Frequently used extraoral maxillofacial prosthetic materials and their longevity - A comprehensive review

The longevity of an extraoral prosthesis depends on its physical and mechanical properties and user maintenance. Faced with multiple outcome measures, researchers find it difficult to determine the most appropriate extraoral prosthetic material. This comprehensive review evaluates the most used extraoral prosthesis materials and qualitatively assesses their longevity and function. The study aims to identify and interpret the results of current updates on the factors that affect longevity and functionality. This comprehensive review summarizes and evaluates differences in the properties of commonly used extraoral maxillofacial prosthetic materials. The review was planned to focus on all factors related to the longevity and function of the extraoral maxillofacial prosthetics. An electronic search covered English articles in PubMed, Scopus, Google Scholar, Web of Science, and grey literature. Manual searching was also performed. Six authors participated in the screening. Search engines extracted 1107 records, and 88 studies were included for qualitative and bias assessments. Silicones are the most frequently used extraoral maxillofacial prosthetic materials. Heat-cured silicones are more color-stable than those cured at room temperature. Additional ingredients and processing techniques affect prosthesis longevity.

Effects of different primers and colouring solutions on orthodontic bonding: shear bond strength and colour change

OBJECTIVES

This in vitro study evaluated the effect of different colouring solutions and primer systems used in the bonding of brackets on enamel colour change and bond strength.

MATERIALS AND METHODS

120 premolar teeth were divided into four main groups; brackets were bonded with 37% orthophosphoric acid + Transbond XT Primer in Group 1, 3 M Single Bond Universal in Group 2, Transbond Plus SEP in Group 3, and G-Premio Bond in Group 4. Each group was divided into three subgroups, and the teeth were placed in a cup containing coffee and tea mixture, in a cup containing cola and in distilled water. A bond strength test was applied to all teeth. Colour measurements of all teeth were performed at 2 different times: before bonding and after the bond strength test.

RESULTS

The average bond strength of the 37% orthophosphoric acid group was higher than that of the other groups. The effect of primer and solution groups on colour change was statistically significant (p = 0.001 and p = 0.023, respectively).

CONCLUSIONS

In this study, the bond strength was clinically sufficient in all primer groups. The highest colour change was observed when the tea-coffee solution and Transbond Plus SEP primer were used.

CLINICAL RELEVANCE

This study has identified enamel discoloration and bond strength from different colouring solutions and primer systems used for bonding braces, which can be used to inform clinicians and patients to achieve better treatment results.

A collagen-based theranostic wound dressing with visual, long-lasting infection detection capability

Continuous wound monitoring is one strategy to minimise infection severity and inform prompt variations in therapeutic care following infection diagnosis. However, integration of this functionality in therapeutic wound dressings is still challenging. We hypothesised that a theranostic dressing could be realised by integrating a collagen-based wound contact layer with previously demonstrated wound healing capability, and a halochromic dye, i.e. bromothymol blue (BTB), undergoing colour change following infection-associated pH changes (pH: 5-6 ➔ >7). Two different BTB integration strategies, i.e. electrospinning and drop-casting, were pursued to introduce long-lasting visual infection detection capability through retention of BTB within the dressing. Both systems had an average BTB loading efficiency of 99 wt% and displayed a colour change within 1 min of contact with simulated wound fluid. Drop-cast samples retained up to 85 wt% of BTB after 96 h in a near-infected wound environment, in contrast to the fibre-bearing prototypes, which released over 80 wt% of BTB over the same time period. An increase in collagen denaturation temperature (DSC) and red shifts (ATR-FTIR) suggest the formation of secondary interactions between the collagen-based hydrogel and the BTB, which are attributed to count for the long-lasting dye confinement and durable dressing colour change. Given the high L929 fibroblast viability in drop-cast sample extracts (92 %, 7 days), the presented multiscale design is simple, cell- and regulatory-friendly, and compliant with industrial scale-up. This design, therefore, offers a new platform for the development of theranostic dressings enabling accelerated wound healing and prompt infection diagnosis.

