Demineralization of tooth enamel following radiation therapy; An in vitro microstructure and microhardness analysis.

OBJECTIVE: The objective of this study is to evaluate the effects of radiotherapy doses on mineral density and percentage mineral volume of human permanent tooth enamel. MATERIALS AND METHODS: Synchrotron radiation Xray microcomputed tomography (SRµCT) and microhardness testing were carried out on 8 and 20 tooth samples, respectively. Enamel mineral density was derived from SRµCT technique using ImageJ software. Microhardness samples were subjected to Vickers indentations followed by calculation of microhardness and percentage mineral volume values using respective mathematical measures. Data were analyzed using paired t-test at a significance level of 5%. Qualitative analysis of the enamel microstructure was done with two-dimensional projection images and scanned electron micrographs using µCT and field emission scanning electron microscopy, respectively. RESULTS: Vickers microhardness and SRµCT techniques showed a decrease in microhardness and an increase in mineral density, respectively, in postirradiated samples. These changes were related to mineral density variation and alteration of hydroxyapatite crystal lattice in enamel surface. Enamel microstructure showed key features such as microporosities and loss of smooth homogeneous surface. These indicate tribological loss and delamination of enamel which might lead to radiation caries. CONCLUSIONS: Tooth surface loss might be a major contributing factor for radiation caries in head-and-neck cancer patients prescribed to radiotherapy. Such direct effects of radiotherapy cause enamel abrasion, delamination, and damage to the dentinoenamel junction. Suitable measures should, therefore, be worked out to protect nontarget oral tissues such as teeth while delivering effective dosages to target regions.

In vivo assessment of the corrosion of nickel-titanium orthodontic archwires by using scanning electron microscopy and atomic force microscopy.

This study was undertaken to assess in vivo the corrosion in two commercial nickel-titanium (NiTi) orthodontic archwires removed from the oral cavity of patients using fluoride mouthwashes. Five volunteers took part in this study on the corrosion behavior of two brands of NiTi archwires (3M and AO (brand of archwire)) during use of two mouthwashes with neutral sodium fluoride 1.1%, one with acidulated fluoride 1.1%, and one with placebo and a control group. Each patient used one mouthwash in three different periods of time for 1 min a day for 30 days. The archwires were assessed with scanning electron microscopy and atomic force microscopy for qualitative and quantitative analysis. The values obtained with atomic force microscopy (AFM) were submitted to normality test, two-way analysis of variance, and Tukey's test at a significance level of 5%. The AFM images showed a gradual qualitative increase in the roughness of both types of wire between the treatments: control < placebo < neutral fluoride < acidulated fluoride. The arithmetic average of the roughness and root mean square of the roughness were similar. As for 3M archwires, only the acidulated fluoride group differed statistically from the others. As for AO archwires, the control and placebo groups did not differ from each other, but differed from the other fluoride treatments. The group using neutral fluoride also differed significantly from the acidulated fluoride group. 3M archwires were not affected by daily oral challenges. AO archwires were not affected by daily oral challenges either; their association with fluoride, either neutral or acidulated, increased their roughness.

New missense variants in RELT causing hypomineralised amelogenesis imperfecta.

Amelogenesis imperfecta (AI) is a heterogeneous group of genetic diseases characterised by dental enamel malformation. Pathogenic variants in at least 33 genes cause syndromic or non-syndromic AI. Recently variants in RELT, encoding an orphan receptor in the tumour necrosis factor (TNF) superfamily, were found to cause recessive AI, as part of a syndrome encompassing small stature and severe childhood infections. Here we describe four additional families with autosomal recessive hypomineralised AI due to previously unreported homozygous mutations in RELT. Three families carried a homozygous missense variant in the fourth exon (c.164C>T, p.(T55I)) and a fourth family carried a homozygous missense variant in the 11th exon (c.1264C>T, p.(R422W)). We found no evidence of additional syndromic symptoms in affected individuals. Analyses of tooth microstructure with computerised tomography and scanning electron microscopy suggest a role for RELT in ameloblasts' coordination and interaction with the enamel matrix. Microsatellite genotyping in families segregating the T55I variant reveals a shared founder haplotype. These findings extend the RELT pathogenic variant spectrum, reveal a founder mutation in the UK Pakistani population and provide detailed analysis of human teeth affected by this hypomineralised phenotype, but do not support a possible syndromic presentation in all those with RELT-variant associated AI.

