Flap Thickness as a Predictor of Root Coverage:
A Systematic Review
Debby Hwang* and Hom-Lay Wang*
Background: Thick gingival tissue eases manipulation, maintains
vascularity, and promotes wound healing during and after surgery.
A few recent case reports correlate greater flap thickness to mean
and complete root coverage after mucogingival therapy for recession
erature on this subject and to combine existing data to verify the pres-
enceofany associationbetween gingivalthicknessand root coverage
Methods: Human studies that reported the number and class of
recessions, measured flap thickness at a well-defined location, de-
scribed the method of root coverage used, followed results for at
least 3 months, and detailed mean root coverage underwent review
and statistical analysis. Investigations were scored from 1 to 5 based
on methodological quality. Weighted gingival thickness and weighted
mean root coverage was calculated based on standard error. Statis-
tical analysis used the Mann-Whitney test, analysis of variance
a number of factors (i.e., thickness, treatment type, and follow-up
time) and mean and complete root coverage. A significant P value
was set at <0.05.
Results: Fifteen investigations met the inclusion criteria. All of these
tions varied. Treatment modalities included coronally advanced flap,
connective tissue graft, and guided tissue regeneration with and with-
out adjuncts. A significant moderate correlation occurred between
to Mann-Whitney analysis, a critical threshold thickness >1.1 mm
existed for weighted mean and complete root coverage (P <0.02). The
type of treatment rendered also influenced root coverage. Further sim-
ple linear regression revealed a high correlation between weighted
thickness and weighted mean root coverage in connective tissue graft-
ing and guided tissue regeneration (r = 0.909 and 0.714, respectively)
but not coronally advanced flap therapy. Study score and follow-up
time did not affect the percentage of root coverage.
Conclusion: Within the limits of this review, a positive association
exists between weighted flap thickness and mean and complete root
coverage. J Periodontol 2006;77:1625-1634.
Connective tissue; gingiva;guidedtissue regeneration, periodontal;
nered formal scientific evaluation
until recently. Nonetheless, abun-
dant empirical evidence suggests
that thick tissue, subjectively de-
termined, resists trauma and sub-
sequent recession, enables tissue
manipulation, promotes creeping
esthetics, exhibits less clinical
inflammation, and renders pre-
dictable surgical procedures.1-11
A dense gingival biotype may
reflect underlying osseous mor-
phology; that is, the thicker the
gingiva, the greater its bony sup-
port.3However, this is not always
the case. By itself, thick soft
tissue has two factors that en-
courage its survival. The first, a
high volume of extracellular ma-
trix and collagen, allows it to
withstand collapse and contrac-
tion. Likewise, more layers of
physical damage and microbial
ingress. The second and argu-
ably more essential
its increased vascularity. Greater
perfusion enhances oxygenation,
clearance of toxic products, im-
mune response, and growth-factor
migration. In short, it boosts wound
healing. Supraperiosteal vessels,
for the most part, feed the free
and attached gingiva in a caudoc-
n oft-cited prerequisite for
surgical success, gingival
thickness hasnot gar-
* Graduate Periodontics, University of Michigan School of Dentistry, Ann Arbor, MI.
J Periodontol • October 2006
of these structures and vessels from the bone and
periodontal ligament (PDL), whose major sources are
the superior and inferior alveolar arteries, exist such
that some collateral circulation occurs upon surgical
trauma. Flap survival depends on the degree of
primary and collateral blood supply.15-22Ischemia
results from a lack of either. Full-thickness flaps
preserve gingival vascular patency and display dila-
tion of the supraperiosteal vessels; if there is proper
tissue adaptation, revascularization between flap and
underlying bone establishes within days.23,24Be-
cause flap vasculature isleft intact, the wound usually
heals, individual anatomical variations in the level of
collateral blood supply notwithstanding.
Conversely, split-thickness flaps leave fewer gingi-
val capillaries intact, and subsequently, rely heavily
on the compensatory blood flow from bone and
PDL. If few vessels exist (i.e., thin bone and unusually
sparse vasculature) or if the flap itself has too few pat-
ent arterioles, necrosis results.14,25-30Indeed, Wood
et al.,31and others,32,33observed that partial thick-
ness flaps lost more radicular bone than their muco-
periosteal counterparts (0.98 mm versus 0.62 mm,
respectively), contrary to previous reports. Wood
tissue (CT); partial dissection of this biotype led to
severing of the few vessels present and eventual flap
flap may react similarly to a split-thickness flap over
an avascular area. Separated from its underlying col-
lateral source, a thin full-thickness flap may not have
sufficient blood supply to support itself, let alone a
graft or other material inserted below it. Thus, the
thicker the gingiva, the better the blood supply.
It is intuitive that copious tissue facilitates peri-
odontal stability, especially after treatment. But how
much tissue does one require? What dimension de-
fines thick gingiva? Where should it be measured?
How should it be measured? Where should it be thick-
est (e.g., base, radicular area, margin, or papilla)?
