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At least 163 records · Page 9Linked to original sources
PubMed1993

Evaluation of two dentin adhesives in cervical lesions.

The clinical effectiveness of two dentin adhesives, Clearfil New Bond and Scotchbond 2, was evaluated in two different cavity designs. Group A was without enamel bevel or acid etch and with a butt-joint cavity; and group B had enamel bevel, acid etch, and feather-edged cavities. The retentive rate and marginal adaptation were monitored for 2 years. In the Clearfil system, 21% of group A restorations failed after 2 years, whereas virtually all the group B restorations (99%) were retained. In addition, after 2 years, the total of debonded group A restorations in the Scotchbond 2 system expanded to 13%, whereas no restorations from group B were lost. There was clearly marginal deterioration in time irrespective of the bonding system. Nevertheless, the marginal adaptation of cervical lesions restored with Clearfil New Bond adhesive in combination with Clearfil Ray composite resin revealed fewer defects compared with the Scotchbond 2 adhesive with Silux Plus composite resin restorations. SEM evaluation disclosed composite resin remnants on the dentin surface in cavities with lost fillings, which indicates partial cohesive failure of the adhesive joint.

Composite Resins↗
PubMed1995

Assessment of tooth wear in an ageing population.

A random sample of 2222 adults aged 45 years and over was taken from the age/sex registers of two general medical practices in Newcastle upon Tyne, and asked to take part in a dental health survey. A total of 1002 individuals agreed to take part and were visited in their homes. Five hundred and eighty-six subjects were dentate and able to undergo an assessment of tooth wear using the Tooth Wear Index (TWI). Increasing wear with increasing age was observed for all cervical and occlusal/incisal tooth surfaces. Occlusal/incisal surfaces displayed some of the highest mean wear scores, especially in the older age cohorts. With the exception of lingual surfaces of maxillary anterior teeth, no significant variation in tooth wear with age was noted for buccal or lingual surfaces. Greater mean wear scores were observed among males than females, but there was little variation between subjects of different social class backgrounds. The threshold levels of wear suggested for use with the TWI may require modification for use among elderly populations.

Age Factors↗
PubMed1990

A modified Gustafson method of age estimation from teeth.

Modifications to the Gustafson method of age estimation from teeth are described. They are designed to minimise the subjective nature of the scoring technique and to quantify the regressive changes in the enamel, dentine and cementum. Randomly selected teeth from 25 Indians were examined by the Gustafson method and by our own modification. It was shown that our modified method resulted in more accurate and reproducible age estimations than did the original method.

Age Determination by Teeth↗
PubMed1993

A new method for dental age estimation in adults.

Several statistical methods have been proposed for estimation of age from teeth in human adults. Due to the smallness of the material or statistical shortcomings in previous reports, improvements of the methods were desirable and seemed possible. As a contribution to such improvement various age-related changes have been studied in a material of 1000 teeth. For each type of change the kind of measurement most strongly related to age was chosen, and a multiple regression analysis was run with age as the dependent variable, using SPSS/PC+ statistical program. Statistically significant formulae were calculated for each type of tooth excluding molars. Because the sex of a deceased body may be unknown and the tooth colour influenced by changes after death, separate formulae excluding these factors were calculated. For the calculated formulae the Pearson correlation (tau) varied from 0.76 in mandibular second premolars (SEX and COLOUR excluded), to 0.91 for maxillary central incisors; a rather promising result compared with other methods. In addition, the intercorrelations between the age-related factors were calculated after control for the effect of age. In some types of teeth, but not in all, some of the factors displayed significant intercorrelation. To compare these formulae with previous methods an unbiased test in another independent material is needed.

Age Determination by Teeth↗
PubMed1990

Australian aboriginal tooth succession, interproximal attrition, and Begg's theory.

In 1954, P.R. Begg analyzed interproximal attrition as a prehistorically universal mechanism to reduce tooth size. With modern processed diets and the virtual disappearance of constant interproximal attrition, Begg asserted, teeth remain too large for the arches and become crowded. Later investigators have questioned Begg's estimate of attritional tooth-size reduction, as well as aspects of his theory relating the succession sequence of permanent teeth to different malocclusions. The present paper examines the theory using longitudinal casts and records of modern Australian aborigines who are among the first generation lacking notable interproximal attrition thanks to a "modernized" diet. Deciduous and permanent tooth size, arch size, and occlusal relational variables were analyzed with respect to the expected occlusal outcomes in the absence of attritional tooth reduction. Permanent incisor overjet correlated with crowding status, as predicted by Begg. On the other hand, longer teeth did not relate to crowding in general nor to crowding in relevant local areas or during developmental stages. Unfavorable leeway space did not relate clearly to crowding or other malocclusions. Lowered correlations among structures and narrowness of the maxilla related more significantly to malocclusion. These results are in keeping with recent thinking that small jaws rather than large teeth underlie tooth/arch discrepancy.

