Review Article Vol. 3/No.

2/July-December, 2020

Biologic width-A Review

Bhochhibhoya A1, Shrestha R2
1
Lecturer, Department of Dentistry, Tribhuvan University Dental Teaching Hospital, Institute of Medicine, Tribhuvan
University, Kathmandu, Nepal.
2
Lecturer, Periodontology and Oral Implantology Unit, Department of Dental Surgery, National Academy of Medical
Sciences, Kathmandu, Nepal.

Abstract
Replacement of missing, damaged or unaesthetic tooth by dental prostheses helps the patient to
rehabilitate structure and function of the lost tissues. During delivery of the prostheses, the overall
health of the oral tissues, including the periodontium, must be considered. The gingival tissues must be
healthy and it is of paramount importance to respect the biologic width of the tissues. The biologic width
varies among different individuals and at different sites of the same individual. Instead of following
a mean value, each patient should be examined to determine the biologic width. In case violation of
biologic width is anticipated, appropriate measures should be adopted to maintain the dimensions of
the biologic width.

Key words: Biologic width; Crown lengthening; Margins; Orthodontic extrusion.

Introduction Localised dental-prosthesis-related factors

D ental prostheses are used for the predisposing to periodontitis include:4

restoration of damaged, unaesthetic, a) Restoration margins placed within the
or dysfunctional tooth, or to replace one or supracrestal attached tissues
more missing natural teeth.1 While prostheses b) Clinical procedures related to the fabrication
serve to cater optimal quality of life to the of indirect restorations
individual, faulty prostheses, on the other hand, c) Hypersensitivity/toxicity reactions to dental
contribute to detriment the periodontium.2 materials
Tooth and prostheses related factors have been
introduced as a separate category in the recent Dental prostheses should be fabricated
American Academy of Periodontology (AAP) harmonising with the natural hard and soft
Classification of Periodontal and Peri-implant tissues. Infringement of the periodontal tissues
Diseases and Conditions as other conditions results in loss of the supporting tissues. The
affecting the periodontium under Periodontal dimension of the soft tissue, which is attached to
Diseases and conditions.3 the portion of the tooth coronal to the crest of the
alveolar bone, termed biologic width5, should
be preserved. Histologically, the biologic width
is composed of the junctional epithelium and
supracrestal connective tissue attachment. The
AAP 2017 has replaced the term supracrestal
*Corresponding Author
tissue attachment and the term biologic barrier
Dr. Rejina Shrestha, Lecturer
Periodontology and Oral Implantology Unit,
has been suggested.6 Maintenance of biological
Department of Dental Surgery, National Academy of width is essential for the optimal periodontal
Medical Sciences, Kathmandu, Nepal health, which again is dependent on the properly
E-mail: rejinashrestha811@gmail.com
designed restorations.7

