Periodontal & Prosthodontic Interface

Question 1

What may occur if restorations are provided in the presence of active periodontal disease?

Answer 1

It may eventually cause the failure of the restoration and the tooth.

Question 2

What may happen when restorations are provided in the presence of inflammation?

Answer 2

The tooth restoration interface may become exposed when the inflammation subsides.

Question 3

When may you provide restorations before resolving inflammation, peri disease?

Answer 3

The exception to this is the provision of emergency care or treatment required to stabilise progression of disease e.g. temporisation of a caries lesion.

Question 4

When may inflammation set in (physiologically as well as mechanical)?

Answer 4

Inflammation may set in when the epithelial integrity (primary defence barrier) is breached by pathogenic microflora and their metabolic products, as well as a result of trauma during restorative procedures or by restorations.

Question 5

What factors influence disease severity and activity?

Answer 5

Influenced by host susceptibility and response, tissue characteristics, virulence factors of the organisms, and iatrogenicity of restorations or prostheses.

Question 6

The iatrogenicity of restorations or prostheses can influence disease activity and severity. Expand on this.

Answer 6

Iatrogenecity may result from design characteristics and/or the biomechanical interactions of restorations with the periodontal tissues e.g. a subgingival/overhanging margin.

Question 7

What must be considered and addressed to be able to deliver a successful restorative dental treatment?

Answer 7

A sound understanding of the biology- anatomy and physiology- of the hard and soft tissues involved, immuno-pathogenesis mechanisms, biomimetics, biomechanical and biochemical aspects of dental biomaterials and their interactions with the intraoral tissues are essential.

Question 8

What is the biological width?

Answer 8

The vertical dimension of the dentogingival complex, which comprises the sulcular depth, the junctional epithelium and connective tissue attachment

Question 9

Why is the biological width important?

Answer 9

It provides the natural seal around the tooth, protecting it from the unchecked ingress of pathogenic organisms in to the connective tissue i.e. primary defence barrier

Question 10

What are the guides to measuring the biological width?

Answer 10

Biological width has been defined as the measurement between the depth of the gingival sulcus and the crest of alveolar bone.

Question 11

What happens when a restoration is extended into the biological width?

Answer 11

There is an attempt to re-establish the biologic width. This results in persistent gingival inflammation within the attachment apparatus. Gram negative and anaerobic organisms thrive in the environment leading to progression of persistent inflammation.

Question 12

What can be done in clinic to assess and avoid impingement of the biological width?

Answer 12

The location of the margins of a restoration must be carefully planned prior to tooth preparation.
To avoid consequences of violation of the biologic width, must measure the probing depth to account for the sulcus depth. A radiograph must be taken to assess the crestal bone level and its relationship to the location of the planned margin.

Question 13

What should the distance between the planned margin location and the alveolar bone crest be?

Answer 13

The distance between the planned margin location and alveolar bone crest must be at least 3mm.

Question 14

What kind of gingival phenotypes are there?

Answer 14

Gingivae may be either thick & flat or thin & scalloped.

Question 15

Is thin & scalloped or thick and flat more susceptible to recession?

Answer 15

Thin and scalloped gingivae are more susceptible to recession compared to thick and flat gingivae.

Question 16

During tooth preparation, impression making or the restoration process, what factors can cause pronounced gingival recession?

Answer 16

Any trauma during tooth prep, impression making or the restoration process to the gingival margin, overhanging or subgingival extension of restorations are all likely to cause pronounced gingival recession.

Question 17

Where is the zenith of the tooth?

Where is the zenith point on central incisors, lateral incisors and canines?

Answer 17

Zenith point is the height of contour of the gingival scallop.
The zenith point is distal to the long axis of central incisors and canines, while on lateral incisor the zenith is coincident with the long axis.

Question 18

Label image 1

Answer 18

A: zenith
B: long axis of the tooth

Question 19

Where should the gingival margins of the central incisors, lateral incisors and canines be?

Answer 19

Height of the gingival margins of the central incisors and canines should be at the same level.
Lateral incisal gingival margin height is up to 1mm incisal to a line joining the height of the gingival margins of centrals and canines.

Question 20

Contact area and interdental embrasures wise, what percentage of tooth contacts to create contact area between:
A) between centrals
B) between central and lateral
C) between lateral and canine

Answer 20

A) between centrals- 50% of the length of the central incisor
B) between central and lateral- 40% of the central incisor
C) between lateral and canine- 30% of the central incisor

Question 21

What is the distance between the gingival margin to the alveolar crest?

Answer 21

3mm

Question 22

How far should the distance be from the contact point to the crest of the interproximal bone?

Answer 22

The distance from the contact point to the crest of the interproximal bone should be 5mm or less for the papilla to be present 100% of the time.

Question 23

If the distance from the contact point to the crest of the interproximal bone is 6mm or 7mm, what happens?

Answer 23

The papilla is less likely to be present compared to when the distance is 6mm or less.

Question 24

Why is attached gingiva around the teeth important?

Answer 24

To minimise the risk of gingival recession and to increase patient comfort when performing OH procedures.

Question 25

In what circumstances may the mesiodistal dimension of a crown be increased (and not approximate that of a natural tooth)?

Answer 25

To reduce diastema or gingival embrasure space.

Question 26

If increasing the mesial distal width of a crown (and not following the approximate of the natural tooth), what must be checked prior to increasing it?

Answer 26

If the roots of the adjacent teeth are in close proximity then there will be less room for increase of the mesiodistal dimension.
Therefore, check distance between roots on radiograph prior to increasing MD crown dimension.

Question 27

By how much can the facio-lingual dimension of the prosthetic crown be increased and why?

Answer 27

The facio-lingual dimension of the crown should not be increased more than 0.5mm from the gingival margin as it may induce plaque retention.

Question 28

What is the emergence profile?

Answer 28

The profile of a restoration as it emerges from the gingival margin, termed emergence profile, should be straight or flat for the first 0.5mm of the restoration to maintain healthy gingival tissues.

Question 29

What should the emergence angle be of maxillary anterior crowns, veneers and composite resin build ups?

Answer 29

Angle of 15 degrees.

Question 30

What should an ideal interproximal contour permit?

Answer 30

• good access to oral hygiene
• does not compress the papilla
• allows proper phonetics
• is in harmony with the adjacent teeth
• provides effective and properly located and shaped proximal contacts

Question 31

What may poor marginal adaptation cause?

Answer 31

Plaque accumulation and therefore caries development

Question 32

The finish line/gingival margins of a tooth prep must have what characteristics?

Answer 32

Must be smooth

No unsupported enamel remaining

Question 33

What must an impression of a tooth prep for a crown capture? And why?

Answer 33

Detail of the finish line
Relationship of the gingival tissues to the finish line
Part of the unprepared tooth structure beyond the finish line

All essential for the construction of quality restorations

Question 34

In terms of RPD, are acrylic partial dentures or Co-Cr better at providing gingival relief?

Answer 34

Co-Cr is better at providing gingival relief

Question 35

Why are some stainless steel clasps such as in image 2 in mucosa supported acrylic RPD not beneficial?

Answer 35

They have a gum stripping effect.

The clasp will act as a plaque trap and therefore plaque control is essential by patient.