Distal Implants Research Articles

Comparison of the Biomechanical Effect of Distal İmplants Placed at Different Angles in the All-On-Four Technique: A Nonlinear Finite Element Analysis: (Effect of Distal Implant Angles in All-on-Four)

IntroductionThe "All-on-four" technique addresses this by placing two vertical implants in the anterior region and two posterior implants angled up to 45 degrees. This study evaluates stress distribution on bone, implants, abutments, gingiva, and prostheses based on posterior implant angulation, using both standard and angled neck implants. Additionally, angled neck implants were used alongside standard implants. MethodsTo evaluate the biomechanical stress and displacement behavior of implants placed at 15°, 30°, 45°, and 30° neck-angled in the interforaminal region of using the All-on-four technique, under a 200N masticatory force on bone, implant, abutment, and prosthesis, using the FEA method with a nonlinear solver. ResultsThe stress values measured in the neck region of the angled implant and abutment placed in the distal region were highest in model IV (305 and 420 MPa), followed model III (282 and 359 MPa), model II (192 and 337 MPa) and lowest in model I (177 and 225 MPa), respectively. The mean elemental von Mises stress in the mandibular bone region where the implant was placed was highest in model I (56 MPa) and lowest in model III (40.4 MPa). ConclusionAs the angle of insertion of the implant into the bone increases, the biomechanical stress value on the implant and abutment also increases. Among the models, the lowest von Mises stress values on the implant and abutment were measured in model I and model II. Models with low stress values can be recommended for patients with clinical conditions and biomechanical risk factors.

Retrospective Radiographic Analysis of Peri-Implant Bone Loss in Mandibular Full-Arch Implant Rehabilitations.

Can the type of implant rehabilitation influence peri-implant bone loss in case of full-arch mandibular prosthesis? The purpose of the study was to assess, using orthopantomograms (OPGs), the bone loss around implants in different types of implant-supported prosthetic rehabilitations and identify potential risk factors, associated with the number and location of implants, that may have an association with bone defects. A radiographic study was conducted on 22,317 OPGs from 2010 to 2024. All OPGs with implant-supported prosthetic mandibular rehabilitations were included in the study. A total of 155 OPGs were evaluated, with peri-implant bone loss identified in 64 (41.3%). Distal implants (furthest from the center) across various positioning patterns were most susceptible to bone loss, with positions 3.6 and 4.6 demonstrating the most frequent occurrence (25 and 26 cases, respectively). The χ2 test revealed significant associations between both the implant positioning pattern (p < 0.001) and number of implants (p < 0.001) with peri-implant bone loss. Also, by updating the sample of OPGs, increased susceptibility to bone resorption was found for implants placed distal to the mental foramen compared to mesial ones in full-arch-implant-supported fixed prostheses. Prospective clinical studies will therefore be useful in investigating this finding further.

A Finite Element Analysis to Study the Stress Distribution on Distal Implants in All-on-Six Treatment Concepts as Affected Tilted and Short Implant.

The number of implants and their respective configurations for implant-supported treatment modalities have been studied for 4 implant-supported prostheses; however, it is not yet clear whether the use of tilting or short implants in rehabilitation would result in substantially improved bone/implant/prosthesis biomechanics in all-on-six concepts. This study compared the biomechanical behavior of tilted long implants and axially short implants to support fixed prostheses in an atrophic maxilla with all-on-six treatment concepts. Three different implant configurations were planned, and six models were obtained with posterior maxilla D3 and D4 bone densities in this study. Implants proper for the all-on-four concept were placed in all models. In models 1 and 2, the short implant was placed; in models 3 and 4, 30°, the mesial-angled implant was placed; and in models 5 and 6, 45°, the mesial-angled implant was placed to the molar region. In the models created, 200 N vertical and 150 N oblique (45° angled buccopalatal direction) forces were implemented to the bilateral tooth regions 4-5-6 on the rigid titanium-supported fixed hybrid prosthesis made on these models. When the stress values in the models were investigated, the oblique forces had higher stress values than the vertical forces did. When the stresses created by oblique forces were assessed, the highest values were observed in the models created with short implants, and the lowest stress values were observed in the models made with 30° angle to mesial. When bone densities were assessed, more stress values were noted in models with D4 bone density. It has been shown that mesial tilted long implants placed in the posterior molar region, in addition to all four implant treatment concepts, create less stress against undesirable oblique forces compared with short implants.

