Journal of Dental Medicine

Background and Aim: The majority of commercial curing units in dentistry are of halogen lamp type. The new polymerizing units such as blue LED are introduced in recent years. One of the important side effects of light curing is the temperature rise in composite resin polymerization which can affect the vitality of tooth pulp. The purpose of this study was to evaluate the temperature rise in two different composite resins during polymerization with halogen lamps and blue LED.

Materials and Methods: This experimental study investigated the temperature rise in two different composites (Hybrid, Tetric Ceram/Nanofilled, Filteke Supreme) of A2 shade polymerized with two halogen lamps (Coltolux 50, 350 mW/cm2 and Optilux 501 in standard, 820 mW/cm2 and Ramp, 100-1030 mW/cm2 operating modes) and one blue LED with the intensity of 620 mW/cm2. Five samples for each group were prepared and temperature rise was monitored using a k-type thermocouple. Data were analyzed by one-way ANOVA, two-way ANOVA and Tukey HSD tests with P<0.05 as the limit of significance.

Results: Light curing units and composite resins had statistically significant influence on the temperature rise (p<0.05). Significantly, lower temperature rise occurred in case of illumination with Coltolux 50.There was no significant difference between Optilux 501 in standard curing mode and LED. Tetric Ceram showed higher temperature rise.

Conclusion: According to the results of this study the high power halogen lamp and LED could produce significant heat which may be harmful to the dental pulp.

Background and Aim: Handpieces are in current use in dental practice. Cross contamination from these instruments is very high because of their direct contact with blood and saliva. The purpose of this study was the evaluation of antiviral effects of different disinfectants on dental handpieces.

Materials and Methods: In this experimental study, the effects of 5 groups of different materials and methods of sterilization and disinfection on virus elimination from dental handpieces were evaluated. Groups were as follows: 1- autoclave 2- Solarsept 3- Unisepta 4- Sodium hypochlorite (2% solution of household bleach) 5- Sanosil. 14 handpieces in each group were washed, dried and autoclaved, then contaminated with polio and Herpes Simplex virus type I. Samples were washed with sterile distilled water. Antiviral agents were applied according to the manufacturer or previous investigations. After washing with water, the instruments were washed with MEM (Minimum Essential Medium) and two samples of cell culture from each handpiece were prepared. In each group one handpiece was treated as control. The results were recorded after one week.

Results: The percent of negative cell cultures in each group were as follow: A- For Poliovirus: 1- Autoclave: 100%. 2- Solarsept: 28.6%. 3- Unisepta: 0%. 4- Sodium hypochlorite: 28.6%. 5- Sanosil 92.9%. B- For Herpesvirus: 1- Autoclave: 100%. 2- Solarsept: 100%. 3- Unisepta: 100%. 4- Sodium hypochlorite: 57.1%. 5- Sanosil: 100%.

Conclusion: According to our findings autoclave is the best method for virus elimination from dental handpieces. Sanosil with 92.9% efficiency was the best solution. Solarsept, hypochlorite with special method and Unisepta had the lowest effectiveness.

Background and Aim: Dental Amalgam is a common restorative material for posterior teeth. Because of Hg content in the composition of amalgam, during the handling of material, mercury may release as vapor in the environment. Excess amount of mercury vapor can cause serious health problems in dental personnel. The aim of this investigation was to determine mercury vapor concentration in working environment of dentists in Tehran.

Materials and Methods: 211 dental clinics were participated in this cross-sectional study. The clinics were randomly selected from different regions of Tehran (north, center, south, east and west). The dentists were asked to complete a questionnaire including items on demographic characteristics such as age, sex and work history, method of handling of amalgam, environmental characteristics and general health conditions. Environmental measurements of mercury vapor in dentists’ offices were done by mercury absorption tubes (Hydrar) and personal pumps (SKC, 222-3, England) as suggested in NIOSH method. Analysis of air samples was done by atomic absorption spectrophotometery (cold vapor). The data were analyzed by non-parametric tests (Kruskall Wallis, Mann-Whitney and Kendall).P<0.05 as the level of significance.

