The International Journal of Oral & Maxillofacial Implants, 03/2002

Purpose: This observational study examined the resorptive behavior of normal neonatal rabbit osteoclasts grown on slices of bovine cortical bone as compared to samples of commercially available bone substitute biomaterials. It also examined the surface characteristics of these materials. Materials and Methods: The 11 materials tested fell into 3 groups: (1) bone-derived, including freeze-dried human rib block, human demineralized freeze-dried bone, and deproteinated bovine bone; (2)synthetic hydroxyapatites (HA); and (3) synthetic non-HA, including coated methacrylates and coated silica glass. After 4 days in culture, 1 group of samples of each material underwent scanning electron microscopy (SEM) to evaluate resorptive pitting versus controls, while another group underwent tartrate-resistant acid phosphatase staining and light microscopy to examine osteoclast numbers and morphology. The 2 bovinederived HA materials also underwent immunohistochemical staining and surface chemistry analysis. Results: While most of these materials supported osteoclast attachment, some spreading, and survival in culture, only the bone-derived materials, with the exception of sintered deproteinated bovine bone, showed large scalloped-edged resorption pits with trails and exposed collagen when examined by SEM, although not to the same extent as unprocessed natural bone material. The HA materials and the sintered deproteinated bovine bone showed evidence of etching with smaller pits but no evidence of resorptive trail formation. The non-HA materials showed no evidence of pit formation or trails. Under immunohistochemical staining, Bio-Oss appeared to be positive for type I collagen after osteoclast activity on its surface, while Osteograf/N showed no positive staining. Surface chemistry analysis revealed nitrogen present in Bio-Oss specimens (0.17% to 0.47%), while there was no nitrogen detected in the Osteograf/N (0.00%); the percent nitrogen observed in normal bovine bone controls was 6.01% to 9.25%. Discussion: The bone-derived materials supported osteoclast activity on the material surface in a way that facilitated formation of the more complex resorption pits in vitro. Assuming the rate of pit formation observed in vitro mimics that observed in vivo, the quantity and type of osteoclastic remodeling seen on non-bone-derived materials-and perhaps sintered bone-derived materials-would be extremely slow to negligible. Physiologic removal of non-bone-derived bone substitutes in vivo may occur by methods other than osteoclast resorption. Conclusions: Allogenous and xenogenous bone-derived materials that undergo delayed physiologic resorption may be more appropriately used with a staged surgical approach when used in sites intended to support osseointegrated dental implants. The combination of collagen staining and the presence of nitrogen suggest that there may be residual protein in Bio-Oss.

Purpose: To examine the effect of phosphoric acid solution on the anodic oxide film of titanium. Materials and Methods: Commercially pure grade 2 titanium specimens were prepared and anodized in phosphoric acid solution at a constant current density (70 A/m2). Specimens were evaluated by means of scanning electron microscopy, x-ray diffraction analysis, electron probe microanalysis, energy-dispersive spectroscopy, profilometry, and atomic force microscopy. Results: The anodic oxide film was observed to consist of a porous or non-uniform layer and a dense or uniform layer. X-ray diffraction and energy-dispersive spectroscopic analyses indicated that the film consisted of a mixture of anatase and amorphous oxide, with the incorporation of phosphorus. Discussion: The degree of oxide crystallinity was observed to increase with an increase in voltage but decreased as the electrolyte concentration was increased. In addition, the concentration of phosphorus also increased as the electrolyte concentration and voltage increased. Conclusions: Electrolyte concentration and voltage play an important role in governing the anodic oxide thickness, composition, and degree of oxide crystallinity.

