Spacing in the human deciduous dentition in relation to tooth size and dental arch size

Crown dimensions of primary teeth-A systematic review and meta-analysis

Odontometrics, also known as metric traits, includes mesiodistal, buccolingual dimensions, and crown height. The purpose of this study was to assess pancontinental odontometric variations in the crown dimensions of primary teeth. Ten electronic databases were searched to identify studies that measured crown dimensions of primary teeth, published in English language, without year restriction up to July 2020. Studies included cross-sectional research measuring on casts, subjects, and on radiographs of healthy children. Meta-analysis was performed, and risk of bias was assessed using modified Newcastle-Ottawa Scale. Eighty-seven observational studies were included, with 24,634 participants (9487 males, 11,083 females; 19 studies lacked gender information). Only one study showed a low bias risk, whereas 81 and 5 studies had moderate and high risk, respectively. Sixty-five studies included for meta-analysis revealed heterogeneity in mean mesiodistal dimensions of maxillary first molars from Asia (I² -99.7%), buccolingual measurements of mandibular first molars from Europe (I² -99.9%), crown height of mandibular second molars from Africa and Europe (I² -79.8%). Among mesiodistal and buccolingual dimensions, Australians have larger while Asians have smaller teeth. Pertaining to crown height, very few studies could be found in the literature. This review highlights the variations in crown dimensions of primary teeth among populations.

Supernumerary roots in maxillary deciduous canines: A rare anomaly with a long history

OBJECTIVE

To describe two maxillary deciduous bi-rooted canines, one archeological and one modern, and examine the possible etiology of this condition.

DESIGN

Two cases of bi-rooted canines were described and compared to published examples. Both specimens were radiographed and measured and compared to one-rooted samples. The archeological specimen was scanned using CBCT to facilitate detailed examination of the deciduous teeth. The extracted modern tooth was embedded in epoxy resin and two coronal sections were cut, one through the crown and one through the roots and examined with a light microscope.

RESULTS

The bi-rooted canines were larger than the control samples. They showed none of the features commonly associated with gemination. The radiographs and scans showed that the canine roots in the archeological case diverged mesio-distally like the buccal roots in the adjacent first deciduous molar. In the clinical case, the root trunk was elongated mesio-distally and the furcation was located very close to the apex with a C-shaped root canal.

CONCLUSIONS

Both variants of the condition described above are rare in deciduous canines. They do not seem to be associated with fusion or gemination. However, as the teeth are relatively flattened bucco-lingually and we tentatively propose that this form results from spatial constraints during the early stages of crown development that have contributed to the development of additional roots. The megadont dimension of the recent bi-rooted deciduous canine may affect root development and the necessity of two mesio-distally located roots for anchorage in the maxilla.

Incisor liability and its effects among East Asian children

BACKGROUND/PURPOSE

Incisor liability is the discrepancy in the sum of the mesiodistal crown width between the primary and permanent incisors. Incisor liability affects the integrity and eruption of the permanent incisors during the transition from the primary to permanent dentition. This study investigated the incisor liability in the primary dentition of Taiwanese children.

METHODS

The digital periapical films of 203 upper arches of 105 boys and 98 girls and 195 lower arches of 119 boys and 76 girls aged between 3 and 6 years were selected in this retrospective study. The mesiodistal crown widths of the primary and permanent incisors were measured using the medical imaging software for both arches. Differences in incisor liability values were statistically analyzed.

RESULTS

The mean ± standard deviation of the incisor liability values were 8.32 ± 1.88 and 6.91 ± 1.13 mm for the upper and lower arches, respectively, in all children. The incisor liability was closely related with the total crown widths of the permanent incisors for upper and lower arches. The incisor liability values were higher among boys than girls for the upper but not lower arch.

CONCLUSION

Incisor liability differs depending on ethnicity. In Taiwanese children, incisor liability was closely related with the crown widths of the permanent incisors. The incisor liability values of boys were higher than those of girls in the upper arch but not the lower arch.

Correlating spacing in the primary dentition and caries experience in preschool children

PURPOSE

To evaluate the correlation between spacing in the primary dentition and caries experience.