Australia↗
PubMed1991

Adaptability of the adult primate craniofacial complex to asymmetrical lateral forces.

The adaptability of the adult craniofacial skeleton to altered functional relationships has been reported. An experimental quantification of these changes is lacking, however, and the possible underlying mechanisms of the alterations have not been explained. The purpose of this investigation was to evaluate the effect that lateral displacement of the mandible has on the dentoalveolar, craniofacial, and neuromuscular system in the adult rhesus monkey. Ten adult monkeys were studied; five served as controls, three were fitted with bilaterally inclined mandibular splints designed to deviate the mandible toward the left on closure, and two animals had flat splints to provide even occlusal contact. Pretreatment and posttreatment assessment of dentoalveolar and craniofacial change was made from mounted study casts, cephalometric head films, electromyograms and computed tomograms. Axial computed tomographic scans were used to evaluate potential changes in bone density at the lower part of the mandible, the condyle, the coronoid process, the neck of the condyle, and the zygomatic arch by means of a one-way analysis of variance. Changes in the measured variables were not observed in the control animals or in the animals with flat splints. Animals with inclined splints, however, demonstrated attrition and intrusion of maxillary molars and mild proclination of the maxillary incisors. Posttreatment computed tomographic scans in these animals showed significantly increased bone density in the right coronoid process (p less than 0.05) and bilaterally at the necks of the condyles (p less than 0.005). Resting electromyographic activity remained low and was not significantly different among the three groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed2005

Prevention of enamel demineralization: an in-vitro study using light-cured filled sealant.

INTRODUCTION: Enamel demineralization is an undesirable side effect of orthodontic treatment with fixed appliances. The purpose of this in-vitro study was to evaluate the efficacy of applying a light-cured filled sealant onto the buccal tooth surfaces to prevent demineralization. METHODS: Fifty extracted human third molars were allocated to 1 of 5 groups: (1) enamel surface untreated (control); (2) surface etched; (3) fluoride varnish applied; (4) enamel etched and coated with a light-cured, unfilled sealant (control sealant); and (5) enamel etched and coated with a light-cured, filled sealant (Pro Seal, Reliance Orthodontic Products, Itasca, Ill). The enamel surface of each specimen was brushed for 15,000 strokes with nonfluoride toothpaste slurry with a piston-action brushing machine under a standardized load. All samples were then cycled for 14 days through a daily procedure of demineralization for 6 hours and remineralization for 17 hours. Then the teeth were sectioned and evaluated quantitatively by cross-sectional microhardness testing. RESULTS: Demineralization in the Pro Seal group was significantly less (P < .05) than in the other groups. Teeth treated with fluoride varnish exhibited 30% less demineralization than the control teeth, the enamel-etched teeth, and the teeth treated with a light-cured, unfilled sealant (P < .05). CONCLUSIONS: Pro Seal can be considered for use as a preventive method to reduce enamel demineralization adjacent to orthodontic attachments, particularly in patients who exhibit poor compliance with oral hygiene and home fluoride use.

Analysis of Variance↗
PubMed2004

The laboratory assessment of enamel erosion: a review.

OBJECTIVES: To review the various methods and techniques available to assess enamel erosion in vitro. DATA: Peer reviewed scientific articles. SOURCES: Medline and Web of Science searches and manual searching. STUDY SELECTION: Laboratory based assessments only included. CONCLUSIONS: A number of macroscopic and microscopic techniques have been used to assess enamel erosion in vitro and in situ. This review examines techniques which are either well established or comparatively novel techniques that are being explored for their potential.

Dental Enamel↗
PubMed2004

A safety study in vitro for the effects of an in-office bleaching system on the integrity of enamel and dentine.

