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PubMed2002

Helical axis errors affect computer-generated occlusal contacts.

A helical axis describing mandibular motion can be calculated from two distinct positions of the mandible; however, as these positions come closer together, calculation errors increase. This study investigated the effects of errors in the calculated helical axis on simulated mandibular motion by the measurement of changes in occlusal contacts. A standard helical axis was calculated from a simulated lateral movement. A series of digital interocclusal records from centric to a 5 degree mandibular rotation about the standard helical axis was created. Digital dental cast models were aligned to the interocclusal records. Helical axis parameters and occlusal contacts calculated with the use of the aligned digital models were compared with those of the standard. Helical axes calculated from mandibular positions separated by 1.5 degrees to 5.0 degrees yielded equivalent occlusal contacts. Qualitatively, contacts for helical axes calculated from jaw rotations of 0.7 degrees or larger were nearly identical to those of the standard.

Computer Simulation↗
PubMed2003

Predoctoral clinical curriculum models at U.S. and Canadian dental schools.

In fall 2002, the ADEA Section on Comprehensive Care and General Dentistry conducted a survey of the predoctoral clinical curriculum models at sixty-four North American dental schools. Fifty-eight percent of the schools reported that most patient care is provided in a comprehensive care clinic setting, 22 percent reported that most patient care is provided in discipline-specific settings, and 20 percent reported a hybrid of comprehensive care and discipline-specific settings. While ten Primarily Discipline-Based (PD) schools have instituted new Primarily Comprehensive Care (PCC) or Hybrid clinical curricula since 1997, one PCC school has converted to a Hybrid model, and one PCC school has converted to a PD model. PCC curriculum models were frequently associated with the following institutional factors: more densely populated metropolitan areas; private institutional sponsorship; location within a university medical center; larger class size; and more students enrolled in advanced training at the school. Curriculum factors frequently associated with PCC models included the following: increased use of simulation technology: higher proportion of clinical/teaching track faculty; higher proportion of part-time faculty; higher proportion of generalist faculty; same faculty supervising both treatment planning and patient treatment; and use of competency exams as the main requirement for completion of the curriculum.

Canada↗
PubMed1998

An in vitro study of the passivity of splints in dental trauma.

OBJECTIVES: The purpose of this research was to evaluate the passivity of splints which were constructed with orthodontic materials since a force could unintentionally be generated by the appliance and perturb the healing process of the injured teeth. METHODS: A specific data acquisition system, with a 2D force transducer, was developed to evaluate its passivity. Four types of splints were studied on a maxillary dental arch model and the splints were constructed with 0.559 mm standard edgewise brackets, with stainless steel square or round orthodontic wires and with 0.254 mm preformed ligatures or 3.05 mm elastomeric ones. The studied orthodontic wires were straight-lengthened or Arch Blank preformed types and three sizes of square wires and five sizes of round ones were tested. RESULTS: The orthodontic appliances were rarely passive but the splints constructed with elastomeric ligatures and an Arch Blank preformed wire were significantly different from those constructed with stainless steel ligatures and a straight wire or with stainless steel ligatures and an Arch Blank preformed wire or with elastomeric ligatures and a straight wire (P < 0.05). The best control of passivity was obtained with the 0.432 mm x 0.432 mm splints (P < 0.05) and the mean force generated by those appliances was 0.13 x 10(-2) N. CONCLUSIONS: The choice of orthodontic materials influenced the passivity of dental splints and it would seem that elastomeric ligatures and an Arch Blank preformed wire should be used for its construction.

Analysis of Variance↗
PubMedDate not supplied

An articulation curriculum for dental assisting and dental hygiene radiography/radiology instruction.

This paper reports on an articulation model for dental radiography instruction developed by a task force composed of dental assisting and dental hygiene educators, with the assistance of various committees and groups. The task force participants determined that core courses in didactics, preclinical laboratory study, and clinical radiography should be identical for dental assistants and dental hygiene students. They also determined that an additional course was necessary for dental hygiene students to develop adequate skills in interpreting radiographs to meet the level presently required by national and regional examinations.

Curriculum↗
PubMed2003

Evaluation of proximal contacts of posterior composite restorations with 4 placement techniques.

