Digital Implant Dentistry: Reducing Treatment Time, Cost, and Manual Skill Development

INTRODUCTION
Today, clinical implant treatments require years of manual skill development on the parts of the surgeon, restorative dentist, and dental technician. This can be accomplished using digital technologies to plan and place a restoratively driven implant and its restoration in just 2 patient visits.^1,2 The significance of this approach is a reduced learning curve, coupled with minimization of manual skill development and the use of open digital software, which will allow more dental professionals to become involved in providing implant therapy earlier in their careers. This will result in reduced cost, making implants available to millions more of patients who could benefit from them.³ The ability to do this has been previously reported, but one element required manual laboratory intervention, and that was the matrix to hold the provision crown at surgery for bonding to the abutment.¹

This case report presents a method to accomplish surgical placement and prosthetic rehabilitation of an implant in a totally digital workflow.

CASE REPORT
Appointment 1: Treatment Planning
A 56-year-old male presented for replacement of a missing mandibular right first molar (tooth No. 30). The tooth was lost 5 years previous to this visit, secondary to unsuccessful endodontic therapy. A comprehensive examination revealed no remarkable medical history and an otherwise healthy dentition. Alternative treatments were discussed, including risks and benefits of each, and the patient then stated a preference for an immediate implant restoration as opposed to a conventional fixed partial denture (bridge) option. Due to the patient’s stated time constraints and an aversion to conventional impressions, we elected to use a completely digital treatment plan that could be accomplished in 2 visits.

Accordingly, a CBCT scan (i-CAT, Next Generation [Imaging Sciences International]) was done in addition to an intraoral optical scan (iTero Scanner [Align Technology]). The iTero digital intraoral tooth and soft-tissue surface scan in Surface Tesselation Language (STL) file format and DICOM file were imported into Straumann’s Dental Wings Open Software (DWOS) CAD/CAM program, and both files were digitally merged using reference points to provide both hard- and soft-tissue anatomy (Figure 1).

A tooth from the digital tooth library in the planning program was inserted into the edentulous space and shaped to approximate the soft tissue and adjacent teeth. It should be noted that this library tooth has limited design capability but is adequate to determine occlusal proximal labial and lingual guidelines for positioning a prosthetic-driven implant plan (Figure 2).

The STL files were then exported to restoration planning software (Straumann CARES Visual CAD software [Straumann]), and a full-contour screw-retained restoration was digitally formed around a prefabricated temporary abutment (Straumann RC Variobase Abutment, with screw No. 025.4921) and a provisional polymethyl meth­acrylate (PMMA) crown (Straumann Polycon AE) to approximate the edentulous ridge contact areas and the occlusion (Figure 3). Buccal, lingual, and occlusal indexing wings were then digitally added to the crown to interface above the height of contour with the buccal, lingual, and occlusal aspects of the adjacent teeth. These wings were added so that at the surgical appointment, the restoration could be indexed into the edentulous space over the implant-supported temporary abutment and joined to it with autopolymerizing PMMA acrylic resin at implant insertion. Emergence profile was designed for a bone level implant (Straumann Bone Level Implants: guided Ø 4.8 x 10.00 mm No. 021.6310G).

Once this was done, the plan in the form of STL files was exported to the milling center (Straumann) for the fabrication of a CAD/CAM full-contour PMMA provisional restoration. Also, the STL files were exported back to the implant planning software (coDiagnostiX [Dental Wings]). The template was designed digitally and caseXchanged (coDiagnostiX) to the template production facility (Pro Precision Guides). A virtual construction of the surgical template was created without any physical model and then 3-D printed. Finally, implant planning software provided the drilling protocol for No. 30 (Figure 4).

A temporary abutment (RC Variobase Abutment, with screw No. 025.4921) and the implant (Straumann Bone Level Implant: guided Ø 4.8 x 10.00 mm No. 021.6310G) were ordered.

At this point, all the elements required for treatment had been assembled and the patient was given a second appointment time (Figure 5).

Appointment 2: Implant Placement and Restoration Delivery
The patient was in good health. He was premedicated with amoxicillin 2,000 mg one hour before surgery; a Medrol dose pack was begun in morning one day prior to surgery; chlorhexidine rinse after breakfast and before sleep with 15 cc for 30 seconds one week before implantation; and alprazolam 0.5 mg at bedtime the night before surgery and then one hour before surgery.

Prior to surgical implant placement, the inspection windows on the surgical template were checked for a gap-free fit in the patient’s mouth (Figure 6). Local anesthesia was obtained via inferior alveolar and lingual nerve block, and long buccal local infiltration (4 cc of Xylocaine 1:100,000). To seat the surgical template and increase keratinized tissue on the buccal side of the implant, a full-thickness flap was elevated (Figure 7). The implant was placed according to the drilling protocol (Figure 8) and the temporary cylinder was placed. The provisional resin restoration—which had been milled with a hollow 1.5-mm space for the temporary cylinder—was then placed over the temporary cylinder and suspended in place to the adjacent teeth with the wings that had been digitally formed in the planning program. Autopolymerizing PMMA (Temporary Bridge Resin [Dentsply Sirona Restorative]) was flowed into the space surrounding the temporary abutment and allowed to cure, luting the abutment together (Figure 9). The crown assembly was removed from the implant. The indexing wings were removed and the emergence profile was shaped and polished (Figure 10). The provisional restoration was torqued to 35 Ncm and the access hole filled with cotton and Fermit N (Ivoclar Vivadent). The crown was adjusted into slight infraocclusion and relieved from interproximal contact so any adjacent tooth movement or occlusal forces would not cause micromovement of the implant during the osseointegration period. The soft tissue was closed with 3-0 silk sutures and the patient was discharged with instructions to not eat on that side of his mouth for the next 3 months while the implant underwent osseointegration (Figure 11). Figure 12 shows healing at 3 months post-implant placement.

