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Ultra-high molecular weight polyethylene knee prostheses of two different sizes (i.e. characterised by different contact areas) were run on a knee wear simulator in two tests differing for the applied load. Gravimetric and micro-Raman spectroscopic analyses were performed to investigate at macroscopic and molecular levels the effects of contact area and applied load on the morphology of the knee components. The larger prostheses showed a higher mass loss in both tests, while Raman spectroscopy showed a more significant polymer degradation in the smaller prostheses, suggesting that a lower contact area is responsible for a higher wear at the molecular wear, but for a lower gravimetric wear. Raman measurements showed that in the second test (using a higher applied load), the wear mechanism changed with respect to the first test: the less severe conditions used in the latter resulted in an increase in the orthorhombic content, while the more severe conditions used in the former determined an increase and rearrangement of the amorphous phase. The results here reported allow to gain more insights into the effects of contact area, applied load and contact stress on wear. Preliminary micro-Raman analyses on in vivo worn knee prostheses confirmed the results obtained in vitro: the retrievals of smaller size were found more degraded at molecular level than those of larger size. These findings showed that the conditions used in the in vitro tests well simulate the knee kinematics of the knee joint and thus the in vivo wear.

Commercial root end filling materials, namely two zinc oxide eugenol-based cements [intermediate restorative material (IRM), Superseal], a glass ionomer cement (Vitrebond) and three calcium-silicate mineral trioxide aggregate (MTA)-based cements (ProRoot MTA, MTA Angelus, and Tech Biosealer root end), were examined for their ability to: (a) release calcium (Ca(2+) ) and hydroxyl (OH(-) ) ions (biointeractivity) and (b) form apatite (Ap) and/or calcium phosphate (CaP) precursors. Materials were immersed in Hank's balanced salt solution (HBSS) for 1-28 days. Ca(2+) and OH(-) release were measured by ion selective probes, surface analysis was performed by environmental scanning electron microscopy/energy dispersive X-ray analysis, micro-Raman, and Fourier transform infrared spectroscopy. IRM and Superseal released small quantities of Ca(2+) and no OH(-) ions. Uneven sparse nonapatitic Ca-poor amorphous CaP (ACP) deposits were observed after 24 h soaking. Vitrebond did not release either Ca(2+) or OH(-) ions, but uneven nonapatitic Ca-poor CaP deposits were detected after 7 days soaking. ProRoot MTA, MTA Angelus, and Tech Biosealer root end released significant amounts of Ca(2+) and OH(-) ions throughout the experiment. After 1 day soaking, nanospherulites of CaP deposits formed by amorphous calcium/magnesium phosphate (ACP) Ap precursors were detected. A more mature ACP phase was present on ProRoot MTA and on Tech Biosealer root end at all times. In conclusion, zinc oxide and glass ionomer cements had little or no ability to release mineralizing ions: they simply act as substrates for the possible chemical bonding/adsorption of environmental ions and precipitation of nonapatitic Ca-poor ACP deposits. On the contrary, calcium-silicate cements showed a high calcium release and basifying effect and generally a pronounced formation of more mature ACP apatitic precursors correlated with their higher ion-releasing ability.

L’ultima generazione di materiale ceramico per la fabbricazione di protesi totali di anca è presente sul mercato come Biolox® delta. Questo materiale è un composito di allumina e zirconia tetragonale stabilizzata con ittria (Y-TZP). La presenza di zirconia, oltre a migliorare le proprietà meccaniche, introduce una maggiore tendenza al deterioramento del materiale a causa della cosiddetta transizione tetragonale-monoclino (t-m). L’analisi micro-Raman offre un potente strumento per lo studio di questi meccanismi di degradazione: in accordo con il metodo di Katagiri1 è stato possibile quantificare la frazione volumetrica di zirconia monoclina (Vm) individuando nell’usura il fattore decisivo che in vivo ha determinato la trasformazione t-m (che è innescata anche semplicemente dall’acqua). I dati ottenuti hanno inoltre permesso di ottenere informazioni sulla cinetica e sul meccanismo di trasformazione consentendo la validazione di protocolli di invecchiamento accelerato in vitro messi a punto da altri autori per simulare l’effetto in vivo.

