Dental Occlusion and Arch Formation

Flashcards on Dental Occlusion and Arch Formation

Parabolic Curve Dental Arch

Horseshoe/U-shaped dental arch formation.

Segments of U-shaped Dental Arch

Anterior, Middle, and Posterior segments.

Maxillary Arch Size

Larger than the mandibular arch, creating horizontal space (overjet).

Anterior Segment of Dental Arch

Semicircular, equally bisected by the midline, running through facial surfaces of anterior teeth and the first half of the first premolars.

Middle Segment of Dental Arch

Straight line, flared out, not symmetrical to create space, overlapping the mesial half of the first molar.

Posterior Segment of Dental Arch

Straight line parallel to the midline, slightly directed to the midline, narrow and converging at the distal half of the dental arch (3rd molars).

Centric Occlusion

Reference point for contact relationship between upper and lower teeth at maximum intercuspation; condyles resting in the most retrusive and unstrained position in the glenoid fossa.

Tooth Contact Rule

Each tooth (except 1 & 8) contacts two opposing teeth, minimizing overeruption and mesial drifting.

Normal Overbite

3-5mm; upper teeth covering the lower teeth for a short distance.

Upper Central Incisor Occlusion

Incisal ridge is free from contact, overlaps the entire width to the mesial half of lower 1

• Mesial outline: midline in harmony/united with that of the upper 1

• Distal Outline: center and above the midline of the lower 2

• Cingulum free from contact

Lower Central Incisor Occlusion

• Labio-incisal ridge: strikes 1 near the incisal & middle 1/3 junction.

• Mesial outline in line with the median & mesial outline of the upper 1.

• Distal Outline: located at the mesial 2/3; junction between the middle and distal 1/3 of the upper 1

• Cingulum is free from contact

Upper Canine Occlusion

Cusp is free of contact, located in the labial embrasure of 5&4.

• Tip of the cusp mesial to the contact area of lower teeth.

• Mesial outline: labial and above the cusp tip of the lower 3

• Distal outline: labial and above the cusp tip of the lower 4

• Cingulum free from contact.

Lower Canine Occlusion

• Cusp tip labially and directly below the linguo-incisal embrasure of 2&3.

• Mesial outline is slightly distal to the midline of 2.

• Distal outline centered at the midline of 3.

• Cingulum is free from contact.

Upper First Premolar Occlusion

Follows the 'Bull Rule': Buccal of Upper & Lower, Lingual of Upper & Lower are free from contact (free from contact).

• Buccal cusp: free from contact; located buccal and above the embrasure between lower 4 and lower 5

• Mesial outline: buccal and above the cusp tip of the lower 4

• Distal outline: buccal and above the cusp tip of the lower 5

• Lingual cusp: in contact with DMR of lower 4

Lower First Premolar Occlusion

• Buccal cusp: in contact with MMR of upper 4 & located below the occlusal embrasure of the upper 3&4.

• Mesial outline: placed directly under the lingual ridge of upper 3

• Distal outline: sit in the triangular ridge of the buccal cusp of the upper 4

• Lingual cusp: free from contact, lie below the lingual embrasure of the upper 3 and 4

Upper First Molar Occlusion

• Mesiobuccal cusp free from contact, lying buccal to mesio-buccal groove of lower 6.

• Distobuccal cusp free from contact, lying distal to the disto-buccal groove.

• Mesiolingual cusp situated in the center of the central fossa of 6.

• Distolingual cusp in contact with MMR of 7.

Lower First Molar Occlusion

• Mesiobuccal cusp in contact with DMR of upper 5 & MMR of upper 6 (only exception)

• Distobuccal cusp rests in the central fossa of upper 6.

• Distal cusp rests in the distal triangular fossa of upper 6.

• Mesiolingual cusp free from contact, located in the lingual embrasure of the upper 5&6

• Distolingual cusp: free from contact, located lingual to the lingual developmental grooves of upper 6

• Mesial portion in occlusion with distal part of upper 5

• DMR of lower 6 is slightly mesial to the DMR of the upper 6