The International Journal of Oral & Maxillofacial Implants, 02/2002

Purpose: Currently, a number of bioresorbable and biodegradable membranes used for guided bone regeneration lead to incomplete tissue regeneration. Poor mechanical properties, short degradation time, and the lack of integrated biologic components result in the inability to create and maintain an appropriate environment and to actively support tissue remodeling. In the present study, the osteogenic potential of human calvarial periosteal cells in combination with ultrathin polycaprolactone (pc2) membranes of a slow biodegradation rate was investigated. Materials and Methods: In vitro and in vivo analyses of the tissue-engineered constructs were conducted using imaging techniques, immunohistochemistry, and histology. Two types of membranes were investigated. Group 1 consisted of a plain membrane, and in group 2 membranes were treated with sodium hydroxide. Results: In vitro results showed that osteoblast-like cells attached and proliferated on the membranes with the formation of extracellular matrix. Sodium hydroxide-treated membranes showed enhanced cell attachment and proliferation kinetics, resulting in a dense cellular layer after 2 weeks in culture. In vivo mineralized tissue formation in association with vascularization was observed. Extracellular matrix calcification with nodule formation was detected via histology as well as scanning electron microscopy. Discussion: PCL membranes support the attachment, growth, and osteogenic differentiation of human primary osteoblast-like cells. Sodium hydroxide-treated membranes demonstrated increased cell attachment resulting from increased hydrophilicity. Conclusion: These findings have potential application in the development of a new generation of osteoconductive membranes. Keywords: guided bone regeneration, periosteal cells, polycaprolactone membrane, tissue engineering

Purpose: This study measured the gold screw preload at the gold cylinder-abutment screw joint interface obtained by 3 torque delivery systems. Materials and Methods: Using a precalibrated, straingauged standard abutment as the load cell, 3 torque delivery systems tested were shown to have significant differences in gold screw preload when a gold cylinder was attached. Results: Mean preloads measured were 291.2 N for hand torque drivers set at 10 Ncm, 340.3 N for electronic torque controllers at low setting/10 Ncm, 384.4 N for electronic torque controllers at high setting/10 Ncm; and 140.8 N for hand-tightening with a prosthetic slot screwdriver. Significant differences in screw preload were also found between operators using a hand torque driver. Discussion: Hand-tightening delivered insufficient preload and cannot be recommended for final gold screw tightening. Different electronic torque controller units set at 10 Ncm induced mean gold screw preloads that ranged from 264.1 N to as high as 501.2 N. Conclusion: Electronic torque controllers should be regularly recalibrated to ensure optimal output. Keywords: gold screws, screwdriver, screw joint, screw preload, strain gauge, torque controller, torque driver

Purpose: Potential treatments using autologous thrombocyte growth factors are an important reason to improve methods for isolating platelet-rich plasma (PRP). Two methods for extracting PRP directly by the surgeon are currently available; this study was conducted to compare the growth factor levels in the resulting PRP. Materials and Methods: Whole blood was drawn from 46 healthy donors (17 men, 29 women) aged 20 to 59 years (29.9 ± 7.8). PRP was then separated from each sample by both the PCCS (3i) and Curasan (PRP Kit, Curasan) methods. Results: The growth factor content differed significantly for TGF-ß1 (PCCS 467.1 ng/mL; Curasan 79.7 ng/mL) (sign test P .0001) and PDGF-AB (PCCS 251.8 ng/mL; Curasan 314.1 ng/mL) (P .0001); this was less significant for IGF-I (PCCS 91.0 ng/mL; Curasan 69.5 ng/mL) (P .02). The higher platelet count in the PCCS PRP (PCCS 2,232,500/µL; Curasan 1,140,500/µL) seemed to correlate with a higher level of TGF-ß1 (Spearman's correlation coefficient, rS = 0.7), whereas the higher leukocyte count in the Curasan PRP (PCCS 15,300/µL; Curasan 33,150/µL) had only a minor correlation with higher levels of PDGF-AB (rS = 0.46). Discussion: The PCCS end product has both a higher platelet count and a higher total content of the growth factors investigated. Nevertheless, the biologic effect of the evaluated growth factor levels remains unknown. The amount of PRP necessary to achieve the intended biologic effects still remains unclear. Conclusion: PRP contains growth factors in high concentrations. Precise predictions of growth factor levels based on the thrombocyte counts of whole blood or PRP appeared limited. There are different sources for growth fators (platelets, leukocytes, plasma). Keywords: autologous, buffy coat, growth factor level, platelet-rich plasma, thrombocyte concentrate

