Emergence profile inadequate. Note ledge as restoration emerges from implant
10.2 Restorative Space
Restorative complications such as material failure leading to repair or replacement of the veneering materials or complete framework fracture leading to failure of the entire prosthetic restoration
Changing the treatment plan from one restoration type to another to accommodate the space requirements
Neither of the above scenarios is ideal and can be avoided by good communication between the surgical and restorative team prior to implementation of the therapy. The clinician must evaluate whether the patient exhibits minimal, moderate or advanced resorption to determine the available restorative space and therefore the ideal type of prosthesis to be fabricated.
Monolithic full-contour zirconia-fixed restorations require 10 mm or more of space from the head of the implant to the opposing dentition.
Porcelain fused to metal/zirconia-fixed restorations requires 12 mm or more of space from the head of the implant to the opposing dentition.
Acrylic resin bonded to titanium fixed restorations will require 15 mm or more from the head of the implant to the opposing dentition.
Implant-supported over-dentures will require 16 mm or more of space from the implant to the opposing dentition .
10.3 Nature of Opposing Dentition
Another study focused on occlusal surface design using noble metals, feldspathic porcelain and acrylic . Type 3 and 4 gold alloy has been favoured as an occlusal material for stability of occlusal contacts and maintenance of the vertical dimension of the restoration. Patients however prefer tooth-coloured materials for the occlusal surface. Historically feldspathic porcelain has been the material of choice but over the last 10 years zirconia has been increasingly used on the occlusal surface. One concern has been the effect of zirconia on the opposing dentition. Laboratory studies have compared zirconia’s wear capacity to that of feldspathic porcelain and it was reported that zirconia was less abrasive to the opposing dentition than feldspathic porcelain . There is a paucity of data on this subject in vivo and further studies are required.
Maximum aesthetics with minimal staining over time with use of ceramics in the maxilla
Absence of reported, “clicking” by patients with opposing ceramic surfaces
Flexibility and resiliency in the system
Reduced costs (Fig. 10.7)
One disadvantage would be increased wear of the mandibular acrylic-based restorations. This can be considered a controlled failure and the patient must be made aware that the acrylic resin teeth will most likely need to be replaced every 5–7 years.
10.4 Aesthetic Demands
Similar aesthetics can be achieved when noble alloy and zirconia frameworks are used as a substructure. From an optical perspective both materials block the transmission of light and behave in a similar manner when evaluated aesthetically .
From an aesthetic perspective, ceramic-based restorations with either high noble alloy or zirconia frameworks are less likely to stain over time and result in superior stable long-term aesthetic results compared to acrylic resin bonded to titanium restorations. As mentioned above, ceramics should be considered for maxillary restorations and acrylic resin titanium in the mandible when full-mouth implant rehabilitation is completed.
10.5.1 Framework Cross-Sectional Area for Cantilevers and Around Screw Channels
The longer the cantilever the lower the load to failure
The smaller the connector size the less load to failure
Failure usually occurred in the distal abutment wall 
Limit distal cantilever.
Limit buccal cantilever.
Increase thickness of the framework in the cantilever section distal to the most distal implant.
Limit occlusion on the cantilever.
10.6 Ease of Fabrication and Passivity
The gold standard for fabrication of implant-supported restorations has been through traditional waxing and casting and then layering of feldspathic ceramics. The results achieved with these techniques have been predictable and successful . Cost has been one of the major reasons clinicians have moved away from traditional techniques and have started to use CAD/CAM technology in the manufacture of materials such as titanium and zirconia. These techniques provide a much more efficient workflow, and due to the efficiencies gained from these techniques tend to be less costly than conventional fabrication procedures.
Challenges with screw-retained frameworks have always been achieving passivity. Inaccuracies in fabrication of these frameworks can be traced back to the operator. Often inaccurate impressions and the subsequent technique in fabrication of the master cast have been to blame. Traditional distortions associated with the lost wax process and ceramic firing also contribute to the misfit .
Solutions to obtain passivity involve casting the framework in multiple pieces and soldering. Clinicians have also utilized cement-retained restorations with the lack in passivity being made up by the cement space. The clinician should be cautious in fabricating full-arch cement-retained restorations as this will not allow predictable retrievability . Another approach to achieve a passive screw-retained framework has been the use of the adhesive corrected implant frameworks where individual cylinders were cemented within the framework after it had been cast (KAL technique) .
CAD/CAM technology has eliminated a lot of variables in the fabrication process . An accurate impression, whether it be traditional or optically generated, is critical for an optimal outcome. The laboratory technician’s responsibility is to ensure an accurate pour paying specific attention to correct water powder rations and mixing the die stone with accurate water powder rations for a time specified by the manufacturer. Furthermore, due to the elimination of potential errors the overall workflow has been simplified by utilization of CAD/CAM, which allows frameworks to be produced in fewer clinical steps with less labour in the dental laboratory .
Acrylic resin bonded or milled to titanium
Milled cobalt chromium
Hybrid design with zirconia frameworks and individually cemented crowns (lithium disilicate or zirconia)
10.7 Acrylic Resin Bonded or Milled to Titanium
Bulk for strength
Adequate access for oral hygiene
Minimal display of metal
Retention for acrylic
Adequate space for acrylic resin
Adequate strength in the cantilever section
Attention to cross-sectional area