Treatment Planning for the Edentulous Posterior Maxilla










553
23
Treatment Planning for the Edentulous
Posterior Maxilla
RANDOLPH R. RESNIK AND CARL E. MISCH
H
istorically the maxillary posterior region has been one of
the most dicult regions in the oral cavity to treat. Maxil-
lary posterior partial or complete edentulism is one of the
more common treatment areas in implant dentistry. However, the
maxillary posterior edentulous region presents many unique and
challenging conditions in implant dentistry that many years ago
led to an area with the highest implant failure rate. Over the years
many new surgical protocols and technological advances have led
to this region being as predictable as any other region in the oral
cavity. Most noteworthy of these surgical methods includes sinus
augmentation to increase available bone height, ridge augmentation
to increase bone width, better-designed shorter implants, and modi-
ed surgical approaches to insert implants in poorer bone density.
1
Grafting of the maxillary sinus to overcome the problem of reduced
vertical available bone has become a very popular and predictable
procedure since the 1990’s. After the initial introduction by Tatum
in the mid-1970s and the initial publication of Boyne and James in
1980, many studies have been published about sinus grafting with
results higher than 90%.
2-38
is chapter will address the various
disadvantages inherent with the posterior maxilla, along with the
treatment planning factors and concepts specic to the maxillary
posterior partial or complete edentulous regions.
Inherent Disadvantages of Posterior Maxilla
Treatment
Poor Bone Density
In general the bone quality is poorest in the edentulous posterior
maxilla compared with any other intraoral region.
30
A literature
review of clinical studies reveal poorer bone density may result in
decreased implant loading survival by an average of 16% and has
been reported to be as low as 40%.
31
e cause of the poorer success
rate is related to several factors. Bone strength is directly related to
its density, and the poor density bone of this region is often 5 to 10
times weaker in comparison with bone found in the anterior man-
dible (~ D2 Bone Quality).
32
Bone densities directly inuence the
percent of implant–bone surface contact (bone–implant contact or
BIC), which accounts for the force transmission to the bone. e
bone–implant contact (<30%) is the lowest in D4 (Type 4) bone
compared with other bone densities. e stress patterns distributed
within poor bone density migrate farther toward the apex of the
implant. As a result, bone loss is more pronounced and occurs also
deeper along the implant body, rather than only crestally as in other
denser bone conditions. D4 bone also has been shown to exhibit the
greatest biomechanical elastic modulus dierence compared with
titanium under load.
32
is biomechanical mismatch develops a
higher strain condition to the bone, which may be in the pathologic
overload range. As such, modied surgical protocols are warranted
to increase bone-implant contact.
In the posterior maxilla the poorer decient osseous structures
and the minimal cortical plate on the crest of the ridge will com-
promise the initial implant stability (insertion torque) at the time of
placement (Fig. 23.1). e labial cortical plate is usually thin, and
the ridge is often wide. As a result the lateral cortical bone–implant
contact to stabilize the implant is often insignicant because implant
placement rarely engages the buccal plate. erefore initial healing
of an implant in D4 bone is often compromised, and clinical reports
indicate a lower initial healing success than with D2 or D3 bone.
Fig. . D4 bone density, which is usually found in the posterior maxilla.
This type of bone usually exhibits minimal cortical bone and has very fine
trabeculae.
Deceased

554
PART V Edentulous Site Treatment Planning
Decreased Available Bone
In the posterior maxilla the implant clinician is often confronted
with a decreased bone quantity, thereby compromising implant
placement. e dentate maxilla is usually associated with a thinner
cortical plate on the facial compared with the mandible. Because
the trabecular bone of the posterior maxilla is ner than other
dentate regions, the loss of maxillary posterior teeth usually results
in an initial decrease in bone width at the expense of the labial
bony plate. e width of the posterior maxilla will decrease at a
more rapid rate than in any other region of the jaws.
25
e resorp-
tion phenomenon is accelerated by the loss of vascularization of
the alveolar bone and the existing ne trabecular bone type. How-
ever, because the initial residual ridge is so wide in the posterior
maxilla, even with a signicant decrease in the width of the ridge,
ideal size root form implants usually can be placed (Fig. 23.2).
Increased Pneumatization of the Maxillary Sinus
Pneumatization is a normal physiologic process that occurs in all
paranasal sinuses during the growth period, which results in an
increased volume. Histologic studies have shown that the pneu-
matization process occurs by osteoclastic resorption of the corti-
cal walls of the sinus. However, the etiology of maxillary sinus
pneumatization is poorly understood and has been associated with
heredity, pneumatization drive of the nasal mucous membrane,
craniofacial conguration, bone density, growth hormones, and
intra-sinus air pressure.
39
e pneumatization process has been shown to increase in size
after tooth extraction. Most likely this is a result of a decrease in
functional forces that are transferred to the bone after tooth loss
and the remodeling process involving disuse atrophy according to
Wol’s law.
40
Because of the proximity and possible protrusion of
the maxillary sinus roots into the sinus, the lack of cortical bone
lining after extraction will allow the sinus to expand. Studies have
also shown that pneumatization is greater after molar extraction
in comparison with premolar extractions, mainly because of the
greater resultant defect.
41
Sharan and Madjar
39
in pneumatization
studies showed that a preextraction curving sinus oor resulted in
greater expansion. In addition, when two or more adjacent poste-
rior teeth were extracted or when a second molar was extracted (in
comparison with the rst molar), greater expansion was reported
(Fig. 23.3).
Resultant Increased Crown Height Space
As the vertical bone loss increases, the crown height space increases.
is most likely will result in implant placement inferior to the
adjacent interproximal bone (if present) and inferior to the ideal
apical-coronal position (i.e., 2–3 mm below the free gingival mar-
gin). e inferior positioning results in an increased crown height
space, thereby increasing morbidity to the long-term prognosis of
the implant prosthesis. Sevimay etal.,
42
in a three-dimensional
nite element analysis, showed that when increasing the crown
height from 10 to 20 mm, the strain values placed on the implant
prosthesis increased 72% for tensile stress and 41% for compres-
sive stress (Fig. 23.4). erefore, implant prostheses in this area are
at an increased risk in comparison to other areas of the oral cavity.
Lingual Oriented Ridge Position
As a result of the horizontal bone resorption process the ridge will
progressively shift toward the palate until the ridge is resorbed into
a medially positioned narrower bone volume.
