Response to Nobelpharma’s 1990 Advertisement in the Journal of the American Dental Association and the Journal of Prosthetic Dentistry
IMPLANT SELECTION IS A BALANCE BETWEEN SCIENCE
& CLINICAL REALITY
Nobelpharma’s (formerly Nobel Biocare) recent advertisement (JADA, JPD, Dec. ‘90) asks the legitimate question, "Which Implant System Give You and Your Patients the Most Security?" It then lists a number of marketing statements, referring to them as "FACTS," claiming that, with the Brånemark System®1, "The Weight of Evidence is On Your Side!" One can only answer Nobelpharma’s question if one takes the time to analyze all of Nobelpharma’s marketing claims, both current and abandoned, in relation to published research results. This report will analyze a number of research studies, including the publication of the 20-year results with Brånemark implants at the University of Gothenburg (Adell2, JOMI, Vol. 5, No. 4, 1990). Over the years, Core-Vent has challenged what we have believed to be false and misleading statements in the industry. Core-Vent believes that, after 20+ years of documented studies reporting both the clinical successes and failures of the Brånemark System® and the limitations and complications associated with the pure titanium screw implant designed in 1965, it is time the profession took a hard look at the research rather than rely on Nobelpharma’s slick marketing images and carefully worded implications. If a company has a tendency to exaggerate some facts, its future claims should be closely scrutinized.
1. Nobelpharma falsely claims in its brochure entitled, "THE UNIQUE METHOD OF TISSUE INTEGRATION," that P. I. Brånemark "discovered the ability of bone tissue to unite directly to titanium." As of June, 1990, this same brochure now substitutes the word "observed" for "discovered" because, according to Brånemark’s 1977 textbook, "already in 1951 Leventhal in experimental studies observed that bone appeared to become attached to titanium."
2. Nobelpharma falsely claimed that the Brånemark fixture is "the only implant system that uses osseointegration as a method of achieving a dental prosthesis permanently to the jawbone itself." While this statement, which appeared in a 1988 Nobelpharma brochure, was so blatantly untrue that Nobelpharma retracted it in a letter to hundreds of dentists in this country, this brochure is still in circulation in Japanese and Spanish language versions without correction.
3. Nobelpharma continues to use a picture of what it claims is an osteoblast attached to titanium when, in fact, this same picture appeared in a 1982 article by Albrektsson and Brånemark showing it to be a fibroblast from skin around an ear implant.
4. Adell2 et al. report that, for implants placed between 1971 - 1981, "continuous bridge stability" in the maxilla was 81-82% at 10 years, not the 96% at 5-12 years that Nobelpharma had claimed in previously published advertisements.
BEFORE SELECTING AN IMPLANT SYSTEM, SEPARATE MARKETING HYPE FROM PUBLISHED FACTS
In chapter 10 of Brånemark’s 1985 textbook, Adell defines "continuous bridge stability" as the "quotient of jaws, where the patients enjoy a continuous bridge stability in relation to the total number of jaws treated." But in the recent report, Adell2 creates a new definition of "continuous bridge success" by only counting follow-up from time of "prosthesis placement," to claim that "More than 95% of maxillae had continuous prosthesis stability at 5 and 10 years." Adell’s recent article reveals that, for implants placed between 1971-1981, the five- and ten-year maxillary bridge success rates were only between 81% and 89% using the definition that was operational in the 1980s.
FACT #1: Adell, Brånemark et al.2 document that "Continuous Bridge Stability" in the maxilla was 81-82% at 10 years, not the 96% at 5-12 years that Nobelpharma's advertisements claim.
FACT #2 : Adell2 reports that "survival" was criteria of success with Brånemark Implants because annual removal of all bridges to confirm osseointegration was considered "too time consuming."
FACT #3: Adell2 confirms 13% maxillary-implant fractures at 10 years increasing to 16% at 15 years for 524 Brånemark Implants placed at Univ. of Gothenburg between 1971-76.
