cervical margin design in fpd

1. Dent Clin N Am 48 (2004) 417–431
Cervical margin design
with contemporary
esthetic restorations
Guided by:
Dr. Akshey Sharma
Dr. Pardeep Bansal
Dr. Gagandeep Chahal
Presented by:
Dr Aditi Ghai
PG 2nd year
Dept of Prosthodontics
D.I.R.D.S, Faridkot

2. Metal ceramic and all-ceramic crowns are used
frequently to restore esthetics and function.
One of the essentials for success with either
option is proper tooth preparation, which includes
proper selection and preparation of the cervical
margin of the preparation.
Regardless of the margin geometry, proper
placement of the prepared gingival margin in
relation to the free gingival margin, the epithelial
attachment, and the alveolar housing is
imperative.

3. Wherever esthetics permit – supragingival
margins
High esthetic demands – intra-crevicular margin
placement (requires precision)

4. Margin placed
a short
distance from
free gingival
margin
Minor amount
of gingival
recession
Exposure of
margin and
esthetic
failure
Margin too
deep
Biological
width
violation
Chronic
gingival
inflammation

5. Potential landmarks for accurate margin placement
1. place cervical margins 0.5 mm apical to the Free
Gingival Margin
2. sound through the attachment to probe the
crest of the alveolar bone and to place cervical
margins at least 4mm coronal to that alveolar
crest
With either, prepared cervical margin should follow
the scalloped anatomy of the alveolar bone, the
attachment, and the gingival tissues.

6. Error - Flattening the cervical margin in the inter-
proximal areas leads to violation of biologic width
and elicits a chronic inflammatory response.

7. Criteria for margin selection
1. The selected margin must provide a predictable
level of marginal integrity.
2. To minimize plaque accumulation, the selected
margin must present smooth materials to the
gingival sulcus.
3. In some situations, the margin also must provide
acceptable esthetics.

8. Problems from improper preparation and
placement of cervical margins
1. biologic width violation (function of margin placement;
independent of margin design)
2. metal margins showing through thin marginal gingiva
3. recession exposing the tooth/restorative interface (improper
soft tissue management; independent of margin design)
4. opacity in the cervical third of the restoration
5. roughness of the cervical margin which contributes to plaque
accumulation

9. Margins to consider for
metal ceramic restorations

10. Knife-edge margin
1. Termination is difficult to read on a gypsum die, fit
is often compromised
2. Thin margins are prone to distortion during ceramic
firing
3. Potential for metal display – lack esthetics
4. Limited use - root has been amputated due to
periodontal disease or with cusp fractures where a
knife-edge margin cannot be avoided

11. Chamfer margin
1. Relative inherent lack of specificity of depth
2. Due compromised marginal integrity as a result of
distortion of the metal framework during porcelain
firing
3. Distortion depends on composition of metal alloy
(melting pt.) and cervical geometry of the margin

12. 3 cervical margins seem to meet the criteria for marginal
integrity -shoulder, shoulder-bevel and slant shoulder.
Shoulder and shoulder-bevel margin seem to resist
distortion due to the inherent bulk of metal at the margin
Also meet the criterion related to the use of smooth
materials in the gingival crevice
The shoulder can be used with a metal margin, which can be
highly polished, or with a porcelain margin, which results in
glazed porcelain in the sulcus.
The shoulder-bevel margin has a collar of metal 1 mm or
more in width and thus places highly polished metal in the
sulcus.

13. These restorations have used a shoulder-bevel margin that provides
optimum
marginal integrity and a smooth, polished surface.

14. The use of a shoulder margin with a porcelain labial
margin results in smooth, glazed porcelain in the gingival
crevice.

15. The slant shoulder can be used with a metal collar or with the
so-called disappearing margin.
If metal collar is used, it can be highly polished and thus can
be acceptable as it relates to plaque accumulation
Disappearing margin is rough due to the presence of three
different materials at the terminus
-- oxidized metal (75 times rougher than polished metal),
-- opaque porcelain (rougher than glazed porcelain), and
-- body porcelain (porous because it tends to shrink toward
the greater mass of porcelain coronal to the margin).

16. Third criterion- esthetics
Shoulder-bevel – polished metal collar of 1 mm or more
Steep bevel of approximately 60° should be used to maximize
the slip-joint effect and close the margin Best initial
fit, maintained after firing cycles
Problem with esthetics
used where esthetics is not important.
The margin can be placed partially in the sulcus, in an equi-
gingival position, or a supragingival position.
Metal display – informed consent

17. If esthetics is important, the clinician has
three options.
All ceramic crown - excellent esthetics,
improved longevity, avoid on posteriors.
A shoulder margin with rounded internal angle
should be prepared to end at approximately
90° to the external angle of the labial or
buccal surface.
A slight slant of no more than 5° is
acceptable.
The margin should be as smooth as possible,
and, to provide optimum esthetics and
strength, should be between 1.2 and 1.5 mm in
depth (adequate bulk, cervical margin in
compression during function).

18. When a metal-ceramic restoration is indicated, the
porcelain labial margin (shoulder) and the disappearing
margin (slant shoulder) can be used.
Slant shoulder – inherent roughness – only where
indicated, that is when the cervical margin of the
restoration must be placed a considerable distance
down the root surface.
Low smile line - slant shoulder with a metal collar
If the smile exposes the cervical portion of the
restoration - disappearing margin (hides metal but
opacious appearance – masked with intrinsic coloration)

19. The disappearing margin effectively
hides the metal margin but often results
in cervical opacity.
If patients accept characterization, cervical opacity can often
be masked with internal coloration.

