Dent Clin N Am 48 (2004) 417–431

Cervical margin design with

contemporaryesthetic restorations

Guided by:Dr. Akshey SharmaDr. Pardeep BansalDr. Gagandeep Chahal

Presented by:Dr Aditi GhaiPG 2nd yearDept of ProsthodonticsD.I.R.D.S, Faridkot

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.

Wherever esthetics permit – supragingival margins

High esthetic demands – intra-crevicular margin placement (requires precision)

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

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.

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

Criteria for margin selection1. 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.

Problems from improper preparation and placement of

cervical margins1. 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

Margins to consider for metal ceramic restorations

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

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

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.

These restorations have used a shoulder-bevel margin that provides optimum

marginal integrity and a smooth, polished surface.

The use of a shoulder margin with a porcelain labial margin results in smooth, glazed porcelain in the

gingival crevice.

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).

Third criterion- estheticsShoulder-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

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).

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)

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.

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 strengthplaces glazed porcelain in the gingival sulcus

The porcelain margins illustrated combine good marginal integrity with

excellent esthetics.

These metal-ceramic restorations with porcelain labial margins provide acceptable esthetics when the

margins are hidden with healthy gingival tissues.

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.

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

DiscussionWhen 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.

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.

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.

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

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

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.

*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

*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

*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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