Analysis of the atrophic mandible rehabilitated with fixed total prosthesis on mono or bicortical implants.

Rehabilitation of edentulous atrophic mandibles involves the placement of implants in the anterior segment of the mandible. The primary stability of these implants can be improved using the base of the mandible as complementary anchorage (bicorticalization). This study aimed to analyze the biomechanics of atrophic mandibles rehabilitated with monocortical or bicortical implants. Two three-dimensional virtual models of edentulous mandibles with severe atrophy were prepared. Four monocortical implants were placed in one model (McMM), and four bicortical implants were placed in the other (BcMM). An implant-supported total prosthesis was prepared for each model. Then, a total axial load of 600 N was applied to the posterior teeth, and its effects on the models were analyzed using finite element analysis. The highest compressive stresses were concentrated in the cervical region of the implants in the McMM (-32.562 Mpa); in the BcMM, compressive stresses were distributed in the upper and lower cortex of the mandible, with increased compressive stresses at the distal implants (-63.792 Mpa). Thus, we conclude that axial loading forces are more uniformly distributed in the peri-implant bone when using monocortical implants and concentrated in the apical and cervical regions of the peri-implant bone when using bicortical implants.

Influence of a mesial cantilever on stress, strain, and axial force in fixed partial dentures with a distally tilted implant in the atrophic posterior maxilla.

This study aimed to investigate whether the presence of a mesial cantilever influences the biomechanical behavior and screw loosening in fixed partial dentures (FPDs) with a distally tilted implant in the atrophic posterior maxilla and where to best place the distal implant. Two configurations of implant-supported four-unit FPDs were modelled using finite element analysis. Five interabutment distances were considered. The stress and strain distributions in the implants, abutments, and prosthetic screws were verified under occlusal loading. The development of the axial force on the abutments and screws was also examined. Two-sample t-tests were used to identify differences (P < 0.05). The von Mises stress distributions of the components in the two configurations were similar, as were the maximum plastic strains of the distal prosthetic screws, distal implants, and 30° abutments. The difference in the maximum plastic strains of the straight abutments was statistically significant. The preload of the 30° abutment screws was significantly reduced after the initial loading. In the absence of a mesial cantilever, the axial force on the straight abutments increased. However, when a mesial cantilever was used, the preload of the straight abutments was maintained, and the axial force on the prosthetic screws fluctuated less. The axial force fluctuation of the abutments gradually decreased as the interabutment distance increased. Mesial cantilever usage had minimal effect on stress or strain distribution in FPD implants, abutments, or prostheses. However, it helped resist screw loosening. The distal screw access hole was preferably positioned close to the prosthetic end.

ОБОСНОВАНИЕ ИСПОЛЬЗОВАНИЯ ДОРЗАЛЬНО НАКЛОНЕННЫХ ДИСТАЛЬНЫХ ИСКУССТВЕННЫХ ОПОР ПРОТЯЖЕННЫХ ИМПЛАНТАЦИОННЫХ ПРОТЕЗОВ У ПОЖИЛЫХ ПАЦИЕНТОВ

The subject of the research is implant prosthetics.&#x0D; The goal is to increase the efficiency of implant prosthetics by optimizing the design of the prosthesis.&#x0D; Methodology. 131 patients (57 men and 74 women) aged from 60 to 82 years (mean age 68.3 ± 7.3 years) were examined.&#x0D; The patients were divided into 3 groups: group 1 – 36 patients (14 men and 22 women with an average age of 70.1 ± 5.4 years) with vertical distal implants without dorsal weight; group 2 – 44 people (19 men, 25 women with an average age of 69.4 ± 7.2 years) with inclined distal implants without dorsal weight; group 3 – 51 people (24 men and 27 women with an average age of 68.4 ± 6.8 years) with inclined distal implants, which also carried the dorsal body of the prosthesis with unilateral support on them.&#x0D; The condition of the peri-implant bone was assessed using 16 criteria obtained using clinical and instrumental research methods. The study of the distributions and magnitude of elastic stresses in the peri-implant bone was carried out using mathematical modeling using finite elements.&#x0D; Results. Identical results were obtained for the reaction of the peri-implant bone and mucous membrane of the peri-implant cuff, as well as the levels of preservation of implants and implant prostheses in the long term (2–3 years) in patients with different configurations of the distal parts of extended implant prostheses. Mathematical modeling by the finite element method also showed the non-criticality of the distribution of elastic stresses in the prosthesis, distal implant, compact and cancellous bone with different configurations of the distal parts of the prosthesis.&#x0D; Conclusion. Inclined implants, including those with additional load in the form of a dorsal body with unilateral support, can be quite widely used in elderly patients.

