JOURNAL OF ISFAHAN DENTAL SCHOOL
Year:2008 | Volume:4 | Issue:3|Papers Count:9

Introduction: Yttria stabilized zirconia (YSZ) has been under consideration due to its desired properties for preparing dental restorations. The aim of this research was to produce the YSZ nano powder via sol-gel rout.Materials and methods: The present research was an experimental study and in vitro evaluation. Appropriate amount of zirconium oxide chloride, ZrOC12.8H2O, and yttrium nitrate, Y (NO3)3.6H2O, to reach 3mol% yttrium oxide in final product, were mixed in anhydrous ethanol ona magnetic stirrer. After drying the obtained gel at 50oC, it was calcined at 600oC for 1, 2 and 3hours. Phase identification, particle size and distribution determination, functional group identification and micro structural investigation were performed using XRD, SEM, TEM and FTIR techniques.Results: Results revealed that the tetragonal zirconia phase nano powder has been obtained. Crystallite size of the powder was about 20 nm and the size of particles was about 80 nm. The optimum temperature and time for calcimine process was 600ºC and 3 hours, respectively.Conclusion: The obtained Yttria stabilized zirconia with special characteristics duo to nano scale structure, could be a desired biomaterials for preparing dental restorations such as inlay, on lay, post and core, crown, and bridges in dentistry.

Introduction: Formocresol is the most common medication which has been used for pulpotomy of primary teeth in recent decades. Many investigations have been performed to use diluted Form cresol and to find a substitution. The purpose of this study was to compare the fixation effect of dilute and non-dilute Formocresol.Materials and methods: Eighty primary molar teeth with pulpotomy plan were divided into 4groups, each containing 20 teeth. Pulpotomy was performed using four types of Formocrosol: Original (non-dilute) Formocresol; 1/5 diluted Formocresol; 1/6 dilute Formocresol; and 1/7 diluted Formocresol. Fixation was scrutinized and finally, data was analyzed with Chi-Square test.Results: Original Formocresol, without dilution, was used for the first group, and all the samples were fixed. 90% fixation rate was achieved in the second group, using 1/5 dilute Formocresol. Inthe third and forth groups, 45% and 35% of the samples were fixed using 1/6 and 1/7 dilute Formocresol respectively. After statistical analysis, there was no meaningful difference between thefirst and second groups (p value = 0.244), but the first and second groups were meaningfully different from the third and forth ones (p value < 0.001).Discussion: We found no difference between the first and second groups. As 1/5 dilutes Formocresol was used for the second group, and this has less adverse effects and tang, it could be introduced as a favorable substitution for the original (non-dilute) Formocresol. Moreover, it was concluded that 1/6 and 1/7 dilute Formocresol are not suitable for pulp tissue fixation.

Introduction: Regarding routine application of bleaching treatment in dental practice, this study aimed to determine effect of in-office and at-home bleaching and also a combination of methods on human enamel, using FT-IR spectroscopy.Method and materials: For fifteen non-carious human molars, after prophylaxis with pumice, each tooth was sectioned bucco-lingually. One pieces of each tooth was bleached. For first group in-office bleaching, for second group at-home bleaching, and for third group combination of in office and at-home bleaching was done. Samples were stored in distilled water. Then enamel of teeth was powdered with a high-speed rotary instrument. Spectra of powdered enamel were taken for each sample. The data were analyzed with paired-t and Kruskal-Wallis tests (a = 0.05).Results: On comparing the infrared spectra of non- treated and treated specimens, no structural changes were detected in enamel, but the difference in intensity of phosphate between bleached control sample for in-office bleaching was statistically significant (p value < 0.05). In at-home bleaching and combination of in-office and at-home bleaching, difference in intensity of phosphate and carbonate in treated and non treated specimens was not statistically significant. The difference of intensity of phosphate and carbonate in 3 groups in samples was not statistically significant.Conclusion: In office bleaching agent was capable of reducing mineral content enamel, which may be caused by high concentration of carbamide peroxide. There was no reduction in mineral content of enamel in the presence of fluoride in at-home and combination of at-home and in-office bleaching.

Introduction: Improper coronal restoration after root canal therapy leads to penetration of microorganisms along root canal or through voids of root canal filling to periapical tissues and ultimate failure. The aim of this study was to evaluate the sealing ability of amalgam and C&B Metabond against coronal microleakage of Entrococcus Faecalis.Materials & Methods: In this experimental in vitro study, 54 premolar teeth were randomly divided to two groups of 24 teeth and for each the access cavities were prepared. The pulp chamber floorobturated with amalgam or C&B Metabond in two test groups, a further two groups of three teeth served as negative and positive controls. The external surface of each root, except the apical region, was covered with two layers of nail varnish. The teeth were inserted into Eppendorf plastic tubes and suspended in glass vials containing sterile BHI broth. Entrococcus faecalis were placed in the access of test and control groups and opacity of BHI was examined twice a week. The results were analyzed using fissure exact test and ANOVA (E=0.05).Results: Leakage was present in 13/20 of amalgam group; whilst 4/21 of the samples of C&B Metabondleaked at 3 months period. This difference was statistically significant and the sealing ability of two materials was increased by time lapse (p value < 0.05).Conclusion: C&B Metabond showed better sealing ability as a coronal seal than Amalgam against Entrococous Feacalis at 3 months period and its use is advised for double sealing before final coronal restoration.

