Showing papers in "International Journal of Oral & Maxillofacial Implants in 2005"

Dental implant failure rates and associated risk factors

Abstract: PURPOSE To guide treatment planning by analyzing the rates of dental implant failure to determine associated risk factors. MATERIALS AND METHODS All consecutively treated patients from January 1982 until January 2003 were included in a retrospective cohort study, as defined in the hierarchy of evidence for dental implant literature. Data regarding gender, age, implant location, bone quality, bone volume, and medical history were recorded. Correlations between these data and implant survival were calculated to establish relative risk (RR) ratios. RESULTS Increasing age was strongly associated with the risk of implant failure. Compared to patients younger than 40 years, patients in the 60-to-79 age group had a significantly higher risk of implant failure (RR = 2.24; P < .05). Gender, hypertension, coronary artery disease, pulmonary disease, steroid therapy, chemotherapy, and not being on hormone replacement therapy for postmenopausal women were not associated with a significant increase in implant failure. Smoking (RR = 1.56), diabetes (RR = 2.75), head and neck radiation (RR = 2.73), and postmenopausal estrogen therapy (RR = 2.55) were correlated with a significantly increased failure rate. Overall, implant failure was 8.16% in the maxilla and 4.93% in the mandible (P < .001). DISCUSSION Patients who were over age 60, smoked, had a history of diabetes or head and neck radiation, or were postmenopausal and on hormone replacement therapy experienced significantly increased implant failure compared with healthy patients. CONCLUSION Overall, dental implant failure is low and there are no absolute contraindications to implant placement. Conditions that were found to be correlated with an increased risk of failure should be considered during treatment planning and factored into the informed consent process.

Correlation between placement torque and survival of single-tooth implants.

Abstract: Purpose: This study evaluated the survival parameters of single-tooth implants through clinical and radiographic analysis. Materials and Methods: Implants were restored within a 24-hour period with a provisional crown designed to receive an occlusal masticatory load. This approach was compared to implants restored after a healing period (the control group). Forty-six implants were placed in 23 patients who were each treated with 2 Frialit-2 implants placed in sites between the second premolar in the maxilla or mandible. The manufacturer’s recommended formal surgical procedure was followed, and primary stability was standardized with a minimum insertion torque of 20 Ncm. The sites were randomly selected, and the clinical and radiographic parameters were standardized with individual templates. Results: Data were collected at 24 h, and at 1, 3, 6, 12, 18, and 24 months. The experimental group included 10 failed implants; 9 of the failed implants had been placed with an insertion torque of 20 Ncm. One implant from the control group failed during the 24-month follow-up period. The survival rate was independent of implant length, site position, and bone quality and quantity. Relative risk for implant failure was associated with insertion torque (relative risk 0.79 [CI: 0.66–0.930]; Cox regression) (P � .007), in the experimental group but was not significant for those in the control group (ie, implants placed after a healing period; relative risk 0.78 [CI: 0.34–1.78]; Cox regression) (P � .057). To achieve osseointegration, it was found that an insertion torque above 32 Ncm was necessary (� 2 = 15.68; P � .004). Discussion: A careful evaluation is necessary for a better understanding of the survival rates of immediately loaded implants. In this study, insertion torque was associated with the potential for risk, which can be decreased by 20% per 9.8 Ncm added. Conclusion: Given these results, and considering the number of patients treated, immediate provisional crowns should only be proposed with early loading if an appropriate initial insertion torque has been applied. INT J ORAL MAXILLOFAC IMPLANTS 2005;20:769–776

Early wound healing around endosseous implants: a review of the literature.

Abstract: The knowledge base of information related to early wound healing around endosseous dental implants is rapidly changing and expanding. Unless one is directly involved with creating this pool of information or has an extraordinary interest in the literature of the field, it is difficult to keep up to date with the flow of information. This article is intended to provide the clinician with a state-of-the-art review of the current literature related to early wound healing and the creation of an osseointegrated interface between living and nonliving structures. While some literature dealing with basic laboratory studies including tissue culture is discussed, the primary focus of the article is the in vivo literature, ie, animal and human studies.

In vitro evaluation of bacterial leakage along the implant-abutment interface of different implant systems

Abstract: PURPOSE Microbial leakage and colonization between implants and their abutments may cause inflammatory reactions in the peri-implant tissues. This study evaluated microbial leakage at the implant-abutment interface with a new in vitro model. MATERIALS AND METHODS Bacterial leakage was tested during dynamic loading in a 2-axis chewing simulator. The authors theorized that dynamic loading would decrease the stability of the implant-abutment connections and thereby lead to bacterial penetration along the gap. Five different implant systems with 8 standard implant-abutment combinations for single molar crowns were tested. The internal aspects of the implants were inoculated with a bacterial suspension and connected to the superstructure with the recommended torque. The specimens were immersed in a nutrient solution and loaded with 1,200,000 cycles of 120 N in the chewing simulator. RESULTS Statistically significant differences (P < or = .05) between implant systems with respect to number of chewing cycles until bacterial penetration were found. DISCUSSION The degree of penetration in a specific implant system presumably is a multifactorial condition dependent on the precision of fit between the implant and the abutment, the degree of micromovement between the components, and the torque forces used to connect them. CONCLUSION It was concluded that the newly developed test model is a sensitive tool for the detection of differences between current implant systems with respect to their ability to prevent bacterial penetration at the implant-abutment interface under dynamic loading conditions.

Evaluation of patient and implant characteristics as potential prognostic factors for oral implant failures.

