Enamel pearls and cervical enamel projections on 2 maxillary molars with localized periodontal disease: case report and histologic study

Presented here is an unusual case of teeth with aberrant enamel. One small and 3 large enamel pearls were identified in 2 maxillary third molars of a patient. One long enamel projection was connected to one of the large enamel pearls, along with 2 short cervical enamel projections. The ectopic enamel was associated with advanced localized periodontal destruction. After extraction, the molars were investigated radiographically and under the scanning electron microscope. The 3 large pearls contained distinct dentinal cones. The enamel of the pearls and the long cervical projection exhibited most of the structural attributes of crown enamel but were somewhat irregular, with variable shape and course of the prisms. Morphologic considerations suggest that these enamel pearls were aberrations and should not be regarded as attempts at new cusp or new tooth formation.     

Cervical enamel projections as an etiologic factor in furcation involvement.

Two thousand molars in 200 East Indian skulls were examined for the occurrence, location, and grade of cervical enamel projections. The relationship between the enamel projections and furcation involvements was studied. Several findings resulted. The incidence of cervical enamel projections in molars was 32.6%. The incidence of cervical enamel projections varied between molars. The mandibular second molars showed the highest incidence of enamel projections (51.0%), followed by the maxillary second molars (45.6%). The lowest incidence was seen in the maxillary first molars (13.6%). Grade 1 enamel projections were the most frequently encountered. Cervical enamel projections occurred most frequently on the buccal surfaces of teeth. There was a positive, statistically significant relationship between tooth surfaces with grade 2 and 3 enamel projections and periodontally involved furcations. However, no etiologic relationship was found between grade 1 projections and furcation involvements. There seems to be a physiologic relationship between bone and enamel projections. The alveolar crest has a tendency to follow the outline of the enamel projection, and a channel much wider than a normal periodontal membrane space accommodates the enamel projection as it extends toward the furcation. The results indicate that when cervical enamel projections are severe enough to approach or enter the furcation area (grades 2 and 3), they may be an etiologic factor in the breakdown of these furcations.     

Distribution patterns of enamel fluorosis in permanent dentition

Purpose: To describe the different patterns of the intraoral distribution of enamel fluorosis in permanent dentition. Materials and Methods: This cross-sectional analysis was conducted in Nalgonda district of Andhra Pradesh, India. A group of 1000 school children aged 13-15 years were selected by stratified cluster sampling from four different areas with different levels of naturally occurring fluoride in the drinking water. Fluorosis was recorded using the Thylstrup and Fejerskov index (TFI). Results: The prevalence of fluorosis (TFI score >=1) was 100% at all four fluoride levels. This study revealed two patterns of fluorotic enamel changes in dentition. In high fluoride areas, incisors exhibited lower TFI values than canines, premolars and molars, with the maximum affected being second molars followed by first molars. In low fluoride areas, a steeper profile of dental fluorosis, starting from incisors and first molars through canine and premolars to second molars, was noticed. Conclusion: With the exception of permanent second molars and permanent first molars in high fluoride communities, the intraoral distribution of different degrees of dental fluorosis was related to the completion of primary enamel formation.     

Hypomineralized molars and incisors of unknown origin: treatment outcome at age 18 years

OBJECTIVE: To assess the outcome of treatment of hypomineralized molars and incisors of unknown aetiology (MIH) in 18-year-olds. DESIGN: A follow-up study including clinical examination, panoramic radiography and intraoral photos. SAMPLE AND METHOD: Seventy-six individuals treated at the Eastman Dental Institute in Stockholm during 1978-2001 with the diagnosis MIH. Severity of enamel defects in molars and incisors, prevalence and distribution of extracted molars, type, quality and median duration of restorations, periradicular condition of affected molars, dental occlusion and space closure in cases of extraction, as well as the individual's satisfaction with the treatment, were assessed. RESULTS: Severe defects with enamel surface breakdown in all four molars occurred in 42% of the individuals and 29% had at least one incisor with yellow/brown opacity in the enamel. At follow up, 42% of the individuals had at least one molar extracted; 18% had all four molars extracted. The median duration of the molar restorations (n = 153) was 5 years. Of the individuals with restored molars, 48% had at least one unacceptable restoration. Periradicular pathology was observed in three molars. The sagittal relations did not differ between individuals with and without extraction of molars. Space closure was acceptable in 87% of the individuals with extracted molars. Eighty percent were satisfied with the treatment. CONCLUSIONS: Extraction of molars with severe enamel defects gave good or acceptable results in a majority of the patients while conservative restorative treatment resulted in a need for additional treatment in approximately half of the patients.     

