Self-assessment skills of undergraduate dental students in the preclinical course of complete removable prosthodontics at Tehran University of Medical Sciences.

INTRODUCTION: This study evaluated the self-assessment skills of third-year dental students regarding their performance in complete removable prosthodontics (CRP) preclinical course. METHODS AND MATERIALS: This cross-sectional study was conducted on all third-year dental students attending the International Dental College of Tehran University of Medical Sciences. The students were requested to self-assess their performance in primary impression making, custom tray fabrication, border moulding, final impression making, master cast fabrication, record-base fabrication and tooth arrangement in CRP preclinical course. The performance of dental students in each step was scored by themselves and their mentors. Data were analysed by the Mann-Whitney U, Pearson's correlation and t-tests (α = 0.05). RESULTS: Totally 25 male (55.6%) and 20 female (44.4%) dental students were evaluated. Significant differences were noted between male and female dental students in self-assessment scores regarding adequate extension of the custom tray (p = .027), the correct position of tray handle (p = .020), visibility of vestibular width and depth on the cast (p = .011), the coincidence of upper and lower midlines (p = .005) and correct orientation of maxillary and mandibular planes in the articulator (p = .036). The mean self-assessment score of female students was significantly higher than that of male students (p = .01). The scores given by the mentors were not significantly different for male and female students (p = .975). The difference between the self-assessment score of students and the mentor score was not significant (p = .067) either in males or in females (p > .05). CONCLUSION: Undergraduate dental students favourably self-assessed their performance in all steps of the preclinical course of CRP, comparable with their mentor assessment.

Photobiomodulation effects of pulsed and continuous wave near-infrared laser on the proliferation and migration of human gingival fibroblasts: An in vitro study.

There are limited data on comparison of pulsed and continuous wave in photobiomodulation therapy (PBM). This study aimed to investigate the effect of PBM with 980 nm laser in pulsed and continuous wave on the proliferation and migration of human gingival fibroblasts (HGF) cells. Cultured HGF were divided into three main groups: (1) irradiated in pulsed mode (frequencies of 50 and 25 KHz; energy densities of 3 and 5 J/cm2 ), (2) irradiated in continuous mode (energy densities of 3.2 and 5.2 J/cm2 ), and (3) no irradiation as control group. HGF proliferation rate was measured by MTT assay at 24, 48, and 72 h post irradiation. In addition, HGF migration rate was measured by scratch test at 24 h post PBM. At 24 h, the group received continuous irradiation at 5.2 J/cm2 showed significantly higher proliferation compared with the control group (p = 0.012). At 48 and 72 h, the groups received continuous, and 50 Hz pulsed irradiation at energy densities of 5.2 and 5 J/cm2 respectively, had significantly higher HGF proliferation rates compared to the control (p < 0.05). Only the continuous irradiations were effective in significant increase of the cell migration. In conclusion, continuous PBM at energy density of 5.2 J/cm2 showed promising effect on HGF proliferation and migration.

Perceptions of mandibular asymmetry among orthodontists, oral and maxillofacial surgeons, and laypersons.

Background: Facial asymmetry is one reason orthodontic patients seek treatment. This study assessed the effect of mandibular asymmetry on facial esthetics and treatment needs perceived by laypersons, orthodontists, and maxillofacial surgeons. Materials and Method: In this descriptive cross-sectional study, the frontal image of a model was captured and symmetrized from the facial midline using Adobe Photoshop software. The mandible was rotated 0°-8° with 1° intervals. Images were presented to 41 laypersons, 39 orthodontists, and 29 surgeons using an online questionnaire. The observers rated each image's esthetics with a 0-100 Visual Analog Scale and determined their treatment need by choosing one of the following three choices: No need for treatment, needs treatment, acceptable, but better to be treated. Analysis of variance for repeated measurements model. The regression method, Kruskal-Wallis analysis, was used for statistical analysis and the level of significance was set as P < 0.05. Results: The images with 0° and 1° rotation received the highest esthetic rates among all three groups, while the images with 8° rotation were the least attractive ones. Furthermore, the image esthetic ratings significantly affected their treatment need. Mandibular asymmetry diagnosis threshold was 1° for orthodontists, and 3° for both laypersons and surgeons. The treatment need threshold was 5°, 6°, and 7° for surgeons, orthodontists, and laypersons, respectively. Conclusion: The esthetics of images decreased when mandibular asymmetry increased. Treatment need was also related to increased asymmetry. Orthodontists were the most sensitive group in diagnosis, while surgeons were the most sensitive ones when it came to treatment.