106 Journal of Nepalese Prosthodontic Society (JNPS)

 Biologic width-A Review

Definitions of Biological Width: the sulcus depth were measured. They reported
Khuller N and Sharma N (2009) 8 defined BW the mean sulcus depth of 0.69 mm, epithelial
as the dimension of the soft tissue, which is attachment of 0.97 mm, and connective tissue
attached to the portion of the tooth coronal to attachment of 1.07 mm. The biologic width was
the crest of the alveolar bone. calculated to be 2.04 mm. Thus, on average, it
is essential to maintain 3 mm distance from the
Nevin and Skurow (1984)9 defined it as the bone crest to the cement-enamel junction in
sum of the combined supracrestal fibers, the healthy teeth or until the end of the preparation
junctional epithelium and the sulcus. or the margin of restoration in restored teeth.20
World Workshop on the classification of Vacek et al21 reported variations in the
Periodontal and Peri implant diseases and dimensions of the supracrestal gingival tissue
conditions (2018) defined it as a commonly between teeth and in different sites within the
used clinical term to describe the apico- coronal same tooth. They evaluated 171 cadaver tooth
variable dimensions of the supracrestal attached surfaces and observed mean measurements of
tissues. 1.34 mm for sulcus depth, 1.14 for epithelial
The concept of biologic width must be clear attachment, and 0.77 mm for connective tissue
as many clinicians are unable to practically attachment. The connective tissue attachment
implement it.10 In dentistry, the area of biological was the most consistent measurement. Vacek
width is sometimes called Bermuda Triangle or and colleagues found that the biological
Devil’s Triangle.11,12 width increased anteroposteriorly and 15% of
restoration that impinge the biologic width had
History a biologic width of less than 2.04 mm.
Gottlieb was the first to describe the ‘‘epithelial The dimensions advocated by different authors
attachment’’.13 The ‘‘gingival crevice’’ or to maintain a healthy gingiva are shown in
sulcus was defined by Orban and Mueller14. Table 1.
The connective tissue was described as three-
dimensionally oriented fibers firmly connecting Table 1: Minimum biologic width advocated
tooth structures to the adjacent gingiva by by various authors
Feneis.15 Marfino, Orban and Wentz16 were the Minimum
Authors
requirement
first to demonstrate that gingival connective
Ingber et al (1977)18 3 mm
tissue attachment and junctional epithelium Rosenberg and colleagues (1980
compose the attachment of gingiva to tooth. 3.5 to 4 mm
and 1999)22
Sicher17 described the dentogingival junction as Weinberg and Eskow (2000)23 3.5 to 4 mm
epithelial and connective tissue attachments to Nevins & Skurow (1984)9 3.0 mm
the teeth. Wagenberg and colleagues
5 to 5.25 mm
(1989)24
Historically Walter Cohen first coined the Palomo and Kopczyk 25 1 mm
term “biologic width” and in 1977, Ingber et
al. described the biologic width.18 In 1961, Interproximal Biologic Width is similar to that
Garguilo et al.19 evaluated the average vertical of the facial surface but the total dentogingival
dimensions of the biological width. From 30 complex is different. According to Kois and
autopsy specimens, 287 individual teeth were Spear, the dentogingival complex is 3.0mm
studied and the alveolar crest, the connective facially and 4.5 mm to 5.5 mm interproximally.26
tissue attachment, the epithelial attachment, and The height of interdental papilla was explained

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Bhochhibhoya A et al.

by increased scalloping of the bone. Spear clinical attachment. However, according to the
suggested that additional 1.5 to 2.5 mm of available evidence, it is not possible to determine
interproximal gingival tissue height is seen only if the negative effects is due to dental plaque
in the presence of adjacent teeth. In the absence biofilm, trauma, toxicity of dental materials, or
of the adjacent tooth, the interproximal gingival a combination of these factors.4
tissue be 3.0 mm.26 Tarnow and colleagues
Optimal restoration margins located within
found that the distance from the contact point
the gingival sulcus do not cause gingival
to alveolar crest should not exceeded 5 mm to
inflammation if patients are compliant with
5.5 mm for the gingival tissue to completely fill
self‐performed plaque control and periodic
the interdental space. Greater distance resulted
maintenance. Localized inflammation that
in significant loss of alveolar height.27 Cho et
does not respond to adequate measures of
al also found that the number of papillae that
plaque control may be a sign of dental material
filled the interproximal space also decreased
hypersensitivity.4
as the interproximal distance between the teeth
increased.28 Evaluation of Biologic Width Violation

Importance of biologic width 1. Clinical method

The presence of discomfort during examination
The components of the biologic width serve
of restoration margins indicates biologic width
for adhesion of the junctional epithelium
violation. The clinical signs of biologic width
and insertion of the connective fibers to the
violation are:
dental structure.5 They create a barrier in the
periodontium and prevent microbial penetration. a) Chronic progressive gingival inflammation
If it is impinged, the microorganisms gain around the restoration
access to deeper tisssues and cause destructive b) Bleeding on probing
inflammation. The restorations with rough c) Localized gingival hyperplasia with
surface aid in retention of the biofilm and the minimal bone loss
inability of the patient to clean deep areas d) Gingival recession
further aggravates the biofilm accumulation.
e) Pocket formation
As a consequence, gingival inflammation,
loss of clinical attachment, bone loss, gingival f) Clinical attachment loss
recession, increasing vertical bone resorption g) Alveolar bone loss
and increasing the horizontal component can be h) Gingival hyperplasia
seen.29
Encroachment of restoration into biologic width
Violation of biologic width results in:
30
initiates crestal bone resorption. This occurs to
a) Crestal bone loss allow space for establishment of a minimum
b) Gingival recession with localized bone loss biologic width.31
c) Localized gingival hyperplasia with
minimal bone loss 2. Radiographic evaluation
Radiographs are useful non-invasive tools in the
d) A combination of three
assessment of biological width encroachment.
Tooth supported/retained restorations and their Their use is only limited to interproximal areas.
design, fabrication, delivery, and materials can Parallel profile radiographic (PPR) technique
be associated with plaque retention and loss of has been introduced to measure the dimensions

