Crown components of mandibular molar teeth in 45,X females (Turner syndrome)

Crown heights in the permanent teeth of 47,XXY males and 47,XXX females

OBJECTIVE

Earlier results based on dental casts and radiographs have shown that additional X and Y chromosomes influence permanent and deciduous tooth crown sizes, with 47,XYY males exhibiting greater crown heights than 46,XY males. We studied here the effect of both X and Y chromosomes on tooth crown heights.

MATERIAL AND METHODS

The series consisted of 48 47,XXY males, 22 of their male relatives, and seven 47,XXX females with five female relatives. The population controls consisted of 27 males and 33 females. Measurements of all applicable teeth except for the third molars on both sides of the jaws were made on panoramic radiographs with a sliding digital calliper.

RESULTS

Apart from a few teeth, the mean crown heights in the 47,XXY males were greater than those in the male population controls, the differences being statistically significant for one tooth in the maxilla and ten teeth in the mandible. With the exception of two teeth, the 47,XXX females had taller tooth crowns than the female population controls, the differences in the two teeth being statistically significant. The 47,XXY males had greater tooth crown heights than the 47,XXX females, except in one tooth, and the differences were significant in two teeth. The tooth crown heights of the male relatives of the 47,XXY males and the female relatives of the 47,XXX females were close to those in the general population.

CONCLUSIONS

The present results demonstrated the effect of additional X and Y chromosomes in increasing crown heights. The differences between the 47,XXY males and 47,XXX females indicated a stronger effect of a Y chromosome on tooth crown height than of an X chromosome.

Caries intensity and Streptococcus mutans in the saliva of patients with Turner syndrome

Aim

The aim of this study was to evaluate the caries intensity and Streptococcus mutans (SM) counts in patients with Turner syndrome.

Materials and methods

Nineteen patients aged 20-40 years were clinically and cytogenetically diagnosed with Turner syndrome (45, X). The karyotype was determined by chromosome analysis of peripheral blood lymphocytes. The control group comprised 47 healthy women aged 21-40 years. Both groups included non-smokers with no specific diet, such as a vegetarian or vegan diet, who were generally healthy with good oral hygiene and periodontal condition. Patients treated with antibiotics or steroid preparations in the past 6 months or with diseases or conditions that might affect the oral mucosal environment, such as disorders of salivary secretion and diabetes, were excluded from the study. Decayed, missing, and filled teeth (DMFT) scores and SM counts in saliva were determined.

Results

No colony growth of SM was noticed in 53% of patients with Turner syndrome and 4.2% of controls (p < 0.001). Colony counts of SM ≥ 10⁵ in saliva were observed in none of the patients with Turner syndrome but in 66% of controls (p < 0.001). The mean DMFT score was 1.63 ± 2.52 in patients with Turner syndrome and 14.49 ± 6.88 in controls. Statistically significant differences between the two groups were observed (p < 0.05).

Conclusion

Patients with genetic disorders may have different severities of caries and SM counts in saliva compared to those without genetic disorders. Further studies on saliva properties and genes located on the X chromosome could contribute to determining the effect of the X chromosome on the pathological processes in the oral cavity.

The effect of Ekman-Westborg and Julin trait (generalized megadontia) and localized megadontia on tooth components size and ion content

AIMS

The objective of this study is to compare size, enamel thickness and ion relative concentration in generalized megadontia (Ekman- Westborg and Julin trait) and a localized megadont upper third molar to normal teeth.

MATERIALS AND METHODS

The MD dimensions of permanent teeth were compared to controls. Tooth components of molars were measured from X-rays and compared to controls. The enamel and dentin relative amounts of elements of mandibular first permanent molar and deciduous canines of E-WJ trait girl, and megadont upper third molar were determined using ESD program of SEM and compared to match-paired normal teeth.

RESULTS

The teeth of the girl diagnosed with E-WJ trait were true megadont (larger than mean ± 2SD). The ratio of enamel thickness to M-D dimension of molars of E-WJ trait and localized megadontia molars is reduced in comparison with normal similar teeth. In the enamel, carbon and silica concentrations were different in E-WJ trait teeth.

