N M King

University of Western Australia, Perth, Western Australia, Australia

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Publications (58)101.41 Total impact

  • [show abstract] [hide abstract]
    ABSTRACT: Background/Aims: To investigate the cross-sectional relationship between dental caries experience and adiposity status (general, central, and peripheral adiposity) in 12-year-old children in Hong Kong. Methods: A random sample of 668 12-year-old students was recruited. Clinical assessment for dental caries (DMFT) was conducted using WHO criteria. Anthropometric measurements for body height, body weight, waist circumference (WC), hip circumference and triceps skinfold thickness (TRSKF) were performed to assess general adiposity (weight-height ratio, body mass index); central adiposity (WC; waist-hip ratio, WHR), and peripheral adiposity (TRSKF). Associations between adiposity indices and dental caries experience [prevalence DMFT >0, 'high' experience (DMFT ≥ SiC Index value) and 'very high' experience (DMFT ≥ SiC(10) Index value)] were examined in bivariate and multivariate regression analyses. Results: The response rate was 76.9% (n = 514/668). Regression analyses (adjusted for oral hygiene practice, snacking habits, and socio-demographic factors) identified that WHR z score was associated with 'high' dental caries experience (OR 1.33, 95% CI 1.05, 1.70, p = 0.02), and that WHR z score was associated with 'very high' dental caries experience (OR 1.52, 95% CI 1.10, 2.11, p = 0.01). TRSKF z score was associated with 'very high' dental caries experience (OR 1.47, 95% CI 1.10, 1.96, p = 0.01). Conclusions: In a population-based sample of 12-year-old children in Hong Kong, dental caries experience was associated with adiposity. Central and peripheral, but not general adiposity was associated with dental caries experience. © 2013 S. Karger AG, Basel.
    Caries Research 11/2013; 48(1):32-38. · 2.51 Impact Factor
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    ABSTRACT: Supernumerary teeth are teeth, or tooth-like structures that have either erupted or remain unerupted in addition to the 20 primary and 32 permanent teeth. This paper attempts to (a) provide an overview of the proposed hypotheses and the current understanding of the aetiology of supernumerary teeth, and (b) review the published cases of supernumerary teeth occurring in families. No studies have been able to distinguish between different aetiologies for the different locations of supernumerary teeth, while, from a developmental or molecular perspective, the proposed hypotheses may be plausible and explains the origin of different types of supernumerary teeth. The only clearly evident feature, based on the existing published reports, is that it is logical to state that supernumerary teeth have a genetic component in their aetiology.
    European Archives of Paediatric Dentistry. Official Journal of the European Academy of Paediatric Dentistry. 09/2013;
  • R P Anthonappa, N M King
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    ABSTRACT: BACKGROUND: The literature considers primary failure of eruption (PFE) and infra-occlusion as two separate clinical entities and there are no clearly identified signs and symptoms that aid to facilitate a definitive diagnosis between these two conditions. Therefore, it is the purpose of this report to illustrate a case to emphasise the potential for misdiagnosis when categorising these conditions as two separate clinical entities. CASE REPORT: A 5-year-old Chinese boy was referred for the management of an unerupted primary mandibular left second molar tooth (75). Intra-oral examination revealed a primary dentition, with a PFE of tooth 75. He was scheduled for surgical removal of tooth 75 and placement of a space maintainer. Following improvements in the position of tooth 75 in the subsequent visits, the surgical option was disregarded and eventually tooth 75 erupted and exfoliated despite apparent mechanical obstructions. FOLLOW-UP: During the 6-year follow-up period, tooth 75 moved mesially resorbing the distal root of tooth 74 which was later extracted to facilitate the eruption of tooth 75; which then underwent normal exfoliation. CONCLUSION: While the present case could indicate the unpredictability of infra-occluded teeth, it is postulated that infra-occluded teeth erupt to the occlusal plane and then remain static due to mechanical obstructions, while the adjacent teeth accompany the growing alveolar bone. Conversely, teeth with PFE do not erupt and the mechanical obstructions are secondary factors. Therefore, the patient's age, at the time of diagnosis, may lead to the diagnosis of infra-occlusion; but it could have been PFE.
