Journal of Dental Medicine

Background and Aims: The aim of this in vitro study was to compare shear bond strength of metal brackets bonded to dental porcelain on the basis of presence or absence of silane, type of acid [hydrofluoric acid (HF) or phosphoric acid (H3PO4)] and roughness of porcelain surface (glazed or deglazed) within mouth-like environment.
Materials and Methods: Eighty glazed ceramic disks were randomly divided into 8 groups of 10 disks: group 1 [HF+silane], group 2 [deglazed+HF+silane], group 3 [HF], group 4 [deglazed+HF], group 5 [H3PO4+silane], group 6 [deglazed+H3PO4+silane], group 7 [H3PO4], group 8 [deglazed+H3PO4]. Then the brackets were bonded and thermocycled. After that, shear bond strength test was done using the Zwick device and the type of bond failure was determined under stereomicroscope at 4X magnification. 3-way ANOVA and Kruskal-Wallis were used for statistical analyses.
Results: The shear bond strength for the test groups were as follows: group (1):13.05±7.7 MPa , group (2):25.16±10.66 MPa, group (3):6.7±5.86 MPa, group (4):15.39±8.97 MPa, group (5):12.76±7.91 MPa, group (6):13.57±7.85 MPa, group (7):0.54±0.67 MPa, group (8): 9.34±6.52 MPa. The type of bond failure in all groups was adhesive failure except for group 2. No significant difference in the interaction between (glazed or deglazed), (presence or absence of silane), and type of acid was found (P>0.05).
Conclusion: Under the conditions of this study, the best clinical method was the use of 37% phosphoric acid and silane that resulted in the optimal clinical strength and adhesive bond failure.

Background and Aims: Occupational burnout is a psychological syndrome resulting from continuous tensions which causes absence, conflict, job changing, etc. In spite of much effort done in optimizing the work conditions and satisfying the employed persons, the dentists still suffer from this incident. The purpose of this study was to determine the degree of occupational burnout in Birjand dentists and to provide an approach.
Materials and Methods: In this descriptive-analytical study by the census method, 38 dentists were investigated using Maslach questionnaire. Average values were compared with chi-square and comparison among the groups was performed by Tukey test using SPSS software. P≤0.05 was considered as the level of significance.
Results: In this study, there were 68.4% men and 31.6% women with average age of 37.9 ±7.6 years and average work experience of 12.5±7.3 years, 15.8% single and 84.2% married. Frequency of exhaustion, intense depersonalization, and intense feeling of being unsuccessful was 21.1%, 81.6%, and 100%, respectively. There were no significant differences between occupation burnout dimensions and the other variable, such as gender, sports, marital status, and workday hours (P>0.05).
Conclusion: Protection of this stratum, providing educational programs and creating job variations are necessary for optimizing the work environment. Future studies with more sample size are suggested to determine the effect of factors.

Background and Aims: Cephalometric measurements cannot be performed for screening purposes, therefore orthodontists usually have to use either photographic or anthropometric measurements in such occasions. Finding a valid and reliable alternative could be of great value. The purpose of this study was to evaluate the correlation between McNamara's cephalometric unit difference and a proposed soft tissue equivalent.
Materials and Methods: An anthropometric ruler was redesigned and used in this study. Soft tissue measurements were performed on 36 randomly selected specimens by two investigators. The soft tissue measurements included external auditory meatus to subnasale (Ext-Sn), external auditory meatus to soft tissue pogonion (Ext-Pog), and the difference between them (UDMA´). These measurements were considered as equivalents to cephalometric indices in McNamara's anteroposterior measurements, including maxillary (Co-A) and mandibular (Co-Gn) unit length and their difference (UDMA), respectively.
Results: All soft tissue variables had an intra-class correlation coefficient (ICC) above 0.90. There was a high and significant correlation between cephalometric and anthropometric measurements (P<0.01). The ICC between (Ext-Sn) and (Co-A) was 0.890, 0.869 between (Ext-Pog) and (Co-Gn), and 0.819 between UDMA´ and UDMA.
Conclusion: The proposed anthropometric method showed a good correlation with cephalometric equivalents and the results show that this method could be used for screening purposes, especially when a low-cost, non-invasive method is required. However it cannot be considered as a substitute for cephalometry in diagnostic and treatment purposes.

