Occlusion Flashcards
What kind of dental treatments can affect occlusion?
Tooth restoration
Tooth movement
Tooth adjustment
Tooth removal
What kind of occlusal issues can patients commonly present with?
Tooth wear (attrition, erosion, abrasion, or abfraction)
Overloading
Fractured cusp or restoration
What is the significance of poor occlusion?
Limited evidence suggests that a change in occlusion will precipitate morphological changes in the TMJ
Most likely adaptation occur in teeth and their supporting structures (tooth wear, movement, and fracture)
What causes attrition of incisors?
Possible causes include:
Lack of posterior tooth support
Abrasive restorative material
Bruxism
What are the features of generalized attrition?
Severe wear, fractured teeth and elongated alveolar processes
Dentoalveolar compensation: Limits vertical space for dental restoration
What are splayed teeth?
Outward projection of anterior teeth
What are possible causes of splayed teeth?
Loss of posterior teeth
In conjunction with periodontal problems (Reduced PDL supports)
Soreness of anterior teeth precede tooth movement
Over contouring of palatal surface of maxillary incisors or incisal/labial surfaces of mandibular incisors
What causes pain on biting?
Compression of the periodontal ligament. This can be caused by premature occlusal contacts or occlusal interferences
What causes sensitive teeth?
Could result from occlusal overload. (could be after a poorly finished restoration causing occlusal interferences)
What occlusal issues can cause hypermobility?
After poorly finished restoration causing occlusal interferences
All mobile teeth should be assessed to rule out deflective contacts or occlusal overload as a factor in the cause of the mobility
What does a fractured cusp eventually cause?
Fracture lines routinely develop when a cusp is loaded with heavy occlusal forces
Can precede split tooth
Results in symptoms of cracked tooth syndrome
What are the potential outcomes of poor occlusion?
Incisal wear (attrition)
General attrition
Splayed teeth
Sore teeth (biting sensitivity)
Sensitive teeth (hypersensitivity caused by occlusal overload)
Hypermobility
Fractured cusp
Painful musculature
What causes painful musculature as a result of poor occlusion?
Deflective occlusal interferences that cause jaw joints to displace
Unbalanced muscle contraction
What is occlusion?
Contacts between teeth
The relationship between the incising or masticating surfaces of the maxillary or mandibular teeth or tooth analogues
What are the components of the masticatory system?
Teeth
Periodontal tissues
Articulatory apparatus: Consists of TMJs, Masticatory muscles, and dental occlusion
What does the articulatory apparatus dictate?
Mandibular position and movements
What is the function of each component of the articulatory apparatus?
TMJ: Guiding system
Dental occlusion: Guiding system
Masticatory muscle: Moving system
What are the components of the TMJ?
Condyle head
Articular disc
Glenoid fossa
Provides guidance to the mandible during movement
What are the types of motion that the TMJ can undergo?
Hinge movement: Rotation around the intracondylar axis within the glenoid fossa and this provides <2cm of movement.
Translational movement: Gliding against the articular eminence of >2cm
What is the function of the masseter?
Primarily elevates the mandible, secondarily protrudes the mandible
What is the function of the temporalis?
Elevates and retracts the mandible
What is the function of the lateral pterygoid muscle?
Protrudes the mandible. Laterla movements. Depression
What is the function of the medial pterygoid muscle?
Primarily elevates the mandible, secondarily protrusion and lateral movements
What are the suprahyoid muscles?
Mylohyoid, geniohyoid, stylohyoid and digastric
What are the infrahyoid muscles?
Sternohyoid
Sternothyroid
Thyrohyoid
Omohyoid
What are the TMJ movements that lead to protrusive movements?
Both condyles are in similar gliding motion
What are the TMJ motions responsible for lateral movement?
Working side: Rotational movement around the vertical axis without leaving the glenoid fossa
Non - working side: Gliding against the articular eminence forwards downwards and medially
What is the angle of downward movement during lateral excursion called?
The condylar angle
What is the angle of medial movement during lateral excursion called?
The bennet angle
What is the bennett side shift?
The side movement of the body of the mandible on the working side in the horizontal direction
What is the difference between static and dynamic occlusion?
Centric occlusion or maximal intercuspation in static. Protrusion in dynamic
Centric relation / freedom in centric whereas there is lateral occlusion guidance in dynamic
What controls lateral occlusion guidance in dynamic occlusion?
Canine guided
Group function
Balanced occlusion
What is centric relation in static occlusion?
Maxillomandibular relationship in which the condyles articulate with the thinnest avascular portion of their respective discs with the complex in the anterior-superior position against the shapes of the articular eminencies
The position is independent of tooth contact and reproducible
What is the maximum intercuspation position?
the complete intercuspation of the opposing teeth independent of condylar position:
Bite of convenience
Habitual bite (position)
What is centric occlusion?
If the MIP coincides with CR then this is called centric occlusion.
How common is centric occlusion?
In 90% of the population there is a lack of coincidence of MIP with CR
When is freedom in centric said to occur? When is it not said to occur?
Freedom in centric occlusion occurs when the mandible is able to move anteriorly for a short distance in the same horizontal and sagittal plane while maintaining tooth contact
Alternatively there will be no freedom in centric occlusion if either front teeth or the posterior occlusion do not allow this horizontal movement
What is dynamic occlusion?
Refers to occlusal contacts that can be made whilst the mandible is moving relative to the maxilla.
What are the criteria for ideal occlusion?
Mandibular stability: Contact of inferior and superior teeth must stabilize the mandible in centric position.
Axial load: Occlusal load should be parallel to the long axis of the tooth (load distributed evenly throughout the PDL)
During lateral excursions of the mandible there is no interference in the working side.
During lateral excursions of the mandible there is no disocclusion in the non-working side.
During protrusion there is disocclusion of the posterior teeth.
What are the types of guidance?
Canine guided occlusion (dentate)
Group function (total or partial) (dentate)
Balanced occlusion (bilaterally balanced occlusion) (Edentate)
What is canine guided occlusion?
A form of articulation in which the vertical and horizontal overlap of the canine teeth disengage the posterior teeth in the excursive movements of the mandible. (i.e if mandible is moving laterally both canines can touch the whole way through the motion even when posterior teeth have disconnected)
Complete disclusion of posterior teeth during lateral movement
When is using canine guidance for occlusion not indicated?
Not indicated for teeth that are compromised endodontically or periodontically
What is group function occlusion?
Distribution of lateral forces to a group of teeth
Multiple contact relations between the maxillary and mandibular teeth in lateral movements on the working side whereby simultaneous contact of several teeth acts as a group to distribute occlusal forces
What contacts are seen on lateral movements
On lateral movements, the contacts are on the buccal cusps of the working side
The non-working side has no contacts
What are the types of interferences that can arise?
Working and/or non-working side interferences
Why should interferences be eliminated?
Excessive horizontal and oblique forces will be applied on the restoration or natural teeth causing damage
What is balanced occlusion?
Bilateral, simultaneous, anterior and posterior occlusal contact of teeth in centric and eccentric positions
At least 3 contact points: 2 posterior and 1 anterior
What is balanced occlusion needed for?
Useful for complete denture cases to prevent tipping of the denture
Cross arch balanced occlusion is not indicated for natural dentition
What happens during protrusion in ideal occlusion?
Protrusive or anterior guidance causes disocclusion of posterior teeth
What is mutually protected articulation?
An occlusal scheme in which the posterior teeth prevent excessive contact of the anterior teeth in maximum intercuspation and anterior teeth disengage the posterior teeth in all mandibular excursive movements
