Tooth development is commonly divided into the following stages: the bud stage, the cap, the bell, and finally maturation. The staging of tooth development is an attempt to categorize changes that take place along a continuum; frequently it is difficult to decide what stage should be assigned to a particular developing tooth. This determination is further complicated by the varying appearance of different histological sections of the same developing tooth, which can appear to be different stages.

Bud stage

The bud stage is characterized by the appearance of a tooth bud without a clear arrangement of cells. The stage technically begins once epithelial cells proliferate into the ectomesenchyme of the jaw. The tooth bud itself is the group of cells at the end of the dental lamina.

Alveolar bone (process)

1. The bone in the jaws that contains the teeth alveoli (sockets).

2. Three types of bone :

a. Cribriform plate (alveolar bone proper)

(1) Directly lines and forms the tooth socket. It is compact bone that contains many holes, allowing for the passage of blood vessels. It has no periosteum.

(2) Serves as the attachment site for PDL (Sharpey’s) fibers.

(3) The tooth socket is constantly being remodeled in response to occlusal forces. The bone laid down on the cribriform plate, which also provides attachment for PDL fibers, is known as bundle bone.

(4) It is radiographically known as the lamina dura.

b. Cortical (compact) bone

(1) Lines the buccal and lingual surfaces of the mandible and maxilla.

(2) Is typical compact bone with a periosteum and contains Haversian systems.

(3) Is generally thinner in the maxilla and thicker in the mandible, especially around the buccal area of  the mandibular premolar and molar.

c. Trabecular (cancellous, spongy) bone

(1) Is typical cancellous bone containing Haversian systems.

(2) Is absent in the maxillary anterior teeth region.

3. Alveolar crest (septa)

a. The height of the alveolar crest is usually 1.5 to 2 mm below the CEJ junction.

b. The width is determined by the shape of adjacent teeth.

(1) Narrow crests—found between teeth with relatively flat surfaces.

(2) Widened crests—found between teeth with convex surfaces or teeth spaced apart.

The very first histological evidence of tooth development appear during the second month of intrauterine life. Calcification of deciduous incisors begins at 3-4 months in utero.

MAXILLARY SECOND MOLAR

The second molars are often called 12-year molars because they erupt when a child is about 12 years

Facial: The crown is shorter occluso-cervically and narrower mesiodistally whe compared to the first molar. The distobuccal cusp is visibly smaller than the mesiobuccal cusp. The two buccal roots are more nearly parallel. The roots are more parallel; the apex of the mesial root is on line with the with the buccal developmental groove. Mesial and distal roots tend to be about the same length.

Lingual: The distolingual cusp is smaller than the mesiolingual cusp. The Carabelli trait is absent.

Proximal: The crown is shorter than the first molar and the palatal root has less diverence. The roots tend to remain within the crown profile.

Occlusal: The distolingual cusp is smaller on the second than on the first molar. When it is much reduced in size, the crown outline is described as 'heart-shaped.' The Carabelli trait is usually absent. The order of cusp size, largest to smallest, is the same as the first but is more exaggerated: mesiolingual, mesiobuccal, distobuccal, and distolingual.

Contact Points; Height of Curvature: Both mesial and distal contacts tend to be centered buccolingually below the marginal ridges. Since themolars become shorter, moving from first to this molar, the contacts tend to appear more toward the center of the proximal surfaces.

Roots: There are three roots, two buccal and one lingual. The roots are less divergent than the first with their apices usually falling within the crown profile. The buccal roots tend to incline to the distal.

Note: The distolingual cusp is the most variable feature of this tooth. When it is large, the occlusal is somewhat rhomboidal; when reduced in size the crown is described as triangual or 'heart-shaped.' At times, the root may be fused.

Nutrition and tooth development

As in other aspects of human growth and development, nutrition has an effect on the developing tooth. Essential nutrients for a healthy tooth include calcium, phosphorus, fluoride, and vitamins A, C, and D. Calcium and phosphorus are needed to properly form the hydroxyapatite crystals, and their levels in the blood are maintained by Vitamin D. Vitamin A is necessary for the formation of keratin, as Vitamin C is for collagen. Fluoride is incorporated into the hydroxyapatite crystal of a developing tooth and makes it more resistant to demineralization and subsequent decay.

Deficiencies of these nutrients can have a wide range of effects on tooth development. In situations where calcium, phosphorus, and vitamin D are deficient, the hard structures of a tooth may be less mineralized. A lack of vitamin A can cause a reduction in the amount of enamel formation. Fluoride deficency causes increased demineralization when the tooth is exposed to an acidic environment, and also delays remineralization. Furthermore, an excess of fluoride while a tooth is in development can lead to a condition known as fluorosis.