Maxillary All-on-Four Surgery: A Review Of Intraoperative .
Maxillary All-on-Four Surgery: A Review ofIntraoperative Surgical Principles and ImplantPlacement StrategiesDavid K. Sylvester II, DDSAssistant Clinical Professor, Department of Oral & Maxillofacial Surgery, University of Oklahoma Health Sciences CenterPrivate Practice, ClearChoice Dental Implant Center, St. Louis, Mo.Ole T. Jensen DDS, MSAdjunct Professor, University of Utah School of DentistryThomas D. Berry, DDS, MDPrivate Practice, ClearChoice Dental Implant Center, Atlanta, Ga.John Pappas, DDSPrivate Practice, ClearChoice Dental Implant Center, St. Louis, Mo.BACKGROUNDImplant rehabilitation of full-arch maxillaryedentulism has undergone significant changessince the concept of osseointegration was firstintroduced. Controversy over the ideal numberof implants, axial versus angled implantplacement, and grafting versus graftlesstreatment modalities have been subjects ofcontinuous debate and evolution. Implantsupported full-arch rehabilitation of the maxillawas originally thought to be more difficult thanits mandibular counterpart due to lower overallbone density.The foundation for any implant supported fullarch rehabilitation is the underlying bone. Thedilemma faced by most surgeons is whether totreat this residual bone in an additive fashionthrough bone augmentation, or a graftlessfashion utilizing angled implants secured inresidual bone. Advocates for additive treatmentattempt to procure the bone volume necessaryfor implant support through horizontal andvertical augmentation techniques. Graftlessapproaches seek to offer full-arch implantsupport through creative utilization of angledimplants in existing native bone.Biomechanical analysis of the masticatorysystem repeatedly demonstrated that thegreatest bite forces are located in the posteriorjaws. Anatomic limitations of bone availabilitydue to atrophy and sinus pneumatization makemaxillaryposteriorimplantplacementchallenging. The resulting controversy withregards to full-arch rehabilitation was whetherprostheses with long distal cantilevers could betolerated. If tilting posterior implants couldcircumventanatomiclimitationswhilemaximizing the use of residual bone, cantileverscould be reduced.
Nonaxial placement and loading of implantswas thought to be biomechanically unfavorablepreventing osseointegration and leading toincreased peri-implant bone loss.1 Limitationsimposed by residual maxillary bone availabilityand the requirement for axial placement ofimplants meant cantilever length often neededto be 20 mm or greater in order to providemolar occlusion. Conversely, literature at thetime reported a direct association betweencantilever length and marginal bone loss/failureof underlying implants.2 It had been shown thatprostheses with cantilevers less than 15 mmsurvived better than those with cantileversgreater than 15 mm.3Today, Maxillary All-on-Four is a commontreatment modality utilized by clinicians all overthe world for immediate full-arch rehabilitation.The technique evolved as a graftless solutionwhich sought to reduce treatment time andavoid complications associated with bonegrafting. Potential bone grafting complicationsinclude: increased cost, increase treatment time,donor site morbidity, significant limitationsimposed by chronic systemic medicalconditions, and unpredictable reduction in bonegraft volume as a result of resorption.Tilted implants were proposed as a method toavoid anatomic structures while achievingsufficient biomechanical support. By tiltingimplants, dense cortical bone of the naturalmaxillofacial buttresses could be engaged, evenin cases of severe maxillary atrophy. Theoreticaladvantages of tilting implants included:1. Avoidance of anatomic structures.2. Longer, tilted implants could be placed incases of vertical bone deficiencyobviating the need for bone grafting.3. Bicortical stabilization can be more easilyachieved. Longer, tilted implants makeresidual cortical bone more accessibleresulting in greater primary stability.4. Angled implants provide secondaryresistance to vertical displacement byvirtue of their nonaxial, oblique positionin the archform which is perpendicular toocclusal forces.This stabilization isseparate from insertional torque and isonly enhanced by cross-arch stabilization5. Distal cantilevers are minimized when amore posterior emergence of distalimplants is achieved resulting in greaterbiomechanical stability.6. Anteroposterior spread (AP spread) isenhanced.7. An alternative treatment option forpatients with severe systemic conditionswhich may render them poor candidatesfor bone grafting.ALL-ON-FOUR HISTORYIn 1991 and 1992, Bruggenkate publishedreports of angled implant placement in theposteriormaxillausedtosupport4,5overdentures.In 1995, a one-year primatestudy performed by Celletti et. al. demonstratedosseointegration of both straight and angledimplants. This study provided both clinical andhistologic evidence of implant osseointegrationirrespective of implant angulation.6In 1995, Brånemark published a 10-year survivalstudy of fixed prostheses retained with eitherfour or six implants. This article suggested that,although there was a tendency for increasedfailure rates in patients with only 4 implants, theoverall survival rate for both implants andprostheses was the same for both groups. Priorto this publication, the tendency of someclinicians was to place as many maxillaryimplants as possible in cases of full-archrehabilitation.7 This publication was the first todemonstrate equal success with an implantfoundation consisting of only 4 implants.
