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At least 973 records · Page 54Linked to original sources
PubMed1994

Surface roughness of oral mucosa and its reproduction in dental materials.

An even fitting surface is essential to obtain and maintain a healthy oral mucosa in denture wearers. The present study was designed to clarify the relationship between the surface roughness of oral mucosa and its reproduction in the corresponding fitting surface of acrylic dentures. A silicone elastomer/epoxy replica technique was used for rendering the oral mucosal surface accessible to measurements with a stylus-type profile recorder. The method's ability to reproduce roughness with good traceability was tested and verified. Acrylic fitting surfaces made by standard denture-making technique demonstrated roughness values substantially higher than those of the mucosa, stemming from a high inherent surface roughness of dental stone models. To compensate for this, various separating media for stone models were tested as to their ability of reducing surface roughness. One silicone varnish (Silisol, Dreve AG, Germany) produced an acrylic surface with a roughness value comparable to that of the oral mucosa.

Acrylic Resins↗
PubMed1994

Three-dimensional models for head and neck tumor treatment planning.

The authors have evaluated two types of practical maxillofacial model systems useful to the head and neck surgeon:1. plastic mandibular model generated by three-dimensional computerized tomography (CT) reconstruction, and 2. dental impression model of the maxilla. The first model is expensive and technology intensive; the second is simple but limited. Both three-dimensional models offer several advantages: 1. they provide segmental mandibular relationships that are not known because of oncologic restrictions or previous surgery; 2. they allow preoperative reconstructive planning including prosthesis fabrication and visualization of tumor extent not obvious by two dimensional imaging; and 3. they provide a permanent record for future needs or reconstructions. The disadvantages include cost, time, and possible inaccuracies secondary to image artifacts. We find both models to be of significant practical value in selected head and neck tumor patients.

Adenocarcinoma↗
PubMed1984

Effect of fluoride on growth and acid production by Streptococcus mutans in dental plaque.

The aim of this study was to measure the effect of fluoride on the production of organic acids by Streptococcus mutans in dental plaque. The effect was studied in a simplified model of dental plaque with gnotobiotic rats monoinfected with S. mutans Ny341. Adaptation of S. mutans to fluoride was induced by feeding one group of the rats on fluoride-containing diet and drinking water. No difference was found in the accumulation of S. mutans on the teeth between the fluoride-adapted and the control groups. However, there was a significant difference in the amount of lactic acid in metabolically resting plaque between the groups, lactic acid being lower in the fluoride-adapted plaque. At 5 min after a rinse containing 10% sucrose, a high level of lactic acid was found in plaque from animals not exposed to fluoride. Rinses containing 4 or 20 mM fluoride before the sucrose rinse significantly inhibited the lactic acid production in the control group. In the plaque from rats on fluoridated diet and drinking water the sucrose-induced production of lactic acid was not inhibited by a 4 mM fluoride rinse. Moreover, the production of lactic acid in the fluoride-adapted plaque was prolonged. The results indicate that due to fluoride adaptation the inhibition of acid production is unlikely to be important for the caries-preventive action of fluoride.

Acetates↗
PubMed2006

Centralization of services: standard setting and outcomes.

OBJECTIVE: To test specific standards set in the newly established cleft lip and palate service in three regions of the U.K. The standards relate to record collection and outcomes. DESIGN: Retrospective analysis. PATIENTS: Records of 31 children, 5 years of age, who were born in 1997 with complete unilateral clefts of lip and palate and were treated by surgeons in three regions. MAIN OUTCOME MEASURES: Record collection standards were measured by collecting dental study models. Outcomes were measured with the 5-Year-Old Index. RESULTS: Of the 31 subjects, 52% had excellent and good outcomes. The 31 cases represented 62% of the total records collected. CONCLUSIONS: The three regions examined fell short of the standards set, but the outcomes were improved compared with previous national outcomes. The failings in record collection need to be rectified. This study provides baseline data for further development of cleft services within three regions.

Child, Preschool↗
PubMed2002

Reliability of a 3D surface laser scanner for orthodontic applications.

A device for recreating three-dimensional (3D) objects on a computer is the surface laser scanner. By triangulating distances between the reflecting laser beam and the scanned surface, the surface laser scanner can detect not only an object's length and width but also its depth. The scanner's ease of use has opened various possibilities in laboratory research and clinical investigation. We assessed the reliability of generating 3D object reconstructions using the Minolta Vivid700 3D surface laser scanner (Minolta USA, Ramsey, NJ). Accuracy and reproducibility were tested on a geometrical calibrated cylinder, a dental study model, and a plaster facial model. Tests were conducted at varying distances between the object and the scanner. It was found that (1) in the calibrated cylinder tests, spatial distance measurement was accurate to 0.5 mm (+/- 0.1 mm) in the vertical dimension and 0.3 mm (+/- 0.3 mm) in the horizontal dimension; (2) in the study model test, molar width was accurate to 0.2 mm (+/- 0.1 mm, P >.05), and palatal vault depth could be measured to 0.7 mm (+/- 0.2 mm, P > 0.05); and (3) for the facial model, an accuracy of 1.9 +/- 0.8 mm was obtained. The findings suggest that the surface laser scanner has great research potential because of its accuracy and ease of use. Treatment changes, growth, surgical simulations, and many other orthodontic applications can be approached 3-dimensionally with this device.

