Minimally Invasive Surgical Technique and Modified-MIST in Periodontal Regeneration










Minimally Invasive Periodontal Therapy: Clinical Techniques and Visualization Technology, First Edition.
Edited by Stephen K. Harrel and Thomas G. Wilson Jr.
© 2015 John Wiley & Sons, Inc. Published 2015 by John Wiley & Sons, Inc.
Companion Website: www.wiley.com/go/harrel/minimallyinvasive
117
8
Introduction
Periodontal regenerative technologies are applied to improve short- and long-term
clinical outcomes of periodontally compromised teeth, presenting with deep pock-
ets and reduced periodontal support. The persistence of deep pockets following
active periodontal therapy has been associated with an increased probability of
tooth loss in patients attending supportive periodontal care programs [1]. Teeth
with deep pockets associated with deep intrabony defects are considered a clinical
challenge: periodontal regeneration has been shown to be effective in the treatment
of one-, two-, and three-wall intrabony defects or combinations thereof, from very
deep to very shallow, from very wide to very narrow [2–5]. Therefore, the applica-
tion of regenerative procedures, including minimally invasive procedures, is suited
in deep and shallow intrabony defects.
Regeneration is a healing outcome that can occur when the systemic and local
conditions are favorable. The systemic conditions include the control of peri-
odontitis, a low total bacterial load in the mouth and cessation of smoking habits:
high percentages of bleeding on probing and high bacterial loads as well as ciga-
rette smoking have been associated with reduced clinical outcomes [6–12]. The
local conditions include the presence of space for the formation of the blood clot
at the interface between the flap and the root surface [12–17], the stability of the
Minimally Invasive Surgical
Technique and Modified-MIST
in Periodontal Regeneration
Pierpaolo Sandro Cortellini

118 Minimally Invasive Periodontal Therapy
blood clot to maintain a continuity with the root surface avoiding formation
ofalong junctional epithelium [13,18–20], and the soft tissue protection to avoid
bacterial contamination [10,21–23].
Development of periodontal regenerative medicine in the past 25 years has fol-
lowed two distinctive, though totally interlaced paths. The interest of researchers
has thus far focused on regenerative materials and products on the one side and
on novel surgical approaches on the other side.
In the area of materials and products, three different regenerative concepts have
been explored: (i) barrier membranes, (ii) grafts, and (iii) wound healing modi-
fiers, plus many combinations of the aforementioned concepts [5].
In general, the development of surgical procedures was aimed at complete
preservation of the soft tissues to achieve and maintain primary closure on top
ofthe applied regenerative material/substance during the critical early stages of
healing. Specifically, flap designs attempted to achieve passive primary closure
of the flap combined with optimal wound stability.
In the 1990s, the modified papilla preservation technique (MPPT)[15] and the sim-
plified papilla preservation flap (SPPF)[24] have been tested and proposed. These
clinical innovations in flap design and handling have radically changed surgery and
have allowed a drastic limitation of interdental wound failure to less than 30% of the
treated cases. Further enhancements of clinical outcomes were achieved when an
operative microscope was adopted [25,26]. Authors reported an increased capacity
to manipulate the soft tissues that resulted in an improved potential for primary clo-
sure of the wound to an excellent 92% obtained with microsurgery. Other authors
reported improved outcomes using operative microscopes in different areas of
periodontal surgery, from flap surgery to mucogingival surgery [27–32].
In the past decade, a growing interest for more friendly, patient-oriented sur-
gery have urged clinical investigators to focus their interest in the development
of less invasive approaches [33–35]. Following this path, Cortellini and Tonetti
proposed a minimally invasive surgical technique (MIST) on isolated [36] and
multiple [37]intrabony defects, and a Modified MIST (M-MIST)[38] on isolated
intrabony defects.
Clinical studies and outcomes
Cohort studies and randomized controlled clinical trials reporting outcomes
on the application of minimally invasive surgical approaches are reported in
Tables8.1 and 8.2.
Table8.1 refers to MIST studies in which the interdental papillary tissues have
been elevated to uncover the interdental space completely. This approach is sup-
ported by three cohort studies [36,37,39] and two controlled studies [40,41].
Table8.2 reports studies in which the access to the defect was gained through
the elevation of a small buccal flap, without elevation of the interdental papilla.
This approach is supported by a cohort study [38] and three controlled studies
[42–44]. Interestingly, the cited randomized clinical trials performed using

Table 8.1 Minimally invasive surgical technique (MIST): clinical studies.
MIST
Type of study
(quality of evidence) Interventions
No.
pax
No.
defects CAL gain PD reduction Δ REC
Cortellini and
Tonetti [36]
Case cohort (level 2) MIST + EMD 13 13 4.8 ± 1.9 4.8 ± 1.8 0.1 ± 0.9
Cortellini and
Tonetti [39]
Case cohort (level 2) MIST + EMD 40 40 4.9 ± 1.7 5.2 ± 1.7 0.4 ± 0.7
Cortellini
etal. [37]
Case cohort (level 2) MIST + EMD 20 44 4.4 ± 1.4 4.6 ± 1.3 0.2 ± 0.6
Ribeiro
et al. [40]
RCT (Level 1) MIST 15 15 2.82 ± 1.19* 3.55 ± 0.88* 0.54 ± 0.58*
MIST + EMD 14 14 3.02 ± 1.94* 3.56 ± 2.07* 0.46 ± 0.87*
Ribeiro
et al. [41]
RCT (level 1)
MIST 14 14 2.85 ± 1.19* 3.51 ± 0.90* 0.48 ± 0.51*
MINST (RPL) 13 13 2.56 ± 1.12* 3.13 ± 0.67* 0.45 ± 0.46*
MINST, minimally invasive non surgical technique (RPL with the aid of a microscope); MIST, minimally invasive surgical technique.
