Remineralisation of enamel and dentine with stabilised stannous fluoride dentifrices in a randomised cross-over in situ trial.

OBJECTIVES: To compare the remineralisation efficacy and ion bioavailability of two novel SnF2-containing dentifrices in a blinded, cross-over, randomised in situ clinical study. METHODS: Six participants wore removal palatal appliances holding human enamel and dentine blocks with subsurface lesions. Appliances were worn for two treatment periods of 14 consecutive days each, with a one-week washout period in-between. Participants were randomly allocated to rinse with a 1:5 diluted coded slurry of one of two dentifrices containing either 5 % casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) +1100 ppm F as SnF2 [MIPOP], or 1100 ppm F as SnF2 [CT], for 1 min, four times a day. Saliva was collected post-treatment and analysed for tin, calcium, inorganic phosphate and fluoride ions using atomic absorption spectrophotometry and ion chromatography. Enamel and dentine lesions were analysed for percent remineralisation (%R) using transverse microradiography and percent surface microhardness recovery (%SMHR). RESULTS: MIPOP released significantly higher F (3.00 ± 0.27 mM), Ca (15.23 ± 3.23 mM) and Sn (1.18 ± 0.13 mM) into saliva whereas CT released 2.89 ± 0.32 mM F and only 0.84 ± 0.11 mM Ca and 0.28 ± 0.10 mM Sn. MIPOP produced significantly higher %R than CT: 25.6 ± 1.5 % compared to 15.2 ± 0.7 % in enamel, and 33.6 ± 3.1 % compared to 20.6 ± 1.1 % in dentine. Additionally, MIPOP produced significantly higher %SMHR (18.2 ± 7.9 %) compared to CT (4.1 ± 0.6 %). CONCLUSIONS: Both dentifrices promoted remineralisation, but the MIPOP dentifrice with added CPP-ACP and the ion-stabilising effects of CPP released higher amounts of bioavailable tin and produced significantly higher remineralisation and surface microhardness recovery. CLINICAL SIGNIFICANCE: Modern dentifrices contain SnF2 for a range of oral health benefits. Challenges associated with stability of these formulations can affect ion bioavailability, reducing efficacy. Two dentifrices with SnF2 promoted remineralisation in situ, however the dentifrice with the added saliva biomimetic CPP-ACP was superior and therefore may produce greater health benefits.

Preparedness for practice of newly qualified dental practitioners in the Australian context: an exploratory study.

BACKGROUND: The current study explored the perspectives of preparedness for dental practice from a range of relevant stakeholders (i.e., educators, employers, final-year students, graduates, practitioners, and professional associations) using an anonymous online survey in which participants described either their preparedness for practice, or the preparedness of graduates they have encountered, across six domains. RESULTS: A total of 120 participants completed the survey. Participants were from several Australian states and territories; regional, rural, and urban locations; and working in the public and private sector. Students and new graduates generally felt prepared for activities in all the identified domains. Stakeholders reported consistently that the knowledge of dental profession graduates was at the required level to enter practice in Australia in a safe way. Activities involving the knowledge of clinical entrepreneurship and financial solvency were the dimensions where students and graduates felt least prepared (e.g., explaining fees, negotiating finances). In the domains involving clinical and technical competencies, students and new graduates self-assessed as less prepared around managing dental trauma and medical emergencies. On the other hand, activities around social and community orientation, and to a lesser extent professional attitudes and ethical judgements, were the dimensions where students and graduates felt the most prepared. CONCLUSIONS: Present findings indicate that there appear to be good standards of preparedness for practice for graduate dental professionals. This exploratory study provides insights into the nature of preparedness for Australian dental professionals and provides a basis for targeting education and professional development to address areas of need.

Oral health professionals screening for undiagnosed type-2 diabetes and prediabetes: the iDENTify study.

