A radiographic assessment of enamel thickness in human maxillary incisors

Crown sizes of human teeth are sexually dimorphic, with male larger than female. This holds for most human groups, though the extent of dimorphism varies among populations. It is not known whether size dimorphism is due to differences in enamel thickness, dentine differences, or some combination of the two. This study examined the pattern of variation in enamel thickness on the mesial and distal margins of the four maxillary permanent incisors. Standardized periapical radiographs of the incisors of 115 adolescent American whites were measured. Enamel was significantly thicker on the distal than the mesial margins of both the lateral and central incisors, with a mean difference of 0.1 mm. There was no sexual dimorphism in the maximum mesial or distal enamel thicknesses. In contrast, the widths of the dentine of the crowns were significantly greater in males, by an average of 6.5%. Sexual dimorphism in mesiodistal diameters of the incisors seems, then, to be due to the dentine component, which is the size attained at the end of the bell stage of tooth formation. Sex-specific correlations between enamel thickness and crown width of the dentine were low (and lower for males), indicating considerable independence between regulatory mechanisms of dentine and enamel development.     

Molar polymorphisms and the timing of dentition mineralization

The chronological age, skeletal age, and morphological age at the time of mineralization of 14 stages of the permanent teeth of 121 boys and 111 girls of the serial experimental sample of the Burlington Growth Centre were contrasted according to whether or not the children had 4- or 5-cusped mandibular permanent first molars, and whether or not they had agenesis of one or more third molars. In the boys with 4-cusped mandibular first molars, the mineralization of the teeth occurred at significantly earlier chronological and skeletal ages when they were significantly shorter in stature. Tooth mineralization was not consistently earlier in the girls with 4-cusped molars, but these girls tended to be taller and heavier than those with 5-cusped molars. In contrast, in both sexes with agenesis of third molars, the mineralization of the teeth was significantly delayed according to chronological, skeletal and morphological evaluation. The change in timing of mineralization was greatest for the second premolars and second molars, and least for the first molars.     

A morphometric analysis of the furcation region of mandibular molars

This study examined furcation dimensions and morphology in first and second mandibular molar teeth. One hundred thirty-four extracted human mandibular molars with divergent roots were selected. Teeth were viewed at 7X magnification on a dissecting microscope interfaced with a computer equipped with a state-of-the-art histomorphometry software program. Various aspects of furcation anatomy were measured and recorded. Data were examined by using analysis of variance for all paired comparisons. For nonparametric data, the Kruskal Wallis test was used. Results indicated that 61.94% of buccal and 50.75% of lingual molar surfaces presented with cervical enamel projections (CEPs), with the highest frequency noted in second molars. CEPs ranged from 0.98 mm to 1.33 mm, whereas root trunk heights varied between 2.23 mm and 2.93 mm. Generally, lingual molar surfaces had longer root trunks when compared to buccal surfaces. Root separation increased by approximately 0.5 mm at each 1-mm increment apical to the furcal roof. This study provides new information regarding the furcal anatomy of mandibular molar teeth and supplements previous reports that suggest the CEP is a common problem which must be addressed by clinicians when treating molar teeth.     

Alveolar bone height of primary and first permanent molars in healthy seven- to nine-year-old children

The purpose of the study was to establish baseline values of the alveolar bone height of the primary molars and first permanent molars in sample of healthy U.S. seven- to nine-year-old children. Direct measurements of the distance from the cementoenamel junction (CEJ) to the alveolar crest (AC) on 223 pairs of bitewing radiographs from 223 subjects were made using a digimatic caliper under standardized conditions. The distance from the CEJ to the AC had medians from 0.58 mm to 1.39 mm (range 0.0 to 4.44 mm) for the primary molars and from 0.00 mm to 0.64 mm (range -1.35 to 2.15 mm) for the mesial aspect of the permanent molars. There were no statistically significant differences in the distance from CEJ to AC between teeth on the right and left sides of the mouth. The distances from CEJ to AC were always greater in the maxilla than in the mandible for similar primary molar sites, but only true for the mesial aspect of the permanent first molar at age nine. As a tooth is positioned more anteriorly in the mouth, the distance from CEJ to AC was greater. On the whole, males had greater distances than females and eight-year-olds had larger distances than seven- or nine-year-olds. Differences were observed in the measured distances for the different age and sex-groups and may be attributable to variations in eruption and exfoliation patterns. The distance was significantly greater in areas of interproximal restorations and open contacts, and there was a tendency for the distances to be greater in areas of interproximal caries.     

