The International Journal of Oral & Maxillofacial Implants, 04/2003

Purpose: The treatment of patients with early or immediately loaded dental implants has renewed interest in the behavior of osteoblasts at the implant surface under load. A newly designed dental implant indicated for immediate loading was tested in vivo for early stages of osteoblast behavior at the implant surface. Materials and Methods: Thirty-two implants were placed in the mandibles of 8 minipigs. Half of the implants (n = 16) were immediately loaded under occlusal contacts, and implants placed in non-occlusal relations served as a control. Results: All implants, except 1 that showed signs of tissue infection, healed uneventfully and were stable throughout the experimental period. Ultrastructural analysis of mandibular specimens revealed an intimate attachment of osteoblasts to the material surface beginning as early as day 1. Application of either occlusal or non-occlusal load did not alter the phenotypic morphology of the attached osteoblasts. Transmission electron microscopy and x-ray diffraction analysis demonstrated a direct contact of bone-like minerals over the whole implant surface with no signs of crestal hard tissue alteration. Electron diffraction analysis showed a slight release of titanium from the implant side. Discussion: These results indicate that immediate loading of specially designed dental implants can be performed without disruption of the titanium/bone interface or disturbance of osteoblast physiology in the early loading phase. Conclusion: Immediate loading protocols can be performed without disturbance of normal bone biology.

Purpose: At stage II surgery during dental implant treatment, early marginal bone loss around the implant occasionally occurs despite a lack of apparent causal events, and the etiology of this bone loss is unclear. This study was designed to investigate whether the bone morphogenetic protein-4 (BMP-4) genetic polymorphism is associated with early marginal bone loss around implants. Materials and Methods: The BMP-4 polymorphism was detected by restriction fragment length analysis using HphI digestion after polymerase chain reaction. A total of 262 implants were placed in 41 patients, and early marginal bone loss was observed in 25 of the 109 maxillary implants and 14 of the 153 mandibular implants. Results: In the mandible, the patients with the BMP-4 AV genotype had a significantly higher rate of occurrence of marginal bone loss than those with the BMP-4 VV genotype (P = .012). According to multiple logistic regression analyses, the odds ratio of the AV versus the VV BMP-4 genotype was 8.106 between patients with and those without bone loss in the mandible (95% CI = 1.30 to 50.51; P = .025). Discussion: These results suggest that the BMP-4 genetic polymorphism influences early marginal bone loss around implants. Conclusion: While perhaps premature in recommendation, genetic screening before implant surgery may prove to be a very useful aid to consider the risk of implant treatment.

Purpose: Osseointegration of implants depends on time and the local bone conditions regarding quality and quantity. This led to the bone classification by Lekholm and Zarb. The aim of the present study was to enhance osseointegration of implants through conditioning of the bone bed and to compare in this context the efficacy of bone condensation, an osteoinductive collagen (Colloss), and platelet-rich plasma (PRP). Materials and Methods: Porcine frontal skull bone was used for the preparation of identical-size implant beds. Before placement of the implants (Ankylos, 3.5×4 mm), the implant beds were untreated (control) or conditioned with condensation, Colloss, or PRP. The animals were sacrificed after 2, 4, and 8 weeks. The specimens were then compared and analyzed by microradiography, and statistical analysis was performed using the Wilcoxon signed rank test. Results: At the early observation times, significant effects on the sites of topical bone conditioning in comparison to the control group could be seen regarding the implant-bone interface (2 weeks: control 31%, Colloss 60%, condensation 73%, PRP 47%; 4 weeks: control 39%, Colloss 51%, condensation 40%, PRP 42%) and periimplant bone density (2 weeks: control 31%, Colloss 48%, condensation 59%, PRP 39%; 4 weeks: control 47%, Colloss 53%, condensation 41%, PRP 50%). A leveling of the results between groups was found at 8 weeks (implant-bone interface: control 51%, Colloss 58%, condensation 55%, PRP 62%; peri-implant bone density: control 50%, Colloss 55%, condensation 51%, PRP 51%). Discussion: Overall, bone condensation and Colloss apparently influenced bone formation process from the onset, but over the entire 8-week healing period, differences in bone formation were not significant. Conclusion: It can be stated that, in the initial healing phase, an effect of topical bone conditioning may be achieved by the different described methods.

