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At least 469 records · Page 26Linked to original sources
PubMed2003

A comparative study of dentin thickness of primary human molars.

The aim of the present survey was to evaluate the dentin thickness of buccal, lingual, mesial and distal surfaces of first and second primary molars. These evaluations were done at the middle third of the crowns of twenty extracted non-carious primary teeth separated in two groups (first molars and second molars). Comparisons were performed within-groups and between-groups. The mean values of dentin thickness observed for first molars were 2430 mm (buccal), 1.869 mm (lingual), 1.655 mm (mesial) and 1.664 mm (distal). For second molars the dentin thickness presented 3.006 mm (buccal), 2730 mm (lingual), 2130 mm (mesial) and 2192 mm (distal). The dentin thickness was higher in the buccal surface in both groups (P<0.05; Wilcoxon Test), except for the lingual surface of second molars (P>0.05). No differences were observed between mesial and distal surfaces in both groups (P>0.05). Comparisons between-groups showed that the dentin thickness was higher in all surfaces of second molars (P<0.01; Mann-Whitney Test). It was concluded that there are differences in the dentin thickness between first and second primary human molars and within the different surfaces of such teeth.

Child↗
PubMed1992

Clinical observations on the development of third molars.

In order to investigate the developmental conditions of third molars in Japanese, we studied the panoramic radiographs taken during dental treatment at the Pediatric Outpatient Section of Osaka Dental University Hospital of 9,111 children (4,646 boys and 4,465 girls) between the ages of 7 years 0 months and 16 years 11 months, in addition to 2,769 panoramic radiographs of students of this university (2,312 men 457 women) kept by the Department of Oral Radiology. The following results were obtained. 1. Calcification of the third molars in both boys and girls began as early as 7 years 6 months in the maxilla and 7 years 0 months in the mandible. The average age for initiation of calcification in the maxilla was 9 years 4 months for boys, and 9 years 2 months for girls, while the ages in the mandible were 9 years 1 month and 8 years 9 months, respectively. 2. The average age for completion of the third molar crowns in the maxilla was 11 years 8 months for boys and 11 years 5 months for girls, while in the mandible it was 12 years 4 months and 12 years 3 months, respectively. 3. At greater than 13 years of age, the tooth germ could be found in boys about 70% of the time in the maxilla and 75% of the time in the mandible, while these figures for girls were 65 and 80%, respectively. 4. All four third molars were present in 52.3% of the males and 45.5% of the females, while 9.5% of the males and 12.0% of the females had no third molars at all. 5. The direction of eruption was classified as either vertical, mesial, horizontal, distal, or buccal/lingual type. The rate for the vertical type in males was 70% in the maxilla and 45% in the mandible, while these figures for females were 50 and 40%, respectively. 6. Microdontia of the third molars appeared only in the maxilla. 7. Congenital absence of the third molars was more common in females than males, and occurred more frequently in the maxilla than in the mandible. The results of this study allow a better understanding of the third molars of Japanese and provide an aid to planning in such areas of clinical pediatric practice as guiding occlusal development.

Adolescent↗
PubMedDate not supplied

Caries control and other variables associated with success of primary molar vital pulp therapy.

PURPOSE: This research evaluated initial treatment of deep dental caries with caries control (CC) procedure and the effect of other factors on the success of indirect pulp therapy (IPT) and formocresol pulpotomy (FP). METHODS: Retrospective chart audits were performed on 226 primary molars with deep caries approaching the pulp that were treated using IPT and FP. Mean follow-up was 3.4 years. CC with glass ionomer cement (GIC) was performed on 50 of the 226 teeth 1 to 3 months before pulp therapy. RESULTS: IPT therapy was successful 94% of the time, whereas FP was successful 70% of the time. The initial use of CC increased the IPT/FP success rate to 92% vs a 79% success rate in teeth without CC. Primary molar FP success on primary first molars was 61% vs 83% in second molars. IPT therapy was successful 92% of the time for first molars vs 98% of the time for second molars. Thirty-six percent of the FP-treated teeth exfoliated early vs 2% of the IPT-treated teeth. Primary first molars with reversible pulpitis had a higher success with IPT (85%) vs FP (53%). The type of final restoration did not affect IPT or FP success, except that FPs restored with an immediate IRM (Dentsply/Caulk, Milford, Del) restoration decreased success to 39%. CONCLUSIONS: IPT for the treatment of deep dental caries lesions produced greater long-term success than FP. FP success in primary first molars was lower compared to IPT success, especially in teeth with reversible pulpitis. Also FP-treated teeth showed significantly earlier exfoliation patterns. The prior treatment of deep dental caries lesions with CC procedures improved the subsequent IPT or FP success.

