Ultrastructural studies on implants failure with immediate or late loading

Objectives. The purpose of the present study was to evaluate by scanning electron microscope (SEM) and energy dispersive spectrophotometry (EDS), the degree of bone mineralization of the tissues on the surface of failure dental implants with immediate or late loading. Materials and method. In the study, 8 dental explants from 8 clinically healthy, non-smoking patients were taken. All implants were inserted by the same dental surgeon, 4 of them were immediate loaded and 4 were late prosthetically loaded by the same dentist. The ablation of the implants was performed as atraumatic as possible and they were collected in sterile containers and sent to the BIOMAT Research Center, where they were subjected to SEM and EDS analyses. The ratios between the chemical elements calcium and nitrogen (Ca/N), phosphorus and nitrogen (P/N), respectively calcium and phosphorus (Ca/P) were calculated for each of the 8 samples and were statistically analyzed. Results. If we compare the degree of coverage of the implants with bone tissue in different phases of mineralization, we find that the bone structures occupy a larger surface area of the implants in the cases with immediate loading compared to the cases with late loading. Thus, out of 4 immediately loaded implants, 2 were completely covered, one showed very little exposed areas, and the fourth showed alternating covered and uncovered areas. Regarding the late loaded implants, three showed alternation between covered and uncovered areas and only one was completely covered with bone. Conclusions. The degree of coverage of the explants with bone tissue was better represented for the immediate loading cases. The degree of mineralization of the bone tissue covering the explants was higher for cases with immediate loading. To confirm the obtained results, it is necessary to expand the study on larger batches of samples

FEA on the biomechanical behavior of immediately loaded implants with different sizes

Objectives. The purpose of this research was to study, in the case of immediate loading, the biomechanical effect produced by the length of the implants. Material and method. The study material was a CBCT analysis performed on a patient from one dental office in Bucharest. An segment of edentulous mandibular bone was selected from the CBCT, which was processed with Mimics Innovation Suite, respectively Mimics and 3-matic. After processing the bone segment, two implants of the same manufacturer, with identical design, but different length – 10 and 13 mm respectively, were selected from the BIOMAT database. To simulate immediate loading, the bone-implant interface was not blocked and the mandible was defined with properties that characterize a bone with moderate density. A perpendicular masticatory force of 200N was applied to each of the two implants. The software ANSYS calculated the minimum, maximum values and their geometric means for the possible stresses produced on both the shorter implant (10 mm) and the longer implant (13 mm). Results. In the case of short implants, higher average stresses develop along the entire length of the implant, towards the vestibular bone plate, while in the case of long implants the higher stress seems to be cantoned towards the apical side. Conclusions. The present study shows that, in the case of immediate loading, the use of longer implants (13 mm) reduces by more than 50% the geometric mean of the stresses to which the bone-implant interface is subjected than in the case of the use of shorter implants (10 mm). In both types of implants, higher stresses occur at the level of the screw fixing the abutment in the implant

Comparative FEM study about various posts used on endodontically treated teeth

Objectives. The aim of the present study was to analyze comparatively, through the finite element method (FEM), the biomechanical behavior of different types of devices used to increase the resistance of restorations on endodontically treated teeth, upon the experimental application of a force of 350N. Materials and methods. We studied comparatively three types of posts, respectively: fiberglass post, cast post from Cr-Co-Mo alloy and prefabricated titanium post. Three irretrievable extracted teeth for periodontal reasons were endodontically treated and then specifically prepared for cementation of this devices. The teeth were scanned at a radio-diagnostic center, and the obtained DICOM files were processed with MIMICS and 3-matic and then subjected to finite element analysis with ANSYS. Results. From the 48 simulations carried out for the case of all-ceramic crown coverage, the use of titanium post is associated with 25 situations in which maximum or minimum values appear, the use of cast post presents 12 situations in which maximum or minimum values are developed, the use of fiberglass posts is associated with 10 simulations where maximum or minimum values occur, and in one case the deformations are equal. Regarding the use of the zirconium oxide crown, the results are comparable. Conclusions. The presence of zirconium oxide crowns generally produces less valuable stresses and deformations at the level of the components. The stress and strain values are lowest when using fiberglass posts, followed closely by cast post and far behind by titanium post. In all simulated situations, the limit values of stresses and strains are mostly recorded at the tooth root, which is susceptible to fracture in case of parafunctional forces, followed by the three devices themselves and the covering crowns