Scorpionfish rapidly change colour in response to their background

BACKGROUND

To facilitate background matching in heterogenous environments, some animals rapidly change body colouration. Marine predatory fishes might use this ability to hide from predators and prey. Here, we focus on scorpionfishes (Scorpaenidae), well-camouflaged, bottom-dwelling sit-and-wait predators. We tested whether Scorpaena maderensis and Scorpaena porcus adjust body luminance and hue in response to three artificial backgrounds and thereby achieve background matching. Both scorpionfish species are also red fluorescent, which could contribute to background matching at depth. Therefore, we tested whether red fluorescence is also regulated in response to different backgrounds. The darkest and the lightest backgrounds were grey, while the third background was orange of intermediate luminance. Scorpionfish were placed on all three backgrounds in a randomised repeated measures design. We documented changes in scorpionfish luminance and hue with image analysis and calculated contrast to the backgrounds. Changes were quantified from the visual perspective of two potential prey fishes, the triplefin Tripterygion delaisi and the goby Pomatoschistus flavescens. Additionally, we measured changes in the area of scorpionfish red fluorescence. Because scorpionfish changed quicker than initially expected, we measured luminance change at a higher temporal resolution in a second experiment.

RESULTS

Both scorpionfish species rapidly adjusted luminance and hue in response to a change of background. From prey visual perspective, scorpionfishes' body achromatic and chromatic contrasts against the background were high, indicating imperfect background matching. Chromatic contrasts differed considerably between the two observer species, highlighting the importance of choosing natural observers with care when studying camouflage. Scorpionfish displayed larger areas of red fluorescence with increasing luminance of the background. With the second experiment, we showed that about 50% of the total luminance change observed after one minute is achieved very rapidly, in five to ten seconds.

CONCLUSION

Both scorpionfish species change body luminance and hue in response to different backgrounds within seconds. While the achieved background matching was suboptimal for the artificial backgrounds, we propose that the observed changes were intended to reduce detectability, and are an essential strategy to camouflage in the natural environment.

The clinical relevance of Raynaud's phenomenon symptom characteristics in systemic sclerosis

Raynaud's phenomenon (RP) is a cardinal feature of systemic sclerosis (SSc) and manifests with pain, digital colour change, sensory symptoms, and impaired function. SSc-RP is exacerbated by cold exposure (RP 'attacks') but many patients report persistent symptoms of background digital ischaemia. The aim of our study was to examine the significance of RP with digital colour change with or without symptoms, and persistent colour change in between attacks. Patients with SSc responses were obtained from the Patient Survey of experiences of Raynaud's Phenomenon (PASRAP). We enquired about symptoms associated with Raynaud's attacks, and persistent symptoms in between attacks. Data were analysed as descriptive statistics with appropriate parametric/non-parametric testing. Relevant PASRAP survey question data from 747 evaluable SSc patients from across three continents were analysed. Isolated colour change was rare (29/484, 6%). Digital ulcers were more common in SSc-RP associated with other sensory symptoms (42.1% vs. 24.1%, P=0.057) and more readily treated with phosphodiesterase-type 5 inhibitors (22.5% vs. 10.3%%, P=0.124). Over one-third of patients (n=92/239, 38%) reported persistent colour change in between Raynaud's attacks. Patients with persistent colour change were more likely to have pulmonary arterial hypertension (15.2% vs. 7.5%, P=0.057) and be treated with calcium channel blockers (54.3% vs. 39.0%, P=0.021). SSc-RP with colour change and other symptoms and/or or persistent decolourisation in between attacks were more likely to have vascular complications of SSc and be treated with vascular therapies. Future research should explore the judicious use of vascular therapies as a potential form of disease modification in SSc. Key Points • Isolated colour change without other symptoms is rare in SSc patients. • SSc patients often identify persistent symptoms in between attacks of RP. • SSc-RP with colour change and other symptoms, or persistent decolourisation, may have greater disease severity and be treated with vascular therapies.

