Keywords gingival biotype - gingival thickness - TRAN
Introduction
The gingiva is the part of the oral mucosa that covers the alveolar processes of the
jaws and surrounds the neck of teeth.[1 ] An esthetically pleasing smile is characterized by a well-scalloped gingival margin
at the cement–enamel junction. Gingival biotype is one of the many factors that determine
the long-term success of esthetic restorations. Since the gingiva is frequently encountered
during most dental procedures, clinicians must be acquainted with different biotypes
and their behaviors under similar clinical conditions. This shall not only render
long-term success of restorations but also esthetically promising results.
Gingival biotype is considered as a genetically determined trait[2 ] that describes the thickness of gingiva faciopalatally. Several terms have been
used by various authors in the past ([Table 1 ]). In the most recent consensus report, it was referred to as periodontal phenotype.[3 ] The term periodontal phenotype encompasses the combination of gingival phenotype
(three-dimensional gingival volume) and the buccal bone thickness, that is, the bone
morphotype. Biotype is genetically determined and cannot be modified. However, phenotype
describes a dimension that can change through time depending upon environmental factors
and clinical intervention. It can also be site specific.[3 ]
Table 1
Different forms of gingival tissues as described by various authors
Year
Author
Classification
Abbreviation: CEJ, cement–enamel junction.
1923
Hirschfeld[4 ]
Based on the alveolar contour as thin and thick gingival forms
1969
Oschenbein and Ross[5 ]
Tapered tooth form was associated with scalloped thin type and square tooth form with
flat thick gingiva. Also, the contour of gingiva mimics the contour of the underlying
alveolar bone
1977
Weisgold[6 ]
Based on form and function as thin in scalloped periodontium and thick in flat periodontium
1986
Claffey and Shanley[7 ]
Based on thickness measured by a stainless-steel wire with a cutoff shank of a probe;
thin (≤1.5 mm) and thick (≥2.0 mm)
1991
Olsson and Lindhe[8 ]
Gingival morphology based on tooth dimensions; long narrow central incisors associated
with thin periodontium and thick with square, wide form
1994
Kois[9 ]
Based on the relationship between CEJ and the alveolar crest—normal (alveolar crest
3 mm apical to CEJ), high (alveolar crest less than 3 mm), low (alveolar crest more
than 3 mm)
1996
Eger et al[10 ]
Based on gingival morphology via cluster analysis as normal, thin, thick
2009
De Rouck et al[11 ]
Based on the gingival transparency of probe when inserted in to the sulcus; thick
and thin
2010
Kan et al[12 ]
Based on the tissue morphology and makeup as thick, dense, fibrotic and thin, translucent,
and friable
2018
Jepsen et al[3 ]
Suggested the term periodontal phenotype that describes the combination of gingival
phenotype (i.e., three-dimensional gingival volume) and the buccal bone plate thickness
(bone morphotype)
By observing the periodontal probe shining through the gingival tissue as—probe visible:
thin (≤1 mm)
Probe not visible: thick (>1 mm)
([Figs. 1 ] and [2 ])
Fig. 1 Thin biotype.
Fig. 2 Thick biotype.
A thick biotype is generally related to good periodontal health. It is characterized
by dense tissues and has a sufficient zone of attached gingiva. Thick tissues can
withstand trauma and exhibit less clinical inflammation. It enables manipulation,
encourage creeping attachment, and enhance the esthetics of implants.[13 ]
[14 ]
[15 ]
Thin biotype is characterized by thin gingival tissues. It is almost translucent in
appearance and possess minimal zone of attached gingiva. It is also highly accentuated
that suggests the presence of minimal bone. Also, thin biotype is less resistant to
gingival recession when it is subjected to inflammatory and surgical insults.[6 ]
[16 ] Gingival recession or visible restorative margins can create esthetic problems particularly
when anterior teeth are affected. Hence, determining the tissue biotype is a crucial
step prior to planning any esthetic procedure.
Gingival Biotype Assessment
Different techniques for assessment of gingival biotype are listed in ([Table 2 ]). Other methods for biotype determination include histologic examination of cadaver
jaws, injection needles, and cephalometric radiographs.[18 ] A method that is simple to apply in clinical practice along with being reliable
would be best suited for clinicians to modify treatment plan and produce more predictable
results.
Table 2
Different techniques available for the assessment of gingival biotype
Technique
Advantages
Disadvantages
Visual examination
Gingiva is examined visually and evaluated on the basis of its general appearance
Simple and noninvasive
The degree of tissue thickness cannot be assessed by this method. Low accuracy due
to a high interexaminer variation[17 ]
Direct methods
a. Transgingival probing
Thickness determined with a periodontal probe.
Thick > 1.5 mm
Thin < 1.5 mm
Simple and inexpensive
Invasive nature; requires administration of local anesthesia[18 ]
b. Endodontic reamers, files
Gingiva is first anesthetized and pierced perpendicular to a point lying in the center
of gingival margin and mucogingival junction. Endodontic reamer/file with a rubber
stop are usually used. The measurement is recorded against a digital caliper
Precise measurement
Invasive in nature; could lead to an increase in local volume and patient discomfort
due to local anesthesia administration[19 ]
c. Probe transparency method (TRAN)
Sulcus sampling done on the midfacial aspect of the tooth
Probe visible: thin
Probe not visible: thick
Good accuracy, simple, rapid, and minimally invasive[11 ]
Ultrasonic method
An ultrasonic device with an attached sensitive thin probe is used. It utilizes pulse
echo to determine the thickness of biotype
Precise measurement, digital display, eliminates interexaminer variability, and is
noninvasive
Less feasible due to high cost of equipment and availability is limited[20 ]
Cone beam computed tomography (CBCT)
Thickness of both hard and soft tissues can be visualized and measured
Highly accurate results; no interexaminer variability
Exposure to radiation and increased costs for patients[21 ]
Gingival Biotype and Clinical Perspectives
Flap Procedures
Ample evidence suggests that thin gingiva is more predisposed to recession than gingiva
that is thick. This often leads to dentinal hypersensitivity, abrasion and/or cervical
wear, root caries, and an increase in plaque accumulation.
