Case report: Restoration of 2 Astra Tech implant fixtures ...of a ceramo-metal transverse screw retained prosthesis. The possibility now exists to allow the final restoration to be

32 eLABORATE March/April 2011

Cemented and screw-retained implant pros-theses both present distinct advantages andlimitations. The major difference between the

two strategies is that a screw-retained prosthesiscan be removed by the clinician, while a cementedrestoration is not intended to be retrieved. Each canbe the best option, depending on the objectives ofthe prosthesis, the properties of the implant systemand the philosophy of the practitioner.Many studies have discussed the merits of screw

retained vs cement retained implant restorations.1-3

However, the one major advantage of a screwretained implant restoration is that of retrievability.The ability to remove the restoration allows anybiological and technical failures that may occurduring the lifespan of the restoration to beaddressed. This includes removal of the restorationto retighten loosened abutment screws, replacefailed or fractured components, or even to performroutine periodontal and implant hygiene.In addition, screw retained systems provide a

great variety of transmucosal and prosthetic com-ponents, working well in clinical situations wherethere is limited occlusal space; require no removalof sub-gingival cement and cause no negativesequalae when the cement is not removed. This isparticularly important if the transmucosal to

Case report: Restoration of 2 Astra Tech implant fixtures utilisingcustom Atlantis Abutments and transverse screw retained 3M ESPELava metal free zirconia crowns

By Dr Andrew Chio, BDSc (Melb) and Yugo Hatai

implant | TECHNIQUES

Figure 1.

Figure 2.

eLABORATE 03.11 WEB_eLABORATE 26/06/11 11:44 PM Page 32

March/April 2011 eLABORATE 33


Figure 4. Figure 5.

Figure 6. Figure 7. Figure 8.

implant junction is greater than 3-4mmsubgingivally. The utilisation of a screwretained system, however, is not withoutits disadvantages.Firstly, there is a problem of a lack of

aesthetics at the screw access channel,particularly if the channel is cast in metal.The presence of the screw access openingin ceramo-metal restorations also weakensthe porcelain around the opening and atthe cusp tip rendering the porcelain sus-ceptible to fracturing and chipping inthose areas.Figure 1 shows chipping and fracturing

of the porcelain on the distal aspect of thetransocclusal screw opening on therestoration on 45. The direct compositeresin seal on 46 also shows uneven wearwhen compared to the surrounding porce-lain surface. At the time of presentation,the transocclusal screw retained implantrestorations on 45 and 46 have been infunction for the past 5 years.Figure 2, in comparison, shows the 36

on the contra-lateral side in the samepatient with minimal changes from base

line since the time of delivery. The 36 wasrestored with a cross pinned screwretained implant restoration. At the time ofpresentation, all three implants in the 36,44 and 45 sites were placed and restored atthe same time and have been in functionfor the past 5 years.The centric contact at a screw access

opening, which is often in the centricfossa and may occupy 50%-60% of theinter-cuspal occlusal contact, is usuallydeveloped by the use of direct restorativecomposite to “seal” the transocclusalscrew access. This in turn has the potential to establish unstable occlusalcontacts with the opposing dentition due to the wear of the composite restorative material.One option that is commonly used to

retain the benefits of screw retainedrestorations and concurrently eliminatethe disadvantage associated with thetransocclusal screw access is by cross-pin-ning the prosthesis to the implantabutment. The technique of cross-pinninguses a transverse screw to attach the

restoration to an implant abutment whenaccess for the abutment screw would com-promise the aesthetics and/or structuralintegrity of the prosthesis.This technique traditionally requires the

final restoration to be completed as a fullmetal or as a ceramo-metal prosthesiswhere a rim of metal is placed around thehead of the cross-pin screw to avoidceramic contact (Figure 3). This is toallow the tapping of the coping to housethe transverse screw channel.Figures 4-8 demonstrate the compo-

nents commonly utilised in the provisionof a ceramo-metal transverse screwretained prosthesis.The possibility now exists to allow the

final restoration to be fabricated utilisingmetal free Zirconia based systems.The following case report presents an

alternative of utilising metal free Zirconiabased prostheses (3M™ ESPE™ Lava™)which are attached to custom milled abut-ments (Astra Tech Atlantis™) by theutilisation of transverse screws (cross-pinning technique).