Can the Dynamic Colouration and Patterning of Bluelined Goatfish (Mullidae; Upeneichthys lineatus) Be Perceived by Conspecifics?

Bluelined goatfish (Upeneichthys lineatus) exhibit dynamic body colour changes and transform rapidly from a pale, buff/white, horizontally banded pattern to a conspicuous, vertically striped, red pattern when foraging. This red pattern is potentially an important foraging signal for communication with conspecifics, provided that U. lineatus can detect and discriminate the pattern. Using both physiological and behavioural experiments, we first examined whether U. lineatus possess visual pigments with sensitivity to long ("red") wavelengths of light, and whether they can discriminate the colour red. Microspectrophotometric measurements of retinal photoreceptors showed that while U. lineatuslack visual pigments dedicated to the red part of the spectrum, their pigments likely confer some sensitivity in this spectral band. Behavioural colour discrimination experiments suggested that U. lineatuscan distinguish a red reward stimulus from a grey distractor stimulus of variable brightness. Furthermore, when presented with red stimuli of varying brightness they could mostly discriminate the darker and lighter reds from the grey distractor. We also obtained anatomical estimates of visual acuity, which suggest that U. lineatus can resolve the contrasting bands of conspecifics approximately 7 m away in clear waters. Finally, we measured the spectral reflectance of the red and white colouration on the goatfish body. Visual models suggest that U. lineatus can discriminate both chromatic and achromatic differences in body colouration where longer wavelength light is available. This study demonstrates that U. lineatus have the capacity for colour vision and can likely discriminate colours in the long-wavelength region of the spectrum where the red body pattern reflects light strongly. The ability to see red may therefore provide an advantage in recognising visual signals from conspecifics. This research furthers our understanding of how visual signals have co-evolved with visual abilities, and the role of visual communication in the marine environment.

Investigation of 4D printing of lotus root-compound pigment gel: Effect of pH on rapid colour change

The feasibility was investigated of 4D printing of lotus root gel compounded with a pigment that responds to pH change and alters colour. The pigment comprised of a combination of anthocyanins and lemon yellow; it was used in gel preparation for printing. The flowability and self-support properties of the lotus root-pigment gel were studied to evaluate its 3D printing performance. The gel viscosity decreased with the increase of printing temperature over the range 40, 50, and 60 °C. The gel with a ratio (lotus root powder/compound pigment) of 0.35 extruded smoothly and maintained high formability at temperatures below 60 °C. The pH response of compound pigment enabled the printed sample to change colour from reddish/yellowish to green after spraying with NaHCO₃. The a* and b* values decreased significantly (p < 0.05) after spraying for 1 min. The gel with ratios of 0.30 and 0.35 achieved rapid colour change both superficially and internally. Through several different model designs (apple, Christmas tree, letters, and Chinese characters), high-quality 4D printing could be realized without problem. Thus, lotus root gel can be mixed with suitable pigments in correct proportion for 4D printing at appropriate temperature to ensure good flowability.

Color stability of 3D-printed denture resins: effect of aging, mechanical brushing and immersion in staining medium

PURPOSE

This in-vitro study evaluated and compared the color stability of 3D-printed and conventional heat-polymerized acrylic resins following aging, mechanical brushing, and immersion in staining medium.

MATERIALS AND METHODS

Forty disc-shaped specimens (10 mm in diameter and 3 mm thick) were prepared from two 3D-printed [DentaBASE (DB) and Denture 3D+ (D3D)] and one conventional polymethylmethacrylate (PMMA) denture materials. The specimens were thermo-cycled, subjected to mechanical brushing, and were immersed in either coffee, lemon juice, coke, or artificial saliva (AS) to simulate one and two years of oral use. Color measurements of the specimens were recorded by a spectrophotometer at baseline (T0), and after one (T1) and two years (T2) of simulation. The color changes (∆E) were determined and also quantified according to the National Bureau of Standards (NBS) units. Descriptive statistics, followed by factorial ANOVA and Bonferroni post-hoc test (α=.05), were applied for data analysis.