Results: The mean mercury vapor concentration in dentists’ offices was 8.39(±9.68) µg/m³.There was no significant relationship between the urine mercury of dentists (3.107±3.95) and the air Hg vapor concentration of their offices. Using precapsulated amalgam showed significantly less Hg vapor than bulk amalgam (P=0.034). Also the surface area of working room and air Hg vapor (P=0.009) had a significant relationship (P=0.009 r=0.81). There was not any significant correlation between mercury vapor and other factors such as working hours per day and working days per week, squeezing of triturated amalgam or not, storage medium of set amalgam (water or fixer solution), mercury storage method and type of ventilation.

Conclusion: The concentration of mercury vapor in dental offices' environment was lower than threshold limit value. Based on this study the type of amalgam (precapsulated or not) and area of the working room had significant effect on the mercury vapor concentration of environment.

Background and Aim: Halogen lamp is the commonly used light source for composite photo polymerization. Recently, high power halogen lamps, LED and plasma arc are introduced for improving the polymerization. The aim of this study was to investigate the effect of conventional and high power halogen lamps and LED light curing unit on degree of conversion of two different composite resins.

Materials and Methods: In this in vitro experimental study two halogen units (Coltolux 50 with the intensity of  330 mW/cm² and Optilux 501 with two different operating modes of standard with the intensity of 820 mW/cm² and Ramp with the intentsiy of 100-1030mW/cm²) and one LED light curing unit (620 mW/cm²) were used. The composites were hybrid (Tetric ceram) and nanofilled (Filteke supreme). Each materials/curing method contained three samples and degree of conversion (DC) was measured with FTIR. Data were analyzed statistically with one way and two way ANOVA, Tukey HSD. P<0.05 was considered as the limit of significance.

Results: Tetric ceram revealed higher DCthan Supreme. Tetric ceram showed a significant decrease in DC when Coltolux 50 was used in comparison to LED and Optilux 501. The latters did not show significant effect on DC of this material. DC of Supreme polymerized with various curing modes was not significantly different.

Conclusion: Based on the results of this study, degree of conversion in hybrid composites was higher than nanofilled. In comparison with conventional halogen lamp (Coltolux 50), high intensity halogen lamps and LED unit significantly lead to higher degree of conversion in hybrid composites.

Background and Aim: The efficiency of disinfecting materials and procedures in removal of contamination from dental surfaces and equipments is essential. In authors' previous study, daily use of 2:100 dilution of 5% sodium hypochlorite in water and disposable covers were recommended since HBV contamination was found on semi-critical parts of the operative dentistry department. The aim of this study was to evaluate the HBV contamination following application of the recommended procedures.

Materials and Methods: The study was conducted in two parts. In the first cross-sectional part, samples were collected from 17 sites of dental surfaces. In the second interventional part samples were collected from 10 sites of 9 dental and 3 sites of 2 light cure units, before and after disinfection with 5% sodium hypochlorite solution diluted to 2:100. Sterile cotton swabs moistened with sterile BSAS (Bovine Serum Albumin in Sodium Chloride) solution were used for sampling. Samples were tested by PCR technique in Pasteur Institute, Iran.

Results: None of the samples collected in the first part of the study showed contamination. In the second part of the study, from 96 samples taken from various parts of dental and light cure units, before and after disinfection, there was only one HBV contaminated site before disinfection which showed no contamination after disinfection.

Conclusion: Based on the results of this study, disinfecting procedure with 5% sodium hypochlorite solution diluted to 2:100 along with using disposable covers is effective in preventing HBV contamination.

Background and Aim: Because of polymerization shrinkage and high viscosity of posterior composites, there are some difficulties in using them in posterior restorations. Several methods have been represented to reduce the effect of shrinkage. The aim of this study was to investigate the effect of curing flowable composites under condensable ones in adaptation and microleakage reduction of posterior composite restorations.

