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PubMed1992

[The anatomical characteristics of the root furcations in the molar teeth].

The aim of the present study has been to realize a morphometrical and morphological study on the anatomical characteristics of molar teeth root furcations. Two hundred ninety four molars (147 upper and 147 lower teeth), after extraction and elimination of periodontal ligament residuals by trypsin, have been morphometrically evaluated recording the principal anatomical characters of the furcal and radicular region (root and radicular trunk lengths, mesio-distal and vestibulo-palatal diameters at the cementum-enamel junction, inter-radicular angle width and furcal area extension). By the Pearson's correlation test data such obtained were analyzed to verify the existence of statistically significant correlations among the above mentioned anatomical characteristics. Thirty teeth, selected among the most representatives of the whole sample for their anatomical characters, have been morphologically evaluated: 10 by stereo-microscopical examination, 10 by the observation of non-demineralized histological sections and 10 by scanning electron microscopical examination. Results of the morphometrical evaluation showed that from first to second molar the radicular angle, root length and furcal area width undergo a reduction; differently radicular trunk increases his length. On the basis of this results the Authors try to explain data from recent clinical research testifying that second upper molar is the most frequently extracted tooth. In fact a long radicular trunk is associated with a more apical placement of the furcation entrance and this situation, in conjunction with a narrow inter-radicular angle, can obstruct the insertion of therapeutical instruments, justifying the bad prognosis of the second upper molar involved by periodontal disease. The statistical analysis of anatomical data showed a significant correlation (r = -0.46) among radicular trunk length and inter-radicular angle width (in upper first molars; reverse correlation), root length and inter-radicular angle width (r = 0.51) (lower first molars), vestibular-buccal diameter at the cementum-enamel junction and width of mesial and distal furcal angles (r = 0.43) (upper second molars), the extension of furcal area and the wideness of inter-radicular angle (r = 0.89/0.43). These data are in accord with those from other Authors. Morphological analysis showed the high structural complexity of furcal area in molar teeth with the common observation of cemental crests and pulpal accessory canals orifices; these structures can offer a good receptacle to the subgingival dental plaque and can cause difficulties in debridement and therapeutical treatment of the molar furcal region involved by periodontal disease.(ABSTRACT TRUNCATED AT 400 WORDS)

Histocytological Preparation Techniques↗
PubMed2004

["Molar-incisor hypomineralization"].

Hypocalcification of the enamel is the most common developmental disorder observed in teeth. The prevalence of this kind of hypomineralisation is about 10-19%. These molars are often referred to as cheese molars, because the lesions clinically resemble cheese in color and consistency. Other descriptions are: idiopathic enamel hypomineralisation in the permanent first molars, idiopathic enamel opacities in the permanent first molars, non fluoride enamel hypomineralisation in the permanent first molars, non-endemic mottling of enamel in the permanent first molars. Molar-Incisor Hypomineralisation is today the proposed expression for this disease. Occlusal surfaces of the first permanent molar are most commonly affected. The lesions are more frequent in the upper jaw than in the lower jaw. The incisors are affected to a lesser degree than the molars. Several aetiological factors can cause these defects. Some studies show a relation between intake of dioxins via mother's milk after prolonged breast feeding and developmental defects of the child's teeth. Because the ameloblasts are very sensitive to oxygen supply, complications involving oxygen shortages during birth or respiratory diseases such as asthma or bronchitis and pneumonia are discussed as further aetiological factors. Renal insufficiency, hypoparothyroidism, diarrhoea, malabsorption and malnutrition and high-fever diseases can be other reasons for the occurrence of these defects. Defective enamel can be a locus of lowered resistance for caries. Histologically there are areas of porosity of varying degrees. The affected teeth can be very sensitive to air, cold, warm and mechanical stimuli. Toothbrushing may create toothache in these teeth. We therefore suggest that these patients receive intensified prevention with fluoride varnish, a fissure sealing, GIZ, composits, stainless steel crowns or implants. In some cases an interdisciplinary approach with an orthodontist can result in the extraction of the molars in the age of 8 to 10 years.

Calcium↗
PubMed2004

[Stability of molar relationship after orthodontic treatment in Class II division 1 malocclusions treated by extraction].

