A Retrospective Multicentric Study of 52 Nasal and Trans-nasal Implants in 31 Severe Atrophic Patients to Reduce Anterior Cantilever Bending in Full Arch Implant-supported Fixed Rehabilitation.

PURPOSE: Severe anterior maxillary atrophy offers few implant-supported rehabilitation solutions to Quad Zygoma characterized by a wide anterior cantilever. One of the possible alternatives to consider before the quad zygoma is the extra-long nasal/trans-nasal implant placement. This retrospective multicentric study shows the predictability of nasal/transnasal implant placement in patients affected by severe anterior maxilla atrophy, with residual anatomical features that indicate this surgery. This specific remote anchorage can often be safely involved in immediate loading with other remote anchorages, such as zygoma and pterygoid implants. In this rehabilitation, it's mandatory to reduce the instability of the frameworks and mechanical stress that could unfavorably affect the implant's prognosis due to the overloading derived from anterior bending. MATERIALS AND METHODS: In this retrospective multicentric study, 52 nasal or trans-nasal implants were inserted in 31 atrophic anterior maxillas (Cawood and Howell's class V-VI). All implants were successful after the healing period; even if 27 nasal implants reached an insertional torque equal to or greater than 50 n/cm2, the threshold value estimated to be able to support an immediate load. RESULT: All 52 implants were successful, so the proportion of success was 100%, with a 97.5% one-sided confidence interval of 88.8-100%. The success rate is achieved only if at least two of the following criteria are met: 1) a greater torque than 50 Ncm as a minimum sufficient condition to plan immediate loading; 2) after a healing period of 16 weeks, the secondary stability is clinically and radiographically evaluated to exclude possible coronal bone resorption: this condition allows the successive prosthetic finalization; 3) the possibility of carrying out a full arch rehabilitation with minimal anterior spread. Insertion torque was <50 Newton centimeters (Ncm) in 14 patients (45%) and 50 Ncm in 17 (55%). Mechanical load was delayed in the former and immediate in the latter. The proportion of torque <50 Ncm was higher in men than in women (69% versus 28%, p=0.033). Immediate torque was not significantly affected by age. CONCLUSION: Although the sample is not extremely numerically significant, it conveys a clear and significant clinical, surgical indication as never before in the literature; we can state that nasal/trans nasal implants have been very useful in reducing the anterior cantilever and overcoming the anatomical limitations affecting conventional Quad Zygoma.

Five Steps for the Maintenance and Interception of Complications in Zygomatic Implants.

Zygomatic implants are used for the rehabilitation of the upper jaw of patients with severe and moderate bone atrophy. Possible post-surgical complications include soft tissue dehiscence, sinusitis, and prosthodontic fractures, and maintaining an accurate control is crucial. Additionally, zygomatic implants have a unique peri-implant anatomy, making traditional periodontal parameters unsuitable. The present paper aims to provide guidelines for the maintenance and interception of complications in patients rehabilitated with these kinds of implants. The proposed protocol includes: 1. intra/extraoral and temporo-mandibular joint examination; 2. soft tissue and transmucosal path observation with magnifiers; 3. peri-implant health indices and digital stimulation of tissues; 4. examination of prosthodontic devices; and 5. photographic recording. These steps facilitate the comprehensive evaluation and monitoring of clinical conditions of zygomatic-supported rehabilitations, including dehiscence and occlusal wear during follow-up appointments.

Immediate Versus Delayed Loading of Dental Implants Supporting Fixed Full-Arch Maxillary Prostheses: A 10-year Follow-up Report.

PURPOSE: To compare clinical outcomes of immediate vs delayed implant loading in edentulous maxillae with full-arch fixed prostheses. MATERIALS AND METHODS: Two patient groups were identified for this study: (1) the test group (TG), which included 34 patients (19 women, 15 men; mean age 56.7 years) treated with the Columbus Bridge Protocol with 4 to 6 postextractive implants loaded within 24 hours (163 implants total); and (2) the control group (CG), which included 15 patients (6 women, 9 men; mean age 59.96 years) treated with a traditional two-stage delayed loading rehabilitation using 6 to 9 implants inserted in healed sites (97 implants total). All patients were rehabilitated with full-arch fixed prostheses in the maxilla. RESULTS: At the 10-year follow-up, no difference in the implant cumulative survival rate between the TG (93.25%) and CG (94.85%) was found. Mean bone loss was significantly lower in the TG (mean: 2.11 mm) compared to the CG (mean: 2.65 mm). All original prostheses were maintained and functioning satisfactorily. CONCLUSION: Maxillary full-arch immediate loading represents a valid alternative to the traditional delayed loading rehabilitation.

