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OBJECTIVE: The demand for esthetics has increased in today's world and most parents prefer to preserve their children's primary anterior teeth until their natural exfoliation. However, an intracanal post is required to provide retention for reconstruction of severely damaged anterior teeth due to caries or trauma. Various materials and methods may be used for the fabrication of intracanal posts. This study assessed the fracture strength and fracture mode of primary canine teeth reconstructed with prefabricated and customized polyethylene and glass fiber posts. MATERIALS AND METHODS: This in vitro study evaluated 60 extracted primary canine teeth in four groups (n = 15). After pulpectomy and post space preparation with 4 mm depth, composite resin post, prefabricated glass fiber post (Whitepost), customized glass fiber post (Interlig), or customized polyethylene fiber post (Ribbond) were placed in the root canals to provide retention, and the tooth crown was restored with bulk-fill composite resin. The fracture strength was then measured in a universal testing machine. The fracture mode was also evaluated visually. RESULTS: The mean fracture strength was 22.45 ± 5.06, 33.10 ± 8.5, 30.20 ± 7.33, and 32.61 ± 5.73 N/mm2 in the composite resin post, Whitepost, Interlig, and Ribbond groups, respectively. The fracture strength was significantly lower in the composite group than in the remaining three groups (p = 0.000). No other significant differences were found (p > 0.05). Also, no significant difference was observed among the study groups in the fracture mode (p = 0.241). CONCLUSION: The composite resin post yielded a significantly lower fracture strength than the prefabricated and customized glass and polyethylene fiber posts, but the fracture mode was not significantly different among the four groups.

Asunto(s)

Resinas Compuestas , Diente Canino , Análisis del Estrés Dental , Vidrio , Técnica de Perno Muñón , Fracturas de los Dientes , Diente Primario , Resinas Compuestas/química , Fracturas de los Dientes/prevención & control , Vidrio/química , Técnica de Perno Muñón/instrumentación , Humanos , Técnicas In Vitro , Diseño de Prótesis Dental , Ensayo de Materiales , Materiales Dentales/química , Polietileno/química , Pulpectomía/métodos , Pulpectomía/instrumentación , Polietilenos

RESUMEN

Objectives: This study investigated the efficacy of theobromine in comparison with 0.05% sodium fluoride solution for remineralization of initial enamel caries lesions (IECLs). Materials and Methods: Ninety non-carious extracted premolars were sectioned longitudinally into buccal and lingual segments. Caries-like lesions were induced in each segment using acidified gel. Forty-five buccal segments were used for surface microhardness (SMH) test, and 45 buccal segments were used for energy-dispersive X-ray spectroscopy (EDS). The lingual segments were used as the control group for EDS and SMH test. The baseline SMH was measured with a Vickers hardness tester, and the baseline calcium content was analyzed by EDS. Each test group was divided into three subgroups for treatment with (1) artificial saliva, (2) 1.1 mol/L theobromine, and (3) 0.05% sodium fluoride. Remineralization and demineralization were done by daily pH cycling to simulate the oral environment. Samples in each group were immersed in treatment solutions for 1 min before and after the remineralizing cycle. After a 7-day cycle, the SMH test and EDS analysis were performed again. Data were analyzed using one-way ANOVA, Tukey's post-hoc test, and paired sample t-test (P<0.05). Results: All treatments effectively remineralized the IECLs (P<0.05), and theobromine caused the maximum increase in SMH, which was significantly higher than the value in sodium fluoride group (mean value of 36.56±4.95 versus 23.25±3.92; P=0.000). EDS showed the highest calcium deposition in theobromine group (3.82±1.83wt%). Conclusion: Theobromine is an effective cariostatic agent, and can be considered as a safe alternative to fluoride in preventive dental care.

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BACKGROUND: There is some cases of perforation and undesirable properties of some primary molars stainless steel crowns. AIM: The aim of this study was to compare the physical and mechanical properties of different commercial brands of these crowns. METHODS: In an in vitro study, 10 stainless steel tooth crowns of the second primary mandibular molars size 6 of 4 different commercial brands (a total of 280 crowns) were evaluated. These crowns were included KTR Pre-trimmed and Crimped Nichro Stainless Steel Primary Molar Crowns (KTR, China); 3M Stainless Steel Primary Molar Crowns (ESPE, St paul; USA); NuSmile SSC Pre-contoured (Inc, Houstone, TX; USA) and Kids crown (Shinghung, Seoul; Korea). Corrosion and galvanic corrosion, wear, microhardness, compressive strength, fatigue strength of crowns and weight percent of elements were investigated. RESULTS: The highest rate of microhardness, compressive and Fatigue strength of the crowns were made by Nu Smile > 3M > Kids Crown > KTR respectively. The highest rate of corrosion potential in corrosion and Galvanic corrosion tests was in KTR > Kids crowns > 3M > Nu smile respectively. The order of crown wear was KTR > Kids Crown > 3M > Nu Smile respectively. The highest amount of nickel element was found in the Nu Smile crown and the highest amount of chrome in the 3M crown with a significant difference with others (p < 0.001). The KTR and Kids crowns lacked molybdenum. CONCLUSION: The results showed that Nu Smile crown has better physical and mechanical properties than other evaluated crowns in this study.

