Biologic width is known as the specific distance found between connective tissue attachment and junctional epithelium. In other words it is the height found between deepest points for the gingival sulcus with the alveolar bone crest. The distance is good to consider when it comes to the fabrication of a dental restoration since they have to respect natural architecture of gingival attachment so that the harmful consequences may be avoided. Biologic width is specific to the patient and it may vary starting from 0.75 up to 4.3mm. According to the research, the mean biologic width had been determined to be 2.04 mm and for this, the 1.07mm is being occupied by connective tissue attachment which is approximate to be 0.97mm. Since it is not possible to restore the tooth to precise coronal edge for the junctional epithelium, it is recommended to get rid of the bone in order to reach to 3mm between the alveolar bone and restorative margin. If the restoration fails to take such consideration in its account, then it will violate biologic width and there are three things that can take place, there may be unpredictable loss of the alveolar bone, chronic inflammation for the gingival or chronic pain.
Besides the crown lengthening that establishes the right biologic width, 2mm height of a tooth structure has to be available in order to allow the ferrule effects. Ferrule effects for the teeth, it is the band which exists on the residual tooth structure and not the metal band found on the barrel. Enough vertical tooth structure is needed for the crown to ensure ferrule effect. This had been shown in order to reduce significantly fracture incidence in the tooth treated endodontically. Since the beveled tooth structure is not the same as the vertical axis of a tooth, it will not contribute to a ferrule height in the right way. The need of beveling a crown margin with 1mm, it will mean the additional 1mm of the bone removal in a crown lengthening procedure. However, the restoration is performed without the need to use the bevel.
The studies now had found out that even if the ferrule is needed, it does not have to be given at the expense of a remaining tooth or root structure. At the other hand, it had also shown a difference between effective long term restorations or its failure may be just 1mm for additional tooth structure if it is encased in the ferrule to offer better protection. When the functional and long lasting restoration may not be achieved, it is better to consider the tooth extraction.
Crown to the root ratio
With the human body, the ectodermal tissue works to offer the protection against the invasion of the bacteria with foreign materials. However, the dental and teeth implants have to penetrate within such defensive barrier. This natural seal which is found on these two and which protect the alveolar bone against disease and infection is what it is called biologic width. Biological width is said to be dimension of a soft tissue and it is attached to a portion of a tooth coronal to the alveolar bone.
Biologic width is important in preserving the periodontal health and to remove irritation which can damage periodontium or prosthetic restoration. A millimeter found on a junctional epithelium and at the tip of an alveolar bone, is responsible to keep the inflammation down with the bone resorption or periodontitis development.
Biologic width and margin placement
A dentist is given three different options to the margin placement; they are subgingival, equigingival and suprangingival.
This causes less impact at the periodontium. The margin location is considered to be a non aesthetic area because of a marked difference in the opacity and color of the restorative materials on the tooth. In the beginning of using of a translucent restorative material like resin cement and adhesive dentistry, now it is possible to put the supragingival margins in the aesthetic areas.
The use of the equigingival margin was not something that many people looked out for since it was believed to increase the plaque accumulation compared to subgingival or supragingival margins. This resulted in the gingival inflammation. Even a little gingival recession can create the unsightly display. However, such concern is no longer a question, since the restoration margin may be blended with a tooth since the restoration may be finished faster and it provides a polished and smooth interface on gingival margin.
Any restorative consideration may dictate placement of the restoration margin under gingival tissue on its crest if there is tooth deficiency or caries. It can also be used to hide dental restoration or tooth interface. Invasion to the biologic periodontal area which allows additional retention, it may lead iatrogenic periodontal problem and early loss of the restorative material. The restorative margin is put far below under the tissue crest, which can impinge on attachment apparatus on gingival tissue with constant inflammation which may be created or may get worse when the patient is not able to clean that area. The body will attempt to make a room between the margin and an alveolar bone which allow the space to use in tissue reattachment. It can take place if an alveolar bone that surrounds the teeth is too thin in its width. Thin gingival is prone to the recession compared to the flat periodontium and fibrous tissues which are thicker. The studies for the placement in deep margin had found out that the level in bone does appear to look unchanged. However, the gingival restoration had shown qualitative and quantitative changes within micro flora which increases the plaque index, recession of the pocket depth, gingival fluid and plaque index.
Biologic width categories with margin placement guidelines to follow in order to prevent the width violation
Normal crest person: this is when the patient has the measurement of mid-face of 3.00 mm while proximal measurement may be 3.0 mm up to 4.5 mm. In such situation, gingival tissue will look stable for most of the time.
High crest person: this is rare and it takes time in less than 2 percent. With these patients, the measurement in mid-face does not reach to 3.0mm and proximal measurement would not be over 3.0mm. In such cases, it will not be possible to use intracrevicular margin since the margin can be closer to alveolar bone which result into chronic inflammation with impingement of biologic width
Low crest person: for these patients, measurement on the mid-face is over to 3.0mm while proximal measurement should be over 4.5mm. Low crest takes place in 13 percent people. Low crest people may be described as patient who is susceptible to the secondary recession during the use of crown margin especially installed intracrevicular.