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Written by Bart McFarland, DMD Wednesday, 20 June 2012 13:59
Dentistry is much like life; it is in constant change.
This article will demonstrate a case in which CAD/CAM and 3-dimensional (3-D) cone beam computed technology (CBCT) technologies were used to complement each other.
A BRIEF BACKGROUND
CAD/CAM technology in dentistry allows the clinician to capture an image of the prepared tooth, virtually design a restoration of choice, and then to have the restoration milled for final finishing and patient delivery.
Three-dimensional CBCT involves using x-ray technology to allow the clinician to see the image in 3-D planes. In the author’s opinion, the diagnostic ability of 3-D CBCT could become the standard of care in the future. With this technology, we can place the correct implant size, both in length and width, for the amount of available bone. The next step in 3-D CBCT is the ability to transfer this information to a surgical guide. These guides can be secured in the oral cavity by teeth or osseous structures. After securing the guide, it will act to control the placement of the implant into actual bone as it was placed on the 3-D CBCT image. The placement can not only control the angle but the depth of the implant.
By combining these technologies, doctors can not only place an implant with guided control of depth and lateral angles, but can use CAD/CAM to design and have the crown fabricated before an implant is placed.
Diagnosis and Treatment Planning
A 17-year-old female patient came into our office with a congenitally missing tooth No. 10 (Figure 1). She reported that orthodontic treatment had been completed and that she wanted to restore the space with an implant and crown.
We took a 3-D scan (GALILEOS [Sirona Dental Systems]) to determine the amount of bone available. After acquiring the scan, it was noted there was 5.26 mm of bone located in a buccal-lingual direction, and 16.89 mm of vertical bone (Figure 2). The soft-tissue measurement was more than 11.41 mm in the buccal-lingual direction. There was quite a discrepancy between the soft-tissue measurement and the bone measurement in the buccal-lingual direction.
|Figure 1. Patient presented with congenitally missing tooth No. 10.||Figure 2. The 3-dimensional (3-D) GALILEOS scan (Sirona Dental Systems) to determine available bone.|
|Figure 3. Smile asymmetry was noted and discussed with the patient.|
The clinical examination revealed that the midline of the maxillary and mandibular incisors was correct. The space between teeth Nos. 6 and 8 was 2.0 mm greater in width than the space between teeth Nos. 9 and 11 (Figure 3). The patient was informed that there was a size discrepancy that would have to be considered during the procedure.
The patient’s health history was unremarkable, and she reported that she had no allergies.
A 7-step treatment plan was developed for this particular patient:
- The 3-D GALILEOS scan with radiographic bite wafer (SICAT) in place
- Design a virtual crown using the CEREC 3 software (Sirona Dental Systems), transferring the virtual crown information onto the scan before a virtual implant is placed in the 3-D GALILEOS scan
- Place the virtual implant in the patient’s 3-D GALILEOS scan with the knowledge of bone width, height, and virtual crown position
- Have a surgical guide made
- Place the implant in the model and prep the abutment
- Before implant surgery, make a crown based on surgical guide information
- Place the implant and abutment crown in a single office visit.
The treatment plan was presented and discussed, and informed consent was explained and signed by the patient and her parents.
At the first appointment, treatment began by taking a 3-D GALILEOS scan with a radiographic bite wafer held onto the teeth by a vinyl polysiloxane bite registration material (Futar D [Kettenbach]) (Figure 4). After the scan, alginate impressions (KromaFaze [DUX Dental]) were taken on both the maxillary and mandibular arches. Then, the shade was selected for the crown and recorded.
Next, the maxillary arch stone model was scanned with the CEREC 3 Bluecam (Sirona Dental Systems) to make the virtual crown (Figure 5). At that time, the virtual crown was transferred onto the patient’s 3-D scan (Figure 6) so that proper placement of the implant could be achieved with regard to the planned position of the crown. This is important for several reasons: ability to use stock abutments; easier to restore implant because of proper placement in respect to the placement of the future crown; less expensive for the patient (no custom abutment); less time to restore; more stable restoration due to fewer angles of the abutment; and better aesthetics due to proper placement relative to tissue and bone considerations.
