The Impact of Birth Weight on the Enamel and Dentin Thickness of Mandibular First Molars

The Impact of Birth Weight on the Enamel and Dentin Thickness of Mandibular First Molars | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article The Impact of Birth Weight on the Enamel and Dentin Thickness of Mandibular First Molars Yasaman Bozorgnia, Shahin Mafinejad, Sonia Dokohaki, Nasim Razavi, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8128297/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background Early-life factors such as birth weight influence dental development. However, how birth weight affects enamel and dentin thickness in permanent mandibular first molars remains unknown. Aim Here, we quantitatively assess the impact of birth weight on enamel and dentin thickness in 7- to 8-year-old children. Methods Panoramic radiographs of 75 children were analyzed. The participants were stratified into very low (VLBW), low (LBW), and normal birth weight (NBW) groups. The enamel and dentin thicknesses were measured manually and via computer-assisted analysis. Statistical comparisons were performed via ANOVA and post hoc tests. Results Enamel thickness was not significantly different across the VLBW, LBW, and NBW groups (P > 0.05). In contrast, dentin thickness was significantly greater in the VLBW group in region D (VLBW vs LBW, P = 0.018; VLBW vs NBW, P = 0.047) and in region X (VLBW vs NBW, P = 0.001; LBW vs NBW, P = 0.006). Compared with that of NBW, the molar width of VLBW and LBW increased 1.1–1.2-fold (P = 0.005–0.047). Manual and computerized measurements were highly concordant (P > 0.05). Gender had minimal impact, except for slightly greater enamel thickness in Region C for boys (P = 0.020). Conclusions Birth weight does not affect enamel thickness but is associated with increased dentin thickness and molar width, likely reflecting compensatory growth. These findings challenge the prevailing view that low birth weight predisposes individuals to early tooth fragility and provide a framework for understanding dental development in pediatric populations. Infant Low birth weight Infant Very low birth weight Dental enamel Dentin Dentition Permanent Molar Figures Figure 1 Introduction Dental enamel is the hardest and most mineralized tissue in the human body. Its complex formation processes are governed by genetic factors and influenced by epigenetic and environmental conditions ( 1 ). The formation of deciduous teeth begins early in pregnancy (approximately week 12), with enamel formation completing approximately 12 months after birth. Enamel development in the first permanent teeth starts at week 28, whereas mineralization begins at birth and continues through the first three years of life. As a result, the calcification of permanent first molars is particularly vulnerable to environmental factors around birth. Any disturbances during amelogenesis can cause either quantitative or qualitative defects. Qualitative defects, such as hypomineralization, can lead to conditions such as first molar incisor hypomineralization (MIH) in permanent teeth or hypomineralization of second primary molars (HSPMs) in primary teeth ( 2 ). Premature birth and low birth weight can lead to severe dental problems, such as hypomineralization and hypoplasia, in both primary and permanent teeth( 3 ). Compared with children with normal birth weights, infants born prematurely or with very low birth weights present a greater prevalence of enamel defects in their first permanent molars and incisors ( 1 , 4 ). Dentin, which makes up the majority of teeth, is classified into three categories: primary, secondary, and tertiary (or reparative) dentin ( 5 ). Primary dentin forms during odontogenesis, whereas secondary dentin begins to form before eruption and continues to grow after tooth eruption. The formation of both primary and secondary dentin is regulated by odontoblasts, which are responsible for the majority of dentin production ( 6 ). Few studies in the literature have examined the factors affecting dentin formation on the basis of birth weight. To the best of our knowledge, only one case report has investigated the histopathological features of dentin in preterm children ( 7 ). Conflicting results have been reported regarding the size of permanent teeth. Some studies reported that the tooth crown dimensions of primary teeth and the mesiodistal dimensions of the permanent first molar were smaller by 4–9% in extremely preterm infants ( 8 – 10 ), whereas others reported larger mesiodistal crown dimensions in permanent first molars in prematurely born children ( 11 ). Since mineralization of permanent first molars occurs around birth and considering that infants with lower birth weights tend to experience slower tooth development than those with normal birth weights do, the weight of the child at birth is one of the environmental factors most likely to influence the development of permanent first molars ( 12 , 13 ). Permanent first molars typically erupt at approximately age seven, and panoramic radiographs (OPGs) are routinely available at this age for orthodontic evaluation. Given the contradictory findings in the literature regarding tooth dimensions in low birth weight infants( 14 ), the aim of this study was to investigate the impact of birth weight on enamel and dentin thickness in the first permanent molars of 7- to 8-year-old children, as measured via panoramic radiographs. For increased accuracy, measurements were performed both manually and via computer-assisted methods. Materials and methods This retrospective cohort study was approved by the institutional ethics committee in 2021 and was conducted in North Khorasan Province. Data were collected from children born at Bint Al-Huda Hospital between 2012 and 2013. After written informed consent was obtained from the legal guardians, 75 children aged 7–8 years were selected for the study. The children were divided into three groups on the basis of their birth weight: very low birth weight (VLBW), low birth weight (LBW), and normal birth weight (NBW) ( 13 ). The inclusion criterion was adequate cooperation during orthodontic examination and panoramic radiography. The exclusion criteria were as follows: chronic systemic diseases affecting bone or dental mineralization; missing, restored, or decayed mandibular molars; poor-quality radiographs; or improper head positioning. All participants underwent panoramic radiography as part of their orthodontic examination, and any necessary treatment plans were recommended. The sample size was calculated using Cochran's formula (p = 0.5, d = 0.1, α = 0.1) (p = 0.5, d = 0.1, α = 0.1) ( 15 , 16 ). Based on the sample size calculation, the required number of participants was 67. After applying the correction factor for multiple groups, the sample size was increased to approximately 75 children. Therefore, 25 children were allocated to each group. Panoramic radiographs were obtained using the Carestream CS 9000C device (serial number: FIBI032, product number: GEN-36914, Carestream Health, Rochester, New York, USA) at the dental faculty. Enamel thickness was measured using linear distances at points C, B, A, Y, and Z, while dentin thickness was measured at points F, E, D, and X, as shown in Fig. 1 . The width of the tooth was calculated by adding the values of the X, Y, and Z distances. The researcher used a caliper to measure enamel and dentin thickness in mandibular first molars based on panoramic radiographs. To enhance accuracy, MATLAB Ver. 2017A software, along with the Image Processing Toolbox, was used to analyze the thickness measurements from selected images. A specific region of interest was chosen from all images using the toolbox, and the enamel and dentin thicknesses were calculated accordingly. After processing the images, the obtained measurements were compared between the groups using the software. The use of computerized analysis minimized human error, and the resulting graphs and tables, generated through MATLAB, were clearer and more accurate due to image preprocessing, which increased the validity of the results. Statistical methods Data distribution was assessed using the Kolmogorov‒Smirnov test. To compare enamel and dentin thickness between different weight and gender groups, we employed independent t tests, paired t tests, and analysis of variance (ANOVA). Post hoc tests were used for pairwise group comparisons. All statistical analyses were performed using SPSS software version 26. P values less than 0.05 were considered statistically significant. Results The data were normally distributed, as determined by the Kolmogorov‒Smirnov test (P > 0.05); thus, analysis of variance (ANOVA) was employed. Table 1 presents the mean enamel thickness in the first mandibular molar, which was measured via both manual and computerized methods. No significant differences were detected in any of the specified regions (Y, C, B, A, and Z) when grouped by the birth weight of the children (P > 0.05). Table 1 : Mean enamel thickness (mm) at different points in the first mandibular molar in 7–8-year-old children, categorized by birth weight, via both manual and computerized measurements. P-VALUE NBW LBW VLBW THICKNESS SD Mean SD Mean SD