Purpose: The aim of this study was to determine the clinical effectiveness of placing dental implants with microtextured surfaces into full occlusal loading at the time of placement in partially edentulous patients. Materials and Methods: Two demographically similar groups of 14 patients each were treated with a total of 92 Spline Twist implants (Centerpulse Dental, Carlsbad, CA). Test implants were placed into immediate full occlusal loading, and control implants were restored using a conventional delayed loading procedure. Otherwise, both groups of patients received similar therapy from the same treatment team. Radiographs, periodontal indices, and Periotest values were recorded every 6 months during routine clinical follow-up appointments. The mean loading time for all prostheses was 24 months at the time of this report. Results: No implants failed in the test group, and 1 implant failed before loading in the control group. Cumulative implant success was 98.9% for all implants placed (test group = 100%; control group = 92.9%). Periodontal measurements indicated no significant clinical differences between implants placed into immediate full occlusal loading and those loaded via a conventional delayed protocol. Discussion: Immediate full occlusal loading of partial prostheses supported by microtextured implants in partially edentulous patients demonstrated excellent clinical results, with no adverse periodontal effects after 24 months of function. Additional follow-up will provide invaluable information on the long-term effects of this technique. Conclusion: Immediate full occlusal loading of partial prostheses supported by microtextured implants can be successfully achieved for 24 months in highly motivated patients with excellent oral hygiene.

Purpose: This study assessed the impact of mandibular bone height on masticatory performance following treatment with a mandibular conventional denture (CD) or implant-retained overdenture (IOD). Materials and Methods: Evaluation of masticatory performance in 63 participants was made with original CDs and 6 months after treatment completion with new dentures; 25 patients received a mandibular CD and 38 received a mandibular IOD. Anterior ridge height at the mandibular symphysis was determined on lateral cephalograms to provide subgroups of low (= 21 mm), moderate (> 21 mm, 28 mm), and high (>= 28 mm) ridge height for both CDs and IODs. Masticatory performance tests on the preferred chewing side (PS) and swallowing threshold tests were made with peanuts and carrots. Results: Analysis of variance was used for comparisons of mean change in performance after treatment with study dentures for the 3 bone height groups; this indicated significant differences between the CD and IOD for PS masticatory performance with peanuts (P = .05) and carrots (P = .03). Post hoc tests found significant mean differences between the CDs and IODs with peanuts (P = .008) and carrots (P = .01) only in the low bone height group. Although no significant differences were found in swallowing threshold performance, the mean change scores for subjects with low bone height were greater with the IODs than those with CD for swallowing threshold performance, strokes, and time. Discussion: It is suggested that only in patients with advanced ridge resorption is the mandibular IOD more likely than a CD to result in improvements in masticatory performance. Conclusion: The study indicated that treatment with a mandibular IOD may improve masticatory performance only in persons with a less than adequate mandibular ridge.

Purpose: The objective was to develop a patient-based outcome measure of condition-specific quality of life that would minimize measurement error related to the instrument when used with patients requiring extraoral craniofacial prostheses. Materials and Methods: An item pool of potential questionnaire items covered 10 clinical/technical and social/psychologic domains. They sought how frequently the issue in the item affected patients and how important the problem in the item was. The 139 items were administered to 94 treated patients in 5 centers in the United States, Canada, and the United Kingdom. Items were eliminated using relevance (frequency × importance), frequency of answer endorsement, Cronbach's alpha (internal consistency), and correlation of items on the same subject. International cultural agreement was tested using analysis of variance and Tukey comparisons within each domain. Scoring was transformed to a scale (0 to 100). Results: The final instrument contained 52 items yielding a mean quality-of-life score of 72.5% and a standard deviation of 17.9. Very high internal consistency was demonstrated with a final Cronbach's alpha of 0.967. No international cultural disagreement was found in 9 of the 10 domains. Discussion: The relative weight of each of the domains is (partially) based on the relevance to the patients. Of the 52 items, 29 were identified that do not mention a prosthesis. This subscale has a Cronbach's alpha of 0.976. These items may therefore be useful where within-patient change is of interest. Conclusion: A patient-based outcome measure of condition-specific quality of life has been developed with control of bias and demonstrated performance characteristics.

The use of systematic terminology for implant prostheses can simplify communication within the scientific community. However, a review of the current literature demonstrates the lack of uniformity in this field. It is the purpose of this manuscript to suggest uniform terminology based on conventional prosthodontic terms that will simplify communication in the profession.