Abstract: PURPOSE: The purpose of this study was to evaluate patient, implant, and treatment characteristics to identify possible prognostic factors for implant failure. MATERIALS AND METHODS: Out of a database with different dental implant treatment protocols, a research database of 1 randomly selected implant per patient was created. The database consisted of 487 implants. Of these, 80 were withdrawn, 36 failed, and 371 remained successful during a 5-year follow-up period. Potential risk factors were evaluated by chi-square tests and post hoc analyses. RESULTS: Significant or strongly significant differences were found regarding implant failures as a result of jawbone quality, jaw shape, implant length, treatment protocol, and combinations of jawbone-related characteristics. Responsible clinics and number of implants supporting the restoration were factors that could not be associated with implant failure. DISCUSSION: Implant failures in this study were more often seen when negative patient-related factors were present. Approximately 65% of the patients with a combination of the 2 most negative bone-related factors (jawbone quality 4 and jaw shape D or E) experienced implant failure. However, only 3% of the patients had this combination. Implant length, the only implant-related factor evaluated, was also significantly correlated with the success rate, but implant length could also be regarded as a result of the jawbone volume available. Another negative patient-related factor was the treatment protocol; however, in most cases this was also indirectly or partly related to the status of the jawbone available for implant placement. CONCLUSION: Patient selection appears to be of importance for increasing implant success rates.

In vitro evaluation of the implant-abutment bacterial seal: the locking taper system.

Abstract: Purpose: To test in vitro whether the seal provided by the locking taper used in the implant-abutment connection was capable of preventing the invasion of oral microorganisms. Materials and Methods: Twenty-five wide-body implants (5 � 11 mm) and 25 abutments were divided into 2 groups for a 2phase experiment. The first phase tested the ability of the seal to shield the implant well from outside bacteria; the second phase tested the ability of the seal to prevent bacteria present in the implant well from seeping out. For phase 1, 10 implant-abutment units were immersed in a bacterial broth for 24 hours. The abutments were then separated from the implants and bacterial presence was evaluated using scanning electron microscopy. In phase 2, the tested abutments were inoculated with a droplet of soft agar bacterial gel and assembled with the implant. These units were incubated in a sterile nutrient broth for 72 hours, sampled, and plated to assess bacterial presence. Results: In phase 1, no bacteria were detected in any of the implant wells. In phase 2, no bacteria were detected in the nutrient broth or on the agar plates at 72 hours. Discussion: In implants where a microgap is present, microbial leakage could lead to inflammation and bone loss; thus, it is important to minimize bacterial presence in and around the the implant-abutment junction. Conclusion: The seal provided by the locking taper design has been demonstrated to be hermetic with regard to bacterial invasion in vitro. INT J ORAL MAXILLOFAC IMPLANTS 2005;20:732–737

Bone density assessments of dental implant sites: 2. Quantitative cone-beam computerized tomography.

Abstract: Purpose: Bone density was evaluated in designated implant sites using a novel volumetric computerized tomographic device. Those measurements were then compared with traditional quantitative computerized axial tomography and subjective bone density evaluation. Materials and Methods: Sixtythree potential sites for implant placement in jaws from 9 human cadavers were used. Indicator rods 2 mm in diameter were placed in all sites. Radiographic images representing 1-mm buccolingual slices immediately mesial and distal to the rods were selected. Bone density in Hounsfield units was assessed using quantitative cone-beam computerized tomography (QCBCT) and quantitative computerized tomography (QCT) in a standardized implant area superimposed on the images. Bone density was also subjectively evaluated by 2 independent examiners using the Lekholm and Zarb classification. Results: The QCBCT bone density values were generally found to be higher than the corresponding QCT measurements. The correlations between the QCT and QCBCT values, however, were very high in spite of this systematic difference between the 2 methods. The Lekholm and Zarb ratings for the 2 examiners showed correlation coefficients ranging between 0.46 and 0.60 for the relationships with the QCBCT values. For each of the scores used for the subjective classification, however, a wide range of corresponding QCBCT values was observed. Discussion: High dosage has been the major impediment to the utilization of CT in implant dentistry. The development of a reliable volumetric CT alternative with reduced radiation should provide an effective method for the assessment of both bone quantity and bone density. Conclusions: Access to objective radiographic bone density values should constitute a valuable supplement to subjective bone density evaluations prior to implant placement. QCBCT could be considered an alternative diagnostic tool for preoperative bone density evaluation, especially since the reported radiation dose is minimal. INT J ORAL MAXILLOFAC IMPLANTS 2005;20:416–424

Optimum surface properties of oxidized implants for reinforcement of osseointegration: surface chemistry, oxide thickness, porosity, roughness, and crystal structure.

Abstract: PURPOSE: To investigate detailed surface characterization of oxidized implants in a newly invented electrolyte system and to determine optimal surface oxide properties to enhance the bone response in rabbits. MATERIALS AND METHODS: A total of 100 screw-type titanium implants were prepared and divided into 1 control group (machine-turned implants) and 4 test groups (magnesium ion-incorporated oxidized implants). Forty implants were used for surface analyses. A total of 60 implants, 12 implants from each group, were placed in the tibiae of 10 New Zealand white rabbits and measured with a removal torque test after a healing period of 6 weeks. RESULTS: For the test groups, the oxide thicknesses ranged from about 1,000 to 5,800 nm; for the control group, mean oxide thickness was about 17 nm. The surface morphology showed porous structures for test groups and nonporous barrier film for the control group. Pore diameter ranged from < or = 0.5 microm to < or = 3.0 microm. In regard to surface roughness, arithmetic average height deviation (Sa) values varied from 0.68 to 0.98 microm for test implants and 0.55 microm for control implants; developed surface ratio (Sdr) values ranged from 10.6% to 46% for the test groups and were about 10.6% for the control group. A mixture of anatase and rutile-type crystals were observed in the test groups; amorphous-type crystals were observed in the control group. After a healing period of 6 weeks, removal torque measurements in all 4 test groups demonstrated significantly greater implant integration as compared to machine-turned control implants (P < or = .033). DISCUSSION: Determinant oxide properties of oxidized implants are discussed in association with bone responses. Of all surface properties, RTVs were linearly increased as relative atomic concentrations of magnesium ion increase. CONCLUSIONS: Surface properties of the oxidized implants in the present study, especially surface chemistry, influenced bone responses. The surface chemistry of the optimal oxidized implant should be composed of approximately 9% magnesium at relative atomic concentration in titanium oxide matrix and have an oxide thickness of approximately 1,000 to 5,000 nm, a porosity of about 24%, and a surface roughness of about 0.8 microm in Sa and 27% to 46% in Sdr; its oxide crystal structure should be a mixture of anatase- and rutile-phase crystals.