After the virtual crown was placed on the patient’s 3-D scan, the implant was then placed in the 3-D scan by measuring bone volume; this was done so that the implant would be placed in the optimum position to the bone and soft tissue of the ridge (Figure 7). The virtual implant design was completed and sent to SICAT in Germany to make the surgical guide. Included in the information is the type of implant to be placed along with the size of the implant. There was also a model of the arch in which the implant was placed, and a detailed DVD description that communicated where to place the implant so the surgical guide could be constructed.
|Figure 4. Radiographic bite wafer; vinyl polysiloxane bite registration material (Futar D [Kettenbach]) placed for retention.||Figure 5. Virtual crown was designed using CEREC 3 Bluecam (Sirona Dental Systems) software.|
|Figure 6. Virtual crown transferred to the 3-D scan to aid in proper placement of the implant.||Figure 7. Implant placed on the computed tomography scan using 3-D software.|
The surgical guide came back from SICAT and was placed on the upper model to verify retention (Figure 8). Next, the upper model was used to make a soft-tissue impression (Blu-Mousse [Parkell]) in the area of tooth No. 10 (Figure 9). After the soft-tissue impression was completed, the implant analog was placed into the model by making a notch cut into the model under the area of the crown to be placed. The surgical guide (SICAT) was then placed on the model, and the analog was put into position by the 3i hardware (3.4 analog [BIOMET 3i]) (that replicates the implant holder placed into the surgical guide [Figure 10]). After the analog was in place, dental stone was mixed and poured into the notch of the base of the model to fix the analog onto its surgical position (Figure 11). After the analog was fixed into the model, the gingival tissue was placed (Softissue Moulage [KerrLab]) back into its proper placement by the tissue impression we took earlier (Figure 12). The gingival tissue was formed; then, the abutment was placed onto the analog by screw retention and the gingiva was trimmed around the abutment. Next, the abutment was prepped with diamond burs (Neo Diamond; medium grit No. 11618 [Microcopy]).
Once the abutment was prepped, CEREC liquid (Vita) was placed and blown thin with an oil-free air syringe. CEREC powder (Vita) was then applied, followed by a quick burst of air to rid the surface of any clumps (Figure 13). Next, the CEREC acquisition unit was used to obtain an optical impression of the abutment, the crown designed, and the size of block calculated and displayed. The material chosen for this crown was lithium disilicate (e.max [Ivoclar Vivadent]) (block size: 12 mm). The block was placed in the CEREC Milling Unit (Sirona Dental Systems) and milled. Once completed, the crown was then placed onto the model to check the margins and to adjust the occlusion. (Figure 14). Then, the crown was lightly sprayed with e.max CAD Crystal Glaze Spray (Ivoclar Vivadent) and placed into the oven for 19 minutes. After the oven processing was complete, the crown was then once again placed on the model to confirm the fit and shade (Figure 15).
|Figure 8. Surgical guide received from SICAT (sent to Germany) with surgical information.||Figure 9. Soft-tissue impression with bite registration material.|
|Figure 10. Analog was held in place by the surgical guide.||Figure 11. Stone mixed and poured around the base of the model to fix the analog into surgical position.|
|Figure 12. Gingival tissue was put back into position from the soft tissue impression that was taken earlier.||Figure 13. Abutment was prepped, powdered, and readied for the impression by the CEREC unit.|
|Figure 14. Verifying the fit of the milled lithium disilicate (e.max [Ivoclar Vivadent]) crown.||Figure 15. After oven processing, the crown was seated back onto model to check fit and shade.|
At this point the patient was ready to come back for her second appointment. The patient had already taken 500 mg of amoxicillin one hour before the appointment, as prescribed; she would then continue to take 500 mg 4 times a day for 5 days. After seating the patient in the chair, she swished with a chlorhexidine gluconate solution (Perioguard [Colgate]) for one to 2 minutes. After swishing, her face was wiped down (also using Perioguard) to control the bacterial environment. The template and abutments had already been placed into a shallow bowl containing Perioguard before use (Figure 16).
