Shear bond strength of orthodontic brackets bonded to high-translucent dental zirconia with different surface treatments: An in vitro study

PURPOSE

The objective of this study was to compare the shear bond strengths of orthodontic brackets bonded to translucent dental zirconia samples which are anatomically accurate and treated with various surface treatments.

METHODS

This in vitro study included 156 samples from 3 brands of high-translucent zirconia split into a control group and 4 surface treatment groups: 9.6% hydrofluoric acid etching, 50-micron aluminium oxide particle air abrasion, and 30-micron tribochemical silica coating (TBS) particle air abrasion with and without silane application. After surface treatment, all groups were primed with a 10-MDP primer and bonded to metal orthodontic brackets. Shear bond strength (SBS) was tested and results were compared between all groups. Data analysis consisted of a balanced two-factor factorial ANOVA, a Shapiro-Wilks test, and a non-parametric permutation test. The significance level was set at 0.05.

RESULTS

Among all surface treatments, aluminium oxide particle abrasion produced significantly higher SBS (P≤0.002). Lava™ Plus zirconia samples had significantly higher SBS than Cercon® samples (P<0.0001). TBS surface treatment produced significantly higher SBS on Lava™ Plus samples than it did on the other zirconia brands (P=0.032).

CONCLUSIONS

This study indicated that mechanical abrasion using aluminium oxide in combination with a 10-MDP primer creates a higher SBS to high-translucent zirconia than the bond created by tribochemical silica coating. Also, there was no significant difference in ARI regardless of zirconia brand or surface preparation.

Shear bond strength of adhesive precoated brackets: A comparative in vitro study

OBJECTIVE

This study compared the shear bond strength of orthodontic precoated brackets from different manufacturers.

METHODS

Sixty extracted human premolar teeth were divided into six groups (n=10). The groups were bonded with one of the following brackets: 3M™ Unitek Victory™ Series™ with APC, 3M™ Unitek Clarity™ Advanced Ceramic™ with APC, TP Nu-Edge® NX Cobalt-Chromium and TP In-Vu® ceramic Readi-Base® both with eXact® orthodontic adhesive, 3M™ Unitek Clarity Advanced Ceramic™ and 3M™ Unitek Victory™ Series™ both with Transbond™ XT Adhesive. Each group was tested for shear bond strength using a universal testing machine. Each sample was observed under a dissecting microscope and received an adhesive remnant index (ARI) score. Statistical analysis was performed using Tukey's Standardized Range (HSD) Test to make comparisons among all groups and a Wilcoxon rank-sum test to evaluate for pairwise comparisons between the groups. The P-values<0.05 were considered significant.

RESULTS

The ceramic control was not statistically different from the metal control, 3M™ Victory™ APC™, TP In-Vu® ceramic eXact® or TP Nu-EDGE® eXact® in terms of shear bond strength (7.69±1.41MPa, 7.72±1.25MPa, 8.70±1.93MPa, 4.90±1.76MPa, 5.33±0.78MPa, respectively). However, it was statistically different from 3M™ Ceramic APC™ (10.29±2.78MPa). In terms of modulus, there were no statistical differences. TP's Nu-edge® had the lowest average ARI score, but was not statistically different when compared to the other groups.

CONCLUSION

3M™ Unitek's Ceramic APC had a statistically higher SBS than the non-precoated brackets and TP Orthodontics' precoated brackets. However, all SBS were 4.9 MPA or above, which is deemed clinically acceptable in terms of laboratory forces. There was no statistical difference between manufacturing companies or precoated vs. non-precoated modulus and ARI scores.

Comparison of AudaxCeph®'s fully automated cephalometric tracing technology to a semi-automated approach by human examiners

OBJECTIVE

To compare the reliability of cephalometric landmark identification by an automated tracing software based on convolutional neural networks to human tracers.

MATERIALS AND METHODS

Sixty cephalograms were traced by two board-certified orthodontists and AudaxCeph®'s artificial intelligence software. The following thirteen landmarks were identified in each tracing: Sella, Nasion, A point, B point, Porion, Menton, Pogonion, Orbitale, Gonion, Upper Central Incisor Incisal Edge (U1 Tip), Upper Central Incisor Root Apex (U1 apex), Lower Central Incisor Incisal Edge (L1 Tip), Lower Central Incisor Root Apex (L1 apex). An x-y axis was positioned in the bottom left corner of each cephalogram, and the x- and y-coordinates for the landmarks were exported into Excel. Distributions of landmarks (X, Y, radial distance) were compared using t-tests of equivalence with a 2mm equivalence bound. These compared the AI position to the two orthodontists - and the orthodontists' reliability by comparing equivalence against each other.