Maxillary sinus floor augmentation using a beta-tricalcium phosphate (Cerasorb) alone compared to autogenous bone grafts

Abstract: Purpose: A prospective human clinical study was conducted to determine the clinical and histologic bone formation ability of 2 graft materials, a � -tricalcium phosphate (Cerasorb; Curasan, Kleinostheim, Germany) and autogenous chin bone, in maxillary sinus floor elevation surgery. Materials and Methods: Ten healthy patients underwent a bilateral (n = 6) or unilateral (n = 4) maxillary sinus floor elevation procedure under local anesthesia. In each case, residual posterior maxillary bone height was between 4 and 8 mm. In cases of bilateral sinus floor elevation, the original bone was augmented with a split-mouth design with 100% � -tricalcium phosphate on the test side and 100% chin bone on the contralateral control side. The unilateral cases were augmented with 100% � -tricalcium phosphate. After a healing period of 6 months, ITI full body screw-type implants (Straumann, Waldenburg, Switzerland) were placed. At the time of implant surgery, biopsy samples were removed with a 3.5-mm trephine drill. Results: Sixteen sinus floor elevations were performed. Forty-one implants were placed, 26 on the test side and 15 on the control side. The clinical characteristics at the time of implantation differed, especially regarding clinical appearance and drilling resistance. The increase in height was examined radiographically prior to implantation and was found to be sufficient in all cases. After a mean of nearly 1 year of follow-up, no implant losses or failures had occurred. Discussion: The promising clinical results of the present study and the lack of implant failures are probably mainly the result of requiring an original bone height of at least 4 mm at the implant location. Conclusion: Although autogenous bone grafting is still the gold standard, according to the clinical results, the preimplantation sinus floor elevation procedure used, which involved a limited volume of � -tricalcium phosphate, appeared to be a clinically reliable procedure in this patient population. INT J ORAL MAXILLOFAC IMPLANTS 2005;20:432–440

Comparison of the platelet concentrate collection system with the plasma-rich-in-growth-factors kit to produce platelet-rich plasma: a technical report.

Abstract: PURPOSE The aim of this study was to compare a new method for the production of platelet-rich plasma (PRP), the plasma-rich-in-growth-factors kit (PRGF kit; G.A.C. Medicale San Antonio, Vitoria, Spain), with an established method, the Platelet Concentrate Collection System (PCCS; 3i/Implant Innovations, Palm Beach Gardens, FL) with respect to resulting cellular and growth factor contents. MATERIALS AND METHODS Whole blood was drawn from 51 healthy donors (20 men, 31 women) aged 19 to 59 years (mean +/- SD 35.12 +/- 9.65 years), and PRP was prepared by both methods. RESULTS Platelet counts differed significantly (signed rank test, P < .001 for all) between the donor blood (274,200 +/- 54,050/microL), the PCCS PRP preparation (1,641,800 +/- 426,820/microL), and the PRGF kit PRP preparation (513,630 +/- 139,470/microL). The PCCS concentrated leukocytes (whole blood, 6,992 +/- 2,011/microL; PCCS PRP, 14,153 +/- 7,577/microL), while the PRGF kit produced a leukocyte-poor PRP (65 +/- 108/microL). Higher concentrations of transforming growth factor beta1 (TGF-beta1) and platelet-derived growth factor AB (PDGF-AB) were found in the PCCS PRP (TGF-/beta1, 290 +/- 95 ng/mL; PDGF-AB, 157 +/- 62 ng/mL) than in the Anitua PRGF kit PRP (TGF-beta1, 73 +/- 26 ng/mL; PDGF-AB, 47 +/- 21 ng/mL). Statistical analysis showed significant differences (P < .001 for TGF-beta1 and P < .01 for PDGF-AB). DISCUSSION The results of this study and some data in the literature indicate that the content of growth factors in PRP can vary tremendously, depending on the system used for the preparation of PRP. CONCLUSION PCCS collects more platelets and leukocytes than the PRGF kit. This results in significantly higher growth factor levels. Further in vivo studies are needed to determine whether this results in a clinically different biologic effect.

A prospective multicenter randomized clinical trial of autogenous bone versus beta-tricalcium phosphate graft alone for bilateral sinus elevation: histologic and histomorphometric evaluation.