Figure 3. A view of a cross-pin screw re-tained implant supported ceramo-metalcrown (Image reproduced with permissionfrom the Australian Dental Journal).4



Case reportThe patient presented for the restoration ofthe upper left second premolar 25 andupper left first molar 26 following successful osseointegration of the AstraTech fixtures in the respective sites. Bothteeth had previously been extracted due toa combination of endodontic and pros-thetic failures which rendered both teethunrestorable.Extraction of the teeth was followed by

the routine diagnostic workup for restoration of the edentulous segment with implant retained restorations. Theimplant fixtures were placed and subse-quently restored utilising a delayed loading protocol.Figure 9 shows the healing caps in situ

following confirmation of osseointegra-tion of the Astra Tech implant fixtures.Following confirmation of osseointegra-

tion of the implant fixtures, the patientpresented nine weeks post implant place-ment for the restorative phase of treatment.The healing abutments had been used in

combination with a removable temporiza-tion, in the form of a sectional removableValplast denture.

Shade selectionProviding the appropriate shade imagesfor communication with your laboratoryand dental technician is such an importantfactor to achieve better colour matching.There are a few things to consider:• The photos should be taken prior to anyintra-oral procedures to minimise anyshifts in colour or shade due to dehydra-tion that can occur during and followingthe impression taking procedure and/or 2weeks following completion of bleachingor 48 hours after temps have been placed.

• The position of the shade tab should bein the edge to edge position against thematching teeth.

• Including extra shade tabs with dif-ferent hue/chroma can help determinecorrect colour selection.

• The indication of the shade tab (whatcolour) should be included within the pho-tograph. In Figure 10, only the A2 shadeguide is visible so Figure 11 is ideal.

• Avoid light reflection as much as pos-sible. Figure 11 shows a lot of reflectionon the shade tab that makes selectingthe colour difficult. Figure 10 shows thecorrect amount of light reflection. This

can be achieved by tilting or twistingthe position of the shade tab slightly.Including the gum shade guide makes

the background (the property of the shadetab) and the matching dentition similarwhich helps selecting the correct huearound the cervical third.The healing cap was removed and the

internal configuration of the implantrinsed thoroughly to remove any residualblood or tissue material.It is the author’s opinion that impres-

sions taken at the implant level can offerseveral advantages:• The quality of prosthetic planning andtreatment can be enhanced;

• Implant angulations can be compen-sated for at an early stage;

• Individual anatomic designs can be per-formed through abutment selection andpreparation or through customisedcasting or milling of the abutment.An open tray impression technique was

selected for the impression procedure.Figures 13 and 14 illustrate the implantpick up (or impression coping) inserted toallow for a fixture level impression util-ising an open tray technique.


Figure 9. Healing caps in situ followingconfirmation of osseointegration.

Figures 10 and 11. Examples of shade taking procedure.

Figure 12. Healthy and non-inflamed gingival architecture following removalof the healing caps.

Figure 13 and 14. Implant pick up (or impression coping) inserted to allow for a fixturelevel impression utilising an open tray technique.


March/April 2011 eLABORATE 35


Seating the implant pick-upThe appropriate implant pick up (orimpression coping) was selected andseated securely into the implant.Care is taken to ensure that the internal

hex is correctly engaged before tighteningthe implant guide pin with a hex screw-driver using light finger force.A Directed Flow Impression Tray (3M

ESPE) was prepared with perforations onthe occlusal surfaces of the tray to allowthe implant impression pick-up to pene-trate the tray without any interferences.The prepared penetrations are then cov-ered with wax, which is penetrated by theimplant coping when the impression pro-cedure is undertaken.

