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Guided Restoration Technology | White Paper

GUIDED RESTORATION TECHNOLOGY

INTRODUCTION

During the last decades, porcelain veneers have provided excellent aesthetic results in the treatment of the anterior stage, and their long-term success rate has been proven. At this time, different techniques and designs have emerged on the types of preparation in order to generate an adequate thickness for the restorative material (1–8).

The long-term result of porcelain veneers is directly related to the conservation of the enamel. Literature has shown that the presence or absence of enamel is critical and, as a result, the preser-vative preparation of the veneers is fundamental (1–8).

Porcelain veneers with a minimally invasive reduction are an ideal option, as long as the correct case planning is carried out, following the specific indications necessary for the use of this restorative procedure. The preparation of veneers can be guided by the surface of the existing tooth by means of calibrated drills, an imprecise technique that increases the risk of a more aggressive preparation and consequent dental exposure, or it can be based on the volume/anatomy of the desired final restoration (9, 10).

In 1999, Magne, et. al., proposed a method of preparation that includes the use of silicone keys to transmit the information of the diagnostic waxing. They are used in vestibular, book-shaped with or without support in the adjacent teeth, and in palatal to control the reduction of the incisal edge. Although the clinician can evaluate the position of the future restoration using this method, the procedure has limited precision and is sensitive to the technique, especially since silicone is a flexible material. Plus, the limited visibility through the silicone indexes never lets the clinician observe 100% of the preparation surface (10, 11).

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In 2003, Gürel described aesthetic pre-recontouring temporaries (APT), which consist of the development of a direct or indirect mock-up. After checking again, the parameters related to aesthetics, function, and phonetics, the preparation is done on this APT. The clinician can use the mock-up to verify if more volume of material can be added to achieve a more conservative preparation.

The APT method allows a faster and more conservative preparation that is guided by the position and final anatomy of the restorations. With it, the clinician can evaluate aesthetics, function, and phonetics in situ, before the preparation of the final restorations. That means the clinician does not need to be concerned about teeth alignment, since the preparation will be done individually according to the positioning of these in the arch in relation to the future veneers.

In cases where there are protruding teeth that compromise the passive adjustment of the silicone key, a meticulous reduction must be made. However, the APT has some limitations, such as subtractive cases that require a prior reduction before the simulation can be performed. And, many times before finishing the vestibular preparation, part of the mock-up can be detached. For this reason, a combination of the two techniques—silicone matrices and APT—can be a good solution to overcome some of the limitations described (9-13).

The introduction of digital technology has opened a range of possibilities and workflows, shortening work time and even reducing the cost of veneer fabrication.

In addition to allowing the development of digital diagnostic waxing totally guided by the anatomy of the patient, CAD/CAM design software permits the laboratory technician and the clinician to verify the space needed for the future restoration during the design phase. The technician can readjust the digital waxing easily and efficiently, ensuring the proposed design is as conservative as possible without compromising the aesthetics and/or periodontal health. This digital form clearly increases efficiency, accuracy, and predictability.

The incorporation of 3D-printing technology has brought about the development of new designs of rigid preparation guides that allow clinicians to overcome some limitations of the silicone matrices, such as their flexibility. There are no doubts about the advantages offered by digital technology in the development of diagnostic waxing, as well as 3D-printed guides to control the preparation of the veneers. Despite these benefits, the preparation still depends, to a large extent, on the manual skills and experience of the clinician.

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“THE INTRODUCTION OF DIGITAL TECHNOLOGY HAS OPENED A RANGE OF POSSIBILITIES AND WORKFLOWS”

FirstFit® is the first digital-guided preparation system. It uses its own software, which takes into account the digital diagnostic waxing of the final restorations, making it able to generate preparation guides that will achieve the adequate thickness to accommodate the final restorations. The design of the preparation considers the restorative material, substrate color, and expected final color.

The FirstFit system is similar to the implant-guided surgery systems that currently exist, which allow generating a sequence of printed guides in 3D for a guided veneer preparation. In fact, in selected cases, the FirstFit technique permits the final restorations to be produced before preparing the teeth, eliminating the need for temporary restorations. The system generates guides with a special coupling for the FirstFit handpiece in order to fully control the preparation of the veneers. This means the clinician can prepare the teeth exactly as planned digitally.

The objective of this article is to describe the technique of digitally guided preparation of veneers with the FirstFit system and its indications.