Effect of fermented milk with kefir grains on the in vitro demineralization of bovine tooth enamel / Efecto de la leche fermentada con granos de kéfir sobre la desmineralización in vitro del esmalte dental bovino

The dental caries is a progressive destruction of the teeth tissue due to the disbalance in the normal molecule interactions between the enamel and the bio!lm, which alters the demineralization-remineralization process. Milk fermentation produces caseinphosphopeptides with proved remineralizing capacity of the enamel. The presence of these peptides in fermented milk with ke!r grains has been described. The purpose of this work was to evaluate in vitro the capacity of milk ke!r to prevent the demineralization of dental enamel. Bovine incisors (n=68, 17 per group) were treated for 72 h with different solutions: I: artificial saliva at pH 7.2 , II: demineralizing solution at pH 4.5, III: supernatant of kefir fermented milk at pH 4.5, IV: milk supernatant at pH 4.5. The effects of treatments were evaluated by the change in the weight of the specimens, calcium concentration in the solution and by scanning electron microscopy (SEM) of the enamel. Kefir milk supernatant prevented the demineralization process, that was evidenced by a change in weight and calcium concentration that were not different from group I, although the pH was 4.5. In contrast, group IV showed a decrease in weight and an increase in calcium concentration, compared with group I (one way ANOVA, p<0.05). Images of SEM agree with the values of weight and calcium concentration. These results indicate that kefir milk supernatant has a protective effect on enamel demineralization in vitro. (AU)

La caries dental es una patología debido a un desequilibrio en las interacciones moleculares normales entre el esmalte y la biopelícula, que altera el proceso de desmineralización remineralización. La fermentación de la leche produce fosfopéptidos de caseína con probada capacidad remineralizante del esmalte, y se ha descripto la presencia de estos péptidos en la leche fermentada con granos de kéfir. El propósito de este trabajo fue evaluar in vitro la capacidad del kéfir de leche para prevenir la desmineralización del esmalte dental. Sesenta y ocho incisivos bovinos (17 por grupo) fueron tratados durante 72 h con diferentes soluciones: I: saliva artificial, pH 7.2, II: solución desmineralizante, pH 4.5, III: sobrenadante de leche fermentada con kefir, pH 4.5, IV: sobrenadante de leche, pH 4.5. El proceso de desmineralización se evaluó mediante el cambio en el peso de las muestras, la concentración de calcio en la solución y microscopía electrónica de barrido (SEM) del esmalte. El sobrenadante de leche fermentada con kéfir impidió el proceso de desmineralización, que se evidenció por un cambio en el peso y la concentración de calcio que no discreparon del grupo I, a pesar de haber tenido un pH de 4.5. En contraste, el grupo IV mostró una disminución en el peso y un aumento en la concentración de calcio, en comparación con el grupo I (ANOVA a un criterio, p<0.05). Las imágenes SEM concuerdan con los cambios en el peso y la concentración de calcio en los grupos estudiados. Los datos obtenidos demuestran que el sobrenadante de la leche tratada con kéfir tiene un efecto protector sobre la desmineralización del esmalte in vitro, inducida por el pH ácido. (AU)

Abordaje Terapéutico de la Hipomineralización Molar - Incisal. Revisión Narrativa / Peripheral Odontogenic Fibroma: Case Report

RESUMEN: Hipomineralización Molar-Incisal (MIH) es un trastorno del desarrollo dentario asociado a factores sistémicos, producido por una incompleta mineralización y maduración del esmalte. La prevalencia en niños, a nivel mundial, varía en la literatura entre el 2,4 % y el 40,2 %. Este trastorno que implica al menos un primer molar permanente, pudiendo también verse afectados los incisivos, dependiendo del momento, la duración, la susceptibilidad del individuo y la gravedad de la injuria prenatal, perinatal o postnatal. El esmalte presenta un grado variable de alteración en la translucidez, siendo éste de un espesor normal y de color blanco, o café-amarillo. Si bien se encuentra intacto en el momento de la erupción, puede sufrir fracturas post eruptivas debido a las fuerzas de la masticación, dejando límites definidos. Por lo general, los molares gravemente afectados son extremadamente hipersensibles, propensos a lesiones de caries de rápida progresión, y pueden ser difíciles de tratar en pacientes jóvenes. La atención debe abordar el comportamiento y la ansiedad del niño, con el objetivo de proporcionar restauraciones duraderas en condiciones libres de dolor. La ejecución de medidas preventivas individuales puede posponer el inicio del tratamiento restaurador y reducir la incomodidad del paciente a largo plazo. El diagnóstico precoz permitirá el seguimiento y la instauración de dichas medidas preventivas tan pronto las superficies afectadas sean accesibles. Pese a que los enfoques de tratamiento para MIH han comenzado a ser más claros y los avances en los materiales dentales han proporcionado soluciones clínicas en los casos que se consideraban sin posibilidad de restauración en el pasado, deben llevarse a cabo ensayos clínicos a largo plazo para facilitar aún más el manejo clínico de este cuadro.

