The International Journal of Oral & Maxillofacial Implants, 03/2009

Purpose: A three-dimensional finite element analysis was conducted to evaluate and compare the stress distribution around two prosthesis-implant systems, in which implants were arranged in either a straight-line or an intrabone offset configuration. Materials and Methods: The systems were modeled with three titanium implants placed in the posterior mandible following a straight line along the bone. The straight system was built with three straight implants (no offset). The angled system was built as follows: the first implant (mesial) was an angled implant inclined lingually, the second (median) was straight, and the third (distal) was another angled implant inclined buccally. This buccal incline created an intrabone implant offset owing to the inclination of the angled implants' bodies. Each system received a metal-ceramic prosthesis with crowns that mimicked premolar anatomy. In both systems, an axial load of 100 N and a horizontal load of 20 N were applied on the center of the crown of the middle implant. Results: In both systems, the major von Mises stresses occurred with vertical loading on the mesial and the distal neck area of the first and third implants, respectively: 6.304 MPa on the first implant of the straight system and 6.173 MPa on the third implant in the angled system. The peak stress occurred for the minimum principal stress (S3) on the neck of the first implant for both systems at the level of -8.835 MPa for the straight system and -8.511 MPa for the angled system. There was no stress concentration on the inner or outer angles of the angled implants, on the notches along the implant body, or on any apex. Conclusions: In this analysis, the angled system did not induce a stress concentration in any point around the implants that was different from that of the straight system. The stress distribution was very similar in both systems. Keywords: angled implants, dental implants, dental prosthesis, finite element analysis, offset implants

Purpose: The aim of this study was to compare two types of orthodontic mini-implants, self-tapping and self-drilling, by measurement of the insertion torques and the displacements under lateral loading in an animal model. Materials and Methods: After predrilling of host sites, 27 self-tapping and 27 selfdrilling mini-implants were inserted in vitro in the ilia of country pigs. The axial drilling forces at each host site and the insertion torques during placement were recorded, and the displacements applied by variable lateral force (1 to 9 N) were measured. Analyses of covariance with insertion torques or displacements under lateral loading as the main effect and average drilling forces as the covariate (at the alpha = 5% level) were performed to determine statistical significance. Results: There was a significant difference in peak insertion torque between the self-tapping and self-drilling group (P .05), except when the average drilling force at host sites was less than 1.2 N (P > .05). In addition, this experiment demonstrated that the lateral displacement of the self-tapping group was comparable to that of the self-drilling group (P > .05). Conclusions: During implantation, the self-tapping implants typically had a lower insertion torque than the self-drilling implants. Based on the displacements under lateral loading, however, both the self-tapping and self-drilling implants showed similar resistance to lateral forces. Keywords: biomechanics, bone screws, dental implants, orthodontic appliance, torque

Purpose: The purpose of this study was to analyze electrocardiographic alterations during dental implant surgeries when local anesthetic agents were used. Materials and Methods: Twenty implants were placed in 18 healthy patients. An electrocardiogram and Wincardio software were used to gather recordings from 12 static leads every 2 minutes, continuously record coronary artery (D2) derivations, and automatically measure the following electrocardiographic parameters: heart rate, duration and amplitude of the P wave, PR segment duration, ST segment deviation, QRS complex duration, and duration of the RR, QT, and corrected QT (QTc) intervals. Results: Analysis of variance of the values obtained at the different stages showed significant differences (P .05) for the heart rate and for the duration of the RR and QT intervals. The heart rate increased during the anesthesia, incision, and bone drilling stages, reaching a peak during drilling. Duration of the RR and QT intervals decreased during the incision and drilling stages. Among the electrocardiographic parameters individually assessed, several altered values were found for the duration of the P wave, the QRS complex, and the QT and QTc intervals. Sinusal tachycardia and bradycardia, sinusal arrhythmia, supraventricular extrasystole, ventricular extrasystole, and T-wave inversion were detected. Conclusion: Dental implant placement surgery may induce electrocardiographic alterations. The most frequently found arrhythmias were extrasystole and sinusal tachycardia. The anesthesia, incision, and bone drilling stages exhibited the highest heart rate values and the shortest durations of the RR and QT intervals. Keywords: cardiac arrhythmia, dental implants, electrocardiographics, sedation