Materials and Methods: In this experimental in vitro study, forty class II MO cavities were prepared on extracted intact molar and premolar human teeth. Gingival margins were placed 1 mm apical to CEJ. The teeth were divided into two groups. In group 1, flowable composite (Filek Flow, 3M, ESPE, USA) with 0.5-1 mm thickness was applied and cured following application of bonding agent (Single Bond, 3M, ESPE, USA). The rest of the cavity was filled by condensable composite (p60, 3M, ESPE, USA). In group 2 the flowable composite was not cured, and the condensable composite was applied in two increments. After light curing of composites, all the specimens were thermocycled and then immersed in 0.3% basic fuschin. Specimens were sectioned and evaluated for degree of dye penetration under a stereomicroscope. Data were analyzed by Mann-Whitney test with p<0.05 as the level of significance.

Results:. There was no significant difference between the two studied groups regarding microleakage.

Conclusion: Based on the results of this study, neither cured nor uncured flowable composite under condensable composite can omit microleakage in posterior composite restorations.

Background and Aim: Accurate bone measurements are essential to determine the optimal size and length of dental implants. The magnification factor of radiographic images may vary with the imaging technique used. The purpose of this study was to compare the accuracy of linear tomography and panoramic radiography in vertical measurements, as well as the accuracy of linear tomography in mandibular width estimation.

Materials and Methods: In this test evaluation study, the vertical distances between the crest and the superior border of the inferior alveolar canal, marked with a metal ball, was measured by linear tomography and panoramic radiography in 23 sites of four dry mandible bones. Also the mandibular width was measured at the same sites. Then, the bones were sectioned through the marked spots and the radiographic measurements were compared with actual values.

Results: The vertical magnification factor in tomograms and panoramic radiographs was 1.79 (SD=0.17) and 1.69 (SD=0.23), respectively. The horizontal magnification of tomograms was 1.47 (SD=0.17). A significant correlation was found between the linear tomographic and actual values, regarding vertical dimensions (p<0.001, r=0.968) and width (p<0.001, r=0.813). The correlation was significant but lower in panoramic radiographs (p<0.001, r=0.795). Applying the magnification values suggested by the manufacturer, the mean difference of vertical measurements between the tomographic sections was 2.5 mm (SD=3.4) but 3.8 mm (SD=1.65) in panoramic radiographs. The mean of absolute difference in mandibular width between the tomographic sections and reality was 0.3mm (SD=1.13). In the linear tomograms, 4.3% of vertical and 56.5% of the width measurements were in the ±1mm error limit. Only 4.3% of the vertical measurements were within this range in the panthomographs. The linear regression equation between the actual values and those obtained by radiography in vertical dimensions showed that 87.5% of tomograms and 51.8% of panoramics were located in the ±1 mm error limit.

Conclusion: Based on the results of this study, the linear tomography is more accurate than panoramic radiography in mandibular height estimation. The accuracy of linear tomography in width estimation is within acceptable limits.

Background and Aim: Amalgam is one of the mostly used restorative materials, but has some disadvantages. Microleakage is one of the short comings of amalgam which may lead to sensitivity and recurrent caries. The aim of this study was to evaluate the effect of three dentin bonding systems on reduction of microleakage in amalgam restorations.

Materials and Methods: Class II amalgam restorations were made in 40 noncarious molar and premolar teeth. Then the specimens were divided into four equal groups. Scotch Bond Multi Purpose, Single bond,
iBond, were used as liner in groups one to three respectively and in group four no liner was used. The teeth were restored with high copper spherical amalgam. After thermocycling for 500 cycles at 5⁰C and 55⁰C, the specimens were immersed in basic fuchsin for 24 hours, bisectioned mesiodistally and evaluated under stereomicroscope at X25 for dye penetration. The data were analyzed by Kruskal-wallis and Scheffe. P<0.05 was considered as the level of significance.

Results: The groups showed significant difference (p=0.003). The group four had significantly less microleakage than the first and second groups (p<0.05). The second and third groups showed significantly different microleakage (p=0.038).

