Search

Abstract With a growing global population and ageing demographics, the food industry stands at a pivotal crossroads, necessitating bespoke solutions and groundbreaking innovations. In vitro experiments can help understanding food oral processing and formulating products meeting the specific needs of different populations. However, current in vitro models do not reproduce well human oral anatomy and tongue biomechanics, essential for assessing the behaviour of novel and texturized foods under physiologically relevant oral conditions. In response, we unveil a novel 3D biomimetic artificial mouth, showcasing a pneumatic multi-degree-of-freedom artificial tongue meticulously crafted to mirror the mechanical properties and wettability of the human tongue. This cutting-edge technology, featuring tongue surface papillae, is capable of performing lifelike movements. The comparison with in vivo data demonstrates that it accurately reproduces oral processing of three, vastly different, soft foods. Textural characteristics (firmness, adhesive and cohesive properties) and shear viscosities—measured at oral and oropharyngeal-relevant shear rates—of in vitro food boli closely mirrored those observed in vivo. This in vitro device presents unprecedented opportunities for studying the dynamics of food transformation in the mouth, to adapt texture towards food that can be swallowed with ease and to improve food palatability, accommodating specific health needs critical for older adults (e.g., reduced salivary secretion, tongue weakness or poor coordination).

With a growing global population and ageing demographics, the food industry stands at a pivotal crossroads, necessitating bespoke solutions and groundbreaking innovations. In vitro experiments can help understanding food oral processing and formulating products meeting the specific needs of different populations. However, current in vitro models do not reproduce well human oral anatomy and tongue biomechanics, essential for assessing the behaviour of novel and texturized foods under physiologically relevant oral conditions. In response, we unveil a novel 3D biomimetic artificial mouth, showcasing a pneumatic multi-degree-of-freedom artificial tongue meticulously crafted to mirror the mechanical properties and wettability of the human tongue. This cutting-edge technology, featuring tongue surface papillae, is capable of performing lifelike movements. The comparison with in vivo data demonstrates that it accurately reproduces oral processing of three, vastly different, soft foods. Textural characteristics (firmness, adhesive and cohesive properties) and shear viscosities—measured at oral and oropharyngeal-relevant shear rates—of in vitro food boli closely mirrored those observed in vivo. This in vitro device presents unprecedented opportunities for studying the dynamics of food transformation in the mouth, to adapt texture towards food that can be swallowed with ease and to improve food palatability, accommodating specific health needs critical for older adults (e.g., reduced salivary secretion, tongue weakness or poor coordination). [ABSTRACT FROM AUTHOR]

IntroductionEfforts have always been made to protect valuable compounds of medicine, food and aromatics materials that are highly sensitive to environmental conditions by the encapsulation method. encapsulation of flavors, in addition to its protection, allows the aromatic substance to be released in a long time, and the time and place of its release can be controlled. To design these protection systems requires detailed information on encapsulation and release methods, the nature of walls and aromatic materials (Gunning et al.,1999). For encapsulation of sensitive compounds such as lipophilic materials, it is necessary to produce an emulsion of the desired substance in wall materials such as proteins, polysaccharides or a mixture of them. The important factors in encapsulation are the molecular weight, chemical properties and polarity of the core materials, the properties of the materials of the walls, and finally, the methods used to produce microcapsules. (Jafari et al., 2008).The aim of this study was to produce and evaluate the properties of two and six layer multilayer microcapsules containing limonene using soy protein isolate and starch modified by spray drying. The release of encapsulated limonene was investigated under artificial oral conditions under different stress conditions. The results of this study can be used to predict the release rate of the encapsulated flavors and their release conditions.Materials and MethodsSolution preparation: The solution of SPI (0-3%) was prepared by methods of Huang et al. (2012). The OSA starch stock solution (0-2%) was prepared by methods of Nilsson and Bergens (2007).Emulsion’s preparation: the primary emulsion of the optimum SPI and secondary emulsion of optimum OSA starch concentration prepared by the method of Noshad et al (2015).Microcapsule production: To prepare the Microcapsules, a laboratory spray dryer was used. 180±5 ᵒC, inlet air temperature, 25 (ml/min) feed rate, and 90±10 ᵒC outlet air temperature were used. Six layer microcapsules was also prepared in the same conditions (Ansarifar et al., 2017)The micro structure, morphology and release of limonene were evaluated and finally by Zero order, First order, Higuchi, and Korsemeyer- peppas models were used to the fitting of experimental data.Limonene release: To investigate the release of the encapsulated limonene, the release of these microcapsules (two and six layer) at 37 ° C and pH = 6.8, as well as frequent chewing (0, 50 and 100 rpm) were examined. For the apply of shear stress, an oral simulator was designed and developed by the Department of Food Science and Technology of Ferdowsi University of Mashhad was used. Results and DiscusionThe results of particle size changes of the initial emulsion formed with different levels of soy protein isolate showed that the particle size decreased with increasing the concentration of this protein to 1.5% and then it was increased. The results of zeta potential showed that with increasing the concentration of soy protein isolate to 1.5%, the zeta potential of the samples increased and with more than 1.5%, it did not have much effect on the zeta potential of the samples, which indicates that concentrate of 1.5% soy protein isolate has a good ability to cover surface of limonene particles. Similarly, 1.2% of OSA starch was determined for the secondary layer.SEM images of the microcapsules showed that in the two-layer wall microcapsules have cavities, cracks and shrinkage. In the starting of drying, the rate of moisture lost is high and on the other hand, the wall is not strong enough to withstand the stresses caused by the exit of moisture from the walls, so the microcapsule has cavities. In six-layer microcapsules, a smooth, non-cracked surface was observed, which can be attributed to the wall strength due to the increase in the number of layers. Fourier transform infrared spectroscopic (FTIR) test showed that the outer surface of the microcapsules was covered by OSA starch in two and six layer microcapsules.The release profile of encapsulated limonene showed that the release rate in two layer samples was faster than six layer samples. Also, with increasing shear rate, the amount of release increased. The results of experimental models fitting showed that the first-order model had the best description for releasing limonene from two- and six-layer samples in different conditions. Calculation of diffusion coefficient showed that six-layer microcapsules have a lower diffusion coefficient than two-layer microcapsules, which leads to a decrease in the release rate of limonene.Conclusion The results of this study showed that the layer-by-layer method could be used to produce limonene microcapsules. Soy protein isolate and modified starch can cover limonene droplets well. SEM images showed that the structure of six-layer microcapsules is free of cracks and cavities and has a more uniform surface than two-layer microcapsules. To investigate the mechanism of limonene release from two- and six-layer microcapsules, different kinetic models were used to fit the experimental release data. The results showed that the release of these microcapsules occurred based on the diffusion mechanism and Fick's law, which is the main mechanism of mass transfer in the release process. Also, the results showed that the six-layer microcapsules had a lower diffusion coefficient than the two-layer microcapsules and the release rate was lower in the two-layer microcapsule; This is due to the repetitive coating of soy protein isolate and modified starch around the microcapsules and the increase in wall thickness.