METHODS

One hundred seventy-four clinical records, including photographs during 2017-2019 were assessed for primate, generalised and interdental spaces. The mean of decayed, missing or filled teeth and surfaces (dmft and dmfs) were recorded to quantify the caries experience. Linear regression analyses were used to ascertain correlations between spacing and dental caries. The strength of the associations was quantified using odds ratio (OR) and 95% confidence interval (CI).

RESULTS

Ninety-seven boys and 77 girls were included in the final analysis. Approximately 41% of children had primate space in all four quadrants, and 15% of children had no primate spaces in all four quadrants. 50% of children did not exhibit generalised spacing, while 39% of children showed interdental spacing. Children with no primate space had approximately five surfaces higher dmfs score compared to those with primate space in all four quadrants (95% CI - 9.27 to - 1.23; p < 0.05). Similarly, children with no primate space in the mandible had 6.12 surfaces higher dmfs score compared to those with primate space in the mandibular arch (95% CI - 10.07 to - 2.17; p < 0.05).

CONCLUSIONS

Preschool children with no primate space exhibited a 50% increase in dmfs scores compared to children with primate space.

Genetic contribution to palatal morphology variation using three-dimensional analysis in Australian twins

OBJECTIVE

This study aimed to provide insight into the relative contributions of genetic and environmental factors to palatal morphology variation in a cohort of Australian twins.

METHODS

Healthy Australian twins, aged 12-15 years (45 monozygotic, 46 same sex dizygotic, and 32 opposite-sex dizygotic) were included in the study groups. A scanner was used to obtain three-dimensional data of the maxillary arch. Palatal depth was defined by a line to the deepest point measured from the reference plane at the mid-point of the inter-pre-molar or inter-molar line. This line was then divided into 10 equal sections in order to created 10 different depths for each palatal width. Each palatal width was divided into anterior and posterior areas. Univariate genetic analysis, using the OpenMx structural equation modelling package in R, was carried out on the quantitative data using the normal assumptions of a twin model.

RESULTS

Heritability estimates for anterior palatal width ranged from 0.75 to 0.80, and from 0.78 to 0.86 for posterior palatal width. Estimates for anterior and posterior palatal depth were 0.72 and 0.86, respectively.

CONCLUSIONS

Palatal morphology tends to have a moderate to relatively high genetic contribution overall. Palate height has a higher genetic contribution posteriorly than anteriorly. The width of the deep palate is under marginally less stringent genetic regulation than the width of the shallow palate.

The relationships between the arrangement of teeth, root resorption, and dental maturity in bovine mandibular incisors

Objective

The objective of this study is to investigate the eruption pattern and root resorption of the bovine anterior dentition in relation to growth-related parameters based on dental maturity.

Methods

A cross-sectional study was conducted on 110 bovine anterior mandibles by using standard radiography, cone-beam computed tomography (CBCT), and actual measurements. We determined the relationships between the stages of dental maturity by using a modification of Demirjian's method and various growth-related parameters, such as the activity of the root-resorbing tissue and mobility of the deciduous teeth. The correlation of growth-related parameters with interdental spacing and distal unusual root resorption (DRR) of the deciduous fourth incisor was assessed. The cause of mesial unusual root resorption (MRR) of the deciduous fourth incisor was determined on the basis of the arrangement of the permanent third incisor.

Results

An independent t-test and chi-square test indicated significant differences in growth-related parameters associated with dental arch length discrepancy and factors related to the shedding of deciduous teeth between the low and high dental maturity groups. The samples with interdental spacing and DRR showed a larger sum of mesiodistal permanent crown widths and higher dental maturity than did the respective controls. Samples with MRR tended to show a lingually rotated distal tip of the adjacent tooth crown.

Conclusions

Dental maturity has relevance to the interdental spaces and unusual root resorption of mixed dentition. The position of the adjacent tooth crown on CBCT may be correlated with the occurrence of unusual root resorption of the incisor.

