[A phd completed. The effect of radiotherapy on oral mucosa cell morphology.] / Serie: Hora est. Het effect van radiotherapie op de morfologie van de orale mucosa.

The treatment of oral cancer usually consists of surgical removal of the tumour, possibly followed by radiotherapy. The purpose of this dissertation research was to investigate the effects of radiotherapy on the oral tissues, in particular the superficially positioned epithelial cells in the oral mucosa. Earlier studies with electron microscopy revealed that unradiated oral mucosa cells, when observed at high magnification, contain microplicae (ridges or folds). Together with various saliva components, these microplicae form a protective layer that offers defence against, for instance, microorganisms. Radiotherapy damages these microplicae and may even destroy them altogether. Studies have shown that this effect of radiation can be observed in animals as well as in humans. As the radiation dose increased (50 Gy or more) the destruction of the microplicae was more severe. With a dose of 60 Gy or more the microplicae completely disappeared. This process may play an important role in the occurrence of osteoradionecrosis in the jaw and failure of dental implants placed after radiotherapy.

Microplicae--Specialized Surface Structure of Epithelial Cells of Wet-Surfaced Oral Mucosa.

The surface structure of the superficial cells of the oral mucosa is decorated with numerous membrane ridges, termed microplicae (MPLs). The MPL structure is typical of the epithelial surfaces that are covered with protective mucus. Cell membrane MPLs are no longer seen as passive consequences of cellular activity. The interaction between MPLs and the mucins has been demonstrated, however the role of MPL structure seen on the upper surface of the oral epithelial cells is speculative. The cell surface is of potentially great significance, as it harbors many markers for refined prognosis and targets for oral mucosal diseases and cancer therapy. With these aspects in mind, we conducted the present review of the MPL structure and function in order to form the basis for further studies of MPLs of the oral epithelial cells.

Short (6-mm) nonsubmerged dental implants: results of a Multicenter clinical trial of 1 to 7 years.

Limited bone height restricts the use of long dental implants, so short implants may be selected in these situations. Recent reports on clinical results with short implants have been negative, however, and have suggested that indications for the use of these implants are limited. To verify these findings, a multicenter study of short ITI implants was carried out. In a 6-year period 253 short implants with a length of 6 mm were placed into 126 patients, who were followed up from 1 to 7 years. Altogether 7 implants were removed; 6 of these were located in the maxilla and 1 in the mandible. The quality of survival was comparable with the clinical results of longer implants from the same implant system. Although the clinical results of these short implants were favorable, it is recommended that they be used in combination with longer implants, especially when used in the less dense bone that is often seen in the maxilla.

Osseo-integration of dental implants in radiated mandibles: an experimental study with beagle dogs.

This investigation was planned to detect the ability of radiated bone to integrate with dental implants and to study the load-bearing capacity of these implants. In five beagle dogs, the premolars were extracted, after which one side of the mandible was radiated with 40 Gy. Three months later, two hollow-cylinder implants were placed on each side of the mandible. After a three-month period of osseo-integration, bridges were constructed on the implants, and they were loaded for six months. Both clinical and x-ray examinations showed that all implants had integrated well and bore load without change in their host sites for a six-month period, at which time the dogs were killed.

The defence architecture of the superficial cells of the oral mucosa.

The oral epithelium together with the saliva and its components forms a complex structure which is the first line of defence in the oral cavity. The surface of superficial cells of the oral epithelium contains ridge-like folds, microplicae (MPL), which are typical of the surfaces of areas covered with protective mucus. The role of MPL seen on the upper surface of the oral epithelial cells is still unknown. The salivary mucus gel performs a protective diffusion membrane against harmful substances and this membrane is built up by epithelial cells covered by a highly hydrated and viscous gel, where mucins constitute the scaffold. The interaction between the MPL-structure and the mucins is shown in cornea, so that mucins are expressed on the tips of the MPL of the epithelial cells. We hypothesized that the MPL architecture of oral superficial epithelial cells provides the underlying basis for mucins's protective function as well as in ocular surface. The salivary mucous barrier is required to protect the superficial cells and the MPL-structure together with membrane anchored mucin binding protein (MBP) forms the ground to this mucous barrier. So, oral mucosal barrier complex (OMBC) contains both the MBP-mucin - complex and the MPL-structure of the superficial cells. In the future, studies of the alterations of the salivary mucins and that of the MPL-structure may yield therapeutic opportunities for burning mouth syndrome and perhaps for mucositis causing by irradiation. Focus on cell surface microplication and mucins in oral mucosal biology and oral mucosal diseases is a promising avenue for future research in several ways.

