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Results for “DENTAL MODELS”

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At least 127 records · Page 7Linked to original sources
PubMed2003

The effect of light intensity on double bond conversion and flexural strength of a model, unfilled dental resin.

OBJECTIVE: Two visible light sources (tungsten-quartz-halogen and xenon-arc plasma) with vastly different intensities (200 and 1800 mW/cm(2)) but similar spectral outputs, were used to examine the effects of light intensity on conversion and flexural strength of a model dental resin formulation (75/25wt% bis-GMA/TEGDMA). METHODS: The exact same polymer samples were used to correlate double bond conversion (measured with near-IR spectroscopy) to flexural strength, both immediately after light exposure and after storage. RESULTS: In general, polymers which were irradiated with the high light intensity source exhibited greater double bond conversion. However, increasing the light intensity also increased the maximum temperature reached during polymerization. Therefore, the greater double bond conversion was caused by a combination of both photo and thermal effects. Regardless of the light intensity, a single linear relationship existed between conversion and final flexural strength (measured 4 days after cure) over the conversion range analyzed (50-80%). However, deviations from linearity were noted in several samples that were tested immediately after exposure. SIGNIFICANCE: These findings illustrate that light intensity does not affect the final flexural strength of a dental resin as long as the final conversions are similar.

Analysis of Variance↗
PubMed1998

Bitemarks in forensic odontology.

Person identification is important in criminology, and forensic odontologists are key personnel for identifying a highly individual dentition which could cause a bitemark and which could be used to convict or exculpate a suspect. Bitemarks may be observed in skin, wax, from a dental model indirectly from a photograph, a scanned image of a dental model or food. This paper shows that bitemarks constitute reliable evidence for person identification and that a tolerance of approximately 1mm existed between measurements of a wax bite, dental model, photograph and computer scanned image.

Bites, Human↗
PubMed1984

Socioeconomic demand model for dental visits.

The purpose of the present study was to develop structural socioeconomic demand models for dental visits. The explanatory variables were chosen selectively from the various theories concerning health services utilization. The models were constructed on data from a sociodental survey carried out among workers and staff members at a Danish shipyard. A sample of 988 employees was drawn by stratified random sampling and 841 persons were interviewed regarding dental visits and attitudes towards teeth and dental health services. The structural equations were estimated by means of multiple regression analysis using the two-stage least-squares method. Dental visits were influenced by dental health status, expectations about value of dental care, income, and price of dental care. Dental health was affected by the number of dental visits and age. Residence in rural areas during childhood and age had a negative effect on dental care early in life while years of schooling had a positive effect. Years of schooling had also a positive effect on expectations about value of dental care. The present study has shown that it is possible to construct structural models for the demand for dental care.

Attitude to Health↗
PubMed1995

A laboratory model for dental radiographic studies.

Though a number of laboratory models have been developed to study the effects of X-ray geometry on the appearance and relative positions of anatomical landmarks, such as the amelocemental junction and alveolar crest, many have failed to take into account the three-dimensional nature of the alveolus and its spatial relationships with the teeth. As a result, the findings of many ex vivo investigations must be questioned. The aim of this investigation was to develop and refine a new laboratory method for experimental dental radiography utilizing a series of anatomical radio-opaque acrylic models containing extracted teeth. The method allows adjustment of the beam-object relationship through the use of precision-made wedges, which are able to tilt the models through a series of angles thus simulating in vivo changes in both vertical and horizontal X-ray beam angulation. The technique is capable of being used in studies involving assessment of alveolar bone height or the depth of carious lesions. The precision of the method was tested by radiographing in nine different positions a test device consisting of four small amalgam fillings embedded in a perspex sheet. Following removal and replacement, exposures of the test device were repeated for each position. Five linear distances between pairs of fillings were selected and measured on each radiograph to give a total of 45 measurements per set of films. There was exact agreement in 39 of the measurements recorded and a discrepancy of +/- 0.1 mm in the remaining six. The estimated standard deviation for variation on repeat radiography was 0.258 and the 95% confidence interval 0.214 to 0.325. The precision of the apparatus was thus found to be adequate for the measurement of differences in small distances.

Acrylic Resins↗
PubMed1999

Dental injury models: experimental tools for understanding neuroinflammatory interactions and polymodal nociceptor functions.

