Endodontics (MDS)

During the development of teeth, the apical foramen is funnel shaped with the wider portion extending outward. The mouth of the funnel is filled with periodontal tissue, which is later replaced by dentin and cementum.

The apical foramen is not always the most constricted portion of the root canal as constrictions can and do occur before the extremity of the root is reached. Apical constrictions are found 0.5 to 1.0 mm away from the root apex. The apical foramen is not always located in the center of the root apex as it may exit on the mesial, distal, labial or lingual surface of the root, usually slightly eccentrically.

With increasing age, pulp horns recede, pulp chambers become smaller, root canals get narrower from deposition of secondary and reparative dentin. Dentinal tubules become narrower or even obliterated by the deposition of peritubular dentin.

Hyperparathyroidism may cause pulp calcification and loss of lamina dura rendering execution of endodontic procedures, difficult or impossible.

The arrangement of the four pulp horns; (mesiobuccal, distobuccal, mesiopalatal, and distopalatal) gives the pulpal roof, a rhomboidal shape in cross-section. As the four walls converge towards the floor, where the lingual wall almost disappears, the floor of the pulp chamber appears triangular in cross-section.

During access opening of a tooth, drop of the bur may be felt if the pulp chamber is large, but in partially calcified chambers, the drop is not felt and the operator has to rely on the measurements made to avoid penetration beyond the chamber roof.

Maxillary cuspid is the longest human tooth with the average length of 26 mm. A specimen 33.5 mm in length has been reported.

Pulpectomy or pulp extirpation, is the complete removal of a normal or diseased pulp from the pulp cavity of the tooth. When the tooth has been left open for drainage, and when food or other debris has accumulated in the pulp cavity other than residual necrotic pulp debris, the removal of this material from the pulp cavity is referred to as debridement.

Dens Evaginatus is a developmental anomaly formed during early tooth development by the proliferation and evagination of the enamel epithelium into the stellate reticulum, resulting protuberance of enamel and dentin with a pulp horn usually observed in premolars.

EDTA has been used as an irrigant but its main purpose is as a chelating agent as it removes the smear layer of dentin and leaves virtually no debris on the surface of the dentin.

Intraligamentary injection is considered as intraosseous injection because of the distribution of the anesthetic in the medullary spaces adjacent to the periodontal ligament. In some patients, it causes a transient decrease in blood pressure and an increase in heart rate. These changes are manifested clinically as palpitations and anxiety.

The first step after perforation is to control the bleeding, which helps in locating the perforation and also increases the visibility for locating the root canal orifices.

Dens in dente is an invagination within the crown or root of the lingual surface of the tooth. This malformation may occur in any anterior tooth but it is most commonly observed in maxillary lateral incisors.

Sonic handpieces operate at 1500 to 6500 cycles/mt when filled inside the root canals for cleaning and shaping.

Ledge formation is usually caused by careless instrumentation such as, use of a large instrument out of sequence and insertion of the instrument short of the working length, or by use of a straight or inflexible instrument in a curved canal.

The periapical abcess as with any other abcess contains pus and thus harbors obligate anaerobes.

Except “3” option, all others are advantages of gutta percha as a root canal filling material, which was introduced by Bowman in 1867 and is still the material of choice for majority of dentists.

Presence of pulp stone though creating difficulty in cleaning and shaping the root canals is not caused by the dentist. So, it will not be considered under procedural/iatrogenic problems.

Stains caused by pulp necrosis are intrinsic stains, which do not get removed by extrinsically scaling or polishing. These stains need to internally bleached for good results.

All the agents have been used in the past in an attempt to extirpate pulp painlessly. But with the advent of local anesthesia, all these methods have been labeled inadequate, time consuming and archaic.

Compressed air must not be used for drying the root canal because tissue emphysema may result if an air bubble penetrates the periapical tissues. The emphysema may last as long as a week.

Sometimes a multirooted tooth has an untreatable periodontal lesion on one or more of its roots, but the remaining roots are healthy. So, to avoid extraction of the whole tooth that compromised root is removed which is called radisection.

A tooth whose restoration may require a post and core usually is filled with Gutta percha or sectional/split cone silver cone. The cone is notched 6 mm from the apical tip, and it is sterilized and is cemented in the root canal. The wedged cemented cone is rotated until it breaks at the notch, and the free end is removed to leave enough space for preparation of a post.

The root resorption causes maximum failures in replantation of avulsed teeth frequently followed by ankylosis. The two factors, which reduce the chances of failure by resorption are the reduction of extraoral time of the tooth to be less than 30 mts and the initiation of endodontic treatment a week after replantation. Endodontic treatment can be completed within six months of replantation.

Silver nitrate stains are almost impossible to eliminate without grinding because the stains penetrate the surface of the crowns and are difficult to remove by chemical means.