Abstract：
BACKGROUND: Morphological and morphometric features of the teeth are of interest to various clinical and academic dental and medical fields including prosthodontics, orthodontics, anatomy and anthropology, pathology, archeology, and forensic dentistry. These have been more or less researched in the case of the permanent dentition. However when it comes to the primary dentition, the literature is scarce and controversial. No study worldwide exists on the cutoff points (thresholds) for sex identification; no study exists on metric or nonmetric traits of deciduous teeth in Iranians. Hence, the aim of the study was to assess both the metric and nonmetric traits of primary molars, as well as their cut-off points for sex identification.
METHODS: In this epidemiological cross-sectional study, pretreatment casts of 110 children (51 boys and 59 girls) aged 6 to 12 years were collected. Maxillary and mandibular first and second primary molars were evaluated regarding their metric traits (mesiodistal and buccolingual widths) and 9 nonmetric traits (Accessory cusp on the upper D, Accessory cusp on the lower D, Fifth cusp on the upper E, Carabelli\'s cusp on the upper E, Protostylid on the lower E, Fifth cusp on the lower E, Sixth cusp on the lower E, Tuberculum intermedium [metaconulid] on the lower E, and Deflecting wrinkle on the lower E). ROC curves were used to identify cut-off points for sex determination as well as the usefulness of metric measurements for this purpose. Data were analyzed using independent-samples and paired-samples t-tests, McNemar, Fisher, and chi-square tests, plus Pearson and Spearman correlation coefficients (α = 0.05).
RESULTS: All the primary molars\' coronal dimensions (both mesiodistal and buccolingual) were extremely useful for sex identification (ROC curves, all P values ≤ 0.0000099). Especially, the mandibular primary molars (areas under ROC curves [AUCs] between 85.6 and 90.4%, P values ≤ 0.0000006) were more useful than the maxillary ones (AUCs between 80.4 and 83.1%, P values ≤ 0. 0000099). In the mandible, the first primary molar (maximum AUC = 90.4%) was better than the second molar (maximum AUC = 86.0%). The optimum thresholds for sex determination were reported. Sex dimorphism was significant in buccolingual and mesiodistal crown widths of all the primary molars (all P values ≤ 0.000132), but it was seen only in the case of 2 nonmetric traits: Deflecting wrinkle (P = 0.001) and Tuberculum intermedium (metaconulid, P = 0.029) on the lower Es, taking into account the unilateral and bilateral cases. The occurrence of nonmetric traits was symmetrical between the right and left sides (all P values ≥ 0.250). All mesiodistal and two buccolingual molar measurements were as well symmetrical (P > 0.1); however, two buccolingual measurements were asymmetrical: in the case of the maxillary E (P = 0.0002) and mandibular D (P = 0.019). There were three weak-to-moderate correlations between the nonmetric traits of the mandibular second molars (Spearman correlations between 22.7 and 37.5%, P values ≤ 0.045). Up to 6 concurrent nonmetric traits were observed in the sample, with 53.6% of the sample showing at least 2 concurrent nonmetric traits at the same time, without any sex dimorphism (P = 0.658).
CONCLUSIONS: Sex dimorphism exists considerably in primary molars\' sizes, but it is not as prevalent in their nonmetric traits or abnormalities. Primary molars\' crown sizes are useful for sex identification; we calculated optimum cut-off points for this purpose, for the first time.
METHODS: In this epidemiological cross-sectional study, pretreatment casts of 110 children (51 boys and 59 girls) aged 6 to 12 years were collected. Maxillary and mandibular first and second primary molars were evaluated regarding their metric traits (mesiodistal and buccolingual widths) and 9 nonmetric traits (Accessory cusp on the upper D, Accessory cusp on the lower D, Fifth cusp on the upper E, Carabelli\'s cusp on the upper E, Protostylid on the lower E, Fifth cusp on the lower E, Sixth cusp on the lower E, Tuberculum intermedium [metaconulid] on the lower E, and Deflecting wrinkle on the lower E). ROC curves were used to identify cut-off points for sex determination as well as the usefulness of metric measurements for this purpose. Data were analyzed using independent-samples and paired-samples t-tests, McNemar, Fisher, and chi-square tests, plus Pearson and Spearman correlation coefficients (α = 0.05).
RESULTS: All the primary molars\' coronal dimensions (both mesiodistal and buccolingual) were extremely useful for sex identification (ROC curves, all P values ≤ 0.0000099). Especially, the mandibular primary molars (areas under ROC curves [AUCs] between 85.6 and 90.4%, P values ≤ 0.0000006) were more useful than the maxillary ones (AUCs between 80.4 and 83.1%, P values ≤ 0. 0000099). In the mandible, the first primary molar (maximum AUC = 90.4%) was better than the second molar (maximum AUC = 86.0%). The optimum thresholds for sex determination were reported. Sex dimorphism was significant in buccolingual and mesiodistal crown widths of all the primary molars (all P values ≤ 0.000132), but it was seen only in the case of 2 nonmetric traits: Deflecting wrinkle (P = 0.001) and Tuberculum intermedium (metaconulid, P = 0.029) on the lower Es, taking into account the unilateral and bilateral cases. The occurrence of nonmetric traits was symmetrical between the right and left sides (all P values ≥ 0.250). All mesiodistal and two buccolingual molar measurements were as well symmetrical (P > 0.1); however, two buccolingual measurements were asymmetrical: in the case of the maxillary E (P = 0.0002) and mandibular D (P = 0.019). There were three weak-to-moderate correlations between the nonmetric traits of the mandibular second molars (Spearman correlations between 22.7 and 37.5%, P values ≤ 0.045). Up to 6 concurrent nonmetric traits were observed in the sample, with 53.6% of the sample showing at least 2 concurrent nonmetric traits at the same time, without any sex dimorphism (P = 0.658).