ABSTRACT: Molar Incisor Hypomineralization (MIH) is a tooth development disorder, which is associated with systemic factors, produced by incomplete enamel mineralization and maturation below the enamel surface that is intact at the time of eruption. In literature, the prevalence in children worldwide varies between 2.4 % and 40.2 %. This disorder which involves at least one first permanent molar, and depending on duration, the child's susceptibility as well as the severity of prenatal, perinatal or postnatal insult may also compromise incisors. The defect reveals a variable degree of alteration in the translucency of the enamel, that has initially normal thickness and can be white, yellow or brown. Enamel surface may breakdown after eruption, due to masticatory forces, leaving sharp borders. Usually, severely affected molars are extremely hypersensitive, prone to rapid caries development, and can be difficult to manage in young patients. The complex care involved must address the child's behavior and anxiety, aiming to provide pain free treatment and durable restorations. Intensive individually prescribed preventive programs may postpone the onset of restorative treatment and reduce patient discomfort in the long term. Early identification of such children will allow monitoring and implementation of preventive measures as soon as affected surfaces are accessible. Although treatment approaches for MIH have become more clear, and advances in dental materials have provided clinical solutions in cases that in the past were regarded as unrestorable, long-term clinical trials should be realized to further facilitate clinical management of this dental defect.

Influence of multi-wavelength laser irradiation of enamel and dentin surfaces at 0.355, 2.94, and 9.4 µm on surface morphology, permeability, and acid resistance.

OBJECTIVE: Ultraviolet (UV) and infrared (IR) lasers can be used to specifically target protein, water, and mineral, respectively, in dental hard tissues to produce varying changes in surface morphology, permeability, reflectivity, and acid resistance. The purpose of this study was to explore the influence of laser irradiation and topical fluoride application on the surface morphology, permeability, reflectivity, and acid resistance of enamel and dentin to shed light on the mechanism of interaction and develop more effective treatments. METHODS: Twelve bovine enamel surfaces and twelve bovine dentin surfaces were irradiated with various combinations of lasers operating at 0.355 (Freq.-tripled Nd:YAG (UV) laser), 2.94 (Er:YAG laser), and 9.4 µm (CO2 laser), and surfaces were exposed to an acidulated phosphate fluoride gel and an acid challenge. Changes in the surface morphology, acid resistance, and permeability were measured using digital microscopy, polarized light microscopy, near-IR reflectance, fluorescence, polarization sensitive-optical coherence tomography (PS-OCT), and surface dehydration rate measurements. RESULTS: Different laser treatments dramatically influenced the surface morphology and permeability of both enamel and dentin. CO2 laser irradiation melted tooth surfaces. Er:YAG and UV lasers, while not melting tooth surfaces, showed markedly different surface roughness. Er:YAG irradiation led to significantly rougher enamel and dentin surfaces and led to higher permeability. There were significant differences in acid resistance among the various treatment groups. CONCLUSION: Surface dehydration measurements showed significant changes in permeability after laser treatments, application of fluoride and after exposure to demineralization. CO2 laser irradiation was most effective in inhibiting demineralization on enamel while topical fluoride was most effective for dentin surfaces. Lasers Surg. Med. 49:913-927, 2017. © 2017 Wiley Periodicals, Inc.

Near-IR and CP-OCT imaging of suspected occlusal caries lesions.