Conclusion: Based on the results of this investigation applying dentin bonding agents has no effect on reducing microleakage in amalgam restorations, however more studies are recommended.

Background and Aim: Various studies have shown that reliable bond at the root - post - core interfaces are critical for the clinical success of post - retained restorations. Severe stress concentration at post - cement interface increases post debonding from the root. To form a bonded unit that reduces the risk of fracture, it is important to optimize the adhesion. Therefore, some post surface treatments have been proposed. The purpose of this study was to investigate the influence of various surface treatments of tooth - colored posts on the bonding of resin cement.

Materials and Methods: In this interventional study, 144 tooth colored posts were used in 18 groups (8 samples in each group). The posts included quartz fiber (Matchpost), glass fiber (Glassix), and zirconia ceramic (Cosmopost) and the resin cement was Panavia F 2.0. The posts received the following surface treatments: 1- No surface treatment (control group), 2- Etching with HF and silane, 3- Sandblasting with Cojet sand, 4- Sandblasting with Cojet sand and application of silane, 5- Sandblasting with alumina particles, 6- Sandblasting with alumina particles and application of silane. Then, posts were cemented into acrylic molds with Panavia F 2.0 resin cement. The specimens were placed in water for 2 days and debonded in pull - out test. Statistical analysis was performed using ANOVA followed by Tamhane and Tukey HSD. Failure modes were observed under a stereomicroscope (10 ). P<0.05 was considered as the significant level.

Results: Surface treatments (sandblasting with Cojet and alumina particles ,with or without silane) resulted in improved bond strength of resin cement to glass fiber post (Glassix) and zirconia ceramic (Cosmopost) [p<0/05], but not to the quartz fiber post (Matchpost). In general, higher bond strengths resulted in a to higher percentage of cohesive failures within the cement.

Conclusion: Based on the results of this study, sandblasting with cojet and alumina particles increases bond strength of resin cement to glass fiber post (Glassix) and zirconia ceramic (Cosmopost).Generally, the bond strength of resin cement to the posts is affected by the post's composition and surface treatment.

Background and Aim: Nonmetallic tooth- colored posts adhere to canal walls by dentin bonding agents and resin cements. Better retention and proper distribution of stress result from enough and proper bonding. The purpose of this study was to evaluate bond strength of D.T. Light - post with two different resin cements (self-cure & dual-cure) and to investigate the effect of irrigating solutions applied in root canal on bond strength of the resin cements and D.T.Light- post to root canal wall.

Materials and Methods: In this experimental study 40 single root teeth (maxillary canine & central) were selected and stored in 0.1% thymol solution for one week and transferred to distilled water. The teeth were decoronated 2mm above CEJ. The canal space was mechanically enlarged using k-files (up to # 70). The teeth were randomly divided into two groups. The first group was irrigated with 2.6% NaOCl, and the second was irrigated with normal saline. After drying, the teeth were filled with gutta percha cones using lateral condensing method. After two weeks the post space was prepared and D.T.Light- post was inserted in each subgroup using self or dual-cure cements according to manufacturer's instructions. After thermocycling, the apical part was cut 1cm below CEJ. The remained length was divided into 9 equal sequential sections. Each section was submitted to shear push-out test in universal testing machine. Statistical analysis of the bond strength data was performed using ANOVA and post hoc tests with p<0.05 as the level of significance. All failed specimens were examined under stereomicroscope. Degrees of conversion of the cements were determined by FTIR.

Results: Significant difference in bond strength values were found among sites (P=0.001) and cements (P=0.03). With increasing in depth, bond strength decreased. The mean bond strength value in dual-cure resin cement was higher than self-cure cement. The irrigating solutions caused no significant difference in bond strength (P=0.46). DC% had significant difference in various depths.

Conclusion: According to the results of this investigation, bond strength of dual-cure cement is higher than self-cure one in D.T Light- post because of post's translucency. 2.6% sodium hypochlorite does not affect the bond strength.