Purpose: The purpose of this study was to evaluate the effect of different titanium surface characteristics on the behavior and function of oral fibroblasts as well as the deposition pattern of collagen within the extracellular matrix. Materials and Methods: Titanium surfaces created by machining, acid etching with sulfuric acid (AE1), or acid etching with hydrofluoric acid (AE2) were analyzed using scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy. Rat oral fibroblasts were cultured on different surfaces. Cell spread and morphology of extracellular matrix were evaluated using SEM. Attachment and proliferation of cells were examined by comparing the numbers of attached to detached cells and cell count, respectively. Gene expression was analyzed via reverse transcriptase polymerase chain reaction. Collagen production and deposition were examined via a Sirius red-based stain assay and confocal laser scanning microscopy. Results: The machined surface showed a flat profile with isotropic grooves, the AE1 surface showed a uniformly microscale roughened surface, and the AE2 surface had a grooved profile with intermediate surface roughness. The AE2 surface contained fluoride atoms (2.45% ± 0.44% as F/Ti atomic ratio). Cell attachment was significantly weaker on the machined surface than on the AE1 and AE2 surfaces, whereas no differences were observed between the AE1 and AE2 surfaces. The cell counts on the machined and AE2 surfaces were higher, with a parallel orientation, whereas the cell count was lower and randomly distributed on the AE1 surface. The expression level of fibroblastic genes was similar among surfaces for all time points tested. Collagen production was highest on the machined surface, followed by AE2 and AE1 surfaces. Collagen deposition displayed a parallel pattern on the machined surface, while it was multidirectional on the AE1 and AE2 surfaces. Conclusion: The surface characteristics of titanium affect attachment, spread, and proliferative activity of oral fibroblasts as well as the deposition pattern of collagen in vitro. Keywords: acid etching, collagen, fibroblasts, machined, surface topography, titanium

Purpose: Sites that will receive dental implants need to be quantitatively and qualitatively suitable for this therapy. The treatment of postextraction areas with biomaterials associated with platelet-rich plasma (PRP) might make the repair process more efficient, resulting in desirable bone characteristics. The present study sought to evaluate the effectiveness of PRP in the process of new bone formation when associated with biomaterials. Materials and Methods: Four female dogs were used for this study. Mandibular postextraction sites received implants, along with bone substitutes (Bio-Oss [BO] or Biogran [BG]), on the right side of the mandible and these biomaterials plus PRP on the left side of the mandible. Thirty days later, the tissues were prepared and histologic analyses were carried out to compare the repair processes. Results: PRP accelerated the repair process for both BO and BG; however, the action of PRP associated with BO did not surpass that of BG alone. Conclusions: The addition of PRP appears to accelerate the repair process. Keywords: biomaterials, platelet-rich plasma, repair

Purpose: To evaluate the level of agreement between nonlinear finite element stress analysis (NL-FEA) and ex vivo strain gauge analysis (EV-SGA) on immediately loaded implants. Materials and Methods: Four 4.1-mm-diameter, 12-mm-long implants were placed bilaterally into the lateral and first premolar regions of completely edentulous maxillae of four human cadavers. Two-element 90-degree rosette strain gauges were bonded to the labial cortical bone around the implants, and 100 N maximal load was applied over two miniature load cells on bar-retained overdentures while simultaneous data acquisition from load cells and strain gauges was performed at a sample rate of 10 KHz. Individualized numeric models of the cadavers were constructed, and contact analysis with normal contact detection and separation behavior was performed between the implants and bone. Upon simulation of the loading regimen, axial and lateral strains were recorded. The NL-FEA data and EV-SGA data were compared. Results: There was a high level of agreement regarding the quality of strains, as determined by both techniques, although the mean values obtained with EV-SGA were higher than those found with NL-FEA. However, the strains recorded by NL-FEA did not differ significantly (P .05) from the strains recorded by EV-SGA. Conclusion: Considering the complex biomechanical behavior of human hard and soft tissues, EV-SGA and NL-FEA did not suggest inconsistency in the detection of the quality of strains. Further, the methods provided comparable values for the quantification of strains on implants supporting maxillary overdentures. Keywords: biomechanics, bone, finite element analyses, immediate loading, maxilla, overdenture, strain, strain gauge analysis

