An in vitro microbial-based model for studying caries-preventive agents

Objective. The aim of the study was to develop an in vitro microbial-based caries model to test potentially caries-preventive agents. Material and methods. In this model, cariogenic Streptococcus mutans biofilms are grown on tooth samples within a reaction chamber hermetically surrounded by a bacteria-tight glove box allowing the manipulation of specimens during operation. The specimens were mounted in two rows on the inner and outer rims of a specimen turntable passing several inlet pipes transporting all necessary media. Using 64 lower incisors in 4 experiments, a 10 ppm NaF solution and an experimental potentially caries-preventive glycan solution were tested compared to a water control. The mean lesion depth was determined by confocal laser scanning microscopy. Results. The depths of the caries-like lesions showed no statistically significant difference irrespective of whether the specimens were mounted on the inner or outer rim of the specimen turntable. As expected, the NaF solution inhibited the development of caries-like lesions almost completely. The experimental glycan solution revealed a statistically significantly lower demineralization depth compared to the control and a significantly higher depth compared to the NaF group. The system could be operated over a period of more than 9 weeks without unintentional contamination and the manipulation of the tooth specimens could be accomplished. Conclusions. In conclusion, our in vitro system is suitable for testing potential caries-preventive agents in a reproducible way by using whole tooth samples and offers full access together with the possibility of manipulating the specimens during operation.     

An in vitro microbial-based model for studying caries-preventive agents

OBJECTIVE: The aim of the study was to develop an in vitro microbial-based caries model to test potentially caries-preventive agents. MATERIAL AND METHODS: In this model, cariogenic Streptococcus mutans biofilms are grown on tooth samples within a reaction chamber hermetically surrounded by a bacteria-tight glove box allowing the manipulation of specimens during operation. The specimens were mounted in two rows on the inner and outer rims of a specimen turntable passing several inlet pipes transporting all necessary media. Using 64 lower incisors in 4 experiments, a 10 ppm NaF solution and an experimental potentially caries-preventive glycan solution were tested compared to a water control. The mean lesion depth was determined by confocal laser scanning microscopy. RESULTS: The depths of the caries-like lesions showed no statistically significant difference irrespective of whether the specimens were mounted on the inner or outer rim of the specimen turntable. As expected, the NaF solution inhibited the development of caries-like lesions almost completely. The experimental glycan solution revealed a statistically significantly lower demineralization depth compared to the control and a significantly higher depth compared to the NaF group. The system could be operated over a period of more than 9 weeks without unintentional contamination and the manipulation of the tooth specimens could be accomplished. CONCLUSIONS: In conclusion, our in vitro system is suitable for testing potential caries-preventive agents in a reproducible way by using whole tooth samples and offers full access together with the possibility of manipulating the specimens during operation.     

A novel experimental model for studying transverse orthodontic tooth movement in the rat mandible

Objectives:To establish a rat model of a one-piece mandible using the principles of gingivoperiosteoplasty and guided bone regeneration to fuse the midline symphyseal area.Material and Methods:Twenty-four Sprague-Dawley female rats were divided into two groups: 12 experimental and 12 control. Both groups were imaged using in vivo micro-computed tomography at baseline and at end point (5 months). The experimental group received regenerative surgery at the symphysis area; the control group received no treatment. Outcomes were evaluated by radiographic examination of gross and volumetric bony changes in the symphyseal region of interest marked between the mental foramina bilaterally and the two central incisors near the most coronal margin of the alveolar crests. These landmarks were chosen as they can be reproduced on the computed tomography images at baseline and end point. Histologic examination was performed on all samples at a level 5 mm apical to the alveolar bone crest.Results:Radiologic and histologic examinations of the experimental group revealed complete bony fusion of the symphyseal area in three subjects, partial fusion in five subjects, and thickening of the alveolar bony socket in three subjects; one rat died of anesthesia-related complications. No evidence of fusion or alveolar bone thickening was found in any of the controls.Conclusions:This surgical animal model demonstrates that a rat mandible can be surgically manipulated to mimic the one-piece human mandible. This novel model may prove useful in studying mandibular bone remodeling and orthodontic mandibular tooth movement.     

