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PubMed1995

The role of microbiology in models of dental caries.

Models of dental caries (laboratory, animal, and human in situ models) vary markedly in their microbiological complexity. Laboratory models range from mono-cultures of cariogenic species providing an acidic challenge to enamel, to the development of diverse mixed cultures growing on a habitat-simulating medium in an artificial mouth or chemostat. The latter systems are of value in determining either mechanisms of action or cause-and-effect relationships--e.g., between dietary components or antimicrobial agents and the microflora. Laboratory models have also shown that the sensitivity of oral bacteria to inhibitors is markedly reduced when growing in biofilms such as dental plaque. Animal models have proved unequivocally that caries is an infectious and transmissible disease. Their use has enabled comparisons to be made of (a) the cariogenic potential of different bacterial species, (b) the role of the diet, and (c) the effects of potential anti-caries agents. It has been claimed that no caries-protective agent currently in use has failed a rodent test. In situ human models have been designed to permit the development of "natural" plaque on standardized enamel surfaces freely exposed to the human oral environment. The microflora that develops on unadulterated surfaces is similar in composition to that found at comparable sites on vital teeth. Demineralization can be accelerated by the inoculation of additional cariogenic bacteria coupled with either intra- or extra-oral sucrose rinses. The increased realism associated with the transition from laboratory to human in situ models is countered by a reduced ability to control or manipulate the system for experimental purposes. Thus a hierarchy of tests is needed for the study of anti-caries agents, each requiring a varying degree of microbiological complexity.

Animals↗
PubMed1992

Veterinary dental demonstration models.

This article is about dental models and their construction. It is meant to be informative, entertaining and, hopefully, a little lighthearted. The use of dental models in the veterinary practice has become commonplace. The models are useful for demonstrating to clients and colleagues various dental pathologies and procedures.

Animals↗
PubMed2003

A new technique for the creation of a computerized composite skull model.

PURPOSE: The goals of this study were to develop a technique for creating a computerized composite skull model and to test its accuracy. The computerized composite skull model is the combination of a 3-dimensional (3D) computed tomography (CT) bone model with digital dental models. MATERIALS AND METHODS: A dry skull with intact dentition was used in development of the technique. The creation of the computerized composite skull model was divided into 3 steps. The first step was to create digital dental models. The second step was to create a 3D CT bone model of the craniomaxillofacial skeleton. The last step was to incorporate the digital dental models into the 3D CT skull model, creating a computerized composite skull model. The accuracy of the computerized composite skull model was assessed. Bone-to-bone, tooth-to-tooth, and bone-to-tooth measurements were made on the computerized composite skull model and the dry skull. Pearson correlation coefficient and linear regression tests were performed. RESULTS: A technique to create a computerized composite skull model was developed. This computerized model not only represented bony structures from CT data but also reproduced dentition from digital dental models. For the bone-to-bone measurements, the mean difference between the computerized composite skull model and the dry skull was 0.5 +/- 0.6 mm. For the tooth-to-tooth measurements, the mean difference was 0.1 +/- 0.2 mm. For the bone-to-tooth measurements, the mean difference was 0.2 +/- 0.3 mm. CONCLUSIONS: This study showed the feasibility of creating a computerized composite skull model as well as its accuracy.

Cephalometry↗
PubMed2001

Dental education in Queensland I: the 1-3-1 model.

Dental education worldwide is under great pressure. This pressure is being driven not only by changing patterns of oral disease but also by economic factors both inside and outside universities. Technological advances and changing educational philosophies across the board also impact significantly on what we do and how we do it. This article outlines how the School of Dentistry at The University of Queensland is responding to these pressures within the context of local political, educational and economic realities. The so-called 1-3-1 model that has been adopted involves one year of basic science, three years of applied dental science and one year of extramural clinical practice. This model represents a partnership with the Queensland Department of Health and will: Involve dental education and the Dental School in the provision of health care to the community. Place the Dental School in a position to influence the delivery and quality of oral health care in the population and to assume some of the responsibility for it. Provide a wide range of clinical and community experiences for students prior to graduation. Allow the adoption of modern teaching methods such as Problem Based Learning (PBL) in Years II-IV with all the additional benefits e.g. communication skills. Provide an extended clinical period for the acquisition and development of clinical and technical skills prior to graduation. Be cost-effective both to the university and the health service. Allow for outside input without compromising the knowledge and research base. It is recognised that while the 1-3-1 model may meet the demands of a large, decentralised state such as Queensland, it may not be suitable for all institutions. In this context diversity in approach is one of the strengths of dental education, nationally and internationally.