    European Archives of Paediatric Dentistry. Official Journal of the European Academy of Paediatric Dentistry. 06/2013;
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    ABSTRACT: OBJECTIVES: This investigation aimed to evaluate the secular trend exhibited by developing permanent teeth in 5 to 6 years old southern Chinese children. METHODS: Four hundred radiographs of children born in the years 1981 (n=200) and 2001 (n=200) were randomly selected, and then age and gender matched. Maxillary and mandibular teeth on the left side were scored. The number of tooth developmental stages (n-tds) for each stage of development and total n-tds in crown and root development was calculated. Logistic regression, X(2) test for occurrence of trend and Fisher's exact test were used to evaluate the variations in n-tds between crown and root maturation and also maturation among different teeth. Dental maturation between boys and girls was also compared. RESULTS: In the maxillary dentition, children born in 2001 showed advanced dental maturation (odds ratio, 1.29; P=0.001), and girls exhibited earlier maturation than boys (odds ratio, 1.43; P=0.001). In the mandibular dentition, no significant difference between the years was observed (odds ratio, 0.97; P=0.761), however, girls showed accelerated development than boys (odds ratio, 1.26; P=0.002). Variations in maturation were also observed between individual tooth in the same arch and between the arches. CONCLUSIONS: Children born in 2001 demonstrated accelerated dental development only in the maxillary dentition. Girls born in 1981 and 2001 exhibited advanced maturation than boys. Variations in development among different teeth in the year groups indicate the need for inclusion of all developing teeth to establish a secular change. Am. J. Hum. Biol., 2013. © 2013 Wiley Periodicals, Inc.
    American Journal of Human Biology 02/2013; · 2.34 Impact Factor
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    ABSTRACT: Several papers have been published to illustrate the effectiveness of mineral trioxide aggregate (MTA) as a pulpotomy medicament. Most of these reports do not offer a critical assessment on the data quality. Therefore, this review evaluated whether the currently available evidence is of an appropriate quality to support the long-term effectiveness of MTA as a pulpotomy medicament in primary molars using a standardized assessment criterion. A comprehensive literature search of human clinical outcome studies, which employed MTA as a pulpotomy medicament in primary teeth, was conducted using the MEDLINE database. Two independent observers rated these articles using the standardized assessment criteria. Furthermore, based on the initial sample mentioned in the individual studies and the sample included for the final analysis, the drop-out rates were calculated. Twenty-two studies were included for quality assessment with an excellent interobserver agreement. None of the 22 studies obtained grade A, four studies attained grade B1, five were graded B2 and 13 received grade C. Based on the assessment criteria employed, there was no evidence that MTA was better than present materials and techniques as a pulpotomy medicament. Furthermore, given the low quality of data, it is highly desirable to establish standard requisites for conducting and reporting on pulp therapy studies in primary teeth so as to benefit both researchers and clinicians to produce high-quality studies that are comparable and to prevent the misuse of clinical material and resources.
    International Endodontic Journal 08/2012; · 2.05 Impact Factor
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    ABSTRACT: This study sought to (i) determine the variations in prevalence figures based on the diagnostic tools employed, and (ii) provide an insight into the prevalence of supernumerary teeth. A comprehensive literature search of the prevalence reports on supernumerary teeth was conducted using two databases. Two independent observers rated these articles according to exclusion and inclusion criteria. 28 papers were included in the analysis to determine the variations in the prevalence figures in relation to the method of diagnosis, and 14 studies were included to estimate the prevalence figures for supernumerary teeth. Statistical analysis was computed using analysis of variance (ANOVA), Student Neumann-Keuls (SNK) test and multiple regression analysis. Statistically significant differences were evident in the prevalence figures based only on a clinical examination compared with groups that also employed radiographs (p < 0.05, ANOVA, SNK). The prevalence figures for supernumerary teeth ranged from 0% to 3%. The mean prevalence value for the European white population [1.6% (±0.6)] was lower than that of the southern Chinese population [2.7% (±0.14)]. The overall prevalence of supernumerary teeth for males was significantly higher than for females [relative risk = 1.37 (1.13-1.50)]. Clinical examination plus some types of radiograph(s) are essential for determining the prevalence of supernumerary teeth; nevertheless, it is still underestimated. Several disparities in the prevalence reports make the available data on supernumerary teeth questionable.
