bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Longitudinal Study of Anteroposterior Growth Changes in the Palatine Rugae
Authors: Simmons J.D. , Moore R.N. , Erickson L.C. 
Published: November 2010

Palatine rugae have been used as internal dental cast reference points for quantification of tooth migration. Some, but not all, investigators have reported the medial rugal region to be stable or to show predictable change. The purpose of this study was to use the longitudinal data base of the Child Research Council of Denver to examine the anteroposterior stability of the medial rugal region. Dental casts of 20 females and 21 males with untreated normal Angle Class I occlusions were selected. Time intervals measured were: T1 — primary teeth erupted, T2 — earliest cast with permanent first molars erupted, T3 - earliest cast with canines and pre-molars erupted, and T4 — ages 16 to 22. Distinctive left and right anterior and posterior rugae which appeared on all four casts were identified, the medial ends marked, and the anteroposterior distances measured. The data were evaluated with the paired t test, repeated-measures AN-OVA, and Tukey's multiple comparison procedure. From T1 - T4, the medial rugal region increased 1.4±0.6 mm in females and 2.3±0.8 mm in males. Only two cases showed a trend toward stability. There were no significant differences by side. Significant increases in size occurred between T2 and T3 for females and males and between T3 and T4 for males. Analysis of these data indicates that the medial rugal region increases significantly in anteroposterior length, but not uniformly between the sexes across observation times. Such changes are characteristic of general craniofacial growth and suggest that the rugal region is responding to the differential growth of the underlying bone. Therefore, medial rugal landmarks appear not to be stable reference points for tooth migration research.
The Influence of Vanadate on Calcium Uptake in Maturing Enamel of the Rat Incisor
Authors: Takano Y. , Matsuo S. , Wakisaka S. , Ichikawa H. , Nishikawa S. , Akai M. 
Published: November 2010

The influence of vanadate, a potent inhibitor of Ca2+-ATPase and Na+-K+-ATPase, on 45Ca uptake in maturing enamel of the rat incisor was investigated by a vascular perfusion method combined with 45Ca autoradiography. The morphological integrity of the maturation-stage enamel organ was well-retained during vascular perfusion under all the experimental conditions. Distinct patterns of 45Ca labeling, comparable with those found in previous in vivo 45Ca autoradiographic studies, appeared in the maturing enamel after vascular perfusion with a standard perfusate. One mmol/L vanadate added to the standard perfusate caused a drastic decrease in 45Ca uptake in the maturing enamel, corresponding to the ruffle-ended ameloblasts, leaving narrow peaks of moderate intensity corresponding to the bands of the overlying smooth-ended ameloblasts. The in vitro labeling of exposed enamel surfaces with 45Ca revealed blackening of autoradiographic emulsion in wide bands separated by unlabeled or slightly labeled narrow ones resembling the distribution of smooth-ended ameloblasts in both control and vanadate-treated incisors. Our observations indicate that the ruffle-ended ameloblasts of the rat incisor serve as an efficient diffusion barrier to calcium ions and regulate transcellular calcium transport to the maturing enamel, at least in part, by a vanadate-sensitive mechanism.
Stiffness Increase During the Setting of Dental Composite Resins
Authors: Braem M. , Lambrechts P. , Vanherle G. , Davidson C.L. 
Published: November 2010

Changes in the dynamic Young's modulus under flexure of self-cured and light-cured composite resins during setting were demonstrated to reflect accurately the condition of the curing composite resins. The rate of stiffness increase during setting varied considerably with the product, and the light-cured composite resins generally showed a faster rate of increase of stiffness. In the initial stage, the Young's moduli were very low, especially for the self-cured composite resins. This accounts for the damage (adhesion disruption and cross-linking interruption) that can be inflicted on a freshly placed composite resin filling that is not yet mechanically stabilized. Therefore, such fillings are vulnerable to aggressive distortion for at least 10 to 15 minutes after placement.
Resorption of Residual Ridges (RRR) in Rats
Authors: Nishimura I. , Damiani P.J. , Atwood D.A. 
Published: November 2010