Mean 0.154 0.42 1.79 0.49 1.89 0.62 2.13 A MANUAL 0.879 0.62 2.66 0.62 2.63 0.89 2.75 B 0.314 0.34 2.18 0.37 1.95 0.72 2.13 C 0.125 0.44 1.84 0.45 1.92 0.39 1.63 Y 0.067 0.34 1.58 0.31 1.76 0.37 1.50 Z 0.119 0.43 1.73 0.65 1.85 0.78 2.17 A COMPUTER 0.681 0.63 2.61 0.64 2.55 0.84 2.76 B 0.327 0.35 2.25 0.48 1.99 0.79 2.04 C 0.145 0.50 2.01 0.74 1.89 0.41 1.63 Y 0.829 0.44 1.55 0.68 1.64 0.41 1.56 Z Table 2 presents the mean dentin thickness in the first mandibular molar, which was measured via both manual and computerized techniques. In the manual technique, the mean dentin thickness in regions D and X was significantly different, with P values of 0.043 (D) and 0.002 (X), respectively. In the computerized technique, regions D and F also exhibited significant differences, with P values of 0.043 (D) and 0.006 (F), when the three birth weight groups were compared. Table 2 : Mean dentin thickness (mm) at different points in the first mandibular molar in 7–8-year-old children, categorized by birth weight, via both manual and computerized measurements. P-VALUE NBW LBW VLBW THICKNESS SD Mean SD Mean SD Mean 0.043 * 0.60 4.05 0.76 3.95 0.85 4.56 D MANUAL 0.175 0.51 3.92 0.63 3.76 0.53 4.13 E 0.687 0.81 4.26 0.62 4.34 0.64 4.47 F 0.002 * 0.87 10.24 1.05 11.11 0.89 11.34 X 0.128 0.84 4.14 0.96 4.08 0.91 4.66 D COMPUTER 0.042* 0.63 3.99 0.74 3.58 0.77 4.13 E 0.992 0.83 4.44 0.74 4.43 0.77 4.41 F 0.005* 0.84 10.38 1.09 11.38 1.10 11.31 X *The P value is considered significant at the 0.05 level. On the basis of the LSD post hoc test, in the manual technique, the mean dentin thickness in Region D was significantly greater in the VLBW group than in both the LBW group (P = 0.018) and the NBW group (P = 0.047). In Region X, the mean dentin thickness in the VLBW group (P = 0.001) and the LBW group (P = 0.006) was significantly greater than that in the NBW group, as shown in Table 3. Table 3 : Comparison of average dentin thickness in the first mandibular molar via manual measurement. Areas Groups Groups Mean difference p value Upper extreme Lower Extreme D VLBW LBW -0.32* 0.018 0.111 1.118 NBW 0.81* 0.047 0.006 1.013 LBW NBW -0.105 0.662 -0.586 0.375 X VLBW LBW 0.238 0.459 -0.403 0.880 NBW 1.106* 0.001 0.464 1.749 LBW NBW 0.868* 0.006 0.254 1.482 *The mean difference is significant at the 0.05 level. In the computerized technique, the LSD post hoc test revealed that in Region E, the mean dentin thickness was greater in the VLBW group than in the LBW group. In Region X, the mean dentin thickness was greater in the VLBW group (P = 0.025) and the LBW group (P = 0.010) than in the NBW group, as shown in Table 4. Table 4 : Comparison of average dentin thickness in the first mandibular molar via computerized measurements. Areas Groups Groups Mean difference p value Lower extreme Upper Extreme E VLBW LBW .55023 * 0.046 .0087 1.0917 NBW .14602 0.793 -.3955 .6875 LBW NBW -.40421 0.154 -0.9220 0.1136 X VLBW LBW -.07609 0.973 -0.9038 0.7517 NBW .92707 * 0.025 0.0993 1.7548 LBW NBW 1.00316 * 0.010 0.2117 1.7946 *The mean difference is significant at the 0.05 level. The mean width of the first mandibular molar was compared among the three groups via the post hoc LSD test. The results revealed that the first mandibular width was significantly greater in the VLBW (P = 0.047) and LBW (P = 0.005) groups than in the NBW group. No significant difference was found between the VLBW and LBW groups (P = 0.425). In the computerized technique, the mean width of the first mandibular molar differed significantly between the weight groups (P = 0.094). The pairwise comparison of groups via the post hoc LSD test revealed that the mean width of the first mandibular molar was significant and greater in the LBW group than in the NBW group (P = 0.031). Overall, there was no significant difference in the mean enamel thickness in the Y, B, A, and Z regions between boys and girls (P > 0.05). However, the mean enamel thickness in the C region was significantly greater in boys than in girls (P = 0.020). There was no significant difference in the mean dentin thickness between boys and girls in any region (P > 0.05). Discussion This study aimed to determine the relationships between birth weight and the enamel and dentin thicknesses of the first permanent mandibular molars in 7–8-year-old children. The results indicated that the mean enamel thickness of the first mandibular molar did not differ significantly across the specified regions (Y, C, B, A, and Z) on the basis of birth weight, with similar measurements observed across the three weight groups via both measurement techniques. However, dentin thickness was found to be greater in some areas of the very low birth weight (VLBW) and low birth weight (LBW) groups than in the normal birth weight (NBW) group across both measurement techniques. Importantly, while many studies have focused on deciduous teeth ( 17 , 18 ), this study specifically evaluated permanent teeth. Additionally, previous research has often concentrated on hypoplasia ( 17 – 20 ), whereas the present study assessed sound tooth structure. The results also revealed that in Region D, the mean dentin thickness in the VLBW group was significantly greater than that in both the LBW and NBW groups. In Region X, the mean dentin thickness in the VLBW and LBW groups was significantly greater than that in the NBW group. These findings can be understood in the context of compensatory growth during the catch-up growth phase, which can continue until approximately three years of age in LBW infants. This phase is influenced by several factors, including growth factors, thyroid hormones, insulin, sex steroids, and insulin-like growth factor 1 (IGF-1). These factors are known to influence developmental traits and may accelerate mineralization in bones and connective tissues, which could help explain the observed differences in dentin thickness ( 21 , 22 ). Changes in tooth crown size may reflect general growth disturbances during both prenatal and postnatal development ( 11 ). In this study, the mean width of the first molar was significantly greater in the very low birth weight (VLBW) and low birth weight (LBW) groups than in the normal birth weight (NBW) group. Harila-Kaera et al. reported significant increases in the mesiodistal (MD) and intercuspal distances of the first permanent molars in white preterm boys compared with normal children of certain racial backgrounds, which aligns with the findings of the present study ( 11 ). Apps et al. evaluated 436 twins, divided them into NBW and LBW groups, and reported a positive correlation between tooth dimensions and birth weight. Although they reported no reduction in tooth size in boys with LBW, a 2–3% decrease in tooth size was noted in both deciduous and permanent incisors in girls with LBW ( 9 ). This finding contrasts with our study, which focused on measuring the permanent mandibular molar—the only tooth that begins calcification at birth. As such, birth weight may have a more pronounced effect on this tooth. In our study, we found an increase in size in VLBW and LBW children compared with NBW children. Buhamer et al. conducted a systematic review on the mesiodistal and buccolingual dimensions of permanent teeth and reported that teeth are generally smaller in both dental arches in preterm infants than in full-term infants. They also reported that race and gestational age influence tooth size. In contrast, the present study measured tooth size across different birth weight categories within a diverse ethnic population, focusing specifically on the mandibular molar, which begins calcification at birth ( 23 ). Ebrahim et al. reported that the mesiodistal and buccolingual widths of the first permanent molars, as well as the central and lateral incisors, were smaller in children born very preterm than in normal controls ( 10 ). However, these findings were not consistent with the results of our study, possibly because of differences in race or because their study did not stratify participants on the basis of birth weight, as both preterm and term babies were included in the same group. In a systematic review, Paulsson suggested that, owing to insufficient evidence on the relationship between premature birth and tooth-crown dimensions, further research is needed to clarify this association. In contrast, changes in tooth crown size among naturally born children are often considered multifactorial, with genetics and environmental factors playing significant roles. These changes may reflect general growth disturbances during both the prenatal and postnatal periods. Genetic factors account for approximately 60% of the observed variation in tooth size for both deciduous and permanent teeth ( 14 ). The extent of genetic diversity varies by tooth and its specific dimensions, with some teeth showing greater variability than others ( 11 ). Additionally, compared with deciduous teeth, environmental factors are believed to have a more substantial effect on permanent teeth. Race and sex are also important factors to consider when examining tooth development ( 14 ), which may help explain the differences between the present study and previous studies. Previous studies have documented variations in tooth growth across different sexes