Since the introduction of ceramic-on-ceramic couplings in total hip arthroplasty, continuous efforts have been performed to improve the performance of the prosthetic components. To expand the applications of ceramics, in 2000 an innovative alumina–zirconia composite was introduced in the market. The present study represents the first investigation aimed at characterising at the molecular level BioloxW delta retrievals implanted between 1999 and 2009. Fluorescence and Raman results showed that a progressive improvement of the material properties has occurred in the period between 1999 and 2009. Raman spectroscopy showed that wear was the main cause of the in vivo tetragonal-to-monoclinic zirconia transformation. Our findings validated the in vitro accelerated ageing protocols proposed in the literature to simulate the effects of the in vivo wear, because the mechanism operating in vivo was found to be the same active in vitro. The in vitro fracture of a new femoral head appeared to be an extreme wear condition that determined the most significant changes in the residual stress state and monoclinic content both in the section of the fragments and on their surface. The micro-Raman mapping of the fractured articulating surface showed that the tetragonal-to-monoclinic transformation involved a region much more extended than as reported in the literature.

Negli anni ’90 sono stati introdotti in ambito odontoiatrico i primi cementi a base di silicati di calcio, comunemente denominati cementi MTA (Mineral Trioxide Aggregate). Tali cementi hanno dimostrato interessanti proprietà cliniche in chirurgia endodontica grazie alla possibilità di essere applicati in ambiente umido, ovvero in presenza di sangue o altri fluidi biologici, tipiche condizioni di un sito chirurgico osseo. Recenti studi hanno dimostrato la loro capacità di formare uno strato superficiale di materiale apatitico se immersi in soluzioni simulanti i fluidi biologici (simulated body fluids). È probabile che lo strato apatitico sia responsabile della buona attività osteogenica di questi cementi, ben dimostrata da studi in vitro ed in vivo. La proprietà di formare apatite permette di considerare tali materiali come cementi bioattivi. Questo studio ha confrontato la bioattività di un cemento calcio silicatico endodontico commerciale (White ProRoot MTA, Dentsply, USA) con quella di cementi calcio silicati sperimentali contenenti diverse percentuali di fluoruro di sodio. In particolare quantità rispettivamente dell’1% e del 10% di NaF sono state addizionate a un cemento sperimentale base (wTC-Bi) costituito da dicalcio e tricalcio silicato (belite e alite), tricalcio alluminato, solfato di calcio, cloruro di calcio ed ossido di bismuto. I cementi ottenuti sono stati denominati FTC-Bi ed F10TC-Bi. I cementi sono stati caratterizzati mediante spettroscopia micro-Raman ed ATR/FT-IR prima e dopo immersione per tempi diversi (5 ore-28 giorni) a 37°C, in simulated body fluid DPBS (Dulbecco’s Phosphate Buffered Saline). Le tecniche spettroscopiche hanno mostrato differenze significative tra la composizione dei cementi sperimentali e di ProRoot MTA, principalmente per quanto riguarda le componenti solfato e silicato. Dopo 5 ore di immersione in DPBS, i cementi contenenti fluoruro erano già ricoperti di un deposito di carbonatoapatite di tipo B (evidenziato dalla comparsa della banda Raman a 960 cm-1 e delle bande IR a 1460, 1410, 1025, 960, 870, 600, 560 cm-1) (Figura 1); il deposito era significativamente più spesso che nel caso dei cementi non contenenti fluoruro. Dopo 1 giorno di immersione in DPBS, è stata rivelata la presenza dello ione fluoruro nel reticolo cristallino dell’apatite (in maggior quantità in F10TC-Bi che in FTC). In tutti i cementi, il deposito è sempre andato aumentando in grado di maturazione, spessore ed omogeneità all’aumentare del tempo di immersione. Il cemento F10TC-Bi ha dimostrato una bioattività minore rispetto al cemento FTC-Bi. Tutti i cementi hanno mostrato la formazione di idrossido di calcio nei primi stadi di indurimento (banda IR a 3640 cm-1) ed un aumento significativo del pH del mezzo che resta basico fino a 28 giorni di immersione. In accordo con i dati di bioattività, il cemento F10TC-Bi ha mostrato una minor produzione di idrossido di calcio. In conclusione, lo studio dimostra che i cementi calcio silicati hanno una spiccata bioattività, che può essere ulteriormente aumentata con composti fluorurati.

