| Objects: to do a series of studies about dimensions of pulp chambers and root canal systems of first maxillary premolars by using various radiographic methods(traditional radiographs-PA and RVG digital imaging system ),( i )measure the morphologic characteristics of pulp chambers of first maxillary premolars by use of RVG digital imaging system; (ii)compare RVG digital imaging system with traditional radiographs on differentiating competence of bicanal;(iii) compare RVG digital imaging system with transparent teeth on observations on bicanal.Materials and methods: All experiments were divided into three parts. part 1: we collect 70 extracted first maxillary premolars and for simulating the paralleling device we make one by ourselves in vitro ,which consists of sensor fixation frame, sample fixation frame and X-ray spherical tube fixation loop(pic.1). Taking 15mm-long file paralleling tooth axis as an adjusting standard, mesio-distal radiographs of each tooth were taken by use of RVG digital imaging system (TROPHY ELITYS FRANCE).With the adjusting function of TROPHY WINDOWS measuring software, we measure the following index of pulp chambers. A: buccal- lingal pulp chamber width at the cervix, B: buccal cusp to buccal pulp horns, C: Olingal cusp to olingal pulp horns, D: cusp to pulp chamber ceiling, If first maxillary premolars have bifurcated root or obvious bicanal on pulp chamber floor, we should measure the additional index, E: cusp to pulp chamber floor, F: pulp chamber height, G: pulp chamber ceiling to furcation, H: pulp chamber floor to furcation, I: the distance between the two root canal orifice, J: the distance between the two root canal in the middle, K: the distance between the two apical foramens. These datum are key to analyze the anatomic morphological characteristics of pulp chambers in first maxillary premolars. Part 2: take 10 teeth by random and then prepare dry right maxillary bone segments(having canine and polar section). On these bone segments, alveolar fossa is enlarged in order to alternate different first maxillary premolars. Self-made simulating paralleling device in vitro are composed of the followings. 1 .a film holding frame that can alternate fixation films and RVG detectors;2.a sample fixation frame with optional angle movements horizontally;3.a spherical tube fixation loop. This device has predominance that we just need to move the sample fixation frame and keep the location and distance of film holding frame and spherical tubes unchanged (pic.2). Next, we take traditional radiographs and RVG digital radiographs on standard position, mesially incline to degrees of 10°,20°,30°and distally incline to degrees of 10°,20°,30°both before and after inserting the diagnostic file. Each tooth are taken 14 radiographs individually. Observations: 1, compare RVG digital imaging system with traditional radiographs on differentiating competence of bicanal. 2. compare RVG digital imaging system with traditional radiographs on differentiating competence of bicanal before and after inserting the diagnostic file.3.summerize the radiographic characteristics of the first maxillary premolars with bicanal. Part 3: disposal the surface of 70 first maxillary premolars and assign a number. Using RVG digital imaging system, we take radiographs on standard buccal-lingual, mesio-distal, mesially incline to degrees of 10°,20°,30°and distally incline to degrees of 10°,20°,30°.Each group take 8 films.Observation: 1.observe the root canals' characteristics, types and routes of first maxillary premolars with bicanal through mesio-distal radiographs to analyze the connection between different route of root canals and optimal incline degree which can show bicanal clearly;2:make 70 first maxillary premolars to be transparent teeth and intuitionally observe the characteristics of root canal system. Comparing with the outcome of radiographs, we can conclude the accordant rate of radiographic diagnosis for complex root canals. It will be an evidence for radiographic commentary in clinic.Results:Part 1: the measurement of the pulp chamber of first maxillary premolars.A: buccal- lingal pulp chamber width at the cervix:3.95mm; B:buccal cusp to buccal pulp horns: 5.23mm; C:01ingal cusp to olingal pulp horns:5.41mm; D:cusp to pulp chamber ceiling: 6.93mm; Exusp to pulp chamber floor: 9.44mm;F: pulp chamber height: 2.71mm; G:pulp chamber ceiling to furcation: 6.97mm;H:pulp chamber floor to furcation: 4.17mm. I: the distance between the two root canal orifice: 2.93mm;J: the distance between the two root canal in the middle: 3.37mm;K: the distance between the two apical foramen: 3.55mm.Part 2: in 10 teeth, one is single-canal type; two have two roots; and in bicanal type, there is one 1-2-1 type, three 2-1 type; two 2-2 type and one 1-2 type. There is no obvious difference between RVG digital imaging system and traditional radiographs on differentiating competence of bicanal. RVG digital imaging system. On the aspect of imaging quality, RVG digital imaging system is superior to traditional radiographs on image enhancement, pseudo- color and three dimensions, but inferior to traditional radiographs and original digital images on reversal processing. Having inserting the diagnosis file, the differentiating competence of bicanal of both are enhanced obviously.Part 3: in 70 teeth, radiographs show that there are 15 single canal type,55 two canals. Within bicanal type teeth, there are 1 1-2-1tpye, 7 2-1 type, 45 2-2 type, and 2 1-2 type. The transparent teeth show 12 single canal type,58 two canals. Within bicana type teeth, there are 2 2-1tpye, 8 2-1 type, 46 2-2 type, 8 1-2 type and 2 1-2 type. Therefore, the according rate is 95.68%. In those bicanal teeth, the distance between the two root canal orifice: the maximum is 4.45mm, the minimum is 1.18mm, the mean is 2.93±0.69mm; the distance between the two root canal in the middle: the maximum is 5.82mm,the minimum is 1.63mm,the mean is 3.37±1.30mm. the distance between the two apical foramen: the maximum is 7.64mm, the minimum is 0.36mm,the mean is 3.55±1.82mm. When the distance between the two apical foramen is more than 4mm, mesially or distally incline to 10°is enough to preferably show the bicanal. When the distance between the two apical foramen is less than 2mm, only mesially or distally incline to 30°can distinguish the bicanals. The larger the incline degrees are, the larger the distortion and magnification of radiograpgs are. |
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