Cephalometry↗
PubMed2005

[Classification of maxillary dental arches by correlation and principal component analyses].

PURPOSE: To evaluate the morphology of dental arches. METHODS: 62 (male: 36, female: 26) paired casts having normal dentitions and occlusion were selected from 396 (age: 18 to 26 years old; male: 257, female: 139) sets of dental study models. The maxillary dentitions were preliminarily classified as square, round-square, round and round V-shaped arches based on the conventional morphological descriptions. Midpoints of the incisor edge (I1(R), I1(L), I2(R), &I2(L)), summits of the cuspids (C(R) & C(L)), buccal cusps of the premolars (P1(R), P1(L), P2(R), & P2(L)), mesial buccal cusps of the first and second molars (M1(R), M1(L), M2(R), & M2(L)), and the midpoint (A) of line I1(R)-I1(L) were designated as reference points. From A, let a vertical line intersected line M2(R)-M2(L) at reference point B. The line A-B intersected CR-CL at reference point E. The following items were evaluated: (1) the protrusion of the cuspids by 1. angle I2(R)-C(R)-P1(R) (angle R) + angle I2(L)-C(L)-P1(L) (angle L); (2) the curvature of the anterior teeth by 2. A-B/C(R)-C(L), 3. 180 degrees-angle C(R)-A-C(L), and 4. A-E/C(R)-C(L); (3) the length to width ratio of the dental arch by 5. A-B/M2(R)-M2(L); (4) the degree of roundness of the maxillary arch by estimation of 6. (rtheta(5)-rtheta(4))(R)+(rtheta(5)-rtheta(4))(L); and (5) an item 7. for the differentiation of type I and type II round-square arches by relating the bilateral contour and position of break line P1-P2-M1-M2 (i) to line P1-M2 (ii). The data of items 1, 2, 3, 4, 5, and 6 were further standardized and summarized into three essential principal components: (1) the curvature of the anterior teeth, (2) the curvilinear contour of the dental arch, and (3) the length-to-width ratio of the dental arch. RESULTS: (1) 60% of the maxillary dentitions were round-square arches which showed no prominent principal component; (2) square maxillary arches distinctly showed a small 1. angle R+angle L; (3) round arches were characteristic by small 6 (rtheta(5)-rtheta(4))(R)+(rtheta(5)-rtheta(4))(L) values; and (4) round V-shaped arches had large 2, 3 and 4 values. CONCLUSIONS: We concluded that parameters 1, 2, 3, 4, 5, 6 and 7 were summarized into three principal components (first principal component, second principal component and third principal component). Through three principal component analysis, we can quickly evaluate the morphology of the dental arches clinically. This methods is simple and of validity. And we can also obtain the characteristics of maxillary dental arches.

Adolescent↗
PubMed2003

Statistical inversion for medical x-ray tomography with few radiographs: II. Application to dental radiology.

Diagnostic and operational tasks in dental radiology often require three-dimensional information that is difficult or impossible to see in a projection image. A CT-scan provides the dentist with comprehensive three-dimensional data. However, often CT-scan is impractical and, instead, only a few projection radiographs with sparsely distributed projection directions are available. Statistical (Bayesian) inversion is well-suited approach for reconstruction from such incomplete data. In statistical inversion, a priori information is used to compensate for the incomplete information of the data. The inverse problem is recast in the form of statistical inference from the posterior probability distribution that is based on statistical models of the projection data and the a priori information of the tissue. In this paper, a statistical model for three-dimensional imaging of dentomaxillofacial structures is proposed. Optimization and MCMC algorithms are implemented for the computation of posterior statistics. Results are given with in vitro projection data that were taken with a commercial intraoral x-ray sensor. Examples include limited-angle tomography and full-angle tomography with sparse projection data. Reconstructions with traditional tomographic reconstruction methods are given as reference for the assessment of the estimates that are based on the statistical model.

Algorithms↗
PubMed1998

The Graz hemisphere splint: a new precise, non-invasive method of replacing the dental arch of 3D-models by plaster models.

Three-dimensional (3-D) anatomical models have proven their great value in the field of cranio-maxillofacial surgery. One major disadvantage is the limited representation of the teeth in milled and stereolithographic models. This is mainly caused by the limited resolution of the CT-scan, especially in the plane perpendicular to that of the scan. A new, precise, non-invasive and standardized method of replacing teeth of 3-D models by plaster models is introduced. The accuracy of tooth replacement is analysed. A plastic human skull is scanned with different interscan distances (scan feed), eight 3-D models are fabricated from this data and the positioning precision of the replaced plaster models in the three main axes is examined. Statistical analysis is carried out with a paired samples t-test. A mean positioning deviation of 0.44 and 0.52 mm in all directions is found using a CT feed of 2 and 3 mm. With 4 and 6 mm, the accuracy decreases showing 0.95 mm and 1.08 mm deviation. No significant difference is found between 2 mm and 3 mm scans, but significant differences between 2, 3 mm and 4, 6 mm are found. For the replacement of model teeth, at least three definitive fixed marks are required. With the aid of a hemisphere, used as a marker, the limited resolution in z-direction is overcome. The hemisphere is visible on several scans as semicircles of varying size. In the 3-D model, it allows precise positioning even on the z-axis enabling the exact replacement of teeth for the first time. A scan feed of 3 mm is sufficient for precise tooth replacement.