Prevalence of primate and interdental spaces for primary dentition in 3- to 6-year-old children in Taiwan

BACKGROUND/PURPOSE

Spaced primary dentition plays a critical role in the eruption of permanent teeth and the establishment of ideal occlusion. A lack of these spaces in deciduous dentition may result in disproportionate jaw and tooth sizes. Additionally, spaced primary dentition is significantly affected by ethnic factors. However, few of these studies have been conducted in Asia. The purpose of this study was to investigate the prevalence of spaced primary dentition in Taiwan.

METHODS

One hundred and forty-seven 3- to 6-year-old Taiwanese children (58 girls and 89 boys) were recruited for a cross-sectional study. Primate and interdental spaces were recorded by intraoral photos. The prevalence of spaced dentition was evaluated. The interpersonal agreement of spaced dentition between the upper and lower arches was also assessed.

RESULTS

Most of the subjects had spaced primary dentition. The prevalence of primate space was 83.7% in the upper arch and 61.2% in the lower arch, whereas the prevalence of interdental space was 44.2% in the upper arch and 53.1% in the lower arch. The prevalence rates of interdental space and upper primate space were significantly higher in boys than in girls. Interdental spaces of the lower arch increased with age.

CONCLUSION

Ethnic factors can affect the ratio of spaced dentition. Most of the 3- to 6-year-old Taiwanese children have spaced dentition. The boys have higher incidence of spaced dentition than the girls. Furthermore, primate space is more frequently found in the upper arch than in the lower arch, whereas interdental space is reversed.

Prevalence of spaced and closed dentition and its relation to malocclusion in primary and permanent dentition

An ideal primary dentition is the indicator of future ideal permanent dentition. Absence of primate or secondary spaces in the primary dentition is expression of disproportion between jaw/tooth sizes. Little information is known on the relationship of spacing and closed dentition with malocclusion in relation to primary and permanent dentition. Hence, the present study was conducted to find the relationship of spacing and closed dentition with malocclusion in primary and permanent dentition in children during their deciduous dentition period.

Avaliação comparativa do espaçamento anterior em nipo-brasileiros e leucodermas, na dentição decídua

OBJETIVO: avaliar comparativamente a prevalência das características de espaçamento anterior em nipo-brasileiros e leucodermas, na dentição decídua. MÉTODOS: duas amostras de crianças com 2 a 6 anos de idade foram selecionadas: 405 nipo-brasileiros de 36 escolas do estado de São Paulo e 510 leucodermas de 11 instituições públicas da cidade de São Paulo. As variantes oclusais foram classificadas em quatro categorias, nas arcadas superior e inferior: espaçamento generalizado; somente espaços primatas; ausência de espaços; e apinhamento. Foi aplicada regressão logística para análise do efeito dos fatores idade, sexo e grupo étnico sobre a prevalência das características oclusais (α = 0,05). RESULTADOS: em nipo-brasileiros, o espaçamento generalizado foi a característica mais prevalente nas arcadas superior (46,2%) e inferior (53,3%). A frequência dos espaços primatas foi maior na arcada superior (28,2% versus 15,3%). Para a ausência de espaços (21,7-26,4%) e o apinhamento (4,0-4,9%), a variação entre as arcadas foi relativamente pequena. Em leucodermas, a ausência de espaços e a presença exclusiva dos primatas evidenciaram distribuição similar à observada nos nipo-brasileiros. O espaçamento generalizado foi diagnosticado em aproximadamente 50% das arcadas. A prevalência de apinhamento foi maior na arcada inferior (12,8% versus 3,9%). O único modelo de regressão logística que apresentou algum fator significativo foi o ajustado para a prevalência de apinhamento. Apenas o fator racial foi significativo (p < 0,001). CONCLUSÃO: sugere-se que as características de espaçamento anterior, na dentição decídua, não estariam condicionadas à idade ou ao sexo. Contudo, leucodermas teriam chances 2,8 vezes maiores de apresentar apinhamento na arcada inferior, em comparação aos nipo-brasileiros.