29
e posterior max-
illa continues to remodel toward the midline as the bone resorption
A
B
C–w
C–h
D
Fig. . As bone resorbs in the maxilla, the ridge shifts toward the lin-
gual and encroaches on the maxillary sinus. This also will result in a change
in the relationship of the maxilla and mandible.
A
B
Fig. . Maxillary Sinus Pneumatization. (A and B) After tooth loss
the maxillary sinus expands (non-uniformly) and approaches the maxillary
sinus floor, which decreases available bone for implant placement.

555
CHAPTER 23 Treatment Planning for the Edentulous Posterior Maxilla
process continues. Because of this resorption pattern, the buccal
cusp of the nal prosthesis will usually be cantilevered facially to
satisfy the esthetic requirements at the expense of biomechanics in
the moderate-to-severe atrophic ridges (Fig. 23.5).
Anatomic Location
Because of the maxillary posterior’s anatomic location, access is
a common problem. Especially when lack of opening is present,
surgical placement of implants in the posterior is sometimes dif-
cult because of the lack of interocclusal space. Most commonly,
maximum mouth opening is measured in the anterior by using the
interincisal distance. Studies vary on the denition of a restricted
opening; however, it is usually within the 35- to 40-mm dis-
tance.
43
Because the posterior opening is far less than the anterior,
obtaining sucient space for implant placement or prosthetic
procedures is usually dicult. Insucient space also becomes
increasingly problematic when using a cone beam computed
tomography (CBCT) surgical template for implant placement. In
addition, the lack of space will increase the risk for swallowed or
aspirated objects (Fig. 23.6).
Increased Biting Force
e occlusal forces in the posterior region are greater than in the
anterior regions of the mouth. Studies have shown that the maxi-
mum bite force in the anterior region ranges from 35 to 50 lb/in
2
.
e bite force in the molar region of a dentate person ranges from
200 to 250 lb/in
2
. erefore, a 5:1 ratio exists between the max-
illa and mandible. Parafunctional forces may increase the resultant
force as much as threefold, which leads to greater implant and
prosthetic morbidity.
44-46
As a consequence the maxillary molars
of the natural teeth have 200% more surface area than the premo-
lars and are signicantly wider in diameter (Fig. 23.6).
1
Both of
these features will reduce the stress to bone, which also decreases
A
B
Fig. . Crown Height Space. (A) Measured from the top of the implant to the occlusal plane. (B) As
bone resorbs from Division A to Division D, the vertical height position becomes more apical. This results
in an increased crown height, even if vertical grafting is completed within the sinus.
Fig. . Another component of the maxillary posterior resorption pro-
cess is the shifting of the ridge to the lingual. Because of the lingual posi-
tioning, implants are often placed in a nonideal buccal-lingual position.

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55323Treatment Planning for the Edentulous Posterior MaxillaRANDOLPH R. RESNIK AND CARL E. MISCH†Historically the maxillary posterior region has been one of the most dicult regions in the oral cavity to treat. Maxil-lary posterior partial or complete edentulism is one of the more common treatment areas in implant dentistry. However, the maxillary posterior edentulous region presents many unique and challenging conditions in implant dentistry that many years ago led to an area with the highest implant failure rate. Over the years many new surgical protocols and technological advances have led to this region being as predictable as any other region in the oral cavity. Most noteworthy of these surgical methods includes sinus augmentation to increase available bone height, ridge augmentation to increase bone width, better-designed shorter implants, and modi-ed surgical approaches to insert implants in poorer bone density.1 Grafting of the maxillary sinus to overcome the problem of reduced vertical available bone has become a very popular and predictable procedure since the 1990’s. After the initial introduction by Tatum in the mid-1970s and the initial publication of Boyne and James in 1980, many studies have been published about sinus grafting with results higher than 90%.2-38 is chapter will address the various disadvantages inherent with the posterior maxilla, along with the treatment planning factors and concepts specic to the maxillary posterior partial or complete edentulous regions.Inherent Disadvantages of Posterior Maxilla TreatmentPoor Bone DensityIn general the bone quality is poorest in the edentulous posterior maxilla compared with any other intraoral region.30 A literature review of clinical studies reveal poorer bone density may result in decreased implant loading survival by an average of 16% and has been reported to be as low as 40%.31 e cause of the poorer success rate is related to several factors. Bone strength is directly related to its density, and the poor density bone of this region is often 5 to 10 times weaker in comparison with bone found in the anterior man-dible (~ D2 Bone Quality).32 Bone densities directly inuence the percent of implant–bone surface contact (bone–implant contact or BIC), which accounts for the force transmission to the bone. e bone–implant contact (∼<30%) is the lowest in D4 (Type 4) bone compared with other bone densities. e stress patterns distributed within poor bone density migrate farther toward the apex of the implant. As a result, bone loss is more pronounced and occurs also deeper along the implant body, rather than only crestally as in other denser bone conditions. D4 bone also has been shown to exhibit the greatest biomechanical elastic modulus dierence compared with titanium under load.32 is biomechanical mismatch develops a higher strain condition to the bone, which may be in the pathologic overload range. As such, modied surgical protocols are warranted to increase bone-implant contact.In the posterior maxilla the poorer decient osseous structures and the minimal cortical plate on the crest of the ridge will com-promise the initial implant stability (insertion torque) at the time of placement (Fig. 23.1). e labial cortical plate is usually thin, and the ridge is often wide. As a result the lateral cortical bone–implant contact to stabilize the implant is often insignicant because implant placement rarely engages the buccal plate. erefore initial healing of an implant in D4 bone is often compromised, and clinical reports indicate a lower initial healing success than with D2 or D3 bone. • Fig. . D4 bone density, which is usually found in the posterior maxilla. This type of bone usually exhibits minimal cortical bone and has very fine trabeculae.