Peri-Implant Bone Loss in Fixed Full-Arch Implant-Supported Mandibular Rehabilitation: A Retrospective Radiographic Analysis

Background: the aim of the study was to assess, through orthopantomograms (OPGs), the existence of peri-implant bone loss of distal implants in implant-supported full-arch mandibular restorations. A comparison between full-arch implant-supported rehabilitations performed in the inter-foraminal region and full-arch rehabilitations that include implant insertion distal to the mental foramen was conducted. Methods: a retrospective observational analysis of 17,950 OPGs from 2010 to 2020 was conducted. The presence of fixed implant-supported prostheses in a fully edentulous mandible was the inclusion criteria of the study. OPGs were divided according to the number of implants (four, six, and eight), position of the implants (mesial or distal to the mental foramen), and positioning patterns (models 1, 2, 3, 4, and 5). Results: a total of 51 OPGs were included in the study, 19 of which showed peri-implant bone loss. In particular, 16 belonged to the six-implant rehabilitation group and 3 to the eight-implant rehabilitation group; none of the four-implant-supported rehabilitations were affected by peri-implant bone loss. In all rehabilitations affected by peri-implant bone loss, the distal implant was the most involved, in particular the implant in positions 36 and 46. Conclusions: implants distal to the mental foramina are more susceptible than mesial implants to bone resorption in full-arch fixed implant-supported prostheses. This significant difference should be investigated further for the presence and synergy of biomechanical factors that could act predominantly in this area, such as mandibular flexure and occlusal loading.

Effect of geometric heterogeneity using an auxiliary device on the accuracy of complete arch implant scanning: An in vitro study of different clinical simulations.

Intraoral scanning of implants supporting complete arch prostheses is limited because of the lack of geometric heterogeneity and unique reference points, creating inherent errors in the image stitching process by the scanner software program. The purpose of this in vitro study was to evaluate the significance of geometric heterogeneity on complete arch implant scanning by using a novel auxiliary geometric device. Three different clinical simulations were tested to assess its significance. The study also assessed whether scans produced using the auxiliary device would meet a clinically acceptable threshold. A total of 60 scans (n=20) were performed using an intraoral scanner in 3 different clinical simulations: 2 parallel implants, 4 parallel implants, and 4 implants with a 30-degree posterior angulation of the distal implants. Scanning alternated between using the auxiliary geometric scanning device (test groups; 4IP+, 4IA+, 2IP+) and not using the device (control groups; 4IP-, 4IA-, 2IP-). A reference scan for each model was prepared from a high precision laboratory scanner. The scans were analyzed for accuracy in 3-dimensional deviation, interimplant distance deviation, and angular deviation by using an inspection software program. The effect of the auxiliary device was statistically analyzed by comparing scans of the same group using the paired t test for normally distributed data and the Wilcoxon Signed Rank test when data were not normally distributed (α=.05). Significant effects of the auxiliary geometric device were found in 3-dimensional, distance and angular deviations (P<.05). Scans performed using the device were significantly more accurate in most implant positions (P<.05). Linear and angular deviations were clinically acceptable for all test groups. However, the deviations were above the clinically acceptable threshold for the control groups. Using an auxiliary geometric device significantly improved scanning accuracy and produced scans with clinically acceptable deviations, while standard digital scans exceeded the accepted clinical threshold.

