Prosthetic Platform Research Articles

Influence of implant shape and prosthetic platform on cervical bone resorption: A systematic review

Purpose: The purpose of this systematic review was to critically evaluate the existing literature and answer the question, “Which implant format and prosthetic platform promotes the least cervical resorption?”. Material and method: SCOPUS, PubMed/Medline, Web of Science, EMBASE, Lilacs, and Google Scholar databases were searched in September 2023. Results: The database search resulted in 2850 articles. Of the 12 articles selected for full reading, 2 remained in this systematic review. There is a lack of information to form an opinion and to perform statistical analysis of the data, so descriptive analysis was performed. Conclusions: Based on the studies included in this systematic review, the implant shape influences primary stability and osseointegration, but it is not yet possible to relate it directly to POC. However, the type of prosthetic platform has a direct influence. In addition to the type of prosthetic platform used, the various characteristics related to the shape of the implant must be considered to maintain satisfactory bone levels.

Clinical Application of Angulated Prosthetic Platform Implants: A Retrospective Study.

This retrospective study reports on the survival of two-piece angulated prosthetic platform (APP) implants consecutively placed at a specialist periodontics clinic with a mean follow-up of 28.2 ± 15.6 months (range: 4.0 to 71.0). For 183 returning patients who received 239 implants, the survival rates at follow-up (up to 71 months) were 99.2% and 91.1% at the patient and implant levels, respectively. A majority of patients were nonsmokers and did not have diabetes, with a quarter having a history of treated periodontitis. Eighty percent of patients received a single APP implant. Of the implants, 63% supported a single crown, 28% a fixed partial denture, and 9% a fixed complete denture. Nearly all implants were placed either at tooth extraction or after complete bone healing, in approximately equal numbers. Of the implant sites, approximately 75% received bone grafting, with approximately 25% receiving adjunct soft tissue grafting. For 210 surviving and restored implants with satisfactory intraoral radiographs taken at the last recall (mean follow-up: 28.4 ± 15.5 months; range: 4.0 to 71.0 months), the mean radiographic bone levels were -0.70 ± 0.87 mm (range: -3.60 to 2.15 mm). The results demonstrated clinically successful use of this unique geometry implant for multiple applications with acceptable short- to medium-term clinical outcomes.

Influence of Torque on Platform Deformity of the Tri-Channel Implant: Two- and Three-Dimensional Analysis Using Micro-Computed Tomography.

Background and Objectives: The insertion of the dental implant in the bone is an essential step in prosthetic rehabilitation. The insertion torque has the potential to distort the prosthetic platform, which can cause future biomechanical problems with the continuous action of occlusal forces. The aim of this study is to evaluate different insertion torques in the deformation of tri-channel platform connections through two- and three-dimensional measurements with micro-CT. Materials and Methods: A total of 164 implants were divided into groups (platform diameter and type): 3.5, 3.75, and 4.3 mm NP (narrow platform), and 4.3 mm RP (regular platform). Each implant-platform group was then divided into four subgroups (n = 10) with different torques: T45 (45 Ncm), T80 (80 Ncm), T120 (120 Ncm), and T150 (150 Ncm). The implant-abutment-screw assemblies were scanned and the images obtained were analyzed. Results: A significant difference was observed for the linear and volume measures between the different platforms (p < 0.01) and the different implant insertion torques (p < 0.01). Qualitative analysis suggested a higher deformation resistance for the 3.75 NP compared to the 3.5 NP, and RP was more resistant compared to the NP. Conclusions: The 0.25 mm increment in the implant platform did not increase the resistance to the applied insertion torques; the 4.3 mm implant was significantly stronger compared to the 3.5 mm implant; and the proposed micro-CT analysis was considered valid for both the 2D and 3D analyses of micro-gaps, qualitatively and quantitatively.

Failed Dental Implant: When Titanium Fractures.

