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Results for “DENTAL MODELS”

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At least 1,369 records · Page 76Linked to original sources
PubMed2005

[Application of slightly acidic hypochlorous acid water to the dental field--setting expansion and compressive strength of dental gypsum mixed with slightly acidic hypochlorous acid water].

PURPOSE: This study investigated both the setting expansion and compressive strength of dental gypsum mixed with slightly acidic hypochlorous acid water for the prevention of hospital infection. METHODS: Slightly acidic hypochlorous acid water (PURESTER Mp-240B, Morinaga Milk Industry) was used to mix each of three types of gypsum (model plaster, dental stone and high strength dental stone), and both the setting expansion and compressive strength of these gypsum products were analyzed in comparison with those mixed with tap water. RESULTS: 1. With regard to the setting expansion, a significant difference was not observed between gypsum products mixed with the two types of water, except for both the model plaster and dental stone 30 minutes after the start of mixing. 2. Regarding the compressive strength, a significant difference was not observed between gypsum products mixed with the two types of water, except for the model plaster 90 minutes after the start of mixing. CONCLUSIONS: From the results of the study, it was revealed that both the setting expansion and compressive strength of gypsum products using the slightly acidic hypochlorous acid water showed almost the same characteristics as those using tap water.

Calcium Sulfate↗
PubMed2000

Teaching and assessing behavioural techniques of applied relaxation for reduction of dental fear using a controlled chairside simulation model.

This paper describes a novel method of teaching and assessing relaxation techniques using a controlled chairside simulation model. 50 pre-clinical dental undergraduates provided an evaluation of the teaching model as part of their basic clinical skills teaching. Students were required to demonstrate applied relaxation techniques according to 2 pre-selected clinical vignettes. Inter-observer reliability of assessing student competence was calculated on a varied sample (n=9) using 2 independent observers and found to be adequate. The majority of the students viewed the teaching and assessment method as interesting and clinically relevant. However, a few students reported that the method was less advantageous than using a real patient. It is concluded that using vignettes as part of clinical training accompanied by video-based feedback provides a resourceful learning tool for pre-clinical teaching in the absence of patient contact.

Clinical Competence↗
PubMedDate not supplied

Dental caries and microbial acid production in twins.

OBJECTIVE: To determine the relative contribution of genetic and environmental stimuli on dental caries traits and microbial acid production in a twin model. METHODS: Dental caries examinations and microbial acid production assays were performed on 388 pairs of twins 1.5-8 years old from the city of Montes Claros, Brazil. Genotyping 8 polymorphic DNA markers determined zygosity. Caries exams followed NIDCR criteria modified to distinguish white spot lesions from cavitated lesions. Surface-based caries prevalence rates (SBCPR) were computed and lesion severity was determined by a weighted index (LSI). Biofilm samples were collected from the tongue using a lactic acid indicator swab. Assay scores were categorized based on acid formation as 1 = low, 2 = medium, and 3 = high. Heritability analyses were performed using the SOLAR software package. RESULTS: Heritability estimates for SBCPRs, LSI and for microbial acid production were H = 76.3 (p < 0.001), H = 70.6 (p < 0.001), H = 16.2 (p = 0.0078), respectively. Treating microbial acid production as a covariate in the SBCPR and LSI models did not significantly alter the heritability estimates, i.e. H = 76.5 (p < 0.001) and H = 70.8 (p < 0.001), respectively. CONCLUSIONS: These results suggest that variation in dental caries surface traits has a significant genetic contribution and that microbial acid production is modulated by the environment.

Acids↗
PubMed1976

Analysis of tooth marks in a homicide case. Observations by means of visual description, stereo-photography, scanning electron microscopy and stereometric graphic plotting.

In 1957 a woman was murdered in Oslo. Her left breast exhibited tooth marks. A man was arrested and sentenced to life imprisonment partly because of the dental evidence. He never admitted guilt and filed a petition for retrial. The present author was appointed as new dental expert. The material consisted of the fixed breast, models of the bite mark and models of the teeth of the convict, and several photographs. By means of visual examination, a magnifying glass, a lens stereoscope and a stereomicroscope characteristic details were noted. Stereoscopic picture pairs were taken, the material was studied by means of scanning electron microscopy and a stereometricgraphic plotting method permitting the outline of the tooth mark or the biting edge of a tooth to be registered in great detail in all three dimensions in the form of a contour map. This method has not previously been applied in the analysis of tooth marks in human skin. These examinations revealed no discrepancies but showed many corresponding characteristic features between the tooth marks and the teeth of the convict, resulting in the conclusion that it is highly probable that the tooth marks in the breast were made by the teeth of the convict.

Bites and Stings↗
PubMed2005

[Tissue engineering of dentin-pulp complex-like structures by human dental mesenchymal cells].