Analysis of Different Impression Techniques and Materials on Multiple Implants Through 3-Dimensional Laser Scanner.

OBJECTIVE: The aim of this study was to evaluate the accuracy of 7 different implant impression techniques for full-arch prostheses. MATERIALS AND METHODS: A master cast simulating an edentulous arch with 4 implants was used. Seven impression techniques were tested: open tray with polyether Impregum (OTI); open tray with splint-polyether Impregum (OTSI); closed tray with polyether Impregum; open tray with polyether Ramitec; open tray with splint-polyether Ramitec; closed tray with polyether Ramitec (CTR); open tray with impression plaster (OTP). Five impressions of the master cast were taken for each technique using an impression simulator device. Casts were realized based on those impressions (n = 35). Median values of deviation from the master cast were recorded for each cast through a 3-dimensional laser scanner. RESULTS: Only OTI (P = 0.028) and OTSI (P < 0.001) presented a statistically significant difference compared to the master cast. OTP (P = 0.99) and CTR (P = 0.10) showed median values of deviation close to zero (-0.001 and -0.003 mm, respectively). CONCLUSION: Stiff impression materials (such as plaster or rigid polyether) guarantee greater accuracy in cases of multiple implant impressions of patients with full-arch rehabilitations. Splinting of impression copings with acrylic resin did not improve accuracy.

Dictionary-Driven Ischemia Detection From Cardiac Phase-Resolved Myocardial BOLD MRI at Rest.

Cardiac Phase-resolved Blood-Oxygen-Level Dependent (CP-BOLD) MRI provides a unique opportunity to image an ongoing ischemia at rest. However, it requires post-processing to evaluate the extent of ischemia. To address this, here we propose an unsupervised ischemia detection (UID) method which relies on the inherent spatio-temporal correlation between oxygenation and wall motion to formalize a joint learning and detection problem based on dictionary decomposition. Considering input data of a single subject, it treats ischemia as an anomaly and iteratively learns dictionaries to represent only normal observations (corresponding to myocardial territories remote to ischemia). Anomaly detection is based on a modified version of One-class Support Vector Machines (OCSVM) to regulate directly the margins by incorporating the dictionary-based representation errors. A measure of ischemic extent (IE) is estimated, reflecting the relative portion of the myocardium affected by ischemia. For visualization purposes an ischemia likelihood map is created by estimating posterior probabilities from the OCSVM outputs, thus obtaining how likely the classification is correct. UID is evaluated on synthetic data and in a 2D CP-BOLD data set from a canine experimental model emulating acute coronary syndromes. Comparing early ischemic territories identified with UID against infarct territories (after several hours of ischemia), we find that IE, as measured by UID, is highly correlated (Pearson's r=0.84) with respect to infarct size. When advances in automated registration and segmentation of CP-BOLD images and full coverage 3D acquisitions become available, we hope that this method can enable pixel-level assessment of ischemia with this truly non-invasive imaging technique.

A Luting Technique for Passive Fit of Implant-Supported Fixed Dentures.

Several factors contribute to distortion of implant prostheses during fabrication and could prevent passive, accurate adaptation between implants and implant frameworks. The misfit between implants and restorative components may be significant and possibly lead to biologic or mechanical complications. The aim of this article is to describe a laboratory luting technique used to lute implant cylinders to metal frameworks in implant prostheses. This technique provides accurate, passive fits. According to this technique, titanium implant cylinders provided with corresponding external castable cylinders are used. Implant cylinders are screwed into the analogs in the master cast while the castable cylinders on top are splinted together using castable resin to realize a castable resin pattern. After casting, the framework is adjusted and cemented to the titanium cylinders on the master cast. Due to its ease and quickness of use and clinical efficiencies, this technique is deemed particularly useful in immediate loading rehabilitations.

Effect of Framework in an Implant-Supported Full-Arch Fixed Prosthesis: 3D Finite Element Analysis.

