论文（1）.docx

介绍

Angle 分类由 Edward H. Angle 于 1899 年提出，是临床上最常用的咬合不正分类方法。根据上牙弓和牙弓之间的矢状面，他将咬合不正分为 I、II、III 类三大类（Peck， 2009）。在 cla ssification 系统中，当上第一磨牙的近中颊尖在下第一磨牙的中央裂缝处更远端咬合时，就会发生 Angle II 类咬合不正，这意味着下颌骨更向后颌到上颌骨，通常被称为“远端咬合”。

II 类的 Subtypes

根据覆盖，II 类咬合不正分为 2 个偏差。一个是 II 类 1 分区，表示覆盖增加，另一个是 II 类 2 分区，正常覆盖约为 1-2 毫米，包含 3 个亚型：A、B 和 C。当上尖牙异位时，它是 II 类 C 区的典型特征。对于 II 类 A 区，所有上切牙都略微后倾，对于 II 类 B，只有上中切牙后缩，上侧切牙突出。除了这 2 个偏差外，还有另一种称为 II 类细分的特殊类型，它代表一侧正常的 I 类关系，但另一侧 II 类摩尔关系，它伴有不对称性，特别是下颌骨不对称（Cassidy et al.， 2014）。

II 类病因

在 II/2 类患者的情况下，可以看到上颌骨太窄，导致下颌骨无法滑出以获得适当的咬合位置。这种情况可能导致上颌骨广泛前倾、下颌骨太后倾、上牙弓狭窄、下颌骨小，甚至由于先天因素或不良习惯而出现综合情况。

即使 II/1 类和 II/2 类属于同一组“Angle II 类咬合不正”，这两种偏差的特征之间仍然存在很大差异。 II 类 1 类的病因包括一系列因素，包括骨骼因素，如下颌骨或上颌骨的生长问题;软组织因素，如低渗的上唇;牙齿因素，如上牙拥挤;以及不良习惯，如包括吮吸拇指和吐舌等。通常，张口呼吸的患者会改变舌头、嘴唇和面部肌肉的正常位置。当舌头为了方便口腔呼吸而处于相对较低的位置，并且不再处于支撑上颌骨的正常位置时，上颌骨会变窄，上切牙会突出，这可能会导致嘴唇功能不全，阻碍下颌骨的发育。

C线性特征

正常或升高的下面部高度通常可见于 II/1 类患者，但 II/2 类患者具有下面部高度降低的典型特征。下颌骨的位置总是向后，不符合现代审美趋势（Perović， 2017）。II/2 类咬合不正的病因是遗传因素和环境因素的结合，这意味着遗传因素通常由于生长不足或向前生长受限而导致下颌后缩，有时还伴有软组织功能障碍，使情况恶化。

与正常咬合的患者相比，II 级咬合不正患者表现出明显不同的颅面外观，它会破坏正畸治疗的目标——面部美学的和谐（Alarashi et al.， 2003）。 Angle II 类咬合不正的主要特征是磨牙和犬齿关系以及增加的覆盖和覆合。当存在早期的 II 类咬合关系时，会进一步影响骨骼发育问题，使正畸治疗更加困难，结果也可能受到影响（Varrela， 1998）。更重要的是，大多数时候，II 类患者表现出下颌后缩（Rosenblum， 1995）。毫无疑问， II 类咬合不正患者的气道可以受到干扰，并且在正畸治疗的帮助下可以显着改善这种情况。（TRIPLETT 等人，1989 年）。

T研究的考虑和争议

治疗 Angle II 类咬合不正不仅对改善牙齿功能至关重要，而且对改善面部美学和生活质量也至关重要。II 类咬合不正的治疗方案各不相同，包括拔牙和非拔牙方法，具体取决于咬合不正的严重程度、患者的年龄、期望、经济拮据、临床医生的偏好等。

拔牙的目的是去除某些牙齿，为其余牙齿提供足够的空间，使其余拥挤的牙齿对齐，并调整上下颌之间的咬合关系。另一方面，非拔牙方法侧重于扩大上颌骨和改善牙齿排列以达到预期效果。尽管一些研究表明拔牙可能会影响患者的面部轮廓，但这些研究存在局限性和偏见，他们不能否认拔牙方法在正畸治疗中的重要性（Konstantonis 等人，2018 年）。此外，这里没有证据证明拔牙会使正畸治疗的结果恶化（Benson 等人，2023 年）此外，没有证据证明拔牙会使正畸治疗的结果恶化（Benson 等人，2023 年）

对于非拔牙治疗，早期患者可以使用一些功能性矫治器，可以帮助下颌骨向前移动和上颌骨扩张。在固定器具、可拆卸器具和口外器具的帮助下，有时可以打开空间，并纠正牙齿的倾斜和拥挤。当然，并非所有病例都可以通过这种方法解决，而只有在适当程度的咬合不正、适当的患者年龄和其他要素下才能解决。

对于 II 类咬合不正患者，当拔牙旨在解决拥挤和突出的问题，甚至提高牙弓的对称性时，正畸医生有多种选择。在下牙弓正常但上牙弓有突出覆盖的情况下，拔除上部^{第 1 或}第 2 前磨牙可能是牙医的一种选择，但应始终考虑面部轮廓。还有其他选择，包括拔除所有上下 1^st 前磨牙等。然而，这种类型的治疗并不适合每个患者。一旦所有第一前磨牙都被拔除，双唇都会缩回，这会产生负面影响，尤其是对于大面积嘴唇突出的患者，并恶化他们的面部美学（Janson 等人，2016 年）

事实上，在正畸领域已经有一个世纪以来一直在争论是否通过拔牙治疗咬合不正，“美国正畸之父”——爱德华·安格尔——是支持非拔牙治疗的典型人，而“Calin Case”对此做出了巨大贡献，他是拔牙正畸治疗的支持者（H.C. Pollock， 1964）. 巴西圣保罗大学的研究表明，从 1973 年到 2007 年的 35 年内拔牙频率呈上升趋势，从仅 14.29% 增加到 85.71%，然后下降到 45.45%。它建议正畸治疗应该始终更新，而不是毫无疑问地坚持使用传统方式（Janson 等人，2014 年）。

直到现在，不同的正畸医生可能会对同一患者的治疗计划保持不同的看法。没有足够的数据证明提取治疗与非提取治疗相比在疗效上存在显着差异（Benson等人，2023 年）。

本研究的预测和意义

Angle II 类咬合不正是最常见的正畸问题之一，占全球人口的 20-23%，在欧洲的患病率也高于所有其他国家（Alhammadi 等人，2018 年）。尽管有大量关于 Angle II 类咬合不正管理的文献，但缺乏关于这些情况下拔牙频率的全面数据。更重要的是，还需要探索影响 II 类的因素，例如年龄是影响正畸治疗持续时间的最强影响因素之一（Popowich 等人，2005 年）。此外，对于如何治疗 II 类患者，目前仍存在不同意见的正畸医生。因此，如何管理和治疗 II 类患者，哪些因素影响治疗方案是人们热议的话题。

