Laboratory and clinical evaluation of polymer materials reinforced by fibers used in dentistry.

OBJECTIVE: Fiber-reinforced composites (FRC) because of high strength and a low mass can be widely applied in many fields of dentistry. MATERIALS AND METHODS: The types of fibers commonly used in dentistry with the description of physicochemical properties of the reinforcing phase and polymer resin, are specified. The influence of the method of fiber positioning in the sample, their diameter, length and shape of fibers visible in cross-section on the strength of the FRC material, are underlined. The work also paid attention to the volume of the material that occurs as a result of the absorption of water from the oral environment and changes in bonding between matrix and fiber. RESULTS: The clinical procedures and a description of failures that may possibly happen in the oral cavity presented in the work, confirm that they allow fabrication of minimally invasive, lightweight, durable and biocompatible materials. At the moment, the only material group that can be used by direct technique to reach high load-bearing capacity restorations is FRC. CONCLUSIONS: Long-term treatment effectiveness makes FRCs an alternative to prosthetic restorations whose retention is obtained only as a result of mechanically interlocking to the abutment tooth. The use of FRCs in clinical dentistry is part of value-based medicine.

Application of stem cells in dentistry for bone regeneration.

Stem cells constitute a non-specialised cell pool able for proliferation, self-renewal and differentiation into progeny constantly replacing used up tissue and/or organ fragments. They have been observed to be present in many tissue reservoirs, including stomatognathic system. Oral cavity seems to be a particularly attractive stem cells' source as these cells are richly present and easily accessible in dental and periodontal tissues and they can be used for therapeutic purposes. Their application is also morally and ethically non-controversial. Bone tissue structure restoration together with restoring its weight-bearing and nutritive function depend on the proper function of stem cells supported with other techniques including tissue engineering. Traditionally, bone regeneration means bone restoration supported by newly formed bones supplied by stem cells of tissue reservoir. It may be also indispensable to create a scaffold which may support the bone formation facilitating the transportation of cells and cell stimulating molecules involving both the matrix and bone-forming cells. The regenerative potential of stem cells present in oral cavity can be used, for instance, to restore maxillary and mandibular bones. The bones support natural teeth or prostheses and regress as soon as at least the one tooth is lost or extracted. Bone mass loss makes it difficult to conduct effective dental treatment and reduces the chances of obtaining positive, long-lasting therapeutic effects. It seems that modern and innovative therapies based on stem cells application may bring spectacular effects especially in patients in whom routine medical activities did not lead to satisfactory results.

Advances in the ultrastructural study of the implant-bone interface by backscattered electron imaging.

The biocompatibility of titanium implants in bone depends on the response shown by cells in contact with the implant surface. Several developments have been targeted at achieving successful implant treatment. The aim of this study was to develop a novel preparation procedure to evaluate the bone cell response produced at the bone-implant interface using the technique scanning electron microscopy with backscattered electron imaging (SEM-BSE). Dental prostheses with an SLA-modified or TOP-modified surface were implanted in a toothless part of the mandibula in female pigs. The animals were sacrificed 12 weeks after surgery, at which time block specimens containing the implants were obtained. These specimens were then processed for SEM-BSE by optimizing a protocol involving chemical fixation and heavy metal staining. In addition, element distribution maps for the implant-bone tissue interface were obtained using a microanalytical system based on energy-dispersive X-ray spectrometry (EDS). This novel visualisation approach enabled a comprehensive study of the extracellular matrix and cell components of the host tissues neoformed around the implant. SEM-BSE images also provided ultrastructural details of the bone cells. This technique appears to be an effective and very promising tool for detailed studies on the implant-bone tissue interface and the host response to the bone incorporation process.

Impairment of the oral stereognosis in the partial anterior open bite.

The study was performed in 20 children with partial anterior open bite and in 20 children of a control group. Stereognosis was evaluated on the basis of correct recognition responses to silicone pieces of the different shapes. Pieces were put on the dorsal surface of the tongue close to its apex. It was evident that the stereognostic ability was impaired in children with anterior open bite. This ability also decreased after infiltration anaesthesia of the tongue. The study indicated that the tongue plays an important role in oral stereognosis.

Evaluation of bone loss at single-stage and two-stage implant abutments of fixed partial dentures.

INTRODUCTION: Fixed partial dentures (FPDs) can be supported on implant abutments only or on single-stage and two-stage implants and teeth. PURPOSE: The purpose of this study was a comparative analysis of bone loss at the single-stage and two-stage implant abutments of fixed partial dentures used to restore missing teeth classified as Class I or Class II according to the Kennedy classification. MATERIAL AND METHODS: 32 patients were treated by using 49 FPDs supported on implants and teeth worn for 2-6 years. Bone loss at the implant abutments of FPDs was evaluated by one examiner using a special ruler with a measuring scale and images of implants. Measurements were conducted at 26 single-stage implants and 50 two-stage implant abutments based on panoramic radiographs. RESULTS: Statistical analysis showed that the mean bone loss at implants after 2 years was 0.70 mm +/- 0.50. The mean bone loss at implants after 6 years was 1.73 mm +/- 0.41. The bone loss of the alveolar ridge at the single-stage implants was greater than at the two-stage implants but it was not statistically significant. CONCLUSION: Prosthetic treatment of missing teeth classified as Class I or II according to the Kennedy classification with FPDs may result in bone loss less than 2 mm after 6 years. Both single-stage and two-stage intraosseous implants can be suitable for the implant-prosthetic treatment of patients with alar lack of teeth.

Evaluation of wear of selected prosthetic materials in contact with enamel and dentin.

STATEMENT OF PROBLEM: The proper choice of prosthetic materials for restoration of occlusal surfaces is important for the protection of the hard tissue of the opposing teeth and for regular functioning of the stomatognathic system. PURPOSE: This study evaluated the resistance to wear of gold, Palliag M, Dentacolor, Chromasit, and Stellon materials and the enamel and dentin of natural teeth during functional contacts in an artificial oral environment with and without an abrasion material (Al2 O3 ). MATERIAL AND METHODS: The 5 nonceramic prosthetic materials used in the restoration of occlusal surfaces of fixed partial dentures were examined in contact with enamel and dentin during a simulated masticatory process in 2 environments (with and without abrasion). Wear was evaluated by means of a special device designed for wear examination. RESULTS: The findings highlighted that the wear of nonceramic prosthetic materials in contact with enamel or dentin was similar. Dentin showed greater wear when in contact with these materials than with the enamel surface. CONCLUSION: Artificial environmental factors significantly influenced the wear of the hard tissue of teeth, especially when in contact with materials having low microhardness.

[Nipple dysplasia and androgen syndrome]. / Dysplazja sutków a zespól androgenny.

Among 1500 patients in the reproductive age of Clinical Department of Endocrinological Gynecology in State Hospital in Warszawa, Poland estimated the correlations between the onset of benign breast disease (BBD) and the incidence of androgenic syndrome. Symptoms of the androgenic syndrome stated in cases of 191 women; 51 of them had also benign lesions of the breasts. It makes 26.9 percent women with the symptoms of androgenicity. Clinical studies have correlated mean age patients with acne, hirsutism, menstrual cycle disturbances, gain of weight (androgenic syndrome) and mean age women who have suffered both androgenicity and BBD.