The post-extraction resorption of residual ridges (RRR) is a major and largely unsolved health problem, probably of multifactorial etiology. In order for one to study the role of specific factors in the pathophysiology of RRR, the use of animal models is desirable. The purpose of this study was to establish a reliable animal model and a standardized assay system to measure RRR for future experiments. A new oblique cephalometric device was designed to take pairs of xeroradiographs on the right and left sides of the rat skull and mandible at a 45-degree angle to the horizontal plane. Preliminary studies confirmed the reproducibility of the technique. All molars were extracted with minimal trauma from the right maxilla and mandible in five male Sprague-Dawley rats (40 days old). Longitudinal cephalographic examinations were performed before and immediately after extraction and at two, four, eight, and 12 weeks after extraction. Alveolar bone resorption was measured on enlarged cephalographs (5. 7X) at a point mesial to the mandibular first molar. Sequential mean bone resorption was 0.8 ± 0.2 mm (S.D.), 1.0 ± 0.3, 1.3 ± 0.3, and 1.5 ± 0.4, respectively. Graphically, these findings produced bone loss curves similar to those observed in man. These results indicate that the rat model may be utilized in longitudinal studies of the resorption of the residual ridge.
Analysis of Photo-initiators in Visible-light-cured Dental Composite Resins
Authors: Taira M. , Urabe H. , Hirose T. , Wakasa K. , Yamaki M. 
Published: November 2010

Seven commercial visible-light-cured (VL) dental composite resins were analytically studied for identification of the photo-initiator consisting of photo-sensitizer and reducing agent. Gas-liquid chromatography (GC) was used for the determination of the dilute components extracted from the composite resin. Mass spectroscopy (GC-MS) was used for confirmation of the qualitative data obtained by GC. The results showed that all composite resins examined included camphorquinone (CQ) as a photo-sensitizer. The concentration of CQ in the resin phase, however, ranged from 0.17 to 1.03% w/w. The composite resin with hybrid-sized filler tended to have a higher concentration of CQ than did the micro-filled composite resin. As for the reducing agent, two out of seven brands contained dimethylaminoethyl methacrylate (DMAEMA), and one included dimethyl-p-toluidine (DMPTI). The mixing ratio between CQ and the amine in these three composite resins also varied. Another four brands did not contain either DMAEMA or DMPTI, and would utilize different reducing agents.
Influence of Contraction Mismatch and Cooling Rate on Flexural Failure of PFM Systems
Authors: Coffey J.P. , Anusavice K.J. , Dehoff P.H. , Lee R.B. , Hojjatie B. 
Published: November 2010

The interactive influence of cooling rate and the sign and magnitude of thermal contraction difference between metals and ceramic veneers on bond strength have not been extensively analyzed, although numerous bond-test studies have been reported during the past two decades. A previous analytical study of residual incompatibility stress in bond-test specimens indicated that bond strength values may be of relatively little value if the residual stress state of the metal-ceramic specimens is not considered. The objective of this study was to determine the influence of cooling rate and contraction mismatch on the flexural failure resistance of metal opaque-porcelain strips. Specimens were subjected to four-point loading in an Instron testing machine until crack initiation occurred at the metal-ceramic interface. The residual stress states in the ceramic region were estimated from finite element stress analyses of the bond-test specimens by use of dilatometry data obtained at the cooling rate of 3°Clmin. The total stress induced from the residual stress and the applied flexural load was also determined for these specimens. Statistical analyses of the experimental data revealed that the slowly cooled specimens exhibited a significantly lower (p < 0.05) flexural strength compared with rapidly cooled specimens. Regardless of the cooling technique, metal-ceramic specimens with a negative thermal contraction difference (αm - αp < 0) failed at significantly lower (p < 0.05) flexural loads than did specimens with a positive thermal contraction difference.
A Comparison of Different Treatments for Nocturnal Bruxism
Authors: Pierce C.J. , Gale E.N. 
Published: November 2010

