From Volume 14, Issue 2, April 2021 | Pages 98-104
This case series describes a number of different treatment modalities used in the management of impacted mandibular second molars (MM2s). A variety of cases is used to illustrate a number of ways in which these teeth can be managed, and to demonstrate that each case should be managed on an individual basis, taking into account the overall malocclusion. The importance of early diagnosis and management is highlighted throughout.
The detection, diagnosis and management of impacted MM2s remain a challenge for clinicians. The definition of impaction is tooth retention due to an obstacle in the eruption path, or ectopic position of the tooth germ.1 The incidence of impacted teeth can be seen in the Table 1. The MM2 has an average eruption date of 12.5 years in the UK population. Impaction of MM2 is uncommon and reported to have a prevalence of 0.04–2.3%,7,8 but may be higher when studied in an orthodontic population.
Impactions can be described as being either generalized or localized. Generalized impactions can be associated with syndromes including cleidocranial dysplasia, Down's syndrome and cleft lip and palate. The most common factors in localized impactions include the following:
Complications resulting from impacted teeth include root resorption, caries, periodontal disease, pericoronal inflammation, follicular cysts, malocclusion and pain. They may also complicate the treatment of a deep overbite, as lower second molars aid in levelling the curve of Spee during fixed appliance treatment.9 The impaction of MM2s is described in terms of angulation: mesial, distal and vertical. Mesio-angular and disto-angular impactions were seen to be more commonly related to lack of space, and vertical impactions were associated with local factors such as ankylosis. Mesio-angular MM2s are the most commonly seen, and in those with an initial inclination of more than 20–30 degrees, the risk of impaction is higher.10,11
Management of patients with impacted MM2s involves a full history and examination, including a full orthodontic assessment, as well as appropriate radiographic examination. Consideration can also be given to a cone beam CT scan if plain film radiography provides insufficient information relating to root resorption, position of the MM2, and proximity to the inferior dental nerve.
Very often these patients are referred to the orthodontic department after having undergone orthodontic treatment, where second molars are impacted and have been overlooked. It is, therefore, of the utmost importance that the eruption of MM2s is monitored in all cases to avoid late referrals.
There are a number of treatment options that can be employed in the management of impacted MM2s. The literature has shown numerous modalities involving surgical or orthodontic techniques in the management of these teeth; however, most often, a multidisciplinary approach is required.9,12 Success is often contingent on early diagnosis and intervention.13
Following assessment, management options of MM2 include the following:
In certain cases the MM2 may be left in situ and reviewed regularly, both clinically and radiographically. There is no current guidance on how often radiographic investigations should be carried out. The patient must be warned about the risks, including cyst formation, caries and root resorption. This option may be appropriate where the MM2 is markedly displaced and asymptomatic, and where the risks of surgical treatment outweigh the possible benefit, or the patient declines orthodontic treatment.
A separating elastic, brass ligature wire or spring separator can be used for the treatment of mildly impacted MM2s that are mesially angulated. These allow for relief of tight contacts between the first and second molar, providing space for spontaneous improvement in the position of the MM2.12 This treatment option is straightforward; however, the patient should be regularly monitored while the separating component is in situ to avoid damage to the periodontal tissues.
This option is indicated in a patient who is well motivated, and where the MM2 is in a favourable position for alignment, ie mild/moderate impaction, with no associated ankylosis or primary failure of eruption. It is important to assess the space requirements, and often it will be necessary to create space by extracting the second premolar(s), first molar(s) or third molar(s). If the MM2 is unerupted, an open or closed exposure will also be required and anchorage reinforcement must be considered.
Orthodontic traction and alignment mechanics include the following:
Surgical repositioning of the second molar may be carried out in conjunction with or without extraction of an adjacent third molar tooth. This may be indicated where the MM2 is significantly impacted and the patient is unwilling to undergo orthodontic treatment, or orthodontic treatment is contraindicated. When considering this option there must be sufficient space and the MM2 root should be formed to 1/3 or 1/2 of the total expected root length.15 Ideally, uprighting the MM2 should not exceed an angle of 90 degrees, and it should have no buccal or lingual inclination. A careful atraumatic surgical technique should be employed, and occlusal trauma should be avoided to maximize success.16 Surgical repositioning is associated with risks, including loss of vitality and ankylosis, and therefore, the prognosis for success is guarded. It is a technique that is not commonly used.
Surgical removal of the MM2 can be considered when the MM2 is not amenable to alignment owing to a significant impaction. Once removed, the third molar may be given the chance to erupt into a satisfactory position; however, this is somewhat unpredictable. If extraction is necessary, the ideal time to remove the MM2 is after third molar crown formation, but before root formation is completed, usually between the ages of 11 and 14.17 Traditionally, it was believed that the third molar ought to form an angle of 30 degrees or less with the occlusal surface; however, other studies refute this,18 concluding that the timing of MM2 extraction in terms of third molar development is not critical. Third molars in earlier stages of development at the time of extraction, are likely to take longer to erupt. If the MM2 is to be removed, it is important to consider the opposing molars as there may be a risk of over-eruption and this must be factored into the overall treatment plan.
The case series described involves cases treated in a hospital Orthodontic Department.
