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Utilizing Digital Dentistry and CAD/CAM Prosthetics to Optimize Treatment Outcomes – Part 2: Implant Planning, Placement and Immediate Provisionalization

Perry E. Jones, DDS, MAGD

article by Perry E. Jones, DDS, MAGD

Digital dentistry is helping restorative-driven implant treatment reach its true potential. Intraoral scanning, virtual treatment planning and dental CAD/CAM technology allow doctors to visualize the prosthetic outcome and achieve highly accurate results, no matter how challenging the case. Using these tools, surgical guides and immediate provisional restorations can be digitally fabricated, ensuring the implants are placed in the precise positions needed for an esthetic restoration while providing the patient with a temporary prosthesis that helps fine-tune the restorative design and contour the soft tissue.

In this article, the second of a three-part series, we continue following a case that demonstrates the value of utilizing digital dentistry and CAD/CAM prosthetics to optimize treatment outcomes. The patient initially presented with hopeless maxillary anterior incisors and canines as well as supererupted and crowded lower anterior teeth. In Part 1, the multidisciplinary treatment plan began with pre-implant orthodontic treatment to help correct the occlusal relationship and create space for the planned maxillary implant restoration.

This presentation will focus on digital treatment planning, the guided surgical placement of implants in the edentulous span of the anterior maxilla, and immediate provisionalization with a screw-retained BioTemps® implant bridge. The surgical and provisional phases of treatment begin a fully digital workflow, without the use of conventional stone models, that leads to the delivery of an ideal implant restoration despite the initial functional and esthetic challenges.

Pre-Implant Treatment

In the previous article of this series, we used ClinCheck® software (Align Technology; San Jose, Calif.) to virtually create a tooth movement plan (Figs. 1a, 1b). A series of Invisalign® clear aligners (Align Technology) was created and delivered to the patient (Fig. 2). The movement objectives included improvement in the patient’s deep vertical appearance of overbite, intrusion of the supererupted lower teeth, and resolution of the lower anterior crowding to improve esthetics. The patient was very compliant and, as reported in Part 1, the clinical outcome was excellent, matching the virtual ClinCheck treatment plan (Fig. 3).

Figures 1a, 1b: Prior to implant treatment, ClinCheck software was used to virtually plan the tooth movement needed to correct the occlusion and create space for the planned restoration.

Figures 1a, 1b: Prior to implant treatment, ClinCheck software was used to virtually plan the tooth movement needed to correct the occlusion and create space for the planned restoration.

Figure 2: Mandibular occlusal view with Invisalign aligner in place.

Figure 3: Mandibular occlusal view with rotation and intrusion movements completed.

Digital Treatment Planning

With digital treatment planning and surgical guides, implants can be placed ideally within the bone and in the optimal position to support the prosthesis, simplifying the restorative procedure.1,2 To produce the data needed to virtually plan the case, CBCT scans were taken with the teeth about 10 mm apart to prevent the occlusion of the teeth from obscuring the surface data.

There are limitations to CBCT data. Scatter from metallic restorations as well as inaccuracies in mapping the surface of the teeth and soft tissue make it challenging to design surgical guides directly from CBCT DICOM data. Intraoral digital scanning can be used to accurately provide this information.

In this case, the iTero® Element™ intraoral scanner (Align Technology) was used to create a digital impression of the teeth and soft tissue (Fig. 4). The Element is a fast, efficient system that uses proven, extremely accurate parallel confocal technology, high-definition video capture and a new lightweight wand. The iTero Element digital intraoral scan for this case included the patient’s maxillary and mandibular arches as well as the bite relationship, and took less than two minutes to complete.

The STL file data produced from the intraoral scanner, representing a very accurate map of the surface morphology of the teeth and gums, was merged with the CBCT DICOM data, creating a precise digital rendering of the patient’s mouth (Fig. 5). The file merge was easily executed using the treatment planning software, producing a digital model that was used to precisely determine the implant positions and the design of the surgical guide and prefabricated provisional restoration.

A 3-D virtual wax-up was created to help design the shape and optimal positioning of the 6-unit maxillary anterior screw-retained bridge (Fig. 6). Then, using the digital treatment planning software, the optimal positions for four implants were determined in a manner that best supported screw-retention and the desired contours, margins and esthetics for the planned restoration (Figs. 7a, 7b). The highly accurate CBCT and intraoral scanning data helped ensure that the proposed implant positions were properly situated within the available bone and in relation to the opposing mandibular dentition.