BACKGROUND: As part of an evaluation of an oral healthcare practice-based model that identifies patients with prediabetes or type-2 diabetes, this study reports on the proportion of patients identified with clinically confirmed type-2 diabetes (T2D)/prediabetes and barriers of implementation of the model. METHODOLOGY: Urban and rural oral healthcare practices were invited to participate. Participating practices invited eligible patients to participate in the screening program using the Australian Type-2 Diabetes Risk Assessment Tool (AUSDRISK). Participants were categorised as low, intermediate, or high-risk for prediabetes/T2D. Patients in the intermediate or high-risk category were referred to their General Medical Practitioner (GP) for further investigation. RESULTS: Fifty-one oral healthcare practices and 76 Oral Health Professionals (OHP) participated (60 Dentists, 8 Dental Hygienists, 8 Oral Health Therapists). 797 patients were screened; 102 were low-risk; 331 intermediate-risk; and 364 high-risk for T2D. Of the 695 participants in the intermediate or high-risk groups, 386 (55.5%) were referred to their GP for T2D assessment. Of them, 96 (25.0%) results were returned to OHPs. Of the returned results, six were (6.3%) diagnosed with pre-T2D. CONCLUSION: Patients found to have undiagnosed T2D/prediabetes (6.3%) were within the expected range reported in the literature. Findings indicate that identifying individuals at an elevated risk of having or developing T2D is effective, feasible and could be incorporated into oral healthcare settings. However, this integration may require additional OHPs training and education to ensure that patients at elevated risk of T2D are referred for further assessment.

Breastmilk influences development and composition of the oral microbiome.

Background: Human microbiomes assemble in an ordered, reproducible manner yet there is limited information about early colonisation and development of bacterial communities that constitute the oral microbiome. Aim: The aim of this study was to determine the effect of exposure to breastmilk on assembly of the infant oral microbiome during the first 20 months of life. Methods: The oral microbiomes of 39 infants, 13 who were never breastfed and 26 who were breastfed for more than 10 months, from the longitudinal VicGeneration birth cohort study, were determined at four ages. In total, 519 bacterial taxa were identified and quantified in saliva by sequencing the V4 region of the bacterial 16S rRNA genes. Results: There were significant differences in the development of the oral microbiomes of never breastfed and breastfed infants. Bacterial diversity was significantly higher in never breastfed infants at 2 months, due largely to an increased abundance of Veillonella and species from the Bacteroidetes phylum compared with breastfed infants. Conclusion: These differences likely reflect breastmilk playing a prebiotic role in selection of early-colonising, health-associated oral bacteria, such as the Streptococcus mitis group. The microbiomes of both groups became more heterogenous following the introduction of solid foods.

Temporal development of the infant oral microbiome.

The human oral microbiome is becoming recognized as playing roles in health and disease well beyond the oral cavity over the lifetime of the individual. The oral microbiome is hypothesized to result from specific colonization events followed by a reproducible and ordered development of complex bacterial communities. Colonization events, proliferation, succession and subsequent community development are dependent on a range of host and environmental factors, most notably the neonate diet. It is now becoming apparent that early childhood and prenatal influences can have long term effects on the development of human oral microbiomes. In this review, the temporal development of the infant human oral microbiome is examined, with the effects of prenatal and postnatal influences and the roles of specific bacteria. Dietary and environmental factors, especially breastfeeding, have a significant influence on the development of the infant oral microbiome. The evidence available regarding the roles and functions of early colonizing bacteria is still limited, and gaps in knowledge where further research is needed to elucidate these specific roles in relation to health and disease still exist.

Attitudes and opinions of Oral healthcare professionals on screening for Type-2 diabetes.

BACKGROUND: As part of a larger study on the identification of undiagnosed Type 2 diabetes (T2D), and prediabetes patients in dental settings, this study explored oral healthcare professionals' (OHP) attitudes with respect to the relevance and appropriateness of screening for prediabetes/T2D in general oral healthcare settings. It also aims to gain a deeper understanding of OHPs' concerns and perceived barriers to screening for T2D. METHODS: Semi-structured interviews were conducted with 11 OHPs: eight dentists, two dental hygienists and one oral health therapist. Interviews were audio recorded, transcribed verbatim and analysed using thematic analysis. RESULTS: Themes that emerged from the interviews were organised under three major categories: 1) Implementation: OHPs willingness to screen for prediabetes/T2D; 2) Barriers to implementation of screenings; subdivided into: a) lack of knowledge and formal training about T2D screening methodology; b) concerns about patients' awareness and acceptance of T2D screening in oral healthcare settings; c) costs and reimbursement for the time and resources required to screen patients; and d) legal and scope of practice; and 3) Collaboration and communication between OHPs and General practitioners (GP). CONCLUSIONS: The oral healthcare setting was considered as appropriate for medical screening, and OHPs were willing to participate in screening for prediabetes/T2D. Nonetheless, for the successful implementation of a screening programme, several barriers need to be addressed, and effective medical screening would require collaboration between oral health and medical and other health professionals, as well as clarification of legal and reimbursement issues.

