolar-only extractions (PRMEs) as a control group. Lateral cephalograms taken at four time points-pretreatment, before AFME, posttreatment, and retention-were utilized for statistical analysis by Student's t-test. RESULTS: AFME significantly contributed to the maxillary incisor retraction and subsequent soft tissue change as measured by the Z-angle and lower lip E line. In addition, the bivariate correlation analysis revealed that the soft tissue changes correlated more with maxillary incisor retraction than with mandibular incisor retraction in both the AFME and PRME groups. This finding suggests that, in Class II patients, the lower lip position is most affected by reduction of maxillary incisor proclination. CONCLUSIONS: The AFME approach is useful to improve profiles in severe high Angle Class II division 1 patients who are borderline between PRME treatment and a premolar extraction plus orthognathic surgery approach.     

A comparison of results of second molar and first premolar extraction treatment

The purpose of this study was to examine treatment results of maxillary and mandibular second molar extraction cases and compare them with treatment results of maxillary and mandibular first-premolar extraction cases. Records of 22 maxillary and mandibular second-molar extraction cases and 22 maxillary and mandibular first-premolar extraction cases were evaluated. For each case, pretreatment and posttreatment lateral cephalograms were traced and several cephalometric parameters were compared. From the pretreatment and posttreatment panoramic radiographs, angulations of the maxillary and mandibular third molars were evaluated. Average treatment time, in months, was recorded for both groups. The data obtained from each group were analyzed for statistical difference. The results showed that the two groups had fewer differences than indicated by advocates of second-molar extractions. Analysis of the cephalometric data demonstrated only a few statistical differences between the groups. The maxillary and mandibular incisors in the premolar group were retracted a significantly greater amount than in the second-molar group. The maxillary and mandibular first molars were protracted a greater amount in the premolar group than in the second-molar group. The lower lips in the premolar group were retracted a greater amount than in the second-molar group. The resulting facial profile after extraction of second-molars appears to be no different from that obtained after extraction of first premolars. The pantographic evaluation of the changes in third-molar angulation were not statistically different. In both groups, the maxillary third molars showed an improvement in third-molar angulation, while the mandibular third-molars showed an undesirable increase in angulation. The average treatment time for both groups was not statistically different.     

Soft tissue changes after upper premolar extraction in Class II camouflage therapy

The long-term effect on the facial profile has led many orthodontists to attempt Class II division I camouflage treatment without extraction. Practitioners may cite "dishing in the face" as a reason not to extract. Previous investigations have evaluated the soft tissue response after maxillary incisor retraction, but few have evaluated the effect of maximum retraction in skeletal mandibular deficient Class II patients with essentially no crowding. Twenty-seven Class II division I Caucasian patients with a mean of 8.62 mm of overjet, little to no arch length deficiency, and maximum anchorage requirements were treated with extraction of only maxillary first premolars. Pre- and posttreatment lateral cephalograms were taken. Using several skeletal and soft tissue cephalometric measures, the treatment changes were assessed. The mean maxillary incisor retraction was 5.27 mm, the mean maxillary lip retraction was 2.03 mm, and the mean mandibular lip retraction was 1.23 mm. All the patients finished with good overall facial harmony and balance. The maxillary first premolar extraction for orthodontic camouflage may be a viable treatment option, especially if the patient has full upper lips and only a relative mandibular deficiency.     

两种拔牙模式矫治后相关平面的变化研究

目的研究拔除4颗第一前磨牙（上四下四）和拔除双侧上颌第一前磨牙和下颌第二前磨牙（上四下五）2种拔牙模式矫治前后腭平面、平面及下颌平面的变化。方法固定正畸矫治患者166例,拔除上四下四62例,拔除上四下五7 6例,不拔牙2 8例,测量矫治前后的腭平面角、咬合平面角和下颌平面角等项目。结果 2种拔牙模式患者腭平面和平面的变化差异无统计学意义;拔除上四下四矫治的均角型患者矫治后下颌平面角轻微增加（t=2.97,P〈0.05）;其余患者的改变差异没有统计学意义。结论拔除上四下四和拔除上四下五2种拔牙模式不会导致腭平面、平面的改变,拔除上四下四矫治的均角型患者下颌平面角轻微增加。     