Recent research has shown that peripheral mechanisms of pain are much more complex than previously thought, and they differ for acutely injured normal tissues compared with chronic inflammation or neuropathic (nerve injury) pain. The purpose of the present review is to describe uses of dental injury models as experimental tools for understanding the normal functions of polymodal nociceptive nerves in healthy tissues, their neuroinflammatory interactions, and their roles in healing. A brief review of normal dental innervation and its interactions with healthy pulp tissue will be presented first, as a framework for understanding the changes that occur after injury. Then, the different types of dental injury that allow gradation of the extent of tissue damage will be described, along with the degree and duration of inflammation, the types of reactions in the trigeminal ganglion and brainstem, and the type of healing. The dental injury models have some unique features compared with neuroinflammation paradigms that affect other peripheral tissues such as skin, viscera, and joints. Peripheral inflammation models can all be contrasted to nerve injury studies that produce a different kind of neuroplasticity and neuropathic pain. Each of these models provides different insights about the normal and pathologic functions of peripheral nerve fibers and their effects on tissue homeostasis, inflammation, and wound healing. The physical confinement of dental pulp and its innervation within the tooth, the high incidence of polymodal A-delta and C-fibers in pulp and dentin, and the somatotopic organization of the trigeminal ganglion provide some special advantages for experimental design when dental injury models are used for the study of neuroinflammatory interactions.

Animals↗
PubMed1998

Stability of orthopedic and surgically assisted rapid palatal expansion over time.

At the present time no reports are available on the stability between orthopedic and surgically assisted rapid palatal expansion. This study was designed to examine and compare the dental and skeletal changes over time for both orthopedic maxillary expansion and surgically assisted palatal expansion. The study was divided into two groups. Group one was orthopedically expanded and consisted of 14 males and 10 females. The ages ranged from 6 years to 12 years with a mean of 8.5 years. Group two received surgically assisted rapid palatal expansion and consisted of 12 males and 16 females with ages ranging from 13 years to 35 years and a mean age of 19.25 years. All 52 subjects were white, from the same geographic area, and were treated by the same two operators. Dental models and posterior anterior cephalograms were obtained immediately before and after expansion, at removal of the expansion device, and 1 year after removal of the appliance. A repeated measures analysis of variance test was applied to assess changes over time between groups. The surgical and nonsurgical techniques displayed similar trends over time although the surgical group contained a greater quantity of expansion. Both the orthopedic and the surgical groups showed stable results.

Adolescent↗
PubMed1989

[Spontaneous correction of the rotation of the permanent central lower incisors].

On the basis of a series of dental models from children between five and nine years (twice-yearly examination) with final models being made of 319 of these children at the age of 16, determinations were made of the rotation of the permanent central lower incisors 'shortly after complete eruption of the cutting edge' at the age of 16. The study showed that spontaneous correction amounts to 53% and 60% respectively for an original mesio-lingual rotation (type less than 90 degrees) and for an original disto-lingual rotation (type greater than 90 degrees).

Child↗
PubMed1981

The surgical-orthodontic correction of vertical dentofacial deformities.

Patients with dentofacial deformities must be carefully evaluated to establish a complete diagnosis and exact treatment plan that will achieve optimal functional and esthetic results. Vertical deformities are just one component of existing deformities that may be present. The four primary vertical deformities are: vertical maxillary excess, vertical mandibular excess, vertical maxillary deficiency, and vertical mandibular deficiency. Differential diagnostic features of vertical deformities are presented from the standpoint of clinical, cephalometric, and dental model analyses. Only the vertical deformities were addressed in this paper; it must be realized that vertical components can exist with the anteroposterior, transverse, and asymmetry deformities as well. Orthodontic principles employed for management of vertical deformities were discussed with particular indications for each type of deformity. In addition, the surgical considerations were presented for each of the basic types of vertical deformities. The nature of the deformity will primarily dictate the orthodontics to be utilized as well as the surgical procedures.

Adolescent↗
PubMed1995

Postgraduate general dentistry residency: a clinical model.

