Paolo Francesco Manicone

Development of a new zirconia-toughened alumina: promising mechanical properties and absence of in vitro carcinogenicity.

High purity alumina as well as zirconia ceramics have been widely used as orthopaedic implant biomaterials and dental devices displaying optimal, but sometimes exclusive, mechanical properties. In order to combine the advantages of alumina and zirconia ceramic materials different types of composites have been developed in which either zirconia is dispersed in an alumina matrix or vice versa. Orthopaedic and dental implant biomaterials are expected to be in contact with living tissues for a long period of time and their long term toxicity must be carefully evaluated. In this study we report the development of a high performance chromia-doped Zirconia Toughened Alumina (ZTA) material which displays promising mechanical properties in terms of hardness, strength and fracture toughness that make it suitable for prosthesis even for small joints. The long-term biocompatibility of this material was also evaluated, mainly in terms of DNA damage, mutagenicity and cancerogenetic potential in mammalian cells. The results obtained suggest that this new ZTA material does not display any long-term carcinogenic effect and it is suitable for biomedical applications from a cancerogenetic point of view. In conclusion, we report the development of a new chromia-doped ZTA material with interesting properties both from a mechanical and a biocompatibility point of view which warrant further studies on its suitability as a candidate biomaterial for orthopaedic implants and dental devices.

A novel surgical approach to impacted mandibular third molars to reduce the risk of paresthesia: a case series

PURPOSE Extraction of impacted mandibular third molars (M3s) may cause temporary or permanent neurosensorial disturbances of the inferior alveolar nerve (IAN). Although the incidence of this complication is low, a great range of variability has been reported in the literature. Several methods to reduce or eliminate this complication have been proposed, such as orthodontic-assisted extraction, extraction of the second molar, or intentional odontoectomy. The purpose of this series of cases is to present a novel approach for a riskless extraction of impacted mandibular M3s in contact with the IAN. MATERIALS AND METHODS Nine consecutive patients (4 male and 5 female; mean age 24.9 years, range 18-43 years) required the extraction of 10 horizontally or mesioangular impacted mandibular M3s. In all cases the M3 was in contact with the IAN with a high risk of nerve injury. A staged approached was proposed and accepted by the patients. This approach consisted in the surgical removal of the mesial portion of the anatomic crown to create adequate space for mesial M3 migration. After the migration of the M3 had taken place, the extraction could then be accomplished in a second surgical session minimizing neurological risks. RESULTS All M3s moved mesially within 6 months (mean 174.1 days, range 92-354 days) and could be successfully removed without any neurological consequences. CONCLUSION This technique may be considered as an alternative approach to the extraction of horizontally or mesioangular impacted M3s in proximity to the IAN.

An overview about biomedical applications of micron and nano size tantalum.

Tantalum is obtained from the minerals colombite, tantalite and euxenite. It is greyish silver, heavy and very hard. Tantalum does not react with body fluids and is used to make surgical equipment. Tantalum also does not irritate the body and is used to make surgical sutures as well as implants, such as artificial joints and cranial plates. Bone growth around tantalum covered by calcium phosphate is described by in vitro experimentations. in vivo. Bioactive properties of porous tantalum have been recently developed. Porous tantalum consists of an interconnected porous structure with an average porosity diameter of approximately 400 microm. Hollow spheres with nanometre-to-micrometer dimensions are widely used in different range of applications such as drug delivery carriers and bioreactors. Porous tantalum metal is currently used in orthopaedic for manufacturing of structural component for primary and revision total hip and knee replacements and, more recently, in spine surgery. Good clinical outcomes have been achieved especially in hip revision surgery, using tantalum implants, and promising short term follow up have been reported for knee revision surgery. Some patents for tantalum biomedical applications have been obtained and this article reviews various recent patents on this material. Many patents are developed on tantalum for biomedical application. This paper review some of them with particular interested for biomedical applications in orthopaedic and dentistry.

N-3 polyunsaturated fatty acid effect in periodontal disease: state of art and possible mechanisms involved.

Anti-inflammatory properties have been widely reported for n-3 polyunsaturated fatty acids (PUFAs) and some studies have been focalized on their possible role in the modulation of gingivitis and alveolar bone resorption in periodontal disease (PD). Increased formation of arachidonic acid-derived inflammatory eicosanoids and augmented oxidative stress are two molecular mechanisms pathogenetically involved in the progression of PD and known to be inhibited by n-3 PUFAs in PD setting. The present review will focus also on other molecular pathways and factors known to be altered in the development of PD and known to be subject to n-3 PUFA modulation in other pathological settings different from PD. Overall, the available findings strongly encourage further experimental studies on animals subject to experimental PD and treated with n-3 PUFAs, long term n-3 PUFA intervention studies on PD patients and molecular studies to identify additional potential molecular routes of n-3 PUFA action in PD.

