lateral antrostomy for max sinus augmentation

7/23/2019 Lateral Antrostomy for Max Sinus Augmentation

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I C.E. article_ lateral antrostomy technique

implants1_2013

Lateral antrostomy

technique for

maxillary sinus

augmentationAuthors_Hussam Batal, DDS, DMD, and Olena Norris, DDS

_Implant dentistry has become an integral

treatment modality in dentistry and is to be con-

sidered a viable option in the restoration of par-tially edentulous maxillary arches. However, whenpresented with a deficient maxillary alveolar ridge,placement and/or longevity could be jeopardizedwithout proper treatment. Maxillary sinus aug-mentation has shown to be a successful treatmentoption for restoration of anatomic deficiency in theposterior maxilla; this article will review the lateralantrostomy technique.

_History

Lateral antrostomy technique was first describedby Tatum in 1976, first published by Boyne and Jamesin 1980, and is commonly referred to as lateral an-trostomy approach to the maxillary sinus floor. Cur-rently, this method has become a common surgicaltechnique, as it allows regeneration of bone in theposterior maxilla.

The primary procedural approach involves surgi-cal access through the lateral wall of the zygomaticbuttress of the maxilla followed by elevation of thesinus membrane and placement of bone-graftingmaterial.

An alternative approach, advocated by Summers,is the crestal or “osteotome” technique. This proce-dure is less invasive, with reduced healing and overall

treatment time; however, it is site specific and allowsfor only limited augmentation.

_Anatomy

The maxillary sinus is a pyramidal-shaped cav-ity with four walls with the base facing the lateralnasal wall, the apex extending to the zygomaticbuttress and the anterior extending to canine andpremolar area. The average dimension of an adultsinus is 2.5-3.5 cm in width, 3.6-4.5 cm in height and3.8-4.5 cm in depth; with an approximate volumeof 12-15 cubic cm. Blood supply to the maxillarysinus is derived from the posterior superior alveolar,

infraorbital, greater palatine arteries and terminalbranches of the internal maxillary artery. The extentof pneumatization varies from person to person andincreases with age.

The maxillary sinus is lined with the sinus mem-brane, also known as Schneiderian membrane,which, like the rest of the respiratory tract, consists ofthin pseudo stratified ciliated columnar epithelium.The membrane is continuous with the nasal epithe-lium through the osteum of the middle meatus witha thickness of approximately 0.8 mm. Antral mucosais thinner and less vascular than the respiratory mu-

cosa. Nerve supply to the sinus is derived from thesuperior alveolar branch of the maxillary (V2) divisionof the trigeminal nerve.

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C.E. article_ lateral antrostomy technique I

Proper function of the maxillary sinus dependson the balance of mucous production, transport viaciliated epithelium and adequate drainage throughthe ostium. There are local conditions that affectsinus function; they might be reversible or irrevers-

ible. Irreversible conditions include malignant orbenign tumors of the naso-maxillary region; theseare contraindications for sinus augmentation. Re-versible conditions can be treated prior to sinusaugmentation, one example being the narrowingof the osteomeatal complex that could compromisesinus drainage.

Additional reversible conditions include sinusdisease, such as polyps or mucous retention cysts.Bacterial sinusitis with air fluid level should alwaysbe treated prior to sinus augmentation. The major-ity of these conditions are treated with medical or

endoscopic sinus surgical procedures. Cone-beamcomputerized tomography (CBCT) scan prior tosinus augmentation is strongly recommended butnot considered mandatory. A CT scan yields infor-mation regarding pathology in the sinus or chronicsinusitis and is used for precise location of the lateralapproach to the maxillary sinus cavity. A commonfinding on CT scan, especially in smokers, is mucosalthickening; this condition is not considered con-traindication to sinus augmentation.

_Patient evaluation

Patients referred for posterior maxilla implantplacement with concomitant sinus surgery should

be assessed for possible general risk factors suchas allergic rhinitis, history of chronic or recurrentsinusitis (multiple infections lasting more thanfour weeks or four episodes of acute sinusitis in theprevious 12 months). Chronic use of nasal steroids

or vasoconstrictors, chronic nasal obstruction orrhinorrhea, chronic hyposmia or hypogeusia are alsoto be assessed.

