Periodontal physiology and concepts of occlusal loading of teeth Flashcards
What is the purpose of the PDL?
PDL connects the tooth to the bone.
consists of the junctional epithelium anf the connective tissue.
what is the width of the PDL?
The pdl is a gomphosis joint and PDL width remarkably is constant - Approximately 0.25mm.
So why do we have PDL?
There is pressure when we chew so pressure of occlusion needs to be distributed.
Why do we have a PDL and what are the 2 mechanisms of retention associated with it?
For retention of the tooth.
1. Ankylosis Fusion between alveolar bone and the cementum of teeth. 1. Gomphosis Fibrous mobile root-and-socket joint.
What is an ankylosis joint?
Fusion between alveolar bone and the cementum of teeth.
we see this in sharks
what is a gomphosis joint?
Fibrous mobile root-and-socket joint.
the PDL is a gomphosis joint.
what are the functions of the PDL?
Adsorption of Occlusal Forces:
The PDL is a hydro elastic matrix and is composed of proteoglycans and ground substance. Transmission of forces by PDL fibres to bone and tooth. Also contributes to the elasticity of the bone.
Neuromuscular:
Has Pain fibres and mechanoreceptors for proprioception, masticatory control, and salivation.
Remodelling:
PDL undergoes constant remodelling and adaptive changes in response to loading and movement
How is the PDL maintained?
Maintenance of PDL width via regular mechanical stimulation. effects of occlusal force can lead to hypofunction of the PDL or hyperfunction of the PDL.
what is the hypofunction of the PDL?
Reduced loading can lead to narrow PDL.
this results in:
Bone formation
Narrowing of the ligament space
Hyalinisation of the ligament fibres
leading to overeruption of the tooth, thinning of the pdl
Why does the PDL narrowen with reduced loading?
As there is not enough mechanical stimulation, resulting in collagen fibres becoming:
- Disorganised
- Lower intensity
- Have a patchy appearance.
what is the hyperfunction of the PDL?
Too much pressure with occlusal load.
What does hyperfunction of the PDL in terms of the orientation of a tooth and how?
- Tilt.
- An increase in load affects the tension in both areas marked T. This causes a tilt:
With the tilt caused by hyperfunction of the PDL, what is experienced on the pressure side?
- Loss of fibre orientation
- Osteoclastic bone resorption
- Localised areas of pressure necrosis (ankylosis)
With the tilt caused by hyperfunction of the PDL, what is experienced on the tension side?
- Stretching of fibres
- Bone formation
What does symptoms does hyperfunction of the PDL cause?
- Thicker PDL
- Bone resorption
- Results in pain and tooth mobility
What does normal organisation of the PDL depend on?
Continued mechanical stimulation by occlusal forces.
In response to increased loading what is the PDL’s reaction?
The PDL remodels and shows adaptive changes in response to increased loading.
How can changes to the PDL be reversed?
Removal of the forces causing occlusal load.
What does occlusal loading do to teeth and the PDL?
- Increased mobility
- Widening of the PDL
How does orthodontic movment use the PDL to move teeth?
- How does orthodontic movment use the PDL to move teeth?
- Unidirectional hyperfunction:
give examples of occlusal trauma from multidirectional forces.
Abnormal occlusal function - Occlusal disharmonies
Absence of neuromuscular control of mastication Parafunction eg: bruxism
Abnormal occlusal support (PDL)
Periodontitis
Are loading-based changes reversible?
Loading-based changes are reversible following removal of these forces.
what is tooth mobility ultimately the result of?
Tooth Mobility is ultimately the result of the occlusal load on a tooth.
