The International Journal of Oral & Maxillofacial Implants, 03/2005

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 = 0.5 µm to = 3.0 µm. In regard to surface roughness, arithmetic average height deviation (Sa) values varied from 0.68 to 0.98 µm for test implants and 0.55 µm 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 = .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 µm in Sa and 27% to 46% in Sdr; its oxide crystal structure should be a mixture of anatase- and rutile-phase crystals.

Purpose: The purpose of this investigation was to determine whether early and immediate loading of dental implants resulted in adverse consequences as determined clinically, radiographically, and histologically. Materials and Methods: In a canine model, 48 sand-blasted, large-grit, acid-etched (SLA) surfaced implants were placed at 4 different times before definitive restoration and loading. These times were 3 months (group A), 21 days (group B), 10 days (group C), and 2 days (immediately) (group D) before loading. Each implant was restored at the same time with a single gold screw-retained crown. Immediately after restoration all crowns were placed in function. Standardized periapical radiographs were made 1, 2, and 3 months after restoration. At the end of the study, block sections were obtained for histologic examination. Changes in crestal bone height on the mesial and distal aspects of each implant and the change in bone density of the coronal 3 mm of crestal bone were recorded. Primary, secondary, and total bone-to-implant contact; bone marrow-to-implant contact; and connective tissue-to-implant contact were evaluated histologically. Results: All implants were osseointegrated at the end of the study; no clinical failures of integration were noted. The changes in crestal bone heights for groups A, B, C, and D (means ± SE) were 0.02 ± 0.07 mm, 0.30 ± 0.08 mm, 0.15 ± 0.08 mm, and 0.35 ± 0.18 mm, respectively. Total bone-to-implant contact for the 4 groups was 69.1%, 71.3%, 74.6%, and 75.2%, respectively (P > .57). Discussion: Under the conditions of this study no statistically significant differences were noted between the 4 different loading protocols for any of the parameters recorded. This finding is consistent with other recent studies and case reports. Conclusion: The findings of this study indicate that early and immediate loading of single-unit SLA surfaced implants was possible in this model. (More than 50 references.)

Purpose: Two different graft materials, ß-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 ß-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 ß-tricalcium phosphate (Cerasorb) is a satisfactory graft material, even without autogenous bone.

Purpose: To accurately accomplish the drilling of an implant socket, the use of image-guided navigation has become an option. The aim of this study was to evaluate the 3-dimensional (3D) accuracy of navigation-guided drilled holes. Materials and Methods: Laboratory accuracy measurements were obtained on an acrylic resin model with standardized target holes drilled by a computerized numerical control machine. The model was scanned by a multislice computerized tomography scanner and registered with fiducial marker-based algorithms. Navigated drillings were performed using an optical navigation system based on passive marker technology. Coordinates of drilled holes were determined by a 3D-digitizer probe, and accuracy was assessed for all 5 degrees of freedom using a computer-aided design system (Pro/Engineer). Results: A total of 240 drillings were evaluated. Mean registration error was 0.86 mm (SD 0.25 mm). Target point deviation between preplanned and actual drill starting point was 0.95 mm (SD 0.25 mm). The deviation in terms of full length was 0.97 mm (SD 0.34 mm), and mean angular deviation on the coronal and sagittal planes was 1.35 degrees (SD 0.42 degrees). Discussion: The accuracy of image-guided navigation depends on imaging modalities, patient-to-image registration procedures, and instrument tracking. The technical accuracy and the navigation procedure, as evaluated in the study presented, seem to be of minor influence. Conclusion: The data obtained by this in vitro study demonstrate that the accuracy of navigation-based drilling may be sufficient for clinical practice, particularly in terms of the transferability of preplanned trajectories. However, in vivo clinical trials need to be performed to evaluate the clinical accuracy and treatment quality of navigation-guided interventions.