Despite the widespread use of titanium implants in orthopedic and dental surgeries, concerns have recently emerged regarding potential deformations and fractures after osseointegration. In a recent clinical case, a titanium implant fractured after successful osseointegration. This fracture occurred despite the absence of any significant trauma or excessive external force applied to the area. The fracture was attributed to a combination of factors, including abutment design flaws, material fatigue, and biomechanical stress imposed on the implant during functional loading. This raises concerns about the long-term durability and reliability of titanium implants, particularly in high-stress areas such as the posterior region or weight-bearing bones. An image was made with scanning electron microscopy showing the fracture region near the prosthetic platform and highlighting the knowledge that despite their ductility, titanium implants can fracture.

Assessing a new Frequency Modulation architecture for artificial large area skin-like sensory array deployment in robotic platforms

This work presents a new architecture to deploy large-area artificial skin to enhance the spatial awareness of robotic and prosthetic platforms. Adding sensing information will improve robots’ safety both around humans and in unstructured environments. Unlike biological systems, current artificial platforms lack a fully-integrated skin-like layer that would significantly improve dexterity and capabilities. However, artificial skin is limited by the technical issues of scaling power to and communication from many sensors. Many current solutions are either relatively low-power with limited sensor type e.g. contact only, or capable of multiple sensor type readings at the expense of requiring higher power. Their data acquisition and sampling rates are also constrained by the technique used to transfer them. The solution to address these problems uses frequency modulation (FM) to encode many signals on a single wire. This solution is applied as an internal robotic communication protocol. This work describes the design rational and experimentally validates the concept within the frequency range of tactile mechanoreceptors. The proposed architecture has the potential to enable large-area skin deployment.

Comparative Study by Systematic Review and Meta-Analysis of the Peri-Implant Effect of Two Types of Platforms: Platform-Switching versus Conventional Platforms.

Objective: The aim of the systematic review and meta-analysis carried out was to evaluate the effects of changing the prosthetic platform on peri-implant tissue after 1 year of prosthetic loading. Material and methods: In November 2020, an electronic search was carried out in PubMed, EMBASE, Web of Science, and Scopus databases with the aim of obtaining all the randomized clinical trials that had been published in the preceding 10 years comparing the effects on the peri-implant tissue of implants with a prosthetic platform change and implants with a conventional platform for at least 1 year after prosthetic loading. Randomized model meta-analyses of the selected studies were performed to compare the results of the two implant groups in terms of vertical maintenance of bone level and increased probing depth. Results: Nine studies were included, summing up a total of 475 implants with prosthetic platform exchange and 462 implants with a conventional platform. Implants with prosthetic platform exchange had less peri-implant bone loss than implants with a conventional platform (mean difference of 0.255 mm, statistically significant) but suffered a greater increase in probing depth (mean difference of 0.082 mm, not statistically significant). However, the probing depth from One Study Remove revealed a statistically significant increase of 0.190 mm in the prosthetic platform exchange group compared to the conventional platform group. Conclusion: Implants with platform switching suffer less peri-implant bone loss after 1 year of loading than implants with a conventional platform. Further long-term studies are required to observe how these differences vary over time.

Screw removal torque evaluation in implants with cone morse and external hexagon platforms in anterior cantilever

This study aims to evaluate the screw removal torque on prosthetic platforms of Cone Morse (CM) and External Hexagon (EH) implants in crowns with anterior cantilever. Materials and Methods: in vitro study with a sample consisting of 20 test specimens of 2 elements (21 and 22), with n = 40; load is simulated on element 21 or on cantilever of 22. Samples were divided into 4 groups consisting of 10 test specimens on CM implants (groups 1 and 2), and 10 test specimens on EH implants (groups 3 and 4). The test specimens were manufactured using cylindrical PVC pipes measuring 22 x 19.05 mm filled with acrylic resin. The implants were fixed with a centralization device. Components used were EUCLAs and UCLAs with a chrome-cobalt alloy molten base. The metal bases were scanned, the crowns were digitally waxed, made on CAD/CAM system, and cemented on the metal bases with Panavia cement. Torque was applied using 20N for CM and 32N for EH, according to the manufacturers’ instructions. The test specimens were then subjected to a cycling process consisting of 1,000,000 cycles at a frequency of 2 Hz. The cyclic process applied axial forces to the surface (palate face of 21 and 22). Two cycling processes were carried on, the first on the palate face of 21 and the second on the palate face of 22. Between the two, screws were removed and replaced by new ones. The screw removal torque was measured using a digital torque meter. Results were analyzed with Student’s t test and variance analysis. Statistical calculations were conducted in SPSS 23 using 5% of significance. Results: Student’s t test showed significantly lower removal torque values in comparison with initial torque for both CM and EH connection implants and force applied to elements 21 and 22 (p &lt; 0.001) or 22 (p &lt; 0.001). Considering torque loss, there was no significant effect of the interaction between type of implant connection and site of force application (p = 0.094). Removal torque was significantly lower than initial torque for both implants (CM and EH). Conclusion: Torque loss occurred both in CM and EH. There was no significant effect of the interaction between connections and site of force application.

