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The aim of the current investigation was to evaluate the fracture resistance of one-piece zirconia oral implants with and without all-ceramic incisor crowns after long-term thermomechanical cycling. A total of 48 implants were evaluated. The groups with crowns (C, 24 samples) and without crowns (N, 24 samples) were subdivided according to the loading protocol, resulting in three groups of 8 samples each: Group “0” was not exposed to cyclic loading, whereas groups “5” and “10” were loaded with 5 and 10 million chewing cycles, respectively. This resulted in 6 different groups: C0/N0, C5/N5 and C10/N10. Subsequently, all 48 implants were statically loaded to fracture and bending moments were calculated. All implants survived the artificial aging. For the static loading the following average bending moments were calculated: C0: 326 Ncm, C5: 339 Ncm, C10: 369 Ncm, N0: 339 Ncm, N5: 398 Ncm and N10: 355 Ncm. To a certain extent, thermomechanical cycling resulted in an increase of fracture resistance which did not prove to be statistically significant. Regarding its fracture resistance, the evaluated ceramic implant system made of Y-TZP seems to be able to resist physiological chewing forces long-term. Restauration with all-ceramic single crowns showed no negative influence on fracture resistance.

Sound source characteristics may be one of the main causes of objective speech intelligibility metric inaccuracy. In this study, the influences of the sound source directivity and frequency response were investigated using three typical sound sources: an artificial mouth, a monitor speaker, and a dodecahedral sound source. The results show that, the simultaneous influences of directivity and frequency response on the objective speech intelligibility metric are significant, typically with a variation of 0.147 in speech transmission index (STI); sound source directivity may also result in a noticeable difference in the objective speech intelligibility metric, typically with a variation of 0.123 in STI. In comparison with sound sources with a high directivity index (DI), the measurement results for sound sources with a relatively low DI may be higher when background noise is high, and may be lower when background noise is low. The influence of sound source directivity may also depend on the room acoustic conditions, and at receiver position where reflections are abundant, the influence of sound source directivity may be more significant. Not applying frequency response equalisation resulted in large errors in the values being measured, which deviate from the real values of STI by up to 0.172, depending on the original frequency response characteristics of the sound sources that are used.

Objectives To investigate the effect of saliva substitutes on enamel erosion in vitro. Methods A total of 204 bovine enamel samples were embedded in acrylic resin and allocated to 17 groups (n = 12). The specimens were eroded in an artificial mouth (3 days; 6 × 30 s/days, flow rate: 2 ml/min) using citric acid (pH: 2.5). Immediately after the erosive attacks, saliva substitutes (12 sprays, 3 gels) were applied. Between the erosive cycles the specimens were rinsed with artificial saliva (flowrate: 0.5 ml/min). A SnCl2/AmF/NaF-containing mouthrinse was used as positive control, water spray served as negative control. Enamel loss was measured profilometrically and the data were analyzed using one-way ANOVA followed by Scheffe’s post hoc tests (p Results Four saliva substitutes increased enamel erosion, probably due to the low pH or the content of citric acid. Several saliva substitutes were able to reduce enamel erosion significantly by 60–90% (in the range of the positive control). The protective potential of these products was in the range of the positive control (reduction of enamel loss to 30% of negative control). The erosion-protective potential of these high-viscous products is probably related to their film-forming properties, leading to a mechanical protection of the surface. Conclusion Saliva substitutes containing a very low pH exhibit a distinct erosive potential, while most high-viscous products present an erosion-protective effect. It can be recommended that patients suffering from xerostomia and at high risk for dental erosion should use high-viscous saliva substitutes, but should avoid saliva substitutes with low pH or containing citric acid. Clinical significance It can be recommended that patients suffering from xerostomia and at high risk for dental erosion should use high-viscous saliva substitutes, but should avoid saliva substitutes with low pH or containing citric acid.