RESULTS

The independent factors, namely material, staining medium, and immersion time, and interaction among these factors significantly influenced ∆E (P<.009). Irrespective of the materials, treatments, and time, the highest and the lowest mean ∆Es were observed for PMMA in lemon juice (4.58 ± 1.30) and DB in AS (0.41 ± 0.18), respectively. Regarding the material type, PMMA demonstrated the highest mean ∆E (2.31 ± 1.37), followed by D3D (1.67 ± 0.66), and DB (0.85 ± 0.52), and the difference in ∆E between the materials were statistically significant (P<.001). All the specimens demonstrated a decreased color changes at T2 compared to T1, and this difference in mean ∆E was statistically significant (P<.001).

CONCLUSION

The color changes of 3D-printed denture resins were low compared to conventional heat polymerized PMMA. All the tested materials, irrespective of the staining medium used, demonstrated a significant decrease in ∆E values over time.

Integrated transcriptomics and metabolomics provide novel insight into changes in specialized metabolites in an albino tea cultivar (Camellia sinensis (L.) O. Kuntz)

Tea varieties with specific colours have often been studied by researchers. However, previous studies on the albinism of tea plants have mostly been based on plants with different genetic backgrounds or focused on common components in albino tea leaves, such as amino acids, flavones, and carotenoids. In this study, we conducted widely targeted metabolic and transcriptomic analyses between a wildtype tea genotype (Shuixian, LS) and its albino mutant (Huangjinshuixian, HS). At the molecular level, alteration of gene expression levels in the MEP pathway may have reduced the production of chlorophyll and carotenoids in HS, which could be the main cause of the phenotypic changes in HS. At the metabolite level, a large number of metabolites related to light protection that significantly accumulated in HS, including flavones, anthocyanins, flavonols, flavanones, vitamins and their derivatives, polyphenols, phenolamides. This result, combined with an enzyme activity experiment, suggested that the absence of photosynthetic pigments made the albino tea leaves of HS more vulnerable to UV stress, even under normal light conditions. In addition, except for the common amino acids, we also identified numerous nitrogen-containing compounds, including nucleotides and their derivates, amino acid derivatives, glycerophospholipids, and phenolamides, which implied that significant accumulation of NH₄⁺ in albino tea leaves could not only promote amino acid synthesis but could also activate other specialized metabolic pathways related to nitrogen metabolism. In conclusion, our results provide new information to guide further studies of the extensive metabolic reprogramming events caused by albinism in tea plants.

Influence of a glycolic acid-based final irrigant for photosensitizer removal of photodynamic therapy on the microhardness and colour change of the dentin structure

INTRODUCTION

This study aimed to evaluate the influence of glycolic acid-based final irrigant for photosensitizer removal of photodynamic therapy on the microhardness and colour change of the dentin structure.

METHODS

Eighty extracted single-rooted human incisors were used. Sample preparation and root split resulted in 160 samples, 80 samples being used for microhardness and 80 samples for colour change evaluation. In the first, PDT protocol was performed and 80 samples were randomly divided into 4 groups (n = 20), according to the final irrigation protocol: distilled water (DW); 17 % ethylenediaminetetraacetic acid (EDTA); QMix; 17 % glycolic acid (GA). Microhardness was evaluated using the Vicker tester, before and after, PDT and final irrigation protocols, calculating the percentage of microhardness reduction. In the second evaluation, PDT and final irrigation protocols were performed in the same way. Colour change was evaluated using digital spectrophotometer before and after these protocols, calculating the ΔE colour change using the CIELAB system (L*a*b* values). Specific statistical analysis was performed for both evaluations (α = 5%).

