Chapter 43 Tooth-Supported Fixed Dental Prostheses

Question 1

What are the clinical symptoms of trauma from occlusion?

Answer 1

Angular bony defect
— The presence of angular bony defects cannot per se be regarded as an exclusive symptom of trauma from occlusion. Angular bony defects have been found at teeth affected by trauma from occlusion as well as at teeth with normal occlusal function.

Increased tooth mobility

Question 2

Which of the following is pathologic tooth mobility? p.1126

Answer 2

1. A tooth with increased width of PDL.
2. Reduced alveolar bone height. (In many situations with horizontal bone loss patterns, the increased crown displacement should be regarded as physiologic; the movement of the root within the space of its remaining “normal” PDL is normal)
3. Increased crown displacement in teeth with angular bony defects and/or increased width of PDL.
4. Only progressively increasing tooth mobility, which may occur in conjunction with trauma from occlusion, is characterised by active bone resorption, and which indicates the presence of inflammatory alterations within the PDL tissue, may be considered pathologic.

Question 3

Scenario 1
Increased mobility of a tooth with increased width of the PDL but normal height of the alveolar bone.

Scenario 2
Increased mobility of a tooth with increased width of the PDL and reduced height of the alveolar bone.

Answer 3

If a restoration is designed such that the crown of the tooth in occlusion is subjected to undue forces directed in a buccal direction, bone resorption phenomena develop in the buccomarginal and linguoapical pressure zones with a resulting increase of the width of the PDL in these zones. The tooth becomes hypermobile or moves away from the traumatising position. Since such traumatising forces in teeth with normal periodontium or gingivitis cannot result in pocket formation or loss of connective tissue attachment, the resulting increased mobility of the tooth should be regarded as a physiologic adaptation of the periodontal tissues to the altered functional demands. A proper correction of the anatomy of the occlusal surface of such a tooth will normalise the relationship between the antagonising teeth in occlusion. As a result, apposition of bone will occur in the zones previously exposed to resorption, the width of the PDL will become normalised, and the tooth stabilised. In other words, resorption of alveolar bone which is caused by trauma from occlusion is a reversible process.

Conclusion (scenario 1&2): Occlusal adjustment is an effective therapy against increased tooth mobility when such mobility is caused by an increased width of the periodontal ligament.

Question 4

Increased mobility of a tooth with reduced height of the alveolar bone and normal width of the periodontal ligament

Answer 4

In teeth with normal width of the periodontal ligament, no further bone apposition on the walls of the alveoli can occur.

If such an increased tooth mobility does not interfere with the patient’s chewing function or comfort, no treatment is required.

If the patient experiences the tooth mobility as a disturbing, the mobility can only be reduced in this situation by splitting.

A splint is an appliance designed to stabilise mobile teeth.

• Increased tooth mobility as a result of reduced height of alveolar bone can be accepted and splinting avoided, provided the occlusion is stable (no further migration or increasing mobility of individual teeth) and the degree of existing mobility does not disturb patient’s chewing ability or comfort. Consequently, splinting is indicated when the mobility of a tooth or a group of teeth is so increased that chewing ability and/or comfort are disturbed.

Question 5

Progressive mobility of a tooth as a result of a gradually increasing width of the reduced periodontal ligament

Answer 5

Often in cases of advanced periodontal disease the tissue destruction may have reached a level where extraction of one or several teeth cannot be avoided. In such a dentition, teeth which are still available for periodontal treatment may, after therapy, exhibit such a high degree of mobility or even signs of progressively increasing mobility, that there is an obvious risk that the forces elicited during function may mechanically disrupt the remaining periodontal ligament components and result in the loss of the teeth.

It will only be possible to maintain such teeth by means of a splint .

• Splinting is indicated when the periodontal support is so reduced that the mobility of the teeth is progressively increasing, that is when a tooth or a group of teeth are exposed to extraction forces during function.

Question 6

Increased bridge mobility despite splinting

Answer 6

When a cross-arch bridge/splint exhibits increased mobility, the centre (fulcrum) of the movement must be identified. In order to prevent further increase in the mobility and/or to prevent displacement of the bridge, it is essential to design the occlusion in such a way that when the bridge/splint is in contact with the teeth of the opposing jaw, it is subjected to a balanced load, that is equal force on each side of the fulcrum.

Balanced loading of a mobile bridge/splint has to be established not only in the IP and CR, but also in frontal and lateral exclusive movements of the mandible. A force which tends to displace the bridge in a certain direction has to be counteracted by the introduction of a balancing force on the opposite side of the fulcrum of the movement. For instance, if a cross-arch splint in the maxilla exhibits mobility in the frontal direction in conjunction with protrusive movements of the mandible, the load applied to the bridge in the frontal region has to be counterbalanced by a load in the distal portions of the splint; this means that there must be a simultaneous and equal contact relationship between the occluding teeth in both the frontal and the posterior regions of the splint.
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