# The Pathology of the First Permanent Molar during the Mixed Dentition Stage--Review
## 3 Results and Discussion
### Eruption Pathology
#### 3.1.1 Ectopic Eruption
[PERSON] et al., 1992, assessing the association between ectopic eruption of the maxillary FPM and three other dental and developmental anomalies (ankylosis and infraocclusion of primary molars, ectopic eruption of maxillary amines, and aplasia of premolars), characterized the four conditions studied as \"different manifestations of one syndrome, each manifestation having an incomplete penetrance\" [33]. The authors identified one additional disturbance in 18-28% and two additional disturbances in 2-3% of the children primarily diagnosed with only one dental or developmental disturbance [33]. [PERSON] et al., 2005, concluded that ectopic eruption of the maxillary FPM associated with root resorption of the second primary molar could be an early indicator of later ectopic eruption of the maxillary canine causing incisors root resorption [34]. [PERSON] et al., 2007, reported a high prevalence of other dental anomalies in patients with ectopic eruption compared to controls (60.7% vs. 25%, \(p\) = 0.01) [20]. The most frequently occurring other dental anomalies were: primary molar infraocclusion (32.1%), hypodontia (28.6%), cleft lip and/or palate (25%), and supernumerary teeth (17.9%) [20]. [PERSON] et al., 2012, showed that FPM ectopic eruption is statistically significantly associated with crowding, lateral crossbite, and a tendency towards Class III malocclusion [35]. Other findings were faulty occlusion between individual teeth and Class II malocclusion division I. The prevalence of Class III malocclusion in children with ectopic eruption was almost three times higher than in the overall group (5.9% vs. 2.1%, \(p\) = 0.009) [35]. [PERSON] et al., 2015, found significantly increased widths of the primary second molars and maxillary FPMs (\(p\) < 0.01) and smaller maxillary arch length (\(p\) < 0.01) in the group presenting ectopic eruption as compared to the control group [18]. Anterior and posterior transverse interarch discrepancies, with small maxillary intercanine and intersolar widths, were determined, which suggested that ectopic eruption is associated with severe maxillary hypoplasia [18]. Another finding was the significant maxillary and mandibular tooth crowding in cases with ectopic eruption compared to controls (\(p\) < 0.01) [18]. The authors postulated that the combination of maxillary macrodontia and maxillary arch constriction plays a role in dental crowding, pointing to the involvement of dentoskeletal factors in the etiology of ectopic eruption [18]. In another recent study (2021), [PERSON] et al. [36] determined that the most prevalent dentoskeletal characteristics of the Spanish pediatric population affected by maxillary FPM ectopic eruption were: a shortened anterior cranial base, a retroposition of the maxilla and a more distal position of the affected tooth in relation to the pterygoid vertical. In children with bilateral ectopic eruption, decreased palatal plane values and a more posterior position of the upper incisor was registered [36]. Early diagnosis of FPM ectopic eruption is the most important step in its clinical management. If the disturbance is diagnosed in five- to six-year-olds, an observational strategy of \"watchful waiting\" is indicated, taking into consideration that self-correction is reported to occur in two-thirds of the cases [25; 37]. In cases when locked eruption persists for six months and the resorption of the primary second molar continues to increase, orthodontic intervention is necessary [25; 37] in order to intercept the active phase of FPM eruption [23; 38]. Timing and case selection are the most important aspects in the clinical management of FPM ectopic eruption [31]. The goals of the treatment are:  
* obtaining a normal eruptive pathway [17]
* preserving the primary second molar [17; 39]
* increasing the arch perimeter [39]. Proper clinical management of FPM ectopic eruption is a demanding task for the pediatric dentist and is of great importance for the development of a stable occlusion [23; 38].