Background: Various materials have been used for treating dental caries. Dental caries is a disease that attacks hard tissues of the teeth. The initial phase of caries is a formation of bacterial biofilm, called as dental plaque. Dental restorative materials are expected for preventing secondary caries formation initiated by dental plaque. Initial bacterial adhesion is assumed to be an important stage of dental plaque formation. Bacteria that recognize the receptor for binding to the pellicle on tooth surface are known as initial bacterial colonies. One of the bacteria that plays a role in the early stage of dental plaque formation is Streptococcus mutans (S. mutans). Artificial mouth system (AMS) used in bacterial biofilm research on the oral cavity provides the real condition of oral cavity and continous and intermittent supply of nutrients for bacteria. Purpose: This study aimed to compare the profile of S. mutans bacterial adhesion as the primary etiologic agent for dental caries between using static method and using artificial mouth system, a dinamic. method (AMS). Method: The study was conducted at Faculty of Dentistry and Integrated Research and testing laboratory (LPPT) in Universitas Gadjah Mada from April to August 2015. Composite resin was used as the subject of this research. Twelve composite resins with a diameter of 5 mm and a width of 2 mm were divided into two groups, namely group using static method and group using dynamic method. Static method was performed by submerging the samples into a 100µl suspension of 1.5 x 10 8 CFU/ml S. mutans and 200µl BHI broth. Meanwhile AMS method was carried out by placing the samples at the AMS tube drained with 20 drops/minute of bacterial suspension and sterile aquadest. After 72 hours, five samples from each group were calculated for their biofilm mass using 1% crystal violet and read by a spectrofotometer with a wavelength of 570 nm. Meanwhile, one sample from each group was taken for its surface image using Scanning Electron Microscope (SEM). Result: The results showed that S. mutans biofilm mass in the group using static method was 0.34, while in the group using AMS method was 0.09. The results of the statistical analysis then showed that there was a significant difference (p=0.02) in the formation of bacterial biofilm mass between those groups. SEM image in the group using static method also showed that the attachment of S. mutans was more numerous and had a longer chain than in the group using AMS method. Conclusion: There is a difference in the profile of S. mutans bacterial adhesion between using AMS method and static method.

The authors want to thank O. François (University of Auvergne) for his involvement in the development of the AM2 apparatus and in preparing the figures; and P. Riordan for English revision; Developing masticatory apparatus, chewing robots or an artificial mouth is an old but ever more important goal in food science, nutrition or dental research fields, as reflected by the number of existing digital or biomechanical systems. Whatever the objective of the approach, basic knowledge of the physiology of mastication, adaptation and neurophysiological control is absolutely needed before conceiving an apparatus. Obviously, the final step in the development of a mastication simulator is its validation before performing food or food bolus characterization. This validation step is imperative to avoid biased interpretation and can be performed through in vivo–in vitro comparison of particle size distributions in food boluses obtained after normal mastication. This kind of validated machine offers the chance to produce boluses for other related uses such as nutrient bioaccessibility or digestion studies, for example. Such an apparatus can also be employed to simulate different dental states or ageing conditions

Objective The study aimed to evaluate the erosive effects of acids flowing with different velocities and duration on dentin previously pre-treated with distilled water or human saliva. Methods Bovine dentin surfaces were submitted to a 10 min demineralisation with hydrochloric or citric acid (pH 2.3, 37 °C) in an artificial mouth at flow rates of 3, 2.25, 1.5, 0.75 or 0.15 ml/min or in 30 ml of the respective acid without movement (each subgroup n = 16 specimens). Prior to the demineralisation, half of the specimens of each group were either pre-treated with distilled water or human saliva for 120 min. After 2, 5 and 10 min demineralisation, profilometric traces of dentin loss were performed perpendicular to the direction of acid flow at three sites (A–C) with intervals of 500 μm. The first profile (A) was taken in a distance of 1.5 mm from the acid starting to flow over the sample. Thus, median dentin loss at each site was calculated and statistically analysed by five-way ANOVA. Results Dentin loss increased with increasing acid flow rate and demineralisation time and was higher for demineralisation with citric acid compared to hydrochloric acid. For given flow rates of 0.15 to 3 ml/min, measurement of dentin loss yielded highest values for site A and decreasing values for sites B and C. For all groups, no significant differences of dentin loss were observed between specimens pre-treated with distilled water or human saliva. Conclusion Under the conditions of this study, both duration of demineralisation and acid flow rate but not pre-treatment with distilled water or saliva influence the extent of dentin erosion.