Background and Aim: Decreasing the hardness of dental restorative composites after curing in oral environment can influence their clinical durability. The aim of this study was to evaluate the effect of food-simulating liquids such as 25%, 50%, 75 % ethanol and 50 % heptane on surface hardness of two composites - (Gradia and P60) after curing and immersing time of 24 hours and 7 days.
Materials and Methods: 45 specimens of each composite were prepared in a stainless steel mold with 6 mm diameter and 2 mm depth. 5 specimens of each composite were tested for microhardness immediately after curing as the control group. The other specimens of each composite were randomly divided into eight groups. Each specimen was immersed in one of the following solutions 25%, 50%, 75 % ethanol and 50 % heptane for either 24 hours or 7 days. Then the specimens were taken out of the solutions and washed and dried and transferred to the refrigerator until performing the test. In standard conditions, surface microhardness of specimens was evaluated by the microhardness device based on Vickers. The data were analyzed by one way ANOVA 3 way ANOVA and Tukey Post Hoc tests. The level of significance was set at p<0.05.
Results: Surface hardness of P60 composite was higher than that of Gradia. An analysis of variance in gradia and p60 showed significant difference between the control and all the other groups (P<0.05) except the 25% ethanol (P=0.514). After 24 hours all the solutions had significant effect on Gradia (P<0.05) except 50% and 75% ethanol (P=0.793). After 7 days all the solutions had significant effect on Gradia except 50% and 25% ethanol (P=0.385)and 50% and 75% ethanol (P=0.150) According to P60 after both 24 hours and 7 days all the solutions had significant effect on the hardness. 50 % heptane increased the hardness (P=0.00). 75% ethanol significantly decreased the hardness (P=0.000) followed by 50% (P=0.001) and 25% ethanol (P=0.007).
Conclusion: Based on the results of this study, the effect of time was not significant. P60 showed to be more resistant. 75% ethanol had much more effect followed by 50% and 25% ethanol. Heptane increased the mean surface hardness.

Background and Aims: In spite of the advances achieved in the field of dentin adhesives, the longevity of bond to dentin is still a challenge. According to recent studies, Matrix Metaloproteinase (MMP) inhibitors can increase clinical longevity of bonding and decrease leakage. The aim of this study was to evaluate the amount and pattern of doxycycline release from an experimental dentin adhesive containing this MMP inhibitor.

Materials and Methods: In this experimental study, specimens containing 0.25 and 0.5 loading percent of doxycycline in an experimental monomer were prepared in cylindrical moulds of 12 mm diameter and 2 mm thickness. The adhesive monomer was composed of 12 wt% Bis-GMA, 10 wt% TMPTMA, 28 wt% HEMA and 50 wt% ethanol. Camphorquinone and amine were used as initiators.

Results: Addition of 0.25 and 0.5 w% doxycycline showed linear release in both groups. Increasing the loading percent of doxycycline caused more release. The release continued during the test period.

Conclusion: Doxycycline release was observed from the experimental adhesive. Further studies in this field will help in preparing adhesive systems with more clinical longevity.

Background and Aims: 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).

Materials and Methods: 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 manufacturers' 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.

Results: 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.

Conclusion: 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.

Background and Aims: There is concern that leached components from dental composites may cause adverse changes in the reproductive health. This study aimed to assess the effects of leached components from a hybrid resin composite on the reproductive system of male mice.
Materials and Methods: In the present animal study, twenty adult Syrian male mice were divided into two groups of 10 mice each. In the test group, components which leached from samples made from Filtek Z250 resin composite into 75% ethanol were daily administered to the mice for 28 days. In the control group, the procedure was repeated in the same way as the test group but without placing composite samples in the solution. Then, the body weight, weights of paired testes, Gonado Somatic Index, sperm viability, sperm motility, epididymal sperm reserve and daily sperm production were recorded. Four male mice in each group were mated with untreated female mice for 10 days. After that, the number of pregnant females and number of infants were recorded. The data were analyzed using repeated measures ANOVA, Chi-square test and t-test.
Results: There was a significant reduction in the sperm viability and sperm motility of male mice in the test group compared to the control group (P=0.001). There was no any significant differences in other parameters between two groups (P>0.05).
Conclusion: This study showed that the leached components from resin composites cannot cause infertility but they could potentially cause some adverse effects on the reproductive system of male mice.

