مجله دندانپزشکی دانشگاه علوم پزشکی تهران
سال بیست و سوم شماره 1 (پیاپی 62، بهار 1389)

The elution of residual monomers from cured dental composites to oral cavity has a harmful effect on human health and can affect their clinical durability. The purpose of this study was to evaluate the amount of eluted monomers (Bis-GMA, TEGDMA, UDMA) from two types of composites (Gradia and P60) after exposure to food simulating liquids such as ethanol (25, 50, 75 %) and heptane 50 % for 24 hours and 7 days. Forty specimens of each composite were prepared. Equal numbers of each composite were immersed in tubes containing 2cc volumes of 25, 50, 75 % ethanole and 50 % heptane. The amount of eluted monomers in standard condition such as Bis-GMA, TEGDMA and UDMA was measured by GC/MS (Gas Chromatography/Mass Spectroscopy) and results were statistically analysed by three way and one way ANOVA. P<0.05 was considered as the level of significancy. The results showed that Gradia released more TEGDMA than P60. In assessing the effect of environment, the result showed that ethanol caused releasing monomers more than heptane and the concentration rate of 75 % ethanole resulted in most releasing of monomers. In assessing the effect of time, the observation showed that more monomers were released 7 days compared to 24 hours. Bis-GMA and UDMA were not detected in any solutions in these conditions. Ethanole caused more release of monomers than heptane and 75 % ethanole released the most amount of monomers. Gradia released more amount of TEGDMA than P60.

Overlapping of the proximal surfaces of posterior teeth in the panoramic radiography is a major concern. Therefore, an option has been developed in the panoramic unit of Planmeca Promax, namely improved interproximal mode. This mode causes lower horizental angle with the teeth contact region during the unit rotation decreasing overlapping of the panoramic images of the posterior teeth especially premolar teeth. The present study was done to compare the overlapping of posterior teeth using two techniques of improved interproximal panoramic program and standard panoramic. In this diagnostic study, 32 patients requiring panoramic radiographies at their posterior teeth during their routine diagnosis and treatment process with the mean age of 27.3 years were participated. No patients showed crowding of posterior teeth or missed and restored posterior teeth. The participant's panoramic radiographies were randomly taken by two techniques of improved interproximal panoramic and standard panoramic using Planmeca Promax device. The overlapping of the panoramic images was blindly assessed by an oral radiologist. The overlapping in both techniques was reported by frequency and percentage. The comparisons were done by Chi-square test between two techniques and the odds ratio of overlapping was estimated using regression analysis. In standard panoramic techniques, 38.5% (148 contacts of 384 contacts) of the proximal surfaces overlapped while the overlapping of the proximal surfaces was observed in 18.8% (72 contacts of 384 overall contacts) in improved interproximal technique. Significant differences were noted between two techniques regarding overlapping (P<0.001). Also 66.4% and 39.1% of 4-5 teeth contacts overlapped in standard and improved techniques. The values were reported to be 39.1% and 12.5% in contacts of 5-6 teeth and 10.2% and 4.7% in the contacts of 6-7 teeth in both techniques, respectively. The overlapping odds ratio in improved technique as compared to standard techniques was 2.72 more. While the odds ratio of overlapping in the contact regions of 4-5 and 5-6 teeth was 16.4 and 4.61 as compared to the contact region of 6-7 teeth (all: P<0.001). The lower or upper jaw with the patient's mouth side did not significantly influence the overlapping of the proximal surfaces in both panoramic techniques. Under the limitations of this study, improved interproximal panoramic significantly reduced the overlapping of proximal surfaces in the panoramic radiographies of posterior teeth as compared to the standard panoramic technique. Therefore, it can be used to detect proximal caries in the posterior teeth as a diagnostic tool. Using this option may affect other part of panoramic image which should be investigated in other research.

Lasers with different characteristics have been used to stimulate orthodontic tooth movements and to inhibit the pain during tooth movements. Considering the contradictory finding in this respect, the effect of low level laser therapy (LLLT) was evaluated on the pain during orthodontic tooth movement. In this randomized clinical trial study, 12 patients were included with extracted upper first premolars and required canine retraction into extraction site. While in both sides canines were retracted by Niti coil spring, one side was exposed to GaAlAs laser (890nm). LLLT was done on the buccal and palatal mucosa by slow movement of probe. The patients were asked about their pain on both sides 2 days after beginning of retraction. Pain measurement was evaluated with VAS. Pain perception in LLLT side significantly decreased (P=0.007). Based on the results, single irradiation of GaAlAs laser (12J energy per tooth) can decrease pain perception.

Formocresol is one of the most common pulpotomy medicaments for primary teeth. Because of its systemic and local side effects, it may be essential to use another material instead of formocresol. The aim of this study was to evaluate the histopothalogy of pulp after pulpotomy teeth with sodium hypochlorite and formocresol.

In this randomized clinical trial, 22 canine teeth that must be extracted because of orthodontic treatment were selected. The teeth were randomly divided into 2 groups (n=11) and pulpotomized with formocresol or sodium hypochlorite. These teeth were extracted after 2 months and pulpal response was evaluated according to the degree of inflammation and extent of pulpal involvement. Dentinal bridge formation was also evaluated. The data were analyzed by Mann-Whitney test.

In formocresol group, mild inflammation was seen in 4 and moderate inflammation in 3 and severe inflammation in 4 cases. In sodium hypochlorite group mild inflammation was seen in 6 cases and moderate inflammation in 4 cases and severe inflammation in 1 case. Mann-Whitney test revealed that this difference was not statistically significant (P>0.05). In formocresol group, necrosis was seen in 5 cases, but abscess and internal resorption were not seen in any cases. In sodium hypochlorite group, internal resorption was seen in 3 cases; but necrosis and abscess were not seen in any cases. Mann-Whitney test showed that the difference between two groups was significant in terms of necrosis (P=0.02). In sodium hypochlorite group, dentinal bridge was formed in 3 cases; however, no dentinal bridge formation was seen in formocresol group. Mann-Whitney test showed that this difference was not significant statistically (P>0.05).

