Introduction:

Most oral diseases, despite being preventable, pose a significant burden on healthcare systems worldwide. Untreated dental caries in permanent teeth is the most common health condition. According to the World Health Organization (WHO), an estimated 2 billion people globally suffer from caries in permanent teeth, while 514 million children are affected by caries in primary teeth¹. Among those in mixed dentition, the first permanent molar (FMP) emerges as the tooth most susceptible to this disease², typically erupting around the age of 6 years. It becomes the first permanent tooth to coexist with the oral environment, featuring multiple cusps and deep grooves³. Furthermore, these teeth are prone to enamel developmental defects such as incisor-molar hypomineralization (IMH). Defined in 2001 by Weerheijm et al., IMH represents a qualitative enamel defect characterized by demarcated opacities and decreased mineral density, primarily affecting at least one FMP, typically the most affected tooth^4-6. These lesions can manifest with or without involvement of the incisors, and sometimes affect the second primary molar^4-6. This process of dysfunctional enamel mineralization is classified from mild, characterized by demarcated opacities without post-eruptive enamel breakdown (PEB), to severe, involving PEB with pulp compromise ⁽². The clinical appearance varies from creamy/white to yellow or brown, with or without PEB⁴. Hypomineralized enamel is less hard and more porous than normal enamel due to its higher protein content. Consequently, it has reduced strength and may lead to PEB soon after tooth eruption or later under the influence of masticatory forces, promoting plaque accumulation and early-onset dental caries². The overall prevalence of IMH has been determined to be 19%, meaning approximately 1 in 5 children are affected. No differences have been noted regarding sex and geographic location⁷.

Before determining an appropriate treatment plan for a severely decayed FPM, several factors should be taken into account, including the extent of crown destruction and pulp involvement, the condition of the developing dentition, the severity of dental pain, the attitude of the child and/or parents, the patient's tolerance for prolonged treatment under local anesthesia, socioeconomic factors, and treatment expectations⁸. Treatment options are diverse; a purely preventive approach may be adopted, especially for mild cases, while restorative approaches using temporary or definitive restorations may be adopted for moderate or severe cases. These may later involve endodontic treatment and prosthetic rehabilitation of the affected teeth⁹, potentially culminating in tooth extraction at an appropriate or later stage¹⁰. As such, with the frequent development of caries and dental fractures in these cases, increasingly complex and repetitive restorative treatments are required, which have an uncertain long-term prognosis¹⁰. Consequently, young FPMs with severe damage and pulp involvement often enter a cycle of restorative treatment that ultimately leads to extraction. Nonetheless, if extraction is performed at an appropriate time, it can act as a therapeutic extraction (ExT)⁹. Therefore, some practitioners advocate for the early extraction of these molars, given their likely poor long-term prognosis and potential future need for extraction.

This study aimed to conduct a Scoping Review to assess the determinants of therapeutic extraction of severely damaged first permanent molars in mixed dentition before the eruption of the second permanent molar, with favorable spontaneous closure of the residual space.

Methodology:

A Scoping Review was performed using the PubMed database. The search strategy incorporated MeSH terms and text words (tw): (Molar*(MeSh) OR "First permanent molar*"(tw)) AND ("Tooth Extraction*"(MeSh) OR Extraction(tw)). Additionally, the search included filters for articles in Spanish or English, studies conducted on humans, and with a publication date no older than 10 years.

Initially, 1890 articles were identified based on predefined criteria at the identification stage. During the screening phase, 1863 articles unrelated to the study objective were excluded, resulting in the selection of 27 articles. In the eligibility stage, articles that addressed the extraction of FPMs in mixed dentition were considered for inclusion, while those not focusing on FPM ExT, perception surveys, and editorials were excluded. Ultimately, 7 articles meeting these search criteria were included, then, 3 additional articles were added, totaling 10 articles. The search results are detailed in a flow chart adapted and translated from the PRISMA protocol for systematic reviews¹¹. (See Figure 1).

Figure 1. PRISMA flowchart. 

RESULTS:

The findings from ten studies assessing the determinants of therapeutic extraction of first permanent molars for spontaneous closure of the residual space were presented in both narrative text and table format (See Table 1).

Consequences of FPM extraction:

It is noted that FPM extraction can have positive effects on the anterior teeth vertically, resulting in a slight overjet and a wider interincisal angle¹⁴. Similarly, Saber A. et al. suggest that overbite tends to deepen in over 50% of cases while overjet remains stable, leading to favorable outcomes in the maxilla. Regarding closure of the residual space, spontaneous closure is mentioned as a possibility^19,20. Another beneficial effect is the increase in eruption space, thereby reducing the likelihood of impaction of the TM against the SPM. Acceleration in the development and eruption of the SPM is also observed ⁽¹⁹. Additionally, C. Hahn et al. suggest that this treatment may benefit individuals with dolichofacial and hyperdivergent craniofacial features¹⁷.