The role of cortical zone level and prosthetic platform angle in dental implant mechanical response: A 3D finite element analysis

ObjectiveThe aim of this study was to evaluate the influence of three different dental implant neck geometries, under a combined compressive/shear load using finite element analysis (FEA). The implant neck was positioned in D2 quality bone at the crestal level or 2 mm below. MethodsOne dental implant (4.2 × 9 mm) was digitized by reverse engineering techniques using micro CT and imported into Computer Aided Design (CAD) software. Non-uniform rational B-spline surfaces were reconstructed, generating a 3D volumetric model similar to the digitized implant. Three different models were generated with different implant neck configurations, namely 0°, 10° and 20°. D2 quality bone, composed of cortical and trabecular structure, was modeled using data from CT scans. The implants were included in the bone model using a Boolean operation. Two different fixture insertion depths were simulated for each implant: 2 mm below the crestal bone and exactly at the level of the crestal bone. The obtained models were imported to FEA software in STEP format. Von Mises equivalent strains were analyzed for the peri-implant D2 bone type, considering the magnitude and volume of the affected surrounding cortical and trabecular bone. The highest strain values in both cortical and trabecular tissue at the peri-implant bone interface were extracted and compared. ResultsAll implant models were able to distribute the load at the bone-implant contact (BIC) with a similar strain pattern between the models. At the cervical region, however, differences were observed: the models with 10° and 20° implant neck configurations (Model B and C), showed a lower strain magnitude when compared to the straight neck (Model A). These values were significantly lower when the implants were situated at crestal bone levels. In the apical area, no differences in strain values were observed. SignificanceThe implant neck configuration influenced the strain distribution and magnitude in the cortical bone and cancellous bone tissues. To reduce the strain values and improve the load dissipation in the bone tissue, implants with 10° and 20 neck configuration should be preferred instead of straight implant platforms.

Implant insertion angle and depth: Peri-implant bone stress analysis by the finite element method.

BackgroundThe study aimed to assess the influence of different implant insertion angles and depths on the stresses produced on the surface of peri-implant bone tissue under axial and oblique loading. Material and MethodsThe entire study followed the recommendations of the Checklist for Reporting In-vitro Studies (CRIS). The implant was placed in the region of element 36, according to the following models: M1 (0 mm / 0°); M2 (0 mm / 17°); M3 (0 mm / 30°); M4 (2 mm / 0°); M5 (2 mm / 17°); M6 (2 mm / 30°). The models were subjected to loading, with intensity of 100 N. The stress assessment followed the Mohr-Coulomb criterion and qualitative and quantitative analyses were performed. ResultsAngled implants and installed below the bone crest produced the highest stresses on the cortical bone, and the axial load presented the highest stress peaks on the buccal side of implants perpendicular to the bone crest. Regardless of the type of load (axial or oblique), inclined implants presented the highest stress peaks on the lingual side of the cortical bone. ConclusionsImplants installed perpendicular to and with a prosthetic platform at bone crest height provided the lowest stresses to peri-implant bone tissue under both axial and oblique loading. Key words:Finite element analysis, dental implants, axial loading, biomechanical phenomena.

Implant Volume Loss, Misfit, Screw Loosening, and Stress In Custom Titanium and Zirconia Abutments.