Purpose: This article reports the preliminary data from a clinical study of immediately loaded, full-arch, screw-retained prosthesis with distal extensions (hybrid prosthesis) supported by Osseotite implants placed in the edentulous mandible. Materials and Methods: Fifteen patients who received 103 implants were enrolled in this study. The first 2 patients received both immediately loaded and submerged implants, while the remaining patients had all implants immediately loaded. The first 9 patients received a temporary prosthesis within 4 hours of surgery, and the hybrid prosthesis, made of a titanium framework and acrylic resin teeth, was placed after 6 months. The last 6 patients received the same type of hybrid prosthesis within 36 hours of surgery. Marginal bone loss was monitored via periapical radiographs by a computerized technique. Results: One failure (out of the 92 immediately loaded implants) occurred after 3 weeks of function because of infection. A cumulative success rate of 98.9% was achieved for up to 48 months of follow-up, while the prosthetic cumulative success rate for the same period was 100%. Marginal bone loss at the immediately loaded implants was within the generally accepted conventional limits for standard delayed loading protocols. Discussion: This technique can reduce treatment time but should be applied with caution. Conclusion: The preliminary results of this study suggest that rehabilitation of the edentulous mandible by an immediately loaded hybrid prosthesis supported by 5 to 6 implants may represent a viable alternative treatment to the classical delayed loading protocols.

This retrospective study presents the results of the use of the Frialit-2 System in a private practice setting. A total of 802 implants, both threaded and press-fit, were placed between February 2, 1996, and March 6, 2002. The overall success rate was 97%, and the cumulative survival rate using life table analysis was 96.1%. The statistical breakdown and an analysis of the results of the treatment of this patient population are presented.

Purpose: The aim of the present retrospective study was to evaluate the survival rate of titanium plasma spray-coated cylindric and machined screw-type implants placed in sinuses grafted with anorganic bovine bone mixed with demineralized freeze-dried bone allograft (DFDBA) or with anorganic bovine bone alone. Materials and Methods: The patients included in this study were treated with a 1- or 2-stage technique, according to the volume of residual bone. This determined the possibility of primary stabilization and the duration of the treatment, which was 9 or 12 months, respectively. Results: The overall implant survival rate was 94.5% after a mean functioning period of 6.5 ± 1.9 years. The implant survival rate was better in sinuses grafted with anorganic bovine bone alone than with a mixture of anorganic bovine bone with DFDBA (96.8% versus 90%). The implant survival rate was similar for cylindric and screw-type implants in sinuses grafted with anorganic bovine bone alone. Discussion: Because of the good bone quality, the implant survival rate was similar for cylindric and screw-type implants in sinuses grafted with anorganic bovine bone. Conclusion: Anorganic bovine bone used alone appears to be a suitable material for sinus floor augmentation.

Purpose: The present material reports on prosthodontic complications in a trial of 51 patients with prostheses supported by single-stage implants over a period of 36 months. Materials and Methods: One hundred eighty-six single-stage implants were placed in 51 patients over a 3-year period in 2 carefully controlled prospective clinical trials. Nineteen of the patients (103 implants) were completely edentulous and restored with a maxillary complete denture and a mandibular fixed-detachable complete prosthesis. Single metal-ceramic crowns or fixed partial dentures were fabricated for the remaining 32 patients (83 implants). The fixed restorations were either screw-retained or cemented. Results: All patients/implants were followed for a minimum of 3 years. Complications in the edentulous patients included fracture of denture teeth, fracture of the maxillary denture, and occlusal screw loosening. Occlusal screw loosening and loss of the resin composite access plug were the only complications observed in the patients treated with screw-retained restorations. No complications were found in the patients restored with cemented restorations on solid abutments. Discussion: Problems with prostheses were very common in the completely edentulous patients (13 of 19 patients encountered complications), possibly a result of increased bite force or inadequate laboratory technique. Tooth fractures were seen more frequently in men than in women. Complications occurred in only 5 of the 32 partially edentulous patients. Conclusion: Complications were associated with laboratory-related procedures rather than the implant system itself.