Purpose: The accuracy of a system for image-guided dental implant planning and placement based on individually fabricated oral templates was investigated in a phantom study. Materials and Methods: The study was performed on identical phantoms of a partially edentulous mandible. In one phantom mandible (the master model), pilot boreholes for dental implants were placed. Computerized tomography image data were then acquired. Using a system for template-based dental implant placement, identical boreholes were planned on the image data and then reproduced in the 10 remaining phantom mandibles (the "slave" models). The resulting positions were compared to the positions in the master model using a three-dimensional digitizer arm. Results: The mean deviation of borehole apex positions in the slave phantoms, as compared to the master phantom, was 0.50 ± 0.04 mm and was below 1 mm in 29 of 30 models. The accuracy was highly reproducible, irrespective of the template used and the surgeon involved. Conclusions: The use of templates for image-guided insertion of dental implants is a method with high and reproducible accuracy Keywords: accuracy, dental implants, image-guided surgery, oral templates, stereotaxy

Purpose: The biomechanical effects of different strengths of grafted bone, bicortical anchorage, and dimensional alterations of a dental implant with maxillary sinus augmentation were investigated. Materials and Methods: Sixteen finite element (FE) models that included five implant lengths, two implant diameters, and grafted bone with two levels of stiffness were studied. A posterior maxillary model was constructed from computerized tomographic images of a human skull, and the implant models were created via computer-aided design software (SolidWorks 2006). All materials were assumed to be isotropic and linearly elastic. A 45-degree oblique force of 129 N was applied to the buccal cusp of the first molar. Results: The von Mises stress was highest in the 7-mm-long implant. Stresses in cortical and trabecular bone were reduced by at least 50% for all other implants (length >= 8.5 mm) with bicortical anchorage. Increasing the length of the bicortically anchored implant did not decrease the stress in native bone, but it decreased the stress in sinus grafts by at least 20%. The use of a wide implant decreased the stress by 24% to 42% in cortical bone and 17% to 36% in trabecular bone. Increasing the elastic modulus of grafted bone decreased the stress in native bone by approximately 10%. Conclusions: Bicortical fixation of implants and the presence of grafted bone with greater stiffness reduced the stresses in native bone. Increasing the length of the implant in grafted bone did not reduce the stress in native bone, but it did reduce the stress in grafted bone. The effects of implant diameters on reducing bone stress are primarily a result of the increased contact area between implant and bone. The results of the FE analysis imply that the success of a sinus-augmented dental implant is heavily dependent on the implant design and rigidity of the bone grafts. Keywords: dental implant, finite element analysis, implant diameter, implant length, maxillary sinus augmentation, stiffness of grafted bone

Purpose: To evaluate the amount of bone matrix in autogenous block bone grafts that were fixed with or without perforation of the receptor bed. Materials and Methods: Twelve rabbits received two 5-mm circular osteotomies each in the anterior parietal region. The bone was removed, perforated, and fixed by a titanium screw in the adjacent area, 3 mm from the border of the osteotomies. On the contralateral side, six perforations were made in the receptor site before the graft was fixated by the titanium screw. After 28 days, the animals were sacrificed and specimens were prepared for histologic study. Sections were analyzed with regard to the total area of the graft and the percentages of bone matrix in the graft, interface, and receptor bed. Analyses using the Wilcoxon test (P .05) were performed. Results: No statistically significant differences were found between the groups with or without perforations to the area of the graft (P = .85) or the percentage of hard tissue in the grafts (P = .53), the interface (P = .65), or the receptor bed (P = .18). Conclusion: Based upon this study that used a rabbit model with bone grafts placed in the parietal regions, cortical perforations of the receptor bone did not improve repair of bone grafts and did not increase the amount of bone matrix in the final grafted area. Keywords: animal study, cortical bone perforation, experimental study, histologic analyses