and racial groups. Other influencing factors include poor maternal health during pregnancy, such as thyroid dysfunction, diabetes, high blood pressure, and maternal smoking ( 11 , 23 ). Furthermore, the first permanent molars are the only teeth that begin mineralization at birth, which is why our study focused exclusively on these molars, assessing both dentin and enamel dimensions. In general, the mean enamel thickness in the Y, B, A, and Z regions did not differ significantly between males and females. However, the mean enamel thickness in the C region was significantly greater in males than in females. This finding is consistent with the common observation that boys tend to have larger teeth than girls do. Genes influencing tooth crown size are located on both the X chromosome and the Y chromosome, and the effects of the Y chromosome differ from those of the X chromosome ( 10 , 23 ). Additionally, the enamel and dentin thicknesses in both boys and girls, when stratified by weight, were similar in the majority of the measured areas. Therefore, the results of our study are generalizable to both genders. Owing to the unique circumstances of the COVID-19 pandemic, many patients have failed to attend appointments. Although the final sample size was statistically sufficient, we recommend increasing the sample size in future studies. Given the greater spatial resolution of intraoral radiographs than of extraoral radiographs, we also recommend the use of intraoral radiographs, such as bitewings, in future research. While birth weight appears to have no effect on enamel thickness, lower birth weights may be associated with greater dentin thickness in the first molars. These findings confirm the influence of birth weight, environmental conditions, race, and catch-up growth on tooth development. Conclusion As birth weight decreases, the size of the first mandibular molar increases. However, no significant differences were found in enamel thickness across the weight groups. In contrast, dentin thickness increased in certain areas with lower birth weights. The observed increase in tooth size may have implications for orthodontic treatment planning. The normal enamel thickness observed in underweight children suggests that they are not more susceptible to early tooth decay. Abbreviations • VLBW Very low birth weight • LBW Low birth weight • NBW normal birth weight • MIH Molar Incisor Hypomineralization • HSPM Hypomineralized second primary molars Declarations Ethics approval and consent to participate The study protocol was approved by the Ethics Research Committee of North Khorasan University of Medical Sciences, Bojnurd University of Medical Sciences, Faculty of Dentistry, Dental Research Center (approval number: 1400.130.IR.NKUMS.REC). All procedures were conducted in accordance with the Declaration of Helsinki. Written informed consent for participation was obtained from the parents or legal guardians of all child participants. Consent for publication Not applicable. No identifying images or personal clinical information are included in this manuscript. Competing interests The authors declare that they have no competing interests. Funding No funding was received for this study. Author Contribution Y.B. and N.R. conceptualized the study. M.N. curated the data. M.Y. performed the formal analysis and software processing. S.D. and N.R. conducted the investigation. Y.B. and S.M. developed the methodology. N.R. and Y.B. administered the project and supervised the research. Y.B. and S.D. validated the data. M.Y. and S.M. prepared the visualizations. N.R. and S.D. drafted the original manuscript. N.R. and S.D. reviewed and edited the manuscript. All authors read and approved the final manuscript. Acknowledgement The authors would like to thank North Khorasan University of Medical Sciences for supporting this research. The authors also thank Bint Al-Huda Hospital for providing access to birth records and assisting with data collection. Data Availability The data will be made available upon reasonable request to the corresponding author. References Krishnaji Musale P, Shrikant Soni A, Sunil Kothare S. Etiology and Considerations of Developmental Enamel Defects in Children: A Narrative Review. J Pediatr Rev. 2019;7(3):141–50. 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Prevalence and distribution of developmental enamel defects in primary dentition of Chinese children 3–5 years old. Commun Dent Oral Epidemiol. 1995;23(2):72–9. Pando R, Gat-Yablonski G, Phillip M. Nutrition and catch-up growth. J Pediatr Gastroenterol Nutr. 2010;51:S129–30. Liu X, Luo B, Peng W, Xiong F, Yang F, Wu J. Factors affecting the catch-up growth of preterm infants after discharge in China: a multicenter study based on the health belief model. Ital J Pediatr. 2019;45:1–6. Buhamer SN, Kaklamanos E, Kowash M, Hussein I, Salami A, Al-Halabi M. What is the effect of preterm birth on permanent tooth crown dimensions? A systematic review and meta-analysis. PLoS ONE. 2021;16(11):e0259293. Additional Declarations No competing interests reported. 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10:47:18","extension":"xml","order_by":7,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":78545,"visible":true,"origin":"","legend":"","description":"","filename":"ce1534146b554f0288846cf5e0e4f7251structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8128297/v1/e623bd6647a96718f5318b61.xml"},{"id":99292989,"identity":"d9ef6554-53a9-449f-9363-908f7e1bbcbc","added_by":"auto","created_at":"2025-12-31 10:47:18","extension":"html","order_by":8,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":90199,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8128297/v1/ec83a09722e4d1b419376ea0.html"},{"id":99321273,"identity":"ae063c0a-3df9-4cdb-aa75-b42de1e001d9","added_by":"auto","created_at":"2025-12-31 16:39:17","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":161536,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic representation of the measured areas in enamel and dentin.\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8128297/v1/b17d2f0573eba04fc7220c37.jpeg"},{"id":104976263,"identity":"0678211f-b5a6-49f5-8a2a-02f23103b4df","added_by":"auto","created_at":"2026-03-19 12:12:39","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":795371,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8128297/v1/c86ea3d5-18a0-44e0-93c8-58a445176074.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"The Impact of Birth Weight on the Enamel and Dentin Thickness of Mandibular First Molars","fulltext":[{"header":"Introduction","content":"\u003cp\u003eDental enamel is the hardest and most mineralized tissue in the human body. Its complex formation processes are governed by genetic factors and influenced by epigenetic and environmental conditions (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). The formation of deciduous teeth begins early in pregnancy (approximately week 12), with enamel formation completing approximately 12 months after birth. Enamel development in the first permanent teeth starts at week 28, whereas mineralization begins at birth and continues through the first three years of life. As a result, the calcification of permanent first molars is particularly vulnerable to environmental factors around birth. Any disturbances during amelogenesis can cause either quantitative or qualitative defects. Qualitative defects, such as hypomineralization, can lead to conditions such as first molar incisor hypomineralization (MIH) in permanent teeth or hypomineralization of second primary molars (HSPMs) in primary teeth (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003ePremature birth and low birth weight can lead to severe dental problems, such as hypomineralization and hypoplasia, in both primary and permanent teeth(\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e). Compared with children with normal birth weights, infants born prematurely or with very low birth weights present a greater prevalence of enamel defects in their first permanent molars and incisors (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e). Dentin, which makes up the majority of teeth, is classified into three categories: primary, secondary, and tertiary (or reparative) dentin (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e). Primary dentin forms during odontogenesis, whereas secondary dentin begins to form before eruption and continues to grow after tooth eruption. The formation of both primary and secondary dentin is regulated by odontoblasts, which are responsible for the majority of dentin production (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eFew studies in the literature have examined the factors affecting dentin formation on the basis of birth weight. To the best of our knowledge, only one case report has investigated the histopathological features of dentin in preterm children (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e). Conflicting results have been reported regarding the size of permanent teeth. Some studies reported that the tooth crown dimensions of primary teeth and the mesiodistal dimensions of the permanent first molar were smaller by 4\u0026ndash;9% in extremely preterm infants (\u003cspan additionalcitationids=\"CR9\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e), whereas others reported larger mesiodistal crown dimensions in permanent first molars in prematurely born children (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eSince mineralization of permanent first molars occurs around birth and considering that infants with lower birth weights tend to experience slower tooth development than those with normal birth weights do, the weight of the child at birth is one of the environmental factors most likely to influence the development of permanent first molars (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e).