    Dentomaxillofacial Radiology 06/2012; 41(6):444-9. · 1.15 Impact Factor
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    ABSTRACT: This study evaluated the effect of proanthocyanidin (PA) incorporation into experimental dental adhesives on resin-dentine bond strength. Four experimental hydrophilic adhesives containing different PA concentrations were prepared by combining 50wt% resin comonomer mixtures with 50wt% ethanol. Proanthocyanidin was added to the ethanol-solvated resin to yield three adhesives with PA concentrations of 1.0, 2.0 and 3.0wt%, respectively. A PA-free adhesive served as the control. Flat dentine surfaces from 40 extracted third molars were etched with 32% phosphoric acid. The specimens were randomly assigned to one of the four adhesive groups. Two layers of one of the four experimental adhesives were applied to the etched dentine and light-cured for 20s. Composite build-ups were performed using Filtek Z250 (3M ESPE). After storage in distilled water at 37°C for 24h, twenty-four bonded teeth were sectioned into 0.9 mm×0.9 mm beams and stressed to failure under tension for bond strength testing. Bond strength data were evaluated by one-way ANOVA and Tukey's test (α=0.05). Interfacial nanoleakage was examined in the remaining teeth using a field-emission scanning electron microscope and analysed using the Chi-square test (α=0.05). No significant difference in bond strength was found amongst PA-free, 1% and 2% PA adhesives. However, incorporation of 3% PA into the adhesive significantly lowered bond strength as demonstrated by a greater number of adhesive failures and more extensive nanoleakage along the bonded interface. Incorporation of 2% proanthocyanidin into dental adhesives has no adverse effect on dentine bond strength. The addition of proanthocyanidin to an experimental adhesive has no adverse effect on the immediate resin-dentine bond strength when the concentration of proanthocyanidin in the adhesive is less than or equal to 2%.
    Journal of dentistry 11/2011; 40(3):173-80. · 2.00 Impact Factor
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    ABSTRACT: To investigate the relationship between concentration of fluoride in milk and its re-mineralizing efficacy, and to test whether increasing the volume of fluoridated milk has any effect on its re-mineralizing efficacy. Third molars were painted leaving a 1 mm window on the buccal and/or lingual surfaces. Artificial carious lesions were induced using a de-mineralizing solution. The teeth were then sectioned longitudinally. Specimens were randomly assigned to 15 groups according to different concentrations and volume; i.e., 2.5 ppm, 5 ppm, 7.5 ppm, 10 ppm, 15 ppm, 20 ppm, and 250 ppm of fluoride with 25 ml/section and 50 ml/section. De-ionized water and plain milk were used as controls. Sections were subjected to pH cycling for 20 days. Polarized light microscopy and micro-radiography were utilized to record the lesion characteristics before and after pH cycling. Mean lesion depths decreased significantly in all the fluoride groups, and increased significantly in the control groups. There were no differences in percentage of lesion depth decrease when the volume was doubled for the same fluoride concentration. There were also no statistically significant differences between percentages of decrease in lesion depth when the concentration of fluoride in milk was increased. Fluoridated milk demonstrated a remineralization efficacy on early enamel carious lesions. A 2.5 ppm fluoride milk concentration provided similar remineralization potential to that of higher fluoride concentration in milk.
    Journal of dentistry 09/2011; 39(12):817-24. · 2.00 Impact Factor
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    ABSTRACT: To assess the impact of early childhood caries (ECC) on the quality of life in a population of preschool children and their families in Hong Kong. A random sample of 1,296 Chinese preschool children participated in the survey and were subjected to an oral examination for their ECC status by 2 trained examiners. The parents were asked to respond to the Early Childhood Oral Health Impact Scale (ECOHIS) and an extra set of questions concerning their sociodemographic background. The final data analysis included 1,261 children with a mean (±SD) age of 3.9 ± 0.66 years. The prevalence figures for ECC and severe ECC were 19.9 and 15.2%, respectively. Decayed teeth were found in 34.3% of the children while only 5.2% had filled teeth. The mean (±SD) dmft in this group of children was 1.5 ± 2.98. Higher ECOHIS scores were found in parents with lower education or income level, or with children who were born in mainland China (p < 0.05), or with children who had decayed, missing, or filled teeth (p < 0.001). In multiple regression analyses, decayed teeth and filled teeth in primary dentition were the better predictors (p < 0.001) of the ECOHIS score among the various parent and child characteristics collected in this survey. The findings of this study showed that parents of young children with dental caries experience perceived that both the children and other family members had poorer quality of life.
