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: [email protected]. 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. 1
16
Embed
May 2009 - Predictable Margin Placement for Long Term Esth
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
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.
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.
3
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
4
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.
5
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
6
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)
7
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.
8
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