A Comprehensive Guide to Primary Teeth: Morphology, Development, and Dental Care
Distinguishing Morphological Differences Between Primary and Permanent Teeth
1. The crowns of primary teeth are wider mesiodistally in comparison to crown length than those of permanent teeth.
2. Anterior primary teeth are narrow and long, with notable crown width and length.
3. The roots of primary molars are relatively longer and more slender than the roots of permanent teeth.
4. The cervical ridge of enamel at the cervical third of the anterior crowns is much more prominent labially and lingually in primary teeth than in permanent teeth.
5. The crowns and roots of primary molars are more slender mesiodistally at the cervical third than are those of permanent molars.
6. The cervical ridge on the buccal aspect of the primary molars is much more definite, particularly on the maxillary and mandibular first molars, than that on the permanent molars.
7. The buccal and lingual surfaces of primary molars are flatter above the cervical curvatures than those of permanent molars, which makes the occlusal surface narrower compared with that of permanent teeth.
8. Primary teeth are usually lighter in color than permanent teeth.
Considerations Due to Differences in Morphology
- Special care is required in the formation of the gingival floor during Class II restorations due to the constriction of the neck of primary teeth.
- There is a greater chance of pulp exposure during cavity preparation due to the large pulp chamber.
- The enamel of primary teeth is thin but of uniform thickness.
- Bulbous crowns of primary molars make matrix placement more difficult.
- Porosity in the pulpal floor of primary teeth has been noticed in comparison with permanent teeth.
Maxillary Canine
There is a well-developed sharp cusp.
Straight incisal edge.
Long, slender, tapering root.
Mandibular Central Incisor
Labiolingual measurement is usually only 1mm less than the maxillary central incisor.
The labial aspect presents a flat surface without developmental grooves.
The root is twice the length of the crown.
Mandibular Lateral Incisor
Larger than the mandibular central incisor in all dimensions except labiolingually.
The lingual surface has greater concavity between the marginal ridges.
Incisal edge slopes toward the distal aspect of the tooth.
Mandibular Canine
Similar to the maxillary canine with a few exceptions:
- The crown is slightly shorter.
- The mandibular canine is not as large labiolingually as the maxillary canine.
Mandibular First Molar
Does not resemble any other tooth.
Crown height is greater mesially than distally.
Mesial marginal ridge is very well developed.
Prominent buccal cervical ridge.
Rhomboid outline.
Mandibular Second Molar
Resembles the mandibular first permanent molar.
Five cusps: 3 buccal and 2 lingual.
The 3 buccal cusps are more equal in size.
Periods of Dental Development
1. The Pre-Dentition Period
From birth until the eruption of the first primary tooth.
- The alveolar processes are covered with gum pads.
- Gum pads are divided into labial portions and lingual portions and separated by lingual grooves.
- Gum pads are segmented into 20 segments by transverse grooves.
2. Primary Dentition
Tooth eruption, which is the continuous process of movement of teeth (A, B, D, C, E – ABDCE).
- Begins at about 6-7 months.
Variables that influence eruption:
- Genetics (familial tendencies – African Americans)
- Environmental factors (delayed in low birth weight and ventilator-dependent infants)
- Systemic factors (hyperthyroidism)
3. Mixed Dentition
The period where both primary and permanent teeth are in the mouth together.
- From 6-12 years.
Sequence of eruption:
- Mandible: First molar, central incisor, lateral incisor, canine, first premolar, second premolar, second molar.
- Maxilla: First molar, central incisor, lateral incisor, first premolar, second premolar, canine, second molar.
Problems associated with eruption:
- Difficult eruption
- Eruption cyst and eruption hematoma
- Eruption sequestrum
- Natal and neonatal teeth
Types of Examination Appointments
Complete, recall, emergency.
Aims of the First Session with a Child Patient
- Establish good communication with the child and parent.
- Obtain important background information.
- Examine the child and obtain x-rays if required.
- Introduce the child to a simple treatment procedure.
- Explain treatment aims to the child and parent.
Steps of the First Appointment
- Initial interview and case history.
- Extraoral examination.
- Intraoral soft tissue examination.
- Intraoral hard tissue examination.
- Radiographic examination.
- Special investigations.
Radiographs Used in Pediatric Dentistry
Bitewing, periapical, panoramic, occlusal films, extraoral facial films.
Guidelines for Treatment Planning
- Treatment sessions must be planned efficiently and effectively.
- Use quadrant dentistry.
- Treat posterior teeth before anterior teeth.
- Incipient lesions should always be restored in a caries-active child.
- The last restorative visit should be minimal.
- Always treat the area that is painful to the patient.
Treatment Plan
1. Medical Phase
Patients with a positive medical history are referred to a pediatrician for evaluation and consent.
2. Systemic Phase
Any medication given to modify dental treatment is included in this phase.
3. Preventive Phase
Oral hygiene consultation, oral prophylaxis, pit and fissure sealant, diet consultation.
4. Corrective Phase
Operative dentistry (extraction and minor surgery), space maintainers, orthodontics.
5. Maintenance and Recall
No treatment plan is complete without a recall appointment and follow-up.