    Caries Research 08/2011; 45(4):370-6. · 2.51 Impact Factor
  • Y L Chan, A H W Ngan, N M King
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    ABSTRACT: Despite being an interface between two mechanically mismatched phases of the soft dentine and hard enamel, the dentine-enamel junction (DEJ) in a human tooth is in general capable of withstanding a long working life of repeated dynamic loading. The current poor understanding of the structure and properties of the DEJ has presented a major obstacle to designing better therapeutic protocols for complications concerning the DEJ. In this investigation, it was discovered that the DEJ is a thin, but gradual interface with characteristics transiting from those of dentine to those of enamel. The collagen fibres in dentine enter into the enamel side of the DEJ and terminate in a region in which the hydroxyapatite crystals begin to show enamel characteristics. Using focused ion beam machining, micro-beams were fabricated from regions within 50 μm of the DEJ and were subjected to bend tests. In spite of the similarity in the flexural strength of the DEJ and enamel, fractographs revealed cracks in the DEJ that propagated along structures with dentine characteristics. To the best of our knowledge, this is the first report on the testing of the mechanical properties of the DEJ.
    Journal of the mechanical behavior of biomedical materials. 07/2011; 4(5):785-95.
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    ABSTRACT: The ADA recommends the use of fluoridated dentifrices as soon as the primary teeth erupt, so as to reduce the incidence of dental caries. However young children can ingest a significant amount of dentifrice during normal toothbrushing; this is a potential problem because the permanent teeth are at risk from fluorosis for the first seven years of life. the objective of this paper was to review the literature on the role of fluoride dentifrices in causing dental fluorosis. Search strategy: a search for literature was performed using MEDLINE, OVID with the key words fluorosis, dentifrice, ingestion, and children. The search was limited to English language publications. Subsequently, 31 articles were retrieved, additional relevant articles were collected from the references cited in the initially identified papers. Ultimately, 96 articles were retrieved for review. Fluoride, should be used with caution so that the benefits out-way the adverse affects. Oral health care providers need to systematically assess individual tooth brushing habits and emphasize the advantages of early use of a fluoridated dentifrice whilst still meeting the need for the prudent use of small quantities of dentifrice. Dentifrices with a low concentration of fluoride may be appropriate for young children who are considered to be at low caries risk and the risk of fluorosis is minimal for children who ingest this dentifrice; nevertheless, it appears that more research is still required on the therapeutic effects of fluoride dentifrices which contain fluoride at a low concentration.
    The Journal of clinical pediatric dentistry 01/2011; 36(2):111-21. · 0.34 Impact Factor
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    ABSTRACT: Estimation of age is an important requisite in forensic, judicial and criminal proceedings. Dental age can be estimated from a dataset that has been prepared from a similar or a different population group. Demirjian and his co-workers proposed dental maturity scores from a French-Canadian population and this has served as a reference dataset for evaluation of age for various population groups. Considering the high number of illegal immigrants who have entered Hong Kong from neighboring countries, age estimation studies on southern Chinese is warranted. This study aimed to validate the applicability of Demirjian's dataset on a southern Chinese population. A total of 182 dental panoramic tomographs comprising an equal number of boys and girls with an age range from 3 to 16 years were scored. Dental maturity scores were obtained from the Demirjian's dataset and dental age was calculated. The difference in chronological and estimated dental ages was calculated using the paired t-test. There was a mean overestimation of dental age of 0.62 years for boys (p < 0.01) and 0.36 years for girls (p < 0.01). Demirjian's dataset is not suitable for estimating the age of 3-16 years old southern Chinese children.
    The Journal of forensic odonto-stomatology 01/2011; 29(2):22-8.
