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Periodontal Aspects Related to Fixed

Prosthodontics

presented By

Dr: Raiesa Mohamed Hashem

lecturer of fixed prosthodontics

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These are certain precautions must be followed by

the operator to preserve the periodontium heaalth

which is the foundation of the fixed prosthodontics,

and hence, successful restoration will functions

without conflictions or problems.

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The periodontium:

It is a connective tissue structure attached to the periosteum

of both the mandible and the maxilla that serves to anchor the

teeth in the alveolar processes.

Components of the periodontium

1- Gingiva.

2 - Periodontal ligament.

3- Alveolar bone.

4- Cementum.

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three types of lining of oral cavity composed of The

mucosa:

1- masticatory (keratinized) covering hard palate & the

gingiva,

2- lining mucosa, covering lips, cheek, floor of the mouth&

soft palate.

3- Specialized mucosa ,covering dorsum of the tongue&

taste buds.

g of oral cavity

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Anatomy of the periodontium Free gingiva

,extends from

coronal of the tooth

to the epithelial

attachment

Attached G. from

epith.atach.to

alveolar mucosa ,in

between, is the

mucogingival

junction

Interdental papillae

or(Col st.)

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provides attachment, support, nutrition , synthesis and resorption eriodontiumP

and mechano-reception

the main bulk is periodontal ligament which gives attachment and support to

the tooth in function.

Periodontal ligament fibers

1- Transseptal fibers

2- Alveolar crest fibers

3- Horizontal fibers

4- Oblique fibers

5- Apical fibers

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Periodontal disease

Any condition of the periodontium other than normal.

Most of the gingival diseases are due to microbial plaque which leads to

further progress of the

pathological lesion.

Calculus , acquired pellicle ,materia alba are subsequent results .

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why periodontal disease must be eliminated prior to restorative

dentistry:

1- To locate and determine the gingival margins of restorations properly,

2-The position of teeth is frequently altered in periodontal disease.

3-Inflammation of the periodontium impairs the capacity of abutment teeth

to meet the functional demands made on them.

4-Partial prosthesis constructed on cast made from impression of

diseased gingiva and edentulous mucosa do not fit properly when

periodontal health is restored.

5- Discomfort from tooth mobility interferes with mastication and function.

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Periodontal aspect in regard to fixed prosthodontics

procedures.

(principles or aspects that should be considered when designing a fixed restoration. To preserve the periodontium

1- occlusion and its effect on periodontium. 2- crown margin 3- crown contour 4- embrasure materials and designs 5- splinting 6- pontic materials and designs 7- furcation involvement

8- bridge design

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1- occlusion and its effect on periodontium.

Occlusal forces have a magnitude & direction.

If the magnitude exceed the capacity of the periodontium, injury will results.

Occlusal Trauma:

Occlusal trauma is defined as an injury to the attachment apparatus (periodontal

ligament, alveolar bone, and cementum) as a result of excessive occlusal force.

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Bruxism

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Primary and secondary occlusal trauma

The tissue injury associated with occlusal trauma is often divided into two

categories: primary and secondary.

In primary occlusal trauma, a lesion results from application of excessive

occlusal forces to a tooth or teeth with normal supporting structures:

In secondary occlusal trauma, the lesion is in the periodontium of a tooth with

inadequate or reduced support. The greater the amount of periodontal support

lost due to periodontitis, the more significant occlusion becomes.

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Radiographic signs of the traumatic lesion may include.

-The presence of a widened periodontal ligament space,

- Discontinuity of the lamina dura surrounding the tooth roots,

- Alveolar bone and/or root resorption.

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Occlusal trauma will clinically manifest itself :

- Increasing mobility and/or migration of

the teeth.

- Persistent discomfort or tenderness.

- Pain to percussion or upon biting.

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To prevent occlusal trauma:

- The fixed prosthodontics appliance should be constructed so that it exerts occlusal

forces along the long axis of the tooth.

-- Any malocclusion should be treated first before the completion of the final restoration

-- The occlusion must be checked in centric and lateral excursions as well. Any

premature contacts should be eliminated.

-- The occlusion should be created at a vertical dimension that is stable for the patient.