† Deceased 554PART V Edentulous Site Treatment PlanningDecreased Available BoneIn the posterior maxilla the implant clinician is often confronted with a decreased bone quantity, thereby compromising implant placement. e dentate maxilla is usually associated with a thinner cortical plate on the facial compared with the mandible. Because the trabecular bone of the posterior maxilla is ner than other dentate regions, the loss of maxillary posterior teeth usually results in an initial decrease in bone width at the expense of the labial bony plate. e width of the posterior maxilla will decrease at a more rapid rate than in any other region of the jaws.25 e resorp-tion phenomenon is accelerated by the loss of vascularization of the alveolar bone and the existing ne trabecular bone type. How-ever, because the initial residual ridge is so wide in the posterior maxilla, even with a signicant decrease in the width of the ridge, ideal size root form implants usually can be placed (Fig. 23.2). Increased Pneumatization of the Maxillary SinusPneumatization is a normal physiologic process that occurs in all paranasal sinuses during the growth period, which results in an increased volume. Histologic studies have shown that the pneu-matization process occurs by osteoclastic resorption of the corti-cal walls of the sinus. However, the etiology of maxillary sinus pneumatization is poorly understood and has been associated with heredity, pneumatization drive of the nasal mucous membrane, craniofacial conguration, bone density, growth hormones, and intra-sinus air pressure.39e pneumatization process has been shown to increase in size after tooth extraction. Most likely this is a result of a decrease in functional forces that are transferred to the bone after tooth loss and the remodeling process involving disuse atrophy according to Wol’s law.40 Because of the proximity and possible protrusion of the maxillary sinus roots into the sinus, the lack of cortical bone lining after extraction will allow the sinus to expand. Studies have also shown that pneumatization is greater after molar extraction in comparison with premolar extractions, mainly because of the greater resultant defect.41 Sharan and Madjar39 in pneumatization studies showed that a preextraction curving sinus oor resulted in greater expansion. In addition, when two or more adjacent poste-rior teeth were extracted or when a second molar was extracted (in comparison with the rst molar), greater expansion was reported (Fig. 23.3). Resultant Increased Crown Height SpaceAs the vertical bone loss increases, the crown height space increases. is most likely will result in implant placement inferior to the adjacent interproximal bone (if present) and inferior to the ideal apical-coronal position (i.e., 2–3 mm below the free gingival mar-gin). e inferior positioning results in an increased crown height space, thereby increasing morbidity to the long-term prognosis of the implant prosthesis. Sevimay etal.,42 in a three-dimensional nite element analysis, showed that when increasing the crown height from 10 to 20 mm, the strain values placed on the implant prosthesis increased 72% for tensile stress and 41% for compres-sive stress (Fig. 23.4). erefore, implant prostheses in this area are at an increased risk in comparison to other areas of the oral cavity. Lingual Oriented Ridge PositionAs a result of the horizontal bone resorption process the ridge will progressively shift toward the palate until the ridge is resorbed into a medially positioned narrower bone volume.29 e posterior max-illa continues to remodel toward the midline as the bone resorption ABC–wC–hD• Fig. . As bone resorbs in the maxilla, the ridge shifts toward the lin-gual and encroaches on the maxillary sinus. This also will result in a change in the relationship of the maxilla and mandible.AB• Fig. . Maxillary Sinus Pneumatization. (A and B) After tooth loss the maxillary sinus expands (non-uniformly) and approaches the maxillary sinus floor, which decreases available bone for implant placement. 555CHAPTER 23 Treatment Planning for the Edentulous Posterior Maxillaprocess continues. Because of this resorption pattern, the buccal cusp of the nal prosthesis will usually be cantilevered facially to satisfy the esthetic requirements at the expense of biomechanics in the moderate-to-severe atrophic ridges (Fig. 23.5). Anatomic LocationBecause of the maxillary posterior’s anatomic location, access is a common problem. Especially when lack of opening is present, surgical placement of implants in the posterior is sometimes dif-cult because of the lack of interocclusal space. Most commonly, maximum mouth opening is measured in the anterior by using the interincisal distance. Studies vary on the denition of a restricted opening; however, it is usually within the 35- to 40-mm dis-tance.43 Because the posterior opening is far less than the anterior, obtaining sucient space for implant placement or prosthetic procedures is usually dicult. Insucient space also becomes increasingly problematic when using a cone beam computed tomography (CBCT) surgical template for implant placement. In addition, the lack of space will increase the risk for swallowed or aspirated objects (Fig. 23.6). Increased Biting Forcee occlusal forces in the posterior region are greater than in the anterior regions of the mouth. Studies have shown that the maxi-mum bite force in the anterior region ranges from 35 to 50 lb/in2. e bite force in the molar region of a dentate person ranges from 200 to 250 lb/in2. erefore, a 5:1 ratio exists between the max-illa and mandible. Parafunctional forces may increase the resultant force as much as threefold, which leads to greater implant and prosthetic morbidity.44-46 As a consequence the maxillary molars of the natural teeth have 200% more surface area than the premo-lars and are signicantly wider in diameter (Fig. 23.6).1 Both of these features will reduce the stress to bone, which also decreases AB• Fig. . Crown Height Space. (A) Measured from the top of the implant to the occlusal plane. (B) As bone resorbs from Division A to Division D, the vertical height position becomes more apical. This results in an increased crown height, even if vertical grafting is completed within the sinus.• Fig. . Another component of the maxillary posterior resorption pro-cess is the shifting of the ridge to the lingual. Because of the lingual posi-tioning, implants are often placed in a nonideal buccal-lingual position. 