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PubMed1996

Quantitative determination of total molar concentrations of bioaccumulatable organic micropollutants in water using C18 empore disk and molar detection techniques.

A highly sensitive and quantitative group parameter to determine total molar concentrations of organic micropollutants that can bioaccumulate in the lipid phase of aquatic organisms from effluents, surface water, and drinking water has been developed. C18 empore disk was used as a surrogate lipid phase. The partition process between water and C18 empore disk was employed to simulate the bioaccumulation process. After partition extraction of the water sample, the empore disk was extracted with cyclohexane, and total molar concentrations were determined in these extracts using vapor pressure osmometry (VPO) and gas chromatography/mass spectrometry (GC/MS), respectively. Total molar concentrations bioaccumulated in aquatic biota were estimated from the cyclohexane concentrations. Good accuracy for the total molar determination was obtained using VPO, due to the practically constant molar response factors (43.1 +/- 1.7 V/M) for a wide compound range and to excellent additivity of individual compound responses. Satisfying reproducibility (0-8.3%) of VPO was obtained for sample extracts. The detection limit of VPO in cyclohexane extracts corresponded to 0.60 mM in the lipid phase of aquatic biota. A minimal separation GC/MS system was developed, which enabled highly sensitive and sufficiently accurate total molar determinations. The reproducibility of the GC/MS determination for samples ranged from 0.7 to 22%. The detection limit of GC/MS in cyclohexane extracts corresponded to 0.044 mM in the lipid phase. The determined total molar concentrations in the lipid phase of aquatic biota were in the range of 0.139-168 mM for effluents, 0.26-1.34 mM for surface water systems, and < 0.044 mM for drinking water.

Chemical Phenomena↗

PubMed1982

Attachment levels and crevicular depths at the distal of mandibular second molars following removal of adjacent third molars.

The effect of root planing and curettage on the crevicular depth and periodontal attachment at the distal of mandibular second molars following removal of adjacent impacted or partially erupted third molars was evaluated in 18 patients, between the ages of 18 and 25, presenting with similar bilateral impactions. No significant difference was demonstrated in the crevicular depths and attachment levels between the curetted, root planed side, and the untreated controls. Thus, any benefits derived by root planing and curettage of mandibular second molars immediately following removal of adjacent impacted third molars are minimal. The best means of preserving periodontal attachment on mandibular second molars may be the removal of third molars at an early stage of tooth development.

Adolescent↗

PubMed1991

The role of the prosthodontist in restoring root-resected molars: a study of 70 molar root resections.

Root resection is a complex, multidiscipline technique to eliminate molar furcation invasions. In the short term of 3 or 4 years it has been highly successful, but after 10 years approximately one third fail. A substantial number of failures were attributed to recurrent periodontal disease. This study examined 70 root resected molars in 62 patients for the quality of the resections. Twenty-one (30%) of the resections were considered faulty when subgingival, residual roots, furcal lips, and/or ledges were present. Failures were more frequent in maxillary molars (33.3%) than mandibular molars (22.7%). Clinically hidden roots/lips and ledges in mandibular molars were readily observed in radiographs, but were seen radiographically only 37.5% of the time in maxillary molars. Since subgingival defects are believed to encourage future periodontal disease, it is important that the dentist detect these structures and correct them before proceeding with the permanent restoration.

Adult↗

PubMed1985

Third molar changes following second molar extractions.

Third molars, both upper and lower, do usually erupt into the place of electively removed second molars. None of the third molars in this study group became impacted during the observation period. Second molars in this study were removed before the roots had formed on the third molars. The bifurcation line appears to be a stable reference on the panoramic radiograph. It is the Author's conclusion that the extraction of permanent second molars is best for many patients, and when judiciously applied it is a reasonably safe and conservative modality in orthodontic care.

Adolescent↗

PubMed1998

[The study on the attrition of molars with occlusal hypersensitivity molars in elderly people].