拔除第一前磨牙对第三磨牙倾角的影响

目的研究正畸治疗中拔除第一前磨牙进行矫治和非拔牙矫治对第二磨牙和第三磨牙倾角的影响。方法选择56例上下颌第三磨牙均存在的青少年正畸患者,按拔牙与否分为拔牙组（30例,拔除4颗第一前磨牙）和非拔牙组（26例）,通过术前术后曲面断层片来测量患者上下颌第三磨牙长轴和平面的交角,第二磨牙与平面的交角以及第二、第三磨牙长轴的交角,并进行统计学分析。结果拔牙与非拔牙组矫治前后第三磨牙倾角均有不同程度的改善。与非拔牙组相比,拔牙组上下颌第三磨牙长轴与平面交角的变化量更大,2组间年平均变化量的差异有统计学意义（P<0.05）;2组矫治前后上下颌第二、第三磨牙长轴交角的变化无统计学差异,但其年平均变化量在2组间则有统计学差异（P<0.05）。2组间上颌第二磨牙与平面交角的年平均变化量无统计学差异（P>0.05）,而下颌第二磨牙与平面交角的年平均变化量则有统计学差异（P<0.05）。结论拔除第一前磨牙进行正畸治疗有利于第三磨牙倾角的改善,对第三磨牙萌出有积极意义。     

Posttreatment and postretention changes following orthodontic therapy.

This investigation was performed to determine the changes which occurred in treated orthodontic cases out of retention. The material consisted of 103 cases, of which 74 cases were treated nonextraction and 29 were treated with the extraction of four first premolars. The treatment was accomplished by the full-banded edgewise bioprogressive technique. Five measurements were taken: intercanine, inter-first premolar, intersecond premolar and inter-first molar widths, and incisor to molar distance. The measurements were made on the mandibular arch of the pretreatment, posttreatment, and prostretention casts. The postretention model was obtained a minimum of one year after all retaining devices were removed with an average of 5.2 years. The following conclusions were drawn from the changes in dimensions: 1. The intercanine width was expanded during treatment, but had a strong tendency to return to or close to its original pretreatment width in both nonextraction and extraction cases. 2. The inter-first premolar width showed the greatest treatment increase in width with only a minimal amount of postretention decrease. 3. The second premolar width for nonextraction cases showed a significant amount of increase with a slight tendency for postretention decrease. 4. The second premolar width for extraction cases showed a decrease with treatment and a slight continued decrease postretention. 5. The intermolar width of nonextraction cases showed a significant increase in width with treatment. The extraction cases showed a significant decrease with treatment. However, there were no changes in either extraction or nonextraction cases postretention. 6. The incisor to molar distance decreased with treatment and had a slight tendency to continue to decrease postretention.     

Changes in mandibular incisor position in Class II Division 1 malocclusion treated with premolar extractions

The aim of this study was to investigate the magnitude of mandibular incisor retraction to be expected during full fixed appliance mechanotherapy in Class II Division 1 malocclusions treated with premolar extractions when mandibular incisor retraction was not part of the treatment plan. The material consisted of pretreatment and posttreatment cephalometric films and dental casts of 70 Class II Division 1 malocclusion patients (33 males and 37 females) treated with the preadjusted edgewise appliances. The mandibular first premolars were extracted in 31 subjects, and the mandibular second premolars were extracted in 39. The pretreatment factors that suggested a basis for the extraction choice in the mandibular arch in these patients were found to include the ratio between posterior and anterior facial heights, the maxillary-mandibular plane angle, and the residual space in the mandibular arch. The mandibular incisors were retracted in only 65% of the patients. On average, the mandibular incisors were retracted by 1.02 mm relative to the nasion-pogonion line; there was no significant difference between the 2 extraction groups. Multiple regression analysis showed that the change in the mandibular incisor position is significantly correlated with the residual space in the mandibular arch, the initial distance between the mandibular incisor and the nasion-pogonion line, maxillary-mandibular angle, and the duration of crown labial torque in the mandibular incisors. In combination, these 4 factors could explain 61% of the change in the mandibular incisor position.     

