Occlusion Flashcards
What is the definition of occlusion?
- How the teeth meet together
What joins the TMJ together?
- Condylar head of mandible
- Mandibular fossa of temporal bone
What muscles involved in mandibular movement?
- Muscles of mastication (masseter, Temporalis, Lateral pterygoid, medial pyerygoid
- Suprahyoid
What does the temporalis do?
- Elevate and retracts mandible
- Assists in rotation
What does the lateral pterygoid do?
- Positions disc in closing (Superior - SLP)
- Protrudes and depresses mandible and causes lateral movement (inferior - ILP)
What does the medial pterygoid do?
- Elevates mandible
- Lateral movement and protrusion
What does masseter do?
- Elevates and protracts mandible
- Assists in lateral movement
What are the mandibular movements?
- Rotation (not down and forwards!)
- Translation
- Lateral translation
What is rotation movement also known as?
- Hinge movement
How much mouth opening can occur from rotation movement of TMJ?
- Up to 20mm
What happens to the condyle during rotational movement?
- Condyle and disc remain within articular fossa
How do hinge movement occur?
- Rotation of condylar heads around imaginary horizontal line through rotational centres of condylars
- Line called terminal hinge axis
How can you record the hinge movements measurements?
- Use a facebow
- Measure distance between condyles on terminal hinge axis
How does translation of the condyle occur?
- Mouth closed
- lateral pterygoid contracts
- Articular disc and condyle begin to move
- Travels downwards and forwards along incline of articular eminence
- May also travel laterally (laterotrusive movement)
- Mouth opens
What is Posselts envelope?
- The extremes of mandibular movement
- Border movements of mandible in sagittal plane
- See word doc for diagram
In Posselts envelope what do the abbreviations mean?
ICP = Intercuspal position
E = Edge to Edge
Pr = Protrusion
T = Maximum opening
R = Retruded Axis position
RCP = Retruded contact position
What is ICP?
- Intercuspal position
- Tooth position regardless of condylar position
- The comfortable bite
- Best fit of teeth
- Maximum interdigitation of teeth
- Can be called centric occlusion (CO)
- Mandible slides forward from RCP to achieve ICP
What is Edge to Edge?
- Tooth position
- Teeth slide forward from ICP guiding on palatal surfaces of anterior teeth
- Incisal edges of upper and lower incisors touch
What is protrusion?
- Condyle moves forwards and downwards on articular eminence
- Only incisors +/- canines touch
- No posterior tooth contacts
- Eventually no tooth contacts
What is Maximum opening?
- No tooth contacts
- mouth wide open
- Full translation of condyle over articular eminence
What is retruded axis position?
- No tooth contacts
- Most superior anterior position of condylar head in fossa
- Terminal hinge axis
What is retruded contact position?
- First tooth contact when mandible is in retruded axis position
- ICP is approximately 1mm anterior to RCP in 90% population
What is lateral translation of mandible?
- Has working side and non working side
- Mandible moves either left or right
- If mandible moving right then right = working side and left = non working side
What is lateral translation of the mandible also known as?
- Bennet movement
What is the Bennet angle?
- The path of the nonworking condyle in the horizontal plane during lateral excursion
How can you mark tooth contacts?
- Use fine articulating paper
- Millers forceps
When should you mark tooth contacts?
Before
- Preparing a tooth
- Removing a restoration
After
- Placement of a crown
- Placement of a restoration
What do tripodised contacts show?
- Show where the opposing cusps contact (ICP stops)
What are functional cusps?
- Cusps that occlude with the opposing teeth in the ICP
- Lingual cusps of upper posterior teeth
- Buccal cusps of lower posterior teeth
What are non functioning cusps?
- Cusps that do not occlude with the opposing teeth in the ICP
- Buccal cusps of upper posterior teeth
- Lingual cusps of lower posterior teeth
What is a Fossa?
- Depression or concavity on tooth surface
- Functional cusp of a tooth contacts the fossa of the opposing tooth
What are ICP contacts?
- Lingual cusp of upper molar contacts fossa of lower molar
- Buccal cusp of lower molar contacts fossa of upper molar
What are some problems that can arise in static occlusion?
- Angles classification of incisor relationship
- Overbite
- Overjet
- Anterior crossbite
- Posterior crossbite
- Anterior open bite
- Posterior/lateral open bite
What is Class 1 of Angles classification of incisor relationship?
Class 1 - Incisal edge of mandibular contact cingulum plateau of maxillary
What is Class II div 1 of Angles classification of incisors?
- Mandibular incisor edge lie posterior to cingulum plateau of maxillary central incisors
- Maxillary central incisors proclined or average inclincation
- Increased overjet
What is Class II div 2 of Angles classification of incisors?
- Mandibular incisor edge lie posterior to cingulum plateau of maxillary central incisors
- Maxillary central incisors retro-clined
- Overjet normally minimum but may be increased
What is Class III of Angles classification of incisor relationship?
- Mandibular incisor edges lie anterior to cingulum plateau of maxillary central incisors
- Overjet reduced or reversed
What is overbite?