大多数与 II 类咬合不正相关的现有研究都是基于从当地收集的数据，并且针对全球患者的研究非常有限且证据不足。为了以多样化的方式了解 II 类咬合不正并实现更有效的 II 类治疗，需要收集更多的数据，以便将来为正畸医生提供更多的信息和标准指导。

As a result, the purpose of this study is to provide data on the extraction rate of Angle Class II patients in our clinic to enrich the understanding of the treatment of Class II patients. By analyzing the prevalence of tooth extraction therapy, as well as age gender, age, and other factors, we can figure out the frequency of occurrence and extraction of Class II patients in our clinic, and explore the proportion of Class II patients who receive tooth extraction treatment in our clinic; whether gender and age have certain influencing effects on Class II tooth extraction patients; and whether there are qualified and effective methods for the treatment of Class II patients.

The results of this study may provide information for best practices in managing Angle Class II malocclusion. By providing evidence-based insights, it may be possible to guide clinical orthodontists to make more balanced and optimal decisions, thereby better-fulfilling patients’ satisfaction and better functional and aesthetic outcomes. In addition, this study may also increase the size and diversity of the data and help to develop standardized protocols for the treatment of Class II patients, consequently reducing variability and experimentality in clinical practice and improving the overall quality of orthodontic care.

综上所述，本文为深入分析 Angle II 患者拔牙频率奠定了基础，突出了区域多样性、II 类患者治疗的主要当前趋势以及影响临床治疗的因素。

材料和方法

本研究旨在作为一项回顾性研究，旨在调查过去 15 年我们牙科诊所正畸科 Angle II 级咬合不正患者的拔牙治疗频率、拔牙正畸治疗期间不同情况下 Angle II 患者的频率以及主要分布患者首次接受治疗时的性别和年龄，从而了解 Angle II 级咬合不正患者群体不同情况下拔牙的实用性和决策趋势，以及初始治疗时机对 Angle II 类拔牙正畸治疗的影响。

样品选择

所有样本均从金属盒中选择，保存了 2010-2025 年过去 15 年内在 PTE KK 牙科和口腔外科诊所（匈牙利 Pecs）正畸科接受治疗或至少记录有治疗计划的所有患者的纸箱。这些装有患者纸箱的金属盒按患者姓氏的第一个字母从 A 到 Z 排列。从每个盒子中随机选择大约 15 个纸箱，但每个盒子的选择数量将被修改，其中选择的样品与组的总大小成正比，以平衡每个盒子中样品的分布。在样本选择期间，从金属盒中只能看到纸箱边缘的顶部，可以保证本研究的随机化，总共有 186 例以这种方式被无意中选择了。

基本数据收集

每次随机抽取后，记录纸箱封面上的姓名和保险号码，可以作为每位患者的身份识别，然后打开纸箱，以便查看里面的文件，包括但不限于患者的病史、治疗计划和咨询过程。记录与拔牙相关的信息、已拔除或将要拔除的确切牙齿编号以及角度分类，特别是对于与 II 类关系相关的患者。如果存在分区组或其他情况，不仅包含II 类关系，还包含其他类型的分类，以及犬齿之间或磨牙之间的其他关系，都在 Microsoft World 2019 中详细记录。

Basic data processing and analysis

Among 186 cases, 101 cartons clearly demonstrated the exact classification of patients, while 85 cases displayed unknown classification. What’s more, within the 101 cases with classification types, 84 cases were Angle Class II patients or at least one of the canine or molar side had Angle Class II relationship, 10 patients with Class I relationship, and 7 cartons showed patients having Class III malocclusion. After counting the numbers of patients who were in Class I, Class II, and Class III within these 101 cases, a pie chart was created in the Microsoft Excel 2016 system based on the counting numbers, so that the frequency of every type of Angle Classification occurred in 101 cartons can be seen from the following Figure 1.

此外，在这 186 例病例中，有 58 例显示了几种不同类型的提取。拔牙 58 例中，有 53 例与 Angle II 级关系有关，4 例与 Angle III 有关，为 2 例典型的 Angle III 类患者，全部拔除第一前磨牙;1 例右磨牙 III 类，左上和右第一前磨牙，右下第一磨牙拔除;1 例右尖牙 III 类，全部拔除第一前磨牙。此外，I 类患者仅显示 1 例，所有第一前磨牙均拔除。为了更好地评价正畸治疗期间拔牙的频率和拔牙病例中 II 类的频率，数据包括样本总数（n=186）、拔牙总病例数（n=58）和 Angle I 级拔牙治疗患者人数（n=1），角度类II（n=53）和角度类II（n=4）被输入到Microsoft Excel 2019中，以生成两个饼图，分别在下面的图2和图3中显示。

Counting the number of samples with extraction and without extraction treatment within the 84 cases that were classified as Angle Class II in different types of classification. There were 49 cases that had records of permanent tooth extraction and 35 cases without any extraction record. After inputting these data, a pie chart was created in Microsoft Excel 2019 software, which showed the frequency of extraction in patients with Class II, as Figure 4 displayed below.

Data augmentation and processing

Only the patients who had extraction treatment with clearly known Angle classification relevant to Angle Class II (total 52 patients) were included and then with the help of the name and insurance number of the patients the radiographic images can be checked from the EasyDent V4 Viewer system which is the earlier system saving the radiographic images of the patients who came to the dental clinic in earlier years and VixWin-Tuzer system saved images for more recent years. Both of the systems save the information of patients with first name, surname, insurance number, gender, and date of birth, and serve the purpose of reviewing and saving the radiographic images of patients as long as they have done any kind of diagnostic images at the PTE KK Dental and Oral Surgery Clinic (Pecs, Hungary) and the exact time for each image has also been recorded.

Screened out the patients who only have the treatment plans in the carton without any treatment or orthodontics-related radiographic images, since some of the patients only came for the first time and did not choose to continue the treatment or due to the errors in the sampling process, whether there was a problem with the collection of the name or patients’ insurance number was incorrect, the patients’ information could be queried in the system. After the exclusion criteria, those patients who fulfilled the requirements were documented with the date of birth and the date of the first radiographic images as the first date of the orthodontic treatment, and also the gender of those patients was recorded. There were 4 cases that can’t be found in either of the systems and were removed from the sample pool so a total 45 sample pools related to Angle Class II relationship with extraction were checked from the system and were put on record.

