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PubMed2006

[An in vitro study on the incidence of the second mesiobuccal canal in the mesiobuccal root of the first and second maxillary molars].

OBJECTIVE: To investigate the incidence of the second mesiobuccal canal (MB2) in the mesiobuccal root of the maxillary first and second molars in Chinese population using three techniques, including the clearing technique, spiral CT scanning and serial root sections. METHODS: A total of 216 extracted human first and 334 second maxillary molars were randomly divided into two groups respectively: group A and B. The teeth in group A were cleared. The specimens in group B were subjected to spiral CT scanning, and then the roots were cross-sectioned every 1 mm from the root apex. Under the Dental operating microscope (DOM), the incidence of MB2 were recorded. RESULTS: (1) The incidence of MB2 in the first and the second maxillary molars were 81.48% and 49.70% respectively by clearing, and 77.78% and 47.31% from S-CT scanning, 88.89% and 53.89% respectively from serial root section. The occurrence of MB2 in maxillary first molars was statistically higher than in maxillary second molars (P < 0.05, chi square test). (2) There was no significant difference among the three approaches for detecting the MB2 canal (P > 0.05, chi square test). CONCLUSIONS: Both the maxillary first molars and the second molars have high incidence of MB2.

Dental Pulp Cavity↗
PubMed2006

Effect of the lower third molars on the lower dental arch crowding.

Increasing lower dental arch crowding with the age is a recognized clinical problem, and one that has become more apparent in recent years as more adults retain their teeth longer. One of the theories is that the erupting third molars push anterior teeth forward and cause their crowding. On the other hand, a number of studies found no correlation between lower third molars and lower incisor crowding. Because of all these contrasting findings this study was started to re-evaluate correlation between third molars presence and lower dental arch crowding. The study group consisted of 91 subjects with an average age 21.01+/-4.13 years. The individual, quantitative and cast-based analytical registration of crowding was based on the measurements of mesiodistal width of teeth and related to the length of the appropriate segment of the lower dental arch. No statistically significant third molar presence-specific differences were recorded in the lower dental arch crowding between the groups with erupted, unerupted and agenesis of third molars. Although differences between the groups were not statistically significant, some tendency for crowding in the anterior part of lower dental arch was more expressed in the groups with the presence (erupted 0.57 mm and unerupted 0.74 mm) of third molars, than with agenesis (surplus space 0.03 mm). Nevertheless, the present study do not provide enough evidence to incriminate third molars as being the only or even major etiologic factor in the late lower dental arch crowding.

Adolescent↗
PubMed2006

Conventional root canal therapy of C-shaped mandibular second molar. A case report.

The C-shaped root canal system and treatment implications were first described by Cooke and Cox in 1979. C-shaped canals are most frequently found in mandibular second molars, but they can occur in any mandibular molar, and they have been reported in maxillary molars as well. C-shaped mandibular molars are characterized by a C-shaped groove that connects one or more root canals. This groove can occur anywhere along the root canal system, making it difficult to diagnose and treat. A C-shaped root canal system may appear completely normal at the level of the pulp chamber but can begin to manifest itself in the middle or apical one-third. Furthermore, C-shaped canals are challenging if not impossible to predict radiographically. C-shaped canals in mandibular second molars are found most frequently in the Chinese population, with reports showing up to a 31.5% incidence, as compared to an approximate 7% incidence in the general population. This case report demonstrates an incidence of a C-shaped canal that was unable to be detected radiographically and which contained three separate root canals that communicated in the apical one-third of the root canal system. Canal orifices were located approximately 2 mm below the level of the CEJ, which is in agreement with a recent micro-computed tomography study of C-shaped mandibular molars that found 98% of all C-shaped molars studied had orifices located 1 mm to 3 mm below the CEJ. The CT study also found that all C-shaped canals contained fused roots and confirmed previous findings that the C-shape configuration varies greatly throughout the length of the canal.

Adult↗
PubMed1991

[The extraction of a completely impacted upper second deciduous molar: case report].