CONCLUSIONS

The enamel thickness was reduced in the E-WJ trait and megadont molars, but the relative amount of elements in enamel and dentin was similar to normal. The megadontia is due to a very large tooth germ, as determined by the DEJ, while the ratio of enamel apposition from the total M-D dimension is reduced.

CLINICAL RELEVANCE

Generalized megadontia, as observed in E-WJ trait, is due to large tooth germ, but the enamel thickness is similar to normal. Extractions of permanent teeth are necessary in order to allow normal eruption of teeth.

Tooth Crown Morphology in Turner and Klinefelter Syndrome Individuals from a Croatian Sample

OBJECTIVE

Turner syndrome (TS) and Klinefelter syndrome (KS) represent the two most common X chromosome aneuploidies, each associated with systemic disruptions to growth and development. Effects of these conditions on tooth crown morphology are explored in a sample of Croatian individuals.

MATERIALS AND METHODS

The sample included 57 TS, 37 KS and 88 control individuals. Dental crown morphology was scored on dental casts according to the Turner-Scott Dental Anthropology System.

RESULTS

Incisor shoveling and the hypocone were significantly different between TS individuals and both control and KS individuals. Individuals with TS exhibit lower grades of expression than either group. Furthermore, the number of lingual cusps on the mandibular premolars, the hypoconulid on the mandibular second molar, and cusp 7 on the mandibular first molar were significantly different, though pair-wise comparisons did not elucidate these differences. Tuberculum dentale, distal accessory ridge, and Carabelli's trait were expressed similarly to the control. KS individuals were not significantly different from control individuals for any trait, though this may be related to sample size.

CONCLUSIONS

Previous studies suggest the loss of an X chromosome has a reducing effect on dental crown morphology, which is confirmed in this research. TS individuals exhibit generally simpler dental morphology compared to the control sample, though some traits are expressed comparably to the control sample. The effects of KS are less clear. Though previous studies suggest that the presence of an extra X chromosome increases dental crown dimensions, there was no notable effect on crown morphology in this study.

Influence of long and short arms of X chromosome on maxillary molar crown morphology

Although genes on the human X chromosome reportedly influence tooth crown morphology, little is known about X chromosome activation or inactivation systems relevant to morphological variations. We assessed the relationships between tooth crown size and crown morphological traits in females with Turner syndrome, the variants of which include complete absence of one X chromosome, lack of the short arm (Xp), or duplication of the long arms (Xq), and then estimated the functions of Xp and Xq in the process of unilateral X chromosome inactivation during tooth crown development. The mesiodistal and buccolingual diameters in the maxillary first (M1) and second (M2) permanent molars were compared among X chromosome karyotypes by multiple regression analyses, and their relationships with the development of Carabelli’s cusp and the distolingual cusp were analyzed using logistic regression analysis.

The crown sizes increased in the order of the 46,X,i(Xq) karyotype, 45,X and 45,X/46,XX karyotypes, and control group. A lower frequency of Carabelli’s cusp and higher frequency of a reduced distolingual cusp in M1 were characteristics of Turner syndrome. The overall M1 and M2 crown sizes differed among the X chromosome karyotypes, whereas a smaller crown size was associated with a reduced distolingual cusp but not with Carabelli’s cusp. Considering the differences in chromosome arrangement among females with Turner syndrome and the process of unilateral X chromosome inactivation, the observed results can be considered in terms of quantity or number of promoters/inhibitors during tooth crown development.

The X chromosome karyotypes have a strong influence on the overall crown sizes of the M1 and M2 molars because those karyotypes with variable numbers of active gene regions directly influence tooth germ development in an early stage of human odontogenesis. The later forming cusps, such as the distolingual cusp and Carabelli’s cusp, may be affected by this developmental prerequisite.

Sexual dimorphism of enamel area, coronal dentin area, bicervical diameter and dentinoenamel junction scallop area in longitudinal ground section

Introduction:

Sex determination plays an important role in forensics; several studies done using radiographs, model cast and animal teeth have shown that males possess larger tooth crown and more dentin than that of the females. As physical sectioning of tooth provides more accurate measurement of enamel thickness when compared with other methods, the present study was done to evaluate and compare enamel area (EA), coronal dentin area (CDA), bi-cervical diameter (BCD), average enamel thickness (AET) and dentinoenamel junction scallop area (DEJ-SA) in longitudinal ground sections of first premolars between males and females.

