Abstract

Surgical guides have evolved to the point that they can be created with the aid of computer-assisted tomography (CT) technology. Surgical guides also are used in construction of the prosthesis prior to implant surgery. With existing guide techniques, the prosthesis is screw retained, or cone-shaped temporary abutments may be used to overcome the lack of parallelism of the implants. With the New Twist technique, we are able to create the surgical guide in such a way that optimum bone may be used and the rotational position of the implant may be established for the surgeon and for the laboratory. Custom abutments are inserted at the time of surgery, as is an esthetic, functionally provisional cemented prosthesis. Castings for the finished ceramo-metal bridge are fabricated before surgery is performed. The final prosthesis then is easily constructed by the restorative dentist during just 3 simple patient visits.

Introduction

Surgical guides are created to conform to the prosthetic design. They record the implant location and angulations. Many techniques are available for construction of the surgical template. These are based on available bone as revealed in radiographic studies, placement of prosthetic teeth on diagnostic models, and the nature of the occlusion.1 Computer-assisted tomography (CT), which was introduced by Hounsfield in 1942, allowed for 3-dimensional reconstruction of the area of interest. Cross-sectional slices correlated with panoramic views and axial slices provide accurate representation of the patient's jaws.1 A temporary prosthesis or a diagnostic setup is fabricated before the patient undergoes CT scanning. Radiopaque markers are placed into the radiographic guide, and the patient is scanned while wearing the guide. This diagnostic guide then is incorporated into the scan and is placed in computer software programs such as SimPlant (Materialise Dental, Louven, Belgium), NobelGuide (Nobel Biocare, Göteborg, Sweden), and Implant Logic Systems (Cedarhurst, New York). Optimum positioning of the implants is described in the planning data. These data then can be transmitted to the software company, and a surgical guide can be constructed.2 

Materials and Methods

Existing guides

SimPlant surgical guides are tooth borne, bone borne, or tissue borne.3,4 Factors associated with these guides include the following:

Bone guide

  • The flange can be too long, requiring an extensive flap.

  • A shortened flange can result in instability of the guide.

  • Multiple guides are necessary for sleeves of different sizes for sequential drilling (Figure 1).

Figure 1.

Multiple guides used in SimPlant technique

Figure 1.

Multiple guides used in SimPlant technique

Tissue guide

  • The guide must be made from a duplicate denture.

  • The proportions of radiopaque material in the base portion of the duplicate denture to those in the teeth portion of the denture are critical.

  • It is difficult to communicate with the laboratory regarding preconstruction of the prosthesis.

  • The guide is not stable on soft tissue.

  • Multiple guides are necessary for sleeves of different sizes for sequential drilling (Figure 1).

Tooth-borne guide

  • Models must be sent to the laboratory.

  • Multiple guides are necessary for sleeves of different sizes for sequential drilling (Figure 1).

The SAFE system (Materialise) is used along with SimPlant software to produce the prosthesis prior to implant placement. This system does not record the rotational position of the implant. The finished prosthesis is screw retained and looks similar to a screwed-in denture.5 This system uses SimPlant software and has the same limitations as SimPlant.

Nobel Biocare SurgiGuide

  • This sophisticated guide is geared to construction of the prosthesis before surgery.

  • A single guide is necessary for placement of drills of multiple sizes through the use of reduction sleeves.6 

  • This software has the ability to record the rotational position of the implant, but this information is not transferred to the surgical guide.

  • No provision allows the making of custom abutments or correction of the position of the implant. Thus the implant may not be placed in the optimum bone position.

  • The prosthesis is screw retained, or temporary conical abutments are constructed.

  • Constructing the final cast prosthesis has proved risky because of potential inaccuracies and possible poor fit.

Keystone Dental

This newer software planning program (Keystone Dental, Burlington, Mass) has many features, but a link for creating a sophisticated presurgical prosthesis has not been developed.

These guides do not take into consideration the diameter, rotational position of the implants or analogs. This limitation prohibits the construction and placement of custom or angled abutments in a prefabricated prosthesis in the proper rotational position.

New Twist Technique as a Modification to Existing Surgical Guides

The bold type represents enhancements to the Nobel Biocare protocol and its “Teeth in an Hour” technique:

  • A denture is constructed. The denture should exhibit adequate retention and proper occlusion and should satisfy the patient's esthetic requirements.

  • Radiopaque markings are placed in the denture (Figure 2). Radiopaque gutta percha or temporary stopping is placed in predrilled holes in 6 places on the labial flange of the denture and in 4 places on the palatal side of the denture.

  • A bite registration is taken with a polysiloxine material (Blu-Mousse, Parkell Inc, Farmingdale, NY).

  • The patient is sent for a double CT scan. A scan is taken with the denture in place on the jaw to be treated. A scan of the denture is made with the denture held in position in a jig.

  • The radiologist sends the DICOM files to the dentist via disk or email.

  • Software is used to convert the files to the necessary format. This software combines the scan of the denture with that of the patient. The patient's jaw can be viewed separately or with the prosthesis in place in the computer.

