V.A. Study Three-Year Results Hydroxyapatite-Coated Implants: A Case for Their Use Table of Contents Section 1: Prologue and Data Analysis ...................................................................................................................... 1 Section 2: Introduction .............................................................................................................................................. 3 Section 3: Hydroxyapatite vs. Titanium Implants ...................................................................................................... 4 Section 4: DICRG Study Design .................................................................................................................................. 5 Section 5: Goals of the Paper..................................................................................................................................... 6 Section 6: Results and Discussion .............................................................................................................................. 7 Section 7: References ......................................................................................................................................... 16
Section 1: Prologue and Data Analysis Too often, clinical studies have been conducted and analyzed under the direction and control of implant manufacturers. The validity of such results is, at best, biased by selecting only those clinicians with extensive experience with the implant system in question, or by excluding results from centers that report lower success rates. Without independent controls and peer review mechanisms, there is no assurance that the results even represent consecutively inserted implants. When the lead authors of such studies are owners, employees and/or paid consultants of the company whose products are being evaluated, any claims related to success rates must be considered highly questionable. By the same token, criticism of other implant systems by such corporation-linked spokespersons should be viewed with the same degree of skepticism. The following three-year report on the results of 2,795 implants manufactured by Core-Vent Bio-Engineering provides the dental profession with an unbiased standard for clinical research. This prospective, multi-center study by the U.S. government's Veterans Administration is conducted under the strict controls of an external peer review committee. This distinguished panel of researchers and educators has been assembled to assure the validity of the data and the objectivity of the analysis. By placing different implants within the jaw of the same patient, this study provides a better understanding of the synergy between implant design, material and surgical protocol. The VA study is providing information to serve as a scientific basis for reaching clinical treatment and product design decisions. These results are representative of real-world situations for two important reasons. First, this study includes the results of implants placed by surgeons of various skill and experience levels. Second, this study has not excluded smokers or medically compromised patients. Furthermore, the use of preoperative antibiotics for approximately half of the patients in the study resulted in higher implant survival rates for those patients, while withholding such prophylactic therapy from others reduced the overall success rate, as documented in this paper. Although this unabridged article only reports on the three-year results, the VA study is ongoing. The authors state in the summary that "2,000 implants with four-year data and 1,500 with five-year data" have been documented. They further state that "these data are similar to the 36-month data and, when they are eventually
released, are likely to reinforce the results reported here." The following analysis of the results reported in this 3-year report clearly demonstrate that at least in the 3- to 5-year initial period- HA-coating on an implant neutralizes differences in achievement and maintenance of osseointegration with different qualities of bone and experience levels of surgeons. Similarly, smokers and those patients denied preoperative antibiotic therapy also experienced significantly fewer failures with HA-coated implants than uncoated implants. This report also demonstrates that results with uncoated, acid-etched implants more closely parallel results with HA-coated implants when inserted by moreexperienced clinicians in dense bone, regardless of material (CP Ti vs. Ti alloy) or design (cylinder, basket, screw). Editorial Excerpt: The Search for a More Successful Implant Properly designed, randomized, clinical trials are expensive, time and labor intensive, and require an adequate patient population to provide reliable data. As a result, too few of such studies are done and we find ourselves extrapolating information from case reports, small clinical series, and inadequately controlled retrospective studies. The US Veterans Administration's multi-center, prospective implant study represents a unique opportunity to provide unbiased answers to many of the questions that still trouble clinicians. Through the vision and commitment of one manufacturer a group of outstanding clinicians were given the autonomy to design the research protocol, conduct the study, and publish the results independent of any commercial influence...Congratulations are extended to all those who made this study possible: Dr. Gerald A. Niznick for his generous support, Dr. Harold Morris for his leadership, the more than 100 clinicians for giving so enthusiastically of their time and skill, and the members of the Scientific Advisory and External Review Committees who assured the validity and objectivity of the results.
â€“ Daniel M. Laskin, Editor-in-Chief J Oral Maxillofac Surg 1997;55(11) Suppl 5:1.
Clinical Controversies in Oral and Maxillofacial Surgery Full Text Version Also See Excerpt Published in: J Oral Maxillofac Surg 56: 1303â€“1311, 1998 Authors: Harold F. Morris DDS, MS Codirector, Dental Clinical Research Center; Codirector, Dental Implant Clinical Research Group (DICRG); Codirector, Ankylos Implant Clinical Research Group (AICRG).
Shigeru Ochi, PhD Codirector, Dental Clinical Research Center; Project Codirector and Biostatistician, Dental Implant Clinical Research Group.