Materials and Methods:

A total of 60 extracted first premolar teeth were used for the study, of which 30 were from male and 30 were from female. A longitudinal ground section of 15 maxillary and 15 mandibular premolars of approximately 50 μm was prepared buccolingually at the center of each tooth and mounted on the slide. Multiple photomicrographs were captured with the help of Image Analysis System Software-Progres, Speed XT core 3. EA, CDA, length of the dentinoenamel junction and BCD were measured. Average DEJ-SA and AET were also calculated.

Results:

Mann–Whitney U- test was used for statistical analysis. It was found that EA and AET were significantly greater in females than in males. On the contrary, it was found that CDA was significantly greater in males than in females. However, no significant difference was found in BCD and DEJ-SA between males and females.

Conclusion:

Permanent first premolar can be reliably used in the field of forensic in establishing gender of individuals by measuring its EA, CDA and AET.

Crown heights in the permanent teeth of 47,XYY males

OBJECTIVE

The results in human sex chromosome aneuploidies had shown that the extra Y chromosome increases permanent and deciduous tooth crown sizes in the mesiodistal and labiolingual directions. The hypothesis of the study was that the additional Y chromosome increases the permanent tooth crown growth in a vertical dimension. We also aimed to observe possible sex difference in the permanent tooth crown height.

MATERIAL AND METHODS

Data on 15 47,XYY males or males with an extra Y chromosome, nine male relatives (five brothers and four fathers) and 45 male and 48 female population controls had been gathered previously for Professor Lassi Alvesalo's KVANTTI Research Project. The measurements from panoramic radiographs were performed of all the applicable teeth, except the third molars on both sides of the jaws with a sliding digital calliper.

RESULTS

All the mean tooth crown heights in the 47,XYY males were larger than in the male population controls and the differences were statistically significant in six teeth in the maxilla and 10 teeth in the mandible. Apart from few teeth, the crown heights in the 47,XYY males were larger than in their male relatives, but the difference between these groups was significant only in one tooth. The differences between sexes were statistically significant in eight teeth in the maxilla.

CONCLUSIONS

Based on previous investigations and this work, it is evident that the impact of the extra Y chromosome during tooth crown development is holistic, increasing permanent tooth sizes in three dimensions in a balanced manner.

Root Lengths in 47,XYY Males’ Permanent Teeth

Studies on individuals with sex chromosome anomalies have demonstrated the promoting effect of the Y chromosome on tooth crown enamel and dentin growth. The present research investigated permanent tooth root lengths in 47,XYY males. The measurements were made from panoramic radiographs. The results indicate longer tooth roots in 47,XYY males compared with those in control males and females. The promoting effect of the Y chromosome on dental growth thus continues in the form of root dentin after the completion of crown growth. The results, together with those on tooth crown sizes in 47,XYY males, suggest that growth excesses are evident and final, beginning a few months after birth and continuing up to the age of 14 years, at least. The excess root dentin growth in 47,XYY males, as well as sexual dimorphism in the growth of crown and root dentin, might be caused by the same factor on the Y chromosome.

Crown heights in the permanent teeth of 45,X and 45,X/46,XX females

OBJECTIVE

Previous results regarding human sex chromosome aneuploidies have shown that the X and Y chromosomes affect tooth size and morphology. This study looked for the effect of sex chromosome deficiency on permanent tooth crown heights.

MATERIALS AND METHODS

The material, from the Finnish KVANTTI Research Project, consisted of 97 45,X females and 15 45,X/46,XX females. The controls were 32 sisters and 28 mothers of the 45,X females, eight sisters and two mothers of the 45,X/46,XX females and 35 female population controls. Crown heights of all the available teeth except third molars on both sides of the jaws were measured from panoramic radiographs with a digital calliper according to the defined procedure.