A 7-year old boy visited the dental hospital complaining that the upper left second deciduous molar had not erupted. Radiographs showed that the crown of this tooth existed near the apex of the upper left first molar. Inversion of the second deciduous molar and second premolar was definite. There were no differences in location, size and shape between the left and right second premolars. A tooth-like object was observed near by the germ of the left second premolar. The impacted molar was examined histopathologically after extraction and consequently it was found that it was a supernumerary tooth. New radiographs were made which suggested that the succedaneous premolar developed normally. The tooth germ of the primolar develops on the lingual side of the deciduous molar and moves in the level of the occlusal plane of the primary molar. Later they are found between the divergent roots and, at the end of the pre-eruptive phase, below the roots of the primary molars. We concluded that the supernumerary tooth disturbed this adjustment.

Child↗
PubMed1991

Caries susceptibility of first permanent molars and treatment needs in Sri Lankan children, aged 13-16 years, in 1986.

The caries status of the permanent first molar was studied in 683 school children (aged 13-16 years) selected from six schools in Kandy. Radike (1972) criteria were used for the examination. Of 2732 first molars examined, 37 per cent were found to be carious, filled or missing. Susceptibility to caries was higher in mandibular molars (47 per cent) than in maxillary molars (25 per cent). In 36 per cent of the children all four molars were sound, while in 11 per cent they were all affected by caries. Of 998 DMF units, 676 (68 per cent) were decayed, 189 (19 per cent) filled and 133 (13 per cent) extracted. Seventy-nine per cent of the DF sites were occlusal. Results suggest that a high proportion of carious permanent molars have been neglected without the seeking of professional care. Approaches for preventive and restorative care for the permanent first molar tooth, appropriate in Third World countries, are suggested.

Adolescent↗
PubMed1991

A longitudinal study of the condition of first permanent molars in a group of adolescents with special reference to elective orthodontic tooth extraction.

The aim of this study was to investigate changes in the condition of first permanent molars over the teenage years, with special reference to adolescents who lost premolar teeth for orthodontic purposes. A total of 453 South Wales schoolchildren (219 males and 234 females) were examined at the ages of 11-12 and 19-20 years. At 11-12 years, 89.6 per cent of the cohort had all four first permanent molars, while 3.3 per cent had already lost these teeth. Of those first permanent molars present, 61.7 per cent had some caries experience. At age 19-20, 80.6 per cent of subjects retained four first permanent molars while 4.4 per cent had none. Of the first permanent molars present, 80.6 per cent had been affected by caries. In 60 per cent of the 186 subjects (75 males and 111 females) who had lost premolar teeth in the course of orthodontic treatment, a sound premolar was extracted in preference to a first permanent molar which already had evidence of dental disease. At age 19-20 years, the majority of the first permanent molars were restored and otherwise sound, though a small number which had been restored at age 11-12 years had been lost due to caries.

Adolescent↗
PubMed1990

[Evaluation of preventive dental care for first permanent molars in children].

The prevalence of dental caries in first permanent molars was measured in 220 children who have been under regular dental care at the Pediatric Dental Clinic, Tohoku University School of Dentistry. While the caries prevalence rate of first permanent molars reached approx. 50% five years after the eruption, the number of filled surfaces per restored tooth was less than 2.0. The caries prevalence of the permanent mandibular first molars was significantly higher than the caries prevalence of the permanent maxillary first molars. However, the occlusal surface showed no significant differences between the maxillary and mandibular molars. While comparing the female to male group, the caries prevalence rate was significantly higher and the peak of caries occurrence on every surface was earlier in the females. Pit and fissure sealants were applied to approx. 75% of first permanent molars and the occlusal caries were reduced as a result of sealing. When sealants were applied to the teeth diagnosed as C1, 50% were restored due to development of caries. This was a significantly higher rate than that applied to sound teeth. Our study indicates that most of the occlusal caries occurred in the earlier stage of 1-2 years after the eruption, before sealants were applied. The buccal fissure of the lower molars and the occlusal fissures both showed high caries prevalence. It was suggested that prevention of fissure caries immediately following eruption until the sealant is applied is an important issue in our present dental care system.

