April 1, 2007
by Domenic Belcastro, DDS
The concept of a biologic width was first mentioned by Gargiulo, Wentz and Orban in a landmark paper in 1961.1 Understanding the biology of the dentogingival complex is still the key to creating and maintaining ideal esthetics. In Fig. 1,2 three significant measurements are demonstrated; a 1mm connective tissue attachment, a 1mm epithelial attachment and a 1mm sulcus collectively known as the biologic width (BW). If we violate this biologic width during restorative procedures, the body will respond by trying to reestablish this complex. However unless there is concomitant bony recession it will fail and a permanent inflammatory condition will result. Figure 2A is an example of how mismanagement of this complex can lead to huge disappointments in both esthetics and periodontal health. We can also see in Figures 2B & 2C how the margin of the restoration is within a millimeter of the bony crest interproximately, and is therefore sitting in this delicate biologic zone, (incidentally most biologic width violations usually occur interproximately).
Unfortunately a further problem arises in trying to determine the proper distance between the restorative margin and bony crest. Gargiulo’s paper in 1961 refers to average numbers only, i.e. the 1mm connective attachment and 1mm epithelial attachment are average numbers. Using average numbers will serve as a guideline, but average numbers won’t work in every situation.
Fortunately in 1994, Vacek3 repeated the studies and presented a paper outlining a range of values for biologic width. This range was as low as 1.2mm in some individuals and as high as 4.8mm in others, highlighting the fact that it varies from person to person. The good news is that it is consistent from region to region within an individual. This information can help us when we are managing complex mixed restorations in various parts of the mouth without compromising the periodontium and without “messing-up” the esthetics. However we need a method of measuring the biologic width.
METHOD 1 – SOUNDING TO BONE4,5
What does it mean to sound down to bone and measure the biological width? Mathematically, the biologic width is the distance between the free gingival margin and the alveolar crest, minus the sulcus depth (Fig. 1). For example, if the distance from the free gingival margin to the bone (sounding to bone) is 5mm and the sulcus depth is 2mm, then the difference between the two is the biological width, which in this case would be 3mm and we must respect this number during restorative procedures or surgical procedures.
Problems can arise however when trying to measure down to bone or “sounding to bone.” First this procedure requires the use of anesthetic and a surgical probe. This isn’t a serious problem but it can be inconvenient for the patient especially if you are still at the diagnostic stage and not at the restorative stage of treatment. Secondly, measuring down to bone (i.e. sounding to bone) can be very difficult. It is easy to slide past the marginal bony crest and err in the calculation. Nonetheless this is a very effective method for measuring the biologic width. Is there another way? Yes!
METHOD 2 – MEASURE THE SULCUS
What should the sulcus depth be? What is its significance? The sulcus should be no more and no less than 1mm midfacial. Interproximately, the sulcus should measure between 2.5 to 3.0mm. Variations of this will put you at risk for recession, inflammation or large gingival embrasures (black triangles). Why?
The sulcus is the last of the dentogingival complex to develop after surgery.6 A sulcus depth of less than 1mm should be a warning flag, indicative of incomplete development of the dentogingival complex which is a potential problem following periodontal therapy. When we encounter this situation, trying to determine the amount of time that should be allotted for complete development of this complex is difficult and will depend on how and when the surgery was carried out. In traditional periodontal surgery, the tissues are positioned at the alveolar crest resulting in little to no room for the attachment and sulcus formation.7 Under these conditions, the healing process could take as long as THREE YEARS.6
Interference with this healing process, say by a premature restoration, will result in a biologic width violation and the accompanying inflammation. It is generally accepted today that the marginal tissue be positioned 3mm above the bony crest during surgery to speed up the healing (assuming a 3mm biologic width).8,9,10 If the BW measures 4mm, the tissues would need to be positioned 4mm from the alveolar crest. This approach builds in the connective tissue and epithelial attachment heights as well as the sulcus depth. Generally three months healing is all that is required after this approach.
On rare occasions a biologic width violation may self correct if there is recession (migration of the attachment away from the margin of the restoration) but this is not predictable and would result in an uneven, and unaesthetic free gingival margin!
The bottom line is that only when there is at least a millimeter of probable sulcus can we be sure that the attachment has fully matured and therefore safe to proceed with restorative treatment.