RESULTS

The tooth crown heights were significantly smaller in the 45,X females than in the female population controls, except for the incisors and one canine in the maxilla, whereas the tooth crown heights of the 45,X/46,XX females were close to those of the normal control females. The differences between the 45,X and 45,X/46,XX females were statistically significant, excluding the upper incisor area and a few teeth in the mandible.

CONCLUSIONS

The effect of the sex chromosome deficiency on permanent tooth crown height is due to the magnitude of lacking sex chromosome material. The present results regarding the 45,X females are parallel to previous findings in Turner patients regarding reduced mesiodistal and labiolingual dimensions and tooth crown heights in the permanent dentition.

Accounting for measurement error: a critical but often overlooked process

AIMS

Due to instrument imprecision and human inconsistencies, measurements are not free of error. Technical error of measurement (TEM) is the variability encountered between dimensions when the same specimens are measured at multiple sessions. A goal of a data collection regimen is to minimise TEM. The few studies that actually quantify TEM, regardless of discipline, report that it is substantial and can affect results and inferences. This paper reviews some statistical approaches for identifying and controlling TEM. Statistically, TEM is part of the residual ('unexplained') variance in a statistical test, so accounting for TEM, which requires repeated measurements, enhances the chances of finding a statistically significant difference if one exists.

METHODS

The aim of this paper was to review and discuss common statistical designs relating to types of error and statistical approaches to error accountability. This paper addresses issues of landmark location, validity, technical and systematic error, analysis of variance, scaled measures and correlation coefficients in order to guide the reader towards correct identification of true experimental differences.

CONCLUSIONS

Researchers commonly infer characteristics about populations from comparatively restricted study samples. Most inferences are statistical and, aside from concerns about adequate accounting for known sources of variation with the research design, an important source of variability is measurement error. Variability in locating landmarks that define variables is obvious in odontometrics, cephalometrics and anthropometry, but the same concerns about measurement accuracy and precision extend to all disciplines. With increasing accessibility to computer-assisted methods of data collection, the ease of incorporating repeated measures into statistical designs has improved. Accounting for this technical source of variation increases the chance of finding biologically true differences when they exist.

The frequency of occurrence of abnormal frenal attachment of lips and enamel defects in Turner syndrome

OBJECTIVE

The aim of the work was to register the frequency of occurrence of abnormal frenal attachment of lips and enamel defects and find the correlation between these anomalies and three types of Turner syndrome.

MATERIALS AND METHODS

Fifty patients (aged 20-40 years) were clinically and cytogenetically diagnosed and divided into three groups, according to karyotype: 45,X (17 cases), with structural aberrations of chromosome X (12 cases) and with mosaic karyotype (21 cases). The control group consisted of 51 healthy woman aged 21-40 years. Subjects were screened for developmental anomalies in the labial frenula and enamel defects in three groups of Turner syndrome.

RESULTS

Some significant anomalies of soft and hard tissues were found in studied patients: abnormal frenal attachments (42% of cases), enamel opacities (58% of cases) and enamel hypoplasia (38% of cases). Differences in the occurrence of these anomaly in all group with Turner syndrome in comparison with the control group were significantly different. Enamel defects were prevalent in the patients with karyotype 45,X and patients with structural aberrations of chromosome X in comparison with the mosaic karyotype.

CONCLUSION

The results of the present study have shown, that abnormal attachment of lips and enamel defects were more frequent in Turner syndrome patients than in the control group. Enamel defects were correlated with the karyotypes of Turner syndrome and abnormal attachment of lips was not correlated with the karyotypes of Turner syndrome.

