Digital Workflow - Finalisation of the Definitive Rehabilitation

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Fast, simplified and accurate planning

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AND  

  Finalisation of the definitive rehabilitation I n our first two articles on this Full Digital Workflow Case (published in DT issue 136 and 137) we covered the implant planning and placement phases as well as the primary and secondary phases of temporization using a full digital workflow including optimized scan strategies and 3D printing. In this third article, we will discuss the design and fabrication of the definitive restorations in lithium disilicate and zirconia, demonstrating the advantages of the digital workflow for fast, simplified and accurate planning.

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  1a

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Figs. 1a & b: It was decided that the printed secondary phase provisionals would serve as a basis for the design of the definitive restorations

 Following a period of 3-months to allow the healing of the gingival tissues and development of the emergence profiles around the implant fixtures and the tooth 15 pontic sites, t he f inal phase of conver ting t he provisionals to t he def initive restorations was undertaken. No addition or adjustments were required to the contours developed by the provisional implant restoration at tooth posititions 11 and 21 during the 3month period.

A decision was made, with the patient’s approval, to replicate the aesthetics of the second phase printed provisional restorations (figs. 1a & b). In addition, the occlusal scheme tested in the provisional phase and providing for a mutually protected occlusion was also to be replicated on the definitive rehabilitation.

The master digital impression was then completed utilising the “MAK optimized scan path” as described in detail in part two in this series of articles (Dental 

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Technologies issue 137). The full series of digital scans were then sent to the ceramist along with all the pertinent laboratory prescription and digital shade images necessar y to complete t he def initive restorations in this rehabilitation.

The “second phase” provisional restorations were then re-cemented using a provisional cement (for natural tooth abutments) and re-inserted and torqued to the manufacturer’s recommendation (for implant-based provisionals).

The final goal of the rehabilitation was to restore the natural anterior teeth with bonded lithum disilicate based restorations. A monolithic Zirconia crown was utilized to restore tooth 24, the endodontically-treated upper left premolar. Screw-retained layered Zirconia restorations bonded to ti-bases were planned for the restoration of the single unit implant restorations and the 3-unit implant supported bridge on the upper right quadrant.

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Compromises to the minimum thickness in the temporary or provisional restorations due to the shape of the Easy Temp Abutment

  CAD Design - 3Shape Dental Designer  Implant Components - Easy Temp Abutments (Biohorizons) - Custom Abutment (ZFX)  Ceramic Materials - IPS Emax Zircad Multi MT (Ivoclar-Vivadent) - GC Initial LiSi Press (GC Corporation)  Cement - Multilink Hybrid Abutment HO0 (Ivoclar-Vivadent) 

 The simplicity of the final ceramic fabrication comes from the prior digital planning and the utilization of a full digital workflow. As there were no changes planned to the aesthetics, the anatomical shape of

the teeth and functional requirements from the temporary prosthesis, the redesign of the definitive restorations in the CAD software was not necessary.

Only minor changes to the work order made in the 3Shape Dental Designer was indicated.

➤ Changes to the CAD design done for the definitive restorations

The positions 11 and 21 have been changed to titanium custom abutments instead of using the Easy Temp Abutments (Biohorizons) that were used in the temp phase.

Due to the shape of the Easy Temp Abutment, there were some thickness compromises in the temp phase mostly in the palatal contours of the 11 and 21.

By using the Custom Abutment it is possible to maint ain suppor t for t he ceramic restoration, maintain the bond and maximize the thickness of the ceramic (fig. 2). 

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Ideal design of the custom abutments

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Emergence profile design for the abutment for the upper right and left central incisors

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The choice of custom abutments was also driven by the necessity to narrow the emergence profile of the restorations, which will, in turn, maximize the tissue stability and improve the emergence profile of the implant retained restorations (fig. 3).

In addition, as the ceramic is cemented to the titanium abutment in the lab using Multilink Hybrid Abutment HO 0 opaque resin cement, clean-up af ter t he cementation procedure is not an issue (fig. 4).

Designing the margins subgingival by about 1-1.5 mm from all aspects is important to ensure that no metal is visible.

The posterior bridge extending from the upper right first molar (tooth 16) to the upper right first premolar (tooth 14) was milled using Zircad Multi (Ivoclar-

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Posterior implant restorations incorporating the same componentry utilized in the temporary prosthesis.

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Ideal proportions of the custom abutments

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Restorations ready for processing

Vivadent), a polychromatic, high strength zirconia, with careful attention to the connector thickness and design of the prosthesis.

This aspect is essential to ensure the strength and longevity of the implant retained fixed partial denture.

The restoration 25 was also made using Zircad Multi MT on an Easy Temp Abutment (fig. 5).

