From Volume 8, Issue 4, October 2015 | Pages 132-138
This report presents an interesting case of idiopathic external apical root resorption (IEARR) affecting the non-occluding teeth in a 20-year-old Caucasian male patient with a Class III malocclusion. A review of the current literature is reported and the presenting features of the patient are discussed.
Root resorption seen within the orthodontic population is usually due to pathology, such as that seen in tooth impaction or trauma, or as a consequence of orthodontic treatment itself.1 Brezniack and Wasserstein2 described four types of root resorption: physiological, inflammatory, replacement and idiopathic resorption. This review of the literature aims to describe the current evidence available for idiopathic root resorption and includes the presentation of an interesting case with idiopathic external apical root resorption (IEARR), which appears to be limited to teeth not in occlusal function.
Root resorption has a complex and multifactorial aetiology.1 It occurs as a result of localized inflammation and may have a transient or progressive presentation. It is a complex process in which hard tissue dentine and cementum are lost, usually following localized damage or loss of periodontal ligament3 which is believed to play a protective role maintaining the integrity of the root.4 Dentinoclasts are known to be involved in root resorption, which may be mediated by prostaglandins, bacterial products, macrophage chemotactic factors and osteoclast-activating factors5 following the loss of the protective periodontal ligament element. Dentinoclasts differ from bone-resorbing osteoclasts in that they are smaller, have fewer nuclei and less defined zones of active resorption.4 Transient root resorption is not uncommon and it has been suggested that this is self-limiting in the absence of constant stimulation with cemental-tissue repair.4 Loe and Waerhaug6 suggested that, when multiple teeth show evidence of root resorption, this could be a sign that dental hard tissues have become involved in the osseous process of remodelling.
Classification of root resorption can be divided into internal or external, and divides further according to type or location, although at present there is no consensus on one particular classification (Table 1).4,7
| Site | Type | Aetiology |
|---|---|---|
| Internal | Trauma | |
| Infection | ||
| External | Surface | Trauma |
| Inflammatory | Trauma | |
| Infection | ||
| Replacement (Ankylosis) | Avulsion and re-implantation | |
| Luxation | ||
| Transplantation | ||
| Pressure | Orthodontic tooth movement | |
| Excessive occlusal forces | ||
| Impacted teeth | ||
| Supernumerary teeth | ||
| Tumours | ||
| Cysts | ||
| Related to systemic conditions | Hyperparathyroidism | |
| Paget's disease | ||
| Papillon-Lefèvre syndrome | ||
| Bone dysplasia | ||
| Renal disease | ||
| Hepatic disease | ||
| Invasive (Cervical) | Trauma | |
| Orthodontic tooth movement | ||
| Periodontal treatment | ||
| Intra-coronal tooth bleaching | ||
| Unknown | ||
| Idiopathic | Unknown |
Exfoliation of the deciduous dentition occurs following progressive root resorption and is considered to be a normal physiological process.8,10,11 However, in the permanent dentition root resorption results from pathosis, with many identified causes,7 the most common being infection-related root resorption and orthodontically-induced inflammatory root resorption (OIIRR).12,13 Other local causes include trauma, tumours, cysts, impacted and supernumerary teeth.14
Infection-related root resorption may occur in conjunction with periradicular periodontitis following infection and necrosis of the pulp tissue4 or following infection of the periodontal tissues.7 It is normally expected to arrest following successful endodontic treatment involving instrumentation and disinfection of the root canal space of the infected tooth.7 OIIRR is reported to occur in around 90% of orthodontic patients,1 is usually self-limiting,14,15 but is variable in severity.15,16,17
Idiopathic root resorption was first reported in the dental literature by Mueller and Rony in 1930.18 Since this time, there has been very little further information regarding idiopathic external apical root resorption (IEARR), with most publications relating to individual cases. One systematic review19 identified 32 reported cases of idiopathic external apical root resorption, only two of which affected the entire dentition.19,20,21 Long-term follow-up of idiopathic external root resorption, cervical or apical, is particularly lacking. One case of idiopathic cervical root resorption, which was followed-up over a 6-year period, showed no advancement in the extent of root resorption, which the authors attributed to the bisphosphonate therapy taken by the patient during this time period.22
Previously there have been two types of idiopathic root resorption reported; cervical and apical. Cervical idiopathic root resorption presents as resorption in the cervical region of the tooth advancing towards the pulp, whereas external apical root resorption typically presents at the root apex with progressive blunting of the root apex.23 Idiopathic external apical root resorption is normally first identified as an incidental finding on radiographs, and symptoms usually develop only in the latest stages of this condition with mobility and tooth loss.