OBJECTIVE: The aim of this study was to investigate safety concerns with bleaching procedures by studying the effects of a high concentration hydrogen peroxide (HP) in-surgery bleaching product on enamel and dentine. METHOD: Flat enamel and dentine samples embedded in epoxy resin were prepared from human third molar teeth. Erosion of enamel: groups of enamel samples were treated with 35% HP then citric acid (CA) or brushing with toothpaste or CA alone and water alone. Enamel Loss was measured using a profilometer. Abrasion/erosion of dentine: groups of dentine specimens were treated as follows: Group 1--brushed with water for 30 min. Group 2--brushed with 35% HP for 30 min. Group 3--power bleached for 30 min and then Group 4--brushed with toothpaste for 1 minute. Group 5--water soaked for 30 min followed by brushing with toothpaste for 1 min. Group 6--orange juice soaked for 30 min followed by brushing with toothpaste for 1 min. Treatment effects were measured using a profilometer. Hardness tests: enamel and dentine specimens were hardness tested using a Wallace indenter prior to and post bleaching. Scanning Electron Microscopy: enamel and dentine specimens were taped and the exposed tissue treated with 35% HP and then studied under scanning electronmicroscopy (SEM). RESULTS: Enamel erosion: bleaching enamel samples had no measurable effect on enamel. Pre-bleaching had no significant effect on subsequent CA erosion or brushing. Abrasion/erosion of dentine: no significant differences were found between treatments 1-5 with little change from baseline detected. Orange juice (Group 6) produced considerable and significantly more erosion than other treatments. Hardness tests: there were no significant changes in hardness values for enamel and dentine. SEM: there was no evidence of any topographical changes to either enamel or dentine. CONCLUSION: Using one of the highest concentrations of HP for tooth bleaching procedures and maximum likely peroxide exposure, there was no evidence of deleterious effects on enamel or dentine. It must be assumed that studies which reported adverse effects on enamel and or dentine of bleaches reflect not the bleach itself but the pH of the formulation used.

Beverages↗
PubMed2005

Retention of a resin-modified glass ionomer adhesive in non-carious cervical lesions. A 6-year follow-up.

OBJECTIVES: The purpose of this study was to evaluate the clinical retention of a new resin-modified glass ionomer cement based adhesive combined with a hybrid resin composite or a poly-acid modified resin composite in non-carious cervical lesions during a 6-year period. METHODS: The resin-modified glass ionomer adhesive (Fuji Bond LC), was placed in 73 cervical lesions, 36 with a universal hybrid resin composite (Tetric Ceram) and 37 with a poly-acid modified resin composite (Hytac). Fifty-one in lesions with sclerotic dentin and 22 in non-sclerotic ones. Of the sclerotic lesions 38 were slightly roughened with a diamond bur before conditioning. The restorations were evaluated with slightly modified USPHS criteria every six months during a 6-year period. RESULTS: All except six restorations were evaluated during the 6 years. Twelve (17.9%) were lost, four Tetric Ceram (11.8%) and eight Hytac (24.2%) (p<0.05). Four were found in non-sclerotic lesions (20.0%) and eight in sclerotic lesions (17.0%). The differences between the sclerotic and non-sclerotic and the roughened and non-roughened lesions were not significant. CONCLUSIONS: The resin-modified glass adhesive showed a superior clinical retention combined with the resin composite material, with an annual failure rate of 2%.

Adult↗
PubMed2006

Severe wear and tooth loss in wild ring-tailed lemurs (Lemur catta): a function of feeding ecology, dental structure, and individual life history.

The ring-tailed lemurs at Beza Mahafaly Special Reserve, Madagascar, exhibit a high frequency of severe wear and antemortem tooth loss. As part of a long-term study, we collected dental data on 83 living adult ring-tailed lemurs during 2003 and 2004. Among these individuals, 192 teeth were scored as absent. The most frequently missing tooth position is M1 (24%). As M1 is the first tooth to erupt, its high frequency of absence (primarily a result of wear) is not remarkable. However, the remaining pattern of tooth loss does not correlate with the sequence of eruption. We suggest that this pattern is a function of 1) feeding ecology, as hard, tough tamarind fruit is a key fallback food of ring-tailed lemurs living in gallery forests; 2) food processing, as tamarind fruit is primarily processed in the P3-M1 region of the mouth; and 3) tooth structure, as ring-tailed lemurs possess thin dental enamel. The incongruity between thin enamel and use of a hard, tough fallback food suggests that ring-tailed lemurs living in riverine gallery forests may rely on resources not used in the past. When comparing dental health in the same individuals (n=50) between 2003 and 2004, we found that individual tooth loss can show a rapid increase over the span of one year, increasing by as much as 20%. Despite this rapid loss, individuals are able to survive, sometimes benefiting from unintentional assistance from conspecifics, from which partially processed tamarind fruit is obtained. Although less frequent in this population, these longitudinal data also illustrate that ring-tailed lemurs lose teeth due to damage and disease, similar to other nonhuman primates. The relationship between tooth loss, feeding ecology, dental structure, and individual life history in this population has implications for interpreting behavior based on tooth loss in the hominid fossil record.