With respect to these issues, the literature is some-
what inconsistent. Claffey and Shanley34reported
that subjects with gingiva £1.5 mm thick at a mid-
buccal location lost attachment after supra- and sub-
gingival debridement. No sites with mucosa ‡2 mm
receded. On the other hand, Anderegg et al.35de-
scribed less mean recession in molar teeth covered
by flap tissue >1 mm than those covered by tissue
£1 mm after guided tissue regeneration (GTR) treat-
ment for buccal furcations. They measured thickness
at a mid-buccal location 5 mm apical from the GM.
Perhaps the therapy most influenced by gingival
thickness is plastic surgery; at least the vast majority
of publications on this subject involve root coverage
procedures. Tissue type is essential for grafting,
whether it entails pedicle-based therapies (i.e., rota-
tional or coronal advancement flaps) or grafts ac-
quired from a separate donor site (i.e., CT), as it
reflects vascularization. McFall36listed the thickness
of tissue in the receded area and in the donor site as
key factors inthe treatmentselectionof mucogingival
defects. A thicker recipient site should promote root
coverage and resist further recession. An early study
thick flaps survived twice as often as thin flaps (55.7%
versus 26.5%, respectively) and that thin flaps relied
mostly on collateral circulation from the recipient bed
for oxygen and nutrients.37In an influential explora-
tion, Allen and Miller38treated 37 shallow Class I re-
cessions (<4 mm deep) with coronally advanced
flaps (CAFs) in gingival biotypes exhibiting ‡1 mm
thickness, again determined subjectively and at an
undisclosed location. They achieved complete root
coverage in 84% of sites at 6 months. Five out of six
sites with incomplete coverage displayed only
£0.5 mm of root exposure, a clinically insignificant
amount. Although the investigation suffered from a
lack of comparison with thinner tissue and deficient
tors to evaluate more rigorously the effect of gingival
thickness on recession treatment. Harris addressed
this issue in a root-coverage trial comparing the
membrane.39Harris considered recipient gingiva
thin, and presumably <0.5 mm, if a periodontal probe
could be read through it; in contrast, thick gingiva did
categorization, mean root coverage exceeded 95%
for all combinations of tissue type and treatment
which garnered only 27% of mean coverage. Perhaps
the membrane,placed between the full-thickness flap
and the bone, obstructed the collateral circulation
essential for a thin flap to revascularize and heal.
At present, the literature regarding tissue thickness
and root coverage is still in a nascent stage. Papers
vary greatly with respect to the therapy used, mea-
surement technique, randomization, follow-up time,
and types of defects treated. Therefore, the aim of
this study was threefold: 1) to collect and summarize
clinical data from root coverage studies analyzing
gingival flap thickness in a systematic fashion; 2) to
encourage study standardization to make possible fu-
ture comparisonreviewsand meta-analyses;and3)to
MATERIALS AND METHODS
An online search for human clinical studies in the En-
glish language was performed using MEDLINE, Pre-
MEDLINE, and the Cochrane Oral Health Group trials
register. Publications from January 1960 to January
Flap Thickness as a Predictor of Root Coverage: A Systematic Review
Volume 77 • Number 10
42. Muller HP, Stahl M, Eger T. Dynamics of mucosal
dimensions after root coverage with a bioresorbable
membrane. J Clin Periodontol 2000;27:1-8.
43. Gurgan CA, Oruc AM, Akkaya M. Alterations in loca-
tion of the mucogingival junction 5 years after coro-
nally repositioned flap surgery. J Periodontol 2004;75:
44. Huang LH, Neiva RE, Wang HL. Factors affecting the
outcomes of coronally advanced flap root coverage
procedure. J Periodontol 2005;76:1729-1734.
45. Muller HP, Eger T, Schorb A. Gingival dimensions after
root coverage with free connective tissue grafts. J Clin
46. Muller HP, Stahl M, Eger T. Root coverage employing
an envelope technique or guided tissue regeneration
with a bioabsorbable membrane. J Periodontol 1999;
47. Paolantonio M, Dolci M, Esposito P, et al. Subpedicle
acellular dermal matrix graft and autogenous connec-
tive tissue graft in the treatment of gingival recessions:
A comparative 1-year clinical study. J Periodontol
48. Bittencourt S, Del Peloso Ribeiro E, Sallum EA, Sallum
AW, Nociti FH, Casati MZ. Comparative 6-month clini-
cal study of a semilunar coronally positioned flap and
subepithelial connective tissue graft for the treatment
of gingival recession. J Periodontol 2006;77:174-181.
49. Berlucchi I, Francetti L, Del Fabbro M, Basso M,
Weinstein RL. The influence of anatomical features on
advanced flap and enamel matrix derivative: A 1-year
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50. da Silva RC, Joly JC, de Lima AF, Tatakis DN.
Root coverage using the coronally positioned flap
with or without a subepithelial connective tissue graft.
J Periodontol 2004;75:413-419.
51. Duval BT, Maynard JG, Gunsolley JC, Waldrop TC.
Treatment of human mucogingival defects utilizing a
bioabsorbable membrane with and without a demin-
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Correspondence: Dr. Debby Hwang, Graduate Periodon-
tics, University of Michigan School of Dentistry, 1011 N.
University, Ann Arbor, MI 48109. Fax: 203/254-9201;
Accepted for publication May 4, 2006.
Flap Thickness as a Predictor of Root Coverage: A Systematic Review
Volume 77 • Number 10