OBJECTIVE: To investigate the changes of occlusal relationship in posterior teeth among the pre-treatment, post-treatment, and to analyze some possible factors which may relate to the relapse of posterior occlusal relationship. METHODS: 29 finishing Class II division 1 cases treated by extraction with full records selected were included. The sample consists of 12 males, 17 females. The follow-up lateral head films and study casts were taken at least 2 years after orthodontic treatment. The cephalograms were measured by computerized program and the study casts measured by caliper. RESULTS: Improvements of molar relationship were shown during treatment and a little bit changes during follow-up. During the treatment, the amount of mesial movement of the lower molars was more than the upper molars in dental Class II malocclusion and the amount was similar between upper and lower molars in skeletal Class II malocclusion although the ANB angle decreased significantly. During the follow-up stage, the movement tendency between upper and lower molars was reversed. The sagittal growth pattern of mandible and irregularity of upper incisors were nearly correlated with the relapse of molar relationship. CONCLUSION: The stability of molar relationship is acceptable during the follow-up stage in Class II malocclusion. The improvement of molar relationship depends on the difference of mesial movements between upper and lower molars in dental Class II malocclusion. However, in skeletal Class II malocclusion the improvement of jaw relationship does the effect. The positive growth of mandible and crowding of upper incisors may affect the relapse of molar relationship.

Cephalometry↗
PubMed2004

[A statistic analysis on absence of third molar germs in orthodontic patients].

OBJECTIVE: To examine the absence of the third molar germs in orthodontic patients and to evaluate the relationship between third molar germs and malocclusion. METHODS: The subjects comprised 234 patients (male 92, female 142) from the orthodontic clinic whose ages were 14-18. The assessments of the third molar germs were made from panoramic radiographs, and the assessments of ANB angle were made from lateral cephalograms. All the data were analyzed by statistic chi2 test. RESULTS: The percentage of male who missed one or more third molar gems (37.0%) was higher than that of female (24.6%). There was no significant difference between the absent frequencies of third molar germs on left and right sides in either maxilla or mandible. The absent percentage of third molar germs in skeletal III subjects was higher than those in both skeletal class I and II subjects. The absent difference of third molar germs was in upper arches (P < 0.05), but not in lower arches (P > 0.05). There was no significant difference in absent percentage of third molar germs between skeletal class I and II subjects. CONCLUSION: Male patients have higher absent frequencies of third molar germs than female ones. Skeletal class III patients have higher absence of third molar germs in upper jaws than skeletal class I and II patients.

Adolescent↗
PubMed2006

A comparative assessment of the failure rate of molar tubes bonded with a self-etching primer and conventional acid-etching.

OBJECTIVES: Comparative assessment of the failure rate of molar tubes bonded to first and second molars with a self-etching primer and conventional acid-etching. MATERIAL AND METHODS: Four hundred forty-four molar tubes (246 first molar tubes and 198 second molar tubes) were bonded, using a split-mouth design, on 62 patients (23 male, 39 female; mean age 13.7 years) with the 3M Transbond Plus self-etching primer combined with Transbond XT paste; or with conventional acid-etching, Orthosolo primer, and Enlight adhesive paste. First-time failures were recorded over a period of 15 months. RESULTS: Bond failure per adhesive system, arch (maxilla-mandible), quadrant (left, right) and tooth (first or second molar) were studied. Statistical analysis using logistic regression modeling (alpha = .05) showed that the overall failure rate for the first and second molar tubes was 11% (8% with self-etching primer and 13% with conventional acid-etching). No significant difference was found between the 2 bonding methods. Tooth location and type showed statistically significant associations. Mandibular tubes showed a 3:1 probability for failure compared to maxillary tubes. Right-sided tubes demonstrated 3 times more failures when compared to left-sided tubes, and second molar tubes showed a 3-fold increase in failure. CONCLUSION: Molar tube bonding with self-etching primer shows similar success rates to conventional acid-etching, whereas the mandibular right second molar presents the highest failure incidence.

Acid Etching, Dental↗
PubMed1990

New cavity forms in second deciduous molars which maximize dentin thickness between cavity and pulp chamber.

