Platform switching configuration and peri-implant soft and hard tissue response

Introduction Oral implants are a surgical/prosthetic integrated method to restore missing teeth. Their original configuration provide for matching diameter implant platform and prosthetic components (prosthetic components diameter = implant platform diameter). Longitudinal studies have demonstrated that the matching diameter fixture and prosthetic components configuration leads to a formation of a so called “biologic width” with 1-2 mm of peri-implant bone resorption. Recently published studies have shown that prosthetic components smaller in diameter compared to the implant platform (prosthetic components diameter At the same time, all data expressing bone level changes around platform switched implants, although more positive (0.5mm on average) compared to traditionally restored implants (1.5mm on average), present very often high variability. It might suggest that an individual bone pattern could influence the dimension of biologic width re-establishment and, thus, bone level changes in the long run. Therefore, the aim of this thesis was to verify histologically: 1. How hard and soft tissue adaptation to the platform switching configuration can explain the positive clinical results. 2. The diameter mismatching configuration of platform switched implants could lea to a negative inflammatory response in the middle/short term. 3. An additional aim was to test clinically if an individual bone pattern (structure, “bone quality”) could affect peri-implant bone level changes.Materials and Methods To test these hypotheses, 3 different studies were performed: 1. Animal (minipigs) study to compare the structure of biologic width around implants restored using traditional approach and platform switching histologically. 2. Histological and immunohistochemical studies in human specimens analyzing soft tissue inflammatory reactions after loading around implants restored using traditional approach and platform switching 3. Clinical study comparing radiologic bone level changes with histological and immunohistochemical aspects of bone alterations longitudinally after loading around implants restored using traditional approach and platform switching.Results The most important results were: 1. Compared to traditionally restored implant, the platform switching configuration may have a minor impact on the length of the epithelial component of the biologic width, while the connective tissue compartment was demonstrated to be seated over the implant platform and in direct contact with prosthetic components. 2. No significant difference was found between platform switching and traditional matching diameter configurations in terms of inflammatory infiltrate, microvascular density and collagen content. In all groups, most samples with a wellpreserved junctional epithelium showed a small and localized inflammatory infiltrate associated with not-well-oriented collagen fibers and an increased vascularization. 3. After statistical leveling (standardization) of peri-implant bone remodeling values, a borderline direct correlation between peri-implant bone changes and levels of anabolic biomarkers and a borderline indirect correlation between bone changes and levels of catabolic biomarkers was found.Conclusion From a histologic point of view, the particular design of platform switched implants do not offer a favorable environment for bacterial colonization and subsequent inflammatory infiltration. At the same time, the medialization of biologic width seems to prevent bone downgrowth and could explain the positive soft tissue inflammatory response to this diameter mismatching implant/abutment configuration.Einleitung Dentale Implantate stellen eine kombiniert chirurgisch-prothetische Methode zum Ersatz von fehlenden Zähnen dar. Herkömmlicherweise bestehen diese aus dem Implantat und einer dem Durchmesser des Implantates