The aim of this study was to verify the effect of the implant volume loss, vertical misfit between abutment and prosthetic platform, prosthetic screw loosening torque, and screw stress distribution in titanium and zirconia abutments. Ten CAD/CAM system custom abutments of each material were milled and attached to the titanium implants. The implant volume loss was evaluated by microtomography, the vertical misfit with optical microscopy, and digital torque wrench measured the prosthetic screw loosening. All experimental analyses were performed before and after mechanical cycle (1,000,000 cycles, 100 N/2 Hz). Virtual models of the structures were created for finite element analysis, and the stress on the screw obtained with von Mises procedure. Data were analyzed using an independent t-test, two-way ANOVA for repeated measures, and Tukey's HSD test (a=0.05). There was no significant difference in the implant volume loss for the two abutment materials (p=0.662). Titanium abutments provided higher loosening torque values after mechanical cycling (p<0.001). Lesser marginal misfit was obtained with titanium abutments before and after mechanical cycling (p<0.001). The stress distribution on the screw was similar between abutment materials. In conclusion, CAD/CAM custom titanium abutment reduced the marginal misfit and increased the torque maintenance of prosthetic screws when compared to CAD/CAM custom zirconia abutment.

Platform switch hybrid zygoma implants improve prosthetics and marginal bone protection after extra-sinus placement.

PurposeThe aim of our studdy is clinical evaluation of Platform switch hybrid zygoma implants.Materials and Methods117 zygomatic implants were followed up during this time. They included 55 Brånemark System zygoma implants, 38 Noris implants, and 24 novel iRES hybrid implants with platform switch.ResultsBone quality and quantity are the prerequisite for successful implant treatment. Zygomatic implants are intended for patients with severely resorbed maxilla that cannot accommodate conventional implants without prior extensive bone grafting. Such regenerative procedures, like sinus lifts, prolong implant rehabilitation to several months (12–18). Furthermore, extensive grafts are less predictable showing varying degrees of graft resorption. Zygoma implants enable full, often immediate, reconstruction of the upper dental arch without the need for sinus lift treatment. The original zygoma protocol runs the implants through the sinus, requires general anesthesia, and positions the prosthetic platform of the implants on the palate, which makes prosthesis cumbersome. It also induces risk for post‐op sinusitis. Extra‐sinus approach with novel zygoma hybrid implants bypasses sinuses and positions the implant prosthetic platform on the crest allowing for same good prosthetics as on conventional dental implants. Furthermore, crestal threads and a platform‐switch, of the novel zygoma design, increase implant anchorage and minimize marginal bone loss. The study presents evolution of zygoma implant rehabilitation protocol and zygoma implant design in our clinical practice over 15 years (2004‐2019).ConclusionExtra‐sinus zygomatic implant placement lowers the risk of post‐op sinusitis and makes procedure possible to be done in local anesthesia.

2-years retrospective observational case-control study on survival and marginal bone loss of implants in patients with hereditary coagulopathies.

Evaluating 2-years implant loss and marginal bone loss in patients with hereditary coagulopathies, comparing with a healthy control group. 37 implants in 13 patients (17 haemophilia A, 20 Von-Willebrand disease) versus 26 implants in 13 healthy patients. Data measured through Lagervall-Jansson index (after surgery, at prosthetic loading, at 2 years). Chi-square, Haberman's, ANOVA, Mann-Whitney-U. Significance p<0.05. Haemorrhagic accidents in 2 coagulopathies patients (non-statistical differences). Hereditary coagulopathies patients suffered more hepatitis (p<0.05), HIV (p<0.05) and less previous periodontitis (p<0.01). Non-statistical differences in marginal bone loss among groups. 2 implants were lost in the hereditary coagulopathies and none in the control group (non-statistical differences). Hereditary coagulopathies patients had longer (p<0.001), and narrower implants (p<0.05) placed. 43.2% external prosthetic connection in hereditary coagulopathies patients (p<0.001); change of prosthetic platform more frequent in control group (p<0.05). 2 implants lost: external connection (p<0.05). Survival rate 96.8% (hereditary coagulopathies 94.6%, control group 100%). Implant and marginal bone loss at 2 years is similar in patients with hereditary coagulopathies and control group. Precautions should be taken on the treatment for hereditary coagulopathies patients, through prior haematological protocol. Implant loss only occurred in in a patient with Von-Willebrand´s disease.