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BACKGROUND: This study was carried out to evaluate the effect of root canal filling on the bond strength of three intracanal posts in the primary incisors. MATERIALS AND METHODS: Sixty primary incisors were prepared and then divided into two groups (n = 30). The first group canals obturated with zinc oxide eugenol (ZOE) and Group 2 canals obturated with Metapex. Further, the two group categories were divided into three subgroups (n = 10): (1) short composite post (SCP), (2) glass fiber posts (GFPs) cemented with flowable composite, and (3) GFP with glass ionomer cement (GFP + GIC). The push-out test was performed with a universal testing machine. The results were statistically analyzed with two-way analysis of variance.(α = 0.05). RESULTS: The mean bond strength of the first group obturated with ZOE was lower than that of the second group obturated with Metapex (P = 0.046). Moreover, from a statistical point of view, in all three subgroups, the correlation of mean push-out bond strength between SCP and GFP coated with flowable composite was not substantial at P = 0.97. However, the mean bond strength of SCP was in fact significantly greater than that of the GFP coated with GIC since P = 0.034. CONCLUSION: Using ZOE resulted in the significant reduction of the mean bond strength of the intracanal posts when utilized in the primary anterior teeth. Likewise, SCP and GFP coated with flowable composite showed higher push-out bond strengths for restoring primary anterior teeth.

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INTRODUCTION: Dental caries is a major public health problem, and Streptococcus mutans is considered the main causal agent of dental caries. This study aimed to compare the effect of three re-mineralizing materials: resin infiltrant, fluoride varnish, and nano-hydroxy apatite paste on the surface hardness and adhesion of Streptococcus mutans as noninvasive treatments for initial enamel lesions. METHODS: This experimental study was conducted from December 2015 through March 2016 in Babol, Iran. Artificial enamel lesions were created on 60 enamel surfaces, which were divided into two groups: Group A and Group B (30 subjects per group). Group A was divided into three subgroups (10 samples in each subgroup), including fluoride varnish group, nano-hydroxy apatite paste group (Nano P paste), and resin infiltrant group (Icon-resin). In Group A, the surface hardness of each sample was measured in three stages: First, on an intact enamel (baseline); second, after creating artificial enamel lesions; third, after application of re-mineralizing materials. In Group B, the samples were divided into five subgroups, including intact enamel, demineralized enamel, demineralized enamel treated with fluoride varnish, Nano P paste, and Icon-resin. In Group B, standard Streptococcus mutans bacteria adhesion (PTCC 1683) was examined and reported in terms of colony forming units (CFU/ml). Then, data were analyzed using ANOVA, Kruskal-Wallis, Mann-Whitney, and post hoc tests. RESULTS: In Group A, after treatment with re-mineralizing materials, the Icon-resin group had the highest surface hardness among the studied groups, then the Nano P paste group and fluoride varnish group, respectively (p = 0.035). In Group B, in terms of bacterial adhesion, fluoride varnish group had zero bacterial adhesion level, and then the Nano P paste group, Icon-resin group, intact enamel group, and the de-mineralized enamel group showed bacterial adhesion increasing in order (p < 0.001). CONCLUSION: According to the study among the examined materials, the resin infiltrant increased the tooth surface hardness as the intact enamel and fluoride varnish had the highest reduction level for bacterial adhesion. Nano P paste had an effect between the two materials, both in increasing surface hardness and reducing bacterial adhesion.

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OBJECTIVES: Iron and multivitamin drops are being frequently prescribed in children less than 2 years of age. Due to their low pH levels, these drops may lead to the softening of enamel and accelerate the destructive process. The aim of the present study was to investigate the enamel microhardness of primary teeth after exposing them to iron and multivitamin drops. MATERIALS AND METHODS: Forty healthy anterior teeth were randomly divided into four groups of 10 samples each. Samples were exposed to two iron drops of Kharazmi (Iran) and Ironorm (UK) and two multivitamin drops of Shahdarou (Iran) and Eurovit (Germany) for 5 min. The surface microhardness was measured before and after exposure and data processing was done using statistical paired t-test and analysis of variance (ANOVA) test. The surface structure of the teeth was examined by scanning electron microscope (SEM). RESULTS: In all groups, microhardness was decreased, but it was not significant in Eurovit multivitamin group (P = 0.088). The reduction rate in Kharazmi iron group was significant compared to that in other groups (P < 0.005). Hardness reduction percent for Kharazmi iron drop was 28/12 ± 47/43. In SEM analysis, irregular granular appearance was observed in the enamel exposed to Kharazmi iron drop. CONCLUSION: The results showed that all the studied drugs have the potential to cause erosion; this potential is the most in Kharazmi iron drop and the least in Eurovit multivitamin drops. Therefore, after using these kinds of drops, preventive measures should be used in children.