Objectives: All endodontic sealers may be in contact with apical bone and must have high bioactivity and biological behaviour. The in vitro bioactive behaviour of commercial endodontic sealers for root canal therapy was investigated in real-time on wet fresh and set cements by using ESEM/EDX and micro-Raman. Methods: AH Plus (Dentsply, USA), Calcibiotic Root Canal Sealer - CRCS (Hygienic, USA), Pulp Canal Sealer - PCS and SealApex (Kerr, USA), and three calcium-silicate materials ProRoot MTA (Dentsply, USA), Tech Biosealer Endo (Isasan, Italy) and an experimental flowable MTA (University of Bologna, Italy) were tested. Cement discs were prepared according with manufacturer directions and analyzed in wet conditions by ESEM/EDX and micro-Raman immediately after their preparation (fresh) and after soaking at 37°C in simulated body fluid (HBSS) for 24h and 28d. The release of calcium-&-hydroxyl-ions in soaking water was tested at short times (3,24h and 7d) and at long times (14,28d). Results: Fresh wet samples displayed the elements of material composition. The surface of calcium-silicate cements resulted covered by apatite spherulitic deposits already after 24h and a continuous apatite coating at longer times. No apatite was detected neither on PCS nor on SealApex. CRCS showed some/rare apatite deposits since 24h and AH Plus revealed sporadic apatite deposits after 28d. Calcium-silicate materials and SealApex showed higher calcium-releasing than CRCS. AH Plus and PCS do not released calcium. Only calcium-silicate sealers released hydroxyl-ions. Conclusions: Commercial endodontic sealers resulted unable to induce formation of bone-like apatite layer and suggest a lack or modest level of bioactivity. On the contrary, ProRoot MTA and calcium-silicate cements demonstrated earlier bioactivity.

This thesis was aimed at investigating the physical-chemical properties and the behaviour in physiological environment of two classes of bioceramics: calcium silicate-based dental cements and alumina-based femoral heads for hip joint prostheses. The material characterization was performed using spectroscopic techniques such as that allow to obtain information on the molecular structure of the species and phases present in the analyzed samples. Raman, infrared and fluorescence spectroscopy was principally used. Calcium silicate cements, such as MTA (Mineral Trioxide Aggregate), are hydraulic materials that can set in presence of water: this characteristic makes them suitable for oral surgery and in particular as root-end filling materials. With the aim to improve the properties of commercial MTA cements, several MTA-based experimental formulations have been tested with regard to bioactivity (i.e. apatite forming ability) upon ageing in simulated body fluids. The formation of a bone-like apatite layer may support the integration in bone tissue and represents an essential requirement for osteoconduction and osteoinduction. The spectroscopic studies demonstrated that the experimental materials under study had a good bioactivity and were able to remineralize demineralized dentin. . Bioceramics thanks to their excellent mechanical properties and chemical resistance, are widely used as alternative to polymer (UHMWPE) and metal alloys (Cr-Co) for hip-joint prostesis. In order to investigate the in vivo wear mechanisms of three different generations of commercial bioceramics femoral heads (Biolox®, Biolox® forte, and Biolox® delta), fluorescence and Raman spectroscopy were used to investigate the surface properties and residual stresses of retrieved implants. Spectroscopic results suggested different wear mechanisms in the three sets of retrievals. Since Biolox® delta is a relatively recent material, the Raman results on its retrievals has been reported for the first time allowing to validate the in vitro ageing protocols proposed in the literature to simulate the effects of the in vivo wear.