A graftless surgical technique and mediumlength study using angled implants waspublished by Mattsson et. al. in 1999.8 Thissolution to maxillary full-arch rehabilitation waspostulated to increase treatment lication rates. 86 implants were placedinto 15 patients. Patients were followed for anaverage of 45 months. During this time, oneimplant was lost resulting in a 98.8% implantsurvival rate. All patients had a stable prosthesisat the end of the observation period. Bilateralfenestrations were created into the maxillarysinuses for the purpose of anatomic explorationand bone sounding of the anteromedial sinuswall. Posterior implants were placed parallel tothe sinus walls. Anterior implants were placedaxially.Eighty-eight percent of implantsinstalled had 2-5 exposed palatal threads whichwere not grafted. This finding did not seem tolead to any mucosal problems or marginal boneresorption according to their report. Primaryclosure was obtained at the time of surgery. Inthis study, patients were not allowed to wear aremovable prosthesis for 2 weeks. Implantswere uncovered at 6 months. The authorsconcluded that the maximum use of residualbone stock, angulation of implants, and exposedpalatal implant threads may allow for full-archrehabilitation of severely resorbed maxillas.In 2000, Krekmanov reported placement ofangled implantsin severely resorbed9,10maxillas.An open sinus technique wasperformed by way of a sinus fenestration, and astraight probe was used to sound the anteriorand posterior walls of the sinus. Implants wereplaced parallel to the anterior and posteriorwalls at approximately 30-degree angulations.A total of 75 maxillary implants were placed andfollowed for 18 months. Nineteen implantswere palatally inclined and placed tangential tothe curve of the palate at the molar regionsengaging maximum cortical bone. During theobserved time period only one maxillary implantwas lost.In 2001, Aparicio et. al.11 used a combination ofangled and axial implants as an alternative tosinus grafting in patients with severe maxillaryresorption. Implant surgery was two-stage withburying of implant fixtures at the time ofsurgery. Final restorations consisted of fixedpartial prostheses. Twenty-five patients werefollowed for an average of 37 months (up to 5years). Residual dense bone was engaged byangling implants parallel with the anterior andposterior walls of the sinus. In these instances,posterior implants found apical stabilization inthe pterygomaxillary region, and anteriorimplants were apically stabilized at the piriform.In other instances, the curvature of the palatalvault was apically engaged. A total of 101implants were placed. The overall prosthesissurvival rate was 100%. Tilted implants had asurvival rate of 100%. Axial implants had asurvival rate of 96.5%.At the time, these studies represented a subsetof those available in the body of literature thatsuggested axial and tilted implants hadcomparable success in short and mediumlength follow-up periods. Still, surgeries weretwo-stage with healing periods of 6-8 monthsbefore implant loading. Advances in implantdesign and surface coatings aimed to reducehealing time and increase bone-to-implantcontact. It was found that implant roughness,porosity, topography, and surface energy weresynergistic accelerators of osteointegration.Anodization of implant surfaces as well as airpowered particle abrasion followed by acidwashings were two techniques manufacturersemployed to increase microtexturing of implantsurfaces.12-18In accordance with original principles ofosseointegration, implants were placed andburied beneath the soft tissue for a healing
period to prevent excessive movement. Studieslater emerged showing that limited movementcould be tolerated without disintegration of theimplant.19,20 This finding was perhaps bestreported by Schnitman et. al.21 in 1990. In anattempt to provide his patients with a fixedprovisional appliance during the healing phasefollowing surgery, seven or more mandibularimplants were placed at the time of surgery.Three implants were used to fixate an immediateprovisional appliance while the remainingimplants were buried throughout the healingphase. A surprising discovery was that morethan 90% of the provisional implants remainedintegrated throughout the treatment phase. A10-year follow-up study published in 1997demonstrated that