纳米硬度仪测量人类牙釉质的纳米力学性能分布

目的：人牙釉质内的力学性能分布，对实现釉质的优异性能起到了重要作用，因而本工作的目的是使用结合原子力显微镜（Atomic Force Microscope，AFM）的纳米压痕仪，在纳米尺度上精确测量其分布特点。方法：釉质样本取自成人第三磨牙。使用由AFM控制的纳米压痕仪，定点精确测量釉质样品内的釉柱、釉柱间质和釉质鞘区域的纳米硬度和弹性模量。测量后，用AFM观察压痕形貌。结果：对纳米力学性能的测量结果显示出显著差异，釉质鞘和柱间质的纳米硬度比釉柱的硬度分别低73．5％和12.9％，其弹性模量分别下降了52．6％和7．1％。对压痕形貌的观察也得到了同样的结果。结论：本工作精确测量了人牙釉质的釉柱、柱间质以及釉质鞘的纳米硬度和弹性模量分布。纳米力学性能存在的差异性主要与成分及晶体排列方式有关。     

Enamel thickness and the helicoidal wear plane in modern human mandibular molars

Helicoid occlusion has long been recognized as a feature characterizing the human dentition and has been viewed as an important morphological marker in the transition from Australopithecus to Homo. The hallmark of helicoidal wear is a buccal wear slope in anterior mandibular molars (and a corresponding lingual slope of wear in anterior maxillary molars) reversing to a flat or lingual-oriented one in posterior mandibular molars. If localized increases in enamel thickness are taken as evidence of an adaptation to increased wear resistance, then data on enamel thickness in unworn molars can be used to assess whether the region of greatest wear changes from anterior to posterior in such a way as to provide evidence for the helicoidal wear plane being a structural feature of the orofacial skeleton. Such a hypothesis was supported in a previous study on enamel thickness in modern human maxillary molars. As maxillary and mandibular precisely interdigitate, it is reasonable to expect that a similar pattern of enamel thickness distribution should be present in mandibular molars. To test this, data on the distribution of enamel thickness across functionally relevant regions of the crown were collected on a sample of twenty-nine completely unworn mandibular molars. Results suggest that enamel thickness increases slightly posteriorly but no evidence exists for morphological changes along the mandibular molar series of modern humans to follow a trend towards providing additional tooth material in areas under greater wear in accordance with a helicoidal wear model. This suggests that the patterning of enamel thickness must be viewed in conjunction with other features, such as the biomechanical behaviour of molars during occlusion and axial molar angulation, to ascertain the precise anatomical determinants of this unique feature of the human dentition.     

恒磨牙窝沟釉质表面结构扫描电镜观察

目的观察未萌牙、初萌牙、成年牙咬合面窝沟和光滑面釉质表面的超微结构,比较窝沟釉质表面在萌出前后不同时期的变化。方法用激光龋齿检测仪和显微放射照相法确定咬合面窝沟无龋损的未萌牙6颗、初萌牙7颗、成年牙5颗为研究样本。劈开窝沟,对其窝沟釉质壁的表面及颊面釉质进行扫描电镜观察。结果①未萌牙窝沟侧壁釉质表面可见明显的釉质横纹,釉柱末端凹陷明显并分布有大量的微孔和灶性孔,类似蜂窝状,与颊面釉质表面无明显差别。②初萌牙窝沟侧壁釉质表面表现与未萌牙基本一致,颊面微孔减少。③成年牙窝沟侧壁上部釉质表面可见明显的表浅凹陷,可见少量的微孔,表面较光滑,较致密;窝沟下部的釉质表面结构较疏松,存在较多的微孔和灶性孔,呈蜂窝状结构,与未萌牙相似。结论在未萌牙、初萌牙、成年牙窝沟侧壁下部存在多孔状釉质发育缺陷。成年牙窝沟上部的釉质表面结构接近其颊面,与窝沟底部相比有较大差别,提示窝沟上部釉质在牙萌出后出现修复现象。     