TECHNIQUE The FirstFit system operates on two different workflows. In the one-step methodology, the final restorations take place before the preparation of the teeth for the veneers. For this, after a first visit, the doctor would only have to take final impressions and complete the photographic protocol together with the laboratory order. This approach is indicated especially when the interproximal areas and the cervical third of the teeth to be restored do not need any preparation. Another possibility for the one-step technique, in cases where it is necessary to create an axis of insertion and/or space in the cervical areas, is to remodel these areas by a hand drill, being careful to stay within the limits of the enamel and thus, avoid the need of temporization to subsequently take definitive impressions and send the information to the laboratory. After this, the laboratory provides the preparation guides, along with the veneers, in such a way that the dental preparation and the veneer cementation will be carried out in the same visit.

The two-step approach includes a phase where the teeth are prepared using the FirstFit preparation guides and then the interproximal, cervical, and margins are prepared freehand, according to the needs of the case and the preference of the clinician. After the dental preparation final impressions must be taken in analog or digital form and sent to the laboratory. The laboratory supplies provisional ones (printed or milled) or a conventional silicone key according to the previous mock-up and the digitally planned preparations. Then, in the second phase, the final restorations are cemented.

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CLINICAL CASE A patient came into the clinic for purely aesthetic reasons. A radiological, periodontal, and complete occlusal examination was performed. Prints were taken with polyvinylsiloxane, and photographic and video documentation was made for a complete orofacial study and for treatment planning.

In aesthetic analysis, it was revealed as an inverted incisal curve and diastema, a clinical situation that could be easily corrected by restoration with porcelain veneers (Figure 1). The photographic records, together with the STL files resulting from the scanning of the models, were sent to the laboratory/planning center (DSD Planning Center, Madrid) to perform a diagnostic waxing for veneers of the second premolar to second premolar of both arches.

The integration of 2D photography with the 3D file allowed a facial integration of the digital diagnostic waxing for the evaluation of the aesthetic parameters of the model before 3D printing of the model, increasing predictability and efficiency (Figure 2). The use of algorithms and digital natural forms simulated naturally occurring imperfections, so important for the integration of mouth restorations (14) (Figure 3).

In a second optional appointment, starting from a printed model (FormLabs2), a silicone key was made and brought to the mouth for the mock-up (Figure 4). This worked like an essay of the final restorations, using a resin bis-acryl type, to verify if all the aesthetic, phonetic parameters met the patient’s expectations, as well as to verify if some functional aspects, such as overbite and overjet, were addressed (Figure 5).

Figure 1. Preoperative situation that reveals the inverted initial curve and diastemas in the upper arch.

Figure 2. 2D/3D Facial Integration

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Once the design of the future restorations was approved by the patient, the STL files of the preoperative models and the diagnostic waxing were sent to the VIAX Lab.

Using a proprietary CAD software, a team of dentists and designers considered the final restorations, and the BL3 intended color determined the ideal preparation of each of the teeth to be restored (Figures 6a & 6b). The same software generated the design and sequence of the printed guides in 3D for a guided veneer preparation (Figure 7). The restorations were printed in injectable resin, and lithium-disilicate porcelains (E-max®) were used to produce the final veneers.

Figure 3. Jan Hatjo natural forms

Figure 4. Prototype of the model of the diagnostic waxing

Figure 5. Mock-up

Figure 6 a & b. Software Cad Viax®

Figure 7. Sequence of FirstFit® preparation guides

Figure 8. Turbine of FirstFit® system

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At the third appointment (second, if a mock-up was not physically performed), the teeth were prepared with a turbine specially designed for the FirstFit, which was attached to the guides (Figure 8). A sequence of six guides was used to complete the preparation in a minimally invasive way without margins (vertical preparation type). The guides allowed control of the enamel thickness, which was reduced precisely according to the digital plans (15, 16).

Once the preparation with the guides was finished, the veneers were tested with a flexible, 3D-printed positioning splint specifically designed to aid in the manipulation and settling of the restorations (Figures 9 a–d). This splint facilitated the preparation during engraving of the porcelain with hydrofluoric acid for 20 seconds. The restorations were cleaned subsequently with orthophosphoric acid and an ultrasonic bath with isopropyl alcohol for 4 minutes (Figures 10a & 10b). Then, silane was applied and the veneers were saved until the time of cementation.

For dental conditioning, the pieces were etched with orthophosphoric acid for 15 seconds and rinsed for the same time. Then, Adhese One F Vivapen Adhesive (Ivoclar Vivadent®) was applied according to the manufacturer’s instructions and photopolymerized with light for 15 seconds (Figure 11).

