Journal of Dental Medicine
Year:2001 | Volume:13 | Issue:3-4 (25)|Papers Count:12

Discoloration of composite resins is considered to be a major factor in esthetic restoration failures. The aim of this study was to evaluate color stability of IDM composite (both light and self cure samples namely IL and IS), and to compare it with a self-cure composite (Degufill named DS) and a light cure ormocer composite (Definite, called DL in the Report). 60 disk shaped samples of each composite were prepared, according to ISO-7491. The samples were divided into 3 groups and aged as follows: A- (Control) 7 days in dark 37 c chamber B- Foil covered and kept in 100% humidity, and 370 c in xenotest chamber for 24 hours, then transferred to a dark 370 c chamber for 6 more days.C- Kept in 370 c, 100% humidity under the emission of xenon lamp of xenotest chamber for 24 hours, and then transferred to 370 c dark chamber for 6 more days.The lightness and chromaticity values of samples were measured both before and after aging using a spectrophotometer (Data Flash). The total color changes as well as changes in lightness and chromaticity values were measured in the CIE L * a * b * scale, and analyzed. Color change was recorded to be significant in all samples after aging. The maximum change belonged to IL, which was significantly different from DL and DS. It seems, in order to have a durable esthetic restoration using IDM, more scientific and professional consideration is needed in the production process.

The geometric shape of dental arch (square, tapering, ovoid) is an important factor in stress distribution pattern around dental implant. The aim of this study was to evaluate the role of arch form and the amount of bone loss (normal, moderate, high) in stress distribution around dental implant by considering different load direction. Three arch forms; square, ovoid, and tapering with three different stages of bone loss were designed. Models were divided into three-dimensional elements, which made 5500 nodes. The 143N load was applied at two angles (straight, oblique) at the last fixture, 8mm, and 16 mm from the center of implant on the cantilever. The Sap90 software was used for analyzing the stress distribution in this study. 54 different conditions were evaluated. Results showed that stress concentration changed from support toward fixture due to distally changing the load in the square and ovoid arch forms with normal bone. In the tapering arch with normal bone stress concentration was around the fixture. The amount of stress in normal tapering arch was more than physiologic extend, therefore, application of cantilever in tapering arches is not recommended.

The purpose of this study was to assess the fluoride release of three fluoride- containing materials exposed to fluoride solutions. This study compared the initial fluoride release and release following re-fluoridation (neutral or acidic 2% NaF) of three different filling materials, conventional glass ionomer cement (CGIC), resin- modified glass ionomer cement (RMGIC), polyacid- modified composite resin (PAMCR). Twenty discs of each material, measuring 2mm height and 6mm diameter, were suspended in separate vials of 2cc laboratory artificial saliva. The amount of fluoride release was measured over two periods of 28 days each. Fluoride release was determined at 1, 3, 7, 14 and 28 days of each period. Fluoride was measured with a fluoride ion- specific electrode and an ion analyzer previously calibrated with standard solution. T- test and ANOVA were used to evaluate the data. Fluoride release for all products at days 1 and 3 was significantly greater than the rest of the time intervals. Then, the fluoride release decreased significantly. CGIC released significantly more fluoride than the other products. This was followed by RMGIC, which exhibited significantly more fluoride release than PAMCR. In second period of experiment, the specimens were assigned to two subgroups of ten each. The samples exposed to two different solution of NaF (neutral or acidic). All groups showed the capacity of re-fluoridation and fluoride uptake. The specimens exposed to acidic NaF solution showed statistically more significant rechargeability than the neutral NaF solution. It may be concluded that glass ionomer cements act as a rechargeable slow fluoride release systems and as an effective caries preventive material in caries preventing programs for caries susceptible children.

In this investigation, the position of hyoid bone was compared in three skeletal groups of class I, II and III. The study was based on evaluating 77 lateral cephalometric radiographs, 40 girls and 37 boys, which were divided into 3 groups. Group 1, 2, and 3 consist of 26, 25, and 26 radiographs. 19 cephalometric landmarks and 10 planes were used in order to tracing the radiographs. In all patients, 9 skeletal and 4 cervical vertebrae parameters were measured to determine the hyoid bone. These parameters were compared between three skeletal groups regardless of sex and then, in another statistical analysis, parameters were compared based on patients sex. Statistical analysis showed that in class III patients, the hyoid bone was positioned more anteriorly than two other groups. Also in this group, the hyoid bone had less inclination and it was more horizontal in relation to mandibular plane. In skeletal class II patients this bone was positioned more superiorly than two other groups. Due to these findings it can be concluded that perimandibular muscles and bones could affect the growth of mandible. In addition, comparison of the parameters between two sexes revealed that the hyoid bone was positioned more anteriorly and inferiorly in boys. Also it was shown that in the girls, the position of hyoid bone was closer to the position of this bone in skeletal class I patients.

One of the major goals of preradicular surgery is to create a good apical seal. This can be done by sectioning approximately one third of the apex, preparation of a class I cavity, and filling with a biocompatible material. The purpose of this in vitro study was to compare crack propagation in retro filling with two commercially available amalgams. Thirty-four extracted single rooted teeth were divided into two groups. After instrumentation and filling with Gutta percha by lateral condensation method, three millimeter of apex was resected and retro preparations were done by a low speed hand piece and ½ round bur. Then cavities were filled with cinalloy and luxalloy amalgam in-group "one" and "two" respectively. The surface of resected root ends was examined in two stages, after doing retro preparation and retro filling and the presence of any cracks or structural changes was inspected by stereomicroscope 50 x. Regard to number and type of cracks, the result of this study showed that there was no significant difference between cinalloy or luxalloy retro fillings. By considering the conditions of this study, cinalloy amalgam can be used as a retro filling material.

