Digital Smile Design in interdisciplinary and orthodontic dental treatment planning

It is a fact that esthetic rehabilitation is in high demand. To meet patient expectations, the dental community tends to use digital processes and modern communication techniques to reinforce treatment predictability and overcome esthetic challenges. Currently, digital smile design (DSD) processes offer the whole dental team including the orthodontist a powerful digital approach to improve esthetic analysis, team communication, and collaborative treatment planning, guided by facial harmony.


INTRODUCTION
Digital Smile Design in interdisciplinary and orthodontic dental treatment planning G. Finelle to end-of-treatment compromise situations which are more or less well accepted by the patients.
In many areas of activity, project validation is formalized in the form of a mock-up, sketch, or prototype, which is accessible to all professionals (regardless of specialty) involved in the project.
Although the digital environment is becoming increasingly essential in the dental industry and more specifically in esthetic dentistry and orthodontics, smile preview techniques 3 such as the Digital Smile Design (DSD), developed by Dr. Christian Coachman 4 or VEP 5 (Oral Laboratory Esthetics, Didier and Hélène Crescenzo) are essential reference tools (generally led by the practitioner in charge of esthetic rehabilitation) to understand, plan, communicate, and share therapeutic projects with the team and avoid pitfalls or possible unanticipated compromises.
In other words, the smile preview techniques respond to the need to bring together all the diagnostic elements collected by the team in a multidisciplinary project to make the treatment as predictable as possible.
This article, written for the orthodontic community, has the following aims: -shed light on the concepts and uses of recent smile preview techniques in multidisciplinary management; -describe the clinical and informal protocol through a simple and didactic orthodontic case; -illustrate through concrete examples the principle of Test Drive (mock-up); -give a glimpse of the developments and the perspectives of Smile Design in orthodontic care. DSD is, to date, the most common tool. Thus, the details of this article will focus on this technique only.
During the initial clinical examination, many esthetic parameters must be considered to establish a suitable treatment plan. It is not simply a question of listing them, but of rigorously analyzing them to identify the difficulties and anticipate possible compromises.
DSD is based on esthetic analysis from two-dimensional images. Therefore, the first step of the protocol is to take a series of photographs (facial and intraoral) and videos during the consultation session.
The primary objective of DSD is to improve the understanding of the case and the diagnostic vision by tracing the reference lines of the face (pupillary line, horizontal line of reference, median line of the face, smile line...; Fig. 1). The superposition of the face with the intraoral view allows an analysis of the dental arches (interincisal axis, position of the collars, position of the incisal margins, position of the papillae...) within the orofacial sphere 6 (Fig. 2).
The pathways and shapes are made using a keynote digital presentation software or PowerPoint (Fig. 3). The order of the slides required to design DSD always follows the same procedure described below.           For didactic purposes, the case selected to describe DSD step by step is deliberately chosen because it is a simple case.
A simple case. The more complex the case seems, the more useful the use of smile preview techniques (Figs. 4-9) 7 The detailed analysis file can be made available to the therapeutic team on a "cloud" system (Dropbox, Google Cloud...) allowing an effective and instantaneous collaborative approach between the different practitioners in charge of the treatment. The digital project can then be shared, completed, and carried out by the various specialists involved in the treatment.
In the majority of cases, it seems relevant that DSD be undertaken by the practitioner responsible for the overall management of the treatment and made available to the various people involved.
The purpose of the virtual analysis is formalized in the last "slide" of presentation and available in the form of a virtual synthesis or "smile frame" including the three key photos (vestibular view, occlusal view, 12 o'clock view) as well as the key information concerning the shape, position, and proportion of the teeth involved in the project (Figs. 10,11). DSD is also complemented by several short video recordings for dynamic and functional analysis.
This summary scheme is the reference from which the whole team multidisciplinary team 8 can -indicate the management of the various stakeholders (prosthetist practitioner, implantologist, orthodontist, periodontist); -guide therapeutic decisions; -coordinate the treatment between the different departments; -ensure the process is validated at the end of treatment.
Traditionally, esthetic projects which involve prosthetics or orthodontics are made by dental prosthetists based on an often limited amount of oral or written information. Quite often the project (in the form of wax up or set up), once tried in the mouth in the form of a mock-up, does not fully achieve the treatment aims. The dilution of certain information from the orofacial context between the clinic and the laboratory is often the cause.
It is assumed that the esthetic rehabilitation must take into account the reference information constituting the harmony of the face (horizontal reference plane, facial median line, position and shape of teeth on the dental arch, shade. The real difficulty lies in the faithful transfer of photographic data to the set up (or wax up) and therefore on the final result. Smile preview techniques have been developed to make these information transfers more reproducible.
Thus, the design of the set up or wax up (conventional or digital) is established from 2D photos and a digital virtual project.      To optimize workflow connectivity, the 3D environment is used from the impression stage. An optical impression is made and then exported to software that will ensure the support of the previously established DSD.
During the second appointment, a silicone cast (conventional technique; Fig. (12) allows the project to be tested clinically in the mouth and to evaluate any changes to be made or predict any compromises (Fig. (13) in the context of the face. The setting up of the mock-up is described as the most important step in the DSD protocol. It allows the patient to project themselves into their treatment and to appreciate the improvements to the smile (Figs. 14, 15). It is often at this point that the relationship of trust is established 9 .
Using an optical impression (Fig. (16) and 3D modeling software (Nemosoftware, DSD Connect, Cerec) the integration of the 2D project can now be directly changed into a 3D project in the form of three-dimensional virtual set up (Figs. 17, 18) 10 .
The 3D set up file can be exported to a 3D printer (Fig. 19) to create the resin mock-up and to complete the mock-up stage.    The emergence of facial scanners in the dental industry and more specifically in orthodontics gives us a glimpse into the bright future of virtual diagnostics.
From facial scanners specifically designed for the dental industry (Zirkonzahn, Pritidenta, Planmeca; Fig. 21) or simple iPhone applications using a series of photos to perform 3D facial reconstruction (123Dcatch), the merging of clinical information (face, 3D model, cone beam) as well as smile design software can be done in 3D (modeling software) from the start of the analysis. This method would therefore come into effect from the transferring step from 2D to 3D 12 . Nevertheless, this strategy, although promising, is still in the experimental stage and is largely limited by the compatibility of orthodontic software. Communication between the orthodontist and other members of the multidisciplinary team is one of the keys to therapeutic success in esthetic dentistry (Fig. 11).        time (as a result of a contraindication of purely prosthetic care); -it allows both parties to indicate the common end-of-orthodontic-treatment objectives in the context of an associated prosthetic rehabilitation; -it serves to validate the final positioning before the orthodontic appliance is removed.