Abstract: PURPOSE: Two different graft materials, beta-tricalcium phosphate (Cerasorb) and autogenous bone, were used in the same patient. The objective was to determine whether donor site morbidity could be avoided by using pure-phase beta-tricalcium phosphate (Cerasorb). MATERIALS AND METHODS: Bilateral sinus grafting was performed on 20 selected patients; Cerasorb was used on the experimental side, and autogenous bone was used on the control side. In each patient, one side was randomly designated the experimental side. In 10 of the 20 patients, the maxilla reconstruction included sinus grafting and onlay bone grafting. Implants were placed 6 months after the procedure. In addition to routine panoramic radiographs, in 10 of the 20 patients, 2- and 3-dimensional computerized tomographic examinations were performed pre- and postoperatively and after implantation. Eighty bone biopsy specimens were taken at the time of implant placement. RESULTS: Histologically and histomorphometrically, there was no significant difference between the experimental and control grafts in terms of the quantity and rate of ossification. For each histologic sample, the total surface area, the surface area that consisted of bone, and the surface area that consisted of graft material were measured in mm2, and bone and graft material were analyzed as percentages of the total. The mean percentage bone areas were 36.47% +/- 6.9% and 38.34% +/- 7.4%, respectively; the difference was not significant (P = .25). DISCUSSION AND CONCLUSION: Comparisons with other studies reveal that beta-tricalcium phosphate (Cerasorb) is a satisfactory graft material, even without autogenous bone.

Distribution of the maxillary artery as it relates to sinus floor augmentation.

Abstract: Purpose: Knowledge of the blood supply to the sinus is of importance in sinus augmentation, both as it pertains to vascularization of the sinus graft and as its location relates to the position of the required lateral osteotomy. The purpose of this sl^djuvas to investigate the distribution of the enrJosseous Branches oi the maxillary artery in the area of the proposed lateral window. Materials and Methods; Fifty computerized tomographic (CT) scans from 625 available patients undergoing sinus augmentation surgery at the New York University Department of Implant Dentistry were chosen at random for evaluation. In those cases where the maxillary artery could be identified, measurements were taken to determine the distance between the alveolar crest and the lower border of the vessel. Results; The vessel was radiographically identified in 51.4% of right sinuses and 54.3% of left sinuses in the 50 CT scans. The average height of the artery from the alveolar crest was 16 mm (t 3.5 mm). Discussion: and Conclusions: Because of its location, the intraosseous artery has the potential to cause bleeding complications in approximately 20% of normally positioned lateral window osteotomies. Although a previous anatomic study on cadavers identified the vessel in 100% of the specimens, it could on/y be visualized in 53% of the CT scans in the present series. !NT J ORAL MAXILLOFAC IMPLAMTS 2005:20:784-787

A 5-year follow-up comparative analysis of the efficacy of various osseointegrated dental implant systems: a systematic review of randomized controlled clinical trials.

Abstract: PURPOSE: To test the null hypothesis that there is no difference in failure rates between various root-formed osseointegrated dental implant systems after 5 years of loading. MATERIALS AND METHODS: A search was conducted for all randomized controlled clinical trials (RCTs) comparing different implant systems with a follow-up of 5 years. The Cochrane Oral Health Group's Trials Register, CENTRAL, MEDLINE, and EMBASE were searched. Several dental journals were also searched by hand. Written contacts were established with authors of the identified RCTs and with more than 55 oral implant manufacturers and personal contacts to identify unpublished RCTs. No language restriction was applied. The last electronic search was conducted on February 1, 2005. Screening of eligible studies, quality assessment, and data extraction were conducted in duplicate. Results were expressed as random effect models using weighted mean differences for continuous outcomes and relative risk for dichotomous outcomes with 95% confidence intervals. RESULTS: Ten RCTs were identified. Four of these RCTs, reporting results from a total of 204 patients, were considered suitable for inclusion. Six different implant types were compared. On a per-patient rather than a per-implant basis, there were no statistically significant differences, with the exception of more marginal bone loss around early loaded Southern implants when compared to early loaded Steri-Oss implants (mean difference -0.35 mm; 95% CI -0.70 to -0.01). However, the difference disappeared in the meta-analysis. DISCUSSION AND CONCLUSIONS: There were no clinical differences among implant systems. However, these findings are based on only 4 RCTs with few participants. More RCTs should be conducted with larger patient samples.

Intraoperative computerized navigation for flapless implant surgery and immediate loading in the edentulous mandible.

Abstract: Computerized navigation surgery has evolved to facilitate minimally invasive procedures, the gold standard of surgery today. While flapless implant surgery may be clinically beneficial, it has generally been perceived as a blind procedure limited to straightforward cases that do not pose a risk of cortical plate perforation. The objective of this report is to describe a protocol for flapless implant placement in a completely edentulous mandible using computerized navigation surgery. The Image Guided Implantology system (IGI, DenX Advanced Dental Systems) is described. The IGI system provides real-time imaging of the dental drill and transforms flapless implant surgery into a fully monitored procedure. The highly accurate intraoperative navigation enables precise transfer of the detailed presurgical implant plan to the patient. This is particularly valuable in edentulous jaws lacking any indication of the dental arch. The accurate positioning of the implants, based on the presurgical digital plan, allows fabrication of a provisional fixed prosthesis before the implant surgery for immediate postoperative loading. This innovative protocol can enhance prosthodontic-driven placement of implants in a fully monitored flapless surgery.

A Resonance Frequency Analysis Assessment of Maxillary and Mandibular Immediately Loaded Implants

Abstract: Purpose: This study evaluated the stability of implants in 51 patients following a clinical protocol of immediate functional loading. The stability during the first 3 months following implant placement was assessed according to bone type, implant location, and patient gender. Materials and Methods: Twenty-two male and 29 female patients were treated with 344 Branemark System implants placed in edentulous bone or extraction sites and put into functional loading using the Teeth in a Day protocol. Each implant was tested for primary stability with resonance frequency analysis (RFA) at the time of implant placement, and RFA was performed at examinations 30, 60, and 90 days following surgery. Results: The analysis was based on the 276 implants that were successfully measured using RFA at all postoperative intervals. The clinical implant survival rate was 98.5% for the total population. RFA showed a decrease in bone-implant stability in the first month after implant placement from 70.35 ± 0.5 to 66.38 ± 0.50, followed by increases in stability in the second and third months (68.01 ± 0.50 and 68.82 ± 0.49, respectively), suggesting a process of adaptive bone remodeling around the implant. In general, lower initial stabilities were seen in softer bone types, in the posterior portions of the jaw compared to anterior areas, and in the female population. Discussion and Conclusion: The results of this study suggest an immediate loading protocol should have an undisturbed period of healing for the first 2 months following implant placement. The determination of “predictor” stability levels for different clinical conditions were based on multiple splinted implants, allowing a larger surface area to withstand the distribution of the load. The most significant “predictor” values from a surgical and prosthodontic perspective are those determined in soft bone, in reduced bone, or in areas where lever arms are created as a result of long spans between the implants. (More than 50 references.) INT J ORAL MAXILLOFAC IMPLANTS 2005;20:584–594

An assessment of crown-to-root ratios with short sintered porous-surfaced implants supporting prostheses in partially edentulous patients.