Background and Aims: Considering the great incidence of implant failures due to high stresses around implant and at bone-implant interfaces, the aim of this study was to compare the effects of three different implant-macro designs on the quantity and distribution pattern of stresses around implants.
Materials and Methods: In this experimental in vitro study, three types of implants including Biohorizon (4×10.5 mm), Iler (4×10 mm), and Swiss Plus (4.1×10 mm) were studied by applying photo-elastic method. The implants were placed within photo-elastic models with dimensions of 50×50×10 mm. Then through open tray impressed method, crowns for each implant were constructed and cemented. Vertical and oblique loads of 100 N and 150 N were applied on the cemented crowns within polariscope machine. Then the photographs were evaluated using Isochromatic Fringe Characteristics table.
Results: Under vertical loads of 100 N and 150 N, the values for Biohorizon, Iler, Swiss Plus fixtures at the cervical region were (2.35, 3.60) N, (2.50, 3.10) N, and (1.39, 2.35) N, respectively and in apical region the values were (1.63, 2.35) N, (1.82, 2.35) N, and (2.50, 3.10) N. Under oblique loads, the measures at the cervical region were (4.00, 5.00) N, (1.82, 5.00) N, and (5.20, 6.00) N and in apical region were
(1.39, 2.00) N, (4.00, 2.35) N, and (2.35, 3.00) N, respectively for mentioned implants.
Conclusion: Under vertical loads, the lowest cervical stresses were observed in Swiss Plus fixture and the lowest apical stress values were recorded for Biohorizon fixture. Under oblique loads, the lowest cervical stresses were found in Iler implant and lowest apical stresses were recorded for Bohorizon.

Background and Aims: The bond strength between veneer ceramics and zirconia frameworks is the weakest component in the layered ceramics. Due to the possible effect of adding pigments to the core materials on the bond strength between core and veneer as well as the introduction of new ceramic materials in dentistry, the aim of this study was to compare the zirconia core-veneer microtensile bond strength using two ceramic veneers with or without coloring the core.
Materials and Methods: In this experimental study, 12 disc-shaped specimens were fabricated using a manually aided design- manually aided manufactured (MAD/MAM) zirconia core (Zirkonzahn). Two veneering ceramics of Ceram Kiss and Zirkonzahn ICE were also used to veneer the specimens. Half of the Zirkonzahn discs were remained white and the others were colored by shade A2.Then, the discs were cut into microbars (30 for each group) and the microtensile bond strength of the core-veneer was calculated. The specimens were assessed using scanning electron microscopy (SEM) and the data were analyzed using two-way ANOVA and Student's t-test.
Results: Significant differences with respect to veneer layer were found (P<0.001). No significant differences were seen among colored and uncolored cores (P=0.69).
Conclusion: According to the apparent effect of veneering ceramics on the core-veneer bond strength, careful selection of these agents is essential to achieve adequate bond strength between core and veneer to prevent delaminating and chipping failures of zirconia veneered restorations.

Background and Aims: Lasers with different characteristics have been used to stimulate orthodontic tooth movement. Considering the contradictory findings in this regard, this study was designed to assess the effect of low level laser therapy (LLLT) on the rate of orthodontic tooth movement.
Materials and Methods: In this randomized clinical trial study, 12 patients (4 boys and 8 girls average age:16.9 ± 3.4) with extracted upper first premolars and required canine retraction into extraction site were included. While in both sides canines were retracted by NiTi coil spring, one side was exposed to GaAlAs laser (890 nm). LLLT was done (on the buccal and palatal mucosa by slow movement of probe) at the beginning of the first month. Impression and cast fabrication performed at the beginning of retraction, one and two months later. The amount of retraction on the cast was measured with the aid of a reference plaque fabricated on the rogae using a digital caliper. Data were analyzed using paired sample T-test and one-sample Kolmogorov-Simirnov test.
Results: There was no significant difference in the amounts of canine movement between laser exposed and control sides (P>0.05).
Conclusion: The energy dose of laser used in this study (72 J per each tooth) was not appropriate for increasing dental movement.

