lntraarch relationship refers to the alignment of the teeth within an arch

1. In an ideal alignment teeth should contact at their proximal crests of curvature. A continuous arch form is observed in occlusal view

Curves of the occlusal plane (a line connecting the cusp tips of the canines, premolars, and molars) are observed from the proximal view

Curve of Spee: anterior to posterior curve; for mandibular teeth the curve is concave and for maxillary teeth it is convex

Curve of Wilson- medial to lateral curve for mandibular teeth the curve is also convex and for the maxillary it is convex

2. Contact does not always exist Some permanent dentitions have normal spacing

Primary dentitions often have developmental spacing in the anterior area: some primary den titions have a pattern of spacing called primate spaces between the primary maxillary lateral incisors and canine and between the mandibular canine and first mo1ar

Disturbances to the intraarch alignment are described as

a. Qpen contact where interproximal space exist  because of missing teeth oral habits, dental disease, or overdeveloped frena

b. where contact or position is at an unexpected area because of developmental disturbances, crowding, dental caries or periodontal ligament for their misplaced position: facial, lingual. mesial, supra(supraerupted) infra (infraerupted) and torso (rotated) version

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.

ERUPTION OF THE PERMANENT TOOTH

- At the time at which the deciduous tooth erupts the tooth bud for the permanent tooth has already been building up enamel and dentin.

- When the permanent tooth starts to erupt, pressure on the root of the deciduous tooth causes resorption by the osteoclasts.

- Wolff's law states that when two hard tissues exert pressure on one another the softer of the tissues will be resorbed.

- The dentin and cementum of the root of the deciduous tooth is softer than the enamel of the permanent tooth that is why the root of the deciduous tooth is resorbed.

- Most permanent teeth have erupted and have been in use for 2 years before the root is completely formed.

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.

Dental Terminology.

Cusp: a point or peak on the occlusal surface of molar and premolar teeth and on the incisal edges of canines.

Contact: a point or area where one tooth is in contact (touching) another tooth

Cingulum: a bulge or elevation on the lingual surface of incisors or canines. It makes up the bulk of the cervical third of the lingual surface. Its convexity mesiodistally resembles a girdle  encircling the lingual surface at the cervical.

Fissure: A linear fault that sometimes occurs in a developmental groove by incomplete or imperfect joining of the lobes. A pit is usually found at the end of a developmental groove or a place where two fissures intersect.

Lobe: one of the primary centers of formation in the development of the crown of the tooth.

Mamelon: A lobe seen on anterior teeth; any one of three rounded protuberances seen on the unworn surfaces of freshly erupted anterior teeth.

Ridge: Any linear elevation on the surface of a tooth. It is named according to its location or form. Examples are buccal ridges, incisal ridges, marginal ridges, and so on.

Marginal ridges are those rounded borders of enamel which form the margins of the surfaces of premolars and molars, mesially and distally, and the mesial and distal margins of the incisors and canines lingually.

Triangular ridges are those ridges which descend from the tips of the cusps of molars and premolars toward the central part of the occlusal surface. Transverse ridges are created when a buccal and lingual triangular ridge join.

Oblique ridges are seen on maxillary molars and are a companion to the distal oblique groove.

Cervical ridges are the height of contour at the gingival, on certain deciduous and permanent teeth.

Fossa: An irregular, rounded depression or concavity found on the surface of a tooth. A lingual fossa is found on the lingual surface of incisors. A central fossa is found on the occlusal surface of a molar. They are formed by the converging of ridges terminating at a central point in the bottom of a depression where there is a junction of grooves

Pit: A small pinpoint depression located at the junction of developmental grooves or at the terminals of these groops. A central pit is found in the central fossa on the occlusal surfaces of molars where developmental grooves join. A pit is often the site of the onset of Dental  caries

Developmental groove: A sharply defined, narrow and linear depression formed during tooth development and usually separating lobes or major portions of a tooth.

A supplemental groove is also a shallow linear depression but it is usually less distinct and is more variable than a developmental groove and does not mark the junction of primary parts of a tooth.

Buccal and lingual grooves are developmental grooves found on the buccal and lingual surfaces of posterior teeth.

Tubercle: A small elevation produced by an extra formation of enamel. These occur on the marginal ridges of posterior teeth or on the cingulum of anterior teeth. These are deviations from the typical form.

Interproximal space: The triangular space between the adjacent teeth cervical to the contact point. The base of the triangle is the alveolar bone; the sides are the proximal surfaces of the adjacent teeth.

Sulcus:-An elongated valley or depression in the surface of a tooth formed by the inclines of adjacent cusp or ridges.

Embrasures: When two teeth in the same arch are in contact, their curvatures adjacent to the contact areas form spillway spaces called embrasures. There are three embrasures:

(1) Facial (buccal or labial)

(2) Occlusal or incisal

(3) Lingual

(NOTE: there are three embrasures; the fourth potential space is the interproximal space ).

Maxillary Second Deciduous Molar.

-The notation is A or J.

-It looks like a first permanent molar

-There are three roots.

-Usually it has four well developed cusps.

-It is somwhat rhomboidal in outline.

-They often have the Carabelli trait.

- the shape the maxillary first permanent molar strongly resembles that of the adjacent deciduous second molar.