Home Computer driven aesthetic reconstructions
Computer driven aesthetic reconstructions
At the occasion of this Headlines issue, we decided to publish a unique case which Dr. Tardieu presented at the EAO and which describes a special, non-standard treatment procedure.
In the world of 3D Digital Dentistry, the integration of clinical and aesthetic parameters remains quite a tremendous challenge.
With this procedure, we would like to give you an insight in what 3D Digital Dentistry could bring us in the future. Currently, Materialise Dental is working on the development of a variety of prosthetic applications.
Philippe Tardieu*
Veerle Pattijn**
Dan Stenkilsson***
INTRODUCTION
Today, treatment of aesthetic cases fully includes the participation of the periodontal environment around teeth restorations. There is a consensus about the fact that controlled periodontal tissue management is based on an understanding of the biologic width. Improper management of the periodontal tissues during restorative procedures is a frequent, but often ignored, cause of failure.
Three steps can be defined when dealing with aesthetic reconstructions: planning of teeth, planning of soft tissue emergence and transfer of the planning to the patient’s mouth. Until today, the planning of teeth was done in the dental lab by creating a wax-up of the desired dentition. The soft tissue was trimmed on the plaster model of the patient’s dentition and for the majority of cases the transfer to the patient’s mouth was left to the skill of the periodontist, especially with respect to building up the surrounding tissues.
The aim of this article is to propose a totally new technique not only to make the plan for the new tooth set-up and soft tissue emergence profile, but also to transfer this plan to the patient’s mouth on the one hand on periodontal tissues and on the other hand on teeth level.
This technique involves the use of the following tools for planning: 3D superimposition of a digital image over a CT scan image (i.e. registration of a digitized plaster cast on a CT image), 3D photomapping (showing realistic colors on a 3D object starting from a 2D picture) and use of the “Virtual Teeth” tool. Besides the planning tools, also two types of guides to transfer this planning information to the patient’s mouth are described: (1) a stereolithographic bone-trimming guide to shape the bone and (2) a stereolithographic tooth-trimming guide to help trim the teeth and build up the temporary appliance. This technique is illustrated by a clinical case and the discussion is open regarding the benefits of these new procedures.
CLINICAL CASE
A 53-year-old female is complaining about her non-aesthetic smile. Picture 01 shows the overall complaint of this patient: she shows too much gum when she smiles and she would like to have this fixed.
Picture 02 shows the initial dentition in detail. At a glance, the teeth do not look so bad but a close look reveals a number of problems, which will be difficult to treat. The first upper right molar is covered with a crown and the metal shows. Upper right and left premolars are placed too much inside and look grey when the patient smiles. The upper lateral left incisor is a reshaped natural canine which has been placed in this position with an orthodontic treatment many years ago. This tooth is too much buccally placed and its soft tissue emergence is higher than the soft tissue level of the upper central incisors. Moreover, this tooth looks much bigger than the opposite lateral incisor. The upper left canine is an implant-based restoration and its soft tissue level is also quite high.
The treatment consists of a crown lengthening to adapt the level of the emergence of the teeth in the range going from the first upper right molar to the second upper left premolar. Then, after healing, the teeth will be covered with ceramic crowns.
The originality of this treatment comes from the tools that have been used to perform it. We can define 3 steps in this treatment: teeth planning, soft tissue planning and transfer to the mouth.
TEETH PLANNING
The planning of this case is based on CT images of the patient, combined with digital models and by means of the SimPlant OMS software.
The patient was sent to have a full head CT scan taken, and the DICOM data were subsequently converted to a SimPlant project.
Picture 03 shows the resulting 3D models of the patient’s maxillary bone and teeth.
By means of the Optical Scan Module of SimPlant 12, the digital image of the plaster cast of the patient’s dentition is registered within the CT images (Picture 04).
The photomapping functionality of the SimPlant OMS module has been used to visualize the real image of the soft tissue and teeth on the 3D representation of the plaster cast (Picture 05).
Then using the “Virtual Teeth” tool, a virtual tooth-set up was created (Picture 06).
This is a virtual equivalent of a tooth wax-up which is usually done by the lab technician. The planned final anterior teeth are smaller than the original ones, the upper left lateral incisor is smaller than the original one, the canines are placed a little more lingually and premolars are placed more buccally compared to the original arch. After the tooth planning is done, the soft tissue planning can be started.
SOFT TISSUE PLANNING
The soft tissue planning is probably the more ignored part in aesthetic reconstructions and is a frequent cause of failure or poor results. Soft tissue planning is based on a strong biologically-based approach which involves understanding how to manage the biologic width around teeth and implants. Basic articles from Gargiulo (i) and Vacek (ii) have shown that the distance from the top of the soft tissue to the crest of the bone is around 3mm. This means that the position of the soft tissue is induced by the position of the crest of the alveolus. Starting from the final level of the soft tissue, we can then establish the shape and the position of the bone at a distance of approximately 3mm. This has been documented very well in several articles (iii, iv) about crown lengthening techniques and indications, especially focusing on anterior upper teeth (v, vi). Based on several studies (vii, viii) it is advised to add 1mm to this distance due to the expected healing response of the soft tissue. This means that we plan to reshape the bone at 4mm away from the soft tissue emergence line.
Picture 07 shows the final expected soft tissue outline around the virtual teeth.
After planning the teeth and the soft tissue emergence line, there is a need for transferring this planning to the patient’s mouth.
