Quintessence of Dental Technology 2017

Florin Cofar, DDS1

Ioan Cofar, DDS, CDT1

Lorant Stumpf, CDT2

Ioana Popp, CDT1

Alejandro Pineda, DDS3

Eric Van Dooren, DDS4

________________________

1DENTCOF, Timisoara, Romania.

2CDC Dental Laboratory, Carlow, Ireland.

3Private Practice, Lhasa, Uruguay.

4Private practice limited to prosthodontics, implants, and periodontal plastic surgery, Antwerpen, Belgium.

Correspondence to: Dr Florin Cofar, DENTCOF, 62 Simion Barnutiu Street, Timisoara 300302, Romania. Email: florin.cofar@dentcof.ro

RAW is a digital Skyn workflow that aims to copy intact teeth and transfer this information to dental restorations simply by using digital technology. During this digital workflow, the intricate dental morphology observed on an intact tooth is digitally acquired, duplicated, exported to a tooth to be restored, and preserved throughout the entire oral rehabilitation-from the diagnostic mock-up to the final restoration.

In digital design, the dental morphology and tooth shape seen by the dentist and technician are interpreted by the computer as a three-dimensional geometric mathematical model. Controlling the geometry provides freedom for the practitioner to develop a restorative digital plan that can be followed throughout the treatment of the patient. This article describes the novel concepts for treatment planning and execution in the digital era.

THE PATIENT DIGITAL CLONE (Fig 1)

Traditionally it takes several in-person patient appointments for the dentist to collect all the information needed to proceed with an esthetic treatment plan. These consultations require a significant amount of time and effort by the entire restorative team, which includes laborious hours spent developing wax-ups and putting together the treatment plan.

Fig 1 The digital clone.

The "digital clone" is a modern version of the consultation appointments, in which all data collected are synthesized and assembled digitally for treatment planning. Thus, digital medical and dental records are obtained, STL (STereo Lithography) files are generated by digitally scanning both dental arches, DICOM (Digital Imaging and Communication in Medicine) files are acquired through cone beam computed tomography (CBCT), and a photo-video protocol is produced. This combination of data produces the "patient digital clone," which eliminates the need for the patient to be present during multiple treatment planning sessions, and multiple appointments among different specialists, which would otherwise delay the treatment planning process.

The patient digital clone can be shared digitally among the restorative team, and all those involved are able to assist in real time to create a collaborative and ideal treatment plan. No boundaries exist among restorative dentist, dental technician, and all other specialtists (periodontist, orofacial pain specialist, endodontist, orthodontist), so treatment planning and delivery can be carried out more efficiently.

CREATING A SMILE LIBRARY (Figs 2 and 3)

If shape is geometry, dental morphology is also geometry. Evaluating natural dentition provides an unlimited library of possible tooth designs and teeth arrangements. Every tooth design created by nature is unique. The use of digital scanners (ie, TRIOS 3, 3Shape) allows us to create our own library of tooth designs. Once a patient is scanned, the arch scan can be segmented into individual STL files of each tooth to be restored using tools such as Ortho Analyzer (3Shape). The individual STL files can then be organized into smile libraries, using ScanIt library (3Shape).

Figs 2a and 2b Extracting morphology by segmenting with Ortho Analyzer.

Fig 3 Natural morphology library created using ScanIt library.

USING THE LIBRARY TO DESIGN (Fig 4)

With the RealView function (3Shape Dental Designer), the digital model (STL of the arch) can be aligned with the photographs of the patient. The initial design is made from a facially driven perspective, allowing real-time feedback from the team. Individual STL files are then imported from the digital library and positioned on the area to be restored, and the smile is designed using Smile Composer (3Shape). At any time it is possible to render a preview using the RealView function. Once the diagnostic design of the definitive restorations is finalized, it is added to the scan of the arch and the final STL file is exported for 3D printing to produce the digital mock-up.

Figs 4a and 4b Designing using natural morphology with RealView Function.