\u003c/p\u003e \u003cp\u003ePermanent first molars typically erupt at approximately age seven, and panoramic radiographs (OPGs) are routinely available at this age for orthodontic evaluation. Given the contradictory findings in the literature regarding tooth dimensions in low birth weight infants(\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e), the aim of this study was to investigate the impact of birth weight on enamel and dentin thickness in the first permanent molars of 7- to 8-year-old children, as measured via panoramic radiographs. For increased accuracy, measurements were performed both manually and via computer-assisted methods.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cp\u003e This retrospective cohort study was approved by the institutional ethics committee in 2021 and was conducted in North Khorasan Province. Data were collected from children born at Bint Al-Huda Hospital between 2012 and 2013. After written informed consent was obtained from the legal guardians, 75 children aged 7\u0026ndash;8 years were selected for the study. The children were divided into three groups on the basis of their birth weight: very low birth weight (VLBW), low birth weight (LBW), and normal birth weight (NBW) (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe inclusion criterion was adequate cooperation during orthodontic examination and panoramic radiography.\u003c/p\u003e \u003cp\u003e \u003cb\u003eThe exclusion criteria\u003c/b\u003e were as follows: chronic systemic diseases affecting bone or dental mineralization; missing, restored, or decayed mandibular molars; poor-quality radiographs; or improper head positioning.\u003c/p\u003e \u003cp\u003eAll participants underwent panoramic radiography as part of their orthodontic examination, and any necessary treatment plans were recommended.\u003c/p\u003e \u003cp\u003eThe sample size was calculated using Cochran's formula (p\u0026thinsp;=\u0026thinsp;0.5, d\u0026thinsp;=\u0026thinsp;0.1, α\u0026thinsp;=\u0026thinsp;0.1) (p\u0026thinsp;=\u0026thinsp;0.5, d\u0026thinsp;=\u0026thinsp;0.1, α\u0026thinsp;=\u0026thinsp;0.1) (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e). Based on the sample size calculation, the required number of participants was 67. After applying the correction factor for multiple groups, the sample size was increased to approximately 75 children. Therefore, 25 children were allocated to each group.\u003c/p\u003e \u003cp\u003ePanoramic radiographs were obtained using the Carestream CS 9000C device (serial number: FIBI032, product number: GEN-36914, Carestream Health, Rochester, New York, USA) at the dental faculty. Enamel thickness was measured using linear distances at points C, B, A, Y, and Z, while dentin thickness was measured at points F, E, D, and X, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The width of the tooth was calculated by adding the values of the X, Y, and Z distances. The researcher used a caliper to measure enamel and dentin thickness in mandibular first molars based on panoramic radiographs. To enhance accuracy, MATLAB Ver. 2017A software, along with the Image Processing Toolbox, was used to analyze the thickness measurements from selected images. A specific region of interest was chosen from all images using the toolbox, and the enamel and dentin thicknesses were calculated accordingly. After processing the images, the obtained measurements were compared between the groups using the software. The use of computerized analysis minimized human error, and the resulting graphs and tables, generated through MATLAB, were clearer and more accurate due to image preprocessing, which increased the validity of the results.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStatistical methods\u003c/h2\u003e \u003cp\u003eData distribution was assessed using the Kolmogorov‒Smirnov test. To compare enamel and dentin thickness between different weight and gender groups, we employed independent t tests, paired t tests, and analysis of variance (ANOVA). Post hoc tests were used for pairwise group comparisons. All statistical analyses were performed using SPSS software version 26. P values less than 0.05 were considered statistically significant.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eThe data were normally distributed, as determined by the Kolmogorov‒Smirnov test (P \u0026gt; 0.05); thus, analysis of variance (ANOVA) was employed.\u003c/p\u003e\n\u003cp\u003eTable 1 presents the mean enamel thickness in the first mandibular molar, which was measured via both manual and computerized methods. No significant differences were detected in any of the specified regions (Y, C, B, A, and Z) when grouped by the birth weight of the children (P \u0026gt; 0.05).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1\u003c/strong\u003e: Mean enamel thickness (mm) at different points in the first mandibular molar in 7\u0026ndash;8-year-old children, categorized by birth weight, via both manual and computerized measurements.\u003c/p\u003e\n\u003ctable dir=\"rtl\" border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"589\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 69px;\"\u003e\n \u003cp dir=\"LTR\"\u003eP-VALUE\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"3\" valign=\"top\" style=\"width: 126px;\"\u003e\n \u003cp dir=\"LTR\"\u003eNBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"3\" valign=\"top\" style=\"width: 108px;\"\u003e\n \u003cp dir=\"LTR\"\u003eLBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"3\" valign=\"top\" style=\"width: 112px;\"\u003e\n \u003cp dir=\"LTR\"\u003eVLBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 88px;\"\u003e\n \u003cp dir=\"LTR\"\u003eTHICKNESS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp dir=\"LTR\"\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 65px;\"\u003e\n \u003cp dir=\"LTR\"\u003eSD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp dir=\"LTR\"\u003eMean\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 59px;\"\u003e\n \u003cp dir=\"LTR\"\u003eSD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 49px;\"\u003e\n \u003cp dir=\"LTR\"\u003eMean\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 52px;\"\u003e\n \u003cp dir=\"LTR\"\u003eSD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp dir=\"LTR\"\u003eMean\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 69px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.154\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 64px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.42\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e1.79\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.49\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp dir=\"LTR\"\u003e1.89\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.62\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" 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colspan=\"2\" valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp dir=\"LTR\"\u003e1.95\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e2.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 88px;\"\u003e\n \u003cp dir=\"LTR\"\u003e\u003cstrong\u003eC\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 69px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.125\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 64px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e1.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp dir=\"LTR\"\u003e1.92\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e1.63\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 88px;\"\u003e\n \u003cp dir=\"LTR\"\u003e\u003cstrong\u003eY\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 69px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.067\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 64px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e1.58\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp dir=\"LTR\"\u003e1.76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e1.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 88px;\"\u003e\n \u003cp dir=\"LTR\"\u003e\u003cstrong\u003eZ\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 69px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.119\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 64px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e1.73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.65\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp dir=\"LTR\"\u003e1.85\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e2.