Evaluating color change and hydrogen peroxide penetration in human and bovine teeth through in-office bleaching procedures.

OBJECTIVE: Assess color alteration and hydrogen peroxide (HP) penetration in human and bovine teeth using various in-office bleaching protocols with different application times. MATERIALS AND METHODS: Thirty healthy human premolars and 30 healthy bovine incisors were divided into five groups and subjected to different bleaching protocols: 2 × 15 min, 1 × 30 min, 2 × 20 min, or 1 × 40 min, with a control group for each tooth type. All teeth were treated with 35% HP gel. Color alteration was measured using digital spectrophotometry before and 1 week after bleaching. HP concentration within the pulp was determined via UV-Vis spectrophotometry. Statistical analysis included one-way ANOVA, Tukey's, and Dunnett's tests (α = 0.05). RESULTS: All groups exhibited significant color alteration, with no statistically differences among them (p > 0.05). However, significant differences were observed when compared with their respective control groups (p < 0.05). HP penetration into the pulp was evident in all bleached teeth compared to the control groups (p < 0.05), with the 2 × 20 group showing the highest HP levels within the pulp cavity, irrespective of tooth type (p < 0.05). CONCLUSION: A simplified 1 × 30-min protocol can be recommended as it effectively maintains color alteration and HP penetration, irrespective of whether human or bovine teeth. CLINICAL SIGNIFICANCE: This study suggests that an in-office dental bleaching protocol using a 1 × 30-min session is recommended, as it ensures both effective color change and no increase in the amount of HP penetration.

Glutaraldehyde-based desensitizer does not influence postoperative sensitivity and clinical performance of posterior restorations: A 24-month randomized clinical trial.

OBJECTIVES: To evaluate the influence of a glutaraldehyde-based desensitizer (GL) on postoperative sensitivity (POS) in posterior bulk-fill resin composite restorations using an adhesive applied in the self-etch (SE) and etch-and-rinse (ER) strategies; and to assess the clinical performance of the restorations. METHODS: Posterior resin composite restorations (n = 228) at least 3 mm deep were inserted in 57 subjects using a split-mouth design. The adhesive was applied with/without prior application of a GL. A resin composite was used for all restorations. Spontaneous POS (risk and intensity), as well as POS caused by stimulation with an air blast and assess the response to horizontal and vertical percussion was assessed using two scales in the baseline and after 7, 14, and 30 days. In addition, some parameters were evaluated using FDI criteria up to 24 months of clinical service. RESULTS: No significant POS was observed (p > 0.05). A higher absolute risk and intensity of spontaneous POS was observed within 7 days (35.1%), without statistically significant differences among groups. At 24 months 5 restorations were considered clinically unsatisfactory, and 73 restorations showed minor discrepancies in adaptation, with no significant differences between groups (p > 0.05). SIGNIFICANCE: A GL agent does not influence POS in posterior restorations with bulk-fill resin composite. It may be considered a dispensable clinical step in the restorative protocol.

Intermittent Precipitation-Dependent Interactions, Encompassing Allee Effect, May Yield Vegetation Patterns in a Transitional Parameter Range.

We construct a spatial model that incorporates Allee-type and competition interactions for vegetation as an evolving random field of biomass density. The cumulative effect of close-range precipitation-dependent interactions is controlled by a parameter defining precipitation frequency. We identify a narrow parameter range in which the behavior of the system changes from survival of vegetation to extinction, via a transitional aggregation pattern. The aggregation pattern is tied to the initial configuration and appears to arise differently from Turing's diffusion and differential flow patterns of other models. There is close agreement of our critical transition parameter range with that of the corresponding evolving random mean-field model.

Epidemic highs and lows: a stochastic diffusion model for active cases.

We derive a stochastic epidemic model for the evolving density of infective individuals in a large population. Data shows main features of a typical epidemic consist of low periods interspersed with outbreaks of various intensities and duration. In our stochastic differential model, a novel reproductive term combines a factor expressing the recent notion of 'attenuated Allee effect' and a capacity factor is controlling the size of the process. Simulation of this model produces sample paths of the stochastic density of infectives, which behave much like long-time Covid-19 case data of recent years. Writing the process as a stochastic diffusion allows us to derive its stationary distribution, showing the relative time spent in low levels and in outbursts. Much of the behaviour of the density of infectives can be understood in terms of the interacting drift and diffusion coefficient processes, or, alternatively, in terms of the balance between noise level and the attenuation parameter of the Allee effect. Unexpected results involve the effect of increasing overall noise variance on the density of infectives, in particular on its level-crossing function.

Allee Effects Plus Noise Induce Population Dynamics Resembling Binary Markov Highs and Lows.