Sexual dimorphism in deciduous crown traits of a European derived Australian sample

Sex determination of juvenile skeletal remains is a problematic area affecting physical anthropology, forensic science and archaeology. Sexual dimorphism in the morphometric crown traits of the deciduous dentition may be used to help resolve this issue. Dental stone casts from a European derived Australian sample (n=151) were used to investigate variation within crown traits of the deciduous canine and molars. The metric traits investigated were crown size, trigonid size and talonid size. The morphological features included Carabelli's trait and molar cusp number. Metric crown traits were significantly larger in males (p<0.05). The morphological crown traits were not significantly different between the sexes. The largest degree of sexual dimorphism was 11.11% in the trigonid mesiodistal diameter of the first deciduous molar. This is the first recording of the measurement in a European derived sample. Two multivariate statistics, linear functional discriminant analysis and binary logistic regression, were used to determine the success rate of sex classification from the crown traits. The most suitable was linear functional discriminant analysis, however similar results were found when using binary logistic regression. When using all variables investigated in this study, sex could be classified with accuracy of 70.2% from linear functional discriminant analysis (cross validated). The mandibular teeth had greater sexual dimorphism, classifying sex correctly 74.8% of the time compared to maxillary variables that had a success rate of 55.6%. Our results have shown that morphometric crown traits in the deciduous dentition can be used to classify sex of juvenile skeletons (11 months to 12 years) of European descent from linear functional discriminant analysis with accuracy between 70.2% and 74.8%.

Spacing in deciduous dentition of Polish children in relation to tooth size and dental arch dimensions

AIM

To assess the prevalence of primary and secondary spacing in the deciduous dentition and its correlation to tooth widths and dental arch dimensions.

SUBJECTS AND METHODS

Dental casts of 50 preschool children free from malocclusion, were analysed. The width of each space was measured as the smallest distance between the proximal surfaces of the neighbouring teeth, parallel to the occlusal plane. Crown width was measured as the greatest distance between the mesial and distal surfaces of the crown, parallel to the occlusal plane. Intercanine widths were measured between cusp tips of upper and lower canines. Intermolar widths were measured between the central fossae of the second molars. Arch lengths were measured from the midpoint between the central incisors to the midpoint between the distal surfaces of the deciduous second molars.

RESULTS

The primary spaces were present in the upper dental arch in 90% children, on the average 2.09 mm in maxilla and 1.25 mm in mandible. Their widths were dependent on upper intercanine width. Secondary spacing was present in 92% children in the upper dental arch (mean 2.86 mm) and 90% in the lower (mean 3.08 mm). Lower secondary spacing was correlated to lower intercanine width and lower arch length. Total absence of interdental spacing was found in 4% children.

CONCLUSIONS

Interdental spacing of the deciduous dentition is present in 96% of Polish children. Children with wider intercanine widths have wider primary spaces in maxilla and wider secondary spaces in mandible.

Mesiodistal tooth crown dimensions of the primary dentition: A worldwide survey

This analysis reports on a spatial-temporal survey of published studies of primary tooth crown dimensions in humans (80 samples). Mesiodistal data are analyzed for the 10 tooth crown dimensions. The purpose was to evaluate the numerous case reports (descriptive analyses of single samples) in the literature in order to assess patterning of variation 1) in tooth size, 2) among tooth types, 3) across sexes, 4) with space (historical affinity), and 5) with time. Sexual dimorphism is low in the primary dentition, averaging 2% across all 10 tooth types. All size distributions of the samples are positively skewed because of megadont native Australians. Europeans, who are most frequently represented in the literature, have the smallest tooth crowns of any continental grouping assessed. The method by Darroch Mosimann ([1985] Biometrika 72:241-252) of reducing size effects was used, basically standardizing the data variable-wise, and then ordinating groups on their factor scores. Principal components analysis produced just two canonical axes: overall size (68%) and a front-back (i1-i2-c vs. m1-m2) polarity (11%), based on the intergroup (not ontogenetic) covariance matrix. This second component discriminates between groups with relatively large anterior teeth (Europeans) and those where relatively more tooth substance is apportioned to the molars (Africans and Asians). Size differences predominate over shape between sexes from the same groups. Europeans have small teeth with comparatively large anterior dimensions. Asian and sub-Saharan African samples share features of average crown size but large cheek teeth. Indian and European samples show considerable overlap on both canonical axes, with average size overall but comparatively large anterior teeth. The few Amerindian samples are too variable to characterize. Based on comparisons of archaeological and living samples, tooth size reductions are documented here for Europe, India, and the Near East compared to tooth sizes of Neolithic and Mesolithic samples. The temporal changes parallel those documented elsewhere for the permanent dentition. The biological and anthropological relevance of these distributions is discussed.