TRANSFER TO THE MOUTH
Bone-trimming guide
In the past, solutions have been proposed to help reshape a soft tissue before prosthesis realization, but not for reshaping the bone itself (ix, x). A stereolithographic bone-trimming guide was designed including the planned outline of the bone which is at a distance of 4mm from the final soft tissue line (Picture 08). This bone-trimming guide rests on the remaining teeth and is manufactured by means of stereolithography.
After elevating a flap (split full split) the bone guide helps trim the bone exactly as planned. Picture 09 shows the bone-trimming guide positioned on the patient’s teeth. Almost no bone was removed on the implant site and on the “upper left lateral incisor” site. Most of the osteotomy was needed on the other teeth.
Picture 10 shows the bone level after trimming.
Sutures were performed and 8 weeks of healing time was respected (Picture 11). In some cases, temporary crowns are placed at this step but in this case all teeth except the upper left incisor were alive. Therefore, it was preferred not to trim the teeth at this time.
Tooth-trimming guide
A stereolithographic tooth-trimming guide was performed to help trim the teeth. This guide was fabricated based on a virtual model including the new design of teeth and soft tissue. This guide aids in removing only the necessary parts of dental tissue since it shows the final outline of the final teeth (Picture 12).
Picture 13 shows the prepared teeth, of which an impression is taken.
Despite the fact that the root of the canine was bigger than the root of a lateral incisor, the tooth at position 22 was trimmed in order to be reconstructed as a lateral incisor. Its buccal soft tissue emergence was corrected. Papilla starts growing up in between teeth. For the final teeth an asymmetrical round curve was designed on both central incisors to give a more natural aspect to these teeth (Picture 14).
Before and after smile can be compared on pictures 02 and 15.
DISCUSSION AND RECOMMENDATIONS
This technique can be considered as a strong step forward in managing delicate and demanding aesthetic reconstruction cases. The improvements in using this technique are dual: on the one hand it is beneficial for the surgeons and the prosthodontist and on the other hand the communication with the patient is easier. The “final result” can be shown to the patient, which enhances the collaboration with the patient and his/her understanding of the treatment difficulties.
This technique is still difficult to use due to the fact that the Virtual Teeth tool does not allow easy manipulation of the individual teeth in case of large groups of teeth. Another option is to make a wax-up of the final tooth set-up at the dental lab, and to superimpose the digitized image of this model onto the CT scan.
The bone-trimming guide is really very useful during surgery because we can fully control the osteotomy. This considerably helps in reaching the goals in terms of final soft tissue level. In case of a very thick tissue we can imagine the same kind of guide but used to sculpt the soft tissue itself instead of guiding the bone level.
The tooth-trimming guide is more useful when dealing with veneers than when dealing with full crowns. It is very useful when dealing with living and crowded teeth that we wish to realign.
Finally the patient’s satisfaction is above all expectations: “I am very impressed by the case pictures. It is extremely difficult to capture everything you actually did to make the final bridge but as you know, the details were not simple. The obtained outcome is of the highest level and has met more than any of my expectations. You have helped me obtain a healthy, beautiful smile; one that I have wanted for 30 years. I am very pleased to have met you. Many thanks again.”
REFERENCES
i Gargiulo, A. W., Wentz, F. & Orban B. (1961) Dimension and relations of the dentogingival junction in humans. Journal of Periodontology 32,261-267.
ii Vacek, J. S., Gehr, M. E. Asad, D. A., Richardson, A. C. & Giambarressi, L. I. (1994) The dimension of the human dentogingival junction. International Journal of Periodontics and Restorative Dentistry 14. 154-165.
iii Lee EA. Aesthetic crown lengthening: classification, biologic rationale, and treatment planning considerations. Pract Proced Aesthet Dent. 2004 Nov-Dec;16(10):769-78.
iv Levine DF, Handelsman M, Ravon NA. Crown lengthening surgery: a restorative-driven periodontal procedure. J Calif Dent Assoc. 1999 Feb;27(2):143-51.
v Bensimon GC. Surgical crown-lengthening procedure to enhance esthetics.Int J Periodontics Restorative Dent. 1999 Aug;19(4):332-41.
vi Sonick M. Esthetic crown lengthening for maxillary anterior teeth. Compend Contin Educ Dent. 1997 Aug;18(8):807-12, 814-6, 818-9.
vii Herrero F, Scott JB, Maropis PS, Yukna RA. Clinical comparison of desired versus actual amount of surgical crown lengthening. J Periodontol. 1995 Jul;66(7):568-71.
viii Pontoriero R, Carnevale G. Surgical crown lengthening: a 12-month clinical wound healing study. J Periodontol. 2001 Jul;72(7):841-8.
ix Walker M, Hansen P. Template for surgical crown lengthening: fabrication technique. J Prosthodont. 1998 Dec;7(4):265-7.
x Scutella F, Landi L, Stellino G, Morgano SM. Surgical template for crown lengthening: A clinical report. J Prosthet Dent. 1999 Sep;82(3):253-6.
* DDS from University Paris VII University, PG in Implantology from University of Nice Sophia Antipolis, Adjunct Associate Professor New York University. Private practice in Dubai (UAE).
e-mail: pt@frenchdentistdubai.com
** M Sc Eng, PhD from Catholic University Leuven. Research Engineer at Materialise Dental.
*** Lab technician, Middle East Dental Lab.