Clinical efficacy of enucleation with packet-covered hydroxyapatite implant

Objective To evaluate the efficacy of enucleation with packet-covered hydroxyapatite implant. Methods The data of 45 eyes of 45 patients who were treated with enucleation with packet-covered hydroxyapatite implantation in our hospital from Jul.2011 to Aug.2017 were retrospectively analyzed. Postoperative follow-up was 12 months. Results Among 45 patients, there were 5 cases with traumatic severe ocular rupture, 9 cases with neovascular glaucoma, 26 cases with keroscleral grape swelling, and 5 cases with severe corneal ulcer perforation. After operation, mild lower eyelid relaxation occurred in 2 cases.No other complication, such as exposure of prosthetic ocular platform occured. All the patients had beautiful eyes. Conclusion Implantation of packet-covered hydroxyapatite with four rectus musles covered is simple and effective.The complications such as hydroxyapatite exposure is not easy to occur. Key words: Hydroxyapatite implantation; Muscle cone; Exposure

Influence of Transmucosal Area Morphology on Peri-Implant Bone Loss in Tissue-Level Implants.

To analyze peri-implant bone loss around two types of tissue-level implants (convergent and divergent transmucosal morphology) placed in the same region of either the maxilla or mandible in a single surgical session. This prospective study included 21 patients who each received two implants, one with a convergent transmucosal collar (n = 21) the other with a divergent collar (n = 21). Implants were placed in a single surgical session, by the same clinician, in the same clinical setting at the Prosthodontic and Occlusion Unit, University of Valencia (Spain). The implants (n = 42) were restored with splinted crowns screwed directly onto the prosthetic platforms. Bone loss analysis consisted of measurements taken from periapical radiographs 24 months after loading. Statistical analysis evaluated the homogeneity of the groups using Pearson's chisquare test; bone loss was compared with the Wilcoxon test. Statistical significance was set at 5% (α = .05), with a confidence interval of 95% and a power of 57%. Implants with convergent transmucosal morphology presented less mean peri-implant bone loss (0.29 ± 0.34 mm) than those with divergent transmucosal morphology (0.60 ± 0.63 mm), with a statistically significant difference between the two types of implants (P = .031). Less peri-implant bone loss occurs around supracrestal implants with convergent transmucosal morphology than divergent transmucosal morphology.

Evaluation of three cements in the ability to fill the interior of the dental implant using computerized microtomography

Background The microgap that exists in the interface of the components of 2 or 3 part implants has been the object of studies on their capacity of biological seal (bacterial, fungus…) and micronutrients in the saliva. In vivo studies have shown that the internally of 2 or 3-piece implant and prosthetic components are heavily contaminated with pathogenic bacteria from Peri-implant disease. This heavy contamination affects the external hexagon, Inner Hexagonal and Cone Morse prosthetic platforms. The limitation of prosthetic platforms, external hexagon internal hexagonal and cone morse in converting the mechanical seal into effective biological seal in vivo is a reality. Aim/Hypothesis We propose the investigation of 3 zinc oxide based cements with and without antimicrobial incorporation in the filling of the internal spaces of the implant Abutment. Material and Methods Ten implants (Conexão, Brazil) were used, prosthetic components suggested by the company. Of the implants used 5 were External Hexagon and 5 Morse Cone. All implants had the prosthetic screws tightened with a torque of 32 Ncm. Each screw abutment was initially tightened to 20 Ncm with a digital torque gauge to stabilize the abutment to the implant. The second torque, 32 Ncm, was applied 15 minutes after the initial torque. Subsequently, they were submitted to Micro-CT, being divided into 3 groups- Sealer Implant® Zinc Oxide (Group A) Sealer Implant® própolis Zinc Oxide and Propolis (B) Sealer Implant® Clorex Zinc Oxide and Chlorhexidine (C). All micro-CT scans were acquired on a Triumph multi-modality system (Gamma Medica, Northridge, CA) using the following sampling parameters- tube voltage 80 kVp, tube current 250 A, detector pixel size 50 m, focal spot size 50 m and a field-of-view of 59 or 93 mm. The spatial resolution was 39 and 28 m, and the radiation dose was 8.3 and 19.7 cGy for field-of-view of 93 and 59 mm, respectively. Results The results showed that in all analyzed parts without use of fillers both in the implants 2 or 3 pieces wide spaces inside the implant and abutments. Using the Image software, the internal spaces were quantified. In the Grupo Hexagono Externo it had an average value of 22% of internal space, in Cone Morse 2 pieces 18% and 3 pieces 18%. There was no statistically significant difference between the groups investigated in relation to the empty internal volume. In relation to filling capacity, the cements of Group A, B and C had similar results (P > 0.01). Conclusions and Clinical Implications This study on the filling capacity of the analyzed cements did not find a statistically significant difference between the analyzed groups. the mean filling level was 98% of the internal spaces, which demonstrates efficacy of the analyzed cements being an alternative of material in order to prevent the formation of microbioma and ecosystem within the implants.