Background and Aims: To evaluate the effect of polishing on surface roughness of silorane-based composite using profilometery and Scanning Election Microscopy (SEM) and compare it with that of a methylmethacrylate-based composite and a glass ionomer.

Materials and Methods: In this study, 3 groups (n=28) were tested: specimens of two composites (Filtek P90 and Filtek P60) and a glass ionomer (Fuji IX) which were prepared in polyethylene molds (4 mm diameter×10 mm height). Half of the specimens in each group were finished with 180-grit silicon carbide paper and the remaining were finished with 180-grit, and subsequently polished with 250, 400, 800, 1000, 2000, and 2500-grit silicon carbide papers. The surface roughness was evaluated using a contact profilometer and then mean (R_a) and maximum (R_max) of surface roughness were recorded. Then, the surface of 4 specimens of each subgroup was observed under SEM. Statistical analysis was performed with T-test, ANOVA and Dunnett T3 tests.

Results: In all materials, Ra was different between polishing with 180 and 2500-grit silicon carbide papers. In 180-grit group, only R_a of Filtek P60 and Fuji IX showed significant difference (P=0.01). In 2500-grit group, there was no significant difference between the Ra of Filtek P60 and Filtek P90 (P=0.56).

Conclusion: Polishing is recommended for the glass ionomer and posterior composite restorations.

Background and Aims: Polymerization shrinkage in Methacrylate-based composite is one of the most important factors in composite restorations failure. Silorane-based composite is introduced to compensate this drawback and claimed to have low shrinkage. The aim of this study was to evaluate the polymerization shrinkage of these two composites.

Materials and Methods: In this experimental study, 5 disk shape samples for each resin composites were placed in the centre of metallic ring bonded to microscopic glass slab. Top surface of ring was covered by a glass cover slip. Glass slab and sample were placed on a special LVDT holder in order to light cure from bottom surface and to measure the polymerization shrinkage. In this study, Deflecting Disk method and LVDT (linear variable differential transducer) was used for dimensional change measurement of resin composites. In this study, two LED curing units were used for composite polymerization.

Results: The mean of polymerization shrinkage in Z250 cured with LED and High Power LED was 11.15±0.08µm and 11.51±0.17µm, respectively (P=0.094), and in P90 cured with LED and High Power LED was 1.08±0.06µm and 1.16±0.12µm, respectively (P=0.019).

Conclusion: Silorane-based composite (P90) showed significantly less polymerization shrinkage than that of methacrylate-based composite (Z250). For the two types of composite, there was no significant difference between the two curing units in polymerization shrinkage.

  Background and Aims: Hepatitis B is an important infection route in dentistry requiring different disinfectants to prevent its transmission. The aim of this study was to compare the effects of chemical disinfectants (FD366, ISORAPID and 5% sodium hypochlorite 2/100) to remove Hepatitis B infections from the dental surfaces.

  Materials and Methods: In this experimental laboratory trial, serum of 10 HBV patients was poured into microtubes, FD366, ISORAPID and hypochlorite disinfectants were added to them. PCR experiments with viral diagnostic kits were used to diagnose the virus genome. Real time PCR was used to evaluate after incubation with the disinfectants. The reductions occurred in the viral load of Hepatitis B were statistically analyzed using Kruskal-wallis and Mann-Whitney U tests .

  Results: No significant antiviral efficacy was noted following the application of FD366 and ISORAPID disinfectants (P=0/07). However, hypochlorite showed the most efficacy to disinfect Hepatitis B and a significant difference was found among them (P<0.0001).

  Conclusion: Under the study limitations, FD366 and ISORAPID disinfectants did not show adequate efficacy to remove Hepatitis B virus. Hypochlorite was the most effective disinfectant.