Abstract: Purpose: Implant length, implant surface area, and crown-to-root (c/r) ratio and their relationship to crestal bone levels were analyzed in 2 groups of partially edentulous patients treated with sintered porous-surfaced dental implants. Materials and Methods: One hundred ninety-nine implants were used to restore 74 partially edentulous patients with fixed prostheses. Implants were categorized according to their length (“short” versus “long”) and estimated surface area (“small” versus “large”). “Short” implants had lengths of 5 or 7 mm, while “long” implants were either 9 or 12 mm in length. “Small” implants had estimated surface areas of ≤ 600 mm2 , while “large” implants had estimated surface areas > 600 mm2 . Other data collected included c/r ratio (measured on articulated diagnostic casts), whether or not the implants were splinted, and standardized sequential radiographs. Results: The mean c/r ratio was 1.5 (SD = 0.4; range 0.8 to 3.0), with 78.9% of the implants having a c/r ratio between 1.1 and 2.0. Neither c/r ratio nor estimated implant surface area (small or large) affected steady-state crestal bone levels. However, implant length and whether the implants were splinted did appear to affect bone levels. Long implants had greater crestal bone loss (0.2 mm more) than short implants; splinted implants showed greater crestal bone loss (0.2 mm more) than nonsplinted ones. These differences were statistically significant. Discussion and Conclusions: Sintered porous-surfaced implants performed well in short lengths (7 mm or less) in this series of partially edentulous patients. The data suggested that long implants and/or splinting can result in greater crestal bone loss; longer implants and splinted implants appeared to favor greater crestal bone loss in this investigation. These conclusions are, of course, specific to the implants used and would not be relevant to other implant types. INT J ORAL MAXILLOFAC IMPLANTS 2005;20:69–76

Membrane durability and tissue response of different bioresorbable barrier membranes: a histologic study in the rabbit calvarium.

Abstract: Purpose: The objective of the present study was to histologically evaluate barrier durability and host tissue response of new prototype collagen membranes in comparison to clinically available collagen and synthetic polymer membranes. Materials and Methods: The experimental study was conducted in 20 rabbits with 4 different healing periods of 2, 6, 12, and 28 weeks. Following surgical exposure of the calvarium, 6 circular bone defects (diameter 4 mm, depth 1.5 mm) were drilled into the outer cortex. After the bone had been removed, each defect was covered with 1 of 6 different membranes: 3 collagen prototype membranes, a Bio-Gide collagen membrane (BG), a glycolide-lactide-trimethylene carbonate Osseoquest membrane (OQ), and a polylactide Atrisorb membrane (AS). Histological analysis was performed following staining with toluidine blue and transversal sectioning of the calvarial bone. Results: All collagen membranes showed similar tissue integration characterized by fibrous encapsulation with differentiation of a periosteumlike tissue upon the external bony surface. One prototype collagen membrane displayed clearly longer membrane integrity. The evaluated synthetic membranes demonstrated extended barrier durability but also exhibited inflammatory foreign-body reactions. Discussion: Recent experimental investigations have shown that degradation of collagen membranes may begin within days to weeks of membrane placement. This was confirmed in the present study. However, 1 of the chemically modified collagen prototype membranes exhibited prolonged membrane integrity in the absence of an inflammatory tissue response. Conclusion: Further investigation of the prototype membrane that showed prolonged membrane integrity to evaluate its potential in GBR procedures is needed. INT J ORAL MAXILLOFAC IMPLANTS 2005;20:843–853

Comparative analysis study of 702 dental implants subjected to immediate functional loading and immediate nonfunctional loading to traditional healing periods with a follow-up of up to 24 months.

Abstract: Purpose The aim of this study was to clinically evaluate immediate functionally loaded (IFL) and immediate nonfunctionally loaded (INFL) implants for various indications compared to a control group with a conventional healing period. Materials and methods Two hundred fifty-three patients took part in the study. A total of 702 XiVE implants (Dentsply/Friadent, Mannheim, Germany) were placed: 253 IFL implants, 135 INFL implants, and 314 controls. Results In each of the 3 groups, 2 implants failed. For all the other implants involved, from a clinical and radiographic point of view, osseointegration was successful. Discussion As long as the prerequisites are fulfilled, immediate functional loading and immediate nonfunctional loading are predictable techniques, not only in completely edentulous patients but also in partially edentulous patients. Conclusion Immediate functional loading and immediate nonfunctional loading appear to be techniques that can provide satisfactory implant success rates in selected cases.

Stability measurements of 1-stage implants in the maxilla by means of resonance frequency analysis: a pilot study.