This paper reviews the literature and discusses patient selection for endosseous dental implants and the effect of systemic and local pathology on the success rate of dental implants. Endosseous dental implants may be preferable to conventional dentures in patients with compromised supporting bone or mucosa, xerostomia, allergy to denture materials, severe gag reflex, susceptibility to candidiasis, diseases affecting orofacial motor function or in patients who demand optimal bite force, esthetics, and phonetics. Conventional dentures or fixed partial prostheses may be preferable to endosseous dental implants in growing and epileptic patients and patients at risk of oral carcinoma, anaphylaxis, severe hemorrhage, steroid crisis, endocarditis, osteoradionecrosis, myocardial infarction, or peri-implantitis. A systematic approach to dental implant patient selection is outlined and centralized reporting of dental implant outcomes is recommended. Keywords: endosseous dental implants, patient selection

Purpose: To analyze potential surface alterations in endosseous dental implants induced by irradiation with common dental lasers. Materials and Methods: Sandblasted and acid-etched, plasma-sprayed, hydroxyapatite-coated, and smooth titanium discs were irradiated using Nd:YAG, Ho:YAG, Er:YAG, CO2, and GaAlAs lasers at various power settings. The specimens were examined by scanning electron microscopy and energy dispersive spectroscopy. Results: In an energy-dependent manner, the pulsed YAG lasers induced partial melting, cracking, and crater formation on all 4 surfaces. Within the energy range applied, the CO2 laser caused surface alterations on the hydroxyapatite and plasma coatings as well as in the acid-etched surface. GaAlAs laser irradiation did not damage any of the surfaces. Energy dispersive spectroscopy revealed an altered chemical compound of the surfaces with regard to titanium, oxygen, and silicon. Discussion: The clinical application of most common dental laser systems can induce implant surface alterations. Relevant factors are not only the laser system and power setting, but also the application system. Conclusion: The results of the study indicate that Nd:YAG and Ho:YAG lasers are not suitable for use in decontamination of implant surfaces, irrespective of the power output. With the Er:YAG and CO2 laser, the power output must be limited so as to avoid surface damage. The GaAlAs laser seems to be safe as far as possible surface alterations are concerned. Keywords: energy dispersive spectroscopy, implant surface alteration, peri-implantitis, scanning electron microscopy

Purpose: To evaluate fixed partial dentures (FPDs) supported by a combination of natural teeth and implants in a variety of clinical situations. Materials and Methods: In 30 patients, 86 teeth and 85 implants were used as supports for 30 FPDs of varying extension (mean = 8.6 units); 23 in the maxilla and 7 in the mandible. The prostheses had a removable section fastened with screws to both the implants and to a section cemented on the supporting teeth, and were thus functioning as rigid, fixed partial dentures. Results: Five implants were lost prior to the placement of prostheses, 2 were lost after loading, giving survival rates of 91.0% in the maxilla and 95.5% in the mandible. Complications were predominantly soft tissue-related and were all amenable to treatments. One patient was lost to follow-up. The remaining 29 FPDs remained stable throughout the 3-year observation period. Discussion: Changes in plaque accumulated, bleeding on probing, pocket depths, and marginal bone level were acceptable. The survival rate of implants was comparable to that of similar studies. Further investigations are needed with regard to design for such FPDs. Conclusion: These findings, together with the patient satisfaction experienced, indicated that the combined support of implants and teeth for fixed prostheses may be appropriate treatment for patients. Keywords: combined tooth-implant support, dental implants, fixed partial dentures, mutually screwretained prosthesis sections