Effect of Photobiomodulation Therapy With an 810-nm Diode Laser on Pain Perception Associated With Dental Injections in Children: A Double-Blind Randomized Controlled Clinical Trial.

Introduction: This study investigated the photobiomodulation effect of an 810-nm diode laser in adjunction with topical anesthesia on pain perception during infiltration anesthesia of primary maxillary molars in children. Methods: This double-blind randomized controlled clinical trial was conducted on 64 children (aged 5-9 years) requiring extraction or stainless steel crown for their primary maxillary molars. The patients were randomly allocated into two groups (n=32) of laser and control. In the laser group, the injection site (buccal and palatal mucosa) was irradiated with an 810-nm laser (200 mW, 5.2 J/cm2) after 20% benzocaine topical anesthetic application, while the control group received a placebo laser following topical anesthesia. The pain intensity experienced by children during needle insertion into the buccal and palatal mucosa was determined using a visual analog scale (VAS) and modified behavioral pain scale (MBPS). Results: According to the results of the VAS and MBPS, no significant difference was detected in pain scores between the laser and control groups neither in the buccal nor in the palatal mucosa (P>0.05). Conclusion: Photobiomodulation therapy with an 810-nm laser with the current setting adjunct to topical anesthesia did not promote significant additional effects on the pain intensity.

Comparison of diagnostic effects of infrared imaging, visual inspection, and bitewing radiography in primary occlusal caries of permanent teeth.

Background: This study compared the diagnostic efficacy of VistaCam iX infrared camera, visual inspection, and bitewing-radiographs for the detection of primary occlusal caries of permanent teeth. Materials and Methods: In this in vitro experimental study, 80 extracted human premolars were evaluated. The occlusal surfaces of these teeth were demineralized by immersion in a demineralizing agent. Then, the International Caries Detection and Assessment System (ICDAS II), bitewing-radiography, and Proxi head of VistaCam iX were used to inspect them. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for each diagnostic modality. Data were analyzed using SPSS. Twenty-five at P < 0.05 level of significance with one-way analysis of variance and Games-Howell test. Results: Bitewing-radiography had significantly lower sensitivity than ICDAS II and VistaCam (P < 0.05). ICDAS II was comparable to VistaCam, with no significant difference in sensitivity (P > 0.05). ICDAS II had a significantly higher PPV than bitewing-radiography and VistaCam (P < 0.05). The sensitivity of bitewing radiography was significantly lower than that of ICDAS II and VistaCam (P < 0.05). ICDAS II was comparable to that of VistaCam with no significant differences in sensitivity (P > 0.05). ICDAS II had a considerably higher PPV than bitewing-radiography and VistaCam (P < 0.05). The NPV of ICDAS II visual inspection was significantly higher than that of bitewing-radiography and VistaCam (P < 0.05). The ICDASS II and VistaCam had a repeatability coefficient of 47.4%. For bitewing-radiography and VistaCam, this value was 44.2% and 83.4% for ICDAS II and bitewing-radiography. Conclusion: Visual inspection seems to be superior to bitewing-radiography and VistaCam in detecting primary occlusal caries of permanent teeth.

In Vitro Effect of Photobiomodulation Therapy with 980 nm Diode Laser on Gene Expression of Key Regulators of Bone Remodeling by Human Periodontal Ligament Cells under Mild Orthodontic Forces.