Abstract: PURPOSE The objective of the present study was to determine standard Implant Stability Quotient (ISQ) values for apparently successfully osseointegrated 1-stage implants in the maxilla. MATERIALS AND METHODS To measure implant stability, resonance frequency analysis (RFA) was performed in 35 patients (18 women, 17 men) with a total of 120 maxillary ITI implants. Based on the time interval between implant placement and measurements, the ISQ values of anterior and posterior implants were divided into subgroups: unloaded (n = 41), loaded 1 year (n = 48). Statistical analysis was performed using a mixed-effects model with the variables lading, implant location, and gender as fixed effects. RESULTS The mean ISQ of all measured implants was 52.5 +/- 7.9 (range 40 to 68). Statistical analysis showed no significant differences in ISQ values between the 3 tested time intervals: unloaded (48.8 +/- 3.6), loaded 1 year (53.1 +/- 9.5). Neither for the location in the jaw nor for bone quality (assessed using radiographs) could a significant difference be found. Gender was the only parameter which was found to be significant (P < .003); on average, men showed higher implant stability than women (56.3 +/- 6.6 versus 48.7 +/- 7.4). DISCUSSION Standard values for osseointegrated maxillary ITI implants exhibited an individual range. Single RFA measurements of an implant do not allow assessment of its current status or prediction of its performance. Repeated measurements over a longer time period would be necessary. CONCLUSIONS No significant differences in ISQ values were found between implants with regard to loading period or location in the jaw. Postmenopausal women exhibited significantly lower ISQ values compared to men of the same age group.

Maxillary sinus augmentation: histologic and histomorphometric analysis.

Abstract: PURPOSE: Implant placement in the posterior maxilla may often be contraindicated because of insufficient bone volume and the presence of the maxillary sinus. In these situations, sinus floor l ifting and grafting frequently have been proposed as the best treatment. The aim o f this study was to compare histologically the use of 100% autogenous bone vers us a combination of autogenous bone and corticocancellous pig bone for maxillary sinus augmentation. MATERIALS AND METHODS: Eighteen patients requiring bilateral maxillary sinus augmentation were selecte d for this study. Bone for grafting was harvested from the iliac crest. Each p atient received 100% autogenous bone in 1 randomly selected sinus (contr ol side) and a 1:1 mixture of autogenous bone and corticocancellous pig bone part icles in the contralateral sinus (test side). Five months after the augmentati on procedure, bone biopsy specimens were taken at the time of implant placement. RESULTS: No complications were observed during the surgical pro cedures; all patients healed uneventfully. No signs or symptoms of maxillary sin us disease were observed during the 5 months after surgery. No significant d ifferences in bone percentages were observed in the bone biopsies from test and control sides. DISCUSSION AND CONCLUSION: It could be concluded from this study that corticocancellous pig bone particles can be success fully used in a 1:1 mixture with autogenous bone from the iliac crest for maxil lary sinus augmentation in cases of severely atrophic maxilla.

Immediate loading of single-tooth implants in the posterior region.

Abstract: Purpose The aim of this study was to evaluate the clinical response and safety of immediately loaded single-tooth implants placed in the posterior region of the maxilla and mandible. Materials and methods Single-tooth implants were placed in healed extraction sites in 20 adult patients. Temporary pre-fabricated acrylic resin crowns were prepared and adjusted. The crown occlusion was adjusted to obtain minimal contacts in maximum intercuspation. After 6 weeks a ceramometal or all-ceramic crown was cemented. Radiographic and clinical examinations were made at baseline and at 3, 6, and 12 months. Cortical bone response and peri-implant mucosal responses were evaluated. Results The marginal bone level at the time of implant placement was preserved. The mean change in marginal bone level was 0.01 mm at 12 months. The mean Periotest value after 360 days was -4. The peri-implant mucosal adaptation to the anatomic form of the provisional crown resulted in a natural esthetic outcome, and a gain in papilla length was observed. One implant failure was recorded because of provisional luting cement impaction. Discussion Clinical research has shown that immediate loading is a possible treatment modality. The immediate functional loading of implants placed in this study resulted in bone adaptation to loading. A satisfactory success rate with positive tissue responses was achieved. Conclusions The results of this limited investigation indicated that immediate loading of unsplinted single-tooth implants in the posterior region may be a viable treatment option with an esthetic outcome.

Comparison of dental implant systems: quality of clinical evidence and prediction of 5-year survival.

Abstract: PURPOSE This literature review was conducted to evaluate the quality of current evidence of clinical performance provided by American Dental Association-certified dental implant manufacturers and manufacturers with strong market penetration in the United States. The study also compared the clinical performance of different dental implant systems. MATERIALS AND METHODS A letter was sent to 6 implant manufacturers requesting 10 references each that validated the manufacturer's implant system in a variety of clinical applications. References were reviewed and classified relative to strength of evidence. Data extraction was then performed. Comparisons of implant survival data from 5-year studies were made, and data were pooled to establish an overall 5-year survival rate with confidence intervals (CIs). RESULTS A total of 69 references were provided by the 6 implant manufacturers (Astra Tech, Centerpulse, Dentsply/Friadent, Implant Innovations, Nobel Biocare, and Straumann) but only 59 articles were available for review. Of those references, most were level-4 (case series) or level-5 (expert opinion) articles. Five-year survival data were extracted from 17 articles demonstrating overlap of CIs from the weighted average of the pooled data from each specific manufacturer; substantial equivalence of all implant systems was demonstrated based upon survival alone at 5 years. When all data were pooled, the 5-year survival rate of 96% (CI: 93% to 98%) was observed for a total of 7,398 implants. DISCUSSION No obvious differences in implant survival were observed when comparing implant systems. CONCLUSIONS The evidence supporting implant therapy is generally derived from level-4 case series rather than higher-level cohort or controlled clinical trials. Articles that directly compared different implant systems were not found. Five-year implant survival rates easily exceeded the minimums recommended by the American Dental Association certification program. (More than 50 references.)

Impact of smoking on marginal bone loss.