Clinical Competence↗
PubMed1994

Demonstration of a fluoride dose response with an in situ single-section dental caries model.

The in situ dental caries model developed in Glasgow was evaluated by determining whether it could demonstrate a fluoride dose response in a crossover study using 0, 250, and 1,000 ppm F from sodium fluoride dentifrices. In situ appliances, each carrying four enamel sections with multiple artificial carious lesions, were worn by 12 dentate subjects for three 5-week experimental runs, during which they brushed twice daily with a test paste. Mineral changes in the lesions were measured by analyzing microradiographs, using an image analysis system, after 0, 2, 4, and 5 weeks and the rate of change calculated. Two-way analysis of variance showed no significant intersubject effects (for any of the parameters), but demonstrated strong evidence of a linear fluoride dose effect: total mineral loss (delta z) p = 0.0596; lesion body p = 0.0423; surface zone p = 0.0081. However, the exclusion of the data from 1 low-caries (DMFS = 1), high-calculus-forming subject produced even stronger evidence as to the efficacy of this model (delta z p = 0.0226; lesion body p = 0.0164; surface zone p = 0.0081). Hence, these results suggest this model is useful for studying fluoride products according to guidelines of American Dental Association.

Adult↗
PubMed1989

[Changes of bacterial flora on inbred mouse strains using experimental dental caries model].

In the experimental dental caries model using inbred mouse strains, the bacterial flora of lower molars were investigated during the process of caries induction to examine the differences of bacterial flora between the caries susceptive mouse strains (BALB/cA, C57BL/6N) and the caries resistant mouse strain (C3H/HeN), as well as the relation between the bacterial flora and Streptococcus faecalis that seemed to be the pathogen of caries on this caries model. The total cultivable bacterial number immediately after weaning (3 weeks old) was larger in the caries susceptive strains than in the caries resistant strain. The composition of Gram(+) cocci, Gram(+)rods and Gram(-)rods varied in each strain and Gram(-)cocci were not isolated from any of the strains. The proportion of Gram(+)cocci to the total cultivable bacterial number was larger in the caries susceptive strains than in the caries resistant strain, while S. faecalis was the most predominant species in Gram(+)cocci in all strains. It suggests that S. faecalis existed indigenously on the lower molars of mice at the time of weaning (3 weeks old). The total cultivable bacterial number increased in all strains as feeding with Diet-2000 which contains 30% sucrose started. The number reached its peak on the fifth week, and it either remained the same or slightly declined after that. The number of S. faecalis also reached the peak between third and fifth week. The order of 10(5) - to 10(6) S. faecalis was isolated from the caries susceptive strains, and the order of 10(4) from the caries resistant strain throughout the experimental period. It suggests that C3H/HeN (the caries resistant strain) mice have certain caries resistant factors in the genetic background. Toward the end of the experimental period, S. acidominimus in the caries susceptive mice and Staphylococcus sciuri in the caries resistant mice increased and replaced S. faecalis. Gram(+)rods also increased in the caries susceptive strains. It seems that Gram(+)rods have some relation with the progress of advanced dental caries.

Animals↗
PubMed2006

Dental attrition models predicting temporomandibular joint disease or masticatory muscle pain versus asymptomatic controls.