entsprechenden Aufbaukomponente. Longitudinalstudien haben gezeigt, dass es nach Implantatinsertion zur Ausprägung der sogenannten biologischen Breite mit 1-2mm periimplantärem Knochenverlust kommt. Kürzlich veröffentlichte Studien zeigten, dass ein Missverhältnis zwischen Implantat und Aufbau eine bessere Stabilität des periimplantären Knochenniveaus gewähren. Dennoch bleibt das eher unkonventionelle Konzept dieses sog. „platform switchings“ histologisch fragwürdig und steht unter dem Verdacht, die bakterielle Invasion in den periimplantären Spalt zu begünstigen. Gleichermaßen enthalten alle Daten, welche die Knochenniveauschwankungen um Implantate mit „platform switching“ beschreiben – obwohl diese geringer ausfallen als bei herkömmlich versorgten Implantaten – eine große Schwankungsbreite. Dies könnte bedeuten, dass eine individuelle Knochenstruktur die Dimension der „biologischen Breite“ und darüber hinaus die Veränderungen im Knochenniveau bedingt. Aus diesem Grund war das Ziel dieser Arbeit, die folgenden Fragen histologisch zu ergründen: 1. Wie kann eine Hart- und Weichgewebsadaptation an eine unkonventionelle Implantat-Abutment-Konfiguration positive klinische Ergebnisse erklären? 2. Kann eine durch „platform switching“ auftretende Veränderung mittel-und langfristig zu einer negativen Entzündungsreaktion führen? 3. Ein weiteres Ziel der Untersuchung war es, in einem klinischen Ansatz herauszufinden, ob sich unterschiedliche histologische Knochenstrukturen auf Veränderungen des periimplantären Knochenniveaus auswirken.Material und Methoden Um diese Hypothesen zu untersuchen, wurden drei Studien durchgeführt: 1. Eine Tierstudie (Minipig), um die Struktur der biologischen Breite um herkömmlich und um mittels „platform switching“ versorgte Implantaten histologisch zu untersuchen. 2. Histologische und immunhistochemische Untersuchungen an menschlichem Gewebe zur Beschreibung der Entzündungsreaktion nach Implantatbelastung an herkömmlich und mittels „platform switching“ versorgten Implantaten. 3. Vergleichende klinische Longitudinalstudie zur radiographischen Veränderung des Knochenniveaus bei konventionell und mit „platform switching“ versorten Implantaten.Zusammenfassung der Ergebnisse 1. Im Vergleich zum herkömmlich versorgten Implantat haben Situationen mit „platform switching“ einen geringeren Einfluss auf die Länge der epithelialen Komponente der biologischen Breite, während der Bindegewebsanteil nachgewiesenermaßen über der Implantatplattform und in direktem Kontakt mit den prothetischen Komponenten ansetzte. 2. Es konnte kein statistisch signifikanter Unterschied bei beiden Hauptgruppen in Bezug auf Entzündungsreaktion, Gefäßdichte und Kollagengehalt gefunden werden. In allen Gruppen zeigten die meisten Proben mit gut erhaltenem Epithel eine kleine, lokale Entzündungsreaktion in Verbindung mit wenig organisierten Kollagenfasern und erhöhter Vaskularisation. 3. Nach Standardisierung des periimplantären Knochen-Remodellingsteilweise ist die amerik. Version verwandt worden, also remodeling, teilweise die britische Version, also remodelling. Bitte einheitlch konnte auf eine geringe Korrelation zwischen Knochenniveauveränderung und dem Nachweis von an anabolen Biomarkern, aber einen indirekten Zusammenhang zwischen Veränderung des Knochenniveaus und katabolen Biomarkern geschlossen werden.Schlussfolgerung Aus histologischer Sicht bietet das Verbindungsdesign des „plattform switchings“ dem Eindringen von Bakterien und nachfolgender Ausbreitung einer Entzündungsreaktion kein günstiges Umfeld. Gleichermaßen bewirkt die Ausbildung der biologischen Breite das Ausbleiben eines Knochenverlusts und könnte somit die herkömmliche inflammatorische Reaktion an modifizerten Implant-Abutment Verbindungen erklären. Dennoch zeigten die Ergebnisse der klinisch-histologischen Studie, dass das periimplantäre Knochen-Remodelling von der individuellen Knochenstruktur des Patienten abhängt