This study was designed to devise configuratively ideal cavity formations using 49 second deciduous molars, consisting of 25 extracted from the maxilla and 24 from the mandible. A cavity having at least 1 mm subcavitary (below the cavity) dentin thickness at any point of measurement and having an appropriately formed and positioned retention was defined as an ideal cavity. The same methods were used as in our previous study of first deciduous molars. The following results were obtained: 1. In upper second deciduous molars, the subcavitary dentin thickness was thin at the mesiobuccal side of the cavity; it measured 0.9 mm. In lower second deciduous molars, the subcavitary dentin thickness was thin at the mesiobuccal, distolingual sides of the cavity, and central fossa, where the retentional groove was provided; it measured 0.8-0.9 mm. The other measured values exceeded 1.0 mm. All thickness measurements were very close to the values considered as ideal. 2. In upper second deciduous molars, the margins of the cavity were positioned medially to the summits of respective cusps, 1.8-2.0 mm at the buccal side and 1.5 mm at the lingual side. The entire cavity was located lingually. 3. In lower second deciduous molars, the buccal margin of the cavity was positioned 1.7 mm medially to the summit of the distobuccal cusp and 1.2-1.3 mm medially to the summits of the other buccal cusps. The lingual margin was positioned 1.4-1.5 mm medially to the summits of respective cusps. medially to the summits of respective cusps. 4. The buccolingual width of the cavity amounted to 1/3 of the distance between the summits of the buccal and lingual cusps in both upper and lower second deciduous molars. 5. At the mesial side, the depth of cavity was 1.4 mm at the buccal wall and 1.5 mm at the lingual wall in upper second deciduous molars, and 1.4 mm at the buccal wall and 1.6 mm at the lingual wall in lower second deciduous molars. 6. The width of gingival wall in the proximal box measured 1.0 mm in both upper and lower second deciduous molars.

Child↗
PubMed1990

[Three-dimensional change of the occlusal facets in primary dentition before and after the eruption of first permanent molars].

A system to measure the three-dimensional architecture of the occlusal surface was developed to clarify the three-dimensional change of the morphology of occlusal facets that was considered as the trace mark of the chewing function. The three-dimensional measuring and analyzing system of the occlusal surface was composed of two components, the measuring system to obtain the three-dimensional coordinates on the surface contour of the tooth crown and the analyzing system to calculate the minute morphology in the three dimensions. The reproducibility of this system was evaluated with use of the standard block of stainless steel designed for this purpose and was shown to be very accurate. By application of this system, the three-dimensional changes of the occlusal facets on primary canines and primary second molars were investigated on the serial primary dental casts taken before and after the eruption of the first permanent molars from eleven children (seven boys and four girls). The results were as follows: On the primary second molars of the maxilla and mandible, before the eruption of the first permanent molars, the occlusal facets were distributed mainly on the functional cusps. The occlusal facets were found also on the non-functional cusps after the eruption of first permanent molars. As a consequence, the increase in the number of occlusal facets from before to after the eruption of first permanent molars was statistically significant for both maxillary and mandibular primary second molars. In regard to the morphological change in three dimensions, the occlusal facets that were facing mesially or distally before the eruption of first permanent molars changed its direction buccally or lingually and became almost parallel to the datum plane of the mandibular dental arch after the eruption of the first permanent molars. It was also found that the occlusal facets of both jaws in the occlusal relationship were almost parallel to each other. In addition, the amounts of angular change before and after the eruption of first permanent molars were significantly correlated between the maxillary and mandibular occlusal facets. It can be concluded that the coordinating change of the occlusal facets in three dimensions may exist between both jaws during the development of chewing function.

Child↗
PubMed1990

[Clinical study of ectopic eruption of the permanent first molars].

