Angle classified these relationships by using the first permanent molars

Normal or neutral occlusion (ideal):

Mesiobuccalgroove of the mandibular first molar align with the mesiobuccal cusp of the max laxy first permanent molar

ClassI  malocclusion  normal molar relationships with alterations to other characteristics of the occlusion such as versions, crossbites, excessive overjets, or overbites

Class II malocclusion a distal relation of the mesiobuccal groove of the mandibular first permanent molar to the mesiobuccal cusp of the maxillary first permanent molar

Division I: protruded maxillary anterior teeth

Division II: one or more maxillary anterior teeth retruded

Class III  malocclusion a mesial relation of the mesiobuccal groove of the mandibular first permanent molar to the mesiobuccal cusp of the maxillary molar

HISTOLOGY OF SALIVARY GLANDS

Parotid: so-called watery serous saliva rich in amylase
Submandibular gland: more mucinous
Sublingual: viscous saliva

Parotid Gland:  The parotid is a serous secreting gland.

There are also fat cells in the parotid.

Submandibular Gland

This gland is serous and mucous secreting.

There are serous demilunes

This gland is more serous than mucous

Also fat cells

Sublingual Gland

Serous and mucous secreting

Serous cells in the form of demilunes on the mucous acini.

more mucous than serous cells

Minor Salivary Glands

Minor salivary glands are not found within gingiva and anterior part of the hard palate
Serous minor glands=von Ebner below the sulci of the circumvallate and folliate papillae of the tongue; palatine, glossopalatine glands are pure mucus; some lingual glands are also pure mucus

Functions

Protection: lubricant (glycoprotein); barrier against noxious stimuli; microbial toxins and minor traumas; washing non-adherent and acellular debris; calcium-binding proteins: formation of salivary pellicle
Buffering: bacteria require specific pH conditions; plaque microorganisms produce acids from sugars; phosphate ions and bicarbonate
Digestion: neutralizes esophageal contents, dilutes gastric chyme; forms food bolus; brakes starch
Taste: permits recognition of noxious substances; protein gustin necessary for growth and maturation of taste buds
Antimicrobial: lysozyme hydrolyzes cell walls of some bacteria; lactoferrin binds free iron and deprives bacteria of this essential element; IgA agglutinates microorganisms
Maintenance of tooth integrity: calcium and phosphate ions; ionic exchange with tooth surface
Tissue repair: bleeding time of oral tissues shorter than other tissues; resulting clot less solid than normal; remineralization

1. Errors in development. These are usually genetic.

a. Variability of the individual teeth. In general, the teeth most distal in any class are the most variable.

b. Partial or total anodontia. missing teeth in children,

c. Supernumerary teeth.

d. Microdontia

e. Macrodontia

F. Microdontia

2. Errors in skeletal alignment. Malpositioned jaws disrupt normal tooth relationships.

3. Soft tissue problems.

-Ocasionally, the proper eruption of a tooth is prevented by fibrous connective tissue over the crown of the tooth.

-In the mixed dentition, the deciduous second molars have a special importance for the integrity of the permanent dentition. Consider this: The first permanent molars at age six years erupt distal to the second deciduous molars.

-Permanent posterior teeth exhibit physiological mesial drift, the tendency to drift mesially when space is available. If the deciduous second molars are lost prematurely, the first permanent molars drift anteriorly and block out the second premolars.

An incisor diastema may be present. The plural for diastema is diastemata.

-Important: The deciduous anteriors--incisors and canines are narrower than their permanent successors mesiodistally.

-Important: The deciduous molars are wider that their permanent successors mesiodistally.

-This size difference has clinical significance. The difference is called the leeway space.

The leeway space in the lower arch is approximately 3.4 mm.

-The leeway space in the upper arch is approximately 1.8 mm. In normal development, the leeway space is taken up by the mesial migration of the first permanent molars.

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.

ERUPTION

. Root completion (approximately 50% of the root is formed when eruption begins)

Generally mandibular teeth erupt before maxillary teeth,

Primary teeth

I. Emerge into the oral cavity as follows:

           Maxillary                       Mandibular

Central Incisor                          7½ months                     6 months

Lateral incisor                           9 months                       7 months

Canine                                     18 months                      16 months

First Molar                               14 months                     12 months

Second Molar                          24months                       20 months

The sequence of  primary  tooth development is central incisor, lateral incisor, first molar, second molar

3. Hard tissue formation begins between 4 and 6 months in utero

4. Crowns completed between 1½ and 10 months of age

5. Roots are completed between I½ and3 yearsof age 6 to 18 months after eruption

6. By age 3 years all of the primary and permanent teeth (except for the third molars) are in some stage of development

7. Root resorption of primary teeth is triggered by the pressure exerted by the developing permanent tooth; it is followed by primary tooth exfoliation in sequential patterns

8. The primary dentition ends when the first permanent tooth erupts