Section 2: Introduction Abstract: Controversy exists in the field of implant dentistry concerning the relative merits of commercially pure titanium (or titanium alloy) implants and hydroxyapatite-coated implants. It has been suggested that HA-coatings are unstable, brittle, more susceptible to bacterial infections, and unsupported by long-term clinical data, and that they do not represent a significant advantage over CP-titanium or Ti-Alloy implants. This paper summarizes three years of follow-up data from an ongoing eight-year clinical study of dental implants with emphasis on the comparative survival of HA-coated and non-coated implants from placement up to three years. Over 2,700 implants placed in over 800 patients at 32 study centers were followed and data recorded by stage of treatment, study center, surgeon's experience, patient health statutes, preoperative antibiotic coverage, patient smoking behavior, bone quality and jaw location. For each variable studied, survival rates for HA-coated implants exceeded those for non-coated implants by 10â€“15% in most instances. In situations where clinical conditions presented a particular challenge (inexperienced surgeons, poor bone quality, patients who smoked, no preoperative antibiotics, etc.) the use of HA-coated implants appeared to compensate for the shortcomings.
Since its beginning, modern implantology has held great promise for helping patients with compromised aesthetics, speech or masticatory functions. As clinical studies documenting long-term success with implants began to appear, more and more dentists have embraced the new technology. Much that fueled the rapid growth of implantology consisted of basic science and animal research. While these studies are scientifically valid, they control too many variables to be accurate predictors of clinical performance. The clinical environment routinely involves complex interactions of many variables. Laboratory testing procedures may be appropriate in the early stages of new product development, but they are no substitute for well-designed clinical studies. The Dental Implant Clinic Research Group (DICRG) study sample, consisting of 2,795 implants placed in over 800 patients at 32 clinical centers, represents a meaningful challenge for the clinicians involved. More than half of the patients treated (50.9%) were in ASA health status 2 (mild systemic disease) and 2.5% were in status 3 (severe systemic disease). Smokers were not excluded from the study. Decisions concerning the use of prophylactic antibiotics, and their type and dosage, were left to the individual investigators. Antibiotic coverage was provided preoperatively in only about 50% of cases. Over 80 dentists participating in the study had a wide range of training and prior implant placement experience, ranging from none to considerable, and were equally divided between the two experience categories (those with more than 50 previous placements and those with fewer than 50).1 The DICRG study is a representative mirror of real world conditions, which provides evidence for superiority of HA-coated implants.
V.A. Study Three-Year Results Hydroxyapatite-Coated Implants: A Case for Their Use
Section 3: Hydroxyapatite vs. Titanium Implants Rejection is the body's normal response to a foreign object. The ideal material for dental implants is one that integrates with the bone and is free of adverse tissue responses. The search for improved biocompatibility has resulted in implants fabricated from a variety of materials using different designs, surface textures and coatings. Currently most of the attention centers on two implant materials: titanium (and titanium alloy) and Hydroxyapatite-Coated implants. Titanium Implants Implants made of commercially pure titanium (cpTi) were the first to gain widespread acceptance. Bone does not bond directly to either cpTi or titanium alloy (Ti-6A1-4V) implants. It attaches by means of a complex interaction between the extracellular matrix tissues and the titanium-oxide layer formed when the metals are exposed to air or tissue fluids.2, 3 Micro- and macro-interlocking also contribute to the stability of these implants.4 In an attempt to improve long-term clinical success of titanium implants, their machined surfaces have been altered by adding rough titanium coatings,5â€“7 acid etching,8, 9 grit blasting,10, 11 and grit blasting and acid etching combined5, 12, 13 to increase the strength of attachment. In studies comparing cpTI with Ti-6A1-4V, Albrektsson and others14, 15 report superior bone attachment to cpTI. In contrast, primate studies by Carr and others16, 17 report no difference in osseointegration or removal torque for the two metals. Carr et al.17 also report that HA-coated implants demonstrate approximately a 250 percent higher removal torque than machined cpTi or Ti-6A1-4V implants. In another recent study, Smith et al.18 report no long-term change in systemic metal ion levels with either Ti-6A1-4V or cpTi, which addresses concerns to the contrary expressed in the dental literature about Ti-6A1-4V. Hydroxyapatite-Coated Implants The first clinical use of hydroxyapatite (HA) as coating for endosseous dental implants appeared in 1984.19 HA is a naturally occurring calcium phosphate ceramic that is found in abundance in tooth enamel, dentin and bone. In its synthesized form, it is applied to a Ti-6A1-4V substrate (the usual method is plasma spraying) to form a nontoxic bioactive coating that bonds chemically with adjacent bone.20,21 When HA-coated implants are compared with titanium, there is evidence for more rapid osseointegration with the HA.22 In animal studies, Block20 observed biointegration of HA-coated implants as early as 4 weeks. After 10 months, 90% of the coated implants had a continuous surface layer of lamellar bone connecting the implant with the trabecular bone. In contrast, titanium implants exhibited osseointegration only at 4 months, with 50% implant-bone contact at 10 months.23 In a second study, Block24 found gingival fibers inserting directly into the osseoid tissue covering the HA-coating. In a review of the literature concerning the clinical predictability of HA-coated implants, Biesbrock25 suggested that the characteristics of HA-coated implants indicate their use a) in type IV bone, b) in fresh extraction sites, c) in grafted maxillary sinuses or d) when using shorter implants (10mm or less). To validate these observations, long-term studies are needed. Participants at the 1988 Consensus Conference26 also expressed a need for long-term studies. Thus the launching in 1991 of a major independent clinical study within the Department of Veterans Affairs was a significant landmark. This study, under the direction of the Dental Implant Clinical Research Group, provides new data that will