In recent years the use of titanium implant has received special attention in dentistry. In 1994 an implant clinic has established in Faculty of Dentistry, Tehran University of Medical Science and since then, 289 implants have been placed for 120 patients. In literatures a success rate of 93% and 84% of implants placed in mandible and maxilla respectively, have been reported. The purpose of this study was to evaluate implant success rate at implant clinic of Faculty of Dentistry, Tehran University of Medical Science. This study was based on reviewing the patients' charts. Results showed that success rates for Branmark, ITI, and IMZ implant systems were 94%, 95%, and 97% respectively.The higher success rate achieved in this clinic might be due to shorter period of time which implants were placed. Researches showed that care in patient selection, treatment planning, and following exact surgical and prosthetic principles will lead to a higher success and lower failure rates.

It has been shown that noble alloys require metal collar to resist distortion when subjected to repeat firing cycle of porcelain. Metal collar is undesirable due to esthetic concerns. Since base metal alloys have superior physical properties, it seems that metal collar would not be necessary for obtaining better marginal adaptation of base metal crowns. The Purpose of this study was to evaluate the effect of metal collar on marginal distortion of base metal- ceramic crowns. Twenty base metal copings were constructed and divided into two groups with and without collars. After surface preparation, porcelain was applied onto the surface of specimens. Marginal gap was measured by scanning electron microscope during three stages of crown fabrication: before degassing, after degassing and after glazing. The mean measurements in collarless group were; 21.4±13.4, 21.4±14.9 and 21.9±11.9 µm, respectively, and in- group with collar; 24.7±11.4, 24.0±11.5 and 26.6±11.7 µm, respectively. Two- way ANOVA revealed no significant difference in the mean values between two groups and among different stages of crown fabrication. The results of this study showed that base metal alloys did not distort during crown fabrication and metal collar had no effect on the amount of marginal opening (gap).

Guided Tissue Regeneration (GTR) is the most recent and common method for regeneration of class II forcation molars. However, it requires membrane, which seems expensive for most of the patients. In order to overcome this problem, Coronally Position Flap (CPF) procedure may be applied which arresting the epithelial cell down growth, follow the same aim. This study is aimed to compare GTR technique utilizing bioresorable collagen membrane and CPF utilizing citric acid. Nine patients with grade II forcation defects were selected. Defects were bilateral that randomly assigned into two groups: GTR and CPF groups. Measurements recorded at baseline and after surgery (6 months). Paired-T test was performed on these data. The following results were obtained after 6 months:In both groups significant reduction in probing pocket depth were measured in GTR and CPF groups, 1.55 1nd 1.88 mm, respectively. Also, open vertical probing depth: 0.33, 1.11 mm. Reduction in forcation weight in both groups was 0.22 mm. Bone fill was observed in 0.33% and 51% of defects. No recession was observed in GTR group, in CPF was 0.11 mm. Loss of attached gingiva was 0.34 and 0.78 mm, respectively. No significant difference was found between clinical parameters except OHPD. Comparison of means at the day (0 and 180) in each group showed the success for regeneration of forca. Considering the results, it can be concluded that CPF may substitute for GTR technique.

Recurrent aphtus stomatitis (RAS) is an oral mucous lesion in patients with no other signs of disease. Investigators have always notified the role of immune system especially humoral immunity in aphtus immunopathogenesis. The aim of this case-controlled study was to measure amount of serum immonogiobulins (A, G, M) and complement component (C3 C4) in patients with RAS and to evaluate any relation between differences in these factors and pathogenesis of RAS. Immonogiobulins (A, G, M) and complement components (C3 C4) of 50 patients with RAS were measured using single radial immuno diffusion technique. The results were compared with immonogiobulins (A, G, M) and complement components (C3 C4) of 50 healthy people whom were similar in age and sex with the patients group. Results showed that the patients group had higher level of IgA and IgM while serum IgG was similar in both groups. The C3 was lower in aphtus patients while no significant difference was found in amount of C4. The sex had no significant effect on serum level of measured factors. From the results it can be concluded that the humoral immunity reaction has an important role in immunopathogenesis of RAS. This humoral response might accurse as a result of cellular immunity reaction.

The aim of this study was to evaluate the incidence of postoperative wound dehiscence and infection after early closure of evulsive facial wounds. This treatment was conducted on 28 male patients with evulsive facial wounds. The formation of these evulsive wounds was due to the rupture of temporary cavitation caused by high and extra high velocity missiles. All patients with average age of 18 years old were treated 24-48 hrs aftrer accidents at base hospitals (1988-1990).Primary healing was achieved in 24 subjects from 7 t0 15 days after the standard operation. Wound dehiscences and bacterial infections were observed in 4 subjects.The conclusion can be made from the results is that the early closure of evulsive facial wounds may reduce the rate of wound dehiscence and infection because of high vascularity in this area.

Dentists and dental professional are constantly in contact with round, sharp, hot, and rotating instruments such as burs, scalpel blades, files, etc., in daily practice. Gate Glidden is one of the mentioned instruments used for removing gutta percha from root canal- treated teeth. In this article, a rare case of penetration of a fractured Gate Gildden bur into a dentists elbow is reported and precaution instructions are discussed.

Bone marrow transplant (BMT) has increasingly become a common treatment option for patients whom has their bone marrow affected directly or indirectly by any disease. Because of the level of immunosuppression achieved in BMT, any problems the pediatric patient presents in their oral cavity can become life- threatening and increase the length of hospital stay, the patients discomfort and the treatment cost. This paper discusses the important and unique role that pediatric dentistry has in the multi professional bone marrow transplantation team to help bring out a successful outcome through the prevention and treatment of the acute oral complications often seen in these patients.