Child↗
PubMed1989

[Ivorian typology: study of the crown dimensions of the first permanent molar].

A dental morphology study is of great importance because it allows norms to be established which are adapted to the Ivorian situation. After a study of the canal morphology, we became involved in a study of the canal dimensions of the first permanent molars amongst Ivorian children. As a part of the 260 mouldings taken from 67 boys and 63 girls, we measured the following diametres: the diametre masio-distal (O-M-D) taken between the edge of the mesial bone and the edge of the distal bone. the biggest vestibulo-lingual coronary diametre (OV-LC). the diametre of the vestibulo-lingual at the level of the occlusal table (OV-LC). The data collected allowed us to reach the following conclusions: the first secondary molar with a M-D diametre (10.64 mm) is more important than the M-D diametre of its homologeous upper (10.15). however there is no significant difference between the OV-LC diametre of the first maxillary molar and that of the first mandibular molar. concerning the M-D or V-L diametres, the difference between the left side of the maxillary as with the mandibular is negligble. It's worth noting that the first permanent molar is smaller for girls when compared to boys, as well as their M-D diametres compared to their V-L. A comparative study between the TALLEC and MARSEILLIER plates showed that: the first upper molar for Ivorian children has a M-D diametre practically identical to that of European children, however the V-L and OV-LC diametres are smaller. the first bottom molar slightly bigger in all M-D and V-L diametres in Ivorian children in comparison to European children.

Black People↗
PubMed1989

Prevalence of impacted third molars in dental students.

To study the prevalence of third molar impaction in dental students, the radiographs of 113 female and 144 male students in the age groups 20-39 years were investigated. Half of the individuals had all four third molars, whereas 10% of the individuals lacked all third molars. A radiologic definition of impaction, which is illustrated, is suggested. One or more impacted third molars were found in 33% of the individuals. The difference between the sexes regarding impacted third molars was not significant. Calculated by number of teeth, one fourth of all third molars were impacted and were then mostly in a vertical or mesioangular position. The frequency of impacted third molars was higher in the lower jaw compared to the upper jaw.

Adult↗
PubMed1978

Molar polymorphisms and body growth.

Body growth at adolescence was later in children of the serial experimental sample of the Burlington Growth Centre who had agenesis of third molars of 4-cusped mandibular permanent first molars. These groups of children tended to have later maximum increment of growth, later completion of the growth spurt, less adolescent prepeak gain and greater postpeak gain in height and weight than the children with four third molars and 5-cusped first molars. Growth of the boys differed significantly (P less than 0.05) according to absence or presence of third molars, whereas in girls it differed significantly (P less than 0.05) by the number of cusps of the mandibular first molars. In skeletal age, the children with the molar reductions were slightly advanced before adolescence, fell behind during prepeak adolescent growth, and caught up to the other children by the end of their growth spurt. Later maturation in association with dental reduction may be an evolutionary trend in man.

Adolescent↗
PubMed1981

Use of second molar eruption in age estimation of cattle.

The intra-oral development of the second molar in cattle was examined using a system of molar codes based on degree of eruption. Observations on eight Friesian heifers seen more than once were compared with those from 320 cattle studied by the cross-sectional method. The average ages of the Friesians for a given degree of eruption tended to be higher than those in the larger survey. There were too few data to provide a statistical comparison but, by using the age range for each stage of second upper molar development, it was found that in absolute terms an animal showing no emergence of the tooth was younger than one exhibiting complete eruption of the rostral and caudal units. In addition, in most cases an animal at molar code 1 (rostral unit emerging, caudal unit not visible) was younger than one at molar code 8 (rostral and caudal units both fully up). Although the method of second molar development had limitations in age estimation it did provide an indication at a time before eruption of the first permanent incisor tooth pair and the age range at each stage of molar development tended to be lower than for the permanent rostral teeth.

Age Determination by Teeth↗
PubMed1997

Agreement between practitioners concerning removal of asymptomatic third molars.