Surgical Guide Design and Fabrication

The surgical guide was designed using the CAD features of the digital treatment planning software. First, a gingival extension was “drawn” onto the surface of the teeth that would be used to support the guide during the surgical procedure. Following the simple steps of the software, openings were added for metal guide cylinders that control the depth and angulation of the surgical drills (Figs. 8a, 8b). The design included plastic extensions for the buccal and lingual undercuts such that the guide had retention but was not so tight it could not seat properly. A cross-arch strut was added to the design for extra strength, and windows were incorporated so that proper guide seating could be verified clinically.

Figures 8a, 8b: The surgical guide was designed with openings for metal cylinders through which the osteotomies would be created in precise alignment with the planned implant positions.

Figures 8a, 8b: The surgical guide was designed with openings for metal cylinders through which the osteotomies would be created in precise alignment with the planned implant positions.

Figure 9: The surgical guide was 3-D printed, and the metal guide cylinders were cemented into the openings situated in alignment with the planned implant locations. Note the cross-arch strut added for extra strength.

The design file was then sent to an Objet30 3-D printer (Stratasys; Eden Prairie, Minn.), and the surgical guide was 3-D printed using MED610 polymer, a clear, biocompatible, FDA-approved material suitable for temporary medical placement in the mouth (Fig. 9). After 3-D printing of the surgical guide was complete, the titanium cylinders that control the positioning of the implant osteotomies were cemented into position.

Provisional Design and Fabrication

Due to advancements in dental CAD/CAM technology, precisely fitting BioTemps restorations can now be fabricated in advance of the surgical appointment and immediately connected to the implants. In this case, a 6-unit screw-retained provisional bridge was designed for the edentulous span in the area of teeth #6–11. The digital design included openings in which non-engaging metal cylinders could be bonded so the prosthesis could be immediately secured to four implants using titanium retention screws. Because the implant positions and prosthesis design were determined in tandem using CAD software, the planned implant locations aligned perfectly with the screw-access holes situated in the cingulum areas of the provisional bridge.

Figure 10: Occlusal view of the 6-unit BioTemps implant bridge illustrates screw-retention holes in the cingulum areas of the prosthesis.

Figure 11: Facial view of the 6-unit screw-retained provisional exhibits ovate pontic design, which was added to help contour the soft tissue during the healing phase of implant treatment.

The CAD design file was used to mill the 6-unit BioTemps bridge from poly(methyl methacrylate) (PMMA), a material that is durable yet easily adjusted. The titanium screw-retention cylinders were bonded into the prosthesis, producing a titanium-to-titanium, implant-to-bridge interface for the immediate provisional appliance (Fig. 10). Note that the tissue, or intaglio, surface of the prosthesis was contoured to help develop a correct emergence profile (Fig. 11).

Guided Surgical Placement of Implants

By the time of surgery, the patient’s canine and incisor extraction sites had healed well (Fig. 12). The surgical guide was placed on the supporting teeth and the inspection windows were checked to verify complete seating (Fig. 13). Following IV sedation and administration of local anesthesia, a full-thickness flap was created (Figs. 14a, 14b). The purpose of the full flap was severalfold. Anterior implant esthetics can be challenging, especially in cases where there is a long span of missing teeth. A connective tissue graft was planned, with the palatal connective tissue of the full flap as the donor site. This was needed to augment the interproximal tissue, which had receded during post-extraction healing. Note that the split-thickness graft dissection was not performed until after the implants were placed.

The surgical guide was fully seated, and sequential drills were used to create the implant osteotomies in the precise positions determined with the digital treatment planning software (Fig. 15). It should be noted that the depth of the final drill for each of the four implants was precisely controlled by the metal cylinders of the surgical guide (Fig. 16).

Next, four Inclusive® Tapered Implants (Glidewell Direct; Irvine, Calif.) were placed in their predetermined positions. Each implant was connected to a mount and threaded into the osteotomy site until the shoulder of the mount was in full contact with the guide cylinder (Fig. 17). This controlled the depth of the implants, and the other dimensions of space were controlled by the very close fit of the surgical drills into the guide cylinders.