DISCUSSION
This report highlights the digital interfaces of surgical and prosthetic treatment starting from virtual planning of guided implant placement, template manufacturing, and production of the provisional restoration. Prosthetic components were all premade. This approach shortened the treatment time by 2 appointments with a predictable treatment result. Essentially, the procedure is the acquisition of a surface scan and CBCT scan followed by merging these files in implant planning software, then planning the implant position and the surgical guide. At the planning session, the restoration was digitally designed and subsequently computer milled. During the second visit, the restoration was inserted on the implant immediately. This procedure took about an hour (Figure 13).

Figure 13. Digital implant-restoration workflow.

Others have reported digital placement of implants.⁴ Joda and Brägger³ described an additional intraoral optical impression using an implant scanbody. A second STL file was created immediately after implant placement. Then, after the healing period, that final crown was placed. No immediate temporization was performed, so there was no opportunity to shape the tissue with a temporary restoration,² and the patient was without a restoration for the healing period.

Patel’s paper⁵ reported on a digital workflow: guided implant placement and milled restoration using Dentsply Sirona’s Sirona workflow. Using Sirona software and equipment, the implant position and guide can be planned; however, the restoration cannot be planned until the implant is in place, resulting in the patient spending a long waiting period in the office following surgery for the restoration to be milled. The final restoration was milled and placed. The limitation is that the implant position requires re­scanning after placement to capture the exact rotational and high above bone. Further, the soft tissue is not healed yet, so a definitive restoration may need to be replaced. The advantage of placing the temp restoration is that the final restoration can be placed and fitted to the healed tissue.⁵

In this treatment, a provisional restoration was used, allowing time to for the soft tissue to be shaped during healing. The shortcoming of this approach is that if the clinician goes right through the tissue, the tissue is still going to change as it heals and may lack keratinized tissue on the buccal aspect of the implant. In our method, we give the patient a provisional restoration that can be worn as long as desired; then, at some time in the future (at least beyond a 3- to 4-month osseointegration period), the clinician can then take a precise impression and make a precise restoration.

While we could have fabricated a final restoration for the patient in this case, positioning is a potential problem. There are intrinsic and extrinsic factors associated with the guided instrumentation, which do not allow precise final implant position in terms of height and angulation.^1,6

Currently, a variety of chairside intraoral digital scanning devices are on the market, such as iTero, True Definition (3M), PlanScan (Planmeca/E4D Technologies), CS 3500 (Carestream Dental), TRIOS (3Shape A/S), and the CEREC AC Omnicam (Dentsply Sirona). All these systems present different technology and offer an open platform (except CEREC). These systems have the ability to integrate with design software and chairside or laboratory-milling machines.⁷ The accuracy of the digital approach is dependent on the correct scanning strategy.⁸ Another shortcoming of digital intraoral scanning systems is that they are less accurate for larger scan areas compared to conventional impressions.^9,10

We selected the digital impression iTero system. This scans captured intraoral topography by laser and optical scanning based upon the principle of parallel confocal imaging, providing a 3-D digital impression with high resolution and accuracy (7.0+/-1.4 μm).⁷ An advantage of the iTero scanner is a powder-free scanning system, which allows less error due to irregular powdering in a large area of scanning. It is less time consuming and prevents error due to saliva. It improves the workflow as well. If any movement is detected, the system requires a rescan. Also, this system will capture a virtual bite registration.⁹ The shortcoming of this scan system is that it does not provide complete digital workflow such as design and milling.¹¹ This is an open scan system that allows export of digital image files as an STL format, which can be used for data export with the DWOS and CARES Visual CAD software and shared by any other lab equipped with a CAD/CAM system to manufacture the final restoration.⁹

The digitally formed indexing wings on the provisional crown proved to be effective in positioning it to the adjacent teeth for luting by using autopolymerizing PMMA.

The overall emergence profile was created in the planning program. One of the benefits of this approach is that an ideal emergence profile can be created in the digital planning because the operator can position the implant ideally to its restoration apical-occlusally, mesial-distally, and labial-lingually, and then it is just a matter of connecting the shoulder of the abutment component with the apical portion of the crown. There was only a small space between that area and the shoulder of the temporary abutment. Once the crown was luted to the temporary abutment, both were removed, and a small space between the shoulder of the temporary abutment and the cervical area of the crown was filled with PMMA and polished (Figure 14). However, since the emergence profile is subgingival, this prevents the restoration try-in prior to the surgery. For this patient, it proved not to be a limitation.