Root lengths in the permanent teeth of Klinefelter (47,XXY) men

Earlier studies on human teeth have provided proof of an expression of the X and Y chromosome genes in tooth crown growth. The Y chromosome promotes the growth of permanent tooth crown enamel and dentin, whereas the effect of the X chromosome seems to be restricted mainly on enamel formation. Also, there are evidences that both of the sex chromosomes are expressed in tooth root growth. The permanent tooth crowns in 47,XXY males or individuals with an extra X or Y chromosome show increased size compared to normal men, which is mainly due to increased enamel thickness, the dentin thickness is somewhat reduced. There is some evidence of increased mesio-distal tooth crown size also in their primary dentition. The aim of the present study was to determine their complete permanent tooth root lengths. The study groups consisted of 49 47,XXY males, 22 relative males, 8 relative females, 35 population control males and 46 population control females from the Kvantti research project. Root length measurements were made from panoramic radiographs on both sides of the jaw using a digital sliding calliper. The results showed growth increase in the final tooth root sizes in 47,XXY males which conceivably become evident beginning 8 years after birth up to the age of 14 years, at least. The present results and earlier ones on 45,X and 45,X/46,XX females, normal females and males indicate that the promoting effect of the Y chromosome on tooth root growth is greater than that of the X chromosome. These differential effects are conceivably causative factors in the development of the sexual dimorphism in tooth root size.

Modern human molar enamel thickness and enamel-dentine junction shape

This study examines cross-sections of molar crowns in a diverse modern human sample to quantify variation in enamel thickness and enamel-dentine junction (EDJ) shape. Histological sections were generated from molars sectioned buccolingually across mesial cusps. Enamel cap area, dentine area, EDJ length, and bi-cervical diameter were measured on micrographs using a digitizing tablet. Nine landmarks along the EDJ were defined, and X and Y coordinates were digitized in order to quantify EDJ shape. Upper molars show greater values for the components of enamel thickness, leading to significantly greater average enamel thickness than in lower molars. Average enamel thickness increased significantly from M1 to M3 in both molar rows, due to significantly increasing enamel cap area in upper molars, and decreasing dentine area in lower molars. Differences in EDJ shape were found among maxillary molars in combined and individual populations. Sex differences were also found; males showed significantly greater dentine area, EDJ length, and bi-cervical diameters in certain tooth types, which resulted in females having significantly thicker average enamel. Differences in enamel thickness and EDJ shape within molars were also found among populations, although few consistent trends were evident. This study demonstrates that enamel thickness and EDJ shape vary among molars, between sexes, and among populations; these factors must be considered in the categorization and comparison of ape and human molars, particularly when isolated teeth or fossil taxa are included. Human relative enamel thickness encompasses most values reported for fossil apes and humans, suggesting limited taxonomic value when considered alone.

Root growth in the teeth of 46,XY females

The subjects of this study are women with a male sex chromosome complement or 46,XY females who show the complete form of the testicular feminization syndrome (CTF). The basic endocrine defect is end organ insensitivity to androgens. They are on average tall individuals and also show an increase in head and face dimensions relative to normal females. A size increase is likewise evident in permanent tooth crowns and here we report permanent tooth root lengths in eight 46,XY females, their five female relatives and population control females and males. Measurements were made from panoramic radiographs by a digital calliper according to established procedures on both sides of the jaws. The results show increased root lengths of 46,XY females relative to control females with values similar to those in population control males. The root and crown findings point to evident irreversible growth excesses in 46,XY females beginning 3 years after birth up to the age of 14 years expressing an effect which apparently is influencing in a continuous way. Excess root growth conceivably would develop independently of the possible androgen influence, and it is suggested that the increase results from the direct effect of the genes on the Y chromosome. It is possible that these genes on the Y chromosome are the same that promote tooth crown growth.

Sex- and age-related differences in primary and secondary dentin formation

Clinical studies carried out on dentin thickness in adults, as well as experimental studies carried out on ovariectomized animals, indicate that odontoblast activity, like that of osteoblastic cells, differs in the two sexes. To examine the evidence for differences in odontoblast activity before puberty, we have measured dentin thickness and other crown dimensions from bitewing radiographs of the lower first molars in 240 children aged 4-16 years. The radiographs were obtained from pedodontic clinics throughout Israel. Only teeth without caries or fillings were used, and the study population had minimal attrition. The results showed that dentin thickness, measured on the roof of the pulp chamber, was significantly greater in boys than in girls at all ages, and that the differences increased during puberty. The differences remained highly significant even when standardized for crown size. They demonstrate that dimorphism in dentin thickness is present even in the earliest stages of odontogenesis and increase with puberty.