Based on the results of this study, sodium hypochlorite can be used as a pulpotomy agent in primary teeth.

The main objective of this study was to determine the effect of polyethylene fibers and veneering composites in fiber-reinforced resin systems on the opacity (contrast ratio). The specimens were divided into four groups. Two groups were used as the control groups, with no reinforcement. The fibers of polyethylene (Fibre-Braid) with special basement composites were used as the reinforced framework materials. Filtek Z250 and GRADIA (shade A2) were used as veneering materials. The total thickness of samples was 3 mm with 13 mm diameter. Specimens were prepared in disk shaped metal mold. The composite materials were light-cured according to their manufacturer's instructions. The contrast ratio (CR) of each specimen was determined on black and white backgrounds using reflection spectrophotometer. Reflectance was measured at intervals of 10 nm between 400 nm and 750 nm. Data were analyzed by two-way ANOVA and Tukey HSD test. When contrast ratio were compared among the different types of materials statistically significant differences were observed in both veneering composites (P<0.05). The Z250 resin composite had the lowest CR. It was shown that CR tended to decrease as the wavelength of incident light increased from 400 nm to 750 nm. On the other hand, the most differences in CR between groups were found in longer wavelengths. It was found that polyethylene fibers reduced the amount of the translucency in FRC samples. The results of this study indicate that light reflectance characteristics, including the wavelength dependence, play an important role for the CR of a fiber-reinforced composite.

One of the common human evolutionary anomalies is dental Missing. Evolution of dental system is toward deduction of teeth number. The Missing of third molar is interesting subject for dentists and genetic researches because of its variety in different races. Consideration of bilateral effect of third molar Missing with jaw relation is an important subject. The aim of this study was to evaluate the third molar missing in Cl I and Cl II skeletal (without rotation) and comparison of them together.

The patients of the orthodontic department of school of Dentistry (Tehran University of Medical Sciences) were analyzed. About 121 patients had Cl I and 60 patients had ClI jaw relation. This relation identified based on cephalometric lateral radiographic ANB corner angle. Patient who had rotation in maxilla or mandible based on SN-Go Gn angle were excluded. The incidence of third molars agenesis in individual dentition quadrants, upper and lower jaw and right and left side of dentition was examined from panoramic radiography. AChi-square test was used for statistical analysis of data.

Missing of one or more third molar in skeletal Cl I and Cl II was 43% and 33.3%, respectively. Missing of one or more third molar in Cl II was fewer than Cl I, but no statistically significant differences were seen between them.

There was not a direct relationship between jaw relation and third molar Missing.

Studies show that sucrose containing chewing gums are cariogenic. The aim of this study was to evaluate the effect of two commercial chewing gums with and without sucrose on dental plaque accumulation compared with the control group. In this clinical study, plaque accumulation during three 7-day periods (with two weeks interval) was recorded (Sillness & Loe Index) in a group of 23 volunteer male dental students who chewed in the first two periods sugar-free or sugar-containing chewing gums (Olips and Orbit, respectively) and in the last period did not chew any gum. Participants were asked to chew daily five gum sticks after meals for about twenty minutes. The data were statistically analyzed using Repeated Measure ANOVA and paired-T test. The results showed that chewing any gum even sucrose-containing gum decreased the level of dental plaque accumulation (P<0.001). However, the decreasing effect of sugar-free gums was significantly higher (P<0.001). Although sugar free gum was more effective than sugar containing gum on reducing dental plaque accumulation, chewing even sugar containing gums could decrease the level of dental plaque.

Surgical and prosthodontic implant complications are often the case of inadvertent improper diagnosis, planning, and placement. These complications always pose a significant challenge in implant dentistry. In this article, it is attempted to depict a new technique in which advanced software program along with newly developed CAD/CAM technology called rapid prototyping will be used. This technology permits graphic and complex 3D implant simulation and then fabrication of computer-generated surgical templates. The best position of implants planned at first by taking into consideration of encased bone density of each implants and then existing occlusion. In this paper, the evolution of Computer Guided Implantology and the many benefits achieved from this very sophisticated technology described as a literature review.

A procedure was explained to fabricate a surgical stent to aid the placement of maxillofacial implants for prosthetic auricular rehabilitation. An impression of the defect was made, and a wax pattern of the missing ear completed and evaluated on the patient. The definitive wax prosthesis was processed in clear acrylic resin. Also an occlusal maxillary splint was fabricated and joined to the acrylic resin ear by using an extraoral acrylic resin bar. Surgical stent provides proper orientation of the acrylic resin ear while remaining attached to the maxillary arch. This surgical stent can also be used for radiographic examination

Microstomia is defined as an abnormally small oral orifice. Microstomia can occur as a result of trauma from electrical and thermal lesions, chemical burns and trauma from surgeries. Prosthetic rehabilitation of microstomia patients presents difficulties at all stages, from the preliminary impressions to fabrication of prosthesis. For impression procedures different treatment methods have been suggested. Swing hinge and collapsible dentures are used to provide prosthodontic treatment to patients with microstomia. Not only is such a prosthesis difficult to fabricate, but may be expensive. The literature contains reports on the fabrication of sectional denture with the denture pieces connected by different designs. This article describes a simple method of fabricating a 2-pieces denture using removeable partial denture metal framework to connect the sections, for a patient with limited oral opening. Combination of metal framework and sectional complete denture for a patient with limited oral opening is an acceptable, effective and available method.