FACT #4: Adell2 includes "repairable" fractures as successes in order to claim 81-82% success in maxilla at 10 years; 3i3 sells "Abutment Post for Fractured Brånemark-type Implants" (catalog #APFB1).
* Swede-Vent Fixtures are suspended on disposable titanium fixture mount devices in double-vial sterile packaging. Nobelpharma’s fixture mount costs an additional $141 and must be individually attached prior to insertion, and autoclaved before it can be reused. These single unit prices are as of January 1, 1991, and subject to change without notice.
Nobelpharma’s current advertisements state, among other claims, that, "Unlike some other implants, the Brånemark System®1 is supported by numerous long-term clinical studies." Core-Vent believes that citing the number of studies without evaluating what those studies actually show is a poor method of claiming superiority. In fact, the recently published Adell2 study acknowledges that, "More precise determination as to whether fixtures were osseointegrated could have been achieved if the prostheses were detached annually and individual manual fixture stability tests performed." The article states that this was considered "too time-consuming." The study also reveals that 16% of the 524 maxillary fixtures placed between 1971 and 1976 had fractured by 15 years (13% by 10 years) with an unknown number of these being carried on the statistics as successful if the broken tops could be smoothed and a longer abutment screw used to attach the bridge to the fractured stump –– "if a fixture had fractured and a sufficiently long apical portion remained, it was repaired, re-used and then registered as stable but fractured." If one considers the fact that the Gothenburg study failed to test individual fixtures for mobility because it was considered "too time-consuming" and counted fractured implants as successes if they were still stable, this would indicate that the true implant success rates could only be viewed as speculative, and certainly brings into question the veracity of Nobelpharma’s claims that this is "the only clinical implant study that has survived scientific scrutiny." This demonstrates how success rates can be altered by retrospectively changing the criteria.
CORE-VENT BELIEVES...THE PROFESSION IS LOOKING FOR BETTER PRODUCTS AT REASONABLE PRICES NOT A BETTER WARRANTY AT HIGHER PRICES
One of the "FACTS" that Nobelpharma’s recent advertisement asks the profession to weigh is, "Prior to general marketing, Brånemark System products are tested to verify their effectiveness." In fact, in 1988, Nobelpharma introduced a "self-tapping, conical fixture" that was referred to in its 1988 and 1989-90 catalogs for use "mainly in the maxilla." The catalogs make no mention of use of this implant for bone graft cases, but by 1990, Nobelpharma warned its Canadian customers in writing that this implant should "not be used for other than bone grafted cases or unacceptable bone loss may occur." This implant was eliminated from the 1991 product catalog and is only listed in the "Special Products" catalog selling for 22% more than it could be purchased for in 1990 (5-pack price, no longer available). Nobelpharma also sells a 3.0mm pure titanium fixture, without prior FDA 510k marketing approval. through its "Custom Device" Department. Nobelpharma acknowledges that it is 50% weaker than the standard fixture and, in a disclaimer letter, states that it "has not been included in any short- or long-term clinical evaluations." It also states that, "Nobelpharma assumes no responsibility with respect to the device’s suitability for its intended or recommended purposes." In order to circumvent FDA requirements for pre-market approval, Nobelpharma’s disclosure letter falsely states that the 3.0mm fixture, "is one which is manufactured to your specifications to meet the special needs of a named patient." Since Nobelpharma stocks inventory of this implant, sterile packaged and labeled, it is not a "Custom Device," as defined by either the FDA or Nobelpharma.
Nobelpharma has been faced with increasing documentation and professional awareness of complications associated with their products in a number of published studies, referenced here and in conferences such as the "International Conference on the Prevention of Problems, Complications and Failures," recently held in Malmo, Sweden. On January 1, 1991, Nobelpharma announced the introduction of a 5-year Warranty (effective March 1, 1991). In a special Nobelpharma Update newsletter, Leif Ek, President & CEO, Nobelpharma Sweden, is quoted as saying that, "We can offer this warranty only because the success rates of Brånemark System treatment are so high." Considering the price increase that accompanied this warranty announcement and the above referenced research discrepancies, Mr. Ek would probably be correct in substituting the word "prices" for "success rates."