➤ Easy Temp Abutment (Biohorizons) The Easy Temp Abutments (Biohorizon) were chosen due to the simplicity of their use in the CAD design software. Differing heights of the abutment, starting with a height of 9mm, can be chosen within the CAD implant library to ensure that the ceramics that will be bonded to t he tit anium abutments will be adequately supported (figs. 6 & 7). 

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Planned rehabilitation mounted on a virtual articulator

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Figs. 9 & 10: The virtual model design was completed (in colour and monochrome) ready for 3-D printing

➤ Virtual articulator The planned case was mounted on a virtual articulator to ensure that any occlusal and pathway interferences were detected and eliminated (fig. 8).

It should be noted that the provisional or temporary prosthesis is the main functional test drive for the designed occlusal scheme of the prosthesis and any 

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alterations to the occlusion can be transferred to the final design through a surface or digital scan of the prosthesis after all adjustments in the provisional prosthesis have been finalised.

➤ Virtual model design The virtual model design was completed, ready for printing (figs. 9 and 10).

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Restorations prior to processing

 The posterior implant restorations were milled in ZirCAD Multi MT (Ivoclar-Vivadent). The milled zirconia restorations were then trimmed and cleaned ready for sintering. No pre-sinter staining was required.

The remaining Lithium Disilicate based restorations were milled in wax (fig. 11).

The millable wax is specially formulated to mill perfectly and to cleanly burn-out during the pressing process.

The wax restorations were then sprued and pressed using GC LiSi Press (GC Corporation). 

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Implant Abutments installed on the printed models

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Completed restorations installed on the printed model to allow finalization of the prosthetic rehabilitation

All the lithium disilicate-based restorations were fabr icated to full contour wit h a monolit hic configuration. No cut-back of the base material or layering with feldspathic ceramics was done.

The restorations were instead stained and glazed to mimic natural teeth utilising the Ivocolor Stain and Glaze system (Ivoclar-Vivadent). 

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 Printed models (fig. 12) were utilized for the final checks of the contacts, interproximal spaces and occlusal contacts. This also facilitated the finalization of the aesthetics and final form and texture of the restorations (fig. 13).

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Figs. 14 & 15: Defintive restorations on the printed model prior to insertion and cementation

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Figs. 16 to 18: Definitive restorations ready for finalization

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The printed models have metal analogs that are inserted, but the final fit of the implant restoration, especially in relation to the implant-retained bridge, should come from the CAD design and not the fit of the restoration on the printed model.

The restorations were then tried on the models and adjusted (figs. 14 and 15).

This is because the inserted metal analogs can have minor seating inaccuracies.

The restorations were given final preparations before fitting (figs. 16 to 18). 

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Figs. 19 to 21: Post-operative radiographs of the upper full arch rehabilitation immediate post insert

Following the removal of the provisional restorations (f ig. 19) and t he cleaning of t he natural toot h abutments, the try-in of the restorations was completed assessing the fit, shade, contacts and occlusion (in light centric occlusion) of the fabricated restoration The aesthetics of the case was also confirmed with the patient before the commencing the clinical cementation and insertion procedures.

All the Lithium Disilicate restorations were adhesively bonded to the natural tooth abutments with a universal bonding agent (G-PremioBond (GC Corporation) and a 

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resin-based cement. (G-Cem LinkForce (GC Corporation) using a selective etch protocol.

The implant-based restorations were inserted, and the abutment screw torqued to t he manufacturer’s recommendation. The abutment screw access was then sealed wit h PTFE t ape and a direct composite restoration bonded to the intaglio of the crown with a MDP-based primer and adhesive. An xray was taken to ensure the implant positions (fig. 20).

The final images show the finalised functional and aesthetic rehabilitation completed using a full digital

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Figs. 21 to 23: Full Arch Implant and Bonded Ceramic Rehabilitation – immediate post-operative

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3-month review indicating a stable functional, biological and aesthetic intergration of the upper rehabilitation

workflow, incorporating the use of a novel full arch scanning protocol, the “MAK optimized scan path” (figs. 21 to 24).

 This series of three articles on a full digital workflow case has demonstrated how we can harness digital technologies from the diagnosis and implant planning stages to the planning and fabrication of the definitive

restorations. The techniques used in this case allow both the surgery and the lab to simplify procedures, improve accuracy and the predictability of outcomes.

The validation of the printed temporary restorations on an aesthetic and functional level means that the CAD design can be reused as a blueprint for the definitives, requir ing only minor modif ications, as we have demonstrated in this article. 

By Dr Anthony Mak Dental Surgeon Dr Andrew Chio Dental Surgeon and Mr Brad Groblar Dental Technician 

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