WIXLIB

PRACTICEpanorex is helpful as well, but limited comparedto 3-D CT scan imaging. Once the patient hashad the initial consultation and accepted theproposed options, a diagnostic wax-up of thefinal proposed treatment will be a template tofabricate a radiographic guide. This radiographic guide can be placed in the mouth at the timeof the CT scan. Transferring the restorative template on to the radiographic images is the mostuseful information for determining the surgicalplan. Lack of bone and ridge collapse both horizontally and vertically can be accurately measured. The surgical needs can be identified andthe most predictable options can be presentedto the patient prior to beginning treatment. Thegoals of the final reconstruction, whether fixedor removable, can be determined. The treatmentexpectations can be presented to the patient,with realistic steps of what can and cannot beaccomplished. Only then can the treatment planin a phased approach, be determined by all thetreating doctors on the team. All financial obligations, treatment consent as well as aestheticgoals are established prior to taking any furthersteps.Occasionally, when questionable teeth arestill present, it may be beneficial to have a CTscan prior to removing teeth. This can help maketreatment decisions regarding surgical optionsof timing of implant placement (see discussionlater in article).Pre-surgical planningViewing the CT images which have the crosssectional reformatted images of the bonequantity and quality at each desired implantsite, allows the surgeon to develop the surgical plan. The question most often asked — ‘DoI have enough bone?’ — can be answered withan educated answer. The goals of the restorative dentist can be accomplished or cannot beachieved. In complex fully edentulous cases,whether fixed or removable reconstruction willbe the best outcome can be determined. The surgeon can then modify the radiographic guide tobe used as a surgical guide on the day of surgery. Recent developments in CAD-CAM technology allow the team to perform pre-surgicalplanning on a virtual model and then transferthis information to a clinical surgical guide toassist accurate placement of implants (eg NobelBiocare ARK, Simplant).The hard tissue classification by Lekholm andZarb defined quantity and quality of the edentulous ridge.QualityType 1: Almost the entire jaw is composed ofhomogenous compact bone.Type 2: A thick layer of compact bone surroundsa core of dense trabecular bone.Type 3: A thin layer of cortical bone surroundsa core of dense trabecular bone of favourablestrength.Type 4: A thin layer of cortical bone surrounds acore of low density trabecular bone.BRITISH DENTAL JOURNAL VOLUME 201 NO. 3 AUG 12 20063p139-152.indd 141Quantity: Ridge shape a–e.Shape ‘a’ represents no bone resorption, while‘e’ represents advanced ridge resorption.The pattern of resorption in the anterior maxilla (Figs 5–8) advances posteriorly and superiorly, which greatly affects the aesthetic zoneand lip support. The pattern of resorption of theposterior ridges greatly affects the occlusion andhorizontal overlap of the dentition8 (Figs 9-13).SURGICAL GUIDELINES — TOOTH OR TEETHALREADY MISSINGAdequate osseous ridgeThe Brånemark surgical protocol9 establishedosseointegration as an extremely predictableoption for tooth replacement with excellentlong term stability. Many implant systems havesince been developed which use this concept. Thenumerous shapes and sizes of implants availablefor use on patients today continue to change andare overwhelming. It is extremely important forall members of the team to discuss which components are to be used surgically and restoratively,so that the benefits and limitations are defined.Whether the prosthesis will be screw retained orcement retained can affect the axial inclinationand angle of placement. Due to common anatomical limitations post-extraction (concavitiesand collapse of the ridge circumference), usingcement retained restorations allows greater flexibility at the time of surgical placement.Flap designThe original Brånemark protocol required avestibular flap with a two stage approach. Theimplant was placed and buried under the softtissue and after an adequate period of healing(three months mandible, six months maxilla), asecond stage surgery was performed with crestal incisions to expose the fixtures and connecta trans-epithelial abutment. After adequate softtissue healing, the restorative dentist could fabricate the prosthesis. One stage surgical protocols were developed by ITI in Switzerland10 thatallowed the implant fixture to extend throughthe soft tissues during the period of initial healing. This protocol was duplicated and shown tobe effective using a two stage system with thesame predictability.11 Today this