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.

Ultimate masticatory force as a criterion in implant selection.

Osseointegrated implants often fail because of excessive masticatory forces that cause extremely large stresses in bone tissue. We hypothesized that a proper dental implant could be selected by comparing the ultimate masticatory forces of a wide range of commercially available implants. We determined ultimate oblique masticatory forces for different cylindrical implants, taking into consideration the biomechanical correlation between implant dimensions and stresses in supporting bone. For this purpose, we used the finite element (FE) method and studied von Mises stresses in implant-bone interface areas to evaluate the influence of implant dimensions on stress concentration and on the value of an implant's ultimate masticatory load. Geometric models of a mandibular segment were generated from computed tomography (CT) images and were analyzed with osseointegrated cylindrical implants. Masticatory forces were applied in their natural direction. All materials were assumed to be linearly elastic and isotropic. Critical point in the peri-implant area of bone was determined. The ultimate value of the masticatory load, which generates ultimate stresses at the critical point, was calculated for each implant. These findings provide correct selection of implant dimensions in clinical cases, because corresponding ultimate values of masticatory force were used as a criterion for assessment of their load-carrying capacity and applicability.

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.