We show that the combination of Allee effects and noise can produce a stochastic process with alternating sudden decline to a low population phase, followed, after a random time, by abrupt increase in population density. We introduce a new, flexible, deterministic model of attenuated Allee effects, which interpolates between the logistic and a usual Allee model. Into this model, we incorporate environmental and demographic noise. The solution of the resulting Kolmogorov forward equation shows a dichotomous distribution of residence times with heavy occupation of high, near saturation, and low population states. Investigation of simulated sample paths reveals that indeed attenuated Allee effects and noise, acting together, produce alternating, sustained, low and high population levels. We find that the transition times between the two types of states are approximately exponentially distributed, with different parameters, rendering the embedded hi-low process approximately Markov.

A stochastic model for water-vegetation systems and the effect of decreasing precipitation on semi-arid environments.

Current climate change trends are affecting the magnitude and recurrence of extreme weather events. In particular, several semi-arid regions around the planet are confronting more intense and prolonged lack of precipitation, slowly transforming part of these regions into deserts in some cases. Although it is documented that a decreasing tendency in precipitation might induce earlier disappearance of vegetation, quantifying the relationship between decrease of precipitation and vegetation endurance remains a challenging task due to the inherent complexities involved in distinct scenarios. In this paper we present a model for precipitation-vegetation dynamics in semi-arid landscapes that can be used to explore numerically the impact of decreasing precipitation trends on appearance of desertification events. The model, a stochastic differential equation approximation derived from a Markov jump process, is used to generate extensive simulations that suggest a relationship between precipitation reduction and the desertification process, which might take several years in some instances.

A new surgical procedure for hallux limitus treatment: Double-V osteotomy on the base of the proximal phalanx of the hallux.

The purpose of this study was to evaluate the effectiveness of the new Double-V osteotomy of the first metatarsophalangeal joint (1MPJ) in patients with hallux limitus (HL).A study of 66 patients was performed, 33 patients were treated Cheilectomy and 33 were treated Double-V. All patients underwent an assessment of the passive mobility of the 1MPJ before the procedure, reevaluated 12 months later evaluating dorsiflexion, plantarflexion, and patients status using both the American Orthopaedic Foot and Ankle Society (AOFAS) for Hallux Metatarsophalangeal-Interphalangeal Scale.In comparing the improvement achieved regarding the increase of mobility obtained with surgical treatment, the feet operated with procedure Double-V gained significant degrees of movement increased in all analyzed parameters (P < .05). We achieved 13.33° more than average in dorsiflexion motion and 2.12° more than average in plantarflexion with regard to the feet that were operated with Cheilectomy procedure. Double-V scores on the AOFAS scale improved significantly (P = .000) 91.48 points postoperative, while with the following Cheilectomy only 79.30 points.This new surgical technique, easy to perform and with low complexity in surgical execution and a minimum of complications, produces better clinical and functional results that Cheilectomy alone.

Modeling ephemeral mating encounters in insects: The emergence of mate-finding Allee effects and applications to theoretical models of sterile release.

Lack of successful mating encounters in two-sex insect populations is a mechanism that might trigger reproductive Allee effects. In this paper I examine a function that models ephemeral mating encounters through the expected density of pairs formed by individuals of both sexes at any time. When this function is incorporated in a general system of differential equations for a two-sex population the solutions exhibit the emergence of an Allee effect for low population densities. Compared with current conceptual models for mate-finding Allee effects, the proposed pairing function does not include a parameter that quantifies the Allee effect strength, a feature that might be useful when information to parameterize Allee effects is unavailable. The mating function is then used to numerically explore how mate-finding Allee effects are enhanced by the release of sterile males in theoretical models where (i) the initial sex ratio is skewed, (ii) sterile males are released in pulses and (iii) partial female remating is allowed.

A Model for Mountain Pine Beetle Outbreaks in an Age-Structured Forest: Predicting Severity and Outbreak-Recovery Cycle Period.

The mountain pine beetle (MPB, Dendroctonus ponderosae), a tree-killing bark beetle, has historically been part of the normal disturbance regime in lodgepole pine (Pinus contorta) forests. In recent years, warm winters and summers have allowed MPB populations to achieve synchronous emergence and successful attacks, resulting in widespread population outbreaks and resultant tree mortality across western North America. We develop an age-structured forest demographic model that incorporates temperature-dependent MPB infestations. Stability of fixed points is analyzed as a function of (thermally controlled) MPB population growth rates and indicates the existence of periodic outbreaks that intensify as growth rates increase. We devise analytical methods to predict outbreak severity and duration as well as outbreak return time. After incorporating a spatial aspect and controlling initial stand demographic variation, the model predicts cycle periods that fall within observed outbreak return time ranges. To assess future MPB impact on forests, we use climate model projected temperatures with our model-based approximation methods to predict potential severity of future outbreaks that reflect the effects of changing climate.