Previous treatment of head and neck neoplasms,radiotherapy to head and neck region and otherco-morbidities, including immune-deficiencies, ac-tive bone disease (fibrous dysplasia, Paget’s disease,osteomyelitis), cystic fibrosis, asthma and chronicpulmonary disease should all be included in overallassessment. CT scans can aid in determination ofsinus anatomy and pathology. A thorough intraoralexam should be performed to evaluate general den-

tal pathology, inter-ridge space and alveolar ridgecontour/width.

_Technique

Lateral antrostomy technique is performed supe-rior to the residual alveolar bone. Treatment initiateswith the administration of a single preoperativedose of systemic antibiotic (Amoxicillin, clindamycinor levaquin) and Chlorhexidine 0.12 percent rinse.Local anesthesia is achieved by maxillary vestibularinfiltration and middle/posterior superior alveolarnerve block (V2). Ideally, a mid-crestal or a slightlypalatal incision performed, leaving at least 3 mm ofattached tissue on the facial aspect of the incision,

Figs. 1_Incision design for lateral

antrostomy technique.

Fig. 2_Transillumination technique

aids in establishing maxillary sinus

outline.

Fig. 3_ ‘Trap door’ approach to create

lateral window.

Fig. 1 Fig. 3

Fig. 2



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with anterior and posterior vertical release. Thesevertical incisions should be at least 5 mm away fromthe planned osteotomy (Fig. 1). Full-thickness muco-periosteal flap is then raised and the lateral aspect ofthe maxillary sinus is exposed.

The design of the antrostomy is based on theoutline of the sinus on the CT scan, which also aids indetermining the thickness of the lateral wall of theantrum, position of the antral floor from the crest ofthe ridge, relationships to the teeth (if present) andthe presence of septa. Palatal transillumination can

also aid in establishing the outline of the maxillarysinus (Fig. 2). Osteotomy can be performed usingconventional rotary instruments at 800–50,000 rpmwith irrigation for cooling.

However, ultrasonic hand-pieces are preferred toconventional rotary instruments in order to decreasethe risk of membrane perforation. Bone thinning isaccomplished utilizing light pressure under copiouscooling irrigation. Regardless of the instrumenta-tion used to create the osteotomy, there are gener-ally two techniques to create the lateral window: the“trap door” approach and the “access hole” approach(Figs. 3, 4).

Osteotomy should follow the outline of the sinusand should not be more than 3 mm away from the

floor (Fig. 5); greater distances decrease the abilityof hand-eye coordination and increase the chanceof membrane perforation. The corners of the accesswindow are usually round rather than at right oracute angles, as sharp corners increase the risk ofmembrane perforation when a trap-door approachis used.

The window should be large enough to allow ac-cess for instrumentation. If a trap-door approach isused, the height of the osteotomy should not exceedthe width of the sinus, allowing for final horizontal

positioning of the new floor. Upon thinning of thebone, a bluish hue of the membrane should be noted.Curettes are used to carefully elevate the sinus mem-brane and should always be maintained on the bonyfloor or sinus walls to avoid membrane perforation.

The sequence of membrane elevation is fromthe sinus floor, toward the posterior wall, then su-perior wall and finally to the anterior wall (Fig. 6a).The membrane should be elevated from the medialsinus wall to allow for optima graft placement (Fig.6b); use of an iodophorm gauze strip soaked in 2percent Lidocaine with 1:100,000 epinephrine leftin the space for five minutes minimizes bleedingand allows for better visualization before furtherdissection (Fig. 7).

Fig. 4 Fig. 5

Fig. 6a Fig. 6b

Fig. 4_’Access hole’ approach

to create lateral window.

Fig. 5_Lateral window following the

outline of maxillary sinus

(yellow ine).

Fig. 6a_ Sequence of sinus

membrane elevation: 1, sinus floor;

2, posterior wall; 3, superior wall;

and 4, anterior wall.

Fig. 6b_Elevation of sinus

membrane (medial wall).



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Fig. 7_Use of iodophorm gauze strip

to minimize bleeding and improve

visualization.

Fig. 8a_Bone graft placed after

membrane elevation.

Fig. 8b_Collagen membrane placed

over the lateral window .

Fig. 9_’Double window’ technique

for sinus augmentation in presence

of septum.

The space created after sinus membrane eleva-tion is grafted with optional materials (Fig. 8a). Acollagen resorbable membrane is used to cover thewindow (Fig. 8b) and the mucoperiosteal flap is thenrepositioned and sutured. The presence of antral

septa can create additional difficulty at the timeof surgery; incidence of septa is approximately 30percent and configuration is variable.