trend continues with most implants placed with a one stageprotocol allowing adequate time for healingprior to loading the fixtures. Using the one stagetechnique requires a crestal incision or even aflapless approach, drilling directly through thesoft tissues. Obviously, deciding which casesare suitable for the flapless technique is the keyto a successful outcome; adequate bone widthwith plenty of keratinised soft tissue is desired.Compromising the site while drilling due to lackof visibility is not advised. In the aesthetic zoneit is important to maintain adequate thicknesson the buccal aspect of the implant for longterm stability of the soft tissue contours. Usually this area lacks enough tissue due to resorption subsequent to tooth loss, and augmentation techniques are required. The L. Abram’s roll1412/8/06 10:17:46

PRACTICEFig. 1 (left) Anterior X-section ofthick periodontium with high crest(bone at level of CEJ)Fig. 2 (right) Thin periodontiumwith low crest (Note the bonedehiscence on the buccal surface)Fig. 3 (left) Periodontitis withadvanced bone loss and probingdepths; expect vertical ridge collapseafter tooth extractedFig. 4 (right) Recession; attachmentloss with advanced horizontal boneloss; expect even larger ridge defectafter tooth lossFig. 5 (left) Type ‘a’ ridge (thickperiodontium) with no collapseFig. 6 (right) Loss of vertical heightafter extraction of teeth withmoderate to advanced periodontitis(normal to thick periodontium). Thiswill also present with loss of papillaheight, due to previous interproximalbone defectFig. 7 (left) Expected collapse ofridge after extraction with thinperiodontium (even in healthyenvironment)Fig. 8 (right) Shape ‘c’ or ‘d’. Thinperiodontium with pronouncedscalloped biotype and disease (seeFigs 3-4) will usually shrink more,leaving concavity type defect withknife edge ridgeFig. 9 (left) Posterior x-sectionshowing horizontal overlap and ridgerelationship in healthFig. 10 (right) Tooth loss withminimal ridge collapse. (Type ‘a’ and‘b’ ridge shape)1423p139-152.indd 142BRITISH DENTAL JOURNAL VOLUME 201 NO. 3 AUG 12 20062/8/06 10:19:15

PRACTICEFig. 11 (left) Further resorptioncreates greater interarch distancewith less bone available to place onlyshorter implantsFig. 12 (right) Minimal resorptionallows occlusal scheme to remain thesame as prior to extraction, and idealemergence for crown contoursFig. 13 (left) Buccal collapse of theridges (left) requires implants to beplaced in a more lingual position. Thiscreates restorations with buccal overcontouring and unfavourable loadingconditions on the implant. Thealternative option is to restore withan x-bite relationship. Note on theother side of diagram, short clinicalcrowns require countersinking of theimplants to allow adequate space forrestorative componentsFig. 14 (right) Intra-oral graft sitesinclude ramus and chinFig. 15 (left) Posterior maxillapresents with enlarged sinus andnot enough bone height to placeimplants. Note minimal amount ofvertical ridge height collapseFig. 16 (right) Sinus Lift usingwindow approach through the lateralwall. After adequate bone healing(four to six months), implants arethen placed. Simultaneous bonegrafting and implant placement isa risker procedure. Note crown toimplant ratio will be favourableFig. 17 (left) Note more advancedridge resorption. Sinus Lift withoutreconstruction of ridge height leadsto less favourable crown to implantratio. Placement of the most mesialimplant adjacent to the cuspid toothon the incline creates problem withInterproximal tissues and forcesimplant placement slightly moredistal than ideal in order to protectattachment on distal of cuspidFig. 18 (right) Onlay block graftwith fixation screws to reconstructthe ridge height and improve crowncontoursFig. 19 (left) After adequatehealing, screws are removed andimplants are placed. Note idealcrown/implant ratioFig. 20 (right) Posterior maxilla withideal bone height and widthBRITISH DENTAL JOURNAL VOLUME 201 NO. 3 AUG 12 20063p139-152.indd 1431432/8/06 10:19:48

PRACTICEtechnique12 is often used to transfer the crestalthicker tissue onto the buccal aspect, rather thanusing a punch technique (flapless approach)which is subtractive.Using a two stage protocol in the aestheticzone also allows for an additional opportunityfor surgical intervention with further hard orsoft tissue grafting procedures. Langer13 introduced the sub-epithelial connective tissue graftas a predictable technique for augmenting thintissue and it is especially useful when minorridge resorption is present. The most commondonor site is the palatal tissue mesial to the firstmolar. Another popular donor site is the tuberosity tissue. This area is especially desirable whena thicker graft is needed for ridge augmentation procedures (inlay or pouch