Experiences of oral health: before, during and after becoming a regular user of GC Tooth Mousse Plus®.

BACKGROUND: Clinical trials and laboratory studies from around the world have shown that GC Tooth Mousse Plus® (TMP) is effective in protecting teeth from tooth decay and erosion, buffering dental plaque pH, remineralising white spot lesions and reducing dentine hypersensitivity. However, no other study has assessed the experiences of oral health, before, during and after individuals becoming regular users of TMP. The aim of this study was to identify how participants' oral health status changed after introducing TMP into their oral hygiene routine. METHODS: A qualitative study using Charmaz's grounded theory methodology was conducted. Fifteen purposively sampled regular users of TMP were interviewed. Transcripts were analysed after each interview. Data analysis consisted of transcript coding, detailed memo writing, and data interpretation. RESULTS: Participants described their experiences of oral health and disease, before, during and after introducing TMP into their daily oral hygiene routine, together with the historical, biological, financial, psychosocial, and habitual dimensions of their experiences. Before becoming a regular user of TMP, participants described themselves as having a damaged mouth with vulnerable teeth, dry mouth, and sensitivity. Various aspects of participants' histories were relevant, such as, family history and history of oral disease. Having a damaged mouth with vulnerable teeth, dry mouth and sensitivity was explained by those elements. Despite some initial barriers, once being prescribed TMP by a dental professional, a three-fold process of change was initiated: starting a new oral hygiene routine, persevering daily, and experiencing reinforcing outcomes. This process led to a fundamental lifestyle change. Participants transitioned from having a damaged mouth with vulnerable teeth to having a comfortable mouth with strong teeth; at the same time participants felt empowered by this newly found status of being able to keep their teeth for life. Barriers and facilitators for incorporating TMP on daily oral hygiene routine were also identified. CONCLUSIONS: Participants valued having a comfortable mouth with strong teeth, which did not require repeated restorations. Seeing concrete results in their mouths and experiencing a more comfortable mouth boosted adherence to daily applications of TMP, which was maintained over time.

Higher donor body mass index is associated with increased hemolysis of red blood cells at 42-days of storage: A retrospective analysis of routine quality control data.

BACKGROUND: For reasons unclear, some stored red blood cells (RBCs) have low hemolysis, while others have high hemolysis, which impacts quality consistency. To identify variables that influence hemolysis, routine quality control (QC) data for 42-days-stored RBCs with corresponding donor information were analyzed. STUDY DESIGN AND METHODS: RBC QC and donor data were obtained from a national blood supplier. Regression models and analyses were performed on total cohort stratified by donor sex and by high hemolysis (≥90th percentile) vs control (<90th percentile) samples, including matching. RESULTS: Data included 1734 leukoreduced RBCs (822 female, 912 male), processed by buffy coat-poor or whole blood filtration methods. Male RBCs had larger volume, hemoglobin content, and higher hemolysis than female RBCs (median hemolysis, 0.24% vs 0.21%; all P < .0001). Multivariable regression identified increased body mass index (BMI) and RBC variables were associated with higher hemolysis (P < .0001), along with older female age and buffy coat-poor processing method (P < .002). Logistic regression models comparing the high and control hemolysis subsets, matched for RBC component variables and processing method, identified overweight-obese BMI (>27 kg/m2 ) in males remained the single donor-related variable associated with higher hemolysis (P < .0001); odds ratio, 3 (95% confidence interval [CI], 1.3-6.7), increasing to 4 (95% CI, 1.8-8.6) for obese males (BMI > 30 kg/m2 ). Female donor obesity and older age trended toward higher hemolysis. CONCLUSION: Donor BMI, sex, and female age influence the level of hemolysis of 42-days-stored RBCs. Other factors, not identified in this study, also influence the level of hemolysis.

The prebiotic effect of CPP-ACP sugar-free chewing gum.