*No statistical difference.

Table 8.2 Modified-minimally invasive surgical technique (M-MIST): clinical studies.
M-MIST/SFA Type of study Interventions
No.
pax
No.
defects CAL gain
PD
reduction Δ REC
Cortellini and
Tonetti [38]
Case cohort M-MIST + EMD 15 15 4.5 ± 1.4 4.6 ± 1.5 0.07 ± 0.3
Cortellini and
Tonetti [42]
RCT M-MIST
M-MIST + EMD
M-MIST + EMD + BioOss
15
15
15
15
15
15
4.1 ± 1.4*
4.1 ± 1.2*
3.7 ± 1.3*
4.4 ± 1.6*
4.4 ± 1.2*
4.0 ± 1.3*
0.3 ± 0.6*
0.3 ± 0.5*
0.3 ± 0.7*
Trombelli
etal. [43]
RCT SFA
SFA + HA + GTR
12
12
12
12
4.4 ± 1.5*
4.7 ± 2.5*
5.3 ± 1.5*
5.3 ± 2.4*
0.8 ± 0.8*
0.4 ± 1.4*
Mishra
et al. [44]
RCT
M-MIST
M-MIST + rhPDGF-BB
12
12
12
12
2.6 ± 0.8*
3.0 ± 0.9*
3.8 ± 0.9*
4.2 ± 0.6*
0.5 ± 0.5*
0.8 ± 0.6*
M-MIST, modified minimally invasive surgical technique; SFA, single flap approach; rhPDGF-BB, recombinant human platelet derived growth factor.
*No statistical difference.

Minimally Invasive Surgical Technique and Modified-MIST 121
minimally invasive surgical approaches (with or without papilla elevation) do
not report any difference in terms of clinical outcomes between the minimally
invasive control flap approach and the test in which a regenerative material/
product was introduced under the flap. The reported outcomes raise a series
of hypotheses that focus on the intrinsic healing potential of a wound when
ideal conditions are provided with the surgical approach. In other words, the
outcomes of these studies challenge clinicians with the possibility to obtain
substantial clinical improvements without using products or materials applying
surgical techniques that do enhance per se blood clot and wound stability. In
particular, the advanced flap design of the M-MIST greatly enhances the poten-
tial to provide space and stability for regeneration by leaving the interdental
papillary soft tissues attached to the root surface of the crest-associated tooth
and by avoiding any palatal flap elevation. The interdental soft tissues are the
stable “roof” of a room where the blood fills in and forms a clot. The hanging
papilla prevents the collapse of the soft tissues, thereby maintaining space
forregeneration. The anatomic bone deficiencies are potentially supplemented
by the peculiar flap design that provides additional “soft tissue walls” to the
missing bony walls improving stability: walls of the “room” are the residual
bony walls, the root surface, and the buccal/lingual soft tissues. The minimal
flap extension and elevation also minimizes the damages to the vascular system
favoring the healing process of the tiny soft tissues.
Clinical indications and diagnostic procedures
Delivering periodontal surgery in general and regenerative treatment in particular
requires knowledge, skills, experience, and a well-defined step-by-step approach.
The first step of periodontal therapy is always cause-related therapy, aimed
at obtaining patient compliance, reduction of oral bacterial loads, and control
of gingival infection.
At completion of nonsurgical cause-related therapy, patients have to be care-
fully reevaluated. A full periodontal evaluation should be performed to check for
(Flow chart 8.1) the following aspects:
1. The compliance of the patient in terms of plaque control: a very low load of
bacterial plaque is a major goal of cause-related therapy and key to periodontal
regeneration. Optimal regenerative outcomes have been reported in patients
keeping full-mouth plaque score lower than 15% [5].
2. The control of periodontal infection: low level of bleeding on probing is
another major goal of cause-related therapy and is again extremely important
for the regenerative approach. Optimal regenerative outcomes have been
reported in patients having full-mouth bleeding score lower than 15% [5].
3. The presence of residual pockets or furcations: after successful nonsurgical
phase, most of baseline increased pocket probing depths should have been
resolved or greatly reduced.

122 Minimally Invasive Periodontal Therapy
4. Additional goals of cause-related therapy are control of behavioral and
systemic conditions, such as smoking habits, stress, and systemic diseases
(e.g., diabetes).
The presence of residual deep pocket probing depths might indicate the need
for periodontal surgery. Surgical treatment of pockets can follow different paths
from flap surgery, to resective surgery, to regenerative/reconstructive surgery.
Clinical goals of regenerative surgery are to (i) reduce pocket probing depth
through attachment gain while limiting the gingival recession and (ii) increase
the functional support of the involved teeth. However, periodontal regeneration
is not always applicable [5] (Flow chart 8.2). Ample evidence shows that it is
highly predictable in the treatment of pockets associated with deep and shallow
intrabony defects. Its applicability to furcations is questioned by the scientific
Pockets &
defects
Horizontal bone
destruction
Vertical bone
destruction
Furcation
involvement
NO periodontal
regeneration
1-2-3 wall
intrabony defects
Degree I, II, III
Periodontal
regeneration
Periodontal
regeneration?
Chart 8.2
Post cause-
related therapy
Local
factors
Behavioural
factors
Systemic
factors
Stress
Smoke
> 10/Die
Palque
FMPS < 15%
Infection
FMBS < 15%
Compliance
Diseases
(Diabetes)
Chart 8.1

Minimally Invasive Surgical Technique and Modified-MIST 123
community: good outcomes are reported only for the treatment of degree II
furcations on lower molars. At present, there is no evidence supporting the
application of periodontal regeneration to pockets associated with horizontal
bone destruction.
