All-digital workflow for implant-supported prostheses and natural teeth: technology for everyone?

The dissemination of free content and the sharing of experiences, perfectly combine one of our missions: Make Innovation Make Life Better, helping the entire dental community to approach digital with confidence and awareness.

Below is an interesting article by Dr. Francesco Mangano, whom the entire DGSHAPE would like to thank.

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Dear friends and colleagues,

Dr. Francesco Mangano DDS, PhD, FICD* * Associate Professor, Digital Dentistry, Sechenov University, Moscow, Russia. Editor of the Digital Dentistry Section of the Journal of Dentistry (Elsevier) Q1 journal with an impact factor of 4.3 and a cites core of 6.2. Founding Partner, Active Partner, and Member of the Scientific Committee of the Digital Dentistry Society (DDS) International. Director of the Mangano Digital Academy (MDA), an independent academy that aims to promote the teaching of Digital Dentistry. Author of 128 publications in international journals indexed in Pubmed with a high impact factor and an h-index of 40 (Google Scholar) and 31 (Scopus). He is a self-employed dentist in Gravedona (Como) and dedicates himself exclusively to Digital Dentistry.

Welcome back to DentalTech, Infodent’s section dedicated to the world of digital dentistry. In this issue of November 2021, we will again discuss the topic of #Fulldigitalworkflow. We will show you how a simple job can be completed using examples from our daily practice, thanks to digital technologies. This is the prosthetic completion of a surgical work that we had already presented at the DentalTech last May, entitled: “Guided surgery: a technology for everyone?  ”This time we will focus on the prosthetic restoration, which remains our main objective since this is what the patient asks of us. I firmly believe that with proper preparation and time spent on good training, digital dentistry could be easily applied daily by everyone and could make it easier to treat both simple and complex cases. I am also convinced that the subject is very important and that many aspects still need to be studied in-depth to be fully understood: scientific research is a great help, thanks to its mathematical approach. Enjoy your reading!

CLINICAL CASE #Fulldigitalworkflow FINALISATION OF THE PROSTHESIS_ FULLY DIGITAL_ A SIMPLE CASE: INTRODUCTION

In the last issue of DentalTech in May, we presented a clinical case of implants placed in the mandible, through a new method (Hypnoguide) with customized and laser-sintered titanium templates. As promised, we are now presenting the prosthetic development of the same case, with the entire workflow from the intra- oral scan to the delivery of provisional and definitive restorations. This is the finalization of the case in the mandible; in one of the next issues, we will present the implant and prosthetic rehabilitation carried out in the same patient, in the upper jaw. In this case, we opted for rehabilitation with monolithic restorations in translucent zirconia, both on the natural teeth and on the implants. The approach followed was that of #Fulldigitalworkflow and the #Modelfree protocol. Of course, this approach is only one of many: 3D printing is often indicated and is a valuable aid for dental technicians: physical models are still used today. But this does not detract from the fact that it is now possible to proceed in a fully integrated digital way.

 

CLINICAL CASE

The present case represents the prosthetic development of what was presented in the May 2021 issue of DentalTech.

Photo 2. Intraoral scanner with CS 3700® (Carestream). (A) Antagonist arch; (B) master arch with highlighted mucosal collars; (C, D) master model with screwed-in scanbodies.
Photo 1. Intraoral scanner with CS 3700® (Carestream). (A) Healing 2 months after implant placement, right hemimandible; (B) Healing abutments in the left hemimandible; (C) Scanbodies screwed in on the right; (D) Scanbodies screwed in on the left.

Two months after implant placement (Figs. 1,2), the patient underwent an intraoral CT scan (CS 3700®, Carestream Dental, USA). The scan for the implants included first the capture of the antagonist arch, then the master arch (where the fixtures are located) and the mucosal collars, after the removal of the gauze abutments, finally the capture of the bite (occlusion record), both on the right and on the left.

After the healing abutments are removed, an impression of the mouthguard (occlusal register) is taken on both the right and left sides.

Photo 3. CAD modelling (Exocad®) of individual hybrid abutments and temporary restorations on implants. (A) Abutments and temporary teeth on the right; (B) Abutments and temporary teeth on the left.