A Digital and Conventional Approach to the Rehabilitation of Complete Edentulous with a Toronto Infrastructure-Designed Hybrid Prosthesis: a Case Report

This case describes the prosthetic treatment of a completely edentulous patient treated with the "Toronto Bridge" technique, an implant-supported (all-on-four/all-on-five) hybrid prosthesis.&#x0D; A 42-year-old male patient applied to our clinic for aesthetic and functional problems. After clinical and radiographic examination, the all-on-five treatment concept for the edentulous maxilla and an all-on-four treatment concept for the edentulous mandible were planned. In the maxilla, two distal implants were placed at 30-45° angles, and three straight implants were placed in the anterior region. In the mandible, two distal implants were positioned at the anterior to mental foramina at an angle of 30-45°and two straight implants were placed in the anterior region. The digital impressions were taken, and the infrastructures and veneers were designed according to the "Toronto Bridge" protocol. The infrastructures and veneers were fabricated by milling zirconium blocks and cemented. The occlusion was rechecked for any interferences.&#x0D; This case report showed successful results for the all-on-four/five treatment concept "Toronto Bridge" prostheses at a six-month follow-up, and no complications were observed. This case report suggests that the implant-supported prosthetic treatment of a completely edentulous patient treated with the "Toronto Bridge" treatment technique provides esthetics, phonetics, oral hygiene, and oral comfort, which may be an alternative to an acrylic resin or porcelain fused metal fixed restorations.

Experimental study of the distribution of elasticity in the peri-implant bone during prosthetics

The world continues to study the biomechanics of implant dentures and their artifi-cial supports. At the same time, different attitudes to the inclined position of distal im-plants in the bone and their bilateral (mesial and distal) loading were noted. The lack of a unified view of the problem under consideration set us the goal to study in the experi-ment the distribution of stresses in the peri-implant bone in vertical (sheer) and inclined implants with the absence or presence of a distally located prosthesis body of various lengths with one-sided support on these artificial supports. For the experiment, we used mathematical modeling by the finite element method. It was used to study the distribution and magnitude of elastic stresses in the peri-implant bone. As a geometric model, a model of the upper jaw with an implant prosthesis installed on it, based on 4 implants, was used. It should be noted that the increase in stress in the material of the prosthesis and compact bone was not critical and was much less than the ultimate strength of these media when the distal implant was tilted with the presence of a dorsal body with one-sided support on the distal implant. As for the spongy bone, the stresses in it showed no dependence on the position of the implant as a whole and slightly increased with an increase in the mesiodistal length of the dorsal body of the prosthesis with one-sided support. Thus, mathematical modeling by the finite element method showed the uncritical distribution of elastic stresses in the prosthesis, distal im-plant, compact and cancellous bone

Impact of Device Implant Depth After Left Atrial Appendage Occlusion

BackgroundDevice-related thrombus (DRT) remains one of the main concerns after left atrial appendage occlusion (LAAO). Several risk factors have been proposed, but most cannot be modulated. A modifiable factor such as device implantation depth is a potential target to adjust the risk for DRT. ObjectivesThe aim of this study was to assess the impact of LAAO device implantation depth as a predisposing factor for DRT. MethodsThe study included patients who underwent successful LAAO at 9 centers in Europe and Canada. Patients were classified into 2 groups: proximal device implantation (covered pulmonary ridge [PR] in the lobe and disc cohort or <5 mm from the PR in the single-lobe cohort) and distal device implantation (uncovered PR in the disc and lobe cohort and ≥5 mm in the single-lobe cohort). ResultsA total of 1,317 patients were included. Among these, proximal and distal device implantation was achieved in 732 (55%) and 585 (45%) patients, respectively. No differences in procedural outcomes were observed between the groups. At follow-up, patients with proximal implantation had a lower incidence of DRT (2.3%) than those with distal implantation (12.2%) (P < 0.001). Deeper device implantation and a larger uncovered left atrial appendage area were associated with a higher incidence of DRT (P < 0.001), regardless of device type. In multivariable analysis, distal implant (HR: 5.92; 95% CI: 3.39-10.36) and no or single antiplatelet therapy (HR: 1.62; 95% CI: 0.99-2.62) emerged as independent predictors of DRT. ConclusionsLAAO device implantation depth is an independent risk factor for DRT. Deeper device implantation and larger uncovered left atrial appendage areas were associated with a higher incidence of DRT.

Biomechanical comparison of all-on-4 and all-on-5 implant-supported prostheses with alteration of anterior-posterior spread: a three-dimensional finite element analysis.