Anecdotally, idiopathic root resorption has been described to have an increased prevalence in females.24 This was thought to be due, in part, to increased presentation of females to orthodontic practices, where it is diagnosed as an incidental finding. However, a review of the literature3 indicates that IEARR has been reported more in males. Presentation of idiopathic external apical root resorption does not appear to have any association with a particular age or racial group.3,25
Since idiopathic external apical root resorption is pathology with unknown cause, it is essential to exclude any possible cause, such as previous trauma or previous orthodontic treatment. Sensibility tests and appropriate radiographs should be taken before coming to this diagnosis.
An 11-year-old Caucasian male was originally referred by his general dental practitioner to a local specialist in orthodontics regarding his Class III malocclusion. The specialist had monitored his growth and dental development for 2 years before referral to the Orthodontic Department at Leeds Dental Institute aged 13 years 6 months for an opinion regarding the need for future orthognathic treatment, as his Class III malocclusion had worsened considerably and was now beyond the scope of orthodontic camouflage. The patient had no concerns at this point regarding his malocclusion or facial appearance. The patient had no relevant medical or dental history and no history of dental trauma was noted.
Extra-oral examination revealed a moderate Class 3 skeletal pattern with an increased Frankfort-mandibular plane angle and increased lower anterior face height. No facial asymmetry was detected, although there was a marked degree of malar flattening with some bossing of the frontal bone. There was a familial history of a similar facial appearance.
Intra-oral examination revealed that all permanent teeth were erupted, except for the upper right permanent canine, upper left second premolar and the third molars. The lower labial segment was mildly crowded and at an average inclination. The upper labial segment was severely crowded and proclined, with the upper left permanent canine buccally excluded from the arch and the upper right permanent canine unerupted and buccal. The upper buccal segment was moderately crowded with the upper right second premolar being palatally displaced. In occlusion, the incisor relationship was Class III with a reverse overjet of 2 mm and a reduced overbite of 1 mm. There had been significant mesial drift of the upper first permanent molars with mesio-palatal rotation and a Class I molar relationship on the right and a ¾ unit Class II on the left.
A panoramic radiograph, taken at age 11 years 4 months by the specialist practitioner, had been forwarded with the referral (Figure 1). This showed development of the dentition within normal limits with good root lengths (although the radiograph was of poor quality in the lower incisor region). Cephalometric analysis, from a radiograph, taken at age 13 years 1 month, confirmed the clinical features described (Figure 2).
The patient had very little concern regarding his dento-facial appearance, possibly tempered by anxiety at the prospect of orthognathic surgery. Several options for treatment were presented to the family:
Discussion with the patient revealed that he was particularly anxious to avoid any treatment involving orthognathic surgery. A further review appointment was made on the orthognathic clinic to monitor further growth prior to any orthodontic intervention, giving the patient an opportunity to make a decision regarding the desire for treatment.
Review at age 14 years 5 months, the patient presented with a reverse overjet of -2 mm and an anterior open bite of 2 mm. There was a mandibular asymmetry with the lower centreline deviated to the left by 3 mm but coincident with the midline of the chin. There was a cant of the maxillary occlusal plane. At this point the patient still had no concerns about his dento-facial appearance. As there had been deterioration in the overbite indicating adverse skeletal growth, a further review appointment was made.
At his review appointment, age 15 years 6 months, the patient reported that he continued to be unconcerned regarding his dento-facial appearance. Clinical examination revealed deterioration of the anterior open bite to 4 mm and reverse overjet of -2 mm. The upper permanent canines had erupted buccally, excluded from the maxillary arch, and the upper right second premolar was unerupted and palatally excluded from the arch. The first tooth contact was noted to be on the first permanent molars. Orthodontic records were taken and radiographs updated, revealing the presence of apical root resorption affecting UR 1–3, UL1–3, 5, LL6, LR 4–6 (Figures 3 and 4). There was no family history of short dental roots to their knowledge. Conventional fixed orthodontic treatment was contra-indicated owing to the risk of further root resorption. An extraction only treatment plan was agreed, with the loss of the maxillary canines. The patient was then discharged from the department.
