Osteoregeneration of Critical-Size Defects Using Hydroxyapatite-Chitosan and Silver-Chitosan Nanocomposites.

Bone is a natural nanocomposite composed of proteins and minerals that can regenerate itself. However, there are conditions in which this process is impaired, such as extensive bone defects and infections of the bone or surrounding tissue. This study evaluates the osteoregenerative capacity of bone grafting materials in animals with induced bone defects. Colloidal chitosan dispersion nanocomposites, nanohydroxyapatite−chitosan (NHAP-Q) and nanosilver−chitosan (AgNP-Q), were synthesized and characterized. Non-critical-size defects in Wistar rats were used to evaluate the material's biocompatibility, and critical-size defects in the calvarias of guinea pigs were used to evaluate the regenerative capacity of the bones. Moreover, the toxicity of the nanocomposites was evaluated in the heart, liver, spleen, kidneys, and skin. Histological, radiographic, and electron microscopy tests were also performed. The results showed that neither material produced pathological changes. Radiographic examination showed a significant reduction in defects (75.1% for NHAP-Q and 79.3% for AgNP-Q), angiogenesis, and trabecular formation. A toxicological assessment of all the organs did not show changes in the ultrastructure of tissues, and the distribution of silver was different for different organs (spleen > skin > heart > kidney > liver). The results suggest that both materials are highly biocompatible, and AgNP-Q achieved similar bone regeneration to that reported with autologous bone. The main research outcome of the present study was the combination of two types of NPs to enhance antimicrobial and osteoregeneration activities. These colloidal chitosan dispersions show promise as future biomaterials in the medical field for applications in fast-healing fractures, including broken bones in the oral cavity and hip replacement infections.

Characterization, antibiofilm and biocompatibility properties of chitosan hydrogels loaded with silver nanoparticles and ampicillin: an alternative protection to central venous catheters.

The purpose of this study was to generate novel chitosan hydrogels (CHs) loaded with silver nanoparticles (AgNPs) and ampicillin (AMP) to prevent early formation of biofilms. AgNPs and CHs were characterized by UV-Vis, DLS, TEM, rheology, FT-IR, Raman, and SEM. The antibiofilm effect of the formulations was investigated against four multidrug-resistant and extensively drug-resistant pathogens using a colony biofilm, a high cell density and gradients model. Also, their hemostatic properties and cytotoxic effect were evaluated. Rheology results showed that CHs with AgNPs and AMP are typical non-Newtonian pseudoplastic fluids. The CH with 25 ppm of AgNPs and 50 ppm AMP inhibited the formation of biofilms of Acinetobacter baumannii, Enterococcus faecium and Staphylococcus epidermidis, while a ten-fold increase of the antimicrobial's concentration was needed to inhibit the biofilm of the ß-lactamase positive Enterobacter cloacae. Further, CH with 250 ppm of AgNPs and 500 ppm AMP showed anticoagulant effect, and it was shown that all formulations were biocompatible. Besides to previous reports that described the bioadhesion properties of chitosan, these results suggest that AgNPs and AMP CHs loaded could be used as prophylactic treatment in patients with central venous catheter (CVC), inhibiting the formation of biofilms in their early stages, in addition to their anticoagulant effect and biocompatibility, those properties could keep the functionality of CVC helping to prevent complications such as sepsis and thrombosis.

Efecto del blanqueamiento y el remineralizante sobre la microdureza y micromorfología del esmalte dental / Effect of whitening and remineralizing agent on the microhardness and micromorphology of dental enamel

