Effect of artificial saliva on the mechanical properties of a polymer material reinforced with fiber, used in esthetic tooth restorations.

BACKGROUND: The oral environment can negatively affect the physical properties of fiber-reinforced composite (FRC) materials, which can lead to the deterioration of mechanical stability and reduce the span of their clinical usefulness. OBJECTIVES: The aim of this study was to determine the influence of artificial saliva on the selected mechanical properties of FRC. MATERIAL AND METHODS: The core of the polymer material selected for the study was a bundle of ultrahighmolecular-weight polyethylene (UHMWPE) fibers. Fourteen samples were stored in an incubator at 37°C, in 20 mL of artificial saliva solution, and weighed on days 1 and 28. At the same time, mechanical tests were performed, including the measurements of Young's modulus, tensile stress, maximum tensile force, and tensile deformation. RESULTS: The analysis of basic statistics together with the results of the Shapiro-Wilk test and the distribution of Spearman's rho coefficient showed a strong negative relationship between the pair of variables - tensile deformation and the sorption of synthetic saliva. The results related to Young's modulus of elasticity and tensile stress were not statistically significant. CONCLUSIONS: Water penetration into the space between the fibers does not adversely affect the mechanical properties of the material tested. In the static tensile test, high and desired mechanical strength was observed, which may justify the effective use of this type of material in clinical practice and may be a good alternative to prosthetic restorations, whose retention is obtained only through a mechanical connection with the abutment tooth.

Usefulness of laser ablation ICP-MS for analysis of metallic particles released to oral mucosa after insertion of dental implants.

Despite the fact that titanium is considered highly biocompatible, its presence in the oral cavity (an environment of frequently changing pH and temperature) may result in the release of titanium from intraosseous implants into the oral mucosa, causing a range of reactions from the human body. Fragments of oral mucosa collected from patients after dental implant insertion were analyzed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The study revealed an elevated content of elements (Ti, Al, V) which are components of the metal implants and temporary cover screws. Dynamic ablation of the tissue surface was used in order to obtain maps of the content and distribution of analyzed elements. The material consisted of 30 oral mucosa tissue fragments collected 3-5 months after implantation and 10 samples collected before implantation (control group). The application of optical microscope allowed for indication and confirmation of the location of metal particles prior to LA-ICP-MS analysis. The so-obtained map permitted location of regions containing metal particles. LA-ICP-MS analysis revealed groups of samples with similar properties of metal particles, thus confirming that those metal particles were the main source of the elevated content of metals (Ti, Al, V) in the tissue after implantation. A calibration strategy based on matrix matched solid standards with powdered egg white proteins as matrix material was applied with 34S as an internal standard. The accuracy of the analytical method was verified by ablating pellets of certified reference material ERM-BB422 Fish muscle.

The Physicochemical Characteristics of Prosthetic Materials and Their Influence on Their Clinical Properties.

The use of elastic materials favours degradation of their surface. The period of their clinical usefulness is then shortened, and their further utilisation in the oral cavity may have the reverse effect. The surface properties of such material as well as the influence of the humidity on their surface are very important as they determine the prosthetic materials behavior in the mouth. The surface of such material should be resistant to water. Inverse gas chromatography is an accurate, sensitive technique for studying surface properties. Thanks to using a unique equipment specially designed for IGC technique, Surface Energy Analyzer, it was possible to characterize the surface at 0 and 80% of humidity. Our results show that increased humidity does not affect surface properties of studied prosthetic materials. Their ability to dispersive and specific interactions change in very limited degree. IGC experiment was also applied for the estimation of Hansen solubility parameters that indicate ability of a material to dispersive, polar, and hydrogen-bonding interactions. Relation between the surface characteristics and practical use of soft lining materials with implications for their clinical usefulness is also discussed.

The oral cavity - potential source of stem cells.