Intravascular myopericytoma in the heel: case report and literature review.

Intravascular myopericytoma (IVMP), regarded as a variant of myopericytoma, is a rare tumor. Very few cases have been described, none in the foot.The first case of IVMP located in the heel of the foot is described in this article. A literature review is reported of all cases of IVMP published in the English literature.A 48-year-old man possessed an IVMP on the heel of the right foot. The physical examination and histopathological and ultrasound studies are described. The literature review yielded 5 cases of IVMP, 2 of which were in the thigh and 1 each in the oral mucosa, the periorbital region, and the leg.The possibility that these lesions may be malignant suggests that the histopathological study of vascular tumors should include immunohistochemical tests.

Pest persistence and eradication conditions in a deterministic model for sterile insect release.

The release of sterile insects is an environment friendly pest control method used in integrated pest management programmes. Difference or differential equations based on Knipling's model often provide satisfactory qualitative descriptions of pest populations subject to sterile release at relatively high densities with large mating encounter rates, but fail otherwise. In this paper, I derive and explore numerically deterministic population models that include sterile release together with scarce mating encounters in the particular case of species with long lifespan and multiple matings. The differential equations account separately the effects of mating failure due to sterile male release and the frequency of mating encounters. When insects spatial spread is incorporated through diffusion terms, computations reveal the possibility of steady pest persistence in finite size patches. In the presence of density dependence regulation, it is observed that sterile release might contribute to induce sudden suppression of the pest population.

Optimal sterile insect release for area-wide integrated pest management in a density regulated pest population.

To determine optimal sterile insect release policies in area-wide integrated pest management is a challenge that users of this pest control method inevitably confront. In this note we provide approximations to best policies of release through the use of simulated annealing. The discrete time model for the population dynamics includes the effects of sterile insect release and density dependence in the pest population. Spatial movement is introduced through integrodifference equations, which allow the use of the stochastic search in cases where movement is described through arbitrary dispersal kernels. As a byproduct of the computations, an assessment of appropriate control zone sizes is possible.

Correlation between degree of conversion, resin-dentin bond strength and nanoleakage of simplified etch-and-rinse adhesives.

OBJECTIVES: The aim of this study was to correlate the degree of conversion measured inside the hybrid layer (DC) with the microtensile resin-dentin bond strength (µTBS) and silver nitrate uptake or nanoleakage (SNU) for five simplified etch-and-rinse adhesive systems. METHODS: Fifty-five caries free extracted molars were used in this study. Thirty teeth were used for µTBS/SNU [n=6] and 25 teeth for DC [n=5]. The dentin surfaces were bonded with the following adhesives: Adper Single Bond 2 (SB), Ambar (AB), XP Bond (XP), Tetric N-Bond (TE) and Stae (ST) followed by composite resin build-ups. For µTBS and SNU test, bonded teeth were sectioned in order to obtain stick-shaped specimens (0.8mm(2)), which were tested under tensile stress (0.5mm/min). Three bonded sticks, from each tooth, were not tested in tensile stress and they were immersed in 50% silver nitrate, photo-developed and analyzed by scanning electron microscopy. Longitudinal 1-mm thick sections were prepared for the teeth assigned for DC measurement and evaluated by micro-Raman spectroscopy. RESULTS: ST showed lowest DC, µTBS, and higher SNU (p<0.05). All other adhesives showed similar DC, µTBS, and SNU (p>0.05), except for TE which showed an intermediate SNU level. The DC was positively correlated with µTBS and negatively correlated with SNU (p<0.05). SNU was also negatively correlated with µTBS (p<0.05). SIGNIFICANCE: The measurement of DC inside the hybrid layer can provide some information about bonding performance of adhesive systems since this property showed a good correlation with resin-dentin bond strength and SNU values.

Alternative esthetic management of fluorosis and hypoplasia stains: blending effect obtained with resin infiltration techniques.

STATEMENT OF PROBLEM: New light-polymerized resin composites optimized for rapid infiltration of enamel lesions with resin light curing monomers are commercially available today to prevent enamel lesions from further demineralization and provide a highly conservative therapy. In addition, this technique has proved to be effective treatment for blending white spot lesions because the microporosities of infiltrated lesions are filled with resin. PURPOSE: This clinical report presents and describes cases in which the minimally invasive infiltrant resin technique was used for blending different microporous lesions, mild-to-moderate fluorosis, and hypoplasia stains related to traumatic dental injuries. RESULTS: The fluorosis stain showed visually perceptual improvements. In the cases of hypoplasia, stains were not completely blended. However, the general clinical outcomes of these cases were considered successful and recovered the patients' self-esteem. CONCLUSION: Based on the results obtained, it could be concluded that the resin infiltration technique shows promising results and could be considered a minimally invasive procedure for mild-to-moderate fluorosis and hypoplasia stains. CLINICAL SIGNIFICANCE: This case study allows a better understanding of the concept of the resin infiltration technique applied in other types of porous lesions, increasing its use as a therapeutic alternative for esthetic purposes in the philosophy of minimally invasive dentistry.