BACKGROUND: Contrary to the situation for amalgam restorations, obtaining acceptable proximal contacts with posterior composite restorations can be difficult. Proximal contacts that are less than ideal may permit food impaction and subsequent caries formation and periodontal problems. PURPOSE: The aim of this study was to assess the quality of proximal contacts of posterior composite restorations placed with 4 restorative techniques. METHODS: Seventy-five mounted ivorine teeth with large, standardized MOD cavities were divided into 5 groups of 15 teeth each. The teeth in 4 of these groups were restored with a resin composite and those in the remaining group were restored with amalgam. The restorative techniques for the 4 composite groups were traditional wedge and matrix (Group 1), use of a light-tip attachment (Group 2), use of the Contact Pro hand instrument (Group 3) and use of Beta Quartz glass-ceramic inserts (Group 4). All restorations were completed under simulated clinical conditions. Standards for evaluating proximal contacts were set by preparing 4 dental study models, each model having one type of proximal contact (open, not tight enough, ideal and too tight). All restored teeth were carefully painted with opaque nail polish, except at the contact areas, to conceal restoration type and hence to ensure unbiased evaluation by assessors. Three experienced clinicians independently assessed the quality of the proximal contacts of all restored teeth (total of 150 contacts) relative to the 4 types of contacts exemplified by the dental study models. In cases of disagreement, the clinicians reassessed the disputed contact collectively. RESULTS: Amalgam restorations had 5 contacts that were not tight enough, 20 that were ideal and 5 that were too tight. The Group 1 composite restorations had a total of 25 open contacts and 5 contacts that were not tight enough; the Group 2 composite restorations had 3 open contacts, 13 contacts that were not tight enough and 14 that were ideal; the Group 3 composite restorations had 11 contacts that were not tight enough and 19 that were ideal; and the Group 4 composite restorations had 3 contacts that were not tight enough and 27 that were ideal. None of the composite contacts was judged too tight. CONCLUSIONS: The use of inserts (Group 4) resulted in a better rate of acceptable proximal contacts in posterior composite restorations than the 3 other techniques (90% vs. 0%, 47% and 63% for Group 1, Group 2 and Group 3, respectively).

Bicuspid↗
PubMed1989

A proliferative inflammation in the mandible caused by implantation of an infected dental root. A possible experimental model for chronic osteomyelitis.

In order to provide a better understanding of the reactions of bone affected by an infectious stimulus, infected dental roots were implanted into the mandibular bone of 5 monkeys (Macaca fascicularis). The roots were infected by micro-organisms belonging to the monkeys' oral plaque flora. Following an observation period of 6 months, the monkeys were sacrificed. The mandibles were dissected. Radiographs were taken and then the mandibles were prepared for histology. In the mandibles where the infected roots had been implanted, advanced inflammatory changes were seen. Bacteria, however, were only found within the implanted roots, not in the surrounding tissue in spite of a heavy inflammatory reaction. The interaction between infection and inflammation is discussed on the basis of these observations. The role of possible neural transmittor substances in the pathogenesis of the inflammatory disease is also discussed. The signs and symptoms of the proliferative inflammatory changes provoked in this experiment are compared to those of chronic osteomyelitis.

Animals↗
PubMed2002

Description of dental arch form using the Fourier series.

The aim of this study was to describe the form of the human superior dental arch using Fourier transformations. Forty models made in dental stone from impressions of the maxillary dental arch were used to obtain the reference data, which were expressed in Cartesian coordinates, from the mesovestibular cuspid vertices of molar teeth, vestibular cuspid of premolars, and incisal edge. Fourth-grade equations and Fourier series were calculated from these data. The results indicate that Fourier series more precisely express the form and size of different dental arches, with mixed or permanent dentition, than fourth-grade equations. Details of the mathematical procedure and the precision obtained were provided.

Algorithms↗
PubMed2000

Dental hygiene fear: gender and age differences.