The purpose of this review is to present the current knowledge regarding the hierarchy of stem cells originating from the oral cavity, which could have a potential value when applied to regenerative stomatology. It must be particularly emphasized that the heterogenous nature of its biology and function within oral compartment may predispose them to different types of applications. Stem cells can be perceived as immature, primitive and unspecialized types of cells with the ability to proliferate, self-renew and differentiate into specialized progeny according to the compartmental signaling. Their presence in tissue reservoirs was already discovered in many organs and tissues as well as in the stomatognathic system. The oral cavity appears to be an exceptionally attractive site to acquire stem cells. The common presence and easy access to these cells in dental and peridental tissues provides a real chance to apply them for therapeutic purposes. Such an opportunity would also be neutral to bioethical and moral issues, assuming autologous stem cells employment. Many authors suspect that stem cells have epigenetic memory, so some of their features can be inherited through generations. They are not connected, however, with DNA sequence modifications. It is, therefore, justified to apply the cells, which have the oral cavity as their natural reservoir, in interventions associated with tissue engineering within the stomatognathic system. An increasing number of clinical trials, among which the number of randomized studies with large group of patients is progressively carried out, allows for a prediction that shortly therapeutic methods based on stem cells of dental origin may be implemented to the routine repertoire of clinical practice.

New procedure of quantitative mapping of Ti and Al released from dental implant and Mg, Ca, Fe, Zn, Cu, Mn as physiological elements in oral mucosa by LA-ICP-MS.

A new procedure for determination of elements derived from titanium implants and physiological elements in soft tissues by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is presented. The analytical procedure was developed which involved preparation of in-house matrix matched solid standards with analyte addition based on certified reference material (CRM) MODAS-4 Cormorant Tissue. Addition of gelatin, serving as a binding agent, essentially improved physical properties of standards. Performance of the analytical method was assayed and validated by calculating parameters like precision, detection limits, trueness and recovery of analyte addition using additional CRM - ERM-BB184 Bovine Muscle. Analyte addition was additionally confirmed by microwave digestion of solid standards and analysis by solution nebulization ICP-MS. The detection limits are in range 1.8µgg-1 to 450µgg-1 for Mn and Ca respectively. The precision values range from 7.3% to 42% for Al and Zn respectively. The estimated recoveries of analyte addition line within scope of 83%-153% for Mn and Cu respectively. Oral mucosa samples taken from patients treated with titanium dental implants were examined using developed analytical method. Standards and tissue samples were cryocut into 30µm thin sections. LA-ICP-MS allowed to obtain two-dimensional maps of distribution of elements in tested samples which revealed high content of Ti and Al derived from implants. Photographs from optical microscope displayed numerous particles with µm size in oral mucosa samples which suggests that they are residues from implantation procedure.

Molecular basis of hypohidrotic ectodermal dysplasia: an update.

Recent advances in understanding the molecular events underlying hypohidrotic ectodermal dysplasia (HED) caused by mutations of the genes encoding proteins of the tumor necrosis factor α (TNFα)-related signaling pathway have been presented. These proteins are involved in signal transduction from ectoderm to mesenchyme during development of the fetus and are indispensable for the differentiation of ectoderm-derived structures such as eccrine sweat glands, teeth, hair, skin, and/or nails. Novel data were reviewed and discussed on the structure and functions of the components of TNFα-related signaling pathway, the consequences of mutations of the genes encoding these proteins, and the prospect for further investigations, which might elucidate the origin of HED.

An in-needle extraction technique in determination of organic compounds released from dental tissue conditioners incubated in artificial saliva.

The use of an in-needle technique for direct isolation of analytes from real liquid samples is a new proposal. The in-needle technique has been relatively seldom used for direct sampling of liquid matrix through the needle. In this work the in-needle technique has been applied for the determination of compounds evolved to artificial saliva from dental prosthetic materials. It has been shown that results from the experiment with in-needle device were at least comparable with those obtained with using well known solid phase extraction (SPE). It is worth to mention that in-needle extraction offers some advantages: lower consumption of solvent, shorter step-preparation time and reduced costs. The compounds released from prosthetic materials may affect the stability of tissue conditioners and limit their long-term use in the oral cavity. Examined soft dental materials have been found to be stable as minor amount of various species have been emitted from them. Results of the stability tests of soft dental materials with the use of in-needle device on sample preparation step enable their quick evaluation and estimations of their quality.

The usefulness of psychometric tests in dental treatment of patients aged above 65.

