Week 7 Chptr.6 Occlusion Flashcards
Occlusion
Occlusion describes the relationship of the mandibular and maxillary teeth when the teeth are closed together or during excursive movements when the teeth are touching.
Facial profile class 1
• Facial profile of a person of Class I forms a straight line from top half of face (forehead) to chin (orthognathic)
Tips to remember
Anterior teeth have less bone coverage, therefore their buds begin formation earlier than posterior teeth. This results in most of the anterior teeth erupting before the post teeth.
Some posterior teeth must wait until growth has occurred in the mandible, as they are trapped under the ramus of the mandible
Intercuspation
At 16 months primary molars erupt and establish
-vertical height of primary occlusion, -Intercuspation, the mesial-distal and buccal-lingual relationship that determines how the upper teeth will touch, hit and interlock with lower teeth.
Position and Sequence of Eruption
The upper primary first molars also help establish the anteroposterior (mesial-distal)
relationship of the remaining deciduous teeth because their presence allows the canines and 2nd deciduous molars to erupt around them.
n The primary dentition erupts in a more upright position than permanent teeth replacements.
n Eruption is Complete at 2.5 years for deciduous teeth
Primary Occlusion
3 possible anteroposterior (mesial/distal) molar relationships in PRIMARY OCCLUSION…
1. Mesial Step- 2nd primary mandibular molars (distal surface) are situated more mesial (anteriorly) than the maxillary molars. (most common)
2.
Flush Terminal Plane- 2nd primary mand molars even with each other on both arches
3.
3. Distal Step- 2nd primary mandibular molars are situated more distal (posterior) than the maxillarv
Development of Mesial Step
Development of Mesial Step
• permanent 1st molars erupt and push up against the deciduous molars causing the primate spaces to close ~ causing a chain reaction that pushes all of the interproximal spaces closed (mesial drift)
• a mesial step is further enhanced as the deciduous molars exfoliate and are replaced by narrower permanent premolars
• Extra space is created called LEEWAY SPACE
• mesial step occurs in majority of individuals
Leeway space
n Leeway space is extra space that deciduous canines and molars occupy to help save room for their
permanent successors.
Permanent teeth take up less space.
development of the Mesial Step cont.
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the mandible continues to grow later than the maxilla
O this mesial advancement heads the patient toward a class I relationship (will be discussed later)
a if further growth of the condyle head occurs, an
extreme mesial step results in a class III relationship
a class II relationship results if the mandible does not continue to grow or if the maxilla outgrows the mandible
it is possible for this type of relationship to occur on just one side and the other side remaining in class 1
Horizontal
Alignment
• If this balance of forces is disturbed, a malocclusion, or an abnormal alignment of the teeth within the dental arches, can result. example: tongue thrusting causes maxillary anterior teeth to protrude
• Or overdeveloped lower lip causes
RETRUSION of the lower teeth
Malocclusion of teeth
• Can be detrimental if it adversely affects appearance, comfort, or function
• Can occur in Class I, II, III jaw relationships
• Can be an individual tooth or groups of teeth that affect the occlusal plane
• Labioversion/buccoversion: a tooth out of alignment to the labial or buccal
• Linguoversion: tooth out of alignment that is lingual
Supraeruption, crossbite, edge to edge
• Supraeruption: a tooth that is overerupted, abnormally long relative to the rest of the occlus surfaces
• Crossbite: a tooth or teeth that are out of alignment in a buccal/lingual version”
• Edge to edge: max incisal edges line up with touching mand incisal edges with NO vertical
Horizontal Alignment
• balance between tongue and facial muscles allows proper horizontal alignment of teeth
Retrusion
The lower teeth will be pushed back from under developed lip
Intercuspation
n The intercuspation of the teeth helps prevent tooth deviations in a buccal or lingual direction.
u When the jaws are closed, the buccal cusps of the mandibular posterior teeth are interlocked between the buccal and lingual cusps of the
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maxillary teeth. (like gears)
Vertical Alignment
Vertical alignment
• from a lateral view all the teeth show a slight mesial inclination, with the possible exception of the maxillary third molar 18, 28 (straight)
• anterior teeth have a slight labial protrusion of crowns and their roots seem to incline laterally
O in other words, the anterior teeth tip out to the side and toward the front
Centric relation
- A relationship of the upper jaw to the lower jaw (centric relation).