- Vertical overlap of maxillary central incisors over the mandibular central incisors
- Can be decreased, normal or increased
What is the normal overbite of teeth?
- 2-4mm
What is decreased overbite?
- Can be complete or incomplete
- Incisal edge of mandibular lie more anterior than normal
- More proclined
What is increased overbite?
- Can be complete or incomplete
- Complete can be non-traumatic or traumatic (Ackerly classification)
- Incisal edge of mandibular posterior to cingulum plateau
What is Class 1 of Ackerly classification?
- Lower incisor impinge on palatal mucosa
- Signs of trauma inc inflammation of palatal mucosa with imprint of lower incisor
What is Class II of Ackerly classification?
- Lower incisors incisal edge occlude into palatal gingival crevices of maxillary teeth
- Signs of trauma inc
- Labial splaying of maxillary incisors
- Palatal pocket
What is Class III of Ackerly classification?
- Class II div 2 type of incisor relationship
- Sign of trauma inc
- Stripping of gingiva in relation to palatal surfaces of upper teeth and labial surfaces of lower anterior teeth
What is Class IV of Ackerly classification?
- Lower incisor causing progressive abrasion of palatal surfaces of maxillary teeth
- Signs of trauma inc
- Abrasion of palatal surfaces of upper anterior teeth
- Dentin hypersensitivty
What is Overjet?
- Relationship between maxillary and mandibular teeth in a horizontal plane
What is an anterior crossbite?
- Condition where one or more anterior teeth may be abnormally malpositioned buccal or lingually or labially with reference to opposing teeth
What is a posterior crossbite?
- Condition where one or more posterior teeth may be abnormally malpositioned buccal or lingually or labially with reference to opposing teeth
What is an anterior open bite?
- Lack of vertical overlap of anterior teeth when posterior teeth in full occlusion
What is posterior/ lateral open bite?
- Failure of contact between the posterior teeth when teeth are in full occlusion
What is canine guidance?
- Dynamic occlusion
- Mandible moves to one side and there is only contact between the canines
- No posterior tooth contacts (creates a space)
- Known as mutually protected occlusion
What is the Gold standard of mutually protected occlusion?
- Canine guidance
- Posterior disclusion in lateral excursions
- No non-working/ working side contacts
- No protrusive interferences
What is group function?
- Mandible moves to one side (working side) and multiple teeth contact on that side
- Bilateral group function frequently seen in toothwear
- Most favourable guidance alternative to canine guidance
What is the desirable group of contacts in a group function latero-trusive movement?
- Canines, premolars and mesio-buccal cusp of first molar
- Any contact more posterior not desirable as increased amount of forced placed due to closeness to fulcrum
What is protrusion?
- Condyle moves forwards and downwards on articular eminence
- Only incisors +/- canines touch
- No posterior tooth contacts
What are some problems of dynamic occlusion?
- Occlusal interferences
- Working side
- Non working side
- Protrusive
What occurs during working side occlusal interference?
- Working side contact
- Similar cusps contact e.g. the distal palatal of upper and distal lingual of lower
What occurs during non working side occlusal interference?
- Non working side contact
- Dissimilar cusps contact e.g. palatal of uppers and buccal of lowers
What is protrusive interference?
- Any posterior contacts during protrusion
Why is it important to avoid posterior contacts?
- Teeth are designed to absorb heavy forces in direction of long axis of tooth
- Most teeth not designed to absorb significant lateral forces generated by occlusal interferences
- Musculature gets a rest as less activity if not undesirable posterior contacts
- Occlusal trauma and undesirable tooth movement
What are the types of Bruxism?
- Eccentric
- Centric
What is Eccentric Bruxism?
- Parafunctional grinding of teeth
- Oral habit consisting of involuntary rhythmic or spasmodic or functional gnashing, grinding or clenching of teeth in other than chewing movements of mandible
- May lead to occlusal trauma
What is centric Bruxism?
- Clenching
- Pressing and clamping of jaws and teeth together
- Associated with acute nervous tension or physical effort
What are the clinical signs and symptoms of Bruxism?
- Tooth wear
- Fractured restorations
- Tooth migration
- Tooth mobility
- Muscle pain and fatigue
- Headache
- Earache
- Pain and stiffness in TMJ and surrounding muscles
What are the different types of toothwear?
- Multifactorial
- Abrasion
- Attrition
- Erosion
- Abfraction
How do you classify toothwear?
- Mild
-Moderate - Severe
What is occlusal trauma?
- Injury resulting in tissue changes within attachment apparatus
- Inc PDL, supporting alveolar bone and cementum
- As result of occlusal force/s
What are the classification of occlusal trauma?
Primary - Intact periodontium
Secondary - Reduced periodontium
Fremitus - Palpable or visible movement of tooth when subjected to occlusal force
What is included in the examination checklist for occlusion?
- Incisor relationship
- Guidance
- Overjet/overbite
- ICP contacts
- Working/non working/ protrusive contacts
- Pathology
