Failure of eruption of first and second permanent molars

Failure of eruption of permanent molars is an uncommon condition with a range of possible causative factors. This retrospective study of 35 pediatric subjects assesses the influence of these factors in the prognosis. The study aims to broaden our understanding of an abnormality, which has a considerable clinical impact, and proposes a treatment protocol for the management of these patients.     

Time and duration of eruption of first and second permanent molars: a longitudinal investigation

Abstract – Objective: The aim of this study was to investigate the variation in (i) the time (age) of eruption and (ii) the duration of the eruption of first (M1) and second (M2) permanent molar teeth. Finally, the study also provides data about the association between time of eruption of the first of the M1s and the first of the M2s. Methods: The study was carried out in Nexö Public Dental Health Service, Denmark. All children who, in a period of 12 months, had the first of their M1s or M2s recorded as erupted and the occlusal surface still partly covered by gingiva formed the study groups (N = 69 and 112 children, respectively). The continued eruption of all four molar teeth was recorded at recall intervals not exceeding 4 months until functional occlusion was obtained. Results: First permanent molars: eruption time – girls: from the age of 5 years and 3 months to 7 years and 8 months (mean 6.1 years); boys: from 5 years and 2 months to 7 years and 10 months (mean 6.3 years). The duration of eruption – girls: from 5 to 32 months (mean 15.4 months); boys: from 7 to 28 months (mean 15.0). Second permanent molars: eruption time – girls: from the age of 8 years and 11 months to 14 years and 4 months (mean 11.3 years); boys: from 9 years and 11 months to 13 years and 11 months (mean 12.0 years). The duration of eruption – girls: from 12 to 44 months (mean 27.1 months); boys: from 9 to 45 months (mean 27.9 months). No correlation was found between the time of eruption and the duration of eruption of M1 or M2. There was a strong positive association between the time of eruption of the M1s and the M2s (r_s = 0.81). Conclusions: A tremendous variation was found in time of eruption and in duration of eruption of permanent molars. This variation highlights the importance of individualizing caries preventive strategies for children.     

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第一恒磨牙在萌出过程中过于偏近中可导致第二乳磨牙牙根吸收。第一恒磨牙异位萌出常常造成间隙丧失和牙弓长度减少,严重者可导致第二乳磨牙早失。第一恒磨牙异位萌出分为可逆性和不可逆性,对于不可逆性异位萌出应进行积极的治疗。治疗方法包括主动治疗和被动治疗。前者常用的方法有分牙法以及采用推第一恒磨牙向后的装置;后者通常采用截冠或拔牙的方法。本文对第一恒磨牙异位萌出的临床表现和常用的治疗方法进行了阐述。     

Metachronous bilateral dentigerous cysts associated with permanent first molars

The occurrence of bilateral dentigerous cysts (DC) has been described as being associated mostly with third molars in adult patients. Very few reports show the bilateral occurrence of dentigerous cysts associated with first molars or premolars in childhood. The purpose of this report was to describe the case of a 5-year-old boy with bilateral mandibular dentigerous cysts associated with permanent first molars.     

Root canal anatomy of maxillary first and second permanent molars

AIM: The aim of this investigation was to study the root canal anatomy of maxillary first and second molar teeth from an Irish population sample using a clearing technique. METHODOLOGY: Eighty-three extracted permanent maxillary right first molars and 40 permanent right maxillary second molars were included in this investigation. The specimens were demineralized and then cleared using methyl salicylate. The following observations were made: number of roots, prevalence of fusion, types of root canals using Vertucci's classification, presence and position of lateral canals, presence and position of transverse anastomoses, number and position of apical foramina and the frequency of occurrence of apical deltas. RESULTS: Eleven per cent of maxillary first molars and 43% of maxillary second molars had fused roots. A total of 78% of mesiobuccal roots in maxillary first and 58% in maxillary second molars had two canals. Sixty-two per cent of maxillary first and 50% of maxillary second molars had two apical foramina. There was a significant inverse relationship between age and the occurrence of two canals and between age and the occurrence of transverse anastomoses in both tooth morphotypes (P < or = 0.05). CONCLUSIONS: It is concluded that a significant proportion of the first and second molar specimens studied had two canals in the mesiobuccal root (78% and 58%, respectively) and that the occurrence of two canals and transverse anastomoses decreased significantly with increasing age.     

第一恒磨牙异位萌出治疗方案选择的考量

第一恒磨牙异位萌出分为可逆性异位萌出和不可逆性异位萌出.第一恒磨牙异位萌出的临床危害主要是造成间隙丧失、牙弓长度减少等.本文通过3例推第一恒磨牙向远中开展间隙的病例,阐述第一恒磨牙异位萌出治疗方案选择的考量.     