OBJECTIVES: To determine if chewing gum containing casein phosphopeptide stabilised amorphous calcium phosphate (CPP-ACP) promoted an increase in the abundance of Streptococcus sanguinis and other species associated with dental health in supragingival plaque in a clinical study. MATERIALS AND METHODS: Nineteen participants were recruited for a three-leg cross-over, randomised, controlled clinical trial. Participants chewed a sugar-free gum with or without CPP-ACP six times daily for 20 min over two weeks. The study also involved no gum chewing (no gum) for the same two week period. Participants were randomly assigned to one of the test gums or no gum for each intervention period. Participants abstained from oral hygiene and had washout periods of two weeks between intervention periods. After each intervention period, supragingival plaque was collected and analysed for bacterial composition by sequencing the V4 variable region of the 16S rRNA gene. Data were analysed using a linear mixed model. RESULTS: The CPP-ACP gum intervention produced a significant (p < 0.01) increase in the proportions of S. sanguinis (112%), as well as the commensal species Rothia dentocariosa (127%), Corynebacterium durum (80%) and Streptococcus mitis (55%) when compared with the no gum intervention. All the species that were promoted by the CPP-ACP gum are known to possess one or both of the alkali-producing enzymes arginine deiminase and nitrate reductase. CONCLUSION: This clinical study demonstrated that chewing a sugar-free gum containing CPP-ACP promoted prebiosis by significantly increasing the proportion of S. sanguinis and other health-associated bacterial species in supragingival plaque. CLINICAL SIGNIFICANCE: Regular chewing of CPP-ACP sugar-free gum increases the proportions of health-associated commensal species in supragingival plaque to promote prebiosis and oral homeostasis.

Quantitative analysis of enamel on debonded orthodontic brackets.

INTRODUCTION: Iatrogenic damage to the tooth surface in the form of enamel tearouts can occur during removal of fixed orthodontic appliances. The aim of this study was to assess debonded metal and ceramic brackets attached with a variety of bonding materials to determine how frequently this type of damage occurs. METHODS: Eighty-one patients close to finishing fixed orthodontic treatment were recruited. They had metal brackets bonded with composite resin and a 2-step etch-and-bond technique or ceramic brackets bonded with composite resin and a 2-step etch-and- bond technique, and composite resin with a self-etching primer or resin-modified glass ionomer cement. Debonded brackets were examined by backscattered scanning electron microscopy with energy dispersive x-ray spectroscopy to determine the presence and area of enamel on the base pad. RESULTS: Of the 486 brackets collected, 26.1% exhibited enamel on the bonding material on the bracket base pad. The incidences of enamel tearouts for each group were metal brackets, 13.3%; ceramic brackets, 30.2%; composite resin with self-etching primer, 38.2%; and resin-modified glass ionomer cement, 21.2%. The percentage of the bracket base pad covered in enamel was highly variable, ranging from 0% to 46.1%. CONCLUSIONS: Enamel damage regularly occurred during the debonding process with the degree of damage being highly variable. Damage occurred more frequently when ceramic brackets were used (31.9%) compared with metal brackets (13.3%). Removal of ceramic brackets bonded with resin-modified glass ionomer cement resulted in less damage compared with the resin bonding systems.

Validation of quantitative light-induced fluorescence-digital in the quantification of demarcated hypomineralized lesions of enamel.

AIM: The aim of the present study was to determine the validity of quantitative light-induced fluorescence-digital (QLF-D) in regard to the detection and quantification of developmental demarcated hypomineralized lesions of enamel in vitro when compared to micro-computed tomography (CT) determination of lesion characteristics. A secondary aim was to develop a protocol for 3-D analysis using micro-CT. METHODS: Twenty-four hypomineralized defects were classified as cream/white (CW), yellow/brown (YB), and post-eruptive breakdown. Teeth were scanned using micro-CT. Grayscale and chromatic vertical sections were constructed. Mineral density and porosity percentage were calculated. Fluorescence loss and red fluorescence were determined from images. Linear mixed models were computed. RESULTS: Mineral density and porosity mean values by lesion type were statistically different (P<.001). CW lesions had lower fluorescence loss than YB and broken lesions. Red fluorescence was emitted by the majority of the defects, and the means between lesion types were statistically different (P<.001). The mixed model indicated that mineral density was not correlated with fluorescence loss and lesion type. CONCLUSION: The present findings support QLF-D as a method to detect hypomineralized lesions of different clinical presentation, with red fluorescence putatively related to the severity of the defects. The micro-CT 3-D approach is a reliable method to analyze structural changes in hypomineralized enamel.