INTRODUCTION: Radiographic methods have poor sensitivity for occlusal lesions and by the time the lesions are radiolucent they have typically progressed deep into the dentin. New more sensitive imaging methods are needed to detect occlusal lesions. In this study, cross-polarization optical coherence tomography (CP-OCT) and near-IR imaging were used to image questionable occlusal lesions (QOC's) that were not visible on radiographs but had been scheduled for restoration on 30 test subjects. METHODS: Near-IR reflectance and transillumination probes incorporating a high definition InGaAs camera and near-IR broadband light sources were used to acquire images of the lesions before restoration. The reflectance probe utilized cross-polarization and operated at wavelengths from 1,500 to 1,700 nm where there is an increase in water absorption for higher contrast. The transillumination probe was operated at 1,300 nm where the transparency of enamel is highest. Tomographic images (6 × 6 × 7 mm3 ) of the lesions were acquired using a high-speed swept-source CP-OCT system operating at 1,300 nm before and after removal of the suspected lesion. RESULTS: Near-IR reflectance imaging at 1,500-1,700 nm yielded significantly higher contrast (P < 0.05) of the demineralization in the occlusal grooves compared with visible reflectance imaging. Stains in the occlusal grooves greatly reduced the lesion contrast in the visible range yielding negative values. Only half of the 26 lesions analyzed showed the characteristic surface demineralization and increased reflectivity below the dentinal-enamel junction (DEJ) in 3D OCT images indicative of penetration of the lesion into the dentin. CONCLUSION: This study demonstrates that near-IR imaging methods have great potential for improving the early diagnosis of occlusal lesions. Lasers Surg. Med. 49:215-224, 2017. © 2017 Wiley Periodicals, Inc.

Ultrasonic assessment of the effects of self-assembling peptide scaffolds on preventing enamel demineralization.

OBJECTIVES: This study evaluates the effect of self-assembling peptide P11-4 (Curodont Repair, CDR) on bovine enamel remineralization by measuring changes in ultrasonic propagation velocity. METHODS: Six specimens per group were prepared by sectioning bovine teeth into enamel blocks. These blocks were then immersed in lactic acid buffer solution (pH = 4.75) for 10 min twice a day and stored in artificial saliva. Other specimens were first treated with CDR, followed by a 10-min immersion in the lactic acid buffer solution twice a day, before storage in artificial saliva. The propagation time of longitudinal ultrasonic waves was measured using a pulser/receiver. Six specimens were used for each treatment protocol. The obtained data were statistically analyzed using ANOVA followed by Tukey's honestly significant difference tests (α = 0.05). Specimens were observed using laser scanning microscopy and scanning electron microscopy. RESULTS: Sonic velocity was found to decrease with time for specimens stored in the demineralizing solution. On the other hand, increases in sonic velocity were found for specimens treated with CDR. These specimens also exhibited signs of mineral deposition. CONCLUSIONS: By measuring the ultrasonic propagation velocity, it can be concluded that CDR application has an ability to promote bovine enamel remineralization.

Exploratory Randomized Clinical Trial of an Experimental Gel-to-Foam Fluoride Dentifrice Formulation Using an In Situ Caries Model.

OBJECTIVE: To evaluate the in situ caries performance and safety of two experimental fluoride dentifrice formulations (1450 ppm fluoride) with and without 2% isopentane as an excipient, in comparison to a positive control, currently marketed dentifrice (1450 ppm fluoride) and a negative control dentifrice (0 ppm fluoride). METHODS: This was a single-center, examiner-blind, randomized, controlled, four-treatment cross-over study. During each treatment period, the subject wore a modified mandibular partial denture fitted with two gauze-covered, partially demineralized human enamel specimens, and brushed at home for one timed minute, twice daily, for two weeks. At the end of each treatment period, the enamel specimens were removed from the dentures for analysis. During the week between treatment periods, subjects returned to their usual dental hygiene practices for four to five days, received a dental prophylaxis, and used a study-designated non-fluoride dentifrice for two to three days before starting the next treatment. Treatment effect on enamel specimen remineralization was assessed by surface microhardness (SMH). Enamel fluoride uptake was assessed using microdrill enamel biopsy. RESULTS: All fluoride-containing dentifrices demonstrated significant, superior SMH recovery and levels of fluoride uptake compared to the negative control dentifrice. No significant differences were observed for either efficacy variable between the experimental dentifrice formulations and the positive control dentifrice. No significant difference was observed between the 2% isopentane dentifrice and the 0% isopentane dentifrice for SMH recovery. CONCLUSION: The addition of 2% isopentane did not positively or negatively affect fluoride efficacy in this model.

CO2 laser and topical fluoride therapy in the control of caries lesions on demineralized primary enamel.