DICRG study was designed to allow direct comparisons between HA- and non-HA-coated implants in the same patient. The relative merits of HA- and non-HA-coated implants remain controversial, and debate between their respective adherents continues to enliven discussion in the field of implant dentistry. Reports based on anecdotal data have suggested that HA-coatings are unstable, have an increased susceptibility to bacterial infection, and may be disposed to rapid bone loss or saucerization.25 In addition to being based on isolated case reports, these arguments do not reflect the current state of implant technology. Improvements in the crystallinity of HA-coatings have eliminated a cause of failure in some early implant designs.27, 28 The incorporation of a machined metal collar in most modern HA-coated implants further enhances survival, as the machined surface resists plaque formation and microbial colonization, both of which were common in early implants when soft tissue changes exposed the porous HA-coatings to the oral cavity (Figure 1). As the title of this paper implies, data now becoming available from the comprehensive DICRG study suggest that HA-coated implants are superior to non-HA, especially in those situations where the conditions for treatment are less than ideal.
V.A. Study Three-Year Results Hydroxyapatite-Coated Implants: A Case for Their Use
Section 4: DICRG Study Design In 1990, the Department of Veterans Affairs (DVA) established a clinical research center at the Ann Arbor, Michigan VA Medical Center to focus on issues related to direct patient care. The following year, with a view to resolving some issues raised at the 1988 NIH Consensus Conference on Dental Implants, the Center formed the Dental Implant Clinical Research Group (DICRG) which, with support from the Dr. Gerald Niznick Foundation, designed and activated the largest independent clinical study of dental implants ever attempted in the United States.29 The study sample consists of 2,795 implants, placed in more than 800 patients by more than 80 investigators at 30 DVA Medical Centers nationwide and two dental schools. The study is planned for an eight-year period. Patients are veterans eligible for treatment at VA Dental Centers, and were not selected to optimize study outcomes. To assess the influence of confounding variables, data were recorded for a) surgeon's experience, b) bone quality, c) mobility at placement, d) use of pre-operative antibiotics, e) jaw location, f) sinus lift, g) patient's smoking behavior, and h) patient's health (ASA) status. Data were collected at implant placement, surgical uncovering, placement of the prosthesis, and at regular scheduled follow-up visits. Analysis of results by stage of treatment may help investigators identify patterns of failure specific to one type of implant.
Five major implant manufacturers were invited to participate in this Implant Success Criteria landmark independent study; however, only one agreed to take part. All implants in the study are Spectra-System® implants (Paragon Implant Co., The V.A. Study's Success 29, 32 Encino, CA) in four basic designs: cylinder (Bio-Vent®), grooved (Micro-Vent®), Criterion is Implant Survival, screw (Screw-Vent®), and basket (Core-Vent®), with and without HA-coating. as determined by the following parameters: The Micro-Vent implant is a combination screw and press fit. Each Spectra-System design is specific to a particular jaw region (Table 1). • Absolute lack of clinical Implant selection was randomized within this framework. The density of mobility the HA-coatings tested is about 2.98 g/cc min. with 62% minimum • Absence of unresolved crystallinity and less than 5% porosity. Surface roughness is between 4–6 pain microns. Minimum purity (crystallized and non-crystallized portion) is 96%, with a • Absence of unresolved calcium to phosphorous (Ca/P) ration 1.67. Static Tensile Strength is 50.8 discomfort • Absence of unresolved MPa, minimum. Static Shear Strength is 22.0 MPa, and Dynamic Shear infection Strength (fatigue) 13.8 MPa at 10 million cycles with 25 pounds. Three year x-ray diffraction tests indicate HA content of 98.3% with 68.3% crystallinity. The large study sample, including significant numbers of HAand non-coated implants, provides one of the first direct clinical performance comparisons of HA- and nonHA-coated (titanium and Ti-alloy) implants on such a large scale. An interesting feature of the study is the grouping of research centers into quartiles by rates of successful implant placement. The top quartile, representing the most successful group, provides an estimate of success rates to be expected under ideal conditions. The middle group (second and third qualities combined) represents performance under average conditions. In this manner, both the efficacy (performance under ideal conditions) and effectiveness (performance under average conditions) of the various implant designs and materials can be predicted, thereby increasing the global relevance of these findings. To reduce the possibility of bias and/or conflict of interest, the DICRG planning committee introduced four safeguards unique to this study. They include: I. II.