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 88px;\"\u003e\n \u003cp dir=\"LTR\"\u003e\u003cstrong\u003eA\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"5\" valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp dir=\"LTR\"\u003e\u003cstrong\u003eCOMPUTER\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 69px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.681\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 64px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.63\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e2.61\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp dir=\"LTR\"\u003e2.55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e2.76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 88px;\"\u003e\n \u003cp dir=\"LTR\"\u003e\u003cstrong\u003eB\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 69px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.327\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 64px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e2.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp dir=\"LTR\"\u003e1.99\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.79\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e2.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 88px;\"\u003e\n \u003cp dir=\"LTR\"\u003e\u003cstrong\u003eC\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 69px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.145\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 64px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e2.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.74\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp dir=\"LTR\"\u003e1.89\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.41\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e1.63\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 88px;\"\u003e\n \u003cp dir=\"LTR\"\u003e\u003cstrong\u003eY\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 69px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.829\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 64px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e1.55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.68\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp dir=\"LTR\"\u003e1.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.41\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e1.56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 88px;\"\u003e\n \u003cp dir=\"LTR\"\u003e\u003cstrong\u003eZ\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 69px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 1px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 55px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 1px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 51px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 1px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 55px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 102px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 108px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eTable 2 presents the mean dentin thickness in the first mandibular molar, which was measured via both manual and computerized techniques. In the manual technique, the mean dentin thickness in regions D and X was significantly different, with P values of 0.043 (D) and 0.002 (X), respectively. In the computerized technique, regions D and F also exhibited significant differences, with P values of 0.043 (D) and 0.006 (F), when the three birth weight groups were compared.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2\u003c/strong\u003e: Mean dentin thickness (mm) at different points in the first mandibular molar in 7\u0026ndash;8-year-old children, categorized by birth weight, via both manual and computerized measurements.\u003c/p\u003e\n\u003ctable dir=\"rtl\" border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"589\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 69px;\"\u003e\n \u003cp dir=\"LTR\"\u003eP-VALUE\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"3\" valign=\"top\" style=\"width: 126px;\"\u003e\n \u003cp dir=\"LTR\"\u003eNBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"3\" valign=\"top\" style=\"width: 108px;\"\u003e\n \u003cp dir=\"LTR\"\u003eLBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"3\" valign=\"top\" style=\"width: 112px;\"\u003e\n \u003cp dir=\"LTR\"\u003eVLBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 88px;\"\u003e\n \u003cp dir=\"LTR\"\u003eTHICKNESS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp dir=\"LTR\"\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 65px;\"\u003e\n \u003cp dir=\"LTR\"\u003eSD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp dir=\"LTR\"\u003eMean\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 59px;\"\u003e\n \u003cp dir=\"LTR\"\u003eSD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 49px;\"\u003e\n \u003cp dir=\"LTR\"\u003eMean\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 52px;\"\u003e\n \u003cp dir=\"LTR\"\u003eSD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp dir=\"LTR\"\u003eMean\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 69px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.043 *\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 64px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e4.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp dir=\"LTR\"\u003e3.95\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.85\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e4.56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 88px;\"\u003e\n \u003cp dir=\"LTR\"\u003e\u003cstrong\u003eD\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"4\" valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp dir=\"LTR\"\u003e\u003cstrong\u003eMANUAL\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 69px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.175\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 64px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.51\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e3.92\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.63\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp dir=\"LTR\"\u003e3.76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.53\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e4.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 88px;\"\u003e\n \u003cp dir=\"LTR\"\u003e\u003cstrong\u003eE\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 69px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.687\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 64px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.81\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e4.26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.62\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp dir=\"LTR\"\u003e4.34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e4.47\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 88px;\"\u003e\n \u003cp dir=\"LTR\"\u003e\u003cstrong\u003eF\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 69px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.002 *\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 64px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.87\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e10.24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp dir=\"LTR\"\u003e1.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp dir=\"LTR\"\u003e11.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.89\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e11.34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 88px;\"\u003e\n \u003cp dir=\"LTR\"\u003e\u003cstrong\u003eX\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 69px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.128\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 64px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e4.14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.96\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp dir=\"LTR\"\u003e4.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.91\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e4.66\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 88px;\"\u003e\n \u003cp dir=\"LTR\"\u003e\u003cstrong\u003eD\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"4\" valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp dir=\"LTR\"\u003e\u003cstrong\u003eCOMPUTER\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 69px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.042*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 64px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.63\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e3.99\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.74\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp dir=\"LTR\"\u003e3.58\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.77\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e4.