An accelerated in vitro model for adhesive testing

PURPOSE: To develop a pilot in vitro accelerated laboratory testing protocol for assessing marginal sealing capability of dental adhesives. METHODS: Occlusal cavities were prepared in 20 human molar teeth and restored with Spectrum TPH resin composite. Prime & Bond NT and Prompt L-Pop served as the adhesive for eight teeth each. An experimental self-etching adhesive system was used on the remaining four teeth. Each specimen was subjected in sequential fashion to the following challenges: 400,000 wear cycles in a Leinfelder simulator; 5000 thermocycles between water baths maintained at 5 degrees C and 55 degrees C with a dwell time of 40 seconds in each; and a repetition of the 400,000 wear cycles. Polyvinyl siloxane impressions were made at baseline and after each challenge. Microleakage was assessed following silver nitrate staining and marginal degradation was evaluated using light microscopy and the stone casts made from the impressions taken during the project. RESULTS: Microleakage analysis yielded the following median leakage values: Prime & Bond NT - 0; Prompt L-Pop - 1; and experimental self-etching adhesive - 3. The Wilcoxon sign rank test demonstrated significant differences between all three adhesives (P < or = 0.05). Evaluation of the stone casts demonstrated that marginal gaps were more prevalent after the second wear challenge.     

An artificial biofilm induced secondary caries model for in vitro studies

Background: The aim of this study was to establish a new in vitro model for biofilm induced secondary caries studies using an oral biofilm reactor. Methods: An approximately 2 × 3 × 2 mm³ sized dentino‐enamel Class I cavity was prepared in the middle of a square‐shaped specimen from the mid‐labial portion of bovine incisors. The cavities were partially filled with either Clearfil AP‐X with SE‐Bond or Clearfil AP‐X without any bond. Artificial biofilms were then formed on the resin composite filled surfaces using three species of oral bacteria in an oral biofilm reactor for 20 hours followed by 7‐ or 30‐day incubation periods. Results: The lesions were clearly visible on fluorescence microscopy and by scanning electron microscopy in the enamel at the interface of resin restorations in all samples. The data from image analysis showed that the lesion size was largest in the No‐bond samples with statistically significant differences (p < 0.05). Demineralization along the cavity wall extended deeper in No‐bond compared to SE‐Bond samples and penetration was significantly deeper in No‐bond 30‐day samples. Conclusions: A primary artificial secondary caries model was established using biofilms for in vitro studies and the significance of using a bonding system could also be verified.     

Research methods in dentistry. 6. In vivo and in vitro methods for studying caries lesion progression

This paper describes some of the most used methods for caries lesion progression measurement in in vivo and in vitro research. Clinical measurements are usually limited to visual inspection. Currently available scoring systems and statistical analyses, making use of changes in lesion stage, have the potential to make caries clinical trials more efficient. A method for light fluorescence measurements is capable of measuring small changes in mineral loss for early lesions, In the laboratory, mainly destructive methods are used. The most widely accepted gold standard at the moment is transversal microradiography (TMR). Other microradiographical methods are described, that allow for longitudinal measurements.     

A novel saliva test for caries risk assessment

A new saliva test for caries risk assessment introduced in this study integrates a variety of host factors to predict for children, individual risk levels that are tooth-group specific. These various host factors correlate with caries history, DFT (decayed and filled teeth) or DFS (decayed and filled surfaces) in young adults. The test is based on the pattern of genetically determined oligosaccharides present on salivary glycoproteins. The mechanism behind the test is believed to be centered on the specific oligosaccharides that either facilitate bacterial attachment and colonization at the surface of teeth or protect against colonization by promoting agglutination and removal of free bacteria. It is the ratio of the two classes of oligosaccharides that is very strongly correlated with the numerical range of DFS or DFT observed in a young adult population.     