Taking the impressionA Polyvinyl Siloxane (PVS) impressionmaterial was selected for the fixture levelmaster impression. Kerr’s Take 1 AdvancedLight Body Wash (low viscosity) andMedium/Monophase (medium viscosity)was syringed around the implant pick up andthe impression tray was filled with Kerr’s®

Take 1™Advanced Heavy Body Tray (heavyviscosity) material with a thin overlyingwash of the light body wash material.The rationale for the utilisation of the

PVS material of differing viscosity is toacquire an accurate reproduction of the softtissue and adjacent teeth contours afforded

by the greater flow of the low viscositywash material. The heavy and mediumviscosity material ensures adequaterigidity within the impression material tominimise or eliminate any potential move-ment of the impression coping duringimpression removal and when the implantanalog is fitted and models are poured inthe laboratory.Any potential movement or dislodge-

ment of the impression copings can also befurther minimised by linking the copingswith a pattern resin material such asDuralay (Reliance) or Pattern Resin (GC),a technique which was not employed inthis case.The tray is then seated ensuring the

Guide Pin of the impression coping ispenetrated with wax. Figures 15 and 16show the completed fixture level impres-sions stabilising the guide pins andaccurately capturing the details of theexisting maxillary dentition.

Removing the impressionOnce the impression material has set, theGuide Pin is loosened and completely dis-engaged from the implant beforeremoving the impression. The impressionis then checked for correct and stableretention of the implant pick up.The implant fixtures were then copiously

irrigated and a gel of 0.12% Chlorhexidine

(Curasept, Curaden Swiss) placed into theimplant housing before the healing capswere repositioned and hand tightened.The appointment was then completed

with the impression of the opposing denti-tion and the registration of all necessarybite records.The master fixture level impression, the

opposing impression, the bite recordsalong with the lab prescription and digitalimages were then sent to the ceramist toallow the laboratory phase of the treat-ment to be completed.

Laboratory ProcedureAtlantis AbutmentAtlantis abutments are CAD/CAMcustom abutments with two piece compo-nents that are individually designed fromthe final anticipated or proposed shape ofthe implant retained restoration (i.e. thefinal shape of the tooth).The design process which is accom-

plished utilising the unique Atlantis VAD™

(Virtual Abutment Design) software, allowsthe Atlantis abutment to be digitallydesigned with the ideal bucco-lingual,mesio-distal and inciso-cervical dimensionsbased on the surrounding dentition andopposing occlusion (Figures 19 and 20). It’scompatible with Lava Scan ST so anyaccredited Lava Design Centre is capable ofscanning the abutment (Figure 18).

Figure 15 and 16. Completed fixture level impressions. Figure 17. Fabricated working modelwith gum replica.

Figure 18. Lava Scan ST. Figures 19-20. Atlantis Abutment web order design stage.




The final abutment is then precisionmachined (Figure 21). For this case anAtlantis GoldHue™ Titanium Abutment isselected which has a lifetime warranty andenables the desired aesthetic outcome.Using custom designed abutments instead ofstock abutments offers several advantages:• The possibility to create an optimalemergence profile of the abutment sup-porting long-term aesthetics both forthe soft tissue and the final restoration.

• The abutment design provides optimalsupport and retention for the finalrestoration and at the same time, reducescosts for expensive framework materialsuch as gold alloys. Atlantis Abutmentsare available in the following materials;titanium, gold-shaded (GoldHue) tita-nium (tin coated) and zirconia.

• In screw retained restorations, the marginor the interface of the final restorationand abutment can be placed at a hygieni-cally maintainable level. This may be anadvantage in reducing or eliminating therisk of chronic gingival inflammationwhich has been attributed to the presenceof a microgap beneath the gingival level,left by the use of screw retained systems.(Keller 1998, Lindhe 1998).

• In cement retained restorations, marginscan be placed at a level where there isan easy and safe removal of excessivecement, eliminating peri-implantitiscaused by remaining cement.