3D-PRINTED DIAGNOSTIC MOCK-UP (Figs 5 to 8)

The 3D-printed diagnostic mock-up is an essential step that allows the patient to evaluate the esthetics and give consent for the proposed treatment. However, the diagnostic esthetic design of the smile is generated over the existing dental conditions of the patient. Thus, patients should be informed that the mock-up might feel slightly bulky since it is placed buccally from the existing teeth. Once the patient understands this, the clinicians should videotape the patient before and after placement of the 3D mock-up in the mouth. Since in most cases the design is additive and may be perceived as slightly bulkier than the final restorations, it is always advised to present the patient using frontal photographs or videos. Only after the patient has accepted the diagnostic mock-up and formally agreed to the treatment plan should the restorative team be allowed to surgically intervene.

Fig 5 Transfer of 3D-printed design with silicone index and bis-acryl.

Fig 6 Painting the areas that will be removed. Diagnostic mock-up is used to get consent for the reduction that will follow.

Fig 7 Patient with diagnostic mock-up in place.

Fig 8 Intraoral view of diagnostic mock-up.

DIAGNOSTIC MOCK-UP AS A SURGICAL GUIDE (Figs 9 to 11)

The 3D diagnostic mock-up can be also used as a surgical template for esthetic gingivectomy or crown lengthening. In the clinical case shown, the mock-up ensures proper placement of the gingival zenith. Once the soft tissue is recontoured, as guided by the mock-up, the biologic width is modified using an ultrasonic diamond tip with a flat surface (CV Dentus) under copious water-cooling. The flat surface of the diamond tip allows, in some cases, flapless bone reduction without damaging the soft tissue. In this type of procedure, which is indicated for cases with thin buccal bone, the enamel preparation and scanning can be performed on the same day.

Figs 9a to 9d Soft tissue recontouring sequence. (a) Gingivectomy using diagnostic mock-up as guide. (b) Soft tissue removed. (c) Bone reduction. (d) Biologic width checked.

Fig 10 Situation after crown lengthening.

Figs 11a and 11b Rescanning the area of crown lengthening in a standard copy of the original scan.

FINAL MOCK-UP: PRESERVING THE GEOMETRY

The final digital design of the restorations should maintain the same geometry as the 3D diagnostic mock-up. The only difference is that the geometry of the final design is then revised over the prepared teeth. Thus, only the sagittal axis differs from the diagnostic design, since after soft and hard tissue recontouring and tooth preparation, the final digital design can be repositioned slightly more lingually and the emergence profile revised. At this stage, if the patient is videotaped from the front, the two designs (digital diagnostic and final designs) should look alike, since the geometry used is identical. The variation in sagittal axis between the diagnostic and final designs is translated into an increase in interproximal space and a proper emergence profile. These details are usually not perceived when the patient is photographed or filmed from the front.

FINAL MOCK-UP AS PREPARATION GUIDE (Figs 12 and 13)

While the diagnostic mock-up can serve as a tool for getting the patient's consent for treatment and as the surgical template, the replication of the ideal design intraorally is extremely important for tooth preparation. Ultraconservative preparations are made over the mock-up to ensure maximum preservation of dental tissues.

Fig 12 Using the design as a preparation guide (Aesthetic Pre-evaluative Temporaries, APT).

Fig 13 Final preparations.

3D-PRINTED ALVEOLAR MODEL (Figs 14 and 15)

The digital alveolar model is created from the preparation scan using 3Shape Model Builder. Separate colors can be used for the dies and for the base. Models are printed with a digital 3D printer (Formlabs 2 Desktop Printer). The precision observed in the 3D printing averages 25 microns and can serve definitively as a working model.

Figs 14a and 14b Rescanning the preparations in a standard copy of the original scan.

Figs 15a to 15c 3D-printed alveolar model.

DESIGNING THE RESTORATIONS: SCAN ALIGNMENT

One of the major challenges in the digital workflow is scan alignment. Lack of alignment can produce error...