January 1, 2014
by Carla Cohn, DMD
One of the most common ‘parent questions’ that I hear in my private practice is “when will my child’s adult teeth come in?” More specifically, my parents are enquiring about anterior teeth. My parents and my children are very aware of the development of their peers. They are very quick to compare and contrast their development, as if it were a race. Once they see their friends of similar age beginning to erupt permanent incisors, they begin to wonder when they can expect the same.
What my parents and children are less cognizant of is the development and eruption of the permanent molars. Very many, I would even venture to claim that the majority, are unaware of the eruption of their permanent molars, be that the permanent first or second molars. Routinely upon recall hygiene and examination appointments, I discuss the arrival of these teeth. A common response from my parents is ‘that it is not possible that there are permanent molars, as my child has not lost any teeth yet to allow this.” They are simply less aware of the eruption of these teeth as they are not visualized as easily.
As dental professionals, we are acutely aware of the patterns and stages of growth and development. We are well versed in the average age of eruption and exfoliation. We are reminded on a daily basis that the average is just that — an average.
Age of eruption can vary greatly from child to child. Additionally, these variations occur between children of the same family. First permanent molars erupt between the ages of five-and-a-half and seven years of age. Sequentially first permanent molars are the first permanent tooth in the dentition to erupt (Table 1).1,2
When we are assessing growth and development, either clinically or radiographically, we must be mindful of timing of eruption, sequence of eruption and symmetry, or lack thereof. Delayed eruption and/or lack of symmetry can be the first indication that something is amiss. One of the complications of eruption of first and second primary molars is termed an ectopic eruption. An ectopic eruption can occur when the permanent molar has an altered path of eruption in a mesial angular direction. The permanent molar can erupt in a detrimental position, under the distal of the second primary molar, or impacted against the first permanent molar. This ectopic eruption can adversely affect the tooth located anteriorly. The ectopic eruption can result in external resorption and destruction of the tooth in its path of eruption. Additionally, the tooth that is erupting ectopically can be adversely affected, as it becomes a trap for food and plaque, thereby increasing its susceptibility to decay.
Etiology of the ectopic eruption can be considered multifactorial. Some circumstances may be unusually large tooth size, deviated angulation of path of eruption, discrepancy in size or position of maxilla and delayed calcification of molars. All may have factors in the subsequent ectopic eruption.3
The literature varies in its citations on frequency. Some literature cites that approximately 0.75 percent of the population will present with an ectopically erupted molar.4 However, others cite prevalence between two percent to six percent.5 The frequency is significantly higher in cleft palate patients, up to 25 percent.3,6 Siblings are affected five times higher than the general population.7 Irrespective of the statistics, ectopic eruption is a phenomenon that presents itself frequently enough in private practice to be a concern to the dentist that cares for children. Diagnosis and treatment modalities are important to understand and be able to implement.
Clinically, signs and symptoms of an ectopic eruption include:
• Visualization of a trapped mesial marginal ridge of the erupting molar
• Asymmetrical development
• Mesially tipped permanent molars
• Prematurely mobile primary molar.
The eruption can be assessed upon radiographic examination, either with bite-wing radiographs or panoramic radiograph. Radiographically, the offending ectopic molar can be seen to be erupting with a mesial angulation, often underneath the distal portion of the adjacent primary molar. This may result in external root resorption at best and encroachment on the pulp of the anterior tooth in more severe cases.
Of all first permanent molar ectopic presentations, approximately 66 percent will self correct. Some advise a three to six month observation period after early diagnosis to allow for spontaneous self correction and subsequent normal eruption. Cases that self correct usually do so prior to the age of seven.3 An ectopically erupting molar with a clinical crown that is submerged below the distal of the second primary molar is not able to self-correct and requires intervention.
Treatment is advised to guide the tooth into a more favorable path of eruption to minimize damage to affected dentition, preserve arch length, and to maintain function. Without intervention, sequelae can include premature loss of the anteriorly affected tooth, tipping and rotation of the ectopic molar, space loss and malocclusion. Treatment will depend upon the severity of the impaction. Mildly to moderately impacted molars can be guided easily with elastic orthodontic separators. More severe impactions require more complex treatment options, including potential extraction of the anteriorly affected tooth, removable or fixed appliances, or surgical uprighting.
Case Study 1:
Patient JP presented at eight years of age. His mandibular first permanent molars had erupted, however his maxillary first permanent molars had failed to erupt. Upon radiographic examination it was evident that teeth #16 and #26 were erupting in an ectopic position. A radiograph of #26 at initial diagnosis is shown in Figure 1. Treatment involved placement of an elastic orthodontic separator (Fig. 2) and subsequent monthly observation appointments. Placement of the orthodontic separator can be done with a separator forcep, or by threading two pieces of floss and stretching the separator. Using a sawing motion while forcing interproximally and gingivally. A clinical tip: if the space is extremely tight, as is frequently the case, place a separator as gingivally as possible and allow it to sit for 20 to 30 minutes. This small amount of time is often enough to separate the space ever so slightly. Then remove the partially placed separator and place a new separator in, seating it completely. At recall appointments, do NOT remove the separator. Simply ensure that it is still in place and monitor the eruption. Documentation during treatment is seen in Figures 3 & 4.
FIGURE 1: Pre-operative radiograph. FIGURE 2: Placement of separator
FIGURE 3: Mid treatment. FIGURE 4: Near completion.
Total treatment time for JP was five months, with recalls for observation
every four to six weeks. Note the supereruption of #36 in the final radiograph that had occurred while treatment was in progress. Results after treatment are seen in Figures 5 to 7.
FIGURE 5: Post treatment radiograph. FIGURE 6: Final photo occlusal view.
FIGURE 7: Final photo occlusion.
CASE STUDY 2
Patient MB presented at 14 years and seven months. Her permanent second molars had all erupted in to occlusion with the exception of tooth #47. Upon examination, it was evident that #47 had an ectopic path of eruption (Fig. 8). Much discussion ensued about possible Halterman appliances, surgical intervention and so forth. After much treatment planning, I thought back to all the ectopic first permanent molars that I had uprighted by simply placing an orthodontic separator. With nothing to lose, except for a few months of time, I placed the separator and set out to observe. The same protocol was followed in this case as in case study 1 (JP). Documentation during treatment is seen in Figures 9 to 11. Within 10 months, tooth #47 had erupted into perfect occlusion (Figs. 12 & 13)
FIGURE 8: Preoperative radiograph. FIGURE 9: placement of separator.
FIGURE 12: Post treatment radiograph. FIGURE 13: Final
In conclusion, early and correct diagnosis of an ectopic eruption is critical for this simple procedure. Uses of orthodontic separators are a simple and effective tool for correction of these ectopic eruptions. OH
Dr. Cohn maintains a private practice at Kid’s Dental and at Western Surgery Centre in Winnipeg. She is a clinical instructor, part-time, in the department of Preventive Sciences at the University of Manitoba. Dr. Cohn lectures internationally on children’s dentistry for the general practitioner.
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