This study evaluated the effect of CO2 laser irradiation and topical fluoride therapy in the control of caries progression on primary teeth enamel. 30 fragments (3 × 3 × 2 mm) from primary canines were submitted to an initial cariogenic challenge that consisted of immersion on demineralizing solution for 3 hours and remineralizing solution for 21 hours for 5 days. Fragments were randomly assigned into three groups (n = 10): L: CO2 laser (λ = 10.6 µm), APF: 1.23% acidulated phosphate fluoride, and C: no treatment (control). CO2 laser was applied with 0.5 W power and 0.44 J/cm(2) energy density. Fluoride application was performed with 0.1 g for 1 minute. Cariogenic challenge was conducted for 5 days following protocol previously described. Subsurface Knoop microhardness was measured at 30 µm from the edge. Obtained data were subjected to analysis the variance (ANOVA) and Duncan test with significance of 5%. It was found that the L group showed greater control of deciduous enamel demineralization and were similar to those of APF group, while being statistically different from C group (P ≤ 0.05) that showed the lowest microhardness values. It was concluded that CO2 laser can be an additional resource in caries control progression on primary teeth enamel.

A spectroscopic and surface microhardness study on enamel exposed to beverages supplemented with lower iron concentrations.

OBJECTIVES: This study aimed to compare the in vitro mineral loss and surface microhardness (SMH) changes in human enamel specimens following supplementation of acidic carbonated beverages with low iron concentrations than when treated without. STUDY DESIGN: 180 enamel blocks each from primary and permanent teeth were prepared and equally subdivided (n=10) for their respective treatments in Group 1 (Coca Cola and Sprite without iron supplementation) and Group 2 (beverages supplemented with 2/5 mmol/L FeSO4.7H2O). Following initial SMH estimation, the blocks were subjected to 3 treatment cycles of 5/20 minute incubation periods, equally interspaced by a 5-min treatment in artificial saliva. The calcium and phosphate released after each cycle were analyzed spectrophotometrically and the final SMH was recorded. The results were tested using student's T test, One-way ANOVA and Kruskal Walli's test (p<0.05). RESULTS: Two and five mmol/L FeSO4.7H2O supplementation produced a highly significant SMH change and calcium and phosphate reduction than when treated without (p<.0005). Both the enamel specimens showed similar patterns of mineral loss and SMH reduction, with pronounced effects in the twenty minute incubation cycles. CONCLUSION: Our results suggest that 2 mmol/L FeSO4.7H2O supplementation to acidic beverages is beneficial in reducing mineral loss and preserving surface microhardness of human enamel.

In vitro assessment of the acid resistance of demineralized enamel irradiated with Er, Cr:YSGG and Nd:YAG lasers.

PURPOSE: This study's purpose was to evaluate the acid resistance of demineralized enamel irradiated with high-intensity lasers. METHODS: Enamel fragments were demineralized and treated as follows (N=10): Group 1-no treatment; Group 2-five percent sodium fluoride (NaF) varnish; Group 3-Er, Cr:YSGG laser (8.92 J/cm2, 0.5 W, 20 Hz, 30 seconds); Group 4-NaF and Er, Cr:YSGG laser; Group 5-Er, Cr:YSGG laser and NaF; Group 6-Nd:YAG laser (84.9 J/cm2, 0.5 W, 10 Hz, 30 seconds); Group 7-NaF and Nd:YAG laser; and Group 8-Nd:YAG laser and NaF. The samples were subjected to pH-cycling and assessed by microhardness (analysis of variance; α equals five percent) at different depths from the outer enamel surface. Samples were observed using polarized light microscopy (PLM) and scanning electron microscopy (SEM). RESULTS: There were no significant differences among the experimental groups in any of the subsurface layers evaluated. PLM observation revealed that the extent of demineralization of the irradiated samples was similar to the samples for Group 1 (control). SEM observation showed that irradiated surfaces were ablated and presented areas of melting. CONCLUSIONS: Laser irradiation, with or without applying five percent sodium fluoride, was not capable of increasing the enamel white spot lesions' acid resistance.

A method for monitoring enamel erosion using laser irradiated surfaces and optical coherence tomography.