Diversos estudios han demostrado mayor o menor grado de afectacióndel esmalte después del uso de los distintos tratamientos para blanqueamiento dental. Por este motivo, se han propuesto varios métodos ytratamientos remineralizantes que pudieran revertir los efectos negativosde dicho tratamiento. El objetivo del presente trabajo fue evaluar el efecto del Opalescence PF 15 por ciento (peróxido de carbamida al 15%) y delremineralizante Flor-Opal (NaF al 1.1 por ciento), ambos de la casa comercialUltradent, así como de la saliva artifi cial sobre la microdureza y la micromorfología del esmalte humano. Se utilizaron 10 incisivos centrales superiores recién extraídos provenientes de centros de salud del Puerto de Veracruz, México. Réplicas de estos dientes fueron obtenidas en lasdiferentes fases del tratamiento de blanqueamiento para ser posteriormente observadas en el microscopio electrónico de barrido (MEB). Asimismo, se realizaron mediciones de microdureza en la superficie del esmalte de los dientes seleccionados durante las diferentes fases del tratamiento de blanqueamiento. Se observó que la microdureza del esmalte se ve disminuida (aunque no significativamente) después de la aplicación del peróxido de carbamida al 15 por ciento, y vuelve a subir después de la aplicación de los remineralizantes, para posteriormente volver a descender siete días después del uso de los mismos. Los datos de microdureza coincidieron con los de micromorfología obtenidos enel MEB. Se concluye que el peróxido de carbamida al 15 opr ciento sí afecta lamicromorfología de la superficie del esmalte, además de que disminuyela microdureza del mismo. Con el uso del remineralizante Flor-Opal se onsiguieron mayores valores de microdureza y mejores características micromorfológicas comparado con la saliva artificial.

Studies have shown varying degrees of involvement of the enamel following the use of tooth-whitening treatments. Consequently, a range of methods and remineralizing treatments have been proposed to reverse their negative effects. The aim of this study was, therefore, to evaluate the effect of Opalescence PF 15% (carbamide peroxide 15%) and the remineralizing treatment Flor-Opal (1.1% NaF), both produced by Ultradent, as well as artifi cial saliva on the microhard-ness and micromorphology of human enamel. Ten recently-extracted central incisors from health centers in the port of Veracruz, Mexico, were used. Replicas of these teeth were made at the various stages of the whitening treatment in order to observe these under a scanning electron microscope (SEM). Microhardness measurements were also taken on the surface of the enamel of the teeth selected at each of the various stages of the whitening treatment. The microhardness of the enamel was found to decrease (though not signifi cantly) after the ap-plication of carbamide peroxide 15%, then increase again following the application of the remineralizing agents, only to decrease again seven days after these were applied. The microhardness data coincided with that for micromorphology obtained from the SEM. We conclude that carbamide peroxide 15% does affect the micromorphology of the enamel surface and also decreases its microhardness. Flor-Opal produced higher microhardness values and better micromorphological characteristics compared to artifi cial saliva.

Biologic monitoring and causes of failure in cycles of sterilization in dental care offices in Mexico.

BACKGROUND: Biologic indicator tests (BIs) are considered the most meaningful way to verify sterilization. OBJECTIVE: To monitor the cycles of sterilization using BIs in dry heat sterilizers and steam autoclaves and to identify the causes of failures in the cycles of sterilization in dental offices in San Luis Potosí, México. METHODS: An invitation to participate was sent to 400 dental offices, and 206 practitioners of 200 dental offices were included. A questionnaire was given to each of the participants, asking for the following information: sterilizer type, operational parameters used (eg, temperature, pressure, and length of exposure), frequency of sterilization cycles per day, use of BIs, and maintenance procedures of the sterilizer. Two hundred thirty sterilizers were monitored using BIs. The sterilizers with positive results were monitored a second and third time to identify the cause of the failure. RESULTS: Twenty-two percent of practitioners (n = 46) used BIs, and 17% (n = 39) of the sterilizers reported positive results (bacterial growth). The detected failures were a mistake in the procedure (eg, temperature, time, or pressure), an absence of supervision of the procedure performed by the assistant, and improper maintenance. CONCLUSIONS: There are opportunities to increase information on infection control, to improve the adoption of standard quality control methods for sterilization as a routine process, to improve training on proper testing, and standardize processes.

Predictive values of thermal and electrical dental pulp tests: a clinical study.