Calcium Sulfate↗
PubMed2003

Temperature- and deflection- dependences of orthodontic force with Ni-Ti wires.

Orthodontic forces of Ni-Ti wires examined under the retrained condition on the dental arch model were evaluated with the changes in temperature and deflection. The tested specimens were a commercially available superelastic (W1) wire and two shape memory wires with their nominal A(f) points were 35 degrees C (W2) and 40 degrees C (W3), respectively. They showed typical superelastic hysteresis loops under the restraint condition at 40 degrees C. The force levels were significantly larger than those generally obtained by simple three-bending test. The recovery forces in the plateau region at 1.0 mm deflection were much larger than desired in the clinical guidelines around oral temperatures. In the shape memory wire W3, the recovery force rapidly decreased to zero by a small reduction of the deflection from its maximum. However, the wire again exerted the force with the remaining permanent deflection by temperature rising. It was small compared to the guidelines of desirable orthodontic force and seemed to be useful especially for the hypersensitive patients.

Analysis of Variance↗
PubMed2006

Analysis of dental arch relationships in Swedish unilateral cleft lip and palate subjects: 20-year longitudinal consecutive series treated with delayed hard palate closure.

OBJECTIVE: To evaluate the dental arch relationships for a consecutive series from Goteborg, Sweden, who had delayed hard palate closure. DESIGN: Retrospective study. SETTING: Sahlgrenska University Hospital, Goteborg, Sweden. PATIENTS: The dental study models of 104 consecutive unilateral cleft lip and palate subjects. The study cohort was born between 1979 and 1994. Longitudinal records were available at ages 5 (n = 94), 10 (n = 97), 16 (n = 59), and 19 years (n = 46). Five assessors rated models according to the GOSLON Yardstick on two separate occasions each. INTERVENTIONS: These patients had been operated upon according to the Goteborg protocol of delayed hard palate closure (at age 8 years). RESULTS: 85% of subjects were rated in groups 1 and 2 (excellent or very good outcome), 12% were rated in group 3 (satisfactory), and 3% were assigned to group 4 (poor). No patients presented in Group 5 (very poor). Weighted kappa statistics for double determination of Yardstick allocation for five assessors demonstrated values between .65 and .90 for interrater agreement (good/very good) and between .70 and .90 for intrarater agreement (very good). CONCLUSIONS: Delayed hard palate closure as practiced in Goteborg since 1979 has produced the best GOSLON Yardstick ratings in a consecutive series of patients ever recorded worldwide, since the Yardstick was first used in 1983. However, it is noteworthy that a new protocol has been introduced in Goteborg since 1994, in which hard palate closure is done at 3 years due to concerns regarding speech.

Adolescent↗
PubMed1993

[Application of fuzzy inference to personal identification--sex determination from teeth].

Fuzzy inference has received much attention recently as a new type of computer control technology for application in various fields. In this study I applied fuzzy inference to personal identification in medical jurisprudence. Sex determination program was constructed from teeth using the fuzzy inference technique and was compared with known discriminant analysis. The materials examined were mandibular and maxillary dental plaster models of 100 adult males and females, and 80 infant males and females. For the permanent teeth, measurements were made on crown width and thickness of the mandibular and maxillary central incisors, canines, first premolars, and first molars, and of the width and length of the maxillary dental arch. For the deciduous teeth, measurements were made on crown width and thickness of all teeth. Stepwise discriminant analysis was conducted using these values. The values from 5 selected upper-ranked items were set as input objects of the fuzzy inference program and the probability of maleness obtained from the discriminant analysis was set as the output object. Finally, sex determination program for both permanent and deciduous teeth was constructed using a fuzzy inference software development tool. Each measured value was input into this program and the output results were compared with those of discriminant analysis. The percentages of correct determinations for permanent teeth were 83.0% for males and 86.0% for females using stepwise discriminant analysis, however it increased to 93.0% for males and 89.0% for females using the fuzzy inference program. The percentages of correct determinations for deciduous teeth models were 67.5% for males and 75.0% for females using stepwise discriminant analysis, and increased to 86.3% for males and 81.3% for females using the fuzzy inference program. Among samples with probabilities between 40% and 60%, 3 out of 14 males and 4 out of 13 females were misjudged using stepwise discriminant analysis in cases of permanent teeth. However using fuzzy inference program, it reduced to 0 for males and 3 for females. In case of deciduous teeth, 9 out of 20 males and 9 out of 23 females were misjudged using stepwise discriminant analysis. But it reduced to 5 for males and 4 for females using the fuzzy inference program.

Adult↗