Stomatognathic system dysfunction can be caused by alterations in dental occlusion. True or False
True
Maintaining oral health depends on:
- Optimal joint positions
- Optimal tooth contacts
Posterior teeth contacts:
- Simultaneous and uniform contacts
- It should lead to axial (vertical loads)
- Tripod contact: cusp to fossa (pit)
- There should never be contacts between cusp slopes
What happens when we have contact between cusp slopes
We have prematurities
What happens when we have oblique loads for posterior teeth?
It becomes harmful for the periodontium
Anterior teeth contacts:
- Soft contacts
- Non-axial contacts
What happens to the anterior teeth when we do not have our posterior teeth?
We will not have soft contacts in the anterior teeth, so they tend to collapse
Optimal functional contacts in positions and eccentric movements aka anterior guidance:
- Christensen’s phenomenon
- Protrusion: 4 incisors
Adequate overbite: incisors 2-3 mm, canines 3-4 mm
Slight overjet - Laterality: canine guidance
- No axial loads
Why do canines support non-axial loads better?
- Because they are far from the TMJ
- They have a bigger capacity of proprioception
- They have longer roots
Functions of the anterior guidance
- They allow posterior disocclusion
- They direct the mandibular dynamics
- Masticatory, phonetics, aesthetics
Optimal anterior guidance in laterality and protrusion:
Canine guidance:
- Conditioned by the overbite
- Posterior: NWS: 1mm, WS: 0.5mm
Incisal guidance:
- Conditioned by the overjet and the overbite
- 1mm in posterior
The types of undesirable contacts:
- Prematurities in opening and closing
- Interferences in eccentric movements like protrusion and laterality
What are prematurities?
They are contacts between cusp slopes (shift): between the mesial of the upper cusp and the distal of the lower cusp
Prematurities cause a delay of CR and MI coinciding. True or False
True
What do prematurities lead to?
- Wear facets
- Bone resorption
- External pterygoid pain on palpation
- TMJ click
Protrusion desirable contacts:
- Incisal guidance: mandibular movement forward from MI to edge to edge
- Contacts in anterior teeth:
a. Upper incisors: palatal surface
b. Lower incisors: vestibular surface - No posterior contacts
Absence of incisal guidance in protrusion causes:
- Excessive overjet and a slight overbite
- Anterior open bite
- Class III of angle
- Extruded upper posterior teeth
- Posterior teeth mal position
Where do undesirable contacts (interferences) in protrusion occur?
Between the upper distal ridges against the lower mesial ridges
What do interferences in protrusion cause?
- Wear facets
- Bone resorption
- Temporal or pterygoid pain
Desirable contacts in laterlity:
- Canine guidance
- Canine overbite of 3-4 mm
- Minimal overjet
- No posterior contacts –> escape grooves
Interferences in Laterality:
- On the working side:
- Contacts between homonyms cusps (same side cusps)
- Group function: they are not considered real interferences unless they generate a pathology (if it is the lingual cusp of premolar that is in contact, we have an interference) - On the non-working side:
- Mandibular posterior teeth on NWS move mesially on the maxillary teeth
- They appear between internal slopes of active cusps
When do we have interferences in laterality?
When the canine does not work properly and therefore we do not have a good canine guidance
Consequences of interferences in laterality on WS:
- Wear facets
- Cervical erosion
- Gingival recession
- Myalgia of the elevator muscles
Is it okay if a molar promotes posterior disocclusion?
No, if we let molars promote posterior disocclusion, we are promoting oblique forces
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Chapter 1: Prosthetic Dentistry29
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Chapter 2: Stomatognathic System32
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Chapter 3: Neuromuscular System Function73
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Chapter 4: Study of dental arches44
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Chapter 5: Mandibular positions and movements75
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Chapter 6: Mandibular dynamics25
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Chapter 7: Optimal functional occlusion36
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Chapter 8: Aetiology, pathology and exploration of the TMJ29
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Chapter 9: Articulators and face bows14