more than 80% of egrated.Tolerability of a certainamount of implant micromovement during thehealing phase was not detrimental to overallsurvivability.Having determined that implants could beplaced in both axial and tilted orientations withequal success and knowing that full-archrehabilitation could be achieved with 4 implants,the next logical question was the plausibility ofimmediate function full-arch rehabilitation.Immediate loading of angled and axial implantswas first reported in the mandible and later inthe maxilla.23-25 Maló performed immediatefull-arch rehabilitation of 32 patients with 128implants and documented his success in a oneyear retrospective study. His study highlightedthe use of four implants placed at thecornerstones of the maxillary arch. Anteriorimplants were placed in axial positions whileposterior implants were angled 30-45 degreesand parallel with the anterior sinus wall. Themaxillary sinus was fenestrated bilaterally andprobed to ensure placement of implants withinresidual bone and with maximal anteroposteriorspread. Insertional torque of at least 40 Ncm wasobtained by underpreparing implant osteotomysites and relying on lateral compression ofimplant threads and bicortical stabilization.Implants were loaded with a fixed provisionalrestoration on the day of surgery.Finalprotheses were delivered 12 months aftersurgery. No axial implants failed, and threetilted implants failed resulting in survival rates of100% for axial implants and 95.3% for tiltedimplants.25Medium and long-term follow-up studiespublished by Maló corroborated originalfindings with similar levels of success.26MAXILLARY ALL-ONFOUR SUCCESSNumerous studies have corroborated thesuccess of full-arch implant supportedrehabilitation utilizing 4 angled implants.Chrcanovic et. al.27 compared tilted and axiallyplaced implants in a meta-analysis whichincluded both maxillary and mandibularimplants. The authors compared implant failureand marginal bone loss based on implantangulation.Forty-four publications wereincluded in their study with 5,732 axial implantsand 5,027 tiled implants. There wasn’t anystatistically significant difference in implantfailure rates or marginal bone loss between thegroups.In a similar meta-analysis comparing tiled andaxial implants utilized in immediate functionfull-arch rehabilitation of the maxilla, Menini et.al.28 reported on 1,623 maxillary implants placedinto 324 patients. Of these, 47.9% were tiled and52.1% were axial. Again, there wasn’t anydifference between implant survivability andmarginal bone loss between the groups.Ata-Ali et. al.29 performed three meta-analyseson axial and tilted implants. Their analysis
included 13 publications with implants placed inboth maxillary and mandibular arches. Theyinvestigated 7 retrospective studies and 6prospective studies. There wasn’t any differencein success rates between retrospective andprospective studies.There wasn’t anystatistically significant difference in marginalbone loss or implant survival between axial andtilted implants.A significant limitation of any meta-analysis isvariability of surgical technique, number ofoperators, and operator experience. A 2017retrospective study compared marginal boneloss and implant success between axial andtilted implants placed in the maxilla inaccordance with the All-on-Four protocol atthe Maló Clinic30;891 patients wererehabilitated with 3,564 maxillary implants for 5years.Overall implant success was 96%.Success rates for tilted and axial implants were96.1% and 95.7%, respectively. Marginal boneloss was measured using periapical radiographsat the time of surgery and after 5 years offunction. Axial and tilted implants showed meanbone loss values of 1.14 0.71 mm (range 0-6.9mm) and 1.19 0.82 mm (range 0-8.4 mm),respectively. Three percent of all implantsshowed marginal bone loss of 0.2 mm; while12% showed more than 2 mm of marginal boneloss. Advanced marginal bone loss ( 2.8 mm)occurred in 4% of the implants and wasattributed to biological and mechanicalcomplications. With regard to advancedmarginal bone loss, a slight but statisticallysignificant higher proportion of complicationsoccurred with tilted implants as compared toaxial implants. Smokers and female patientsexhibited a 2-fold increased risk for advancedbone loss. Overall, linear mixed model analysisfrom this study showed that implant