RESULTS

The highest percentage of microhardness reduction was observed in 17 % EDTA, QMix and 17 % GA groups, with no significant difference among them (p > 0.05). Furthermore, none of these protocols was effective in photosensitizer removal, and all final irrigation protocols were statically similar to control group (p > 0.05).

CONCLUSIONS

GA promotes microhardness reduction and also contributes to the colourization of dentin structure during the photosensitizer removal process, followingPDT .

Effects of different bleaching application time on tooth color and mineral alteration

BACKGROUND

The effects of HP-based products upon dental enamel are inconclusive.

PURPOSE

The purpose of this study was to evaluate the colour and mineral changes caused by the bleaching agent applications at different durations on the enamel surface.

BASIC PROCEDURES

60 caries-free lower central incisor extracted for periodontal reasons were standardized for enamel and dentin thickness after cone-beam computed tomography (CBCT) measurements in terms of mineral (n = 24) and colour change (n = 36). All teeth were divided into 3 groups according to different bleaching durations for colour (n = 12) and mineral change (n = 8) measurements. The samples for mineral change were examined with the -energy scattering X-ray (EDX, JSM-6390 LV, Jeol Inc., Japan) device before and 2 weeks after the application. For colour change, the measurement of the samples was performed with spectrophotometer device (VITA EasyShade 4.0, Germany). Opalescence Boost PF 40% (Ultradent Products, USA) was applied for 20 min (min) in Group 1, 40 min in Group 2 and 60 min in Group 3. In order to determine the efficacy of bleaching, colour measurements were repeated at 24 h, 7 and 14 days after the application. In the intragroup comparison, Friedman and Wilcoxon tests were used for non-normally distributions, while repeated variance analysis and paired t test were used for normally distributions in dependent variables. In the intergroup comparison, ANOVA and LSD tests were used for normally distributions, while Kruskal-Wallis and Dunn tests were used for non-normally distributions in independent variables. p < 0.05 was considered significant.

MAIN FINDINGS

In the study, statistically significant difference was observed between all groups in terms of colour change at different measurement times (p < 0.05). The highest ΔE₀₀ values were observed in Group 3 (ΔE₀₀₃ = 8.37 ± 2.15); the lowest value was observed in Group 1 (ΔE₀₀₁ = 4.74 ± 1.26). Ca values were similar increase among all groups (p > 0.05). The highest Ca values were observed in Group 3 (69.91 ± 5.34); the lowest value was observed in Group 2 (66.08 ± 1.50). P values were similar increase among all groups (p > 0.05). The lowest P values were observed in Group 3 (26.54 ± 5.92); the highest value was observed in Group 2 (29.86 ± 2.26).

PRINCIPAL CONCLUSIONS

Effective whitening was achieved in all study groups. When the results are evaluated as versatile in terms of bleaching effectiveness and mineral change, the most ideal bleaching duration was determined as 40 min (Group 2).

Short-term effects of stain-causing beverages on tooth bleaching: A randomized controlled clinical trial

OBJECTIVES

To evaluate the short-term effects of stain-causing beverages on the effectiveness of in-office tooth bleaching.

METHODS

Participants were recruited and randomly divided into 3 groups based on beverages used for rinsing during and after the bleaching procedure: group N (tap water, control group), group C (coffee), and group T (tea). Participants were instructed to rinse with the respective solutions for 30 s, 4 times daily for 4 weeks. All participants received two in-office bleaching treatment sessions with 40 % hydrogen peroxide (Opalescence BOOST PF 40 %, Ultradent); the sessions were separated by a 1-week interval. Tooth colour was assessed using a spectrophotometer (Easyshade, Vita ZahnFabrik) before the bleaching procedure (T0), immediately after the first session of bleaching (T1), immediately after the second session of bleaching (T2), as well as one week (T3) and three weeks after (T4) the end of bleaching. Tooth sensitivity (TS) was ranked using a numerical rating scale (NRS) and a visual analogue scale (VAS) at different time points.