Introduction: External root resorption refers to the loss of cementum and/or dentin from the root of the teeth. 40% mineral loss occurs in conventional radiographies but digital subtraction radiography is capable of localizing a lesion with only 1-5% mineral loss. This in vitro study aimed to determine the accuracy of digital subtraction radiography in diagnosis of simulated external root resorption.Methods and Materials: Ten premolar teeth with clinically intact roots were used were fixed in suitable place between the X-ray tube and CCD sensor. Direct digital radiographs were obtained before and after each lesion was created by 1/2, 1, 2, 4 and 6 round dental burs at facial and proximal surfaces; then digital subtraction images were obtained and observers evaluated all of the images and sensitivity and specificity and accuracy were calculated. Results were compared by J2test.Results: The sensitivity of digital subtraction and direct digital methods in detecting proximal defects were 97.34% and 93.92% respectively (p value = 0.16). The sensitivity of digital subtraction and direct digital radiography in facial surfaces were 98% and 92.6% respectively (p value =0.03). The specificity of direct digital and subtraction methods in proximal surfaces were 91.92%and 96.52% (p value = 0.08) and in facial surfaces were 91.92% and 99.26% respectively (p value= 0.002). The accuracy of digital subtraction radiography in detecting facial lesion was significantly superior to direct digital radiography.Conclusion: Digital subtraction radiography was superior to direct digital radiography in detecting small external root resorptive defects.

Introduction: Treatment plan is based on tow important parameters: diagnosis and etiologic factors. Furcation involvement is a critical point in diagnosis and prognosis determination. It has been noted that clinical and surgical findings of the degree of furcation involvement could be different. The purpose of this study was comparative evaluation of molars Furcation involvement during clinical and surgical measurements.Materials and methods: This descriptive- cross sectional study was performed in periodontics department of Shahid beheshti dental school. Furcation involvement measurements was performed during clinical assessment and open flap surgery for 54 (29 maxillary and 25 mandibular) molar teeth which were candidate for periodontal surgery. The degree of F.I. in different sites of eachmolar tooth was recorded according to Glickman's classification and was analyzed by Kappa coefficient of correlation.Results: There was significant difference in furcation involvement evaluation between clinical and surgical assessment for all sites (buccal, lingual, mesial and distal) and also all involvement degrees. In addition, clinical and surgical assessment of furcation had significant different in all restored teeth.Conclusion: As treatment planning is quite based on clinical evaluation, it is necessary to recognize furcation anatomy and perform exact furcation examination.

Introduction: most endodontically treated teeth need post and core restoration to do acceptable percentage of their function but selection of proper post and core system can be difficult and ambiguous .this study compared the effect of cast post and core and fiberglass post and core system on the fracture resistance and fracture pattern of crowned endodontically treated teeth.Material and method: A total of 30 recently extracted human canines with their crown removed were endodontically treated. Two groups of 15 specimens were formed. Teeth were restored with cast post core in the 1st group and with fiberglass post in the 2ndgroup. All posts were cemented with panavia F2 adhesive system. All fiber posts were restored with composite core. Cemented with zinc phosphate cement. Each specimen embedded in acrylic resin and then scored in universal load-testing machine (Instron). A compressive load was applied at a 45 angle to the long axis of the tooth until fracture at a crosshead speed of 1mm/min. Result: the Fracture resistance of 2 groups according to the (t) test analysis didn't have any significant difference. The mean fracture resistance of the teeth restored with cast-post system were 1489.33 ± 1045.34 and facture resistance of the teeth restored with fiber glass were 1195.93± 624.12 teeth restored with cast post exhibited higher fracture resistance than the other group. Fracture that occur in teeth restored with fiberglass post and composite core usually are restorable and %80 of fracture that occur in teeth restored with cast post and core are not restorable.Discussion: considering that fracture resistance of teeth in tow groups evaluated in this study were not significantly different and fracture of tooth restored with Fiber glass post were from a point that was more easily restorable, compare to cast post and core if seems reasonable to use Fiber glass post in appropriate cases, Although it is suggested to do and evaluate other clinical studies in long term.

Introduction: Periodontal diseases are among the most common diseases of the oral cavity. Different predisposing factors are responsible for initiation of these diseases. One of these factors is difficulties to access the area of plaque accumulation due to morphologic and anatomic variations. The aim of this study was to determine the anatomic and morphologic properties of the root of maxillary 1st premolar.Methods and materials: The root morphology of 162 randomly collected first maxillary premolars was studied. The general characters of the collected teeth including number and length of the roots, length of root trunk, location of furcation in 2 rooted teeth, and the direction of root curvature were determined. Then the roots were sectioned and mean of concavity depth on different root surfaces were measured using stereomicroscope with 32 magnifications. These means were measured in the mesial and distal surfaces of the teeth. The topography of furcation area was also found by a section given 2 mm apical from furcal furnix.Results: 66.6% of teeth were single, 31.48% double and 1.85% were triple rooted. In most of 2rooted teeth, furcation area was located in the middle third of the root. Palatal concavity of buccal root was a common finding in 2 rooted teeth and a significant relation between the concavity, its depth and the location of the furcal area was found. In comparison, the depth of mesial concavity on different surfaces was more than distal concavities. In single rooted teeth, the concavity depth was lower in the middle than the cervical third. In 17.64% of 2 rooted teeth, the width of furcationentrance was smaller than standard gracy curettes.Discussion: Morphologic properties of teeth are not necessarily similar in different population. Therefore, these differences must be considered in dental and periodontal treatment protocols.