INTRODUCTION: Since optical coherence tomography (OCT) is well suited for measuring small dimensional changes on tooth surfaces, OCT has great potential for monitoring tooth erosion. Previous studies have shown that enamel areas ablated by a carbon dioxide laser manifested lower rates of erosion compared to the non-ablated areas. The purpose of this study was to develop a model to monitor erosion in vitro that could potentially be used in vivo. METHODS: Thirteen bovine enamel blocks were used in this in vitro study. Each 10 mm × 2 mm block was partitioned into five regions, the central region was unprotected, the adjacent windows were irradiated by a CO2 laser operating at 9.3 µm with a fluence of 2.4 J/cm(2) , and the outermost windows were coated with acid resistant varnish. The samples were exposed to a pH cycling regimen that caused both erosion and subsurface demineralization for 2, 4 and 6 days. The surfaces were scanned using a time-domain polarization sensitive optical coherence tomography (PS-OCT) system and the degree of surface loss (erosion) and the integrated reflectivity with lesion depth was calculated for each window. RESULTS: There was a large and significant reduction in the depth of surface loss (erosion) and the severity of demineralization in the areas irradiated by the laser. CONCLUSION: Irradiation of the enamel surface with a pulsed carbon dioxide laser at sub-ablative intensities results in significant inhibition of erosion and demineralization under the acid challenge employed in this study. In addition, these results suggest that it may be feasible to modify regions of the enamel surface using the laser to serve as reference marks to monitor the rate of erosion in vivo.

Efficacy of the self-assembling peptide P11-4 in constructing a remineralization scaffold on artificially-induced enamel lesions on smooth surfaces.

OBJECTIVES: The management of white-spot lesions remains a challenge, especially during and after fixed orthodontic treatment. The aim of this in vitro study was to evaluate the efficacy of the newly introduced self-assembling peptide P11-4 (Curodont™) for regenerating demineralized tooth tissue on smooth surfaces. Another aim was to evaluate whether the DIAGNOdent (DD) and VistaProof (VP) fluorescence systems are suitable for differentiating between demineralized and remineralized enamel. MATERIALS AND METHODS: A total of 40 sound samples (buccal surfaces) of extracted human posterior teeth were artificially demineralized. The samples were examined visually as well as via DD and VP. Curodont was applied to 30 samples which were then stored in a remineralizing agent (test group). In control group 1, Curodont was applied to 5 samples which were then stored in water. Control group 2 consisted of 5 samples stored in the remineralizing agent only. Sample surfaces were examined visually and by means of DD and VP after 1 week (t1), 8 weeks (t2), and 12 weeks (t3). All fluorescence measurements were taken twice. Sample surfaces were viewed using a scanning electron microscope (SEM). Statistical analysis was conducted using the IBM SPSS® Statistics and MedCalc® programs. The fluorescence measurements' reproducibility was calculated using the intraclass correlation coefficient (ICC). A χ(2) test was applied to detect any significant differences between the fluorescence measurements of the test and control groups at each examination. Receiver operating characteristic (ROC) curves of DD and VP were constructed and areas under the ROC curve (AUC) were compared (α = 0.05) between the two fluorescence devices. RESULTS: Reproducibility of DD was moderate at t3, while the ICC values were high for all other measurements. Significant differences between the fluorescence measurements at t2 and t3 between the test and control groups (p < 0.001 for DD and VP, respectively) were observed. The performance (AUC) of DD was significantly higher than VP (visual inspection: p = 0.017; SEM: p = 0.030). At t3, all test-group samples displayed a shinier surface than the surface after demineralization. The SEM images of 28 test-group samples exhibited extensive signs of remineralized enamel. CONCLUSION: Based on visual inspection, Curodont proved to be efficacious in all samples. The SEM images revealed large areas of remineralized enamel surface in 93 % of the samples. Both fluorescence systems enabled the detection of differences between the measurements of the test and control groups after 8 and 12 weeks.

Effect of resin composites with sodium trimetaphosphate with or without fluoride on hardness, ion release and enamel demineralization.

PURPOSE: To evaluate the effect of the addition of sodium trimetaphosphate (TMP) with or without fluoride on enamel demineralization, and the hardness and release of fluoride and TMP of resin composites. METHODS: Bovine enamel slabs (4 x 3 x 3 mm) were prepared and selected based on initial surface hardness (n = 96). Eight experimental resin composites were formulated, according to the combination of TMP and sodium fluoride (NaF): TMP/NaF-free (control), 1.6% sodium fluoride (NaF), and 1.5%, 14.1% and 36.8% TMP with and without 1.6% NaF. Resin composite specimens (n = 24) were attached to the enamel slabs with wax and the sets were subjected to pH cycling. Next, surface and cross-sectional hardness and fluoride content of enamel as well as fluoride and TMP release and hardness of the materials were evaluated. Data were statistically analyzed using ANOVA (P < 0.05). RESULTS: The presence of fluoride in enamel was similar in fluoridated resin composites (P > 0.05), but higher than in the other materials (P < 0.05). The combination of 14.1% TMP and fluoride resulted in less demineralization, especially on lesion surface (P < 0.05). The presence of TMP increased fluoride release from the materials and reduced their hardness.