Child↗
PubMed2004

[The effect of coronal preflaring on the working length measurement of root canals in molars].

PURPOSE: To study the influence of coronal preflaring of root canal on the working length measurement in molars. METHODS: 48 molars from 47 adult patients with pulpitis were divided into two groups randomly. 74 root canals of 24 molars were examined in Group 1. After preparing an access cavity, the root canal orifices were located. A 15# K-type file was inserted into root canal to detect resistance at the apical region. 75 root canals of 24 molars were examined in Group 2. Before testing the apical resistance,a size 25# and 20# ProFile.06 taper NiTi rotary instrument was used to enlarge the canal orifice and flare the coronal portion of the root canal. After placing 15# K-type files, a radiograph was taken with the bisecting-angle technique. The distance between the tip of the file and the radiographic apex was measured on the radiographs. Statistical analysis of univariate and multiple logistic regression were carried out for analysis. RESULTS: There was a significant difference between the two groups (P<0.05), there were more accurate measurements in Group 2 than in Group 1. No statistical correlation was found between X-ray measurements and age, sex and the position of molars,while there was significant correlation between maxillary molars and mandibular molars (P<0.05). CONCLUSION: Preflaring the coronal portion of the root canals could significantly increase the accurate measurements of the working length of root canals in molars.

Adult↗
PubMed2004

Agenesis of third molars in young Czech population.

The aim of this study is to evaluate the incidence of third molars agenesis in the Czech population. One thousand patient's panoramic radiographs of the pedostomatological department of Second Stomatological Clinic of The First Faculty of Medicine, Charles University, has been analyzed. The age of probands was ranging between 12 to 21 years inclusive. Patients were divided into 10 groups according to age. In each age group were 100 individuals - 50 boys and 50 girls. Agenesis of 1-4 third molars was present in 22.5% (25.6% in boys and 19.4% in girls). Intersexual difference is significant. Further, the incidence of third molars agenesis in individual dentition quadrants, upper and lower jaw and right and left side of dentition was examined. Neither in boys nor in girls were detected significant differences in these values. Agenesis of just one, any third molar occurs in 10.9% (12.0% in boys and 9.9% in girls). For one individual it is mean 1.9 congenitally missing third molars in boys and 2.0 congenitally missing third molars in girls. These intersexual differences are not significant. In boys, the most frequent agenesis was of one, next of two, then of three and at last of four third molars. In girls, agenesis of two was on the first place, then that of one and lastly and equally of three and of four third molars. The results were compared with literature data.

Adolescent↗
PubMed2005

Maxillary molar intrusion with micro-implant anchorage (MIA).

BACKGROUND: Intrusion of the maxillary molars is difficult to accomplish using traditional methods of anchorage. AIMS: To describe methods of maxillary molar intrusion with the aid of micro-implants. METHODS: Micro-implants provide stable intra-oral anchorage and enable the maxillary molars to be intruded without the usual side effects. Three adult patients are presented showing how micro-implants can be used to intrude the maxillary molars. In the first patient micro-implants were placed in the alveolar process between the second premolar and first molar, in the second patient micro-implants were placed in the palatal alveolar process between the first and second molars, and in the third patient a micro-implant was placed in the palate paramedially. A transpalatal bar was used to prevent bucco- or linguoversion of the molars during intrusion. CONCLUSIONS: The maxillary molars can be intruded with intra-oral anchorage derived from microscrew implants.