肌动蛋白在大鼠磨牙及其发育中的分布研究

目的：探讨肌动蛋白在大鼠磨牙及其发育中的时空分布及意义。方法：建立大鼠牙胚发育模型。用免疫组化方法检测肌动蛋白在成年和发育期磨牙中的表达。结果：肌动蛋白在钟状期外釉上皮细胞，分泌前期成釉细胞和成牙本质细胞及中间层细胞之间，硬组织形成期成釉细胞Tomes'突和成牙本质细胞胞浆呈阳性表达。结论：肌动蛋白在大鼠磨牙发育过程中的分布具有时空特异性。与细胞的分化程度和功能状态密切相关。     

3D X-ray microscopic study of the extent of variations in enamel density in first permanent molars with idiopathic enamel hypomineralisation

OBJECTIVE: To measure mineral concentration distributions within teeth with idiopathic enamel hypomineralisation, a condition in which developmental defects are seen in first permanent molars, and/or incisors. DESIGN: X-ray microtomographic and 3D x-ray microscopy. SETTING: UK University, 2001. MATERIALS AND METHODS: X-ray microtomographic measurements of the extent of hypomineralisation in two affected molars and two contralateral controls extracted from the same patient. RESULTS: The control molars were visibly normal. The affected molars showed hypomineralised yellow opaque enamel with regions of breakdown. X-ray microtomographic images showed; a 20% reduction in mineral concentration of affected enamel (most cases involved full enamel thickness); hypomineralised enamel had a mineral concentration gradient opposite to that of normal enamel; regions of hypomineralisation distributed randomly throughout affected teeth, (apart from cervical region which was less severely affected). CONCLUSIONS: The pattern of mineral concentration suggests a disturbance during the maturation process. Differences in susceptibility of the ameloblasts during different stages of dental development may explain the asymmetric distribution of the defects. Topical fluoride applications may help promote post eruption maturation of the surface layer in these teeth. The use of fissure sealants and adhesive materials appears to prevent further breakdown.     

Mineral content in teeth with Deciduous Molar Hypomineralisation (DMH)

Objectives

We report the mineral (hydroxyapatite) density of sound and opaque areas in DMH molars with sound parts of (carious) deciduous teeth serving as controls.

Methods

Twenty-nine extracted second primary molars obtained from 15 children were studied. Thirteen of these molars were DMH molars with yellow opacities, seven were DMH molars with white opacities, three DMH molars with brown opacities and eleven were molars without DMH. Prior to microCT scanning, the teeth were mounted in impression material (Impregum^®) and stored in water with a thymol crystal. Spot analysis and line scans were performed in areas with opacities and in sound areas.An ANOVA test and t-tests were used to test if there were significant differences between the groups.

Results

The average densities of the hydroxyapatite in yellow and brown opacities (1368 mg HA/cm² and 1407 mg HA/cm², respectively) were significantly lower than in clinically unaffected enamel (1747 mg HA/cm²) of DMH molars or of sound molars (1758 mg HA/cm²). The mineral density in white opacities (1737 mg HA/cm²) was not different from that in the enamel of sound molars. The mineral density values in yellow and brown enamel opacities were in between those of dentine (1018 mg HA/cm²) and enamel.

Conclusions

DMH molars with yellow or brown opacities had a 20–22% lower mineral density in the hypomineralised enamel compared with sound molars. White opacities do not show a lower mineral content. The reduction in enamel mineral content in DMH molars stressed the need for a preventive approach in DMH.     

A three-dimensional analysis of enamel distribution patterns in human permanent first molars

The morphology of the enamel cap and the thickness of the enamel of human molars are regarded as closely related to function. Previously, enamel thickness has been studied in specific sections only, not the distribution patterns of the entire crown. Here, the three-dimensional distribution pattern of the enamel of human permanent first molars was examined with a newly developed system. A distinctive pattern of enamel thickness common to all the individuals examined was found, regardless of the variation in absolute enamel thickness among individuals. It was confirmed that the lingual faces of upper molars and the buccal faces of lower molars have thicker enamel than the other crown faces. Moreover, in lower molars, enamel was significantly thicker at the hypoconid than at the protoconid crown face. The distal face tended to exhibit thicker enamel than either mesial or lingual faces, owing to the thicker hypoconulid enamel. It is suggested that the gradients of thickness within a molar are not necessarily manifested according to direction, but are the result of cusp-specific patterning. The distribution of enamel in the occlusal fovea was found to correspond to the morphology of the outer enamel surface, with the exception of the distinctly thin enamel at and near the tip of the mesiobuccal cusps in both upper and lower molars. The thickness of the enamel in that region might therefore be related to developmental timing or the topography of the enamel–dentine junction, rather than to functional demand. When viewed from a whole-crown, three-dimensional perspective, enamel thickness patterns are in part, but not entirely, explained as an adaptation to functional demand.     