Microleakage of dentin bonding systems used with spherical and admixed amalgams

PURPOSE: To evaluate the effectiveness of the dentin bonding systems (DBS) Tenure, Syntac, Amalgambond and All-Bond 2 using a resin-lined amalgam technique in preventing short-term microleakage in Class V cavity preparations restored with a spherical and an admixed alloy. MATERIALS AND METHODS: Class V cavity preparations were made on the mesial and distal surfaces of non-carious human mandibular molars with the occlusal margins in enamel and gingival margins in cementum. Prepared teeth were randomly assigned to 12 treatment groups (n = 10) consisting of each DBS, no liner and Copalite for both amalgam alloys. Samples were thermocycled, stained and sectioned to evaluate microleakage. RESULTS: The DBS-lined restorations had significantly less microleakage at both occlusal and gingival margins than the Copalite and unlined restorations. Among DBS, Syntac had significantly more microleakage with both alloys than either All-Bond 2 or Amalgambond. These results do not totally correlate to a previous study which used the same experimental design but included viscous liners in addition to the same DBS, indicating a potential difference between resin-lined versus resin-bonded amalgam techniques in preventing microleakage.     

The reliability of apical x-ray pictures in the diagnosis of mandibular bone lesions. A review of the literature and in-vitro study

Using 6 macerated human anatomical preparations of mandibular jaw regions with either front teeth or premolars and molars, the radiological detectability of artificial periapical bone lesions was evaluated in relation to the size of the lesions and to the angle of x-ray projection. The artificial lesions were enlarged stepwise until distinct radiological visibility was attained. For each step of enlargement, x-ray pictures were taken with orthoradial as well as with at 25 degrees mesially and distally excentered projections. All x-ray pictures were evaluated by 6 dentists. The following results were obtained: The size of a periapical bone lesion, at which it is becoming radiologically detectable, varies between the different regions of the lower jaw. Isolated spongiosa lesions being larger than 3 mm in diameter are most often detectable at mandibular front teeth and premolars. Isolated spongiosa lesions at mandibular molars are generally non-detectable. Atypical lesions, e.g. discontinuities of bony structures are particularly difficult to detect radiologically. There were no statistically significant differences in lesion detectability between x-rays of different angle projections.     

Demineralization effects of 10 percent carbamide peroxide

OBJECTIVES: The purpose of this in vitro study was to measure the amount of calcium lost from enamel exposed to a 10% carbamide peroxide solution. METHODS: Nine teeth (3 incisors, 2 premolars, 4 molars) were sectioned to serve as paired test and control specimens. Each tooth half was coated with wax, leaving a uniform 3 mm x 4 mm window of exposed enamel. Test specimens were placed in culture tubes with 1.00 ml of deionized water and 0.02 ml of 10% carbamide peroxide for 6 h; controls were exposed to water alone. Calcium concentrations in the solutions were measured using a Perkin-Elmer 5100 atomic absorption spectrophotometer. RESULTS: Teeth exposed to carbamide peroxide lost an average of 1.06 micrograms/mm2 of calcium. This amount of loss was significantly greater than controls (p < 0.001), according to ANOVA. For comparison, teeth were exposed to a cola beverage for 2.5 min, the time equivalent of drinking a 16 oz. beverage. The amount of calcium lost from these teeth was also about 1 microgram/mm2. CONCLUSIONS: Teeth exposed to 10% carbamide peroxide lost calcium. However, the amount of loss was small, and may not be clinically significant.     

Dental root surface structure as an indicator of age

The purpose of this investigation was to examine the relationship between the root surface structure of human teeth and the age of the individual and also to evaluate whatever contribution this relationship might give to multiple regression methods for age estimation. The material, consisting of 1000 permanent teeth, excluding molars, was examined by means of a new scoring system (Surface Roughness Scores, SRS) for surface roughness, in addition to the scoring systems of Gustafson (RG) and Johanson (RJ) for root resorption. Statistical analyses using the SPSS package indicated a symmetric left/right distribution of root surface structure. The Pearson correlation between age and RJ varied from -0.02 for maxillary central incisors to 0.54 for mandibular central incisors and was approximately the same for RG. These two scoring systems seem to be of little value in methods for age estimation. Correlations between age and the new scoring systems SRS were significant for all teeth and varied from 0.44 for maxillary second premolars to 0.68 for mandibular first premolars. There was no detectable influence of gender or reason for extraction. However, the SRS could not be assessed with sufficient reproducibility, and the estimates were therefore too subjective to be used as the sole criterion for age estimation. This scoring system could, however contribute positively to a multiple regression method.     