The purpose of this study was to investigate the etiology and characteristics of the ectopic eruption of first permanent molars. The subjects were 35 cases (27 maxilla and 8 mandible) with ectopically erupted permanent first molars, which were recognized in 24 out-patients (10 boys and 14 girls) visiting Tohoku University, Dental Hospital. The materials used for the analysis were dental casts, X-ray lateral cephalograms and panoramic radiographs, and both materials of the ectopic and normal groups were compared. The results were as follows: 1) There were no significant differences statistically between the mesio-distal crown diameters of the maxillary permanent first molar, central and lateral incisor, and all deciduous teeth in ectopic group and their mean values in Ono's and Otsubo's studies. 2) There were no significant differences as compared to all parts of the size of the dental arch in ectopic sides with those in the normal sides of same individuals at IIA and IIC of Hellman's developmental stage in dentition. 3) When the sizes of the dental arch in the ectopic group were compared with those of the normal group, the former were smaller at the distance between the mid-point and the canine mesial surface (Fig. 1-4), the ridge of the posterior region of the basal arch and most distal point of the primary second molar (Fig. 1-6) at the Hellman's dental age IIA, while the canine distance to the midline (Fig. 1-1), the dental arch perimeter from mid-point to the distal surface of primary second molar (Fig. 1-4+5), and the distance between the canine and primary second molar, div. X (Fig. 1-7) at Hellman's dental age of IIC were significantly smaller than the latter. 4) Regarding the comparison of the value of the changes in dental arch size between the ectopic group and the normal group from Hellman's dental age of IIA to IIC, the distance between the canine and primary second molar, div. X (Fig. 1-7) decreased markedly and the distance between the ridge of the posterior region of the basal arch and the most distal point of the primary second molar (Fig. 1-6) increased. 5) Results of the analysis of X-ray lateral cephalograms showed that the angle of eruption of first molars in the ectopic group was significantly smaller compared with normal group. 6) According to the cluster analysis on the calcification of tooth germ using panoramic radiographs, similarity among all of the samples was lacking in the ectopic group, especially congenital missing of the second molars and second premolars in the ectopic side and the delayed calcification of the ectopically erupted teeth were found in maxilla.

Child↗
PubMed1989

Shape and number of the roots of the permanent molar teeth.

One hundred ninety-eight mandibular first molars, 198 mandibular second molars, and 122 mandibular third molars, extracted from 99 Indian skulls were examined for the number of dental roots. The number of mandibular molar roots is increased by the appearance of the distolingual root, accessory lingual root, and bifurcation of the mesial root. The bifurcation of the mesial root was investigated in teeth in which it was more than 1/3 and less than 1/3 (apical bifurcation) of the root length. The following results were obtained. The numbers of the roots including apical bifurcation of the mesial root were 2, 3 and 4 in 72.7%, 26.8% and 0.5%, respectively, of the first molars; 1, 2 and 3 in 17.7%, 76.8% and 5.6%, respectively, of the second molars; and 1, 2 and 3 in 16.4%, 77.1% and 5.8%, respectively, of the third molars. The numbers of dental roots excluding apical bifurcation of the mesial root were 2 and 3 in 99.0% and 1.0%, respectively, of the first molars; 1, 2 and 3 in 17.7%, 81.8% and 0.5%, respectively, of the second molars; and 1, 2 and 3 in 16.4%, 77.1% and 5.8%, respectively, of the third molars.

Asian People↗
PubMed1984

Infraocclusion of primary molars. An epidemiological, familial, longitudinal clinical and histological study.

The aims of this thesis were to estimate the prevalence and familial tendencies of infraocclusion of primary molars and analyse the effect of extraction on occlusal development, and to characterise histologically the ankylosis in infraoccluded primary molars and recommend guidelines for treatment. The thesis is based on five investigations. In the prevalence and familial studies, 1059 children and 138 first-degree sibs were investigated. The three longitudinal clinical studies comprised 215 primary molars in infraocclusion and the children were subjected to clinical and radiographic examination and analysis of model casts every six months. The histological study comprised 62 teeth in infraocclusion and 40 in normal positions. In addition, bone biopsies were analysed histologically and by enzyme histochemical methods. The prevalence of infraocclusion of primary molars was found to be age-related and was significantly higher in sibs than in the studied population, which indicates a familial tendency. Infraoccluded primary molars with a successor present generally exfoliated normally. The permanent successors usually erupted six months later than on the normal contralateral side. Extraction of primary molars in infraocclusion meant definite space loss in some cases. With aplasia of the successor, the infraoccluded tooth did not exfoliate within the normal time range and the root resorption was found to be very slow, especially after 12-13 years of age. Very few of the previously reported negative effects of non-treatment of primary molars in infraocclusion on exfoliation, eruption and occlusal development could be confirmed in this study. Most infraoccluded primary molars were ankylosed histologically. No differences were found in the bone biopsies from the infraoccluded and control group. The results indicate that ankylosis in infraoccluded primary molars is not a static condition but part of a remodelling process following normal resorption of the roots. The general treatment policy should be to wait for normal exfoliation of infraoccluded primary molars to take place if the permanent successor is present and in cases with aplasia consider the aplasia per se, the degree of primary root resorption and the risk of progression of the infraocclusion.