PURPOSE: The aim of this study was to analyze through a three-dimensional finite element analysis (3D-FEA) stress distribution on four implants supporting a full-arch implant-supported fixed prosthesis (FFP) using different prosthesis designs. MATERIALS AND METHODS: A 3D edentulous maxillary model was created and four implants were virtually placed into the maxilla and splinted, simulating an FFP without framework, with a cast metal framework, and with a carbon fiber framework. An occlusal load of 150 N was applied, stresses were transmitted into peri-implant bone, and prosthodontic components were recorded. RESULTS: 3D-FEA revealed higher stresses on the implants (up to +55.16%), on peri-implant bone (up to +56.93%), and in the prosthesis (up to +70.71%) when the full-acrylic prosthesis was simulated. The prosthesis with a carbon fiber framework showed an intermediate behavior between that of the other two configurations. CONCLUSION: This study suggests that the presence of a rigid framework in full-arch fixed prostheses provides a better load distribution that decreases the maximum values of stress at the levels of implants, prosthesis, and maxillary bone.

Brånemark Novum® immediate loading rehabilitation of edentulous mandibles: 11-year retrospective study.

OBJECTIVES: Short-term results indicated that the Brånemark Novum® protocol (Nobel Biocare AB, Goteborg, Sweden) allowed successful rehabilitation of mandibular edentulism with immediately loaded implants. Yet, long-term studies are lacking. The aim of the present retrospective study was to report the 11-year outcomes for patients treated according to this protocol. MATERIAL AND METHODS: Four patients treated according to the Brånemark Novum protocol (Nobel Biocare AB) were followed-up to evaluate implant and prosthesis cumulative survival rate (CSR), implant stability (RFA), marginal bone loss by periapical radiographs, probing depth (PD), and possible complications. Clinical and radiographic parameters were evaluated immediately after completion of the treatment and 1, 5, and 11 years after loading. RESULTS: The 11-year implant and prosthesis CSRs were 100%. Implant stability (RFA values) remained stable over the 11-year follow-up. Small bone resorption was found next to distal implants (median 1 mm) after 11 years, while central implants showed greater bone resorption (median 4.5 mm). The PD (mean 3.75 mm at 11 years) grew together with marginal bone loss. One implant complication was detected on a central implant (crater-form bone destruction), and 10 prosthetic complications (fractures of resin or teeth), 80% of which registered on the same parafunctional patient. CONCLUSIONS: The 11-year results demonstrated that the Brånemark Novum protocol (Nobel Biocare AB) is a predictable technique with favorable long-term outcomes. This was a rigid protocol, which could be applied only in patients with specific anatomical characteristics of the lower jaw, but it had the merit of indicating the key factors for full-arch immediate loading rehabilitations.

Single-image super-resolution via linear mapping of interpolated self-examples.

This paper presents a novel example-based single-image superresolution procedure that upscales to high-resolution (HR) a given low-resolution (LR) input image without relying on an external dictionary of image examples. The dictionary instead is built from the LR input image itself, by generating a double pyramid of recursively scaled, and subsequently interpolated, images, from which self-examples are extracted. The upscaling procedure is multipass, i.e., the output image is constructed by means of gradual increases, and consists in learning special linear mapping functions on this double pyramid, as many as the number of patches in the current image to upscale. More precisely, for each LR patch, similar self-examples are found, and, because of them, a linear function is learned to directly map it into its HR version. Iterative back projection is also employed to ensure consistency at each pass of the procedure. Extensive experiments and comparisons with other state-of-the-art methods, based both on external and internal dictionaries, show that our algorithm can produce visually pleasant upscalings, with sharp edges and well reconstructed details. Moreover, when considering objective metrics, such as Peak signal-to-noise ratio and Structural similarity, our method turns out to give the best performance.

Factors affecting the outcome in the immediate loading rehabilitation of the maxilla: a 6-year prospective study.

This prospective study reports the 6-year outcomes for patients rehabilitated with an immediate loading protocol of the maxilla (Columbus Bridge Protocol). In this study, 164 implants were inserted in 37 patients and loaded within 24 to 36 hours. Four implants failed during the first 6 months. At the 6-year follow-up, a mean bone loss of 1.52 mm was found. Significantly (P < .0083) less bone loss was found next to tapered implants compared with cylindric implants and next to machined collar implants compared with full acid-etched implants (P < .0083). No significant differences in bone loss were found in tilted versus upright implants or in mesial versus distal implant sites. In addition, there were no significant differences relating to either the degree of abutment angulation or the reason for tooth loss.