RESULTS

There was no statistical difference between the orthodontists and AudaxCeph®'s automatic tracing software except for the x- and y-dimension of Porion and the y-dimension of L1 apex. The two orthodontists had good intra-examiner reliability with no statistical difference found when comparing them.

CONCLUSION

AudaxCeph®'s automated cephalometric tracing software is a good adjunctive tool to use when diagnosing and treatment planning orthodontic cases.

Comparison of Tie Wing Fracture Resistance of Differing Ceramic Brackets

OBJECTIVE

The aim of this study was to compare the tie wing fracture resistance of 4 different manufacturers' ceramic brackets currently on the market.

METHODS

The tie wings of ceramic brackets from 4 manufacturers were tested with 10 samples in each group. The brackets were Ormco Symetri, 3M Clarity, American Radiance Plus, and Dentsply Ovation S. The brackets were mounted and fixed in a universal testing machine. A stainless steel ligature wire was looped around a tie wing and the mean tensile strength was both tested and recorded.

RESULTS

There was a significant overall difference in tensile strength among the 4 groups (P < .0001) with the 3M Clarity brackets having the highest MPa. When the groups were compared to each other, they also showed a significant difference in mean tensile strength with the exception being the American Radiance Plus and Ormco Symetri brackets.

CONCLUSION

Test results concluded that the 3M Clarity brackets had the highest resistance to tie wing fracture, while the Dentsply Ovation S brackets had the lowest resistance.

Formulation and characterization of experimental orthodontic adhesive containing antibacterial dimethacrylate DABCO monomers: An in vitro study

OBJECTIVE

The purpose of the study was to investigate the antibacterial efficacy and mechanical properties of experimental orthodontic adhesives containing newly synthesized antibacterial dimethacrylate monomers with doubly charged 1,4-diazabicyclo[2.2.2]octane (DABCO) group (dication).

METHODS

Experimental orthodontic adhesives were formulated using varying compositions of synthesized antibacterial dimethacrylate monomers containing DABCO dication, C16DC2DMA and BisC11DCDMA, replacing part of the control group, Transbond™XT. The concentrations of monomers tested were 5% C16DC2DMA, 10% C16DC2DMA, 5% BisC11DCDMA, and 10% BisC11DCDMA. The biofilm-inhibition effects of the experimental adhesives against Streptococcus mutans were tested. Brackets were then bonded to extracted human teeth utilizing the experimental adhesives in the bonding protocol. The shear bond strength and modulus of elasticity of the control and experimental groups were tested. The adhesive remnant index scores were recorded.

RESULTS

The experimental adhesives containing 5% or 10% BisC11DCDMA and 10% C16DC2DMA showed significantly lower S. mutans colony forming units (CFU) than the control. Both BisC11DCDMA experimental groups displayed similar mechanical properties as compared to the control, although 10% C16DC2DMA showed a reduction in shear bond strength as compared to the control. For all experimental adhesives, the adhesive remnant index scores were not significantly different compared to the control.

CONCLUSION

BisC11DCDMA is a novel antibacterial dimethacrylate monomer that exhibits the significant ability to inhibit bacterial growth while maintaining acceptable mechanical properties. When incorporated into orthodontic adhesives, this monomer may reduce the occurrence of white spot lesions around brackets in orthodontic patients.