Adolescent↗
PubMed1994

Ectopic eruption of the maxillary first permanent molar. An epidemiological, familial, aetiological and longitudinal clinical study.

The aims of this thesis were to investigate the prevalence, familial tendency and aetiological factors of ectopic eruption of the maxillary first permanent molar, to analyse associations between ectopic eruption of the maxillary first permanent molar, to analyse associations between ectopic eruption of the maxillary first permanent molar and other tooth and developmental disturbances and cleft lip and/or palate defects, to make a longitudinal evaluation of the effects of orthodontic treatment in irreversible cases and of the prognosis for the atypically resorbed second primary molars in cases of reversible ectopic eruption and to carry out histological studies of second primary molars with extensive resorptions. The thesis is based on eight investigations. The subjects for the prevalence study consisted of 2,903 children. The main subjects in the clinical studies were the children with ectopic eruption of the maxillary first permanent molar from those children. The methods used were radiographic assessments, biometrics, orthodontic treatment, histology, different statistical methods and clinical assessments. The prevalence of ectopic eruption of the maxillary first permanent molar was found to be 4.3 per cent for the population and 21.8 per cent for cleft children. In sibs to children with ectopic eruption the prevalence was 19.8 per cent, indicating a genetic background. The main aetiological factors were the greater mesial angulation and the greater width of the ectopically erupted first permanent molar. In cases of reversible ectopic eruption the atypically resorbed second primary molars remained to the normal exfoliation time in 90 teeth out of 92. Treatment with cervical headgear in 46 children for an average of 9 months resulted in uprighting of the upper first permanent molars to good occlusion and in about 70 per cent of the children sufficient space for the second premolars. In the long-term follow-up, 10 years after treatment, two forms of discriminant analysis were used to evaluate the long-term treatment effects. The analyses showed a uniformity of the cases, indicating that the effects of the eruption disturbance had been corrected and all negative side effects of the treatment were eliminated.

Adolescent↗
PubMedDate not supplied

A genetic study of dentin growth in the mandibular second and third molars of male mice.

Although the influence of genetic and environmental factors on the completed crown size of mandibular molars in mice is well known, such influence on the growth process of the mandibular second and third molars of mice has not yet been clarified. The purpose of the present study is to examine the growth pattern of the dentinal formation and evaluate the relative contributions of both genetic and environmental factors to longitudinal dentin formation by the use of the partial diallel cross-genetic approach, the time-marking method and a computerized image measurement system. The following results were obtained: 1) the onset of dentinal formation in the second molar was on the 6-9th day after birth, while that of the third molar was on the 9-12th day after birth; 2) the best fitted growth curve of the dentinal formation for the first molar was the fifth order polynomial equation, while for the second molar the fourth order polynomial equation was best, and for the third molar the third order polynomial equation was best; 3) maternal effect strongly influenced the second and the third molar dentin growth at an early stage of postnatal growth. Thus, it could be concluded that the dentinal formation growth pattern differed among the three kinds of mouse molars while maternal environmental factors, in addition to genetic factors, played an important role in the mouse second and third molar dentin growth during the early stage of postnatal growth.

Analysis of Variance↗
PubMed1993

Development of postmolar trophoblastic disease after partial molar pregnancy.

We investigated the clinical characteristics of patients with partial molar pregnancy and patients who developed invasive partial mole. Between 1981 and 1990, 349 patients were followed up by the Aichi prefecture trophoblastic disease registration center after partial molar pregnancy. Ten of the 349 patients with partial molar pregnancy developed invasive partial mole, an incidence (2.87%) significantly lower (P < 0.01) than that for the development of invasive complete mole (174/1410, 12.34%) following complete molar pregnancy during the same period. None of the patients had any histologic evidence of choriocarcinoma after partial molar pregnancy. The medical records of these 10 patients were compared with those of 85 of 174 registered patients with invasive complete mole, whose clinical information could be used. The interval from molar delivery to the diagnosis of invasive mole was under 9 weeks (mean, 4.90 weeks) for the patients with invasive partial mole and was significantly shorter than that for the patients with invasive complete mole, from 2 to 18 weeks (mean, 8.12 weeks) (P < 0.01). All 10 patients with invasive partial mole achieved a negative hCG level (< 0.5 mIU/ml) with eight courses or less of chemotherapy (mean, 5.50 courses). The number of courses was the same as that in the invasive complete mole group (mean, 5.70 courses). None of the patients with invasive partial mole developed recurrence. We conclude that all patients with partial molar pregnancy should be followed up as are those with complete molar pregnancy. Some patients with partial molar pregnancy will develop invasive partial mole with a relatively short interval, but remission can be achieved without the recurrence and choriocarcinoma seldom develops after partial molar pregnancy.

