Proceedings of the Finnish Dental Society. Suomen Hammaslaakariseuran toimituksia最新文献

It has been shown that early establishment of mutans streptococci in the mouth of infants increases risk of caries. Extensive studies on the timing of infection, and on sources and routes of transmission of the organism have been performed. Results of many studies suggest that the source of mutans streptococci is the mother, especially her saliva. Methods used to attempt to verify this hypothesis have developed considerably in recent years. Recent research and work in progress using methods based on DNA analysis have increased and will extend knowledge about transmission. This review summarizes the results obtained by different methods of transmission of mutans streptococci. The final goal of studies is to accumulate adequate information for prevention strategies of mutans streptococcal infection.

Eighteen mandibular dimensions (mm) in sex-determined, 10th-12th-century European skulls from burial sites in South-Eastern Hungary were examined to discover whether differences exist between the right and left sides. There was a statistically significant difference in only one dimension, the smallest sagittal diameter of the mandibular neck, in both males and females. The frequencies with which the various 18 dimensions were identical between right and left sides ranged from 39.9% to 82.0% in males, and from 45.9% to 83.2% in females. The examined individual dimensions appeared to be smaller on the right side in 7.0% to 33.7% (mean 19.1%) of the male cases, and in 7.1% to 29.9% (mean 17.9%) of the females, while the right side was larger in 7.7% to 50.9% (mean 22.3%) of the males and in 7.9% to 54.3% (mean 22.5%) of the females. In conclusion, asymmetry of the left and right sides was found between the measured individual mandibular dimensions on average in 41.4% of the males and 40.4% of the females.

The occurrence of dental erosion and the relative importance of some related factors were explored in a cross-sectional study, using blind dental examinations. A sample of 186 workers from four factories was drawn. Among the 157 dentate participants 76 were working in departments containing acid fumes and 81 controls had never worked under such conditions. Out of the dentate participants, 20 (12.7% had erosion). Anterior teeth were affected more often than posterior ones. Exposure to acid fumes, increasing age and frequency of intake of fruits increased the probability of dental erosion. It can be concluded that exposure to acid fumes in the work environment is associated with dental erosion especially on anterior teeth.

During an excavation of the Carmelite monastery in New Varberg, 178 skeletons were found. Many of the skulls were in a bad condition. Thus, the material in the present study consists of 12 complete and 47 partial skulls (maxilla and/or mandible) of 22 monks and 37 ordinary inhabitants. The information collected involved direct inspection of the skulls, segments of the jaws and radiographic examination of the complete skulls. Malocclusion, attrition, temporomandibular joints and arch dimensions were analysed. From the results it is tempting to assume that lack of forceful masticatory function and consequent absence of evenly distributed attrition and observed differences in craniofacial morphology can be a major explanation to the high prevalence of severe malocclusion in modern man.

It often takes quite a long time before caries preventive methods developed in the universities become adopted in practical use in dentistry. This may happen even though the method has been proved effective in long-term trials. It is most important therefore for the universities and the public dental health organisations to work closely together. This may significantly shorten the time interval between the invention and its practical application. The Public Health Center of Espoo has had the priviledge to work closely together both with the Universities of both Helsinki and Kuopio. Some of the most prominent trials conducted in Espoo or Kuopio that have resulted in practical application at Espoo Public Health Center will be described in the following.

Artificial premature synostoses of interparietal, temporoparietal and frontoparietal sutures was induced in 5-day-old rabbits in order to investigate the adaptive capacity of the synchondroseal cartilages. Ten control and 15 experimental animals were killed at the ages of 50 and 100 days. The lengths of occipital and sphenoid bones were significantly increased by 50 days but no longer at 100 days. The angle between the occipital and sphenoid bones was decreased and between the presphenoid and sphenoid bones increased by 50 and 100 days. The results indicate that the growth of the cranial base is to some extent adaptive to the growth of the neural tissues early in postnatal life, but as the growth of the cranial base synchondroses continues much longer than that of the brain the independent growth potential is manifest during the later period.

Costochondral grafts are most commonly used to restore severely affected mandibular condyles in growing children. Despite their world-wide use, the growth of costochondral grafts can vary, excess growth being the most consequential problem. A report is presented her of a patient who sustained facial asymmetry to the left as a consequence of retarded growth in the left mandibular condyle. A costochondral graft was used to replace the left mandibular condyle at the age of 12 years 8 months, but six years after the operation the initially pleasing postoperative appearance had given away to facial asymmetry to the right. This was clearly due to the excess growth of costochondral graft. Possible aetiological factors, intrinsic, functional or both, affecting the growth of costochondral grafts are discussed.

The auditory bulla, the bony capsule enclosing the middle ear, has been extensively studied in dry skulls and fossils, but detailed histological descriptions of the connective tissues involved are lacking. In rodents the membraneously ossified tympanic bone forms the major part of the enlarged auditory bulla. This study demonstrated fairly extensive secondary cartilage formation on the developing tympanic bone of the hamster. The first sign of the secondary cartilage was visible with Alcian blue staining on the 5th postnatal day. The amount of cartilage diminished after 15 days of age, but some cartilage was still present on the tympanic bone at the end of the observation period (25 days of age). While the secondary cartilage was present, a great amount of translative growth occurred in the bony coverage of the tympanic cavity, not only to accommodate the enchondrally growing cochlea within the cavity, but also to create space for the enlarged auditory bulla as an adaptation to low-frequency sensitivity in hearing. The tympanic bone is a derivative of the angular bone in the reptilian lower jaw. The mammalian mandible, a derivative of another membraneous bone of the reptilian lower jaw, the dentary, possesses secondary cartilages in the angular and condylar processes. Do the reptilian dentary and angular utilize secondary cartilage in the process of their transformation to the mammalian phylogenetic level?

The variability of the internal architecture of bone was studied in the mandibular condyle of young rats with the aid of vital staining capable of revealing bone trabeculae. The effect of season and age was observed in Spring- and Fall-born rats 28 and 56 days of age. There was no clear left-right asymmetry in the average direction of the condylar trabeculae, but their ranges of direction within the condyles exhibited such asymmetry. Both the average directions and the internal variability were different in the medial and the lateral sides of the condyles. There were also small but in most respects significant seasonal differences. These findings indicate that even the relatively small mandibular condyle of the rat is a very complex structure.

This paper reviews a series of odontometric, anthropometric and cephalometric investigations of genetic and epigenetic regulation of dental, occlusal and craniofacial development. The results show that genes encoded with the X and Y chromosomes regulate the development of tooth crowns and roots. The Y chromosome seems to affect general somatic growth by regulating both cell function and mitotic activity. The effects of the X chromosome seem to be more restricted and include influences on the growth of cartilaginous structures and dental enamel. The findings also indicate that high masticatory stress promotes jaw growth and decreases occlusal variation, supporting the hypothesis that masticatory activity regulates occlusal and craniofacial development. In addition, the findings suggest that nerve growth may affect bone growth in the craniofacial skeleton.