This study validated a microbial caries model (artificial mouth) for dental caries development to determine the optimal time to create early caries suitable for evaluation of the efficacy of caries therapeutic agents. In all, 40 human enamel blocks were placed in an artificial mouth at 37 °C and 5% CO2 and were exposed to brain heart infusion broth inoculated with S. mutans in continuous circulation (0.3 mL/min). The culture medium was replaced three times daily. Samples were exposed to 10% sucrose for 3 min, 3 times daily to promote biofilm growth. Five samples were harvested from the chamber after 3, 4, 5, 6, 7, 14, 21, and 28 days. At the end of experiment, samples were assessed visually by ICDAS criteria, while lesion depth (LD) and mineral loss (ML) were measured using polarizing light microscopy and transverse microradiography. Data were analyzed by Pearson correlation, ANOVA, and Tukey comparison test (p < 0.05). Results showed significant and strong positive correlation (p < 0.01) between all variables and biofilm growth time. LD and ML profiles of 7-day lesions seem to be the most suitable for remineralization studies. In conclusion, using the evaluated artificial mouth, early-stage caries suitable for products' evaluation studies was produced within 7 days of exposure to microbial biofilm. [ABSTRACT FROM AUTHOR]

This study validated a microbial caries model (artificial mouth) for dental caries development to determine the optimal time to create early caries suitable for evaluation of the efficacy of caries therapeutic agents. In all, 40 human enamel blocks were placed in an artificial mouth at 37 °C and 5% CO2 and were exposed to brain heart infusion broth inoculated with S. mutans in continuous circulation (0.3 mL/min). The culture medium was replaced three times daily. Samples were exposed to 10% sucrose for 3 min, 3 times daily to promote biofilm growth. Five samples were harvested from the chamber after 3, 4, 5, 6, 7, 14, 21, and 28 days. At the end of experiment, samples were assessed visually by ICDAS criteria, while lesion depth (LD) and mineral loss (ML) were measured using polarizing light microscopy and transverse microradiography. Data were analyzed by Pearson correlation, ANOVA, and Tukey comparison test (p < 0.05). Results showed significant and strong positive correlation (p < 0.01) between all variables and biofilm growth time. LD and ML profiles of 7-day lesions seem to be the most suitable for remineralization studies. In conclusion, using the evaluated artificial mouth, early-stage caries suitable for products’ evaluation studies was produced within 7 days of exposure to microbial biofilm.

This article presents the third part of a larger project whose final objective is to study and analyse the effects of viscous thermal losses in a flute wind musical instrument. After implementing the test bench in the first phase and modelling and validating the dynamic behaviour of the simulator, based on the previously implemented test bench (without considering the losses in the system) in the second phase, this third phase deals with the study of the viscous thermal losses that will be generated within the resonator of the flute. These losses are mainly due to the friction of the air inside the resonator with its boundaries and the changes of the temperature within this medium. They are mainly affected by the flute geometry and the materials used in the fabrication of this instrument. After modelling these losses in the frequency domain, they will be represented using a system approach where the fractional order part is separated from the system’s transfer function. Thus, this representation allows us to study, in a precise way, the influence of the fractional order behaviour on the overall system. Effectively, the fractional behavior only appears much below the 20 Hz audible frequencies, but it explains the influence of this order on the frequency response over the range [20–20,000] Hz. Some simulations will be proposed to show the effects of the fractional order on the system response.

