Thinking Out of the Box - The Use of "Virtual" Implant Treatment Planning and Surgery in Challenging Cases

Gary Orentlicher, DMD; Douglas Goldsmith, DDS; and Andrew Horowitz, DMD, MD

Three dimensional "virtual" implant treatment planning and surgery has become a hot topic in implant dentistry. Most major implant manufacturers currently have or are creating software and instrumentation to perform computer-guided implant surgery. Major implant meetings frequently have lecturers extensively speaking on this topic.

Medical-grade computed tomography (CT) scanners and in-office cone beam scanners allow the dentist and surgeon to visualize a patient's bony anatomy in three dimensions before making an incision for implant placement. Visualization of all pertinent vital structures, including nerves, sinuses, soft tissue thicknesses, implant-to-restoration distances, and angulations, are all possible before surgery.^1,2 CT technology makes accurate measurements and digital-image storage possible.^3,4 The images can be imported into proprietary software programs that allow the dentist to "virtually" place implants for a patient on his/her computer (ie, Simplant® [Materialise Dental, Glen Burnie, MD], NobelProcera® [Nobel Biocare, Yorba Linda, CA], EasyGuide® [Keystone Dental, Burlington, MA], Facilitate™ [AstraTech Dental, Waltham, MA]). From the virtual treatment plan, surgical drilling guides can be fabricated. These surgical guides allow the doctor to surgically place the planned implants in the patient's mouth, in the same positions as the virtual treatment plan.

All of the current systems have similar protocols. First, the dentist creates a prosthesis for the patient to wear during their CT scan. This is a partial or full denture (scanning prosthesis) that duplicates the planned final restorations. The CT scan is then taken with the patient wearing the scan prosthesis. This allows the dentist to visualize the relationship of the restorations to the underlying bone. A software program (ie, Simplant, NobelProcera, EasyGuide, etc) is then used to virtually place implants in the ideal position, relating the planned restorations to the underlying bone. The dentist then downloads his virtual treatment plan to the software company for fabrication of a surgical guide. The surgeon uses the surgical guide, with implant-specific drilling instrumentation, to precisely place the implants. This technology is ideally suited for cases where immediate placement of implants is planned.^5-9 The provisional or final restorations can be planned before surgery and placed with minimal if any alteration. The treatment-planning process is truly a restoratively driven treatment plan.

Virtual treatment planning and computer-generated drilling guides benefit the patient by allowing flapless surgery, reduced surgical time, reduced discomfort and swelling, and quicker return to their lives and work.^10-13 It benefits the dentist by reducing chair time, stress at the time of surgery, and potential surgical complications, as well as facilitating an accurate means of placing dental implants according to a predetermined restoratively driven treatment plan.^9,14-18 Cases can be treated as a two-stage, single-stage with healing abutments, or with an immediate, temporary, or final prosthesis insertion.

Computer-generated implant planning and placement can be used for any implant case. In the authors' practice, we have found that these technologies are useful in the following cases:

• Three or more implants in a row.
• Nerve proximity close to planned implant position.
• Questionable bone volume (deficient width, height, or unusual bony contours or concavities).
• Problems related to the proximity of adjacent teeth.
• When the implant position is critical to the planned restoration.
• Complex problems where there has been a significant alteration of the bony anatomy (ie, elective bony recontouring and/or reduction, bone grafting, distraction, pathology, trauma, etc).
• Patients with medical co-morbidities (ie, radiation therapy, blood dyscrasias).

The authors feel that the use of virtual 3-D implant planning and surgery is especially beneficial in the planning of challenging and difficult cases. Many of these patients may have severe resorption of the maxillary and/or mandibular ridges from disuse atrophy or long-term denture wear. They may have lost bone, teeth, and soft tissue as a result of a traumatic injury. Bony defects, of varying sizes, can occur as a result of benign or malignant pathology of the jaws. Reconstructive surgical procedures to treat benign and malignant diseases can leave areas of abnormal bony anatomy and scarred soft tissue. Additionally, head-and-neck cancer patients are often treated with radiation therapy which may potentially alter healing capacity. Previous surgical procedures, including the placement of many different types of dental implants (ie, blade and subperiosteal implants) can leave patients with challenging bony defects. Patients may have congenital or developmental growth deformities that require reconstructive procedures and dental implants. Preparatory soft or hard tissue grafting procedures can result in distorted or abnormal anatomy. Orthopedic and spinal problems may limit the amount of time a patient can sit in a dental chair. Patients may have associated medical problems such as blood dyscrasias, anticoagulation issues, or significant cardiovascular disease. These issues may necessitate specific medication protocols that cannot be altered or adjusted before surgery. Finally, patient stress, anxiety, and phobias can prevent them from undergoing procedures that require long periods in a dental chair.

These challenging cases may require a large amount of planning and preparation. Treatment plans may require multiple sequenced procedures, sometimes using multiple interdisciplinary dental or medical specialties. These cases are ideal for treatment using virtual treatment planning and surgery.^8-11,16 Not only does the technology allow the doctor to visualize atrophic or distorted jaw anatomy before surgery, but it also allows the dentist or surgeon to place implants flaplessly with precision.^10-13 Implants can be placed with accuracy and predictability, with as little trauma to the soft tissue and bone as possible.^10-13 Bleeding, swelling, and alteration of bone and soft tissue vascularization are minimized.^10-13 Implants can be placed quickly, thus minimizing the patient stress, pain, and time in the dental chair.

