3D Printed Crown Lengthening and Reduction Guide

Dr. Faraj Edher and Ms. Ariana Aram
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INTRODUCTION
Digital workflows are becoming more popular in dentistry, offering benefits such as improving communication, aesthetic planning, patient education, efficiency, and predicting treatment outcomes.1-4 Intraoral scanners and computer-aided design (CAD) tools allow for the development of virtual diagnostic files and 3D printed models. Past studies have shown that digital impressions are equally as accurate as conventional impressions.5-9 Three-dimensional printed guides have been used in dentistry for a variety of indications, including implant placements, oral surgery, endodontics, and orthodontics.10

This case highlights an innovative technique utilizing a digital workflow to improve the efficiency and predictability of treatment outcomes. Virtual smile design and CAD were utilized to fabricate a 3D printed guide that acted as both a preparation reduction guide and a gingivectomy guide.

Figure 1. Patient’s smile at consultation visit.

CASE REPORT
A patient presented with a chief complaint of a fractured veneer on her maxillary right central incisor and expressed overall dissatisfaction with her 10-year-old porcelain veneers on both maxillary central incisors. She disliked the short and square-shaped appearance of the teeth and the black triangle between them.

Clinical examination confirmed the fractured veneer, in addition to a space in the midline interdental region and a larger-than-ideal width-to-height ratio for both central incisors (Figure 1). Additionally, there was staining on the left central incisor veneer margins on both veneers.

Figure 2. Keynote smile design (template and treatment visualization). Figure 3. Virtual wax-up and gingivectomy planning.

Treatment Planning
The different treatment options were discussed with the patient, which included gingivoplasty of the maxillary central incisors to improve the width-to-height ratio and subsequent placement of new veneers on the centrals. Alternative options included orthodontic treatment and increasing the width-to-height proportions of the adjacent anterior teeth. These options were presented, and the patient decided to proceed with gingivoplasty and new porcelain veneers.

Figure 4. Reduction and crown lengthening guide design.

Clinical Protocol
During the consultation visit, the dimensions and aesthetics of the central incisors were visualized directly on the patient’s photograph through the use of virtual smile design. Figure 2 shows how applications such as Keynote or PowerPoint can be used chairside to show patients potential treatment designs and outcomes during the consultation visit. Such a platform allows the dentist to superimpose a template that can be adjusted to the patient’s anatomy. For this case, the template was used to elongate the crown height and reduce the black triangle between the centrals. The incisal edges were maintained in their original positions. The design was reviewed and approved by the patient. In this case, the virtual design allowed us to communicate to the patient the width-to-height ratio challenge for the central incisors and the interdental space in the midline.

The software also aids in communicating with the lab regarding the proposed design for the teeth (Figure 2). For simpler cases, this technique can be an effective and efficient way to initially visualize treatment options. More complex cases, such as full-arch rehabilitations, may necessitate more sophisticated virtual smile design software.

During the consultation, an intraoral scanner (TRIOS [3Shape]) was used to create digital models. The lab could then use the digital models to plan the new, ideal position of the gingival margins and create a virtual wax-up for the central incisors (Figure 3).

Figure 5. A 3D printed crown lengthening guide and reduction guide. Figure 6. Comparison of the initial smile design to the final veneers.

A reduction and crown lengthening guide was designed virtually and 3D printed (Form2 [Formlabs]) (Figure 4). The 3D printed guide was used to ensure a precise gingivectomy procedure using a soft-tissue laser (Waterlase [BIOLASE]). The old veneers were removed, and the 3D printed guide was used to assess the amount of additional reduction needed to achieve the required prosthetic space for the new veneers (Figure 5).

After the gingivectomy and preparation were completed, a final digital impression was taken and sent to the lab for fabrication of the lithium disilicate veneers based on the virtual wax-up. The patient was then seen for bonding the veneers to the teeth. Figure 6 shows the close resemblance of the initial virtual smile design to the final veneers.

CONCLUSION
The benefits of using virtual smile design technology are multifold: communication, predictability, and efficiency. When patients are able to visualize potential treatment options in the context of their own smiles during consultation visits, they are more engaged in their care and more confident that their goals are aligned with those of their clinicians. Having such information from the consultation gives patients more opportunity to ask questions earlier on in the process when changes are simpler to make. Digital technology also enhances communication between the clinician and the lab technician. Using digital technology in innovative ways allows for more predictable clinical outcomes and improved efficiency of treatment.


References

  1. Cervino G, Fiorillo L, Arzukanyan AV, et al. Dental restorative digital workflow: Digital smile design from aesthetic to function. Dent J (Basel). 2019;7(2):30. doi:10.3390/dj7020030.
  2. Lin WS, Zandinejad A, Metz MJ, et al. Predictable restorative work flow for computer-aided design/computer-aided manufacture-fabricated ceramic veneers utilizing a virtual smile design principle. Oper Dent. 2015;40(4):357-363. doi:10.2341/13-295-S.
  3. Garcia PP, da Costa RG, Calgaro M, et al. Digital smile design and mock-up technique for esthetic treatment planning with porcelain laminate veneers. J Conserv Dent. 2018;21(4):455-458. doi:10.4103/JCD.JCD_172_18.
  4. Stanley M, Paz AG, Miguel I, et al. Fully digital workflow, integrating dental scan, smile design and CAD-CAM: case report. BMC Oral Health. 2018;18(1):134. doi:10.1186/s12903-018-0597-0.
  5. Aragón ML, Pontes LF, Bichara LM, et al. Validity and reliability of intraoral scanners compared to conventional gypsum models measurements: a systematic review. Eur J Orthod. 2016;38(4):429-434. doi:10.1093/ejo/cjw033.
  6. Favero R, Volpato A, Francesco M, et al. Accuracy of 3D digital modeling of dental arches. Dental Press J Orthod. 2019;24(1):38e1-37e7. doi:10.1590/2177-6709.24.1.38.e1-7.onl.
  7. Kihara H, Hatakeyama W, Komine F, et al. Accuracy and practicality of intraoral scanner in dentistry: A literature review. J Prosthodont Res. 2020;64(2):109-113. doi:10.1016/j.jpor.2019.07.010.
  8. Patzelt SB, Emmanouilidi A, Stampf S, et al. Accuracy of full-arch scans using intraoral scanners. Clin Oral Investig. 2014;18(6):1687-94. doi:10.1007/s00784-013-1132-y.
  9. Amin S, Weber HP, Finkelman M, et al. Digital vs. conventional full-arch implant impressions: a comparative study. Clin Oral Implants Res. 2017;28(11):1360-1367. doi:10.1111/clr.12994.
  10. Dawood A, Marti Marti B, Sauret-Jackson V, et al. 3D printing in dentistry. Br Dent J. 2015;219(11):521-9. doi:10.1038/sj.bdj.2015.914.

Dr. Edher is a specialist in prosthodontics focused on cosmetic transformations and implant reconstructions using advanced digital technology. Dr. Edher is the director of the Digital Dentistry Institute, a global educational organization that conducts comprehensive training programs in digital dentistry and implant dentistry. He is also a clinical assistant professor and guest lecturer at the University of British Columbia. He can be reached at faraj.edher@ddidental.com.

Ms. Aram is a DMD candidate at Harvard School of Dental Medicine. She received her bachelor’s degree in Biological Sciences at Carnegie Mellon University. Her research interests include digital technologies and techniques to improve patient care. She can be reached at ariana_aram@hsdm.harvard.edu.

Disclosure: The authors report no disclosures

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