Background and Aims: Relative displacement of the implant with respect to bone and quality of bone-implant contact play critical roles in the dental implant stability. The goal of this study was to investigate the dental implant stability using non-linear finite elements method. Therefore, bone-implant relative displacement due to applied force to the implant was calculated, and then an appropriate factor for defining quality of bone-implant contact was presented.
Materials and Methods: In order to develop a three dimensional model and compare the results with clinical studies, computed tomography (CT) scan data of a rabbit tibia was considered as a base. The model was exported to ABAQUS 6.9-1 to be analyzed using nonlinear finite elements method. Dynamic analysis was done on the model using the proper boundary condition and dynamic loads.
Results: Force-displacement curves in bone-implant interface were nonlinear. Friction coefficient, which is a criterion for implant stability and relative displacement, approximately became doubled as the vertical contact force was halved. However, the friction coefficient decreased with reduction of coulomb frictional coefficient.
Conclusion: Friction coefficient, which is calculated upon force-displacement curves, could be considered as a criterion to evaluate the dental implant stability. Decrease of the vertical contact force and also using rough surfaces improved the quality of bone-implant contact and stability of dental implant.

Background and Aims: The seal provided by a root canal filling may be compromised by post space preparation. The aim of this study was to compare coronal microleakage around cast posts and prefabricated pins.

Materials and Methods: Thirty-eight extracted single-rooted, maxillary human teeth were prepared with step back method and filled with gutta-percha and sealer. After removing 8 mm of coronal gutta-percha with peeso-reamer drills #2 in twenty canals, the teeth were divided into three groups: cast post & core, prefabricated pin,  and gutta-percha (without any post or pin). After thermocycling, the samples were immersed in India ink for seven days. Finally, the specimens were cleared and the coronal microleakage of dye was then measured by the stereomicroscope. The data were analyzed by One-way ANOVA and Tukey HSD tests.

Results: According to the results, the mean dye penetration in cast posts, pins, and group without post or pin was 3.3 (0.39), 5.2 (0.47), and 7.2 (0.15) mm, respectively. There was no statistically significant difference between the groups (P>0.05).

Conclusion: Considering the importance of adequate filling of crown for prevention of microleakage, the method for coronal filling must be selected with caution. According to the results of this study, no significant difference between microleakage of cast posts and prefabricated pins was observed.

Background and Aims: The aim of this study was to evaluate the quality of an experimental hydrofluoric acid (HF) for preparation of porcelain and to compare it with two commercial hydrofluoric acids in Iranian trademark.

Materials and Methods: A- Evaluation of etch pattern of experimental HF using scanning electron microscope (SEM): 6 feldespathic discs were divided into 3 groups. Each group was etched with related HF (experimental, Ultradent and Kimia) for 1 minute. SEM images were recorded at 3 magnifications. B- Bond strength test: 18 feldespathic discs were considered for each acidic group. Then the porcelain surfaces were etched and bonded to composite with unfilled resin. Consequently, the microshear test was done. C- Microleakage test: 54 discs were divided into 3 groups (n=18). Then the porcelain surfaces were etched and bonded to composite with unfilled resin and finally observed under stereomicroscope. The data were analyzed with one-way ANOVA and Smirnov tests.

Results: SEM analysis showed no difference between groups in terms of etch pattern. Microshear bond strength values for experimental, Kimia, and Ultradent HF were 28.53 (±4.92), 28.21 (±6.61), and 26.14 (±7.61) MPa, respectively. There was no significant difference between the bond strength of test groups (P<0.05). Furthermore, no significant difference was found between the microleakage of test groups (P>0.05).

Conclusion: Quality of experimental HF in terms of etch pattern, microshear bond strength and microleakage of composite/porcelain interface was similar to that of two commercial hydrofluoric acids.