Adult↗
PubMed1990

[Experimental study of the trajectories of the upper first molar with extraoral force. Practical measurement of the movements in the three planes by a magnet-magnetic sensing system].

The upper first molar trajectory under the loading of extraoral force was studied in human subjects. The five loading directions, that is horizontal, upper, lower, high-pull and cervical were tested. Using a magnet-magnetic sensing system, the rectilinear and rotational movements were traced in the three planes, i.e. sagittal, frontal, and horizontal planes. It was concluded; 1. The molar inclined buccally with the loading in all the applied directions. 2. New evidence was found in the horizontal plane, i.e. the molar rotated mesially with the loading in the lower direction. The rotation may depend on the direction of the loop at the terminal of the inner-bow. Therefore it was suggested that the form of the loop affected the molar movements. 3. With the loading in the horizontal direction, the distal movement of the molar was evident and small displacement was observed in the extruded direction. 4. Loading both in upper and lower directions, the rotation of the molar was more evident than the rectilinear displacement. It was suggested that these loading would not be applicable to control the tooth in the rectilinear movements. 5. With the high-pull loading, the molar inclined mesially and shifted distally a little. On the other hand, it was greatly intruded. The results suggested that effective distal and intrusive movements would be expected by bending the outer-bow downward, since this procedure would prevent the tooth from tipping mesially. 6. The loading in the cervical direction caused large distal movement of the molar. Extrusion was also evident as it was expected from the loading direction.

Dental Stress Analysis↗
PubMed1990

[The condition of dentition and the prediction of eruption at lower third molars of Japanese adolescent males].

This study was examined the relationships between the condition of dentition of lower third molar and malocclusions and shape of mandibles, and to predict eruption for third molars by their relationships. Data were obtained from 90 degrees and 60 degrees rotated cephalometlic radiographs, orthopantomographic radiographs, mandibular occlusal films and gnathostatic models of 101 males showing a complete permanent dentition anterior to the second molars and who had not had extraction lower their molars and orthodontic treatments, were selected from 147 dental students at Asahi University. they were divided into 8 groups by condition of lower third molar dentitions. Bilateral presence of lower third molar occurred in 69.3% and unilateral in 20.8% on 60 degrees rotated cephalometlic radiographs. Bilateral eruption or half eruption occurred in 24.7% and impaction in 44.6% on gnathostatic models. Coronal arch length of erupted cases was longer than that of impacted cases. A apired t-test revealed the significant difference (p less than 0.05). Over bite of impacted cases were deeper than that of erupted cases (p less than 0.05). Arch length discrepancy of presented and impacted cases were larger. There were normal occlusions in each group. Most mal-occlusions were prognathia, second to deep bite, bi-maxillary. The most frequent lower arch conditions were crowding (65%). I. M. P. A. of bilateral impacted cases were langer. Mandiblar length (Cd-Pog) of erupted cases were longer. The distance from Xi-point to the distal surface of second molar was border at 25mm for lower third molar eruption.

Adolescent↗
PubMed1995

Focal c-fos expression in developing rat molars: correlations with subsequent intradental and epithelial sensory innervation.

The purpose of this study was to analyze the temporal and spatial patterns of expression of the inducible transcription protein Fos and the Fos-related antigens (Fra) in developing rat teeth. Immunoreactivity (IR) for Fos/Fra was analyzed at postnatal age 1-35 days. A transient gradient of Fos/Fra-IR was found in all the molars in the coronal odontoblasts along sites of dentinogenesis, with numerous cells and intense staining near the pulp horn tip, and fewer cells and less staining in mid-crown and cervical pulp. This gradient was well established in first molars of the one day old rats; it was first seen in second molars in the 2 day old rats; and it was found in third molars at 10 days. The Fos/Fra-IR was transient and faded after a few days. Rat molars have a tilted orientation so that maxillary molar crown cusps point in a posterior direction and mandibular crowns in the anterior direction. In each set of molars dentinogenesis was initiated along the side of each pulp horn closest to the gingival surface, i.e. anterior for maxillary crowns and posterior for mandibular crowns; and the Fos/Fra-IR first appeared next to those asymmetric sites. As the wave of dentinogenesis spread around the crown, it was accompanied by odontoblastic expression of Fos/Fra-IR that had decreasing intensity in mid- and cervical crown. Molar root pulp lacked Fos/Fra-IR, and incisor teeth only had odontoblastic and ameloblastic immunoreactivity in the 1 day old rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1994

The importance of endodontic access in locating maxillary and mandibular molar canals.

