Stages of Occlusion Development

Study Notes

Occlusion

Occlusion refers to the way the maxillary and mandibular teeth come together.

Stages of Development of Occlusion

Predental/Gum Pads Stage: From birth to 6 months
Primary Dentition Stage: From eruption of the first deciduous tooth to the eruption of the first permanent molar (6 months to 6 years)
Mixed Dentition Stage: From eruption of the first permanent molar to the shedding of the last deciduous tooth
Permanent Dentition Stage: Starts with the shedding of the last deciduous tooth and is completed with the eruption of all permanent teeth

Predental/Gum Pads Stage

Gum Pads: The alveolar arches at the time of birth.
- Shape: Smooth and firm with transverse grooves separating the gum pads into 10 segments
- Lateral Sulcus: Groove between the canine and first molar region
- Gingival Groove: Separates gum pad from the palate and is the lingual extension of the gum pads
- Dental Groove: Starts at the incisive papilla and extends backward to touch the gingival groove in the canine region
Relationship Between Upper and Lower Gum Pads:
- Complete Overjet: Maxillary gum pad is wider and overlaps the mandibular gum pad
- Lower Lateral Sulcus: Usually distal to the upper lateral sulcus (Class II pattern)
- Anterior Open Bite (Infantile Open Bite): Tongue protrudes anteriorly through this space. This helps in suckling and is a self-correcting anomaly by eruption of primary teeth.
Natal and Neonatal Teeth:
- Natal teeth: Present at birth
- Neonatal teeth: Erupt within the first month
- Radiographic evaluation is recommended.

Primary Dentition

Duration: Starts from the eruption of the first deciduous tooth (usually the mandibular central incisors) and ends with the eruption of the first permanent molar.
Sequence and Time of Eruption: Typically complete by 2.5 years of age. Typically the following is the eruption sequence:
- Central incisors
- Lateral incisors
- First molars
- Canines
- Second molars
Root Formation: Complete by 3 years of age
Normal Signs of Primary Dentition:
- Spaced Anteriors: In the upper and lower anterior segments to accommodate larger permanent teeth
- Primate/Simian/Anthropoid Space: Present mesial to the maxillary canine and distal to the mandibular canine. This space is used for Early Mesial Shift in the Mandibular Arch.
- Almost Vertical Inclination of the Anteriors: Due to this inclination, the interincisal angle is very obtuse.
- Overbite: Initially deep, but reduces over time due to eruption of primary molars and rapid attrition of incisors.
- Molar Relationship: Described in terms of terminal planes (distal surfaces of maxillary and mandibular second deciduous molars).
  - Flush Terminal Plane: Normal - Both maxillary and mandibular planes are at the same level anteroposteriorly
  - Mesial Step: Abnormal - Distal surface of mandibular deciduous second molar is mesial to the distal surface of maxillary deciduous second molar.
  - Distal Step: Abnormal - Distal surface of mandibular deciduous second molar is more distal than the distal surface of maxillary deciduous second molar.