Effects of a three-dimensional bimetric maxillary distalizing arch

This study aimed to investigate the dental effects of a three-dimensional (3D) bimetric maxillary distalizing arch. The Wilson rapid molar distalization appliance for Class II molar correction was used in 14 patients (10 girls and four boys with a mean age of 12.18 years). The open coil springs were activated with bent Omega stops and Class II intermaxillary elastics. The mandibular anchorage was gained by a 0.016 x 0.016 utility arch with a 3D lingual arch or a lip bumper with a standard lingual arch. The lateral cephalograms taken before and after treatment formed the material of the research. A Wilcoxon test was used to statistically evaluate the treatment effects. The results showed that the distal tipping of the maxillary first and second molars, and first and second premolars and canines were statistically significant. Significant distal movement occurred in all posterior and canine teeth. The maxillary first molar distalization was found to be 3.5 mm. The maxillary incisor showed significant proclination and protrusion. The decrease in overbite was found to be statistically significant. The mandibular plane angle significantly increased by a mean of 0.5 mm. In addition, significant soft tissue changes were observed.     

正畸拔除第一前磨牙后第三磨牙倾斜度的变化

目的 探讨正畸拔除第一前磨牙对第三磨牙倾斜度的影响。方法 选择37例拔牙和32例非拔牙患者,分别在治疗前和治疗后的曲面断层片上测量第三磨牙长轴与平面的交角以及第二、第三磨牙长轴的交角。用U检验来比较两组患者第三磨牙倾斜度在治疗前后的变化。结果 拔牙组和非拔牙组间治疗前后下颌第三磨牙长轴与平面和第二磨牙长轴交角的差异均具有统计学意义（P<0.05）;拔牙组和非拔牙组治疗前后上颌第三磨牙长轴与平面和第二磨牙交角的差异没有统计学意义（P>0.05）。在拔牙组,治疗后下颌第三磨牙比上颌第三磨牙更直立。结论 拔除前磨牙的正畸治疗能够改善第三磨牙的倾斜角度。     

A relatively minor adult case becomes significantly complex: A lesson in humility.

A 41-year-old white woman with no particular concerns about facial esthetics was first seen with bilateral Class II molar relationship, a Class I right canine, and a Class II left canine. Overjet was 3 mm and overbite was 0.5 mm, with no incisor contact. A maxillary right premolar was missing for unknown reasons and all 4 third molars had previously been extracted. The maxillary midline was 2 mm to the right of the facial midline, and the mandibular midline was 3.5 mm to the left of the maxillary midline. There was 7 mm of crowding in the maxillary arch and 6 mm of crowding in the mandibular arch, with an increased curve of Spee. The patient had a well-positioned maxilla, a retrognathic mandible with increased convexity, a Class II denture base relationship, and a vertical facial pattern. The treatment plan consisted of extracting the maxillary left first premolar and the mandibular left central incisor. After 4 months of treatment, an open bite from second premolar to second premolar was noted. After 6 months of treatment, the patient expressed concern with her chin position and mentalis hyperactivity. It was apparent that the orthodontic treatment had resulted in molar extrusion, which the musculature was not able to withstand. Treatment continued and the case was set up for posterior maxillary impaction and mandibular advancement surgical procedures.     