Tooth as graft material: Histologic study.

BACKGROUND An effective regenerative protocol is key to reestablish and maintain the hard and soft tissue dimensions over time. The choice of the graft material and its properties also could have an impact on the results. To prevent alveolar ridge dimensional changes, since numerous graft materials have been suggested and in the past years, a growing interest in teeth material has been observed as a valuable alternative to synthetic biomaterials. AIM The aim of the study was to explore the histomorphometric outcomes of tooth derivative materials as used as bone substitute material in socket preservation procedure. METHODS After alveolar socket preservation (ASP) procedures using autologous demineralized tooth as graft material prepared by means of an innovative device, was evaluated. A total of 101 histological samples, from 96 subjects, were analyzed by evaluating the total amount of bone (BV), residual tooth material (residual graft, TT), and vital bone (VB). The section from each sample was then split in nine subsections, resulting in 909 subsections, to allow statistical comparison between the different areas. RESULTS It was not noticed a statistically significant difference between maxillary and mandibular sites, being the amount of VB in upper jaw sites 37.9 ± 21.9% and 38.0 ± 22.0% in lower jaw sites and the amount of TT was 7.7 ± 12.2% in maxilla and 7.0 ± 11.1% in mandibles. None of the other considered parameters, including defect type and section position, were statistically correlated to the results of the histomorphometric analysis. CONCLUSIONS ASP procedure using demineralized autologous tooth-derived biomaterial may be a predictable procedure to produce new vital bone potentially capable to support dental implant rehabilitation

Mechanical testing of thin-walled zirconia abutments

Although the use of zirconia abutments for implant-supported restorations has gained momentum with the increasing demand for esthetics, little informed design rationale has been developed to characterize their fatigue behavior under different clinical scenarios. However, to prevent the zirconia from fracturing, the use of a titanium connection in bi-component aesthetic abutments has been suggested. Objective Mechanical testing of customized thin-walled titanium-zirconia abutments at the connection with the implant was performed in order to characterize the fatigue behavior and the failure modes for straight and angled abutments. Material and Methods Twenty custom-made bi-component abutments were tested according to ISO 14801:2007 either at a straight or a 25° angle inclination (n=10 each group). Fatigue was conducted at 15 Hz for 5 million cycles in dry conditions at 20°C±5°C. Mean values and standard deviations were calculated for each group. All comparisons were performed by t-tests assuming unequal variances. The level of statistical significance was set at p≤0.05. Failed samples were inspected in a polarized-light and then in a scanning electron microscope. Results Straight and angled abutments mean maximum load was 296.7 N and 1,145 N, the dynamic loading mean Fmax was 237.4 N and 240.7 N, respectively. No significant differences resulted between the straight and angled bi-component abutments in both static (p=0.253) and dynamic testing (p=0.135). A significant difference in the bending moment required for fracture was detected between the groups (p=0.01). Fractures in the angled group occurred mainly at the point of load application, whereas in the straight abutments, fractures were located coronally and close to the thinly designed areas at the cervical region. Conclusion Angled or straight thin-walled zirconia abutments presented similar Fmax under fatigue testing despite the different bending moments required for fracture. The main implication is that although zirconia angled or straight abutments presented similar mechanical behavior, the failure mode tended to be more catastrophic in straight (fracture at the cervical region) compared to angled abutments. ^le

Bacterial inactivation/sterilization by argon plasma treatment on contaminated titanium implant surfaces: in vitro study

Background: Surface treatment by argon plasma is widely used as the last step of the manufacturing process of titanium implant fixtures before their sterilization by gamma rays. The possibility of using such a technology in the daily clinical practice is particularly fascinating. The aim of the present study was to assess the effects of the argon plasma treatment on different titanium implant surfaces previously exposed in vitro to bacterial contamination. Material and Methods: Sterile c.p. titanium implant discs with turned (T, Sa: 0.8μm), sandblasted/acid-etched (SAE, Sa: 1.3μm) and titanium plasma sprayed (TPS, Sa: 3.0μm) surface were used in this study. A strain of Aggregatibacter actinomycetemcomitans ATCC3718 was grown at 37°C under anaerobic conditions for 24 h and then transferred on six discs for each of the three surface types. After 24 hours, a half of the contaminated discs (control group) were directly used to evaluate the colony forming units (CFUs). The other half of the contaminated discs (test group) were treated in an argon plasma chamber for 12 minutes at room temperature prior to be analyzed for CFU counting. All assays were performed using triplicate samples of each material in 3 different experiments. Results: When the CFU counting was carried out on control discs, a total of 1.50x106±1.4x105, 1.55x106±7.07x104 and 3.15x106±2.12x105 CFU was respectively assessed for T, SAE and TPS discs, without statistically significant differences among the three surfaces. On the contrary, any trace of bacterial contamination was assessed for titanium discs treated in the argon plasma chamber prior to be analyzed, irrespectively to the implant surface tested. Conclusions: Within the limit of this study, reported data suggested that the argon plasma technology could be efficiently used to decontaminate/sterilize previously infected titanium implant surfaces