Intrabony defects have been classified according to their morphology in
terms of residual bony walls, width of the defect (or radiographic angle), and
in terms of their topographic extension around the tooth [45]. Three-wall,
two-wall, and one-wall defects have been defined on the basis of the number
of residual alveolar bone walls. Frequently, intrabony defects present a complex
anatomy consisting of a three-wall component in the most apical portion of the
defect, and two- and/or one-wall components in the more superficial portions.
Such defects are frequently referred to as combination defects. It is therefore
mandatory to clearly diagnose the type of bone defect associated with the
pocket. This assessment is based on periodontal probing. The presence of an
interproximal intrabony defect is anticipated when there is a difference in the
interproximal attachment level between two neighboring teeth. This difference
represents the intrabony component of the defect: if the mesial surface of a tooth
has an attachment level of 10 mm and the distal surface of the neighboring tooth
has an attachment level of 4 mm, the depth of the intrabony component is 6 mm
(Figure8.1a–d). The diagnosis has tobe confirmed with a periapical radiograph
that provides relevant information about the morphology of both the defect and
the root. However, in many instances, the radiograph underestimates the real
depth of the defect.
When the presence of an intrabony defect is confirmed, the morphology and
extension of the defect and/or the presence of additional defects at neighboring
teeth should be carefully inspected. Bone sounding under local anesthetic is highly
recommended as a very predictable diagnostic tool to get sound information on
the extension of bone destruction.
Figure 8.1 (a) The periodontal probe shows a 10 mm pocket on the distal side of the lower
right second premolar. (b) A probing depth of 4 mm is detected at the mesial side of the lower
right first molar.
(a)
(b)

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Minimally Invasive Periodontal Therapy: Clinical Techniques and Visualization Technology, First Edition. Edited by Stephen K. Harrel and Thomas G. Wilson Jr. © 2015 John Wiley & Sons, Inc. Published 2015 by John Wiley & Sons, Inc.Companion Website: www.wiley.com/go/harrel/minimallyinvasive1178IntroductionPeriodontal regenerative technologies are applied to improve short- and long-term clinical outcomes of periodontally compromised teeth, presenting with deep pock-ets and reduced periodontal support. The persistence of deep pockets following active periodontal therapy has been associated with an increased probability of tooth loss in patients attending supportive periodontal care programs [1]. Teeth with deep pockets associated with deep intrabony defects are considered a clinical challenge: periodontal regeneration has been shown to be effective in the treatment of one-, two-, and three-wall intrabony defects or combinations thereof, from very deep to very shallow, from very wide to very narrow [2–5]. Therefore, the applica-tion of regenerative procedures, including minimally invasive procedures, is suited in deep and shallow intrabony defects.Regeneration is a healing outcome that can occur when the systemic and local conditions are favorable. The systemic conditions include the control of peri-odontitis, a low total bacterial load in the mouth and cessation of smoking habits: high percentages of bleeding on probing and high bacterial loads as well as ciga-rette smoking have been associated with reduced clinical outcomes [6–12]. The local conditions include the presence of space for the formation of the blood clot at the interface between the flap and the root surface [12–17], the stability of the Minimally Invasive Surgical Technique and Modified-MIST in Periodontal RegenerationPierpaolo Sandro Cortellini 118 Minimally Invasive Periodontal Therapyblood clot to maintain a continuity with the root surface avoiding formation ofalong junctional epithelium [13,18–20], and the soft tissue protection to avoid bacterial contamination [10,21–23].Development of periodontal regenerative medicine in the past 25 years has fol-lowed two distinctive, though totally interlaced paths. The interest of researchers has thus far focused on regenerative materials and products on the one side and on novel surgical approaches on the other side.In the area of materials and products, three different regenerative concepts have been explored: (i) barrier membranes, (ii) grafts, and (iii) wound healing modi-fiers, plus many combinations of the aforementioned concepts [5].In general, the development of surgical procedures was aimed at complete preservation of the soft tissues to achieve and maintain primary closure on top ofthe applied regenerative material/substance during the critical early stages of healing. Specifically, flap designs attempted to achieve passive primary closure of the flap combined with optimal wound stability.In the 1990s, the modified papilla preservation technique (MPPT)[15] and the sim-plified papilla preservation flap (SPPF)[24] have been tested and proposed. These clinical innovations in flap design and handling have radically changed surgery and have allowed a drastic limitation of interdental wound failure to less than 30% of the treated cases. Further enhancements of clinical outcomes were achieved when an operative microscope was adopted [25,26]. Authors reported an increased capacity to manipulate the soft tissues that resulted in an improved potential for primary clo-sure of the wound to an excellent 92% obtained with microsurgery. Other authors reported improved outcomes using operative microscopes in different areas of periodontal surgery, from flap surgery to mucogingival surgery [27–32].In the past decade, a growing interest for more friendly, patient-oriented sur-gery have urged clinical investigators to focus their interest in the development of less invasive approaches [33–35]. Following this path, Cortellini and Tonetti proposed a minimally invasive surgical technique (MIST) on isolated [36] and multiple [37]intrabony defects, and a Modified MIST (M-MIST)[38] on isolated intrabony defects.Clinical studies and outcomesCohort studies and randomized controlled clinical trials reporting outcomes on the application of minimally invasive surgical approaches are reported in Tables8.1 and 8.2.Table8.1 refers to MIST studies in which the interdental papillary tissues