Today, the major shortcoming of this method is that the software programs are not integrated along all aspects. For example, the restoration for implant planning lacks full digital manipulation, so it is required on part of the planner to spend some time in interface software estimating. The final implant plan then needs to be exported back into coDiagnostiX for the production of the 3-D printed of the surgical template.¹

The final provisional restoration, however, is done in different software that allows full digital manipulation.

CLOSING COMMENTS
This report has shown that it is possible to plan and perform implantation and immediate restoration in 2 patient visits without the need for significant manual skills on the part of the implant team. The significance of this approach is a reduced learning curve and minimization of manual skill development that, in the future, will allow more dentists to become involved in providing implant therapy earlier in their careers and, thus, through increased completion and other business axioms, help to make implants available at reduced cost to millions of patients who could benefit from these services.

References

1. Schnitman PA, Han RK. Completely digital two-visit immediately loaded implants: proof of concept. J Oral Implantol. 2015;41:429-436.
2. Joda T, Buser D. Digital implant dentistry—a workflow in five steps. CAD/CAM. 2013;4:16-20.
3. Joda T, Brägger U. Digital vs. conventional implant prosthetic workflows: a cost/time analysis. Clin Oral Implants Res. 2015;26:1430-1435.
4. Lanis A, Álvarez Del Canto O. The combination of digital surface scanners and cone beam computed tomography technology for guided implant surgery using 3Shape implant studio software: a case history report. Int J Prosthodont. 2015;28:169-178.
5. Patel N. Integrating three-dimensional digital technologies for comprehensive implant dentistry. J Am Dent Assoc. 2010;141(suppl 2):20S-24S.
6. Tapie L, Lebon N, Mawussi B, et al. Understanding dental CAD/CAM for restorations—accuracy from a mechanical engineering viewpoint. Int J Comput Dent. 2015;18:343-367.
7. Hack GD, Patzelt SBM. Evaluation of the accuracy of 6 intraoral scanning devices: an in vitro investigation. ADA Professional Product Review. A Publication of the Council on Scientific Affairs. September 25, 2015.
8. Ender A, Mehl A. Influence of scanning strategies on the accuracy of digital intraoral scanning systems. Int J Comput Dent. 2013;16:11-21.
9. Reich S, Vollborn T, Mehl A, et al. Intraoral optical impression systems—an overview. Int J Comput Dent. 2013;16:143-162.
10. Ender A, Mehl A. Full arch scans: conventional versus digital impressions, an vitro study. Int J Comput Dent. 2011;14:11-21.
11. Ting-Shu S, Jian S. Intraoral digital impression technique: a review. J Prosthodont. 2015;24:313-321.

Dr. Schnitman received his DDS and MSD from New York University. He is in private practice specializing in implant dentistry in Wellesley Hills, Mass, and teaches implant surgery and restoration at the Harvard School of Dental Medicine (HDSM). He is an Honored Fellow of the American Academy of Implant Dentistry (AAID), a Fellow of the Academy of Osseointegration, and a Diplomate of the American Board of Oral Implantology/Implant Dentistry. He is a past president of the AAID and the American Board of Oral Implantology/Implant Dentistry, and he is founder and former chairman of the department of implant dentistry at Harvard. He was co-chairman of the Harvard/NIH Consensus Development Conference on Dental Implants. He has been published widely and lectures internationally on dental implants. He can be reached via the website dental­implantsofboston.com.

Dr. Escobar received her DDS from New York University in 2012 and her advanced graduate education prosthodontics and master in medical sciences degree in 2015 at HSDM. She maintains a private practice, Dental Implants of Boston, in Wellesley Hills, Mass. She is a lecturer on implant dentistry in the department of restorative dentistry and biomaterial sciences at the HSDM. She can be reached at dental­implantsofboston.com.

Dr. Florencio is a fourth-year DMSc candidate and prosthodontics resident at the HSDM. He received his DDS from the Federal University of Rio Grande do Norte, Natal, Brazil, and completed his advanced education in general dentistry residency at University of Florida in Gainesville. He can be reached at florenciodds@gmail.com.

Dr. Jung received her DDS degree from New York University College of Dentistry with Omicron Kappa Upsilon Omega Chapter in 2012. She completed advanced graduate education program in prosthodontics and received a master of medical sciences degree from the the HSDM in 2015. She joined the dental research lab in the department of prosthodontics at Seoul National University. She can be reached via email at soominjung@gmail.com.

Mr. Radics is originally from Basel, Switzerland, where he obtained his Swiss dental technology diploma in 1998. In 1999, he came to the HSDM to train in implant restorations with professor H. P. Weber and continued working as his technician until 2010. He remained at the HSDM as a senior instructional dental technologist until his promotion to clinical operations lab and materials manager in 2014. A member of the International Team of Implantology and the Harvard Odontological Society, he helped create the Digital Dental Lab at the HSDM and teaches digital technology to students. He has spoken internationally on dental technology. He can be reached at andreas_radics@hsdm.harvard.edu.

Disclosures: The authors report no disclosures.

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