AIMS: To determine whether patients with temporomandibular joint disease or masticatory muscle pain can be usefully differentiated from asymptomatic controls using multifactorial classification tree models of attrition severity and/or rates. METHODS: Measures of attrition severity and rates in patients diagnosed with disc displacement (n = 52), osteoarthrosis (n = 74), or masticatory muscle pain only (n = 43) were compared against those in asymptomatic controls (n = 132). Cross-validated classification tree models were tested for fit with sensitivity, specificity, accuracy and log likelihood accountability. RESULTS: The model for identifying asymptomatic controls only required the three measures of attrition severity (anterior, mediotrusive and laterotrusive posterior) to be differentiated from the patients with a 74.2 +/- 3.8% cross-validation accuracy. This compared with cross-validation accuracies of 69.7 +/- 3.7% for differentiating disc displacement using anterior and laterotrusive attrition severity, 68.7 +/- 3.9% for differentiating disc displacement using anterior and laterotrusive attrition rates, 70.9 +/- 3.3% for differentiating osteoarthrosis using anterior attrition severity and rates, 94.6 +/- 2.1% for differentiating myofascial pain using mediotrusive and laterotrusive attrition severity, and 92.0 +/- 2.1% for differentiating myofascial pain using mediotrusive and anterior attrition rates. The myofascial pain models exceeded the > or =75% sensitivity and > or =90% specificity thresholds recommended for diagnostic tests, and the asymptomatic control model approached these thresholds. CONCLUSION: Multifactorial models using attrition severity and rates may differentiate masticatory muscle pain patients from asymptomatic controls, and have some predictive value for differentiating intracapsular temporomandibular disorder patients as well.

Adolescent↗
PubMed1991

[Models and manikins in dental education].

Different available types of dental models and manikin used for preclinical odontological education are analyzed. On the basis of their composition are classified in biological, artificial, and mixed models. According to their usage, those ones are classified in demonstration, exploration, and working models. Each of them are studied, remarkable aspects in odontological education are emphasized.

Audiovisual Aids↗
PubMedDate not supplied

The problem-oriented dental record: a key to dental hygiene treatment planning and the problem-solving model for dental hygiene practice.

The problem-solving model for dental hygiene practice requires careful assessment, planning, implementation and evaluation to provide quality dental hygiene care. To facilitate this problem-solving approach, a method of recording information in an organized and highly communicative manner must be established. This paper describes the components of a problem-oriented dental record used by students at the Vancouver Community College and discusses the benefits of using this tool in clinical practice.

Dental Hygienists↗
PubMed2005

Three-dimensional computer-generated head model reconstructed from cephalograms, facial photographs, and dental cast models.

PURPOSE: Three-dimensional (3D) computer models of the human craniofacial structure have been constructed with computed tomography (CT). However, the high cost of CT and the radiation exposure are drawbacks to this method. Attempts to create a 3D reconstruction from lateral and frontal cephalograms have failed because of problems with magnification, distortion, and limitations of landmark identification, among others. We introduce a new method that creates a standard head model for a patient from anatomic measurement points extracted from x-ray images, facial stereo photographs, and dental casts. MATERIAL: To obtain precise 3D coordinates from cephalograms, several equations were introduced to compensate for radiographic image magnification and distortion. RESULTS: By comparing the constructed model and 3D-CT images, this method proved to be accurate. CONCLUSIONS: It is possible to produce a 3D head model on a personal computer and to view it from any desired angle; this will provide easy-to-understand information for patients and establish a diagnostic or therapeutic method for communication with other health care providers.

Adult↗
PubMed2004

Tooth segmentation of dental study models using range images.

The accurate segmentation of the teeth from the digitized representation of a dental study model is an important component in computer-based algorithms for orthodontic feature detection and measurement and in the simulation of orthodontic procedures such as tooth rearrangement. This paper presents an automated method for tooth segmentation from the three-dimensional (3-D) digitized image captured by a laser scanner. We avoid the complexity of directly processing 3-D mesh data by proposing the innovative idea of detecting features on two range images computed from the 3-D image. The dental arch is first obtained from the plan-view range image. Using the arch as the reference, a panoramic range image of the dental model can be computed. The interstices between the teeth are detected separately in the two range images, and results from both views are combined for a determination of interstice locations and orientations. Finally, the teeth are separated from the gums by delineating the gum margin. The algorithm was tested on 34 dental models representing a variety of malocclusions and was found to be robust and accurate.

Algorithms↗