Negli anni ’90 il primo cemento endodontico a base di silicati di calcio è stato introdotto in commercio con l’acronimo MTA (Mineral Trioxide Aggregate). I cementi MTA hanno la caratteristica di indurirsi in presenza di acqua e quindi anche di sangue o altri fluidi biologici, condizioni tipiche di un sito chirurgico osseo. Tuttavia, una delle principali limitazioni dei primi cementi MTA è il loro elevato tempo di indurimento, con conseguente rischio di dissoluzione e dilavamento del cemento dal sito chirurgico. In diversi materiali ad uso odontoiatrico, ad esempio nei cementi vetro-ionomerici, è stato possibile ottenere una diminuzione del tempo di indurimento (ed un miglioramento delle proprietà meccaniche) incorporando la componente inorganica (fluoro-silico alluminato) in una matrice polimerica fotopolimerizzabile. Nella presente ricerca tale strategia è stata seguita per produrre un cemento MTA fotopolimerizzabile (lc-MTA), allo scopo di estenderne le applicazioni chirurgiche anche in siti chirurgici estremamente umidi per la presenza di sangue. A questo scopo, un cemento calcio silicatico di base (wTC-Ba) costituito da dicalcio e tricalcio silicato (belite e alite), tricalcio alluminato, solfato di calcio, cloruro di calcio e solfato di bario è stato addizionato di una componente organica liquida costituita da 2-idrossietil metacrilato (HEMA), trietilenglicole dimetacrilato (TEGDMA), canforochinone e etil-4-(dimetilammino) benzoato, che è stata successivamente fotopolimerizzata per ottenere il composito lc-MTA. Questo studio è stato mirato a valutare l’effetto della componente polimerica sulla capacità del cemento formare uno strato apatitico in ambiente fisiologico (bioattività), caratteristica che riveste una certa importanza perché probabilmente con l’attività osteoge-nica/osteoinduttiva di questa classe di cementi. I cementi lc-MTA e wTC-Ba (utilizzato come materiale di controllo privo della componente fotopolimerizzabile) sono stati caratterizzati mediante spettroscopia micro-Raman ed ATR/FT-IR prima e dopo immersione per tempi diversi (1-28 giorni) a 37°C, in DPBS (Dulbecco’s Phosphate Buffered Saline), una soluzione simulante i fluidi biologici. Le tecniche spettroscopiche hanno mostrato che il composito non è semplicemente una miscela fisica delle due componenti poiché tra di esse si instaurano delle interazioni. Dopo 1 giorno di immersione in DPBS, entrambi i cementi sono già ricoperti di un deposito di carbonatoapatite di tipo B (evidenziato dalla comparsa delle bande Raman a 1070 e 960 cm-1 ed IR a 1460, 1410, 1025, 960, 870, 600, 560 cm-1) (Figura 1). In base all’intensità relativa delle bande dell’apatite e delle componenti del cemento, si può affermare che il deposito è significativamente più spesso sul cemento composito lc-MTA e questa situazione permane fino a 28 giorni di immersione. La componente polimerica gioca quindi un ruolo fondamentale, come mostrato dagli studi di bioattività condotti sulle componenti polimeriche poli-HEMA, poli-TEGDMA e poli(HEMA-co-TEGDMA): esse sono in grado di enucleare una componente apatitica in seguito a immersione in soluzioni metastabili contenenti ioni Ca2+ e PO43- in un rapporto Ca/P di 1.67.

