Spatial distribution of groundwater fluoride levels and population at risk for dental caries and dental fluorosis in Sri Lanka

Objectives: To investigate the distribution of groundwater fluoride levels in Sri Lanka in relation to its population distribution to determine the population at risk for dental caries or dental fluorosis. Methods: The study used the most upgraded spatial distribution map of groundwater fluoride levels in Sri Lanka, and it was overlaid with a census of population data of the country. Results: The results indicated that 12% of children aged <12 years were at risk for dental fluorosis, while 81.4% of those who lived in low-fluoride zones were vulnerable for development of dental decay. Overall, 82.4% of the country’s population lived in low-fluoride zones and 11.2% were at risk of potential health hazards posed by ingestion of excessive fluoride. Conclusion: The spatial approach provides a useful decision-support tool for developing an oral health strategy of safe fluoride use based on predicted oral health risks in communities.Key words: Groundwater, dental fluorosis, dental caries, spatial distribution     

Influence of bony defects on implant stability

Introduction: The purpose of this study was to analyze the evolution of implant mechanical stability in different types/sizes of bony defects using both Periotest and Osstell devices as “objective tools.” Materials and methods: Thirty‐two implants were randomly allocated to one of the four types of bone defects: marginal bone loss, peri‐apical bone defect, constant width dehiscence and constant length dehiscences. Periotest/Osstell measurements were completed before and during staged bone removal (to enlarge defect size). Results: Significant differences (P<0.05) with initial values were found after a 2 mm marginal bone removal (Osstell/Periotest); for a peri‐apical bone lesion, after removal of 5 mm (Osstell) or 8 mm (Periotest); for a 6‐mm‐long dehiscence, after removal up to 180° of the implant perimeter (Osstell/Periotest); for a 3‐mm‐wide dehiscence, after removal of 10 mm (Osstell) or 6 mm (Periotest). Conclusion: Periotest and Osstell are in general not very sensitive in the identification of peri‐implant bone destruction, except for marginal bone loss. To cite this article:
Merheb J, Coucke W, Jacobs R, Naert I, Quirynen M. Influence of bony defects on implant stability.
Clin. Oral Impl. Res. 21 , 2010; 919–923.
doi: 10.1111/j.1600‐0501.2010.01932.x     

Anterior and posterior neck muscle activation during a variety of biting tasks

Bruxism may be involved in the aetiology of myofascial neck pain. The objective of this study was to test the hypothesis that anterior and posterior neck muscles co-contract during jaw clenching. Ten test subjects developed different feedback-controlled submaximum bite forces in a variety of bite-force directions by means of bite-force transducers. The electromyographic activity of the sternocleidomastoid and supra/infrahyoidal muscles, and of the semispinalis capitis, semispinalis cervicis, and multifidi muscles was recorded by use of surface electrodes and intramuscular wire electrodes, respectively. For normalization of electromyography data, maximum voluntary contraction tasks of the neck muscles were conducted in eight different loading directions. The results confirmed co-contraction of the neck muscles in the range of 2-14% of the maximum voluntary contraction at a bite force ranging from 50 to 300 N. Significant activity differences were observed as a result of the different force levels and force directions exerted by the jaw muscles. Long-lasting tonic activation of specific neck muscles triggered by the jaw-clenching tasks was also detected. These findings support the assumption of a relationship between jaw clenching and the activity of the neck muscles investigated. The low level of co-contraction activity, however, requires further study to elucidate possible pathophysiological interactions at the level of single motor units.