Purpose: Modern implant dentistry requires the application of torque during various treatment steps. This study investigated seven different surgical motors for the accuracy of the applied torque and their reliability. Materials and Methods: The following surgical motors were evaluated: Chiropro 980 (Bienair), INTRAsurg 300 and INTRAsurg 500 (KaVo), Osseocare (Nobel Biocare), Surgic XT (NSK), Elcomed SA-200 C (W&H), and Osseo System (XO Dentalcare). The torque was measured during typical surgical and prosthetic procedures using a special load transfer mechanism for a torque gauge. For each setting, 30 measurements were made and means were calculated. Results: The highest percentage shortfall was 20.5% at a set torque of 11.4 Ncm (absolute deviation of -2.4 Ncm). The highest percentage by which a torque was exceeded was 54.6% (absolute deviation of 5.5 Ncm). The lowest value for absolute shortfall was found to be -5.6 Ncm at a set torque of 45 Ncm. The highest absolute exceeded was 15 Ncm at a set torque of 40 Ncm. Potentially problematic torque values were identified in the low-torque-value setting, as the implant position may be changed if a machine driver applies excessive torque to the firststage healing screw. In addition, in the indication of immediate loading in the high-set-torque group, torque values above the critical value of 50 Ncm may be unwittingly applied while working with a set torque of 40 Ncm. Conclusion: For most of the clinically relevant torque settings, precise values were measured, although a few devices delivered potentially problematic torque values for some of the indications. Keywords: analysis of variance, dental equipment, dental implants, immediate loading, prosthetic complications, reproducibility of results, torque controller

Purpose: The development of gap-free abutments is a challenging problem, because the gap between the implant and the abutment, which is a consequence of current manufacturing limitations, can serve as a reservoir for pathogens. This may lead to peri-implantitis, a major cause of implant failure. Therefore, the aim of this study was to design and fabricate a gap-free abutment using a shape memory alloy with improved ability to prevent microleakage at the implant-abutment gap. Materials and Methods: The abutment was designed using the shape memory alloy nitinol and based on mathematical calculations considering the temperature-related, reversible changes to its crystalline alloy structure. The abutment prototypes were tested for their susceptibility to microbes in vitro, under static and dynamic conditions, by contaminating the abutments before assembly using a bacterial solution. Microbacterial tests were performed after cultivation of the implants for 1 week. The results were tested for statistically significant differences using the chi-square test. Results: The mathematical calculations met the clinical requirements using a contact pressure of 2 x 108 Nm2 with a preload of 1.9 kN on cooled abutments. After recooling, the contact pressure was 1.3 Nm2, allowing for easy disassembly. Microbacterial analysis revealed no penetration of Escherichia coli under static conditions either in the control group or in the prototypes. Under dynamic conditions, however, the prototypes showed significantly reduced bacterial leakage compared to the controls. Conclusions: The data presented here demonstrate that dental implants fabricated with gap-free abutments using a shape memory alloy showed significantly reduced bacterial leakage versus conventional implants. This improvement could minimize clinical problems such as peri-implantitis and consequently enhance the long-term success of dental implants. Keywords: abutment, dental implants, microleakage, nitinol, peri-implantitis, shape memory alloy

Purpose: The purpose of this study was to evaluate and to compare the bone-cutting performance and intraosseous temperature development of three modern ultrasonic devices for bone surgery (UDBS). Materials and Methods: The following UDBS and associated cutting tips (straight bone saws) were used in this study: (1) Piezosurgery II professional, tip OT 7 (Mectron); (2) Piezotome, tip BS 1 (Acteon); and (3) SurgySonic, tip ES007 (American Dental Systems/Günther Jerney). In the experimental setup UDBS, handpieces were immobilized, and bone specimens from the middiaphysis of a bovine femur were moved in a longitudinal direction under the cutting tip to a standardized depth of 3.0 mm. Intraosseous temperature development was measured using a glass-fiber isolated thermocouple. The cutting performance was defined by the time required to reach the cutting depth of 3.0 mm. Statistical analysis was performed using the Wilcoxon rank sum test. Results: The median increase (25th through 75th percentiles) of the local intraosseous temperature was 3.0°C (2.2°C to 4.2°C) for the SurgySonic, 2.2°C (1.8°C to 3.2°C) for the Piezosurgery II, and 1.1°C (0.7°C to 1.6°C) for the Piezotome. The median cutting performance was 0.31 mm/s (0.11 to 0.46 mm/s) for the Piezotome, 0.25 mm/s (0.23 to 0.27 mm/s) for the Piezosurgery II, and 0.04 mm/s (0.03 to 0.05 mm/s) for the SurgySonic. Conclusions: Among the three tested UDBS, the Piezotome and the Piezosurgery II showed a significantly higher cutting performance than the SurgySonic. The Piezotome produced the smallest increase in intraosseous temperature. Keywords: cutting performance, intraosseous temperature development, material testing, ultrasonic bone surgery