Abstract Dynamic flavor release curves from chewing gum were measured using an Artificial Mouth coupled to the AFFIRM®. A flavor distribution model for chewing gum is proposed, where flavor is present as droplets in both the hydrophilic (water-soluble) and the hydrophobic (water insoluble) parts of the chewing gum and as molecularly dissolved in the hydrophobic part of the gum. During mastication, the flavor droplets in the water-soluble phase are released and responsible for an initial burst release. The flavor droplets captured in the gum-base are pushed towards the interface by mastication and are responsible for the subsequent release. The flavor molecules dissolved in the gum-base, released by diffusion, are only responsible for the release at very long time scales. It was found that the oil-water partition constant is an important parameter to explain the flavor release, where hydrophobic components show slower and longer release, while more hydrophilic components show more burst release. Graphical abstract Unlabelled Image Highlights • Initial flavor release is primarily induced due to the washing out of the water phase. • Flavor release at later times is caused by release of oil + flavor droplets during mastication. • Release of flavors through diffusion is negligible. • The hydrophobicity of the flavor compound predicts its release from the chewing gum. • Less than 4% of the flavor is released during a 15 min mastication period. [ABSTRACT FROM AUTHOR]

A dental biofilm forms a distinct environment where microorganisms live in a matrix of extracellular polysaccharides. The biofilm favors certain bacteria and creates a habitat that functions differently compared to planktonic bacteria. Reproducible model systems which help to address various questions related to biofilm formation, the process of caries development, and its prevention are needed and are continuously developed. Recent research using both batch culture, continuous culture and flow cells in caries biofilm formation is presented. The development of new techniques and equipment has led to a deeper understanding of how caries biofilms function. Biofilm models have also been used in the development of materials inhibiting secondary caries. This short review summarizes available models to study these questions.

Objectives: The objective of this study was to investigate the effect of different glass ionomer cements on secondary caries inhibition in a fully automated in vitro biofilm model.Materials and methods: One hundred and twenty-four extracted third molars received class V cavities and were filled with one conventional (Ketac Molar/KM), and two resin-modified glass ionomer cements (Photac Fil/PF, Ketac N100/KN, 3M Espe). A bonded resin composite (Single Bond Plus/Filtek Supreme XTE) served as control. After 14 days water storage at 37 °C, specimens were thermocycled (10,000 × 5/55 °C). Over a period of 10 days, specimens were subjected to cariogenic challenge for 3/4/6 h/day. Demineralization was caused by Streptococcus mutans (DSM 20523) alternatingly being rinsed over specimens using artificial saliva. After biological loading, teeth were cut longitudinally and demineralization depths were evaluated at the margins and at a distance of 0.5 mm from the margins using fluorescence microscopy. Marginal quality was investigated under a SEM at ×200 magnification.Results: Four-hour demineralization depths were for enamel margins (EM), enamel (E), dentin margin (DM), and dentin (D) (μm ± SD): KM: EM 12 ± 8, E 33 ± 7, DM 56 ± 11, D 79 ± 6; PF: EM 19 ± 13, E 34 ± 13, DM 53 ± 10, D 77 ± 12; and KN: EM 26 ± 5, E 38 ± 6, DM 57 ± 11, D 71 ± 7. For all glass ionomer cements (GICs), demineralization depth at the margins was less compared to 0.5 mm distance, with demineralization depth having been correlated to duration of cariogenic challenge (ANOVA [mod. LSD, p < 0.05]). Compared to the bonded resin composite, all GICs exhibited caries inhibition at restoration margins in enamel and dentin.Conclusions: Fluoride-releasing GIC materials exhibit a secondary caries inhibiting effect in vitro.Clinical relevance: Glass ionomer cements have a higher secondary caries inhibiting effect than resin composites. [ABSTRACT FROM AUTHOR]

Background and Aims The aim of this study was to evaluate the influence of the composition of the non-volatile wine matrix on the temporal aroma release profile using an artificial mouth device coupled online to a proton transfer reaction - time-of-flight - mass spectrometer ( PTR- ToF- MS). Methods and Results Five wines, white, sparkling, young red, aged red and sweet wines, were lyophilised, de-aromatised and reconstituted to equal ethanol concentration and spiked with eight target aroma compounds and human saliva. Aroma release was monitored in real time by using an artificial mouth coupled to a PTR- ToF- MS. Matrix composition had a considerable influence on the temporal aroma release parameters [maximum intensity: Imax and area under the curve ( AUC)] in the first 30 s of aroma monitoring. In general, red wines showed the highest aroma release, sweet wines the lowest. Conclusions The physicochemical characteristics of the aroma compounds and the wine matrix composition play a significant role on the temporal aroma release from wines. The formation of complexes between wine polyphenols and saliva glycoproteins appears to change wine polarity favoring the release of hydrophobic aroma compounds. Significance of the Study This study has highlighted the importance of considering the wine non-volatile composition as a necessary parameter to understand wine aroma perception during the dynamics of wine intake. [ABSTRACT FROM AUTHOR]