Comparative study of the measurement of enamel demineralization and remineralization using transverse microradiography and electron probe microanalysis.

Transverse microradiography (TMR) and electron probe microanalysis (EPMA) are commonly used for characterizing dental tissues. TMR utilizes an approximately monochromatic X-ray beam to determine the mass attenuation of the sample, which is converted to volume percent mineral (vol%min). An EPMA stimulates the emission of characteristic X-rays from a variable volume of sample (dependent on density) to provide compositional information. The aim of this study was to compare the assessment of sound, demineralized, and remineralized enamel using both techniques. Human enamel samples were demineralized and a part of each was subsequently remineralized. The same line profile through each demineralized lesion was analyzed using TMR and EPMA to determine vol%min and wt% elemental composition and atomic concentration ratio information, respectively. The vol%min and wt% values determined by each technique were significantly correlated but the absolute values were not similar. This was attributable to the complex ultrastructural composition, the variable density of the samples analyzed, and the nonlinear interaction of the EPMA-generated X-rays. EPMA remains an important technique for obtaining atomic ratio information, but its limitations in determining absolute mineral content indicate that it should not be used in place of TMR for determining the mineral density of dental hard tissues.

Antibiotic susceptibility of Aggregatibacter actinomycetemcomitans JP2 in a biofilm.

BACKGROUND: Localized aggressive periodontitis (LAgP) is an inflammatory disease associated with specific bacteria, particularly Aggregatibacter actinomycetemcomitans, which can result in early tooth loss. The bacteria grow as a biofilm known as subgingival plaque. Treatment includes mechanical debridement of the biofilm, often associated with empirical antibiotic treatment. OBJECTIVE: The aims of this study were to test in vitro the sensitivity of A. actinomycetemcomitans JP2 during planktonic and biofilm growth to doxycycline and to the combination of metronidazole and amoxicillin, which are two antibiotic protocols commonly used in clinical practice. DESIGN: Two in vitro biofilm models were used to test the effects of the antibiotics: a static 96-well plate assay was used to investigate the effect of these antibiotics on biofilm formation whilst a flow chamber model was used to examine the effect on established biofilms. RESULTS: Of the antibiotics tested in this model system, doxycycline was most efficacious with a minimal inhibitory concentration (MIC) against planktonic cells of 0.21 mg/L and minimal biofilm inhibitory concentration (MBIC) of 2.10 mg/L. The most commonly prescribed antibiotic regimen, amoxicillin + metronidazole, was much less effective against both planktonic and biofilm cells with an MIC and MBIC of 12.0 mg/L and 20.2 mg/L, respectively. A single treatment of the clinically achievable concentration of 10 mg/L doxycycline to sparse A. actinomycetemcomitans biofilms in the flow chamber model resulted in significant decreases in biofilm thickness, biovolume, and cell viability. Dense A. actinomycetemcomitans biofilms were significantly more resistant to doxycycline treatment. Low concentrations of antibiotics enhanced biofilm formation. CONCLUSION: A. actinomycetemcomitans JP2 homotypic biofilms were more susceptible in vitro to doxycycline than amoxicillin + metronidazole.

Streptococcus mutans biofilm disruption by κ-casein glycopeptide.