CONCLUSIONS: Sex dimorphism exists considerably in primary molars\' sizes, but it is not as prevalent in their nonmetric traits or abnormalities. Primary molars\' crown sizes are useful for sex identification; we calculated optimum cut-off points for this purpose, for the first time.
摘要：
背景：牙齿的形态和形态特征对包括口腔修复在内的各种临床和学术牙科和医学领域都有兴趣，正畸学,解剖学和人类学,病理学,考古学,和法医牙科。这些在恒牙的情况下已经或多或少地进行了研究。然而，当涉及到原发性牙列时，文学是稀缺和有争议的。全球范围内没有关于性别识别的截止点（阈值）的研究；没有关于伊朗人乳牙的公制或非公制特征的研究。因此，这项研究的目的是评估初级磨牙的度量和非度量特征，以及他们性别鉴定的截止点。
方法：在这项流行病学横断面研究中，收集了110名6至12岁儿童（51名男孩和59名女孩）的预处理模型。评估了上颌和下颌第一和第二初级磨牙的公制特征（中远侧和颊舌宽度）和9个非公制特征（上D的副尖，下部D上的附件尖点，上E的第五个尖点，卡拉贝利在上E的尖端，下部E上的原型，下E的第五个尖点，下E的第六个尖点，下部E上的中间结核[metaconulid]，和下E上的偏转皱纹)。ROC曲线用于鉴定性别确定的截止点以及用于此目的的度量测量的有用性。数据采用独立样本和配对样本t检验进行分析，McNemar,费希尔,和卡方检验，加上皮尔逊和斯皮尔曼相关系数(α=0.05)。
结果：所有初级磨牙的冠状尺寸（近中远端和颊舌）对于性别鉴定非常有用（ROC曲线，所有P值≤0.0000099)。尤其是,下颌初级磨牙（ROC曲线下的面积[AUC]在85.6％和90.4％之间，P值≤0.0000006）比上颌骨更有用（AUC在80.4和83.1％之间，P值≤0。0000099)。在下颌骨中，第一伯摩尔（最大AUC=90.4％）优于第二摩尔（最大AUC=86.0％）。报告了性别确定的最佳阈值。所有初级磨牙的颊舌和中远端冠宽度均具有性别二态性（所有P值≤0.000132），但是仅在2个非度量特征的情况下才看到：偏转皱纹（P=0.001）和中间结核（metaconulid，P=0.029)在较低的Es上，考虑到单方面和双边情况。非度量性状的出现在右侧和左侧之间是对称的（所有P值≥0.250）。所有近端侧磨牙和两个颊舌磨牙的测量结果均对称（P>0.1）；然而，两个颊舌测量是不对称的：上颌E（P=0.0002）和下颌D（P=0.019）。下颌第二磨牙的非度量特征之间存在三种弱到中度的相关性（Spearman相关性介于22.7％和37.5％之间，P值≤0.045)。在样本中观察到多达6个并发非度量性状，53.6%的样本同时显示至少2个并发非计量特征，无任何性别二态性（P=0.658）。
结论：性二态性相当存在于原发性磨牙的大小，但在他们的非度量特征或异常方面并不普遍。初级磨牙牙冠的大小对于性别识别是有用的;我们为此计算了最佳的截止点，第一次。
方法：在这项流行病学横断面研究中，收集了110名6至12岁儿童（51名男孩和59名女孩）的预处理模型。评估了上颌和下颌第一和第二初级磨牙的公制特征（中远侧和颊舌宽度）和9个非公制特征（上D的副尖，下部D上的附件尖点，上E的第五个尖点，卡拉贝利在上E的尖端，下部E上的原型，下E的第五个尖点，下E的第六个尖点，下部E上的中间结核[metaconulid]，和下E上的偏转皱纹)。ROC曲线用于鉴定性别确定的截止点以及用于此目的的度量测量的有用性。数据采用独立样本和配对样本t检验进行分析，McNemar,费希尔,和卡方检验，加上皮尔逊和斯皮尔曼相关系数(α=0.05)。
结果：所有初级磨牙的冠状尺寸（近中远端和颊舌）对于性别鉴定非常有用（ROC曲线，所有P值≤0.0000099)。尤其是,下颌初级磨牙（ROC曲线下的面积[AUC]在85.6％和90.4％之间，P值≤0.0000006）比上颌骨更有用（AUC在80.4和83.1％之间，P值≤0。0000099)。在下颌骨中，第一伯摩尔（最大AUC=90.4％）优于第二摩尔（最大AUC=86.0％）。报告了性别确定的最佳阈值。所有初级磨牙的颊舌和中远端冠宽度均具有性别二态性（所有P值≤0.000132），但是仅在2个非度量特征的情况下才看到：偏转皱纹（P=0.001）和中间结核（metaconulid，P=0.029)在较低的Es上，考虑到单方面和双边情况。非度量性状的出现在右侧和左侧之间是对称的（所有P值≥0.250）。所有近端侧磨牙和两个颊舌磨牙的测量结果均对称（P>0.1）；然而，两个颊舌测量是不对称的：上颌E（P=0.0002）和下颌D（P=0.019）。下颌第二磨牙的非度量特征之间存在三种弱到中度的相关性（Spearman相关性介于22.7％和37.5％之间，P值≤0.045)。在样本中观察到多达6个并发非度量性状，53.6%的样本同时显示至少2个并发非计量特征，无任何性别二态性（P=0.658）。
结论：性二态性相当存在于原发性磨牙的大小，但在他们的非度量特征或异常方面并不普遍。初级磨牙牙冠的大小对于性别识别是有用的;我们为此计算了最佳的截止点，第一次。