• Total playability area and correct tuned playability area are measured for the saxophone. • Adjusting lip position extends the total dynamic range of the sound pressure. • Objective parameters are defined to characterize the playability of a saxophone mouthpiece. The embouchure of a musician plays a crucial role in the correct tuning of an instrument. This work examines the influence of lip position, lip force and blowing pressure on the tuning of an alto saxophone mouthpiece. The measurements were collected by means of an artificial mouth setup which mimics the realistic playing condition. The range of lip forces and blowing pressures in which the mouthpiece generates a chosen note, is defined as the total playability area (TPA) for that note. Sound pressure level within the TPA and correct tuning playability area (CTPA) are measured for four different lip positions. Sound pressure is nearly independent of blowing pressure but increases strongly with decreasing lip force. The slope of this decrease is a characterization of the mouthpiece. In the airflow/pressure zone where sound is being produced, airflow increases as blowing pressure decreases, so an extrapolated airflow at zero blowing pressure can be calculated. The hydrodynamic resistance and extrapolated airflow are calculated for all notes and averages and variabilities are determined as parameters which characterize the mouthpiece. Results confirm that the lowest notes on a saxophone are difficult to play in an acceptable tuning. Adjusting lip position extends the total dynamic range of the sound pressure. The hydrodynamic resistance is similar across notes. The extrapolated airflow strongly depends on note. The study provides foundation for objective characterization of the playability of different mouthpiece types. [ABSTRACT FROM AUTHOR]

Abstract: The impact of odour on taste has been widely studied and it is less the case for aroma and texture perceptions. The relations between odour and texture notably are not very clear and results from previous works are not in accordance. Furthermore, there is little information on the impact of an odour, representative of an aroma released in human mouth, presented via the orthonasal route on other perceptions. Most of the time, investigations dealing with sensory interactions were carried out on food model matrices which lead to a problem for extrapolation of the results to real food products. The aim of the study was to measure the impact of an odorant flow on aroma, taste and texture perceptions when eating a complex real food. To fulfill the objective, apple was chosen as a complex and familiar real food matrix and an innovative device, called ‘Mouth to Nose Merging System’ was designed, validated and used in this work. It involved (1) an in vitro chewing simulator called ‘artificial mouth’ and delivering an odorant extract similar to the aroma released in human mouth; (2) in vivo olfactory receptors of a judge’s nose, from a trained panel. The study showed that apple texture perception can be modified by the apple odorant extract. The latter did not modify aroma and taste perception. The method gave promising results for investigating cognitive interactions resulting from food consumption as odour and texture interactions were underlined. [Copyright &y& Elsevier]

Alumina-toughened zirconia (ATZ) is a possible alternative material to titanium for oral implants. No data are available on the fracture strength of ATZ oral implants. The purpose of this study was to examine one-piece implants made of ATZ ceramic under artificial loading conditions and to compare the fracture strength of these implants with implants fabricated from tetragonal zirconium dioxide poylcrystal (TZP)-A. A total of 72 implants, 48 ATZ implants (groups A and B) and 24 TZP-A implants (group C), were investigated. A chamfer preparation at the implant heads was performed on all implants of groups B and C. Eight implants of each group underwent 1.2 or five million thermomechanical loading cycles in the chewing simulator (load value: 98 N). Further eight implants of each group were not cyclic loaded. Finally, the fracture strength of all implants was determined using a universal testing machine. No implant fractured during loading in the chewing simulator. All implants were placed in the universal testing machine to evaluate fracture strength. The mean fracture strength values±standard deviations for the implants without artificial loading were 1734±165 N (ATZ, no preparation), 1220±85 N (ATZ, with preparation), and 578±49 N (TZP-A, with preparation); 1489±190 N (ATZ, no preparation), 1064±121 N (ATZ, with preparation), and 607±57 N (TZP-A, with preparation) with 1.2 million loading cycles; and 1358±187 N (ATZ, no preparation), 1098±97 N (ATZ, with preparation), and 516±45 N (TZP-A, with preparation) with five million cycles. The ATZ implants showed significantly higher mean fracture strengths compared with the TZP-A implants. Modification of the implant head using diamond burs and increased loading time also led to a significant decrease in fracture strength. The ATZ implants showed an increased mechanical stability compared with the TZP-A. Modification of the implant head resulted in a decrease in fracture strength. However, within the limits of this in vitro investigation it can be concluded that ATZ implants will withstand functional loading over an estimated period of 20 years. Kohal R-J, Wolkewitz M, Mueller C. Alumina-reinforced zirconia implants: survival rate and fracture strength in a masticatory simulation trial. Clin. Oral Impl. Res. , 2010; 1345-1352. doi: 10.1111/j.1600-0501.2010.01954.x [ABSTRACT FROM AUTHOR]

Objectives: The aim of this pilot study was to investigate the anticaries activity of a nanoemulsion composed of soybean oil, water, Triton X-100 and cetylpyridinium chloride.Methods: Tooth blocks (3 mm length x 3 mm width x 2 mm thickness) were cut from smooth surfaces of selected molar teeth using a water-cooled diamond wire saw. The blocks were randomly assigned to three experimental groups: (A) nanoemulsion, (B) 0.12% chlorhexidine gluconate, and (C) no treatment. The formation of dental caries in human tooth enamel was tested using a continuous flow dual-organism (Streptococcus mutans and Lactobacillus casei), biofilm model, which acts as an artificial mouth and simulates the biological and physiological activities observed within the oral environment. Experimental groups A and B were treated with their respective solutions once daily for 30 s on each occasion, while group C received no treatment. 10% sucrose was supplied every 6 h for 6 min to simulate meals and pH cycling. The experiment lasted for 5 days, and the tooth blocks were harvested and processed for demineralization assessment using transverse microradiography (TMR).Results: For both lesion depth and mineral loss, statistical analysis indicated that Emulsion was significantly lower than Control and Chlorhexidine, and Chlorhexidine was significantly lower than Control.Conclusions: We conclude that cetylpyridinium-containing nanoemulsions appear to present a feasible means of preventing the occurrence of early caries. [ABSTRACT FROM AUTHOR]