Fabrication of Lava Zirconia with screw channelConsidering the longevity of restorations,well supported coping design is essential.Double scanning is a must in most cases,especially in the posterior region. Func-tional cusps and marginal ridges are wherethe most support is necessary as that iswhere the occlusion is and prevents poten-tial chipping of veneering porcelain.An accredited 3M ESPE Lava Milling

Centre creates the screw channel in thezirconia coping at green stage using thebur (Figure 25). In order to make an indi-cation, where to put a whole through, acollar needs to be created prior to scan-ning in wax and communicated with themilling centre (Figure 23). It is ideal tohave any force/pressure exerted by theconical head of the screw to be on the zir-conia framework, not the veneeringporcelain. The depth of the collar is deter-mined based on the position of theabutment, final position of the restorationsand the length of the screws. A spru wax(3-4mm in diameter) can be used to createthe base of the screw channel. In this casea pressed spru is used to make a definedcircle for better indication (Figure 24) sothe milling centre can put a hole throughexactly in the middle of the circle, whichis the centre of the zirconia collar. Figure25 shows the completed Lava zirconiacopings with screw channel.

Cross pinning techniqueFigure 27 shows a ‘must have tool’ in orderto process the cross pinning technique. Tocreate a thread within the titanium abut-ment to secure the screw there are a fewsteps to go through.5

Step 1: Set the handpiece speed at 8,000rpm. Take Bur #33000660 and make adimple in the position where you want todrill (Figure 28).Step 2: Apply the special Bredent Millingand Drilling Oil (Figure 29). With Bur#3300063 drill a hole where you havemade the dimple (Figure 30). It is impor-tant that the drilling path aims towards thecentre of the abutment to avoid creating anoval shaped hole, which would end up cut-ting a thread on two faces only.Step 3: Blow out the hole with air, cleanthe area of metal filings, etc.Step 4: Use a generous amount of oil duringthis stage. Insert the tapping tool markedM1.4V #33000671 into the holder andplace a drop of oil into the hole and a droponto the tap. Holding the instrument withtwo fingers only, tap the hole gently. In aclockwise motion, screw the tap in 180°. Thenstop and unwind it 90°. Add a drip of oil andtap in a clockwise direction again another180°. Unwind 90° then tap another 180° andso on until you are through. Marking a dot onevery 90° is advised so that the position canbe easily determined. Unwind the tap (Figure31), then steam clean the metal filings.

Figure 21. Completed Atlantis GoldHueTitanium Abutment.

Figure 22. Completed GoldHue on Model. Figure 23. Support wax-up with collar forscrew channel.

Figure 24. Lava Zirconia scanning stage. Figure 25. Oversized kit for Lava MillingCentre (Bredent from Binder Dental).

Figure 26. Completed Lava Zirconia copings.



Figure 27. Drilling and Tapping Kit (Bredent, Binder Dental).

Figure 28. Making a dimple on the abut-ment, Bur #33000660

Figure 29. Applying Bredent Miling andDrilling Oil.

Figure 30. Creating a screw channel onthe abutment with Bur #3300063.

Figure 31. Tapping. Figure 32. Completed Lava Zirconia cop-ings with cross-pinning technique.

Figure 33. Completed restorations. Figure 34. Blocking out the undercut andapplying Pattern Resin (GC).

Figure 35. Completed Transfer Jig on the Model.

Fabrication of transfer jig and abutment installationIn general, dental implant abutments aredesigned to accommodate the final restora-tions in only one position, especially whenthe custom abutment is used. As internalhex is designed to accommodate abut-ments in several different positions, alaboratory fabricated transfer jig should beused to ensure correct seating and orienta-tion of the abutments.To fabricate the jig, the abutment has to

be screwed onto the correct position usinglab screws which have been secured on asolid model, not on a sectioned model.Then block out all the undercuts with den-ture wax placing a spru wax in the accesshole of the abutment to allow the abutmentscrew to be screwed into the implantthrough the jig in the mouth. Apply a gen-erous amount of Vaseline as a separatorthen apply a reasonable amount of non-

shrinkable acrylic resin material such asPattern Resin (GC) (Figure 34). Once it’sset, trim up and polish using pumice inlow speed. Figure 35 shows the completedtransfer jig on the model.The following components were then

delivered back to the clinician for the com-pletion of installation of the restorations:• Custom milled Atlantis Abutments withthe corresponding abutment screws;