Following placement of the four implants, the 6-unit screw-retained BioTemps bridge was tried in to verify the fit of the non-engaging metal cylinders to the implants (Figs. 18a, 18b). Because the provisional bridge design was determined in unison with the virtually planned implant positions, which were executed with precision using the surgical guide, the screw-access holes aligned perfectly.

Next, a dissection was performed on the palatal full-thickness flap to harvest the tissue needed for the split-thickness graft (Figs. 19a, 19b). The connective tissue graft was then positioned within the full-thickness flap (Figs. 20a, 20b). The 6-unit BioTemps bridge was delivered, and the prosthetic screws were checked to ensure complete seating (Fig. 21). With the split-thickness graft and provisional implant prosthesis in place, the flap was sutured (Fig. 22).

The occlusion was checked for interferences that might exert unwanted forces onto the provisional restoration and implants. No adjustments were necessary, as the prefabricated screw-retained 6-unit bridge exhibited clinical fit and occlusion that mirrored the virtual wax-up (Fig. 23).

Postoperative Clinical Results

Postoperative healing was excellent (Fig. 24). The Inclusive Tapered Implants were stable and well-integrated after four months (Fig. 25). The patient reported that she had experienced little discomfort. The connective tissue graft appeared to improve the contours of the interproximal gingiva. The soft tissue adapted well to the intaglio surface of the BioTemps provisional bridge and had developed optimal contours around the implants and in the areas of the pontics (Fig. 26). From an anterior view, there appeared to be adequate gingival fill of the embrasures, confirming that the CAD-designed BioTemps bridge was effective in contouring the soft tissue in preparation for an esthetic final restoration (Fig. 27).

Figure 24: Four months postoperative, excellent healing was observed around the provisional implant bridge, including improved soft-tissue esthetics.

Figure 25: Panoramic radiograph shows integration of Inclusive Tapered Implants four months after placement.

Figure 26: Occlusal view of anterior edentulous span illustrates emergence profile development in the areas of the implants and pontics.

Figure 27: Anterior view of screw-retained BioTemps bridge in maximum intercuspation.

Conclusion

The digital tools, CAD/CAM prosthetics and restorative-driven approach utilized in this case helped address the many dental issues with which this patient presented for treatment. By the time the restorative phase of treatment began, the use of intraoral scanning, CBCT analysis, virtual treatment planning, guided surgery and immediate provisionalization helped establish the implant positioning, soft-tissue esthetics and occlusal scheme needed for an ideal prosthetic outcome. As other published reports confirm, the state-of-the-art tools and techniques described in this series are producing highly accurate, predictable results in a wide variety of clinical indications.3-6

Part 3 Preview

In the final article of this series, we will discuss the planning and milling of the final 6-unit screw-retained implant bridge. Fabricated from BruxZir® Full-Strength Solid Zirconia, the final restoration illustrates the precision and versatility of dental CAD/CAM technology, which, based on changes made to the PMMA try-in appliance, is used to fine-tune the final prosthetic design for optimal function, esthetics and occlusion. Stay tuned to see the results that can be achieved utilizing the latest in digital technology.

NOTE: Digital treatment planning and corresponding imagery featured in this case provided by Zach Dalmau, R&D Project Manager at Glidewell Laboratories.

References

  1. Farley NE, Kennedy K, McGlumphy EA, Clelland NL. Split-mouth comparison of the accuracy of computer-generated and conventional surgical guides. Int J Oral Maxillofac Implants. 2013 Mar-Apr;28(2):563-72.
  2. Jones PE. Creating surgical guides using CBCT and intraoral scanning. Inclusive. 2012;3(3):83-90.
  3. Jones PE. Clinical case report: iTero digital scanning technology and tooth-supported surgical guides. Inclusive. 2013;4(2):55-64.
  4. Jones PE. Accurate implant placement. Dent Today. 2013 Nov;32(11):124-8.
  5. Jones PE. Implant planning and placement with a guided surgical guide. Dental Products Report. August 2014.
  6. Deeb GR, Soliman O, Alsaad F, Jones P, Deluke D, Laskin DM. Simultaneous virtual planning implant surgical guides and immediate laboratory-fabricated provisionals: an impressionless technique. J Oral Implantol. 2016 Aug;42(4):363-9.
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