The adipocyte component of bone marrow in heterotopic bone induced by demineralized incisor grafts.

The relative proportion of adipocytes to hematopoietic elements in the marrow of heterotopically induced bone evaluated 4-42 weeks post implantation of demineralized murine incisors was estimated by histological analysis of hematoxylin-eosin stained tissue sections. Using computerized image analysis of microphotographs,the proportion of nuclear cells vs. adipocytes was ascertained. The percentage of adipocytes in marrow increases over time. Such an effect, the replacement of myelopoietic marrow by adipogenic (yellow) marrow and the resorption of induced bone, is observed in human osteoporosis. A decline in the non-adipogenic cell compartments of bone marrow accompanying induced bone begins in the fourth week of induction, gradually progresses until the 26th week, and does not change after that. The luminosity, a parameter used in image analysis and proportional to the number of nuclear cells, was 124 ± 3 in hematopoietic femoral bone marrow, and that of bone marrow of the induced bone was of a similar value (117 ± 8) in the fourth week. An evident decline in luminosity of bone marrow filling the foci of heterotopic bone was observed in samples taken at nine weeks (82 ± 20). This process progressed until the 26th week, reaching a luminosity of 70 ± 21. At the 42nd week, the luminosity remained at the same level (71 ± 27). This indicates that the replacement of hematopoietic bone marrow of heterotopically induced bone by unilocular adipocytes begins relatively early (the fourth week) and is persistent.

Frecuencia y severidad de la hipomineralización molar incisal en pacientes atendidos en las clínicas odontológicas de la Universidad de La Frontera, Chile / Frequency and Severity of the Molar Incisor Hypomineralization in Patients Treated at the Dental Clinic of the Universidad de La Frontera, Chile

La Hipomineralización Molar Incisal (MIH) es una alteración del desarrollo dentario, que estaría asociada a causas de origen sistémico, e involucra al menos uno o más primeros molares permanentes, pudiendo estar comprometidos los incisivos. La prevalencia de este síndrome varía en la literatura entre 2,5 a 40 por ciento en la población infantil mundial. El objetivo de este estudio fue determinar la frecuencia y grado de severidad de MIH entre los pacientes atendidos en la Clínica de Odontopediatría de pregrado y postgrado de la Universidad de La Frontera y los posibles factores asociados. Se realizó un estudio descriptivo en 334 niños entre 6 y 13 años de edad. El examen fue realizado por 2 examinadores en las clínicas de la Universidad de la Frontera. Se estableció el diagnóstico, de acuerdo a los criterios establecidos por Weerheijm et al. (2003) y la severidad según a los criterios propuestos por Mathu-Muju & Wright (2006). La prevalencia encontrada correspondió a 16,8 por ciento. De estos, el 57 por ciento mostró signos severos de MIH, el 20 por ciento signos moderados y 23 por ciento signos leves. No hubo diferencias significativas por sexo y edad respecto a la presencia de MIH o su severidad. El 87 por ciento de los afectados reportó antecedentes mórbidos en el período comprendido desde el preparto hasta la primera infancia. Esta patología presenta alta prevalencia en los pacientes muestreados, comparable a la establecida en estudios realizados a nivel mundial.

Molar incisor hypomineralization (MIH) is a tooth development disorder, which would be associated with systemic causes, and involves at least one or more first permanent molars, incisors may be compromised. The prevalence of this syndrome varies in literature between 2.5 to 40 percent of the world's children. The aim of this study was to determine the frequency and severity of MIH between patients attended at the Graduate Pediatric Dentistry Clinic of the Universidad de La Frontera and the possible associated factors. We conducted a descriptive study of 334 children between 6 and 13 years of age. The review was conducted by 2 examiners at the Universidad de La Frontera. The diagnosis, according to the criteria established by Weerheijm et al (2003) and severity according to the criteria proposed by Mathu-Muju & Wright (2006). The prevalence found corresponded to 16.8 percent. Of these, 57 percent showed severe signs of MIH, 20 percent and 23 percent moderate and mild signs respectively. No significant differences by sex and age for the presence of MIH or its severity. 87 percent of those affected reported morbid history in the period from pre-early childhood. This disorder has high prevalence in patients sampled, comparable to that established in studies worldwide.