Product or professional bias: DICRG investigators had no vested interest in any implant design or material through lectureships or consultancies, nor any contract with the sponsor or its representatives, except to obtain product. Study design: The study was partially randomized to further reduce the potential for bias. Patients from different geographical regions and dentists with various training, experience and skill backgrounds were included to insure that the generic results would be more relevant to most dentists worldwide. Data bias: Access to the data was limited to a small group in Data Management Center of the VA Medical Center in Ann Arbor, Michigan. At no time prior to publication do sponsors have access to the data. Scientific Advisory/External Review Committee: This independent review committee monitored the study to help insure adherence to the protocol, patient safety, confidentiality of data and that the conclusions are not overstated, but in fact were supported fully by the data.
V.A. Study Three-Year Results Hydroxyapatite-Coated Implants: A Case for Their Use
Section 5: Goals of the Paper The authors have been asked to present the case for hydroxyapatite coatings and, while the case can be argued in many ways, it seemed most useful to adopt a pragmatic approach. What most dentists want to know, ultimately, is how well implants perform not under theoretical or laboratory conditions, but under real-world clinical conditions. Only this quality of information is meaningful in treating the large numbers of compromised patients who can benefit most from implant supported or retained prostheses.
studies are supported by implant manufacturers and are designed to optimize results. Only highly skilled dentists are selected to participate, pre-operative antibiotic use is mandated, implants placed under less than ideal conditions (mobility at placement, augmentation provided at any stage of treatment, inadequate ridge width and height) are excluded from the study. Studies like this evaluate product efficacy (performance under ideal conditions). In contrast, the present study includes not only skilled dentists and patients in excellent health, but also average dentists treating average patients in order to measure effectiveness (performance under average conditions). Out of the vast amount of new data now becoming available from the DICRG study, this paper focuses on direct comparison of HA- and non-HA-coated implants, both their overall performance and survival under conditions that might be termed unfavorable, but which nevertheless represent the clinical environments familiar to most dentists. Variables examined include smoking, surgeon's experience, bone density, pre-operative antibiotic coverage, and the patients' health status. Performance of implants mobile at placement and those placed in the maxillary posterior are examined. In each of these cases, the comparative survival data for HA- and non-HA-coated implants are presented. It is hoped that this approach, encompassing a wide range of commonly encountered problems, will prove helpful to practitioners faced with the necessity of making day-to-day choices in a field where the questions have no easy answers.
V.A. Study Three-Year Results Hydroxyapatite-Coated Implants: A Case for Their Use
Section 6: Results and Discussion A total of 2795 Spectra-System implants (Paragon Implant Company, Encino, CA) were placed in all bone densities and jaw regions and uncovered by DICRG investigators. The Spectra-System is made up of cylinder (Bio-Vent), grooved (Micro-Vent) screw (Screw-Vent) and basket (Core-Vent) designs in cpTi and Ti-6Al4V, some with HA-coating (Figs. 1a窶電). Because implant failures (defined as removal of the implant for any reason) at all stages of treatment may be influenced by the experience levels of the surgeon and other members of the implant team,30 the data were collected for each stage of implant treatment. If failures are concentrated at one stage, this approach can help to pinpoint causality.
Implant survival at each stage is shown in Table 2. Figures for the period from placement to uncovering and those for the time of uncovering are combined. In this healing period, 97.4% of all implants survived irrespective of design or coating status. Survival between uncovering and loading of the prosthesis was 97.3%. In the period following insertion and loading of the prosthesis up to 36 months, 98.4% survived. Survival for all stages of treatment between implant placement and 36 months was 93.0%.
Table 1: Spectra-System Implants Used in the DICRG Study Strata
Survival for HA-coated vs. Non-coated by stages was as follows: From placement through uncovering, 99.1% vs. 94.6%; from uncovering to loading of the prosthesis, 99.1% vs. 94.4%; loading of prosthesis through 36 months 98.9% vs. 97.6%. Cumulative survival for the entire period from placement through 36 months was 97% for HA-coated designs compared with 86.5% for the non-coated ones. At each stage of treatment, the HA-coated implants had higher rates of survival than non-HA-coated implants. Rosenberg31 suggested that early failures (prior to clinical loading) tend to be associated with surgical trauma or an infectious complication. If this is the case, the DICRG survival data may suggest that HAcoated implants are somehow more resistant to the effects of surgical trauma or infection. Regardless of the mechanism, the performance of HA-coated implants was found to be superior to non-HA-coated implants. Table 1 Abbreviations: HA, hydroxyapatite; Ti, titanium; cp, commercially pure; UCE, maxillary completely edentulous; LCE, mandibular completely edentulous; UP, maxillary partially edentulous; LP, mandibular partially edentulous; UST, maxillary single tooth; mmD, millimeter diameter. a. b. c. d.