Adult↗
PubMed2006

Evaluating controlling factors to Al(i)/(Ca + Mg) molar ratio in acidic soil water, southern and southwestern China: multivariate approach.

Al(i)/(Ca + Mg) molar ratio in soil water has been used as an indicator to the effects of acid deposition on terrestrial ecosystems. However, the main factors controlling this ratio have not been well documented in southern and southwestern China. In this study, we presented the variation in inorganic aluminum (Al(i)) and Al(i)/(Ca + Mg) molar ratio in different sites and soil horizons based on two to three years monitoring data, and evaluated the main factors controlling Al(i)/(Ca + Mg) molar ratio using principle component analysis (PCA) and partial least square (PLS) regression. Monitoring data showed although Al(i)/(Ca + Mg) molar ratios in most soil water were lower than assumed critical 1.0, higher molar ratios were found in some soil water at TSP and LXH site. Besides acid loading, both soil properties and soil water chemistry affected the value of Al(i)/(Ca + Mg) molar ratio in soil water. Partial least square (PLS) indicated that they had different relative importance in different soil horizons. In A-horizon, soil aluminum saturation (AlS) had higher influence on Al(i)/(Ca + Mg) molar ratio than soil water chemistry did; higher soil aluminum saturation (AlS) led to higher Al(i)/(Ca + Mg) molar ratio in soil water. In the deeper horizons (i.e., B(1)-, B(2)- and BC-horizon), inorganic aluminum (Al(i)) in soil water had more and more important role in regulating Al(i)/(Ca + Mg) molar ratio. On regional scale, soil aluminum saturation (AlS) as well as cation exchange capacity (CEC) was the dominant factor controlling Al(i)/(Ca + Mg) molar ratio. This should be paid enough attention on when making regional acid rain control policy in China.

Acids↗
PubMed1992

Molar villous fluid suppresses mononuclear cell cytotoxicity.

Complete molar pregnancy tissue is an allograft to the mother because all molar chromosomes are of paternal origin. Interactions between molar tissue and the maternal immune system may be important in the natural history of complete molar pregnancy. Molar villous fluid (MVF) has previously been demonstrated to suppress both mitogen and interleukin-2-induced T lymphocyte proliferation. The current study was undertaken to evaluate the potential effect of MVF on the cytotoxic activity of mononuclear cells (MNC) and lymphokine-activated mononuclear cells (LA-MNC). Sera and molar villous fluid were obtained from four women at the time of molar evacuation. K-562 erythroblastoid cells were used as target cells for MNC-mediated lysis, and JEG-3 choriocarcinoma cells were used as targets for LA-MNC-mediated lysis in a 51Cr release assay. Relative to patient sera, all MVF tested significantly inhibited both MNC and LA-MNC lysis of target cells (48.3 and 91% mean inhibition, respectively; P < 0.05). This study provides additional evidence that molar gestational tissue produces factor(s) that suppress maternal immunologic responses. Potential therapies may become available to reduce or eliminate the immunosuppressive effects of molar gestations resulting in a more favorable clinical outcome in patients with complete molar pregnancy and postmolar gestational trophoblastic tumors.

Choriocarcinoma↗
PubMed2005

Molar mass distributions by gradient liquid chromatography: predicting and tailoring selectivity.