have been elevated to uncover the interdental space completely. This approach is sup-ported by three cohort studies [36,37,39] and two controlled studies [40,41].Table8.2 reports studies in which the access to the defect was gained through the elevation of a small buccal flap, without elevation of the interdental papilla. This approach is supported by a cohort study [38] and three controlled studies [42–44]. Interestingly, the cited randomized clinical trials performed using Table 8.1 Minimally invasive surgical technique (MIST): clinical studies.MISTType of study (quality of evidence) InterventionsNo. paxNo. defects CAL gain PD reduction Δ RECCortellini and Tonetti [36]Case cohort (level 2) MIST + EMD 13 13 4.8 ± 1.9 4.8 ± 1.8 0.1 ± 0.9Cortellini and Tonetti [39]Case cohort (level 2) MIST + EMD 40 40 4.9 ± 1.7 5.2 ± 1.7 0.4 ± 0.7Cortellini etal. [37]Case cohort (level 2) MIST + EMD 20 44 4.4 ± 1.4 4.6 ± 1.3 0.2 ± 0.6Ribeiro et al. [40]RCT (Level 1) MIST 15 15 2.82 ± 1.19* 3.55 ± 0.88* 0.54 ± 0.58*MIST + EMD 14 14 3.02 ± 1.94* 3.56 ± 2.07* 0.46 ± 0.87*Ribeiro et al. [41]RCT (level 1)MIST 14 14 2.85 ± 1.19* 3.51 ± 0.90* 0.48 ± 0.51*MINST (RPL) 13 13 2.56 ± 1.12* 3.13 ± 0.67* 0.45 ± 0.46*MINST, minimally invasive non surgical technique (RPL with the aid of a microscope); MIST, minimally invasive surgical technique.*No statistical difference. Table 8.2 Modified-minimally invasive surgical technique (M-MIST): clinical studies.M-MIST/SFA Type of study InterventionsNo. paxNo. defects CAL gainPD reduction Δ RECCortellini and Tonetti [38]Case cohort M-MIST + EMD 15 15 4.5 ± 1.4 4.6 ± 1.5 0.07 ± 0.3Cortellini and Tonetti [42]RCT M-MISTM-MIST + EMDM-MIST + EMD + BioOss1515151515154.1 ± 1.4*4.1 ± 1.2*3.7 ± 1.3*4.4 ± 1.6*4.4 ± 1.2*4.0 ± 1.3*0.3 ± 0.6*0.3 ± 0.5*0.3 ± 0.7*Trombelli etal. [43]RCT SFASFA + HA + GTR121212124.4 ± 1.5*4.7 ± 2.5*5.3 ± 1.5*5.3 ± 2.4*0.8 ± 0.8*0.4 ± 1.4*Mishra et al. [44]RCTM-MISTM-MIST + rhPDGF-BB121212122.6 ± 0.8*3.0 ± 0.9*3.8 ± 0.9*4.2 ± 0.6*0.5 ± 0.5*0.8 ± 0.6*M-MIST, modified minimally invasive surgical technique; SFA, single flap approach; rhPDGF-BB, recombinant human platelet derived growth factor.*No statistical difference. Minimally Invasive Surgical Technique and Modified-MIST 121minimally invasive surgical approaches (with or without papilla elevation) do not report any difference in terms of clinical outcomes between the minimally invasive control flap approach and the test in which a regenerative material/product was introduced under the flap. The reported outcomes raise a series of hypotheses that focus on the intrinsic healing potential of a wound when ideal conditions are provided with the surgical approach. In other words, the outcomes of these studies challenge clinicians with the possibility to obtain substantial clinical improvements without using products or materials applying surgical techniques that do enhance per se blood clot and wound stability. In particular, the advanced flap design of the M-MIST greatly enhances the poten-tial to provide space and stability for regeneration by leaving the interdental papillary soft tissues attached to the root surface of the crest-associated tooth and by avoiding any palatal flap elevation. The interdental soft tissues are the stable “roof” of a room where the blood fills in and forms a clot. The hanging papilla prevents the collapse of the soft tissues, thereby maintaining space forregeneration. The anatomic bone deficiencies are potentially supplemented by the peculiar flap design that provides additional “soft tissue walls” to the missing bony walls improving stability: walls of the “room” are the residual bony walls, the root surface, and the buccal/lingual soft tissues. The minimal flap extension and elevation also minimizes the damages to the vascular system favoring the healing process of the tiny soft tissues.Clinical indications and diagnostic proceduresDelivering periodontal surgery in general and regenerative treatment in particular requires knowledge, skills, experience, and a well-defined step-by-step approach.The first step of periodontal therapy is always cause-related therapy, aimed at obtaining patient compliance, reduction of oral bacterial loads, and control of gingival infection.At completion of nonsurgical cause-related therapy, patients have to be care-fully reevaluated. A full periodontal evaluation should be performed to check for (Flow chart 8.1) the following aspects:1. The compliance of the patient in terms of plaque control: a very low load of bacterial plaque is a major goal of cause-related therapy and key to periodontal regeneration. Optimal regenerative outcomes have been reported in patients keeping full-mouth plaque score lower than 15% [5].2. The control of periodontal infection: low level of bleeding on probing is another major goal of cause-related therapy and is again extremely important for the regenerative approach. Optimal regenerative outcomes have been reported in patients having full-mouth bleeding score lower than 15% [5].3. The presence of residual pockets or furcations: after successful nonsurgical phase, most of baseline increased pocket probing depths should have been resolved or greatly reduced. 122 Minimally Invasive Periodontal Therapy4. Additional goals of cause-related therapy are control of behavioral and systemic conditions, such as smoking habits, stress, and systemic diseases (e.g., diabetes).The presence of residual deep pocket probing depths might indicate the need for periodontal surgery. Surgical treatment of pockets can follow different paths from flap surgery, to resective surgery, to regenerative/reconstructive surgery. Clinical goals of regenerative surgery are to (i) reduce pocket probing depth through attachment gain while limiting the gingival recession and (ii) increase the functional support of the involved teeth. However, periodontal regeneration is not always applicable [5] (Flow chart 8.2). Ample evidence shows that it is highly predictable in the treatment of pockets associated with deep and shallow intrabony defects. Its applicability to furcations is questioned by the scientific Pockets &defectsHorizontal bonedestructionVertical bonedestructionFurcationinvolvementNO periodontalregeneration1-2-3 wallintrabony defectsDegree I, II, IIIPeriodontalregenerationPeriodontalregeneration?Chart 8.2 Post cause-related therapyLocalfactorsBehaviouralfactorsSystemicfactorsStressSmoke> 10/DiePalqueFMPS < 15%InfectionFMBS < 