Objective To evaluate the fracture resistance of two-piece zirconia oral implants after long-term thermomechanical cycling in an aqueous environment. Non-loaded samples and a one-piece implant system served as control groups. Methods A total of 48 zirconia implants were evaluated: 16 one-piece implants (ATZ; Group A) and 32 differently connected two-piece implants (16 screwed, Group B; 16 bonded, Group C) made of Y-TZP-A (implant+abutment; B) and Y-TZP-A/ATZ (implant/abutment; C), respectively. These groups were divided into two subgroups composed of 8 samples. The samples of subgroups 1 (A1, B1, C1) were not exposed to any cyclic loading, whereas subgroups 2 (A2, B2, C2) were loaded with 10 million cycles (98 N). Subsequently, all 48 implants were statically loaded to fracture. Results A constant load on distinct lever arms resulted in different exerted bending moments during the dynamic loading (A2: 23.4 Ncm, B2: 17.9 Ncm, C2: 32.3 Ncm). All implants survived the long-term thermomechanical cycling. For the static loading the following average bending moments were calculated: A1/A2: 362/399 Ncm; B1/B2: 398/346 Ncm; C1/C2: 380/252 Ncm. Foregoing dynamic loading significantly increased fracture resistance of Group A implants, whereas Group B/C implants showed significantly decreased values. Potentially owed to the experimental setup in an aqueous environment of 60 °C, 5/8 C2 samples showed mobility between implant and abutment due to debonding after dynamic loading conditions. Significance The evaluated ceramic implant systems seem to be able to resist physiological chewing forces long-term. Within the limitations of the experimental setup, the connecting mechanism of Group C implants might be a weak point.

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.

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.

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.

Summary. Objectives. Glass ionomer cements (GIC) have been modified in an attempt to improve their mechanical properties. The objective of the present paper was to compare the two-body and three-body wear of four modified GIC. The tested materials were Fuji IX (GC Corporation), Hi-Fi (Shofu) and Ketac Molar Aplicap (3M/ESPE). The cermet cement Ketac Silver Maxicap (3M/ESPE) was used as reference material. Methods. Two-body wear tests were carried out in the computer controlled ‘artificial mouth’ of the Munich Dental School, three-body wear was tested with the ACTA wear machine. Results. The resulting average two-body wear rates (in µm) were: Fuji IX 327 (SD ± 82)

Complete removal of failed posterior resin composite fillings is time-expensive and involves the risk of removing sound tooth substance. In any case of failure within the composite material, intra-oral repair would be favourable. This in vitro study was conducted to examine the effect of different preparation and bonding modes on integrity of repaired restorations. Forty-eight direct Class II resin composite restorations (Syntac Classic/Tetric Ceram) were placed in extracted human third molars. The specimens were stored for 365 days and then replaced partially by removing the central part of the proximal box with all margins located in composite. The partial repairs were placed with the same materials after pre-treatment with a silicon carbide bur and Syntac Classic (n = 8). Preparation modes have been (i) box-only parallel, (ii) box-only with undercuts, (iii) box with undercuts and additional occlusal retention. The repairs were performed either with (i) Tetric Ceram or with (ii) Tetric Flow as thin lining covered with Tetric Ceram. Before and after thermomechanical loading (100 000 cycles of 50 N and 2500 cycles between +5 and +55 degrees C in an artificial mouth), marginal quality between aged and freshly applied composite was evaluated by SEM at x200 magnification and microleakage was observed by light microscopy at x50 magnification. Box-only preparations exhibited a better fatigue resistance than preparations with additional occlusal retention. This observation was independent from the presence of undercuts (P < 0.05). An intermediary layer of flowable resin composite tended to result in better marginal quality, however, not being statistically significant.

Objective: Aspects of an Artificial Mouth System (AMS) to model the caries process in bovine enamel biofilm induced white spot enamel lesions (WSEL) were analyzed. Methods: Square shaped and polished bovine enamel slabs were covered with modeling wax and 2.5 mm diameter window was prepared to expose enamel surface at the center of each slab. Artificial biofilms were grown inside an AMS on the slabs using freshly cultured S. mutans (MT8148) in suspended in phosphate buffered saline (PBS), heart infusion (HI) with 1% sucrose and PBS for 20, 30 and 40 hrs at 37°C. The severity of demineralization was quantified by Quantitative Light-induced Fluorescence (QLF, Inspektor, Netherlands). All experiments were repeated three times (n=5 for each group). Results: A circular WSEL could clearly be detected at the center of each slab by naked eyes, which was prominent after dehydration by mild air drying. QLF data showed that severity of demineralization occurred with the increase of time interval, after 40 hours both ΔF (23+/-2.9) and ΔQ (148.75+/- 26.78) were significantly more compared to ΔF (10.14+/-2.3) and ΔQ (47.63+/-30.67) of 20 hours. Conclusion: An advanced in vitro model of biolfilm induced WSEL was developed that showed promises to be useful in studying enamel demineralization. DOI: http://dx.doi.org/10.3329/cdcj.v9i1.11829 City Dental College Journal Vol.9(1) 2012 4-6