OBJECTIVE: The aim of this study was to analyze the occurrence of some psychological disorders in elderly people in three different social settings and to evaluate the impact of those problems on the adaptation of denture wearers to removable prostheses. MATERIALS AND METHODS: The study was conducted in three social settings: the geriatric clinic of a university hospital, nursing homes and a Third Age University school (TAU). Each group consisted of 70 randomly selected individuals. Of the total number of 210 subjects, 183 persons wore maxillary removable dentures while 150 had mandibular prostheses. Some symptoms of psychological disorders were diagnosed on the basis of results provided by two tests: GHQ and GDS. For identification of an inter-relationship between the use of removable dentures and the psychic status, the difficulties in adaptation to removable dentures were evaluated. RESULTS: Statistical analysis showed that the number of individuals with depressive symptoms was significantly lower in the group of TAU students than among the nursing home residents. No statistically significant difference in the occurrence of depression was found between the group of hospital patients and the students of TAU. A comparison of the GDS test results with the incidence of denture use difficulties indicated a significant inter-relationship. CONCLUSIONS: The GHQ and GDS tests may prove useful in the prosthetic treatment of those removable denture wearers who complain of oral discomfort without manifesting any visible causes. The proportion of elderly with signs of psychic disorders is significantly lower among TAU students than nursing home residents and hospital patients.

Changes of oral sensibility in subjects with partial anterior open bite and the incorrect position of the tongue.

Neuromuscular disorders lead to an imbalance in the position of the jaw. The aim of this study has been to analyse gnostic sensibility in subjects with partial anterior open bite and the incorrect position of the tongue. The study involved 20 subjects with partial anterior open bite and an incorrect tongue position. The control group consisted of 20 individuals with correct occlusion and tongue position. The basic study method was a stereognostic examination using 4 silicon shapes - a square, triangle, circle and semicircle. The accuracy of shape identification and the time that the subjects needed to identify the shapes were analysed before and after the tip of the tongue was anaesthetized. Results showed that correct identification of the shapes was 7.4% worse in the study group than in the control group and that the difference was greatest when the tip of the tongue was anaesthetized - 28.8%. The time needed to identify the shapes was shorter in the study group than in the control group. The results indicate that people with partial anterior open bite and incorrect tongue position exhibit impaired gnostic sensibility, especially at the tip of the tongue. Impaired gnostic sensibility, which is a symptom of the disturbed sensomotoric correlation of the tongue, leads to the tongue's incorrect position in the process of swallowing and speaking.

Effect of denture cleansers on chemical and mechanical behavior of selected soft lining materials.

OBJECTIVES: The aim of this investigation was to determine the effect of storage in disinfectants and artificial saliva on a series of commercial soft lining materials for dentures. Changes in mechanical properties and the nature of chemicals released into these solutions were studied. METHODS: Four soft lining materials were studied (Vertex Soft® and Villacryl Soft®, both of which are plasticized acrylics; Molloplast B® and Mollosil®, both of which are silicone elastomers). All were cured according to manufacturers' instructions, and then cylindrical specimens (6 mm height × 10 mm diameter) prepared. These were stored under various conditions then loaded in uniaxial compression and the stress measured at a strain corresponding to a 10% deformation to determine Young's modulus. Storage involved exposure either to the following disinfectants: 2% aqueous chlorhexidine gluconate, 2% aqueous sodium hypochlorite, Corega Tabs® cleansing tablets or 3% aqueous hydrogen peroxide; or to artificial saliva. For the latter, storage involved either immersion in artificial saliva at 37°C for the whole study, or immersion for 16h a day and dry at room temperature for the next 8h each day. GC/MS was used to determine species leached into these solutions. RESULTS: The acrylic materials Villacryl Soft and Vertex Soft became less elastic on storage for up to 28 days whereas the silicone materials Molloplast B and Mollosil, showed no change in elastic properties. Various compounds were found to be released from these materials, including EGDMA, methyl methacrylate and dibutyl phthalate. Generally, the silicones were more stable than acrylics, releasing smaller amounts of the various eluants. In all cases, amounts eluted were well below permitted exposure limits. SIGNIFICANCE: Practical denture cleansing agents affect the properties of soft lining materials, reducing their elastomeric character, acrylics being more adversely affected than the silicones. These changes are associated with the loss of various chemicals, including plasticizers and monomers, from the soft lining materials.

Analysis of colour stability of selected provisional prosthetic materials: an in vitro study.