15%ComplianceDiseases(Diabetes)Chart 8.1 Minimally Invasive Surgical Technique and Modified-MIST 123community: good outcomes are reported only for the treatment of degree II furcations on lower molars. At present, there is no evidence supporting the application of periodontal regeneration to pockets associated with horizontal bone destruction.Intrabony defects have been classified according to their morphology in terms of residual bony walls, width of the defect (or radiographic angle), and in terms of their topographic extension around the tooth [45]. Three-wall, two-wall, and one-wall defects have been defined on the basis of the number of residual alveolar bone walls. Frequently, intrabony defects present a complex anatomy consisting of a three-wall component in the most apical portion of the defect, and two- and/or one-wall components in the more superficial portions. Such defects are frequently referred to as combination defects. It is therefore mandatory to clearly diagnose the type of bone defect associated with the pocket. This assessment is based on periodontal probing. The presence of an interproximal intrabony defect is anticipated when there is a difference in the interproximal attachment level between two neighboring teeth. This difference represents the intrabony component of the defect: if the mesial surface of a tooth has an attachment level of 10 mm and the distal surface of the neighboring tooth has an attachment level of 4 mm, the depth of the intrabony component is 6 mm (Figure8.1a–d). The diagnosis has tobe confirmed with a periapical radiograph that provides relevant information about the morphology of both the defect and the root. However, in many instances, the radiograph underestimates the real depth of the defect.When the presence of an intrabony defect is confirmed, the morphology and extension of the defect and/or the presence of additional defects at neighboring teeth should be carefully inspected. Bone sounding under local anesthetic is highly recommended as a very predictable diagnostic tool to get sound information on the extension of bone destruction.Figure 8.1 (a) The periodontal probe shows a 10 mm pocket on the distal side of the lower right second premolar. (b) A probing depth of 4 mm is detected at the mesial side of the lower right first molar.(a)(b) 124 Minimally Invasive Periodontal TherapyThis accurate diagnosis is necessary to select the type of surgical approach and the regenerative materials to be applied to the given clinical condition. In fact, different surgical approaches have been developed through time,which incorpo-rate clear differences in terms of flap design and suturing technique. All the pro-posed surgical techniques have a common foundation in the attempt to fully preserve the defect-associated interdental papillae and all the buccal and lingual keratinized gingiva by applying intrasulcular incisions. The traditional papilla RegererativeapproachIntrabony defectInvolving 1/2 sides ofthe rootInvolving 3/4 sides ofthe root & very severeCleansablefrom BuccalYESM-MIST MISTPapillapreservation flapsNOChart 8.3 Figure 8.1 (Continued) (c) The intrabony component of this three-wall defect is 6 mm. (d) Radiographic image of the intrabony defect.(c)(d) Minimally Invasive Surgical Technique and Modified-MIST 125preservation flaps [15,24] are large and very mobile flaps that allow for ample accessibility and visibility of the defect area, for easy application of biomaterials and barriers, and for the coronal positioning of the buccal flap to cover barriers and biomaterials. The MIST [36], on the contrary, was designed to mobilize just the defect-associated papilla and to reduce flap extension as much as possible. The Modified-MIST [38], based on the elevation of a tiny buccal flap, further enhanced this concept by avoiding the interdental papilla as well as the palatal flap dissection and elevation.The flow chart 8.3 indicates how to select the flap design according to the defect morphology and extension. Whenever a bone defect involves one or two sides of a root and is cleansable from a small buccal window, an M-MIST can be applied. If such a defect is not cleansable from the buccal window, the interdental papilla is elevated applying a MIST approach. A large papilla preservation flap (MPPT or SPPF), extended to the neighboring teeth and including also a periosteal incision and/or vertical releasing incisions, will be chosen in the presence of a very severe and deep defect, involving three or four sides of the root, requiring ample visibility for instrumentation and the placement of biomaterials and/or barriers.Minimally invasive surgical techniqueThe MIST [36,39] is based on the elevation of the defect-associated interdental papilla along with minimally extended buccal and lingual flaps.The entry incision is performed on the buccal side of the interdental papilla that is dissected with two different approaches according to the width of the inter-dental space. The width of the interdental space is measured with a periodontal probe as the distance between the two root surfaces; the periodontal probe is posi-tioned horizontally about 2 mm apical to the tip of papilla. In some instances the interdental space is uneven on the buccal and on the lingual/palatal aspect: for example, frequently, the interdental space between the upper cuspid and the bicuspid is narrower on the palatal side than on the buccal one. In these instances, the measurement has to be taken on the palatal side.In narrow interdental spaces (<2 mm), a buccal diagonal cut is selected, as described in the simplified papilla preservation flap (SPPF)[24]. This incision starts in the interdental sulcus of the defect-associated tooth: the microblade runs toward the contact point, strictly intrasulcular, then crosses diagonally the inter-dental papilla as close as possible to the papilla tip (the contact point is the limit for the interdental intrasulcular advancement of the blade); the blade cuts through the papilla, hitting the root surface of the crest-associated tooth (Figure8.2a and b).Conversely, a buccal horizontal cut is performed in wide interdental spaces (≥2 mm), according to the modified papilla preservation technique (MPPT) [7,15]. The incision is performed through the buccal interdental tissues about midway between the tip and the base of the papilla, keeping the microblade 90° with respect to the gingival surface (Figure8.3a and b). 