Centric relation is defined as the relationship of the mandible to the maxilla when the condyles of the
TMJ are in their most upward, backward and unstrained position (mandible is pushed backwards)
Position of the mandible relative to maxilla determined by the maximum contraction of the muscles of the jaw
Centric Occlusion
- A relationship of the maxillary teeth to the mandibular teeth (centric occlusion).
Acromegaly
n
Acromegaly: is a condition where a crossbite all the mandibular teeth occurs u WHY? growth hormone causes the mandible to grow faster than the maxilla
There are 2 basic classifications of occlusion:
- Skeletal; based on the relationship of the bone of the maxilla to the bone of the mandible
1 Referred to as skeletal classification- because related to the bones. - Dental; based on the relationship of the teeth of the mandible to the teeth of the maxilla.
• Referred to as dental classification because it is concerned with the teeth.
Skeletal classification
3 classes
classes of relationship:
a Class I: The maxilla and mandible are in normal
relationship to each other.
B neutroclusion
§ Class /I: The mandible is retruded. (it has a distal relationship with the maxilla.)
• Retrognathic.
B Class III: The mandible is protruded.(it has a mesial relationship with the maxilla.) Prognathic
Occlusion inventor
• Dr. Edward Angle defined classes of jaw relationships in 1887.
• Each class of occlusion is defined by the relationship of the 1st teeth to erupt in the permanent dentition, max/mand 1st molars
• If the 1st molars are absent, the relationship btw the max/mand canines
• “ideal occlusion” the teeth are aligned within each arch so that they fit together and function harmoniously, interdigitation, in Class |
relationshin
Class 1
Class 2
Class 2
2 Divisions
Class 3
Lateral Mandibular Glide (Lateral
Excursion)
In lateral excursion the mandible moves toward the right or left side.
u The side to which the mandible moves is refer to as the working side, and the other side is referred to as the nonworking side (when no teeth are in contact with each other).
Canine rise
In lateral mandibular glide, only a few pairs of interlocking cusps make occlusal contact, the canines carry the bulk of the contact
This is referred to as CANINE RISE
As mand canine opens and glides down the lingual surface of the max canine
Group function
it is common to have the premolars/canines occluding in lateral excursion
u when the premolars also occlude during lateral
excursion it is called group function u The canines should still be the dominant occluding teeth, the premolars only assist through part of the lateral side
Premature Contact
if one tooth hits more than the others, it becomes an interference and bears more force than the others, becoming a premature contact area
Stolarized Molars
• The max first molar is tipped mesially so that it touches the mandibular 1st molar and 2nd molars
• In contact with 2
• teeth
Black’s classification of cavities
(see photos on following pgs.) 5 classifications
Class 1
Class I
•Cavities located in pits or fissures. These are located in the occlusal surfaces of molars and premolars, the occlusal two-thirds of the buccal surfaces of molars, the lingual surfaces of upper incisors, and occasionally in the lingual surfaces of upper molars.
Black’s classification of cavities
(see photos on following pgs.) 5 classifications
Class 2
Cavities located in the proximal surfaces of molars and premolars.
Class 3
Class III
n Cavities in the proximal surfaces of canines. and incisors not involving the incisal angle
Class 4
Cavities in the proximal surfaces of incisors or canines which also involve one or both of the incisal angles.
Class V
Class 5
Cavities located in the gingival third of the labial, buccal, lingual, or palatal surfaces of any tooth.
