Dental Anatomy Question And Answers

Dental Anatomy

Question 1. Write briefly about different tooth numbering systems.
(or)
FDI system of dental nomenclature.

Answer:

It is necessary to substitute the lengthy names of the individual teeth with some symbol.

• Thus, various numbering teeth by some symbol were introduced to designate individual teeth by a number or alphabetical letter.

1. Zsigmondy/palmer system:

1. It was introduced by Adolph Zsigmondy of Vienna in 1861 for permanent dentition and modified for primary dentition in 1874.

Read And Learn More: BDS Previous Examination Question And Answers

For permanent dentition:

• As per this system, the oral cavity is divided into four quadrants and each permanent tooth has a specific number.
• Numbering progresses posteriorly from the midline.
• The central incisor was designated as 1 ending up with 8 for the third molar.

\(\begin{array}{l|l}
87654321 & 12345678 \\
\hline 87654321 & 12345678
\end{array}\)

For primary dentition:

• The deciduous central incisors are designated A & progress posteriorly up to the 2nd deciduous molar alphabetically designated E.

\(\begin{array}{l|l}
\text { EDCBA } & \text { ABCDE } \\
\hline \text { EDCBA } & \text { ABCDE }
\end{array}\)

2. Universal system:

For permanent dentition:

• In this system, the numbering starts from the right maxillary 3rd molar designated 1 to 16 designated to the left maxillary 3rd molar.
• Then beginning with the mandibular left 3rd molar, the teeth are numbered 17 to 32.

\(\begin{array}{l|l}
12345678 & 910111213141516 \\
\hline 3231302928272625 & 2423222120191817
\end{array}\)

For primary dentition:

• Alphabets are used starting from A-J for maxillary left 2nd molar.
• Then beginning with the mandibular left 2nd molar, the teeth are named K to T.

\(\begin{array}{l|l}
\text { ABCED } & \text { FGH I J } \\
\hline \text { TSRQP } & \text { ONMLK }
\end{array}\)

3. FDI numbering system:

• It is a two-digit system proposed by the federation dentaire international (FDI)

For permanent dentition:

• The first digit indicates the quadrant and is numbered from 1 to 4.
• The second digit indicates the tooth number starting from the central incisor as 1 to the 3rd molar as 8.

Thus,

For primary dentition:

\(\begin{array}{l|l}
1817161514131211 & 2122232425262728 \\
\hline 4847464544434241 & 3132333435363738
\end{array}\)

• The first digit indicating quadrant is numbered from 5 to 8.
• The second digit is numbered from 1 to 5 from the central incisor to 2nd molar

\(\begin{array}{l|l}
5554535251 & 6162636465 \\
\hline 8584838281 & 7172737475
\end{array}\)

Question 2. CUSP.
Answer:

• It is an elevation or mound on the crown portion of a tooth making up a divisional part of the occlusal surface.
• It is an integral part of the occlusal surface.
• Generally, posterior teeth will have cusps.
• Different sets of teeth have different numbers of cusps.
• Example: Mandibular 1st permanent molar has 5 cusps.
• A small cusp, for example, cusps of clarabella present over permanent maxillary first molar is called caplet.

Function:

• Shearing & tearing of food substances.

Question 3. Ridge.
Answer:

• It is any linear elevation on the surface of a tooth. It is named according to its location.

1. Marginal ridge:

• They are rounded borders of the enamel forming mesial and distal margins of the occlusal surfaces of posterior teeth and lingual surfaces of certain anterior teeth.

2. Traingular ridge:

• It is a ridge descending from the cusp tip of the premolars and molars towards the central part of the occlusal surface.

3. Oblique ridge:

• It crosses the occlusal surfaces of maxillary molars obliquely.
• It is formed by the union of the triangular ridge of the distobuccal cusp and the distal cusp ridge of the mesiolingual cusp.

4. Transverse ridge:

• It is formed by buccal and lingual triangular ridges.

Question 4. Fossa.
Answer:

• It is an irregular depression or concavity found on the tooth surface.

Depending on their locations, they are named as:

1. Lingual fossa – on the lingual surface of incisor.
2. Central fossa – On the occlusal surface of molars.
3. Triangular fossa – On occlusal surfaces of molars & premolars mesial or distal to the marginal ridges.
   • Sometimes found on the lingual surfaces of maxillary incisors at the edge of the lingual fossae.