556PART V Edentulous Site Treatment Planningthe strain of the bone. Following this natural selection, implant support should be greater in the posterior molar region than any other area of the mouth.1 erefore the decrease in bone quantity and quality and increased forces should be considered in the treat-ment plan of this region of the mouth (Fig. 23.7).47 Requirement of Greater Surface Area Diameter Implants and Minimized Occlusal ForcesWhen treatment planning in the posterior maxilla to combat biomechanical forces, ideally conditions should be simulated as those found with natural teeth. Because stresses occur primarily at the crestal region, biomechanical designs of implants to minimize their noxious eects should be implemented.47 Implant diameter is an eective method to increase surface area at the crestal region and combat the forces.47,48 Ideally Division B implants are not used in the posterior maxilla. A 12-year retrospective study of 653 sinus grafts performed by Misch revealed 14 implant failures.49 Eight implant failures were caused by implant fracture at the neck of smaller- diameter implants. erefore implants of at least 5 mm in diameter are suggested, or multiple splinted 4-mm implants in the molar area.Over the years the concept of implant length has become less important to long-term implant success. Because the majority of force is transmitted only to the middle-crestal area of the implant, less emphasis is now placed on the need for longer implants. In general the better the bone quality, the less critical the implant length. However, with poorer bone quality, or extensive graft areas, greater length increases the surface area, allowing for better initial xation or primary stability.In certain cases, increasing implant number is an excellent method to decrease associated stresses. Normally one implant is indicated for each missing tooth. However, if narrower implants are indicated, then more implants should be placed and splinted ABC• Fig. . (A) It is often difficult to have adequate space for implant placement, especially in the posterior maxilla. With the popularity of guided surgery, it becomes even more difficult because greater space is required for implant placement. (B) Standard surgical drill, (C) Guided drill kits contain drills that are usually longer (∼10 mm) than regular-size drills.• Fig. . Increased biting force may lead to accelerated crestal bone loss, along with mechanical stress complications such as fractured pros-theses, screw loosening, and fractured implants. 557CHAPTER 23 Treatment Planning for the Edentulous Posterior Maxillatogether to reduce stresses to the bone. If excessive force factors are present, two implants for each molar are then recommended.And lastly, posterior cantilevers on implant prostheses should be minimized. Narrow occlusal tables with centered implant con-tact points prevent shear type of forces, which are detrimental to the implant interface (Fig. 23.8). Maxillary Sinus Has High Incidence of Pathologye maxillary sinus has the highest incidence of pathology in comparison with any of the other paranasal sinuses. Most stud-ies report 30% to 40% of asymptomatic patients have some type of pathology present in their sinuses (i.e., inammation, cysts, mucoceles, rhinosinusitis, fungal infections, carcinomas, antro-liths). erefore because many posterior maxillas require grafting, the presence of pathology results in complications and delayed treatment (Fig. 23.9).51,52 Treatment HistoryTreatment of the Posterior Maxilla—Literature ReviewOver the years several strategies have been advocated to restore the posterior maxilla and address the deciency of bone volume and poor bone quality. e various approaches can be categorized as follows:• Avoidthemaxillarysinusandplaceimplantsanteriorly,poste-riorly, or medially.52-54• Placeimplantsandperforatethesinusoor.55,56• Performsinusaugmentationprocedureswithsimultaneousordelayed implant placement.2-6,13,57-62• Elevatesinusoorduringimplantplacement.2,3,5,57-66• Usealternativetypesofimplants.• Usesubperiostealimplants.67,68• Perform horizontal osteotomy, interpositional bone grafting,and endosteal implants.69,70In the early days of oral implantology, implants were inserted in the posterior maxilla without modifying the maxillary sinus topography. Shorter-length implants were often placed below the antrum. e decreased surface area, compounded by poor bone quality, resulted in poor implant stability and increased failure rates. Attempts to place larger endosteal implants posterior to the antrum and into the tuberosity and pterygoid plates also resulted in compromised situations. Although feasible from a surgical standpoint, rarely are third- or fourth-molar abutments indicated for proper prosthodontic support. is approach often requires a greater pontic space (i.e., three or more pontics between the ante-rior and posterior implants). e resultant prosthesis span will result in excessive exibility of the prosthesis, unretained restora-tions, excess stresses, and implant failure.In the late 1960s Linkow reported that the blade-vent implant could be blunted and the maxillary sinus membrane slightly ele-vated to allow implant placement “into” the sinus in the posterior maxilla.71 is technique required the presence of at least 7 mm of vertical bone height below the antrum.Root Surface Areas of Maxillary Teeth450400350300250200150100500205(1.1)179(1.0)273(1.5)234(1.3)433(2.4)220(1.2)431(2.4)• Fig. . Root surface areas are significantly greater in the posterior versus the anterior.AB• Fig. . The maxillary sinus has a high incidence of pathology, which can range from (A) cystic lesions and (B) completely opacified sinus cavities. 558PART V Edentulous Site Treatment PlanningGeiger and Pesch55 reported that ceramic implants placed through the maxillary sinus oor could heal and stabilize with-out complication. Brånemark etal.56 have shown that implants may be placed into the maxillary sinus without consequence if integration occurs between the implants and the bone below the sinus. Yet they also report a higher failure rate (70% success rate for 5–10 years) for this technique. Ashkinazy54 and others have reported on using tomographic radiographs to determine whether adequate bone exists on the palatal aspect of the maxillary sinus for blade implants. However, Stoler72 stated that after 25 consecu-tive computed tomographic scans of maxillae, adequate bone for implant support was not found on the medial aspect of the sinus. us it seems that if sucient bone is present medial to the sinus, it is the rare exception.In the early 1970s Tatum2,3,58,63 began to augment the poste-rior maxilla with onlay autogenous rib bone to produce adequate vertical bone for implant support. He found that onlay grafts below the existing alveolar crest would decrease the posterior intradental height signicantly, yet very little bone for endosteal implants would be gained. erefore in 1974 Tatum developed a modied Caldwell-Luc procedure for elevation of the sinus mem-brane and subantral (SA) augmentation.2,3 e Caldwell-Luc pro-cedure was established by the American George Caldwell and the Frenchman Henry Luc, who in 1893 described a new technique and procedure to access the maxillary sinus using a lateral win-dow.73 e crestal ridge of the maxilla was infractured and used to elevate the maxillary sinus membrane. Autogenous bone was then added in the area previously occupied by the inferior third of the sinus. Endosteal implants were inserted in the grafted bone after approximately 6 months. Implants were then loaded with a nal prosthesis after an additional 6 months.2,3In 1975 Tatum developed a lateral approach surgical technique that allowed the elevation of the sinus membrane and implant placement in the same surgical appointment. e implant