126 Minimally Invasive Periodontal TherapyIn both the SPPF and MPPT incisions, the microblade is aimed at reaching the underlying bone: it may be necessary to run the scalpel two or three times to get a sharp separation between the buccal and the lingual interdental soft tissues.The buccal incision is then continued in the interdental and buccal sulcus ofthe defect- and crest-associated teeth. The mesio-distal extension is kept to a minimum: when an isolated interdental defect is made, the incision should not invade the next interdental papillae. The lingual/palatal incision is very similar to the buccal one: care has to be taken not to damage the defect-associated papilla, keeping the microblade strictly intrasulcular.Both the buccal and the lingual intrasulcular incisions should reach the residual bone; then, buccal and lingual full thickness flaps are elevated with tiny periosteal elevators to uncover the defect and the residual bone crest (Figure8.4a–i). The corono-apico elevation is meant to expose 1–2 mm of bone crest: should the elevation require a greater apical extension (e.g., in cases in which the buccal or Figure 8.2 (a) The interdental space between the central and lateral incisor is narrow. (b) The microblade is positioned in the interdental space to cut a diagonal incision according tothe principles of the SPPF.(a)(b)Figure 8.3 (a) The interdental space between the premolar and the molar is wide. (b) The microblade is positioned in the interdental space to cut a horizontal incision according to the principles of the MPPT.(a)(b) Minimally Invasive Surgical Technique and Modified-MIST 127Figure 8.4 (a) Fifty-five-year-old patient presenting with chronic generalized periodontitis reported a family history for periodontitis, was systemically healthy, and a nonsmoker. Aftercause-related therapy, FMPS and FMBS were less than 15%, and most of the pockets were resolved. A pocket was still present at the upper right lateral incisor. (b) The radiograph shows the presence of a narrow intrabony defect associated with a suprabony component. (c)A7 mm pocket associated with a 2 mm recession was measured at the mesial aspect of thelateral incisor. A 6 mm pocket was also detectable on the mid-palatal side. The clinical objective was to reduce the probing depth, thereby minimizing the retraction of the gingival margin. (d, e) The surgical site was approached with a MIST. The buccal flap involved the defect-associated interdental papilla and was minimally extended to the mid-buccal area ofthe lateral and central incisors. The interdental papilla was reflected toward the palatal side. The palatal flap was minimally elevated. A narrow 5 mm 1–2 wall intrabony defect wasevident after debridement. (a)(c)(d)(b)(e) 128 Minimally Invasive Periodontal Therapylingual bone wall(s) is missing or the defect is involving an ample area of the lin-gual side), the flap has to be extended in mesial or distal direction to allow for a greater flap mobility (Figure 8.5a–m). In some instances, buccal and/or lingual vertical releasing incisions can be added to increase the reflection of the flaps. These additional incisions are to be performed only when necessary and are aimed at increasing the access to the defect. No split thickness incisions are used—the Figure 8.4 (Continued) (f) Following delivery of amelogenins, a single modified internal mattress suture was positioned to close the flap. (g) The 1-year photograph shows healthy condition of the treated area. (h) A 2 mm probing depth at 1 year compares with the 7 mm recorded at baseline. The gingival margin is stable. (i) The radiograph shows the resolution of the intrabony component ofthe defect.(f)(g)(h)(i) Figure 8.5 (a) A 62-year-old male presenting with chronic generalized periodontitis. He reported a family history for periodontitis, was systemically healthy and former smoker. At baseline FMPS and FMBS were over 80%. Cause-related therapy required about 3 months, after which FMPS and FMBS were reduced to less than 15%. Pockets were still present on few teeth, including the lower left first molar. (b) The radiograph, shows the presence of a 45° wide intrabony defect distal to the first molar. (c) The periodontal probe reveals a 7 mm pocket associated with 1 mm recession distal to the molar. A 6 mm pocket was also present on the distal and the mid-palatal side. The clinical objective was to reduce the probing depth. (d, e) The site was approached with a MIST. The buccal flap involved only the defect-associated interdental papilla and was extended to the mid-buccal area of the two molars. The lingual flap was extended also to the papilla between molar and premolar, to obtain proper access for defect debridement. A 6 mm three-wall intrabony defect was evident after debridement. The bone defect extended to the lingual side, reaching the mesial root of the first molar. (a)(b)(e)(d)(c)(f) Figure 8.5 (Continued) (f, g) Amelogenins were used as regenerative material. The flap was sutured with a single modified internal mattress suture at the defect associated papilla. The papilla mesial to the first molar was sutured with a passing suture. (i, j) Primary closure was maintained at 1 week, when sutures were removed. (k) The 1-year radiograph shows the complete resolution of the intrabony component of the defect. (l) The 3-year photograph shows 4 mm probing depth. (m) The 3-year radiograph shows stability of the regenerated bone.(h)(g)(i)(j)(k)(l)(m) Minimally Invasive Surgical Technique and Modified-MIST 131aim of flap elevation being to expose the coronal edge of the residual bone crest. In most of the cases, the reflection of the buccal flap does not involve the mucogingival junction.When both the buccal and lingual flaps are reflected, scaling and root planing are performed by means of minicurettes and sonic/ultrasonic instruments. The aim of instrumentation is to fully remove soft tissue from the bone defect and to carefully debride and plane the root surface. Once thoroughly cleaned, the defect can be treated with different regenerative materials, such as amelogenins, growth factors, autologous bone grafts, allograft materials, or combinations thereof. Barrier membranes are not to be used in combination with the MIST: barrier placement, in fact, requires a larger extension of the flap and, frequently, a split thickness approach, according to the surgical design of the modified papilla preservation technique [7,15] and the simplified papilla preservation flap [24]. The use of amelogenins