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CAD/CAM - international magazine of digital dentistry

3-D technology opinion | 37CAD/CAM 2 2016 Anoptionforanimmediatecompleteupperdenture was offered but refused. The second option of an implant retained removable overdenture was re- fused as well. The option of a fully fixed screw- retained prosthesis retained by six implants was accepted. This is the "All-on-4" concept developed by Paolo Maló with the distal most implants being tilted to extend the A-P spread. Some unique challenges pertain to this case in- cluded an existing bi-maxillary skeletal protrusion, narrow dental arch form, a large gingival display whensmilingandacollapsedverticaldimension.All wereaddressedinthepreparationlaboratoryphase and during the surgical visit. A single lower central incisor in cross bite would be extracted along with a severely hyper-erupted, cariously involved lower right second molar and a hopeless lower left molar (Fig. 28). The treatment to be performed was out- lined with a definitive sequencing to be followed. All maxillary teeth would be extracted, and suffi- cient alveolplasty was estimated to hide the transi- tion zone of the prosthesis under the upper lip and remove pathology. The implant plan called for six maxillary implants to be installed and positioned based upon the proposed tooth positions. I anticipated that they needed to be placed palatally to the existing teeth and more upright based upon the 3-D imaging. The existing bone angulation was steep and had to be considered when placing the immediate im- plants. Alginate upper and lower impressions were obtained and the diagnostic casts were used to set up proposed tooth positions. Measurement of the amount of bone reduction were given to the lab to create a bone reduction guide. The bone volume was suitable for the placement of six im- plants in strategically determined sites. Tooth posi- tions determined where the screw access holes exited through the occlusa fossa or cingulum area. Due to the extreme angulations I anticipated some compromises would be necessary with the actual placements. A duplicate clear version of the immediate denture was used to facilitate the surgery. The occlusal scheme was arranged to re- duce stress on the immediate implants with cross arch stabilisation, anterior guidance, centric stops inmaximumintercuspation,andnarrowbuccallin- gual occlusal tables, with no interferences in lateral excursions. The lower molars were scheduled for extraction as tooth #18 was restoratively hopeless and tooth #31 was hyper-erupted, extensively de- cayed and left little vertical for an opposing tooth. Thelowerfirstmolarsweremissingandareplanned forreplacementandwillbedigitallyintegratedinto the treatment plan when the definitive maxillary prosthesis is finalised. All of the planning culminated in the surgical visit on January 29, 2016. Alex’s treatment required a collaborative approach, which included an oral and maxillofacial surgeon, restorative dentist (in this case me), dental technician and three surgical assistants working in tandem to complete all the necessary procedures. The entire afternoon was scheduled for this case as it would be necessary as part of the three phases of treatment to insert the fixed screw-retained provisional prosthesis as the final part of the visit. Major oral reconstruction ne- cessitated I.V. sedation to accomplish the extensive alveolplasty(Fig.29)andremovalofallthemaxillary teeth, lower molars and tooth #25. It took some time to remove all teeth that were scheduled for extraction and reduce many millime- tres of alveolar bone. Under my direction and with input from the lab technician, the OMS provided a base for six implants in the #3, 5, 7, 10, 12, and 14 sites. The most distal implants were placed in a dis- tally angulated manner to gain a wider A-P spread. This will provide more stabilisation and distribute the forces in the molar regions. We utilised a clear duplicate denture to visualise the crest and place the implants inside the labial crown positions. Each osteotomy site was under prepared to increase insertion torque and initial stability. Active implant are bone condensing as they are threaded into Fig. 27 Fig. 28 22016

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