Il primo utilizzo dell’allumina per la fabbricazione di protesi totali di anca risale al 1970. Da allora, i progressi nella scienza dei materiali hanno permesso di ottenere ceramici dalle prestazioni sempre migliori apportando notevoli vantaggi per il paziente. L’ultima generazione di materiale ceramico per ortopedia è stata introdotta in commercio nel 2000 con il nome di Biolox® delta (CeramTec AG). Questo materiale è un composito costituito principalmente da una matrice di allumina (circa 75% in peso) in cui sono dispersi grani di zirconia tetragonale cristallina stabilizzata con ittria, Y-TZP (circa 24% in peso, 17% in volume). La matrice di allumina conferisce durezza al materiale, mentre l’Y-TZP ne migliora le proprietà meccaniche. Infatti, in condizioni di stress (per esempio in corrispondenza di una crepa che avanza), i grani di Y-TZP vanno incontro ad una trasformazione di fase da tetragonale a monoclino (t-m) che blocca l’avanzamento della crepa in seguito all’aumento di volume dei grani di zirconia. Altri ossidi presenti nel composito (Cr2O3 e SrO) contribuiscono al miglioramento del materiale. La trasformazione t-m nelle Biolox® delta e nelle componenti Y-TZP è un argomento ancora dibattuto, perché vari autori hanno riportato che questa trasformazione comporta una degradazione del materiale che può incidere significativamente sul tempo di vita della protesi. D’altro canto il produttore dichiara che le componenti Biolox® delta sono state sviluppate proprio per evitare fenomeni di degradazione. In questo studio, teste femorali Biolox® delta espiantate per mobilizzazione asettica all’Istituto Ortopedico Rizzoli (follow-up medio 3.2 anni; range 1 mese - 8 anni) sono state analizzate mediante spettroscopia micro-Raman per chiarire questi meccanismi. Gli spettri Raman sono stati utilizzati, in accordo al metodo di Katagiri [1], per valutare la frazione volumetrica di zirconia monoclina (Vm). I dati riportati in Figura 1A (Vm misurati sui bordi delle testine non sottoposte a stress, considerati come controllo) mostrano che il materiale è progressivamente migliorato nel corso degli anni, mostrando una progressiva diminuzione di Vm. L’usura è apparsa il fattore decisivo che in vivo ha determinato la trasformazione t-m (che è innescata anche semplicemente dall’acqua), soprattutto nelle componenti meno recenti (Figura 1B). I dati ottenuti hanno anche permesso di ottenere informazioni sulla cinetica e sul meccanismo di trasformazione e di validare i protocolli di invecchiamento accelerato in vitro che sono stati messi a punto da altri autori per simulare l’effetto in vivo.

Although polyethylene is a satisfactory bearing for many patients, total hip replacements are being performed in younger and more active patients, who challenge the limitations of the standard material. Polyethylene wear problem plays out as a biological disaster in the body. Any use of the joint, such as walking in the case of hips, results in a cyclic articulation of the polymer cup against the metal or ceramic ball. Ceramic-on-ceramic (COC) hip bearings (alumina & zirconia) were introduced to solve polyethylene problems such as osteolysis and wear. Ceramics appears to be ideally suited to joint prosthesis, because of their hardness and excellent biocompatibility. Alumina was introduced more than 40 years ago with good clinical results. Zirconia has become a very popular alternative to alumina because of its higher mechanical properties and higher toughness. Nevertheless, problems related to the steam sterilisation and the hydrothermal stability of zirconia in the body havae been reported. Zirconia needs an addition of yttria to be used at room temperature, but undergoes slow degradation as a consequence of progressive crystal transformation with time. To better understand the wear mechanism of ceramic bearings, in this study, we investigated several long-term retrivals of different materials developed during last decades; Biolox, Biolox-Forte and Delta components were studied through scanning electron miscroscope (SEM) amd fluorescence spectroscopy. The residual stress state in the worn specimens was evaluated by the frequency shift and broadening of the fluorescence bands due to the Cr3+ ions naturally present in alumina ceramics as trace impurities or expressly added by the manufacturer in Delta components. The analysed specimens were all wear failures without fracture, to avoid possible influences of other parameters on the failure mode. The study of worn ceramic retrievals is useful to very if damage patterns generated by hip jount wear simulation are comparable to those evident on explanted prostheses due to physiologic hip function.