Abstract: PURPOSE To compare marginal implant bone loss (MBL), survival, and radiographic evidence of success of dental implants among smokers and nonsmokers. MATERIALS AND METHODS Consecutive records of 161 patients (aged 23 to 89 years, mean 57 years) treated with a total of 646 implants between the years 1995 and 1998 were examined. Patients were divided into 3 groups: nonsmokers, moderate smokers, and heavy smokers. Tobacco exposure was calculated by cigarettes per day and by pack-years. Follow-up ranged from 1 to 7 years (mean 3.8 years). Postoperative panoramic radiographs obtained before implant exposure and annually thereafter were analyzed for MBL changes. The influence of smoking and other variables on MBL was analyzed at all implant sites. RESULTS Generally, smokers had more MBL than nonsmokers (0.153 +/- 0.092 mm and 0.047 +/- 0.048 mm, respectively; P < .001). When each jaw was examined separately, smoking had a greater effect on MBL in the maxilla than in the mandible (0.158 +/- 0.171 mm versus 0.146 +/- 0.158 mm, respectively; P < .001). Furthermore, in the maxilla, heavy smokers had the greatest amount of MBL (0.1897 +/- 0.1825 mm), followed by moderate smokers (0.123 +/- 0.156 mm) and nonsmokers (0.0460 +/- 0.070 mm) (P < .001). In the mandible, there was no distinction between heavy and moderate smokers, and both had greater MBL than nonsmokers (P < .001). Only 3 of the 646 implants failed; the cumulative survival rate was 99.5%. Overall radiographic success rate was 93.2%. Nonsmokers had a higher radiographic success rate (97.1%) than smokers (87.8%) (P < .001). CONCLUSIONS This study demonstrated a relationship between MBL and smoking habits. A higher incidence of MBL was found in the smoking group, and this was more pronounced in the maxilla.

Implants in the posterior maxilla: a comparative clinical and radiologic study.

Abstract: Purpose: The aim of this study was to evaluate implants placed according to several methods of sinus floor augmentation. Materials and Methods: Forty-eight patients (median age of 62 years, range 23 to 89) had been treated at least 3 years prior to examination with screw-type implants in the posterior maxilla. Depending on the vertical dimension of the residual bone, 1 of 3 surgical procedures had been performed: sinus lift by lateral antrostomy (SL) in 13 patients; osteotome technique (OT) in 18 patients; standard implantation in 17 patients (control). In each patient 1 implant was randomly chosen for analysis (48 implants with a mean observation time of 4.6 ± 1.4 years). Examination included probing pocket depth (PPD) measurement and radiographic examination. Radiographs were digitized to assess the marginal bone level. Differences between the groups were tested using analysis of variance, the Student t test and the Kruskal-Wallis test. Results: Mean PPD was 3.0 mm for the SL, 3.1 mm for OT, and 3.1 mm for control. The mean radiographic bone level was 1.53 mm for SL, 2.40 mm for OT, and 1.96 mm for control. No statistically significant differences were found between the groups for either of these parameters. Discussion and Conclusion: Clinical examinations as well as radiographically stable bone levels indicated similar biomechanical conditions for prosthetic restorations when applying the 3 surgical procedures tested. I NT J ORAL MAXILLOFAC IMPLANTS 2005;20:231–237

Survival estimates and risk factors for failure with 6 x 5.7-mm implants.

Abstract: Purpose: Short dental implants facilitate prosthetic restoration in the setting of limited alveolar bone height. The study objectives were to (1) estimate the 1-year survival of Bicon 6 � 5.7-mm implants, (2) compare the 1-year survival of 6 � 5.7-mm implants with that of non–6 � 5.7-mm implants, and (3) identify risk factors associated with implant failure. Materials and Methods: A retrospective cohort study design was used. The sample was composed of patients who had received at least one 6 � 5.7mm implant. Predictor variables were categorized as demographic, health status, anatomic, implantspecific, prosthetic, perioperative, and reconstructive. The outcome variable was implant failure, defined as explantation. Appropriate descriptive, bivariate, and multivariate survival statistics were computed. Results: The sample was composed of 35 patients in whom 172 implants had been placed (45 of which were 6 � 5.7-mm). The 1-year survival rates for 6 � 5.7-mm and non–6 � 5.7-mm implants were 92.2% and 95.2%, respectively (P = .76). After adjusting for covariates in a multivariate model, implant size was not associated with failure (P = .95). Discussion: The comparable survival estimates for 6 � 5.7-mm implants and non–6 � 5.7-mm implants in this study suggested that 6 � 5.7mm implants can become osseointegrated and bear a functional load after placement. Conclusions: The survival of 6 � 5.7-mm implants was comparable to that of non–6 � 5.7-mm implants. INT J ORAL MAXILLOFAC IMPLANTS 2005;20:930–937

The effects of ion beam-assisted deposition of hydroxyapatite on the grit-blasted surface of endosseous implants in rabbit tibiae.

Abstract: PURPOSE This study was undertaken to evaluate ion beam-assisted deposition (IBAD) of hydroxyapatite (HA) on the grit-blasted surface of endosseous dental implants 6 weeks postplacement. MATERIALS AND METHODS A total of 40 implants was placed in the tibiae of 10 New Zealand white rabbits. Twenty implants were grit-blasted only and the other 20 were grit-blasted and coated with HA by the IBAD method. After 6 weeks of healing, the rabbits were sacrificed and removal torque tests, histomorphometry, and morphometric analysis of microtomographic images were performed. RESULTS The HA-coated group showed significantly higher removal torque, bone-to-implant contact, and bone volume than the other group. DISCUSSION AND CONCLUSION In a previous study, the authors suggested that HA coating deposited on a machined surface by the IBAD method showed results comparable to or more favorable than the results obtained with a blasted surface. This study indicated that the HA coating produced by the IBAD method was also very effective on the aluminum oxide-blasted surface, as demonstrated by the early formation of osseointegration. Morphometric analysis by microtomography showed some promise in measuring the osseointegration rate. (More than 50 references.)