Following are two examples that are descriptive of challenging cases that have benefited by planning and surgery using these technologies.

CASE 1

A 75-year-old woman presented with severe atrophy of her maxillary and mandibular ridges from long-term denture wear (Figure 1). She was unhappy with her inability to retain her dentures and function normally. After discussion of her options, it was determined that implant-stabilized overdentures was her best option.

Because of the severe atrophy of her maxillary and mandibular ridges, it was impossible to determine the anatomy of the underlying bone for the evaluation and placement of dental implants. Barium upper and lower dentures were fabricated (Figure 2) using the Simplant® protocol. While wearing these barium dentures, CAT scans were taken (Figure 3). After evaluation of the scans and determination of the full extent of the atrophy of the ridges, the patient was virtually treatment planned for five Endopore® implants (Sybron Implant Solutions, Orange, CA) in the maxilla and six Nobel Biocare implants in the mandible (Figure 4). Bone-borne SurgiGuides™ (Materialise Dental) were ordered based on the virtual treatment plan (Figure 5).

Using the SurgiGuides, all of the implants were successfully placed in one visit (Figure 6; Figure 7; Figure 8). After allowing for 4 months of osseointegration, a framework and overdenture was successfully fabricated and inserted in each arch (Figure 9 and Figure 10).

CASE 2

A 15-year-old girl was born with an incomplete expression of a cleft palate, multiple congenitally missing teeth, and associated atrophy and hypoplasia of her upper jaw. A concomitant severe Class III skeletal malocclusion was present (Figure 11).

Using cephalometric and dental model analysis, it was determined that a staged surgical, orthodontic, and prosthetic treatment plan was indicated for this patient. The first stage involved a CT scan of the patient's maxilla. The DICOM images generated from this scan were sent for fabrication of a stereolithic medical model (Medical® Modeling, Medical Modeling, Inc, Golden, CO). Using this stereolithic model, a maxillary anterior segmental osteotomy for distraction osteogenesis was planned. Pediatric maxillary distractors (KLS Martin, Tuttlingen, Germany) were prebent and positioned on the model to determine the ideal vector of distraction (Figure 12; Figure 13; Figure 14).

In the operating room, an anterior maxillary osteotomy for distraction osteogenesis with bilateral placement of the maxillary distractors was performed (Figure 13 and Figure 14). After a 7-day healing latency period, the distractors were activated at a rate of 0.9 mm per day. The anterior maxilla was distracted anteriorly, a total of 8 mm, advancing the anterior maxilla and creating space and bone in the maxillary premolar regions for dental implants. Once the distraction was complete, the maxilla was allowed to heal and consolidate for 3 months. The distractors were then removed in the office under IV sedation and local anesthesia. One month later, block bone grafts were harvested from the chin and grafted to the distracted bone to augment the width of the areas for future implant placement (Figure 15). In total, 8 mm to 9 mm of new bone was created on each side of the arch for implant placement (Figure 16).

Two months later, impressions were made and a maxillary radiographic guide and radiographic index were fabricated according to the NobelGuide™ (Nobel Biocare) protocol (Figure 17). A second CT scan was then taken with the patient wearing these appliances. Using the Procera software, implants were virtually planned in the sites where the maxilla was distracted and grafted (Figure 18 and Figure 19). Using the NobelGuide, implants were placed in the areas of teeth Nos. 4, 5, and 12 (Figure 20 and Figure 21).

After allowing 4 months of osseointegration, the three implants were used by the patient's orthodontist for absolute orthodontic anchorage in the movement of the patient's remaining maxillary dentition (Figure 22). Once orthodontics is completed, restoration of the implants and dentition will be completed.

CONCLUSION

Patients present to our offices and clinics with many multifactorial reconstructive problems, both small and large. Jaw atrophy, trauma, congenital deformities, growth abnormalities, pathology, previous surgeries, and medical and psychiatric issues all can create challenging reconstructive cases for the dental implant surgeon. CT-guided "virtual" implant treatment planning and surgery is especially beneficial in the planning and treatment of patients who present with these challenging and difficult cases.

DISCLOSURE

Drs. Orentlicher and Goldsmith have received honoraria from Nobel Biocare and Materialise, and are current consultants for Keystone Dental.

ACKNOWLEDGMENT

The authors would like to thank Dr. Leonard Kobren (Case 1: prosthodontist), Dr. Irwin Miller (Case 2: restorative dentist), and Dr. Gerald Gardner (Case 2: orthodontist) for their help in treating these challenging cases.

References

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2. Pattijn V, van Cleynenbreugel T, vander Sloten J, et al. Structural and radiological parameters for the nondestructive characterisation of trabecular bone. Ann Biomed Eng.2001;29(12):1064-1073.