Purpose: The authors' aim was to perform a histomorphometric study of the healing of bone defects created adjacent to titanium and hydroxyapatite (HA) -coated implants and covered with either a resorbable or a nonresorbable membrane in combination with different filler materials and to evaluate to what degree coating, membrane, and/or filler influenced the healing of the defects. Materials and Methods: Posterior teeth were extracted from the mandibles of 10 baboons, and 12 implants were placed in each animal in the edentulous areas. The implants were either titanium or HA-coated, the membranes were either Vicryl, Gore-Tex, or Resolut, and the filler was either demineralized freeze-dried bone (DFDB), autogenous bone, or Biocoral. The implants were observed for either 3, 6, 9, 12, or 18 months. The volume of newly generated tissue and the relative contribution of bone, marrow, and filler were evaluated, as was relative extension of resorption, formation, and quiescent surface. Results: The results indicated that autogenous bone is still the gold standard, but both the DFDB and Biocoral compared favorably to it. Both filler materials were being gradually replaced by bone; this process was not yet finished at 18 months postsurgery. Discussion: Since even the sterilization of DFDB cannot exclude the possibility of a disease transmission, it is important to find an appropriate substitute. Both filler and membranes contributed to the re-establishment of the original volume; better results were achieved with the Vicryl and Gore-Tex membranes than with the Resolut. Biocoral can be considered an effective material. Conclusion: A bony defect is not necessarily a contraindication for the placement of an implant. (More than 50 references.)

Purpose: To evaluate the survival rate of immediately loaded ITI sand-blasted, large-grit, acid-etched (SLA) solid-screw dental implants in the edentulous maxilla after 8 months of loading. Materials and Methods: Twenty-eight patients (mean age 63 years) with edentulous maxillae each received 6 implants and 1 implant-supported fixed provisional prosthesis within 24 hours after surgery. After a mean healing time of 15 weeks, the patient received a definitive, screw-retained, implant-supported fixed prosthesis. A total of 168 implants were placed. Clinical parameters were registered after 1 month of loading with the implant-supported fixed prostheses as well as 8 months after implant placement. Radiologic examinations and assessments were made at implant placement and after 8 months. Results: The mean marginal bone level at implant placement was 1.6 mm (range 0 to 5.1; SD 1.1) apical of the reference point (the implant shoulder). The mean marginal bone level at the 8-month follow-up was 3.2 mm (range 0.4 to 5.9; SD 1.1) apical of the reference point. Three implants failed during the healing period. Discussion: The improved results in the present study might be a result of the positive effect of splinting the implants immediately after placement. Conclusion: ITI SLA solid-screw implants immediately loaded (ie, loaded within 24 hours of placement) and supporting fixed prostheses had successful survival rates after 8 months. The present results constitute a solid baseline for future follow-up studies.

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.)

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: Sixty-three 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.

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.

Purpose: A prospective human clinical study was conducted to determine the clinical and histologic bone formation ability of 2 graft materials, a ß-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% ß-tricalcium phosphate on the test side and 100% chin bone on the contralateral control side. The unilateral cases were augmented with 100% ß-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 ß-tricalcium phosphate, appeared to be a clinically reliable procedure in this patient population.

Purpose: The aim of the present study was to evaluate zygomatic bone thickness considering a possible relationship between this parameter and cephalic index (CI) for better use of CI in the implant placement technique. Materials and Methods: CI was calculated for 60 dry Brazilian skulls. The zygomatic bones of the skulls were divided into 13 standardized sections for measurement. Bilateral measurements of zygomatic bone thickness were made on dry skulls. Results: Sections 5, 6, 8, and 9 were appropriate for implant anchorage in terms of location. The mean thicknesses of these sections were 6.05 mm for section 5, 3.15 mm for section 6, 6.13 mm for section 8, and 4.75 mm for section 9. In only 1 section, section 8, did mean thickness on 1 side of of the skull differ significantly from mean thickness on the other side (P .001). Discussion: For the relationship between quadrant thickness and CI, sections 6 and 8 varied independently of CI. Section 5 associated with brachycephaly, and section 9 associated with subbrachycephaly, presented variations in the corresponding thickness. Conclusion: Based on the results, implants should be placed in sections 5 and 8, since they presented the greatest thickness, except in brachycephalic subjects, where thickness was greatest in section 5, and in subbrachycephalic subjects, where thickness was greatest in section 9. CI did not prove to be an appropriate parameter for evaluating zygomatic bone thickness for this sampling. (More than 50 references.)

