Root Resorption - An Endodontic Enigma

Dr. Vimal Sikri, Senior Lecturer, Govt. Dental College and Hospital, Amritsar, Punjab.
Dr. Poonam Sikri, Senior Lecturer, Govt. Dental College and Hospital, Amritsar, Punjab.

ABSTRACT

Root resorption is of main concern to the endodontists. Early diagnosis, removal of the cause if feasible, proper treatment and reinforcement of the resorbed root is mandatory for achieving success. Efforts should be directed towards maintaining the integrity and vitality of the periodontal ligament of the luxated and the displaced teeth.

INTRODUCTION

Idiopathic is the unfortunate, but commonly employed word in the medical field. Dentists often come across certain ailments which defy all the scientific logic and remain unexplained. Root resorption is one such ailment which is of concern to the dentist in general and the endodontist in particular. Various causes of root resorption have been hypothesized such as trauma, impaction, replantation, bleaching etc. However, on occasions, these cases, singly or collectively do not fully explain the aetiology of root resorption and therefore the affix 'idiopathic' is used (Fig. 1).

American association of endodontists have defined root resorption as a physiological and pathological process which results in loss of cementum and or/ dentine from the root surface. On the basis of the site of origin of resorption it may be either internal or external and further, apical or cervical.

Henry and Weinman have reported as high as 90% prevalence of root resorption in their study on 5800 teeth while Massler and Perreault have reported that resorption of teeth in Indians are found five times more often than in the United States. Females present higher incidence of root resorption than males. Root resorption in presence of periodontal diseases is found three times more often than in uninvolved teeth.

The present paper is an attempt to summarise our knowledge regarding aetiology, clinical manifestations and management of root resorption.

Root resorption can be classified as (I) internal and (II) external resorption.

I. Internal Resorption

Internal resorption is seen as a radiolucent area around the pulpal cavity, usually of incisors and mandibular molars (Fig. 2). Radiographs are mandatory for diagnosing internal resorption. However, sometimes it may manifest clinically as 'pink spot' when resorption progresses to an extent that the vascular pulpal tissue is seen through the overlying thinned dental hard tissues. Also, during pulp extirpation if excessive bleeding occurs clinically, internal resorption should be suspected.

Fig. I : Cervical and apical root
resorption (idiopathic)
Fig. 2 : Internal resorption
- Mandibular first molar

The vascular changes in the pulp subsequent to trauma, orthodontic tooth movement, chronic pulpitis, direct and indirect pulp capping and pulpotomy may lead to internal resorption. Circulatory changes produce active hyperemia which increase local oxygen tension, thereby lowering the pH. These collectively alter the metabolism of the pulp. Vascular changes attract numerous macrophages which eventually differentiate into osteoclasts. Multinucleated giant cells are also described in lacunae next to polymorphonuclear neutrophils. Finally, the connective tissue may undergo metaplasia and be changed to granulation tissue.

Management

Prompt endodontic treatment is imperative in all diagnosed cases of internal root resorption. Root canal treatment with calcium hydroxide is the method of choice. Calcium hydroxide reduces the inflammatory response and initiates prompt healing. Because of its higher pH, when placed in the root canal and the resorptive lacunae, calcium hydroxide will neutralize the lactic acid from macrophages and osteoclasts. Moreover, higher pH at the resorption site is unfavourable for collagenase cells. Calcium hydroxide arrests the osteoclastic activity and stimulates repair. The root canal and the defect is filled with gutta-percha preferaly using vertical condensation. Success depends upon filling the canal as well as the voids fully. As long as no communication exists with oral fluids, there is no perforation of root-canal wall and the site is covered with epithelial attachment, calcium hydroxide treatment is quite successful. Frank and Weine are of the view that even perforation site can be healed by non-surgical method using calcium hydroxide. However, if resorption has led to perforation which communicates with the oral fluids, the treatment of choice is surgery, and filling the defect with silver amalgam.

II. External Resorption

The crown of an unerrupted tooth is protected from resorption by the reduced enamel epithelium. Similarly, the epithelial rests of Mallasez are believed to maintain the integrity of the periodontal ligament and thereby prevent root resorption.