Purpose: The aim of this study was to identify risk factors for the development of clinical signs of periimplant mucositis and for the presence of periodontal pathogens and to determine a possible correlation between these clinical signs and the presence of periodontal pathogens. Materials and Methods: In 100 patients, a modified Plaque Index (PI), a modified Sulcular Bleeding Index (BOP), and pocket probing depth (PPD) were recorded. Patients with one implant site that scored positive for PI, BOP, and PPD >= 5 mm were considered to have peri-implant mucositis. A sample taken at the implant with the deepest pocket was analyzed for periodontal pathogens. Implant surface roughness, smoking, augmentation at the implant site, type of dentition, and radiation therapy were recorded as possible cofactors in the disease process. Results: Thirty-one patients showed clinical signs of peri-implant mucositis and, in 25 implant sites, periodontal pathogens were found. Smoking showed a statistically significant correlation with clinical signs of peri-implant mucositis (univariate analysis). For periodontal pathogens at the implant site, the type of dentition was statistically significant. In the multivariate analysis of the clinical signs of peri-implant mucositis, smoking and radiation therapy were significant explanatory variables. Seventy-two percent of the patients showed agreement for finding either clinical signs of peri-implant mucositis and periodontal pathogens or for no clinical signs and no pathogens. The sensitivity for diagnosis of peri-implant mucositis was 45%, and the specificity was 84%. Conclusions: Smoking was the most important risk factor in the formation of peri-implant mucositis. Radiation therapy was an explanatory variable for the occurrence of inflammation. Implant surface roughness, augmentation at the implant site, and type of dentition had little influence on clinical signs of peri-implant mucositis. The type of dentition influences the periodontal microbiota at the implant site. Keywords: dental implants, peri-implant mucositis, periodontal pathogens, risk factors

Purpose: Altering the vertical dimension of occlusion (VDO) by increasing the interarch distance is common in oral rehabilitation, but little is known about the ability of implant patients, who lack sensory perception in implanted regions, to adapt to such changes. This study sought to evaluate the outcome of increasing VDO in patients restored with implant-supported fixed restorations opposed by restored natural teeth or implant-supported restorations. Materials and Methods: VDO was increased by 3 to 5 mm to address the individual prosthetic needs of 30 patients. Group A (control) consisted of 10 patients with fixed restorations on natural dentition that opposed the natural dentition in a new VDO relationship. Two test groups consisted of 10 patients each, with fixed implant-supported restorations opposing either the restored natural dentition (group B) or fixed implant-supported restorations (group C). After an average follow-up of 66 months, marginal bone changes were calculated using standardized periapical radiographs, and mechanical prosthetic maintenance data were collected from patient files. The results were analyzed using Kruskal-Wallis one-way analysis of variance to identify significant differences between the groups. Results: All patients successfully adapted to the new VDO. Two patients in group B and four in group C reported tooth clenching or grinding, which abated after 2 to 3 months (P .05). More bone loss and tooth failures were observed in group A, and more mechanical complications, such as porcelain fractures, were observed in group C (P .05). Conclusion: Within the limitations of this study, alteration of VDO was an acceptable procedure in patients with implantsupported fixed restorations, but precautions should be taken to prevent mechanical problems. Keywords: dental implants, occlusion, teeth, vertical dimension of occlusion