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    ABSTRACT: This study evaluated chlorhexidine release from experimental, chlorhexidine-incorporated polymethyl methacrylate (PMMA)-based resin cements prepared from Super-Bond C&B (Sun Medical) and examined the antimicrobial activity against Streptococcus mutans and Enterococcus faecalis. Chlorhexidine diacetate was added into PMMA polymer to obtain chlorhexidine concentration of 0.0, 1.0, 2.0, 3.0, and 4.0 wt %. Chlorhexidine-incorporated, cured resin disks were immersed in distilled water at 37 degrees C for 5 weeks, and the chlorhexidine release was analyzed by high-performance liquid chromatography. The antibacterial effect of freshly mixed resin cements was examined using the agar diffusion test. For the direct contact test, the wells (n = 6) of microtiter plates were coated with cements. The coated wells were aged up to 3 weeks prior to the placement of bacterial suspensions directly on cured cements. The 3.0 and 4.0% chlorhexidine-incorporated cement exhibited chlorhexidine release for 5 weeks; however, more than 98% of chlorhexidine was retained in resin matrix. No release was detected from the 1.0 and 2.0% incorporated cement at 1 week and 2 weeks, respectively. The agar diffusion test failed to detect antibacterial effects against Enterococcus faecalis, whereas the direct contact test revealed the antibacterial effect of 3.0 and 4.0% incorporated cements against each microbe for 2 weeks. The 3.0 and 4.0% chlorhexidine-incorporated resin cement possessed prolonged chlorhexidine release and antibacterial properties for 2 weeks.
    Journal of Biomedical Materials Research Part B Applied Biomaterials 07/2010; 94(1):134-40. · 2.31 Impact Factor
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    ABSTRACT: This study investigated the effect of incorporating chlorhexidine in a self-etching primer on the bond strength of an adhesive resin cement to dentine and on antibacterial activity. Experimental self-etching primers were prepared by adding chlorhexidine (CHX) diacetate to ED primer 2.0 (Kuraray Medical Inc.) to obtain chlorhexidine concentrations of 1.0 wt% and 2.0 wt%. Human occlusal dentine surfaces were conditioned for 30 s using the experimental primers or pure ED primer. Composite blocks were luted using Panavia F 2.0 (Kuraray Medical Inc.). After storage in water for 24 h, the bonded teeth were sectioned into 0.9 mm x 0.9 mm beams and stressed to failure in tension to examine microtensile bond strength (microTBS). Fractured surfaces were examined with a field-emission scanning electron microscopy (FE-SEM). The morphology of dentine surfaces that were conditioned with each primer was also observed under FE-SEM. An agar diffusion test was performed to examine the antibacterial effect of each primer against Streptococcus mutans and Enterococcus faecalis. Addition of chlorhexidine to the primer had significant effects (p<0.001) on microTBS and antibacterial effect. No significant difference in microTBS was found between the groups that contained 0% and 1% chlorhexidine in the primer (p=0.095). Conversely, the group that contained 2% chlorhexidine showed significantly lower microTBS and pronounced cohesive failures within the thin layer of the primer. Incorporation of chlorhexidine into ED primer 2.0 showed significant antibacterial activities. Conditioning with the 1% chlorhexidine-containing primer had no adverse effect on microTBS.
    Journal of dentistry 03/2010; 38(6):496-502. · 2.00 Impact Factor
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    Nigel M King, S Tongkoom, H M Wong
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    ABSTRACT: Aim: To investigate the prevalence of twelve dental traits in the primary dentition of southern Chinese and compare to these figures with those from different ethnic groups. Materials and Methods: The material used in the study consisted of study casts collected from 936 randomly selected 5-year-old children (493 males and 443 females) in Hong Kong. The anomalies were assessed using diagnostic criteria that have been most often been cited in the published literature. Results: Of the twelve dental traits studied, the prevalence figures of seventh accessory cusp (89.0%), distal trigonid crest (33.5%) and metaconid ridge (84.0%) in the southern Chinese children were higher than reported for other ethnic groups. The prevalence figures for distinct and strong types of protostylid (13.7% and 0.9%), in this study, were also found to be higher than for other populations. However, the prevalence of deflecting wrinkle was 63.0% which was the lowest re-ported for Mongoloids. The prevalences of double lingual tubercle (22.5%) and "Y" type of occlusal groove pattern (80.1%) in southern Chinese children were found to be lower then for other ethnic groups. Conclusion: Higher prevalences of seventh accessory cusp, distal trigonid crest and metaconid ridge can be considered to be characteristics of the southern Chinese primary dentition.