20. The margin of choice in esthetic situations when using
metal-ceramic crowns is a shoulder design with a porcelain
labial margin.
thickness of ceramic material at the margin so that a
predictable esthetic result is assured
excellent strength
places glazed porcelain in the gingival sulcus
The porcelain margins illustrated combine good marginal integrity with
excellent esthetics.

21. These metal-ceramic restorations with porcelain labial
margins provide acceptable esthetics when the margins are
hidden with healthy gingival tissues.

22. The preparation for porcelain labial or buccal margins
mandates a shoulder margin on the buccal half of the
tooth and a shoulder bevel or chamfer on the lingual half.
The premolar has been prepared for a porcelain shoulder margin, and
the molar has been prepared for a shoulder-bevel margin.

23. Controversies
Use of 360° porcelain margin (improved light transmission)
Termination of gingival extension of the metal
substructure relative to the shoulder margin (metal
framework be cut back 1 mm from the shoulder margin)
With all-ceramic crowns, the optimum finish line is a shoulder
margin with rounded internal angle with a width of 1.2 to 1.5 mm.
This depth may have to be reduced to 1.0 mm with triangular-
shaped teeth.
It should meet the external surface of the tooth at an angle of
90

24. Discussion
When preparing teeth for esthetic crown restorations, the
clinician must determine which cervical finish line is
appropriate for each specific clinical situation.
All cervical margins must be placed in the correct position
relative to the free gingival margin, the epithelial
attachment, and the alveolar housing.
With all-ceramic crowns, the optimum finish line is a
shoulder margin with rounded internal angle with a width of
1.2 to 1.5 mm.
This depth may have to be reduced to 1.0 mm with
triangular-shaped teeth.
It should meet the external surface of the tooth at an
angle of 90.

25. With metal-ceramic crowns, knife-edge margins and chamfer
margins should generally be avoided due to concerns with fit.
Shoulder-bevel margins are the margins of choice in situations
where esthetics is not important because of their documented
ability to provide optimum fit and the ability to polish the
inherent metal collar.
Shoulder margins with a labial or buccal porcelain margin are
indicated in situations where esthetics is paramount.
These margins should be prepared at 90° to the external tooth
surface, should be exceptionally smooth, and should have a width
of 1.2 mm.
The metal substructure should be finished 1.0 mm from the
shoulder margin to permit optimum light transmission without
sacrificing strength.

26. Slant shoulder margins are necessary when the tooth preparation
extends some distance on the root surface.
In situations where these margins are not visible, they should use a
metal collar.
In situations where the smile exposes these margins, the
disappearing margin approach should be used.

27. An analysis of margin configurations for metal-ceramic
crowns
Donovan, T and Prince, J 1985, J Prosthet Dent, vol. 53, no. 2, pp. 153
Esthetics, marginal integrity, and periodontal health are the three
major determinants of marginal configuration with metal-ceramic
crowns. The advantages, disadvantages, and indications for each type
of margin configuration are as follows:
Beveled shoulder
Advantages
1. Marginal closure
2. Relative lack of distortion
3. Polished surface at margin
Disadvantages
1. Bevel must be steep to be effective
2. Esthetics
Indications: Nonesthetic regions

28. Sloped shoulder
Advantages
1. Minimum metal display
2. Less intrusion into crevice
3. Simplified laboratory technique
Disadvantages
1. Difficult tooth preparation
2. Potential distortion
3. Rough materials at margin edge
Indications: Esthetic regions in patients with excellent
oral hygiene

29. Margin designs for esthetic restoration: An
overview
Chatterjee, Journal of Advanced Oral Research, Vol 3; Issue 1: April 2012
*Jalalian E et al (2008) evaluated the effect of a
sloping shoulder and a shoulder bevel on the marginal
integrity of porcelain-fused-to-metal (PFM) veneer
crowns
*Marginal integrity of both preparation designs was
found to be similar.
*Since the sloping shoulder design offers biological and
esthetical advantages over the shoulder bevel, its use is
indicated for anterior restorations.

30. *Gardner et al. (1997) compared the load necessary to
cause porcelain failure on traditionally fabricated
metal–ceramic crowns cemented to metal tooth analogs
with two different types of margins.
*The load required to cause porcelain fracture in the
crowns with porcelain facial margins was statistically
significantly greater than the load required to cause
porcelain fracture for crowns with metal collars

31. *Bishop K et al. (1996) reviewed margin design for
porcelain fused to metal restorations which extend onto
the root.
*A 90 degree shoulder is probably the most commonly used
margin design. This increases the risk of irreversible
damage to the pulp, particularly on exposed roots.
*So more conservative designs, such as the 135 degree
shoulder or deep chamfer, should be considered

32. *Omar et al. (1987) conducted a scanning electron
microscopy of the marginal fit of ceramo-metal
restorations with facially butted porcelain margins.
*The marginal openings for facially butted metal ceramic
crowns were greater than the bevelled shoulder
marginal design.
*Aesthetics and the favourable contour of the facially
butted porcelain are distinct advantages but are
accompanied by increased laboratory time.

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