Occlusion Flashcards
Define occlusion
Contacts between teeth
The relationship of the dental arches when tooth contact is made
Determinants of occlusion
TMJ - tempomandibular joint/positioning
Muscles of mastication
Teeth
Neuromuscular control
TMJ allow 2 types of movement?
Hinge
Sliding movement
How are muscles of mastication controlled and how do they move?
Under control of neuromuscular system
Exert powerful forces and can produce fine, controlled movement
Neuromuscular control
- what is it?
Feedback system to CNS from periodontal ligament, muscles, tendons, TMJ
Emotional, environmental stress can over ride this - sensitive system
What is an ideal occlusion?
Teeth are aligned such that the masticatory loads are within the physiological range
Lateral jaw movements occur without undue mechanical interference
In the rest position of the jaw, the gap between the teeth is correct for the individual
The tooth alignment is aesthetically pleasing
Physiological occlusion?
Occlusion within the patient’s adaptability
There is no breakdown of the periodontium, no tooth wear, teeth stay in position
Adaptive mechanisms
- New jaw position
- Condylar remodelling
- Teeth can change their position
Pathological occlusion
A pattern of occlusal contact resulting in one or more of the elements of the masticatory system being overstretched therefore may cause parafunction
Symtoms
- Pain/Temporomandibular disorders
- Fracture
- Tooth wear – localised or generalised
- Drifting, mobility
Concepts in occlusion that cause differences in individuals
- dental arches - size varies
- angulation of teeth within alveolus varies considerably
- intercuspal position (ICP)
Intercuspal position (ICP) - what is it? varies depending on?
Position of the mandible when the maxillary and mandibular teeth are maximally meshed together (maximum intercuspation)
Varies depending on the size of the arches and the position of the teeth
Malocclusion - what is it? what causes it?
An anatomical variation rather than an abnormality
Malocclusions result from one or combination:
- malposition of individual teeth
- malrelationship of the dental arches
- variation in skeletal morphology of the jaws
Classifications of malocclusion
Angles molar classification
- position of the first molar
Incisor classification
- position of the incisor teeth
Angles class 1 molar relationship
The mesiobuccal cusp of the upper first molar occludes with the mesiobuccal groove of the lower first molar
Angles class 2 molar relationship the mesiobuccal cusp on the upper first molar occludes mesial to the class 1 position
The mesiobuccal cusp off the upper first molar occludes mesial / more anterior to the class 1 position
Angles class 3 molar relationship
The mesiobuccal cusp of the upper first molar occludes distal / more posterior to the class 1 position
Angles molar classification
Class 1
Class 2
Class 3
Incisor classification
British institute classification
The position of the contact of the lower incisor with the palatal surface of the upper incisor
Class I
Class II div 1
Class II div 2
Class III
Incisor relationships
Over jet - distance between the tip of the lower incisor and upper incisor (measured in mm)
Overbite - distance between the tip of the lower incisor and upper incisor (measured in mm)
Incisor relationships - class 1
Incisor tip of lower incisor occlude with the palatial (mid) third of upper central incisors
Incisor relationships - class 2
Division 1 and 2
Division 1 - upper incisors occlude anterior to the lowers
Division 2 - upper incisors try to meet lower incisors - retroclined
Crowding?
Teeth are markedly out of line of the dental arch because there is disproportion between size of arch and size of teeth
Anterior open bite
Occurs when there is no incisor contact and no incisor overbite
Eg from dummy / suck thumb
Crossbite
A transverse abnormality of the dental arches where there is an asymmetrical bite
Unilateral / bilateral
(Some teeth over and some under)
What are guidance teeth?
The teeth that determine the movement of the jaw
- incisal guidance
- canine guidance
- group function
Occlusal examination - what do we look for
Extra oral examination - skeletal pattern
Intra oral examination -
- soft tissue factors
- generally shape of arches
- missing teeth
- crowding / cross bite
- occlusal relationships - Angles incisor
- guidance teeth / presence of interferences
Use of articulating paper / study models
Orthodontics
directed towards alteration of the occlusion of the teeth and the jaw relationships
Periodontics
- does it affect occluding surfaces of teeth?
Periodontal disease does not directly affect the occluding surfaces of the teeth.
Trauma from the occlusion has been linked with periodontal disease for many years
Despite extensive research over many years, the role of occlusion in the aetiology and pathogenesis of inflammatory periodontitis is still not fully understood
There is no scientific evidence to show that trauma from occlusion causes gingivitis or periodontitis
The p’d ligament physiologically adapts to increased occlusal loading by resorption of the alveolar crestal bone resulting in increased tooth mobility
Occlusal trauma may be a co-factor which can increase the rate of progression/mobility of an existing periodontal disease
Why is occlusion important in paediatric dentistry?
The difference between paediatric dentistry and most other branches of dentistry is that in the child the occlusion is changing
In children we have to make the right clinical decisions for the future occlusion
Issues within paediatric dentistry
- premature loss of primary teeth = shifting of midline / disruption of developing occlusion
- submerging teeth
- premature loss of a first permanent molar
- missing permanent tooth
- prevention of crowding in the permanent dentition
- decision to restore / extract