The in vitro marginal fit of five different all-ceramic crown systems (In-Ceram, Empress staining technique, Empress veneering technique, Celay feldspathic system, Celay In-Ceram system) was evaluated before and after cyclic preloading in an artificial mouth. The crowns were adhesively luted to extracted natural maxillary incisors prepared with a 90 degrees shoulder. The results were compared to those for porcelain-fused-to-metal (PFM) crowns with circular porcelain-butt margins which were cemented with zinc phosphate cement. The analysis of the marginal discrepancies showed significant (P < 0.001) differences among the groups. Crown cementation increased the marginal gaps significantly (P < 0.01). Empress staining technique crowns showed the smallest marginal gaps (median 47 microm), followed by conventional In-Ceram crowns (median 60 microm) and Empress veneer technique crowns (median 62 microm). Celay In-Ceram crowns displayed marginal openings with a median of 78 microm, followed by Celay feldspathic crowns with a median of 99 microm. The marginal gap of the PFM control crowns showed a median of 64 microm. Ageing in the chewing simulator had no significant influence on the marginal fit of all specimens. The study indicates that all the tested all-ceramic crowns have clinically acceptable margins. However, in vivo investigations of all all-ceramic crown systems should be made before clinical routine.

OBJECTIVE This in vitro study aimed to investigate the preventive effect of brushing with anti-erosive toothpastes compared to a conventional fluoride toothpaste on dentine erosion. MATERIALS AND METHODS Bovine dentine specimens (n=12 per subgroup) were eroded in an artificial mouth (6 days, 6×30 s/day) using either citric acid (pH:2.5) or a hydrochloric acid/pepsin solution (pH:1.6), simulating extrinsic or intrinsic erosive conditions, respectively. In between, the specimens were rinsed with artificial saliva. Twice daily, the specimens were brushed for 15 s in an automatic brushing machine at 2.5 N with a conventional fluoride toothpaste slurry (elmex, AmF) or toothpaste slurries with anti-erosive formulations: Apacare (NaF/1% nHAP), Biorepair (ZnCO3-HAP), Chitodent (Chitosan), elmex Erosionsschutz (NaF/AmF/SnCl2/Chitosan), mirasensitive hap (NaF/30% HAP), Sensodyne Proschmelz (NaF/KNO3). Unbrushed specimens served as control. Dentine loss was measured profilometrically and statistically analysed using two-way and one-way ANOVA followed by Scheffe's post hoc tests. RDA-values of all toothpastes were determined, and linear mixed models were applied to analyse the influence of toothpaste abrasivity on dentine wear (p

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.

Bovine enamel has been a good model for human enamel across a broad range of studies. The present work sought to consider if bovine enamel would be a suitable substitute for human enamel in experiments on simulated oral lubrication. Enamel samples of the same size were prepared from bovine and human teeth for use as maxillary and mandibular elements in a miniature artificial mouth. Sliding speeds from 1.99 to 7.84 mm/s and occlusal forces of 3.8-19.5 N were used. Water and four solutions consisting of a mucin-rich fraction, a statherin-rich fraction, 3[(3-cholamidopropyl)-dimethylammonio]-1-propanesulphonate and sodium dodecyl sulphate were evaluated. The high correlations between widely different lubricants on the two enamel substrates gives confidence in the use of bovine enamel as a model for human enamel in salivary lubrication studies. Knoop hardness indentations on enamel samples were combined with friction data and calculations of the true contact area to give a method for the indirect determination of surface shear. The calculated surface shear value was compared with published values obtained by punch shear testing.

The release of mercury vapor from class I amalgam restorations prepared in human molar teeth was studied during chewing simulations in an artificial mouth of a bi-axial servo-hydraulic mechanical test system. So that the total mercury released from the restoration over a fixed time could be determined, a closed chamber surrounded the envelope of chewing motion. In addition, the influence of sampling frequency on mercury release was corrected by the use of different sampling frequencies over a fixed time interval of mercury release measurement and extrapolation to zero sampling time. Thus, a combination of a closed environment and an extrapolation method to determine the mercury release under continuous sampling was used to determine the mercury released under normal breathing conditions. The measured mercury release rate data were used to calculate the potential daily mercury dose in a patient due to a single amalgam restoration, following the method previously outlined by Berglund. The mercury release from both a conventional and a high-copper amalgam was evaluated at different age intervals after the restoration was placed in the teeth. The results show that while the age of the amalgam and the amalgam type influence the extent of mercury release during the initial non-steady-state conditions, the steady-state value of mercury daily dose due to a single amalgam filling is 0.03 ug/day, which is well below the calculated threshold-limiting value (TLV) of 82.29 μg/day considered dangerous for occupational exposure in the United States.