不同拔牙模式正畸矫治对成年女性牙弓宽度和软组织正貌的影响

目的：研究不同拔牙模式对安氏Ⅱ1错牙合成年女性治疗前后牙弓宽度和面部软组织正貌的影响。方法：将40例安氏Ⅱ1错牙合需拔牙矫治的成年女性患者随机分为两组。 A组拔除上颌2颗第一前磨牙,下颌拔除2颗第二前磨牙,B组拔除4颗第一前磨牙。分析比较两组病例治疗前后牙弓宽度和面部软组织正貌指标的变化。结果：正畸治疗后,组内比较显示两组病例上下颌尖牙间宽度均增加,上下颌第一磨牙间宽度均减小,差异有统计学意义（P＜0.05）;组间比较仅下颌尖牙和下颌第一磨牙间宽度变化有统计学意义（P＜0.05）,B组下颌尖牙宽度增加量大于A组,B组下颌第一磨牙牙弓宽度减小量小于A组。治疗前后比较,两组病例在面宽、口裂宽、下颌角间宽、容貌面长和鼻下颏下距的差异均无统计学意义（P＞0.05）。Pearson相关性分析显示牙弓宽度与软组织正貌指标之间无相关关系（P＞0.05）。结论：安氏Ⅱ1错牙合病例正畸矫治后成年女性软组织正貌的变化不受拔牙模式影响,不同拔牙模式仅影响矫治后牙弓宽度的变化。     

Class II subdivision treatment success rate with symmetric and asymmetric extraction protocols.

The purpose of this study was to compare the success rates of Class II subdivision malocclusion patients treated with either symmetric or asymmetric extractions. The sample consisted of 51 patients with Class II subdivision malocclusion. The patients were divided into 2 groups. Group 1 included 28 patients who were treated with 4 premolar extractions. The 23 patients in group 2 were treated with 3 premolar extractions (2 maxillary premolars and 1 mandibular premolar on the Class I side). The initial and final study models were evaluated by means of Grainger's treatment priority index (TPI). Individual evaluations of improvements in maxillary-to-mandibular dental midline deviation, overjet, and overbite were also made. The final mean TPI and the mean improvement in TPI and in the other variables of each group were compared with independent t tests. The results showed a statistically significant difference only for the improvement in maxillary-to-mandibular dental midline deviation of the groups. The 3-premolar-extraction group had a greater improvement of the initial interdental midline deviation. There is a tendency for a slightly better treatment success rate when Class II subdivision patients are treated with asymmetric extraction of 3 premolars, compared with extraction of 4 premolars.     

Degeneration of tooth germ in the developing dentition of the gray short-tailed opossum (Monodelphis domestica)

The aim of this study was to examine the developmental aspects of the dental lamina and the tooth germ of the marsupial opossum (Monodelphis domestica), and to clarify the dental formula of this animal. Specimens were 12-, 16-, and 18-d-old opossums. 3-D reconstructions were constructed from frontal serial sections. In these animals, the tooth germs of the deciduous maxillary and mandibular canine, deciduous third premolar and first molar, and the deciduous maxillary first incisor and second molar had a successional dental lamina and a replacement tooth germ. The tooth germ of the deciduous maxillary fourth incisor and the mandibular first incisor were reduced. The dental lamina was continuous in each jaw except for the deciduous maxillary first incisor. The first dentition (deciduous dentition) remained as the permanent dentition on the deciduous maxillary first incisor, and the deciduous maxillary and mandibular canine and first molar. The maxillary fourth incisor and the mandibular first incisor were the second dentition (successional dentition). Only the deciduous third premolars were replaced. These results showed monophyodonty caused by both deciduous and replacement tooth germ degeneration.     

Treatment of an adult with several missing teeth and atrophic old mandibular first molar extraction sites

This report describes the orthodontic treatment of a woman, aged 34 years 2 months, with several missing teeth and atrophic mandibular first molar extraction sites. We had planned to close the spaces from the missing maxillary canines with mesial movement of the premolars and molars. In the mandibular arch, protraction of the second molars into first molar extraction sites and reduction of the mandibular incisor protrusion were performed. No miniscrews or bone plates were used. A modified helical loop was used, and it can be considered a simple and an efficient orthodontic method of closing the spaces without mesial or lingual tipping and rotation. Pleasing esthetic and functional results were achieved.     