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 88px;\"\u003e\n \u003cp dir=\"LTR\"\u003e\u003cstrong\u003eE\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 69px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.992\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 64px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.83\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e4.44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.74\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp dir=\"LTR\"\u003e4.43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.77\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e4.41\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 88px;\"\u003e\n \u003cp dir=\"LTR\"\u003e\u003cstrong\u003eF\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 69px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.005*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 64px;\"\u003e\n \u003cp dir=\"LTR\"\u003e0.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e10.38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp dir=\"LTR\"\u003e1.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp dir=\"LTR\"\u003e11.38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp dir=\"LTR\"\u003e1.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 62px;\"\u003e\n \u003cp dir=\"LTR\"\u003e11.31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 88px;\"\u003e\n \u003cp dir=\"LTR\"\u003e\u003cstrong\u003eX\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 69px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 1px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 55px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 1px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 51px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 1px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 55px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 102px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 108px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e*The P value is considered significant at the 0.05 level.\u003c/p\u003e\n\u003cp\u003eOn the basis of the LSD post hoc test, in the manual technique, the mean dentin thickness in Region D was significantly greater in the VLBW group than in both the LBW group (P = 0.018) and the NBW group (P = 0.047). In Region X, the mean dentin thickness in the VLBW group (P = 0.001) and the LBW group (P = 0.006) was significantly greater than that in the NBW group, as shown in Table 3.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 3\u003c/strong\u003e: Comparison of average dentin thickness in the first mandibular molar via manual measurement.\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003eAreas\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 81px;\"\u003e\n \u003cp\u003eGroups\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003eGroups\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003eMean difference\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003ep value\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003eUpper\u003c/p\u003e\n \u003cp\u003eextreme\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003eLower\u003c/p\u003e\n \u003cp\u003eExtreme\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 81px;\"\u003e\n \u003cp\u003eVLBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003eLBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e-0.32*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.018\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e0.111\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e1.118\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003eNBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e0.81*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.047\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e0.006\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e1.013\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 81px;\"\u003e\n \u003cp\u003eLBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003eNBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e-0.105\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e0.662\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e-0.586\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e0.375\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eX\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 81px;\"\u003e\n \u003cp\u003eVLBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003eLBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e0.238\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e0.459\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e-0.403\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e0.880\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003eNBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e1.106*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e0.464\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e1.749\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 81px;\"\u003e\n \u003cp\u003eLBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003eNBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e0.868*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.006\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e0.254\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e1.482\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e*The mean difference is significant at the 0.05 level.\u003c/p\u003e\n\u003cp\u003eIn the computerized technique, the LSD post hoc test revealed that in Region E, the mean dentin thickness was greater in the VLBW group than in the LBW group. In Region X, the mean dentin thickness was greater in the VLBW group (P = 0.025) and the LBW group (P = 0.010) than in the NBW group, as shown in Table 4.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 4\u003c/strong\u003e: Comparison of average dentin thickness in the first mandibular molar via computerized measurements.\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" class=\"fr-table-selection-hover\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003eAreas\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 81px;\"\u003e\n \u003cp\u003eGroups\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003eGroups\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003eMean difference\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003ep value\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003eLower\u003c/p\u003e\n \u003cp\u003eextreme\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003eUpper\u003c/p\u003e\n \u003cp\u003eExtreme\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eE\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 81px;\"\u003e\n \u003cp\u003eVLBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003eLBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e.55023\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e0.046\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e.0087\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 90px;\"\u003e\n \u003cp\u003e1.0917\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003eNBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e.14602\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e0.793\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e-.3955\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 90px;\"\u003e\n \u003cp\u003e.6875\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 81px;\"\u003e\n \u003cp\u003eLBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003eNBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e-.40421\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e0.154\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e-0.9220\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e0.1136\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eX\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 81px;\"\u003e\n \u003cp\u003eVLBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003eLBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e-.07609\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e0.973\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e-0.9038\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e0.7517\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003eNBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e.92707\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e0.025\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e0.0993\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e1.7548\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 81px;\"\u003e\n \u003cp\u003eLBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003eNBW\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e1.00316\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e0.010\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e0.2117\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 90px;\"\u003e\n \u003cp\u003e1.7946\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e*The mean difference is significant at the 0.05 level.\u003c/p\u003e\n\u003cp\u003eThe mean width of the first mandibular molar was compared among the three groups via the post hoc LSD test. The results revealed that the first mandibular width was significantly greater in the VLBW (P = 0.047) and LBW (P = 0.005) groups than in the NBW group. No significant difference was found between the VLBW and LBW groups (P = 0.425). In the computerized technique, the mean width of the first mandibular molar differed significantly between the weight groups (P = 0.094). The pairwise comparison of groups via the post hoc LSD test revealed that the mean width of the first mandibular molar was significant and greater in the LBW group than in the NBW group (P = 0.031).