Age Factors↗
PubMed2005

In vivo correlation of noncarious cervical lesions and occlusal wear.

STATEMENT OF PROBLEM: The etiology of noncarious cervical lesions is not well understood. An understanding of the etiology helps the clinician determine appropriate treatment and management strategies. Purpose This study evaluated the relationship between noncarious cervical lesions and occlusal (or incisal) wear. MATERIAL AND METHODS: Casts (n = 299) made from dental students were articulated in a semi-adjustable articulator and evaluated. Data included the presence and contour of noncarious cervical lesions (NCLs) and the presence, location, and severity of any occlusal/incisal wear facets. Also included were Angle's classification, occlusal guidance patterns, midline, presence of tori, tooth restoration, reverse articulation (crossbite), open occlusal relationship, and posterior excursive contacts where present. Following a calibration procedure, 2 evaluators made independent observations on the casts. The first evaluator recorded for each tooth in each subject: presence and severity of NCLs, presence and extent of occlusal/proximal restorations, and presence of reverse articulation and open occlusal relationship. Following the first evaluation red rope wax was placed at the cervical margins of each tooth for the purpose of blinding the second evaluator from NCL observations. The second evaluator recorded severity and location of occlusal/incisal wear, presence or absence of posterior excursive contacts, Angle's classification, occlusal guidance pattern, any midline discrepancy, and presence or absence of tori. The Spearman correlation coefficient and chi 2 tests were used to analyze the data (alpha=.05). RESULTS: There was no relationship between noncarious cervical lesions and occlusal/incisal wear. There was also no correlation between NCLs and other parameters examined. CONCLUSIONS: Under the conditions of this study, noncarious cervical lesions are not related to occlusal wear.

Adult↗
PubMed2005

Finite element analysis of mechanism of cervical lesion formation in simulated molars during mastication and parafunction.

STATEMENT OF PROBLEM: The mechanical theory of cervical lesion formation is popular; however, the mechanism of formation of these lesions is not fully explained. PURPOSE: The aim of this study was calculation of the stresses and Tsai-Wu strength ratio in the cervical area of the mandibular molar during grinding, clenching, and mastication, as well as theoretical investigation of the mechanism of cervical lesion formation in teeth. MATERIAL AND METHODS: A 2-dimensional finite element model of the mandibular first molar and crown of the opposing maxillary molar in the frontal section was developed. Computational simulation of mastication of a bolus with high elastic modulus, including grinding and clenching, was performed. Pairs of contact elements were used between the bolus and occlusal surfaces of the teeth. The analysis was nonlinear. During these simulations, the pressure exerted on the occlusal surface and the state of stresses in the mandibular molar were calculated. To evaluate the strength of anisotropic tooth tissues, the Tsai-Wu failure criterion was applied. This criterion considers the difference in strength of materials due to tensile, compressive, and shear stresses. RESULTS: Significant pressures were exerted on lingual cusps of the mandibular molar model during computer simulations of physiological and pathological load. In enamel elements close to the buccal cemento-enamel junction (CEJ) of the studied tooth, tensile stresses were observed which exceeded the strength of the enamel. In this area, the Tsai-Wu strength ratio reached values higher than 1. According to the Tsai-Wu criterion, these elements were damaged and, thus, were removed from the computer tooth model. During subsequent modeling of the tooth with the initiated cervical lesion, the Tsai-Wu ratio exceeded 1 along the dentino-enamel junction (DEJ), creating an overhang of enamel in the cervical area. Application of minimal horizontal force caused a fracture of this fragile, unsupported enamel fragment. CONCLUSIONS: Overloading of theoretical teeth by computer simulation resulted in enamel damage at the CEJ and led to initiation of a cervical lesion. Subsequent overloading resulted in enamel destruction along the DEJ. The overhanging enamel fragment may easily be chipped. This process was repeated during subsequent tooth overloading and caused enlarging of the lesion.

Anisotropy↗