One hundred bruxers were evaluated for bruxing activity before, during, and after treatment with a portable electromyograph (EMG). A six-month post-treatment follow-up of bruxing activity was obtained. Experimental treatment groups consisted of diurnal biofeedback, nocturnal biofeedback, massed negative practice, and splint therapy. A no-treatment control group was included. The comparative efficacy of treatments was determined by analyses of variance. Both EMG-measured frequency of bruxing episodes and duration of bruxing activity decreased significantly for nocturnal biofeedback and splint therapy treatments but not for massed negative practice, diurnal biofeedback (relaxation), or the no-treatment control group. The two-week treatment effects were transient, and bruxing activity generally returned to baseline levels when treatment was withdrawn. These findings are consistent with the findings of previous researchers with regard to nocturnal biofeedback and splint therapy but differ from previous findings for massed negative practice therapy.
Artificial Caries around Restorations in Roots
Authors: Purton D.G. , Rodda J.C. 
Published: November 2010

An artificial caries technique was used to produce caries-like lesions in the cavity walls adjacent to micro filled resin restorations with and without dentin bonding agent, and glass-ionomer cement restorations, in the roots of extracted teeth. The lesions had histological characteristics similar to those of natural lesions and to those of the lesions produced by other experimental methods. The zonal pattern of the lesions was examined by means of polarized light microscopy and microradiography, and the depth of the lesions was measured for assessment of the microleakage around the restorations. Three cavity cleaning regimes — water spray alone, 50% citric acid, and a proprietary cleaner — were compared in conjunction with the three restorative methods. Cavity cleaning with the citric acid or the proprietary cleaner, and the use of a fluoride-releasing restorative material, acted to reduce the depths of the lesions. Glass-ionomer cement restorations in cavities cleaned with citric acid showed lesions significantly shallower than those treated with other restorations. The glass-ionomer cement was soluble in the acidic environment but promoted the precipitation of minerals in the lesions. The use of a dentin bonding agent did not affect the depth of demineralization around the micro filled resin restorations.
Assessing Composite Resin Wear in Primary Molars: Four-year Findings
Authors: Vann W.F. , Barkmeier W.W. , Mahler D.B. 
Published: November 2010

Many investigators have reported minimal wear of resin restorations in primary molars. Until recently, quantitative wear assessments have not been reported. The purpose of this investigation was (1) to present and contrast data from two 48-month clinical trials wherein quantitative wear assessments were used to evaluate wear of resin restorations in primary molars, and (2) to compare these results with those using the USPHS method of wear assessment. The data were collected from two different clinical trials. One was conducted at the University of California in San Francisco by Tonn and Ryge (TR Trial). The other was conducted at the University of North Carolina at Chapel Hill by Oldenburg, Vann, and Dilley (OVD Trial). The OVD Trial had a sample size of 45 patients with 106 restorations; the TR Trial had 44 patients with 96 restorations. The restorations in both trials were Class I and II restorations in occlusion. They were placed with the experimental light-cured posterior composite resin F-70, later marketed as Ful-Fill®. At baseline, six, 12, 24, 36, and 48 months, restorations were evaluated by two evaluators trained in USPHS criteria as well as by a quantitative method of wear assessment, the standard cast technique as described by Leinfelder. Interstudy comparisons were made by Chi-square tests (USPHS evaluations) and ANOVA (quantitative assessments). The results showed that resin restorations in primary molars exhibited progressive wear with time in service. The rate and quantity of wear were very similar to those seen in permanent posterior teeth over 36 months. Findings agree with previous reports that the USPHS evaluation criteria are insensitive in detecting early wear in primary molars.
A Theoretical Model of Loading and Eminence Development of the Postnatal Human Temporomandibular Joint
Authors: Nickel J.C. , McLachlan K.R. , Smith D.M. 
Published: November 2010

The objectives of the present study were to characterize the loading of the immature TMJ, and to develop a theoretical model to explain the relationship between joint loading and development of the eminence of the human TMJ. The osteological remains of forty individuals, ages ranging from birth to twenty years, were used to provide metric coordinates of the three-dimensional relationships of the anatomy of the biting apparatus. The data were used, in a numerical model of TMJ loading (Smith et al., 1986), to calculate the magnitudes and directions of condylar loading. The following conclusions were drawn: (i) static equilibrium cannot be satisfied unless the immature TMJ is loaded; (ii) in the neonate, the direction of condylar loading is approximately vertical but, as the child matures, the angle of condylar loading becomes more oblique; and (iii) evidence is given in support of the hypothesis that early development of the eminence is consequent upon the stimulation of bone growth by the appropriate position and timing of loading of the immature condyle on the temporal component of the joint.
Micro-analysis of Mineral Saturation Within Enamel During Lactic Acid Demineralization
Authors: Vogel G.L. , Carey C.M. , Chow L.C. , Gregory T.M. , Brown W.E. 
Published: November 2010