Immediate versus delayed loading of dental implants in edentulous patients' maxillae: a 6-year prospective study.

PURPOSE: This study compared the surgical protocol efficacy of immediate and delayed implant loading in edentulous maxillae opposed by natural or restored mandibular dentitions over an observational period of 6 years or longer. The selected outcome determinants included individual implant survival data, progressive measurements of peri-implant bone resorption, prosthodontic survival and success data, and report of complications. MATERIALS AND METHODS: A convenience sample of 49 patients requiring fixed implant-supported maxillary prostheses was split into two groups. The test group (34 patients) was treated according to the Columbus Bridge Protocol, which prescribes the insertion of four to six implants, including distally tilted implants, and load within 24 hours. The control group (15 patients) was treated via a two-stage surgical protocol of 6 to 9 straight implants that were loaded a mean 8.75 months after stage-one implant surgery. Two hundred sixty implants (test: n = 163, control: n = 97) were placed, and all subjects were ultimately treated with screw-retained full-arch prostheses. RESULTS: Two patients dropped out (one in the test group and one in the control group) by the time of the scheduled sixth annual visit. The other patients were followed up for 75.2 months (range: 72 to 90 months). At the 6-year follow-up, no differences in implant cumulative survival rates were found between groups. Significantly less bone loss was found in the test group (mean: 1.62 mm) compared with the control group (mean: 2.44 mm). All of the original prostheses were maintained throughout the study's observation period and were functioning satisfactorily at each patient's last recall appointment. CONCLUSION: Patients who received immediate and delayed implant loading in their edentulous maxillae demonstrated similar survival outcomes. However, less marginal bone loss was recorded around the immediately loaded implants over the study's 6-year follow-up period.

Peri-implantitis: a systematic review of recently published papers.

PURPOSE: This systematic review considers possible etiologic factors and definitions of peri-implantitis as reported in the recent literature. MATERIALS AND METHODS: An electronic search of databases plus a hand search of the most relevant journals published between January 2005 and September 2012 were performed. RESULTS: The electronic and manual searches yielded 640 and 14 titles, respectively. From the independent doublecheck of the titles and abstracts, 24 full texts were downloaded (18 clinical studies and 6 animal studies). After reading the full texts, 10 articles (4 clinical studies and 6 animal studies) were included in this review. None of the human articles selected provided sufficient evidence to address the research question, and no human clinical evidence is available to support a cause-effect relationship between peri-implantitis and bacterial accumulation and/or occlusal overload. The animal literature is also not unanimous regarding a specific peri-implantitis etiology. However, a correlation between periodontitis and smoking histories was cited as contributing to a higher incidence of peri-implantitis. CONCLUSION: The available scientific literature is characterized by an absence of a unanimous consensus regarding the etiology of peri-implantitis and its specific relationship to periodontitis. Furthermore, both the choice of the term peri-implantitis and its definition remain controversial.

Shock absorption capacity of restorative materials for dental implant prostheses: an in vitro study.

PURPOSE: To measure the vertical occlusal forces transmitted through crowns made of different restorative materials onto simulated peri-implant bone. MATERIALS AND METHODS: The study was conducted using a masticatory robot that is able to reproduce the mandibular movements and forces exerted during mastication. During robot mastication, the forces transmitted onto the simulated peri-implant bone were recorded using nine different restorative materials for the simulated single crown: zirconia, two glass-ceramics, a gold alloy, three composite resins, and two acrylic resins. Three identical sample crowns for each material were used. Each crown was placed under 100 masticatory cycles, occluding with the flat upper surface of the robot to evaluate the vertical forces transmitted. Two-way analysis of variance was used. Alpha was set at .05. RESULTS: The statistical evaluation of the force peaks recorded on the vertical z-axis showed mean values of 641.8 N for zirconia; 484.5 N and 344.5 N, respectively, for the two glass-ceramics; 344.8 N for gold alloy; 293.6 N, 236 N, and 187.4 N, respectively, for the three composite resins; and 39.3 N and 28.3 N, respectively, for the two acrylic resins. Significant differences were found between materials (P < .0001), except for the comparison between gold alloy and one of the glass-ceramics. CONCLUSION: Composite and above all acrylic resin crowns were more able to absorb shock from occlusal forces than crowns made of zirconia, ceramic material, or gold alloy.