technique)14 inthe anterior aesthetic zone. Palacci15 has alsodescribed rotated flap techniques for papillaregeneration. It is always important to define thetype of defect, and realise that building the supporting bone beneath the soft tissue will producethe most predictable outcome. The bony architecture provides the scaffold that supports thesoft tissue around proper implant positioning.POSITION AND ANGULATION OF IMPLANTPresurgical analysis has determined the bestavailable sites for placement. In the partiallyedentulous case, being aware of the root morphology and inclination of teeth adjacent tothe implant site is crucial. If a radiographicguide was used at the time of CT scan and thenadapted for use as a surgical guide, mishaps willbe prevented. If a surgical guide is fabricatedwithout the knowledge of the root positions orbony deficiencies, then careful interpretationand adjustments by the surgeon is required. Theinitial drilling (round bur) starting point can bemoved and the angulation of the implant tippedto avoid bone dehiscence or fenestration. Themore palatal the movement, the deeper sub-gingivally the implant platform must be positionedto accommodate for the emergence of the restorative components through the soft tissue. Idealdimensions16 are 3–4 mm subgingival, with thebuccal aspect of the implant platform at least 1mm or more palatal or lingual to the future buccal aspect of the restoration at the level of thegingival margin. Placing a wider platform in theanterior aesthetic region provides for a smoothergingival restorative interface (platform does nothave to be as deep), but invites greater risk ofapical migration of the soft tissue margin. Theconcept of ‘platform switching’ – using a narrower restorative component on a wider implantplatform (possible only with some implantsystems, eg 3i) – is interesting.17 It appears tohelp support the soft tissue and prevent crestalresorption of the bone at the level of the implantplatform. At this time further research is needed.Dense boneDense bone (Type 1 & 2) requires careful attention to drilling with adequate irrigation in ordernot to overheat the bone. Care should be taken1443p139-152.indd 144to debride the osteotomy site from bone debrisand to widen the site to the manufacturer’s recommended diameter prior to tapping the site.Placing the implant into too tight a site can leadto failure due to pressure necrosis. The shape ofthe implant, parallel walled vs. tapered will alsogreatly affect the tightness (primary stability).Softer boneType 3 and 4 bone requires modification of thedrilling protocol. Care must be taken to underprepare the osteotomy site. Over-preparationor inadvertent implant angulation changescan preclude placement of the implant. Usingthe Osteotome technique18 can also help initial stabilisation by compressing the availablesoft bone instead of compromising the site withdrilling. Tapered implants have an advantage insofter bone due to the wedging effect at the timeof placement. The tapered implant is more challenging at the time of placement, because thedepth of the prepared site needs to be exactlyat the level of where the desired final positionof the implant needs to be placed. As opposedto a parallel wall implant that can be placeddeeper if desired, due to the ability to sink theimplant into the prepared site. The twist drillsfor the parallel wall implants have markings,which prepare the depth slightly longer thanthe implant length. Due to this design and extratip at the end of the drill, care should always betaken when drilling above vital structures suchas the alveolar canal in the posterior mandible.Bi-cortical fixation in softer sites helpsanchor the fixture especially in the posteriormaxilla. Engaging the sinus floor is suggestedto achieve this anchorage.Countersinking into the crestal bone maycause loss of initial stabilisation at the time ofplacement. The need to countersink the implantis usually restorative driven for aesthetic andemergence purposes or due to lack of restorative space. The original protocol requiredcountersinking to protect the implant fromtrans-mucosal forces generated by removable appliances over the implant head. In softerbone, it is preferable to place the platform ofthe implant at the crest or supra-crestal if spaceallows for adequate emergence.The deficient osseous ridge (Figs 34-61)Lack of vertical heightAnterior maxilla: Vertical resorption of theridge will affect the aesthetic result in partiallyedentulous cases. In fully edentulous cases theamount of loss might limit treatment to removable overdentures.Options for surgical correction include: Onlay bone grafting Distraction osteogenesis.The onlay block graft19 requires an autogenous block of bone be taken from either intraoral sites (Ramus or chin) (see Fig. 14) or extraoral site (iliac crest or calvaria). The greater thedefect, the more bone required. Analysis of theBRITISH DENTAL JOURNAL VOLUME 201 NO. 3 AUG 12 20062/8/06 10:20:16