Occlusion and tooth/arch dimensions in the primary dentition of preschool Jordanian children

OBJECTIVES

To assess tooth and arch dimensions, occlusal relationships and the presence of spacing or crowding in primary dentition of Jordanian children.

STUDY DESIGN

A list of 10 kindergartens was randomly selected in the governate of Irbid, Jordan. A total of 1048 children (2.5-6 years old) with complete primary dentitions were examined for occlusal relationships in three planes, and the presence of spacing or crowding. Of those, study casts were taken for 87 randomly selected 4-5-year-old children (39 girls, 48 boys). Measurements of tooth and arch dimensions were made using electronic digital sliding callipers.

RESULTS

In general, males had larger mesiodistal tooth width and larger arch dimensions. Bilateral mesial step molar relationship was found in 47.7% of children followed by bilateral flush terminal molar relationship in 37% and bilateral distal step in 3.7%. Asymmetric right/left molar relationship was found in 11.6% of children examined. Class I canine relationship was found in 57% of children, followed by Class II canines in 29% and Class III canines in 3.7%. Fifty per cent of children examined had Class I incisors, 24.7% had Class II Division 1, 13.5% had Class II Division 2 and 11.8% showed reversed overjet. Ideal overbite was seen in 44.3% of children, reduced overbite in 21.8%, increased overbite in 28.2% and 5.7% had anterior openbite. Buccal crossbite was seen in 7% of the sample. Generalized spacing was found in 61.8% and 61.1% of children in the upper and lower arches, respectively. Anthropoid spaces were found in 70% of the upper arches and in 51% of the lower arches.

CONCLUSIONS

Males had larger tooth/arch dimension than that of females in the primary dentition stage. Mesial step molar relationship was found in 47.7% of the subjects followed by flush terminal molar relationship in 37%. The majority of children examined had spaced primary dentition.

A study of occlusal variation in the primary dentition of Australian twins and singletons

In this study, we quantified the extent of variation in different occlusal features of Australian children of European descent with complete primary dentitions, but no permanent teeth present in the mouth. The study group consisted of 412 individuals, aged between 3 and 7 years, including 70 monozygous (MZ) twin pairs, 68 same-sexed dizygous (DZ) twin pairs, 11 opposite-sexed DZ twin pairs, and 114 singletons. Occlusal traits, including inter-dental spacing, incisal overbite and overjet, arch breadth and arch depth, were obtained directly from dental casts or indirectly from photocopies or impressions of the casts. Descriptive statistics summarised the data and indicated that distributions were similar to those published for other populations. Univariate genetic analysis, using the structural equation modelling package Mx, was carried out on the quantitative data using the normal assumptions of the twin model. Genetic modelling indicated that a model incorporating additive genetic (A) and unique environmental variation (E) was the most parsimonious for interdental spacing, overbite, overjet and arch dimensions. Estimates of heritability for interdental spacing ranged from 0.62 to 0.81. Estimates for overbite and overjet were 0.53 and 0.28, respectively, and estimates for arch dimensions ranged from 0.69 to 0.89. These results indicated a moderate to relatively high genetic contribution to observed variation.