Purpose: This experimental study in adult female sheep examined the value of nonresorbable porous hydroxyapatite (HA) as a grafting material in a single-stage sinus-lift procedure. Materials and Methods: Two titanium plasma-flame-sprayed cylindric implants were placed bilaterally in each of 54 sinuses in 27 adult female sheep. In 2 groups of 18 sinuses each, the subantral hollow space was filled with porous HA or autogenous cancellous bone harvested from the iliac crest, respectively. Eighteen sinuses were not augmented and served as controls. The time course of new bone formation and bone remodeling was evaluated by sequential polyfluorochrome labeling. Observation periods were 12, 16, and 26 weeks after the surgical procedure. Six sinuses per observation period and test group were available for histologic evaluation. Results: All implants were osseointegrated in the local host bone. New bone formation was observed in a triangular area bounded by the implant surface, local buccal antral wall, and submucous connective tissue around all implants. The mean length of bone-implant contact was 3.9 ± 0.3 mm in the control group, 5.7 ± 0.3 mm in the autogenous bone group, and 5.9 ± 0.3 mm in the group augmented with porous HA. During the observation period, the relative length of direct boneimplant contact increased from 20% to 25.1% in the control group, from 30.4% to 35.5% in the autogenous bone group, and from 29.8% to 41.7% in the HA group. At a distance of 1 mm from the implant, the mean bone volume was 29.7 ± 15.7% in the autogenous bone group. In the group augmented with HA the mean bone volume was 11.2 ± 13.0%. Discussion: There was no significant difference between HA and autogenous bone regarding bone-implant contact (P = .89). Conclusions: Both groups showed a significantly greater bone-implant contact (HA: P = .002; autogenous bone: P = .0005) than the empty control group. However, since the results varied widely, the use of HA alone for sinus grafting should be used with discretion in sinus-lift procedures.

Purpose: This study investigated the influence of cigarette smoke on bone healing around titanium implants placed in rats. Materials and Methods: After administration of anesthesia, the tibia surface was exposed and screw-shaped titanium implants (4.0 mm in length and 2.2 mm in diameter) were placed bilaterally (1 each side). The animals (n = 32) were randomly assigned to either group 1 (control, n = 18) or group 2 (intermittent cigarette smoke inhalation, n = 14). After 60 days, the animals were sacrificed and undecalcified sections obtained. Bone density (the proportion of mineralized bone in a 500-µm-wide zone lateral to the implant) was measured in the cortical (zone A) and cancellous bone (zone B) areas. Results: In zone A, a slight difference in bone density was noted between the groups (96.18% ± 1.08% and 95.38 ± 1.17% in groups 1 and 2, respectively; P > .05) but was not statistically significant. In contrast, bone density was significantly decreased in zone B in the animals that were exposed to cigarette smoke (17.57 ± 6.45% and 11.30 ± 6.81% for groups 1 and 2, respectively; P .05). Discussion: Whether different results would be observed if animals were exposed to cigarette smoke for a longer period of time and/or before implant placement remains to be investigated. Conclusion: Although intermittent cigarette smoke exposure may not seriously affect cortical bone density, it may jeopardize bone quality around titanium implants in the cancellous bone area.

Purpose: The aim of this study was to evaluate by finite element analysis the influence of the design of 3 different dental implants on micromovements, cervical shearing stress intensity, and stress distribution after occlusal loading. Materials and Methods: The first investigated implant was a classical cylinder, the second was reinforced by 2 bicortical locking pins, and the third was an expanding dental implant. The parameters analyzed were the implant's geometry, the quality of the cancellous bone, and the orientation of occlusal loading. Results: It was found that initial stability of the locking pin implant was greater than the initial stability of the other investigated implant designs, regardless of the quality of cancellous bone and orientation of occlusal loading; in low-rigidity cancellous bone, under a horizontal load (500 N), decreasing displacement compared to those of the other investigated implants was 16 µm. The apical expansion and locking pin implants exhibited favorable behavior regarding the distribution and intensity of cervical shearing stresses; in low-rigidity cancellous bone, under horizontal load, decreasing cervical stresses compared with those of the cylindric implant were 10 MPa for the apical expansion implant and 150 MPa for the locking pin implant. Discussion: For the cylindric implant, stresses were concentrated in the neck region; for the apical expansion implant, stresses were evenly distributed from the neck to the apex of the implant. For the locking pin implant, stresses around the neck were moderate and appeared concentrated around the pins. Conclusions: Initial stability of the pin implant was greater than that of the expanding implant, but the expanding implant showed the most favorable stress distribution.