UNLABELLED: Caseinomacropeptide (CMP), the variably phosphorylated and glycosylated forms of the bovine milk protein fragment, κ-casein(106-169), is produced during cheese production and has been shown to have a range of antibacterial bioactivities. OBJECTIVES: To characterise the biofilm disruptive component of CMP and compare its activity with the known antimicrobial agents chlorhexidine and zinc ions. METHODS: Streptococcus mutans biofilms were grown in flow cells with an artificial saliva medium containing sucrose and treated with CMP and the glycosylated forms of κ-casein(106-169) (κ-casein glycopeptide, KCG). The biofilms were imaged using confocal laser scanning microscopy (CLSM) and quantified by COMSTAT software analysis. A static biofilm assay and flow cytometric analysis were used to examine the mechanism of action of chlorhexidine and a combination of KCG with the known antimicrobial agent ZnCl2 (KCG-Zn). RESULTS: CLSM analysis showed that S. mutans produced robust, structured biofilms with an average thickness of 7.37µm and a biovolume of 3.88µm(3)/µm(2) substratum after 16h of incubation in the flow cell system. A single application of 10mg/mL CMP that contained 2.4mg/mL KCG significantly reduced total biofilm biovolume and average biofilm thickness by 53% and 61%, respectively. This was statistically the same as a 2.4mg/mL KCG treatment that reduced the total biovolume and average thickness by 59% and 69%, respectively, suggesting the KCG was the biofilm disruptive component of CMP. Chlorhexidine treatment (0.1%) caused similar effects in the flow cell model. KCG-Zn caused significantly more disruption of the biofilms than either KCG or ZnCl2 treatment alone. In a static biofilm model chlorhexidine was shown to work by disrupting bacterial membrane integrity whilst KCG-Zn had no effect on membrane integrity. CONCLUSIONS: KCG and KCG-Zn may have potential as natural biofilm disruptive agents.

Choosing the esthetic angle of the face: experiments with laypersons and prosthodontists.

STATEMENT OF PROBLEM: Most faces are not symmetrical, and this complicates the task of aligning the anterior segment of the teeth for the restorative dentist, orthodontist, or oral and maxillofacial surgeon. The dental literature provides conflicting advice regarding guidelines for aligning the anterior teeth. PURPOSE: The purpose of this study was to determine the sensitivity of laypersons to variations in the alignment of the anterior segment within a symmetrical face, and to investigate which guidelines were preferred by laypersons and prosthodontists when aligning this segment. MATERIAL AND METHODS: Lay participants (21) were shown a series of 25 modified images of faces on a computer screen and asked to indicate 'noticeability' of tilt and, with another series of 19 images, preference for angulation of the anterior segment. Prosthodontists (14) were shown a further set of 7 images and asked to use a Clinometer to select an appropriate angle. Statistical comparisons were performed with multinomial goodness-of-fit tests and repeated measures ANOVA, followed by Sidak multiple comparisons tests (α=.05). RESULTS: The average angle at which the tilt of the anterior segment within a symmetrical face became noticeable to the laypersons was approximately 1 degree. No significant correlation (P=.15) was found between the laypersons' choice of angle for the anterior segment and the angle of the eyes, lips, or horizon, but an angle of 0 degrees was chosen significantly more often than the other angles offered (P<.001). The prosthodontists generally chose an angle close to zero. CONCLUSIONS: The results suggest that the threshold tilt within a symmetrical face, for noticeability by laypersons, is about 1 degree, and that for both laypersons and prosthodontists, the most important guideline is not any individual facial feature or the horizon but the face as a whole.

The clinical application of surface pH measurements to longitudinally assess white spot enamel lesions.

OBJECTIVES: Means of objectively assessing white spot enamel lesions (WSEL) are critical for determining their potential activity and monitoring the success of preventive treatments. The aim of this study was to determine whether surface pH measurements of WSEL changed during a preventive course of care designed to remineralize the lesions. METHODS: Eight healthy subjects (1 male and 7 females) with at least one WSEL were recruited (19-64 years). Each subject was placed on a preventive treatment program including the daily application of a CPP-ACP paste (MI paste, GC Corp., Japan) with custom fitted trays for more than 6 months. The surface pH values of sound enamel and WSEL were monitored for up to 2 years using a micro-pH sensor. The visual appearance of the WSEL was monitored via digital photography, and images were analyzed qualitatively on a 5-point scale to assess the success of the remineralization preventive program. The relationship between the qualitative assessment of WSEL appearance and the WSEL pH was investigated using a Spearman's rho non-parametric correlation. RESULTS: The surface pH of the WSEL was different to that of the sound enamel surrounding it in all patients at all times. All lesions showed visual improvement as the treatment period progressed. The pH of the WSEL increased towards that of sound enamel over the course of treatment significantly correlating with the visual improvement of the lesion (rho=0.63, p<0.0001). CONCLUSIONS: The clinical assessment of WSEL surface pH changes with time may have utility as an additional objective measure for the assessment of WSEL activity.

Enamel microhardness and bond strengths of self-etching primer adhesives.

