Dental Hypotheses

: 2014  |  Volume : 5  |  Issue : 4  |  Page : 164--167

Remember the periroot sheet in orthodontic treatment of ectodermal dysplasia patients

Izabella Vest Hansen, Henriette Vedtofte, Inger Kjær 
 Department of Odontology, Orthodontic Section, Health Science Faculty, Copenhagen University, København, Denmark

Correspondence Address:
Prof. Inger Kjær
dr. odont. et. dr. med. Orthodontics Section, Department of Odontology Faculty of Health and Medical Sciences, University of Copenhagen 20 Nørre Allé, DK-2200 Copenhagen N


Introduction: Root resorption has various etiologies. Recent studies have demonstrated a periroot sheet covering the root. The outermost layer of this sheet is the Malassez«SQ» epithelial layer. Tooth malformations are seen in ectodermal dysplasia and it is believed that the ectodermal layer in the periroot sheet differs in cases of ectodermal dysplasia. Case reports: Three cases of unexpected severe root resorption are demonstrated. Two cases were diagnosed with ectodermal dysplasia and the third appeared with thin, curly hair and absence of eyebrows but no ectodermal diagnosis. In the ectodermal cases, there were severe orthodontically provoked resorptions on the teeth that appeared to be permanent but were possibly primary. In the third case, there was heavy resorption on permanent teeth due to orthodontic treatment. Discussion: The orthodontist should be aware that aggressive resorption can occur in cases not diagnosed with ectodermal dysplasia but with signs of ectodermal deviations, and that tooth morphology, hair, and skin are important to observe before proceeding with treatment.

How to cite this article:
Hansen IV, Vedtofte H, Kjær I. Remember the periroot sheet in orthodontic treatment of ectodermal dysplasia patients.Dent Hypotheses 2014;5:164-167

How to cite this URL:
Hansen IV, Vedtofte H, Kjær I. Remember the periroot sheet in orthodontic treatment of ectodermal dysplasia patients. Dent Hypotheses [serial online] 2014 [cited 2020 Sep 23 ];5:164-167
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Ectodermal dysplasia has many different phenotypic characteristics. [1] These different characteristics are in turn associated with different genotypes. One of the well-known phenotypic characteristics in ectodermal dysplasia is congenital absence of multiple teeth. [2] However, there are also cases of ectodermal dysplasia in which there are few or no teeth missing. In all cases of ectodermal dysplasia, orthodontic treatment may still be relevant.

Root resorption has been reported on primary roots, mostly in case reports, but the explanation for root resorption occurrence has not been concluded. This is due to that resorption on permanent roots has seemingly not been described. The aim of this report is to describe resorption of permanent tooth roots and propose a reasonable explanation for this phenomenon.

Recent studies have found and described a characteristic three-layer tissue structure called the periroot sheet which surrounds the permanent root. [3],[4] These cell layers are as follows:

The inner cell layer closest to the root is an innervation layer. A mesodermal fiber layer covers this innervation layer and accordingly composes the middle layer of the periroot sheet. [3] The outermost layer is an ectodermal cell layer, which is composed of Malassez' epithelium. [3]

In the primary dentition, these three layers are also present. The outer ectodermal layer is less apparent, with only small clusters of ectodermal cells. [5] The difference in the periroot sheet between the root of the primary tooth undergoing resorption during normal development and the root of the permanent tooth not undergoing resorption might indicate the importance of the ectodermal layer as a protective layer against resorption [6] [Figure 1].{Figure 1}

This hypothesis can also explain why resorption can occur in the ectodermal layer of the periroot sheet of a permanent tooth from a patient with ectodermal dysplasia.

 Case Reports

The present case report illustrates three cases of ectodermal dysplasia, of which two have multiple agenesis and one does not. The purpose is to observe how orthodontic treatment, even with great precautions and gentle forces have provoked undesirable root resorption.

Case 1

An eleven and a half-year-old boy with thin, curly hair and fair skin and missing eyebrows was received by the orthodontist for orthodontic treatment [Figure 2]. There is no information about disease or genetically inherited conditions in the family or medicinal use. Orthodontically, there is extreme crowding in the maxilla and the mandible [Figure 2]. All of the teeth were present.{Figure 2}

The second maxillary premolar on the right side had been extracted. The root of the first maxillary molar on the right side appears short.

At 12 years old, he receives a hyrax maxillary appliance and later a fixed appliance. During treatment, the mandibular first molar in the right side was in infraposition and later extracted [Figure 3]. The root of the first maxillary molar in the right side appeared shorter. After removal of the hyrax appliance, it was clear that the roots of the maxillary incisors had resorbed significantly [Figure 4] and [Figure 5].{Figure 3}{Figure 4}{Figure 5}

Cases 2 and 3

These are both cases with a known diagnosis of ectodermal dysplasia. Both have multiple agenesis and tooth malformations. The hair and skin are characteristic for anhidrotic ectodermal dysplasia. In both cases, minor treatments were applied with gentle forces - in case 2 (girl, 14 years), the goal was to guide a canine into the right position [Figure 5], [Figure 6] and [Figure 7] and in case 3 (boy, 12 years), the purpose was to upright the central maxillary incisors [Figure 8] and [Figure 9].{Figure 6}{Figure 7}{Figure 8}{Figure 9}


Studies on ectodermal dysplasia and the involvement of the dentition are dominated by studies on tooth agenesis [7] and malformation. [8] Root resorption has only been sporadically mentioned in multiple agenesis cases. [9]

Because all of the teeth were present in case 1, it was not considered that the patient had ectodermal dysplasia. The treatment plan shows however that both the maxillary molar resorption before the treatment began and the infraposition of the mandibular first molar are signs that indicated a less protective periroot sheet in the periodontal membrane. [10] These signs, in combination with the thin, curly hair and missing eyebrows are warnings that demonstrate that such treatment should not follow the ideal guidelines for treatment of crowdings, but should follow an alternative treatment plan.

In both cases 2 and 3, the teeth undergoing resorption appeared to be permanent, possibly malformed teeth, but whether the teeth are primary or permanent is uncertain. Both cases were diagnosed with ectodermal dysplasia and precautions were taken with gentle orthodontic forces.


These cases demonstrate how the orthodontist should be aware of the periroot sheet and specifically its ectodermal component. Even in cases without a diagnosis of ectodermal deviations and without tooth agenesis, unexpected resorption may occur. It is, therefore, essential also to carefully observe the tooth morphology, hair, nails, and skin before proceeding with orthodontic treatment.


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