should also include the application of EDTA for 2 min on the air-dried root surface; the root surface is then thoroughly washed and gently air-dried to apply amelogenins.The suture technique is based on the application of a single modified internal mattress suture (the use of a 6-0 PTFE suture is suggested) to provide a primary intention closure of the interdental papilla. The primary intention seal can be improved by applying additional passing sutures (the use of 6-0 or 7-0 monofil-aments is suggested), when needed.The MIST can also be used to treat multiple intrabony defects on adjacent teeth [37]. In this instance, the technique requires a mesio-distal extension of the flap toinclude all the defects-associated teeth and to allow for the elevation of all thedefect-associated papillae. Although the mesio-distal extension is increased, the corono-apical elevation of the full thickness buccal and lingual/palatal flap is minimal, according to the previously reported principles.Modified MISTThe M-MIST has been proposed to further reduce invasivity and patient side effects, and to increase the odds for primary closure of the wound and for blood clot stability [38]. The overall idea of the M-MIST is to provide a very small inter-dental access to the defect through a small buccal window (Figure8.6a–i). The entry incision is performed on the buccal side of the interdental papilla and follows the same principles described for the MIST approach. The interdental incisions involve the buccal aspect of the teeth neighboring the defect and do not involve the next papillae. When the microblade has completed a sharp dissection of gingiva, a triangular buccal flap is minimally elevated to expose the residual buccal bone crest. Once the buccal flap has been reflected, the microblade is posi-tioned to dissect the supracrestal interdental tissue from the granulation tissue: the blade should aim at the buccal surface of the lingual bony wall. The angula-tion of the blade will, therefore, be different with different bone anatomies: the more apical the lingual/palatal bone destruction, the greater the corono-apical 132 Minimally Invasive Periodontal TherapyFigure 8.6 (a) A 35-year-old male presenting with aggressive localized periodontitis. He reported a family history for periodontitis, was systemically healthy, and a nonsmoker. At baseline FMPS was 30% and FMBS 58%. After cause-related therapy, FMPS and FMBS were reduced to less than 15%. A pocket was still present on the lower right first molar. (b) The radiograph shows the presence of a 40° wide intrabony defect mesial to the first molar. (c) The periodontal probe reveals a 6 mm pocket associated with 2 mm recession limited to the mesial side of the molar. The clinical objective was to reduce the probing depth. (d) The site was approached with an M-MIST. The tiny triangular buccal flap involved only the defect-associated interdental papilla and was minimally extended to the mid-area of mesial root of the molar andof the premolar. The interdental papilla was not reflected, and the lingual flap was not elevated. The granulation tissue was removed from under the papilla, and root debridement wasperformed through the small buccal window. (e) The three-wall intrabony defect was 6 mm deep. (f) Amelogenins were delivered into the defect. (a)(b)(c)(d)(e)(f) Minimally Invasive Surgical Technique and Modified-MIST 133inclination of the blade. When the blade has sharply separated the papillary from the granulation tissue, the latter is removed with minicurettes. The interdental papilla is not detached from the residual interdental bone crest and supracrestal fibers, and the palatal flap is not elevated. Then, the root surface is thoroughly scaled and planed by the combined action of minicurettes and sonic/ultrasonic instruments. Special attention has to be paid to avoid any trauma to the supra-crestal fibers of the defect-associated papilla. As reported for the MIST, the bone defect can be treated with different regenerative materials, such as amelogenins, growth factors, autologous bone grafts, allograft materials, or combinations thereof, but not barrier membranes.All the reported clinical steps are performed through the small buccal “surgical window” and require magnifying devices and optimal illumination of the sur-gical field, such as an operative microscope or magnifying lenses. The primary closure of the surgical wound is achieved using a modified internal mattress suture and eventually the application of additional passing sutures, as described for the MIST technique (Figure8.7a–j).(g)(h)(i)Figure 8.6 (Continued) (g) The flap was closed with a single modified internal mattress suture.(h) At 1 year, a probing depth of 2 mm was associated with 2 mm of gingival recession. (i) The 1-year radiograph shows the almost complete resolution of the intrabony component ofthe defect. Figure 8.7 (a) A 59-year-old male presenting with chronic generalized periodontitis. He did not report a family history for periodontitis, was systemically healthy, and a former smoker. FMPS and FMBS were reduced to less than 15% after cause-related therapy. Pockets were still present on some teeth, including the upper right cuspid. (b) The radiograph shows the presence of a narrow intrabony defect mesial to the cuspid. (a)(b)(c)(d)(e)(f) Minimally Invasive Surgical Technique and Modified-MIST 135(g)(h)(i)(j)Figure 8.7 (Continued) (c) The periodontal probe reveals a 7 mm pocket and a consistent gingival recession. The clinical objective was to reduce the probing depth minimizing any furthergingival retraction. (d) The site was approached with an M-MIST. The tiny triangular buccal flap involved only the defect-associated papilla. The interdental papilla was not reflectedand thelingual flap was not elevated. After removal of the granulation tissue from under the papilla, rootdebridement was performed through the small buccal window. (e) A 6 mm-deep one-, two-, andthree-wall intrabony defect was evident after debridement. Thedefect was treated witha combination of amelogenins and a filler to minimize the collapse of the papilla. (f). The flap wasclosed with a modified internal mattress suture and an additional passing suture. (g) The postoperative radiograph shows the presence of biomaterial filling the intrabony component of the defect. (h) Sutures were removed at 1 week. Primary closure of theflap was maintained. (i)At1 year, probing depth was 3 mm. There was no increment ofgingival recession. (j) The 1-year radiograph shows the complete resolution of the intrabony component of the defect. 