Purpose: Cellular fibronectin staining is decreased in adult periodontitis, which implies elastase-mediated degradation of periodontal tissues. The purpose of this study was to determine whether failing dental implants display similar changes. Materials and Methods: Cellular fibronectin and its integrin receptors were identified by immunohistochemistry and quantified by computerized image analysis. Results: Cellular fibronectin was found in blood vessel walls, epithelial basement membranes, and fibroblasts. Quantitative results of cellular fibronectin staining were as follows: failing dental implants, median 26.5% (Q3-Q1 = 23%); adult periodontitis, median 5.5% (Q3-Q1 = 5.6%); normal controls, median 12.2% (Q3-Q1 = 7.5%). Cellular fibronectin staining was increased around failing dental implants but decreased in adult periodontitis compared to healthy controls. Discussion: The distribution of integrin receptor subunits 4, 5, and 1 of cellular fibronectin was similar in failing dental implants. The pathomechanisms in adult periodontitis and failing dental implants seem to differ. Conclusions: Adult periodontitis is characterized by proteolysis/loss of cellular fibronectin, whereas failing dental implants are characterized by increased cellular fibronectin deposition, probably as a result of titanium-induced local synthesis and relatively modest degradation.

Purpose: To evaluate the bone contact percentage around a proprietary high-temperature dual-etched (DE) implant surface (Osseotite) versus implants with machined, hydroxyapatite (HA), and titanium plasma-sprayed (TPS) surfaces. Materials and Methods: Each implant type was placed in rabbit tibiae of the same animal and assessed at 1 to 8 weeks. Histologic sections were prepared and analyzed histomorphometrically. Results: The DE implant surface achieved higher levels of bone contact percentage than the other surfaces. This enhanced contact level was apparent by 3 weeks and seen at all time intervals except 2 weeks, at which machined exceeded the DE mean. In evaluating which surface outscored the others in each individual rabbit, there was a statistically significant confidence for the DE surface (P .001). The other 3 surfaces failed to show significance, although the numeric scores for the TPS surfaces were below random expectations and the machined scores were slightly above. There was no correlation between degree of roughness and bone contact percentage. Discussion: Arbitrarily roughening the implant surface may not result in a large change in bone conductivity. The specific texture of the DE process yielded more contact, possibly as the result of better fibrin clot retention and growth factor enhancement. Conclusions: There was no advantage demonstrated in this model to an HA surface over titanium. The bone contact to the rough HA surface scored similarly to that for the TPS surface of similar roughness, and well below that for the DE titanium surface. The DE surface appeared to have an advantage in bone contact percentage, particularly in early healing in a rabbit tibia model.

Purpose: The different implant systems available today present several types of surface treatment, with the aim of optimization of bone-implant contact. This study compared 4 different types of implant surfaces. Materials and Methods: The first, second, third, and fourth mandibular premolars were extracted from 5 young adult mongrel male dogs. Ninety days after removal, four 3.75-mm-diameter, 10-mm-long screw-type implants (Paragon) were placed with different surface treatments in mandibular hemiarches. The dogs received 2 implants of each of the following surface treatments: smooth (machined), titanium plasma spray (TPS), hydroxyapatite coating (HA), and sandblasting with soluble particles (SBM). The implants were maintained unloaded for 90 days. After this period, the animals were sacrificed, and the hemimandibles were extracted and histologically processed to obtain nondecalcified sections. Two longitudinal ground sections were made for each implant and analyzed under light microscopy coupled to a computerized system for histomorphometry. Results: The following means were obtained for bone-implant contact percentage: machined = 41.7%, TPS = 48.9%, HA = 57.9%, and SBM = 68.5%. Discussion: The means for all treatments that added roughness to the implant surface were numerically superior to the mean found for the machined surface. However, this difference was statistically significant only between groups SBM and machined (Tukey test, P .05). Conclusions: The SBM-treated surface provided a greater bone-implant contact than a machined surface after 90 days without loading in this model.

Purpose: The purpose of this study was to observe, after removing occlusal trauma and conducting plaque control, possible macroscopic and histologic changes in peri-implant tissue that had deteriorated resulting from experimental peri-implantitis, and to investigate the necessity for treatment procedures for peri-implantitis. Materials and Methods: Four monkeys (Macaca fascicularis) in good general health were used in this experiment. Three months after the second premolar and the first molar were extracted from the right mandible, 2 IMZ experimental implants were placed in each monkey. After a 3-month osseointegration period, a second surgery was conducted, followed by making an impression for fabrication of the prosthesis. Excessive occlusal height of the prosthesis was adjusted to 250µm, and the experiment was continued for 8 weeks after placement of the prosthesis. Three models were created: (1) A superstructure with an excessive occlusal height was used for 8 weeks without any brushing (positive control, model P); (2) after the first 4 weeks with a prosthesis with excessive occlusal height and no brushing, the superstructure was removed and not used for the last 4 weeks while brushing was conducted (experimental model, model E); and (3) for 8 weeks, a prosthesis with an appropriate occlusal height was used with brushing (negative control, model N). Results: When these 3 models were compared with each other, macroscopic findings indicated inflammation only in model P. Mobility of implants was not seen in any model. Histopathologic observations revealed a slight difference between model E and model P in terms of the degree of inflammatory cell infiltration in the connective tissue. Discussion: No difference was found in the degree of bone resorption. Partial tearing was observed at the contact region between epithelial tissue and implant surfaces. Conclusions: (1) The contact between implants and epithelial or connective tissue is fragile; (2) inflammation and occlusion must be controlled more prudently than in the case of natural teeth; and (3) once periimplantitis has progressed, the control of occlusion and inflammation is probably not sufficient to promote the healing mechanism.