The Variolink Esthetic Light Resin Cement (Ivoclar Vivadent®) was applied, and, with the help of the positioning splint, all of the veneers were placed in position at the same time. Once placed, all of the remaining material was cleaned with a fine-tipped brush to subsequently polymerize each veneer in a single point on the vestibular. The Light Probe Pin-Point Tip (Ivoclar Vivadent) allowed the excess cement to be removed without causing its displacement (Figure 12).

Figure 9c. Definitive preparation with FirstFit® guide

Figure 9d. Positioning splint

helps keep the veneers in place

Figure 9 a & b. Sequence of FirstFit® preparation guides

Figure 10 a & b. Positioning splint facilitates the engraving of the veneers

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“THE PORCELAIN VENEERS HAVE PROVIDED EXCELLENT AESTHETIC RESULTS IN THE TREATMENT

OF THE PREVIOUS SECTOR”

After each veneer was photopolymerized for 40 seconds, the positioning splint was removed, and glycerin was applied to the margins to allow the polymerization of the layer inhibited by oxygen. All margins were cleaned with a curette (scalpel number 12), and the interproximal excess was removed with a Ceri Saw (DenMat) and dental floss (Figure 13). Finally, the margins were polished with a contra-angle drill. The occlusion was checked, and the X-rays were taken for control purposes.

The patient has followed up for the last 12 months and does not report problems (Figure 14).

CONCLUSION The FirstFit system allows clinicians to control and guide the preparation of veneers with a minimally invasive approach. In selected cases, it lets them create veneers before preparing them for the mouth, avoiding the need for provisional restorations and permitting them to finish the case in only two appointments.

Figure 11. Acid etching for 15 seconds

Figure 12. Positioning splint helps maintain the veneers in place

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Figure 13. Elimination of excesses

Figure 14. Postoperative smile

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2. Friedman MJ. Porcelain veneer restorations: a clinician’s opinion about a disturbing trend. J Esthet Restor Dent. 2001; 13 (5): 318-327.

3. Peumans et al. A prospective 10-year clinical trial of porcelain veneers. J Adhes Dent. 2004; 6 (1): 65-76.

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8. Edelhoff D, Sorensen JA. Tooth structure removal associated with various preparation designs for anterior teeth. J Prosthet Dent. 2002; 87 (5): 503-9.

9. Coachman C, Gurel G, Calamita M, Morimoto S, Paolucci B. The influence of tooth color on preparation design for laminate veneers from a minimally invasive perspective: case report. Int J periodontics Restorative Dent 2014; 34: 453-459.

10. Magne P, Belser UC. Novel porcelain laminate preparation approach driven by a diagnostic mock-up. J Esthet Restor Dent. 2004; 16 (1): 7-16; discussion 17-8. Review

11. Magne P, Douglas WH. Additive contour of porcelain veneers: a key element in enamel preservation, adhesion, and esthetics for aging dentition. J Adhes Dent. 1999 Spring; 1 (1): 81-92.

12. Gürel G. Predictable, precise, and repeatable tooth preparation for porcelain laminate veneers. Pract Proced Aesthet Dent. 2003 Jan-Feb; 15 (1): 17-24; quiz 26

13. Gurel G. The science and art of porcelain laminate veneers. Chicago: Quintessence Publishing Co, 2003.

14. Imburgia M et al. Minimally invasive vertical preparation design for ceramic veneers. Int J Esthet Dent. 2016; 11 (4): 460-471.

15. Karagözoğlu İ, Toksavul S, Toman M.3D quantification of clinical marginal and internal gap of porcelain laminate veneers with minimal and without tooth preparation and 2-year clinical evaluation. Quintessence Int. 2016; 47 (6): 461-71.

16. Richert R, Goujat A, Venet L, Viguie G, Viennot S, Robinson P, Farges JC, Fages M, Ducret M. Intraoral Scanner Technologies: A Review to Make a Successful Impression. J Healthc Eng. 2017; 2017: 8427595.

17. Hajto, J. Previous-Naturally Beautiful Previous Teeth-Theory, Practice and Design Teamwork Media, 2015.

Dr. Diego de Castro Adán Degree in Dentistry from the University of Zaragoza. R&D VIAX Europe Dental Technologies.

Dr. Patricia Elías Ortiz Degree in Dentistry from the European University of Madrid. R&D VIAX Europe Dental Technologies.

Dr. Marta López Marín DMD, MsD. Master in Periodontics, Implantology and Aesthetics. Master in Dental Science (University of Seville).

Dr. Luken Arbeola Dentist specialist in Prosthesis and Aesthetics and Director of Education of Digital Smile Design (DSD).

Dr. Bruno Pereira da Silva PhD. Associate Professor of the Master of Periodontics of the University of Seville.