Purpose: This article provides preliminary clinical results on the Osseotite NT implant, which was developed to simplify surgical procedure and cover an extended range of indications. Placement characteristics of NT and standard Osseotite implants were also compared in an in vitro study. Materials and Methods: The in vitro placement characteristics of NT and standard Osseotite implants of 4.0 mm diameter and 8.5 to 15 mm in length were compared. In addition, a total of 182 NT implants (96 maxillary and 86 mandibular) were placed in 92 patients; of these, 87.9% were placed using a 1-stage technique. The implants were placed in healed sites (43.9%), fresh extraction sockets (37.4%), or recent extraction sites (2 months postextraction) (18.7%). Before restoration, healing times of 3 to 4 months in the mandible and 5 to 6 months in the maxilla were allowed. The entered implant length in the osteotomy site before contacting the bony walls (EILOS) was compared, as well as the number of turns and the time required to seat the implants. Cumulative survival rates (CSRs) were calculated for up to 18 months of follow-up after surgery. Results: The EILOS was between 47.3% and 57.6% of implant length for the NT implants; for the standard implants, it was between 12.0% and 21.2%. With the NT implants, the number of turns and the placement time were reduced by 61% to 64% and 61% to 65%, respectively. In the clinical study, 4 implants failed during the healing period; none failed after prosthesis placement. The CSR was 97.79% for implants placed into fresh or recent extraction sites; in healed sites, the CSR was 98.75%. The cumulative prosthetic success rate was 100%. Discussion: This new implant design is seated with special drills; the drilling sequence requires less time and less torque than that used for standard implants. The low failure rate after prosthetic loading was consistent with that observed for standard Osseotite implants. Conclusion: These preliminary data suggest that the NT implant can be predictable in healed sites and fresh or relatively recent extraction sockets.

Purpose: This in vitro study evaluated the accuracy of master casts obtained by using (1) copings modified by sandblasting and coating their roughened surfaces with impression adhesive before final impression procedures and (2) gold machined UCLA abutments as impression copings in final impression procedures for single-tooth implant replacement cases. Materials and Methods: A polymeric resin model with a standard single implant was used to simulate a clinical situation. A group of 20 impressions were made using square impression copings sandblasted to roughen their external surfaces at a supragingival level and then coated with Impregum polyether adhesive; a second group of 20 impressions were made using gold machined UCLA abutments as impression copings. The castable part of the UCLA abutments was secured with resin to the gold machined section of the UCLA abutment to prevent movement of the castable part itself on the gold machined portion during the impression procedures; the castable portion of the UCLA was also coated with the Impregum polyether adhesive to improve the stability of the gold machined UCLA abutment inside the impression material. Master casts fabricated for both groups were analyzed to detect rotational position change of the hexagon on the implant replicas in the master casts with reference to the resin model. Results: The rotational position changes of the hexagon on implant replicas were significantly less variable in the master casts obtained using gold machined UCLA abutments as impression copings than in the master casts achieved with the roughened square impression copings. Discussion: Improved precision of the impression was achieved when the gold machined UCLA abutments were used as impression copings. Conclusion: This report suggests that using gold machined UCLA abutments as impression copings in the final impression procedures can enable the clinician to achieve a more accurate orientation of the implant replicas in the laboratory master casts for single-tooth implant replacement cases.

Several implant components in their original glass vial and peel-back packages were subjected to sterility testing to determine whether the contents remained sterile after the expiration date marked on the package had passed. The results from a university microbiology laboratory showed that the contents remained sterile for 6 to 11 years after the expiration dates.

Proper placement and orientation of dental implants is a requirement for the optimum function and esthetics of the definitive restoration. Surgical template stability during the surgical phase is a key element in the success of proper implant placement. Therefore, any clinical tool that enhances the precision of reproduction is of value. This article describes a simple, noninvasive, cost-effective technique for surgical template stabilization utilizing 2 transitional implants placed the same day as the definitive implants.