The name, insurance number, gender, detailed data of extraction (specific site of the extracted tooth), type of Angle Classification, date of birth, first date of treatment date of all the 45 medical records were entered into Microsoft Excel 2019 software for data registration and entered in the form of a spreadsheet as shown in Table-1 below. After that, the age of the Class II patients, when they initiated their orthodontic treatment with extraction, was calculated by subtracting the date of birth of patients from the date of first starting orthodontic treatment, and the calculated valve was then rounded to an integer and placed in the table.

Name	保险号码	性	萃取	分类	出生日期	_第一次治疗日期	接受治疗的年龄

表 1

Augmented data analysis

During the real clinic practice, there were not only the typical Class II Division 1 and Division 2, other situations can also be seen in the sample base. According to the 45 sample cases that belonged to Class II malocclusion with permanent tooth extraction therapy and were recorded into Table 2, the descriptive statistics were used to summarize the demographic and clinical characteristics of these patients by putting the spreadsheet mentioned above from Microsoft Excel 2019 into IBM SPSS Statistics software. A crosstab was created to examine the frequency of different types of Class II patients in different types of extraction methods, as Figure 5 shows below. Another pie chart was conducted in Microsoft Excel 2019 to clarify the proportion of classic Class II/1 and Class II/2 patients during extraction treatment of Class II malocclusion, after excluding the 20 cases of which only known by Class II without the subtype and combing the rest of the samples as other Class II type, and this can be checked from the following Figure 6.

In order to evaluate whether gender, age, and initial treatment time have an impact on the extraction treatment of Class II patients, once all the data had been input into the spreadsheet, the completeness and the accuracy of these data were checked again before the data analysis, and then counted the total number of female patients (n=32) and total number of male patients (n=13). Rearranged a new table for it and created the pie chart on Microsoft Excel 2019 software demarcating the percentage of each gender occupied the total number of the extraction, as Figure 7 "Gender ratio" below to analyze whether gender has a significant difference in extraction method treating Class II malocclusion.

Aiming to analyze how gender influences Class II/1 and Class II/2 separately, a new table was created in Microsoft Excel 2019 as shown below, which only arranged the female and male distribution in Class II/1 and Class II/2 which means that excluding the 9 cases known as Class II, 10 other subtypes of Class II patients and only keeping the rest 26 cases (Table 2). According to this table, Figure 8 and Figure 9 were created in Microsoft Excel 2019 to display how gender distribution in Class II/1 and Class II/2 patients with orthodontic extraction.

Table 2

Apart from that, a bar chart (Figure 10) which can be checked in the ’results’ part, was also conducted in Microsoft Excel 2019 to demonstrate the distribution of different sexes in both Class II/1 and Class II/2 cases.

Through the data of 45 cases mentioned above in Table 1, boxing out all the calculated initial treatment ages of the patients in these 45 cases, and utilizing Box-and-Whisker Plot with the help of Microsoft Excel 2019 software to analyze the distribution of the ages, and then Figure 11 was created as it is shown below. Apart from this, another Box Plot was also applied with the same method, while only boxing the data in the date of 1_st treatment column, to visualize the major distribution of duration for these patients, as Figure 12 demonstrates underneath.

结果

The following content introduces the results of statistical analysis conducted to investigate the frequency of extraction in patients with Angle Class II malocclusion. Key findings include frequency of Class II cases that occurred in orthodontic treatment, frequency of extraction during orthodontic management, distribution of Class II across extraction cases, gender ratio in tooth extraction cases of Class II patients, distribution of patients’ age and initial treatment time, frequency of different types of Class II in different extraction methods, the association between Class II types and extraction status. Variable descriptive statistics and visualizations (e.g., pie charts, box plots, Crosstabs) were used to summarize the findings.

Frequency of Class II

The 186 sample cases included 85 cases with unknown type of Angle classification and a total of 101 cases whose classification is clearly known in the carton files, of which 84 cases were Class II (83%), 10 patients belonged to Class I malocclusion (7%), and 7 patients were Angle Class III (7%). This indicates that the majority of the samples are patients who were in Angle Class II or at least had a Class II relationship in the molar or canine region, which may be related to factors such as healthcare needs, case sources, and also regional factors. Although the proportion of Class III patients was slightly higher than that of Class I patients, there was no significant statistical difference between these two groups.

图 1

Frequency of extraction

Within the randomly selected 186 cases, 58 patients had the extraction during orthodontic treatment (31%), and 128 cases (69%) were treated without the extraction method. During the orthodontic treatment, approximately within one-third of the situation extraction is considered part of the treatment process. This demonstrated that for the entire study sample, non-extraction treatment was relatively more common in orthodontic management, but about one-third of patients' tooth extraction was still chosen due to clinical factors such as crowding and malocclusion. For Class II patients who often appear in the orthodontic clinical practice, it is very important to reveal their tooth removal frequency and factors that affect the decision of tooth extraction therapy, so the following content will further explore which types of classification are more inclined to remove teeth during orthodontic treatment.

图 2

Frequency of Class II in extraction cases

Among the 58 patients known as Class II patients who underwent tooth extraction therapy, 53 patients (91%) were in Class II malocclusion or related to Angle Class II, only 1 patient (2%) was in Angle Class I, and 4 cases (7%) came from patients with Class III malocclusion. It can be directly found from the pie chart (Figure 3) that Class II patients showed a particularly prominent proportion in tooth extraction cases. This indicates that Class II is the most common type of malocclusion in tooth extraction cases collected in this study. Thus, it is evident that Class II malocclusion occupies an extremely essential position, whether it is only for tooth extraction cases or for samples that have received orthodontic treatment. Because this study mainly focuses on the frequency of extraction for Class II patients in our clinic, the impact of other relevant factors (such as gender, age, and classification types) on Class II patients with tooth extraction strategy will also be further assessed below.

图 3

Frequency of extraction in Class II

As mentioned before, there were 84 cases known as Class II patients and 49 patients had extraction within that. From Figure 2, it can be seen that Class II patients undergoing the removal of the tooth consisted of 58% of the total, while 42% of Class II patients had non-extraction treatment. The tooth extraction method occupied around two-thirds of the treatment in Class II patients.

图 4

Frequency of different extraction modes in Class II

In clinical practice, not only the both sides Class II/1 or Class II/2 can be seen, but also the combination of other types of Angle classification in the same patient can be observed, and the extraction types corresponding to different cases are not the same, so to evaluate frequency of different types of Class II in different extraction methods, the crosstab was created as shown in Figure 5. This table (figure 5) shows the distribution of different types of Class II malocclusion that occurred in patients’ mouths (such as only left side Class II, only left canine Class II) in specific extraction combinations after eliminating the 4 cases that can not be checked from the EasyDent V4 Viewer system and VixWin-Tuzer system.

The rows and columns of the table listed each type of Class II and its corresponding extraction site (e.g., 14, 24, 34, 44, 32, 15, 34, etc.). Using the number of FDI World Dental Federation Numbering System to represent the position of extracted teeth.

