Pages 173-180, Language: English
Sixty-seven patients ranging in age from 16 to 86 years were included in this 3- to 5-year retrospective report focusing on implant survival and marginal bone remodeling in relation to implant diameter. A total of 299 Brånemark implants (3.75-mm diameter: 141; 4.0-mm diameter: 61; 5.0-mm diameter: 97) were placed in 16 completely and 51 partially edentulous arches. Seven of the 141 implants in the 3.75-mm-diameter group failed (5%). The corresponding value for the 4.0-mm-wide implants was 2 of 61 (3%). The highest failure rate, 18% (17/97), was seen for the 5.0-mm-diameter implants. The least favorable cumulative survival rates were seen in mandibles after 5 years and involving 4.0-mm- and 5.0-mm-diameter implants (84.8% and 73.0%, respectively). The marginal bone loss was generally low over the 5-year period. When the data were evaluated by the Cox regression analysis, a relationship was found between implant failure and implant diameter (P < .05), with a higher failure rate for the 5.0-mm-diameter implant. However, no relationship could be seen between implant failure and jaw type, or bone quality and quantity (P > .05). Neither was any relationship seen between marginal bone loss and bone quality and quantity, implant diameter, or jaw type when tested by multiple linear regression analysis (P > .05). A learning curve, poor bone quality, and changed implant design were suggested as possible reasons for the less positive outcome seen for the 5.0-mm-diameter implant. The fact that this implant was often used as a rescue implant when the standard ones were not considered suitable or did not reach initial stability was another plausible explanation.
Keywords: Brånemark system, diameter, titanium oral implant, treatment result
Pages 181-188, Language: English
The use of teeth as abutments for fixed and removable partial dentures can result in biologically destructive consequences. Teeth adjacent to edentulous spaces should exhibit improved prognoses if restorative trauma is to be avoided or minimized. Implants offer a method of tooth replacement without relying upon the surrounding dentition for support. This investigation evaluates implant survival and prosthetic complications of implants that replaced single missing teeth and were placed in clinical practice during a 10-year period. It further examines preoperative status and survival of teeth adjacent to these implant restorations during the same 10-year time span. Ninety-nine patients treated with 116 implants and 112 single-tooth implant prostheses in a prosthodontic practice were examined between 1988 and 1998. The purpose of this study was to evaluate the role of implants in preventing the use of intact teeth for initial support of prostheses and in avoiding the use of additional teeth as abutments upon the replacement of existing restorations. Three implants failed over a 10-year period, for a survival rate of 97.4%. Complications included the loss of 2 implant crowns, screw loosening, broken screws, cement washout, margin exposure, and porcelain fracture. Of 196 teeth adjacent to edentulous spaces, 156 (79.6%) were intact or minimally restored. Only 3 of these teeth were restored as part of initial prosthodontic therapy. Over the ensuing 10 years, only 1 tooth required a replacement restoration, and 1 tooth was extracted. Results of this patient evaluation demonstrated that implant survival over a 10-year period was favorable, with minimal prosthetic complications. Furthermore, teeth adjacent to single-tooth implants exhibited an extremely low complication rate. This report indicates that implants can be effective in preserving intact teeth in patients undergoing initial prosthodontic therapy and in preventing the use of additional teeth as abutments in patients whose existing prostheses must be replaced.
Keywords: abutment, biologic risks, dental implants, fixed partial denture, single-tooth implant, survival, tooth loss, tooth preservation
Pages 189-196, Language: English
The purpose of this study was to evaluate the quality of the bone matrix around commercially pure titanium implants at 3 and 6 months postplacement in sheep. Implants were placed in the corticotrabecular areas of both femurs in 6 animals. Each animal received 4 Euroteknika implants in the right femur and 4 Nobel Biocare implants in the left femur. Bone blocks containing the implants were studied undecalcified after being embedded in methylmethacrylate. Sections were stained with toluidine blue and basic fuchsin. The amount of bone around the implants, the contact interface between the implant and bone, and the mineral apposition rates were measured. The fractional amount of woven bone could be quantified because of its high glycosaminoglycan content. No differences could be observed between the 2 types of implants. Total bone volume did not increase around both types of implants between 3 and 6 months, indicating that ankylosis was rapidly achieved. In contrast, in the area in contact with the implant, the bone-titanium interface drastically increased and the mineral apposition rate decreased. The fractional volume of woven bone around implants was considerably reduced after 6 months. Bone quality around implants was improved at 6 months (volume of woven bone near zero), and true osteonic structures were observed in close contact with titanium. The remodeling process appeared to improve bone quality and increase the bone-titanium interface around implants, while the net bone quantity necessary to immobilize implants was achieved rapidly and remained unchanged.