• The finished LAVA Zirconia metal freecrowns;

• The transverse screws;• A transfer jig to facilitate the accuratetransfer of the abutments from themodel to the implants intra-orally.

Abutment installationThe customised Atlantis Abutments wereseated using the transfer jig ensuring cor-rect seating and orientation of theabutments. The abutments and screws

were then inserted and manually tightenedusing a hex screw driver (Figure 36). Thetransfer jig was then removed and the cor-rect positioning of the abutments werealso confirmed visually by trying in theLAVA crowns individually and ensuringthat the transverse screw channel on thecrowns lined up with the tapped channelon the Atlantis Abutment.The two LAVA crowns were then seated

and tried in simultaneously and the routineprocess of checking the marginal integrityof the restoration, abutment interface andinterproximal contacts carried out. Theprocess was completed by checking theocclusion in both centric articulation andprotrusive movements.

Final tighteningOnce the verification and any necessaryadjustments were completed, the abut-ments were tightened to the prescribed




torque using the hex screw driver andtorque wrench. In this case, both the abut-ments were torqued to 25Ncm2 which is theindicated tightening torque by Astra Tech.The abutment access is then closed using

polytetrafluoroethylene (PTFE) tape to sealthe screw access channel to protect thescrew head of the abutment as describedby Moraguez et al.6 The tape will easily

facilitate future screw access, and findingsproved a lesser bacterial contaminationmanifested by bad smells (Figure 39).In addition to the protocol described, a

further seal of 3M ESPE Cavit™ was alsoplaced once the PTFE tape was insertedand tamped down with a cotton pelletmoistened with chlorhexidine solution(BISCO Cavity Cleanser™).

Installation of final crownsThe 3M ESPE Lava crowns were thenseated and the transverse screw insertedinto the palatal screw channels of therestorations. The transverse screw was thenmanually tightened with the Bredent Trans-verse Screw Driver Tip fitted to a Biomet-3iContra Angle Torque Driver (Figure 40).The use of this mechanism allowed thetightening of the transverse screw to bedone outside the confines of the oral cavity.Blanching of the surrounding tissues was

observed following immediate completionof the insertion process. However, theblanching resolved after a period of 5-10minutes negating the need to either adjustthe contours of the restorations or to incor-porate a releasing incision to reduce thepressure exerted by the restorations on thesurrounding soft tissues.The final check and any adjustment of

the occlusion were then carried out withthe patient in an upright position. Oncecompleted, all necessary hygiene and postinsertion instructions were relayed to thepatient before completing the restorativedelivery appointment.The final images demonstrate the inte-

gration of aesthetics and function of thetransverse screw retained Lava Zirconiacrowns (metal free) with the patient’s den-tition (Figures 42 and 43). The one monthreview also revealed resolution of anyresidual blanching of the surrounding softtissues that was present immediately fol-lowing the placement of the restorationsand the development of ideal periodontaland soft tissue architecture and health.In summary, the use of 3M ESPE Lava

Zirconia metal free restorations retainedto the implant abutment with the use of transverse screws (cross-pinning) pro-vides a viable alternative to traditionalceramo-metal screw retained restorations,when retrievability and aesthetics aredesired parameters for the success of thepresenting case.

AcknowledgementThe authors would like to thank Dr AdamRosenberg for an excellent implant fixtureplacement as well as Precise DentalMilling Services for their consistent highquality Lava Zirconia copings. We thankour article sponsors 3M ESPE and AstraTech as well as the Smile by Yugo team fortheir assistance with this article. Greatteam work all round guys!


