Importance of diameter-to-length ratio in selecting dental implants: a methodological finite element study.

Implant dimensions greatly influence load transfer characteristics and the lifetime of a dental system. Excessive stresses at peri-implant area may result in bone failure. Finding the critical point at the implant-bone interface and evaluating the influence of implant diameter-to-length ratio on adjacent bone stresses makes it possible to select implant dimensions. For this, different cylindrical implants were numerically analysed using geometrical models generated from computed tomography images of mandible with osseointegrated implants. All materials were assumed to be linearly elastic and isotropic. Masticatory load was applied in its natural direction, oblique to occlusal plane. Maximum von Mises stresses were located around the implant neck at the critical point of its intersection with the plane of loading and were functions of implant diameter-to-length ratio. It was demonstrated that there exists a certain spectrum of diameter-to-length ratios, which will keep maximum bone stresses at a preset level chosen in accordance with patient's bone strength.

Team approach in treatment of extensive maxillofacial defects - five case report serie.

Long-lasting functional and esthetic rehabilitation and good health-related quality of life of patients with maxillofacial defects is based on effective interdisciplinary cooperation especially of surgeons, dentists and technicians. Extensive defects occur after the first phase of the oncologic surgery and immediately after injuries. Subsequent plastic surgery is the initial step of functional reconstruction and creates a base for future fabrication of post-operative dentures and implant-born epitheses. Five clinical reports demonstrate complex rehabilitation of typical maxillofacial defects solved within the multidisciplinary cooperation. Four patients with oncological diagnoses and complex surgical treatment, resp. radio- and chemotherapy are reported with interim and long-term prosthetic solutions. One patient suffered from a congenital malformation. Titanium implants were inserted in defect bone margins using two-phase method. Healing time was at minimum three months and after this period superstructures were applied. Artificial eyes were made of both glass and acrylic materials. Retention of presented postoperative prostheses was reliable; patients were satisfied with the functional and esthetical results of the reconstruction. Prognosis of the rehabilitation depends on the histological stability of adjacent tissues, quality of osseointegration and durability of materials used (silicones, acrylates). Satisfactory health-related quality of life of these patients is based on the multidisciplinary healthcare.

Ozone and its usage in general medicine and dentistry. A review article.

Ozone, an allotropic form of oxygen, is successfully used in the treatment of different diseases for more than a hundred years. It is highly valued for various effects, such as antimicrobial, antihypoxic, analgesic, immunostimulating etc. on biological systems. These mechanisms of action supported with a lot of case reports and scientific studies allow using it in different fields of medicine. This review of literature is another attempt to summarize different modalities of ozone application in dentistry. Further studies are necessary to standardize indications and treatment protocols of this promising medical agent.

New trends in prosthetic dentistry.

Prosthetic dentistry is one of the fundamental pillars of dentistry. Even though it is highly specialized in replacement of missing teeth and adjacent soft and hard oral tissues, the cooperation with other branches of dentistry is very important. It usually provides final stages of rehabilitation of the whole maxillofacial system. The loss of several teeth doesn't have to be an immediate threat to the function of the whole dentition, but it can initiate serious problems related to the whole orofacial region, psychics and the wellbeing of the patient. From this point of view prosthetic dentistry is a valuable tool with high therapeutical and preventive character. Modern prosthetics offers classical solutions with simple fixed and removable dentures, and advanced solutions with dental implants support for rehabilitation of dental defects. Final quality and prognosis of prosthetic treatment depends both on materials and technologies used and on the patients' motivation and dental care. Superior esthetical demands and biocompatibility issues drive dental manufacturers to introduce new materials with defined properties. Nowadays the most sophisticated systems are based on ceramics, dental implants and CAD/CAM technologies.

Long-term clinical evaluation of fixed dentures--two to fifteen years after insertion.

Fixed denture durability is characterized as a period of time for which a dental appliance satisfies functional and esthetic requirements. First of all, its durability is based on the properties of materials it is made of, and depends, at the same time, on the characteristics of biological environment, in which the denture is placed. The purpose of this study was a long-term monitoring of changes taking place in the fixed dental constructions during their application in the oral cavity. These changes were to be evaluated for different types of materials used for fixed dentures manufacturing, namely metal alloys, ceramics, and plastics. A set of 454 full crowns from 134 patients divided in 6 clinical studies was examined and both qualitative and quantitative changes evaluated after 2 and 8 to 15 years after cementation. Clinical assessment adopted the United States Public Health Service System criteria. Alloys of precious metals veneered with ceramics are considered the optimal method of choice for both high precision of execution and consideration of future changes brought on by the use of the dentures.

A two-year clinical study of metal-ceramic and metal-polymer crowns.

The purpose of this study was to compare full metal crowns with two different types of veneering material - ceramics and polymer after a two-year period in a function. The aim was to evaluate the changes of occlusal relief, marginal adaptation, break of material, changes of shape and color and gingival status. One hundred and two crowns were examined in 34 patients immediately after cementation, and they were reviewed within two years of crown placement. These fixed restorations were checked according two modified US Public Health Service System criteria. After two years the crowns were found clinically intact in 94% for metal-ceramics versus 98% for metal-polymer. No crown was lost. There were found significant differences in positions of a crown margin between both materials and marginal adaptation between initial (baseline) and follow-up results. Gingival health at baseline was related in optimal in 67% versus 77%, after two years in 43% versus 71%. Slight mismatch in color occurred in 0 versus 60% crowns, obvious mismatch was apparent in 0 versus 21% crowns after two years. Within the limitations of this study, it was found that the examined metal crowns with two different veneerings are very stable fixed restorations, mechanical resistance and integrity of polymer material was surprisingly good but its color stability presented mismatch after two-years period. Ceramic veneering was excellent in color match but there were three visible cracks of the ceramic layer.

[Stomatologic care of patients with the Melkersson-Rosenthal syndrome]. / Stomatologická péce o pacienty s Melkersonovým-Rosenthalovým syndromem.

The authors describe the problems of diagnosis, treatment, prevention and dispensarization of patients suffering from Melkerson-Rosenthal's syndrome in a dental department. They describe in detail the manifestations of the syndrome in the orofacial area. Comprehensive dental care is based on studies of the pertinent literature and the authors' own experience.

[Complex stomatologic care in patients with anorexia nervosa]. / Komplexní stomatologická péce o nemocné s mentální anorexií.

The authors describe a group of 25 patients with anorexia nervosa treated at the Psychiatric Clinic, First Medical Faculty, Charles University. They compare their experience with dental treatment of these patients with data in the literature. Extensive dental damage in these patients calls for comprehensive dental care which is not only time consuming but frequently also pretentious from the economic aspect. The authors recommend therefore dispensary care and emphasize the necessity of collaboration between the psychiatrist and stomatologist.