ABSTRACT
Recognizing canal configuration is necessary for correct endodontic therapy; and having no information about canal configuration results in failure of therapy. Since one of the most effective factors in canal configuration is race, we decided to conduct a laboratory and clinical research in Isfahan. The aim was to recognize canal configuration of the maxillary second premolars and compare the clinical and laboratory results.1- Laboratory study [In vitro]:At first we selected 105 maxillary second premolars and then disinfected them in CLONA 5.25%. We made a correct access cavity on the teeth. In order to vacate pulp tissue in chamber and canals, we placed them in H2O2 35% for 15 days. Then, we placed them in HNO3 [5%] for 3 days in order to be decalcified. 70%,90%,100% isopropyl alcohol was used to dehydrate the teeth. After the above processes, we injected India ink in -1.8 P in the canals and sealed access cavity by zonaline cement. Methyl Salicylate was used to clear the teeth and the configuration of the canals were observed directly. 2- Clinical study [In vivo]: In this study, we selected 132 maxillary second premolars of patiuents treated at the graduate and under graduate departments of Isfahan University School of Dentistry. Then we studied every radiograph using a negatoscope and the results of both methods were analyzed and compared. 1-Laboratory [In vitro] Out of 105 maxillary second Premolars[researchable], 30 type I [28.6%], 13 type II [%12.4], 48 type III [45.7%], 12 type IV [11.4%] and 2 with three canal [1.9%] were observed according to the Weine classification.2-Clinical [In vivo] Results: Out of 132 maxillary second premolars, 82 were type I [62.13%], 21 type II [15.91%], 25 type III [18.92%], and 4 were type IV [3.04%] . In this study, three canals were not observed. The results of this study are different from other researches. Perhaps, race and method of study were influential. Also, the clinical results were different from laboratory results as the laboratory study method is more exact
ABSTRACT
Silent period is defined as transient electromyographic activity following a stimulus of some kind during a sustained period of muscle contraction. The exact mechanism of this reflex and the factors that influence it are still unknown. One important unanswered question is the relationship between the length of muscle and duration of silent period. The aim of this study was to compare the silent period duration of masseter muscle before and after placement of an occlusal splint in the mouth. Twenty five persons with complete dentition [28 natural teeth with no prosthesis and class I occlusion, without signs and symptoms of muscle or TMJ dysfunction and without history of orthodontic treatment were chosen for this study. The mean age of subjects was 22.3 years. For each subject, a maxillary occlusal splint with 3mm thickness in premolar area was fabricated and adjusted. Silent duration was measured during maximum muscle activity using chin tap as stimulus. Silent period was evoked and measured 3 times and the mean of the measurements was used as individual SPD. The mean SPD taken without splint was 20.03 +/- 1 and 14.19 +/- 0.83 with splint. Pair Wise Comparison test with use of LSD test showed that the mean SPD with and without splint were significantly [P<0.05] different. The result of this study showed that placement of a splint shortens the SPD of masseter muscle, significantly. Therefore, it is suggested that SPD can be used as a Para clinical factor to evaluate the full mouth restorative treatments that probably change VD. It also shows that muscle and TMJ receptors have a more important role in SPD than periodontal receptors