Alumina and Zirconia Ceramic for Orthopaedic and Dental Devices

Ceramic materials are made of an inorganic non-metallic oxide. Usually ceramics are divided into two groups: silicon ceramics and aluminous ceramics. Ceramics are also divided into crystalline and non-crystalline depending on inner molecular organization. Depending on their in vivo behaviour, ceramics are classified as bioresorbable, bioreactive or bioinert. Alumina and zirconia are bioinert ceramics; their low reactivity togheter with their good mechanical features (low wear and high stability) led to use them in many biomedical restorative devices. Their most popular application is in arthroprosthetic joints where they have proven to be very effective, that make their use suitable especially in younger, more active patients. Also dental use of these materials was proposed to achieve aesthetic and reliability of dental restorations.

Staged Removal of Horizontally Impacted Third Molars to Reduce Risk of Inferior Alveolar Nerve Injury

Damage to the inferior alveolar nerve (IAN) during third molar extraction is a major concern for patients and clinicians. A wide range of the incidence of temporary and permanent neurologic disturbances of the IAN as a consequence of mandibular impacted third molar extraction has been reported in the literature. The incidence of IAN injury reported in the literature ranges from 1.3% to 5.3%. The risk of this complication depends mainly on the position of the impacted tooth in relation to the inferior alveolar canal. To reduce this risk, several approaches have been proposed. Some authors advocated orthodontic-assisted extraction of the impacted mandibular third molars. Others introduced partial odontectomy, that is, the surgical removal of the anatomic crown leaving the roots in place. This case report describes a novel approach to the extraction of horizontally and mesially inclined impacted third molars with the root apexes in close contact with the IAN.

In vivo characterization of Zirconia Toughened Alumina material: a comparative animal study.

The development of a new chromia-doped Zirconia Toughened Alumina (ZTA) material was previously reported as displaying mechanical properties suitable for implants with load bearing applications, such as orthopaedic and dental implants. This type of biomaterial is expected to be in contact with living tissues for a long period of time and its long-term toxicity must be carefully evaluated. In this study the suitability of this ZTA material as a candidate biomaterial for orthopaedic implants and dental devices was further investigated in vivo in comparison to alumina and zirconia, which are currently used in orthopaedic and dental surgery. Cylinders of the materials were implanted in vivo in white rabbits, and local and systemic tissue reactions were analyzed at different time intervals after surgery. Radiologic examinations displayed the absence of radiolucence around cylinders and no signs of implant loosening up to twelve months. No tumours developed in the animals either locally (at the site of implantation), or systemically in the peripheral organs. The results obtained suggest that this new ZTA material does not display any long term pathogenic effect in vivo. These findings extend our previous observations on the biocompatibility and the absence of any long-term carcinogenic effect in vitro of this material which displays interesting properties for biomedical applications. In conclusion, we report the in vivo characterization of a new chromia-doped ZTA material and confirm its suitability as a candidate biomaterial for orthopaedic implants and dental devices since it does not give any local nor systemic toxicity even after a long period of time after implantation.

Morphological Modifications in Osteoarthritis: A Scanning Electron Microscopy Study

The chondrocyte, the only cellular component of adult articular cartilage, plays a key role in the pathogenesis of osteoarthritis (OA). The evolution of this process is very slow: the first changes involve the cell-matrix morphofunctional unit known as chondron. In this study we analyzed the cartilage of 10 patients with primary osteoarthritis. The cartilage was retrieved during total knee replacement (TKR) and maxillofacial surgery procedures. All patients presented an osteoarthritis of at least grade III. The preparation of the specimens was made by taking cartilage from both well-preserved and macroscopically degenerated areas. Specimens underwent histological evaluation with conventional staining and ultrastructural analysis. Age appeared to be a high risk factor in the development of articular cartilage damages. Depth of injury was also found to be age-related as more extensive lesions were found in the elderly, either in the knee or in the mandibular condyle. Whatever the cause of possible damage, Scanning Electron Microscopy (SEM) observations showed that at the beginning most degenerative changes in articular cartilage involved the chondron unit, a concept first introduced by Benninghoff. These changes generally go through three phases. During OA progression all degenerative changes begin from the chondron, which is why it is extremely important to understand the molecular anatomy and physiology of this pericellular microenvironment and its form, function and failure in adult articular cartilage. It is also fundamental to understand the mechanism of adaptation of the cartilage and bone disruptions, given the physiological relationship between these tissues, essential to maintain normal joint structure and function.

