Morphology and Development of Primary and Permanent Teeth l Pediatric dentistry MCQs for dental students

Morphology and Development of Primary and Permanent Teeth l Pediatric dentistry & Children teeth MCQs for dental students

 

Introduction in children teeth & pediatric dentistry

Morphological Terms

Cusp—

• A pointed or rounded projection on the occlusal surface of a tooth.

Pit and Fissure :

• are anatomic landmarks on a tooth where the enamel folds inward. Fissures are formed during the development of grooves but the enamel in the area is not fully fused. As a result, a deep linear depression forms in the enamel’s surface structure. Pit and fissure are vulnerable to caries decay as these structure favor the food lodgment and growth of cariogenic plaque.

Ridge :

• are any linear, flat elevations on teeth, and are named according to their location.

Cingulum :

• is a convexity found on the lingual surface of anterior teeth. It is frequently identifiable as an inverted V -shaped ridge.

Mammelons:

• are three rounded protuberances which are present on the incisal edge of newly erupted incisors. They are the remnants of three lobes of formation of these teeth, the fourth lobe represented by the cingulum .These prominences are developmental structures and are of no clinical significance. Usually they are worn off early in the life of the tooth.

The cusp of Carabelli, or Carabelli’s tubercle :

• is an accessory cusp(fifth cusp) at the mesiopalatal line angle of maxillary first molars.

Oblique ridge:

• is an elevated prominence that crosses the occlusal table of a maxillary molar from the mesiolingual to distobuccal cusp.

Embrasures:

• Embrasures are triangularly shaped spaces located between the proximal surfaces of adjacent teeth. The borders of embrasures are formed by the interdental papilla of the gingiva, the adjacent teeth, and the contact point where the two teeth meet. There are four embrasures for every contact area; facial, lingual (or palatal), occlusal or incisal, and cervical.

   Function of embrasure

1. Form spillways between teeth to direct food away from the gingiva.
2. Provide a mechanism for teeth to be more self cleansing. .
3. Embrasures also protect the gingiva from undue frictional trauma.

N.B

• Human dentition consist two set of teeth, the primary set and permanent set. The primary teeth are 20 in number and consist of a central incisors, lateral incisors, a cuspid. a first molar and a second molar in each quadrant of the mouth from the midline posteriorly.

• The permanent teeth are 32 in number. The permanent dentition consist of central incisors, lateral incisors, canine, First premolar, second premolar, first molar, second molar and third molar in each quadrant of the mouth from midline posteriorly. The permanent incisors, canine and premolars replace and come in position of the primary teeth and are known as succedaneous teeth. The central incisor, lateral and second premolars replace and come in position of the primary teeth and are known as succedaneous teeth.

• The permanent molars which do not replace no primary teeth and erupt posterior to primary teeth are known as accessional teeth.

 

Function of Primary Teeth

1. Digestion and assimilation of the food—The developing child must have adequate diet and nutrition for healthy and normal growth. The primary dentition is very vital and indeed critical for the mechanical preparation of the child’s food for digestion and assimilation during the most active period of growth and development of the child.
2. Function of stimulating the growth of the alveolar bone and jaw. The primary teeth play an important role for stimulating the growth of jaw and of the alveolar bone.
3. Maintenance of dental arch space—primary teeth play very important role for maintaining the dental arch integrity. Early loss of primary teeth may leads to loss of dental arch and subsequent sequel of arch loss which include crowding, ectopic eruption, impaction, malocclusion of the developing permanent dentition. 
4. Role in the development of permanent dentition and occlusion. The presence of physiological spacing, primate or anthropoid spaces, leeway spaces, are vital for a healthy and favorable development of permanent dentition. The intactness of the primary dentition is similarly important for healthy and favorable development of permanent dentition and occlusion. Any premature loss of primary teeth may leads to unfavorable development of permanent dentition and occlusion.
5. Development of speech. The ability to use teeth for pronunciation is acquired entirely with the help of primary teeth. premature loss of primary teeth may leads to difficulties in pronunciation of the sounds f, v, s, z and Th.
6. Aesthetic Primary teeth serve esthetic function by improving the facial appearance of the child which is important for self confidence in child as disfigured teeth make the child self-conscious and this attitude can influence the behavior, activity, self-esteem and performance of the child.

 

Morphological differences between primary and permanent teeth

Primary teeth.

CROWN :

1. No- of primary teeth are—20
2. Primary dentition tenure—6 month to 6 year
3. The enamel and dentin are thinner
4. Absence of mammelons
5. Primary tooth crown is lighter in color. The color of first primary teeth is bluish White in color, also known as milky white. The primary teeth are known as milky white as the refractive index of these teeth is same as that of milk which is 1.
6. The mesiodistal dimension of the crown of the primary teeth are wider than their cervico incisal or cervico-occlusal length .
7. The crown of the primary teeth have a cup shaped (anteriors) or squat appearance (molars).
8. Pronounced cervical ridges or bulge especially on the buccal aspect of primary molar.
9. pronounced cervical constriction and more bulbous crown.
10. Narrow occlusal table due to convergence of buccal. and lingual surfaces towards the occlusal table.
11. Broad and flat contact area.
12. Enamel rods at the cervix orient occlusally from the DE]
13. Supplemental grooves are more.

PULP :

1. Larger pulp chamber relative to crown size
2. Pulp horn are more pronounced and is closer to the outer surface.
3. Primary pulp is highly cellular and vascular .
4. More thickness of dentin over the central fossa of the molars.
5. Radicular pulp is more thin, tortuous and branching path.
6. Pulpal chamber floor is porous- More number of accessory canal in furcation area.
7. Roots are more larger and slender in comparison to crown size.

Permanent teeth

CROWN :

1. No. of permanent teeth—32.
2. Permanent dentition tenure—from 6 year of life onwards.
3. Enamel and dentin are comparatively more thicker.
4. Mamelons are present on the incisal edges of a newly erupted tooth.
5. Permanent tooth is darker in color and are grayish or yellowish white in color.
6. The permanent teeth have more cervico-occlusal dimension than the primary teeth.
7. The crown of the permanent teeth especially anterior has a longer appearance.
8. Cervical ridges are flat.
9. Less pronounced cervical constriction and less bulbous crown.
10. More Wide occlusal table.
11. Contact area are less broad and are situated more occlusally.
12. Enamel rods slope gingivally at the cervix.
13. Supplemental grooves are less.

PULP :

1. Pulp chamber is small relative to crown size.
2. The pulp horns are comparatively less pronounced.
3. As compared to primary pulp, permanent pulp has less degree of pulpal vascularity and cellularity.
4. Less thickness of dentin over the pulpal wall at occlusal fossa of molars.
5. Radicular pulp is large and round.
6. Pulpal floor have no accessory canal.
7. Roots are shorter as compared to crown.