Practical communication is helpful in creating an optimal treatment result when removal of supporting bone is coordinated with the surgical placement of dental implants Certainly, there are many available techniques for creating surgical guides based on CBCT images (Simplant, Nobel Guide, etc.).
The shape of the X-ray beam, the limited scan volume, the processing algorithms and patient movement create areas of interpretation that can alter the accuracy of the detail when converting the raw data to create a viewable image. In preparing for the surgical placement of dental implants to support a fixed prosthesis, it can be valuable to identify potential surprises that could arise during surgery in order to provide an appropriate degree of flexibility for the surgeon while maintaining focus on the definitive treatment result.
Fixed hybrid (fixed-detachable) prostheses were traditionally designed for maladaptive denture patients with significant alveolar bone loss in the mandibular arch. This patient presented with structural concerns with the remaining maxillary dentition with significant alveolar bone, along with a history of cocaine use with specific expectations for a dental implant supported fixed restoration A surgical guide had to account for reduction of the supporting structures along with information related to the placement of the dental implants that would allow for some flexibility in the form of mid-surgery modifications to the plan.
A vacuum formed thermoplastic surgical guide provides the opportunity to make use of known reference points with the goal of providing meaningful information to the surgeon for the removal of supporting bone and placement of the dental implants. The MiniSTAR S (Great Lakes Orthodontics) has the ability to apply positive pressure onto the master cast while simultaneously creating a vacuum beneath the working model to optimize the adaptability of the thermoplastic material while maintaining the master cast.
1. Construct a working model, and evaluate the existing tooth position using the CBCT image to identify useful landmarks as well as teeth that could be used as retention features during the surgical procedure. Mark desired location for the soft tissue (red line) and hard tissue (green line) on the model.
2. Drill holes to the desired three-dimensional position on the cast in the desired dental implant location and place a pin similar to the 2.0mm twist drill to evaluate. Remove the pins and position cast within the vacuum-forming machine using lead pellets to expose the area for the surgical guide.
3. Heat the 1.0 mm thick Copyplast material (Great Lakes Orthodontics), apply air pressure with vacuum, and cooling cycle. Cut holes in the area of the guide pins and trim extensions to the red line to demonstrate desired location of soft tissue.
4. Heat the 1.5 mm thick Splint Biocryl material and press over the Copyplast material on the master cast.Â Apply the same air pressure with vacuum and cooling cycle and cut holes to allow for guide pins. Cut holes in the area of the guide pins and trim extensions to the green line as the desired location of the alveolar bone.
5. Replace the pins and add the Straumann drilling sleeves to the guides pins. Adapt auto-polymerizing clear acrylic resin around the drilling Sleeves and cure. Remove the drilling sleeves and refine by creating buccal access in the clear acrylic resin. Â Add GC resin (contrasting red color) to hold the drilling sleeves allowing removal mid-surgery.
Teeth 2, 8 and 9 served as reference points for use during the surgical procedure and provided stable retention for the surgical guide.
The Copyplast portion was inserted after removal of 4-7, 10-13 to communicate the desired soft tissue level during bone reduction. The Splint Biocryl segment fit over the Copyplast to communicate implant position extending to the desired location of the supporting bone. The three teeth were removed prior to insertion of the immediate prosthesis.
Douglas G. Benting, DDS, MS, FACP, Spear Visiting Faculty [Â www.drbenting.com ]