FULL 3D ACQUISITION -FACIAL SCANNER
It differs from the following methods:

Orthodontic DSD without prosthetic support
The purely orthodontic virtual project differs from the prosthetic project, in that it implies that only the position of the teeth will be modified, it also preserves the structural integrity of these teeth. This is why the summary plots represent the contour of the original teeth in their original and final positions (esthetic project; Fig. 8).
The overlap of the two situations illustrates the importance of the movements to be applied by the orthodontist from the three 2D views described previously. The case illustrated in this article belongs in this category. A revaluation at the end of the orthodontic treatment may cause the general practitioner to conduct minor complementary treatments (gingivectomy, composite, ceramic implants).

Orthodontic DSD followed by prosthetic support
Frequently, the management of esthetic rehabilitations in adult patients Finelle G. Digital Smile Design in interdisciplinary and orthodontic dental treatment planning changes the position and shape of the teeth which takes up orthodontic and prosthetic (and/or implant) time. Under these circumstances, an orthodontic set up must be planned in line with the final prosthetic rehabilitation project in the context of minimally invasive dentistry.
Therefore, at the end of the orthodontic treatment, the volume of the displaced teeth should, as far as possible: -be contained within the desired future volume of the prosthetic project; -allow, in the case of adhesive restorations (facets), a prosthetic rehabilitation with a minimum amount of preparation at the expense of dental structures.
In this situation, two projects will be established: -Project 1 (intermediate orthodontics): orthodontic exclusions (see above); -Project 2 prefiguring how to achieve the restorations after orthodontic treatment.
In addition to the detailed case discussed in this article, three examples of multidisciplinary approaches guided by a virtual facial project are presented here to illustrate the therapeutic orientations taken before the start of treatment.
At a time when requests for esthetic rehabilitations and the demands of our patients are growing, it is up to practitioners to devise strategies to consolidate communication and avoid results that fall short of the expectations of patients or the practitioner themselves. Smile preview techniques are used to establish a predictable treatment plan based on facial analysis (not confined to inside the mouth). Constant and continuous developments in the field of digital orthodontics have led to interesting ideas for ensuring continuity between the design of the DSD project and the automated creation of orthodontic devices.