Introduction: The all-on-4 concept is widely used in clinical practice. However, the biomechanical changes following the alteration of anterior-posterior (AP) spread in all-on-4 implant-supported prostheses have not been extensively studied. Methods: Three-dimensional finite element analysis was used to compare the biomechanical behavior of all-on-4 and all-on-5 implant-supported prostheses with a change in anterior-posterior (AP) spread. A three-dimensional finite element analysis was performed on a geometrical mandible model containing 4 or 5 implants. Four different implant configurations were modeled by varying the angle of inclination of the distal implants (0°and 30°), including all-on-4a, all-on-4b, all-on-5a, and all-on-5b, and a 100 N force was successively applied to the anterior and unilateral posterior teeth to observe and analyze the differences in the biomechanical behavior of each model under the static influence at different position. Results: Adding an anterior implant to the dental arch according to the all-on-4 concept with a distal 30° tilt angle implant exhibited the best biomechanical behavior. However, when the distal implant was implanted axially, there was no significant difference between the all-on-4 and all-on-5 groups. Discussion: In the all-on-5 group, increasing the AP spread with tilted terminal implants showed better biomechanical behavior. It can be concluded that placing an additional implant in the midline of the atrophic edentulous mandible and increasing the AP spread might be beneficial in improving the biomechanical behavior of tilted distal implants.

In Silico Mechanical Effort Analysis of the All-On-4 Design Performed with Platform-Switching Distal Short Dental Implants.

This study evaluated the mechanical behavior of the All-on-4 concept performed with short-length distal implants with platform-switching (PSW) connection by using finite element analysis (FEA). Three models of the All-on-4 configuration were generated in human atrophic mandibles. The models consisted of tilted standard (AO4T; θ = 30°; 11 mm-length), straight standard (AO4S; θ = 0°; 11 mm-length) and straight short (AO4Sh; θ = 0°; 8 mm-length) distal implants. A resultant force of 300 N was performed obliquely in the left side and posterior region of the prosthetic bar. The von Mises equivalent stress (svm) and maximum and minimum principal stresses (smax and smin) were performed at the level of the prosthetic components/implants and peri-implant bone crest, respectively. The AO4S configuration showed the lowest values of svm in the ML and DL abutments (37.53 MPa and 232.77 MPa, respectively) and dental implants (91.53 MPa and 231.21 MPa, respectively). The highest values of smax and smin were noticed in the peri-implant bone crest of the AO4T design. All models presented lower odds of technical failures. The highest odds of peri-implant bone overload may occur when the All-on-4 concept is performed with standard-length 30o-angled distal implants with PSW connection.

Axial versus Tilted Distal Implants in All-on-4 Mandibular Screw-Retained Prosthesis. A Randomized Controlled Trial

Axial versus Tilted Distal Implants in All-on-4 Mandibular Screw-Retained Prosthesis. A Randomized Controlled Trial

Three-Dimensional FEA Analysis of the Stress Distribution on Titanium and Graphene Frameworks Supported by 3 or 6-Implant Models

Titanium is the main component of dental implants. It is also routinely used as a framework material for implant-supported full-arch prostheses due to its low density, biocompatibility, and other mechanical properties. Remarkable mechanical properties such as lesser mass density and higher young's modulus of graphene have gained popularity among scientists, improving the properties of biomedical implants. Thus, our study aimed to compare the outcome through the von Mises stresses generated on All-on-6 and All-on-3 implant models, as well as on the framework, and evaluate the effect of stress patterns on the crestal bone around implants in the mandible. FEA (Finite Element Analysis) study was carried out using edentulous mandible models. Four 3D FEA models with 3 and 6 implants were used (Model 1: Titanium bar-supported 6 straight implants; Model 2: Graphene bar-supported 6 straight implants; Model 3: Titanium bar-supported 3 implants with 30 degrees-tilted; Model 4: Graphene bar-supported 3 implants with 30 degrees-tilted) in order to simulate endosseous implant designs. The implant measuring 4.2 mm in diameter and 11.5 mm in length were used. The most distal implants in the 3-implant models were placed with angulation of 30 degrees; in 6 implants, they were vertically placed. All the models were analyzed for vertical and oblique axis with a single force magnitude of 100 N. In all four implant models and under loading conditions, the peak stress points were always on the neck of the most distal implant. von Mises stresses were within the normal stress range. In a conventional six-straight implant model supported by a titanium framework, the cortical stress in the region of implants was 25.27 MPa, whereas, in the graphene framework, it was 12.18 MPa. Under vertical load, there was a significant difference in the cortical stress around the tilted implants (30 degrees) in the 3-implant system of titanium and graphene frameworks, respectively, 70.31 MPa and 21.27 MPa. The graphene framework demonstrated better results than the titanium framework for the conventional six-implant system under vertical load, achieving stress of 30.09 MPa and 76.60 MPa, respectively. In the case of the 3-implant system, a significant difference in the bar stress was observed between graphene and titanium, respectively, 256.32 MPa and 180.1 MPa of bar stress. Within the limitation of this study, the peri-implant stresses were decreased using graphene framework models. Hence, it was possible to conclude that the best load-bearing capacity results were found in the graphene framework group compared to the titanium framework for All-on-6 and All-on-3 implant models, even though both materials are reliable options used as framework materials in implant-supported full-arch prostheses.