This study investigated the effect of photobiomodulation (PBM) with 980 nm diode laser as monotherapy and in combination with compressive and tensile orthodontic forces on expression of osteoprotegerin (OPG), receptor activator of nuclear factor-κB ligand (RANKL), sclerostin (SOST) and periostin (POSTN), by human periodontal ligament cells. Isolated cells were cultured and subjected to either tensile (10% elongation) or compressive forces (25 g cm-2 ) for 24 and 48 h. Subsequently, the cells received PBM (100 mW power, 3 or 6 J cm-2 energy density) immediately after load cycle. RT-PCR was applied to assess the genes expression. Data were analyzed by one-way ANOVA, followed by post hoc Tukey test (P ≤ 0.05). We found that PBM in combination with orthodontic forces led to upregulation of bone resorption genes (RANKL and SOST) at the pressure side and their downregulation at the tension side. The expression of osteogenic genes (OPG and POSTN) increased at the tension side and decreased at the pressure side. PBM alone did not affect gene expression. In conclusion, these findings suggest that this PBM protocol may be effective in enhancement of the gene expression in favor of bone remodeling acceleration that should be confirmed in future animal and human studies.

Knowledge and attitude in implant dentistry training courses amongst undergraduate dental students at Tehran University of Medical Sciences.

INTRODUCTION: Due to the increase of implant treatments in daily practice, graduates should be well acquainted with appropriate diagnostic and therapeutic knowledge in implantology. This study sought to assess the knowledge and attitude of undergraduate students towards the benefits of their courses in the implant dentistry curriculum. MATERIALS AND METHODS: This survey study was performed on all senior dental students at Pardis International Campus, School of Dentistry of Tehran University of Medical Sciences. Data collection was carried out through a questionnaire containing various items on knowledge and attitude. The validity and reliability of the questionnaire were already approved. Collected data were coded, entered in Microsoft Excel 2019, and analysed by t-test (α = .05). RESULTS: Forty questionnaires were filled out by 28 female and 12 male students. Only 7.5% and 12.5% of students reported that they had adequate knowledge to conduct the surgical and prosthetic steps of dental implant treatment, respectively. The majority of students had a positive attitude towards the quality of theoretical education. However, less than 50% of them perceived the same about their practical education. No significant difference existed between male and female students regarding their responses to the knowledge and attitude questions (p = .458 and p = .288, respectively). Ninety percent of the students felt the need for further education regarding dental implant treatment in the undergraduate curriculum. CONCLUSION: Despite the satisfaction of the theoretical knowledge, most senior students believed that they did not achieve adequate expertise to practice after graduation and were willing to receive further practical training in implantology.

Different scoring methods of the VARK questionnaire to evaluate dentistry Students' learning styles.

INTRODUCTION: The way students process and organise information to facilitate learning is known as learning style. Knowing one's learning style can improve learning and help teachers choose their teaching methods more effectively. This study was conducted to investigate different scoring methods of the VARK questionnaire and compare different learning styles in different stages of dental school. MATERIALS AND METHODS: Students in three stages of the dental school participated in this study: basic sciences, preclinical and clinical. The validated reliable Persian VARK questionnaire was utilised. Collected data were computed and analysed in three ways: raw, normalised and weighted scoring by ANOVA and chi-squared tests (α = .05). RESULT: The most favoured learning style was auditory; however, the prevalence of other learning styles varied through stages. On analyses of visual and auditory learning styles by all methods of scoring, no significant difference was seen in different stages (study time). The kinetic learning style, using normalised scoring method, was used more significantly when the grade increased (p-value = .028). However, in the weighted method, this effect was not significant. The read-write learning style using all three scoring methods showed an inverse relationship with the level of education (p-value <.05), which means the tendency to use this style of learning decreased when the level of education increased. CONCLUSION: As the educational level increases, students are more inclined to use kinetic and less likely to employ read-write learning style. There was not a significant difference in the use of visual and aural learning styles in any stages of dental school.

Perspectives and Preferences of Preschoolers and Their Parents Regarding Dentist's Attire and Gender.

