From Volume 39, Issue 9, November 2012 | Pages 656-661
Ectopic eruption of the first permanent molar is a relatively common occurence in the developing dentition. A range of treatment options are available to the clinician provided that diagnosis is made early. Non-treatment can result in premature exfoliation of the second primary molar, space loss and impaction of the second premolar. This paper will describe the management of ectopic first permanent molars, using clinical examples to illustrate the available treatment options.
The eruption of teeth is a complex process and can be disturbed by genetic, cellular, molecular or tissue causes.1 Ectopic eruption describes the eruption of a tooth into an atypical position.2 The incidence of ectopic eruption of maxillary first molars varies between 2% and 6%.3 It affects both sexes equally.1 It occurs 25 times more often in the maxilla than mandible.4 The aetiology is not completely understood. Local factors have been suggested.5 A strong genetic element, including a higher incidence in patients with cleft lip and palate, has also been reported.6,7 Ectopic eruption is classified according to its effect on the primary second molar tooth1 (Table 1 and Figure 1). Ectopic molars can be further differentiated into reversible (permanent molar spontaneously self corrects and erupts in a normal position) or irreversible (permanent molar remains blocked by the primary molar). The aims of treatment of an irreversible ectopic first molar tooth are movement of the tooth distally to regain space and correction of the mesial angulation to allow normal eruption.8 Spontaneous correction can occur, but in the majority of cases this will have occurred before seven years of age.9 This paper will describe the management of ectopic first permanent molars, using clinical examples to illustrate the available treatment options.
| Ectopic Eruption Grade | Severity | Effect on primary molar |
|---|---|---|
| Grade 1 | Mild | Limited resorption to the cementum or with minimum dentine penetration |
| Grade 2 | Moderate | Resorption of the dentine without pulp exposure |
| Grade 3 | Severe | Resorption of the distal root leading to pulp exposure |
| Grade 4 | Very severe | Resorption that affects the mesial root of the primary second molar |
The aetiology of ectopic molars may be considered to be multifactorial. A number of authors have described different predisposing factors. A high familial tendency has been noted.9 Local factors, such as mesial angulation of the first permanent molar, larger than average width of the first permanent molar, crowding and unfavourable shape of the second primary molar crown, have been suggested.5 Cleft lip and palate patients are four times more likely to have an ectopic molar.10
A thorough clinical examination is essential in order to diagnose ectopic first molar eruption. In children 7 years or older, a permanent first molar crown can often be observed clearly locked behind a second primary molar11 (Figure 2). In most ectopic cases, the crown of the first permanent molar is tilted mesially.12 Radiographs should be used for early diagnosis in a 5–7 year-old child.11 A bitewing radiograph is usually sufficient but an orthopantomograph can be useful in determining the presence of the permanent teeth (Figures 3 and 4). High positioning of the first permanent molar, on a radiograph, intimately associated with the distobuccal root of the second primary molar and/or a mesial inclination of the permanent tooth, are indications of an ectopically erupting molar tooth.11 Ectopic eruption should also be suspected if there is asymmetric eruption between the upper left and right first permanent molars.
Ectopic eruption of a permanent first molar can cause pain and infection around a second primary molar. In more severe cases, it leads to premature exfoliation of the primary molar1(Figure 5). The resultant mesial migration of the first permanent molar occupies the space of the second premolar. This results in a decrease in arch length and can cause delayed eruption or impaction of the second premolar.1 For these reasons, early intervention is advisable.
Most cases of ectopically erupting permanent molars spontaneously self-correct (50–69%).4 However, a lack of timely intervention may result in loss of the primary molars and lack of space for eruption of the second premolar as the permanent molar erupts mesially.1 The method of treament of an ectopically erupting first permant molar will depend on a number of factors:
Age of the patient;
Status of the second primary molar;
Presence of the second premolar;
Severity of impaction.
Spontaneous correction usually occurs before seven years of age.9 In patients who are diagnosed before the age of eight, a six-month observation period is advisable.12 If spontaneous correction has not occurred within this six-month period, the tooth may be assumed to be irreversibly impacted and some form of active treament is required. Early diagnosis is essential to stop root resorption of the deciduous tooth1 (Figure 5).