This report will also analyze a number of studies and relate them to the design improvements that are incorporated in the Screw-Vent® and Conical, Self-tapping Swede-Vent™ Implants. It also cites research that supports the use of titanium alloy for added strength of both implant and prosthetic components. Core-Vent’s emphasis on abutment strength, precision and rotational stability will also be documented (page 8) by reference to independent studies. We are proud of the distinction of being the most popular implant system (CRA Newsletter, December 1990) as well as being the cost-containment leader, most complete prosthodontic system, and offering the most widely available, reasonably priced education courses (CRA Newsletter, January 1991).
THE MYTH OF PURE TITANIUM’S EXCLUSIVE RELATIONSHIP TO SUCCESSFUL OSSEOINTEGRATION HAS COME TO AN END
Medical grade titanium alloy has been the standard in the orthopedic industry since the early 1970s. As Professor Frank Young, editor of the Journal of Biomaterials, stated in a presentation to the 1988 NIH Consensus Conference on Implants, "Commercially pure titanium has barely adequate (low hardness and tensile strength) mechanical properties for dental implant applications, and although it is a logical starting material, unalloyed metals usually are not found to be optimum...the clinical success of the titanium alloys under relatively crude conditions is remarkable."
FACT #5: Zarb4 reporting on 244 Brånemark implants documents fractures with 53 gold screws and 9 abutment screws.
FACT #6: Prof. Young (editor, Journal of Biomaterials) reports at the NIH Implant Consensus Conference that "Commercially pure titanium has barely adequate mechanical properties for dental implant applications."
FACT #7: Linder5 (Swedish) confirms titanium alloy osseointegrates as well as pure titanium.
FACT #8: Laney6, Sones7 and Desjardins8 report non retrievability of fractured pure titanium abutment screws resulting in loss of the implant.
The Screw-Vent Implant was introduced in 1986 in pure titanium, matching the Brånemark Implant in material, threads and dimensions. It offered design advantages, such as a straight neck that eliminated countersinking and threads to the apex for self-tapping insertion and fixation to cortical bone. Based on the many studies that show equal osseointegration between pure titanium and titanium alloy implants, the Screw-Vent Implant is now also available in medical grade titanium alloy for added strength and to reduce the chance of stripping the internal hex during self-tapping insertion. This medical grade alloy is composed of 90% titanium.
In an article in the September 1985 issue of the Journal of Prosthetic Dentistry entitled, "Titanium, The Mystery Metal of Implant Dentistry," Parr et al. state, "Many of the titanium alloys, in which Ti is present in concentrations of 85% to 95%, maintain the passivity of pure titanium...Titanium, both as pure metal and as alloy, is easily passivated forming a stable (TiO2) surface oxide that makes the metal corrosion resistant...The clinical significance of the data is substantiated by more than 20 years of clinical experience with pure Ti and Ti-6Al-4V alloys...Ti alloys are extremely resistant to corrosion fatigue making titanium alloy the metal of choice when high corrosion fatigue strength is desired."
The Core-Vent® Implant, made of medical grade titanium alloy, was introduced in 1982. This implant has proven to be highly successful in achieving and maintaining osseointegration. The five-year study of 1605 Core-Vent implants by Patrick et al., Journal of Oral Implantology, Vol. XV, No. 2, 1989, reports a success rate of 96% for both maxilla and mandible.
Titanium Alloy Has 60% Greater Tensile Strength Than Pure Titanium
Swedish Study5 Shows No Difference in Osseointegration Between Pure Titanium and Titanium Alloy
A study was published in the December 1988 issue of the Journal of Prosthetic Dentistry by Lum and Beirne entitled, "Osseointegration of Two Types of Implants in Nonhuman Primates." The independent study directly compares the response of the bone to unloaded as well as occlusally loaded Core-Vent and Brånemark implants at the light microscopic level. Histologic examination revealed that both types of implants achieved osseointegration and maintained the direct contact with bone after five months of being in function. The results were the same after one year as confirmed in a later report in Clinical Dentistry.