Purpose: To examine the accuracy of 3 mechanical torque wrenches. Materials and Methods: The torque outputs of the Nobel Biocare, Straumann ITI, and DynaTorq ITL mechanical torque-limiting devices were determined using a special setup on an Instron test machine. The devices were held in the test setup and oriented so that activation of the drivers caused a pure torsion effect. Results: Significant differences generally existed between individual units and the target torque levels for the Nobel Biocare torque controller. Discussion: The mean torque values of the ITI and ITL devices were within 10% of their respective target torque levels. Knowledge of applied torque levels to the screws that retain implant abutments and their attached prostheses is necessary to achieve optimal preload. The ITI and ITL devices tested in this study were capable of providing consistent torque at or near their respective targets. Conclusion: The torque output of each individual device deviated in varying degrees from target torque values. Keywords: dental implants, mechanical devices, torque control

Purpose: To investigate the effects of bone grafting and radiotherapy on implant survival rates. Materials and Methods: This follow-up study involved 36 patients with 180 implants who were treated between January 1989 and December 2000 by prosthodontic rehabilitation using osseointegrated implants following jaw resection. They comprised 20 patients with malignant tumors, 12 with benign tumors, and 2 patients each with osteomyelitis and cysts. Results: A total of 15 implants (11 in the maxilla and 4 in the mandible) were removed for various reasons during the follow-up study. Implant survival rates were calculated using the Kaplan-Meier method; the overall survival rate for the 180 implants was 88.6%. Specific implant survival rates were as follows: in residual bone, 73.8% for the maxilla and 95.2% for the mandible; in grafted bone, 80% for the maxilla and 94.1% for the mandible; in irradiated bone, 79.7%; and in nonirradiated bone, 93.5%. Discussion: Radiotherapy, a dose of 30 Gy, was performed in patients with malignant tumors but not in patients with benign tumors, cysts, or osteomyelitis. No differences were found in the results for implants placed due to jaw resection for malignant tumors and those for implants placed due to benign tumors, cysts, or osteomyelitis. Implants lost varied in length from 7 to 18 mm. Among these, loss was more frequent with shorter implants (lengths to 10 mm). Conclusion: The clinical results obtained in the present study compare favorably with those obtained by others. However, jaw reconstruction and rehabilitation should not be performed by the oral surgeon alone; oral and maxillofacial function should be restored using a team approach in close cooperation with specialists in prosthodontics and periodontics to improve the result of implant treatment. Keywords: dental implants, resected jaw

Purpose: A 3-dimensional finite element model consisting of a bone block and 2 simulated premolar crowns supported by 2 adjacent cylindric implants without immediately surrounding cortical bone was generated and used to investigate the effects of prosthesis materials and prosthesis splinting on the peri-implant bone stress under static loads. Materials and Methods: The peri-implant maximum equivalent bone stress (von Mises [VM] stress) was evaluated when a vertical or a horizontal load of 1 N was applied to the center of a single resin, gold alloy, or porcelain crown, nonsplinted or splinted to the adjacent crown. Results: The numeric results indicated that: (1) in a single crown, no significant difference could be found in the maximum VM stress between different materials for both vertical and horizontal loading; (2) splinting the crowns reduced the maximum VM stress induced by the horizontal load, and the maximum VM stress increased about 14% for the horizontal loading when the restorative material was changed from gold alloy or porcelain to resin. Discussion: Under the condition of this study's analysis, prosthesis materials of a single crown have insignificant effects on the peri-implant bone stress. Splinting the crowns reduced the peri-implant bone stress under horizontal load, and gold alloy and porcelain each demonstrated less peri-implant bone stress than resin in the splinted crown situation under static horizontal load. Conclusion: Splinting the crowns of adjacent implants with relatively stiff restorative materials is recommended for implants surrounded by poor-quality bone. Keywords: dental implants, finite element analysis, prosthesis material