In brass instruments the player's lips are used as a control valve that allows an oscillating flow of air into the instrument. The behaviour of this valve, the lip-reed, is determined by both the pressure difference across the lips and the open area between the lips. Computer simulations of brass instrument playing frequently represent the lips as an oscillating system with one degree of freedom, representing the height of the lip opening. This study aims to provide experimental evidence to determine values of an exponential coefficient q defining the area-height function for the lips of trombone players. A high speed digital video camera and transparent mouthpiece have been used to produce detailed images of the motion of the vibrating lips of a range of musicians and an artificial mouth over a large set of playing frequencies and sound levels. These images are analysed to investigate how the open area varies as a function of the height between the lips.

It is well established that the development of new technologies for early detection and quantitative monitoring of dental caries at its early stage could provide health and economic benefits ranging from timely preventive interventions to reduction of the time required for clinical trials of anti-caries agents. However, the new technologies currently used in clinical setting cannot assess and monitor caries using the actual mineral concentration within the lesion, while a laboratory-based microcomputed tomography (MCT) has been shown to possess this capability. Thus we envision the establishment of mathematical equations relating the measurements of each of the clinical technologies to that of MCT will enable the mineral concentration of lesions detected and assessed in clinical practice to be extrapolated from the equation, and this will facilitate preventitive care in dentistry to lower treatment cost. We utilize MCT and the two prominent clinical caries assessment devices (Quantitative Light-induced Fluorescence [QLF] and Diagnodent) to longitudinally monitor the development of caries in a continuous flow mixed-organisms biofilm model (artificial mouth), and then used the collected data to establish mathematical equation relating the measurements of each of the clinical technologies to that of MCT. A linear correlation was observed between the measurements of MicroCT and that of QLF and Diagnodent. Thus mineral density in a carious lesion detected and measured using QLF or Diagnodent can be extrapolated using the developed equation. This highlights the usefulness of MCT for monitoring the progress of an early caries being treated with therapeutic agents in clinical practice or trials.

International audience

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.

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.Keywords: dental caries; batch culture; continuous culture; artificial mouth; flow cell; microcosm(Published: 3 March 2015)Citation: Journal of Oral Microbiology 2015, 7: 26149 - http://dx.doi.org/10.3402/jom.v7.2614

The objective was to investigate associations between the results of an in vitro and an in vivo study using an artificial mouth and a study of adhesive fixed partial dentures (AFPD) begun in 1985 [1]. Twenty extracted human molars and 20 human upper incisors were inserted into PMMA resin, 6 mm apart to represent a gap. Two preparation methods (identical to those in in vivo conditions) were used: a retentive preparation technique (posterior) and a non-retentive preparation technique (anterior). The frameworks of the bridges consisted of CoCr-alloy with a ceramic veneered pontic to replace the missing tooth. The bonding surfaces of the posterior AFPDs were conditioned with a tribochemical system, while the anterior AFPDs were sandblasted. All AFPDs were inserted using a dual curing composite cement. During thermal-cycling and mechanical loading (TCML: 6000 x 5 degrees C, 1.2 x 10(6) x 50 N, 1.66 Hz) in an artificial environment, the frequency and type of failures were observed. The above mentioned loading parameters were hypothesized to represent a period of 5 years under oral conditions. The results were compared to those of similar bridge-types in the in vivo study. The Kaplan-Meier estimations showed similar graphs for in vivo and in vitro with both types of AFPDs. In vivo and in vitro, the retentively prepared AFPDs were markedly more successful. With regard to the failure types, the simulation-parameters seemed to represent a loading stress that was comparable to in vivo conditions.

The manufacture of musical instruments is a domain where the know-how is primordial and rules of the profession are hard to explain and to formalise. In this article we present a new experimental approach with the aim of assisting the manufacture of musical instruments. In this perspective, we have developed an “artificial mouth” that permits to make objective tests on instruments (trumpet or trombone), overlooking the natural adaptation faculty of the musician.