Objectives: For decades, the white coat has been the uniform of medical professionals. Recently, medical professionals show interest to use alternatives. We aimed to evaluate the perspectives and preferences of children and their parents regarding dentists' attire and gender. Materials and Methods: This cross-sectional study was performed on 4-to 6-year-olds and their parents referred to dental clinics of Tehran School of Dentistry in 2018. Parents completed a questionnaire on demographics and dental fear, and both parents and children were asked about their preferences regarding the gender of dentist and the color of the dentist's attire. Statistical analysis was performed by the logistic regression model. Results: Totally, 148 children (mean age of 5.42±0.71 years, 48% girls) and their parents participated in the study. Most of the participants (81.2% of the children and 68.0% of the parents) preferred colored coats compared with white coat. More than half of the parents preferred a female dentist for their children (56.5%) while most children preferred a male dentist (54.8%). Boys preferred a male dentist as well (P=0.01). The children were reluctant to go for a dental visit and preferred to be visited by a dentist of the same gender as themselves (P=0.041). Conclusion: Wearing colored coats by dentists and giving a chance to choose the gender of dentist in polyclinics may increase the children's cooperation in pediatric settings.

Effect of surface treatment with laser on repair bond strength of composite resin to ceramic.

Background: Small chipping or fracture of ceramic restorations may be repaired by composite resin instead of replacing the restoration. This method is faster and cheaper compared to restoration replacement. Several strategies have been suggested to obtain a high repair shear bond strength (SBS). This study aimed to assess the efficacy of some new ceramic surface treatments (laser and universal adhesive) to enhance the repair bond strength of composite resin to ceramic compared to the conventional method. Materials and Methods: This in vitro study evaluated 80 IPS Empress Esthetic ceramic plates in eight groups (n = 10). The ceramic surface was polished with 320-grit silicon carbide paper under running water, rinsed with water spray for 10 s and dried. The samples were then divided into two subgroups for mechanical surface preparation with hydrofluoric (HF) acid and Er: YAG laser (2 W, 200 m J, 10 Hz, 10 s). Each group was divided into two subgroups for use/no use of silane. The conventional or universal adhesive was then applied on the samples in each subgroup. Composite cylinders were bonded to the ceramic surface using plastic tubes. The samples were stored in distilled water at 37°C for 24 h and subjected to an SBS test. Data were analyzed using one-way ANOVA (P < 0.05). Results: The interaction effect of variables on SBS was significant. Maximum SBS was noted in HF acid + silane + conventional adhesive group (mean: 12.0481 MPa). Minimum SBS was noted in the laser + conventional adhesive group (mean: 2.5766 MPa). Surface treatment with HF acid yielded significantly higher SBS than laser (P < 0.001). The interaction effect of conventional/universal adhesive and use/no use of silane on SBS was statistically significant. Conclusion: The repair SBS was higher in groups treated with HF acid compared to laser. Ceramic surface treatment with HF plus silane plus conventional adhesive yielded a higher SBS as well as HF plus Universal adhesive. Thus, the application of silane as a separate step can be omitted in the repair of ceramic restorations with universal adhesives.

In vitro Effect of 810 nm and 940 nm Diode Laser Irradiation on Proliferation of Human Gingival Fibroblasts and Expression of Procollagen Gene.

Factors promoting fibroblast proliferation and collagen synthesis can subsequently enhance wound healing. This study aimed to assess the effect of 810 and 940 nm diode laser on fibroblast proliferation and procollagen gene expression. In this study, human gingival fibroblasts were cultured in Dulbecco's modified Eagle's medium and underwent 810 and 940 nm diode laser irradiation once, twice, thrice and four times at 1, 3, 5 and 7 days after culture. The methyl thiazolyl tetrazolium assay was performed to assess the proliferation while the real-time polymerase chain reaction was performed to assess the expression of procollagen gene at the mRNA level. We applied two-way ANOVA and Tukey's test for analysis. Wavelength had no significant effect on the proliferation of gingival fibroblasts, but increasing the number of irradiation sessions of both wavelengths increased the proliferation of human gingival fibroblasts. Significant differences were noted in the number of human gingival fibroblasts between groups irradiated 1 and 4 and also 2 and 4 times. Procollagen gene was well expressed in all groups but its expression was significantly higher in 940 nm laser group after four irradiation cycles. Four times radiation of 940 nm laser seems to be more effective than all others.

