Cytotoxic Evaluation of Elastomeric Dental Impression Materials on a Permanent Mouse Cell Line and on a Primary Human Gingival Fibroblast Culture

The need for clinically relevant in vitro tests of dental materials is widely recognized. Nearly all dental impression materials are introduced into the mouth just after mixing and allowed to set in contact with the oral tissues. Under these conditions, the materials may be toxic to cells or may sensitize the tissues. The aim of the present study is to evaluate the potential cytotoxicity of new preparations of elastomeric dental impression materials: A) four vinylpolysiloxanes: Elite H-D Putty and Elite H-D Light Body (Zhermack, Badia Polesine, Rovigo, Italy); Express Putty and Express Light Body (3M ESPE AG Seefeld, Germany) and B) two polyethers: Impregum Penta and Permadyne Penta L (3M ESPE AG Seefeld, Germany). The cytotoxicity of these impression materials were examined using two different cell lines: Balb/c 3T3 (permanent cell line) and human gingival fibroblasts (primary cell line) and their effects were studied by indirect and direct tests. The direct tests are performed by placing one sample of the impression materials in the centre of the Petri dishes at the time of the seeding of cells. The cell growth was evaluated at the 12th and 24th hours by cell number. The indirect tests were performed by incubating a square of 1 cm diameter impression material in 5 mL of medium at 37 °C for 24 hours (“eluates”). Subconfluent cultures are incubated with “eluates” for 24 hours. The MTT-formazan production is the method used for measuring the cell viability. The results indicate that: a) polyether materials are cytotoxic under both experimental conditions; b) among vinylpolysiloxanes, only Express Light Body (3M ESPE AG Seefeld, Germany) induces clear inhibition of cellular viability of Balb/c 3T3 evaluated by direct and indirect tests and c) the primary cell line is less sensitive to the toxic effect than the permanent cell line

Load bearing capability of three-units 4Y-TZP monolithic fixed dental prostheses: An innovative model for reliable testing

In this work, three-units monolithic fixed dental prostheses (FDPs) have been analysed and a novel model for reliable testing has been proposed. Such model is based on a new design of the polymeric base of the FDP, realised via additive manufacturing (AM) - a solution that conveys at the same time quick manufacturability, low cost, custom-ability, and design freedom. By means of this new model, the load-bearing capability of three-units monolithic FDPs has been thoroughly tested; in particular, three different analyses were performed: (i) analytical with a beam-like model, (ii) numerical, using non-linear three-dimensional Finite Elements (FE) models and (iii) experimental, by static bending test. The FDPs considered in this work were manufactured using a fourth-generation zirconia, namely 4Y-TZP. The findings demonstrated the undoubted advantages of the new base configuration, which minimized the effect of the base (which as a matter of fact is absent in in-vivo conditions) on the stress state of the connectors in the FDPs, and increased the repeatability and reliability of the experimental bending tests, able to determine the load bearing capability of the 4Y-TZP FDPs

bioactive nanocomposites for dental application obtained by reactive suspension method

AbstractHydroxyapatite (HA) filled poly(methyl methacrylate)/poly(hydroxyethyl methacrylate) (PMMA/PHEMA) blends were prepared by reactive suspension method: HA was synthesized by co-precipitation process directly within a HEMA solution and the so-obtained suspension was polymerized in the presence of PMMA. HA particles were obtained in form of nanorods with a length of 50–200 nm and a diameter of 10–30 nm. A significant increase in glass transition temperature was observed in the nanocomposites with respect to the unfilled polymer blends. Dynamic-mechanical thermal analysis showed a significant increase in the storage modulus in the nanocomposites measured in the rubbery region. This increase was unpredicted by Mooney's predictive equation and was attributed to the presence of cross-linking points due to the in situ generated HA particles. An increase in the elastic modulus was also observed at room temperature in compression and three-point bending tests. The presence of HA in the polymer blends resulte..

Long-term short implants performance: Systematic review and meta - Analysisofthe essential assessment parameters

Lack of standard criteria in the outcome assessment makes it difficult to draw conclusions on the clinical performance of short implants and, under these circumstances, determine the reasons for implant failure. This study evaluated, through a systematic review of the literature and meta-analysis, the essential parameters required to assess the long-term clinical performance of short and extra-short implants. Electronic databases (Pubmed- MEDLINE, Cochrane Library Database, Embase, and Lilacs) were searched by two independent reviewers, without language limitation, to identify eligible papers. References from the selected articles were also reviewed. The review included clinical trials involving short dental implants placed in humans, published between January 2000 and March 2014, which described the parameters applied for outcome\u2019s measurements and provided data on survival rates. Thirteen methodologically acceptable studies were selected and 24 parameters were identified. The most frequent parameters assessed were the marginal bone loss and the cumulative implant survival rate, followed by implant failure rate and biological complications such as bleeding on probing and probing pocket depths. Only cumulative implant survival rate data allows meta-analysis revealing a positive effect size (from 0.052 (fixed) to 0.042 (random)), which means that short implant appears to be a successful treatment option. Mechanical complications and crown-to-implant (C/I) ratio measurement were also commonly described, however, considering the available evidence; no strong conclusions could be drawn since different methods were used to assess each parameter. By means of this literature review, a standard evaluation scheme is proposed, being helpful to regiment further investigations and comparisons on future studies