Purpose: This study presents a clinical, radiographic, laboratory, and histologic/histomorphometric analysis of the use of mandibular ramus block autografts for vertical alveolar ridge augmentation and implant placement. Materials and Methods: Autogenous block autografts were fixed at the recipient site with fixation screws while a mixture of autogenous bone marrow and inorganic bovine material (Bio-Oss) was used at the periphery. All grafts appeared well incorporated at the recipient site during reentry surgery. Results: Radiographic measurements revealed an average of 6.12 mm vertical ridge augmentation 1 month after surgery and 5.12 mm 4 to 6 months after surgery. Laboratory volumetric measurements revealed an average of 0.91 mL alveolar ridge augmentation 1 month after surgery and 0.75 mL 6 months postoperatively. Linear laboratory measurements revealed 6.12 mm of vertical ridge augmentation 1 month postoperatively and 4.37 mm 4 to 6 months after surgery. Histologic evaluation indicated signs of active remodeling in all the specimens. Histomorphometric analysis of the peripheral particulate bone indicated bone present at 34.33% of the grafted area, while 42.17% of the area was occupied by fibrous tissue and 23.50% by residual Bio-Oss particles. Discussion: The results demonstrated the potential of mandibular block autografts harvested from the ascending ramus to maintain their vitality. Volumetric resorption rate of 17.58% and radiographic resorption rate of 16.34% were in accordance with previously published literature. Early exposure appeared to compromise the results, while late exposures did not affect the vitality of the block autografts. Conclusion: Mandibular block autografts can maintain their vitality when used for vertical alveolar ridge augmentation. Inorganic bovine mineral (Bio-Oss) can be used at the periphery of the block graft when mixed with autogenous bone marrow. Keywords: block grafts, vertical ridge augmentation

Purpose: To evaluate the clinical outcome of implants placed into sites grafted with bioactive glass. Materials and Methods: Seventeen consecutively treated patients were referred to a private specialist surgical practice for the repair of dentoalveolar defects, and/or ridge maintenance at the site of extraction sockets, prior to implantation. Bioactive glass available in 1 of 2 forms was utilized as an alloplastic grafting material. Bone cores were trephined out at the time of implantation and processed and examined to evaluate the tissue response under the light microscope. Implant mobility, marginal bone levels, and soft tissue health were all evaluated over a 2- to 3-year follow-up period to determine treatment success. Results: A total of 40 Astra Tech dental implants were placed. The overall sucess rate at the end of the study was 88.6% for implants that were in function for a mean period of 29.2 months (22 to 24 months). One patient with 5 successful implants died at 18 months after functional loading. At that time the cumulative success rate was 90%. Another patient who was diagnosed with cancer of the large bowel lost 3 implants. If this patient were excluded from the data, the cumulative success rate increases to 96.8%. Mean marginal bone loss measured 0.5 mm mesially and 0.4 mm distally over a maximum follow-up of 36 months. Human histology demonstrated that connective tissue was seen to exist without any inflammatory response, for up to 6 months. Increasing evidence of bone formation was seen in direct relation to the boactive glass material beyond this time frame. Discussion: The need to repair and augment dentoalveolar defects necessitates the use of autogenous bone or a substitute that may be seen to avoid the additional morbidity of a donor site procedure and without risk of cross infection. The use of bioactive glass has been proposed as a viable bone substitute. The current study draws attention to the long healing time required to achieve even a small amount of new bone incorporation into the graft, as seen histologically. However, the high rate of osseointegration and continued medium-term function of implants placed into these grafted sites would indicate that the use of bioactive glass does not prohibit osseointegration. However, it is likely that the initial integration will have derived from those areas in contact with native bone. Conclusion: Implants will survive for up to 3 years in sites grafted with bioactive glass, even when such grafts appear to only slowly conduct new bone growth. Keywords: alloplast, augmentation, bioactive glass, dental implants

Purpose: To categorize and review complications related to implant dentistry that have resulted in legal actions. Materials and Methods: The records of 61 patients (39 women and 22 men) were retrospectively evaluated according to a structured form. Ages ranged from 28 years to 78 years (mean 49 ± 12 years). The time lag in months between actual damage and legal action ranged from 0 months to 60 months (mean 12.7 months). Results: Implant type, length, width, and locations varied widely and had no impact on the liability report. Half of the lawsuits were filed as a result of actual body damage (loss of sensation, oroantral fistula, life-threatening bleeding); 35% of the lawsuits were filed because of late complications; and 15% were related to immediate complications not leading to actual body damage. The dental consultants acknowledged liability in 41 of 61 cases. The clinician's errors that led to the reported complication were classified as preoperative in 39 of 41 cases. The doctor's attitude was considered positive in 40 cases and negative in 17 cases. Discussion and Conclusions: Clinicians should report as soon as possible to their insurance companies to get professional help. The main causes for lawsuits are actual body injury and major disappointment. Practitioners should dedicate a significant part of the entire treatment time to preoperative diagnosis and planning. Keywords: dental implants, injury, lawsuit, malpractice