system used was a one-piece ceramic implant, and a permucosal post was required during the healing period. Early ceramic implants were not designed adequately for this procedure, and results with the tech-nique were unpredictable. In 1981 Tatum58 developed a submerged titanium implant for use in the posterior maxilla.3 e advantages of submerged healing, the use of titanium instead of aluminum oxide as a biomaterial, improved biomechanics, and improved sur-gical technique made this implant modality more predictable.From 1974 to 1979 the primary graft material for the sinus graft procedure was autologous bone. In 1980 the application of the SA augmentation technique with a lateral maxillary approach was fur-ther expanded by Tatum with the use of synthetic bone. at same year, Boyne and James4 reported on the use of autogenous bone for SA grafts. Most of the data published in the 1980s were anecdotal or based on very small sample sizes. In 1987 Misch5 organized a treatment approach to the posterior maxilla based on the amount of bone below the antrum, and in 1989 he expanded the treatment approach to include the available bone width related to the surgical approach and implant design (Fig. 23.10).61,62 Since then, minor modications regarding the graft materials or surgical approach have been proposed.In the 1990s the profession developed a much greater interest in the sinus graft technique.13 Several reports ourished in the litera-ture, reporting on minor changes in the technique, dierent materials used in the graft, dierent origins for the autogenous portion of the graft, histomorphometric data relative to the graft healing, and other retrospective studies relative to the survival rates of implants placed in grafted sinuses with a simultaneous or delayed approach.60-62,74-87Long-term results have been reported by Tatum et al.60 to be greater than 95% in more than 1500 SA augmentations per-formed. e sinus graft procedure has been the most predictable method to grow bone height from 5 to 20 mm compared with any other intraoral bone-grafting technique, with a graft success rate and an implant survival rate greater than 95%.An alternative technique, which was a less invasive tech-nique using osteotomes, was introduced in 1994 by Summers.88 And more recently, newer techniques include the use of shorter implants, placement of implants to avoid the sinus, elongated zygomatic implants, and pterygoid plate implants. Sinus Graft Options for the Posterior MaxillaA classication based on the amount of available bone height between the oor of the antrum and the crest of the residual ridge in the region of the ideal implant locations was presented by Misch5 in 1987 and later modied by Resnik in 2017 (Table 23.1). is protocol detailed a surgical approach, bone graft mate-rial, and timetable for healing before prosthetic reconstruction. In 1988 Cawood and Howell also classied the edentulous pos-terior maxilla, which included the loss of bone and pneumatiza-tion of the maxillary sinus.89 In 1995 Misch modied his 1987 classication to include the lateral dimension of the sinus cavity, and this dimension was used to modify the healing period proto-col, because smaller-width sinuses (0–10 mm) tend to form bone faster than larger-width (>15 mm) sinuses. Other classications of the sinus graft procedure have been proposed by Jensen90 in 1998 and Chiapasco80,91 in 2003. In 2017 Resnik further modied the Misch classication to include dierent augmentation techniques and the use of short implants with regard to existing force factors.Subantral classificationSA1 SA2SA3 SA4• Fig. . In 1987 Misch presented four subantral treatment options based on the amount of bone below the maxillary sinus. Subantral aug-mentation category 1 (SA-1) sinus used traditional implant approaches. SA-2 used a sinus lift procedure within the osteotomy. For SA-3 and SA-4 a Tatum sinus graft procedure is performed before implant insertion. 559CHAPTER 23 Treatment Planning for the Edentulous Posterior MaxillaMisch-Resnik Maxillary Posterior Classificationere exist four treatment classications based on the amount of bone available below the maxillary sinus (i.e., SA-1, SA-2, SA-3, and SA-4). Because implants in the posterior maxilla are susceptible to biomechanical stress, each category has been fur-ther divided into two divisions: favorable and unfavorable force factors.Favorable Conditions• Goodqualityofbone(D2/D3bone)withthepresenceofcor-tical bone• Minimalocclusalforcefactors• Noparafunction• Idealcrown/implantratioUnfavorable Conditions• Parafunction,highforcefactors• Poorqualityofbone(D3/D4bone)withnocorticalbone• Increasedocclusalforcefactors• Parafunctionalforcespresent• Poorcrown/implantratioSubantral Option 1: Conventional Implant Placemente rst SA treatment option, SA-1, is applied when there exists sucient available bone height to permit the placement of end-osteal implants without entry into the sinus proper. e mini-mum “ideal” bone height is related to force factors and the bone density. For posterior maxillae with favorable force factors, a small-length implant (~ 8 mm) may be used as long as there exists sucient bone for a minimum width to accommodate a 5-mm-diameter implant. For unfavorable force factors a minimum of 10 mm of height is required.Patients with narrower bone volume (Division B) may be treated with osteoplasty or augmentation to increase the width of bone. e insertion of smaller surface area implants is not sug-gested because the forces are greater in the posterior regions of the mouth, and the bone density is less than in most regions. In addition, the narrow ridge is often more medial than the central fossa of the mandibular teeth and will result in an oset load on the restoration, which will increase the strain to the bone. Osteo-plasty in the SA-1 posterior maxilla may change the SA category if the height of the remaining bone is less than 8/10 mm after the bone modication is completed. Augmentation for width may be accomplished with membrane grafting, bone spreading, and autogenous onlay or appositional grafts. Larger-diameter implants are often required in the molar region, and bone spreading to place wider implants is the most common approach when the bone density is poor. If less than 2.5 mm of width is available in the posterior edentulous region (Division C−w), the most predict-able treatment option is to increase width with onlay autogenous bone grafts.92 After graft maturation the area is then reevaluated to determine the proper treatment plan classication. However, Division C−w posterior maxillas are unpredictable and require an increased skill set.Although a common axiom in implant dentistry is to remain 2 mm or more from an opposing landmark, this is not indicated in the SA region (i.e., inferior oor of the sinus). As long as pathol-ogy is not present in the maxillary sinus, there exist no contrain-dications for placement of implants at the level of or engaging the cortical plate of the sinus oor. Healing of implants in the SA-1 category is allowed to continue uneventfully for a minimum of 4 to 6 months, depending on the bone density.Usuallyprogres-sive loading is recommended during the prosthetic phases of the treatment when D3 or D4 bone is present (Figs. 23.11 and 23.12; Box 23.1).  