introduction l tooth crown & root morphology MCQs for dental students

introduction l tooth crown & root morphology MCQs (multiple choice question) for dental students

 introduction in Dental anatomy

Overview

•           Each tooth has two parts—crown and root—separated by a cervical line or cementoenamel junction.
•           Each tooth is composed of the following surfaces: facial (labial/buccal), proximal (mesial/distal), masticatory (incisal/occlusal) and palatal/lingual surfaces.
•           The crown and root are traditionally classified into three-third cervico-occlusally, faciolingually and mesiodistally for description purposes.
•           The anatomical landmarks in the crown are cusp, tubercle, lobe, cingulum, ridge, fossa, groove, sulcus and pits while anatomical landmarks in the root are the apex, apical foramen, root trunk and furcation area.

INTRODUCTION

• The subject Tooth Morphology involves the study of the anatomical topography of teeth. Learning about the terminologies is important to understand the subject in a better manner.

PARTS OF A TOOTH

• Each tooth has two parts—crown and root— separated by a cervical line or cementoenamel junction (CEJ).

Crown

•           The crown is the portion of the tooth which is covered by enamel. The crown portion may have an incisal ridge or edge in the case of an incisor or a single or two or more cusps in the cases of canines, premolars and molars.
•           On the basis of the position of the crown in the oral cavity, two types of crown terminologies are used which are as follows:

1. Anatomical crown: 

• It refers to the crown (entire) which is covered by enamel, regardless of whether it is completely erupted or not. The size of the anatomical crown remains constant throughout the lifetime of the tooth, except in cases of attrition or any other physical wearing of tooth surface.

Applied Morphology

• If sufficient anatomical crown is not present for placing full restorative crowns, pins or posts can be placed in the root following root canal treatment to build up the crown height with restorative materials.

2. Clinical crown:

• It refers to the crown which is visible clinically, and it is what one sees when looking into the mouth. The height of the clinical crown is determined by the position of the gingival margin.
• The clinical crown may be smaller than the anatomical crown, such as in a newly erupted tooth where only a part of the anatomical crown is visible and the cervical portion of the crown is still covered by gingiva.
• The clinical crown can also be larger than the anatomical crown in cases where there has been recession of the gingiva with root exposure.

Root

• The portion of the tooth covered by cementum is known as the root. The tooth may have either a single root or multiple roots. Single roots are seen in anterior teeth, mandibular premolars and maxillary second premolars. Multiple roots are seen in molars and premolars. 
• In maxillary first premolars and mandibular molars, two roots are present, and in maxillary molars, three roots are present Bifurcation or trifurcation is the term used for the division of the root into two or three segments, i.e., bifurcation is seen in maxillary first premolars and mandibular molars and trifurcation is seen in maxillary molars.