If the primary molar is displaying symptoms of irreversible pulpitis or has increased mobility, extraction may be the best option. Space loss may occur following extraction (Figure 6). This can be prevented using a simple removable appliance or another suitable type of space maintainer (Figure 7).
The incidence of congenitally missing second premolars was found to be 18% in patients with cleft lip and cleft palate.13 If the second premolar is absent, it may be advisable to extract the primary molar and allow the permanent molar to erupt mesially and close the space. An orthopantomograph may be required to diagnose the absence or presence of the second premolar and an assessment of the malocclusion by a qualified specialist would be helpful (Figure 4).
As described previously, ectopic first molars can be given a grade from 1–4, depending on their severity1 (Table 1 and Figure 1). Grade 1 ectopic molars should be observed and given the opportunity to correct spontaneously.
Grade 2 molars require active treatment which may involve interproximal wedging or distal tipping. Numerous techniques have been described and these will be discussed in more detail below.12
Grade 3 molars are generally treated through active distal tipping of the ectopic permanent molar. This can be achieved by using a removable appliance (Figures 8, 9, 10) or by placing fixed brackets (Figures 11, 12). It may require extraction of the primary molar.
When the ectopic eruption is so severe that the mesial root of the second primary molar is affected (Grade 4), extraction of the primary tooth is advisable. Yet again, the malocclusion should be fully assessed by a specialist to determine whether space loss should be prevented.
These can be divided into interproximal wedging and distal tipping. A simple elastic separator, soft brass wire or a metal Kesling separator can be used for interproximal wedging. Distal tipping of the ectopic first molar requires the use of a removable or fixed orthodontic appliance.
The separating medium should be placed between the first permanent molar and second primary molar. Careful supervision of these techniques is essential.14 Apical dislodgement of the separator or brass wire can induce infection and early loss of the primary molar.12
An elastomeric separator can be used when little movement is required and there is minor resorption of the primary molar. The ectopic molars can be stretched into position by using a separator forceps or by using two pieces of dental floss (Figures 13, 14). This separation technique is not routinely recommended because it can become dislodged apically and cause periodontal irritation. The separator may be difficult to locate and retrieve in such cases. It may be used by an experienced operator provided the patient is reviewed every two weeks (Figures 15, 16).
This is an alternative to the elastomeric separator. It may be difficult to place, however, if the point of contact between the permanent molar and the primary molar is deep below the cemento-enamel junction of the primary molar.
If a small amount of movement is needed, but little of the mesial surface of the first permanent molar is visible clinically, a brass wire can be used. A 0.02” or 0.025” brass wire is threaded around the contact point between the primary and permanent molars then twisted to tighten the wire. The disadvantages of this approach are that it may be necessary to anaesthetize the soft tissue and it can be difficult to thread the wire around the contact point when subgingival.
If resorption of the primary molar is severe and the permanent molar has moved significantly, distal movement of the permanent molar is required. The clinician can fabricate a transpalatal arch (TPA) on the primary molars with a cantilever arm extending from the appliance distally. An elastomeric band or spring can then be hooked from the end of the cantilever arm to a button which has been bonded on to the permanent molar to initiate distal movement of the ectopic molar (Figure 8).
Again, a TPA is placed on the primary molars to stabilize these teeth and a bracket is placed on the buccal surface of the permanent molar. A flexible sectional nickel titanium wire is used to upright the molar (Figures 11, 12).
After the first permanent molar is repositioned, relapse may often occur.12 The simplest way to prevent this is to place a molar band with a distal extension on to the occlusal surface of the second primary molar.12 The patient is checked every 6–8 weeks and the band is not removed until after the permanent molar has erupted sufficiently to prevent relapse.12 If the second primary molar is extracted, a Nance or palatal arch appliance can be used on the corrected molar to maintain its position.
The incidence of ectopically erupting permanent molars is relatively common. Dentists need to be aware of the potential sequelae of this condition and the available treatment options. Early diagnosis and treatment can save the patient, and his/her parents, time and future expense.