SEM and EDS comparative studies about the homogeneity of some cements used for luting of posts

Objectives. The aim of the study was to evaluate comparatively by scanning electron microscope (SEM) and energy dispersive spectrophotometry (EDS) the physical and chemical homogeneity of some luting materials used for cementation of three types of posts. Materials and method. We selected 12 irretrievable monoradicular teeth extracted in our dental offices. After extraction, all teeth were prepared for cementation with 4 different cements (NANOCORE DUAL, CEMBEST, PANAVIA SA and CEMENT-ONE) of three types of posts: prefabricated titanium post, FibreKleer 4x fiberglass post (Pentron) and post cast from NiCrMo alloy. Afterwards, the samples were embedded in resin and prepared metallographically for examination with the Phenom ProX scanning electron microscope equipped with an energy dispersive spectrophotometer with X Rays. Results. SEM studies provide valuable ultrastructural information regarding the degree of filling with luting materials. The four studied cements do not present an inhomogeneous composition in the EDS analysis, not having significantly increased values between the 2 analyzed points for each of the 12 samples taken in the study. Conclusions. Among the four luting materials studied comparatively, PANAVIA SA seems to best fill the existing spaces between posts and the limits of dental preparations, being closely followed by CEMENT-One and CEMBEST. In last place is NANOCORE DUAL, which presents discontinuities in the mass of material and at the border with the preparations

Maxillary Sinus Floor Augmentation to Enable One-Stage Implant Placement by Using Bovine Bone Substitute and Platelet-Rich Fibrin

Nowadays it is possible to perform an optimal implant placement and to achieve a good long-term prognosis for an implant-borne prosthesis in the grafted posterior maxilla. This study evaluates the efficiency of one-stage piezosurgery by using as graft material a combination of particulate bovine bone substitutes with platelet-rich fibrin to achieve sinus lift. We included in this study 14 cases of one-stage sinus lift surgeries during which we placed 30 standard implants. The mean vertical bone height gain was 10.12 mm six months after surgery, and the mean postoperative follow-up time was 43.79 months. There were no major complications during or after surgery, and all implants are in use. Therefore, it can be concluded that one-stage sinus piezosurgery using particulate bovine bone substitutes and platelet-rich fibrin can be applied as a predictable and effective technique in the treatment of the posterior edentulous maxilla ensuring 4-5 mm vertical bone height

Assessment of Force Retention between Milled Metallic and Ceramic Telescopic Crowns with Different Taper Angles Used for Oral Rehabilitation

The present study assessed the retention forces corresponding to different telescopic systems used in removable prosthetic dentures. The telescopic systems were represented by Co–Cr alloy or zirconia-based primary crowns and Co–Cr secondary crowns. All crowns were manufactured using computer-aided design/computer-aided manufacturing technology (CAD/CAM). Two types of reference abutment teeth (upper canine and first upper molar) were selected in order to obtain the telescopic crowns and two taper angles—of 0° and 2°—were used for the design of the crowns. A number of 120 samples of telescopic crowns were obtained and subjected to mechanical tests, following a specific protocol, on a mechanical testing equipment. The retention of the telescopic systems was evaluated for different sets of cycles (up to 360), represented by movements that simulate the intraoral insertion and disinsertion of the telescopic systems. The present study highlights that the telescopic systems in which the primary crown is made of zirconia ceramics presents more advantages than those made of Co–Cr. All telescopic systems studied, highlighted that by modifying the taper angle from 0° to 2°, the retention forces have decreased, irrespective of the materials used for the fabrication of the primary crown, suggesting that by using a taper angle of 0°, which is known to be ideal, more efficient, and reliable prosthesis can be developed. Thus, even though the ceramic–metallic telescopic system exhibited the highest retention, all telescopic crowns evaluated registered values between 2–7 N, indicating that they are suitable for clinical use