Purpose: The aims of the current study were to: (1) evaluate the results of vertical guided bone regeneration (GBR) with particulate autogenous bone grafts, (2) determine clinically and radiographically the success and survival rates of 82 implants placed in such surgical sites after prosthetic loading for 12 to 72 months, and (3) compare defects that were treated simultaneously with sinus augmentation and vertical GBR to other areas of the jaw treated with vertical GBR only. Materials and Methods: Eighty-two implants were inserted in 35 patients with 36 three-dimensional vertical bone defects. The patients were divided into three groups: single missing teeth (group A), multiple missing teeth (group B), and vertical defects in the posterior maxilla only (group C). All group C subjects were treated simultaneously with sinus and vertical augmentations. All patients were treated with vertical ridge augmentation utilizing titanium-reinforced polytetrafluoroethylene (e-PTFE) membranes and particulated autografts. After removal of the e-PTFE membrane, all sites received a collagen membrane. Results: At membrane removal, mean vertical augmentation was 5.5 mm (± 2.29 mm). Mean combined crestal remodeling was 1.01 mm (± 0.57 mm) at 12 months, which remained stable through the 6-year followup period. There were no statistically significant differences between the three groups in mean marginal bone remodeling. One defect had a bone graft complication (2.78%, 95% CI: 0.00%, 8.15%). The overall implant survival rate was 100% with a cumulative success rate of 94.7%. Conclusions: (1) Vertical augmentation with e-PTFE membranes and particulated autografts is a safe and predictable treatment; (2) success and survival rates of implants placed in vertically augmented bone with the GBR technique appear similar to implants placed in native bone under loading conditions; (3) success and failure rates of implants placed into bone regenerated simultanously with sinus and vertical augmentation techniques compare favorably to those requiring only vertical augmentation. Keywords: autogenous bone graft, barrier membranes, guided bone regeneration, sinus augmentation, vertical ridge augmentation

Purpose: The purpose of the study was to evaluate, using finite element analysis, the stress patterns induced in cortical bone by three distinct implant-supported prosthetic designs. Materials and Methods: The first two models consisted of a prosthesis supported by four implants, the distal two of which were tilted, with different cantilever lengths (5 mm and 15 mm). The third design consisted of a prosthesis supported by five conventionally placed implants and a 15-mm cantilever. Results: In the tilted model with 5-mm cantilever and in the nontilted model, the maximum value of compressive stress (-18 MPa) was found near the cervical area of the distal implant. Higher values for compressive stress were predicted near the cervical area of the distal implant in the tilted model with a 15-mm cantilever, as compared to the tilted model with the 5-mm cantilever. For the tilted model with the 5-mm cantilever, peak values of tensile stress were predicted near the cervical area of both the distal (1.25 MPa) and the mesial implants (2.5 MPa). For the nontilted model, the peak value was found near the cervical area of the in-between implant (5 MPa). For the tilted model with 15-mm cantilever, tensile stress values were higher than in the tilted model with 5-mm cantilever. Conclusions: No significant difference in stress patterns between the tilted 5-mm and the nontilted 15-mm configuration was predicted. The tilted configuration with a 15-mm cantilever was found to induce higher stress values than the tilted configuration with a 5-mm cantilever Keywords: biomechanics, edentulism, finite element analysis, implant-supported prosthesis, tilted implant

Purpose: The literature suggests that predictable integration can be achieved when dental implant placement is combined with immediate fixed provisional restoration in a variety of clinical situations. Fewer data are available, however, regarding outcomes for immediate provisional restoration of implants in the edentulous maxilla. This report presents 1-year data acquired from a long-term prospective clinical trial designed to assess outcomes following the immediate provisional fixed restoration of implants in the atrophic edentulous maxilla without the use of bone augmentation. Materials and Methods: Fifty-one subjects diagnosed with an atrophic edentulous maxilla received a total of 306 implants (six implants per subject) followed by fixed provisional restoration within 24 hours of implant placement. No subjects underwent grafting to enhance bone volume in preparation for implant treatment. Data acquired included bone quantity and quality, implant dimensions, implant locations, and implant placement stability. Subjects returned for 1-year follow-up examinations to assess implant integration and restoration function. Periapical radiographs were obtained and compared to baseline images to assess marginal bone height maintenance. Results: At the 3-month followup examination, 294 of 306 implants placed in 51 subjects were found to be integrated. This represents a cumulative implant survival rate of 96%. At the 1-year follow-up examination, mean marginal bone loss of 0.5 mm was noted, with no further loss of implants. Conclusions: These results support the contention that predictable long-term outcomes may be obtained for the atrophic edentulous maxilla when treated with an implant rehabilitation protocol that includes immediate fixed provisional restoration without the use of bone grafting. This strategy offers a promising treatment alternative for the patient with an atrophic edentulous maxilla. Keywords: dental implants, edentulous maxilla, immediate restoration