Prosthetic restorative materials (that are) used for temporary fixed dentures tend to exhibit variable discolouration over several weeks of use. The aim of this study was to perform a spectrophotometric analysis of the influence of selected discolouring factors on the colour stability of provisional prosthetic materials in vitro. In the study, the following prosthetic materials for short-term use in the oral cavity were evaluated: Luxatemp, Structur 2S.C., Protemp II, Zhermacryl STC and Dentalon Plus. Samples of these materials were immersed in coffee, tea and dark fruit juice for 60 h at different pH values. Colour was evaluated by determining the monochromatic coefficients of light reflected by the samples, using a spectrophotometric method. Results received in artificial light (illuminant A) were compared with those obtained in daylight (illuminant D65). Changes in colour and its parameters according to the CIE L*a*b* system were analysed. The analysis (of the colour and colour parameters) of the tested materials in two types of light showed that Structur displayed the greatest tendency to discolouration and that the least tendency to discolouration was exhibited by Dentalon Plus. The fact that colour parameters obtained in two types of light were not identical suggests that changes in the colour of the same material may be perceived differently, depending on the illuminant. Provisional prosthetic materials show variable colour stability under different conditions in the oral cavity. The colour of prosthetic materials may be perceived differently, depending on the illuminant and the effect of the environment in which they are used.

The influence of denture cleansers on the release of organic compounds from soft lining materials.

Biocompatibility constitutes the most fundamental requirement with respect to all dental materials to be applied within the oral cavity. In its environment, various toxic compounds may be released by dental materials which pose potential threats to the patient's health. Due to the fact that dentures remain in the oral cavity for a very long time, a detailed examination and verification of prosthetic materials with a view to their toxicity seems to be essential. By using very sensitive measurement techniques such as gas chromatography, one may determine which compounds are released by these materials. The aim of this paper was to determine the influence of various denture cleansers on the release of organic compounds from four soft dental materials used in prosthetics for lining dentures. These materials when placed in commonly used disinfectants (Corega Tabs, sodium hypochlorite, chlorhexidine, hydrogen peroxide), as well as in artificial saliva, produced 13 chemical compounds such as monomers (methyl methacrylate, ethyl methacrylate, dodecyl methacrylate), plasticizers (dibutyl phthalate, diethyl phthalate, tributyl acetylcitrate) and others (e.g. benzophenone). A comparison of chemical compounds released from acrylic-based materials and those released from silica-based materials demonstrated that acrylic-based materials are less resistant to disinfectants.

Luminescence of selected dental composites in vitro.

OBJECTIVES: The work was motivated by the necessity to evaluate the emission changes of dental composites, as the emission under UV light is one of the important optical parameters of the hard tooth tissue. METHODS: Fulfill extra, Artemis and Durafill VS materials in A3.5 shade were tested. Coffee, tea, red wine and distilled water (blank) were used as staining drinks. The samples were soaked for 7 days. Total luminescence matrices were collected with an interval of 1 nm in emission and 10nm in excitation, in the front-face geometry. RESULTS: The exposure of dental composites to staining drinks caused a reduction in luminescence intensity by up to 40%, the magnitude of the reduction depending on the drink and on the composite material. In the special case of the intrinsically weak fluorescent Durafill VS, the exposure to coffee apparently caused an increase in luminescence intensity due to coffee components adsorbed on the sample surface. SIGNIFICANCE: It is important to improve the emission stability of dental composites. The presently proposed methods are effective in evaluating the emission of dental composites. Emission needs to be tested in addition to color, as the two parameters are uncorrelated.

Electron ionisation and electrospray ionisation mass spectrometric study of a series of isomeric methyl-, dimethyl- and trimethylalloxazines.

Electron ionisation (EI) mass spectra and electrospray ionisation (ESI) mass spectra at different cone voltages of a series of isomeric methyl- and dimethylalloxazines are discussed, and compared with those of lumichrome, and 1- and 3-methyllumichrome. Examination of ESI mass spectra taken at a higher cone voltage and the use of isotope-labelled methanol allow us to discuss the fragmentation pathways of [M+H]+ and [M-H](-) ions. The fragmentation pathways of all of the compounds and the characteristic fragment ions formed in EI-MS are compared with published data. The influence of methyl and dimethyl substituents in the benzene ring on the fragmentation pathways leading to the loss of 43 and 45 Da upon both electron and electrospray ionisation is described.