RESULTS

No significant difference in the whiteness index (W), △E, △a* and △b* values among the 3 groups was observed at any time interval (P for all > 0.05). At T4, the △L* value in group C was significantly lower than that in groups T and N (P = 0.022 and P = 0.001, respectively), though no significant difference in △L* values was observed among the 3 groups at T1 (P = 0.402), T2 (P = 0.643) and T3 (P = 0.177). Additionally, no significant difference was found in the TS values among the 3 groups at any of the evaluation time points (P for all > 0.05).

CONCLUSIONS

Exposure to coffee or tea during the bleaching treatment period did not affect the effectiveness of the treatment. However, exposure to coffee after the bleaching treatment did affect the effectiveness of the treatment. Exposure to stain-causing beverages did not affect the bleaching-induced TS (ClinicalTrials.gov Identifier: NCT03933527).

CLINICAL SIGNIFICANCE

The consumption of coffee or tea during tooth bleaching may not interfere with the colour change produced by the treatment. However, clinicians should advise their patients to refrain from, at least to some extent, consuming coffee after the bleaching procedure to maintain the effectiveness of the treatment.

Experimental manipulation of perceived predation risk and cortisol generates contrasting trait trajectories in plastic crucian carp

Most animals constitute potential prey and must respond appropriately to predator-mediated stress in order to survive. Numerous prey also adaptively tailor their response to the prevailing level of risk and stress imposed by their natural enemies, i.e. they adopt an inducible defence strategy. Predator exposure may activate the stress axis, and drive the expression of anti-predator traits that facilitate survival in a high-risk environment (the predation-stress hypothesis). Here, we quantified two key morphological anti-predator traits, body morphology and coloration, in crucian carp reared in the presence or absence of a predator (pike) in addition to experimental manipulation of physiological stress via implants containing either cortisol or a cortisol inhibitor. We found that predator-exposed fish expressed a deeper-bodied phenotype and darker body coloration as compared with non-exposed individuals. Skin analyses revealed that an increase in the amount of melanophores caused the dramatic colour change in predator-exposed fish. Increased melanization is costly, and the darker body coloration may act as an inducible defence against predation, via a conspicuous signal of the morphological defence or by crypsis towards dark environments and a nocturnal lifestyle. By contrast, the phenotype of individuals carrying cortisol implants did not mirror the phenotype of predator-exposed fish but instead exhibited opposite trajectories of trait change: a shallow-bodied morphology with a lighter body coloration as compared with sham-treated fish. The cortisol inhibitor did not influence the phenotype of fish i.e. neither body depth nor body coloration differed between this group and predator-exposed fish with a sham implant. However, our results illuminate a potential link between stress physiology and morphological defence expression.

Social and physiological drivers of rapid colour change in a tropical toad

Dynamic sexual dichromatism occurs when males and females differ in colouration for a limited time. Although this trait has been primarily studied in cephalopods, chameleons, and fishes, recent analyses suggest that dynamic dichromatism is prevalent among anurans and may be mediated through sexual selection and sex recognition. Yellow toads, Incilius luetkenii, exhibit dynamic dichromatism during explosive breeding events at the onset of the rainy season: males change from a cryptic brown to a bright yellow and back again during the brief mating event. We tested the hypothesis that dynamic dichromatism in yellow toads is influenced by conspecific interactions and mediated through sex hormones and stress hormones. We placed male toads into one of four social treatments (with three other males, one male, one female, or no other toads). Immediately before and after each one-hour treatment, we quantified male colour with a reflectance spectrometer and we collected a blood sample to assess plasma concentrations of both testosterone and corticosterone. We found that males held with conspecific animals showed the brightest yellow colour and showed little or no change in their corticosterone levels. Across treatments, toads with duller yellow colour had higher levels of corticosterone. Male colour showed no association with testosterone. Interestingly, males showed substantial temporal variation in colour and corticosterone: toads were duller yellow and exhibited greater levels of corticosterone post-treatment across subsequent days at the onset of the rainy season. Our findings reveal that both conspecific interactions and corticosterone are involved in the dynamic colour change of yellow toads.