Purpose: The aim of this study was to evaluate implant-supported restorations supported by palatally positioned implants as an alternative treatment for rehabilitation of the atrophic maxilla and to assess the satisfaction of patients with the results. Materials and Methods: A retrospective case study was conducted on completely edentulous subjects who received palatally positioned implants (placed and loaded) between January 2000 and January 2004. Inclusion criteria were patients with severely resorbed edentulous maxillae (Class IV or V maxillary atrophy, according to the Cawood and Howell classification) who requested implant-supported restorations and had a follow-up period of at least 24 months after implant loading. Panoramic radiographs and maxillary computerized tomograms had been made for all patients prior to treatment. Mesial and distal implant bone loss was measured on panoramic radiographs, and the largest value was designated as the bone loss for the implant in question. Subjects indicated their degree of satisfaction with the new prosthesis after 12 months on a visual analogue scale. Results: Sixty-nine patients with severely resorbed edentulous maxillae were included in the study. Four hundred and ninety implants (six to eight in each patient) were placed to support 69 fixed prostheses; 330 were in palatal positions and 160 were in molar positions (84 over the crest in the first molar position and 76 in anatomic buttresses). The success rate of palatally positioned implants was 97.8% (323/330). The mean bone loss of implants with palatal anchorage after 2 years of loading was 0.61 mm (range, 0 to 3.10 mm). All patients had stable prostheses at the end of the observation period. Patients were satisfied with comfort and stability, ability to speak, ease of cleaning, esthetics, and function of the prosthesis. Conclusion: Implants placed in a palatal position may be a viable alternative for rehabilitation of the atrophied maxilla. Keywords: dental implants, fixed prosthesis, maxillary atrophy, palatal position, visual analog scale

Purpose: A retrospective study on the performance of endosseous implants in a population of patients with severe epilepsy and additional motor and/or intellectual impairments was performed. Materials and Methods: All residents of an inpatient center for persons affected by severe, refractory epilepsy and multiple disabilities who received endosseous implants between 1991 and April 2007 were included in the study. Implant survival was analyzed using the Kaplan-Meier method. A subset of patients who were treated between 1991 and 2004 was invited to participate in a clinical and radiographic evaluation in 2004 and 2005. Results: A total of 61 patients were treated between 1991 and April 2007 (n = 134 implants). Three of these implants in three different patients failed during the observation period, demonstrating an estimated probability of functional implant survival of 97.6% (SE 1.4%) after 16 years. In patients who were seen during the clinical evaluation in 2004 (n = 76 implants), only mild inflammation of the peri-implant mucosa was generally observed (Gingival-Bleeding Index = 1), despite the fact that the level of oral hygiene was considered inadequate around 55 of 76 implants (72%). Obvious signs of drug-induced gingival hyperplasia in relation to the implants were not observed. Probing depths averaged approximately 2 mm. Stable marginal bone levels were observed on the radiographs. Conclusions: Dental implant treatment in a population of patients with severe epilepsy and additional disabilities seems to be a viable treatment option. Implant loss is rare. Although adequate plaque control was not feasible in all patients, marginal bone levels remained stable. Keywords: dental implants, epilepsy, retrospective study

The aim of this article is to explain the use of a computer-aided three-dimensional planning protocol in combination with previously placed mini-implants and computer-aided design/computer-assisted manufacture (CAD/CAM) technology to restore a completely edentulous patient. Mini-implants were used to establish a setup for computerized tomographic imaging and a surgical template. The software and its three-dimensional simulation allowed the authors to plan ideal implant placement, digitally integrating the future prosthetic and anatomic situations to design the definitive superstructure. The CAD/CAM superstructure is produced digitally with a precise fit and occlusion and good esthetics, and is placed immediately after surgery Keywords: computer-aided design/computer-assisted manufacture, dental implants, guided surgery, immediate loading, mini-implants