Purpose: A zygomatic implant can be an effective device for rehabilitation of the severely resorbed maxilla. If zygomatic implants are used, onlay bone grafting or sinus augmentation would likely not be necessary. Where an anterior onlay bone graft is required, extension of the graft in the posterior region could be reduced. The results of the application of zygomatic implants in 9 patients and clinical evaluation of this therapy are reported. Materials and Methods: Nine patients received a total of 15 zygomatic implants. Six to 8 months elapsed for healing before second-stage surgery was performed. Six months after prosthetic treatment, patients' opinions were solicited by means of a questionnaire. Results: No implant was removed at the time of abutment connection surgery or during the follow-up period. In many cases, the zygomatic implant platform was located palatal to the alveolar ridge. However, no patients complained of any continuing speech impediment following superstructure fabrication. Computed tomograms taken before implant placement and 6 months after implant placement showed no sign of sinusitis in any patient. Discussion: The zygomatic implant allows shorter treatment time and hospitalization. However, there can be some problems in the application of zygomatic implants. Conclusion: It is necessary to investigate long-term clinical prognosis.

Purpose: Placement of dental implants requires precise planning that accounts for anatomic limitations and restorative goals. Diagnosis can be made with the assistance of computerized tomographic (CT) scanning, but transfer of planning to the surgical field is limited. Recently, novel CAD/CAM techniques such as stereolithographic rapid prototyping have been developed to build surgical guides in an attempt to improve precision of implant placement. However, comparison of these advanced techniques to traditional surgical guides has not been performed. The goal of this study was to compare the accuracy of a conventional surgical guide to that of a stereolithographic surgical guide. Materials and Methods: CT scanning of epoxy edentulous mandibles was performed using a cone beam CT scanner with high isotropic spatial resolution, while planning for 5 implants on each side of the jaw was performed using a commercially available software package. Five surgeons performed osteotomies on a jaw identical to the initial model; on the right side a conventional surgical guide (control side) was used, and on the left side a stereolithographic guide was used (test side). Each jaw was then CT scanned, and a registration method was applied to match it to the initial planning. Measurements included distances between planned implants and actual osteotomies. Results: The average distance between the planned implant and the actual osteotomy was 1.5 mm at the entrance and 2.1 mm at the apex when the control guide was used. The same measurements were significantly reduced to 0.9 mm and 1.0 mm when the test guide was used. Variations were also reduced with the test guide, within surgeons and between surgeons. Discussion: Surgical guidance for implant placement relieves the clinician from multiple perioperative decisions. Precise implant placement is under investigation using sophisticated guidance methods, including CAD/CAM templates. Conclusion: Within the limits of this study, implant placement was improved by using a stereolithographic surgical guide.

Purpose: The Straumann Orthosystem (Institut Straumann, Waldenburg, Switzerland) describes a technique that involves placement of titanium implants (4 or 6 mm long and 3.3 mm in diameter) into the midsagittal hard palate for orthodontic anchorage. The aim of this study was to determine the quantity of bone in the midline of the anterior hard palate, and specifically the thickness inferior to the incisive canal. Materials and Methods: Twenty-five dry skulls were radiographed with a standardized cephalometric technique. The vertical thickness of the midsagittal palate was then measured to the nearest tenth of a millimeter. Next, gutta-percha was injected into the incisive canal, and the radiograph was repeated. The bone thicknesses were then measured from the inferior hard palate to the most inferior part of the radiopaque canal. This is defined as the actual bone available for the implant without violating the canal. Results: The measurements have shown that an average of 8.6 ± 1.3 mm of bone is theoretically available for the implant. However, considering the canal (where only bone thickness inferior to it is utilized and measured), only 4.3 ± 1.6 mm of bone exists. The canal itself averaged 2.5 ± 0.6 mm in diameter. Discussion: Prior studies have overestimated the amount of bone available for implants in the median hard palate. The main reason for this is that the incisive canal is not well visualized on cephalometric radiographs of live patients. Conclusion: This study supports the continued use of implants, as approximately 50% of skulls still had the requisite minimum 4 mm of bone inferior to the incisive canal for maximum osseointegration with the 4-mm implants. However, 6- mm implants should be used with caution.