The use of CT scans prior to sinus graft surgeryallows for additional information regarding theconfiguration of the septa and potential modifica-tion of the procedure depending on the location ofthe septa. Double window antrostomy approach ispreferred in the presence of septa, with one windowanterior to the septa and one posterior, elevating thesinus membrane from the lateral walls and above thesepta (Fig. 9).

Post-operatively, patients are given a seven-day course of antibiotic (500 mg Amoxicillin threetimes per day, 500 mg Levaquin per day or 300 mg

Clindamycin four times per day), Chlorhexidine 0.12percent rinse (twice daily) and sinus precautions fora week, especially if sinus perforation was noted. Pa-tients with history of chronic sinusitis could benefitfrom the use of nasal decongestants (Oxymetazoline

0.05 percent and sodium chloride 0.65 percent). Thegraft should be left to heal for a minimum of fourto nine months, dependent on the type of graftingmaterial used. In cases of simultaneous implants andsinus augmentation, the sinus membrane should beelevated prior to starting the implant osteotomy.

Prior to placement of the implant, the medialand anterior aspect of the sinus should be grafted(Fig. 10).

_Success rate

Variables that affect success rate of implants incombination with sinus floor elevation include im-plant surface, type of bone graft, residual height of

Fig. 7 Fig. 8a

Fig. 8b Fig. 9



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bone, sinus membrane perforation and placement ofcollagen membrane over the lateral window.

Implant surfaceThe annual failure rate for machine surface

implants is significantly higher (p < 0.0001) thanfor rough surface implants. Rough surface im-plants have 1.19 percent annual failure rate withthree-year survival of 96.5 percent, as comparedto machined surface implants with annual failurerate of 6.86 percent and three-year success rate of81.4 percent. The healing phase failure rate for ma-chined surface implants is 8.1 percent, compared to1.1 percent for rough surface implants.

Bone graft types

Grafting material can be of human, animal,BMP or synthetic origin. Autogenous bone grafts

(iliac crest, calvarial bone, chin, anterior ramus,alveolar ridge, tuberosity) remain the gold standardin bone-augmentation procedures; however, many

allografts, xenografts and alloplastic materials havealso been used successfully. Regardless of the type ofbone graft, there is strong evidence that all graftingmaterials are effective, differing only in duration ofhealing time and amount of bone formation.

Studies suggest the best grafting protocol is co-agulum with autogenous particulate bone, alone orwith DBBM or DFDBA, with an estimated three-yearsurvival rate 96.8-99.8 percent for rough surfaceimplants. Studies have also shown that particulatebone grafts provide better outcomes, as compared toblock grafts. Wallace et al reports an implant survivalrate for iliac block grafts of 80.40 percent comparedto a rate of 94.83 percent for particulate grafts.Testori et al has similar reports that use of particu-

Fig. 10_Simultaneous implant

placement with sinus augmentation.

Anterior and medial part of the sinus

grafted prior to implant placement.

Figs. 11a_Angle of the anterior

maxillary sinus wall.

Fig. 11b_Wide and narrow angle of

the floor of the sinus.

Fig. 12_Packing of graft material

against floor and anterior wall of

maxillary sinus.

Fig. 10

Fig. 11a

Fig. 11b Fig. 12



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late grafts alone increases implant survival to 92.5percent as compared to 82.9 percent for autogenousblock grafts alone.

It has been demonstrated that grafted sinusesmay undergo re-expansion over time, in particular,during the initial two to three years after the proce-dure. The use of nonresorbable or slowly resorbablegrafting materials should prevent this phenomenon.If particulated autogenous bone is used with xe-nografts or alloplastic materials, such as DBBM orHA, it should reduce the risk of bone resorption andsinus re-pneumatization.

Residual bone height

Sinus grafting and implant placement can be ac-complished as a one-stage or two-stage procedure,with the decision often dictated by the amount andquality of the residual alveolar bone. This is attribut-

able to the fact that it is difficult to achieve primarystability with a decrease in residual bone height(RBH). RBH can be measured on the periapical ra-

diograph. In 1996, the Sinus Consensus Conferenceissued recommendations, dependent on the verticaldimension of the residual bone between the alveolarcrest and the maxillary sinus floor. When RBH isgreater than 10 mm (Class A), a classical implantprocedure should be performed. When RBH is 7 mmto 9 mm (Class B), an osteotome technique shouldbe applied in combination with immediate implantplacement.

