Exploring novel technologies for improved efficiency

Dr Les Kalman

Tue. 8. August 2023

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For all dentists, it is a professional duty to provide safe, quality and competent oral healthcare to patients^.1 Clinicians strive to do this by learning new information, practising newly acquired skills and implementing new workflows. As digital dentistry continues to evolve and expand, dentists need to further explore various technologies, as it has become apparent that it is possible to maintain or elevate the standard of patient care.² Many dental technologies may provide superior accuracy,³ improved efficiency⁴ and an enhanced experience for the clinician and patient.⁵

The dental profession will also need to re-evaluate and modify workflows, in order to limit its carbon footprint and environmental impact.⁶ Employing technological workflows may result in a more sustainable approach to healthcare.⁷

Efficiency and sustainability can be negatively affected by inaccurate workflows. Consider the unfortunate event of a prosthodontic remake that is clinically unacceptable. This can be a challenging situation for both the patient and clinician to endure, as it results in an unproductive appointment, inefficient use of time and additional expenses.⁸ In addition, the environmental impact can be significant, owing to the non productive use of resources (e.g. electricity and disposable materials) and carbon emissions from both the patient commute and the return and delivery of the prosthodontic remake.⁹

There have been several developments in digital dentistry that have modernised workflows to improve efficiency, cost and the overall dental experience. There may also be additional efficiencies in terms of fabrication time, material requirements and cost. These factors may also help improve the overall sustainability of dentistry. This report will illustrate three technologies: 3D-printed zirconia anterior indirect restorations, a digital dental colour identification and communication app, and 3D-printed latticed zirconia implant bars.

Novel technologies

3D-printed zirconia

Zirconia has traditionally been used in the posterior region, owing to its high strength.¹⁰ Zirconia has recently experienced a resurgence as an alternative material for the anterior region, for use in veneers¹¹ and crowns owing to its strength, translucency, minimal preparation requirement¹¹ and the ability of layering material after milling.¹²

Zirconia is essentially milled through subtractive manufacturing. That is, the prosthodontic unit is fabricated from a larger piece of zirconia. The milling is completed with drills through a CAM workflow. This approach has been the standard, but may have disadvantages, especially in terms of sustainability.¹³

Fig. 1: Design for crown for tooth #11, facial view. (All images: Dr Les Kalman)

Fig. 2: Design for crown for tooth #11, lingual view.

Fig. 3: Design for crown for tooth #11, internal view.

Fig. 4: Design for veneer for tooth #22, facial view.

Fig. 5: Design for veneer for tooth #22, lingual view.

Fig. 6: Virtual patient crown case.

Fig. 7: Virtual patient veneer case.

3D printing, or additive manufacturing, was used for the fabrication of an anterior crown and veneer. The workflow involved using dental software (exocad) to digitally design a crown on tooth #11 (Figs. 1–3) and a veneer on tooth #22 (Figs. 4 & 5). The prosthetic designs were based on two separate patient cases (Figs. 6 & 7), which were part of a larger study that will be published in the near future. The patient models were originally scanned (Straumann CARES 3, Straumann), and digital files were subsequently created. The prosthetic designs were then sent to a facility as STL files and printed in zirconia.

Fig. 8: 3D-printed crown for tooth #11, facial view.

Fig. 9: 3D-printed crown for tooth #11, lingual view.

Fig. 10: 3D-printed crown for tooth #11, proximal view.

Fig. 11: 3D-printed crown for tooth #11, internal view.

Fig. 12: 3D-printed veneer for tooth #22, facial view.

Fig. 13: 3D-printed veneer for tooth #22, lingual view.

Fig. 14: 3D-printed veneer for tooth #22, proximal view.

The STL files were not subject to digital modification (the prosthetic units were printed directly from the STL files), and the designs were printed with a lithography-based ceramic technology (Lithoz) using LithaCon 3Y 210 ceramic material (Figs. 8–14). The powder composition of the material is 3 mol% yttria-stabilised zirconia, and the material has a reported four-point bending strength of 935MPa and surface roughness (Ra) of < 1 μm. The prosthetic units underwent de-binding and sintering and were delivered for in vitro evaluation. The crown and veneer were ordered as triplets (three prints of the same file), for assessment.

Fig. 15: Dental colour identification and communication software homepage.

There were no noticeable differences between the units, based on macrophotography. These units were also not stained or glazed, but this process will be explored in an upcoming investigation.