Dual-curing resin cement with colour indicator for adhesively cemented restorations to dental tissues: Change of colour by curing and some physical properties

The study was aimed to investigate a color indicator containing dual curing resin composite luting cement and to plot the color change to the time of solidification of the cement. In addition some physical properties were studied. Specimens were made of a dual-cure resin cement (Maxcem Elite™ Chroma, Kerr, Orange, CA, USA) and polymerized by autopolymerization only, or with light initiated polymerization. A spectrophotometer was used to quantify the color change of the cement as plotted with the curing time. The efficacy of the curing process was studied by measuring water sorption and the ultimate flexural properties of the cement. The results showed that the flexural strength of cement after autopolymerization was 27.3 MPa and after light initiated polymerization 48.1 MPa. Young’s modulus of bending was 2089.3 MPa and 3781.5 MPa respectively for the same cement samples. Water sorption after two weeks for the autopolymerization cement samples was −1.12 wt% and for the light initiated polymerization samples 0.56 wt%. Non-parametric Spearman’s correlation was measured for autopolymerized cement samples between variables for color and solidification load (N), which showed a strong correlation between curing process and color change (p < 0.05). There was a correlation between the color change and degree of monomer conversion of the dual curing resin composite luting cement which contained a color indicator system for polymerization reaction. The study also suggested that autopolymerization only resulted in suboptimal polymerization of the cement. By additional light curing considerably higher flexural properties were obtained.

Evaluation of colour change and surface roughness of two resin-based composites when exposed to beverages commonly used by children: an in-vitro study

AIM

To evaluate and compare the surface roughness and colour change of microhybrid and nanocomposite after exposure to beverages commonly used by children.

METHODS

Thirty discs were prepared using Filtek Z250 and Filtek Supreme composites. Discs were immersed in distilled water, orange juice and Coca-Cola. Colour and surface roughness were measured at baseline and on days 15 and 30.

RESULTS

Filtek Z250 and Filtek Supreme showed no significant difference in surface roughness and colour change at all measurement times. Immersion solution had a significant effect on surface roughness as well as colour change. Specimens immersed in Coca-Cola demonstrated the highest effect, followed by those immersed in orange juice, while specimens immersed in distilled water had the least effect. There was a significant increase in surface roughness and colour change over time. The change in colour was more evident in the period between baseline measurements and after 15 days. There was a significant interaction between media type and time.

CONCLUSIONS

Both composites showed no significant difference in roughness and colour change at all measurement times. There was a significant increase in surface roughness and colour change in all immersion solutions tested over time. Coca-Cola caused unacceptable colour change.

Colour change of twig-mimicking peppered moth larvae is a continuous reaction norm that increases camouflage against avian predators

Camouflage, and in particular background-matching, is one of the most common anti-predator strategies observed in nature. Animals can improve their match to the colour/pattern of their surroundings through background selection, and/or by plastic colour change. Colour change can occur rapidly (a few seconds), or it may be slow, taking hours to days. Many studies have explored the cues and mechanisms behind rapid colour change, but there is a considerable lack of information about slow colour change in the context of predation: the cues that initiate it, and the range of phenotypes that are produced. Here we show that peppered moth (Biston betularia) larvae respond to colour and luminance of the twigs they rest on, and exhibit a continuous reaction norm of phenotypes. When presented with a heterogeneous environment of mixed twig colours, individual larvae specialise crypsis towards one colour rather than developing an intermediate colour. Flexible colour change in this species has likely evolved in association with wind dispersal and polyphagy, which result in caterpillars settling and feeding in a diverse range of visual environments. This is the first example of visually induced slow colour change in Lepidoptera that has been objectively quantified and measured from the visual perspective of natural predators.