\u003c/p\u003e\n\u003cp\u003eOverall, there was no significant difference in the mean enamel thickness in the Y, B, A, and Z regions between boys and girls (P \u0026gt; 0.05). However, the mean enamel thickness in the C region was significantly greater in boys than in girls (P = 0.020). There was no significant difference in the mean dentin thickness between boys and girls in any region (P \u0026gt; 0.05).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study aimed to determine the relationships between birth weight and the enamel and dentin thicknesses of the first permanent mandibular molars in 7\u0026ndash;8-year-old children. The results indicated that the mean enamel thickness of the first mandibular molar did not differ significantly across the specified regions (Y, C, B, A, and Z) on the basis of birth weight, with similar measurements observed across the three weight groups via both measurement techniques. However, dentin thickness was found to be greater in some areas of the very low birth weight (VLBW) and low birth weight (LBW) groups than in the normal birth weight (NBW) group across both measurement techniques.\u003c/p\u003e \u003cp\u003eImportantly, while many studies have focused on deciduous teeth (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e), this study specifically evaluated permanent teeth. Additionally, previous research has often concentrated on hypoplasia (\u003cspan additionalcitationids=\"CR18 CR19\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e), whereas the present study assessed sound tooth structure. The results also revealed that in Region D, the mean dentin thickness in the VLBW group was significantly greater than that in both the LBW and NBW groups. In Region X, the mean dentin thickness in the VLBW and LBW groups was significantly greater than that in the NBW group.\u003c/p\u003e \u003cp\u003eThese findings can be understood in the context of compensatory growth during the catch-up growth phase, which can continue until approximately three years of age in LBW infants. This phase is influenced by several factors, including growth factors, thyroid hormones, insulin, sex steroids, and insulin-like growth factor 1 (IGF-1). These factors are known to influence developmental traits and may accelerate mineralization in bones and connective tissues, which could help explain the observed differences in dentin thickness (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eChanges in tooth crown size may reflect general growth disturbances during both prenatal and postnatal development (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e). In this study, the mean width of the first molar was significantly greater in the very low birth weight (VLBW) and low birth weight (LBW) groups than in the normal birth weight (NBW) group. Harila-Kaera et al. reported significant increases in the mesiodistal (MD) and intercuspal distances of the first permanent molars in white preterm boys compared with normal children of certain racial backgrounds, which aligns with the findings of the present study (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eApps et al. evaluated 436 twins, divided them into NBW and LBW groups, and reported a positive correlation between tooth dimensions and birth weight. Although they reported no reduction in tooth size in boys with LBW, a 2\u0026ndash;3% decrease in tooth size was noted in both deciduous and permanent incisors in girls with LBW (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e). This finding contrasts with our study, which focused on measuring the permanent mandibular molar\u0026mdash;the only tooth that begins calcification at birth. As such, birth weight may have a more pronounced effect on this tooth. In our study, we found an increase in size in VLBW and LBW children compared with NBW children.\u003c/p\u003e \u003cp\u003eBuhamer et al. conducted a systematic review on the mesiodistal and buccolingual dimensions of permanent teeth and reported that teeth are generally smaller in both dental arches in preterm infants than in full-term infants. They also reported that race and gestational age influence tooth size. In contrast, the present study measured tooth size across different birth weight categories within a diverse ethnic population, focusing specifically on the mandibular molar, which begins calcification at birth (\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eEbrahim et al. reported that the mesiodistal and buccolingual widths of the first permanent molars, as well as the central and lateral incisors, were smaller in children born very preterm than in normal controls (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e). However, these findings were not consistent with the results of our study, possibly because of differences in race or because their study did not stratify participants on the basis of birth weight, as both preterm and term babies were included in the same group. In a systematic review, Paulsson suggested that, owing to insufficient evidence on the relationship between premature birth and tooth-crown dimensions, further research is needed to clarify this association.\u003c/p\u003e \u003cp\u003eIn contrast, changes in tooth crown size among naturally born children are often considered multifactorial, with genetics and environmental factors playing significant roles. These changes may reflect general growth disturbances during both the prenatal and postnatal periods. Genetic factors account for approximately 60% of the observed variation in tooth size for both deciduous and permanent teeth (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e). The extent of genetic diversity varies by tooth and its specific dimensions, with some teeth showing greater variability than others (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e). Additionally, compared with deciduous teeth, environmental factors are believed to have a more substantial effect on permanent teeth. Race and sex are also important factors to consider when examining tooth development (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e), which may help explain the differences between the present study and previous studies.\u003c/p\u003e \u003cp\u003ePrevious studies have documented variations in tooth growth across different sexes and racial groups. Other influencing factors include poor maternal health during pregnancy, such as thyroid dysfunction, diabetes, high blood pressure, and maternal smoking (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e). Furthermore, the first permanent molars are the only teeth that begin mineralization at birth, which is why our study focused exclusively on these molars, assessing both dentin and enamel dimensions.\u003c/p\u003e \u003cp\u003eIn general, the mean enamel thickness in the Y, B, A, and Z regions did not differ significantly between males and females. However, the mean enamel thickness in the C region was significantly greater in males than in females. This finding is consistent with the common observation that boys tend to have larger teeth than girls do. Genes influencing tooth crown size are located on both the X chromosome and the Y chromosome, and the effects of the Y chromosome differ from those of the X chromosome (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e). Additionally, the enamel and dentin thicknesses in both boys and girls, when stratified by weight, were similar in the majority of the measured areas. Therefore, the results of our study are generalizable to both genders.\u003c/p\u003e \u003cp\u003eOwing to the unique circumstances of the COVID-19 pandemic, many patients have failed to attend appointments. Although the final sample size was statistically sufficient, we recommend increasing the sample size in future studies. Given the greater spatial resolution of intraoral radiographs than of extraoral radiographs, we also recommend the use of intraoral radiographs, such as bitewings, in future research.\u003c/p\u003e \u003cp\u003eWhile birth weight appears to have no effect on enamel thickness, lower birth weights may be associated with greater dentin thickness in the first molars. These findings confirm the influence of birth weight, environmental conditions, race, and catch-up growth on tooth development.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eAs birth weight decreases, the size of the first mandibular molar increases. However, no significant differences were found in enamel thickness across the weight groups. In contrast, dentin thickness increased in certain areas with lower birth weights. The observed increase in tooth size may have implications for orthodontic treatment planning. The normal enamel thickness observed in underweight children suggests that they are not more susceptible to early tooth decay.