The principle of straight-line access is discussed with particular reference to endodontic access of either maxillary or mandibular molar teeth. Modifications to the traditional triangular access opening are described that will make it easier for a practitioner to locate and instrument the fourth canal system commonly found in molar teeth. The high frequency of a fourth canal in molar teeth makes it essential to anticipate and find all canals during molar endodontic therapy. Quite frequently, the general practitioner attempting molar endodontic therapy should expect to locate a second canal in the mesiobuccal root of the maxillary molar and a second canal in the distal root of a mandibular molar. The possibility of extra roots over and above the norm should also be anticipated and looked for carefully. Proper angulation and interpretation of radiographs help to identify chamber and root anatomy. A two-step access opening is advocated when making access openings on molar teeth if a coronal crack in the crown is to be seen early in treatment. A method of unroofing the pulp chamber and pre-flaring the canal orifice to facilitate the subsequent shaping of the entire root-canal system is described. Clinical and laboratory examples are pictured to illustrate modifications or errors in the standard endodontic access opening.

Dental Pulp Cavity↗
PubMed1994

[The extraction of the lower third molars: germectomy or late avulsion?].

INTRODUCTION: Lower third molars show the highest incidence of impaction and have been held responsible for pathologies such as pericoronitis, periodontitis, second molars tooth-crown resorption, pain, cysts or odontogenic tumors, primary or secondary crowding of the dentition. Early removal of these teeth to prevent the overmentioned problems is widely acknowledged, as many studies demonstrated a direct correlation between age and incidence of complications. These studies mostly refer to adult patients, while studies about germectomies are few. Because recent contributions showed that the risk of development of these pathologies in presence of impacted third molars is quite low while a certain morbidity associated to this procedure may be expected, a very careful risk to benefit ratio must be considered. The purpose of this study was therefore to compare the incidence of complications and side effects in three age groups, in order to obtain some informations about the choice of the best moment for operation. MATERIALS AND METHODS: The patients, 462 females and 406 males, were divided, according to age, in the following three groups: group A included patients from 9 to 16 years; group B included patients from 17 to 24 years; group C included patients over 24 years. All patients were treated under local anesthesia; surgical procedure and instruments were standardized. RESULTS: In group A, formed by 500 germectomies, the incidence of complications was 2.6% (10 instances of secondary infections, 2 instances of trismus, 1 instance of excessive postoperative bleeding). Group B included 570 procedures and the incidence of complications was 2.8% (3 instances of alveolar osteitis, 7 instances of secondary infections, 2 instances of excessive postoperative bleeding, 2 instances od second molar lesions, 1 instance of inferior alveolar nerve paresthesia, 1 instance of trismus). Group C included 430 procedures and the incidence of complications was 7.4% (2 instances of second molar lesions, 9 instances of alveolar osteitis, 8 instances of secondary infections, 4 instances of excessive postoperative bleeding, 6 instances of inferior alveolar nerve paresthesia, 3 instances of trismus). All complications were transient; in one instance only of mandibular nerve paresthesia in group C symptoms were still present 25 months after the operation. DISCUSSION AND CONCLUSIONS: This study has shown no significant differences between group A and B, while complications significantly increase in group C. Recent researches have shown that: a) there is a low risk of development of pathologies correlated to third molar impaction; b) nowadays there are not valid criteria to evaluate the future eruption of the impacted tooth; c) a direct correlation between third molar impaction and anterior dental crowding hasn't been demonstrated yet; d) morbidity of the procedure is relevant. Therefore germectomy should be performed: a) if morphostructural alterations or ectopic impactions are present; b) in case eruption is not allowed for dysplastic alterations of the germs or pathological processes of the mandible; c) to gain space in the posterior segments of the lower jaw when distalization of first and second molars is necessary; d) in case of excessive anterior-posterior mandibular growth.