Caries prevalence in the deciduous dentition of a mediaeval population from the south-west of Scotland

The prevalence, distribution and location of dental caries were studied in the deciduous dentition of 185 skeletons aged between 6 months and 13 years from a large, mostly mediaeval, cemetery, where successive phases of use could be distinguished. The main phases dated from 1240 to 1440 AD. During this period, no consistent trend or pattern of caries was identified, but there was a significantly higher caries prevalence in the age band 6-12.9 years than in the age band 0.1-5.9 years. The caries prevalence in the juveniles from the earlier Northumbrian, or Anglo-Saxon, phase of the cemetery was higher than in any mediaeval phase group, with mostly approximal surfaces affected. In the mediaeval population, first deciduous molars generally showed lower caries prevalence than second deciduous molars, significantly lower for the older age band, and maxillary molars consistently showed lower levels than mandibular molars. The highest caries rate, shown by mandibular second molars in the older age band, was 7.9%. In deciduous molars, the occlusal surface was most frequently affected by caries, whereas in the permanent molars of the same population the approximal surfaces had shown the highest level of attack. The overall caries prevalence in deciduous teeth in the mediaeval population of Whithorn was 2.3% of the teeth present, lower than the levels found in previous Scottish and English population groups, including a small assemblage of children from the Scottish sites of Elcho, Southwick and Kirkhill.     

Hypodontia of primary and permanent teeth in a sample of Saudi children

Hypodontia, congenitally missing teeth is more common in permanent than primary dentition. The present investigation reports the prevalence and pattern of hypodontia in the primary and permanent dentitions, excluding third molars in a sample of Saudi children. The sample consists of 1,300 children, aged 5 to 10 years of age. Clinical and radiographic examinations were performed. The prevalence of children with hypodontia was found to be 2.6 percent. The mandibular second premolar was the tooth most frequently absent and account for 45 percent of the total missing teeth. In primary dentition, the maxillary lateral incisor was the tooth most frequently absent (9%). A peg-shaped permanent maxillary lateral incisor was present in 0.7 percent of the sample. Congenitally missing teeth were almost equally distributed between maxillary (52%) and mandibular (48%) arches.     

Polymerisation shrinkage around composite resin restorations--an in vitro study

The aim of this study was to determine the degree of penetration of a fluorescent adhesive at the margins of 3 brands of posterior composite resin restorative materials. Seventy-eight extracted human premolar teeth were used. Class II cavities were prepared on both approximal surfaces of each tooth in such a manner that the gingival wall was situated apical to the amelo-cemental junction. The enamel of the cavity walls was bevelled, etched and treated with the enamel bonding agent recommended by the manufacturer. The 3 brands of composite resin used were: Fulfil, Estilux Posterior and P 50. The teeth were divided at random into 3 groups of 26 premolars each. The mesial and distal cavities of each tooth in the group were filled with the same brand. The resin was inserted in two increments in both the mesial and distal cavities and polymerised. The margins of one restoration in each tooth was coated with fluorescent adhesive and cured. All the restored teeth were embedded in clear epoxy resin and then sectioned. The mounted sections were examined at 100X magnification with fluorescent light. The polymerisation contraction gap at different areas of the tooth/restoration interface and the degree of penetration of the fluorescent adhesive into the gap was determined. The fluorescent adhesive penetrated the contraction gaps in all 3 posterior restorative materials to varying degrees. The defects observed were similar in all 3 brands and the differences in degree of penetration were not statistically significant (p > 0.05).     

Evaluation of fluoride uptake by enamel in children from fluoride dentifrices

Fluoride dentifrices are well accepted for their caries preventive effects. Although it is generally accepted that the presence of fluoride in the enamel protects teeth against carious attack, at the same time, there is some concern that ingestion of fluoride from toothpastes may substantially contribute to the total intake of this element. The present study was undertaken to clinically evaluate the fluoride uptake by human enamel after the use of lower concentrations of fluoride dentifrices and compare their potency to higher concentration in increasing the uptake of fluoride by enamel. Enamel biopsy was conducted on first permanent molars of 100 school children, aged 6-8 years before brushing and at intervals of one hour, 3 weeks, 6 weeks and 12 weeks following brushing with different concentrations of fluoride dentifrices. The fluoride content of the enamel biopsy samples were estimated using the Orion microprocessor ion analyser and by taking into consideration the enamel biopsy mass and depth of the etch. The results of the present study suggest that low fluoride concentration dentifrices provide similar fluoride uptake by enamel when compared with that of higher concentrations.     