Dental graduates today are expected to be knowledgeable in many more areas than their predecessors. Changing technology and increased competition require entering the dental profession with more experience and skills. One approach to achieving this skill level is a postgraduate general dentistry residency in a clinical setting during the year following dental school graduation (PGY1). The clinical residency provides new dentists with additional hands-on training and reinforces classroom learning. HealthPartners was selected as a clinical rotation for residents in the advanced general dentistry program at the University of Minnesota Dental School. The program provides dental graduates in PGY1 training in all areas of practice. The HealthPartners rotation is highly unique. It is a staff model HMO with a clinical, multi-specialty setting. Today, HealthPartners--a Minnesota-based healthcare organization--has 116,000 members with prepaid dental benefits. Residents trained in the program develop increased skills in all areas of dental practice. In addition, they develop a good working knowledge in the basic sciences. Methods of instruction include didactic training in the form of seminars, lectures, and clinical training in HealthPartners' dental clinics.

Clinical Competence↗
PubMed2005

Development and characterization of an animal model of dental sinusitis.

CONCLUSION: The results of this study confirm that the present rabbit model of dental maxillary sinusitis (dMxS) is reproducible and simulates human dental sinusitis with respect to initiation, progression and inflammation. It is applicable to further studies of sinusitis of odontogenic origin. OBJECTIVES: To induce acute dMxS in rabbits by using their own oral microflora to create a periapical infection and to follow morphological, radiographic, bacteriological and histological changes to the sinus mucosa. MATERIAL AND METHODS: The experimental animals comprised 26 New Zealand White rabbits. Maxillary premolar root canals were identified bilaterally and the continuously growing germs of the roots were severed by diathermy. The animals were randomized into 2 groups: in Group 1 (n=20) the teeth were left open for the entire study period; in Group 2 (n=6) the root canals were sealed 1 week after the initial intervention. The animals in Group 1 were sacrificed at intervals ranging from 2 h to 9 months after intervention. All animals in Group 2 were sacrificed 6 months after intervention. After macroscopic and radiographic examination, post-mortem inspection of the paranasal sinus cavity and maxillary complex and microbiological sampling, the entire nasal sinus complex with the hard palate in situ was resected and processed for serial coronal sectioning. RESULTS: In Group 1, after 3 months, the radiographic changes ranged from widening of the periodontal space to bone reaction. At sacrifice, changes in the sinus mucosa ranged from signs of mucosal inflammation to purulent dMxS. Microbial growth, predominantly Gram-negative aerobes, increased over time. In Group 2, the findings were generally more pronounced. Anaerobic microorganisms were predominant. In both groups the findings were consistent with dMxS.

Animals↗
PubMed2000

Introduction to multilevel modelling in dental research.

OBJECTIVE: To explain the concepts and application of multilevel modelling (MLM) and how it can be applied to the analysis of dental research data. BASIC DESIGN: Methodological in nature, this article introduces MLM through actual and hypothetical dental examples. SETTING: Examples of MLM in periodontal research illustrate cross-sectional and longitudinal analyses of hierarchical dental data. Multilevel multivariate modelling is illustrated by an example in orthodontic research. The potential implications of study design in the context MLM is extensively discussed, including study sample size and accounting for examiner variability. RESULTS: The fine detail and greater insight provided by MLM enables dental researchers to review and revise old hypotheses and to generate new ones that could not be addressed by single-level methods. CONCLUSIONS: MLM has the potential to increase our understanding of oral disease and health and offers the opportunity to rethink some aspects of dental research procedure.

Analysis of Variance↗
PubMed2000

Introduction to Bayesian modelling in dental research.

OBJECTIVE: To explain the concepts and application of Bayesian modelling and how it can be applied to the analysis of dental research data. BASIC DESIGN: Methodological in nature, this article introduces Bayesian modelling through hypothetical dental examples. SETTING: The synthesis of RCT results with previous evidence, including expert opinion, is used to illustrate full Bayesian modelling. Meta-analysis, in the form of empirical Bayesian modelling, is introduced. An example of full Bayesian modelling is described for the synthesis of evidence from several studies that investigate the success of root canal treatment. Hierarchical (Bayesian) modelling is demonstrated for a survey of childhood caries, where surface data is nested within subjects. RESULTS: Bayesian methods enhance interpretation of research evidence through the synthesis of information from multiple sources. CONCLUSIONS: Bayesian modelling is now readily accessible to clinical researchers and is able to augment the application of clinical decision making in the development of guidelines and clinical practice.

Bayes Theorem↗