Adolescent↗
PubMed1993

An investigation of accessory canals in furcation areas of human primary molars: Part 2. Latex perfusion studies of the internal and external furcation areas to demonstrate accessory canals.

Four classes of accessory canals: "true," "blind," "looping" and "enclosed" canals have been suggested to exist in furcation areas of primary teeth. Although the existence of accessory canals in the furcation areas and roots of permanent teeth has been demonstrated, their presence in furcation areas of primary teeth is uncertain. This investigation was conducted to determine the presence or absence of accessory canals in the furcation areas of human primary molars using a variety of latex perfusion techniques. Twenty extracted, noncarious human primary molars were placed in fixative and then sectioned on a hard tissue cutting machine: ten teeth were cut transversely 2.0 mm coronal to the floor of the pulpal chamber and ten teeth were cut transversely 2.0 mm apical to the external furcation area. The internal and external furcation surfaces of these sectioned molars were debrided with sodium hypochlorite/hydrogen peroxide solutions, rinsed in water and dried to remove organic materials, which might obscure the existence of possible canals. Twenty of these extracted teeth were examined by SEM to detect the possible presence of accessory foramina in the internal and external furcation areas (Part 1). Twenty percent of the molars examined by SEM on the IFA and 50 percent of the molars examined by SEM on the EFA exhibited accessory foramina. Twenty molars were perfused with low viscosity latex using vacuum [negative] pressure (10 molars) and positive pressure (10 molars) to detect the possible existence of the patency and the extent of such accessory canals in the internal and external furcation areas (Part 2).(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗
PubMed1995

Study of cervical pulp horns in human primary molars.

This study confirmed that cervical pulp horns exist in human primary molars as the following results were found: 1. Fifteen cervical pulp horns were observed in the 40 extracted primary molars group (37.5%), 2. Ten cervical pulp horns were observed out of the 26 Indian primary molars group (38.5%), 3. Buccal extension of cervical pulp horns is 0.23 mm in the extracted primary molars group and 0.36 mm in the Indian primary molars group on average, 4. Cervical pulp horns of primary molars tend to be presented bilaterally in the same individual, 5. The percent of occurrence of cervical pulp horns in primary molars (37.6%, 38.5%) was lower than that of the permanent molar (77.1%).

Child, Preschool↗
PubMed1977

Molar polymorphisms and the timing of dentition mineralization.

The chronological age, skeletal age, and morphological age at the time of mineralization of 14 stages of the permanent teeth of 121 boys and 111 girls of the serial experimental sample of the Burlington Growth Centre were contrasted according to whether or not the children had 4- or 5-cusped mandibular permanent first molars, and whether or not they had agenesis of one or more third molars. In the boys with 4-cusped mandibular first molars, the mineralization of the teeth occurred at significantly earlier chronological and skeletal ages when they were significantly shorter in stature. Tooth mineralization was not consistently earlier in the girls with 4-cusped molars, but these girls tended to be taller and heavier than those with 5-cusped molars. In contrast, in both sexes with agenesis of third molars, the mineralization of the teeth was significantly delayed according to chronological, skeletal and morphological evaluation. The change in timing of mineralization was greatest for the second premolars and second molars, and least for the first molars.

Age Factors↗
PubMed2006

Molar-mass characterization of cationic polymers for gene delivery by aqueous size-exclusion chromatography.

