The mixed dentition

I. Transition dentition between 6 and 12 years of age with primary tooth exfoliation and permanent tooth eruption

2. Its characteristic features have led this to be called the ugly duckling stage because of

a. Edentulated areas

b. Disproportionately sized teeth

c. Various clinical crown heights

d. Crowding

e. Enlarged and edematous gingiva

f. Different tooth colors

INNERVATION OF THE DENTIN-PULP COMPLEX

1. Dentine Pulp
2. Dentin
3. Nerve Fibre Bundle
4. Nerve fibres

The nerve bundles entering the tooth pulp consist principally of sensory afferent fibers from the trigeminal nerve and sympathetic branches from the superior cervical ganglion. There are non-myelinated (C fibers) and myelinated (less than non, A-delta, A-beta) fibers. Some nerve endings terminate on or in association with the odontoblasts and others in the predentinal tubules of the crown. Few fibers are found among odontoblasts of the root.
In the cell-free zone one can find the plexus of Raschkow.

The periodontium, which is the supporting structure of a tooth, consists of the cementum, periodontal ligaments, gingiva, and alveolar bone. Cementum is the only one of these that is a part of a tooth. Alveolar bone surrounds the roots of teeth to provide support and creates what is commonly called a "socket". Periodontal ligaments connect the alveolar bone to the cementum, and the gingiva is the surrounding tissue visible in the mouth.

Periodontal ligaments

Histology of the Periodontal Ligament (PDL)

Embryogenesis of the periodontal ligament
The PDL forms from the dental follicle shortly after root development begins
The periodontal ligament is characterized by connective tissue. The thinnest portion is at the middle third of the root. Its width decreases with age. It is a tissue with a high turnover rate.

MAXILLARY FIRST BICUSPID (PREMOLARS)

It is considered to be the typical bicuspid. (The word "bicuspid" means "having two cusps.")

Facial: The buccal surface is quite rounded and this tooth resembles the maxillary canine. The buccal cusp is long; from that cusp tip, the prominent buccal ridge descends to the cervical line of the tooth.

Lingual: The lingual cusp is smaller and the tip of that cusp is shifted toward the mesial. The lingual surface is rounded in all aspects.

Proximal: The mesial aspect of this tooth has a distinctive concavity in the cervical third that extends onto the root. It is called variously the mesial developmental depression, mesial concavity, or the 'canine fossa'--a misleading description since it is on the premolar. The distal aspect of the maxillary first permanent molar also has a developmental depression. The mesial marginal developmental groove is a distinctive feature of this tooth.

Occlusal: There are two well-defined cusps buccal and lingual. The larger cusp is the buccal; its cusp tip is located midway mesiodistally. The lingual cusp tip is shifted mesially. The occlusal outline presents a hexagonal appearance. On the mesial marginal ridge is a distinctive feature, the mesial marginal developmental groove.

Contact Points;The distal contact area is located more buccal than is the mesial contact area.

Root Surface:-The root is quite flat on the mesial and distal surfaces. In about 50 percent of maxillary first bicuspids, the root is divided in the apical third, and when it so divided, the tips of the facial and lingual roots are slender and finely tapered.

THE DECIDUOUS DENTITION

I. The Deciduous Dentition

-It is also known as the primary, baby, milk or lacteal dentition.

diphyodont, that is, with two sets of teeth. The term deciduous means literally 'to fall off.'

  There are twenty deciduous teeth that are classified into three classes. There are ten maxillary teeth and ten mandibular teeth. The dentition consists of incisors, canines and molars.

Introduction. The Jaws and Dental Arches

The teeth are arranged in upper and lower arches. Those of the upper are called maxillary; those of the lower are mandibular.

1. The maxilla is actually two bones forming the upper jaw; they are rigidly attached to the skull..
2. The mandible is a horseshoe shaped bone which articulates with the skull by way of the temporomandibular joint the TMJ.
3. The dental arches, the individual row of teeth forming a tooth row attached to their respective jaw bones have a distinctive shape known as a catenary arch.