In the first row of the table shows the types of extraction: upper lateral incisors and lower first premolar extraction; upper first premolar extraction; all first premolar extraction; upper first premolars, lower left first premolar and lower right premolar extraction; upper first premolars and lower second premolars extraction; upper right second premolar and lower first premolars extraction; upper and lower first premolars and third molars extraction; upper left first premolar and lower first premolar extraction; lower left incisor extraction; lower second molars extraction; lower third molars extraction. The percentage of each type of classification is under the corresponding extraction method and ’Count’ means the number of the case. It can be easily found that among the known 45 cases, there were 11 methods for tooth extraction in Class II, which revealed the complexity of tooth extraction. Within the analyzed 45 cases in this study, except the type which was only known as Class II, and not counting the typical Class II/1 or Class II/2 type, there were still 8 subtypes of Class II malocclusion. It is not difficult to discover that even if the number of samples is limited, the treatment plan of Class II patients with extraction is complicated and needs to be researched.

According to the statistical results, it can be seen that the majority of the patients were concentrated in Class II/1 (5 cases) and Class II/2 (21 cases) when not counting the 9 Class II samples without exact subtype or division. What’s more, the Classic Four-Premolar Extraction Plan involving teeth 14, 24, 34, 44 removal was the most frequent (accounting for about 60%) and the second most common type of extraction in Class II patients was the extraction of upper first premolars pattern (13.3%), while the third most frequent type was teeth 14, 24, 35, 45 extraction pattern occupying 8.9% sample cases. Some classifications (such as ’left Class II, right Class III’) were rarely seen and often correspond to a single tooth extraction strategy.

Because the the number of samples of subtype of Class II is limited or only with one single case, which indicates these types of ’mixed malocclusion relationship’ exists in clinical practice, but it is not enough to support more in-depth statistical tests. Overall, this Crosstab shows that: first, the various subtypes of Class II have a certain tendency to concentrate on which teeth to extract; second, a few cases display the complex left-right differences or canine relationship differences, and their tooth extraction strategies are more individualized; third, the expected frequencies of some groups are quite low, which need to be interpreted with caution in subsequent analysis to avoid excessive interferences. What’s more, the following content in the ’Discussion’ paragraph will further combine factors related to patients’ age, treatment time, gender, and other environmental factors to explore the potential causes and clinical significance of these differences. However, due to the limited sample size of individual combinations, more cases need to be accumulated to obtain a more stable distribution pattern and more precise and reliable result.

图 5

Frequency of Class II/1 & Class II/2 in Class II extracted cases

As can be seen from Figure 5, there were 9 patients only known the classified as Class II without the subtypes. By excluding these samples as mentioned above, figure 6 was produced aiming to show the frequency of the classic Class II/1, Class II/2, and other atypical Class II.

图 6

Gender ratio

Gender, as one of the variables in the data, may also be a part of the relevant influencing factors, so it should be used to analyze whether it has an impact on the treatment of Class II with tooth extraction. In order to explore whether tooth extraction treatment is evenly distributed between different sexes and whether there is a gender bias, a pie chart was created and is shown below in Figure 4 with the help of a sample pool which consisting 45 cases that demonstrated clear information about the name, insurance number, gender, classification type, extraction details, date of birth and first time for the orthodontic treatment. Among the 45 patients who underwent Class II with tooth extraction treatment, 32 were female patients, accounting for 71% of the total, and the rest 13 were male patients, occupying 29% of the total. As can be seen from the figure within Class II patients who had tooth extraction therapy, about two-thirds of the medical records were female so the female patient group constituted a remarkably large majority within the overall population with extraction treatment meanwhile only around one-third were male patients, which may illustrate that gender distribution is indeed not uniformed between women and men, and the reasons for this may include but not limited to patients’ requirements, degree of crowding, environmental factors, etc.

图 7

Then the distribution of gender in each type was clearly shown in Figures 8 & 9. As for Class II/1, 60% were female compared with 67% of female patients in Class II/2 with extraction. There were 40% of Class II/1 cases with extraction were male patients, and 33% of the total in Class II/2 patients with tooth removal. It is obvious that no matter which Division of Class II the patients were in, the female was the major group in orthodontic treatment with extraction. No matter whether for analysis of gender ratio in Class II treatment with extraction or in the evaluation of Class II/1 and Class II/2 cases with tooth elimination, female patients always dominated in all situations.

图 8图 9

As seen from Figure 7, the number of female patients was quite huge, that’s why another Bar Chart was created to check the ratio of female and male patients in both Class II/1 and Class II/2 situations.

图 10

It is easy to see from Figure 10 that no matter whether for the female or male patients, the ratio of Class II/1 and Class II/2 was nearly 2: 8. Based on Figure 7, it demonstrated that female patients not only having high numbers in total Class II patients but the large amount in each subtype of Class II, which might be needed to explore the reasons for it and waning for orthodontists.

Age distribution

In addition to gender, the age of the patients when he/she started the orthodontic management is also a variable, and whether it has a certain impact on treatment needs to be discovered too. Therefore, the time for initial treatment of Class II patients with tooth removal was also evaluated. In order to understand what age patients generally are at the beginning of treatment and which age group of patients most frequently started treatment, a Box Plot figure was produced based on the sample library. Within the 45 patients who had Class II malocclusion and extraction during orthodontic treatment, the Box Plot figure as Figure 5 shown below illustrates that the maximal age within the sample pool was 23 years old and the lowest age was 7 which indicates that there was a certain span in the age of the youngest and oldest Class II patients with extraction treatment in this study. The lower border of the box (Q1 = 11 years old) and the upper border of the box (Q3= 16 years) indicate that 50% of patients started orthodontic treatment with extraction therapy between the ages of 11 and 16. The median is 13 years old, and the mean is about 13.42 years old. The two numbers are quite close, illustrating that the distribution of this group of samples is more concentrated in the adolescent stage. This result is consistent with the common timing of orthodontic intervention for adolescents. It also shows that some of the Class II patients postponed the treatment until adulthood or began the therapy at a younger age, reflecting the individual differences in treatment decisions and rate of growth in real cases and also indicates the cognitive differences betweeen different patients.

图 11

Distribution of initial timing

As time goes by, orthodontic treatment methods will also be modified or changed. All the sample cases in this study were randomly selected from the cases in the past 15 years, so for the purpose of understanding the time period in which the data of this paper is mainly distributed, the Box Plot was used again to analyze the time when Class II tooth extraction patients started treatment. As can be seen from Figure 6 below, the distribution of the time for all of the 45 samples mentioned above in this study is relatively wide, with the earliest record being October 6, 2010, and the last being February 8, 2024. The box presents that more than half of the cases started orthodontic evaluation or treatment between August 2016 (Q1) and December of 2022 (Q3), and the median of the Box Plot is about September 30, 2019, and the mean is June 3, 2019. This distribution shows that most of the patients initiated orthodontic management in the four-year period from 2016 to 2022, while some cases were started at an earlier or later time, which may be related to patients’ personal growth, economic conditions, psychosocial factors, awareness of medical treatment and other factors. Overall, although there are individual differences in the time point of starting treatment, it is mainly concentrated in the past 5-8 years, which is consistent with the current medical trend of orthodontics.