Screw-Vent–3.75 mmD (3.5-mmD collar); 8, 10, 13, 16 mm long. Micro-Vent–3.25 mmD (3.5-mmD collar) and 4.25 mmD (4.5-mmD collar); 7,10, 13, 16 mm long. Bio-Vent–3.5 mmD (3.5-mmD collar) and 4.5-mmD (4.5-mmD collar) 8, 10.5, 13, 16mm long. Core-Vent–4.3 mmD (3.5-mmD collar) and 5.3 mmD (4.5-mmD collar); 8, 10.5, 13, 16 mm long.
Upper Completely Edentulous (UCE) Left to Right: cpTi Screw (a) HA Screw (a) HA Grooved (b)
Upper Single Tooth (UCE) HA Grooved (b)
Upper Posterior (UP) Left to Right: HA Cylinder (c) HA Grooved (b)
Lower Completely Edentulous (LCE) Left to Right: Ti Alloy Screw (a) Ti Alloy Basket (d) HA Cylinder (c)
Lower Posterior (LP) Left to Right: HA Cylinder (c) Ti Alloy Basket (d)
V.A. Study Three-Year Results Hydroxyapatite-Coated Implants: A Case for Their Use Influence of the Research Center on Implant Survival Approximately 60% of all failures occurred at 5 to 6 research centers. These failures appear to be related to both the experience of the surgeon and the number of surgical procedures required with the different implant designs. Placement in the posterior jaw region increases the degree of technical difficulty associated with all implants. In an effort to assess the advantages of HA-coated implants under a variety of clinical conditions, it is instructive to compare the performance of the implants placed at the various research centers.32 The
centers were ranked by implant survival through surgical uncovering and, based on this ranking, assigned to one of three groups comprising the upper quartile (most successful), middle two quartiles (average), and the lower quartile (least successful). Results are given in Table 2. The most successful group reported 97.9% survival over a 36-month period. The data from this group should be compared with that from other reported "efficacy" studies designed and conducted to optimize clinical success. It is likely that dentists in this group could place almost any implant design and expect good clinical performance. The average group reported 93% survival. This group provides the best estimate as to the true "generic" clinical performance of most implants. The challenge to dental implant researchers is to identify implant designs and materials that will provide satisfactory long-term clinical performance in the hands of most dentists when treating average patients. The greatest deviation appears in the least Table 3: Implant Survival by Research Center All Implants (n=2,925)
Most Successful (Top 25%)
Average (Middle 50%)
Least Successful (Lower 25%)
Table 2: Implant Survival by Stage of Treatment All Implants (n=2,795)
*NOTE: P-U represents the period from placement of the implant to uncovering; U-L represents the period from uncovering to loading of the prosthesis; L-36 represents the period from loading of the prosthesis to 36 months; P-36 represents the period from placement of the implant to 36 months.
successful group, which recorded only 82.1% survival. Even in this group, the centers did not experience problems with all implants, but only with certain designs and these designs differed for each center. Other factors possibly contributing to high failure rates included: 1) the surgeons who had limited experience placing implants,15 2) a member of the original implant research team moved and was replaced with a less experienced clinician, 3) the patient population was less healthy, less motivated and from a lower economic group.
A comparison of survival rates for HA- and nonHA-coated implants in the top, middle and lower success groups shows a consistently higher rate of survival for HA-coated implants in all three groups. In the most successful group, 99.2% of HA-coated implants survived compared with 95.6% of non-HAcoated implants. In the middle average group, survival was 96.6% and 87%. In the least successful group, 85.9% of the HA-coated implants survived compared with 72.2% of non-HA-coated implants.
Surgeon's Experience and Implant Survival In order to assess the importance of the surgeon's experience on survival of HA- and non-HA-coated implants, surgeons in the DICRG study were divided into two groups: those who had previously placed 50 or more implants and those with experience of less than 50 previous placements. Implant survival for both groups was compared for both HA- and non-HA-coated implants at all stages of treatment. The cumulative results through 36 months are given in Table 4. Of 2795 implants placed, 1487 were placed by surgeons with 50 or more implants experience and 1308 by surgeons with implant placement experience of less than 50. Overall survival for the 50+ group was only slightly higher: 93.7% vs. 92.2% for the 50- group. The most striking difference was between HA- and non-HA-coated implants, which had differences in survival of around 10% for both experience groups. The benefit of prior surgical implant experience appears to be minimal when analyzing the overall database and is greatly overshadowed by implant type.