A 15-year-old male patient presented with a Class I incisor relationship on a mild Class II skeletal base with average vertical proportions (Figures 1–4). This was complicated by:
A joint orthodontic–surgical–restorative treatment approach was initiated. Surgical management included extraction of the URB and the poor prognosis UR2, enucleation of the cyst associated with LL7, and surgical exposure and bonding of a gold chain to UR3 and LL7 under general anaesthetic. Orthodontic treatment included upper and lower preadjusted edgewise fixed appliances. Elastic traction was applied to UR3 and LL7 using elastic chain to a 19/25 stainless steel archwire. The UR3 and LL7 were aligned successfully. Space was opened and maintained in the UR2 region where a resin-bonded bridge was placed with a view to an implant upon completion of growth.
A 13-year-old female patient presented with a Class II division 2 incisor relationship on a moderate Class II skeletal base, with reduced vertical proportions, complicated by:
A joint orthodontic–surgical–restorative treatment approach was undertaken. The treatment options, risks and benefits were discussed at length. Surgical treatment involved extraction URE, surgical removal UL3, and exposure and bonding of the LL7. LL8 was not removed because there was sufficient space for alignment of LL7. UL3 was removed rather than aligned because of the patient's reluctance to undergo lengthy treatment. Orthodontic treatment involved preadjusted edgewise fixed appliances to align the arches, optimize the UL3 space for a prosthetic replacement, and to allow for vertical traction using intermaxillary elastics from LL7 to the upper appliance. A successful outcome was seen with full eruption of LL7 (Figure 6). The UL3 space was ultimately restored with a resin-bonded bridge.
A 19-year-old female presented post-orthodontic treatment with a lingually inclined, partially erupted impacted LR7, and overerupted UR7. A detailed history revealed that the patient had presented to the orthodontist at age 13 with a Class II division 1 incisor relationship on a moderate Class II skeletal base. This was complicated by a severely impacted LR3, and unerupted LR7 and LL7. This patient underwent 21 months of orthodontic treatment with upper and lower fixed appliances in conjunction with extractions of UR4, UL4, LR3 and LL5. At the debonding stage, at age 15 years (Figure 7), LR7 was partially erupted and had not been included in the lower fixed appliance. A decision was made for the LR7 to be monitored in primary care.
It became apparent that by age 19 years, the LR7 position had deteriorated. This resulted in the patient having difficulty cleaning the area and inflammation of surrounding gingivae was evident. A new dental panoramic tomograph was taken, which revealed LR7 to be in a less favourable position, and LR8 was also mesially angulated (Figure 8).
After assessment on the joint orthodontic–surgical clinic, the following treatment options were discussed:
The patient was reluctant to undergo further orthodontic treatment and, therefore, the fourth option was chosen. New upper and lower vacuum-formed retainers were fabricated and extended to cover half the occlusal surfaces of the upper terminal molars to limit further overeruption of UR7. This patient then attended regular appointments with the hygienist, and for monitoring of LR7 in primary care.
A 13-year-old female had presented to the department aged 11 with a Class I incisor relationship on a mild Class II skeletal base, with average vertical proportions. This was complicated by:
The lower 7s were unerupted at this stage (Figure 9).
The patient underwent extractions of the UR4 and UL4, in conjunction with a Nance palatal arch and upper and lower preadjusted edgewise fixed appliances. The incisor and molar relationships were maintained, and the canines allowed to erupt spontaneously and were then aligned.
During treatment, the lower 7s partially erupted and became mesially impacted. Separators were placed and replaced regularly over a period of 2 months, where some improvement in their position was noted. Various mechanics were used, including continuous NiTi archwires, pushcoil and vertical elastics, which resulted in correction of LR7, LL7 (Figures 10 and 11).
A 17-year-old male presented with a Class III incisor relationship on a mild Class III skeletal base, with average vertical proportions. This was complicated by:
Treatment options were discussed. The patient was reluctant to undergo comprehensive treatment with upper and lower fixed appliances, and therefore, only lower arch treatment was carried out as follows:
At the treatment planning stage, the patient was also advised of the possibility of surgical removal of LL8; however, this was not required.
The cases described highlight the difficulties faced when attempting to treat an impacted MM2. It is evident that there are multiple treatment options, and the treatment plan must be tailored to each individual case with a full understanding of the risks and benefits involved. The treatment plan is dependent on a myriad of factors, including the severity of impaction, angulation of the impacted tooth, presence and position of the third molar, prognosis of remaining teeth, malocclusion, and patient cooperation.1
Each case presented demonstrates the use of different treatment modalities, as well as the need for a multidisciplinary approach to the management of impacted MM2. They also highlight the importance of monitoring MM2s, especially around the age of eruption, and for the following years, until complete eruption or development is has occurred.
This paper also highlights the importance of monitoring the eruption of second molars during orthodontic treatment, as often, impacted second molars are noted post-debond. This may then result in the patient having to undergo a second course of treatment, which is less than ideal.
The recommended age to treat MM2 impactions has been described as being 11–14 years, before root formation of the second molar and development of the third molar is completed. There is often competition for space in this region between the second and third molars, where insufficient space for the second molar can result in impaction.9
Successful management of mandibular second molars is dependent on early detection, diagnosis and treatment. Often, late diagnosis results in a patient being referred following a course of orthodontic treatment, resulting in retreatment being necessary to achieve a satisfactory outcome. No single method of treatment has been shown to be consistently successful in managing impacted mandibular second molars, and each case should be treated on its merits. Good lines of communication with our maxillofacial colleagues are paramount in these challenging cases.