The study conducted in a bacterial-based in vitro caries model aimed to determine whether typical inner secondary caries lesions can be detected at cavity walls of restorations with selected gap widths when the development of outer lesions is inhibited. Sixty bovine tooth specimens were randomly assigned to the following groups: test group 50 (TG50; gap, 50 μm), test group 100 (TG100; gap, 100 μm), test group 250 (TG250; gap, 250 μm) and a control group (CG; gap, 250 μm). The outer tooth surface of the test group specimens was covered with an acid-resistant varnish to inhibit the development of an outer caries lesion. After incubation in the caries model, the area of demineralization at the cavity wall was determined by confocal laser scanning microscopy. All test group specimens demonstrated only wall lesions. The CG specimens developed outer and wall lesions. The TG250 specimens showed significantly less wall lesion area compared to the CG ( p < 0.05). In the test groups, a statistically significant increase ( p < 0.05) in lesion area could be detected in enamel between TG50 and TG250 and in dentine between TG50 and TG100. In conclusion, the inner wall lesions of secondary caries can develop without the presence of outer lesions and therefore can be regarded as an entity on their own. The extent of independently developed wall lesions increased with gap width in the present setting. [ABSTRACT FROM AUTHOR]

Background: Zirconia oral implants are a new topic in implant dentistry. So far, no data are available on the biomechanical behavior of two-piece zirconia implants. Therefore, the purpose of this pilot investigation was to test in vitro the fracture strength of two-piece cylindrical zirconia implants after aging in a chewing simulator. Materials and Methods: This laboratory in vitro investigation comprised three different treatment groups. Each group consisted of 16 specimens. In group 1, two-piece zirconia implants were restored with zirconia crowns (zirconia copings veneered with Triceram®; Esprident, Ispringen, Germany), and in group 2 zirconia implants received Empress® 2 single crowns (Ivoclar Vivadent AG, Schaan, Liechtenstein). The implants, including the abutments, in the two zirconia groups were identical. In group 3, similar titanium implants were reconstructed with porcelain-fused-to-metal crowns. Eight samples of each group were submitted to artificial aging with a long-term load test in the artificial mouth (chewing simulator). Subsequently, all not artificially aged samples and all artificially aged samples that survived the long-term loading of each group were submitted to a fracture strength test in a universal testing machine. For the pairwise comparisons in the different test groups with or without artificial loading and between the different groups at a given artificial loading condition, the Wilcoxon rank-sum test for independent samples was used. The significance level was set at 5%. Results: One sample of group 1 (veneer fracture), none of group 2, and six samples of group 3 (implant abutment screw fractures) failed while exposed to the artificial mouth. The values for the fracture strength after artificial loading with 1.2 million cycles for group 1 were between 45 and 377 N (mean: 275.7 N), in group 2 between 240 and 314 N (mean: 280.7 N), and in the titanium group between 45 and 582 N (mean: 165.7 N). The fracture strength results without artificial load for group 1 amounted to between 270 and 393 N (mean: 325.1 N), for group 2 between 235 and 321 N (mean: 281.8 N), and between 474 and 765 N (mean: 595.2 N) for the titanium group. The failure mode during the fracture testing in the zirconia implant groups was a fracture of the implant head and a bending/fracture of the abutment screw in the titanium group. Conclusions: Within the limits of this pilot investigation, the biomechanical stability of all tested prototype implant groups seems to be – compared with the possibly exerted occlusal forces – borderline for clinical use. A high number of failures occurred already during the artificial loading in the titanium group at the abutment screw level. The zirconia implant groups showed irreparable implant head fractures at relatively low fracture loads. Therefore, the clinical use of the presented prototype implants has to be questioned. [ABSTRACT FROM AUTHOR]

Background: Zirconia (ZrO2) might be an alternative material to titanium (Ti) for dental implant fabrication. However, no data are available on the fracture strength of one-piece ZrO2 oral implants. Purpose: The objective of this study was to evaluate the fracture strength of ZrO2 implants after exposure to the artificial mouth. Materials and Methods: One hundred twenty ZrO2 and Ti implants were used. The Ti implants were divided into two control groups (A and B). ZrO2 implants manufactured from yttria-stabilized tetragonal ZrO2 polycrystal (Y-TZP) in group C, from Y-TZP dotted with alumina (Y-TZP-A) in group D, and from Y-TZP-A with a modified surface in groups E and F were used. In group F, the implant heads were prepared, and in group G, the implants were restored with ZrO2 crowns. Each group included 16 samples with the exception of group D, which included 24 samples. A subgroup of each implant type (eight implants) was subjected to thermomechanical cycling in a chewing simulator prior to fracture testing. Test specimens were then loaded until a fracture occurred. Results: Seven of the 120 samples failed in the chewing simulator. ZrO2 implant fracture occurred at 725 to 850 N when the implants were not prepared, and at 539 to 607 N when prepared. The samples in group A fractured at the level of the abutment screw. All ZrO2 implants fractured at the level of the Technovit® resin (Heraeus Kulzer GmbH & Co., Wehrheim, Germany). No fracture of the ZrO2 crowns in group G was observed. Conclusion: Mean fracture strength values obtained were all within the limits of clinical acceptance. However, implant preparation had a statistically significant negative influence on the implant fracture strength. Long-term clinical data are necessary before one-piece ZrO2 implants can be recommended for daily practice. [ABSTRACT FROM AUTHOR]