INTRODUCTION: For a diagnostic test to be useful, it is necessary to determine the probability that the test will provide the correct diagnosis. Therefore, it is necessary to calculate the predictive value of diagnostics. The aim of the present study was to identify the sensitivity, specificity, positive and negative predictive values, accuracy, and reproducibility of thermal and electrical tests of pulp sensitivity. METHODS: The thermal tests studied were the 1, 1, 1, 2-tetrafluoroethane (cold) and hot gutta-percha (hot) tests. For the electrical test, the Analytic Technology Pulp Tester (Analytic Technology, Redmond, WA) was used. A total of 110 teeth were tested: 60 teeth with vital pulp and 50 teeth with necrotic pulps (disease prevalence of 45%). The ideal standard was established by direct pulp inspection. RESULTS: The sensitivities of the diagnostic tests were 0.88 for the cold test, 0.86 for the heat test, and 0.76 for the electrical test, and the specificity was 1.0 for all 3 tests. The negative predictive value was 0.90 for the cold test, 0.89 for the heat test, and 0.83 for the electrical test, and the positive predictive value was 1.0 for all 3 tests. The highest accuracy (0.94) and reproducibility (0.88) were observed for the cold test. CONCLUSIONS: The cold test was the most accurate method for diagnostic testing.

Peripheral arterial disease associated with caries and periodontal disease.

BACKGROUND: Peripheral arterial disease (PAD) is an important cardiovascular disorder of the peripheral arteries. Chronic infections, such as periodontitis, may play an important role in the etiology and pathophysiology of PAD and other cardiovascular conditions. Recently, Streptococcus mutans has been found with high frequency in atheromatous plaques. The aim of this study is to evaluate the possible clinical and microbiologic association between PAD and periodontitis and dental caries. METHODS: Thirty patients with PAD and 30 control individuals were selected. PAD and its severity were established by the use of the ankle-brachial index (ABI). Clinical attachment loss (AL); probing depth; decayed, missing, and filled teeth (DMFT) index; and C-reactive protein (CRP) levels were evaluated. The presence of bacterial DNA from Streptococcus mutans, Porphyromonas gingivalis, Tannerella forsythia, Prevotella intermedia, Treponema denticola, and Aggregatibacter actinomycetemcomitans was identified by polymerase chain reaction in subgingival biofilm and serum. RESULTS: Patients with ≥30% AL ≥ 4 mm had six-fold increased risk of having PAD (odds ratio = 8.18; 95% confidence interval = 1.21 to 35.23; P = 0.031). There was statistical difference in the CRP (P = 0.0413) and DMFT index (P = 0.0002), with elevated number of missing teeth (P = 0.0459) in the PAD group compared with the control group. There were no significant differences in the frequency of bacteria in serum and subgingival plaque. CONCLUSION: There was a positive relationship between periodontitis based on AL and PAD determined by the ABI (odds ratio = 8.18).

Shear bond strength evaluation of bonded molar tubes on fluorotic molars.

OBJECTIVE: To study the shear bond strength (SBS), sites of failure, and micromorphology of bonded molar tubes used on teeth affected by dental fluorosis. MATERIALS AND METHODS: This in vitro study included 140 first molars classified according to Dean's index for dental fluorosis. Samples were divided into seven groups: (1) healthy teeth etched for 15 seconds, (2) teeth with moderate fluorosis (MOF) etched for 15 seconds, (3) teeth with MOF etched for 150 seconds, (4) teeth with MOF microabrasion etched for 15 seconds, (5) teeth with severe fluorosis (SEF) etched for 15 seconds, (6) teeth with SEF etched for 150 seconds, and (7) teeth with SEF microabrasion etched for 15 seconds. All samples were incubated and were then submitted to the SBS test and evaluated with the modified adhesive remnant index (ARI) and analyzed by using a scanning electronic microscope. RESULTS: The SBS mean value for healthy enamel was 20 ± 10.2 MPa. For the group with MOF, the etched 150-second mean value was the highest (19 ± 7.6 MPa); for the group with SEF treated with microabrasion and etched for 15 seconds, the mean value was (13 ± 4.1 MPa). Significant differences (P ≤ .05) were found in the ARI between healthy and fluorosed groups. CONCLUSIONS: Fluorotic enamel affects the adhesion of bonded molar tubes. The use of overetching in cases of MOF and the combination of microabrasion and etching in SEF provides a suitable adhesion for fixed appliance therapy.