In this study, the physicochemical factors responsible for caries-like lesion propagation were investigated by means of a micro-analytical system used to study the fluid within a lesion during a simulation of the decay process. Four 500-μm-thick serial sections prepared from a single human molar were mounted between glass plates with only the natural surface of the tooth exposed. Microwells were then drilled into sound and pre-existing carious regions of the section through one of the plates. These microwells were then filled with fluid under mineral oil, and after a week of equilibration, the natural surface of the section was exposed to a lesion-producing fluid. The concentrations of calcium, phosphate, and hydrogen ions of the fluid in the wells were then followed as a function of time as the lesion advanced. The results of this study, in which lactic acid was used to demineralize enamel, were consistent with those previously reported (Vogel et aL, 1987a): The solution within the lesion remained saturated during the acid attack. Differences in initial mobilities of the calcium and phosphate and other ions, a result of the permselectivity of the enamel, increased the concentrations within the lesion and permanently changed the ratio of these ions in the lesion solution. Based on these results, we suggest that the ionic permselectivity of tooth enamel can have a profound effect on the transport of mineral from a caries lesion.
The Effects of Sugars Intake and Frequency of Ingestion on Dental Caries Increment in a Three-year Longitudinal Study
Authors: Burt B.A. , Eklund S.A. , Morgan K.J. , Larkin F.E. , Guire K.E. , Brown L.O. , Weintraub J.A. 
Published: November 2010

A three-year longitudinal study was carried out with a group of children, initially aged 11-15, residing in non-fluoridated rural communities in south-central Michigan. This report analyzes the relation between caries increment and consumption of sugars from all sources to see if accepted relationships have changed with the caries decline in the United States. There were 499 children who provided three or more 24-hour dietary recall interviews, and who received dental examinations at baseline and after three years. Caries increment averaged 2.91 DMFS over the three years, with 81 % of new lesions on pit-and-fissure surfaces. Consumption of sugars from all sources averaged 156 g per day for males and 127 g per day for females, an average of 52 kg per person per year. Sugars constituted one-quarter of total caloric intake for both boys and girls, and the average number of eating occasions per day was 4.3. Children who consumed a higher proportion of their total energy intake as sugars had a higher increment of approximal caries, though there was little relation to pit-and-fissure caries. The average number of daily eating occasions was not related to caries increment, nor was the average number of sugary snacks (defined as foods with 15% or more of sugars) consumed between meals, but the average consumption of between-meal sugars was related to the approximal caries increment. When children were categorized by high caries increment compared with no caries increment, a tendency toward more frequent snacks was seen in the high-caries children. In an age of generally declining caries, it was concluded that higher average daily consumption of sugars, and higher between-meal consumption of sugars, was still a risk factor for children susceptible to approximal caries. Overall frequency of eating and frequency of ingestion of sugary foods between meals, however, were both poorly related to approximal caries increment. Pit-and-fissure caries could not be related to any aspect of sugars consumption.
Effect of Zeta Potential and Surface Energy on Bacterial Adhesion to Uncoated and Saliva-coated Human Enamel and Dentin
Authors: Weerkamp A.H. , Uyen H.M. , Busscher H.J. 
Published: November 2010