BRUNSTROM, J. M., A. W. MacRAE, and B. ROBERTS. Mouth-state dependent changes in the judged pleasantness of water at different temperatures. PHYSIOL BEHAV 61 (5) 667–669, 1996.—Dehydration increases the pleasantness of cold (0°C) water (Boulze et al., 1983, Physiol. Behav. 30:97–102, 1983). The hypothesis that the mouth dryness induced by dehydration mediates this hedonic shift was investigated. Hydrated assessors ( n = 16) judged 3°C water as more pleasant after artificial mouth drying than did controls ( n = 16). Mouth drying failed to influence similar judgements of water 13°C, 23°C, and 33°C. We propose that preference shifts depend on temperature because cold water offers more rewarding relief from the sensations resulting from mouth dryness. Measures on saliva production were consistent with this proposal. Assessors swilled with water (3°C, 13°C, 23°C, and 33°C) for 5 s and then emptied their mouths. Measures of subsequent saliva flow confirmed that cold (3°C) water induces an elevated rate of saliva flow and consequently leaves the mouth in a wetter state.

Mechanisms of salivary lubrication can be quantitatively measured by a reduction in the coefficient of friction. It is important that lubrication be assessed under the conditions of the oral cavity to properly assess lubrication regimes. The relative lubricity of three artificial salivas and two controls were assessed at a bovine enamel interface in an artificial mouth with a range of conditions that approximate oral function. Statistical analysis indicated that the enamel lubricity of sodium dodecylsul-fate (SDS) and Oracare-D saliva substitutes were different from the other saliva substitutes and water. The low friction with Oracare-D and SDS saliva substitutes was because of resident amphipaths adsorbed at the enamel interface. Amphipaths adsorbed on enamel may provide a reduction in interocculsal friction and its resulting complications for patients with xerostomia.

The objectives of this review are to compare the models that are used to simulate the caries process in cardiology research and to suggest how these models might be used to assess caries-inhibitory properties of dental materials. Available caries-simulation models fall into the following classifications: 1) in vitro demineralization using acid buffers, 2) in vitro demineralization using bacterially generated acids, 3) in vitro demineralization/remineralization using a pH-cycling system, 4) an artificial mouth where a bacterially generated acid challenge is interspersed with a "saliva" treatment, 5) in vivo animal model (generally with rats), 6) in situ demineralization and/or remineralization using enamel or dentin blocks or slices in the human mouth, and 7) in vivo studies using teeth scheduled for extraction in the human mouth. Most dental materials studies have used simple in vitro demineralization models or component release experiments, each of which is inadequate to answer the questions that are being asked about the caries-inhibitory properties of the material being tested. Experimental methods must be chosen with care to ensure that the material to be tested is examined in an appropriate mode. The ultimate goal is to correctly predict clinical outcomes. The design or redesign of a model must eventually be tied to documented clinical outcomes to improve the model and allow for future successful development of new materials.

International audience; The influence of the first and second resonance frequencies on tuning, timbre (or tone colour) and ease of playing is investigated for reed instruments, such as the clarinet, alto saxophone and oboe. Theoretical analyses of the eflects of the reed and the player embouchure (i.e. lip position and pressure on the reed) are reviewed, as well as the consequences of inharmonicity in the resonance frequencies. This review allows us to present interesting interpretations of the numerous experiments reported here. Three kinds of results are given: (I) comparison of playing frequencies andfirst resonance frequencies, for severalfmgerings with or without open register hole, leading to the deJinition of a frequency independent length correction for the embouchure; (2) examination of the eflect of inharmonicity of the two jirst resonance frequencies on both tone colour and ease of playing, the causes coming from either the player embouchure or the instrument construction; (3) comparison between theory and experiment for the inharmonicity produced by the changes in conicity in oboes, leading to an interpretation of the maker's choices. The results show how judicious use of simple tools, such as calculations or measurements of input impedance or playing data obtained using an arttjicial mouth, can be of help to the understanding of instrument construction and to the instrument designer.

The serpent is a lip‐excited wind instrument with an air column length of around 2 m and an approximately conical bore. In the form in which it emerged in France in the sixteenth century, it is a wooden tube with six finger holes and a chromatic compass of three octaves. The serpent suffers from some problems related to the fact that all the holes are covered directly by the fingers. The holes are grouped in two clusters, and the hole diameter is too small to provide adequate venting. The ophicleide, invented in the early nineteenth century, has a similar bore profile to the serpent. Eleven or more side holes in the thin‐walled metal tube are covered by lever‐operated padded keys; these allow most notes to be obtained without cross fingering, and the size and placing of the holes are not limited by the anatomy of the human hand. Several acoustical investigation techniques, including input impedance analysis, pulse reflectometry and excitation by an artificial mouth, have been used to investigate the extent to which the ophicleide is a successful solution to the acoustical problems posed by the serpent.