PRACTICEdimensions required will dictate which donorsite is preferable. Extra-oral sites require general anaesthesia and increase the risk of greatermorbidity. Intra-oral block grafts are better suited for partially edentulous situations. The blockof cortical cancellous bone is carefully adaptedto the recipient site and fixated with screws tostabilise the graft during the healing period.Building vertical height is the least predictableof all the grafting options.Distraction Osteogenesis20 allows the existing bone to be transferred to a more coronalposition after surgical osteotomy cuts andplacement of a device that is activated daily inthe mouth. After several weeks of movement,the bone is left to mature for a few months priorto implant placement.Posterior maxilla: The posterior maxilla has historically always been the most challenging site toachieve success. The most common site for toothloss in the periodontally compromised patient isthe maxillary molars due to furcation involvement.21 Due to a combination of periodontal boneloss and sinus proximity, limited bone height isusually available for implants (Fig. 15). The boneis also usually soft (type 3 or 4), which makes initial stabilisation difficult to achieve. Several techniques have been developed and perfected overthe last decade to improve the surgical options inthe posterior maxilla (Figs 16-24).The Sinus Lift procedure22 reported byBoyne et al. showed that it is possible to openthe maxillary sinus through the lateral wall,elevate the sinus membrane and pack bonegrafting material into the space. Many types ofbone grafting materials are available. Autogenous bone has always been the most predictable option that has set the gold standard.Intra-oral bone can be harvested from the chin,ramus or tuberosity areas. This bone is groundand the particulated graft material is best combined with an osteo-conductive material of thesurgeon’s choice (eg Hydroxy-apatite, Bio-ossor freeze dried bone). Using Platelet Rich Plasma23 to aid the healing response is an additional option. It is more predictable to performthe sinus lift graft, and then wait 5-6 monthsfor healing prior to implant placement. If 5 mmor more of bone height is available, simultaneous implant placement with sinus lift and bonegrafting is possible, with less predictability. If 7or 8 mm of height is available, then placementof the implants with an osteotome techniquefor increasing the length of implant is possible(see Figs 20-24). The protocol calls for drillingthe initial twist drills at least 3 mm short ofthe sinus floor. The osteotome is placed intothe osteotomy. The sinus floor is in-fractured,thereby raising the membrane and creatingspace for the graft. Bone graft material canthen be pushed into the preparation site priorto placing the implant. This technique is popular, because it seems less invasive as comparedto the sinus lift via the lateral wall technique,but obviously it requires careful patient selection. It is a technique sensitive procedure, goodBRITISH DENTAL JOURNAL VOLUME 201 NO. 3 AUG 12 20063p139-152.indd 145for single tooth replacement, but with lesspredictability, due to the greater potential forsinus membrane perforation.Posterior mandible: The inferior alveolarnerve needs to be visualised in order not to causenerve damage such as paraesthesia. It often limitsimplant placement to short wide implants. Alternative options are the nerve transposition procedure24 which has a high morbidity and rate ofnerve damage, or to consider distal cantileveringof the prosthesis off implants placed mesial to theforamina. Distraction osteogenesis can also beused if inter-arch space is not a problem.Lack of horizontal widthAnterior maxilla: The pattern of resorption usually creates knife-edge ridges or ridges that aretoo thin due to concavities (Fig. 8). The anterior incisal foramen is sometimes large and canrestrict implant placement in the maxillary central positions (Fig. 37).Knife-edge ridges are best treated with veneergrafts19 using an intra-oral block of corticalcancellous autogenous bone stabilised with fixation screws (Figs 25-26). Unlike onlay grafts,these veneer grafts are more predictable. Concavity defects can be treated with block grafts,but these also respond favourably

3. Treatment planning of implants in the aesthetic zone 4. Surgical guidelines for dental implant placement 5. Immediate implant placement: treatment planning and surgical steps for successful outcomes 6. Treatment planning of the edentulous maxilla 7. Treatment planning of the edentulous mandible 8. Impress