ABSTRACT
INTRODUCTION: Our aims in this study were to (1) develop a method of measuring 3-dimensional (3D) tooth movement using a 3D surface laser scanner, (2) test the accuracy of this method, and (3) compare the measurements with those from cephalometric radiographs. METHODS: A method of superimposing pretreatment and posttreatment models on the palatal rugae was developed, and an experimental model was prepared to evaluate the accuracy and reliability of the laser scanner. Records were obtained from a prospective longitudinal randomized clinical trial evaluating anchorage loss with headgears and midpalatal osseointegrated implants as a source of anchorage in Chesterfield, United Kingdom. The pretreatment and posttreatment study models were analyzed by using a 3D laser scanner to measure the 3D tooth movement. RESULTS: The laser scanner was accurate to 0.0235 mm for anteroposterior measurements and 0.0071 mm for buccolingual movements for every 0.5 mm of movement. The study model analysis showed that mesial molar movements were 1.38 mm on the right side and 1.11 mm on the left side for the implant group, and 2.24 mm on right side and 1.63 mm on left side for the headgear group, with no statistically significant difference between the groups. The results for vertical movement of molars showed extrusion on both sides in both groups but no statistically significant difference between the groups. In the transverse plane, the results were not statistically significantly different between the groups. The results from superimposition of lateral cephalograms were similar to those obtained from the scanner. CONCLUSIONS: The 3D laser scanner provides accurate and reliable measurements of tooth displacement and can be considered an alternative to cephalometric radiographs.
Subject(s)
Cephalometry/instrumentation , Imaging, Three-Dimensional/instrumentation , Lasers , Tooth Movement Techniques , Cephalometry/methods , Extraoral Traction Appliances , Humans , Image Interpretation, Computer-Assisted/methods , Imaging, Three-Dimensional/methods , Models, Anatomic , Models, Dental , Orthodontic Anchorage Procedures , Outcome Assessment, Health Care , Radiography, Dental , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
UNLABELLED: It is hypothesised that exogenous nitrite acidified by metabolic products of acidogenic bacteria in the mouth will be converted to products which inhibit growth of the bacteria in question which contribute to dental caries. OBJECTIVES: The aims of this study were (1) to test the activity of both sodium nitrate and sodium nitrite at differing concentrations on the ability of Streptococcus mutans to lower the pH of its surroundings and hence (2) to determine whether either nitrate or nitrite might be bactericidal or bacteriostatic against S. mutans. METHODS: S. mutans NCTC 10449(T) was cultured in a liquid medium to which either sodium nitrate or sodium nitrite was added to a final concentration of 0.0, 0.2, 2.0, 20 or 200 mM, of which the first acted as a test substance negative control. After 24 h, the cultures were streaked onto agar to test for growth and the remaining culture used for pH measurement. The Mann-Whitney U-Test was used for statistical comparison of pH values. RESULTS: Nitrite at concentrations of 20 and 200 mM had a highly significant inhibitory effect (p < 0.001) on the ability of S. mutans NCTC 10449(T) to lower pH. Moreover, bacteria that had been subjected to these levels of nitrite were unable to recover on solid medium. Nitrate had no such effect on either the growth of the bacteria or on their ability to lower pH. CONCLUSIONS: It is concluded that nitrite, at final concentrations of either 20 or 200 mM, is both bactericidal and anti-acidogenic with respect to S. mutans, while lower concentrations of nitrite and all concentrations of nitrate are ineffective. Nitrite might be worthy of consideration as a mouth-rinse constituent.