图 12

讨论

本研究主要探讨了本院 Angle II 类患者的拔牙频率、不同类型 II 类患者的不同拔牙方法，以及患者性别和年龄对 II 类拔牙患者的影响。

Through statistical analysis of clinical case data, the results demonstrated that 58% of Class II patients underwent tooth extraction treatment, while 42% did not. In Angle Class II patients, it is much easier to see the tooth extraction strategy, meanwhile, the most commonly used extraction mode among Class II patients is the Classic Four-Premolar Extraction Plan (teeth 14, 24, 34, 44 removals), accounting for around 60% of the total. Further analysis showed that different Class II subtypes (such as left Class II, right Class III; left molar Class I, canine Class II and right molar Class II, canine Class III) also have significant differences in extraction pattern, and different subtypes of Class II malocclusion corresponds to different extraction pattern, which demonstrates that the subtypes of Class II are closely related to the specific treatment plan. In addition, there is no standard extraction protocol to deal with Angle Class II patients, so evaluating patients precisely and with exact situations of malocclusion is not only the important step to having the right diagnosis but an individualized treatment plan and treatment is an essential step for treating patients. What’s more, it was found that the main distribution was shown in female patients, and treatment time always started from the age of 11-16 in this study in Class II patients with extraction strategy.

These results not only confirm the main influence of types of Class II on orthodontic treatment plans, but also provide a reference for clinical practice, emphasizing the necessary of indivisualization of diagnosis and treatment strategy during orthodontic treatment, and the influence of age and gender of Class II patients with extraction. In conclusion, this study draws attention to the orthodontic treatment with tooth elimination for highly occurred Class II patients should always be individualized even if there are some popular extraction methods.

The results of this study show that Class II patients were dominant in our clinic which occupied 83% of the sample pool. However, this conclusion is different from (Alhammadi et al., 2018)—a systemic review showed 19.56% Class II patients out of the total, which was obtained by searching various search engines. The huge difference may come from regional factors because this study only collected cases of patients admitted by our clinic that is limited to the Hungarian region while they used samples of malocclusion patients from all over the world.

Not only that, in the (Perkowski et al., 2024) article, Konrad Perkowski also wrote that the most common type of malocclusion in Poland was Class I consisting of 53% of the total, followed by Class II, and finally 8% Class III. Thus, it may not only be due to geographic factors, but also to deviations in data processing, because most of the classifications were by observing the handwritten documents in the cartons, and during the recording process, those samples whose classification can’t be found or recognized were discarded. As a result, only 101 medical records were kept from 186 files, and the result of Class II patients’ frequency from the total sample base may likely be affected by the excluded 85 cases. Another article written by de Sousa Dardengo et al. showed 49.5% of Class I patients and 46.9% of Class II patients appeared within their sample base (de Sousa Dardengo et al., 2016), so that it is not difficult to see the difference in the frequency of different Angle classifications occurs in different regions which can be influenced by multiple factors. Different regions may have different dietary habits, different living environments, and different races which will also have different genes, so the types of malocclusions may indeed vary greatly in different regions.

Furthermore, there is a certain degree of difference between the frequency of tooth extraction in Angle Class II patients in this research and the study published by de Sousa Dardengo et al. (de Sousa Dardengo et al., 2016). This study showed that 58% of Class II patients underwent extraction orthodontic treatment, while they stated that 49% of Class II patients had tooth extraction with treatment. Apart from the regional factors that may affect the results of both articles, the size of the sample base also may cause the difference, because they collected 1484 samples in the study compared to 186 samples selected in this article. However, although the sample size is not large, it captures the distinctive features of our clinic exceptionally well. It reflects that a high proportion of Class II patients in our clinic required extraction treatment, which might be influenced by some local factors that needed further investigation. There might be some factors related to the preference of orthodontists or patients, or even some regional factors (such as habits, diet, and genes) which may cause more severe crowding or discrepancy in the background. As mentioned in an article about the decision of extraction proposed by Baumrind et al. (Baumrind et al., 1996), it is mentioned that whether it is about Class I or Class II patients, the most common reason for tooth extraction is often due to crowding problems, and severe Class II malocclusion is also one of the main reasons for tooth extraction. What’s more, in the article written by Jackson et al. about the frequency of tooth extraction, it is mentioned that patients with Class II do have a higher frequency of tooth extraction (Jackson et al., 2017). Therefore, it is necessary to analyze the cases of tooth extraction in Angle Class II patients.

Moreover, in this study, the proportions of Class II/1 and Class II/2 are 14% and 58%, respectively, and the rest of the other subtypes of Class II consist of 28% of the total, which shows that Class II/2 accomplishes the majority. This is different from the analysis of the proportion of Class II subdivision in Guiherme Janson et al. article (Janson, de Lima, et al., 2007), in which 61.36% are type I 18.18% are Division II and the rest 20.45% are mixed. The possible reason is that the races of the patients are different. This article mainly focuses on malocclusion cases in Hungary, while in the study mentioned above, Guiherme Janson et al. collected samples almost from Brazil. What’s more, both of the articles have certain regional restrictions and the number of samples used is relatively limited, because this study aims to analyze the patients who only appeared in our clinic, while they also only focused on the patients who occurred in their clinic and a total 44 samples were examined. As a result, both articles lack universality. In addition, females account for two-thirds of the samples in this research. In contrast, the ratio of females to males is almost the same in that article, which may also be different to a certain extent. However, another article in Iran, which is proposed by Tahmasbi et al. shows that Class II/1 patients having more extraction treatment that occupied 59.6% of the total in a 1222 sample pool (Tahmasbi et al., 2022).

Although non-extraction treatment for Class II/2 patients can have a smoother treatment procedure, long-term stability can’t be promised so extraction should be done when orthodontists find the necessity of tooth elimination.(Selwyn-Barnett, 1991) The occurrence of a large number of Class II/2 patients who had orthodontic therapy with tooth extraction in the sample base in this study may be because of the high severity of the Class II/2 malocclusion and the demand for treatment efficiency, which were taken into consideration by the orthodontist. In clinical practice, tooth extraction treatment may be more helpful in correcting the occlusal relationship of Class II/2 patients and maintaining a higher success rate. It may reflect the high occurrence of complex Class II/2 patients in our clinic which causes the selection bias. Because our clinic as the public dental clinic at the University of Pecs, most of the local residents who meet more severe problems such as pronounced deep overbite in Class II/2 may choose or even be referred to visit our clinic to have a complicated treatment rather than the private clinic. All the reasons mentioned above will increase the number of patients with Class II/2 tooth extraction in this study. This also explains why the frequency of tooth extraction in this study is much higher than that in other studies.