orientationdoes not significantly contribute to peri-implantbone loss or implant success after 5 years.Survival rates of axial and tilted implants rangefrom 95-100%.MAXILLARY AGERELATED CHANGESIn general, the pattern of maxillary boneresorption progresses in a predictable fashionwith remodeling of the horizontal and verticaldimensions occurring first followed bymorphologic changes of underlying basal bone.In a randomized, cross-sectional study of 300dried human skulls, Cawood and Howellobserved dimensional changes of edentulousjaws and translated their findings into aclassification system still used today.31 There are6 classes.Class I jaws are dentate withsupporting alveolar bone. Class VI jaws showloss of all supporting alveolar bone with atrophyof basal bone. Following dental extractions,diminutive changes in the horizontal dimensionare observed first followed by vertical bone loss.These patterns correspond with Cawood andHowell Class III and IV maxillas, respectively.Underlying basal bone is more resistant toprogressive resorption. Residual flat and thendepressed alveolar ridgeforms correspond withCawood and Howell Class V and VI maxillas.These patterns of resorption give the impressionof a maxilla that narrows posteriorly whileretruding in an AP dimension, all withconcomitantlossofverticalheight.Simultaneous patterns of mandibular resorptionresult in a progressive pseudo class III jawrelationship and a concave facial profile.Rate of alveolar bone loss and time are not alinear relationship.In a study observingreduction of the alveolar ridge in patientswearing conventional dentures, Tallgren32observed the greatest dimensional changesoccurred within the first year of edentulism.Pneumatization of the maxillary sinusesfollowing dental extractions further contributes
to dimensional changes of the maxillofacialcomplex. Subantral bone mass is lost firstfollowed by a decrease in bone mass betweenthe sinus and nasal cavities. This is bestobserved on orthopantomography.33Anatomic regions most resistant to atrophy arethe natural maxillofacial buttresses (Figure 1).These sites are subjected to continued loadbearing forces throughout life. Cortical bone inthe piriform regions, pterygomaxillary regions,zygomaticomaxillary regions, and midline nasalcrest are often the most resistant to atrophy.3335Figure 1: Vertical facial buttresses.CLINICAL PATIENTASSESSMENTSuccessful All-on-Four rehabilitation is acomplex, patient-tailored, and prostheticallydriven treatment solution. Prosthetic material,teeth size, lip support, incisor positioning, teethshow at rest and animation, phonetics, orofacialmusculature, bite force, parafunctional habits,and alterations to the occlusal verticaldimension are just some of the factors used todetermineinterarchprostheticspacerequirements by the restorative clinician. Manyof these treatment planning parameters arebeyond the scope of this paper. In all cases, thefinal prosthetic design dictates the verticalposition of the maxillary osteotomy which, inturn, directs functional implant positions andangulations.The vertical position of themaxillary osteotomy after extractions andalveolar reduction is sometimes referred to asthe “All-on-Four Shelf”.46At a minimum, 15 mm of vertical space per archis needed to meet prosthetic spacerequirements.Any less than this verticalrequirement greatly weakens both the interimand final prostheses.Significant patientvariabilityexistsamongAll-on-Four candidates. For some, this requirement willnecessitate teeth removal and significantalveolar bone reduction. In others, years ofedentulism and progressive atrophy mayrequire very little alveolar recontouring at thetime of surgery.It is equally important that the interfacebetween the prosthesis and the residual ridge,often termed the “transition zone”,47 beconcealed when the patient’s lip is at rest andduring a full, animated smile. Inadequatealveolar reduction can result in catastrophicesthetic outcomes, particularly in patients with ahigh smile line.RADIOGRAPHICASSESSMENTAn initial, cursory appreciation of bone volumeand overall dental condition can easily beobtained with an orthopantomogram orpanoramic reconstruction of an CBCT. As partof a presurgical method for evaluating bonevolume in maxillary full-arch rehabilitation,Bedrossian et. al.47 advocated the visual divisionof the maxilla into 3 zones.