External root resorption of decidous teeth is physiological which leads to their subsequent shedding.

Pathological external root resorption is more common as compared to internal resorption. Orthodontic tooth movement, endodontic infection, bleaching and reimplantation are some of the etiological factors. Follicular cysts, ameloblastomas and malignancies commonly produce external resorption. Certain systemic diseases viz. Hyperparathyriodism, Paget's disease, Calcinosis, Gaucher's disease, Turner's syndrome etc. can cause resorption of cementum. Above all, idiopathic resorption do occur in certain cases.

Pressure from an impacted tooth may be a cause of external root resorption (Fig. 3). Coomb and Moore have presented a case of resorption of lateral incisor due to the presence of an impacted canine.


Fig. 3 : Resorption of the lateral incisor
because of an impacted canine
Fig. 4 : Root resorption at the apical
third due to endodontic infection

A good percentage of orthodontically treated teeth show root resorption, sometimes as late as 4-5 years after the treatment. Rotation of teeth usually increases the incidence of resorption.

Endodontic infection is often the cause of external root resorption (Fig. 4). During luxation and displacement injuries, resorption is initiated because of trauma. Trauma usually results in fracture of apical alveolar region causing haemorrhage and necrosis of bone. Abnormal forces may injure the periodontal ligament causing necrosis of fibers and related bone and cementum surfaces. If allowed to progress, total cementum resorption can occur (Fig. 5).

Cervical Resorption

It is seen clinically and radiographically as a single resorption lacuna just below the epithelial attachment. The damaged area colonizes the root resorbing cells. The necessary stimulus in the form of bacterial products often come from the gingival sulcus and the tubules of the cervical dentine. It spreads in an irregular manner and later includes the alveolar bone. Usually the cervical resorption is transient but if prolonged, it may lead to necrosis of periodontal ligament and ankylosis. Cervical resorption is a frequent sequelae to root planning and other periodontal treatments.

Bleaching of teeth is frequently followed by cervical root resorption. When heat and hydrogen peroxide are applied during bleaching it is hypothetised that the heat drives the caustic hydrogen peroxide through the tubules and chemically changes the nature of the cementum leading to resorption. Only heat and/or hydrogen peroxide are unlikely to cause resorption.

Fig. 5 : Complete cementum resorption of
maxillary central incisor following trauma
Fig. 6 : Apical root resorption
following replantation


Fig. 7 : Apical root resorption
following replantation
Fig. 8 : Concurrent internal and external
root resorption in maxillary central incisor


Resorption due to Reimplantation

The most common complication of reimplanted teeth is root resorption (Fig. 6, Fig. 7). If the luxated tooth remains out of the mouth for long, the cells on the root surface get dry and die, thereby decreasing the success of the treated tooth. With the necrosis of the periodontal membrane, the tooth become part of the normal bone. The resorbing cells are osteoclasts which are present during remodelling of bone.

Radiologically the periodontal ligament space is invisible and the ingrowth of bony tissue into the dental tissue is evident. It may take a long time for the total root to resorb and ultimately the crown breaks off at the cementoenamel junction.

Rarely, concurrent internal and external root resorption is seen (Fig. 8). Fisher et al have reported such a case.

Prevention and Management

The resorption occuring because of reimplantation and ankylosis are beyond the scope of therapeutic measures. However, if resorption is due to inflammation, root canal treatment, using calcium hydroxide is useful. In most of the cases, only root canal treatment stops the progress of root resorption, especially the apical resorption. In extensive cases, surgical intervention is necessary with root planing and treatment with trichloroacetic acid.

In cases of cervical resorption, a cavity can be prepared and filled with glass ionomer cement or silver amalgam after raising the flap.

In all cases of root resorption considerable reinforcement with stainless steel post is mandatory. This will increase the resistance to fracture. Recently introduced Thermafil and other preparation of combined silver cone and gutta-percha can be helpful in strengthening the weakened root.

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[Article as appeared in J. Endodontology, 1993, page 11. Slight cosmetic changes done to make fit on a web page]