Effect of vulcanization temperature and dental stone colour on colour degradation of maxillofacial silicone elastomers

Background

Colour degradation is a major problem in maxillofacial silicone elastomers. Recent studies have focused on colour stability and the mechanical properties of the silicone elastomers. A colour match is also essential for the acceptance of the prosthesis by the patient. The aim of this study is to assess the colour degradation of the silicone elastomer after being moulded in different colours of dental stones at two different vulcanization temperatures.

Methods

Five different colours of dental stones were used to fabricate a total of 120 silicone blocks using a Cosmesil M511 maxillofacial silicone elastomer. Vulcanization was completed at two different temperatures (25 and 100° Celsius). Colour measurements were obtained with a Conica Minolta spectrophotometer. The CIEDE2000 formula was used to calculate the colour differences (∆E00). Two-way ANOVA, one-way ANOVA with Bonferroni corrected post-hoc p values and independent samples t-test were used for the statistical analyses.

Results

High temperature vulcanization causes lightening of the maxillofacial silicone elastomers without regard to the dental stone colour (p = 0.001). Specimens moulded in green stone lightened least at room temperature (p = 0.999). Compared to the control group, at high temperature, all specimens moulded in coloured dental stones darkened significantly (p < 0.001 for white, blue and yellow; p = 0.006 for green; p = 0.045 for reddish-brown). In the high temperature group, the shift to a green chroma was significant in the white, yellow and green dental stones groups (p = 0.001, p = 0.002, p < 0.001, respectively). The mean b* of the high temperature control group was higher than that of the room temperature control group (p < 0.001). The only ∆E00 score lower than the perceptibility threshold for dental materials (∆E00 = 1.30) was between the room temperature control group and the room temperature green dental stone group (∆E00 = 0.96).

Conclusions

Green and blue dental stones cause less colour degradation in silicone elastomers. Reddish-brown dental stones cause the most colour degradation in silicone elastomers. At 100 °C, the colour of the silicone elastomer lightens and yellows even if the elastomer is vulcanized in a stainless steel mould. White, yellow and reddish-brown dental stones make the silicone elastomer appear more yellow even if the elastomer is vulcanized at room temperature.

Shape, colour plasticity, and habitat use indicate morph-specific camouflage strategies in a marine shrimp

Background

Colour and shape polymorphisms are important features of many species and may allow individuals to exploit a wider array of habitats, including through behavioural differences among morphs. In addition, differences among individuals in behaviour and morphology may reflect different strategies, for example utilising different approaches to camouflage. Hippolyte obliquimanus is a small shrimp species inhabiting different shallow-water vegetated habitats. Populations comprise two main morphs: homogeneous shrimp of variable colour (H) and transparent individuals with coloured stripes (ST). These morphs follow different distribution patterns between their main algal habitats; the brown weed Sargassum furcatum and the pink-red weed Galaxaura marginata. In this study, we first investigated morph-specific colour change and habitat selection, as mechanisms underlying camouflage and spatial distribution patterns in nature. Then, we examined habitat fidelity, mobility, and morphological traits, further indicating patterns of habitat use.

Results

H shrimp are capable of changing colour in just a few days towards their algal background, achieving better concealment in the more marginal, and less preferred, red weed habitat. Furthermore, laboratory trials showed that habitat fidelity is higher for H shrimp, whereas swimming activity is higher for the ST morph, aligned to morphological evidence indicating these two morphs comprise a more benthic (H) and a more pelagic (ST) life-style, respectively.

Conclusions

Results suggest that H shrimp utilise a camouflage strategy specialised to a limited number of backgrounds at any one time, whereas ST individuals comprise a phenotype with more generalist camouflage (transparency) linked to a more generalist background utilisation. The coexistence within a population of distinct morphotypes with apparently alternative strategies of habitat use and camouflage may reflect differential responses to substantial seasonal changes in macroalgal cover. Our findings also demonstrate how colour change, behaviour, morphology, and background use all interact in achieving camouflage.

Electronic supplementary material

The online version of this article (doi:10.1186/s12862-016-0796-8) contains supplementary material, which is available to authorized users.