Objective: A liner must perform as a barrier and protect the dental pulpal complex. Calcium-silicate MTA materials recently used for pulp capping demonstrate the ability to form hydroxyapatite when immersed in simulated body fluid (Gandolfi et al. 2009, 2010). TheraCal is a light-curable resin formula which contains CaO mineral oxides, designed to be used as liner and pulp capping material that demonstrates good biocompatibility/absence of cytotoxicity. The aim of this study is to evaluate the ability of this material to form hydroxyapatite when immersed in a phosphate-containing solution. Method: TheraCal (Bisco Inc, USA), Control paste (without mineral oxides) (Bisco Inc, USA), ProRoot MTA (Dentsply, USA) were used. Sample discs (n=10 for each material) were prepared. The materials were placed in a PVC mold (8mm dia x 1.6mm) and light-cured on both surfaces for 20 seconds (per manufacture) using a LED light, after the application of a transparent polyester strip. The discs were de-molded, immersed in 10mL of a phosphate-containing solution (Dulbecco's Phosphate Buffered Saline, DPBS) in a sealed container and stored at 37°C. The surface chemistry, morphology and formation of apatite on samples surface after 1, 7, 14 and 28 days of immersion in DPBS was assessed by ESEM-EDX, micro-Raman and FT-IR techniques. Results: TheraCal demonstrated the capacity to form apatite on its surface after 24 hours immersion in DPBS, as did ProRoot MTA. Amorphous apatite (952 cm-1 Raman band) was detected within the first 24 hours, while a more crystalline apatite (960 cm-1 Raman band) was noticed at 7days. No deposit was detected on the Control. Conclusions: TheraCal is a calcium-releasing material able to induce the formation of apatite and represents a promising material in direct pulp-capping clinical/surgical procedures. The ability to form apatite may play a critical/positive role in new dentin formation.

Objectives: Calcium silicate cements (portland-derived cements and MTAs) are hydraulic cements capable of calcium release during their hydration and setting reaction when soaked in water and body fluids. They were developed as root-end filling materials but their clinical applications was extended to various situations, like perforation, pulp capping and apexification. The aim of this study was to evaluate the bioactivity (expressed by surface morphological modifications and chemical transformations) of two calcium-silicate cements soaked in Simulated Body Fluid (SBF) phosphate-containing. Materials and Methods: ProRoot MTA (Dentsply, USA) and experimental calcium-silicate cement (Retro TC, Italy) were used. The surface morphology and chemical properties of freshly prepared cements and of 14-days aged cements were investigated with micro-Raman, FTIR-ATR and ESEM/EDX. The ageing was performed by soaking the samples in 5ml of phosphate containing solution (SBF) for different times till 14 days. Samples in sealed holder were stored at 37°C. Results: ESEM/EDX analysis of freshly prepared cements showed the formation of needle-like crystals network on the surface. After 24 hours spherical precipitates (spherulites) deposited on the surface. The aggregation of these globular micro-crystals created bigger formations forming a surface coating. After 14 days of soaking the samples surface appeared irregular and porous. Raman analysis of fresh samples emphasized the typical bands of portland cement components, that corresponded to alite, belite and ettringite. After a 24 hours of soaking, Raman and FTIR analysis registered the same bands with a better-defined profile and the appearance of phosphate bands. Aged samples displayed calcium-phosphate bands (carbonate-apatite). Conclusions: this study demonstrated the bioactivity of calcium-silicate cements consisting in the ability to produce bone-like apatite when surrounded by a simulated body fluid. Calcium ions released from the cement react with phosphate ions from the solution inducing the formation of calcium phosphate deposits which stratify on the cement surface (biocoating).

NDI-C6 has been extensively studied for its semiconducting properties and its processability. It is known to have several polymorphs and a high thermal expansion. Here we report the full thermal characterization of NDI-C6 by combining differential scanning calorimetry, variable temperature X-ray powder diffraction, and hot stage microscopy, which revealed two different thermal behaviours depending on the annealing process. The ranking of stability was determined by the temperature and energy involved in the transitions: Form alpha is stable from RT up to 175 degrees C, Form beta is metastable at all temperatures, Form gamma is stable in the range 175-178 degrees C, and Form delta in the range 178-207 degrees C followed by the melt at 207 degrees C. We determined the crystal structure of Form gamma at 54 degrees C from powder. The analysis of the thermal expansion principal axis shows that Form alpha and Form gamma possess negative thermal expansion (X1) and massive positive thermal expansion (X3) which are correlated to the thermal behaviour observed. We were able to isolate pure Form alpha, Form beta, and Form gamma in thin films and we found a new metastable form, called Form epsilon, by spin coating deposition of a toluene solution of NDI-C6 on Si/SiO2 substrates.