Analysis of the molecular structure of human enamel with fluorosis using micro-Raman spectroscopy.

The aim of this study was to analyze the molecular structure of enamel with fluorosis using micro-Raman spectroscopy and compare it with that of healthy enamel. Eighty extracted human molars were classified into four fluorosis groups according to the Thylstrup-Fejerskov Index (TFI) [TFI: 0, Healthy enamel; 1-3, mild; 4-5, moderate; 6-9, severe fluorosis]. All samples were analyzed by micro-Raman spectroscopy. The integral areas of ν(1) (960 cm(-1)) phosphate peak as well as B-type carbonate peak (1070 cm(-1)) were obtained to analyze structural differences among the specimens. Although the differences were not statistically significant (P > 0.05), the mean of integral areas of ν(1) phosphate peak among groups indicated greater mineralization in the severe fluorosis group. However, there were statistically significant differences in the intensities, and the integral areas of B-type carbonate peak among groups (P < 0.05). Therefore, mineralization of the carbonate peak at 1070 cm(-1) decreased significantly in fluorotic groups, suggesting that carbonate ions are easily dissolved in the presence of fluoride. Although structurally fluorotic teeth are not more susceptible to dental caries, serious alteration in its surface topography may cause retention of bacterial plaque and formation of enamel caries. Micro-Raman spectroscopy is a useful tool for analyzing the molecular structure of healthy and fluorotic human enamel.

Nanostructure evaluation of healthy and fluorotic dentin by atomic force microscopy before and after phosphoric acid etching.

The aim was to characterize by atomic force microscopy (AFM) the nanostructure of human dentin surfaces affected by dental fluorosis (DF) before and after phosphoric acid etching. This study included 240 human dentin samples classified according to the severity of DF, which were divided into four groups using the Thylstrup-Fejerskov Index (TFI). Samples were analyzed by AFM before and after acid etching for 15, 30, and 60 s. The roughness (R(a)) for healthy dentin, and dentin with mild, moderate, and severe fluorosis were 440 nm, 442 nm, 445 nm, and 449 nm, respectively. After 15, 30, and 60 s of acid etching, all healthy and fluorotic dentin samples increased in roughness (p<0.05). The diameter of dentinal tubule orifices (D(t)) in healthy human dentin increased after acid etching for 60 s. We conclude that effective etching times are 15 s for healthy and mild dentin fluorosis, 30-s for moderately fluorosed dentin, and 45-60 s for severe fluorotic dentin.

Characterization of healthy and fluorotic enamel by atomic force microscopy.

The aim was to characterize the external structure, roughness, and absolute depth profile (ADP) of fluorotic enamel compared with healthy enamel. Eighty extracted human molars were classified into four groups [TFI: 0, control (C); 1-3, mild (MI); 4-5, moderate (MO); 6-9, severe fluorosis (S)] according to the Thylstrup-Fejerskov Index (TFI). All samples were analyzed by atomic force microscopy.The mean values of enamel surface roughness (ESR) in nm were: Group C, 92.6; Group MI, 188.8; Group MO, 246.9; and Group S, 532.2. The mean values of absolute depth profile in nm were: C, 1,065.7; MI, 2,360.7; MO, 2,536.7; and S, 6,146.2. The differences between mean ESR and mean ADP among groups were statistically significant (p < 0.05). This structural study confirms at the nanometer level that there is a positive association between fluorosis severity, ESR, and ADP, and there is an association with the clinical findings of fluorosis measured by TFI as well.