Effect of Clinical Rotation Timing on Learning Quality of Dental Students.

Objective: Dental educational curricula are under constant modification and improvement. However, designing a comprehensive, efficient, and flexible curriculum is still challenging for the authorities. An efficient curriculum should obviate the educational needs of students and promote their knowledge and expertise for future practice. Time planning of clinical rotations is highly important for optimization of the learning process. This study aimed to compare the efficacy of two different timing models of clinical rotations, namely four versus two rotations in each semester. Materials and Methods: A total of 74 dental students and 54 faculty members of Tehran University of Medical Science that experienced both rotation models for two consecutive years (2018 and 2019) participated in this study. A questionnaire was designed to assess different aspects of the two timing-models. Results: A one-sample t-test indicated that students' and faculty members' mean perception were significantly better regarding the two-rotation program. Conclusion: This study indicated that changing the time planning of educational rotations can affect different aspects of education.

Cytotoxicity Comparison of a Calcium Silicate-Based Resin Cement versus Conventional Self-Adhesive Resin Cement and a Resin-Modified Glass Ionomer: Cell Viability Analysis

Abstract Objective: To compare the cytotoxicity level of a new calcium silicate-based resin cement (TheraCem) with two commonly used cements, including a conventional self-adhesive resin cement (Panavia SA) and a resinmodified glass ionomer cement (FujiCem2), on the human gingival fibroblast cells after 24 and 48 hours. Material and Methods: Twelve discs of each cement type were fabricated. The extract of cement disks was made by incubating them in the cell medium. Human gingival fibroblast cells were cultured and exposed to cement extracts for 24 h and 48 h. MTT assay was performed on extracts and optical density and cell viability rates were calculated by the spectrophotometer device at 570 nm. Data were analyzed using ANOVA and Tukey HSD tests. Results: The cell viability rates after 24 hours and 48 hours were as follows: TheraCem: 89.24% and 85.46%, Panavia SA: 49.51% and 46.57% and FujiCem2: 50.63% and 47.36%. TheraCem represented the highest cell viability rate. However, no significant difference was noted between Panavia SA and FujiCem2. Time had no significant effect on cell viability. Conclusion: TheraCem exhibited the best results among three tested cements and was considered non-toxic. Panavia SA and FujiCem2 were not significantly different regarding the cell viability rate. Time had no significant effect on the cytotoxicity level of cements (AU).

Evaluation of Compressive Strength of Several Pulp Capping Materials.

STATEMENT OF THE PROBLEM: Adequate compressive strength is an important characteristic for an ideal liner. PURPOSE: This study aimed to assess the compressive strength of several commonly used liners. MATERIALS AND METHOD: This in vitro, experimental study evaluated 120 samples fabricated of Dycal, Calcimol LC, Vitrebond, Activa Bioactive, and TheraCal LC (n=24) liners according to the manufacturers' instructions. The samples were fabricated using a cylindrical stainless steel mold with 6±0.1 mm height and 4±0.1 mm internal diameter. Half of the samples in each group (n=12) underwent compressive strength test immediately after completion of their primary setting while the other half (n=12) underwent compressive strength test after 24 h. During this period, the samples were immersed in deionized water (grade 3) and incubated at 37±1°C and 100% humidity for 24 h. The compressive strength was measured using a universal testing machine. Data were analyzed using two-way ANOVA followed by Tukey's post-hoc test. RESULTS: The compressive strength of the five liners was significantly different (p< 0.05). Calcimol LC showed maximum compressive strength both immediately after setting and after 24 h. The compressive strength at 24 h was significantly higher than the primary compressive strength in all groups (p< 0.05). CONCLUSION: Within the limitations of this study, it seems that Calcimol LC, Activa Bioactive Liner, and TheraCal LC have adequate compressive strength and can be used alone to provide adequate support for the restorative materials.