On the contrary, unfavorable effects are observed in the mandible. Due to bone characteristics, mesial inclination of the SPM may occur, resulting in residual space ^{12,14-16,19,20}. Similarly, rotation and distal inclination of the second premolar towards the space of the extracted FPM can occur ^15,19. Furthermore, there is a possibility of extrusion of the antagonistic FPM following extraction, which can be prevented by splinting or cementing a transpalatal bar ⁽¹⁷.

Table 1. Therapeutic Extraction Determinants of the First Permanent Molar for Spontaneous Closure of the Residual Space According to the Reviewed Articles. Abbreviations: FPM (First Permanent Molar), SPM (Second Permanent Molar), and TM (Third Molar).

Discussion:

In scientific literature, the indication for compensating extractions (extraction of the antagonist) and balancing extractions (extraction of the contralateral) has been discussed, with various proposals suggesting that these treatments may not be necessary, especially in patients with Angle Class II and dental crowding^12,13,15,17. However, the majority of authors assert that orthodontic treatment should follow therapeutic extraction ^{(12-17, 19)} .

Determining the ideal chronological age for ExT has also sparked discussion. While some emphasize specific age ranges, such as between 8 and 10.5 years, others focus on the age of 9 years. Some prioritize the developmental stages of the FPM, SPM, and second premolar ^12-18.

As a result of the ExT, a verticalization effect on the anterior teeth is observed, characterized by a small or stable overjet, increased interincisal angle, and overbite¹⁴. This would be particularly favorable in patients with dolichofacial and hyperdivergent growth patterns¹⁷. Additionally, extraction is noted to have a positive impact on the development and eruption of TM, by increasing eruption space and reducing the likelihood of impaction¹⁹. Moreover, an early eruption of the SPM is observed²⁰.

Most authors consider ExT a successful treatment with a favorable long-term prognosis when total closure of the residual space is achieved. Furthermore, a higher success rate has been observed in the maxilla, ranging between 70% and 90% of cases. However, this rate decreases to 48% and 49% in mandibular cases^13,14,21. Consequently, a positive trend is noted in the prognosis of ExT for maxillary permanent molars compared to mandibular ones. Conversely, Teo T. et al. emphasize that adhering to the three key radiographic factors- development stage of the SPM and second premolar, and the radiographic presence of the TM-can lead to a higher degree of closure of the residual space¹⁹. Additionally, M.A. Barceló et al. suggest benefits in crowded dentition and, conversely, advise against ExT in dentitions with diastemas¹⁶. Moreover, the decision-making process for ExT in the mandible is complicated by factors such as the mesial inclination of the SPM and chronological age, which simultaneously influence the prognosis and potential sequelae^{(12, 14-16, 19, 20)}. Similarly, another factor contributing to a better prognosis is to consider the stage of development of the SPM. Hence, it is crucial to estimate Demirjian’s stage E, observing the early bifurcation of its root^12,15,19-21. Also, according to Nolla's classification, the first third of the calcified root -corresponding to stages 6 and 7- should be observed¹⁶. Expanding on this, other authors suggest that the SPM should be positioned above the cementoenamel junction of the FPM¹⁷⁾ and exhibit a mesial angulation^12,19.

Another significant factor to take into account is the development of the second premolar; it is advisable that it reaches Demirjian’s stage F¹⁹. Furthermore, it is proposed that the favorable positioning of this second premolar would entail the crown being located within the bifurcation of the second primary molar to avoid collateral effects such as ectopia of the second premolar, i.e., the distal rotation and inclination of this premolar towards the space of the extracted FPM^15,19. In this regard, C. Hahn et al. recommend extracting the second primary molar when the SPM exhibits furcation calcification¹⁷.

In the mandibular arch, the presence of the TM proves to be a significant factor in predicting successful closure of the residual space^18,21. However, its presence cannot always be confirmed, as the appearance of the germ may be delayed¹². It is worth noting that following the extraction of the FPM in both jaws, there is an increased likelihood of earlier and adequate eruption of the TM, attributed to the additional eruption space created by the extraction¹⁶.

These findings underscore the complexity and necessity of a comprehensive assessment when considering this treatment option in the pediatric population. It is crucial to consider dental maturity, developmental stages, and specific anatomical aspects of each tooth to thoroughly and effectively address strategies for therapeutic extraction.

Conclusion:

Therapeutic extraction of the permanent first molar before the eruption of the second molar (around 9 years of age) can often anticipate favorable spontaneous closure of the residual space, particularly in the maxillary arch. Greater success has been observed when three key radiographic factors are met: presence of the third molar germ, the second molar at Demirjian’s stage E, and the second premolar at Demirjian’s stage F.