The interaction of fluoride with plaque and the underlying enamel was studied in an artificial mouth after topical application of three different fluoride solutions. Streptococcus mutans

The retention and behaviour of fluoride contained in plaque and underlying enamel has been studied in the artificial mouth. Artificial plaque was grown either on bovine enamel or on platinum foil. At

口呼吸における口腔内外の気流の実態を把握するために, 流体力学的手法を用いて流れの可視化を行った. 可視化実験に先立って, 銅板製のヒト口腔3倍大矢状断模型で等電位線の測定を行い, 口腔内外の気流の傾向や概略が推測できた. 引き続いてプラスチック製の口腔模型を用いて, 色素法やアルミ粉トレーサー懸濁法による水流実験を行った. その結果としては, (1) 口腔に流入する空気は, とくに下唇下方からの流れが直接皮膚面に沿って進入する. (2) 口呼吸時の吸気の方向や速度は, 上下切歯の植立角度や開口度, また被蓋関係に強く影響される. (3) 前歯の被蓋関係が正常な場合, 上下切歯の切歯間を高速で通過した層流は, その幅を拡げることなく, 上顎切歯の口蓋面に沿って進み, この歯の歯肉に衝突したのち, 大部分は口蓋から若干離れて咽頭へ進む. (4)流れの可視化法は口呼吸の実態解明にきわめて有効な方法であると考える.

To induce artificial mouth breathing on experimental animals has extremely been difficult because of its immediate death following nasal sealing treatment, and we could find only an imitating experiment reported by Butcher et al (J. Periodont. 32: 38, 1961). The purpose of this study is to induce absolute mouth breathing in rats and to investigate histopathological changes of their gingival tissues. Thirty six of Wister strain rats were equally divided into control and experimental groups. To induce absolute mouth breathing artificially, the nose of all experimental animals were sutured using thin wire and metallic buttones. After two weeks of experimental period, animals were sacrificed and materials were obtained.Consequently, we could find much more remarkable hyperkeratinization of epithelial layers in the experimental animals than the control. Inf lammatoric changes, however, were found in both groups of animals, but less in control. As the conclusion of this investigation, absolute mouth breathing may induce hyperkeratinization of the epithelial tissues, but does not initiate gingival inflammation following two weeks of experiment.

Sound human premolar teeth were incubated with Streptococcus mutans in an artificial mouth for 6 days. The enamel lesions produced were studied by microradiography and in polarized light. The lesions displayed an almost intact surface zone and a banded appearance in the underlying demineralized zone, although all the features of slowly progressing natural lesions were not seen.

The wear of dental amalgam by a smear mechanism and amalgam transfer onto the opposing cusp was confirmed by simulated studies in an artificial mouth. The coefficient of wear for dental amalgam was 4.89×10−5. Calculation of the coefficient of friction for the enamel/amalgam couple indicated that friction was overcome by shallow slippage and shear within the amalgam. On the basis of these facts, the good wear performance of both the amalgam and the opposing enamel was rationalized. A retrospective clinical correlation of amalgam wear in an artificial mouth showed a correlation coefficient of 0.938 as far as the mean wear values were concerned. Further the wear rates in both studies were linear except in a narrow region at time zero. The variances, however, in the 2 studies were very different. The desirability of in vitro studies to reproduce the same variance, as well as the same mean values, is a point for further discussion and experimentation.

A method for measuring frictional forces on enamel of natural teeth and restorative materials was developed using the Artificial Oral Environment. Enamel/enamel systems were tested using different oral fluids in a minienvironmental chamber capable of introducing biologic fluids between the occluding surfaces. Matched, extracted opposing human premolars mounted in physiologic occlusion under an occlusal load of 3 pounds were bruxed at approximate masticatory velocities. A load cell measured the resulting horizontal forces and an X-Y record was attained. 31 independent measurements of friction in both buccal and lingual directions were performed with the teeth dry, and with human saliva, Xerolube, and distilled water intervening. It was found that typical values for enamel/enamel coefficients of friction, μ, were in the range of 0.1–0.42. μ was independent of different fluids within any one enamel/enamel couple (coefficient of variation was typically 10%). However, the coefficient of friction of the enamel pair was highly dependent on surface texture. Roughening virgin enamel led to a 3 fold increase in μ. Conversely surfactants present in mineral oil reduced the friction of roughened enamel by 3 fold. Where the wear process is by abrasion it is likely that the reduction of the tangential forces due to friction could lead to reduced loss of contour. It is likely that finishing procedures in dentistry are important in this process. Finally, the production of low friction restorative materials are clearly indicated as a future development.