X-ray microtomographic study of mineral concentration distribution in deciduous enamel

OBJECTIVE: To determine the mineral concentration distribution in deciduous enamel by quantitative X-ray microtomography (XMT). DESIGN: Tooth rods ( approximately 2 mm x 2 mm) were removed from the mid-buccal region of 11 deciduous molars. Three XMT slices were taken at 1.5, 2.0 and 2.5 mm from the amelocemental junction. The distribution and variation in mineral concentration of enamel were studied from the XMT images. RESULTS: The mean mineral concentration for all the teeth was 2.81 (S.D. = 0.065) g cm(-3). There was no notable difference in the mean mineral concentration values between the three XMT slices of each tooth. However, there was up to 8% variation between different teeth (2.69-2.92 g cm(-3)). Gradients of increasing mineral concentration from the amelodentinal junction (ADJ) to the external surface were found, ranging from 0.08 to 0.60 mg cm(-3) microm(-1) with a mean of 0.366 mg cm(-3) microm(-1). The mineral concentration gradients in the occlusal slices were steeper than those in the cervical slices. The difference in mineral concentration between the inner and outer enamel ranged from 1.5 to 8.7%. CONCLUSION: In view of the large variation in both the means and the gradients of mineral concentration in deciduous molars, the mineral distribution of each experimental tooth should be measured as baseline data in studies of caries progression.     

Scanning electron microscopy of the three different types of cementum in the molar teeth of the guinea pig

The aim of this study was to observe the three-dimensional distribution and structural characteristics of the three different types of cementum in the molar teeth of guinea pig by means of scanning electron microscopy. Twenty-five 4-week-old male guinea pigs were used in this study. Using decalcified and undecalcified specimens with or without NaOH maceration, we examined the mandibles, maxillae and extracted molars by scanning electron microscopy. Guinea pig molars consist of two longitudinal, deeply folded lamina cores covered by enamel on all surfaces, except the buccal surface of the upper molars and the lingual surface of the lower molars. In the regions without enamel, we observed continuous thin belt-like layers of conventional acellular cementum on the dentin surface. On the enamel-covered surfaces, two different types of coronal cementum were found: small circular islands of coronal cementum called cementum pearls, which were distributed widely at almost regular intervals on the peripheral enamel surface from the apical fifth to the occlusal surface; and cartilage-like cementum, which occupied almost all of the occlusal half of the two longitudinally folded grooves. The present study demonstrated the unique distribution pattern of the three different types of cementum in guinea pig molars. These cementum types may contribute to the requirements for many different functions such as mastication, anchorage and continuous tooth eruption.     

Dental erosion in mice with impaired salivary gland function

Abstract

Objective: Salivary flow rate exerts an essential impact on the development and progression of dental erosion. In this work, the experimental dental erosion in non-obese diabetic (NOD) mice with reduced salivary flow rate was induced, and the erosive effect of acidic drinks on their dentition was studied.

Material and methods: Three acidic drinks (sports drink, cola light drink and sugar containing cola drink) were given to adult NOD mice (groups: N?=?11) as the only drink for 6?weeks. Two control groups were included; wild type and NOD control (groups: N?=?9). Experimental and control (water) teeth were dissected out and observed by scanning electron microscopy (SEM). Mandibular first molars were subsequently embedded in Epon, ground transversely, observed again by SEM, and the enamel thickness and tooth height were measured.

Results: Mandibular molars were considerably more eroded than maxillary molars. The erosive process started at the top of the cusps and subsequently extended in the cervical, mesio-distal, and pulpal direction. Erosive lesions were evident in increased succession from sports drink, cola light to cola drink exposed mandibular molars, with the lingual tooth height being approximately 23%, 26%, and 37% lower, respectively, compared to the control. The lingual enamel was approximately 48% thinner in sports drink molars and 62% thinner in cola light molars. In cola drink molars, the lingual enamel was totally eroded, and significant erosion of dentine was evident.

