DEVELOPMENT OF OCCLUSION

Predental periodThe deciduous dentition periodThe mixed dentition periodThe permanent dentition period

Predental period

Gum pad : Definition- alveolar process at

birthShape- upper gum pad is horse

shoe shape & lower gum pad is U shape

Color- pinkConsistancy – firm

The deciduous dentition period

Eruption sequence of deciduous incisors◦Lower central incisor◦upper central incisor◦Lower lateral incisor◦upper lateral incisor◦Lower primary first molar◦Upper primary first molar◦Lower and upper primary canines◦Lower and upper primary second molars

The deciduous dentition period

Features of deciduous dentition ◦Spaced dentition◦Deep overbite◦Shallow Overjet◦Terminal plane relationship

The deciduous dentition period

Features of deciduous dentition ◦Spaced dentition--- primate space.

The deciduous dentition period

Features of deciduous dentition ◦Terminal plane relationship

Flash terminal

Mesial step

Distal step

The mixed dentition period

1ST TRANSITIONAL PERIODINTERTRANSITIOANL PERIOD2ND TRANSITIONAL PERIOD

The mixed dentition period

1ST TRANSITIONAL PERIOD◦Eruption of the first molar at 6th year◦ Replacement of incisor

Incisor lability---- In maxilla 7.6mm In mandible 6 mm

incisor liability is compensated by Interdental spacing of deciduous teeth Labial eruption of permanent teeth Increased intercanine arch width

The mixed dentition period

Ugly duckling stage- Around the age of 8 yrs a midline diatema is commonly seen in the upper arch

Ugly duckling stageCrown of the canine impinge on developing lateral incisor roots, thus driving the roots medially and causing the crown to flare laterally

The roots of central incisor are also forced together thus causing midline diastema

Ugly duckling stage

This period from the eruption of lateral incisor to canine is termed as the ugly duckling stageWith the eruption of canine, the impingement from the root shifts incisally thus driving the incisor crown medially, resulting in closure of the diastema

The mixed dentition period

INTER-TRANSITIONAL PERIOD ◦No significant change occurs at this

stage

The mixed dentition period

2ND TRANSITIONAL PERIOD ◦Replacement of deciduous canine

and molar◦Lee way space

The mixed dentition periodLee way space : the sum of the

mesiodistal width of the primary canine and the primary first and second molars is larger than the sum of the permanent canine and first and second premolars --- This difference is called the leeway space and is present in both the maxillary and mandibular arch.

The leeway space is larger in the mandibular arch (3.4mm) than in the maxillary arch (1.9mm).

Occlusion in permanent dentitionMolar relationship -

◦Distal surface of the distal marginal ridge of upper 6 contacts and occludes with the mesial surface of the mesial marginal ridge of lower 7

◦the mesiobuccal cusp of upper 6 lies in the groove between the mesial and middle cusps of lower 6

◦ the mesiolingual cusp of 6 seats in the centralfossa of 6.

Occlusion in permanent dentition2. Crown angulation. Gingival aspect of

the long axis of each crown lies distal to its occlusal aspect.

3. Crown inclination. The gingival aspect of the labial surface of the crown  of 2112 lies palatal to the incisal aspect. Otherwise, the gingival aspect of the labial or buccal surface of the crowns of all other teeth lies labial or buccal to the incisal/occlusal aspect.

Occlusion in permanent dentition4. No rotations.5. No spaces.6. Flat or mildly increased

(<_1.5mm) curve of Spee. Functional occlusal relations .