According to this classification, Zone 1 is definedas the intercanine region. Zone 2 is the premolarregion, and Zone 3 is the molar region. Amplebone present in all 3 zones implies that axialimplants can be placed anywhere in the arch.Residual bone present in zones 1 and 2 isamendable to tilted posterior implants inclinedto avoid the anterior wall of the maxillary sinus.The presence of bone only in zone 1 makesposterior implant support difficult to achieve. Inthese instances, a transantral approach may beconsidered if sufficient subantral bone is presentfor crestal stability. If not, apical fixation in moredistant anatomic sites such as the zygoma orpterygoid process may be considered. Finally, incases where no substantial bone is present in allthree zones, graftless implant rehabilitationrequires sole fixation in the zygomas, pterygoidprocesses, and the midline nasal crest.Preliminary radiographic evaluation should bevisualized at the vertical level of the proposedmaxillary osteotomy. Often, the reduction ofsubantral and subnasal alveolar bone places thefuture All-on-Four shelf in close proximity tothe sinus and nasal cavities while decreasing theamount of vertical bone available for fixation.As
Tilted implants had a survival rate of 100%. Axial implants had a survival rate of 96.5%. At the time, these studies represented a subset of those available in the body of literature that suggested axial and tilted implants had comparable s
Plastic surgery Cosmetic Surgery Reconstructive Surgery Aesthetic Surgical & Non-Surgical procedures Craniofacial Surgery Rhinoplasty & Otoplasty Hand Surgery or Chiroplasty Oral and Maxillofacial Surgery Trauma Surgery Skin Rejuvenation and Resurfacing Anesthesia for Plastic Surgery
concentrates for implant site development: a systematic review of histomorphometric studies Miriam Ting1*, Philip Afshar2, Arik Adhami2, Stanton M. Braid3 and Jon B. Suzuki4,5 Abstract Maxillary sinus pneumatization following dental tooth extract ions and maxillary alveolar bone resorption frequently leaves inadequate bone levels for implant .
91% [9]. Interestingly, our case not only showed maxil-lary and mandibular distomolars, but also appeared bi-lateral distomolars. Elif Kaya et al. [9] at 2015 reported only three cases of bilateral maxillary distomolars in 10, 111 patients aged 18–60years old. Concerning our case, it is infrequent to find bilateral maxillary distomolars. In
deciduous canines and first molars in the dental arch, andgood-quality panoramic radiographs. Exclusion cri-teria were previous orthodontic treatment, premature loss of the maxillary deciduous canines and first molars, labially retained maxillary permanent canines, aplasia
case, clinical steps and treatment plan was modified to suit the patient's need. It was decided to give a maxillary complete denture (liquid supported) opposing conventional lower complete denture. [Fig-1]: Intraoral view of maxillary arch. [Fig-2]: Maxillary secondary impression by window technique
Oral Maxillofacial Surgery 1. Management of Patients with Impacted Third Molar Teeth 2. Management of Pericoronitis 3. Management and Prevention of Dry Socket 4. Management of Unilateral Fractures of the Condyle Orthodontics 1. The Management of the Palatally Ectopic Maxillary Canine 2. Management of Unerupted Maxillary Incisors Paediatric .
The device performed as des ired'a'nd was as safe and as effective as the predicate devices. . Plastic and Reconstructive Surgery. N81Jrosuirgery, Gastrointestinal and Affili ted Organ Surgery, Urological Surgery, Orthopedic Surgery, Gynecological Surgery, ThoraclO Surgery, Lta aoscopic Surgery. .
Jennifer S. Schwartz, MD Assistant Professor of Surgery Department of Surgery Division of General & Gastrointestinal Surgery The Ohio State University Wexner Medical Center Robotics in General Surgery Objectives Brief History of Robotics in General Surgery Robotic General Surgery