Spectrophotometric evaluation of color alterations with a new dental bleaching product in patients wearing orthodontic appliances.

INTRODUCTION: Our objective was to assess the effectiveness of a new bleaching agent (8% hydrogen peroxide) used in patients wearing fixed orthodontic appliances. METHODS: Six anterior maxillary teeth of 40 patients aged 18 to 40 years were assessed. The patients were divided into 2 groups (20 in each group): in group A, the patients used the bleaching agent during orthodontic treatment; in group B, the patients used the bleaching agent after orthodontic treatment. For each group, a record of the initial tooth shade was taken with a polyvinyl siloxane matrix and a spectrophotometer. The groups had bleaching treatments with an 8% hydrogen peroxide product (Opalescence Treswhite Ortho, Ultradent, Opal Orthodontics, South Jordan, Utah) for 10 days in 45-minute sessions. For group A, the treatment was performed 10 days before finishing orthodontic treatment; at the end of the treatment, a new tooth shade record was taken with the polyvinyl siloxane matrix and a spectrophotometer. The subjects in group B had the same bleaching protocol after their brackets were removed. RESULTS: It was observed that, for the group without brackets, the color alteration ranged from 3 to 12 (mean, 8; median, 8.3); for the group with brackets, the range was between 4 and 13 (mean, 9; median, 8.5), indicating significant tooth bleaching in both groups with and without brackets (P >0.05). CONCLUSIONS: Opalescence Treswhite Ortho was shown to be an efficient bleaching agent in patients wearing fixed orthodontic appliances.

A model for the transmission dynamics of Orientia tsutsugamushi among its natural reservoirs.

The bacteria Orientia tsutsugamushi is the causative agent of scrub typhus, a prevalent disease in Asian countries that can affect humans and which shows an alarming increase of cases during the last years, especially in rural areas. Unfortunately, there is no vaccine for scrub typhus, and antibiotic treatments successfully used in the past appear to be inefficient to treat some strains of O. tsutsugamushi. We introduce a mathematical model that approximates the dynamics of the bacteria among its natural reservoirs. After computing the basic reproductive number from the proposed model, we explore its sensitivity to the parameter values that may be affected by application of control measures. This theoretical model may be of interest to pest managers as well as health authorities interested in gaining insight into the public management of the disease, through a better understanding of its qualitative dynamics.

The effect of patterns of infectiousness on epidemic size.

In the course of an infectious disease in a population, each infected individual presents a different pattern of progress through the disease, producing a corresponding pattern of infectiousness. We postulate a stochastic infectiousness process for each individual with an almost surely finite integral, or total infectiousness. Individuals also have different contact rates. We show that the distribution of the final epidemic size depends only on the contact rates and the integrated infectiousness. As a particular case, zero infectiousness on an initial time interval corresponds to a period of latency, which does not affect the final epidemic size in general stochastic and deterministic epidemic models, as is well known from the literature.

Screening Two Lycopersicon peruvianum Collections for Resistance to Tomato spotted wilt virus.

The United States Department of Agriculture (USDA) Research Service and the Tomato Genetics Resource Center (TGRC) Lycopersicon peruvianum germplasm collections (16,335 plants from 285 accessions) were screened with the Tomato spotted wilt virus (TSWV) isolates TSWV6 from Hawaii, and Anwa-1 from Western Australia. Using TSWV6 to screen for resistance, 10,634 L. peruvianum plants from 280 accessions were screened for resistance, resulting in 168 (60%) accessions with 1,437 (14%) plants indicating resistance, with all 1,404 89S (Sw-5+/Sw-5+) and 1,456 89R (Sw-5/Sw-5) controls infected. When using Anwa-1 for screening, 864 (15%) of 5,701 L. peruvianum plants were uninfected from 106 of the 181 accessions tested, and 472 (95%) of the 495 89S and 421 (73%) of the 574 89R controls were infected. Of the 172 accessions tested with both isolates, 54 were resistant to one isolate but not the other. Additionally, more accessions from the USDA than from the TGRC collection indicated resistance. TSWV-resistant accessions were somewhat equally distributed throughout the L. peruvianum geographic range, with an observation that northern Chile and southern Peru seemed to have an unusually high portion of accession indicating resistance. The value of Sw-5 is discussed in relationship to potential additional sources of TSWV resistance.