Abstract: This work aimed to select artificial mouth extraction conditions to obtain an aroma extract of bread close to that perceived in the human mouth in terms of similarity and intensity. Once the representative extraction conditions were determined, they were used to show the influence of mastication and the effect of saliva on bread aroma release. The significance of mastication was shown by comparing headspace aromatic extracts with artificial mouth extracts. The results showed that headspace extraction, associated with a previous crushing of bread, did not provide an extract similar to that obtained after mastication. The determination of the influence of saliva on bread aroma was done respecting the ratio between saliva and bread in the human oral cavity. The results revealed that bread was crushed differently in the presence of saliva than in the presence of water. In addition, saliva had a significant influence on the volatile composition of bread extracts. [Copyright &y& Elsevier]

The prevalence of root-surface caries is increasing. We hypothesized that some restorative materials are protective against cariogenic challenge on root surfaces. Our goal was to study the effects of different restorative materials on root surfaces incubated with an oral biofilm generated in an artificial mouth. A biofilm of Streptococcus mutans, Streptococcus sobrinus, Lactobacillus rhamnosus, and Actinomyces naeslundii was co-cultured for 21 days on 24 glass-ionomer cement, resin-modified glass-ionomer cement, or resin-composite-restored root surfaces. These surfaces were then examined with Fourier transform infrared spectroscopy and scanning electron energy-dispersive spectroscopy. Only glass-ionomer restorations showed a significant increase in log calcium-to-phosphorus ratio (P < 0.01), and a significantly lower log amide I-to-hydrogen phosphate ratio on the root surface after incubation in the artificial mouth. Glass-ionomer restoratives conferred a preventive effect on the root surfaces against initial cariogenic challenge with a mixed-species oral biofilm without therapeutic intervention. [ABSTRACT FROM AUTHOR]

Objectives: The purpose of this pilot investigation was to test whether zirconia implants restored with different all-ceramic crowns would fulfill the biomechanical requirements for clinical use. Therefore, all-ceramic Empress®-1 and Procera® crowns were cemented on zirconia implants and exposed to the artificial mouth. Afterwards, the fracture strength of the all-ceramic implant–crown systems was evaluated. Conventional titanium implants restored with porcelain-fused-to-metal (PFM) crowns served as controls. Material and methods: Sixteen titanium implants with 16 PFM crowns and 32 zirconia implants with 16 Empress®-1 crowns and 16 Procera® crowns each—i.e., three implant–crown groups—were used in this investigation. The titanium implants were fabricated using the ReImplant® system and the zirconia implants using the Celay® system. The upper left central incisor served as a model for the fabrication of the implants and the crowns. Eight samples of each group were submitted to a long-term load test in the artificial mouth (1.2 million chewing cycles). Subsequently, a fracture strength test was performed with seven of the eight crowns. The remaining eight samples of each group were not submitted to the long-term load in the artificial mouth but were fracture-tested immediately. One loaded and one unloaded sample of each group were evaluated regarding the marginal fit of the crowns. Results: All test samples survived the exposure to the artificial mouth. Three Empress®-1 crowns showed cracks in the area of the loading steatite ball. The values for the fracture load in the titanium implant–PFM crown group without artificial loading ranged between 420 and 610 N (mean: 531.4 N), between 460 and 570 N (mean: 512.9 N) in the Empress®-1 crown group, and in the Procera® crown group the values were between 475 and 700 N (mean: 575.7 N) when not loaded artificially. The results when the specimens were loaded artificially with 1.2 million cycles were as follows: the titanium implant–PFM crowns fractured between 440 and 950 N (mean: 668.6 N), the Empress®-1 crowns between 290 and 550 N (mean: 410.7 N), and the Procera® crowns between 450 and 725 N (mean: 555.5 N). No statistically significant differences could be found among the groups without artificial load. The fracture values for the PFM and the Procera® crowns after artificial loading were statistically significantly higher than that for the loaded Empress®-1 crowns. There was no significant difference between the PFM crown group and the Procera® group. Conclusions: Within the limits of this pilot investigation, it seems that zirconia implants restored with the Procera® crowns possibly fulfill the biomechanical requirements for anterior teeth. However, further investigations with larger sample sizes have to confirm these preliminary results. As three Empress®-1 crowns showed crack development in the loading area of the steatite balls in the artificial mouth, their clinical use on zirconia implants has to be questioned. [ABSTRACT FROM AUTHOR]