OBJECTIVE: To investigate and compare agreement within two groups of dental practitioners, family dentists and oral surgeons, in their decisions regarding removal of asymptomatic mandibular third molars. SUBJECTS: Ten oral surgeons and 18 family dentists from South Wales with experience ranging from 5 to 28 years. METHODOLOGY: Participants were presented with periapical radiographs of 36 asymptomatic, mandibular third molars and were informed of the age and gender of the patients and the degree of eruption of the third molars. Participants were asked to indicate whether they thought that the third molar should be removed or not. The degree of agreement between participants was measured by kappa indices for multiple raters. RESULTS: The kappa indices were 0.14 for the oral surgeons and 0.09 for the family dentists, indicating poor agreement beyond chance. Although in most cases the participants decided not to remove the third molar, they did so inconsistently, that is, they did not make this decision on the same cases. There were also differences in the inclination of the participants to suggest removal of the 36 third molars. CONCLUSION: Poor inter-observer agreement suggested that treatment decisions regarding asymptomatic third molars are based more on subjective beliefs and habitual practices than on rational decision making.

Adult↗
PubMedDate not supplied

The differences in the chronology and calcification of second molars between angle Class III and Class II occlusions in Japanese children.

The purpose of this study was to examine the differences in the times of eruption and calcification of the permanent dentition between skeletal class III and class II groups. (And also to examine the relationship between the time of eruption and the type of malocclusion) Fifty-three children, ages seven to ten years, were selected. Of these, twenty-six children (twelve boys and fourteen girls) were Angle class III with minus ANB and twenty-seven children (eleven boys and sixteen girls) were Angle class II with five or more ANB. Panoramic radiographs and cephalometric radiographs were used. The panoramic radiographs showed that the calcification of the maxillary second molars in class II were earlier than in class III using Nolla's classification. There was no statistically significant difference, however, for mean values of calcification stages, using Nolla's classification, between boys and girls. The cephalometric and panoramic radiographs showed that the times of eruption and calcification were earlier in the maxillary second molars than in the mandibular second molars for class II. In contrast, the times of eruption and calcification were earlier in the mandibular second molars than in the maxillary second molars for class III. The times of eruption and calcification of the maxillary molars were significantly related to the length of the ANS-PNS. The longer the ANS-PNS, the earlier were the times of eruption and calcification. There was a significant relationship between the ANB angle and the time of eruption, as well as the ANB angle and calcification. The larger ANB had earlier calcification and chronology of maxillary second molars.

Cephalometry↗
PubMed1996

Completely submerged primary molars.

Two mixed dentition cases have been presented which became quite complicated because of ankylosed and submerged primary second molars. These cases demonstrate the need for an early orthodontic evaluation and interceptive orthodontics. The orthodontic and surgical procedures required for these two patients could have easily been avoided by removing the ankylosed primary molars and placing space maintainers. (Of course this depends upon the parents responding to their dental recall notices.) If a submerging primary molar is retained too long, the second premolar may become displaced superiorly and the permanent first molar may migrate mesially as it erupts. Both of these problems can be prevented by extracting the ankylosed primary second molar before it submerges below the mesial height of contour of the permanent first molar. A fixed space maintainer then becomes necessary to prevent loss of arch length by mesial migration of the permanent molar.

Ankylosis↗
PubMed1998

A morphometric analysis of the furcation region of mandibular molars.

This study examined furcation dimensions and morphology in first and second mandibular molar teeth. One hundred thirty-four extracted human mandibular molars with divergent roots were selected. Teeth were viewed at 7X magnification on a dissecting microscope interfaced with a computer equipped with a state-of-the-art histomorphometry software program. Various aspects of furcation anatomy were measured and recorded. Data were examined by using analysis of variance for all paired comparisons. For nonparametric data, the Kruskal Wallis test was used. Results indicated that 61.94% of buccal and 50.75% of lingual molar surfaces presented with cervical enamel projections (CEPs), with the highest frequency noted in second molars. CEPs ranged from 0.98 mm to 1.33 mm, whereas root trunk heights varied between 2.23 mm and 2.93 mm. Generally, lingual molar surfaces had longer root trunks when compared to buccal surfaces. Root separation increased by approximately 0.5 mm at each 1-mm increment apical to the furcal roof. This study provides new information regarding the furcal anatomy of mandibular molar teeth and supplements previous reports that suggest the CEP is a common problem which must be addressed by clinicians when treating molar teeth.