Biomechanical analysis of stress around the tilted implants with different cantilever lengths in all-on-4 concept

BackgroundMany clinical studies have reported the high success rate of the All-on-4 concept. In the present study, we aimed to compare the stress distribution with different tilted distal implants and cantilever lengths in an All-on-4 system using the two-dimensional photoelastic method and to establish the All-on-4 implant photoelastic model by computer-aided design (CAD) and rapid prototyping (RP). MethodsThe data of the human edentulous mandible were acquired by computed tomography (CT). Three human edentulous mandible All-on-4 implant models with different distally inclined implant holes were fabricated using Mimic, Geomagic Studio software, and a light solidifying fast shaping machine. Then the final photoelastic models were established through the traditional method. Each of the three models had four NobelSpeedy Replace implants between the interforaminal regions. The two posterior implants were placed 0, 15, and 45 degrees distally before the mental foramen. The four implants were splinted by wrought cobalt-chromium alloy frameworks. Each of the three photoelastic models was submitted to a 150 N vertical load at five points on the framework: the central fossa of the mandibular first molar, and 0 mm, 5 mm, 10 mm, and 15 mm of the cantilever length. The stress produced in the models was photographed with a digital camera, and the highest value of the stressed fringe pattern was recorded.ResultsThe All-on-4 implant photoelastic model established by CAD and RP was highly controllable and easy to modify. The position and inclination of implants were accurate, and the frameworks could be passively emplaced. The stress values were higher around a single tilted implant compared with the distal implant in All-on-4 with the same inclination. The 0-degree distal implant and 45-degree distal implant demonstrated the highest and lowest stress when loading at the central fossa of the mandibular first molar, respectively. With the same inclination of distal implant, the peri-implant bone stress increased as the length of cantilever increased.ConclusionThe method of establishing the All-on-4 implant photoelastic model by CAD and RP was highly controllable, convenient, fast, and accurate. The tilted implants splinted in the fully fixed prosthesis with reduced cantilever lengths did not increase the stress level compared with the vertical distal implants.And this illustrated that the influence of cantilever on stress distribution was greater than the influence of implant inlination.

The Influence of rhBMP-7 Associated with Nanometric Hydroxyapatite Coatings Titanium Implant on the Osseointegration: A Pre-Clinical Study.

Background: Bioceramic nanometer coatings have been regarded as potential substitutes for plasma-sprayed hydroxyapatite coatings, and the association with bone morphogenetic protein (BMP) is an attempt to achieve faster osseointegration to hasten oral rehabilitation. Objective: This study aimed to investigate the effect of recombinant human bone morphogenetic protein-7 (rhBMP-7) on the osseointegration of titanium implants coated with a thin film surface of hydroxyapatite (HA). Methods: Two implants (n = 24) were placed in each white New Zealand rabbits’ femur (n = 6). Implants were placed in the right femur after standard instrumentation (A and B) and in the left femur after an over-instrumentation (C and D), preventing bone-implant contact. The distal implants were installed associated with rhBMP-7 (groups B [regular instrumentation] and D [over-instrumentation]) and, also, in the absence of without BMP (control groups A [regular instrumentation] and C [over-instrumentation]). After 4 weeks, the animals were euthanized. The bone blocks containing the implants were embedded in methyl methacrylate and sectioned parallel to the long axis of the implant, which were analyzed by image segmentation. The data were analyzed using a nonparametric statistical method. Results: We observed that Group A had a mean bone formation of 35.6% compared to Group B, which had 48.6% (p > 0.05). Moreover, this group showed 28.3% of connective tissue compared to Group A, with 39.3%. In the over-instrumented groups, rhBMP-7 (Group D) showed an enhanced and significant increase in bone formation when compared with the group without rhBMP-7 (Group C). Conclusion: We concluded that the association of rhBMP-7 to thin nanostructure HA-coated implants promoted greater new bone area than the same implants in the absence of rhBMP-7, mainly in cases of over-instrumented implant sites.