An evaluation of the incisive nerve block and combination inferior alveolar and incisive nerve blocks in mandibular anesthesia

The purpose of this study was to measure the degree of anesthesia obtained with the incisive nerve block, the inferior alveolar nerve block and a combination of both injections in mandibular teeth. Using a repeated measures design, 40 subjects randomly received an incisive nerve block, a conventional inferior alveolar nerve block, or a combination inferior alveolar nerve block plus an incisive nerve block using either lidocaine or saline (control), at four successive appointments. The mandibular teeth and contralateral canine (+/- controls) were blindly tested with an Analytic Technology pulp tester at 4-min cycles for 60 min. An 80 reading indicated complete pulpal anesthesia. The incisive nerve block alone did not result in successful pulpal anesthesia in the central, lateral, first, and second molars. It was successful in the first and second premolars but the duration was approximately 30 min. The combination inferior alveolar nerve block plus incisive nerve block was successful in the first and second premolars, and enhanced anesthesia for the laterals and first molars.     

The cervical third of deciduous teeth. An ultrastructural study of the heard tissues by SEM

As information on amelocemental junction of deciduous teeth is limited, this topographical area was investigated by scanning electron microscopy (SEM) to verify differences from that of permanent teeth. Twenty-six carious and non-carious human maxillary and mandibular primary teeth were placed in a fixative immediately after extraction. Pulpal tissue was removed from the pulpal chambers and root. The primary teeth blocked onto stubs and all specimens were platinum coated and examined by SEM. In these specimens an overlapping of cementum onto to enamel and an edge to edge relationship was dominant. No gaps between enamel and cementum were observed. The amelocemental junction of deciduous teeth seem to differ to that described for permanent teeth.     

The fluoride content of enamel as a diagnostic aid in fluorosis

This study was undertaken to compare the fluoride content ([F]) of sound and hypoplastic enamel of dogs' teeth for use as a diagnostic aid for fluorosis. Enamel biopsies (0.5N HClO4; 15 seconds; 3.143 mm2) were conducted on macroscopically sound areas of the middle buccal surfaces of the right upper canine teeth. The [F], and the calcium concentrations of the etching solutions were determined using the potentiometric analytical method and the flame spectrophotometer respectively. Depth of etch (DOE) was calculated. The results of the study showed that the higher [F] in the hypoplastic enamel when compared to that of sound enamel (p > 0.05), was more a result than a cause of the hypoplasia. In this study, the [F] of the enamel was used successfully to exclude the possibility of fluorosis.     

Tooth mobility and resolution of experimental periodontitis. An experimental study in the dog

The aim of the present experiment was to study alterations in the mobility of teeth that occurred during resolution of experimentally induced periodontitis lesions in the dog. 5, 1-year-old, beagle dogs were used in the study. The left and right 4th, 3rd, and 2nd mandibular premolars (4P4, 3P3, 2P2) served as experimental teeth. Periodontal tissue breakdown was initiated by placing plaque-collecting cotton-floss ligatures around the neck of the experimental teeth. The ligatures were replaced to the level of the receding gingival margin 1 x every month. On Day 120, the ligatures were removed and debridement was performed. A groove, parallel to the long axis of the mesial root, was prepared in the mesio-buccal surface of the crowns of 2P and P2. Guided by the groove and with a probing force of 0.5 N, a probe was inserted into the buccal gingival pocket of the mesial root and was attached to the buccal surface. Biopsies including both the mesial and distal root of 2P and P2 and the surrounding hard and soft tissues were harvested. The biopsy procedure was repeated in a similar manner 15 days (i.e. Day 135) and 3 months (i.e. Day 225) after ligature removal in the 4th (4P4) and 3rd (3P3) premolar regions. After fixation, decalcification and sectioning, the biopsy material was exposed to histometric and morphometric measurements. Assessment of the mobility of the experimental teeth was performed on Days 120, 135 and 225 using the Periotest system.(ABSTRACT TRUNCATED AT 250 WORDS)     

Peer approaches for increasing HIV awareness on a college campus

PURPOSE: To compare the accuracy of clinical examination performed with bitewing radiographs or clinical examination using tooth separation to identify carious lesion activity. MATERIALS AND METHODS: 320 surfaces from 40 bitewing radiographs were examined for approximal caries on the maxillary and mandibular primary molars of 20 patients 3-10 years old. The patients were divided into three groups: (1) Absence of the permanent first molar; (2) Partial eruption of the permanent first molar; and (3) Full eruption of the permanent first molar. Two examiners evaluated the radiographs using a megascope, a magnifying glass (x2), and an amplifying image screen. Approximal radiolucencies were identified on 72 surfaces. Following the radiographic examinations, the two examiners performed conventional clinical inspection using a No. 4 dental mirror, a No. 5 dental explorer, and an air-water syringe, with artificial light and relative isolation. The separation method was performed with elastic bands, which were removed after 24 hours, and the clinical examination conducted as in the non-separation group. RESULTS: The correlation between the extension of interproximal radiolucent lesions in primary dentition and their clinical diagnoses following separation of the teeth, was similar to findings on literature evaluating the permanent dentition. On radiographic findings for enamel lesions, white spots predominated both in the inner (100%) and in the outer (94%) half of enamel upon clinical examination with separation of teeth. For radiolucent lesions in dentin, on the other hand, cavities predominated over white spot lesions (84%). In Groups 1 and 2 (young primary), white spots occurred in cases where the radiolucent lesions reached the dentin (15% and 25%), similar to findings for young permanent teeth. Clinical diagnosis performed with the mechanical separation of teeth cannot be considered conclusive for the primary dentition.     