    The Open Anthropology Journal 01/2010; 3:37-53.
  • Y L Chan, A H W Ngan, N M King
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    ABSTRACT: Failure of the enamel adjacent to the defects in teeth with molar incisor hypomineralization (MIH) limits the success rate of the restorations placed in these teeth and this frequently leads to their ultimate extraction. To understand the cause, a state-of-the-art combination of focused ion beam (FIB) and nanoindentation techniques was used to evaluate the fracture properties and microstructure of enamel from specific regions of two MIH teeth. Nanoindentation, bend tests on micro-cantilevers and transmission electron microscopy (TEM) were employed to compare the microstructure and mechanical properties of the unaffected, opaque and transitional region in two MIH teeth. Special attention was paid to the transitional region in all the experiments in an attempt to identify its role in affecting the overall integrity of the MIH teeth. The enamel in the transitional region, despite its translucent appearance under the naked eye, was found, under TEM, to have prism sheaths that were significantly less mineralized than unaffected enamel and were proved to be weaker in holding the prisms together when measured using bend tests on micro-cantilever samples machined from the region. The enamel in the transitional region adjacent to the demarcated defects in MIH has notable alterations in their prism sheaths which likely contribute to their lowered mechanical properties.
    Journal of dentistry 11/2009; 38(3):237-44. · 2.00 Impact Factor
  • Y L Chan, A H W Ngan, N M King
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    ABSTRACT: In this paper, the usefulness of the specimen shaping ability of focused ion beam (FIB) milling in the micrometer scale and the high force resolution of the nanoindentation technique are demonstrated on human primary teeth. Micro-cantilevers, with a triangular cross-section <5 microm in width and 10 microm in length, were produced within 50 microm of the dentin-enamel junction (DEJ) using FIB milling, and were point-loaded at their free ends at 20 microN/s until failure using a nanoindenter. The elastic modulus and flexural strength of such micro-samples of human enamel, and their variation with respect to prism orientation, were studied and compared to data from bulk enamel measured using nanoindentation and three-point bend tests. The elastic modulus of the micro-cantilever samples was found to be comparable to that obtained by nanoindentation on bulk samples, but it demonstrated significant anisotropy commensurate with the microstructure of enamel which was not measurable using nanoindentation on bulk samples. The flexural strength of the enamel micro-cantilevers also exhibited strong anisotropy, and was about one order of magnitude higher than that of bulk specimens measured by three-point bending. Through a Weibull analysis, this size dependence of the strength was found to be similar to the normal behaviour in brittle materials. The flexural strength of the enamel samples was also found to be sensitive to changes in the degree of mineralization of the samples.
    Journal of the mechanical behavior of biomedical materials. 09/2009; 2(4):375-83.
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    ABSTRACT: This study examined the effect of saliva contamination on the microtensile bond strength (microTBS) of resin luting cements to dentin. For RelyX ARC (ARC, 3M ESPE), dentin surfaces were etched with 32% phosphoric acid. The subgroups were: ARC-control (uncontaminated), ARC-I (saliva contamination, blot-dried), ARC-II (saliva contamination, rinse, blot-dried) and ARC-III (saliva contamination, rinse, re-etch, rinse, blot-dried). For Panavia F 2.0 (PF, Kuraray), the subgroups were: PF-control (uncontaminated), PF-I (saliva contamination, dried), PF-II (saliva contamination, rinse, dried), PF-III (primer, saliva contamination, dried), PF-IV (primer, saliva contamination, dried, primer re-applied) and PF-V (primer, saliva contamination, rinse, dried, primer re-applied). Composite blocks were luted onto dentin using the two cements. Bonded specimens were sectioned into 0.9 mm x 0.9 mm beams for muTBS testing. Representative fractured beams were prepared for fractographic analysis. For ARC, salivary contamination of etched dentin (ARC-I) significantly lowered bond strength (p=0.001). Rinsing saliva off with water (ARC-II) restored bond strength to control level. Re-etching dentin surface after rinsing (ARC-III) resulted in the lowest bond strength (p<0.001). For PF, salivary contamination of dentin before (PF-I) and after application of primer (PF-III and PF-IV) significantly lowered bond strength (p<0.001). Rinsing saliva off with water and re-application of primer (PF-II and PF-V) improved bond strength. Saliva contamination during luting deteriorated the bond quality of resin cements. Decontamination by rinsing with water was most effective in restoring the bond strength of RelyX ARC. Decontamination by water-rinsing and primer re-application after rinsing improved the bond strength of Panavia F 2.0.