After careful verification of the goodness of the occlusion register, the area of the mucosal collars was highlighted and the scanbodies were screwed in. In this case, the implants (Anyridge®, Megagen, South Korea) provided for the screwing of 13 mm high scanbodies. It is essential to ensure that the position of the scanbodies and the coupling of the hexagons are correct. If there is any doubt, it is best to check by X-ray that the CT abutments are correctly inserted into the fixtures.  The STL files derived from the intraoral scan are sent to the dental technician who models in CAD (Valletta®, Exocad, Germany) a provisional and preliminary dental restoration to be adapted to the natural stumps of the frontal group, and the individual definitive stumps to be screwed onto the implants, with the corresponding provisional restoration (picture 3). The use of individual hybrid abutments consisting of a company-supplied titanium Tibase, onto which an individual CAD-modelled and milled zirconia abutment is placed, has clear advantages over the conventional alternative of a screw-retained superstructure.

Firstly, the interface with the soft tissues is managed through zirconia from the very first provisionalization: this allows a better tissue healing with the formation of an adequate biological seal, compared to what can be achieved when resins or PMMA are used in the emergence. Secondly, the individual hybrid titanium/zirconia abutment allows to manage the emergence anatomically better than the modeling of a screw-retained superstructure, in terms of volumes. The third and last aspect that should not be overlooked is that the individual hybrid abutment is permanently screwed onto the implant and is never removed. This prevents damage to the soft-tissue bond that has been formed when the temporary restoration is replaced by the permanent one.

This does not occur in the case of a screw-retained superstructure, where the removal of the temporary and its replacement with the permanent determines the inevitable loss of any mucosal seal. These advantages are important and are a good reason to go down a technically more difficult route, such as the individual abutment, which represents an extra interface to be managed in CAD. It is necessary to maintain rigorous precision with strict phase control to ensure a good clinical outcome in the medium and long term.

Photo 1. The DGSHAPE DWX-52D 5-axis milling machine is reliable, accurate, and easy to use, making it an ideal solution for dental laboratories that do not want to compromise on the quality of their production.

After milling the temporary PMMA dental restorations and zirconium oxide hybrid abutments on a powerful 5-axis milling machine (DWX-52D®, DGSHAPE, a Roland company, Japan), the abutments are sintered and cemented extra orally on a titanium bonding base in the laboratory. The dental restorations are then ready for delivery.

Photo 4. Application of temporary dental restorations on implants. (A) Zirconia stumps on the right; (B) Temporary dental restorations on the right; (C) Zirconia stumps on the left; (D) Temporary dental restorations on the left.

During the second appointment at the practice, we apply the temporary and preliminary dental restoration to the anterior group.

The latter is correctly modeled in CAD following the preparation of the teeth and the screwing of the various hybrid abutments onto the implants, with the cementing of the temporary teeth on top (Photo 4).

At the same time, the final impression is made using the double wire technique, in order to clearly show the margins of the prosthetic preparation, always using the same intraoral scanner.

This impression is also captured with the provisional teeth on already cemented implants, in order to give a definite occlusal reference, based on the initial intraoral scan study cases involving discrete chewing enhancement (in this case, the patient requested that the upper arch be treated at a later date, after completing the full rehabilitation of the lower arch) (Photo 5). It is important at this stage to use all available tools with the intraoral scanner.

A scanned image was then also captured, and already aligned with the previous one, with the anterior provisional tooth restoration in situ, already fitted and functionalized (Photo 6). This scan is useful for the dental technician to have anatomical and functional limits with which to model the anatomy of future permanent dental restorations. The dental technician can then model the final dental restorations on a natural stump, with simple monolithic crowns made of translucent zirconia (Photo 7). At the same time, it models the final dental restorations on the implants, without the need for further scans.

The ability to check the thickness of monolithic dental restorations in 3D is one of the great advantages of CAD (Photo 8).

As the protocol calls for a model-free process, it was considered appropriate to check the marginal closures, approximal fit, and occlusal contacts of the shapes of future final dental restorations, using 5-axis milled replicas (copies?).

The CAM software used for milling (Millbox®, CIMsystem, Italy) (Photos 9,10) was always the same and allowed the work to be carried out predictably and simply, guaranteeing absolute quality. Thanks to this software, it was possible to check the marginal closures, and the quality of the interproximal and occlusal contacts, it was also possible to make a monolithic translucent zirconia finish.

 

 

Photo 11. Monolithic translucent zirconia restorations cemented to natural stumps and implants. (A) Front view; (B) top view; (C) dental implant restorations on the right; (D) the temporary dental restorations on the left.

Cementing was carried out in detail, and the procedure was completed (Photo 11) with both the patient and the operator being fully satisfied.

Published on Infodent November 2021 – DentalTech section

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