PREDICTABLE MARGIN PLACEMENT FOR LONG TERM

ESTHETICS & GINGIVAL HEALTH

Authors – Dr. Vijaya A. Wagh*

Dr. Abhijit Wagh**

* Professor & Head, Dept. of Prosthetic Dentistry, College of Dental Science & Hospital,

Rau, Indore.

** Postgraduate student, Dept. of Conservative Dentistry, Modern Dental College

& Research Centre, Gandhinagar, Indore.

Correspondence Address: Dr. Vijaya A. Wagh – Professor & Head, Dept. of Prosthetic

Dentistry, College of Dental Science & Hospital, Jhoomer Ghat, Rau, Indore.

Mobile - +919981705243. Email: vijayawagh03@yahoo.co.in.

Abstract

Prosthodontics today aims at maximum biologic compatibility of dental prostheses /

restorations with the surrounding oral environment. Margin placement is critical for long term

periodontal health. The concept of Biologic Width can provide definite guidelines for margin

placement. This article discusses margin placement & describes a practical way to use the

concept of Biologic Width for margin placement. Four categories of Biologic width are

diagnosed i.e. Normal crest, High crest, Low crest Stable, Low crest Unstable using the

procedures of Bone sounding & Sulcus probing.

Key Words: Biologic Width, Crown margin placement, Intra-crevicular margins (Subgingival

margins), Perio-restorative interface.

1

A healthy co-existence between dental restorations and their surrounding periodontal

structures is the goal of the conscientious dentist and the expectation of the informed patient.

This co-existence is tested the most at the perio-restorative interface or margins of

restorations. Placement of restorative margins is critical to the longetivity of the restoration,

health of the periodontium and also esthetics.

Margins of crowns may be located above, at, or below the crest of the gingival margin.

Research points out that, intra-crevicular margins create a protected enclosed area that

encourages more rapid plaque accumulation and its sequelae. In addition, this area is also

inaccessible for effective oral hygiene. The term intra-crevicular is more specific and correct

than subgingival margins because it implies confinement within the gingival crevice/sulcus

whereas subgingival margins can extend into the junctional epithelium and connective tissue,

which is a violation of the Biologic Width.

The term “Biologic Width” (Fig 1, 2) refers to the combined connective tissue – epithelial

attachment from the crest of the alveolar bone to the base of the gingival sulcus1. These 2

zones form a biologic seal around the neck of the tooth that act as a barrier to the entry of

micro-organisms into the underlying tissues. It was first described by Garguilo et al2.

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Fig 1

Fig 2

Despite the obvious advantages of supragingival margins3, there are clinical situations

requiring intra-crevicular placement. These clinical situations are:

1. Esthetic requirements

2. Subgingivally fractured endodontically treated teeth

3. Old subgingival restorations

4. Cervical caries extending below the gingival crest, abrasion or erosion etc.

5. Short clinical crowns

6. Elimination of root hypersensitivity

Although need for Esthetics dictates placement of intra-crevicular margins, a study published

by Watson & Crispin4 showed that many patients did choose the optimum gingival health

offered by supra-gingival margin placement over the less healthy, improved esthetic attempt

of a sub-gingival margin, if the patients understood the circumstances and were given a

choice. The study also showed that 83% of dentists do not analyze tooth visibility when

deciding on margin placement for esthetic appearance and only 64% of dentists actually

assess the patient’s desires before deciding where to place the margin.

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In spite of considering all this, if the restorative margin must be extended below the gingival

margin atleast four factors have to be paid attention to. They are:

1. Emergence profile.

2. Finishing of margins.

3. Zone of attached gingiva.

4. Violation of Biologic width.

This article discusses margin placement in relation to the concept of Biologic width and

describes a practical way use to this concept. The 1st three factors are not within the scope of

this article.

In 1961, Gargiulo et al published his classic study of dimensions on attachment

measurements. They reported that the mean measurement of the epithelial attachment plus

connective tissue attachment was 2.04mm.2 (Fig 3)

Fig 3

In 1977, Ingber et al described “Biologic Width” and credited D. Walter Cohen for first

coining the term5. The contemporary and more accurate term which expresses function and

diversity of the component tissues without reference to the dimensions to describe biologic

width is “Sub-crevicular attachment complex”.

Wilson & Maynard (1981) cautioned against extending restorations so far subgingivally that

the attachment is damaged. They state that “some distance of unprepared tooth structure

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Gingival

Sulcus

Epithelial

Attachment

Connective

Tissue

Attachment

should remain between the finish line of the prepared tooth and the junctional epithelium.