When the RBH is 4 mm to 6 mm (Class C), a lateralapproach involving a grafting material with immedi-ate or delayed implant placement is recommended.Finally, when RBH is 1 mm to 3 mm (Class D), alateral approach involving bone-grafting materialand delayed implant placement should be used. In

Fig. 13a_Classification of sinus

membrane perforation.

Fig. 13b_Class II (mesial) perforationof sinus membrane.

Fig. 14a_Repair of membrane

perforation with collagen membrane.

Fig. 14b_Mixture of autogenous

grafts, DBBM and PRGF.

Fig. 13a Fig. 13b

Fig. 14a Fig. 14b

Classification of

sinus membrane perforation



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general, immediate placement is not indicated whenthe residual height is less than 4 mm and in cases ofpoor bone quality.

It has been demonstrated that immediate implantplacement with less than 5 mm residual bone heightnoted significantly lower implant survival rates ascompared to placement in more than 5 mm residualbone. The implant success rate is 96 percent whenRBH is 5 mm or more and 85.7 percent when RBH is4 mm or less.

Membrane over window

Positive effects of membrane are:• prevents soft tissue ingrowth,• contains particulate graft material,• increases vital bone formation,• increases implant survival rate• and promotes positive outcome when used for

perforation repairs.Several studies have shown increased bone for-

mation when membrane is placed over the lateralwindow.

Membrane perforation

Studies show no difference in success rates in caseswith or without sinus membrane perforation. If repairis successful, membrane perforation does not appearto be associated with post-operative complication orreduced implant survival.

_Complications of lateral antrostomy

Complications may occur intraoperatively or post-operatively. Common intraoperative complicationsare perforation of the sinus membrane, bleeding andperforation of the buccal flap (very rarely). Bleedingfrom the lateral antrostomy is rare and usually tem-porary in nature. Branches of the posterior superioralveolar artery are present in lateral maxillary sinus

wall and could be injured during preparation of thelateral window, especially in cases of extensive maxil-lary resorption.

Excessive bleeding may occur with elevation ofsinus membrane from the medial wall of the antrum,which is a location of the lateral nasal artery (branch ofthe sphenopalatine artery). The most common intra-operative complication is sinus membrane perfora-tion. Membrane perforations may cause increased riskof short-term complications, such as acute or chronicsinus infections, bacterial invasion of the graft or lossof the graft material into the sinus. Sinus membrane

perforation occurs in 11 percent to 56 percent ofprocedures during preparation of the lateral window,sinus membrane elevation or placement of the bonegraft. Several factors affect the rate of perforation.

First factor is the thickness of the sinus mem-brane — rate of perforation of 41 percent reportedwith sinus membrane of less than 1.5 mm. Secondfactor is the width of the sinus (Fig. 11), i.e., the anglebetween the medial and the lateral walls. The narrowerthe angle, the higher the incidence of perforation —0 percent incidence in angles greater than 60 degreesand 62 percent with angles less than 30 degrees. The

angle is narrower in the anterior portion of the sinusand wider in the posterior aspect of the sinus.

Consequently, we recommend elevation of thefloor, posterior wall, superior and anterior walls; suchsequencing allows elevation from a wider portion tothe narrower portion of the sinus. In addition, placingthe window 3 mm above the floor and anterior wallwill allow better coordination of eye-hand move-ment and decrease incidence of perforation. Thirdfactor is the presence of septa; these cases are betterapproached utilizing a two-window approach withelevation of the membrane around the septum at thelast stage (Fig. 12).

Perforation during placement of the graft is usu-ally because of pressure against the membrane; this

Fig. 15a_Migration of the implant

into maxillary sinus.

Fig. 15b_Removal of implant from

maxillary sinus .

Fig. 15a Fig. 15b



can be avoided by packing the graft against the floorand anterior wall (Fig. 13). Utilizing ultrasonic drillsalso decreases the risk of membrane perforation,with incidence of perforation of 3–7 percent; ascompared to 16-46 percent utilizing conventionaldrills.

Membrane perforation types

Membrane perforations are classified based ontheir location. Class I perforations typically occuralong the apical wall of the prepared sinus window.Class II perforations occur along the lateral or

crestal aspects of prepared sinus window, and theyare subdivided as mesial, distal and crestal. Class IIIperforations occur at any location within the bodyof the prepared sinus widow (Fig. 14).

Upon discovery of a perforation, ascertainits size and extend the osteotomy to gain bettervisualization and access to the sinus window. Intactmembrane elevation should proceed in the areaaway from the site of the perforation and only afterobtaining enough reflection of the membrane; themembrane in the area of the perforation should bereflected.