Figure 36. Transfer Jig in the mouth. Figure 37. Installed and torqued AtlantisAbutments from the occlusal view.

Figure 38. Installed Atlantis Abutmentsfrom the buccal view.

Figure 39. Inserted PTFE tape providingan easily removable ‘seal’, should retrieval of the abutment be necessary.

Figure 40. Bredent tip inserted on a Biomet-3i Contra Angle Torque Driver.

Figure 41. Biomet-3i Contra AngleTorque Driver Kit.

Figure 42. Completed restorations (imme-diate) from the palatal view demonstrat-ing the transverse screw configuration.

Figure 43. Completed restorations (immediate) from the occlusal view.



About the authorsDr Andrew Chio graduated from the Uni-versity of Melbourne with first classhonours in 1995. He currently maintains aprivate general practice in the Melbournesuburb of Carnegie where the emphasis ison rehabilitative and aesthetic dentistry incombination with general and preventiveneeds. He has completed numerous cur-riculums and CE programs from all fieldsof dentistry with strong influences from thephilosophy and teaching from the LasVegas Institute of Advanced Dental Educa-tion (LVI), Pascal Magne and Carl Misch.

Yugo Hatai is a Master Ceramist and recog-nised as one of Australia’s most talenteddental technicians. His ability to recreate anatural tooth with his artistic flair and hispassion for creating beautiful smiles havechanged many patient’s lives and hasearned the respect of leading cliniciansacross the globe. Yugo has publishednumerous articles nationally and interna-tionally including articles in LVI Visions,the European Journal of Esthetic Dentistry

and QZ (Quintessenz Zahntechnik). Yugo’slecturing began in 2008 presenting 3MESPE Lava which was a great success aswell as at the NZIDT National Conference.Yugo has the ability to satisfy the demandsof leading clinicians in all areas of restora-tive work whilst always challenging newtechniques and product selection, and inMarch 2010 Yugo was selected as the onlyAustralian leader for the 3M ESPE GlobalDental Technician Opinion Leader Group.Yugo established Smile By Yugo in 2008 tocreate a space to fit his vision to fuseFashion and Art into dentistry in the com-plex area of aesthetic dentistry whilstmaking restorative work look as natural aspossible. In 2011, following the successfulgrowth of Smile by Yugo, he establishedSchool of Yugo, an innovative trainingfacility organization and presents a MasterCeramist Course with 60 CPD. Yugo is amember of the American Academy of Cos-metic Dentistry (AACD) and has alsocompleted numerous dentist and technicianLVI courses being the most qualified LVItechnician in Australia.

References1. Chee W, Felton DA, Johnson PF, Sul-livan DY. Cemented versus screw-retainedimplant prostheses: which is better? Int JOralMaxillofac Implants 1999;14:137-141.2. Gervais MJ, Wilson PR. A rationale forretrievability of fixed, implant-supportedprostheses. A complication-based analysis.Int J Prosthodont 2007;20:13–24.3. Michalakis KX, Hirayama H, GarefisPD. Cement-retained versus screw-retainedimplant restorations: a critical review. Int JOral Maxillofac Implants 2003;18:719-728.4. Gervias MJ, Hatzipanagiotis P, WilsonPR. Cross-pinning: the philosophy ofretrievability applied practically to fixed,implant-supported prosthesis. AustralianDental Journal 2008; 53: 74-82.5. Bartels T. Zirconia bridges: Retrievableand aesthetic. eLABORATE 2010 Vol 7,No 2 Mar/Apr; 50-51.6. Moraquez OD, Belser UC. The use ofpolytetrafluoroethylene tape for the man-agement of screw access channels inimplant supported prosthesis. J ProsthetDent 2010 Mar;103(3): 189-91.



Documents

Case report: Restoration of 2 Astra Tech implant fixtures ...of a ceramo-metal transverse screw retained prosthesis. The possibility now exists to allow the final restoration to be