Ideally, this should be 0.5mm”.6

Nevins & Skurow (1984) stated that the biologic width should be considered 3mm in length

measured coronally from the alveolar crest. They assumed that the restorations placed at

that level would actually terminate above the attachment and within the gingival sulcus.7

Fugazzatto, Silvers, and Johnson advocate locating margins subgingivally. They suggest

the margins should be 3mm coronal to the alveolar crest to provide space for the biologic

width and to have the restoration terminate 1mm above the base of the sulcus 8,9,10.

According to Ferencz J, when the sulcus is less than 1mm or may be 0.5 mm on probing, the

placement of the restoration 0.5mm intra-crevicularly encroaches on the attachment. In such

a case, margin placement should not enter the crevice but terminate just at or above the

gingival margin.11

The problem with the concept of Biologic width was that it is just an arithmetic mean & not the

same for every patient. The dimension is not constant, it depends on the location of the tooth

in the alveolus, varies from tooth to tooth and also from the aspect of the tooth. Its constancy

can only be found in the healthy dentition. It is hence difficult to determine clinically. So

although, the importance of Biologic Width is acknowledged by every dentist, the clinicians

have been unable to utilize this concept in a practical manner due to the lack of operating

guidelines. Also, intra-crevicular margins may give rise to varied gingival reactions like either

iatrogenic marginal inflammation or gingival recession due to violation of the biologic width.

However, some cases may show healthy tissue around the crown and long term stability12.

If the dentist is able to predict the response of the gingiva using the concept of Biologic Width

prior to preparing the teeth to receive crowns, he is in a better position to determine the

optimal position of margin placement as well as to inform the patient of the probable long

term effects of crown margin on gingival health and esthetics.

Kois in the year 1994 published his classic papers on biologic width. He has proposed 3

categories of biologic width based on the total dimension of attachment plus the sulcus depth 13,14. This makes it a practical approach to operationally define Biologic Width using the

procedure of bone sounding and sulcus probing.

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The most exact & clinically determinable landmark of choice is the healthy stable gingival

margin. To determine the biologic width i.e. distance between gingival crest & alveolar crest,

a procedure termed as bone sounding (Fig 4) is carried out. The patient is anaesthetized

and a periodontal probe is placed in the sulcus & pushed through the attachment apparatus

till the tip of the probe engages alveolar bone. Measurements in the anterior teeth or esthetic

zone are taken mid-facially and proximally at the facio-proximal line angle.12,14

Fig 4 : Bone sounding procedure

Based on this measurement, the three categories of Biologic Width (Fig 5)

described are:12,14

1. Normal crest

2. High crest

3. Low crest

a. Unstable

b. Stable

Fig 5 : Categories of Crests

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1. Normal Crest – (Fig 6)

Fig 6 : Normal Crest

In this patient the mid-facial measurement is 3.00mm & proximal measurement is 3-

4.5mm. It occurs 85% of times & gingival tissue tends to be long term stable. In this, the

margins of the crown should be placed 0.5mm intra-crevicularly i.e. minimum 2.5mm from

alveolar bone. This is well tolerated and stable long term.

2. High Crest – (Fig 7)

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Fig 7 : High Crest

The mid-facial measurement is less than 3mm & proximal measurement is also less

than 3mm. In this patient, intra-crevicular margins result in biologic width impingement

(because it is too close to alveolar bone) & chronic inflammation, hence contraindicated. This

occurs 2% of times. It should be noted that High crest is more often seen in the proximal

surface adjacent to an edentulous site, which is because subsequent to tooth extraction the

inter-proximal papilla is not supported causing its collapse commonly and resulting in a high

crest situation.

3. Low crest – (Fig 8)

Fig 8 : Low Crest

Occurs 13% of times. In this group, the mid-facial measurement is greater than 3mm &

proximal measurement is greater than 4.5mm. This patient is more susceptible to

recession secondary to placement of an intra-crevicular crown margin. Even routine

placement of a retraction cord subsequent to crown preparation injures the attachment

apparatus. However, on healing, it tends to go back to a normal crest position resulting in

gingival recession.