Quantitative remineralization evolution kinetics of artificially demineralized human enamel using photothermal radiometry and modulated luminescence.

Human molars were subjected to demineralization in acid gel followed by incubation in remineralization solutions without or with fluoride (1 or 1000 ppm). Photothermal radiometry (PTR) and modulated luminescence (LUM) frequency scans were performed prior to and during de/remineralization treatments. Transverse Micro-Radiography (TMR) analysis followed at treatment conclusion to determine mineral loss and lesion depth. The remineralization process illustrated a complex interplay between surface and subsurface mineral deposition, confining the thermal-wave centroid toward the dominating layer. Experimental amplitudes and phases were fitted to a coupled diffuse-photon-density-wave and thermal-wave theoretical model used to quantitatively evaluate evolving changes in thermal and optical properties of de/remineralized enamel lesions. Additional information obtained from the LUM data corroborated the remineralization kinetics affecting the PTR signals. The results pointed to enhanced effectiveness of subsurface lesion remineralization in the presence of fluoride.

The use of sodium trimetaphosphate as a biomimetic analog of matrix phosphoproteins for remineralization of artificial caries-like dentin.

OBJECTIVES: This study examined the use of sodium trimetaphosphate (STMP) as a biomimetic analog of matrix phosphoproteins for remineralization of artificial carious-affected dentin. METHODS: Artificial carious lesions with lesion depths of 300±30µm were created by pH-cycling. 2.5% hydrolyzed STMP was applied to the artificial carious lesions to phosphorylate the partially-demineralized collagen matrix. Half of the STMP-treated specimens were bonded with One-Step. The adhesive and non-adhesive infiltrated specimens were remineralized in a Portland cement-simulated body fluid system containing polyacrylic acid (PAA) to stabilize amorphous calcium phosphate as nanoprecursors. Micro-computed tomography (micro-CT) and transmission electron microscopy (TEM) were used to evaluate the results of remineralization after a 4-month period. RESULTS: In absence of PAA and STMP as biomimetic analogs (control groups), there was no remineralization irrespective of whether the lesions were infiltrated with adhesive. For the STMP-treated experimental groups immersed in PAA-containing simulated body fluid, specimens without adhesive infiltration were more heavily remineralized than those infiltrated with adhesive. Statistical analysis of the 4-month micro-CT data revealed significant differences in the lesion depth, relative mineral content along the lesion surface and changes in ΔZ between the non-adhesive and adhesive experimental groups (p<0.05 for all the three parameters). TEM examination indicated that collagen degradation occurred in both the non-adhesive and adhesive control and experimental groups after 4 months of remineralization. SIGNIFICANCE: Biomimetic remineralization using STMP is a promising method to remineralize artificial carious lesions particularly in areas devoid of seed crystallites. Future studies should consider the incorporation of MMP-inhibitors within the partially-demineralized collagen matrix to prevent collagen degradation during remineralization.

Preventive effect of iron gel with or without fluoride on bovine enamel erosion in vitro.

BACKGROUND: The aim of this study was to evaluate the preventive effect in vitro of experimental gel containing iron and/or fluoride on the erosion of bovine enamel. METHODS: To standardize the blocks (n = 80), specimens (4 x 4 mm) were previously selected to measure the initial microhardness. The blocks were randomly allocated into four groups of 20 samples each: C (control, placebo gel); F (fluoride gel, 1.23% NaF); Fe (iron gel, 10 mmol/L FeSO(4)) and F + Fe (fluoride + iron gel). The gels were applied and removed after 1 minute. The blocks were then submitted to six alternating remineralization and demineralization cycles. The beverage Coca-Cola (10 minutes, 30 mL) was used for demineralization, and artificial saliva (1 hour) for remineralization. The effect of erosion was measured by wear analysis (profilometry). Data were analysed by ANOVA and the Tukey test for individual comparisons (p <0.05). RESULTS: The mean wear (+/- SD, microm) was C: 0.94 +/- 0.22; F: 0.55 +/- 0.12; Fe: 0.49 +/- 0.11 and F + Fe: 0.55 +/- 0.13. When the experimental gels were used, there was statistically significant reduction in enamel wear in comparison with the control (p <0.001). However, the experimental gels did not differ significantly among them. CONCLUSIONS: The gels containing iron with or without fluoride are capable of interfering with the dissolution dental enamel in the presence of erosive challenge.