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u0026bull; \u003cb\u003eVLBW\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eVery low birth weight\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u0026bull; \u003cb\u003eLBW\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eLow birth weight\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u0026bull; \u003cb\u003eNBW\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003enormal birth weight\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u0026bull; \u003cb\u003eMIH\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eMolar Incisor Hypomineralization\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u0026bull; \u003cb\u003eHSPM\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eHypomineralized second primary molars\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eEthics approval and consent to participate\u003c/h2\u003e \u003cp\u003e The study protocol was approved by the Ethics Research Committee of North Khorasan University of Medical Sciences, Bojnurd University of Medical Sciences, Faculty of Dentistry, Dental Research Center (approval number: 1400.130.IR.NKUMS.REC). All procedures were conducted in accordance with the Declaration of Helsinki. Written informed consent for participation was obtained from the parents or legal guardians of all child participants.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eConsent for publication\u003c/strong\u003e \u003cp\u003eNot applicable. No identifying images or personal clinical information are included in this manuscript.\u003c/p\u003e \u003c/p\u003e\u003cp\u003e \u003ch2\u003eCompeting interests\u003c/h2\u003e \u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eNo funding was received for this study.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eY.B. and N.R. conceptualized the study. M.N. curated the data. M.Y. performed the formal analysis and software processing. S.D. and N.R. conducted the investigation. Y.B. and S.M. developed the methodology. N.R. and Y.B. administered the project and supervised the research. Y.B. and S.D. validated the data. M.Y. and S.M. prepared the visualizations. N.R. and S.D. drafted the original manuscript. N.R. and S.D. reviewed and edited the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThe authors would like to thank North Khorasan University of Medical Sciences for supporting this research. The authors also thank Bint Al-Huda Hospital for providing access to birth records and assisting with data collection.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe data will be made available upon reasonable request to the corresponding author.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eKrishnaji Musale P, Shrikant Soni A, Sunil Kothare S. Etiology and Considerations of Developmental Enamel Defects in Children: A Narrative Review. J Pediatr Rev. 2019;7(3):141\u0026ndash;50.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAlshehhi A, Al Halabi M, Hussein I, Salami A, Hassan A, Kowash M. Enamel defects and caries prevalence in preterm children aged 5\u0026ndash;10 years in Dubai. Libyan J Med. 2020;15(1).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKoberova R, Radochova V, Zemankova J, Ryskova L, Broukal Z, Merglova V. Evaluation of the risk factors of dental caries in children with very low birth weight and normal birth weight. BMC Oral Health. 2021;21:1\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTsang AKL. The special needs of preterm children\u0026ndash;an oral health perspective. Dent Clin. 2016;60(3):737\u0026ndash;56.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChiego DJ. Essentials of Oral histology and embryology-MENA adapted reprint E-book. Elsevier Health Sciences; 2017.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMj\u0026ouml;r IA. Dentin permeability: the basis for understanding pulp reactions and adhesive technology. Braz Dent J. 2009;20:3\u0026ndash;16.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFunao-Tanigawa J, Onishi T, Sakurai A, Kojima A, Homma H, Ooshima T, et al. Histopathological characteristics of primary teeth in pre-term very low birth-weight child: Case report. Pediatr Dent J. 2010;20(2):182\u0026ndash;5.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFearne JM, Brook AH. Small primary tooth-crown size in low birthweight children. Early Hum Dev. 1993;33(2):81\u0026ndash;90.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eApps MV, Hughes TE, Townsend GC. The effect of birthweight on tooth-size variability in twins. Twin Res Hum Genet. 2004;7(5):415\u0026ndash;20.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEbrahim E, Paulsson L. The impact of premature birth on the permanent tooth size of incisors and first molars. Eur J Orthod. 2017;39(6):622\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHarila-Kaera V, Heikkinen T, Alvesalo L, Osborne RH. Permanent tooth crown dimensions in prematurely born children. Early Hum Dev. 2001;62(2):131\u0026ndash;47.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDempsey Pa, Townsend GC. Genetic and environmental contributions to variation in human tooth size. Heredity. 2001;86(6):685\u0026ndash;93.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBozorgnia Y, Mafinejad S, Dokohaki S, Razavi N, Shabani R. The effect of birth weight on tooth development by Demirjian\u0026rsquo;s method. Clin Oral Invest. 2024;28(7):411.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePaulsson L, Bondemark L, S\u0026ouml;derfeldt B. A systematic review of the consequences of premature birth on palatal morphology, dental occlusion, tooth-crown dimensions, and tooth maturity and eruption. Angle Orthod. 2004;74(2):269\u0026ndash;79.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJain S, Gupta A, Jain D. Estimation of sample size in dental research. Int Dent Med J Adv Res. 2015;1(1):1\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePourhoseingholi MA, Vahedi M, Rahimzadeh M. Sample size calculation in medical studies. Gastroenterol Hepatol bed bench. 2013;6(1):14.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAine L, Backstr\u0026ouml;m M, M\u0026auml;ki R, Kuusela AL, Koivisto AM, Ikonen RS, et al. Enamel defects in primary and permanent teeth of children born prematurely. 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PLoS ONE. 2021;16(11):e0259293.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Infant, Low birth weight, Infant, Very low birth weight, Dental enamel, Dentin, Dentition, Permanent, Molar","lastPublishedDoi":"10.21203/rs.3.rs-8128297/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8128297/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eEarly-life factors such as birth weight influence dental development. However, how birth weight affects enamel and dentin thickness in permanent mandibular first molars remains unknown.\u003c/p\u003e\u003ch2\u003eAim\u003c/h2\u003e \u003cp\u003eHere, we quantitatively assess the impact of birth weight on enamel and dentin thickness in 7- to 8-year-old children.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003ePanoramic radiographs of 75 children were analyzed. The participants were stratified into very low (VLBW), low (LBW), and normal birth weight (NBW) groups. The enamel and dentin thicknesses were measured manually and via computer-assisted analysis. Statistical comparisons were performed via ANOVA and post hoc tests.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eEnamel thickness was not significantly different across the VLBW, LBW, and NBW groups (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05). In contrast, dentin thickness was significantly greater in the VLBW group in region D (VLBW vs LBW, P\u0026thinsp;=\u0026thinsp;0.018; VLBW vs NBW, P\u0026thinsp;=\u0026thinsp;0.047) and in region X (VLBW vs NBW, P\u0026thinsp;=\u0026thinsp;0.001; LBW vs NBW, P\u0026thinsp;=\u0026thinsp;0.006). Compared with that of NBW, the molar width of VLBW and LBW increased 1.1\u0026ndash;1.2-fold (P\u0026thinsp;=\u0026thinsp;0.005\u0026ndash;0.047). Manual and computerized measurements were highly concordant (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05). Gender had minimal impact, except for slightly greater enamel thickness in Region C for boys (P\u0026thinsp;=\u0026thinsp;0.020).\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eBirth weight does not affect enamel thickness but is associated with increased dentin thickness and molar width, likely reflecting compensatory growth. These findings challenge the prevailing view that low birth weight predisposes individuals to early tooth fragility and provide a framework for understanding dental development in pediatric populations.\u003c/p\u003e","manuscriptTitle":"The Impact of Birth Weight on the Enamel and Dentin Thickness of Mandibular First Molars","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-31 10:47:13","doi":"10.21203/rs.3.rs-8128297/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"3a886c60-8998-4c32-9115-b01930740485","owner":[],"postedDate":"December 31st, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-03-19T12:12:11+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-31 10:47:13","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8128297","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8128297","identity":"rs-8128297","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}