Dental Anatomy & Occlusion

1.

Which characteristic below is common to all mandibular anterior teeth?
- A.
  
  Distinct cingula with grooves and pits
- B.
  
  Incisal edges that are facial to the root axis line
- C.
  
  Facial surfaces that are marked by pronounced labial ridges
- D.
  
  Continuous convexity incisoapically on the facial surface
Correct Answer
D. Continuous convexity incisoapically on the facial surface

Explanation
Three Characteristics of all mandibular anterior teeth:
1. Indistinct cingula with smooth lingual anatomy without grooves and pits
2. Incisal edges lingual to the root axis line
3. Continuous convexity incisoapically on the facial surface

Specific information pertaining to mandibular central incisors:
They only occlude with one other tooth

Remember: the Canines (both maxillary and mandibular) are the only teeth with labial ridges

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2.

A clinical examination of your patient reveals two lower incisors centered on the midline. The patient gives a history of a car accident when he was young where he lost two of his lower front teeth. He says that his dentist used braces to fill in the gaps. Which of the following criteria would be most reliable to decide if the remaining teeth were lateral or central incisors?
- A.
  
  Difference in root length
- B.
  
  Difference in ratio of crown length to root length
- C.
  
  Degree of slope of the incisal edge when viewed facially
- D.
  
  Difference in rotation of the crown on the root
Correct Answer
D. Difference in rotation of the crown on the root

Explanation
***The mandibular lateral incisor crown tips slightly to the distal relative to the root (facial view)
Other ways to distinguis the mandibular lateral from the mandibular central:
-The lateral is larger overall (especially mesiodistally)
-The lateral is not as bilaterally symmetrical as the central incisor
- The cingulum on the lateral is slightly distal to the center
On the lateral incisor, the mesial marginal ridge is longer than the distal marginal ridge. On centrals, they are the same length
-Lateral incisors have the distal proximal contacts more apical than the mesial contacts. Centrals are at the same level
-Lateral incisors have the distoincisal angels more rounded than the mesioincisal angles. On centrals, the angles are nearly the same
Note: Both the mandibular central and lateral have a lingual cervical line that is positioned more apically than the facial cervical line.

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Dental Anatomy & Occlusion

Which characteristic below is common to all mandibular anterior teeth?