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.     

Extraction treatment of a Class II division 2 malocclusion with mandibular posterior discrepancy and changes in stomatognathic function

This case report describes the successful extraction treatment of a Class II division 2 malocclusion with mandibular posterior discrepancy and a congenitally missing maxillary lateral incisor on the left side. The posterior space in the mandibular arch was small, and the mandibular second molars were impacted, with distal tipping. The discrepancies in the maxillary and mandibular arches were resolved by extraction of the maxillary lateral incisor on the right side and the mandibular second premolars on both sides. The mesial movement of the mandibular first molars occurred appropriately, with the second molars moving into an upright position. A lip bumper was used with a preadjusted edgewise appliance in the maxillary dentition to reinforce molar anchorage and labial movement of the retroclined incisors. Despite the extraction treatment, a deep bite could be corrected without aggravation as a result of the lip bumper and utility arch in the mandibular dentition. Thus, an Angle Class I molar relationship and an ideal overbite were achieved. The occlusal contact area and masticatory muscle activities during maximum clenching increased after treatment. The maximum closing velocity and the maximum gape during chewing increased, and the chewing pattern changed from the chopping to grinding type. The findings in the present case suggest that the correction of a deep bite might be effective for improving stomatognathic function.     

Frequency evaluation of different extraction protocols in orthodontic treatment during 35?years

Background

Studies that show frequencies of different orthodontic treatment protocols can be used as valuable parameters in the interpretation of treatment tendency with time. The purpose of this retrospective study was to evaluate all orthodontic treatment planning conducted at the Orthodontic Department at Bauru Dental School, University of São Paulo, Brazil, since 1973, in order to investigate extraction and non-extraction protocol frequencies selected at each considered period.

Methods

The sample comprised 3,413 records of treated patients and was evaluated according to the protocol choice, divided into 10 groups: Protocol 0 (non-extraction); Protocol 1 (four first premolar extractions); Protocol 2 (two first maxillary and two second mandibular premolars); Protocol 3 (two maxillary premolar extractions); Protocol 4 (four second premolars); Protocol 5 (asymmetric premolar extractions); Protocol 6 (incisor or canine extractions); Protocol 7 (first or second molar extractions); Protocol 8 (atypical extractions) and Protocol 9 (agenesis and previously missing permanent teeth). These protocols were evaluated in seven 5-year intervals: Interval 1 (1973 to 1977); Interval 2 (1978 to 1982); Interval 3 (1983 to 1987); Interval 4 (1988 to 1992); Interval 5 (1993 to 1997); Interval 6 (1998 to 2002); Interval 7 (2003 to 2007). The frequency of each protocol was compared between the seven intervals, using the proportion test (P < 0.05).

Results

The results showed that 10 protocol frequencies were significantly different among the 7 time intervals.

Conclusions

The non-extraction protocol frequency increased gradually with consequent reduction of extraction treatments. The four premolar extraction protocol frequency decreased gradually while the two maxillary premolar extraction protocol has maintained the same frequency of indications throughout time.     

Mandibular second premolar extraction--postretention evaluation of stability and relapse

The dental casts and cephalometric radiographs of 46 patients, treated with mandibular second premolar extraction and edgewise orthodontic mechanotherapy, were evaluated for changes over a minimum 10-year postretention period. The sample was divided into two groups: early (mixed dentition) extraction of mandibular second premolars and late (permanent dentition) extraction of mandibular second premolars. Results showed no difference in long-term stability between the two groups. Arch length and arch width decreased with time and incisor irregularity increased throughout the postretention period. No predictors or associations could be found to help the clinician in determining the long-term prognosis in terms of stability. The sample was regrouped according to the postretention degree of incisor irregularity. Statistically significant differences in cephalometric measurements were found between the minimally crowded group and the moderately to severely crowded group.