The artificial mouth is a robotic device that simulates a human mouth. It consists of moveable lips and an adjustable air supply. In this study the use of a genetic algorithm to compute air pressure and lip pressure values so that the artificial mouth can correctly play five notes on a brass instrument is investigated. In order to properly play a brass instrument, a player must apply proper tension between the lips and apply proper airflow so that the lips vibrate at the proper frequency. A fast search algorithm was needed because it takes about 4 seconds to measure the frequency produced by each combination of pressure parameters. This measurement is slow because of the slow moving mechanics of the system and a delay produced while the notes are measured for pitch. The efficiency of this algorithm was compared to an exhaustive search. Experimentation was performed using various combinations of genetic parameters, including population size, crossover rate, and mutation rate. The genetic search was shown to be about 10 times faster than the exhaustive search because the genetic algorithm searches only very small portions of the search space. [ABSTRACT FROM AUTHOR]

The purpose of this in vitro study was to evaluate the fracture resistance of single-tooth implant-supported all-ceramic restorations, composed of zirconium dioxide all ceramic restorations on different implant abutments, and to identify the weakest component of the restorative system. Forty-eight standardized maxillary central incisor zirconia crowns (Procera) were fabricated for two test groups and one control group (group Al: alumina abutments; group Zr: zirconia abutments; control group Ti: titanium abutments). All abutments were placed on the implants (Replace) using titanium screws. The crowns were adhesively luted using a resin luting agent (Panavia 21) and artificially aged through dynamic loading and thermal cycling. Afterwards, all specimens were tested for fracture resistance using compressive load on the palatal surfaces of the crowns. Pair-wise Wilcoxon rank tests were performed to test for differences in fracture resistance values with a global significance level of 0·05. All test specimens survived aging in the artificial mouth. No screw loosening was recorded. The median fracture resistance was 1251, 241 and 457 N for groups Ti, Al and Zr respectively. Statistically significant differences were found for the comparisons of group Ti with groups Al and Zr ( P < 0·00001), and for the comparison of group Al with Zr ( P < 0·00001). Results of this study showed that all tested implant-supported restorations have the potential to withstand physiological occlusal forces applied in the anterior region. Because of the low fracture resistance values of group Al, the combination of zirconia crowns and alumina abutments should carefully be considered before clinical application. [ABSTRACT FROM AUTHOR]

Summary: Objectives: This in vitro study tested the influence of diverse stress simulation parameters on the fracture strength of all-ceramic three-unit fixed partial dentures (FPDs). Methods: All-ceramic FPDs made of Empress 2 (Ivoclar-Vivadent, FL) were exposed to thermal cycling and mechanical loading (TCML) with varying loading parameters such as chewing force (amount, frequency), thermal loading, lateral jaw motion, abutment material, artificial periodontium or antagonistic denture. To investigate the influence of the abutment material, human teeth, polymer abutments and alloy abutments were used. Two different TCML devices with pneumatic or weight loading were compared. FPDs without aging were used as a control. Results and Significance: Combined thermal and mechanical loading significantly reduced the FPD fracture resistance from 1832N to 410N. Duplication of chewing frequency, phase load increase or additional lateral movement did not effect the results. Increasing chewing force, artificial periodontium, and antagonist or abutment material reduced the fracture resistance of the tested FPDs. Different devices with weight or pneumatic loading had no significant influence on the loading capacity of the FPDs. Artificial aging should be performed combining thermal cycling with mechanical loading. Simulation of the artificial periodontium, human antagonists and abutments should be included to achieve a significant aging. [Copyright &y& Elsevier]

The objective of the study was to investigate the association between the presence of residual caries (inner affected dentin) on the cavity walls of cavity preparations and the further development of secondary caries lesions. Two 2 × 5 × 2 mm cavities, one in the apical portion (A) and one in the cervical portion (C) of the root, were prepared on both the lingual (L) and buccal (B) surfaces of 18 extracted human roots. The apical cavities (AB and AL) were artificially demineralized for 30 min using a decalcifying solution, followed by staining with a caries detector dye and then excavation of irreversibly demineralized dentin, leaving behind a layer of inner carious dentin. The cervical cavities (CB and CL) remained intact with sound dentin on the cavity walls. All cavities were then restored with composite resin. Following restoration, lingual specimens (AL and CL) were completely covered by an acid-resistant varnish to prevent further demineralization. All specimens were then incubated in an in vitro microbial artificial mouth model for 3 days in order to develop secondary carious lesions. At the end of the study all specimens were processed for energy-dispersive X-ray analysis of Ca concentration adjacent to the border between dentin and restoration. Statistical analysis of Ca concentrations revealed that the presence of affected inner dentin does not increase the susceptibility to secondary caries. Therefore, it was concluded that conservative cavity preparations leaving behind affected dentin do not increase the risk of secondary caries development. Copyright © 2006 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Summary: Objectives: The aim of the study was to establish a bacterial based in vitro caries model to test the caries preventive effect of fissure sealants and to investigate whether a self-etching adhesive (Xeno III) used as fissure sealant is equally effective in preventing secondary caries compared to a conventional sealant (Delton) when applied on saliva contaminated and non-contaminated fissures. Methods: Forty caries-free upper premolars were randomly divided into two groups. Group A was sealed with a conventional resin-based fissure sealant (Delton) after phosphoric acid etching. Group B was sealed with a self-etching adhesive (Xeno III) without prior etching. To simulate the clinical situation of saliva contamination, the distal part of each tooth was slightly moistened with saliva before sealant application. After thermo-cycling, the specimens were exposed to a cariogenic Streptococcus mutans biofilm in an artificial mouth model. Depths of demineralization were measured on serial sections by confocal laser scanning microscopy. If a demineralization was detected underneath the whole fissure sealing the sample was rated as ‘total failure’. Results: Significantly higher numbers of total failures could be found in the Xeno III group compared to the Delton group in areas without saliva contamination. On contaminated areas, no significant difference could be found. There was no significant difference regarding the depth of the primary carious lesions between groups. Conclusion: The study supports our recent findings that our caries model is capable to produce secondary caries-like lesions at fissure sealings. Based on the present in vitro data, it cannot be recommended to use the self-etching adhesive Xeno III solely as a fissure sealant. [Copyright &y& Elsevier]