Apart from that, this study also mentions that extraction of upper and lower first premolars is the most common extraction mode during the treatment of Angle Class II patients, which is consistent with the research results of (Jackson et al., 2017). that based on the patients’ data of the Orthodontic Clinic of the School of Dentistry of the State University of Rioo de Janeiro from 1980-2011. Jackson et al. have found that the most frequent method of extraction is the removal of all first premolars, followed by the method of extraction of maxillary first premolars, and the data of this study further supports this conclusion.

However, compared with the results of the study (Janson et al., 2014), it shows some similarities but not exactly the same. As for that study, it is mainly based on the frequency of different extraction methods changing over time at the Department of Orthodontics, Bauru Dental School, University of Sao Paulo, Brazil since 1973. It has been found that the frequency of extraction of 4 first premolars gradually decreased over time, from 65.72% to 10.72% (from 1973 to 2007), and the frequency of extraction of 2 upper first premolars maintained a relatively stable frequency of about 10%, while in this study for recent years shows 60% and 13.3 %, respectively, which is different from the conclusions over the past few years drawn by Guilherme Janson. The reason may be that the samples of this study are concentrated on Class II patients and different types of classification may further lead to differences in the selection of tooth extraction strategies. In addition, differences in race and culture may also cause different types of Class II and distinct severity of Class II, because this study only targeted the patients in Hungary that belong to Europe, and the data used by Guilherme Janson were from Brazil which is in South America. Even if the specific proportion exhibited dissimilarities, the conclusion that the most commonly used mode of tooth 14,24,34,44 and 14,24 removal is the same.

Extraction of all 4 first premolars may need longer treatment time compared with the non-extraction method, (Elias et al., 2024) but also it was mentioned that the extraction strategy can increase the efficiency of Angle Class II patients’ treatment when compared with the non-extraction method (Janson, Barros, et al., 2007). However, this study also pointed out that the Class II extraction mode should always be individualized, which means the exact tooth removal site will be modified depending on the patients’ specific situation, rather than following the trend of extraction method. Different treatment modes can cause different orthodontic outcomes in Class II patients.(George et al., 2021) Besides, in (Vaden et al., 2018), it is proposed that when dealing with Class II patients, orthodontists should pay more attention to where the space is easier to put the teeth into the ideal position and consider the dental, skeletal, and esthetic factors too. Therefore, this study also mentions that when considering treatment options, not only the types of classification, efficiency, and difficulties of treatment should be noticed, but also more attention should be paid to factors such as patients’ race, gender, and age. This is consistent with the concept that orthodontists should individualized personal treatment plan for patients without affecting by the untested proposal. (Peck, 2017)

It is worth noticing that the dental relationship and conditions of each patient are unique. It is not limited to which Class II division, subdivision, or combination of types the patient belongs to, but also the specific condition of the teeth, such as whether root canal treatment has been done, whether a caries profunda can be seen, etc., as well as the patient's expectations and requirements and many other factors. This series of situations or in other words, problem lists will make each patient's case should be analyzed separately, but some reference and guidance can be obtained through a big database. Just like in this article, even if the number of Class II patients is limited, there are still many kinds of situations that can be found so the orthodontist has different treatment methods for each patient. This shows that if a proper protocol for treating Class II patients is required, a large number of Class II medical records in the background can be found to support it so that more complete and reliable advice in the future can be provided to orthodontists, so as to achieve better treatment results and long-term success.

As can be seen from this article female consists 60% of Class II patients with extraction treatment, and no matter whether in Class II/1 or Class II/2 patients with extraction methods, the distributions of different sexes are quite similar, showing around 40% male and 60% female, which indicates that gender may not be the main factor in determining the type of Division in Angle Class II patients. The result of the article published by de Sousa Dardengo shows no difference in the frequency of extraction between the two genders (de Sousa Dardengo et al., 2016). But this study finds that in our clinic female patients consist of 60% of total Class II patients who need tooth extraction therapy. This may indicate that female patients in Pecs may be more susceptible to Class II malocclusion and may be because female patients pay more attention to their dentition and facial profile which is expressed as the patients’ requirements during orthodontic treatment.

Females may be more concerned about aesthetics, so when tooth extraction is needed to improve the malocclusion which may disturb facial harmony, they may be more likely to accept treatment. Compared with boys, girls are more particular about facial appearance and have higher requirements for orthodontic treatments.(Christopherson et al., 2009) However, after tooth extraction, the lower lip will be more prominent than Ricketts' esthetic plane. (Alarashi et al., 2003) Therefore, orthodontists should analyze each situation before tooth extraction and do the best treatment to improve facial esthetics. This also reminds us that during clinical communication, special attention should be paid to female patients' expectations of aesthetic effects. When making an orthodontic plan, we should not only pay attention to the function of the teeth, but also formulate personalized esthetic designs based on the patient's face shape, facial profile (chin heartbeat, lip protrusion), etc., and strengthen communication with the patient to ensure that the goals are consistent with the patient. It may reflect the phenomenon of high attention paid to appearance by females in the social and cultural context. Further research can explore the impact of cultural factors on orthodontic treatment decisions. On another level, this phenomenon may be related to genes, which may lead to a higher risk of Class II in women in this area. Studying whether women in this area are truly affected by genetic factors especially those that happen to people who live here around may provide more hints for future treatments, making diagnosis and treatments more effective.

Patients between the ages of 11 to 16 comprise more than half of the sample pool of this study, which shows that the major phase for treating Class II patients with tooth extraction therapy is around the late adolescent phase. The mean age of patients when initiating the orthodontic therapy is around 13 years old, which is similar to the average age of adolescents showing 12.5 in the article proposed by Dyer et al. demonstrating the effects of age on treatment plans (Dyer et al., 1991). Alsaggaf et al. mentioned in an article about factors affecting orthodontic treatment options for Class II patients that in addition to some external factors, for individual patients, the age of the patients is most often considered because it affects the orthodontic treatment plan.(Alsaggaf et al., 2022). Apart from that, the range of age in this study is consistent with the idea proposed by Smith that orthodontic treatment should be initiated when patients’ age is between 8 years old to age of 15 so that long-term success and better results could be sustained and less post-treatment relapse (Smith, 1947) In conclusion, the results of this study are consistent with previous literature to a certain extent, but also have some differences, which explains the diversity of sample characteristics, regional differences, and cultural backgrounds.

