| The following is a transcript of the address delivered by Dr. Julian Osorio to Peridontal Associates on October 8, 1997. |
|---|
Implant dentistry of the past has proven to be complicated, costly, and daunting to the average practitioner. This simplified system will make implants more accessible to the average patient. Increased efficiency and efficacy will bring implants to the forefront of restorative dentistry as a conventional tool to be used by every dentist.
The impetus to develop this concept was born out of sheer frustration in following the protocol established by existing implant technologies. The major obstacle I faced was the consistently vexing and costly process I incurred as a dentist trying to bring the wonderful benefits of implant dentistry to my patients.
The existing technology was not designed with the restoring dentist or prosthodontist in mind. The emphasis was on the surgical phase of the implant procedure, and the needs of the restorative dentist were an afterthought and were essentially ignored. The results exhibited this fact in the unacceptable esthetics of the final crown. I present here a chronological evaluation of the shortcomings of the existing technologies that led me to the development of this innovative approach to implant dentistry.
My first and last Cera One abutment case displayed a multitude of complications. Placement of the fixture and healing abutment by the periodontist constituted the simple phase of the overall implant procedure. Even before the patient sat in the prosthodontist's chair, the healing abutment had the tendency to loosen resulting in tissue entrapment. Hours and hours of work were required chairside to create a provisional, and as a result numerous anesthetic injections were necessary to keep the patient comfortable. In addition, recontouring and excision of the highly vascularized soft tissue around the abutment was highly unpredictable and imprecise.
One of my major frustrations at that time was the unpredictable placement of the abutment onto the fixture. To verify that the abutment was fully seated, the process required an inordinate number of radiographs and unnecessary exposure of the patient to radiation. Radiographs were needed to verify the abutment position on the fixture, the crown seating position on the abutment, and absence of excess cement around the margins after cementation. It seemed no mystery to me that a general dentist would option for the conventional three-unit bridge over the painstakingly difficult placement of implant crowns.
The next case involved another set of difficulties in achieving the proper esthetics of the implant crown. The patient presented a cracked bicuspid and opted for an implant over the conventional four-unit bridge. The reality of the surgical placement of the fixture into bone is very predictable from the osseointegration point of view; but no matter how accurate the periodontist or oral surgeon are with the positioning at the surgical phase, is still unpredictable from the restorative point of view. The best possible angulation of the fixture does not always allow for optimum position of the abutment and esthetics of the crown. In most cases, unless you are dealing with the lower posteriors where a wide table is present to obtain the long axis in a very good position, there is no way to get exact placement such that the axis hole emerges from the center or the central groove of the given tooth. In this case, the angulation of the post was towards the facial.
At stage two, there were two nice round healing caps. Unfortunately, the shape of the roots of natural teeth is not round. Generally, roots have oval, triangular, ovoidal or square shapes not consistent with the round shape of the healing caps.
Once the estheticone was in place, radiographs were taken to confirm the position of the abutment. The healing caps would strip off occasionally and acrylic would not adhere to the abutment either, making fabrication of the provisional time consuming and difficult. Often times when making the final impression, and since at that time more than today, it was common practice for the periodontist to place the abutment, I would realize that the angulation was completely off only afterwards, making it necessary to select a different abutment.
At this point, I decided to use a custom abutment. The best available at the time was the Impac one piece abutment. In order to customize these abutments, an impression of the fixtures was made and analogs placed on the impression to create a master cast. Once they were waxed and cast, a custom screwdriver had to be fabricated to screw the abutment completely down onto the fixture. I was then faced with another problem: the internal threads of the fixture did not match the internal threads of the analog, which I did not realize. The result was that once the abutments were placed in the fixtures, the crowns would not fit. In this case, two adjacent implant crowns needed to be splinted and it was necessary to section and post solder them to correct the position. I realized that the next step had to be an improvement on the one-piece component. This one was limited by the discrepancy between the laboratory and clinical situations.
In recognizing the need to improve the discrepancy between the cast/lab and chair side situations led to the utilization of the two piece component. With this system, a transfer guide could be made which could be used with accuracy in both situations.
Another case presented a greater challenge, with six fixtures in different places of the arches, each with a different angulation towards the facial. Accounted time spent chair side never took less than six or seven hours because once the healing abutment was removed, the tissue would collapse in seconds. An abutment and crown with a nice emergence profile could be fabricated, but placement of these pieces was extremely difficult and painful for the patient. Radiographs again had to be taken to assure the proper position of placement of the abutment onto the fixture. Tissue around the fixture was so firm that retraction cord had to be placed or the tissue had to be cut and recontoured in order to remove or replace the components.
A beautiful end result was achieved with proper esthetics and correct position, but with considerable cost due to the chair time needed. The process required the skill and education of a prosthodontist to wade through the obstacles.