Analysis of Variance↗
PubMed1990

Covalent crosslinking of myosin subfragment-1 and heavy meromyosin to actin at various molar ratios: different correlations between ATPase activity and crosslinking extent.

This paper describes a systematic study of crosslinking of skeletal muscle myosin subfragment-1 (S1) and heavy meromyosin (HMM) to F-actin in the rigor state with 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC). We followed the time courses of S1 or HMM head crosslinking at various actin:S1 or actin:HMM head molar ratios and the resulting superactivation of ATPase activity. The ATPase activity of the covalent complexes was measured at 0.5 M KCl, where the covalent complexes retain superactivated ATPase activity but the activity of uncrosslinked myosin heads is not activated by actin. S1 crosslinking was slowest at the actin:S1 molar ratio of 1:1, but faster at larger molar ratios, where more than 80% of added S1 could be crosslinked to actin. In spite of the dependence of crosslinking rate on actin:S1 ratio, there were two linear correlations between ATPase activity and the extent of S1 crosslinking to actin: one for S1 crosslinked to actin at actin:S1 molar ratios more than 2.7:1 and the other for S1 crosslinked at a molar ratio of 1:1. Extrapolation of the former correlation line to 100% crosslinked S1 gave an ATPase activity of 39 s-1 for actin-S1 covalent complex at 25 degrees C, whereas that of the other correlation line gave 21 s-1. The latter smaller activity suggests that the interface between actin and S1 in their rigor complexes at a molar ratio of 1:1 is different from that at molar ratios of more than 2.7:1. The acto-HMM crosslinking rate depended on the ratio of actin to HMM head, like that of S1 crosslinking to actin. The ATPase activity of crosslinked actin-HMM was, unlike that of actin-S1 covalent complexes, bell-shaped as a function of the crosslinked heads, but chymotryptic conversion of HMM to S1 in the covalent complexes made the bell-shaped characteristics disappear and increased the activity close to that of actin-S1 covalent complexes. These results indicate that some physical constraint imposed on myosin heads suppresses the actin-activated ATPase activity of HMM crosslinked to actin.

Actins↗
PubMed1982

Immunopathologic study of the implantation site in molar pregnancy.

The implantation sites of 11 molar pregnancies were examined for the deposition of immunoglobulin and complemented by direct immunofluorescence. None of the 10 women experiencing their first molar pregnancy had immunoglobulin or complement deposition in the implantation site. The one patient with immunoglobulin and complement deposition in the implantation site was aslo the only patient experiencing a second molar pregnancy. Immunofluorescent staining for IgG, IgM, and C3 was confirmed to the decidual arteries in this patient and was unassociated with endovascular trophoblastic deposits. While only one of the 10 women with their first molar pregnancy had focal vasculitis at the implantation site, the patient with her second consecutive mole had diffuse vasculitis. Because molar implantation sites are generally free of immunoglobulin and complement deposition, molar pregnancies do not appear to induce a vigorous host humoral immune response at the time of presentation at the molar implantation site.

Adult↗
PubMed1985

Risk factors for complete molar pregnancy from a case-control study.

Demographic, reproductive, and dietary histories for 90 white women with complete molar pregnancy were compared in a multivariate analysis with those of 90 parous controls matched to cases by residence, birth year, and race. Women with molar pregnancy were more likely to have been born outside North America (relative risk = 1.9, p = 0.05), were more likely to have been past age 30 at time of their molar pregnancy (relative risk = 1.6, p = 0.05), and were more likely to have diets deficient in the vitamin A precursor carotene. Women with dietary scores for carotene above the control median had a relative risk for molar pregnancy of 0.6 (p = 0.02). In addition, there was a significant trend for decreasing risk for molar pregnancy with increasing consumption of carotene. Although other nutritional deficiencies in patients with complete molar pregnancy may exist, carotene is a biologically plausible candidate for a nutritional risk factor that could explain the geographic distribution of molar pregnancy.

Adult↗