Studies aimed at examining gender and age differences as they relate to dental anxiety have begun to appear in the literature. The purpose of this investigation was to explore fear and anxiety in a dental hygiene setting and evaluate gender and age differences among four sub-scales of dental hygiene fear. The Dental Hygiene Fear Survey (DHFS) was developed to address patient reaction to dental hygiene treatment. The University of Washington Dental Fears Model was the theoretical model used for it identifies four domains of dental fear: fear of specific stimuli, generalized anxiety, fear of catastrophe, and distrust. Males and females respond differently to dental hygiene treatment with women reporting significantly (p<.05) greater fear overall than males. Examination of the four dental hygiene fear sub-scales show that females report greater fear (p<.05) in relation to specific fear and generalized anxiety. There were no significant differences across age categories on total fear scores or within any of the sub-scales. Characterization of the dental hygiene fear patient along with knowledge of procedures that elicit anxiety can assist the practitioner in recognizing dental hygiene-related fear. With this foundation, the practitioner can then develop management strategies specific to this phenomenon.

Adult↗
PubMed2004

Non extraction short-term arch changes.

OBJECTIVES: to examine the Cetlin protocol for short-term dentoalveolar changes in the sagittal and transversal planes in non-extraction treatment. MATERIALS AND METHODS: eighty patients with Class II, div.1 malocclusion treated with the Cetlin protocol, comprising upper distalizing plate, extraoral traction, and lower lip bumper. Dental study models were examined before treatment and after molar Class II correction during which upper molars were mechanically distalized, distobuccally rotated and expanded. RESULTS: the upper arch perimeter increased significantly. The lip bumper produced functional expansion of the lower arch, especially in the transverse plane, with an important increase in the arch perimeter. CONCLUSIONS: in the short-term, the Cetlin protocol made the following improvements: 1) molar correction, 2) resolution or improvement of crowding, 3) space recovery in both arches for leveling the curve of Spee and final adjustments. Further improvements in intercuspation can be made, if necessary, by fixed appliance therapy.

Activator Appliances↗
PubMed2003

Modeling of the viscoelastic behavior of dental light-activated resin composites during curing.

OBJECTIVE: Three models consisting of springs and dashpots were investigated to describe the viscoelastic behavior of a commercial light-activated restorative composite during curing. METHODS: Stress-strain data on Z100 were recorded by means of a dynamic test method performed on a universal testing machine. The model was tested by matching its response to experimental data and the material parameters, E (Young's modulus) and eta (viscosity), associated with the model were calculated. RESULTS: The universal testing machine generated reliable stress-strain data on the fast curing, light-activated resin composite during curing. The high polymerization rate of Z100 had a negative effect on the viscous flow capability of the material. A predictive model of the viscoelastic behavior of Z100 during curing was carried out, using the Maxwell model for the initial 3 min in the curing process and the Kelvin model for the remainder of the process. SIGNIFICANCE: Dental researchers analyzing shrinkage stress problems by mathematical modeling can obtain a good quantitative estimate of the shrinkage stress development of Z100 before the restoration is actually made.

Composite Resins↗
PubMed1982

The demand for dental health.

This study evaluates the determinants of demand for dental health in the context of an econometric model where dental health and dental care are jointly endogenous. The theoretical analysis is based on the application of economic theory to production activities occurring at the individual or household level. A number of hypotheses concerning the change in demand for home and market dental care with respect to price and income changes are posited and empirically tested. Additional hypotheses concerning the relation between dental care and dental health are also examined statistically while controlling for a variety of sociodemographic and economic factors. One of the key empirical findings is that the net price elasticity for dental services is quite low (-0.2) for this sample of individuals with high dental insurance coverage.

Dental Care↗
PubMedDate not supplied

A deep model of the incidence of dental caries on proximal surfaces.

As a component of an analysis of the benefits of alternative frequencies of bitewing radiographs to detect dental caries, the authors developed and validated a model to generate an individual's probability distribution for new carious lesions in a year. The model postulates two sources of variability in caries incidence--differences in individuals' underlying caries susceptibilities and a random component. The model is used to examine the nature of caries risk over time. The large random fluctuations in an individual's caries susceptibility from year to year, combined with the random nature of caries attack, makes it difficult to predict future caries experience from the individual's caries experience in the recent past. By modeling the process giving rise to observed incidence data rather than focusing directly on the observed data, i.e., by developing a deep rather than a surface model, the authors have elucidated underlying disease dynamics and provided a basis for generalizing from the particular data used to develop the model.

Adolescent↗