Physicochemical surface characteristics of early plaque-forming bacteria and of human tooth surfaces were measured to establish their role in bacterial adhesion to intact dental tissue slabs. In addition, the influence of an experimental salivary pellicle was evaluated. Strains of S. mutans, S. sanguis, S. salivarius, A. viscosus, and A. odontolyticus showed relatively high surface free energies (range, 99-128 mJ.m-2) and carried a negative surface charge, at both physiological (μ = 0.057) and low (μ = 0.020) ionic strengths of the medium. Very large differences in hydrophobicity were detected when the hexadecane adsorption test was used for measurement. Powdered enamel and dentin were also negatively charged at low ionic strength but were slightly positively charged in the physiological buffer. The surface free energy of enamel and dentin increased upon saliva coating, whereas the surface charge was always negative. The adhesion experiments showed: (1) large differences in the binding of various bacteria to the same surface; (2) an up to 20-fold difference in the binding of the same bacterium to different surfaces, although the binding of some strains was relatively independent of the type of surface or presence of a salivary pellicle; (3) a significant decrease in adhesion when the ionic strength of the medium was lowered, due to increased electrostatic repulsion (however, the adhesion of some bacteria was independent of the ionic strength of the medium); (4) different time-dependent adherence kinetics, depending on both the bacteria and nature of the solid surface; and (5) a propensity for plaque streptococci to bind to uncoated dentin.
Periodontal Disease in Adolescents: Some Clinical and Microbiologic Correlates of Attachment Loss
Authors: Carlos J.P. , Wolfe M.D. , Zambon J.J. , Kingman A. 
Published: November 2010

The influence of several clinical and microbiological variables on the site-specific risk of attachment loss was studied in Navajo Indian adolescents aged 14-19. Diagnoses were made at mesio-buccal sites of the four first permanent molars. Case-control analytical methods were used, with A. actinomycetemcomitans, B. gingivalis, and B. intermedius considered the "risk" variables, and with calculus, gingival bleeding, age, and gender treated as possible confounders. The presence of B. intermedius significantly increased the likelihood that attachment loss would be diagnosed at a site (odds ratio = 2.86). However, this association was confounded by calculus and gingival bleeding; when either or both were present, the effect of B. intermedius was markedly weaker. Step-wise multiple logistic regression analyses showed that, of the variables considered, the combination of calculus, gingival bleeding, and B. intermedius gave the most parsimonious explanation of the presence of attachment loss. The chance that attachment loss would be diagnosed was increased five times when calculus was present, 16.5 times in the presence of both calculus and gingival bleeding, and 37 times when these variables plus B. intermedius were observed at a particular site.
Tempering Stresses in Feldspathic Porcelain
Authors: Dehoff P.H. , Anusavice K.J. 
Published: November 2010

The objective of this study was to develop an analytical model to calculate transient and residual (tempering) stresses in dental porcelain plates subjected to cooling rates used by commercial laboratories. The model incorporates linear viscoelasticity and structural relaxation effects. The viscosities of three experimental body porcelains and three experimental opaque porcelains as a function of temperature were calculated from creep rates measured in a bending beam viscometer. Measurements were made under thermal equilibrium conditions for temperatures ranging from 550°C to 625°C. Thermal expansion data measured in a differential dilatometer at slow heating rates were supplied by the manufacturer. Temperature distribution in the plates as a function of convective heat transfer coefficient, initial plate temperature, and plate thickness was calculated by use of standard numerical techniques. Calculations of transient and residual stress were performed for one body porcelain, for two plate thicknesses, and for three variable cooling rates. Calculated surface residual stresses were strongly dependent on plate thickness, cooling rate, and initial soak temperature. For the cases studied, the maximum residual surface compressive stress was 26.4 MPa.
The Detection of Incipient Caries with Tracer Dyes
Authors: O'Brien W.J. , Vazquez L. , Johnston W.M. 
Published: November 2010

The purpose of this study was to determine the increase in color contrast produced by the use of a tracer dye in detection of incipient caries lesions with transillumination. Twenty four caries-free first premolars were immersed in an acid gelatin for production of artificial incipient caries lesions. After the lesions had developed, these teeth were photographed by transillumination. Two photographs were taken of each tooth. The first photograph showed the lesion without dye. A blue tracer dye was then added and absorbed by the lesion, and a second photograph was taken. The data on the color difference were obtained by use of a reflectance colorimeter and showed a four-fold increase between the lesion and surrounding area with the dye. A two-way analysis of variance was used for the statistical interpretation. The color difference between the lesion without the dye and then with the dye was significant. The use of the blue tracer dye, therefore, significantly increased the contrast in the images of the artificial incipient lesions.