A group of Swedish researchers, Linder at al.5 (Acta Orthop Scand 1989;60:129-134), reported on the osseointegration of both pure titanium and titanium alloy implants. Their research, conducted in the tibia of rabbits, states that the sections were "...analyzed (histo)morphometrically using a Merz grid to estimate the amount of periosteal and endosteal new bone formation." In evaluating 76 implants, including 38 pure titanium and 10 titanium alloy implants, only three implants failed to osseointegrate (two were pure titanium and one was stainless steel). The authors concluded that, "With the exception of these three cases, the bony reaction was remarkably consistent."
Adell Reports 16% of Brånemark Implants Fracture in Maxilla
A study by Adell, Brånemark et al.2 (JOMI, Vol. 5, #4, 1990), reporting the "Long-term Follow up Study of Osseointegrated Implants in the Treatment of Totally Edentulous Jaws," included "Routine Group 1," consisting of 524 maxillary and 480 mandibular implants placed in edentulous jaws between July 1971 and June 3, 1976. For this group, the study reports an implant fracture rate for the maxilla of 7% at 5 years, 13% at 10 years and 16% at 15 years. The fracture rate was less dramatic in the mandible for this group of patients (4% by 10 years) and for subsequent groups with shorter follow-up periods. Laney7 (Mayo Clinic) has experienced at least three Brånemark Implant fractures presumably using the greatest of prosthetic expertise. Implant fractures with the Brånemark Implant are frequent enough that the 3i®3 company makes an "Abutment Post for Fractured Brånemark-type Implants: Catalog No. APFB1). With the increased use of implants in the posterior of partially edentulous jaws and the introduction of Nobelpharma’s new conical abutments that allow overlapping of metal to meet esthetic demands, it is reasonable to assume that the implant will be subjected to increased lateral forces that could result in an increase in the reported level of Brånemark Implant fractures. Metal fatigue is a function of time as shown by the progressive increase in fracture of pure titanium Brånemark Implants (see Adell).
Design Also Contributes to Implant Fractures
The wider neck of the Brånemark Implant, a byproduct of the external hex design, requires over 2mm of countersinking in order to place the implant level with the crest of the ridge. An additional 1.5mm of crestal bone loss occurs in the first year in function (Brånemark et al., Osseointegrated Implants, 1977) due to high stress concentrations for compression on the base of the countersink. With 3.5mm of crestal bone support lost, the weakest part of the implant, the minor diameter of the first thread, is left unsupported by bone and subject to fracture. The fact that so few fractures have been documented with the pure titanium Screw-Vent Implants may be attributed to the fact that, because of its internal Hex-Thread® connection (U.S. Pat. #4,960,381), it was able to be designed with a smaller diameter straight neck. This eliminates the need for countersinking and minimizes crestal bone loss from stress concentrations. The result is that the first thread of the Screw-Vent, where the wall thickness is the least, is more likely to be well buried in bone. It would logically follow that fewer fractures will occur with the "CST" Swede-Vent because its conical neck eliminates the need for countersinking in the maxilla and the first thread of this implant is almost 1mm further apical than on the standard Brånemark design.
FACT #9: Laney6 reports three fractures with Brånemark Implants placed in lower jaws at Mayo Clinic.
FACT #10: Brånemark9 reports 2mm bone loss from countersinking plus 1.5mm of additional crestal bone loss in first year from stress concentration under wider neck –– 3.5mm total loss.
FACT #11: Iaccona10 documents only 0.6-0.8mm of crestal bone loss with Screw-Vent within first year. The internal hex allows narrow neck design eliminating the need for countersinking.
FACT #12: Laney6 reports complete failure with Brånemark Implants in 8 maxillary cases treated at Mayo Clinic; Mito11 documents 25% of stable Brånemark Implants followed at UCLA for 2-3 years lost osseointegration.