3. Todd A, Gher M, Quintero G, Richardson AC. Interpretation of linear and computed tomograms in the assessment of implant recipient sites. J Periodontol. 1993;64(12):1243-1249.

4. Gehr ME, Richardson AC. The accuracy of dental radiographic techniques used for evaluation of implant fixture placement. Int J Periodont Rest Dent. 1995;15(3):268-283.

5. Tardieu P, Vrielinick l, Escolano E. Computer-assisted implant placement. A case report: Treatment of the mandible. Int J Oral Maxillofac Implants. 2003;18:599-604.

6. van Steenberghe D, Naert I, Andersson M, et al. A custom template and definite prosthesis allowing immediate implant loading in the maxilla: A clinical report. Int J Oral Maxillofac Implants. 2002;17(5):663-670.

7. van Steenberghe D, Ericsson I, Van Cleynenbreugel J, et al. High precision planning for oral implants based on 3D CT scanning. A new surgical technique for immediate and delayed loading. Appl Osseoint Res. 2004;4:27-30.

8. Wendelhag I, van Steenberghe D, Blombäck U, Glauser R. Immediate function in edentulous maxillae with flapless surgery including a 3-D CT-scan based treatment planning procedure. Clin Oral Implants Res. 2004;Special Issue. Abstract. Poster 144.

9. van Steenberghe D, Glauser R, Blombäck U, et al. A computed tomographic scan derived customized surgical template and fixed prosthesis for flapless surgery and immediate loading of implants in fully edentulous maxillae. A prospective multicenter study. Clin Impl Dent Rel Res. 2005;7(Suppl 1):S111-S120.

10. Hahn J. Single stage, immediate loading, and flapless surgery. J Oral Implantology. 2000;26(3):193-198.

11. Campelo LD, Dominguez Camara JR. Flapless implant surgery: a 10-year clinical retrospective analysis. J Oral Maxillofac Implants. 2002;17(2): 271-276.

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13. Becker W, Wikesjo UM, Sennerby L, et al. Histologic evaluation of implants following flapless and flapped surgery: a study in canines. J Periodontol. 2006;77(10):1717-1722.

14. Tardieu P, Vrielinck L. Implantologie assistée par ordinateur: le propramme SimPlant/SurgiCase™ et le SAFE System™ mis en charge immediate d'un bridge mandibulaire avec des impalt transmuqueux. Implant. 2003;9: 15-28.

15. Tardieu P, Vrielinck L, Escolano E, et al. Computer-assisted implant placement : scan template, simplant, surgiguide, and SAFE System. Int J Periodontics Rest Dent. 2007;27(2):141-149.

16. Vrielinck L, Politis C, Schepers S, et al. Image-based planning and clinical validation of zygoma and pterygoid implant placement in patients with severe bone atrophy using customized drill guides. Preliminary results from a prospective clinical follow-up study. Int J Oral Maxillofac Surg. 2003;32(1):7-14.

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Figure 1 Case 1. Maxilla and mandible, preoperative view.
Figure 2 Barium scan prosthesis, mandible.		Figure 3 Preoperative CT scan, maxilla and mandible, while wearing scanning prosthesis.
Figure 4 Virtual implant placement, maxilla and mandible. Note the short Endopore implants used in the maxilla.
Figure 5 Stereolithographic model and bone-borne SurgiGuides, maxilla and mandible.
Figure 6 Implant placement, maxilla; SurgiGuide was used.
Figure 7 Implant placement, mandible, using implant-specific drilling instrumentation and SurgiGuide (left). Final implant placement with healing abutments (right).
Figure 8 Virtual treatment plan, maxilla and mandible, and postoperative panorex (center).
Figure 9 Overdenture framework, maxilla and mandible.
Figure 10 Final overdenture fabrication.
Figure 11 Case 2. Preoperative occlusion frontal, right, and left sides.
Figure 12 Facial stereolithographic model (Medical Modeling) with precontoured and secured maxillary distractors; osteotomies drawn in.
Figure 13 Distractor, prebent and secured to planned osteotomy site, right side (left). Intraoral segmental osteotomy with distractor in place, right side (right).
Figure 14 Distractor, prebent and secured to planned osteotomy site, left side (left). Intraoral segmental osteotomy with distractor in place, left side (right).
Figure 15 Block bone grafts, right and left maxilla.
Figure 16 Pretreatment maxillary arch (left) and posttreatment maxillary model (right). Note increased arch space created in bicuspid areas (arrows).
Figure 17 Scanning prosthesis, maxilla.
Figure 18 NobelProcera software image, right and left maxilla, distracted bone and block graft with stabilization screws.
Figure 19 NobelProcera virtual treatment plan of three implants in the maxilla. Note the congenital incomplete closure of the hard palate.
Figure 20 NobelGuide fabricated from the virtual treatment plan.		Figure 21 Postoperative panorex; implants placed using NobelGuide.
Figure 22 Frontal and occlusal postoperative occlusion (orthodontics in progress).
ABOUT THE AUTORS
Gary Orentlicher, DMD Private Practice Scarsdale, New York
Douglas Goldsmith, DDS Private Practice Scarsdale, New York
Andrew Horowitz, DMD, MD Private Practice Scarsdale, New York