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Low crest stable or unstable –

All Low crest attachment patients do not give the same response to injury. Only some are

susceptible to gingival recession while others have quite a stable attachment apparatus. The

difference is based on the depth of the sulcus

E.g.: Bone sounding patient A (Fig 9) shows the mid-facial distance from gingival crest to

alveolar crest as 5mm. On bone sounding patient B (Fig 10), the measurement is again 5

mm. Hence, by definition both are Low crest. However, they are not the same. Patient A has

sulcus depth of 3mm & attachment of 2mm, whereas patient B has sulcus depth of

1mm & attachment apparatus of 4mm.

Fig 9 : Low crest unstable Fig 10 : Low crest stable

In such a case, patient A is unstable, as there is greater sulcus depth hence more

unsupported tissue, which is not stable. This makes the patient more susceptible to gingival

recession & is classified as a Low crest unstable.

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Whereas patient B is less susceptible to gingival recession due to a more substantial

attachment apparatus (4.0mm) & responds more like a normal crest patient & is classified as

Low crest stable patient.

Hence to diagnose a Low crest patient as Stable or Unstable, the dentist should perform

sulcus probing in addition to bone sounding. Sulcus probing is an inexact art15 because of

many variables like probe diameter, probing force, angle of the probe & amount of

inflammation in the attachment. However, a determination of sulcus depth is necessary to

determine if a Low crest patient has a tendency to be long term stable or unstable in the face

of an insult to the attachment.

Summary –

When preparing anterior teeth or teeth in the esthetic zone for indirect restorations or

prostheses, it is essential that the dentist determine the crest category. This will allow the

optimal placement of restoration margins. Also, the dentist will be in better position to inform

the patient of the probable long term effects of crown margins on his/her gingival health and

esthetics.

In a Normal Crest patient the intra-crevicular margin should be no closer than

2.5mm from the alveolar crest for long term gingival health and esthetics.

In case of High Crest situations, placement of an intra-crevicular margin is likely to

result in chronic inflammation.

In Low Crest situations, the sulcus depth is also determined and a Stable Low

Crest patient may be treated like a Normal Crest patient. However, if the sulcus is

deeper & the patient is in the Unstable Low Crest category, the dentist can expect an

intra-crevicular margin placement to result in gingival recession.

In any of the situations, the gingiva on the proximal surface adjacent to an

edentulous site is usually in a High crest position, hence the finish line should end

just at the crest of the gingival margin to avoid chronic inflammation of the inter-

dental gingiva.

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References:

1. Rosentiel et al – Contemporary Fixed Prosthodontics, 3rd Ed, Mosby pub.

2. Garguilo AW et al – Dimensions & relations of the dentogingival junctions in humans. J.

Periodont, 1961; 32: 261-267.

3. Newcomb GM - The relationship between the location of sub gingival crown margins &

gingival inflammation. J. Periodont, 1974; 45: 151-154.

4. Watson J, Crispin BJ – margin placement of esthetic veneer crowns: Part III- Attitudes of

patients & dentists. JPD, 1981; 45: 499-501.

5. Ingber JS et al – The “Biologic Width” – A concept in periodontics & restorative dentistry.

Alpha Omegan. 1977; 70: 62-65.

6. Maynard JG, Wilson K – Physiologic dimensions of the periodontium: Fundamental to

successful restorative dentistry. J. Periodont, 1979; 50: 170-174.

7. Nevins M, Skurow HM – The intracrevicular restorative margin, the biologic width & the

maintenance of the gingival margin. Int. J. Periodont Rest Dent, 1984; 4: 30-49.

8. Fugazzotto PA – Periodontal & restorative inter-relationship: The isolated restoration.

JADA, 1985; 110: 915-917.

9. Silvers JJ – Periodontal & restorative considerations for crown lengthening. Quint. Int.,

1985; 60: 833-835.

10.Johnson G, Leary J – Pontic design & localized ridge augmentation in FPD design, DCNA,

1992; 36: 3, 591-598.

11.Ferencz J – Maintaining & enhancing gingival architecture in fixed prosthodontics. JPD,

1991; 65: 5, 650-657.

12.J. William Robbins – Tissue management in restorative dentistry. Fn. Esth. & Rest. Dent.,

Series 1; No 3: 2-5.

13.Kois JC – Altering gingival levels: The restorative connection, Part 1-Biologic variables. J.

Esthet. Dent., 1994; 6: 3-6.

14.Kois JC – The restorative-periodontal interface: Biological parameters. Periodontol 2000’,

1996; 11: 29-38.

15. Weisgold AS – Contours of the full crown restoration. Alpha Omegan, 1977; 70: 77-89.

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