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3D Printing – Special Trays

The 3D Printing market is set to be worth $33 billion by 2023

It seems that every industry is finding uses for 3D Printers and the dental market is not alone.

For the last 10-15 years, orthodontic labs have been printing models to manufacture aligners and removeable appliances. General restorative labs have also made the switch to digital and seen the benefits. As with all technology, the printers have got faster, cheaper and shrunk in size.

In parallel to 3D printer development, the range of resins available has increased. Resin development can take longer than the printer development due to related factors such as cytotoxicity, biocompatibility and medical devices approval – the time frame for approvals can take years.

2018/2019 looks set to hot up even further. Let’s have a look at some of the traditional models/devices which can now be digitised:

  1. I think we all know that models can be printed whether it is a from an intraoral scan or even a scanned impression (this isn’t always successful). Not forgetting the design phase of course. We use ExoCAD Model Creator®.
  2. Retainers can be made from a 3D printed horseshoe – see above.
  3. Surgical guides or stents have normally been hand made by the technician. Now a clinician can take an intraoral scan and the technician can design the guide in a CAD package such 3Shape Implant Studio®.
  4. A clear Indirect Bonding Tray can be printed to aid the clinician in place the brackets for metal braces.
  5. Gingiva mask can be printed. It is a pink flexible material which can be used in conjunction with printed models.
  6. Temporary (Class 1) and Permanent (Class 2a) teeth can now be printed in various colour shades. There will surely be some impact on milled crowns in the future.
  7. Custom/Special Trays can be printed – whether from an intraoral scan, a scanned impression or a scan of a model.

In this article, we’d like to look at Special Trays and how they can be digitised for use in in fixed/removeable prosthodontics and implants.

With a removeable prosthesis, the aim of the special tray may be to enable the dentist to record the tissues in a particular state of displacement and improve the retention support and stability of the non-permanent denture.

For a fixed prosthesis, the special tray helps when there is an unusual distribution of missing teeth, or the arch form leads to uneven distribution of the impression material due to the stock tray being a poor fit. If the last tooth in the arch is to be included in the preparation, a special tray minimises ‘drags’ which might have appeared in the first impression. With loose teeth, a custom tray will enable a more fluid impression material to be used minimising suction and is still retained in the tray.

For implants, the special tray is used to achieve accurate fabrication of an implant-retained prosthesis. The impression needs to record an exact registration of the relative position and orientation of the implant in relation to other implants, teeth and soft tissue.

Normally, the clinician will take primary impressions using stock trays and send them to the lab for plaster models to be made and then a special tray to be fashioned. The special tray is hand made over the model and then sent back to the clinician to take a secondary impression.

The traditional process for making dentures is time consuming, messy and involves multiple stages. We are not going to cover all the stages as the reader is very familiar with this.

Forward thinking labs are looking to digitise processes where possible. One of the most labour-intensive areas is the prosthetic department.

The two commercial factors in determining whether 3D printing is viable for a specific device or appliance are time and cost. Custom trays can now be printed in less than 1 hour on a 3D printer at a cost of circa £2.00. So, now 3D printed special trays become a viable option.

How does the workflow change? The clinician will send the first impression tray into the lab. The lab will either scan the impression or more likely make a plaster model and then scan it. The technician will digitally design the customer tray, adding drain holes and a handle. Once the design is complete, it can be saved as an STL file and then transferred to the 3D printer nesting software. Usually trays are printed vertically with drain holes and a number of supports.

Structo are one of the fastest growing 3D printer manufacturers in the world. Their ground-breaking Structo DentaForm and OrthoForm 3D printers are designed solely for the dental market. Structo technology utilises their patented MLSA system which prints very fast yet has a large build plate.

                   

Structo DentaForm                 Craig Howlin, CEO at Sparkle and Richard Buckle, Research Director at Techceram

Structo had developed their Tray resin but were looking for a real-world application in order to conduct a market test. Coincidently, Sparkle Dental Labs in Bolton were making 30-40 special trays a day and looking to digitise the special tray process. So, Techceram joined up the dots and Sparkle Dental Labs became the first lab worldwide to print Structo Tray resin. Techceram’s technicians worked to write custom script to reduce the number of supports and apply drain holes. Structo Tray is a pink resin, so it has a natural colour which fits in well in the clinical environment. It is slightly flexible, so the patient has a more comfortable experience when the tray is in the mouth.

In terms of the impact at Sparkle, the results have been excellent. 7 trays can be printed flat in 1 hour or 12 hanging in 2 hours. After cleaning in IPA and then 10 minutes in a light cure unit, it is off to the technician for a final polish and then into the post (or delivery by driver) to the clinician.

Techceram have also introduced the NextDent 5100 Figure 4 3D printer which can print 2 flat trays in 30 minutes or 5 hanging in 1 hour.


Special tray printed using Structo Tray resin                 Special tray printed using NextDent Tray resin

If you are would like more advice about going digital and you are looking to bring traditional processes into the 21st Century, then please do not hesitate to speak to us on 01274 416664 or email us at info@techceram.com