Most of the chief complaints which prompt the patient to seek orthodontic treatment in any populations are either incisor protrusion or crowding [1, 12]. The presence of these clinical problems, even with a Class I molar relationship, had influenced the extraction sequence decision, and the choice of particular extraction sequences seems to have been based largely on clinical opinion [13, 14]. There have been a number of previous studies demonstrating that premolars are the most commonly extracted teeth for orthodontic purposes due to their location between anterior and posterior segments [15, 16]. When comparing first and second premolars, the first premolars are more often extracted because of their position, being located nearer to the problem site. Therefore, it is easier for anchorage control in solving the patient’s chief complaint [17]. On the other hand, when second premolars are extracted, the posterior teeth could be expected to move more forward than after a first premolar extraction, leaving inadequate remaining space for the relief of crowding and the retraction of anterior teeth [18]. This is the reason why, in the past, orthodontists almost always chose to extract the first premolars and keep the second premolars, even though the second premolars might be in far worse condition than the first premolar.
However, this was not found to be the case in the present study. We found that most orthodontists and laypersons set tooth condition as the most important factor above others: for example, space closure, treatment time, or expense, when deciding which tooth to remove. Our study demonstrated that a number of orthodontists and laypersons choosing maxillary second premolar removal instead of healthy maxillary first premolar removal increased for larger lesion sizes. That might be because most laypersons who participate in this study are well educated; 80% of them having a bachelor’s degree. They prefer to keep a healthy tooth rather than a carious tooth, even though they are informed of the requirement for the additional anchorage device. Otherwise, anterior tooth retraction or alignment of the teeth might not be optimal. In part of the orthodontists’ opinion, we found that their decision was significantly related to the familiarity with the use of MIA. Orthodontists who typically placed mini-implants themselves were likely to decide to remove the second premolar with a smaller lesion compared with those who were not familiar with mini-implant usage. This finding supported the idea of MIA causing a paradigm shift in the orthodontic world by not only making an unpredictable movement possible, such as retraction of the whole maxillary dentition in Class II division 1 malocclusions to achieve a Class I canine and molar relationship without extraction [19], intrusion of the entire maxillary dentition to correct gummy smile [20], and intrusion of the upper posterior region to correct anterior open bite [21], but also its impact on orthodontists’ decision towards extraction choice.
It is well known that closure of the premolar extraction sites occurs by retraction of anterior segments, mesial movement of posterior segments, or both. Maximum anchorage is indicated to prevent mesial movement of the posterior segments. One cephalometric study has shown that greater mean maxillary incisor retraction was found in the maxillary first premolar extraction group than in the maxillary second premolar group [7]. Therefore, patients also need to consider the additional anchorage requirement when choosing to remove the maxillary second premolar, in order to use the extraction space in a similar way to that when extracting the maxillary first premolar. In the past, headgear has been used as a standard maximum anchorage system. However, it is almost always rejected by patients because of social and esthetic concerns [22]. The present study also showed that the larger the size of the caries lesion, the higher the percentage of laypersons who accepted wearing an anchorage device, including headgear. This part of our result revealed the preference of laypersons in the twenty-first century towards the type of additional anchorage devices. Although a TPA was found to be the most popular choice, unfortunately, it was reported to be associated with anchorage loss during retraction of maxillary anterior teeth [23]. MIA, which was as effective as headgear with the non-compliance approach [24], is preferred by patients to the alternative approaches available.
To our knowledge, the present work was the first study investigating attitudes of laypersons towards their decision of tooth extraction. Nowadays, there is a growing awareness of conflict between orthodontists and patients [25]. We believe that a greater communication before starting the treatment is needed which will lead to improved relationships and to a lessening of misunderstanding. Our data supported this assumption by showing that both groups of respondents agreed that it is necessary to discuss the treatment plan together, particularly concerning tooth removal. Therefore, our results are not only helpful in the process of treatment planning between orthodontists and orthodontic patients but also could be useful for general practitioners by preventing unnecessary treatment on a severely carious second premolar if the patient intends to receive orthodontic treatment in the near future.
Nevertheless, some limitations in this study should be noted. First, the response rate from orthodontists was quite low (43.8%), although the number was almost similar to other studies using the same method in the same population [26]. In the matter of gender, the predominantly female sample of orthodontists (68.3%) could be representative of the true population (64.8% female) [26]. Second, the data acquired in this study towards extraction decision was based on one particular situation, which was to decide between maxillary first or second premolar extraction in a Class I Angle classification with anterior crowding or protrusion with the need of maximum anchorage in the upper arch. Our data showed that most of orthodontists’ extraction decision (65.5%) was influenced by how to manage the anchorage situation: maximum, moderate, or minimum. Thus, we decided to create the questionnaire by focusing only on a maximum anchorage situation for the reasons of eliminating this confounding factor and reducing the complications. Different results might also be found if it was the situation in the lower arch, as every orthodontist knows the differences in anchorage control between in the maxilla and the mandible. Therefore, this set of data should be applied with caution, and further study is required with the series of questionnaire including several types of anchorage in both arches.