The age of patients when to start the orthodontic interventions not only reflects that orthodontists always want to treat Class II patients during the adolescent phase which shows extensive growth in patients so that more flexible orthodontic treatment can be used instead of adulthood. What can be noticed is that not only do orthodontists pay attention to early Class II patients, but also that as time changes, more and more patients' guardians have a more correct understanding of orthodontics and will support and pay attention to their children's early orthodontic treatment. Therefore, a large number of children can have the opportunity that come to the clinic for treatment at an early stage, rather than waiting until the patients are older to receive orthodontic therapy. It not only reflects the golden period for treatment but also reflects that even if many patients have started interventional treatments in the early teenage stage, the final treatments still include tooth extraction treatment. This shows that in many cases, intervention alone in the growth phase of patients may not be enough to achieve the total correction. Even if orthodontic treatment is started at an early stage, more invasive treatment assistance will still be required. This also demonstrates that it is still difficult to intervene in some more serious growth and developmental problems, skeletal discrepancy, and crowding problems at this stage. Orthodontists are still unable to effectively intervene in patients' malocclusion no matter in which period of patients and this is a topic that may need to be explored or overcome in the future: how to better and more effectively intervene in such growth and development abnormalities. However, there is another study pointed out that the articles that can support the stability and efficiency of orthodontic treatment for adolescents are not strong enough.(Millett et al., 2012). That’s why more research is needed to explore orthodontic therapy for Class II/2 patients.

This study analyzed the relevant characteristics of tooth extraction frequency in Angle Class II patients in our hospital, including the influences of gender, age, types of Class II, and other subtypes of Class II malocclusion. These results demonstrated that there were a variety of tooth extraction methods for different types of Class II patients, and the age of patients when having initial treatment was basically within the adolescent period. The tooth extraction rate of female patients was relatively higher than that of male patients, which may be because of some environmental and genetic factors and the demand of female patients for beauty. In addition, the frequency of tooth extraction of all patients was slightly higher compared with that of other places, and the tooth extraction rate of Class II Division 2 patients was also significantly higher than that of Division 1, which shows that the severity and complexity of Class II/2 patients in the sample of this study were generally high.

These findings suggest that tooth extraction decisions are not only influenced by the patient's physiological factors, but may also be related to environmental factors, social culture, and technological development trends. When formulating orthodontic treatment plans, orthodontists need to comprehensively consider the patient's specific situation and treatment goals in order to achieve the best treatment effects, maintain long-term stability, and reasonably meet the patients’ expectations.

Although this study provides new insights into the frequency of tooth extraction in Class II patients, its limitations include the data being collected from a single institution and the small size of the sample pool which shows the characteristics of this clinic rather than representative of the wider population or other regions so that limit lit generalizability. All medical records were collected from a single orthodontist, which has a certain degree of specificity. Future studies should expand the sample size, diversify the sample sources, and conduct more comprehensive analysis based on the patient's subjective wishes and lifestyle habits, so as to provide further basis for the personalization and precision of future orthodontic treatment, thereby increasing the success rate of treatment and meeting the requirements of patients.

结论

For recent decades, treatments of Angle Class II malocclusion have been the cornerstone of orthodontic research and practice, due to its high prevalence and significant impact on patients’ dentition and facial configurance. Among a variety of treatment methods, the decision of tooth extraction is still one of the most controversial and clinically significant topics. Although there are a lot of studies on it, there are huge differences in understanding the frequency of tooth extraction and the cause-related factors of this group of patients. This study tries to figure out the prevalence of Angle Class II patients and the potential factors that could cause this problem through the data system of our clinic, thereby exploring its clinical and theoretical implications.

The findings of this study provide a comprehensive view of different extraction modes for Class II patients. Analyzing 84 Class II patients, approximately 58% of patients had extraction records and 42% of Class II patients were treated without extraction. It shows that Class II patients exhibited more extraction treatments in our clinic. Furthermore, the data also indicates the decision of extraction may be influenced by types of malocclusion, patients' gender, age, and orthodontists’ preference.

One of the most striking findings is the variable types of Class II occurring in the dental clinical practice, and the extraction types should always be individualized. Therefore, the high occurrence of Class II/2 patients with extraction treatments may reflect the effects of clinicians’ preferences and regional factors on the results. In the meantime, it emphasizes the importance of the data diversity and size for the analysis of Class II patients.

These findings not only prove some of the existing articles but also expand insights into the multidimensional nature of treating Class II patients, by providing more data based on our dental clinic.

The impactions of these findings are multi-faced. From an academic perspective, it proposed that the requirements of the cause-related factors should be explored, no matter from a genetic view or an environmental view. Clinically, it supports the theory that the individualization of the treatment plans should always be considered whenever treating Class II patients, since types of Angle Class II vary, every different type needs precise analysis and optimal treatment corresponding to its own situation. The finding suggests that not only the problems of the dentition and physical factors should be taken into consideration, but also the requirements of the patients and their expectations are also essential during the treatment process. These have significant importance in maintaining long-term success and stability.

Even though there are some necessary findings, this study is not without limitations. One is that, this is also retrospective research, which essentially limits the ability to establish causal relationships. Further research may focus on the prospective, longitudinal designs which could provide a more comprehensive overview to understand the impact of extraction and non-extraction treatments in Angle Class II patients.

Additionally, the size of the samples is limited and came from a single institution and single orthodontist, which may indicate the characteristics of the local area and the preference of the clinician, but it can’t provide orthodontists as guidance. More studies should aim to include more geographically and culturally diverse populations to enhance the generalizability of the findings.

In conclusion, this study offers an exploration of the frequency and some influencing factors of tooth extraction in Angle Class II malocclusion, providing new clues on one of the most debated aspects of orthodontic treatments. As the field of orthodontics continues to evolve, the integration of advanced diagnosis, evidence-supported protocols, and different emerging technologies will be a new challenge and more effective solutions for treating Class II patients at the same time. This research serves as a stepping stone toward that goal, encouraging continuous exploration for the treatment of Angle Class II patients.

Acknowledgement

Words are not enough to express my gratitude to my teacher and most respected supervisor, Dr. Dawasheh Ali. Without your help, encouragement, and patient teaching, I would not be able to complete this thesis and experience the extraordinary life at Pecs University.

I would like to thank my parents, relatives, friends and my boyfriend. It is your support that allows me to fulfill my dream. It’s you make me strong, and I love you.

书目

Alarashi, M., Franchi, L., Marinelli, A., & Defraia, E. Morphometric Analysis of the Transverse Dentoskeletal Features of Class II Malocclusion in the Mixed Dentition. In Angle Orthodontist (Vol. 73, Issue 1) 2003; 73(1):21-5.

Alhammadi, M. S., Halboub, E., Fayed, M. S., Labib, A., & El-Saaidi, C. Global distribution of malocclusion traits: A systematic review. Dental Press Journal of Orthodontics 2018; 23(6):40.e1-40.e10.