Interobserver variability of dynamic MR imaging of the temporomandibular joint

PurposeThis study investigated the interobserver variability of dynamic magnetic resonance (MR) imaging of the temporomandibular joint (TMJ).Materials and methodsSixty-two patients with internal derangement of the TMJ (124 TMJs) were investigated with a 1.5-T MR imaging system during physiological opening and closing of the mouth. Two readers evaluated independently the quality of the dynamic examination (Q: nondiagnostic, diagnostic, optimal), condylar motion (CM: limited, suboptimal, optimal), condylar orientation (CO: in-plane, through-plane shift), disc visibility and movement (DV: visible, nonvisible; DM: normal, reducing, nonreducing dislocation) and joint effusion (JE: present, absent). For each TMJ, the condylar path was measured by tracing the position of the condyle in the frames of the dynamic acquisition. Agreement between the two readers was assessed with Cohen’s Kappa and the Bland-Altman method.ResultsInterobserver agreement was almost perfect for Q (nondiagnostic, diagnostic, optimal: 0.8%, 4.9%, 94.3%; κ=1), CM (limited, suboptimal, optimal: 14%, 26.4%, 59.5%; κ=0.84) and DV (visible, nonvisible: 100%, 0%). Substantial agreement was found for DM (normal, reducing, nonreducing: 66.1%, 14.8%, 19.1%; κ=0.64) and JE (present, absent: 41.3%, 58.7%; κ=0.67). Moderate agreement was found for CO (in-plane, through-plane shift: 94.2%, 5.8%; κ=0.41). As for the condylar path, the means of the percentage differences and limits of agreement (LA) were −3% (LA: −34.5%, 28.3%) on the right and −1.2% (LA: −35%, 32.6%) on the left.ConclusionsIn dynamic imaging of the TMJ, qualitative assessment of condyle-disc movement and joint effusion is minimally dependent on the reader’s evaluation. Measurement of the condylar pathway shows an interobserver variability of ±30%.RiassuntoObiettivoScopo del nostro lavoro è stato valutare la variabilità inter-osservatore della risonanza magnetica (RM) dinamica dell’articolazione temporo-mandibolare (ATM).Materiali e metodiSessantadue pazienti con disfunzione condilo-meniscale (124 ATM) sono stati studiati con tecnica RM dinamica dell’ATM su apparecchio da 1,5 T durante movimento fisiologico di apertura e chiusura buccale. Due lettori hanno valutato indipendentemente la qualità dell’esame (Q: non diagnostico, diagnostico, ottimale), il movimento condilare (MC: limitato, subottimale, ottimale), l’orientamento condilare (OC: nel piano, fuori dal piano), visibilità e movimento del disco (VD: visibile, non visibile; M: normale, dislocazione ridotta, dislocazione non ridotta) e il fluido articolare (F: presente, assente). Per ogni ATM, è stato inoltre misurato il percorso condilare demarcando la posizione del condilo nei frame dell’acquisizione dinamica. È stata stimata la concordanza tra i due osservatori (κ di Cohen, Bland-Altman).RisultatiLa concordanza è risultata ottimale per Q (non diagnostico, diagnostico, ottimale: 0,8%, 4,9%, 94,3%; κ=1), MC (limitato, subottimale, ottimale: 14%, 26,4%, 59,5%; κ=0,84) e VD (visibile, non visibile: 100%, 0%), buona per M (normale, dislocazione riducibile, non riducibile: 66,1%, 14,8%, 19,1%; κ=0,64) e V (presente, assente: 41,3%, 58,7%; κ=0,67), moderata per OC (nel piano, fuori dal piano: 94,2%, 5,8%; κ=0,41). Per il percorso condilare, la media delle differenze percentualizzate ed i limiti di concordanza (LC) sono risultati −3%, (LC: −34,5%, 28,3%) a destra e −1,2% (LC: −35%, 32,6%) a sinistra.ConclusioniLa valutazione qualitativa del movimento condilo-meniscale e della presenza di fluido intraarticolare nell’imaging dinamico dell’ATM è solo minimamente dipendente dalla stima dell’osservatore, mentre la misurazione del tracciato condilare presenta una variabilità inter-osservatore pari a ±30%.

MRI assessment of temporomandibular disorders: an approach to diagnostic and therapeutic setting

Abstract Aims: The aim of this study was to evaluate the relationship between the clinical and the radiological data obtained by magnetic resonance imaging (MRI) in patients with temporomandibular disorder (TMD). Methodology: The study group included 17 patients with symptoms of TMDs. The radiological assessments before and after therapy was evaluated by MRI; in the clinical analysis, signs and associated symptoms have been assessed. Results: With MRI before therapy, we were able to distinguish the specific type of TMD that each patient had. At the end of the treatment, a general improvement of the clinical status was noticed; MRI, however, showed the permanence of several degrees of condyle–disc incoordination in some patients. Conclusions: Certainly TMDs can be diagnosed without MRI; nevertheless, MRI gives us the possibility to obtain objective data of the patients concerned. Symptoms recorded during a clinical evaluation cannot be the only terms of diagnosis; MRI provides objective data in the diagnostic and post-therapy phases.