Maxillary Implant Success Rates in Swedish Study May Fail to Meet Albrektsson/Zarb Criteria of 85% at 5 Years and 80% at 10 years (JOMI, Vol. 1, 1986)
Adell et al.2 document 5- and 10-year results for what they termed "Routine Group II" implants placed in Gothenburg between July 1976 and June 1981. With 394 maxillary implants, the 5- and 10-year implant survival rates were 89% and 82% respectively. Implant survival was the actual criterion of success, not osseointegration, as evidenced by the authors’ acknowledgement that bridges were not removed annually to conduct "individual manual fixture stability tests." Furthermore, an unknown number of fractured fixtures were being counted as successes. Based on these factors, the actual success rates are speculative.
Implant Design Can Affect Initial Stability and Increase Clinical Success in the Maxilla
Adell2 states that "The only cortical reinforcement to initially support the fixtures was frequently the cortical lining of the nose or the maxillary sinus. With these quantitative and qualitative maxillary deficiencies, it is surprising that the survival rates for prostheses and fixtures were so positive." The Conical Neck, Self-Tapping CST Swede-Vent and the Screw-Vent, with its straight neck, both take this factor into consideration by eliminating the need for a bone tapping instrument to cut the threads to engage cortical bone under the nose and sinus. Countersinking is not required with the Screw-Vent in the maxilla, thus preserving crestal cortical bone and further adding to initial stability.
HA Coating Increases Bone-Implant Contact During the Critical First Year
Implants fail to osseointegrate if movement occurs during the submerged healing period. They lose osseointegration, once placed in function, if inadequate bone-to-metal interface has been established to withstand occlusal loading. Of course, cortical bone is better able to provide stability for the implant and should be engaged wherever possible, preferably by threads. Adell2 confirms that the majority of implant failures due to loss of osseointegration takes place in the first year following insertion. A study conducted at UCLA (Mito; 1989 CDA Journal) documents that 25% of the Brånemark Implants placed in the maxilla and followed for 24-36 months lost osseointegration after initially having been diagnosed as stable. All the losses occurred in the first six months following prosthetic attachment.
Gottlander’s13 doctoral thesis, University of Gothenburg, demonstrates the establishment of more complete attachment of bone to the HA coated surface of an implant in the first six weeks following placement in rabbits. These results, histologically comparing coated and uncoated titanium implants in rabbits, are reported, but misinterpreted, in a recent issue of Nobelpharma News (Vol. 4, #3, 1990). The chart contained in the article clearly shows about 55-90% (median = 72%) surface contact with HA coated implants at six weeks compared to only 30-70% (median = 50%) with titanium alone. The author is quoted as referring to this 22% difference in the median at six weeks as "statistically insignificant." On the other hand, the chart shows one-year results of approximately 40-75% contact for the HA coated implants (median = 67%) for titanium alone. Gottlander is quoted by Nobelpharma News as claiming that this median difference of only 10% at one year in favor of titanium is "significantly higher."
It appears to be misleading for Gottlander to conclude that a median difference of 22% in favor of the HA coated implant at six weeks was "statistically insignificant" while claiming that a median difference of only 10% in favor of the titanium uncoated implant at one year was significant. The headlines of the article in the newspaper of Nobelpharma, a company selling only pure titanium implants, state that "Dr. Magnus Gottlander, M.D., has proven hydroxylapatite to be ineffective in strengthening and making an implant-bone bond form more substantially." This statement is false and misleading since Gottlander’s study, as reported by Nobelpharma News, did not measure push-out strength differences, only percentage of bone contact. Cook14 and others have studied attachment strengths and found HA to have significant advantages. Gottlander and Nobelpharma have missed the potential clinical significance of increasing the percentage of bone contact during the critical early healing and loading periods. This is especially true in the porous bone of the maxilla, where Adell2, Mito11, Jaffin12 and others have now clearly demonstrated it is a problem area for the pure titanium, screw implants of the Brånemark design (wide neck, no apical threads). In Type IV bone, Jaffin documents 44% failure with Brånemark fixtures in the maxilla and 37% in the posterior mandible. The article states, "Diagnosis of Type IV bone is usually made at osteotomy. By this time, the tentative restorative treatment plan has usually been decided." Based on this, it is logical to routinely select implant designs (self-tapping with apical threads) and material (HA coating) that enhance initial stability in these areas of higher risk.