Healing Times for Treatment CategoriesProcedureHeight (mm): Favorable/Unfavorable Conditions ProcedureHealing Time (Months): GraftHealing Time (Months): ImplantSA-1 ≥ 8 / ≥ 10 Division A root form placement No Graft 4–6 (no bone grafting)SA-2 ≥ 6 / ≥ 8 Sinus “bump”; simultaneous Division A root form placement No Graft 6–8 (no bone grafting)SA-3 ≥ 5 / ≥ 8 Sinus graft (transcrestal or lateral wall + implant placement) 6–8 6–8aSA-4 < 5 / < 5 Lateral wall approach sinus graft; delayed Division A root form placement 6–8 6–10aaEvaluate at implant insertion.SA, Subantral augmentation option. TABLE 23.1• Fig. . Subantral option 1 (SA-1) technique that includes implant placement that does not enter the sinus proper. 560PART V Edentulous Site Treatment PlanningSubantral Option 2: Sinus Lift and Simultaneous Implant Placemente second SA option, SA-2, is selected when there is a minimum of 6/8 mm of vertical bone present (Fig. 23.11). In the SA-2 tech-nique the sinus oor is elevated via the implant osteotomy 1 to 2 mm (Figs. 23.12 and 23.13). is technique was originally devel-oped by Tatum2,3 in 1970 and published by Misch5 in 1987 and many years later by Summers93 in 1994. e endosteal implant osteotomy is prepared as determined by the density of bone pro-tocol. e depth of the osteotomy is approximately 1 to 2 mm short of the oor of the antrum. A cupped-shape osteotome of the same diameter (or slightly smaller) as the nal osteotomy is selected.94 It is of a dierent end shape than osteotomes used for bone spreading.93 e osteotome is inserted and tapped rmly in 0.5- to 1-mm increments beyond the osteotomy until its nal position up to 2 mm beyond the prepared implant osteotomy. is surgical approach causes a greenstick-type fracture in the antral oor and slowly elevates the unprepared bone and sinus membrane over the broad-based osteotome. e implant may be inserted into the osteotomy after the sinus membrane elevation and extend up to 2 mm above the oor of the sinus. e implant is slowly threaded into position so that the membrane is less likely to tear as it is elevated. e apical portion of the implant engages the denser bone on the cortical oor, with bone over the apex, and an intact sinus membrane. e implant may ideally extend up to 2 mm beyond the sinus oor, and the 1- to 2-mm bony covering over the apex may result in as much as a 3-mm elevation of the sinus mucosa (Fig. 23.14).Because of the autologous bone present above the apical portion of the implant, along with the osteoprogenitor cell–rich sinus mem-brane, new bone formation is accelerated. e success of the intact sinus membrane elevation cannot be conrmed before or at the time of implant placement. Attempts to feel the elevation of the membrane from within an 8-mm-deep implant osteotomy that is approximately 3 mm in diameter may easily cause separation of the sinus lining.e patient’s prosthodontic treatment may proceed similar to that in the SA-1 category. If inadequate bone is formed around the apical portion of an implant after initial healing, the progressive loading protocol for D4 bone is suggested.Some authors have reported the attempted SA-2 sinus lift procedure to gain more than 3 mm of implant vertical height. SA-1aSA-1bSA-1: Implant Placement – does not penetrate sinusUnfavorable Conditions :• D4 bone• High force factors• Increased C-I Ratio• Implant Height: Host Bone ≥ 8 mm• Implant Length:  8 mm• Implant Height: Host Bone ≥ 10 mm• Implant Length:  10 mmFavorable Conditions :• D2/D3 bone• Minimal occlusal force factors• Favorable C-I Ratio• Fig. . Subantral option 1 (SA-1) protocol decision tree related to favorable versus unfavorable fac-tors. C-I, Crown/implant.IndicationsFavorable conditions: >8 mm host bone (implant ≥8 mm in length)Unfavorable conditions: >10 mm host bone (implant ≥10 mm in length)*See Surgical Protocol (Chapter 37) • BOX 23.1 SA-1: Implant Placement—Does Not Penetrate Sinus• Fig. . Subantral option 2 (SA-2) technique with implant placement that includes a small bump into the sinus (∼1 mm). 561CHAPTER 23 Treatment Planning for the Edentulous Posterior MaxillaBlind surgical techniques such as the SA-2 technique increase the risk for sinus membrane perforation. When the sinus mucosa is perforated, the risk for postoperative infection increases. Mem-brane perforation is the primary reason why the SA-2 technique is restricted to elevating the membrane only 1 to 2 mm. In addi-tion, the presence of a septum in the area of elevation increases the possibility of a perforation. If a sinus infection occurs, a bac-terial smear layer may accumulate on the implant apex, which may precipitate mucociliary clearance issues and possible sinus infections.Worth and Stoneman95 have reported a comparable phenom-enon of bone growth under an elevated sinus membrane, called halo formation. ey observed the natural elevation of the sinus membrane around teeth with periapical disease. e elevation of the membrane resulted in new bone formation once the tooth infection was eliminated (Figs. 23.13 and 23.14; Box 23.2). Subantral Option 3: Sinus Graft with Immediate Endosteal Implant Placemente third approach to the maxillary posterior edentulous region, SA-3, is indicated when at least 5 mm of vertical bone height and sucient width are present between the antral oor and the crest of the residual ridge in the area of the required prosthodontic abutment (Fig. 23.15). e 5-mm minimum is necessary because this is the amount of bone needed to achieve rigid xation for implant placement.ere exist two dierent options for the grafting of the sinus area in the SA-3 protocol. In the rst technique the bone graft is performed transcrestally. e osteotomy is performed, and the oor is fractured similar to the SA-2 technique. Before the implant placement, the layering technique is used consisting of a collagen membrane (rst layer) and allograft (second layer). Autogenous bone may be placed in SA-3 cases when poor bone quality is present.e second technique is the Tatum lateral maxillary wall approach. With this procedure an osteotomy of the lateral maxil-lary wall is performed to allow for bone graft placement before dental implant insertion. is results in a lateral access window, which exposes the sinus membrane and allows for the lateral win-dow to be rotated in and upward in a superior position. As long as there is sucient width, the implant may be placed at the same time after the grafting is complete. e graft material selected is usually allograft, unless there is easy access to autogenous bone. Autogenous bone is of less importance because of the existing host bone (minimum 5 mm of height) (Boxes 23.1 and 23.2). When the original ridge width is Division B or C−w, membrane grafting or onlay graft in conjunction with the sinus augmentation