The patient was re-referred at age 20 years and 7 months by his general dental practitioner, regarding pain due to occlusal loading related to the upper right first and second molars, which were the first occlusal contacts with the lower second molars. A soft bite splint had been provided but this had not alleviated his symptoms. The patient's malocclusion had deteriorated further and he now presented with a severe Class 3 skeletal pattern with an increased Frankfort-mandibular plane angle and increased lower anterior face height. There was moderate crowding in the lower labial segment and spacing in the upper labial segment with mild crowding in the upper buccal segment. In occlusion, his overjet remained stable at -2 mm with a worsening of the anterior openbite to 7 mm. The first occlusal contacts were noted on the upper left first molar and the upper right second molar. The molar relationship was ½ unit Class II on the right and a full unit Class III on the left; the upper left first molar to right first molar in crossbite (Figures 5 a-e). A further orthopantomagram (OPT) (Figure 6) revealed an increase in the severity of the root resorption noted on previous radiographic investigations 5 years previously and in comparison to the original radiographs taken 9 years previously. The teeth in occlusal contact showed little evidence of root resorption (UR7, UL 6–7, LL7, LR7). Owing to the limitations of two-dimensional radiography, full estimation of root length is not possible with these views. Assessment of the three-dimensional nature of root resorption and root length would need further radiological investigations, such as cone-beam CT.26 This would not be indicated in this case as there would be no patient benefit from further radiation exposure.
An opinion was gained from a consultant in restorative dentistry regarding redistribution of occlusal forces to include more of the posterior dentition. It was felt that the anterior openbite was too great to achieve redistribution of the occlusal forces. The patient has not been provided with any active treatment, only advice regarding relief of his symptoms.
In 1975, Newman25 questioned previous suggestions of endocrinopathy (hypothyroidism and malnutrition) as a possible aetiological factor in external root resorption on the grounds that these conclusions had been reached without sufficient evidence. However, case reports published since then have reinforced this link and there are suggestions of multiple factors associated with IEARR. There has been shown to be a relationship of generalized root resorption with hyperparathyroidism,27 hypoparathyroidism,28 hypophosphatasia,29 Paget's disease of the bone,30 Goltz syndrome31 and Papillon-Lefèvre syndrome.32
Genetic factors are considered to account for 50% of the variation in orthodontically-induced inflammatory apical root resorption (OIIRR) and IL-1B may account for 15% of variation, with reduced levels being linked to increased root resorption. Increased levels of prostaglandin PGE2 have been linked to increased root resorption in rat studies, but this link has not been confirmed in humans.33 It is thought that genetic factors influencing IEARR are heterogeneous, which can manifest with different mechanisms or site-specific presentation in the individual.34 Newman25 demonstrated a familial link, which implicates a genetic factor in IEARR, but a specific genetic influence has yet to be identified.
Histological and haematological analysis of cases with IEARR has not improved our understanding of a potential aetiology. Schätzle et al35 analysed two extracted teeth showing signs of root resorption. Histological examination revealed resorption and evidence of ankylosis. The most striking finding was generalized resorption of approximately 2 mm apical to the cemento-enamel junction. Further reports have revealed irregular cellular cemental-type tissue covering the dentine.22 Iwamatsu-Kobayashi et al22 noted that no multinucleated odontoblasts were seen around the resorbed dentine, which differs from Moody et al,36 who identified odontoclasts on the dentine surface and additionally found fibrous tissue filling resorption cavities. The histological reports generally find chronic non-specific inflammation24 and suggestions of a disturbance of periodontal ligament regulation of mineralization.35 Various investigations into potential haematological factors have not yielded conclusive results. Haematological investigations included assessment of full blood count, calcium, phosphorus, alkaline phosphatase, sodium, potassium, serum proteins, lipids, vitamin D, parathyroid hormone, osteocalcin, serum creatinine, liver function tests and thyroid function tests; all of which yielded results within normal limits.23,37,38,39 Omer et al additionally performed urinalysis, but again obtained no abnormal results.38
In a study of 88 teeth extracted as a consequence of periodontal disease,40 the authors showed that teeth with antagonistic occlusal contacts have significantly increased radicular root resorption compared to unopposed teeth. Severity of periodontal disease correlated with the extent of root resorption. This finding was attributed to excessive movements of the tooth during normal masticatory function, thereby having greater impact on periodontal ligament and its function in repair and remodelling of root surfaces. However, in the case presented above, the only teeth in contact appeared to show little evidence of root resorption. Proffit et al have suggested ‘jiggling forces’, intermittent forces on the tooth in two different directions, as a cause of external apical root resorption, although evidence for this is lacking.41 It may be that soft tissue forces from the lips and tongue are contributory to jiggling forces playing a factor in the root resorption seen in this case. Research by Motokawa et al demonstrated a significant decrease in root area and concurrent elongation and narrowing of that root in a study of hypofunction in rat molars.42 However, this was only shown to be significant on 1 of 5 molar roots, so the clinical significance of this in humans cannot be ascertained. It is not known whether the lack of an intercuspating occlusion allows greater soft tissue pressure to act on the dentition or whether occlusal contact in periodontally healthy teeth has a protective effect against root resorption.