Effect of an Educational Pamphlet on Knowledge and Performance of Fitness Trainers about Traumatic Dental Injuries.

Objectives : Traumatic dental injuries (TDIs) commonly occur in sport clubs. The knowledge and performance of fitness trainers play an important role in management of such injuries. This study sought to assess the effect of an educational pamphlet on knowledge level and performance of fitness trainers about TDIs in Tehran in 2018. Materials and Methods: In this interventional study, a pamphlet was designed to enhance the knowledge level of fitness trainers. Ninety-five fitness trainers were randomly divided into two groups of intervention and control (n=49 in the control group and n=46 in the interventional group), and were requested to fill out a valid and reliable researcher-designed questionnaire about TDIs before and 1 month after pamphlet distribution. The questionnaire consisted of three domains of demographic information, knowledge questions, and performance questions. The results were analyzed using SPSS 25 via the Chi-square test and repeated measures ANOVA considering the intervention as the between-subject factor. Results: The knowledge score of fitness trainers about TDIs was not adequately high in the intervention or the control group before the intervention. After the intervention, the performance of participants improved in both groups. This increase was significantly greater in the intervention group (P=0.035). There was no significant difference between the two groups in the knowledge domain (P=0.185). Conclusion: Educational pamphlets can effectively enhance the knowledge level of fitness trainers about TDIs. However, the magnitude of this effect was not significant in our study. Future studies are recommended to compare the efficacy of educational pamphlets with other educational tools.

Survival of Dyna Implants: A Retrospective Study with 1 to 6 Years of Follow up.

Objectives: Dental implants are a prominent scientific breakthrough and are frequently applied for replacement of the missing teeth. From the clinicians' point of view, long-term studies are essential to find out the predictability of dental implant systems. Materials and Methods: In this retrospective study, 1,626 patients who received 4,389 Dyna implants in a private office between 2013-2019 were evaluated. All statistical analyses were performed using SPSS 25 for Windows. P values less than 0.1 were considered significant for regression analysis. Results: Dyna implant ts (4389) placed from 2013 to 2019 were evaluated in this study. One-hundred and thirty-three (3.03%) implants failed during the healing period or recall visits. Eighty-nine implants (2.03%) failed immediately and 44 (1%) failed after 3 months. Conclusion: The present study showed that the Dyna dental implant system had high implant survival, and it had all the survival criteria similar to world-class dental implant systems.

Surface microhardness of a self-adhesive composite in comparison with conventional composite resins.

BACKGROUND: The surface microhardness of dental composites greatly affects the durability of restorations. OBJECTIVES: The aim of this study was to compare the surface microhardness of a self-adhesive composite with that of other conventional composites. The effect aging has on surface microhardness was also evaluated. MATERIAL AND METHODS: In this in vitro experimental study, the composite resins were poured into molds measuring 3 mm × 3 mm × 6 mm and cured for 40 s. The samples were then immersed in distilled water at 37°C for 24 h. After polishing, the surface microhardness of the samples was measured using the Vickers hardness tester. For this purpose, a 100-gram load was applied to 3 points on the surface of each composite sample for 20 s, and the mean value of surface microhardness was used as the Vickers hardness number. The samples were then subjected to 30,000 thermal cycles at 5-55°C in order to age them; after that, their surface microhardness was measured again. The one-way analysis of variance (ANOVA) was used for the statistical analysis. RESULTS: The maximum hardness value before and after aging belonged to Filtek® Z250, followed by Premise™ Flow and Vertise™ Flow, with significant differences between them (p < 0.001). After aging, the surface microhardness of all composites decreased significantly (p < 0.001). The effect of aging on surface microhardness was the same in all groups (p > 0.05). CONCLUSIONS: The surface microhardness of composites was significantly different before and after aging. All composites experienced a reduction in their surface microhardness after aging.

The effect of laser-activated bleaching with 445 nm and 915 nm diode lasers on enamel micro-hardness; an in vitro study.