The aim of this study was to determine the relationship between enamel surface microhardness and microshear bond strength (microSBS). Buccal and lingual mid-coronal enamel sections were prepared from 22 permanent human molars and divided into two groups, each comprising the buccal and lingual enamel from 11 teeth, to analyze two self-etching primer adhesives (Clearfil SE Bond and Tokuyama Bond Force). One-half of each enamel surface was tested using the Vickers hardness test with 10 indentations at 1 N and a 15-s dwell time. A hybrid resin composite was bonded to the other half of the enamel surface with the adhesive system assigned to the group. After 24 h of water storage of specimens at 37 degrees C, the microSBS test was carried out on a universal testing machine at a crosshead speed of 1 mm min(-1) until bond failure occurred. The mean microSBS was regressed on the mean Vickers hardness number (VHN) using a weighted regression analysis in order to explore the relationship between enamel hardness and microSBS. The weights used were the inverse of the variance of the microSBS means. Neither separate correlation analyses for each adhesive nor combined regression analyses showed a significant correlation between the VHN and the microSBS. These results suggest that the microSBS of the self-etch adhesive systems are not influenced by enamel surface microhardness.

A prospective clinical study of bone augmentation techniques at immediate implants.

The efficacy of combinations of membranes and autogenous bone grafts at immediate implants were compared in a prospective study. Sixty-two consecutively treated patients each received an immediate implant for a single tooth replacement at a maxillary anterior or premolar site. Dimensions of the peri-implant defect at the implant collar were measured as follows: vertical defect height (VDH), horizontal defect depth (HDD) and horizontal defect width (HDW). Each implant randomly received one of five augmentation treatments and were submerged with connective tissue grafts: Group 1 (n=12)--expanded polytetrafluoroethylene membrane only, Group 2 (n=11)--resorbable polylactide/polyglycolide copolymer membrane only, Group 3 (n=13)--resorbable membrane and autogenous bone graft; Group 4 (n=14)--autogenous bone graft only, and Group 5 (n=12)--no membrane and no bone graft control. At re-entry, all groups showed significant reduction in VDH, HDD and HDW. Comparisons between groups showed no significant differences for VDH (mean 75.4%) and HDD (mean 77%) reduction. Significant differences were observed between groups for HDW reduction (range, 34.1-67.3%), with membrane-treated Groups 1, 2 and 3 showing the greatest reduction. In the presence of dehiscence defects of the labial plate, HDW reduction of 66.6% was achieved with membrane use compared with 37.7% without membranes. Over 50% more labial plate resorption occurred in the presence of a dehiscence defect irrespective of the augmentation treatment used. The results indicate that VDH and HDD reduction at defects adjacent to immediate implants may be achieved without the use of membranes and/or bone grafts.

Leukemia risk associated with low-level benzene exposure.

BACKGROUND: Men who were part of an Australian petroleum industry cohort had previously been found to have an excess of lympho-hematopoietic cancer. Occupational benzene exposure is a possible cause of this excess. METHODS: We conducted a case-control study of lympho-hematopoietic cancer nested within the existing cohort study to examine the role of benzene exposure. Cases identified between 1981 and 1999 (N = 79) were age-matched to 5 control subjects from the cohort. We estimated each subject's benzene exposure using occupational histories, local site-specific information, and an algorithm using Australian petroleum industry monitoring data. RESULTS: Matched analyses showed that the risk of leukemia was increased at cumulative exposures above 2 ppm-years and with intensity of exposure of highest exposed job over 0.8 ppm. Risk increased with higher exposures; for the 13 case-sets with greater than 8 ppm-years cumulative exposure, the odds ratio was 11.3 (95% confidence interval = 2.85-45.1). The risk of leukemia was not associated with start date or duration of employment. The association with type of workplace was explained by cumulative exposure. There is limited evidence that short-term high exposures carry more risk than the same amount of exposure spread over a longer period. The risks for acute nonlymphocytic leukemia and chronic lymphocytic leukemia were raised for the highest exposed workers. No association was found between non-Hodgkin lymphoma or multiple myeloma and benzene exposure, nor between tobacco or alcohol consumption and any of the cancers. CONCLUSIONS: We found an excess risk of leukemia associated with cumulative benzene exposures and benzene exposure intensities that were considerably lower than reported in previous studies. No evidence was found of a threshold cumulative exposure below which there was no risk.