OBJECTIVE: To establish three-dimensional culture model of human dental mesenchymal cells and bioengineer in vivo with ceramic bovine bone (CBB) and Collagraft as scaffolds. METHODS: Human dental mesenchymal cells induced upon stimulation of bFGF and IGF-1 or TGF-beta(1) were implanted onto CBB and Collagraft containing the same kinds of growth factors respectively. Then cell/scaffold constructs were transplanted into nude mice to establish in vivo culture model of dental mesenchymal cells. Control groups were set up at the same time. After 4 weeks or 10 weeks, the implants were taken out for histological and immunohistochemical analysis. RESULTS: Within 10-week implant tissues, typical dentin-pulp complex-like structures were generated in scaffolds containing growth factors. Human dentin sialoprotein (DSP) was expressed in the newly formed dentin. This phenomenon wasn't observed in control groups and 4-week implants. CONCLUSIONS: Dentin-pulp complex-like structures could be bioengineered successfully with human dental mesenchymal cells and CBB or Collagrafts containing growth factors in nude mice.

Animals↗
PubMed2002

A three-dimensional model for the tooth-loss patterns by multi-plane regression analysis.

The construction of dental condition models is one of the useful methods for analysis of epidemiological surveys. The purpose of this investigation was to make a simple model with clear turning points for the longitudinal tooth-loss patterns of Japanese adults by means of multi-plane regression analysis. Since 1957, the Japanese Ministry of Health and Welfare has carried out national surveys of dental conditions every six years. The data of present tooth numbers by age (24-79 years) and sex from these surveys were used for this study. When there are turning points between two variables, intersecting straight lines regression is a valid means. However, a new method was developed so that the data of this study had three variables. The new three-dimensional model by multi-plane regression analysis seemed to fit tooth-loss patterns of Japanese adults within three phases. Younger subjects are represented in the first phase followed by the third phase of elders, where tooth loss was rather slow. However, in the second phase, middle-aged subjects, people lost their teeth rapidly. Thus, prolongation of the first phase could be an important factor to improve overall dental health.

Adult↗
PubMed2000

Release of prostaglandin E2, IL-6 and IL-8 from human oral epithelial culture models after exposure to compounds of dental materials.

A three-dimensional human tissue model based on TR146 cells isolated from a squamous cell carcinoma of the buccal mucosa was used to test for the release of the proinflammatory molecules prostaglandin E2 (PGE2), interleukin 6 (IL-6), and interleukin 8 (IL-8) after exposure to nickel chloride (NiCl2), cobalt chloride (COCl2), palladium chloride (PdCl2), and triethylene glycol dimethacrylate (TEGDMA). These compounds have documented adverse biological effects in vitro. The release of PGE2 from the tissue culture models was inversely correlated with cell viability (MTT assay). Toxic concentrations of NiCl2 and CoCl2 induced the release of PGE2 by factors of about 200-300 compared to controls, but PdCl2 which was nontoxic enhanced PGE2 levels about 10-fold. TEGDMA, however, did not stimulate PGE2 release. None or weakly toxic concentrations of Ni and Co chloride induced IL-6 and IL-8 release by a factor of 5-10 compared to controls. The amounts of IL-6 were induced 25- to 30-fold by PdCl2 under physiological conditions, and IL-8 levels were also slightly enhanced. Nontoxic TEGDMA concentrations induced IL-6 levels 5-fold, but IL-8 amounts increased only slightly. We conclude that a steep rise of PGE2 is closely associated with cytotoxicity. On the other hand, the specific induction of IL-6 occurs at much lower concentrations. Therefore, the measurement of this cytokine may be included as another parameter in evaluating the biological activity of dental materials under nontoxic experimental conditions in vitro.

Biocompatible Materials↗
PubMed2000

The potential impact of the North American Free Trade Agreement on American dental licensure: a European community model.

Appropriate licensure is a significant barrier to entry to the practice of dentistry. The history of dental licensure in the United States is briefly examined, and current dental licensure requirements in the United States and Mexico are noted. The impact that establishment of the European Community had on dental licensure in Europe is examined, noting that changes were the result of political, rather than professional, input. Requirements of NAFTA are examined to see how they will impact current American dental licensure requirements. Some migration of dental professionals between the United States and Mexico is expected as a result of NAFTA.

Commerce↗
PubMed1994

Chemostat flow cell system: an in vitro model for the evaluation of antiplaque agents.