BACKGROUND: The appearance of the teeth is of great importance to patients, particularly tooth color. In recent years, tooth whitening has been one of the most popular ways to restore tooth color. Bleaching gels can be affected by heat, light or laser, which can improve its effects. This study intends to examine the effects of two different wavelengths of diode laser (445 & 915 nm) after the bleaching process, on the enamel micro-hardness. METHODS: A total of 65 caries-free humans third molars were randomly divided into five groups (N = 13): first group: bleaching gel activated with 915 nm diode laser (1.5 W), second: bleaching gel activated with 915-nm (2.5 W), third: bleaching gel activated with 445-nm (1 W), fourth: bleaching gel activated with 445-nm (1.5 W), fifth (control group): bleaching gel without laser activation. Micro-hardness test (Vickers test) was performed before and after the treatment. The data were submitted to repeated measurement ANOVA and Tukey's HSD post hoc test (α = 0.05). RESULTS: Enamel micro-hardness did not change significantly in groups 3 and 4 but decreased in groups 1 and 2. Group 2 showed the most reduction in micro-hardness. There were no significant changes in the control group. CONCLUSION: According to the results of this study, 445 nm Diode laser did not reduce enamel micro-hardness, making it suitable for bleaching treatments. However, more studies are required to consider other factors, such as color changes and pulp temperature.

Color stability of self-adhering composite resins in different solutions.

BACKGROUND: The success of composite resin restorations depends to a great extent on their color stability. However, discoloration is still a problem in composite resin restorations. OBJECTIVES: The aim of the study was to evaluate the effect of different staining solutions on the color stability of composite resins. MATERIAL AND METHODS: A total of 96 composite disks, 2 mm in height and 8 mm in diameter, were fabricated of 3 commercially available composite resins. The samples were divided into 4 groups of 8 and were immersed in 4 staining solutions: coffee, tea, soda, and artificial saliva. The color parameters of the samples were measured and recorded before as well as 2, 4 and 8 weeks after immersion by spectrophotometry, using the CIELAB color space. A color change (ΔE) ≤3.3 was considered the acceptable threshold for visual perception. The results were analyzed using the one-way analysis of variance (ANOVA) and Tukey's post hoc test (p < 0.05). RESULTS: All the composite resins in the study showed discoloration in all the staining solutions. The ΔE of VertiseTM Flow was the highest in the tea solution. The lowest ΔE occurred in the FiltekTM Z250 composite in artificial saliva. CONCLUSIONS: This in vitro study showed that the color stability of tooth-colored restorations can be influenced by dietary habits.

Effect of Two Methods of Remineralization and Resin Infiltration on Surface Hardness of Artificially Induced Enamel Lesions.

STATEMENT OF THE PROBLEM: The progression of incipient carious lesions may be simply prevented by non-invasive remineralization of lesions, eliminating the need for invasive and high-cost restorative procedures. PURPOSE: This study aimed to assess the effect of two commonly used remineralizing agents and resin infiltration on surface micro hardness of incipient enamel lesions at different time points. MATERIALS AND METHOD: In this in vitro study, 45 intact human maxillary central incisors were selected. After disinfection, enamel samples measuring 5x5x2.5 mm were cut out of the labial surface of the teeth. The surface of samples was polished and they were mounted in auto-polymerizing acrylic resin. According to Amaechi's method, samples were immersed in acidified hydroxyethylcellulose system (pH= 4.5) for 96 hours to induce white spot lesions (WSLs). The baseline value of surface micro hardness of samples was measured using a Vickers hardness tester, then the samples were randomly divided into three groups (n=15) based on different remineralization methods: MI-Paste Plus, Remin Pro and ICON-Infiltrant according to the manufacturer's instructions. All samples were stored in anti-dry mouth treatment agent during the experiment and their surface hardness was measured at 15 days (T1) and 20 weeks (T2). RESULTS: The hardness of samples in MI-Paste Plus and Remin Pro groups significantly increased at both T1 and T2 (p< 0.001) but this increase was not significant in ICON group (p> 0.05). CONCLUSION: MI-Paste Plus and Remin Pro can efficiently increase the hardness of incipient enamel lesions.