Colour identification and communication app

The assessment of dental colour or shade remains a challenge in dentistry. One study has indicated that the accurate determination of colour only occurs about 49% of the time in dental schools.¹⁴ Moreover, colour is often limited to that of enamel, there being little focus on mucosal colour, as related to full-arch prostheses. It must be stressed that the inaccurate determination of colour is inefficient and has a negative impact on sustainability.

A novel digital workflow using SmileShade (Fig. 15) was employed as a demonstration to identify and communicate the colour of the 3D-printed anterior prostheses. The software was activated on an iPad and paired with the wireless Bluetooth sensor. The sensor was placed over the facial surface of the crown and veneer (Fig. 16), and it recorded the colour and then transmitted the information back to the iPad. The process took approximately 3 seconds. Dental colour was expressed as an objective output in CMYK, RGB, LAB and HEX colour models and as a VITA shade (Figs. 17 & 18). The high dynamic range micro colour sensor has an automatic temperature control and interdevice repeatability of < 1ΔE. The software will also feature IPS e.max shades in future.

On the software’s data input page, the operator has the option of entering all pertinent data related to the project and/or patient (Fig. 19). The software combines this information and the colour identification data for complete colour communication (Figs. 20 & 21).

Fig. 16: Digital colour identification sensor.

Fig. 17: 3D-printed crown colour result.

Fig. 18: 3D-printed veneer colour result.

Fig. 19: Dental colour identification and identification software data input options.

Fig. 20: 3D-printed crown colour data set.

Fig. 21: 3D-printed veneer colour data set.

3D-printed latticed zirconia implant bar

Non-metal treatment options in implant dentistry have become increasingly popular,¹⁵ based on patient preferences and recent advances in materials and technologies. 3D-printed zirconia, the same material and process described for anterior indirect restorations, may also be employed for the fabrication of implant overdenture bars (Fig. 22). Moreover, owing to the nature of additive manufacturing, complex geometries can be incorporated into structural designs. Consequently, our current investigation explored the incorporation of a lattice structure into a 3D-printed zirconia implant bar (Fig. 23). With this approach, there is an opportunity to save material, time and cost, positively affecting efficiency and sustainability.

The same workflow as previously described was used for the latticed implant bar. An STL file was sent for fabrication (Lithoz), and several identical implant bars were produced by additive manufacturing (Fig. 24). These bars will be tested for fit and strength and published in the near future.

Fig. 22: 3D-printed zirconia implant bar.

Fig. 23: Lattice structure incorporated into a 3D-printed bar. (Image courtesy of ADEISS)

Fig. 24: Soft-tissue implant model, 3D-printed latticed zirconia implant bar and a compatible Ivotion (Ivoclar) complete mandibular denture.

Discussion

The 3D-printed crown and veneer were comparable in appearance to conventionally manufactured (milled) zirconia restorations (study in progress). The prostheses seemed very durable and fitted well with the model. Of particular interest was that the printed prostheses were nearly identical to the designs submitted, strengthening the need for accurate digital design. The 3D-printed implant bar demonstrated similar characteristics, and results will be published in the future. The colour identification and communication software provided a simple workflow and accurate and objective results. Further software modifications are in progress in a comparison study.

3D printing has made significant advances, especially regarding the fabrication of zirconia prostheses. The additive manufacturing workflow seems to provide significant advantages, in terms of material used, fabrication time, efficiency and cost,^{16, 17}all in a seemingly more sustainable approach.¹⁸ Similarly, digital dentistry provides a virtual workflow that saves time and cost and provides an improved experience for the clinician and patient. Subsequently, this results in a more sustainable approach to the delivery of treatment.⁶ Additional research is required to evaluate physical properties and clinical outcomes and to establish metrics to better understand the possibility of sustainability.

Conclusion

There are numerous technologies that are novel and innovative in dentistry. Clinicians and technicians should try to be open-minded in exploring and assessing these technologies and consider how their clinical workflow may be modified. Many technological tools not only maintain the standard of care, but improve accuracy and efficiency, elevate the dental experience and may have a positive impact on sustainability.

Conflict of interest

The author is involved with externally funded research to explore 3D-printed zirconia crowns, veneers and implant bars, through collaborative research with Lithoz. The author is the inventor and co-owner of the colour identification and communication software mentioned in this article.

Editorial note:

This article was published in digital—international magazine of digital dentistry vol. 4, issue 1/2023. The complete list of references can be found here.