Infection-related external apical root resorption is conventionally treated successfully with endodontic therapy.4,43 At present there is no proposed protocol for management of cases with idiopathic apical external root resorption. There has been one reported case of endodontically treating teeth affected by IEARR. Sogur et al managed widespread IEARR in an 18-year old patient by extirpating vital pulps of teeth which gave non-vital responses to electric pulp testing and placing monthly calcium hydroxide dressings for 6 months.19 These teeth were subsequently conventionally root-filled and 18-month follow-up showed no further root resorption. However, the consensus opinion in previously published case reports agree that management is principally related to long-term monitoring, with intervention only in cases of symptoms, or where tooth loss is immediately inevitable. Where tooth loss is inevitable because of IEARR, planning the placement of dental implants has been advocated, although the long-term success of this strategy is lacking.
Idiopathic external apical root resorption continues to be poorly understood. Laboratory studies of rats with OIRR have provided some evidence to show that the extent of root resorption may be reduced when thyroxine is administered in conjunction with orthodontic pressure.44 Loberg and Engstrom prescribed thryoxine supplements in three cases at increased risk of OIIRR, each of which had a successful outcome with no progression of root resorption.45 The clinical effectiveness of thyroxine treatment has not been investigated.
Currently, there is no treatment modality that is effective against the progression of IEARR. To date, management is based on long-term review3 and symptomatic relief of the consequences of root resorption, namely tooth mobility and restorative replacement of lost teeth.
Monitoring root resorption associated with IEARR is by radiographic analysis. Dental panoramic tomograms are taken in orthodontics to assess the dentition and supporting structures; they typically have a radiation dose of less than 30 mSv26,46 and may provide a useful overview of root resorption. Serial peri-apical radiographs can provide more accurate measurements,26 but these may be technique sensitive as elongation or foreshortening of root lengths may occur dependent on film and x-ray tube positioning, and carry a radiation dose of around 32mSv.26 Cone beam CT is the most accurate radiographic technique currently available for measuring root resorption, but has an effective dose between 48–652 mSv.46 Assessment of this patient's DPT at initial presentation did not show any signs of root resorption and therefore no further radiological examinations were needed to assess the dentition at that time, and no orthodontic intervention was required. On review of the patient aged 15 years 6 months, a further dental panoramic tomogram was taken which revealed resorption of several teeth and the decision for an extraction only treatment plan was devised as orthodontic tooth movement was contra-indicated in a patient already showing signs of IARR. Therefore, no further radiation was indicated as it would not have changed the management of this patient. When the patient was re-referred age 20 years, a further DPT was taken to assess if his symptoms could be attributed to any specific changes, and allowed global comparisons to be made between the DPTs. Whilst serial cone beam CTs or peri-apical radiographs would have provided accurate measurements of the extent of root resorption, it would not have altered the outcome or prognosis for this patient, and as such could not be justified46 according to IR(ME) R 47 principles of keeping radiographic doses as low as reasonably practicable.
IEARR is a diagnosis of exclusion and should only be applied once other causes of root resorption have been eliminated. This case report seeks to add another unusual case to the current literature in this poorly understood area. Only by evaluation of greater numbers of cases can possible relationships between affected individuals be identified to elucidate common features or genetic similarities. Additionally, it is important that an appropriate management approach is developed. The lack of long-term data makes it difficult to ascertain whether endodontic therapy of affected teeth is more appropriate management than monitoring progression. Further research is indicated into long-term consequences in these patients and identification of potential aetiological factors.