We developed an experimental in vitro model of dental plaque to assess the potential efficacy of antiplaque agents. The model used a chemostat, which provided a continuous source of 5 species of oral bacteria grown in an artificial "saliva-like" medium. This mixture was pumped through six flow cells, each containing two types of surfaces on which plaque formed and was subsequently measured. Formation of bacterial plaque on hydroxyapatite surfaces was assessed by measurement of the DNA and protein content of the plaque film. The amount of bacterial plaque formed on germanium surfaces was measured by attenuated total reflectance (ATR/FT-IR) spectroscopy. Plaque viability was also assessed by a fluorescent staining technique. The quantity of plaque formed on both types of surfaces gradually increased with the duration of flow (from 24 to 72 h) through the cells during a 72-hour experimental period. The flow cells were then pulsed with experimental treatment solutions for 30 s, twice daily. Parallel to results of human clinical studies, the model was capable of discriminating among water, a placebo mouthrinse, and an active antimicrobial mouthrinse formulation containing 0.03% triclosan. It therefore offers a valuable alternative to animal model testing and allows for more rapid evaluations under well-controlled experimental conditions.

Actinomyces viscosus↗
PubMed2002

The relationship between acid-etch patterns and bond survival in vivo.

The aim of this study was to investigate the relationship between acid-etch quality and bond survival in vivo. The subjects were 29 orthodontic patients. High-resolution silicone impressions were taken of the buccal tooth surfaces after etching for 30 seconds with 37% phosphoric acid. The impressions were replicated in epoxy resin and examined under high magnification in a scanning electron microscope. A 4-point classification system and histometric techniques were used to evaluate etch patterns on the enamel surfaces where orthodontic brackets were to be bonded. After impressions were made, all teeth (including first molars) were bonded with 0.022-in Andrews' prescription brackets ("A" Company, San Diego, Calif) and Right-On composite (TP Orthodontics, Leeds, England). The first date of bond failure for each tooth was recorded; it varied from 1 to 806 days. An ideal etch pattern was found on less than 5% of the orthodontic bonding area; type C pattern (pitted enamel surface) occupied the greatest area. Overall, the failure rate was 55.8% over 26 months; the greatest failure rate occurred in first molars. Multiple regression analysis revealed a positive and statistically significant relationship between the area occupied by ideal etch type and the length of survival of the bond (P <.001).

Acid Etching, Dental↗
PubMed2003

Guided bone regeneration around titanium plasma-sprayed, acid-etched, and hydroxyapatite-coated implants in the canine model.

BACKGROUND: Endosseous dental implants with rough surfaces have been designed to improve early healing, especially in areas of poor bone or insufficient bone quantity. The aim of this study was to histomorphometrically assess the bone-to-implant contact on 3 different rough-surfaced implants following guided bone regeneration. METHODS: Mandibular premolars and first molars were extracted in 12 dogs, and healing was allowed for 6 months. Six implant osteotomy sites were prepared, 3 per side, followed by the creation of 7.3 mm wide by 5 mm deep surgical defects in the coronal section of the osteotomy sites. Ten-mm long titanium screw-type implants with titanium plasma-sprayed (TPS), hydroxyapatite-coated (HA), or acid-etched (AE) surfaces were placed; the surrounding defects were filled with canine demineralized freeze-dried bone allograft; implants/grafts were covered with expanded polytetrafluoroethylene membranes; and the tissue was closed. Following a healing period of 4 months, the animals were sacrificed and mandibular blocks were harvested for histomorphometric analysis. RESULTS: The mean percentage of bone-to-implant contact in the defect and non-defect areas for the different implant surfaces was: AE 16.24% defect, and 28.78% non-defect; TPS 25.08% defect, and 16.96% non-defect; and HA 48.25% defect and 26.60% non-defect. Within the defect, the mean difference in the bone-to-implant contact was significant for HA compared to TPS (P < 0.0001) and HA versus AE (P < 0.0001); TPS versus AE was not significant (P = 0.063). In the non-defect areas, the mean difference in the bone-to-implant contact was significant for AE versus TPS (P = 0.010); all other comparisons were not significant. There were 18 membrane exposures in the 72 implant sites. Data were analyzed again to assess the impact of membrane complications. Using a 1-way analysis of variance, the bone-to-implant contact was compared between the sites with and without membrane complications. No significant differences were seen in the defect areas or in the non-defect areas between the sites with and without membrane complications. CONCLUSION: In this study, the bone-to-implant contact in regenerated bone was greatest when an HA-coated implant was used.

Acid Etching, Dental↗
PubMed1975

The shape of the dental arch.

The shape of the dental arcade was measured in a cross-sectional study of 2,040 sets of maxillary and mandibular study casts of Caucasoids, Mongoloids, and Negroids between 4 and 20 years of age. Three methods of dental arcade analysis were used: dental arch area, dental arch index, and length of the arc of the dental arcade. Each of these computational techniques showed that a different growth pattern was shared by the three ethic groups, and important factor to be taken into consideration in orthodontic treatment.

Adolescent↗