Next, the surgical guide (SICAT) was placed on the teeth to check the fit. Then, the patient was anesthetized using 30-gauge needle (Safemate [Medpro]) and one carpule of Septocaine 4% (Septodont). The guide was placed again, and a tissue punch was used to remove the plug of tissue needed to gain access to the bone for the osteotomy. After the tissue punch reached bone, and the tissue plug was removed, an end cutting curette (Salvan Dental) was used to cut the tissue at the base. The surgical guide was placed back into the mouth and the bone starter bur from BIOMET 3i was used to make an indention for the first osteotomy drill. The first drill used was the 2.0 drill; a key was placed into the surgical guide made for the 2.0 drill. With the key in place, there was no wavering either buccally or lingually and there was a vertical stop to control the depth. With the drill kept well irrigated, it was guided to the vertical seat. The next osteotomy was done with a 2.75 drill with the key changed to match the 2.75 drill; it also had a vertical stop. The last used drill was a 3.0, and it also had its own key for vertical and buccal-lingual directional guiding and stops.
Next, the implant mount holder that attaches to the handpiece was used to place the implant into the osteotomy through the surgical guide. This was also completely guided, so the implant went where it was designed to go, as planned in the original 3-D scan. Next, the surgical guide was removed from the implant using a tool from the 3i kit. The reverse-threaded screw released the surgical guide from the implant and, once a surgical guide was off, the implant abutment was retrieved from the disinfectant solution and placed onto the implant. A periapical radiograph was then taken to verify fit. After fit verification, the abutment was torqued to 35 ncm. Next, the crown was retrieved from the disinfectant and tried-in to verify fit. Then, cotton was placed down into the abutment and covered with a semi-flexible composite resin (Fermit-N [Ivoclar Vivadent]) and light-cured for 20 seconds. The crown was cemented with Rely-X Luting Plus (3M ESPE) and cleaned. The occlusion was adjusted and a final x-ray taken. After the implant was placed, another scan was taken to check the position of the implant (Figure 17). Postoperative photos were also taken for records (Figure 18). The patient was given an ice pack to place for 12 hours on the area, and a soft biteguard to wear for approximately 3 months. The patient was also placed on some pain medication and a soft-food diet.
|Figure 16. Template, abutment, and crown placed in disinfectant solution before surgery.||Figure 17. After implant placed, 3-D scan taken to verify proper placement of implant.|
|Figure 18. Postoperative photo, immediately after surgery.||Figure 19. Periapical radiograph taken at one year.|
|Figure 20. Postoperative photo of implant crown at one year.||Figure 21. Periapical radiograph taken at the 2-year recall.|
The patient was in for a recall at one-year and a radiograph and photos were taken again as a part of the follow-up (Figures 19 and 20). The periapical radiograph was taken at the 2-year recall (Figure 21).
Using surgical guides allows a safe and accurate way to place implants, and when done in conjunction with the latest CAD/CAM technology, it can be very aesthetic and efficient. This case, consisting of an implant surgery and the final seating of the implant crown, took about 40 minutes, because all the planning was done before the surgery began.
The combination of CAD/CAM and 3-D CB has a bright future in dentistry for both clinicians and their patients.
Dr. McFarland received his DMD degree from the University of Kentucky. He received his Fellowship accreditation from Doctors of Oral Conscious Sedation and his Masters accreditation from International Congress of Oral Implantology. His practice focuses on computerized dentistry; therefore he lectures on both of these computerized technologies to doctors and hygienists around the United States. He invented and patented a Safemate safety needle that is used for dentistry and medicine. His private practice is in Paris, Ky, and he can be reached at (859) 987-4775.
Disclosure: Dr. McFarland is a CEREC trainer and GALILEOS trainer for Patterson Dental.
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