Membrane perforation repair

Membrane repair varies and is dependent on

the size and location of the perforation. With ClassI perforations, sinus membrane elevation proceedsalong a normal course and apical to the displace-ment of the sinus membrane, resulting in it foldingover itself and thus sealing the perforation. In casesof Class II perforations, extend the osteotomy me-sially or distally to expose intact sinus membrane;if more than 3 mm of perforation is present or themembrane does not fold on itself, place a collagenmembrane over the perforation area.

In cases of Class II perforations, when it is notpossible to remove additional bone mesial to the

prepared sinus window or in Class III cases of ex-tensive sinus perforations, a membrane is shapedand inserted into the sinus window with its endsextruding out of the window. In general, duringplacement of the bone graft, the membrane will getdisplaced medially and inferiorly.

Extruding aspects of the membrane can besecured to the external aspect of the alveolar bonewith fixation tacks to decrease displacement of themembrane. Curettes are used to mold the mem-brane to ensure adequate space for augmentationmaterial. In addition to using a membrane, the useof consolidated particulate graft material decreasesthe incidence of migration of graft material intothe sinus.

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Fig. 16_ Graft infection:

thickening of the sinus

membrane, air pockets in the graft

around implant.

Fig. 16



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Common post-operative complications are de-hiscence of the incision line, migration of implantinto the sinus (Fig. 15), loss of graft material,antral ostium obstruction, oral antral communica-tion, graft infection (Fig. 16) and maxillary sinusi-

tis. Postoperative infection has been reported in2-5 percent of cases. Symptoms associated withpost-op infection include erythema, tenderness,swelling, purulent discharge, nasal congestion andfistula.

Patients with a history of chronic sinus infection orsinus disease are at higher risk for post-operative graftinfection or sinusitis. Untreated periapical pathology,extended surgical time and bacterial contaminationof the graft may also contribute to infection. The twomost common postoperative complications are graftinfection or postoperative sinusitis; CT scans help to

establish proper diagnosis (Fig. 17).Antibiotics provide coverage for common sinusmicroorganisms, such as S. Pneumonia, H. Influenza

and M. Catarrhalis. Appropriate antibiotic therapyis Augmentin in non-penicillin allergic patients andLevaquin in penicillin allergic patients. Treatment ofpostoperative infection includes antibiotic therapyand incision-drainage with cultures and removal ofthe graft, if infection does not respond to antibiotictherapy. _

_References

1) Toscano et al. The effects of piezoelectric use on open sinus

lift perforation. J of perio, 2004.

2) Pjetursson BE et al. Systematic review of the success of

sinus floor elevation and survival of implants inserted in

combination with sinus floor elevation. Clin Periodontol,

2008; 35 (Suppl 8): 216–240.

3) Tarnow et al. Int J of perio and restorative dent. 2000

4) Levin et al. Smoking and complications of onlay bone grafts

and sinus lift operations. Int J of oral maxillo fac implants.

2004.

5) Chen et al. Implant placement immediately after the lateral

approach to the trap door window procedure to create

a maxillary sinus lift without bone grafting: a two-yearretrospective evaluation of 47 implants in 33 patients. JOMS.

2007.

6) Cho et al. Influence of anatomy on Schneiderian membrane

perforation during sinus elevation. Prac proced aesthet dent.

2001

7) Darby et al. Ridge Preservation Technique for Implant

Therapy. The Int J of OMFS. v24: 260–271; 2009.

8) Fugazzotto A, Vlassis J. A simplified Classification and Repair

System for Sinus Membrane Perforations. J Periodontol

2003; 74:1534–1541.

9) Del Fabbro M, Testori T. Systematic Review of Survival Ratesfor Implants Placed in the Grafted Maxillary Sinus. Int J

Periodontics Restorative Dent 2004; 24:565–577.

10) Jensen, Ole. The Sinus Bone Graft, second Edition.

11) Tawil G, Mawla M. Sinus floor elevation using a bovine bone

mineral (Bio-Oss) with or without the concomitant use of

a bilayered collagen barrier (Bio-Gide): A clinical report of

immediate and delayed implant placement. Int J Oral Maxillo-

fac Implants 2001;16:713–721.

implants1 2013

Hussam Batal is assistant professor in the departmentof oral and maxillofacial surgery at Boston University.

Olena Norris is senior resident in the department of oraland maxillofacial surgery at Boston University.

_about the authors

lateral antrostomy for max sinus augmentation

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