136 Minimally Invasive Periodontal TherapyChoice of the regenerative materialSelection of the regenerative material is based on the defect anatomy and on theflap design chosen to access the defect. As clearly seen from a review of the scientific literature [5], the clinical decision to implant a barrier and/or a filler takes its foundations in the need to stabilize the blood clot and the sur-gical flap. This becomes more necessary when treating a one-wall or a wide two-wall defect. The need for extra stabilization of the treated area increases when a large flap with high degree of mobility is designed. When treating narrow two-wall and three-wall defects, the bone anatomy per se provides enough stability, especially when a low-mobility, minimally invasive flap in designed. The published evidence shows that, applying the M-MIST, the flap alone without additional use of regenerative materials, the outcomes are as good as with the additional use of regenerative materials. Therefore, when approaching a site with minimally invasive surgery, apossible decisional tree is the following:1. When an M-MIST approach is applied, amelogenins or growth factors, or noregenerative materials are the possible choices, irrespective of the bone anatomy. In other words, there is no great need for a supportive biomaterial, and most probably, there is little advantage in using regenerative substances (Figure8.8a–d).2. If a MIST approach is applied, amelogenins or growth factors can be used in containing defects (narrow two-wall and three-wall) or in combination with a filler in noncontaining defects (one-wall or a wide two-wall).Technical implicationsApplication of MIST and M-MIST requires surgical skills and a proper surgical setting. The major problem to overcome applying minimally invasive surgery is the problem of visibility and manipulation of the surgical field, in particular, with the M-MIST approach. In fact, the minimal flap reflection reduces the angle of vision and, especially, the light penetration into the surgical field. High magnification and direct optimal illumination provided by a surgical micro-scope or magnifying lenses can be of great help. In addition, the soft tissue manipulation during instrumentation requires special care since the flaps, not fully reflected, lay very close to the working field. Small instruments, such as small periosteal elevators and tiny tissue forceps are mandatory as well as their gentle application to soft and hard tissues. Microblades, minicurettes, and miniscissors allow for a full control of the incision, debridement, and refine-ment of the surgical area, as well as sutures from 6-0 to 8-0 are requested for the wound closure. Minimally Invasive Surgical Technique and Modified-MIST 137Postsurgical protocolsPostsurgical and early home care protocols are directly taken from the experiences developed from running many controlled clinical trials [7,46–51]. An empirical protocol for the control of bacterial contamination consisting of doxicycline (100 mg bid for 1 week), 0.12% chlorhexidine mouth rinsing three times per day, and weekly prophylaxis is prescribed. Sutures are removed after 1 week. Patients are requested to avoid normal brushing, flossing, and chewing in the treated area for periods of 4–6 weeks. A postsurgical soft toothbrush soaked in chlorhexidine is used from week 1 to gently wipe the treated area. Patients can resume full oral hygiene and chewing function in the treated area 4–6 weeks after suture removal. At the end of the “early healing phase,” patients are placed on periodontal maintenance every 3 months’ recall system. A general suggestion to avoid any invasive clinical interven-tion, such as hard subgingival instrumentation, restorative dentistry, orthodontics, and additional surgery, for a period of about 9 months is also part of a strategy that is aimed at optimizing the clinical outcomes of periodontal regeneration.Figure 8.8 (a, b) Severe intrabony defect distal to the first lower molar, associated with a deep interproximal pocket. (c, d) Three years after regenerative therapy, the bone defect was completely resolved and the pocket eliminated. The site was treated with M-MIST alone, without any additional regenerative material.(a)(b)(c)(d) 138 Minimally Invasive Periodontal TherapyPostoperative period and local side effectsFrom the very beginning of the “guided tissue regeneration era,” it was apparent the frequent occurrence of complications, in particular, exposure of barriers. It amounted to almost 100% of the cases in the pre-papilla preservation technique period and was reportedly reduced to an amount ranging from 50% to 6% when papilla preservation flaps were adopted [5]. A consistent decrease of complica-tions was observed when barriers were not incorporated in the surgical procedure. In particular, the adoption of amelogenins largely reduced the prevalence of complications [4,23,49].The development of minimally invasive surgery has further reduced the amount of complications and side effects in the postoperative period.Primary closure of the flap was reported in 100% of cases treated with MIST and maintained in 95% of the cases at 1 week in single sites [36,39] and in 100% of the cases in treatment of multiple sites [37]. Edema was noted in few cases [36,37,39]. No postsurgical hematoma, suppuration, flap dehiscence, presence of granulation tissue, or other complications were reported in any of the treated sites [36,37,39]. Root sensitivity is not a frequent occurrence. It was reported at 1 week by about 20% of the patients and rapidly decreased in the following weeks; at week 6, only one patient still reported some root sensitivity [39]. Ribeiro et al. [40] reported that the extent of root hypersensitivity, and edema was minimum, and no patients developed hematomas.When applying the M-MIST [38], the reported primary closure was obtained and maintained in 100% of the cases. In a second controlled study [31], one M-MIST/EMD/BMDX site presented at suture removal (week 1) with a slight discontinuity of the interdental wound. At week 2, the gap appeared closed.No edema, hematoma, or suppuration was noted in any of the treated sites [31,38].ConclusionsMinimally invasive surgery should be considered a true reality in the field of periodontal regeneration. 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