OBJECTIVE: To investigate the attrition of molars in old people who suffered from occlusal hypersensitivity. METHODS: 113 maxillary and mandibular molars of old people (47-74 years old) who had dentine hypersensitivity caused by attrition were studied. The Lavelle's criteria were used. RESULTS: When the attrition reached to the e type, the rate of lesion rose up quickly (19.47%), the highest incidence was seen in g type (41.59%). The hypersensitivity occurred as 48.67% in the first molar, 51.33% in the second molar, 53.10% in enamel-dentin junction, and 38.05% in dentine concave site. CONCLUSION: The rate of hypersensitivity rises with the severity of attrition. There is no significant difference between the first molar and the second molar, but the incidence of hypersensitivity in enamel-dentin junction is significantly higher than in dentine concave site (P < 0.05).

Aged↗

PubMed1994

Fractal geometric analysis of material from molar and non-molar pregnancies.

Histological sections from 25 non-molar pregnancies, nine partial hydatidiform moles, and 16 complete hydatidiform moles were examined (diagnosis was taken as the consensus of seven experienced histopathologists) and the fractal dimension was measured using a box-counting method implemented on a microcomputer-based image analysis system. The fractal dimensions of the different diagnostic categories were normally distributed with a mean of 1.50 for non-molar pregnancies, 1.44 for partial moles, and 1.42 for complete moles. All the measured fractal dimensions were greater than the topological dimension (1), demonstrating that the specimens had a fractal element to their structure. There was a significant difference between the fractal dimensions of non-molar pregnancies and complete moles (P = 0.0005), but not between partial moles and non-molar pregnancies (P = 0.0823) or complete and partial moles (P = 0.4400). Using the fractal dimension to predict the histopathological diagnosis assigned 56 per cent of the cases to the correct category with a kappa statistic of 0.26, so the fractal dimension, used alone, is not a useful morphometric discriminant in the diagnosis of molar and non-molar pregnancy.

Female↗

PubMed2002

[Eruption disturbances of the second molar in the upper jaw by the third molar].

Eruption disturbances of the upper second permanent molars are quite rare, mostly asymptomatic and usually discovered by coincidence on a panoramic x-ray. The exact cause of eruption disturbances is unknown. A panoramic image related to the chronological age shows whether there is an eruption disturbance or not. Treatment modalities of eruption disturbance of the upper second permanent molar in combination with an unerupted third molar are being discussed in this article. Mostly the third molar is removed and the second one will erupt. Eruption disturbances that are discovered after completion of the root formation usually will not lead to spontaneous eruption of the second molar, even when the obstruction has been removed.

Adolescent↗

PubMed1981

The effect of buffer molarity on axonal exposure and axoaxonal apposition in the rat molar pulp.

Axons in the rat molar pulp have been examined morphometrically to determine axonal size and the degree of axonal exposure and axoaxonal apposition in tissue fixed by perfusion using 2% glutaraldehyde in cacodylate buffers ranging in molarity form 0.025 M to 0.4 M. Between 31.2% and 45.0% of the axons were incompletely ensheathed. This proportion of axons exposed was linearly related to the buffer molarity (P less than 0.05) and was approximately double that found in more central axons. Between 32.3% and 45.0% of the axons were in contact with other axons. This proportion was not linearly related to buffer molarity but was least ten times higher than that observed in more centrally positioned nerve fibers in the inferior alveolar nerves. Increasing buffer molarity reduced the size of the axons, a relationship not found in the more central axons. It is suggested that axonal exposure and axoaxonal apposition are constant, significant features of pulpal nerve fibers that may be related to the onset and spread of nociceptive activity. The permeability properties of pulpal axons may differ from those of more centrally placed axons.

Animals↗

PubMed2006

Concrescence of a mandibular third molar and a supernumerary fourth molar: report of a rare case.

Concrescence represents a rare developmental anomaly in which two fully formed teeth are joined along the root surfaces by cementum. Maxillary molars are the teeth most frequently involved, especially a third molar and a supernumerary tooth. Very few cases have been reported about the concrescence of a third molar and a supernumerary tooth. According to our current knowledge, this case report is the first in the literature in which concrescence is observed between a third molar and a supernumerary fourth molar in the mandible.

Adult↗

PubMed1977

Effects on lower third molars after extraction of second molars.

The material consisted of 78 cases, 44 males and 34 females of the ages of 10-15 years. The orthodontic treatment followed the diagnosis of Class II malocclusion with crowding in the lower jaw. In addition to extraction of lower second molar the treatment consisted of distal driving of lower first molars in different ways. The treated cases were assessed by use of study models and lateral oblique X-rays. No third molars were treated in any cases. The results showed that in the majority of cases the third molars were adequate substitutes for the extracted second molars.