    Journal of dentistry 08/2009; 37(12):923-31. · 2.00 Impact Factor
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    ABSTRACT: The aim of this study was to investigate the effect of pre-treatment by chlorhexidine on the microtensile bond strength (mTBS) of resin cements and nanoleakage at the resin-dentine interfaces. Cylindrical composite blocks were luted to human dentine using resin cements (RelyX ARC, 3M ESPE: ARC; Panavia F, Kuraray Medical Inc.: PF; RelyX Unicem, 3M ESPE: UN) with/without pre-treatment by 2% chlorhexidine digluconate (CAVITY CLEANSER, Bisco, Inc., Schaumburg, IL, USA). CAVITY CLEANSER was applied on the acid etched dentine for 60s in the ARC group, and on smear layer-covered dentine in the PF and UN groups. After storage in water for 24h, the bonded teeth were sectioned into 1mm thick slabs and further into 0.9mm x 0.9mm beams. After immersion in water or ammoniacal silver nitrate for 24h, the beams were stressed to failure in tension. The fractured surfaces were examined by field-emission scanning electron microscopy (FE-SEM) using backscattered electron mode. The silver-stained slabs were used to examine nanoleakage within the bonded interface by FE-SEM. The resin cement and chlorhexidine treatment had significant effects (p<0.0001) on mTBS; while the storage media had no significant effect (p=0.435). The mTBS of ARC was significantly higher than the other cements. Chlorhexidine reduced mTBS and produced pronounced nanoleakage when PF and UC were luted to dentine. Pre-treatment with chlorhexidine affected the integrity of dentine bonding with PF and UC, while there was no adverse effect on coupling of ARC.
    Journal of dentistry 03/2009; 37(6):440-8. · 2.00 Impact Factor
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    ABSTRACT: This study examined the effect of temperature on water sorption and solubility characteristics of four commercial dental adhesives. The null hypothesis tested was that temperature has no effect on the water sorption and solubility characteristics of these adhesives. The tested materials were: three-step etch-and-rinse (All-Bond 2, AB), two-step etch-and-rinse (One-Step, OS), two-step self-etch (Clearfil SE Bond, SE) and one-step self-etch (Clearfil S3 Bond, S3) adhesives. Seven resin disks (6mm in diameterx1mm in thickness) were prepared from each tested material and were stored in deionized water at 23 degrees C, 37 degrees C and 55 degrees C. Water sorption and solubility of the resin disks were measured before and after water immersion and desiccation following two consecutive sorption and desorption cycles. The water sorption and solubility values obtained were analyzed using two-way ANOVA and Tukey's multiple comparison tests. The relationships between maximum water sorption, solubility and kinetics of water diffusion with temperature were evaluated by means of Pearson correlation statistic. OS exhibited the highest water sorption and solubility values in the second sorption-desorption cycle at 55 degrees C (p<0.001). This is followed by S3, SE and AB with no significant difference between SE and AB. Significant positive correlations were observed between maximum water sorption (r=0.307, p<0.01), solubility (r=0.244, p<0.05), water sorption (r=0.651, p<0.001) and desorption (r=0.733, p<0.001) diffusion coefficients (obtained using Fick's law of diffusion) with temperature in the second cycle. High temperatures increased water sorption of simplified adhesives. Such water sorption may contribute to the failure of resin-dentin bonds.
    Journal of Dentistry 01/2009; 37(2):122-32. · 3.20 Impact Factor

Publication Stats

742 Citations
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101.41 Total Impact Points

Institutions

  • 2013
    • University of Western Australia
      • School of Dentistry
      Perth, Western Australia, Australia
  • 1997–2011
    • The University of Hong Kong
      • • Department of Mechanical Engineering
      • • Faculty of Dentistry
      Hong Kong, Hong Kong
  • 2005
    • Georgia Health Sciences University
      • College of Dental Medicine
      Augusta, GA, United States

Disciplines