Purpose: This randomized clinical trial examined implant overdenture (IOD) fabrication and maintenance time and costs, adjustment and repair incidence, and patient satisfaction after 1 year. Materials and Methods: Sixty-four patients received 2 mandibular implants and an IOD with either a bar with 2 clips or 2 ball attachments for denture retention. Results: Fabrication time, number of appointments, and chair time for adjustments were similar for the 2 denture designs. The most common adjustments for both types were to the IOD contours. Ball-attachment dentures required about 8 times longer for repairs than bar-clip prostheses. Approximately 84% of patients with ball-attachment dentures needed at least 1 repair, versus 20% of those with a bar-clip mechanism. The most common repairs were replacement of the cap spring or cap for the ball-attachment IOD and replacement of a lost or loose clip for bar-clip dentures. Discussion: Patients were equally and highly satisfied with the improvements in function, comfort, and appearance with both types of IOD compared to their original conventional dentures. Conclusions: Given equivalent levels of patient satisfaction with either method of retention and a much higher repair rate for the ball attachment, it is suggested that a bar-clip design be used rather than the particular ball attachment utilized in this study.

Purpose: Cortical bone is a determinant of implant esthetics and may contribute to the biomechanical integrity of the implant-supported prosthesis. Historically, approximately 1.0 to 1.5 mm of bone loss has occurred immediately following second-stage surgery and implant loading. Recent consideration of implant design suggests that surface topography may affect crestal bone responses at the implant interface. The aim of this retrospective study of 102 implants in 48 subjects supporting posterior fixed partial dentures was to radiographically define the behavior of crestal bone at TiO2 grit-blasted implants following surgical placement and subsequent loading in the posterior maxilla and mandible. Materials and Methods: The crestal bone position relative to the implant reference point (junction of the crestal bevel with the TiO2 grit-blasted surface) was evaluated at implant placement, at abutment placement, and 6 to 36 months following restoration, with an average recall period of 2.3 years. The implant position and dimension were recorded. A single investigator using 7 magnification assessed all radiographs. Results: Crestal bone loss from the time of implant placement up to 36 months following restoration ranged from 0.0 to 2.1 mm. Of the 102 implants, 14 implants showed greater than 1.0 mm of crestal bone loss. They were not clustered at any particular tooth position. Eighty of the implants showed less than 0.5 mm of radiographically measured bone loss. Mean crestal bone loss was 0.36 mm (± 0.6 mm). Averages of 0.57 and 0.24 mm loss were shown for 3.5- and 4.0-mm-diameter implants, respectively (P .051). Bone gain was seen at several 4.0-mm- diameter implants. Discussion: This retrospective evaluation indicates that the radiographically measured bone loss may be expected to be less than 1 mm following placement and loading of TiO2 grit-blasted implants. The close approximation of bone with the implant/abutment interface suggests the attenuation of any microgap-induced bone loss. Additional reasons for crestal bone maintenance may include factors attributed to implant surface roughness and loading along a tapered implant/abutment interface. Conclusions: Several clinical advantages for maintaining crestal bone at implants supporting posterior prostheses can be identified.