Table 4: Implant Survival by Surgeon's Experience
Patient's Health (ASA) Status and Implant Survival
All Implants (n=2,795)
The patient's health status can have an influence on HA97.6% 96.3% initial success and ultimate survival of endosseous Coated (n=888) (n=837) (n=1,725) dental implants. For the purposes of this study, patients were assigned to one of three groups corresponding to Non-HA87.8% 84.9% their American Society of Anesthesiologists (ASA) health Coated (n=599) (n=471) 33 status. Under this classification system, developed by (n=1,070) the ASA in 1962 as a screening tool, patients were Group 1 (50 Group 2 (less designated as 1 (healthy), 2 (mild systemic disease) or 3 or more than 50 (severe systemic disease that is not incapacitating) and data implants placed) implants placed) were recorded for 2750 of the 2795 implants placed. Results are given in Table 5. Although in general those with severe systemic disease were excluded from the study as a matter of protocol, the sample did include 71 patients (2.5%) classified as ASA 3. The remainder included 1297 (46.4%) in status ASA 1 and 1422 (51.0%) in ASA 2. Table 5: Implant Survival by Patient Health Status for all Stages of Treatment to 36 Months All Implants (n=2,790)
ASA 1 (Healthy)
ASA 2 (Mild Disease)
ASA 3 (Severe Disease)
* ASA status reported for 966 implants
For all implants in the study from the time of implant placement to 36 months, survival in healthy patients was 92%, in mild disease patients 94.1%, and in those with severe disease 87.3%. Results were similar when HA-coated implants were looked at separately. Failures were slightly higher in the ASA 1 (healthy) group than in ASA 2 (mild disease) and highest in ASA 3 (severe disease). In the entire period from placement of the implants to 36 months, the healthy patients exhibited 96.6% survival, mild disease 97.7% survival, and 90.7% survival for severe systemic disease. For non-HA-coated implants, survival rates were lower. For the entire period between placement and
36 months, survival for the healthy group (ASA 1) was 83.8% for ASA2 (mild disease) 88.9%, and for ASA 3 (severe disease) 82.1%. Non-HA-coated implants presented significantly higher risk of failure than HAcoated implants in all patients, regardless of health status.
Influence of Preoperative Antibiotic use on Implant Survival Previously published findings from the DICRG study reported a dramatic improvement in overall implant survival through Stage II surgery when pre-operative antibiotic coverage was provided.34 The risk of implant failure increased approximately two to three times when pre-operative antibiotics were not used. More recent clinical data suggest that the benefits of pre-operative antibiotics extend for a period of up to 36 months.18 These data indicate that the survival rate, up to 36 months, for all implants with preoperative antibiotic coverage is 95.1% (N=1555), while for implants with no coverage it is 90.3% (N=1240). Pre-operative antibiotics improved the survival rate of all types of implants at all stages of treatment. Of particular interest to this paper is how the HA-coated implants performed, compared with the non-HAcoated ones, under the more problematic conditions where no coverage was provided. Comparative survival rates are shown in Table 6. Slightly more than half of the implants in the study were placed with pre-operative antibiotics. Of these 1555 implants with antibiotic coverage, 960 (61.7%) were HAcoated and 590 (37.8%) were non-HA-coated implants. Of all implants provided pre-operative coverage, 98.2% of the HA designs survived between the time of placement and 36 months, compared to 90% of non-HA-coated implants. Survival of implants without pre-operative antibiotic coverage was 95.4% compared to non-HA-coated implants. Smoking and Survival of all Implants Placed
Table 6: Implant Survival and Preoperative Antibiotic Usage for All Stages of Treatment to 36 Months All Implants (n=2,795)
82.3% (n=480) No
Preoperative The use of tobacco as a significant risk factor in human Preoperative 35-37 Antibiotic health has been thoroughly documented. Studies have Antibiotic Usage also shown that smoking has a negative impact on the Usage (n=1,555) 38-39 (n=1,240) For these survival of endosseous dental implants. reasons many implant studies exclude smokers from their samples. The DICRG study was designed deliberately to be inclusive of those marginal groups (smokers, patients with systemic disease, those with poor bone quality) that are common to every patient population. Of the 2,795 implants placed in the DICRG study, 36% (1005) were placed in current smokers and 42.3% (1183) in those who had never smoked. Another 607 (21%) were previous smokers (data not reported here). Results are shown in Table 7.