Conclusion: Reduced salivary flow, together with a high consumption of acidic drinks, results in severe erosion of NOD mice molars.     

Relationship between periodontal furcation involvement and molar cervical enamel projections

A total of 78 individuals ages 21 to 61 years with periodontal furcation involvement was examined for the presence of cervical enamel projections on the buccal surfaces of molar teeth. The furcal defects and cervical enamel projections (CEPs) of molars were diagnosed by probing, periapical roentgenographs, flap operation and inspection. Plaque index (PlI) and gingival index (GI) were recorded for the buccal and lingual surfaces of molars examined. The percentage of CEPs in the 78 individuals examined was 67.9%. The prevalence of CEPs in all molars examined was 45.2%. The prevalence of CEPs in molars with and without furcal involvements were 82.5% and 17.5%, respectively. The frequency of CEP in molars occurred in the following order: mandibular first molars, maxillary first molars, mandibular second molars and maxillary second molars. Statistical analyses (Chi-square test) revealed a significant difference between periodontal furcation involvements and the presence of CEPs. Results of this study also indicated that the furcal involvements with CEPs were associated with poor oral hygiene as measured by GI and PlI.     

Prevalence and distribution of developmental enamel defects in primary dentition of Chinese children 3–5 years old

Abstract A total of 1344 children, 3–5 yr old, from two rural counties, Haidian and Miyun, close to Beijing, China, were examined in 1992. A modified DDE Index was employed in this study, and a pre-designed formula was used to calculate an enamel detect score (EDS) for each individual in the study. Oral examination was performed by one dentist under natural light using a standard mouth mirror and dental probe. Developmental enamel lesions were diagnosed without drying or cleaning the teeth prior to examination. Results from this study showed that primary teeth with defective enamel were seen in 23.9% of the children examined, opacity in 1.6%, and hypoplasia in 22.2%. Among the teeth, maxillary central and lateral incisors were affected by enamel hypoplasia most often (40.8% and 39.2%), followed by maxillary canines (25.7%), maxillary 1st molars (22.1%), and mandibular 1st molars (18.5%). The enamel defects occurred more frequently on the buccal surfaces of teeth than on any other surface. The study did not find a significant association of the children's age, family socioeconomic status, and anthropometric measurements with the distribution of enamel defects. However, there was a significantly higher prevalence of teeth with defects in males compared to females (P < 0.001), as well as mean tooth surfaces with defects (P < 0.05), and mean EDS (P < 0.05). Children born prematurely were shown to have four times more enamel lesions than children who were full term (P < 0.01). Children with low birth weight also showed a statistically significant higher prevalence of enamel defects (P < 0.05) and a greater severity of hypoplastic lesions measured by EDS (P < 0.05) than those with normal birth weight. The results indicate that nutrition during fetal development is important in determining normal development of enamel in primary teeth. Nutritional status (diagnosed by anthropometric measurements) after the critical period was not associated with enamel defects induced earlier in life. The study suggested, therefore, that nutrition is important for maintaining proper development of the teeth only during the critical period when teeth are susceptible to the formation of defects.     

On the origin of intrinsic matrix of acellular extrinsic fiber cementum: studies on growing cementum pearls of normal and bisphosphonate-affected guinea pig molars

Cementum pearls (CPs) belong to a type of acellular extrinsic fiber cementum (AEFC) that form on the maturing enamel of guinea pig molars. This study aimed to elucidate the forming process of intrinsic matrix of AEFC using the CPs of normal and bisphosphonate-affected guinea pig molars as experimental models. A group of guinea pigs were subjected to continuous administration of 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) for 2 wk to inhibit mineralization of growing CPs. Fenestration of the enamel organ and migration of periodontal cells on to the exposed surface of maturing enamel appeared to be unaffected by HEBP, whereas de novo formation as well as growth of pre-existing CPs did not proceed under the same conditions. Immunoreactions for osteopontin were located exclusively on the mineralized matrix of preformed CPs, implying the absence of additional deposition or accumulation of putative intrinsic cementum matrix on the affected CPs, where the propagation of mineral phase had been arrested. In both normal and HEBP-treated groups, distinct enzymatic reactions for alkaline phosphatase appeared on the cells of the periodontal ligament associated closely with the sites of CP formation, and along the mineralization front of CPs. These observations suggest that the mineralization process per se plays a central role in the deposition of AEFC matrix and that alkaline phosphatase of periodontal cells penetrating through the enamel organ to the maturing enamel surface plays a key role in the mineralization process of CPs.     