Extra-Sinus Zygomatic Implants to Avoid Chronic Sinusitis and Prosthetic Arch Malposition: 12 Years of Experience.

This report retrospectively at the 12-year follow-up results of the treatment and rehabilitation of edentulous maxillae, applying extra-sinus zygomatic implants alone or in combination with intra-sinus zygomatic implants. We recruited 22 patients with 35 zygomatic Brånemark system implants; 24 implants in the standard Brånemark protocol through the sinus and 11 extra-sinus implants outside the sinus. Additionally, 147 regular implants were placed. The minimum follow-up period was 50 months to a maximum of 152 months. The zygoma survival rate after 12 years was 97.15%. Chronic sinusitis occurred in 11.42% of patients. We lost 1 (2.85%) zygomatic implant placed through the sinus and none of those in the extra-sinus position. The survival rate of the regular implants was 93.87%. Chronic sinusitis occurred in 4 patients (11.42%) who received zygomatic implants using standard protocol through the sinus. None of the extra-sinus zygoma patients developed sinusitis. Peri-implantitis was detected with only 3 zygomatic implants. In the original P-I Brånemark zygoma protocol the implants were passing through the sinus, which resulted in chronic sinusitis in some patients and malposition of the prosthetic platform toward the palate. These complications can be avoided by the extra-sinus placement of zygoma implants as demonstrated in this study.

Study About the Precision of Surgical Guides Used in Implantology

The purpose of this study was to detect the precision of inserting dental implants using 3 types of surgical guides on 3 groups of patients according to the degree of implantologist experience. In this study, 27 patients were taken, in 3 groups of 9 patients, who addressed to dental offices in which were implantologists with 1 year (group A), 6 years (group B) and 11 years (group C) of experience in surgery. Lot A, operated by a 1-year physician with experience in implantology, had the smallest deviation, demonstrating the increased attention that he had to the interventions. Comparing B and C lots, the smallest deviations were recorded for group C, operated by implantologist with greater experience in implantology. By comparing the deviations according to the type of surgical guide used, the smallest deviations at the apex and prosthetic platform were made in patients where the implants were inserted with a bone supported guide, followed by dental-gingival and mucosal guide. In terms of axis of implantation, the lowest values were recorded for the dental-gingival guide, followed by the bone and mucosal guide. The study has a number of limitations (low number of patients undergoing study, low dispensation period), which requires more extensive future studies to validate the results.

Accuracy of fit of implant-supported bars fabricated on definitive casts made by different dental stones.