Table 7. Implant Survival in Current Smokers and Those Who Have Never Smoked (all Stages of Treatment to 36 Months) All Implants (n=2,188)
Current Smokers (n=1,005)
Never Smoked (n=1,183)
Non-smokers fared slightly better at each stage of treatment. For the entire study period from placement to 36 months, implant survival in current smokers was 91.1% compared to 93.4% for those who had never smoked. Recently published DICRG data38 found that survival of HA-coated implants in smokers was 93.9% compared with 86.7% for non-HA-coated implants. These results suggest that HA-coated implants may offer a clinically significant advantage over non-coated implants by mitigating the influence of smoking on implant survival. The most recent analysis of the DICRG database reinforces these findings. HA-coated implants had half or fewer failures than non-HA-coated implants at every stage of treatment, except loading of the prosthesis (1.1% for current smokers compared to 1% for nonsmokers). Between the placement of the HA-coated implants and 36 months, survival in current smokers was 95.5% compared to
97.6% for the those who never smoked. Results were less conclusive for the 629 non-HA-coated implants placed in the two groups. For the entire period from placement-36 months, failures for non-HA-coated implants in smokers were 16.2% (83.8% survival) and 13.1% in those who never smoked (86.9% survival). While both HA- and non-HA-coated implants performed better in patients who had never smoked than in smokers, the most striking differences were found in smokers, where HA-coated implants still achieved 95.5% survival, compared with 83.8% for non-HA-coated implants. These figures, covering a three-year period, support the conclusion that the use of HA-coated implants in smokers improves the chance for a favorable outcome.
Mobility at Placement and Implant Survival An implant may exhibit slight mobility at placement due to an oversized osteotomy site. In such cases, the dentist is faced with several options: 1) leave the implant in place and hope that it will be successfully osseointegrated at the time of uncovering; 2) remove the implant and replace it with on of a larger diameter and/or different design/material; or 3) remove the implant and permit the site to heal before attempting to place a new implant. This last option is not attractive to either the dentist or the patient; however, it is not known what the probability for successful integration may be for the implant designs or materials that currently are available.
Of the 2795 implants placed in this study, 89 were slightly mobile at the time of placement. In the period between placement and 36 months, 79.8% of the implants mobile at placement survived compared with 93.4% of those not mobile at placement. For the entire period from placement to 36 months, survival of HA-coated implants that were mobile at placement was 91.8% compared with 63.6% of non-HA-coated implants. Bone Quality and Implant Survival by Stage of Treatment The influence of bone density on osseointegration and long term implant survival is well documented.40-42 For this study, radiographs and tactile sensation were used to evaluate bone quality, which was classified according to the Lekholm-Zarb system.43 Of 2787 implants for which data were recorded, distribution by bone quality was as follows: Q-1 bone, 241; Q-2 bone, 1276; Q-3 bone, 1030; Q-4 bone, 240. The predominance of types 2 and 3 conforms to expectations concerning the distribution of bone density in edentulous or partially edentulous patients. Survival data for this variable are presented for each stage of treatment as well as for the entire period from placement to 36 months. Results for HA-coated and non-HA-coated implants are shown in Fig. 1 and Table 8. Type Q-1 Bone: This bone type, consisting of a dense homogeneous cortical bone with a small trabecular core, generally presents the most favorable environment for osseointegration. In the present study, 241 implants were placed in Q-1 bone, of which 43.2% (104 of 241) were HA-coated and 56.8% (137 of 241) were non-HA-coated. The HA-coated implants performed consistently better in Q-1 bone throughout the first three years of the study. From placement to 36 months, 98.1% of the HA-coated implants survived compared to 90.5% of the non-HA-coated implants. Even in the most favorable bone density, survival of HA-coated implants was about 8% higher than non-HA-coated after 36 months. Type Q-2 bone: Type Q-2 bone, which has a large dense layer of cortical bone surrounding a dense trabecular core, appears with much greater frequency than Q-1. Of 1276 implants placed in Q-2 bone, 701 were HA-coated and 575 were non-HA-coated. Survival rates throughout the treatment period were similar to those seen in Q-1 bone. In the entire Fig. 1. Implant Survival by bone quality for all stages of study period from implant placement through 36 months, HAtreatment to 36 months. coated implant survival was 97.4% compared to 89.7% for nonHA-coated designs. At the end of the 36-month evaluation period, the difference between total survival for the two implant types is 7.7%.
Table 8. Implant Survival by Bone Quality for all Stages of Treatment to 36 Months
Placement to Uncovering
Uncovering to loading of Prosthesis
Loading of Prosthesis to 36 months
Type Q-3 Bone: This bone quality exhibits a thinner layer of cortical bone surrounding a dense trabecular core. Of the 1030 implants in Q-3 bone, 722 were HA-coated and 308 non-HA-coated. For the 36 months study period, cumulative survival for HA-coated implants was 96.7% compared with 80.5% for non-HA-coated. Q-3 bone represents a less dense bone, which has the potential for reduced survival of implants placed into it when compared to Q-2 bone. As the bone density decreased, survival of the non-HAcoated implants also decreased, while survival of the HA-coated implants differed only slightly from survival in Q-2 bone (96.7% compared to 97.4%). In this instance the difference in survival rates between the two types was 16.2%.