The eruption of permanent incisors and first molars in prematurely born children

The purpose of this work was to examine whether the clinical eruption of the permanent first molars and incisors is affected by pre-term birth. The data applied to 328 prematurely born white and black children and 1804 control children who participated in the Collaborative Perinatal Project (USA) in the early 1960s and 1970s. The dental examinations had been performed in a cross-sectional manner at ages varying from 6 to 12 years in 95 per cent of cases (range 5-14 years). Dental casts were placed in matched pairs by sex, race and conceptional age for comparison of the four clinical stages of eruption of the permanent incisors and first molars between the pre-term and control children. The results showed significantly (P < 0.05) earlier tooth eruption in the pre-term children. The findings suggest that the eruption process is earlier in those teeth that go through a sensitive period circumnatally, being at the pre-eruptive stages and entering the first phases of mineralization under the influence of various neonatal systemic factors and accelerated growth period (catch-up growth) with related unknown mechanisms, which may influence the eruption of the permanent incisors and first molars in prematurely born children.     

Ectopic eruption of maxillary first permanent molars and association with other tooth and developmental disturbances.

The associations between tooth and eruption disturbances in four groups of children selected primarily with only one diagnosed eruption or developmental disturbance in each group was analysed. Ninety-two children were primarily diagnosed with ectopic eruption of maxillary first permanent molars, 93 children with infra-occlusion and ankylosis of primary molars, 91 children with ectopic eruption of maxillary canines, and 97 children with aplasia of premolars. Of the children studied 69-79 per cent had only a single one of the four disturbances studied. In 18-28 per cent there was one additional disturbance and in 2-3 per cent two additional disturbances. From chi square contingency tests, it was found that infra-occlusion of primary molars and aplasia of premolars exhibited a higher prevalence in both directions compared to the expected population prevalence. Ectopic eruption of maxillary canines showed a significantly higher prevalence than expected in all the other three groups. Our interpretation is that these results support the hypothesis of a common, presumably hereditary, aetiology. Thus, the four conditions studied would be different manifestations of one syndrome, each manifestation having an incomplete penetrance. With closer follow-up of the maxillary canines during the eruption period in children with some of the other three disturbances, prophylactic, or early interceptive measures may be taken and complicated orthodontic treatment be reduced or avoided.     

Caries vulnerability of first and second permanent molars in urban Nigerians.

Caries prevalence and distribution were studied in 820 Nigerians aged 15, 19, 20 and 21 yr. Contrary to observations in most Western countries, approximately twice as many second permanent molars as first permanent molars were carious, at all ages. This apparently anomalous caries distribution pattern was observed mainly in those with low caries experience (mean DMF ? 5) and is difficult to explain in purely environmental terms. Genetic factors may be involved.     

Carabelli's trait on maxillary second deciduous molars and first permanent molars in Hindus

The maxillary casts of 211 Gujarati Hindu children were examined for the occurrence of Carabelli's trait on the maxillary second deciduous molar (dm²). The trait was absent in 11.8 per cent. The tubercle form was present in 19.9 per cent and groove and pit in 58.3 per cent and 7.8 per cent respectively. The trait was usually present bilaterally. A further study of 192 dental casts out of 211 showed that the trait was present on the dm² if it was present on M¹ with a statistical significance at 5 per cent level.     

Morphological characteristics of inter-radicular space of the first and second lower permanent molars

In this study, 537 extracted molars (261 first and 276 second molars) with well developed roots were examined to assess the width of the interradicular space and the shape of the furcation vault. The roots were set widely apart in 91.6% of the first and 64.8% of the second permanent molars, while the roots set closely together were observed in 8.4% and 27.9% of the first and second molars, respectively. Fuseg roots were found in second molars only, in 7.2% of cases. A flat furcation fornix was detected in 18.3% of the first and 14.0% of the second molars, whereas a convex shape was observed in 20.7% of the first and 10.5% of the second molars, respectively (P less than 0.001). A convex shape of furcation was found in 8.0% of the first and 27.3% of the second molars, respectively (P less than 0.001). Interradicular ridge was present in a very high percentage (52.9% of the first and 48.0% of the second molars). A concave shape of furcation fornix was statistically more frequent in molars with closely set roots for the first and second permanent molars (P less than 0.001). It seemed that the width of the interradicular space had no influence on the prevalence of interradicular bridges, regardless of type of molars involved.     

Directionality of dental trait frequency between human second deciduous and first permanent molars

Dental traits were scored for second deciduous molars (dm2) and first permanent molars (M1) on casts of the dental arches of children aged 7-11 years. The children were from four different ethnic groups. The overall frequency of traits differed between the groups but the relative frequency of expression of traits in the two teeth showed a similar pattern. Traits such as continuous oblique ridge, Carabelli cusp, Y pattern and 7th cusp, that appear in the early stages of development, were more frequent in dm2 than in M1. Wrinkling, occlusal tubercles and marginal ridge cusps were more frequent in M1; these appear later. Thus the relative frequency of traits in these teeth reflects their ontogenetic history.