Unfortunately there are times when we will encounter a situation where there is more than 1mm of sulcus depth and we face a different risk, the risk of recession. Why? The attachment can easily support 1mm of sulcus midfacial (3mm interprox.), it may not support 2 or more mm of depth.5 If we carry out restorative procedures in cases where there is more than 1mm of sulcus depth midfacial there is a risk of tissue shrinkage back to the 1mm sulcus depth leaving our margins exposed during the insertion appointment. Only when there is a 1mm sulcus depth midfacial, (3mm interprox.) can be we confident that the tissue will remain stable and risk free of recession. RECESSION CANNOT PROGRESS INTO THE ATTACHMENT; YOU MUST HAVE BONE LOSS FIRST!
We can take advantage of this information in a number of different ways. For example, if we are planning a restoration and we know the sulcus depth is more than 1mm; one strategy to consider is whether the case may benefit esthetically by increased crown length. If so, a minor gingivectomy to establish a 1mm sulcus will improve the esthetics but also prevent disappointment due to recession. This type of crown lengthening (gingivectomy) can be carried out during the restorative appointment. On the other hand if the sulcus depth measures more than 1mm and if increased crown lengths are contraindicated esthetically, then other modes of treatment including orthodontics in combination with periodontics may be required for ideal results. THE BOTTOM LINE… THE EASIEST WAY TO PREDICT THE GINGIVAL RESPONSE TO A PLANNED RESTORATION IS TO MEASURE THE SULCUS DEPTH BOTH MIDFACIAL AND INTERPROXIMALLY!
Why is the sulcus depth different interproximally? It’s related to proper papilla form. Papilla usually measure 4.5mm in height and will regenerate in three years if removed.6 Tarnow has shown that if the distance from the contact point between two teeth to the alveolar crest is 5mm or less, the papilla will fill the embrasure 100% of the time.11 Choquet et al showed this to be true for implants as well!12 Recently Hae-Sung Cho et al reviewed the effects of interproximal distance between roots and the existence of interdental papilla according to the distance from the contact point to the alveolar crest13 and found that tooth (root) proximity has a direct effect on the presence of papilla.
Where does this magic number 5mm come from (i.e. why are papillae 4.5mm in heights above the bone). As stated previously we know there is on average a 1mm connective tissue attachment, a 1mm epithelial attachment, plus 1mm of sulcus depth labial lingual for a total of 3mm. So where does the other 1-2mm come from? The last 1.5mm is the interproximal contact factor which leads to 2.5 to 3mm of interproximal sulcus depth. This i
nterproximal contact factor is due to the predefined volume of tissue papillas have and the fact that this tissue can be pushed or squeezed into different shapes.14 By manipulating the interproximal surfaces of a restoration or of natural teeth you will influence the shape of the papilla, the interproximal sulcus depth and the corresponding gingival embrasure (Figs. 3A & B). This is important because it has significant applications in everyday dentistry.
Consider the following. In this anterior veneer case (Fig. 4) special care was taken in managing the dentogingival complex to ensure that no biologic width violations, recession or black triangles would develop after seating the final restorations. As we worked through the diagnostic wax up, the provisionals and the try in, we found that the final restorations appear to have an open gingival embrasure (black triangle) in the worst possible location, between the central incisors? There also appears to be recession on the left cupid. The question now is how do we manage the black triangle and apparent recession? The answer lies in the sulcus depth. Therefore, probe the sulcus! Why? If the interproximal sulcus depth is less than 3mm the tissues can be expected to rebound back to this height on their own. If the sulcus depth interproximally measures 3mm or greater, no such spontaneous rebounding should be expected and a permanent black triangle will result. In this case the interproximal sulcus depth measured less than 3mm and the tissues were allowed to rebound back to their original position and fill in the embrasure. The midfacial sulcus depth of the left cuspid measured zero at try in and therefore we can expect the recession to spontaneously rebound as well as the 1mm sulcus redevelops.
Why did the black triangle and apparent recession develop in the first place? The tissues were apically displaced during retraction cord procedures and held there inadvertently with the provisional. This happens all the time during routine restorative procedures. By measuring the sulcus depth and noting it was less than normal we can be certain that the tissue would relax enough to re-establish the natural sulcus depth and contour and fill in the open embrasure of the central and the apparent recession of the cuspid (Figs. 4A-H).