渗透树脂治疗乳牙釉质早期龋的体外研究

目的：探讨渗透树脂治疗人工脱矿乳牙釉质早期龋对其釉质显微硬度的影响。方法：选取5～7岁儿童因滞留拔除的无龋下颌乳中切牙21颗,制备人工脱矿釉质模型后,随机将其分为空白对照组、脱矿组、渗透树脂治疗组,每组7个样本,采用显微硬度测试仪测量各组牙釉质显微硬度,观察釉质显微硬度的变化。结果：空白对照组、渗透树脂治疗组牙釉质表面显微硬度明显高于脱矿组,差异具有统计学意义（P＜0．01）;渗透树脂治疗组显微硬度低于空白对照组,差异具有统计学意义（P＜0．01）。结论：乳牙釉质脱矿后牙釉质表面显微硬度降低,渗透树脂治疗釉质脱矿可提高牙釉质表面的显微硬度。     

An in vitro comparison of fluorescence-aided caries excavation and conventional excavation by microhardness testing

Objective

The aim of this in vitro study was to compare fluorescence-aided caries excavation with conventional excavation based on the Martens and Vickers hardness of dentin at the cavity floor after caries removal.

Materials and methods

In total, 20 extracted human teeth with dentin caries were bisected through the lesion center into two halves, which were assigned to either the fluorescence-aided caries excavation group or the conventional excavation group. After the treatment, embedding, mounting, and polishing, a line of indentations from the dental pulp across the sound dentin to the cavity floor was made on each sample. The data were compared with Student’s t and Mann–Whitney U tests.

Results

The calculated Vickers hardness of the sound dentin was 57?±?10 kg/mm² in the fluorescence-aided caries excavation group and 59?±?8 kg/mm² in the conventional excavation group, which is consistent with the previous studies. The absolute and relative Martens hardness measurements of the cavity floor were 224?±?93 N/mm² and 46?±?17 %, respectively, in the fluorescence-aided caries excavation group and 412?±?75 N/mm² and 81?±?14 %, respectively, in the conventional excavation group. Based on either the Martens or Vickers hardness, both the absolute and relative microhardness measurements of the cavity floor after fluorescence-aided caries excavation were significantly lower than the values obtained by conventional excavation.

Conclusion

Fluorescence-aided caries excavation showed the tissue-preserving property and was more conservative than the conventional excavation in this in vitro study.     

Efficacy of the dual-action GA-KR12 peptide for remineralising initial enamel caries: an in vitro study

Clinical Oral Investigations - To investigate the antibiofilm and remineralising effects of the dual-action peptide GA-KR12 on artificial enamel caries. Enamel blocks with artificial caries were...     

Development of an in situ root caries model. A. In vitro investigations

OBJECTIVES: The paper describes preliminary in vitro investigations, the objectives of which were to examine the influence of certain experimental parameters on artificial carious lesion formation in root hard tissues, and their remineralisation. These experiments formed part of a wider study that aimed to develop an in situ model of root caries, based on the existing coronal caries model used in Liverpool. The present studies examined the effects (a) of the anatomical origin of the dentine, the presence or absence of cementum, the exposure time and the type of demineralising system, on lesion development, and (b) of baseline lesion size on the extent and location of mineral re-precipitation. METHODS: Mineral content parameters in plano-parallel sections taken from dentine lesions were determined by computer-controlled transverse microradiography. RESULTS: The importance of the anatomical origin of the dentine on lesion formation was investigated by comparing in vitro lesion formation in premolar and molar dentine, and in dentine from apical, middle and coronal thirds of the root: no difference was observed between these sites. Lesions formed more rapidly in acid buffer solutions than in acid gel systems, and were more reliably produced when cementum was removed. The effect of baseline lesion size on subsequent in vitro remineralisation demonstrated that a small baseline mineral content was associated with a larger percentage mineral gain. The location of mineral deposition throughout the lesion was also influenced by baseline mineral content parameters. CONCLUSIONS: The results form a basis for the further development of an in situ dentinal caries model, providing data to suggest that manipulation of parameters involved in the preparation of artificial carious lesions has a significant effect on the behaviour of the lesion, particularly the phenomenon of remineralisation. Further work is needed to investigate the behaviour of the model in situ.     