The oral cavity supports a great diversity of micro-organisms, ranging from aerobes to strict anaerobes. The tooth surface, saliva and soft tissues each contain their own commensal flora. Dental plaque, the microbial community on the tooth surface, has been the subject of much investigation because of its role in the aetiology of both dental caries and periodontal disease. Two different approaches have been used to simulate the oral environment in an attempt to understand microbial behaviour in the mouth: one of these is the artificial mouth, the other is the chemostat.

The wear of a posterior composite against a maxillary palatal cusp was studied in an artificial mouth. The coefficient of wear for the composite was 2.58×10 −5 . A retrospective clinical correlation with composite wear in the artificial mouth showed a correlation coefficient of 0.84 at 1 year of wear. The artificial mouth studies support a parabolic relationship between depth of composite wear and time. The ratio of 6 months depth of wear compared to 3 years was found to be 41% which supports the Leinfelder finding (5) of 49%. However, the correlation with the linear studies of Braem (2,3) was good as far as the mean depth of wear at 1 year was concerned. The disagreement between the linear and parabolic studies is small during the early wear process, but becomes serious during a longer term. It is important for future clinical wear studies to resolve the question of the nature of the wear rate curve in posterior composites, if accurate prediction of long term performance is to be achieved.

The integration of two closed mechanical loops was used to produce a force-movement cycle, using servo-hydraulics. Several of the parameters were of interest in clinically-simulated laboratory studies. The system represented the first phase in developing an artificial oral environment.

A new system for in vitro decalcification, the agar-saliva method, has been used to produce gross carious lesions which closely resemble, by all available criteria, those produced by the carious process in the mouth. In addition, incipient lesions have been formed rapidly and have been found to be indistinguishable histochemically and microradiographically from natural lesions. The method is rapid and effective for evaluating anticaries agents, as determined by comparing materials whose action in clinical trials has been reported in the literature. A similar discrimination of known agents was produced by the use of the Pigman artificial mouth. Stannous fluoride (2%) was shown to be a more effective agent than sodium fluoride (2%), a result which agrees with clinical reports. In comparisons at lower concentrations, stannous fluoride was found to be even more strikingly superior to sodium fluoride in preventing decalcification in the in vitro system. A dentifrice containing stannous fluoride was found to be an effective agent against decalcification. The caries reducing effect of this dentifrice has been shown in clinical studies. The more effective application of the dentifrice was found to be a brushing technique, as opposed to a simple covering of the teeth with the paste. Examples have been shown to illustrate visual, fluorescent, transmitted light and microradiographic techniques for evaluating progress of decalcification in in vitro systems.

For the work described in this report, freshly extracted teeth were mounted in plastic boxes and the surfaces were photographed at a magnification of about 8×. The mounted teeth were placed in cylindrical glass funnels and a bacteriologic medium was allowed to flow dropwise over the individual teeth. The teeth were inoculated at weekly intervals by soaking for thirty minutes in a sample of pooled saliva. Usually at regular intervals, the teeth were examined at a magnification of 30× and photographed when necessary. Under these conditions, lesions of the enamel have been produced which are very similar in appearance and position to natural carious lesions. By the use of bilaterally identical teeth, it has been shown that tooth surfaces brushed twice daily remain fairly sound for long periods, whereas unbrushed or roughened areas soften rapidly. Typical regions of attack of brushed teeth are developmental pits and grooves, particularly on the occlusal surfaces, proximal surfaces, and cervical areas near the cementoenamel junction. The mode of attack is quite different when a strictly decalcifying medium is used without bacterial development. Individual teeth exhibit considerable difference in resistance to enamel attack. Apparently deciduous and unerupted teeth are much less resistant than old erupted teeth. Enamel attack has been observed only when glucose is present in the media, and when streptococci, lactobacilli, or both have developed. In the absence of glucose, the tooth surfaces remain intact for long periods. Dentine is decalcified under these conditions, but usually the structure is retained. Some instances of dentine destruction have been noted; in current investigations the conditions necessary for dentine destruction are under active investigation.

Attention is drawn to the advantages of the so-called “artificial mouth” in investigations into experimental lesions similar to caries. The design of an all-glass apparatus suitable for multiple operation is described. Continuous and intermittent flow feed systems and a siphon for supplying Seitz filtered saliva have been evolved. The methods used for mounting and sterilizing the experimental teeth are described. It has been possible to produce, by salivary inoculation, a bacterial plaque on a sterile tooth surface.