Purpose: The use of computed tomography (CT) based intraoperative navigation has greatly improved surgery in many specialties. In this study, the precision of the SMN system (Zeiss, Oberkochen, Germany) for navigated drilling and following implant placement in the maxilla was evaluated. This study should demonstrate the suitability of navigation systems for computer-assisted implantation in the maxilla to avoid perforation of the maxillary sinus. Materials and Methods: Sixty target drillings were carried out on 10 standardized polyurethane milling models after CT scanning. The models were produced with cranial open maxillary sinuses. The CT scans were performed with a slice distance of 1 mm. Then the CT data were transferred to the workstation of the SMN system and registration of the reference markers (fiducials) for superposition of the native and CT model was done. Referencing of the model was performed with the aid of a drilling tool. This drilling tool was used for later navigation-assisted drilling into the maxilla. The target of drilling was the maxillary sinus floor. The aim was to come as near as possible without perforation. The distance from the bottom of the drilling holes to the maxillary sinus floor was measured after sectioning of the model. In another 10 models, implants were placed after performing 60 navigated drilling holes. Results: In the first part of the study, an average drilling depth of 6.97 mm and a mean distance to the sinus floor of 0.11 mm (standard deviation = 0.2) was found. In 13 specimens, the inferior border of the sinus was perforated. In the second part of the study, a perforation of the sinus floor by the implants was seen in 47 cases. The mean distance to the maxillary sinus was 0.25 mm (standard deviation = 0.2). Discussion and Conclusions: High precision of CT-based navigation for controlled preimplant drilling was seen, but a high incidence of penetrations into the maxillary sinus was caused by the subsequent implant placement. Keywords: computer-assisted implantation, dental implants, maxillary sinus, navigation

Purpose: This article is a retrospective clinical analysis of implants placed with a flapless approach. Materials and Methods: Seven hundred seventy implants were placed in 359 patients to restore both completely edentulous and partially edentulous arches with fixed prostheses or removable complete dentures. Each patient was examined after 3 months, 6 months, 1 year, and then once every year. Prostheses were removed, if possible, and implant mobility was assessed, periapical radiographs were obtained, and periodontal probing was performed. Implants were considered failed if they had mobility or pain, had to be removed, or if they showed more than 0.5 mm of bone loss per year and signs of active peri-implantitis. Results: The cumulative success rate for implants placed using a flapless 1- stage surgical technique after a 10-year period varied from 74.1% for implants placed in 1990 to 100% at 2000. Discussion: Since flapless implant placement is a generally "blind" surgical technique, care must be taken when placing implants. Angulation of the implants affected by drilling is critcal to avoid perforation of the cortical plates, both lingual or buccal, especially on the lingual in the mandibular molar area and the anterior maxilla. There should be no problem if the patient has been appropriately selected and an appropriate width of bone is available for implant placement. There is a learning curve to every surgical procedure, after which it becomes routine. There are many advantages for the patient as well as for the surgeon, since the procedure is less time consuming, bleeding is minimal, implant placement is expedited, and there is no need to place and remove sutures. Conclusion: Flapless implant surgery is a predictable procedure if patient selection and surgical technique are appropriate. Keywords: dental implants, implant surgery, soft tissue flaps

Dental abnormalities associated with ectodermal dysplasia (ED) can result in severe functional and esthetic problems. To correct these problems, dental implants have increasingly become the treatment of choice. This patient study illustrates the use of implants to rehabilitate a 20-year-old ED patient who initially presented with only 2 permanent and 6 primary teeth in the maxilla. Along with conventional endosseous implants, 2 specially designed zygomatic implants were utilized to avoid the need for bone grafting in the patient's severely resorbed maxilla. This expedited achievement of the final satisfactory result. Keywords: ectodermal dysplasia, endosseous dental implants, implant-supported dental prosthesis, zygoma