BackgroundThe purpose of this study was to evaluate the accuracy of fitting of an implant supported screw-retained bar made on definitive casts produced by 4 different dental stone products.Material and MethodsThe dental stones tested were QuickRock (Protechno), FujiRock (GC), Jade Stone (Whip Mix) and Moldasynt (Heraeus). Three external hexagon implants were placed in a polyoxymethylene block. Definitive impressions were made using monophase high viscosity polyvinylsiloxane in combination with custom trays. Then, definitive models from the different types of dental stones were fabricated. Three castable cylinders with a machined non-enganging base were cast and connected with a very small quantity of PMMA to a cast bar, which was used to verify the marginal discrepancies between the abutments and the prosthetic platforms of the implants. For that purpose special software and a camera mounted on an optical microscope were used. The gap was measured by taking 10 measurements on each abutment, after the Sheffield test was applied. Twelve definitive casts were fabricated for each gypsum product and 40 measurements were performed for each cast. Mean, minimum, and maximum values were calculated. The Shapiro-Wilk test of normality was performed. Mann-Whitney test (P<.06) was used for the statistical analysis of the measurements.ResultsThe non-parametric Kruskal-Wallis test revealed a statistically significant effect of the stone factor on the marginal discrepancy for all Sheffield test combinations: 1. Abutment 2 when screw was fastened on abutment 1 (χ2=3, df=35.33, P<0.01), 2. Abutment 3 when the screw was fastened on abutment 1 (χ2=3, df=37.74, P<0.01), 3. Abutment 1 when the screw was fastened on abutment 3 (χ2=3, df=39.79, P<0.01), 4. Abutment 2 when the screw was fastened on abutment 3 (χ2=3, df=37.26, P<0.01).ConclusionsA significant correlation exists between marginal discrepancy and different dental gypsum products used for the fabrication of definitive casts for implant supported bars. The smallest marginal discrepancy was noted on implant supported bars fabricated on definitive casts made by Type III mounting stone. The biggest marginal discrepancy was noted on implant supported bars fabricated on definitive casts made by Type V dental stone. The marginal discrepancies presented on implant supported bars fabricated on definitive casts made by two types of Type IV dental stone were not significantly different. Key words:Dental implant, passive fit, dental stones, marginal discrepancy.

Effect of different types of prosthetic platforms on stress-distribution in dental implant-supported prostheses

A biomechanical analysis of different types of implant connections is relevant to clinical practice because it may impact the longevity of the rehabilitation treatment. Therefore, the objective of this study is to evaluate the Morse taper connections and the stress distribution of structures associated with the platform switching (PSW) concept. It will do this by obtaining data on the biomechanical behavior of the main structure in relation to the dental implant using the 3-dimensional finite element methodology. Four models were simulated (with each containing a single prosthesis over the implant) in the molar region, with the following specifications: M1 and M2 is an external hexagonal implant on a regular platform; M3 is an external hexagonal implant using PSW concept; and M4 is a Morse taper implant. The modeling process involved the use of images from InVesalius CT (computed tomography) processing software, which were refined using Rhinoceros 4.0 and SolidWorks 2011 CAD software. The models were then exported into the finite element program (FEMAP 11.0) to configure the meshes. The models were processed using NeiNastram software. The main results are that M1 (regular diameter 4mm) had the highest stress concentration area and highest microstrain concentration for bone tissue, dental implants, and the retaining screw (P<0.05). Using the PSW concept increases the area of the stress concentrations in the retaining screw (P<0.05) more than in the regular platform implant. It was concluded that the increase in diameter is beneficial for stress distribution and that the PSW concept had higher stress concentrations in the retaining screw and the crown compared to the regular platform implant.

Marginal bone level around conical connection tapered implants with platform switching: A multicenter retrospective study at 14 months follow-up

Aim The long-term success of dental implants mainly depends on marginal bone stability around the fixtures. The development of prosthetic abutments with reduced width in relation to the implant prosthetic platform (platform switching) and/or tighter implant/abutment connections seem to have a potential in reducing crestal bone resorption. The aim of the present study was to examine the effect of platform switching and conical connection design, on marginal bone loss around newly designed dental implants.Materials and Methods Subjects who underwent implant therapy in three different centers, were enrolled in the present retrospective study. Patients were rehabilitated with tapered platform-switched dental implants. To evaluate marginal bone level changes over time, the mesial and distal bone height was radiographically evaluated on the day of implant placement (baseline) and 14 months post-implantation.Results One hundred and twelve conical tapered platform-switched implants were placed in three different centers in 37 patients, with mean age of 53 years. The survival rate was 100% after an average follow-up of 14 months. During the first year, marginal bone loss was 0.67±0.45mm. No statistically significant differences were recorded between the different centers. Conclusions Within the limitations of the present retrospective study, limited marginal bone loss and 100% implant survival rate were observed over 14 months of follow-up. The results showed high crestal bone stability around the newly designed conical tapered platform-switched implants.