Purpose: The behavior of provisional implants in edentulous maxillae/mandibles used for anchoring removable interim overdentures was followed for the time of the intended healing of the definitive implants. Materials and Methods: Twenty-eight edentulous arches (19 maxillae, 9 mandibles) were provided with 77 provisional implants (2 to 4 in maxillae; 2 or 3 in mandibles) for anchoring removable interim prostheses (overdentures). The provisional implants were to be maintained until final restoration (6 to 9 months in the maxilla and 3 months in the mandible). The loss rate of provisional implants and handling and behavior of the anchored overdenture were monitored until the definitive prosthetic restoration was placed. Results: Twenty-three (29.8%) of the 77 provisional implants were lost prematurely. The loss rate of maxillary provisional implants (21/58; 36.2%) was significantly higher than that of mandibular implants (2/19; 10.5%) (P .01). Determination of terminal stability (by means of the Periotest) of the provisional implants showed higher stability in the mandible (+3.8 ± 2.3) than in the maxilla (+8.6 ± 3.9) (P .05). In obvious contrast to mandibular interim overdentures, handling of maxillary interim overdentures was found to improve significantly during the follow-up period (P .01). Discussion and Conclusion: With both the low loss rate in the mandible and the higher loss rate seen in the maxilla, placement of provisional implants fulfills the requirements for initiating immediate prosthetic rehabilitation. The removable interim overdenture can be adequately stabilized and provides for added patient comfort and satisfaction as compared to a conventional complete denture. An important aspect of the continued use of provisional implants concerns the expectations placed in these implants by both clinician and patient, which are quite different than those for definitive implants.

Purpose: Over the last few years, particular attention has been paid to the implant surface and its influence on the formation and maintenance of surrounding bone. The surface of Osseotite implants (Implant Innovations) is produced by a process of thermal etching, which produces a surface with an average roughness that is twice that of machined implants produced by the same manufacturer. In addition to reducing osseointegration time, this factor appears to favor its maintenance over time. This study presents the results of a clinical trial of Osseotite implants. Materials and Methods: Five hundred fifty-five Osseotite implants were placed in 244 patients over 5 years, between September 1996 and September 2001. The average follow-up period from implant placement was 26 months (SD 13.1). Results: After the first surgical stage, 8 failures were noted in 6 patients. Life table analysis showed a cumulative survival rate of 98.5%, but no implant was lost after prosthetic loading, with a 100% survival rate both for the mandible and for the maxilla. For the prosthetic loading time, only the implants with more than 12 months of loading were considered, obtaining an average prosthetic loading time of 34 months (SD 9.2). Discussion: The implant survival rate after loading was 100% both in the anterior and posterior regions, and no difference was noted in relation to the different types of prostheses, or length and width of implants. Conclusion: The results obtained in this retrospective study population revealed an acceptable survival rate for these implant-supported restorations.

Bone augmentation for implant dentistry has become a necessary procedure for a number of edentulous patients. Calvarial bone grafting constitutes an important tool in achieving maxillary augmentation and sinus elevation. Much effort has been directed toward improving graft survival and volumetric maintenance. The purpose of the present study was to evaluate the histologic results of the calvarial onlay graft for maxillary reconstruction before implant placement. Two patients underwent maxillary augmentation using autogenous calvarial onlay grafts. After a 4-month healing period, biopsies of the augmented regions were performed and implants were placed. The implants were loaded after 5 months and then clinically examined after 15 months of function. Biopsies showed that calvarial onlay grafts were well incorporated into the pre-existing bone after a 4-month period. Histologic and histomorphometric findings demonstrated a living bone that showed features characteristic of mature and compact osseous tissue. The restored implants were stable and osseointegrated after a 15-month period of follow-up. The use of calvarial onlay grafts can be a predictable and successful method to achieve maxillary augmentation, allowing appropriate placement of implants and stable prosthetic restorations.

The authors present a case of immediate loading of mandibular implants using a 5-step procedure. The first step consists of building a scannographic template, the second step consists of taking a computerized tomographic (CT) scan, and the third step consists of implant planning using SurgiCase software. The final 2 steps consist of implant placement using a drill guide created by stereolithography and placement of the prosthesis. Using a CT scan-based planning system, the surgeon is able to select the optimal locations for implant placement. By incorporating the prosthetic planning using a scannographic template, the treatment is optimized from a prosthetic point of view. Furthermore, the use of a stereolithographic drill guide allows a physical transfer of the implant planning to the patient's mouth. The scannographic template is designed so that it can be transformed into a temporary fixed prosthesis for immediate loading, and the definitive restoration is placed 3 months later.