Keywords: animal study, bone histomorphometry, bone quality, dental implant, woven bone
Pages 197-209, Language: English
During a 12-year period (1984 to 1997), 32 consecutive patients with advanced maxillary bone compromise received surgical-prosthodontic rehabilitation. The most frequent procedure used was maxillary augmentation with a free nonvascularized autogenous onlay block bone graft, and the average time of prosthesis function was 67 months. Twenty-eight patients underwent a 1-stage procedure, in which endosseous implants were placed simultaneously for internal rigid skeletal fixation of the onlay bone graft, and 4 patients underwent a 2-stage procedure, in which endosseous implants were placed secondarily 6 months after complete healing of the previously placed onlay bone graft, which initially was stabilized by titanium miniplates and lag screws. Treatment success was evaluated separately for the first 7 consecutively treated patients (developmental group) and for the next 25 consecutive patients (routine group). Assessment was made of implant survival relative to etiology of bone loss, implant type and length, type of prosthesis, type of opposing occlusion, type of surgical procedure, and presence of discontinuity. The implant survival rate was 91% in the 25 routine patients and 65% in the 7 developmental patients. Implant type and length, prosthesis type, opposing occlusion, and the presence or absence of discontinuity significantly impacted treatment outcome. Onlay block bone graft success (96%) in all 32 treated patients and prosthetic success (96%) in the last 25 patients was recorded.
Keywords: autogenous bone graft, discontinuity, endosseous implant, maxilla, nonvascular, occlusion, onlay, prosthesis, reconstruction
Pages 210-216, Language: English
A total of 264 implants was placed in 143 patients using different immediate or delayed-immediate implant placement techniques in 12 different centers participating in a prospective multicenter study. The reason for tooth extraction was evaluated; bone quality and quantity were classified; socket depths were registered; and data on implant type, size, and position were collected. One hundred thirty-nine suprastructures were placed on 228 implants in 126 patients. A follow-up evaluation was done on 125 patients after 1 year of loading and on 107 patients after 3 years of loading. Clinical parameters (bleeding or not bleeding, pocket depth, and implant mobility) were evaluated after 1 and 3 years, and the marginal bone level after 1 year of loading was measured on radiographs. Clinical comparisons were performed to evaluate implant loss in relation to implant type, size, position, bone quality and quantity, socket depth, reason for tooth extraction, and placement method. In addition, life table analysis was done for cumulative implant survival rates. There was no clinical difference with respect to socket depth or when comparing the different placement methods. A higher failure rate was found for short implants in the posterior region of the maxilla and when periodontitis was cited as a reason for tooth extraction. Mean marginal bone resorption from the time of loading to the 1-year follow-up was 0.8 mm in the maxilla and 0.5 mm in the mandible. Over a period of 3 years, the implant survival rate was 92.4% in the maxilla and 94.7% in the mandible.
Keywords: Brånemark system, delayed immediate implant placement, immediate implant placement, long-term multicenter investigation
Pages 217-225, Language: English
In this study, the specific objective was to investigate the combined effect of different treatments of transforming growth factor-ß (TGF-ß) and hydroxyapatite (HA) on osteoblast response in vitro. Since the nature of bone cell responses in vitro is influenced by the properties of HA ceramics, this study was divided into 2 components: a chemical and crystallographic characterization of the HA ceramics, and an in vitro cell culture study. Sintered HA samples were observed to have the highest crystallite size, compared to as-received HA and calcined HA samples. No differences in surface roughness and chemical composition were observed between the sintered, calcined, and as-received HA surfaces. In concurrence with the x-ray diffraction, high-resolution x-ray photoelectron spectroscopy of Ca 2p also indicated a higher crystallinity on sintered HA samples compared to calcined and as-received HA samples. Protein production by osteoblast cells was not statistically different on the 3 HA surfaces in the absence of TGF-ß. However, there was a dose-dependent increase in TGF-ß-stimulated protein production on the 3 different HA surfaces. As indicated by increased alkaline phosphatase-specific activity, as well as 1,25 (OH2) vitamin D3-stimulated osteocalcin production, a more differentiated osteoblastlike phenotype was observed on the sintered HA surfaces compared to the as-received HA and calcined HA surfaces. An increased osteoblast-like cell activity on sintered HA surfaces in the presence of different TGF-ß dosage suggested that sintering of HA surfaces may play an important role in governing cellular response.
Keywords: alkaline phosphatase activity, heat treatments, hydroxyapatite, osteocalcin concentration, transforming growth factor-ß
Pages 226-232, Language: English
The purpose of this study was to assess the effects of modifying titanium surfaces, in terms of wettability, roughness, and mode of sterilization, on the ability of the oral bacterium Streptococcus sanguis to colonize. An in vitro model system was developed. All surfaces were colonized by the bacteria, but to significantly different levels. Titanium samples that exhibited rough or hydrophobic (low wettability) surfaces, along with all autoclaved surfaces, were preferentially colonized (P < .01). Titanium surfaces that had been repeatedly autoclaved were colonized with the levels of bacteria 3 to 4 orders of magnitude higher than other modes of sterilization. This may have implications relative to the commonly used method of autoclaving titanium implants, which may ultimately enhance bacterial biofilm formation on these surfaces.
