Hitherto, little attention has been given to the problem of canal calcification following orthodontic tooth movement. The study of 50 consecutive patients undergoing orthodontic treatment, revealed the develop ment of discrete canal calcification in 12 patients. The possible mechanism of canal calcification and its implications are discussed.

Orthodontic tooth movement is achieved through different force systems which move the teeth to pre­ determined positions. The secondary changes attributed to orthodontic treatment include root resorption and periodontal problems which have received considerable research attention and clini­ cal concern. The effect of variation of therapeutic forces on the pulp has been studied by very few researchers.1 Root canal calcification or dystrophic mineralization of the pulp, which is a possible side effect of orthodontic treatment is mentioned in endodontic literature.2
Complete canal calcification has been reported by several authors3-7 but a history of direct physical trauma to the tooth could be elicited. Daugherty8 reported that orthodontic trauma was severe enough in very few cases to cause secondary dentine deposition to the extent of obstructing the entire pulp chamber. In 1982, Delvanis1 reported
the complete calcification of the root canal in two of the forty six cases treated by fixed appliances. Three teeth had evidence of canal calcification to the extent of canal obliteration. There was a history of irregular and long treatment. Headgear therapy for a prolonged period was used in one of the cases.
The purpose of this study was to evaluate the effects of orthodontic therapy by removable and fixed appliances on the pulp of the teeth. Thus, determines whether canal calcification was just an isolated problem, or a significant iatrogenic effect of orthodontic therapy.

A total of 50 patients, 18 males and 32 females, were studied. Removable appliances were used in 35 patients [Fig. 1] and 15 patients were treated by Begg's differential force technique [Fig. 2]. All 50 patients were under retention for a minimum period of six months. The age of the patients ranged between 13 and 33 years at the time of treatment. Teeth from central incisors to second bicuspids in both arches were studied. Two-digit system of nomenclature proposed by Federation Dentaire Internationale was used for the sake of conveni­ ence.
Radiographic evaluation of the dentition was performed with intraoral periapical radiographs using short cone X-ray plant. A standardized pro­ cedure was followed to have identical projections of roentgenograms before and after orthodontic treatment. Distortion of film was kept to minimum. An exposure of 0.8 sec. was given in all cases.
The changes in the radiographs were seen with the help of a magnifying lens in comparing the pre- treatment and post-treatment radiographs. Films were separately studied by three calibrated indi­ viduals and compared only after all opinions have been tabulated. A majority's opinion determined the category. Root canal calcification was categorized into:
1  Discrete calcification [Fig. 3]: Localized areas of calcifications in the root canal which were         not sufficient to completely obliterate the root canal.
2.  Diffuse calcification [Fig.4]: Calcification caused complete obliteration of the root canal.

A total of 910 teeth (450 in maxilla and 460 in mandible) were studied. None of the teeth studied was affected by diffuse calcification. Discrete cal­ cification was seen in twelve teeth, seven in the maxillary arch and five in the mandibular arch. The maximum teeth affected by discrete canal calcifica- tion were four upper right central incisors, followed by three upper left central incisors, two lower right central incisors, and one each of lower left central, lower left lateral and lower right lateral incisor [Table 1]. The incidence of calcification was higher (10 teeth-1.56%) in patients treated by removable appliances The teeth affected were four upper right central incisors, two upper left central incisors, one lower left central incisor, two lower right central incisors, and one lower right lateral incisor. Inci­ dence of discrete canal calcification was lower in fixed appliance treated cases 2 teeth (0.74%), One upper left central incisor and one left lower central incisor were affected by discrete canal calcification. In the patients affected, no history of physical trauma prior to orthodontic treatment could be eli­ cited and none of them had prolonged treatment.

The incidence of canal calcification increases with age2 and it is also known to occur following trauma to the teeth. However, in our patients, who were of a young age group, there was no history of trauma except the orthodontic tooth movement. As reported by Ingle,9 the trauma which was insuf­ ficient to devitalize the pulp may stimulate it to lay down reparative dentine eventually obliterating the entire pulp and root canal. Calcification usually begins in the coronal portion of the pulp and extends towards the apex however, it may have an irregular distribution.4 The increased incidence of canal calcification in our patients treated with removable appliances may be due to the variation in forces generated by these appliances. On the other   hand,   forces   generated   by   the   fixed appliances are less variable and can be precisely controlled.
It is possible to diagnose the narrowing of the canal space by constant monitoring, in the patients undergoing orthodontic treatment or retention. The diagnosis of discrete canal calcification during active treatment or retention calls for the opinion of a competent endodontist. The endodontic treat­ ment at this stage may be of conservative nature only. Once complete obliteration of the root canal has taken place, conservative endodontic treat­ ment is not possible and the tooth becomes discol­ ored and unacceptable to the patient. Surgical intervention with retrograde amalgam filling9 and even extraction with prosthetic replacement may be necessary.
The importance of early diagnosis of canal cal­ cification during orthodontic treatment is obvious. The authors feel that constant monitoring of the patients undergoing active orthodontic treatment or during retention should become a routine prac­ tice. Monitoring will lead to an early diagnosis of a narrowing canal and save the patient from the psychological trauma and the orthodontist from the blame of negligence. The exact cause and ulti­ mate fate of the canal calcification needs to be studied further.