Background and Aims: Improper feeding is one of the most important etiologic factors in early childhood caries (ECC). In some clinical trials, breast feeding (BF) is mentioned as a causing factor in ECC. Results in this topic are different or even controversial. It is vital that all general advices given out are consistent with general health education messages. The aim of this study was to conduct a systematic review on the relationship between breast feeding and early childhood caries. 

Materials and Methods: Articles, guidelines, related books, and specific databases such as SID, PubMed, Scirus, Elsevier, American Association of Pediatric Dentistry (AAPD), American Association of Pediatrics (AAP) and American Dental Association (ADA) were searched for related topics cited since 1990. Early childhood caries definition, breast feeding and other variables such as sample size, study location and study design were analyzed.

Results: According to data analysis, there was a lack of methodological consistency and inconsistent definitions of ECC and BF in the literature making it difficult to draw conclusions. Results about relationship between prolonged BF and ECC were inconclusive. There was a positive relationship between nocturnal BF and ECC. A history of BF did not have any effect on the caries incidence.

Conclusion: Because of the role of breast feeding in children^'s health, it is important to inform the parents about the possibility of dental caries due to nocturnal breast feeding.

Background and Aims: The oral impact on daily performance (OIDP) is one of the oral health-related quality of life indices to measure physical, social and mental consequences of the oral health status. This study aimed to evaluate the OIDP index in patients referring to Tehran dental school.

Materials and Methods: Four hundred and ninety nine patients referring to patients' clinic in Dental School of Tehran University of Medical Sciences in spring 2011 participated in this study. They were interviewed for demographic factors including age, gender and level of education, and OIDP index questionnaire before receiving any treatment. Statistical analysis was carried out by means of linear regression modeling.

Results: 85.6% of patients confirmed that they had at least one oral impact on daily performance during the last 6 months. The most prevalent performances affected were eating (50.1%) and smiling and showing teeth without shame (12.8%). The mean OIDP score for the population was 5.6 ranging from 0 to 36. Linear regression modeling controlling for age, gender and years of education revealed that older patients and those with lower education had significantly higher OIDP scores.

Conclusion: The effect of oral health on daily performance was clear. The association among age, education and oral impact on daily performance indicates the need for more comprehensive preventive oral health care for adults with lower educational level.

Background and Aims: The aim of this study was to measure the degree of conversion (DC) of three types of composite resins (micro-hybrid, nano-hybrid and Ormocer) with different light curing units (LED LCU and QTH LCU) in two depths.

Materials and Methods: Three commercially available dental resin composites were used in this study: (Tetric Ceram, Ivoclar Vivadent, Liechtenstein-A2 shade), (Tetric Evoceram, Ivoclar Vivadent, Liechtenstein-A2 shade), (Ceram X, Dentsply, Germany-M₂ shade). Specimens were divided into two groups, 5 specimens were photo-activated by QTH unit (Coltolux 75-Colten) and the other five specimens were cured by LED (Demi-Kerr). Then each specimen was sectioned at the top surface and at 2-mm depth. The DC was measured by FT-IR
(Bruker-tensor 27). The data were analyzed by 3-way ANOVA test.

Results: There was significant difference between tested composite resins (P<0.001). The results of top surfaces were significantly different from those observed at 2-mm depth (P<0.001). The type of curing unit affected the polymerization of Ceram X resin composite.

Conclusion: This study showed a significant difference in the degree of conversion in different thicknesses within three groups of resin composites.

Background and Aims: Increasing demands for health care's services on one hand and limited resources on the other hand brings about pressure over governments to find out a mechanism for fair and appropriate distribution of resources. Economic analysis is one of the appropriate tools for policy making on this priority. The aim of this study was to assess capital and consumption of oral health units of health care centers in Yazd city and comparing it with revenue of these centers and determining of cost effectiveness.
Materials and Methods: In this descriptive cross sectional study, all health care centers of Yazd city with active dentistry department were evaluated.  The data has been extracted from current documents in health care center of county based issued receipts and daily information registers.
Results: Expended cost for providing of oral hygiene services in second half of 2008 in 13 medical health centers of Yazd included active dentistry section was 557.887.500 Rials and revenue to cost ratio was about 34%. The most provided service was related to tooth extraction and the average of tooth restoration in each working day was 0.48.
Conclusion: With attention to low tariffs of dentistry services in medical health centers and paying subsidy to target groups, expenses of oral hygiene are always more than its revenue.