Keywords: colonization, hydrophobicity, implant, modes of sterilization, Streptococcus sanguis, titanium
Pages 233-238, Language: English
Two hydroxyapatite-coated implants were retrieved after 12 months of loading because of a fracture of the abutments. The specimens were treated to obtain thin ground sections, and a microprobe chemical analysis was done under a scanning electron microscope equipped with an energy-dispersive x-ray analysis and cathodoluminescence system. Under light microscopy, close contact between the bone and the hydroxyapatite coating was seen, with no gaps at the interface. In some areas of the coating a reduction of the coating thickness could be observed, along with the presence of some detached hydroxyapatite particles embedded in newly formed bone. The chemical analysis of the cathodoluminescent areas at the interface showed a reduced calcium:phosphorus ratio in this region.
Keywords: cathodoluminescence, hydroxyapatite, interface, osseointegration, titanium implants
Pages 239-247, Language: English
Hydroxyapatite (HA) used as a coating for implants can exhibit varying levels of interaction with the biologic environment. The crystallinity of the HA-based coating has been shown to control the rate of dissolution and appears to play a role in the initial cellular interaction with the implant surfaces. An osteoblastic cell attachment assay was employed to examine the cell attachment to untreated and pretreated (pH 5.2, 24 hours) titanium and HA coatings of low (50%), medium (75%), and high (90%) crystallinity. A slightly higher percentage of cell attachment (%CA) was found on untreated and pretreated HA surfaces as compared to the titanium surface. No significant difference could be found in the %CA between the 3 levels of crystallinity. However, higher levels of %CA were observed on pretreated HA surfaces than on untreated HA surfaces (t test, P < .05). Elevated calcium and phosphate levels in culture medium did not have any effect on cell attachment. Scanning electron microscopic examinations revealed surface degradation of the HA coating following pretreatment in the simulated inflammatory media (pH 5.2, 24 hours). The results suggest that the altered surface topography may influence the initial cell attachment to HA surfaces.
Keywords: cell adhesion, crystallinity, dissolution, hydroxyapatite, osseointegration, osteoblast
Pages 248-257, Language: English
The aim of this work was to study the behavior of vertical and horizontal enlargement ratios in panoramic tomography in various implant regions of the maxilla and the mandible. A method is presented that admits determination of regional enlargement ratios as a function of the implant region. Clearly defined characteristics of the implant body (Frialit-2 implants) are used as reference points. The vertical enlargement ratio varied between 1.21 and 1.29 on optimal orthograde adjusted tomographs, depending on the measured area. The horizontal enlargement ratio at the coronal end of the implant varied between 1.15 and 1.35. As it is below the vertical value in the lateral tooth area, this contributes to the distortion of the implant structures depicted. The horizontal enlargement at the apical end of the implant varies between 1.12 and 1.44. The difference in horizontal enlargement ratios also causes a distortion of the implant structures shown on the panoramic tomograph. Based on this study scenario, panoramic tomography may be well suited to preimplant diagnosis, particularly in the vertical dimension. With regard to transparent templates designed for implant placement, an enlargement of 1.3 in the perpendicular line and 1.35 in the horizontal line is proposed.
Keywords: area-dependent, enlargement, Frialit-2, implant dentistry, panoramic tomography, radiographic measuring
Pages 258-264, Language: English
In this report, the problems of insufficient bone and soft tissue after extraction of maxillary incisors were addressed concurrently prior to endosseous implant placement, by combining the use of a diphenylphosphorylazide-cross-linked Type I collagen membrane and a resorbable space-making biomaterial composed of 200-µm porous hydroxyapatite granules blended in Type I collagen and chondroitin-4-sulfate. Upon flap reflection 8 months postsurgery, the horizontal deficiencies were almost completely resolved, membranes completely resorbed and the defects filled with hard, bonelike tissue, with a few superficial hydroxyapatite granules. Histologic evaluation of the bone biopsies obtained at the implantation sites revealed dense, well-reconstructed alveolar bone with a few traces of hydroxyapatite granules that had been completely resorbed. Tomodensitometric evaluation indicated that bone regeneration ranged from 14% to 58%, with an average bone gain of 29.77%. Four nonsubmerged ITI titanium implants placed in the augmented bone have been in function for more than 5 years, with no clinical or radiographic signs of hard or soft tissue breakdown. Bacterial sampling at dental sites with periodontitis 1 month prior to periodontal therapy and at implant sites for up to 30 months demonstrated rapid colonization of implant surfaces by periodontopathogens without causing any detrimental effect to implant integration.