Assessment of correlation between computerized tomography values of the bone and cutting torque values at implant placement: a clinical study.

Abstract: PURPOSE The relationship between computerized tomography (CT) values of bone surrounding endosseous implants and the cutting torque values required for self-tapping during implant placement was examined for the purpose of predicting the initial stability (bone quality) during implant placement by presurgical CT scan examinations and determining whether it can be quantified. MATERIALS AND METHODS The study sample consisted of 13 subjects with 56 implants. Sites for implant placement were determined based on CT data using implant planning software. The average CT values of the bone surrounding the simulated implants were calculated by the software. Using a stereolithographic drill guide, implants were placed at the locations indicated by the protocol. The cutting torque values required for self-tapping were measured during implant placement. The resulting CT values and cutting torque values were analyzed statistically for correlation. RESULTS The correlation was considered significant at a level of .01 or less, and the correlation coefficient was 0.77. DISCUSSION There was a strong correlation between CT values and cutting torque values in the clinical cases evaluated. These results indicate that it may be possible to predict and quantify initial implant stability and bone quality from presurgical CT diagnosis and implant simulation. CONCLUSION Presurgical CT examination may be an effective technique for predicting initial stability of the implant and bone quality.

Interproximal Papilla Levels Following Early Versus Delayed Placement of Single-Tooth Implants: A Controlled Clinical Trial

Abstract: Purpose: The aim of this study was to evaluate interproximal papillae and clinical crown height following the placement of single-tooth implants according to early and delayed protocols. Materials and Methods: Forty-five patients were randomly allocated to either the “early” group or the “delayed” group. They were treated with a single-tooth acid-etched Osseotite implant in the maxillary or mandibular anterior or premolar region an average of 10 days (in the case of early placement) or 3 months (in the case of delayed placement) following tooth extraction. Interproximal papilla dimensions and clinical crown height were evaluated using a score index in 39 patients who attended a follow-up visit 16 to 18 months after prosthesis delivery. The patients were evaluated in photographs taken 1 week after crown placement (baseline) and approximately 1.5 years after crown placement (follow-up). Results: It was demonstrated by logistic regression the risk of presenting no papilla or a negative papilla was 7 times greater at baseline for delayed cases than for early cases (33% versus 8%). However, the soft tissue fill in the proximal spaces improved significantly from baseline to the 1.5-year follow-up in both groups, with no significant difference between the groups found at follow-up. The papilla height almost 2 years after implant placement was inversely correlated with patient age. The clinical crown height was acceptable in significantly more cases in the early group than in the delayed group at follow-up. Half of the crowns in the delayed group exhibited an inappropriate height; of these, almost two thirds were assessed to be too short. Discussion and Conclusion: Early placement of single-tooth implants may be preferable to delayed implant placement technique in terms of early generation of interproximal papillae and the achievement of an appropriate clinical crown height, but no difference in papilla dimensions was seen at 1.5 years after seating of the implant crown. I NT J ORAL MAXILLOFAC IMPLANTS 2005;20:753–761

Migration of implants into the maxillary sinus: two clinical cases.

Abstract: Invasion of the maxillary sinus is a relatively frequent complication in dental implant treatment of patients with inadequate bone height in the posterior maxilla. This event usually occurs during surgery and sometimes produces sinusitis. There is a paucity of reports in the literature of implants migrating into the sinus cavity after a period of function. In the 2 clinical cases presented, an intraosseous apical movement of the implants was produced several years after placement of the implants. Hypotheses and possible mechanisms by which an implant may migrate into the maxillary sinus are described.

Implant prosthodontic rehabilitation of fibula free-flap reconstructed mandibles: a Memorial Sloan-Kettering Cancer Center review of prognostic factors and implant outcomes.

Abstract: Purpose This study aimed to estimate the cumulative survival rates (CSRs) of implants placed in reconstructed mandibles and to identify prognostic factors that may influence implant survival. Materials and methods The charts of 24 patients (10 male, 14 female) who had undergone mandibular resection and reconstruction with fibula free-flaps treated with implant-supported prostheses from April 1986 through December 2001 were reviewed. Information on demographics, surgical characteristics, treatment modalities, dentition, implant parameters, prostheses, and hyperbaric oxygen therapy (HBO) was gathered. Kaplan-Meier survival estimates were generated for the 100 implants that satisfied the inclusion criteria. Multivariate Cox proportional hazards regression models accounting for correlated implants within subjects were developed to identify prognostic factors for implant survival. Results Ninteen implants had been placed in native mandible (3 in irradiated bone) and 81 in fibula bone flap. Six implants failed during the follow-up period (mean 51.7 months). The overall 5- and 10-year CSRs were 97.0% and 79.9%, respectively. In the univariate analysis, variables associated with implant survival were age, gender, chemotherapy, radiation therapy, HBO, irradiated bone, implant diameter, xerostomia, trismus, opposing dentition, and type of prosthesis. At 5 years, the CSR of implants in patients with HBO was 86.7%; HBO was statistically associated with an increased risk for implant failure (P = .005, hazard ratio = 19.79, 95% CI: 2.42 to 161.71). Discussion The CSR was lower when implants were placed in a previously irradiated mandible. There is still a lack of reliable clinical evidence to support the effectiveness of HBO in these patients. Conclusions A high survival rate was demonstrated for implants placed in fibula free-flap reconstructed mandibles. The finding that HBO was a risk factor can probably be attributed to the small sample size; further study is needed in this patient population.