Outcomes assessment of the regional health information exchange: a five-year follow-up study.

BACKGROUND: The implementation of a technology such as health information exchange (HIE) through a Regional Health Information System (RHIS) may improve the mobilization of health care information electronically across organizations. There is a need to coordinate care and bring together regional and local stakeholders. OBJECTIVES: To describe how HIE had influenced health care delivery in one hospital district area in Finland. METHOD: Trend analysis was used to evaluate the influence of a regional HIE. We conducted a retrospective, longitudinal study for the period 2004-2008 for the eleven federations of municipalities in the study area. We reviewed statistical health data from the time of implementation of an RHIS. The t-test was used to determine statistical significance. The selected outcomes were the data obtained from the regional database on total appointments, emergency department visits, laboratory tests and radiology examinations, and selected laboratory tests and radiology examinations carried out in both primary care and special health care. RESULTS: Access to HIE may have influenced health care delivery in the study area. There are indications that there is a connection between access to regional HIE and the number of laboratory tests and radiology examinations performed in both primary care and specialized health care, as observed in the decreased frequency in outcomes such as radiology examinations, number of appointments, and emergency department visits in the study environment. The decreased frequencies of the latter suggest an increased efficiency of outpatient care, but we were not able to estimate to what extent the readily available comprehensive clinical information contributed to these trends. CONCLUSION: Outcome assessment of HIE through an RHIS is essential for the success of health information technology (HIT) and as evidence to use in the decision-making process. As health care information becomes more digital, it increases the potential for a strong HIE effect on health care delivery.

The placement of angled implants in the edentulous maxillae for the use of overdentures.

Although most retention problems of prostheses are concentrated in the mandible, patients have similar problems in the maxillae. Retention of prostheses can be improved by the use of two or four implants, either with retentive anchors or with a bar in the frontal part of the maxillae. The method of planning and placement of I.T.I. Bonefit implants is described.

ITI implants in combination with bone grafts: design and biomechanical aspects.

In this article we describe the implantation of ITI implants in combination with bone grafts. Two different cases were considered: the augmentation of an atrophic maxilla or mandible where the transplant was fixed by means of ITI implants and the implantation into free transplants fixed by means of the THORP reconstruction plate system. These indications require 2-stage procedures with submerged implants and transplants during the healing period. For this new applications, standard ITI implants were combined with specially developed new transgingival units of high manufacturing precision. The new design resulted in a maximum tightening moment of 4.0 N.m versus 1.25 N.m achievable with a conventional 2-mm screw. Dynamic testing showed that, for the range of tightening moments of 0.25 N.m up to 1.0 N.m, the loosening moment after 2,000,000 cycles remained approximately 10% above the tightening moment. For the clinical application a tightening moment of 0.35-0.5 N.m is recommended. The special design and the high precision of the extension parts results in a tight adaptation between the primary implant and the extension parts, which may be important for microbiological reasons.

Titanium implants and lateral forces. An experimental study with sheep.

The purpose of this study was to investigate the resistance of titanium implants to horizontal forces in a sheep model. Twenty implants were inserted into the foreheads of 5 sheep, 4 implants on each animal. After a healing period of 3 months, abutments were mounted on the implants. After a further healing period of 3 weeks, the implants were loaded with a horizontal pull of orthodontic elastics. The force varied between 250 and 350 grams. The duration of loading was 3 months. After the loading period the animals were sacrificed and the forehead bones with implants were fixed in formalin and evaluated histologically. In the histological specimens no signs of infection or bone loss were found around the implants. The results of the present study encourage the use of titanium implants also in cases where constant lateral forces are present.

Osseointegration of dental implants in bone irradiated with 40, 50 or 60 gy doses. An experimental study with beagle dogs.

Construction of different kinds of prostheses on irradiated bone tissues after tumour surgery is a complicated part of modern implantology. In irradiated regions of the jaws where the bone layers are thin and the blood supply also is minimal, knowledge of the impact of each dose of radiation is very important. The aim of this study was to compare the bone response around titanium implants loaded with fixed bridges in dog mandibles irradiated with total doses of 40, 50 or 60 Gy. The results suggest that after irradiation with 40-50 Gy, when the dose is fractioned in order to achieve higher tolerance of the tissues compared with single dose irradiation, titanium implants may become osseointegrated in the mandibles. For high success rates, however, careful planning of radiotherapy and selection of implantation site with an adequate blood supply are essential.