Keywords: bone regeneration, collagen membrane, guided tissue regeneration, human histology, hydroxyapatite, oral implant, resorbability
Pages 265-270, Language: English
Endosseous implants have traditionally been surgically placed by oral and maxillofacial surgeons, periodontists, and general practitioners. The purpose of this study was to examine surgical referral patterns for patients receiving implants in the treatment of partial edentulism. The records of 542 patients who received 1,313 implants between 1993 and 1997 were analyzed. Data relative to anatomic area, patient demographics, type of implant system, and any complication encountered were collected. Surgical cohorts were compared using Wilcoxon's rank-sum or chi-square tests, and complication rates were estimated using survival analysis methods. Results indicate no significant difference (P > .05) between cohorts with regard to placement of implants in the anatomic locations of the anterior mandible, anterior maxilla, posterior mandible, and posterior maxilla. Patient demographic information was not statistically different, with the exception of mean patient age, where oral and maxillofacial surgeons have seen younger patients (P < .0001). Relatively few complications were seen, with no significant difference in complication rates between cohorts (P > .05). The type of implant system used showed no significant difference with respect to anatomic location or complication occurrence (P > .05). This study indicates that implant surgical referral patterns were similar in this setting between periodontal and oral and maxillofacial surgeons, with the only difference being a tendency to refer younger patients to the oral surgeons.
Keywords: oral surgeon, partial edentulism, periodontist, referral trends
Pages 271-277, Language: English
The quality of the tissue-implant interface was evaluated using light and scanning electron microscopy with morphometric analysis. Nine dogs were implanted with 3 types of dental implants (titanium, zirconia, or alumina). A total of 24 dental implants was placed in mandibular bone previously filled with coral carbonate calcium (corail) or hydroxyapatite. The study results in breaking the concept of osseointegration into 2 phases: "osseocoaptation," which concerns only the interface (physical contact between the implants and the bone without interpenetration process), and "osseocoalescence," which relies on an interpenetration of the bioactive material, which almost entirely disappears, being substituted by newly formed bone. There was no significant statistical difference between the 3 types of implants. Both fillings showed good ossecoalescence properties. However, hydroxyapatite led to fibrous encystment, preventing osseocoaptation of implants, in contrast with calcium carbonate filling.
Keywords: bone filler materials, implants, osseocoalescence, osseocoaptation
Pages 278-281, Language: English
The torque output of the Nobelpharma electric torque controller was determined using a special setup on an Instron test machine. The devices were held in a vice and oriented so that activation of the drivers caused a pure torsion effect. Measured torque levels generally varied significantly between individual devices. Further, significant differences generally existed between the nominal torque levels and the corresponding measured values. Torque application errors varied from target values by 1% to 165%. For the clinician to deliver appropriate torque levels, these data indicate that a simple means for chairside calibration and adjustment should be available.
Keywords: biomechanics, implants, prosthodontics, torque control
Pages 282-289, Language: English
A 3-dimensional bone-implant finite element model was created. The objective was to further investigate the mechanical environment of cortical bone adjacent to the threads of a retromolar endosseous implant used for orthodontic anchorage to mesially translate mandibular molars in response to normal functional loading. This study emphasizes the stress invariants around and between the threads of the implant for future comparison to histomorphometric data from an ongoing clinical study. A strong stress pattern change was found immediately around the implant, which was reflected by a moderate change of stresses between the threads and a significant increase in stress at the tips of the threads.
Keywords: dental implant, finite element analysis, mechanical response
Pages 290-294, Language: English
Extraoral implants are used increasingly frequently in the wake of ablative tumor surgery and adjuvant radiation or chemotherapy for craniofacial rehabilitation with facial prostheses and epitheses. However, high rates of nonintegration and implant loss have been reported for extraoral implants, especially for those in the periorbital region following irradiation. This case report and corresponding histologic evaluation describe the osseointegration pattern in irradiated periorbital bone, based on the example of 3 retrieved, clinically integrated, stable titanium screw implants.
Keywords: bone-titanium interface, extraoral implants, facial prostheses, irradiated bone, osseointegration
Pages 295-297, Language: English
As implant-assisted dentistry continues to grow, increasing emphasis is being placed on the surgical positioning of implants so that they can be optimally restored. While this is essential for esthetics with fixed implant restorations, it is equally important with implant overdentures, where the type of retentive mechanism, artificial tooth position, and denture flange contour may be affected by implant position. Unfortunately, surgical guides or templates may be used less often with overdenture cases because of the associated time, costs, and difficulty in positioning during surgery, leading to compromised implant location or orientation. This paper describes a prototype paralleling device that can aid in the surgical positioning of implants for overdentures.
Keywords: implant overdenture, implant position, paralleling device, surgical guide