108 Journal of Nepalese Prosthodontic Society (JNPS)

 Biologic width-A Review

of the dento gingival unit (DGU).32 It is used to 3. Low crest patient

measure both length and thickness of the DGU. It is seen in 13% of the individuals. If the
3. Bone sounding margins are placed subgingivally in these cases,
After application of local anesthesia, the there might be two types of reaction based
area is probed till the bone is felt. Then, the on the depth of the sulcus. If the attachment
sulcus depth is measured and subtracted. If apparatus is thick and the sulcus is shallow,
the distance is less than 2 mm, biologic width it is less susceptible to gingival recession and
violation can be confirmed.33 The transulcular if the attachment apparatus is narrow with
periodontal probing was described by Jardini deeper sulcus, it is more susceptible to gingival
and Pustiglione.34 The following considerations recession.
must be considered for bone sounding:
Dimensions of periodontium
1. The gingiva must be healthy.
Maynard and Wilson38 categorised the
2. The measurement should be repeated on
periodontium into three-dimensions
more than one tooth to ensure accurate
assessment, and reduce individual and site • Superficial physiologic: It represents the
variations. free and attached gingiva surrounding the
tooth.
Factors influencing the biologic width5,35-37
• Crevicular physiologic: It represents
a) Location/inclination of the tooth in the the gingival dimension from the gingival
socket margin to the junctional epithelium.
b) Different teeth • Subcrevicular physiologic: It is analogous
c) Site of the tooth to the biologic width and consists of the
d) Gingival biotype junctional epithelium and connective tissue
e) Keratinised tissue attachment.

Categories of biologic width:35 Types of margin

There are three categories of biologic width Margins can be placed in three ways:
1. Normal crest patient Supragingival margin
The maximum number of individuals, i.e., 85% This margin type is easy for preparation of the
of the individuals have normal crest patient. tooth and finishing of the margin. The impression
The gingival tissues are stable for a long-term. can be taken easily with proper duplication
In these cases, when the crown margin is placed of the margins. The margins are mainly given
0.5 mm subgingivally, it is tolerated well by the in non-esthetic areas owing to the color and
gingiva. opacity contrast present in restorative materials.
If translucent restorative materials are used,
2. High crest patient they can also be given in esthetic areas. They
It is seen in 2% of the individuals and is found are the least irritating to the periodontal tissue.
in a proximal surface adjacent to an edentulous Equigingival margin
site. If the margins are placed subgingivally The restoration and the tooth margin can be
in these cases, the margins will be closer to blended easily. Tooth preparation and finishing
alveolar bone and biologic width is violated. is easy and it gives a smooth, polished interface
at the gingival margin. But, traditionally, it was

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Bhochhibhoya A et al.

said to favour accumulation of plaque giving subgingivally at the beginning of the study
rise to gingival inflammation.5 period and after 5 years, only 32% of the crown
margins remained below the gingival margin.
Subgingival margin
Subgingival margins should be given if dental Waerhaug stated that subgingival restorations
caries or tooth deficiencies extend apically are plaque-retentive areas and are inaccessible
beyond the gingival crest.39 It is also used for to scaling instruments. They will continue
optimal esthetic output. But, too far placement to accumulate plaque even after adequate
of the subgingival margin will impinge on the supragingival plaque control measures are
periodontal apparatus. Constant inflammation carried out. Later, he demonstrated that gingivitis
occurs and the condition is aggravated by the and attachment loss was associated with sub
patient’s inability to clean this area. Biologic marginal restorations in monkeys and dogs.43
width violation will lead to gingival recession Clinical and histological observations of human
and bone loss. Thin alveolar bone increases teeth was done by Dragoo and Williams44.
the risk of alveolar bone loss and thin gingiva They demonstrated that compared to shoulder
increases the risk of gingival recession.5 The preparations, compromised healing was
more common finding with deep margin associated with gingival bevel crown margins.
placement is unchanged bone level but gingival Orkin et al.42 demonstrated that subgingival
inflammation will develop and persist on the restorations had a greater chance of bleeding
restored tooth.40 This type of margin is not and gingival recession than supragingival
accessible for finishing and polishing which restorations. Stetler and Bissada45 demonstrated
acts as a niche for bacterial growth.41 To prevent that teeth with subgingival restorations and
these complications, the contour should be narrow zones of keratinized gingiva showed
proper, polishing of the restoration should be significantly higher gingival index scores
done and biologic width must be respected. The than teeth with sub marginal restorations with
amount of attached gingiva should also be taken wide zones of keratinized gingiva. Keratinised
into account. gingiva should be carefully evaluated before
plcing subgingival restorations.
Margin placement42
Flores-de-je-Coby et al46 demonstrated that
1. If the sulcus probes 1.5 mm or less, the subgingival margins demonstrated increased
restorative margin could be placed 0.5 mm plaque, gingival index scores, and probing
below the gingival tissue crest. depths. More spirochetes, fusiforms, rods, and
2. If the sulcus probes >1.5 mm, the restorative filamentous bacteria were found to be associated
margin can be placed in half the depth of with subgingival margins.
the sulcus.
Method to correct biologic width violation
3. If the sulcus is >2 mm, gingivectomy could
be performed to lengthen the tooth, and The biologic width has inter-personal and intra-
create a 1.5 mm sulcus. Then the patient can personal variability. There is no magic number
be treated as per rule 1. which can be recommended and each site of
each patient must be evaluated before coming to
In a study done by Valderhaug and Birkeland41,
a definite conclusion.47 In case a biologic width
114 patients with 329 total crown restorations
is violated, the following procedures should be
were evaluated. 59% of the crowns were located
considered:

110 Journal of Nepalese Prosthodontic Society (JNPS)

 Biologic width-A Review

1. Surgical crown lengthening: root ratio and gingival recession. It should not
• Gingivectomy be done during surgical crown lengthening of a
single tooth in the esthetic zone. In such cases,
• Apically positioned flap (APF)
forced eruption should be considered to prevent
• APF with osseous reduction negative architecture.
2. Orthodontic procedure
Orthodontic procedures
• Forced eruption
Forced eruption
• Forced eruption combined with
In forced eruption, tooth is intentionally moved
fiberotomy
in a coronal direction using gentle continuous
• Orthodontic Extrusion associated with force. The force stretches gingival and
Supracrestal Fiberotomy and Root periodontal fibers resulting in a coronal shift
Planing (OEFRP): of gingiva and bone.49 It was first advocated by
Heithersay49 for teeth with horizontal fractures.
Surgical crown lengthening
Orthodontic extrusion was advocated in
As the term indicates, it is used to lengthen the anterior area where surgical crown lengthening
crown. Various measures are: cannot be accomplished. It minimizes gingival
Gingivectomy recession and loss of bone support on adjacent
External bevel gingivectomy is both successful teeth.50,51
and predictable surgical procedure and is Orthodontic extrusion requires an activation
indicated in hyperplasia or pseudopocket along period of 4-6 weeks and 6-8 weeks retention
with presence of adequate amount of keratinized period for tooth to become stabilized in its new
tissue.48 Internal bevel gingivectomy is carried position. Additional surgical crown lengthening
out if reduction of excessive pocket depth and may be required after forced eruption. The
exposure of coronal tooth is required in absence contraindications are inadequate crown-to-root
of sufficient zone of attached gingiva.8 ratio, lack of occlusal clearance and periodontal
Apically positioned flap (APF) complications.
Apically positioned flap is recommended Forced eruption with fiberotomy
when crown lengthening of multiple teeth in Combination of orthodontic extrusion and
a quadrant or sextant of dentition is required severance of supracrestal fibers, termed
and there is a biologic width of more than supracrestal fiberotomy is also used for crown
3 mm. Pocket reduction can be done at the lengthening. If fibrotomy is performed during
same surgery. It should not be done for during the forced tooth eruption procedure, the crestal
surgical crown lengthening of a single tooth in bone, and the gingival margin are retrieved at
the esthetic zone. their pretreatment location. Thus, the tooth-
APF with osseous reduction gingiva interface at adjacent teeth is unaltered.
It is the most common procedure for clinical Fibrotomy is performed once every 7-10 days
crown lengthening. It is done in inadequate during the phase of forced tooth eruption.27
zone of attached gingiva and biologic width Orthodontic Extrusion associated with
less than 3 mm. Detailed evaluation should be Supracrestal Fiberotomy and Root Planing
done before carrying out osseous reduction as it (OEFRP): It is a flapless technique for crown
compromises periodontal support of the tooth, lengthening after orthodontic extrusion. The
causes furcation involvement, poor crown-to- OEFRP procedure must be carried out every 2
Journal of Nepalese Prosthodontic Society (JNPS) 111
Bhochhibhoya A et al.

weeks during the entire extrusive orthodontic 6. Parashar A, Zingade A, Sanikop S, Gupta S,
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