How do implant threads and diameters affect the all-on-four success? A 3D finite element analysis study

The effect of different thread designs and diameters on the all-on-four concept is unclear. The aim of the study was to clarify the differences in stress distribution of dental implants with various thread designs and diameters based on the all-on-four concept with three dimensional (3D) finite element analysis (FEA). A 3D model of a totally edentulous mandible was used to perform the FEA. Four different models (M1, M2, M3, and M4) including 3.5 and 4.3 mm diameter dental implants with active and passive threaded designs were generated. The dental implants were positioned according to the all-on-four concept. The Von Mises stresses on dental implants and maximum and minimum principal stresses (Pmax and Pmin) on bony structures were calculated under vertical, oblique and horizontal loads. For Von Mises stresses, the highest stress values were detected on the distal implants for all models. Distal implants had also the highest stress values for vertical loading. The Von Mises stresses were found to be concentrated around the implant's neck. In all models the highest Pmax and Pmin stresses occurred in the bone surrounding the distal implant. It was noted that the active threaded implants showed the highest Pmax and Pmin stress values. The implant thread design and diameter might have a strong influence on the stress values in the all-on-four concept.

The effect of mandibular flexure on the design of implant-supported fixed restorations of different facial types under two loading conditions by three-dimensional finite element analysis.

Objective: Investigating the biomechanical effects of mandibular flexure (MF) on the design of implant-supported fixed restorations in edentulous jaws of different facial types. Methods: Three-dimensional finite element models were established to analyze mandibular displacement and stress distribution of implant-supported fixed restorations (four or six implants, different implant numbers and sites, and the design of the superstructure across the dental arch in one or two or three pieces, under the loading conditions of maximum opening or right unilateral molar occlusion) in mandibular edentulous patients of three different facial types (brachyfacial, mesofacial, and dolichofacial types). Results: The brachyfacial type presented higher mandibular flexure and stress in the overall restorative system, followed by the mesofacial and dolichofacial types. During jaw opening and occlusal movements, the one-piece framework showed the lowest bone stress values surrounding the anterior implants and gradually increased to the distal position, and the three-piece framework showed the highest stress values for peri-implant bones. Also, the split framework could greatly increase the stress on abutments and frameworks. Moreover, fixed implant prostheses with cantilevers can generate high amounts of biomechanical stress and strain on implants and surrounding bones. The bone surrounding the anterior implant increased in stress values as the most distal implants were more distally located regardless of frameworks. The zirconia framework demonstrated higher stresses than the titanium framework. Conclusion: The design of edentulous fixed implant-supported restorations can be optimized for facial types. For patients of the brachyfacial type or with high masticatory muscle strength, the non-segmented framework without a cantilever provides an optimal biomechanical environment.

Biomechanical comparison of four treatment models for the totally edentulous maxilla: a finite element analysis

The aim of this study is to evaluate by finite element analysis different techniques of totally edentulous maxilla rehabilitation, considering implants, bone tissue, metallic infra-structure, and prosthetic abutments characteristics, by means of a three-dimensional model. Stress distribution on bone tissue, implants, and abutments was analyzed with four configurations (six implants axially installed, all-on-four technique, M-4 technique, and four conventional implants with two zygomatic implants). Greater tension on bone tissue were found around distal implants, in all treatment groups, but not exceeding resistance limits of cortical bone. Von Mises stress was higher on the distal region of distal implants of all-on-four and M-4 techniques. Higher stress concentration was seen on angled abutments of zygomatic implants. The highest values of minimal compression stresses were concentrated on peri implant-bone tissue, especially in the model of All-on-4. Therefore, the present finite element analysis revealed that the four configurations of treatment (six implants axially installed, all-on-four technique, M-4 technique, and four conventional implants with two zygomatic implants) for the totally edentulous maxilla are feasible and safe, from a biomechanical point of view.