  • Virtual surgery is performed on the patient. Implants are chosen and are placed in optimum position for a cement-retained case (Figure 3a and b). With the latitude to construct custom or angled abutments, the case can be planned with use of the maximum available bone. Implants do not have to be placed in a position wherein a screw hole must be in alignment with the long axis of the implants and the cingula of the anterior teeth or the central fossae of the posterior teeth.

  • The surgical guide is constructed within the computer.

  • The plan is sent electronically to Nobel Biocare.

  • A surgical guide, a duplicate denture, and necessary parts are ordered.

  • A marking is made on the guide adjacent to the labial surface of the individual sleeves (Figures 4 and 5).

  • The duplicate denture and the surgical guide along with a bite registration are sent to the dental laboratory.

  • The laboratory places the implant analogs into the New Twist Guided Cylinders (Figure 6), which are oriented with the labial markings, and pours a soft tissue model (Figure 7). New Twist Guided Cylinders have an indexing guide on them. The index can be an external hex, an external tri-lobe, or an internal hex. Thus the internal hex, the internal tri-lobe, or the external hex of available implant analogs can be accommodated.

  • The duplicate denture is placed on the soft tissue model, and the case is articulated (Figure 8).

  • An index is made of the setup, and custom cast abutments are constructed. These abutments are constructed to fall within the confines of the index of the setup and are made parallel to each other to allow the insertion of a cemented prosthesis.

  • Cast copings are made on these abutments, but they are not soldered at this time.

  • An acrylic temporary bridge is made to fit the custom abutments, and the laboratory work is sent to the dentist.

  • The patient is anesthetized, and the surgical guide is inserted into the patient's mouth. The patient bites on the bite registration. The guide is secured by anchor pins that pass through the guide into the patient's bone.

  • The Nobel Biocare surgical protocol is followed for the making of osteotomies.

  • The implants are inserted with the rotational mark on the labial side of the implant driver, with care taken to stop at the mark on the labial side of the individually marked sleeves and/or guide.

  • The surgical guide is removed.

  • Custom abutments are inserted into the implants (Figure 9a).

  • Cast copings are placed on the abutments and are joined with acrylic, then a pickup impression is taken (Figure 9b and c).

  • The temporary bridge is cemented, and the indexing impression is sent to the laboratory for joining (Figure 9d).

  • In approximately 4 months, the temporary bridge is removed, the joined castings are tried in, and a bite registration is taken.

  • A bisque try-in of the porcelain is made.

  • The completed bridge then is inserted (Figure 10).

Figures 2

and 3. Figure 2. Denture with radiopaque markings to be used as radiographic guide. Figure 3. Computer-assisted tomography (CT) planning: (a) View with the bone in place. (b) View with only implants visible

Figures 2

and 3. Figure 2. Denture with radiopaque markings to be used as radiographic guide. Figure 3. Computer-assisted tomography (CT) planning: (a) View with the bone in place. (b) View with only implants visible

Figures 4–7. Figure 4. Facial markings on mouth side of the surgical guide. Figure 5. Facial markings on tissue side of the surgical guide. Figure 6. New Twist Guided Cylinders. Figure 7. Construction of soft tissue model

Figures 4–7. Figure 4. Facial markings on mouth side of the surgical guide. Figure 5. Facial markings on tissue side of the surgical guide. Figure 6. New Twist Guided Cylinders. Figure 7. Construction of soft tissue model

Figures 8–10. Figure 8. Model articulated with the use of duplicate denture. Figure 9. Intraoral view of (a) abutments, (b) copings, (c) solder index, and (d) fixed cemented temporary restoration. Figure 10. Completed porcelain bridgework

Figures 8–10. Figure 8. Model articulated with the use of duplicate denture. Figure 9. Intraoral view of (a) abutments, (b) copings, (c) solder index, and (d) fixed cemented temporary restoration. Figure 10. Completed porcelain bridgework

Results

A fixed, cement-retained esthetic temporary prosthesis thus is constructed in one visit. Completion of the final cemented prosthesis requires 3 additional visits for noninvasive procedures.

Discussion

Key steps in this procedure involve indexing of the implant analogs and communication of this information to the surgeon via the surgical guide. This technique permits restorative doctors to construct a fixed prosthesis of the same quality as the ones they have been providing for their patients on natural teeth. This highly esthetic prosthesis eliminates the need for all additional hardware and screws included in the screw-retained prosthesis.

The surgeon still can perform flapless surgery while minimizing discomfort to the patient. This method can be performed through the team approach of the restorative dentist who works with a surgical specialist, or by the implantologist who provides both surgical and prosthetic treatment. In either scenario, this technique should motivate treating doctors to use surgical guides more frequently to achieve desired results for their patients.

Acknowledgments

Thanks to Scott Salmon of Ion Design for his assistance in taking my idea and helping to transfer it to a working model. He provided the specifications for the guided cylinder and the layouts and drawings of the surgical guide modifications. Steven Pigliacolli from the Marotta Dental Studio in Farmingdale, New York, performed the laboratory work and provided photographs of the laboratory procedures.

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Trevor Bavar, DDS, is a private practitioner in Yonkers, New York, who serves as clinical professor at New York University College of Dentistry in New York, NY. Address correspondence to Dr Bavar at 1925 Central Park Avenue, Yonkers, NY 10710. (e-mail: bavar@bavar.com)