Background and Aims: Calcium hydroxide has a pronounced antimicrobial activity against most of the bacterial species found in infected root canals and endodontic infections. It is one of the most frequently used intracanal medications in endodontic therapy. The objective of this study was to determine the antimicrobial efficacy of six calcium hydroxide formulations (mixed with saline, lidocaine 2%, chlorhexidine 2%, chlorhexidine 0.2%, Iodine Potassium iodide (IKI) 2%, and glycerin) on Enterococcus faecalis using agar diffusion test.
Materials and Methods: Twelve culture plates were incubated with Enterococcus faecalis. Five cavities were made in each plate with 5 mm diameter and 4 mm depth. Two plates were randomly considered for each calcium hydroxide formulation and filled completely with creamy mixture of tested materials. The plates were incubated at 37ºC for 48 hours. The diameter of inhibition zone around each well was recorded in millimetres and data were submitted to ANOVA and Tukey tests.
Results: The results of this study showed that all tested calcium hydroxide pastes had good antimicrobial activity. The antimicrobial activity of calcium hydroxide mixed with lidocaine, chlorhexidine 2% and IKI 2% were significantly greater than that of calcium hydroxide mixed with saline (P<0.001). No significant differences in the antimicrobial  were found between the other groups (P>0.01).
Conclusion: Considering the results of this study, lidocaine 2%, chlorhexidine 2% and IKI 2% are suggested to be used for preparation of calcium hydroxide paste. Further studies with different methods are needed for confirming these results.

Background and Aims: Different mechanisms have been developed for connecting abutment to implant. One of the most popular mechanisms is Tapered Integrated Screw (TIS), which is a Tapered Interference Fit (TIF) with a screw integrated at the bottom of that. The aim of this study was to investigate the mechanism of TIS and effective factors in employing TIS during design and implementation processes using an analytic method.

Materials and Methods: Relevant equations were developed to predict tightening and loosening torques, contact pressure and preloads with and without bone tissue in this analysis. The efficiency is defined as the ratio of the loosening torque to the tightening torque. The effects of the change in elastic modulus and thickness of the bone on operation of this mechanism were investigated.

Results: In this study, 14 independent parameters such as taper angle, friction coefficient, abutment and implant geometry that are effective on performance of TIS mechanism were presented. The role of some factors was shown in the performance of ITI implant using sensitivity analysis.

Conclusion: It was shown that friction coefficient, contact length, and implant radius play major roles on tightening and loosening torques and efficiency of the mechanism. Furthermore, the results revealed that the change in the elastic modulus and thickness of the bone influenced the efficiency of the mechanism less than 15%.

Background and Aims: Discoloration of resin composites is considered to be the major factor in esthetic restoration failures. The aim of this study was to evaluate the color stability of resin composites after rebonding with two different adhesive materials.

Materials and Methods: Forty five composite disc samples were divided into three groups (n=15). The surface of specimens was finished by polishing disc and rubber. In group 1, any additional phase was not performed. In group 2, composite discs were etched by %37 orthophosphoric acid, then Margin- bond was used for rebonding. In group 3, the etching procedure was in the same manner used for group 2, but Permaseal was used after etching. After the first phase of spectrophotometric measurement, the specimens were dipped in coffee mix for 3 weeks for aging the specimens. Then the second phase of spectrophotometric evaluation was performed. Collected data was analyzed using one-way ANOVA test followed by Tukey test. P<0.05 was considered as the level of significance.

Results: The mean total color difference (∆E) observed in groups 1 to 3 were 1.4±0.34, 5.24±1.51, and 7.44±1.34, respectively. Statistical significant differences were shown between the groups (P<0.001).