is a possible treatment option, and usually the case is classied as SA-4 because implant placement will be delayed.e 5-mm minimum of initial bone height in an SA-3 poste-rior maxilla may have cortical bone on the residual crest, and cor-tical-like bone on the original antral oor may stabilize an implant that is inserted at the time of the graft and permit its primary stability. erefore an endosteal implant may be inserted at this appointment and has been advocated for many years by Misch5 and others (Figs. 23.15 and 23.16; Box 23.3).12,15,59 Subantral Option 4: Sinus Graft Healing and Extended Delay of Implant InsertionIn the fourth option for implant treatment of the posterior max-illa, SA-4, the maxillary sinus region for future endosteal implant insertion is rst augmented. is option is indicated when less than 5 mm remains between the residual crest of bone and the oor of the maxillary sinus. ere is inadequate vertical bone in SA-2aSA-2bSA-2: Implant Placement + Elevation (1 –2 mm)Unfavorable Conditions:• D4 bone• High force factors• Increased C-I Ratio• Implant Height: Host Bone ≥ 6 mm• Implant Length:Bone Height + 1 – 2 mm• Implant Height: Host Bone ≥ 8 mm• Implant Length: Bone Height + 1 – 2 mmFavorable Conditions:• D2/D3 bone• Minimal occlusal force factors• Favorable C-I Ratio• Fig. . Subantral option 2 (SA-2) protocol decision tree related to favorable versus unfavorable factors.IndicationsFavorable conditions: > 6 mm host bone (Implant length= Bone height + 1-2)Unfavorable conditions: > 8 mm host bone (Implant length= Bone height + 1-2)*See Surgical Protocol (Chapter 37) • BOX 23.2 SA-2: Implant Placement: Membrane Bump 1-2mm No Graft (Osteotome Technique) 562PART V Edentulous Site Treatment Planningthese conditions to predictably place an implant at the same time as the sinus graft and less recipient bone to act as a vascular bed for the graft and for primary stability (Fig. 23.17). e SA-4 protocol corresponds to a larger antrum and minimal host bone on the lateral, anterior, and distal regions of the graft, because the antrum generally has expanded more aggressively into these regions.Unfortunately, inSA-4posterior maxillasthere is lessautolo-gous bone to harvest in the tuberosity, which further delays the bone regeneration in the site. In addition, there are usually fewer septa or webs in the sinus, which decreases complications, and it typically exhibits longer mediodistal and lateromedial dimensions. erefore the fewer bony walls, less favorable vascular bed, minimal local autologous bone, and larger graft volume all mandate a longer healing period and slightly altered surgical approach.e Tatum lateral wall approach for sinus graft is performed as in the previous SA-3 procedure (lateral wall). Most SA-4 regions pro-vide better surgical access than the SA-3 counterparts because the antrum oor is closer to the crest compared with the SA-3 maxilla. e medial wall of the sinus membrane is elevated to the level of the height of the lateral window so that adequate height is available for future endosteal implant placement.e combination of graft materials used and their placement are similar to those for the SA-3 technique. However, less autog-enous bone is often harvested from the tuberosity, so in some cases an additional harvest site may be required, most often from the mandible (i.e., from the ascending ramus). Because of the compromised host bone present, more autogenous bone is required.ABSA-3aSA-3bSA-3: Sinus Augmentation + Implant PlacementUnfavorable Conditions:• D4 bone• High force factors• Increased C-I Ratio• Implant Height: Host Bone ≥ 5 mm• Implant length: Bone Height + 3 – 4 mm (Crestal) Bone Height + ≥ 4 mm (Lateral)•:• Implant Height: Host bone ≥ 8 mmImplant LengthBone Height + 3 – 4 mm (Crestal)Bone Height + ≥ 4 mm (Lateral)Favorable Conditions:• D2/D3 bone• Minimal occlusal force factors• Favorable C-I RatioC• Fig. . Subantral Option 3 (SA-3) Technique. (A) Implant placement with bone graft (crestal). (B) Implant placement with bone graft (lateral wall). (C) Decision tree related to favorable versus unfavorable factors and crestal versus lateral wall technique. 563CHAPTER 23 Treatment Planning for the Edentulous Posterior Maxillae augmented region is left to mature for 6 to 10 months before reentry for placement of endosteal implants. e amount of initial healing is related to the antral size (including small, medium, or large lateral-medial size) and the amount of autolo-gous bone used in the inferior third of the antrum. Typically the width of crestal bone is wide enough in SA-4 regions for the place-ment of root form implants after the graft matures.e implant placement surgery at reentry for the SA-4 tech-nique is similar to SA-1 with one exception. e previous access window may appear completely healed with bone; soft and lled with loose graft material, or with cone-shaped brous tissue ingrowth (with the base of the cone toward the lateral wall); or in any variation states. If the graft site appears clinically as bone, the implant osteotomy and placement follow the surgical approach designatedbythebonedensity.UsuallywiththeSA-4technique,implant placement is completed under a stage II process.e time interval for stage II uncovery and prosthetic proce-dures after implant insertion is dependent on the density of bone at the reentry implant placement. e crest of the ridge and the original antral oor may be the only cortical bone in the region for implant xation. e most common bone density observed is D4, and often it is softer than the region in general. Progressive load-ing after uncovery is most important when the bone is particularly soft and less dense.e width of the host site for sinus grafts is most often Division A; however, when Division C−w to B exists, guided bone regen-eration or an onlay graft for width is indicated. When the graft cannot be secured to the host bone, it is often ideal to perform the sinus graft 6 to 9 months before the bone graft for width. After graft maturation the implants may be inserted.ere are many advantages of the SA-4 technique over the SA-3 technique: 1. e healing of the graft may be assessed before the implant placement surgery via a CBCT scan. Because of the advances in CBCT technology, radiation exposure is not a signicant disadvantage. In addition, the bone quality may be evaluated during the implant osteotomy before implant insertion. e healing time for the implant is no longer arbitrary but more patient specic. 