Hospice and managed care

Carbon dioxide (CO2) lasers are capable of producing surface irregularities in human enamel which resemble those resulting from etching of enamel with orthophosphoric acid. This report presents the results of a laboratory study which examined the effect of selected tooth-related variables on shear bond strength between a current generation bonding agent (Scotchbond MultiPurpose) and acid-etched or laser-conditioned human enamel. There were no significant differences in shear bond strength between human maxillary central incisor teeth, first premolars, and third molars in either the acid etch or laser-conditioned groups. Polishing of enamel to give a flat surface increased the shear bond strength obtained with acid etching, but did not alter significantly bond strengths achieved with laser conditioning. There was a tendency for a higher bond strength with acid etching, but not with laser conditioning, in porcine molar enamel compared with human molar and bovine incisor enamel. In terms of the mode of operation of the laser, the repetitively pulsed mode resulted in a two-fold improvement in shear bond strength compared with the single pulse mode. These results indicate that shear bond strengths in the order of 10 MPa can be obtained reliably on human teeth using laser conditioning with pulsed modes in the absence of any other preparation of the natural enamel surface.     

Prevalence of developmental enamel defects and dental caries in rural pre-school Thai children

The prevalence of developmental enamel defects and dental caries was assessed in 344 Karen children aged 1-4 years who were chronically (70 per cent) and acutely malnourished (9.3 per cent) The teeth were cleaned with gauze to facilitate detection of hypoplastic lesions on labial surfaces of maxillary incisors. At least one tooth with defective enamel was seen in 31.9 per cent of children, while enamel hypoplasia was present in 22.7 per cent of children. Enamel defects were found in 21.2 per cent of teeth, with hypoplasia and opacities occurring in 14.6 and 6.6 per cent of teeth, respectively. Gender did not alter the prevalence of defects. The upper central incisors were affected more than lateral incisors. The prevalence of dental caries was 31.9 per cent with a mean dt of 1.1. The prevalence of caries associated with enamel hypoplasia was significantly greater than that associated with opacities and sound enamel (P < 0.0005).     

Utilization of periodic markings in enamel to obtain information on tooth growth

Enamel retains two fundamental periodic markings: the prism cross-striations, marking a diurnal rhythm of prism elongation, and the striae of Retzius, a longer-term marker of formation of the enamel surface. It is argued that, while artefacts superficially resembling prism cross-striations can be observed, these should not mislead an experienced histologist and that true cross-striations are reliable markers of the daily incremental apposition of enamel. The incremental markings can be used to elucidate several aspects of tooth crown growth. (1) Rate of enamel apposition. In some teeth, e. g., hominoid permanent teeth, the enamel apposition rate increases progressively between the inner and outer enamel, while in others the apposition rate appears to be uniform. (2) Crown formation time. This can be estimated on intact teeth, using counts of perikymata (surface traces of the striae), together with information on the time interval between successive striae. Much better estimates can be obtained from sections, using counts of cross-striations. (3) Pattern of crown formation. The rate at which new enamel formation extends over the presumptive enamel-dentine junction (extension rate) can be estimated from knowledge of the cross-striation interval together with angular measurements of prisms and striae. Multiple measurements of the extension rate within a tooth can be used to provide an estimate of crown formation time. The main application of extension rate measurements is to give quantitative information on the pattern of crown formation. In large primate teeth, the extension rate is high early in crown formation and slower later in crown formation. In smaller, more rapidly-formed teeth, a gradient in extension rate appears to be absent. Enamel thickness is negatively correlated with extension rate among primates. This seems to be a mechanism ensuring that there is sufficient time for enamel maturation to be completed before eruption takes place. Among primates it appears that variation in the prism pattern (i.e., the extent to which the outline of the pattern 3 prisms is closed or open) is correlated with the extension rate. It is postulated that the extension rate controls prism shape by influencing the morphology of the Tomes process pits during their initial formation.