The influence of platform switching on the biomechanical aspects of the implant-abutment system. A three dimensional finite element study

Objective: To evaluate the biomechanical scenario of platform switching geometric implant-abutment configuration relative to standard configurations by means of finite element analysis.Study Design: A 3D Finite Element Analysis (FEA) was performed on 3 different implant-abutment configurations: a 3.8 mm implant with a matching diameter abutment (Standard Control Design, SCD), a 5.5 mm implant with matching diameter abutment (Wider Control Design, WCD), and a 5.5mm implant with a 3.8 mm abutment (Experimental Design, ED). All the different experimental groups were discretized to over 60000 elements and 100000 nodes, and 130N vertical (axial) and 90N horizontal loads were applied on the coronal portion of the abutment. Von Mises stresses were evaluated and maximum and minimum values were acquired for each implantabutment configuration. Results: The load-induced Von Mises stress (maximum to minumum ranges) on the implant ranged from 150 MPa to 58 Pa (SCD); 45 MPa to 55 Pa (WCD); 190 MPa to 64 Pa (ED). The Von Mises stress on the abutment ranged from 150 MPa to 52 MPa (SCD); 70 MPa to 55 MPa (WCD), and 85 MPa to 42 MPa respectively (ED). The maximum stresses transmitted from the implant-abutment system to the cortical and trabecular bone were 67 Pa and 52 MPa (SCD); 54 Pa and 27 MPa (WCD); 64 Pa and 42 MPa (ED), respectively. When the implant body was evaluated for stresses, a substantial decrease in their levels were observed at the threaded implant region due to the diametral mismatch between implant and abutment for the ED configuration. Conclusion: The platform switching configuration led to not only to a relative decrease in stress levels compared to narrow and wide standard configurations, but also to a notable stress field shift from bone towards the implant system, potentially resulting in lower crestal bone overloading. © Medicina Oral S. L

The influence of platform switching on the biomechanical aspects of the implant-abutment system. A three dimensional finite element study

Objective: To evaluate the biomechanical scenario of platform switching geometric implant-abutment configuration relative to standard configurations by means of finite element analysis.Study Design: A 3D Finite Element Analysis (FEA) was performed on 3 different implant-abutment configurations: a 3.8 mm implant with a matching diameter abutment (Standard Control Design, SCD), a 5.5 mm implant with matching diameter abutment (Wider Control Design, WCD), and a 5.5mm implant with a 3.8 mm abutment (Experimental Design, ED). All the different experimental groups were discretized to over 60000 elements and 100000 nodes, and 130N vertical (axial) and 90N horizontal loads were applied on the coronal portion of the abutment. Von Mises stresses were evaluated and maximum and minimum values were acquired for each implantabutment configuration. Results: The load-induced Von Mises stress (maximum to minumum ranges) on the implant ranged from 150 MPa to 58 Pa (SCD); 45 MPa to 55 Pa (WCD); 190 MPa to 64 Pa (ED). The Von Mises stress on the abutment ranged from 150 MPa to 52 MPa (SCD); 70 MPa to 55 MPa (WCD), and 85 MPa to 42 MPa respectively (ED). The maximum stresses transmitted from the implant-abutment system to the cortical and trabecular bone were 67 Pa and 52 MPa (SCD); 54 Pa and 27 MPa (WCD); 64 Pa and 42 MPa (ED), respectively. When the implant body was evaluated for stresses, a substantial decrease in their levels were observed at the threaded implant region due to the diametral mismatch between implant and abutment for the ED configuration. Conclusion: The platform switching configuration led to not only to a relative decrease in stress levels compared to narrow and wide standard configurations, but also to a notable stress field shift from bone towards the implant system, potentially resulting in lower crestal bone overloading. © Medicina Oral S. L