Type Q-4 Bone: Q-4 bone has a thin cortical layer surrounding a low-density trabecular Placement to core. It presents the least favorable 36 months Non90.5 89.7 80.5 76.1 environment for implant placement, and only HA 240 implants included in the study were placed in this bone type. Of these 240 implants, 77.2% were HA-coated and only 14.6% non-HA-coated. For the entire study period from the time of placement to 36 months, HA-coated implants attained 95.5% survival compared to 76.1% for non-HA-coated implants. The difference in survival was 19.4%. Despite the small sample size, these results form a consistent pattern with those obtained for other bone densities. They suggest a distinct advantage, up to three years from the time of placement, in using HAcoated implants in areas of less dense bone. HA
Maxillary Posterior Jaw Region The maxillary posterior region is the most challenging placement site, both by reason of its position (both posterior arches are less accessible than the anterior ones and thus demanding of greater skill on the surgeon's part)
and because it generally presents bone quality of lower density than other regions.39 On occasion, sinuses may have been enlarged to the extent that there is insufficient bone to anchor implants. In general, the DICRG study protocol excluded any augmentation for the purpose of placing an implant; however, exceptions were made in cases where the patient satisfied the criteria for placement in other jaw regions, and where it was clearly in the patient's best interest to surgically elevate the floor of the maxillary sinuses in order to provide adequate bone for anchorage. These implants were followed as nonstudy implants but have been included for the purpose of this 36 month analysis.
Two types of HA implant designs - cylindrical (Bio-Vent) and grooved (Micro-Vent) - were randomized in the maxillary posterior region (Table 1). Non-HA-coated implants were not Upper Lower Lower Maxillary placed in this area because the site-specific Completely Partially Completely Posterior Spectra-System designs used in the DICRG Edentulous Edentulous Edentulous (n=395) (n=596) (n=701) (n=856) study do not call for non-HA-coated implants in the maxillary posterior (Table 1). Of the 395 HA93.3% 99.0% 99.3% implants placed in the maxillary posterior 97%* coated (n=404) (n=388) (n=302) region, 157 were Bio-Vent cylinder implants and 238 were Micro-Vent implants with a Non72.9% 83.4% 93.0% grooved body and apical threads. Survival HANone (n=192) (n=313) (n=554) between placement and 36 months was 97% coated for all implants placed. The Micro-Vent design, * Cylinder Implant, 96.2%. Grooved Implant, 97.5%. with its combination screw and press fit surgical protocol, exhibited a slightly higher rate of survival (97.5%) than the Bio-Vent cylinder with only a press fit surgical protocol (96.2%). Table 9. Implant Survival by Bone Quality for all Stages of Treatment to 36 Months
Of all five study strata in the DICRG study, the maxillary posterior partially edentulous stratum had the highest overall survival rate in spite of the comparatively poor bone quality normally found in this region. A possible explanation for this anomaly is the fact that implants placed in the maxillary posterior region were exclusively HA designs which included a press fit surgical protocol. No non-HA-coated implants were placed in the maxillary posterior region. For comparison purposes, figures are given for the upper completely edentulous stratum (maxillary in which 404 HA- and 192 non-HA-coated implants were placed (Table 9). Survival in this region was 93.3% for the Micro-Vent and Screw-Vent HA implants and 72% for cpTi Screw-Vent implants. In the Lower Partially Edentulous stratum, 99.0% of the Bio-Vent HA (N=388) and 83.4% of the Core-Vent Ti alloy (N=313) implants succeeded, and in the lower completely edentulous stratum, 99.3% of the Bio-Vent HA (N=302) implants survived compared with 93.0% of non-HA-coated Core-Vent and Screw-Vent Ti alloy implants (N=554). anterior)
Summary The information on which this paper is based comprises a small fraction of the large database compiled from the DICRG study. These results represent early performance of HA implants (up to 36 months). The study has been ongoing for six years and we now have over 2,000 implants with four-year data and 1,500 with five-year data. These data are similar to the 36-month data, and when they are eventually released, they are likely to reinforce the results reported here. Meanwhile, the evidence presented in this paper, along with other corroborating studies cited in the introduction, are sufficient grounds to reach a conclusion. The ideal implant design and material is one that is easy to use, requires average skills, involves minimal bone trauma, presents a biocompatible contact surface, and produces a high rate of survival in most patients. Based on 36 month survival in the DICRG study, HA implants appear to satisfy these basic requirements better than the other implants in the study. HA implants were placed in the most challenging bone types and jaw regions, in patients with compromised medical histories, by dentists with different training, skills and experience, under less than ideal clinical conditions, and still exhibited the highest survival rates of all implants at every point in the treatment up to 36 months.
V.A. Study Three-Year Results Hydroxyapatite-Coated Implants: A Case for Their Use
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