August 1, 2005
by Gilbert Tremblay, BSc, DMD
Less than 15 years ago, diagnosis and treatment planning were largely based on study models, along with standard radiology procedures such as panorex, periapicals, occlusals and cephalometric radiograph. Since the introduction of radiological computer-assisted imaging, diagnosis and treatment planning has advanced toward a higher level of precision and predictability–giving the practitioner a better surgical result.
In fact, computed tomography [CT] enables precise evaluation of the position of dental implants relative to critical structures such as the inferior alveolar canal, the mental foramen, maxillary sinus, nasal cavity, incisive foramen, anterior mandibular nerve loop, adjacent teeth, and buccal or lingual cortical plates. In approximately 95 percent of the cases that use computed tomography, bone quantity measurements have an accuracy of 1mm. This is only true for 30 percent of the cases where panoramic radiology is used for measurements. Furthermore, for mandibular cases, the inferior alveolar canal cannot be identified in more than 30 percent of the cases that use periapical, panoramic or tomography techniques. It can be identify with computed tomography nearly 100 percent of the time.1
THE POTENTIAL OF COMPUTER TECHNOLOGY
Computerized assisted technology offers the dental surgeon an array of different applications related to implant surgery. Beside providing diagnostic information and allowing the evaluation of proposed implant sites, one may also develop a 3D image of a maxilla and mandible (SimPlant, Materialize Medical USA), a stereo-lithographic template (Materialize Medical USA), surgical bone or soft tissue templates, and prosthesis fabrication (Technobar, SinLab Biostructures, Blainville, QC).
INNOVATING WITH THE TECHNOLOGY
Here is a case study related to advanced mandibular resorption (div C, Misch-Judy). This female has severe vertical bone loss in her posterior ridges. Both mandibular foramen exiting superiorly on the surface of each corresponding ridge. Using computerized technology, an incision guide (GT incision guide) was processed to help orientate the scalpel over the crest of the mandibular ridge avoiding the mandibular nerve, eliminate possible iatrogenic nerve damage and to help speed-up the incision process.
In fact, one can fabricate an incision guide from a stereolithic model that localizes all major structures (i.e. colour the actual mental nerve), which will help direct the initial incision at the time of surgery.
The following is a case presentation illustrating the different computerized applications. They will be used for the initial case preparation, during the surgery and for the final prosthesis.
The patient is a 52-year-old woman who presented with an ill-fitting lower denture, she was complaining of an “electric shock” sensation in her lower lip. Severe vertical resorption was observed in her mandible. The patient had lost all of her upper and lower teeth more than 30 years ago. She was interested in obtaining implant-supported prostheses. Three treatment plan options where presented to the patient. An iliac bone graph followed by an implant supported prosthesis, a five implants between the mandible foramen with an implant supported prosthesis, or a new lower denture. The patient did not want the iliac crest graft, and decided to proceed with the second option.
This computer-assisted case allowed several steps of the treatment planning and execution to be enhance.
A GT incision guide rendered the incision predictable and safe relative to the mandible nerve, reduced irregularity in the incision line design pattern and lowered the total surgical time.
The bone supported osteotomy guide optimized the implant positioning therefore allowing a prosthesis with better force distribution, increasing patient comfort and decreased healing time and convalescence, and finally reduced surgical time.
A Technobar computerized titanium bar eliminates all soldering joints and the lack of precision that can occur when articulating all the different bar components in the conventional manner. Accordingly to the Technobar laboratory (SinLab, Boisbriand, QC), there is only a 5 micron discrepancy between the cast and the bar fabrication. Since the Technobar bar is much lighter then the conventional bar, patient comfort is increased.
One may say that electronic surgery, GT surgical guides, bone osteotomy guides are time consuming to prepare, but my experience with this case was the extra preparation procedure is largely compensated by the fact that the surgery can proceed faster, reduce operatory time, more precision, better predictability, less iatrogenic outcomes, and it is more beneficial for the patients’ healing.
Dr. Tremblay has a private practice with an emphasis on implant, reconstructive and esthetic dentistry in Pierrefonds, QC. Professional memberships include a Fellow of the International Congress of Oral Implantology, member of the SimPlant Academy and the American Academy of Cosmetic Dentistry.
Oral Health welcomes this original article.
1.Misch C.E.: Implant dentistry; computed tomography, pp. 84, 85, St-Louis, 1999, Mosby.
2.Misch C.E.: Short versus long implant concepts- Functional surface area, Oral Health, 1999, p13-21.
3.Morton D, Jaffin R, Weber H.P, Immediate restoration and loading of dental implants: clinical considerations and protocols, Oral and Maxillofacial Implants, 2004, vol. 19, p 103-108.
4.Cochran D, Morton D, Weber H.P, Consensus Statements and recommended clinical procedures regarding loading protocols for endosseous dental implant, Oral and maxillofacial implants, 2004, vol. 19, p. 109-113.
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