Caries-preventive potential of an adhesive patch after thermomechanical loading--a microbial-based in vitro study

PURPOSE: To assess the enamel-protective potential of a newly devised adhesive patch for smooth enamel sealing. MATERIALS AND METHODS: Approximal surfaces of 30 extracted molars were divided into three areas: the buccal thirds were treated with a flowable composite (Tetric Flow, Ivoclar Vivadent) and served as negative control sites, the lingual thirds were left untreated and served as positive control sites, and the middle thirds served as the test areas. This was sealed with either 1. a twofold application of an unfilled resin (Heliobond, Ivoclar Vivadent), 2. an adhesive prototype patch (Ivoclar Vivadent), or 3. an adhesive patch in combination with a flowable composite. After thermomechanical loading and demineralization in a microbial-based artificial caries chamber, demineralization depth was assessed using a confocal laser scanning microscope. RESULTS: Negative control sites treated with the flowable composite showed no signs of demineralization. Areas treated with the patch showed no signs of demineralization, irrespective of whether it was used in combination with a flowable composite or directly bonded to the enamel. Caries-like lesions in untreated sites showed a mean depth of 134.3 +/- 35.9 microm. Demineralization depth at sites treated with the unfilled resin was 76.2 +/- 26.5 microm (p = 0.023). CONCLUSIONS: Under the conditions of the present study, the adhesive patch under investigation completely protected the underlying enamel from demineralization. This merits further study to assess its potential as an interproximal sealant.     

A cluster analysis model for caries risk assessment

Cluster analysis was applied to determine, the natural grouping of individuals, among sixty 8-10-year-old children, and to identify the most significant set of markers for risk assessment. The risk clusters were obtained with initial clinical and bacteriological measurements including dmf + DMFS, active caries, mutans streptococci and lactobacilli counts in plaque or saliva on two media, and Snyder's test results. The morbidity clusters were constructed with the final clinical indexes and incidence after 18 months (dependent variables). A risk cluster was identified that included the following significant initial variables; dmf + DMFS, active caries, counts of mutans streptococci from plaque on TSY20B and lactobacilli in saliva, and Snyder's test results. This set of markers identified 86% of the children at high risk who developed high morbidity, as well as 94% of children in the low-risk cluster who developed low or no caries. The results of this investigation provide the basis to develop a system for caries risk assessment.     

A physicochemical bench-scale caries model

A diffusion cell comprising two compartments separated by a commerical membrane of known ion permselectivity was used as an experimental model to study factors which may affect caries formation. One compartment (the "lesion") contained an excess of hydroxyapatite or fluorapatite crystals, and its solution was kept near saturation by stirring. An unsaturated acidic calcium phosphate solution flowed continuously through the other compartment (the "plaque-saliva"), thus providing the driving force for dissolution of the crystals as modified by the permeability of the membrane and/or the presence of fluoride. Calcium, phosphate, fluoride, and chloride concentrations, pH, and membrane potential were measured at steady state. The permselective character of the membrane profoundly affected the solution in the "lesion": The initial Ca/P ratio of 1.6 was shifted, at steady state, to less than 1.1 ("neutral" membrane), to less than 0.48 (cation-permselective membrane), and to 3.3 (anion-permselective membrane). All the membranes caused Ca and PO4 concentrations in the "lesion" to increase (e.g., with the cation-permselective membrane, the Ca 22-fold and the PO4 75-fold). Substantial membrane potentials were encountered in all cases. The pH of the steady-state solution was always less than before diffusion was initiated; the average decrease was 1.1 units. In every case, the pH, and the Ca and PO4 concentrations of the F- -containing solution were less than those in the F- -free solution. The changes induced by the "neutral" membrane were unexpectedly large. In two cases, H3PO4 was diffusing against its chemical potential gradient at steady state. The results are relevant for understanding and for modeling of the caries process.