Soft Tissue Contour Impression with Analogic or Digital Work Flow: A Case Report

Transferring precise information to the dental laboratory is one of the key factors to achieving clinical success. The aim of the present study was to describe classical and digital work-flows used to rehabilitate an implant with a convergent collar in the aesthetic zone following the BOPT (biologically oriented preparation technique) approach and to report the three years follow-up outcomes of two patients rehabilitated following such procedures

Plasma of argon enhances the adhesion of murine osteoblasts on different graft materials

OBJECTIVE Plasma of argon treatment was demonstrated to increase material surface energy leading to stronger and faster interaction with cells. The aim of the present in vitro study was to test the effect of plasma treatment on different graft materials. MATERIALS AND METHODS Synthetic hydroxyapatite (Mg-HA), biphasic calcium phosphate (BCP), cancellous and cortical xenogeneic bone matrices (CaBM, CoBM) were used representing commonly used classes of bone substitute materials. Fifty serially numbered disks with a 10mm-diameter from each graft material were randomly divided into two groups: test group (argon plasma treatment) and control group (absence of treatment). Cell morphology (using pre-osteoblastic murine cells) and protein adsorption were analyzed at all samples from both the test and control group. Differences between groups were analyzed using the Mann-Whitney test setting the level of significance at p<0.05. RESULTS Plasma treatment significantly increased the protein adsorption at all samples. Similarly, plasma treatment significantly increased cell adhesion in all groups. CONCLUSIONS Data confirmed that non-atmospheric plasma of argon treatment led to an increase of protein adsorption and cell adhesion in all groups of graft material to a similar extent. CLINICAL RELEVANCE Plasma of argon is able to improve the surface conditions of graft materials

Guided implant surgery and sinus lift in severely resorbed maxillae: A retrospective clinical study with up to 10 years of follow-up

Objectives In the posterior maxilla, due to the presence of maxillary sinus, residual bone height lower than 3mm is a critical factor that can affect implant stability and survival. The use of guided surgery may facilitate the surgical procedures and the implant insertion in case of severely resorbed maxillae. Moreover, it may have beneficial effects on the long-term survival and success of implant-supported restorations. This study aimed to evaluate implant supported restorations on severely resorbed maxilla (&lt;3 mm) after sinus lift with collagenated xenograft and guided surgery. Methods Forty-three patients with need for implant rehabilitation and residual bone height between 1 and 3 mm were recruited. Surgical and prosthetical aspects were planned following digital approach with the use of Realguide 5.0 (3diemme, Varese, Italy). Lateral window sinus lift was performed and implants were placed simultaneously to the augmentation procedure with a tooth-supported pilot drill surgical template. A pre-hydrated collagenated porcine bone matrix was adopted as regenerative material. Computer-aided-design/computer-aided-manufacturing (CAD/CAM) restorations were delivered after six months of healing. Milled titanium chamfer abutments with CAD/CAM crowns were used. Bone height at implant site level was measured using an image software analysis applied to the pre- and post-surgical radiographs and at the follow-up. Biological and technical complications were recorded during all the follow-up periods. Results Fifty-four sinus were treated. After a mean follow-up time of 5.11 years (SD: 2.47), no implants were lost nor showed signs of disease. The mean pristine bone height was 2.07 mm (SD: 075). At the final evaluation the augmented sinus height was 12.83 mm (SD: 1.23). Two cases experienced minor perforation of the membrane, while five patients developed minimal post-operative complications, completely resolved with pharmacologic therapy. No mid-term biological complications were experienced by the patients. No cases experienced peri-implant mucositis and peri-implantitis during the whole follow-up period. Four patients (7.4%) faced an unscrewing of the prosthesis. Conclusions The present study showed the efficacy in the mid-term of the digital planning and the guided surgery in restoring severely resorbed posterior maxilla with dental implants