FACT #13: Adell2 acknowledges that "cortical lining of nose and maxillary sinus may be only initial support." Screw-Vent and CST Swede-Vent Implants, with self tapping apical threads, engage cortical bone in maxilla which enhances stability.
FACT #14: Jaffin and Berman12 report excessive loss of Brånemark fixtures (44%) in Type IV (low density trabecular) bone in maxilla.
FACT #15: Gottlander13 reports more early bone to-implant contact with HA coating; Cook14 reports increased attachment strength with HA: both should increase success in maxilla.
This review of the research makes a compelling argument for the design and material concepts that are incorporated in the Screw-Vent titanium alloy implant available with HA coating. For those surgical specialists whose referring dentists are trained to use an external hex implant, the CST Swede-Vent in pure titanium, with or without HA coating, offers many of the design advantages of the Screw-Vent. The Veterans Administration has selected the Spectra-System™ exclusively to be included in its prospective, multi-center study of 680 patients. This study will be monitored by external and internal peer review committees to assure strict adherence to the protocol and accurate reporting of the results. Core-Vent Corporation’s confidence in its products is evidenced by its financial support for this study, estimated to cost approximately $23 million in total direct and indirect costs. We are prepared to let the facts speak for themselves –– just as we have done in this analysis of the Brånemark System®1 and other relevant research.
Compare Prosthetic Systems for Precision, Strength and
Jemt15 reports on 23 Brånemark implants used for single tooth replacements –– 13 become unstable in the first year in function (3 of these become unstable more than once).
Ohrnell, Brånemark et al.16 report "a very common problem is loosening of the center screw which leads to a loose abutment and rotation of the crown." They proposed lengthening the external hex from 0.7mm to 1.2mm to overcome this loosening (Screw-Vent has a 1.7mm internal hex –– US Pat #4,960,381).
Barzilay17 compares prosthetic stability with Nobelpharma (120 microns rotation between mating hexes) and Swede-Vent with zero rotation due to its Taper Lock™ design (Pat. Pend.).
McGlumphy18 compares Swede Vent abutments to Nobelpharma’s and finds Swede-Vent 30% stronger.
Binon19 compares precision between implant and abutment for Nobelpharma, 3i and Swede-Vent components –– Swede-Vent was best at only 14µ of gap vs. Nobelpharma with 49µ.
1. Brånemark System is a registered trademark of Nobelpharma AB.
2. Adell et al., JOMI, Vol. 5, No. 4, 1990.
3. 3i is a registered trademark of Implant Innovations, Inc.
4. Zarb et al., JPD, Vol. 64, No. 2, Aug. 1990.
5. Linder et al., Acta Orthop Scand, No. 60, 1989.
6. Laney, Presentation at Quint Impl Symp, Madrid, Nov. 1990.
7. Sones, JPD, Vol. 62, No. 5, Nov. 1990.
8. Desjardins, Dental Implant Prosthodontics, J.B. Lippincott Company, 1991.
9. Brånemark et al., Osseointegrated Implants, 1977, pg. 109.
10. Iaccona, Stoneybrook Univ., submitted for publication.
11. Mito et al., JCDA, Vol. 17, No. 3, March 1989.
12. Jaffin, Berman, J. Periodontol, Vol. 62, No. 1, 1991.
13. Gottlander, Vol. 4, no. 3, Nobelpharma News.
14. Cook et al., JOMI, Vol. 2, No. 1, 1987.
15. Jemt et al., Int J Perio Rest Dent, Vol. 10, No. 5, 1990
16. Ohrnell, Brånemark et al., Int Quint J, 1988.
17. Barzilay, Study at Eastman Center, NY
18. McGlumphy, J Dent Research, March 1989
19. Binon, 2nd Int Congress Mayo Clinic, 1990