New technology tried to circumvent this problem by creating an abutment taking into account the emergence profile. The problem with the abutment is that if the angulation is off, this emergence profile abutment only increases the possibility of losing vertical tissue height. Essentially, more tissue is being pushed out of the way. This technology is useful only for upper and lower molars, or when the fixture is in the perfect position. For the anterior teeth, where esthetics is a primary concern, the procedure is defective because of the delicacy with which the tissue needs to be handled. These abutments do not allow for the tissue to heal as desired.
The next case involved a one-stage procedure using the ITI system. This procedure allowed the tissue to heal around the abutment instead of the usual system, which required the cutting of the tissue to conform to the shape of the abutment. This was probably the most natural and esthetically pleasing gingival tissue I had seen around an implant. A temporary of the correct size could be made using a UCLA cylinder that was waxed and cast with the same emergence profile of the contours of the bicuspid it was replacing. Still, too many parts and too many steps were required to achieve these results. Also if the angulation was off, as is often the case with maxillary anterior teeth, the esthetic results were highly compromised.
This led to the idea of using computer-generated parts using CAD-CAM to create implant abutments. With a predetermined predictable finish line (a hex), we could solve the problems of marginal integrity which arose when CAD-CAM was used in conventional restorative dentistry.
In 1995, the first case to prove the usefulness of the new manufacturing technology used a fixture impression coping luted to the surgical guide. A shrink-free resin (G-C resin or Duralay) was used to secure it in place to be able to carry it to the laboratory. This guide allowed us to place an analog to determine the exact position of the fixture at Stage 1.
Our system at this time consisted of an analog, a screw, a guiding post, an impression coping, an abutment, and a provisional restoration. At Stage 2, the fit of the abutment could be visually confirmed, reducing the number of radiographs that were necessary. The only problem at that time was that the abutment still did not allow a precise site and emergence profile to emerge from under the tissue. (Since then, we have completed many cases and have learned to determine the contour, to avoid this problem.) Since the abutment was now easily placed in the correct position, we knew we eventually would be able to achieve an anatomically correct position. The abutment still had to be modified chair side with a carbide-finishing bur to reduce its size and thus develop the emergence profile subgingivally. We were moving closer to a solution of making implant technology accessible to mainstream dentistry.
The next case involving a lateral used tissue guiding healing caps to recontour the tissue around the fixture at the time of Stage 1. At Stage 2, a provisional was placed to guide the tissue to heal around the contour of the provisional. This was a proactive approach to implant dentistry that allowed us to take control of the situation and control the final restorative phases; especially, the esthetics of the implant procedure.
I began to look for a software engineer who could make this into a reality. I worked with three different teams of engineers with no success, and finally came across a biomedical consulting and manufacturing firm who put me in contact with Andrew Ziegler, my partner today.
Using software programs based on statistics that take the measurement of seven specific points around the site in question, the size of the abutment can be manufactured with predictability. Final impressions can be taken at Stage 1 and placement of the final crown can occur at Stage 2.
This new technology will allow use of either lateral retention with a screw or a cemented crown. On the lateral retention system, the problem remaining is the interface between the abutment and the crown, which must be sealed to avoid seepage where fluids run into the fixture site. In either type, the crown can be easily removed and replaced if for some reason the need arises in the future. If the size of the post and tooth does not allow for enough space for an abutment, porcelain can be baked onto the fixture. The system will be able to utilize gold, titanium and ceramic abutments.
The problem of using a shrink-free resin (GC resin or Duralay) in making an impression during surgery and the possibility of contamination of the surgical site are eliminated through the use of custom made impression copings. This coping snaps into the fixture and is secured by making an impression with a bite registration type impression material with the coping in place. Our goal is to provide a sterile impression coping and impression material kit to the general dentist, periodontist or oral surgeon who will be placing the fixture and making the fixture impression. A master cast made from an alginate impression is all that is required to set the analog and obtain the measurements to fabricate the abutment as well as the interproximal contact points and the occlusion. Input into the software program of seven simple measurements containing the tooth and arch dimensions will create a custom made abutment using any hex configuration.
All manufacturing processes take the human component out of fabrication of the abutments, eliminating additional laboratory fees and inaccuracies. Even polishing of components is mechanized through industrial processes. The price of the system will be less than what you are paying for all the components you are using now. Keep in mind that you will never have to buy another component, including the screwdrivers. The abutment will be provided at Stage 2 with a positioning and an anti-rotating stent which will allow the torquing of the screw to 20 or 32 Ncm, whichever is recommended.
In order to bring implant dentistry to the mainstream, the implant components need to be produced to benefit both the dentist and the patient, not just those profiting from the production of the parts.
smap
The Silver Eagle coins also appeal to collectors. . write research paper, would you like to.