We report on the development and the initial testing of a new microbial-based caries model. Specimens were fixed on a rotating mount within a reaction chamber hermetically surrounded by a sterilised glove box. A cariogenic environment was obtained by inoculation with Streptococcus mutans (ATCC 25175) combined with a continuously repeating supply of sucrose solution, trypticase soy broth and artificial saliva applied by dripping. Twenty-five caries-free upper premolars were used. The mesial parts of the occlusal fissures had been sealed with a resin-based fissure sealant (test group 1). To produce marginal gaps, the distal parts had been moistened with saliva before resin application (test group 2). Five teeth served as control and were exposed to all fluids under sterile conditions before being removed from the system after 7 days. Test specimens were infected with S. mutans and were incubated for another 14 days. No unintentional contamination occurred during the 3-week period of operation. Demineralizations were evaluated by using confocal laser scanning microscopy. Only the test specimens showed clearly visible signs of biofilm formation and caries-like lesions. The mean primary lesion depth did not differ significantly between test groups. Wall lesion depths and surface areas of demineralizations underneath the fissure sealants were significantly higher in test group 2. Thus, our model allows the simultaneous production of primary and secondary caries-like enamel lesions in a considerable number of specimens and facilitates the possibility to manipulate and transfer them without necessarily terminating the experiment, opening new possibilities for in vitro caries research. Copyright © 2005 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

The question of what limits the amplitude of the oscillations of clarinet-like instruments is investigated. The study is based on numerical simulations in which two kind of losses are taken into account: linear losses and non-linear losses localised at the open end of the tube. The influence of the amount of losses on the saturation process and on the playing range of clarinet-like instruments is shown. Results are confirmed by experiments using an artificial mouth in which the non-linear losses are varied using several terminations with different geometries. [Copyright &y& Elsevier]

The complexity of the oral environment, and ethical problems associated with studies of oral diseases in humans inevitably directed the attention to development of laboratory models, that simulate the human oral microcosm. These developments and in particular the in vitro ‘artificial mouth’ systems have progressed from simple and basic apparatus devised by Magitot and Miller at the end of 19th century to the currently available, highly sophisticated, computer-controlled, multi-station artificial mouth systems. These advances have metamorphosed from the early studies devised primarily to investigate factors affecting the carious process to the present designs that evaluate growth, pathogenicity, metabolism and mineralization of dental plaque under highly controlled conditions. The modern ‘artificial mouth systems’ can evaluate microbial interactions in simulated dental plaque and similar biofilms and monitor their physical, chemical, biological and molecular features to a very high degree of accuracy. We review and trace here the historical aspects and developments leading to the currently available artificial mouth systems and discuss their contribution to the study of oral flora, especially related to many variants of dental caries. [Copyright &y& Elsevier]

Survival rate and fracture strength of incisors restored with different post and core systems after exposure in the artificial mouth. The survival rate and fracture resistance of 40 decapitated endodontically treated maxillary central incisors using four different post and core systems covered with all-ceramic copings was evaluated after exposure in the artificial mouth. Ten samples of the following post and core systems were investigated: high precious metal post (Permador®*) and core (Olympia®[sup †]) (A), zirconia post (Cerapost®*) with a pre-fabricated bonded ceramic core (Ceracap®*) (B), resin-ceramic post (experimental) with a pre-fabricated bonded ceramic core (Ceracap®) (C) anda zirconia post (Cerapost®) with a custom made ceramic core (Cosmo Ingots®[sup ‡]) (D). The all-ceramic copings (Procera®[sup §]) were cemented using Panavia TC®[sup ¶]. The survival rates after 1 200 000 cycles in the artificial mouth are as follows: 90% (A), 80% (B), 60% (C) and 100% (D). The results of the means and standard deviations (s.d.) of the fracture resistance during static loading are: 1270 ± 312·5 (A), 1494·5 ± 333·5 (B), 1146·7 ± 182·6 (C) and 463·3 ± 46·2 (D). There are statistically significant differences between all groups with the exception of A and B, and A and C (Wilcoxon test). None of the zirconia posts with custom made ceramic cores covered with all-ceramic copings fractured during dynamic loading in the artificial mouth. The mean fracture strength during static loading was less favourable than that of groups A, B and C but above the clinical necessary level. [ABSTRACT FROM AUTHOR]