- There should be even simultaneous contacts on all teeth during centric closure.

The distinction between primary and secondary forms of occlusal trauma, based on

the amounts of remaining periodontium, serves as primarily diagnostic purposes.

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crown margin. -2 CROWN MARGINS are the weakest point in the restoration, through which percolation of saliva & food may cause recurrent caires.

SO…,it must be.. Smooth, rounded ,accurately fitting the preparation,& free of

any porosity.

Factors affecting health of the gingival tissue. -A

1- accuracy and fitness of the restoration margins on the preparation.

2- depth of gingival encroachment i.e length of crown margin.

Over extended margins may cause tearing of epithelial attachment and

pocket formation

3- width of gingival encroachment i.e thickness of the margin

thick margin lead to pressure on the gingival tissue and blanching.

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Crown margin placement

Supragingival margin placement

Advantages:

1- Favorable reaction to gingiva.

2- Common path of insertion.

3- Easily evaluate restoration at recall appointment.

4- Avoid pulpal injury.

5- Metal finishing technique is easer.

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Supragingival margins, mainly in posterior area

with adequate occlusogingival height

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Restorative consideration frequently dictates the placement of restoration

margins beneath the gingival tissue crest. Restorations may need to be

extended gingival:

Indications of Subgingival margin placement.

1- Esthetics

2- Sever cervical erosion, restoration or caries extending beyond

gingival crest.

3- To increase retention in case of teeth with short occlusogingival

height.

4- Elimination of persistent root hypersensitivity.

5- Patient with high caries index and bad oral hygiene.

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From a periodontal point of view

Both supragingival and equigingival margins are well

tolerated. The greatest biologic risk occurs when placing

margins subgingivally.

1. These margins are not as accessible as supragingival or equigingival

margins for finishing procedures, and in addition,

2. if the margin is placed too far below the gingival tissue crest, it violates

the gingival attachment apparatus( biologic width).

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The biologic width: is the dimension of space that the healthy gingival tissues occupy above the alveolar bone. the combined

c.t.epith.attatchment from crest of alveolar bone to the base of

gingival sulcus.*

Importance of biologic width

The biologic width allows gingival fibers to

establish direct contact with the tooth and acts as

a barrier to prevent penetration of microorganisms

in the sulcus into the underlying periodontal tissues

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Two different responses can be observed from the involved

gingival tissues. One possibility is that bone loss of an

unpredictable nature and gingival tissue recession.

Other factors is the likelihood of recession. These variables

include whether the gingiva is thick and fibrotic or thin and

fragile and whether the periodontium is highly scalloped or

flat in its gingival form. It has been found that highly

scalloped thin gingiva is more prone to recession than a flat

and’ thick fibrous tissue.

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Two the more common finding with

deep margin placement is that the

bone level appears to remain

unchanged, but gingival

inflammation develops and persists.

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Margin placement guidelines.

1. If the sulcus probes 1.5 mm or less: place the restoration margin

0.5 mm below the gingival tissue crest.

2. If the sulcus probes more than 1.5 mm: place the margin one half

the depth of the sulcus below the tissue crest.

3. If a sulcus greater than 2 mm is found: especially on the facial

aspect of the tooth, then evaluate to see whether a gingivectomy could

be performed to lengthen the teeth and create a 1.5-mm sulcus. Then

the patient can be treated using Rule 1.

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Nature of the margin:

Periodontal health is enhanced by the rounding, dulling and polishing

of sharp margin.

The over extended wax pattern or failure to determine the

finish line on the impression leads to failure to determine the

finish line on the die.

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Defective margin

: open margin -1

Leads to micro leakage of food debris and bacteria between tooth and restoration.

- Caries

overhanging margin: -2

Causes irritation and plaque accumulation.

:sharp margin -3

Continuous irritation to the gingiva.

:rough margin -4

Cause accumulation of plaque

Gingival inflammation and periodontal disease.

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Margin examination.

Examined with finger tip for any rough or sharp margin.

- Casting with overhangs precipitate colonization of the

subgingival area with micro flora resembling chronic

periodontal disease, while the ideal casting harbored only

bacteria that are found in healthy gingival crevices.

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