Immediate versus delayed loading of dental implants in edentulous maxillae: a 36-month prospective study.

PURPOSE: The aim of this study was to compare survival rates and radiographic outcomes of immediate and delayed implant loading in edentulous maxillae. MATERIALS AND METHODS: Forty-nine patients in need of maxillary full-arch treatment were randomized into two groups: test group (n = 34) treated following the Columbus Bridge Protocol with 4 to 6 implants loaded within 24 hours and a control group (n = 15) treated following the ad modum Branemark protocol with 6 to 9 implants loaded a mean 8.75 months after surgery. Two hundred sixty implants (test: n = 163, control: n = 97) were placed, and subjects were treated with screw-retained full-arch prostheses. Bone levels were measured at baseline and at 1, 2, and 3 years and analyzed using repeated-measures analysis of variance. RESULTS: All patients appeared at all scheduled recall visits. No differences in cumulative survival rates were found between groups at 36 months. Ten implants (6.1%) failed in the test group; four (4.1%) failed in the control group. At 36 months, no prosthetic failures were detected. Significantly less bone loss was found in the test group at all time intervals (P < .001). The average bone level from the implant-abutment connection was 1.3 mm in the test group and 1.9 mm in the control group at 12 months, 1.5 mm and 2.2 mm at 24 months, and 1.6 mm and 2.3 mm at 36 months, respectively. CONCLUSION: In the edentulous maxilla, the Columbus Bridge Protocol involving immediate loading of implants placed in both healed and fresh extraction sites exhibited equivalent implant survival and less marginal bone loss at 3 years compared to the conventional two-stage delayed loading protocol. Int J Prosthodont 2011;24:294-302.

The influence of cantilever length and implant inclination on stress distribution in maxillary implant-supported fixed dentures.

STATEMENT OF PROBLEM: The benefits and limitations of jaw treatments with tilted versus vertical implants, as well as prosthesis design with and without posterior cantilevers, have been extensively discussed. However, biomechanical advantages associated with cantilevers in fixed dentures (FDs) and tilted implants in the maxillae are less well documented. PURPOSE: The purpose of this study was to compare and analyze, via 3-dimensional (3-D) finite element analysis, stresses transmitted to tilted versus vertical implants and the surrounding periimplant bone in the maxillae. MATERIAL AND METHODS: A 3-D edentulous maxillary model was created using customized computer software (FEMAP 8.3). Four implants were virtually placed in the premaxilla and splinted with an FD. Keeping the prosthesis length constant, 4 different configurations were evaluated with the distal implants inclined 0, 15, 30, and 45 degrees; cantilever extensions were 13, 9, 5, and 0 mm, respectively. A vertical load (150 N) was applied to the distal portion of the posterior cantilevers. Von Mises' stress values transmitted to periimplant bone and at the metal framework of FDs on implants were evaluated in cancellous and cortical bone. RESULTS: The maximum stresses recorded in periimplant bone for the vertical implants were 75.0 MPa (distal implants), 35.0 MPa (mesial implants), and 95.0 MPa for the metal frameworks. Tilted distal implants, with consequent reduction of the posterior cantilevers, resulted in decreased stress values for all of the variables: -12.9%, -18.3%, and -11.5% for the 15-degree configuration; -47.5%, -52.6%, and -31.3% for the 30-degree configuration; and -73.5%, -77.7%, and -85.6% for the 45-degree configuration CONCLUSIONS: Finite element analysis data regarding rehabilitation of atrophic maxillae revealed that tilted distal implants, rigidly splinted with an FD, decrease stress in the periimplant bone and frameworks. This treatment modality seems to be a valid therapeutic alternative to conventional maxillary fixed complete prostheses supported by vertical dental implants with posterior cantilevers.

The use of a masticatory robot to analyze the shock absorption capacity of different restorative materials for prosthetic implants: a preliminary report.