Question 5. Sulcus.
Answer:

• It is a long depression or valley over the occlusal surfaces of the posterior teeth between the ridges and cusps.
• The inclines of the valley meet at an angle.
• It has a development groove at the junction of its incline.

Question 6. Grooves.
Answer:

• They are development faults, clefts, or shallow grooves usually found on the occlusal or buccal& lingual surfaces of posterior teeth.

1. Development groove:

• A groove separates the primary parts of the crown or root.

2. Supplemental groove:

• It is a shallow linear depression on the tooth surface, supplemental to the developmental groove.

3. Buccal and lingual grooves:

• Found on the buccal and lingual surfaces of posterior teeth.

Appearance:

• They may be

1. Shallow and wide
2. Deep and narrow

Function:

• Play an important role in the initiation of tooth decay.

Question 7. Pits.
Answer:

• These are small or pin-point deep depressions in enamel, sometimes in dentin.

Site:

• At the junction of developmental grooves or at the terminals of those grooves.
• The central pit is located in the central fossa. Fossa of molars where developmental grooves join.

Significance:

• They act as areas for the initiation of dental carries.

Question  8. Mamelons.
Answer:

• It is any one of the three rounded protuberances found on the incisal ridges of newly erupted incisor teeth.

Significance:

• It represents a primary section of the formation in the development of the crown.

Fate:

• They are worn out with usage.

Variation:

• They may be missing by birth as in the case of congenital syphilis.

Question 9. Tubercle and cingulum.
Answer:

Tubercle:

• It is a smaller elevation on some portion of the crown produced by an extra formation of enamel.

Cingulum:

• It is the lingual lobe of an anterior tooth.
• It makes up the bulk of the cervical third of the lingual surface.

Question 10. Line angle and point angle.
Answer:

Line angle:

• It is formed by the junction of two surfaces and is named after the two surfaces forming this angle.
• The line angles in the anterior teeth are
  • Mesiolabial, distolabial
  • Mesiolingual, distolingual
  • Labioincisal, linguoincisal.
• Line angles for posterior teeth are
• • Mesiobuccal, distobuccal
  • Mesiolingual, distolingual
  • Mesio-occlusal, distoocclusal
  • Bucco-occlusal, linguo-occlusal.

Point angle:

• It is formed by the junction of three surfaces and is named after the surfaces forming it.
• The point angles of anterior teeth are.
  • Mesiobuccoocclusal
  • Distobuccooclusal
  • Mesiolinguoocclusal
  • Distolinguoocclusal

Question 11. Crown.
Answer:

• Each tooth is made up of a crown and root.
• The crown is covered by enamel
• The junction between the crown and root is called Cemento Enamel Junction (CEJ) or cervical line.
• The main bulk of the crown is made up of dentin.
• It also contains a pulp chamber.
• It has
  • An incisal edge in incisors
  • One cusp in canine
  • Two/more cusps in premolars and molars.
• It is never covered by bone tissue after it is fully erupted but is partly covered by soft tissue called gingiva.

Question 12. Dental formula.
Answer:

• The denomination of each tooth is represented by the initial letter in its name.
• I-incisors, C-canine, P-premolar, M-molar.
• Each letter is followed by a horizontal line and the number of each type of tooth is placed above the line for maxilla and below the line for mandible.
• The formula includes one side only.
• The formula for deciduous teeth is.

\(\mathrm{I} \frac{2}{2} \quad \mathrm{C} \frac{1}{1} \mathrm{M} \frac{3}{3}=10[latex]

• The formula for permanent teeth is

[latex]\mathrm{I} \frac{2}{2} \mathrm{C} \frac{1}{1} \mathrm{P} \frac{2}{2} \mathrm{M} \frac{3}{3}=16\)

Question 13. Name tooth numbering systems.
Answer:

• Zsigmondy/plamer system
• Universal notation system.
• Two-digit system by FDI

Question 14. Define: fissure, ridge
Answer:

Fissure:

• Fissure is defined as the deep cleft between adjoining cusps
• It consists of an organic plug composed of reduced enamel epithelium, microorganisms forming dental plaque, and oral debris
• It has increased susceptibility to caries

Ridge:

• It is any linear elevation on the surface of the tooth
• It is named according to its location – buccal ridge, incisal ridge, marginal ridge.