2. Postoperative sinus graft infection occurs in approximately 3% to 5% of patients, which is much higher than the percent-age for implant placement surgery. If the sinus graft becomes infected with an implant in place, a bacterial smear layer may develop on the implant and make future bone contact with the implant less predictable. e infection is also more dicult to treat when the implants are in place, and may result in greater resorption of the graft as a consequence. If the infection cannot be adequately treated, the graft and implant must be removed. erefore there is also a decreased risk for losing the graft and implant if a postoperative infection occurs with a delayed implant insertion. Reports in the literature indeed indicate a higher failure rate of implants when inserted simultaneously compared with a delayed approach.60,80,91,92 3. Blood vessels are required to form and remodel bone. A tita-nium implant in the center of the sinus graft does not provide a source of blood vessels; therefore obtaining a vascular sup-ply is more dicult and usually requires an incraesed healing time. 4. Bone width augmentation may be indicated in conjunction with sinus grafts to restore proper maxillomandibular ridge relationships or increase the implant diameter in the molar region. Augmentation may be performed simultaneously with the sinus graft. As a result, larger-diameter implants may be placed with the SA-4 technique. 5. e bone in the sinus graft will be much denser after ideal heal-ing with the SA-4 approach. As such, implant angulation and position may be improved because it is not dictated by existing anatomic limitations at the time of the sinus graft.e primary disadvantage of the SA-4 approach is the delayed implant placement, thereby requiring an additional surgery (Figs. 23.17 and 23.18; Box 23.4). SA-3: Implant Placement + Sinus GraftCRESTALGraft Material Added* 3 - 4 mm maximumelevationLATERAL WALLGraft Material Added> 4 - 15 mm elevation• Fig. . Subantral option 3 (SA-3) technique that includes crestal ver-sus lateral wall techniques.IndicationsFavorable conditions: > 5 mm host bone (Implant length = Bone height + 3-4 mm (crestal), > 4-15 mm (lateral)Unfavorable conditions: > 8 mm host bone (Implant length= Bone height+ 3-4 mm (crestal), > 4-15 mm (lateral)*See Surgical Protocol (Chapter 37) • BOX 23.3 SA-3: Subantral Option 3 Requirements Graft + Implant Placement: Sinus Grafted with Implant Placement (Lateral Wall or Osteotome)SA-4 : Sinus AugmentationFavorableorUnfavorable Condition• < 5 mm of host bone• Unfavorable SA-3 Conditions (i.e. ridge augmentation needed)• Existing sinus pathologyDelayed ImplantPlacement• Fig. . Subantral Option 4 (SA-4) Bone-Grafting Indications. 564PART V Edentulous Site Treatment PlanningSummaryIn the past the posterior maxilla has been reported as the least predictable area for implant survival. Causes cited include inad-equate bone quantity, poor bone density, dicult access, and high occlusal forces. Previous implant modalities attempted to avoid this region, with approaches such as excessive cantilevers when posterior implants are not inserted or an increased number of pontics when implants are placed posterior to the antrum.e maxillary sinus may be elevated and SA bone regener-ated to improve implant height. Tatum began to develop these techniques as early as the mid-1970s. Misch developed four options for treatment of the posterior maxilla in 1987 based on the height of bone between the oor of the antrum and the crest of the residual bone. ese options were further modied by Resnik to include specic bony dimensions dependent on favorable ver-sus unfavorable conditions as well as the transcrestal augmenta-tion technique and short length implants. Although management of the posterior maxilla presents many challenges for the implant practitioner, progress on a number of fronts has made it increas-ingly possible to create successful bone-supported prostheses in this region by adhering to the classications described earlier in this chapter (Box 23.5).References 1. Misch CE. Treatment planning for edentulous maxillary posterior region. In: Misch CE, ed. Contemporary Implant Dentistry. St Louis: Mosby; 1993. 2. Tatum OH. Maxillary Subantral Grafting. Lecture presented at Ala-bama Implant Study Group. 1977. 3. Tatum OH. Maxillary and sinus implant reconstruction. Dent Clin North Am. 1986;30:207–229. 4. Boyne PJ, James RA. Grafting of the maxillary sinus oor with autogenous marrow and bone. J Oral Surg. 1980;38:613–616. 5. Misch CE. Maxillary sinus augmentation for endosteal implants: organized alternative treatment plans. Int J Oral Implant. 1987;4: 49–58. 6. Smiler DG, Holmes RE. Sinus lift procedure using porous hydroxyl-apatite: a preliminary clinical report. J Oral Implantol. 1987;13:2–14. 7. Chanavaz M. Maxillary sinus: anatomy, physiology, surgery and bone grafting relating to implantology—eleven years of clinical experience. J Oral Implantol. 1990;16:199–209. 8. Tidwell JK, Blijdorp PA, Stoelinga PJW, etal. Composite grafting of the maxillary sinus for placement of endosteal implants. Int J Oral Maxillofac Surg. 1992;21:204–209. 9. Smiler DG, Johnson PW, Lozada JL, et al. Sinus lift grafts and endosseous implants: treatment of the atrophic posterior maxilla. Dental Clin North Am. 1992;36:151–186. 10. Jensen J, Sindet-Petersen S, Oliver AJ. Varying treatment strategies for reconstruction of maxillary atrophy with implants: results in 98 patients. J Oral Maxillofac Surg. 1994;52:210–216.AB• Fig. . Subantral Option 4 (SA-4) Protocol. (A) Lateral wall sinus grafting (Phase 1). (B) Delayed implant placement after sufficient healing (Phase 2).IndicationsFavorable or unfavorable conditions: <5 mm host bone*See Surgical Protocol (Chapter 37) • BOX 23.4 Subantral Option 4 Requirements Graft: Sinus Grafted (Lateral Wall) with Delayed Implant Placement<5 mm SA-4 Lateral wall5 mm SA-3 or SA-46 mm SA-2, SA-3, or SA-47 mm SA-2, SA-3, or SA-48 mm SA-1, SA-2, or SA-39 mm SA-1, SA-210 mm SA-1 or SA-2>10 mm SA-1 SA, Subantral option. • BOX 23.5 Summary of Treatment Protocol with Respect to Available Bone 565CHAPTER 23 Treatment Planning for the Edentulous Posterior Maxilla 11. Chiapasco M, Ronchi P. Sinus lift and endosseous implants: pre-liminary surgical and prosthetic results. Eur J Prosthodont Rest Dent. 1994;3:15–21. 12. Blomqvist JE, Alberius P, Isaksson S. Retrospective analysis of one-stage maxillary sinus augmentation with endosseous implants. Int J Oral Maxillofac Implants. 1996;11:512–521. 13. Jensen OT, Shulman LB, Block MS, et al. Report of the sinus consensus conference of 1996. Int J Oral Maxillofac Implants. 1998;13(suppl):11–45. 14. Valentini P, Abensur DJ. Maxillary sinus grafting with anorganic bovine bone: a clinical report of long-term results. Int J Oral Maxil-lofac Impl. 2003;18:556–560. 15. Lozada JL, Emanuelli S, James RA, etal. Root form implants in subantral grafted sites. J Cal Dent Assoc. 1993;21:31–35. 16. Wallace SS, Froum SJ. Eect of maxillary sinus augmentation on the survival of endosseous dental implants. A systematic review. Ann Periodontol. 2003;8:328–343. 17. Del Fabbro M, Testori T, Francetti L, etal. Systematic review of survival rates for implants placed in grafted maxillary sinus. Int J Periodont Restorative Dent. 2004;24:565–577. 18. Peleg M, Garg AK, Mazor Z. Predictability of simultaneous implant placement in the severely atrophic posterior maxilla: a 9-year longi-tudinal experience study of 2132 implants placed into 731 human sinus grafts. 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