Sexually dimorphic mandibular morphology in the first few years of life

Sex differences in the youngest skeletons are very subtle, and any method that can separate males and females significantly better than chance will be of value. Compounding the problem is a paucity of immature skeletons of documented age and sex. In 1992, S.R.L. examined 62 juvenile mandibles of white and black South Africans of known age and sex (from birth to 19 years) from the Dart Collection to determine if the sexes could be differentiated by morphologic traits. By age 6 years, adult chin shapes were already recognizable. Prior to that age, differences were observed in the shape of the inferior border of the symphysis and outline of the body. The male chin base extends steeply downward relative to the adjacent body, coming to a point or squaring off at the symphysis. In females, the symphysis descends gradually to a more rounded base, and even when pointed, the transition is not abrupt. On the outer border of the corpus, the sides diverge sharply to form a \_/ shape from a roughly horizontal anterior region in males, while the female contour is rounded, reflecting the smoothly curved transition from front to sides. These traits were manifest from the eruption of the central incisors until about 4 years of age. The features were tested on all 19 Dart Collection mandibles in that age range. Average accuracy for three different testers was 81%, and males were consistently identified more accurately than females. This new method was then tested on a known sex sample of 11 individuals from 0 to 7 years of age. These included CT scans of 9 French children and the remains of 2 South African black forensic cases. Sexing accuracy was 82% (9/11). The only two missexed cases were both female and over age 6 years. In conclusion, the results of this study indicate that it is possible to determine the sex of very young mandibles. The new sexually dimorphic morphologic configurations introduced here have demonstrated repeatable discrimination with the highest level of accuracy (81%) reported and tested for this age group. Preliminary research indicates that both the male and female shapes are clearly recognizable in archaeologic and premodern hominids as well as chimpanzees.

Comparison of dental arch measurements in the primary dentition between contemporary and historic samples

The purpose of this study was to investigate secular changes that may have occurred in dental arch dimensions by comparing a sample of contemporary North American white children (born between 1992 and 1995) in the primary dentition to those children found in an earlier study of North American white children (born between 1946 and 1948). The sample of contemporary children has been followed prospectively since birth and was assessed at 4(1/2) to 5 years of age. Data for the historic sample were obtained from 5-year-old children who were enrolled in the Iowa Growth Study. The 2 samples were similar in terms of geographic location, racial and ethnic backgrounds, and socioeconomic status. To further enhance the comparison and to match the 2 groups, the 2 samples were restricted to white children with a normal overjet (<4 mm) and normal anteroposterior molar relationship, no anterior open bite, and no crossbite. In addition, individuals were excluded if any permanent teeth were erupted. Measurements of maxillary and mandibular arch lengths and intercanine and intermolar arch widths were made, with measurements of overjet and overbite. The results indicated that maxillary and mandibular arch lengths in both sexes were significantly shorter in the contemporary sample; all arch widths were significantly smaller in contemporary boys, but not in girls. These findings suggest that average arch dimensions may be smaller in contemporary children than in past generations. Further research is needed to determine whether smaller arch dimensions are associated with more crowding in the primary, mixed, and permanent dentitions.

Radiographic interproximal angulations: implications for rotational panoramic radiography

Axial radiographs were taken on 160 subjects at the screening clinic of the Dental School, University of Texas Health Science Center at San Antonio. Intermeatal and midsagittal lines, together with coordinate axes and polynomial curves that represent the average dental arch form, were overlaid on each radiograph. Coordinate references for interproximal tangents at 3154 contacts along the average dental arch form were digitized and angulations between the arch form and midsagittal plane calculated. Interproximal angulations at the average arch form were found to vary greatly but the average fluctuated around 90 degrees over the length of the arch. Optimal beam angulations were shown to be considerably different from central ray angulations of current panoramic machines, and although most machines demonstrated favorable interproximal beam angulation in the anterior region, discrepancy in the premolar region ranged from 15 degrees to over 40 degrees. Overall the OrthOralix SD (Gendex Dental Systems, S.r.l., Monza, Italy) orthogonal projection and PM 2002 CC (Planmeca Inc. Helsinki, Finland) deviate least from optimal interproximal angulation over most of the dental arch. However, the Planmeca gives a better angulation in the canine/premolar region, whereas the OP5/10 (Palomex Instrumentarium Corp., Helsinki, Finland) is comparable with the OrthOralix SD in the molar region.