Adolescent↗

PubMedDate not supplied

Influence of approximal caries in primary molars on caries rate for the mesial surface of the first permanent molar in swedish children from 6 to 12 years of age.

The objective was to assess the influence on the caries rate for the mesial surface of the first permanent molar (6m) of the caries status of the distal surface of the second primary molar (05d) in children from 6 to 12 years of age. The study design was retrospective and included 374 children with an average of 5 sets of bite-wing radiographs. The mean age of the children was 6.7 years when the first bite-wing radiographs were taken and 11.5 years at the time of the latest radiographs included in the study. The approximal surfaces were classified according to a scoring system: 0 = no visible radiolucency, 1= radiolucency in the outer half of the enamel, 2 = radiolucency in the inner half up to the enamel-dentin border, 3 = radiolucency with a broken enamel-dentin border but with no obvious involvement of the dentin, 4 = radiolucency with obvious spread in the outer half of the dentin, and score 5 = radiolucency in the inner half of the dentin. The influence of the status of 05d on the caries rate for 6m (state > or =2) was assessed by using a model for dependence between the two neighbouring surfaces. Presence or absence of approximal caries in the distal surface of the first primary molars (04d) and/or the mesial surface of the second primary molars (05m) at the time of eruption of 6m was also related to the caries rate for 6m. The caries rate for 6m was 15 times higher if 05d had developed enamel/enamel-dentin border caries (state 2 or 3) compared to a radiographically sound 05d (state 0 or 1). No significant increase in the caries rate for 6m was found when 05d had deeper unrestored dentin caries than when 05d had superficial caries (state 2 or 3). Furthermore, for preventing caries in 6m, no benefit could be found from restoring an 05d with dentin caries with amalgam as opposed to leaving the carious lesion unrestored until exfoliation. The caries rates for 6m and 05d were 3.4 and 2.7 times higher, respectively, in the presence of dentin caries/restoration in 04d/05m compared to absence of dentin caries in these molar surfaces at the time of eruption of 6m. In conclusion, the caries rate for 6m depended on the status of 05d and increased 15 times if 05d had enamel/enamel-dentin border caries compared to a sound 05d. Deeper unrestored or restored dentin lesions in 05d did not result in a higher caries rate for 6m compared with more shallow carious lesions in 05d.

Chi-Square Distribution↗

PubMed1992

Partial molar volumes of the amino acid side-chains of proteins in aqueous solution: some comments on their estimation using partial molar volumes of amino acids and small peptides.

The partial molar volumes of some amino acid side-chains were determined in two recent studies [Makhatadze, G.I., et al. (1990) Biopolymers 30, 1001, and Reading, J.F. & Hedwig, G.R. (1990) J. Chem. Soc. Faraday Trans. 86, 3117] using partial molar volume data, V02, in aqueous solution at 25 degrees C for some peptides of sequence Gly-X-Gly, where X is an amino acid. These side-chain partial molar volumes are critically compared with those obtained using V02 data for amino acids. It is concluded that side-chain partial molar volumes calculated using V02 data for the tripeptides are better estimates of side-chain partial molar volumes in proteins than are those determined using V02 data for amino acids.

Amino Acid Sequence↗

PubMed1993

Visual and radiographic diagnosis of occlusal caries in first permanent molars and in second primary molars.

Diagnosis of early occlusal caries has proved more difficult than that affecting smooth or approximal surfaces. With time, this type of lesion has come to form a greater proportion of caries as a whole and its accurate diagnosis is consequently becoming more important. The most widely used methods of diagnosis are visual inspection and bitewing radiography but the value of both of these for occlusal caries has been questioned. The aim of this study was to investigate the validity of diagnosis using each of these two methods in extracted teeth. A total of 100 first permanent molars and 100 second primary molars were used and teeth and sites with questionable or borderline caries were selected for examination. The condition of the tooth on section was used to validate. In these samples sensitivity of radiographic diagnosis was greater than that of visual diagnosis. Both methods showed good specificity. When radiographs were used together with visual examination the status of 82% of first permanent molars and 91% of second primary molars were correctly classified.