In the next case (Figs. 5A-F) the patient’s front four teeth were to be veneered but first we wanted to correct the uneven gingival levels. Specifically we would prefer that the free gingival margin of tooth #12 be positioned 1.5mm apically to fall in line with the free gingival margins of the adjacent anteriors.
How do we determine if this is a simple gingivectomy or a surgical flap procedure requiring bone removal? The answer lies in the sulcus depth. So probe the sulcus! Why? If the sulcus probes more than 1mm midfacial (would need to be approx. 2.5mm in total) we can just trim the excess tissue with a scalpel and continue on with the restorative treatment. On the other hand, if the sulcus midfacially measures only 1mm, a gingivectomy would cut into the attachment and ultimately lead to a biologic width violation. In this particular case the sulcus measured only 1mm midfacially and therefore a simple gingivectomy procedure was contraindicated and a flap procedure with enough bone removal (1.5mm) was needed to accommodate the attachment and a 1mm sulcus depth at the desired free gingival margin height. Furthermore, where to place the contacts and where the final papilla ends up can be is easily calculated. This was completed very predictably without creating a biologic width violation, recession or black triangles (Fig. 5F).
We can make use of this information in other ways. Consider this final case. The patient in Fig. 6A was nearing the end of orthodontic treatment and was concerned about the resultant black triangles. One option offered to her by her attending orthodontist was to deband and try to restore away the open gingival embrasures. But is this possible? Consider what the emergence from the midfacial point of the tooth to the midfacial point of the papilla would be and what the resulting restoration would have to look like to accomplish this. The result would have been a very skewed, over contoured, large and unaesthetic restoration. Furthermore, what would the biological price of this treatment be? Is there another alternative? Where do we start?
The question that needs to be asked is whether this is a papilla problem or a tooth shape problem? Let’s start by measuring the sulcus. Why? Again we know that under normal circumstances the attachment can support 3mm of sulcus interproximally with proper interproximal tooth form and contact (ref. Tarnow and Choquet10,11). What if we measure the sulcus interproximally and find it to be less than 3mm? Consider that large open embrasures act like diastemas (no interprox. contact factor) and therefore we should expect less than 3mm of sulcus interproximally. In fact we should expect something closer to the buccal or lingual sulcus depth, (i.e. 1mm). In Figs. 6B & C we see that both sides measure approximately 1.5mm interproximately. This is significant because we know we can expect up to 3mm interproximately by squeezing the papilla between the contacts. In fact if we do the math right we can figure out exactly how much stripping is needed and where to place the new height of contour to correct this “black triangle.”
To do it, measure 3mm from the base of the sulcus to determine where the papilla ideally should be. Then understand the contact point of each tooth should also be at this level. Therefore create a new height of contour interproximally at this 3mm level. Then instruct the orthodontist to continue to squeeze the teeth together and the papilla will follow. The proviso for all of this is that we have enough root separation between the teeth and overjet to accommodate the movements. We also need to be sure that no Bolton factor exists or is created during the stripping (i.e. teeth that are too small for the given arch).
We will do this one embrasure at a time starting with the centrals to control these movements (Figs. 6D). Now after more active treatment the resulting black triangles are beginning to reduce (Fig. 6E) but we are not finished. We continue the process to improve the centrals and the right lateral (Figs. 6F & G). We are starting to see full closure of these embrasures (Figs. 6H & I). We repeat this process for left side (Figs. 6J & K). Notice the space opening up between the lateral and the cuspids (Fig. 6L). We continue the process until all the black triangles are closed (Figs. 6M, N & O). Case is completed with no restorations, no black triangles, and NO MAINTENANCE (Fig. 6P).
The key to managing all these cases was an understanding of the dentogingival complex and the use of the sulcus depth to predict the gingival response.
In a follow-up article, we will build on these concepts to achieve ideal esthetics in more complex situations.
Thanks to Dr. Angelos Metaxas for the orthodontics supplied in the final case. All surgery and restorative work completed by Dr. Domenic Belcastro.
Dr. Belcastro is a contributing consultant for esthetics to Oral Health Journal.
Oral Health welcomes this original article.
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