Modern human molar enamel thickness and enamel-dentine junction shape

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

Marginal adaptation of inlay-retained adhesive fixed partial dentures after mechanical and thermal stress: an in vitro study.

STATEMENT OF PROBLEM: There are no studies that analyze the long-term durability of minimally invasive fixed partial dentures (FPDs) by comparing different methods of adhesive bonding. PURPOSE: This in vitro study examined the influence of cavity design and operative technique on the marginal adaptation of resin-bonded composite FPDs. MATERIAL AND METHODS: Slot-inlay tooth preparations with cavity margins located in enamel were prepared in 18 maxillary canines and 18 maxillary first molars designated as abutments. The specimens were divided equally into 3 experimental groups. In all groups, butt joint tooth preparations were created in canines and molars. In group 2, canines were prepared additionally with a 1.5-mm wide palatal bevel in enamel. After pretests with modification spaces of 11 and 17 mm (length), 2 missing premolars were replaced by the ceromer Targis and reinforced with the glass-fiber material Vectris. The prostheses were inserted with Tetric Ceram with use of an ultrasonic-supported, high-viscosity technique. Restorations were selectively bonded to cavity finish lines in groups 1 and 2 ("selective bonding"). In group 3, restorations were bonded totally to the whole cavity surface ("total bonding"). The restorations were stressed in a computer-controlled masticator. Marginal quality was examined with an SEM at x 200. RESULTS: The percent area of optimal margins after thermomechanical loading between composite and enamel in each group was as follows: group 1, 86.2% +/- 12.3% for canines and 95.5% +/- 3.5% for molars; group 2, 95.3% +/- 2.1% for canines and 96.2% +/- 2.7% for molars; and group 3, 95% +/- 0.9% for canines and 86.4% +/- 3.2% for molars. The marginal quality for molars inserted with total bonding was significantly lower (P< or =.05). CONCLUSION: Within the limitations of this study, the selective bonding technique for slot inlay-retained fixed partial dentures resulted in a negligible loss of marginal quality after extensive mechanical and thermal stress. The selective bonding technique is recommended for box-shaped cavity preparations.     

Risk factors in the occurrence of enamel defects of the first permanent molars among schoolchildren in Western Australia

Abstract – Background: The prevalence of enamel defects in the first permanent molars among children in Western Australia is higher than that reported for some European countries. The cause(s) of the defects, both white diffuse opacities and demarcated opacities, with or without hypoplasia, continue to be investigated. A recent review identified childhood illnesses and exposure to environmental toxins as putative causal factors for the occurrence of demarcated opacities (usually in association with hypoplasia). Diffuse opacities have been reported to be associated with exposure to the antibiotic amoxicillin, adjusted for otitis media and fluoride. The aim of this study was to examine the possible risk factors for enamel defects in the first permanent molars among children in Western Australia. Methods: Children attending pre‐primary schools (1999–2000 year of birth) in metropolitan Perth, Western Australia, were invited to participate in the study. In 2005, before the child’s first permanent molars had erupted, parents completed a questionnaire about the mother’s health during pregnancy, and their child’s health for the first 3 years. The first permanent molars were classified for type and extent of enamel defects using the modified Developmental Defects of Enamel (DDE) index. Caries experience and the presence of enamel defects on the deciduous molars and canines were also recorded using the WHO criteria. Bivariate, multinomial logistic and logistic regression analyses were used to test the factors for their influence on the occurrence of the enamel defects. Results: Five hundred and fifty children were examined for the occurrence of enamel defects on the first permanent molars. Multinomial logistic regression indicated that neonatal health conditions, prematurity (OR 2.75) and other health conditions (OR 2.40) were significant risk factors for the occurrence of diffuse enamel defects. Infection during the neonatal period was a strong risk factor for the occurrence of demarcated enamel defects (OR 6.88). Increased deciduous tooth caries experience increased the risk of demarcated enamel defects by 10% (OR 1.10) and living further from a heavy industrial area increased the risk of diffuse enamel defects nearly twofold (OR 1.93). Conclusions: Neonatal health factors were found to be important risk factors for the occurrence of enamel defects in first permanent molars. The effects of residential location and the association between deciduous tooth caries experience and enamel defects require further investigations.