The physiological linkage between molar inclination and dental macrowear pattern

Objectives: Exact symmetry and perfect balance between opposite jaw halves, as well as between antagonistic teeth, is not frequently observed in natural masticatory systems. Research results show that asymmetry in our body, skull, and jaws is often related to genetic, epigenetic, environmental and individual ontogenetic factors. Our study aims to provide evidence for a significant link between masticatory asymmetry and occlusal contact between antagonist teeth by testing the hypothesis that tooth inclination is one of the mechanisms driving distribution of wear in masticatory phases in addition to dietary and cultural habits. Materials and Methods: The present work investigates the relationship between dental macrowear patterns and tooth inclinations on a sample of complete maxillary and mandibular 3D models of dental arches from 19 young and adult Yuendumu Aboriginal individuals. The analysis was carried out on first molars (M1) from all quadrants. Occlusal Fingerprint Analysis was used for the quantification of macrowear patterns, and 2D cross-sectional geometric analysis was carried out to investigate asymmetry in dental arches. Results: The asymmetry is highly variable on both arches, and it is associated with differences in the inclination of upper M1 crowns. Each molar has variable inclination (buccal/lingual) which influence tooth to tooth contact, producing greater or lesser variation in wear pattern. Interindividual variability of morphological variation of the occlusal relationship has to be considered in macrowear analysis. Discussion: Our results suggest that overall asymmetry in the masticatory apparatus in modern humans affects occlusal contact areas between antagonist teeth influencing macrowear and chewing efficiency during ontogeny

TITANIO IN PROTESI RIMOVIBILE. PRESUPPOSTI TEORICI

L'impiego del titanio nel campo dei biomateriali ha consentito un notevole progresso in numerose discipline chirurgiche, quali l'ortopedia, la cardiochirurgia, la chirurgia maxillo-faccial

TITANIO IN PROTESI RIMOVIBILE. APPLICAZIONI CLINICHE

Le applicazioni del titanio in protesi rimovibile prevedono il rispetto scrupoloso delle indicazioni operative descritte in una precedente comunicazion

Protesi parziale rimovibile ancorata a impianti: attualità e prospettive future

la protesi parziale rimovibile ancorata a impianti intende rappresentare una concreta alternativa al trattamento inamo-amovibile tradizionale sostenuta da elementi naturali

Passività e carico immediato con tecnica analogica: standard conoscitivi

Più in generale, questa problematica inficia la vita e il successo della riabilitazione implantare per motivazioni di carattere: - biologico: dolore, senso di tensione, perdita dell’osso marginale e fallimento dell’osteointegrazione; - meccanico: allentamento delle viti protesiche, blocco o frattura della vite dell’abutment o frattura delle diverse componenti. L’imprecisione della struttura, anche chiamata misfit o mancanza di passività, non ha a oggi una definizione univoca. Alcuni autori (Wee et al. 1999; Sorrentino et al. 2010) considerano passivo un framework che non imprime forze statiche o dinamiche alla protesi o all’osso perimplantare, altri autori (Jemt et Book 1996) scelgono una definizione più clinica indicando la corretta passività di una struttura con l’assenza di problematiche a breve e lungo termine. La definizione di Jemt e Book è secondo il nostro parere preferibile, in quanto suggerisce la possibilità, riscontrata dalla clinica quotidiana, di considerare accettabile una quota di tolleranza tra le componenti implantoprotesiche biologicamente sopportata. Data l’impossibilità di ottenere un sistema totalmente passivo, è pertanto accettabile un grado di tolleranza che non causi complicanze cliniche sul breve, medio e sul lungo periodo. Di quanto sia la valutazione quantitativa di questo gap, la letteratura è discordante e tiene in considerazione la situazione protesica e biologica della riabilitazione. Il misfit strutturale è problematica comune alla protesi su dente naturale e su impianti cementati e avvitati, ma è su questi ultimi che riveste un ruolo di primo piano per via della mancanza di un sistema di ammortizzamento efficace. Se il legamento parodontale di un dente sano consente una mobilità, e quindi un ammortizzamento, pari a 100μm, così non è nell’impianto dove il tessuto osseo corticale offre solo 10μm di libertà di movimento (Lindhe et al. 2015). Pertanto, un dente naturale è in grado di tollerare misfit del framework maggiori rispetto a un impianto, sebbene sia comunque auspicabile la massima precisione. Nelle riabilitazioni fisse su impianti multipli, procedendo nel ragionamento, si distinguono sistematiche ritentive avvitate e cementate. Per opinione comune, con la seconda è più semplice ottenere la passività: questa osservazione manca di precisione. In protesi cementata è più tollerato il misfit strutturale grazie al cemento, che consente 40μm circa di gioco tra le varie componenti (Shillingburg 2012). La ritenzione in protesi avvitata non consente questo grado di misfit, poiché la vite sottoposta a precarico fissa rigidamente le strutture. Definito il problema e la sua rilevanza clinica, in questo articolo abbiamo proceduto all’analisi e alla classificazione delle cause di misfit durante il flusso di lavoro in implantoprotesi multipla avvitata con una metodica esclusivamente analogica. Vengono inoltre offerte delle possibili soluzioni ricavate dall’analisi della letteratura biomedica e dalla nostra pratica quotidiana