The primary determinant of the effectiveness of treating mucogingival defects is thickness
of gingival tissues at the surgical site. A flap thickness of 0.8 to 1.2 mm was found
to be associated with a more predictable prognosis. Also, flap margins can be inadvertently
thinned that may increase the risk of postoperative recession, especially if the biotype
is thin.[22 ] Therefore, clinicians must handle flaps carefully in such situations.
Recommendation: Patients with a thinner biotype can ideally be treated with connective
tissue graft technique combined with a coronally advanced flap that will produce a
pseudo-thick biotype to avoid unesthetic or undesirable results.[23 ]
Crown Lengthening Procedures
Determination of biotype is an important factor to be considered during crown lengthening
procedures. Following full-thickness flap procedures, bone resorption of ~0.5 to 0.8
mm is seen to occur.[18 ] Hence, it is difficult to predict the final hard and soft tissue position following
flap procedures. This could possibly manifest as gingival recession specially in thin
biotype.
Recommendation: Permanent restorations are recommended after a healing period of 6
months specially in the anterior esthetic region. Tissue thickness may be improved
by soft tissue grafting 6 to 8 weeks prior to crown lengthening procedures.[24 ]
Restorative Procedures
Thin periodontal biotypes being friable, the possibility of recession increases after
crown preparation. Overcontoured restorations are found to particularly lead to the
development of tissue injury and gingival recession especially in thin biotype. Thicker
biotypes have greater resistance to tissue recession and can better mask the margins
of restorations that are even placed subgingivally.[14 ]
Recommendation: It is advisable to position the margins of prepared restorations supragingivally
in thin biotype cases. Failing to do so may cause a grayish hue of the restorative
margin to be visible through the thin and translucent gingival tissues thereby compromising
esthetics specially in anterior esthetic regions.[14 ]
Gingival Retraction Cords
Precautions must be undertaken in thin biotype cases to prevent soft tissue injury
especially in procedures that involve the placement of retraction cords. Thin cords
are usually advised for retraction.
Recommendation: Chances of recession increase if cord is kept for more than 15 minutes.[14 ] Also, the cord must be moist while removal to avoid tissue tears.
Implant Dentistry
Thick tissues are preferred around dental implants as they conceal titanium of implants
better and also are accommodating to different implant positions.[25 ]
[26 ] Therefore, compared with a thin biotype, thicker tissues are favored around implants.
Also, significantly less bone resorption is seen in thick biotypes after implant placement
compared with thin biotypes.
Recommendation: An immediate implant placement can be considered in a thick biotype
with predictable outcomes as it can help to preserve the osseous structures.[27 ]
[28 ] However, a delayed implant placement is preferable when the thickness of the surrounding
tissues is not sufficient.
Orthodontic Therapy
Pretreatment assessment of the biotype prior to orthodontic therapy is an important
step as perforation of cortical plate may occur especially in thin biotype leading
to soft tissue recession and exposure of root.[29 ]
Recommendation: Nonsurgical periodontal therapy and/or surgical correction of any
soft or hard tissue defects using membranes and grafts may be required during orthodontic
phase.[30 ] Such procedures can be performed either before or after orthodontic therapy to create
a pseudo-thick biotype to prevent tissue collapse.
Tooth Extraction
In comparison to thin biotypes, thick biotypes are associated with minimal ridge atrophy
after extraction. Excessive forces can cause fracture of buccal alveolar plate in
thin biotype resulting in bone resorption and unpredictable bone healing.[31 ]
Recommendation: Undue extraction forces in thin biotype cases should be avoided to
minimize ridge atrophy and buccal alveolar plate fracture.
Gingival Biotype Enhancement Techniques
Presence of thin gingival biotype can impede outcomes of many esthetic dental therapies.
Prospects of enhancing the biotype in such cases exists. When a thin biotype is surgically
converted to a thick one, it is termed as “pseudo-thick gingiva.” Such procedures
are done mainly to achieve stable results that are functionally and esthetically acceptable.
The most reliable and frequently reported technique of enhancing tissue thickness
is the use of connective tissue grafts (CTG).[32 ] It can either be harvested from the palate or tuberosity and then placed subepithelially
at the site of interest. The use of acellular dermal matrix as an alternative to CTG
has also been documented in numerous literature.
Use of platelet rich fibrin membrane: Platelets release several growth factors like
platelet derived growth factors and endothelial growth factor.[33 ]
Membranes that are fetal in origin such as amnion and chorion membranes have also
been used.[34 ] These allografts are derived from the human placenta. They are usually placed under
a tunnel or pouch or coronally advanced flap and then sutured.
Conclusion
Gingival biotype behaves differently when exposed to insults thereby dictating the
outcomes of numerous dental procedures. Biotype assessment in routine clinical examination
should be considered imperative to avoid unaesthetic treatment consequences. Advancements
over the decades in periodontal surgical techniques have provided several opportunities
of improving tissue quality. Such techniques not only augment the restorative environment
but also provide desirable treatment outcomes. Hence, biotype should be considered
as an integral component during inter- and multidisciplinary treatment approaches
that provide clinicians with the required insights and precautions necessary for tissue
handling.