Child↗

PubMed1986

A histologic study of the width and nature of inter-radicular spaces in human adult pre-molars and molars.

Serial sections of jaw segments from a human post mortem population of 29 individuals providing 116 posterior interproximal sites were examined at the light microscopic level. Minimum inter-root distances at the locale of closest proximity ranged from more than 4 mm to less than 0.1 mm. They were located in the coronal third of pre-molars and mandibular first and second molars and the middle third of maxillary first molars and second molar interproximal spaces. Cancellous bone flanked by lamina dura was found between 89.6% of the teeth examined and was observed where inter-root distances exceeded 0.5 mm. At sites of less than 0.5 mm, cancellous bone was not observed, and, instead, adjacent laminae durae appeared fused (7.7%). Bone was not observed between root surfaces which were less than 0.3 mm apart, but in these instances the roots were connected by a periodontal ligament.

Adult↗

PubMed1993

Symptoms and lesions associated with retained or partially erupted third molars. Some variables of third-molar surgery in Norwegian general practice.

A questionnaire on third-molar problems was mailed to a systematic random sample of 200 Norwegian general dental practitioners in November 1991. A 88% return rate was obtained. The following conclusions were drawn: on an average, 3.8 patients with lesions or complaints from retained or partially erupted third molars were seen in general practice in 1 month, and most of these consultations were associated with partially erupted third molars. A mean of 1.3 surgical removals of third molars was performed in general practice in 1 month. The mean one-way travel time for patients to specialists in oral surgery was 1.3 h, and variations were not related to surgical activity in practice. Fourteen per cent of the general practitioners refer surgical cases to non-specialists.

Adult↗

PubMed2006

Ankylosis of primary molar along with congenitally missing first permanent molar.

Ankylosis of primary mandibular molars has been routinely found to be associated with various developmental disturbances in permanent dentition such as aplasia of the succedaneous tooth, ectopic eruption of the premolar, infraoclusion of the ankylosed tooth leading to tipping of the first permanent molar etc. This article describes a rare case where there was ankylosis of a mandibular second primary molar along with congenitally missing first permanent molar which resulted in the transposition of second premolar. Treatment options and prognosis of the case are discussed.

Adolescent↗

PubMed1991

The relationship between caries experience in the deciduous molars at 5 years and in first permanent molars of the same child at 7 years.

The sensitivity and specificity of predictors of caries in the first permanent molars based on caries experience in the deciduous molars were tested, using longitudinal data derived from a group of 565 children examined at the ages of 5 and 7 years. The best predictor of caries experience in the first permanent molars at the age of 7 years in this group of children was found to be caries experience in three or more deciduous molars at the age of five.

Age Factors↗

PubMed1997

Molar enthalpy and molar volume of methylene and benzene homologues in reversed-phase liquid chromatography.

In this study, thermodynamic properties are measured for methylene and benzene homologues in reversed-phase liquid chromatography using octadecylsilica stationary phases and methanol mobile phase. The change in molar enthalpy (delta H degree) is determined from graphs of the logarithm of the capacity factor versus the inverse temperature (15 to 60 degrees C), whereas the change in molar volume (delta V degrees) is determined from graphs of the logarithm of the capacity factor versus pressure (830 to 5000 p.s.i.). For octadecylsilica phases with low bonding density (2.7 mumol m-2), delta H degree and delta V degree are small and are relatively unaffected by temperature and pressure. These thermodynamic parameters are linearly related to the homologue number for the methylene homologues, but not for the benzene homologues. For the ethylene group, delta delta H degree and delta delta V degree are in the order of -0.41 kcal mol-1 and -1.0 cm3 mol-1, respectively, at 30 degrees C. As the bonding density increases (5.4 mumol m-2), the molar volume and molar enthalpy decrease in a significant and nonlinear manner with the homologue number. Moreover, these thermodynamic parameters are markedly affected by temperature and pressure. For the ethylene group, delta delta H degree and delta delta V degree are in the order of -3.65 kcal mol-1 and -14.1 cm3 mol-1, respectively, at 30 degrees C. The theoretical and practical implications of these measurements are discussed with respect to the retention mechanism in reversed-phase liquid chromatography.

Benzene↗