Conclusion: Rebonding with adhesive materials used in this study did not increase the color stability of 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: Successful pediatric dentistry depends not only on the dentist's technical skills, but also on his ability to acquire and maintain a child's cooperation. The correction of dentist’ action in this area affects the view of parents and increases the quality of dental services. The objective of this study was to evaluate the attitudes of general dentists toward methods of controlling pediatrics’ behavior in Isfahan.

Materials and Methods: This study is descriptive, analytic, and cross-sectional. For this research, 100 general dentists of Isfahan city were selected with simple random sampling technique and were asked to complete the questionnaire which was included four different management techniques. The data were analyzed with t-test, P earson’s correlation , ANOVA and Kruskal-Wallis.

Results: The methods accepted by dentists were Tell-Show-Do (4.0 ± 0.5), Voice control (3.5 ± 0.4), active restraint (3.0 ± 0.5) and Hand-Over-Mouth (2.9 ± 0.5) respectively. The mean score of female dentists’ attitudes was more toward the method of active restraint and less toward Hand-Over-Mouth technique. Also the average score of middle aged dentists’ attitudes toward Voice Control method was less than young dentists and toward Hand-Over-Mouth was higher. The general dentists with more number of pediatric patients had less consent on the method of Hand-Over-Mouth (P=0.004) and active restraint (P=0.034).

Conclusion: There were significant correlation between attitude of general dentists toward behavior management techniques with age, gender, clinical experience and the number of pediatric patients. General dentists have fewer tendencies to aggressive behavior management techniques.

  Background and Aims: Application of fluoride products is known as one of the most successful interventions to prevent dental caries. This study aimed to compare the costs of in-office fluoride therapy versus salt fluoridation in Iranian population.

  Materials and Methods: In this study, the costs relating to the use of in-office fluoride therapy were analyzed using Activity Based Costing during 2011 from two perspectives. From the perspective of service provider, direct medical costs and indirect costs and from the view of service recipient, three parts: direct medical and non-medical costs and indirect costs, were considered. Costing for public consumption of salt fluoridation was estimated based on salt processing costs, including purchase, installation, monitoring, maintenance and repair of machinery, equipment, personnel expenses and cost of raw materials, used in this study.

  Results: Costs relating to performing a single in-office fluoride therapy was estimated to be 245,032 Rials from the perspective of service providers, and 239,600 Rials from the patient view. Estimated total cost to produce fluoridated salt for a unit of 10 million populations, was calculated to be 35 billion and 940 million Rials or 3, 594 Rials per person per year.

  Conclusion: It was concluded that per-capita costs of community based salt fluoridation was far less than in-office fluoride therapy. Salt fluoridation could be advised to be an affordable way to prevent dental caries in Iranian population.

  Background and Aims : In this in vitro study, the long-term bond strength of a self-adhesive resin cement and conventional resin cements to human enamel and dentin was compared .

  Materials and Methods: 80 sections of intact human third molars were randomly assigned into eight groups according to the cement type [Rely X Unicem (RXU), Rely X ARC (RXA)], bond substrate (enamel, dentin) and the duration of water storage (24 h or 1 year). Rods of cements (0.75×1 mm) were prepared on the top surface of specimens using Tygon tubes. The micro-shear bond strengths of specimens were measured by a micro-tensile tester. Data were analyzed using Wilcoxon signed ranks and Mann Whitney tests ( α =0.05).

  Results: The bond strengths of RXA and RXU cements to enamel after 24h were 18.56±4.08 MPa and 14.99±4.17 MPa, and after 1 year were 19.41±6.24 MPa and 15.51±6.17 MPa, respectively. The bond strengths of RXA and RXU cements to dentin were 13.36±4.02 MPa and 14.16±4.69 MPa after 24h , and 14.63±5.96 MPa and 14.08±6.72 MPa after 1 year, respectively. Tooth substrate had significant effect only on the shear bond strength of RXA cement after 24h (P=0.01), while no other significant differences were found in this study (P>0.05).

  Conclusion: According to the results of this study, one-step self-adhesive and multi-step conventional resin cements were similarly effective in bonding to enamel and dentin after 1 year water storage.