PURPOSE: This study was conducted to measure, in vitro, the chewing load forces transmitted through crowns made of different prosthetic restorative materials onto dental implants. MATERIALS AND METHODS: A masticatory robot capable of reproducing the mandibular movements and the forces exerted during chewing was used. The forces transmitted to the simulated peri-implant bone during the robot mastication were analyzed using four different occlusal materials: three resin composites and one glass ceramic crown. RESULTS: The ceramic crowns transmitted significantly greater forces (up to +63.06%, P < .0001) than the composite crowns tested. CONCLUSION: Composite crowns are better able to absorb shock from occlusal forces than crowns made of ceramic material.

Immediate function with fixed implant-supported maxillary dentures: a 12-month pilot study.

STATEMENT OF PROBLEM: Immediate occlusal loading of dental implants in the edentulous mandible has proven to be an effective, reliable, and predictable procedure. There is little long-term data available on similar treatments in the edentulous maxilla. PURPOSE: The purpose of this study was to evaluate the 12-month implant survival after immediate loading of 4 to 6 implants with fixed screw-retained prostheses in edentulous maxillae. MATERIAL AND METHODS: Twenty-one patients, edentulous or with remaining teeth to be extracted in the maxilla, received 4 to 6 implants (n=111). The patients were restored with screw-retained fixed provisional prostheses supported by palladium-alloy frameworks within 24 hours after surgery. Insertion torques for implants were at least 40 Ncm. Implants, grouped as tapered or cylindrical screws, were placed in healed bone or extraction sockets. Implants were also classified as either vertical or off-angle. Definitive prostheses were placed after a mean healing time of 18 weeks. Radiographic examinations were made at the time of placement of provisional prostheses and 12 months later. Between-groups bone resorption was compared using 2-way ANOVA (alpha=.05). RESULTS: The mean follow-up time for all of the patients was 20 months (range, 13 to 28 months). The cumulative implant survival rate at the 12-month follow-up visits (after surgery) was 92.8%; the prostheses survival rate was 100%. No significant differences were found between the survival of tapered or cylindrical screw-type implants placed in postextraction sockets versus those in healed edentulous sites or between vertical and off-angle placed implants. Eight implants failed during the first 3 months, 5 of which were the most distal implants. The mean reduction in marginal bone height over the 12-month observation period was 0.84 mm (CI 95%; 0.68-0.99 mm). CONCLUSIONS: In this study with 12-month follow-up, 4 to 6 implants were sufficient to successfully support fixed implant screw-retained prostheses in the edentulous maxillae of 21 patients.

Robotic chewing simulator for dental materials testing on a sensor-equipped implant setup.

PURPOSE: This study describes a mechanical chewing simulator that is able to reproduce mandibular movements in 3 dimensions and the forces exerted during mastication. The aim of this work was to validate the described device, which can be used to test the ability of different restorative materials to withstand stress. MATERIALS AND METHODS: To validate the masticatory robot, 5 identical samples for each of 3 different restorative materials (an acrylic resin, a composite resin, and a glass ceramic) were created. Each sample underwent 5 minutes of chewing in the robot. The forces transmitted to the simulated peri-implant bone were collected. Two-way analysis of variance was used to evaluate the results. RESULTS: There were significant differences between the materials, and internal comparisons also showed significant differences (P < .0001). CONCLUSION: The different elastic moduli of the restorative materials significantly affected stress transmission at the simulated bone-implant interface, and the masticatory robot was able to identify this difference. The very low levels of variation confirm the precision of the machine during data collection and validate the reliability of the method, showing effective repeatability of the tests.

Three-dimensional finite element analysis of load transmission using different implant inclinations and cantilever lengths.

Many clinical studies have reported high survival rates for tilted implants. However, tilted implants transmit increased stress to bone when compared to vertically placed implants. Theoretical (computer-based), laboratory, and clinical studies are warranted to effectively address this issue. In this study, a 3-dimensional finite element analysis was performed to analyze the stress values surrounding tilted versus vertical implants. The results revealed laboratory and biomechanical evidence that distal tilting of implants, splinted in full fixed prostheses without cantilevers, reduced the amount of stress generated around the peri-implant bone when compared to the levels of stress seen in peri-implant bone with vertical implants and cantilevered segments in similar full fixed prostheses.