3. Which one of the following is true? I. While opening an access cavity in premolars and molars with large restoration, a serious loss of material occurs in the crown which may result in fractures. II. Opening in access cavity wider than needed in size would prevent access to certain canals III. Opening access cavities excessively wider may in premolars and molars with large restoration, a serious loss of material occurs in the crown, which may result in fractures. a. Only I b. I and II c. Only III d. I and III e. I, II and III

The correct answer is:<br /><br />d. I and III<br /><br />Explanation:<br />I. While opening an access cavity in premolars and molars with large restoration, a serious loss of material occurs in the crown which may result in fractures. This statement is true as excessive removal of tooth structure during the preparation for a restoration can lead to fractures in the crown.<br /><br />III. Opening access cavities excessively wider may result in a serious loss of material occurs in the crown, which may result in fractures. This statement is also true as creating an access cavity that is too wide can compromise the structural integrity of the tooth and increase the risk of fractures.<br /><br />II. Opening in access cavity wider than needed in size would prevent access to certain canals. This statement is not necessarily true as the size of the access cavity is determined by the specific needs of the tooth and the canals being accessed. It is not inherently true that making the access cavity wider than needed would prevent access to certain canals.