PURPOSE: This study was performed to develop a reliable aqueous size-exclusion chromatography (SEC) method to obtain the absolute molar masses and distributions of various cationic polymers used in gene delivery. METHODS: Water-soluble cationic [2-(dimethylamino) ethyl methacrylate] polymers (PDEs) with different molar masses and low polydispersities were synthesized by living polymerization and these were used to optimize the SEC conditions. Online coupled multiangle light scattering (MALS) detection was applied to obtain the absolute molar masses. Narrow fractions of high molar mass were obtained by semipreparative SEC. RESULTS: It was found that 0.3 M NaAc (pH 4.4) is a suitable eluent in combination with Shodex OHpak SB columns for SEC analysis of PDEs and other cationic polymers, such as poly(L-lysine) and poly(ethylene imine). The absolute molar masses of different PDEs were determined directly using SEC-MALS. A calibration curve was established using narrow PDEs. CONCLUSIONS: A reliable routine method for molar-mass characterization of cationic polymers was established. Because standards of known molar masses with narrow distributions are not commercially available for most polymers used in pharmaceutics and biotechnology, the procedure described in this work can also be applied for molar-mass characterization of other water-soluble polymers.

Cations↗
PubMedDate not supplied

Serum proteins in vesicular fluid of hydatidiform moles: a lack of selectivity of molar trophoblast in the transfer of maternal serum proteins.

Complete hydatidiform moles, an abnormal pregnancy of androgenetic origin consisting of swollen villi without an embryo, were studied to determine the protein constitution of vesicular fluids in the swollen villi and the ability of the molar tissue to synthesize protein. All 16 serum proteins tested were identified in the molar fluid. A reverse correlation was obtained when the logarithms of the molar fluid versus maternal serum concentration ratios of different proteins were plotted against the logarithms of their molecular weights. Logarithmic regression analysis showed a linear regression with a high coefficient (gamma = 0.9626). Phenotyping of haptoglobin in the molar fluid and in the parental sera indicated a definite contribution of maternal proteins to the molar fluid. The molar tissues synthesized no serum proteins but produced human chorionic gonadotrophin beta-subunit (hCG-beta) and pregnancy-specific beta 1-glycoprotein (SP1) when examined in tissue cultures metabolically labelled with [35S]methionine. These findings indicate that a variety of maternal serum protein components is transferred to the molar fluid without being selected by the molar trophoblastic cells.

Blood Proteins↗
PubMed2003

Phase-separation-induced fractionation in molar mass in aqueous mixtures of gelatin and dextran.

An overview of the effects of phase separation of aqueous mixtures of gelatin and dextran on the fractionation in molar mass of these two components is given. Molar mass distributions in coexisting phases were investigated using size exclusion chromatography with multiangle laser light scattering. The initial molar mass of the native material, concentration, and temperature were varied. The results show a strong fractionation in molar mass for both components. The molar mass of the native material and concentration appeared to be the only factors that affected the final molar mass distributions, temperature having no effect. The results show that in the molar mass range where fractionation is the strongest, i.e., roughly below the maximum in the distribution, fractionation is governed by a Boltzmann factor e(-deltaG/kT), where deltaG denotes the free energy involved in transferring a polymer with a certain length from the enriched to the depleted phase, and in this case turns out to be proportional to the molar mass. Comparison of the results of phase separation with results on dialysis shows that water affinity is not the driving force for the phase separation of gelatin and dextran in aqueous solution. The gelation properties of gelatin in both phases were also determined. The gelation properties of gelatin in the coexisting phases differ from those of native gelatin. In particular, the gelatin in the gelatin-poor phase shows strong differences compared to the native material.

Journal Article↗
PubMed1989

Pattern of caries experience in permanent molars in a 15-year-old African population.

Some epidemiologic studies from Africa report higher DMF values in second than in first molars. It is generally accepted that the maturation of dental enamel influences the susceptibility of teeth to caries. The purpose of the present study was to test the hypothesis that DMF values of second molars will be higher than those of first molars if the first molars have reached a high degree of maturation before being exposed to increased cariogenic challenge. The study was carried out in a group of 15-year-old students attending secondary schools in Botswana (n = 287). The results showed that in children who assumingly had had a traditional diet during childhood the DMF values were higher in second molars than in first molars. In children who grew up in a more urbanized setting, the results were opposite. The observed differences were due to differences in caries experience in first molars only. The DMF values of second molars did not vary among the groups. Oral hygiene, sugar consumption and knowledge level at age 15 seemed to have no effect upon the caries pattern studied. It is concluded that the results support the hypothesis tested.

Adolescent↗