Alsaggaf DH, Afify AR, Zawawi KH, Alsulaimani FF. Factors influencing the orthodontic treatment plan in Class II malocclusion. Am J Orthod Dentofacial Orthop. 2022;161(6):829-837.e1.

Baumrind, S., Korn, E. L., Boyd, R. L., Maxwell, R., & San Francisco, D. The decision to extract: Part H. Analysis stated reasons for extraction of clinicians’. In AM J ORTHOD DENTOFAC ORTHOP 1996; Volume 109, Issue 4, 393 – 402

Benson, P. E., Alshawy, E., Fenton, G. D., Frawley, T., Misra, S., Ng, T., Smith Sheffield, G., upon Tyne, N., Kingdom, U., & Arabia, S. Extraction vs nonextraction of premolars for orthodontic treatment: A scoping review examining the extent, range, and characteristics of the literature. American Journal of Orthodontics and Dentofacial Orthopedics 2023; 164(0889–5406), 368–376.

Cassidy, S. E., Jackson, S. R., Turpin, D. L., Ramsay, D. S., Spiekerman, C., & Huang, G. J. Classification and treatment of Class II subdivision malocclusions. American Journal of Orthodontics and Dentofacial Orthopedics 2014; 145(4), 443–451.

Christopherson, E. A., Briskie, D., & Inglehart, M. R. Objective, subjective, and self-assessment of preadolescent orthodontic treatment need - A function of age, gender, and ethnic/racial background? Journal of Public Health Dentistry 2009; 69(1), 9–17.

de Sousa Dardengo, C., Fernandes, L. Q. P., & Júnior, J. C. Frequency of orthodontic extraction. Dental Press Journal of Orthodontics 2016; 21(1), 54–59.

Dyer, G. S., Harris, E. F., & Vaden, J. L. Age effects on orthodontic treatment: adolescents contrasted with adults. American Journal of Orthodontics and Dentofacial Orthopedics : Official Publication of the American Association of Orthodontists, Its Constituent Societies, and the American Board of Orthodontics 1991; 100(6), 523–530.

Elias, K. G., Sivamurthy, G., & Bearn, D. R. Extraction vs nonextraction orthodontic treatment: a systematic review and meta-analysis. The Angle Orthodontist 2024; 94(1), 83–106.

George SM, Campbell PM, Tadlock LP, Schneiderman E, Buschang PH. Keys to Class II correction: A comparison of 2 extraction protocols. American Journal of Orthodontics and Dentofacial Orthopedics 2021; 159(3), 333–342.

H.C. Pollock. The extraction debate of 1911 by Case, Dewey, and Cryer. American Journal of Orthodontics 1964; 50: 656-658.

Jackson, T. H., Guez, C., Lin, F. C., Proffit, W. R., & Ko, C. C. Extraction frequencies at a university orthodontic clinic in the 21st century: Demographic and diagnostic factors affecting the likelihood of extraction. American Journal of Orthodontics and Dentofacial Orthopedics 2017; 151(3), 456–462.

Janson, G., Barros, S. E. C., de Freitas, M. R., Henriques, J. F. C., & Pinzan, A. Class II treatment efficiency in maxillary premolar extraction and nonextraction protocols. American Journal of Orthodontics and Dentofacial Orthopedics 2007; 132(4), 490–498.

Janson, G., de Lima, K. J. R. S., Woodside, D. G., Metaxas, A., de Freitas, M. R., & Henriques, J. F. C. Class II subdivision malocclusion types and evaluation of their asymmetries. American Journal of Orthodontics and Dentofacial Orthopedics 2007; 131(1), 57–66.

Janson, G., Maria, F. R. T., & Bombonatti, R. Frequency evaluation of different extraction protocols in orthodontic treatment during 35 years. Progress in Orthodontics 2014; 15(1):51.

Janson, G., Mendes, L. M., Junqueira, C. H. Z., & Garib, D. G. Soft-Tissue changes in class ii malocclusion patients treated with extractions: A systematic review. In European Journal of Orthodontics 2016; Vol. 38, Issue 6, pp. 631–637

Konstantonis, D., Vasileiou, D., Papageorgiou, S. N., & Eliades, T. Soft tissue changes following extraction vs. nonextraction orthodontic fixed appliance treatment: a systematic review and meta-analysis. In European Journal of Oral Sciences 2018; Vol. 126, Issue 3, pp. 167–179

Millett, D. T., Cunningham, S. J., O’Brien, K. D., Benson, P. E., & De Oliveira, C. M. Treatment and stability of Class II Division 2 malocclusion in children and adolescents: A systematic review. American Journal of Orthodontics and Dentofacial Orthopedics 2012; 142(2):159-169.e9.

Peck S. The contributions of Edward H. Angle to dental public health. In Community Dental Health 2009; Vol. 26, Issue 3, pp. 130–131

Peck, S. Extractions, retention and stability: the search for orthodontic truth. European Journal of Orthodontics 2017; 39(2), 109–115.

Perkowski, K., Marczyńska-Stolarek, M., Regulski, P., & Tomczyk, J. Characteristics of dental malocclusion in a 18th/19th century population from Radom (Poland). International Journal of Paleopathology 2024; 47:21–26

Perović, T. The influence of class II division 2 malocclusions on the harmony of the human face profile. Medical Science Monitor 2017; 23, 5589–5598.

Rosenblum RE. Class II malocclusion: mandibular retrusion or maxillary protrusion? Angle Orthod. 1995;65(1):49-62.

Selwyn-Barnett, B. J. Rationale of treatment for Class II division 2 malocclusion. In British journal of orthodontics 1991; Vol. 18, Issue 3, pp. 173–181

Smith, D. J. When to start orthodontic treatment considering age and relative growth. American Journal of Orthodontics and Oral Surgery 1947; 33(1), 36–42.

Tahmasbi, S., Rezaei Behzadi, Z., Shabestari, S. B., Namdari, M., Vahid-Dastjerdi, E., & Hamedi E A Associate, R. Frequency of Orthodontic Extractions and Malocclusion-Related Factors in a University Setting During a 25-Year Period 2022; 151(3):456-462.

TRIPLETT, W. W., LUND, B. A., WESTBROOK, P. R., & OLSEN, K. D. Obstructive Sleep Apnea Syndrome in Patients With Class II Malocclusion. Mayo Clinic Proceedings 1989; 64(6), 644–652

Vaden, J. L., Williams, R. A., & Goforth, R. L. Class II correction: Extraction or nonextraction? American Journal of Orthodontics and Dentofacial Orthopedics 2018; 154(6), 860–876.

Varrela, J. Early developmental traits in class II malocclusion. Acta Odontologica Scandinavica 1998; 56(6), 375–377.