Interactive liquid chromatography (iLC) for polymer analysis is usually applied to the characterisation of distributions other than molar mass. In particular, its use for the determination of chemical-composition, functionality-type and tacticity distributions has been demonstrated. The application of iLC for the determination of molar mass distributions (MMDs), however, has not yet been fully explored. An expanded version of the reversed-phase liquid chromatography model has been developed to describe and predict how the retention behaviour of polydisperse polystyrene samples changes with molar mass. The relationship between molar mass and the parameters of the model has been investigated in some detail and non-linear correlations were found. From the model and the relationships between the model parameters and molar mass, calibration curves (retention time versus molar mass) were constructed to predict changes in chromatographic selectivity across a given molar mass range. These calibration curves were compared to experimentally obtained curves and, in most cases, excellent agreement was found. The dramatic enhancement in selectivity that can be obtained with iLC in comparison to size-exclusion chromatography (SEC) was illustrated by measuring matrix-assisted laser desorption ionisation (MALDI) MS spectra of fractions collected during a gradient-LC separation. In the low-molar mass range, essentially monodisperse fractions were obtained. Calibration curves, predicted by the model and validated experimentally using narrow-dispersity standards and MALDI-MS spectra of fractions, were used to determine the molar mass distribution of some narrowly distributed polystyrene samples. Molar mass distributions for such standards were found to be somewhat lower than the values reported by the manufacturers. The results also deviated from those obtained by MALDI-MS.

Calibration↗
PubMed2006

The physical-mechanical performance of the new Ketac Molar Easymix compared to commercially available glass ionomer restoratives.

OBJECTIVES: To evaluate the time dependence of physical-mechanical performance of glass ionomer restoratives. METHODS: The physical-mechanical properties of Ketac Molar Easymix in comparison to four handmix glass ionomer restoratives were evaluated by testing the compressive and flexural strength, acid erosion and solubility. By testing the properties in the early and late setting phase it was determined how fast the level of material characteristics is achieved. IR spectroscopy was used for monitoring the acid-base reaction. RESULTS: The compressive strength after 1 and 24h setting time show that Ketac Molar Easymix and Fuji IX demonstrate a significantly higher performance. Ketac Molar Easymix exhibits by far the highest flexural strength 1h after start of setting. After 24h, it remains at this high level and only Vitro Molar and Fuji IX come close. Ketac Molar Easymix and Fuji IX show the lowest solubility in neutral media after 24h and 7d. It is remarkable that the solubilities of Ionofil Molar, Vitro Molar and Vidrion R stored in water for 24h are higher than those of Ketac Molar Easymix and Fuji IX obtained after 7d water immersion. In acidic media Ketac Molar Easymix is least prone to acid erosion. CONCLUSIONS: For clinical success of a filling material the early achievement of a high physical-mechanical performance is mandatory to minimize the risk of early damage to a restoration. With the high flexural strength reached after 1h combined with the lowest susceptibility for acid-attack and solubility in water, Ketac Molar Easymix, from 3M ESPE, provides the best performance of any materials tested.

Analysis of Variance↗
PubMed2006

[Distribution characters and affecting factors of Al(i)/(Ca + Mg) molar ratio in acid forest soils].

By using principle component analysis (PCA) and partial least square (PLS) regression, this paper studied the distribution characters and their affecting factors of Al(i)/(Ca + Mg) molar ratio in acid forest soils in southern and southwestern China. The monitoring data from 2000 to 2002 showed that in most cases, the Al(i)/(Ca + Mg) molar ratio in soil moisture was lower than assumed critical value 1.0, indicating that significant aluminum toxicity to vegetation was not occurred in the study regions. PLS regression suggested that soil aluminum saturation (AlS) was the dominant factor affecting the Al(i)/(Ca + Mg) molar ratio in soil A horizon. Higher AlS led to a higher Al(i)/ (Ca + Mg) molar ratio in soil moisture. Despite of its lower acid deposition, Liuxihe basin had a higher Al(i)/(Ca + Mg) molar ratio in soil A horizon than other catchments, mainly due to its higher AIS. In deeper soil horizons (B1, B2 and BC), the inorganic aluminum (Al(i)) in soil moisture was the main factor affecting Al(i)/(Ca + Mg) molar ratio. Higher inorganic aluminum concentration resulted in higher Al(i)/(Ca + Mg) molar ratio. In each of study catchments, the vertical distribution of Al(i)/(Ca + Mg) molar ratio was basically identical with the distribution of inorganic aluminum (Al(i)) through soil profile. It was concluded that soil aluminum saturation was the main factor controlling the regional variation of Al(i)/(Ca + Mg) molar ratio in soil moisture, and the vertical distribution of soil Al(i)/(Ca + Mg) molar ratio in each site was mainly due to the vertical change of inorganic aluminum in soil moisture.

Acids↗