Purpose: To investigate the bone tissue response at the interface of loaded and non-loaded implants used in an orthopedic anchorage system after a continuous, non-axial force application of 5 N over 2 months. Materials and Methods: Twenty-nine Brånemark System implants were placed in the zygomatic arches of 5 dogs. After a healing period of 8 weeks, 20 implants (4 in each dog) were loaded during 8 weeks with a large non-axial orthopedic force application of 5 N. This force was directed between the implants and a maxillary splint to move the maxilla forward. Nine implants were not loaded during this period. At the termination of the experiment, all 29 implants were retrieved for radiographic as well as for histologic analysis. Computer-based histomorphometric quantifications were performed via light microscopy and computer software. Bone-metal contact (BMC), bone surface area (BSA) inside the threads, and the bone mirror area (BMA) of the implants were measured. Statistical comparisons between the loaded and non-loaded implants were carried out. In the group of loaded implants a 2-factor analysis of variance was used. Results: There were no statistically significant differences found in BMC, BSA, and BMA between the loaded and non-loaded implants, both for all the threads and for only the cervical region of the implants. Nor were there statistically significant differences between the non-pressure and pressure sides or for different lengths of the loaded implants. Discussion: The loaded implants maintained the osseointegration achieved during the 8-week healing period. Conclusions: The results of this study indicate that titanium implants can be used as anchorage for orthopedic force application systems.

Purpose: Altered mandibular sensation following implant surgery may result in liability claims. Therefore the authors conducted a retrospective analysis of all liability claims related to persistent altered sensation following placement of mandibular implants reported to the Medical Consultants International (MCI) Company from 1992 to 1999. Materials and Methods: Reports related to persistent altered mandibular sensation in 16 patients (12 women and 4 men) who underwent implant surgery in Israel were examined. The MCI files were retrospectively evaluated according to a structured form. The parameters studied included patient age and gender, implant location and length, imaging modality, and the time between actual damage and filing of a claim (ie, letter of demand or lawsuit). Results: The time in months between actual damage and filing of claim ranged from 0 to 60 months (mean 21.5 months). No cases were found involving transient changes in sensation. The female/male ratio was 3:1. Implant length was equal to or longer than 13 mm in 6 of 7 implants placed in the molar region. In the premolar area, nerve injury was evident in 6 of 7 cases where implants shorter than 12 mm were used. Conclusions: Transient nerve injury rarely results in legal action. Maximum effort should be devoted to accurately determining the appropriate implant length in the mandible.

Most reports on alveolar distraction have been related to vertical distraction in the mandible and the maxilla. There have been few reports on horizontal or oblique alveolar distraction. A case of an atrophic subtotal maxillary alveolus distracted 10 mm anteriorly and 5 mm vertically, followed by the placement of 9 implants, is presented. A healthy, 55-year-old woman presented with a chief complaint of mobility of all maxillary teeth. All remaining 11 teeth except the maxillary left second molar were diagnosed as being involved with advanced marginal periodontitis, and were considered hopeless and subsequently extracted. Three months after extraction, a horizontal osteotomy was performed with a bone saw between the bilateral second premolar regions, extending vertically distal to the second premolars, without involving the maxillary sinuses. After confirming mobility of the alveolar bone, a distraction device was seated with titanium miniscrews and adhesive resin cement over the hard palate. After a 7-day waiting period, the maxillary alveolus was distracted anteroinferiorly 0.25 mm twice a day for 25 consecutive days. The distraction process was completed uneventfully. Postdistraction computed tomography demonstrated that the maxillary alveolus was adequately distracted to place implants in an ideal position. Nine endosseous implants were placed 4 months after seating the distraction device. All implants had good primary stability and were submerged. All implants osseointegrated, although 2 anterior implants were replaced due to disintegration resulting from transmucosal overloading of the interim removable prosthesis. No significant marginal bone resorption was seen around the implants 16 months after implant placement. It was concluded that alveolar distraction can be very useful for augmenting the atrophic alveolus, not only vertically but also horizontally or obliquely.

Purpose: To examine the use of the buccal fat pad (BFP) for correction of maxillary osseous defects, preliminary to dental implant reconstructions, and to present patients in whom this technique was used. Materials and Methods: The blood supply of the BFP was investigated with a special laser Doppler flowmetry fiberoptic probe in situ before herniation and after placement of the pedicled BFP over maxillary bone grafts. Results: The possibility of using the BFP pedicle flap to provide an immediate blood supply to a recipient site was confirmed, as it promotes rapid neo-vascularization of the grafted material over which it is placed. No complications were seen in the present patients. Discussion: The BFP has an additional protective function of providing for a multiple-layer wound closure over all types of maxillary bone grafts, thereby preventing graft exposure and enhancing success. Conclusions: With its high blood flow, the BFP may offer protection and early blood supply to maxillary and sinus bone grafts.