RDA Dental Charting, Tooth Morphology, and Occlusion 2 — Questions and Answers

Question 1: Using the Universal Numbering System, what number is assigned to the maxillary left central incisor?

#8
#9 (Correct answer)
#24
#25

Correct answer: #9

In the Universal Numbering System, #9 is the maxillary left central incisor. Numbering begins at #1 (upper right third molar) and goes across the top to #16, then down to #17 and across the bottom to #32.

The Universal (ADA) Numbering System numbers permanent teeth 1–32. Beginning with #1 at the maxillary right third molar, numbers proceed across the maxillary arch to #16 at the maxillary left third molar, then drop to #17 at the mandibular left third molar and proceed back to #32 at the mandibular right third molar. The maxillary right central incisor is #8; the maxillary left central incisor is #9. Primary teeth use letters A–T.

Question 2: Which tooth surface faces toward the cheek?

Lingual
Mesial
Buccal (Correct answer)
Occlusal

Correct answer: Buccal

The buccal surface faces the cheek (buccinator muscle). For anterior teeth, the term 'labial' is used instead, referring to the surface facing the lips.

Tooth surfaces are named by their orientation: buccal (toward the cheek for posterior teeth), labial (toward the lips for anterior teeth), lingual (toward the tongue), mesial (toward the midline), distal (away from the midline), and occlusal/incisal (the biting surface). Correct surface identification is essential for dental charting, identifying cavity locations, and communicating treatment needs.

Question 3: What is the name of the type of occlusion where the mesiobuccal cusp of the maxillary first molar occludes in the buccal groove of the mandibular first molar?

Class II, Division 1
Class I (Correct answer)
Class III
End-to-end

Correct answer: Class I

Class I occlusion (Angle's Classification) describes the ideal relationship where the mesiobuccal cusp of the maxillary first molar occludes in the buccal groove of the mandibular first molar.

Angle's Classification of Occlusion describes the molar relationship: Class I is ideal, with the mesiobuccal cusp of the maxillary first molar in the buccal groove of the mandibular first molar. Class II (retrognathic) has the mandible positioned posteriorly, further divided into Division 1 (protruded maxillary anteriors) and Division 2 (retroclined maxillary anteriors). Class III (prognathic) has the mandible positioned anteriorly. These classifications guide orthodontic diagnosis and treatment planning.

Question 4: On a dental chart, which symbol typically indicates a tooth that has been extracted?

Circle around the tooth number
X through the tooth (Correct answer)
Red outline
Blue shading

Correct answer: X through the tooth

A tooth that has been extracted is typically indicated by an X through the tooth number or diagram on a dental chart.

Dental charting uses standardized symbols to communicate clinical findings. An X through a tooth or tooth number indicates extraction. Other common symbols include: circles or outlines for existing restorations (often color-coded: blue/black for existing, red for treatment needed), diagonal lines for decayed surfaces, and specific symbols for crowns, bridges, implants, and root canals. Consistent charting is essential for legal documentation and continuity of care.

Question 5: Which permanent tooth has a distinctive Carabelli's cusp?

Mandibular first molar
Maxillary first molar (Correct answer)
Maxillary first premolar
Mandibular second premolar

Correct answer: Maxillary first molar

Carabelli's cusp (or cusp of Carabelli) is a fifth cusp sometimes found on the mesiolingual surface of the maxillary first molar. It is a morphological variation.

The cusp of Carabelli is an accessory cusp located on the mesiolingual surface of the maxillary first molar. It is a common morphological variant, present in varying degrees in a significant portion of the population. It may range from a slight groove to a fully developed cusp. Its presence is important for tooth identification in forensic dentistry and for understanding normal crown morphology. The maxillary first molar has four major cusps (mesiolingual, distolingual, mesiobuccal, distobuccal) plus the occasional Carabelli cusp.

Question 6: What is the name of the space between two adjacent teeth?

Sulcus
Embrasure
Interproximal space (Correct answer)
Furcation

Correct answer: Interproximal space

The interproximal space (also called the interdental space) is the space between adjacent teeth, normally occupied by the interdental papilla.

The interproximal (interdental) space exists between adjacent teeth in the dental arch. In a healthy dentition, this space is filled by the interdental papilla. The embrasure is the V-shaped space formed by the diverging tooth surfaces above the contact area, classified as facial, lingual, occlusal/incisal, or gingival embrasures. Proper understanding of interproximal anatomy is essential for flossing instruction, restoration design, and periodontal assessment.

RDA Dental Charting, Tooth Morphology, and Occlusion 2

Using the Universal Numbering System, what number is assigned to the maxillary left central incisor?