Quantifying the degree of white spot lesions on enamel caused by different commercial beverages using the Canary Caries Detection System: An in vitro study

Background. The use of sports and energy drinks has drastically increased in the adolescent population. This population often is in orthodontic treatment, and the use of such drinks with poor oral hygiene promotes the development of white spot lesions (WSLs). Quantifying the degree of the lesion has been limited in the past. The hypothesis was that the Canary Caries Detection System could be used to quantify the degree of WSLs caused by different commercial beverages. Methods. A total of 105 extracted human premolars were divided into seven groups (n=15). Each group was tested in one of six beverages or a phosphate-buffered solution (control). The teeth were exposed to its beverage three times a day for 15 minutes for 28 days. Canary numbers and ambient light and fluorescent photographs were collected at baseline (T0 ) and on days 14 (T1 ) and 28 (T2 ). Results. The paired t test and one-way ANOVA found that T0 to T1 measurements were statistically significant (P<0.0015) and that T0 to T2 measurements were statistically significant (P<0.0001). Visually, the ambient light photographs and fluorescent photographs from T0 to T1 and T1 to T2 correlated with the increase in Canary numbers. Conclusion. This in vitro study revealed a statistically significant increase in the T0 to T1 Canary numbers and a statistically significant increase from T0 to T2 Canary numbers for all the test beverages. Changes in Canary numbers indicated significant changes in mineral density (i.e., demineralization) and development of WSLs on enamel after exposure to sports and energy beverages.

Formulation and characterization of antibacterial orthodontic adhesive

OBJECTIVE

The objective of this study was to formulate experimental orthodontic bracket adhesives and test their mechanical properties, fluoride release and antibacterial activity.

METHODS

Four experimental antibacterial orthodontic bracket adhesives were prepared with different compositions of synthesized antibacterial monomers replacing total 5% of dental monomers in the control Transbond XT (3M): 5%C11, 3.5%C11+1.5%C2, 5%C16, and 3.5%C16+1.5%C2. Transbond XT alone was used as control. These groups were used to bond premolar brackets to extracted premolars. Shear bond strength (SBS) was tested using an Instron machine. For antibacterial test, disk specimens (10mm diameter, 1mm thick, n=4) were fabricated and incubated with cultures of cariogenic Streptococcus mutans for 48h, and following gentle sonication, S. mutans biofilms in colony-forming-units (CFU) on the disks were enumerated by plating on agar medium. The data were analyzed using ANOVA and Tukey test (α=0.05).

RESULTS

All experimental groups had similar shear bond strength (no significant difference) to the control. All experimental groups showed significant inhibitory effect against S. mutans biofilm formation, when compared to the control, but there was no significant difference between experimental groups.

CONCLUSION

Antibacterial orthodontic adhesive can be fabricated to have similar mechanical properties but better caries-inhibitory effect than current adhesive.

Shear bond strength of orthodontic brackets bonded to a new all-ceramic crown composed of lithium silicate infused with zirconia: An in vitro comparative study

AIM

This study sought to determine whether a clinically acceptable shear bond strength (SBS) of metal orthodontic brackets is achievable to CAD/CAM (Computer-Aided Design/Manufacturing) lithium silicate infused with zirconia and whether a chemical pre-treatment bonding protocol produced a higher shear bond strength.

MATERIALS AND METHODS

Twenty lithium silicate infused with zirconia (CELTRA® DUO) samples, twenty zirconia samples, and twenty lithium disilicate samples were fabricated to replicate the facial surface of a mandibular left first molar. The samples were split into two test groups, one of which received a chemical pre-treatment protocol (hydrofluoric acid etch). Shear bond strength testing was conducted and the mean, maximum, minimal, and standard deviation SBS values for each were calculated and recorded in MPa. An Adhesive Resin Index (ARI) score was also assigned to each sample to assess the mode of bond failure.

RESULTS

SBS of the lithium silicate infused with zirconia groups were significantly less than the chemically pre-treated lithium disilicate group, however both materials, when chemical pre-treatment protocol was used, were not statistically different than the enamel control.

CONCLUSIONS

Orthodontic bonding to lithium silicate infused with zirconia yielded a weaker shear bond strength than bonding to traditional lithium disilicate, however, when the surface was pre-treated with hydrofluoric acid etch it provides a bond strength that is within an acceptable clinical range.

Effectiveness of Vanish XT in Reducing the Development of White Spot Lesions: An In Vitro Study

PURPOSE

To evaluate the effectiveness of Vanish XT in preventing white spot lesions (WSLs) when placed around orthodontic brackets. The efficacy of Vanish XT was compared with that of Pro Seal, a commercially available product already proven in preventing demineralization.

MATERIALS AND METHODS

Sixty extracted human canine teeth were divided into three groups (n = 20). The two experimental groups were treated with either Vanish XT or Pro Seal. A third group received no treatment (control). Ethidium bromide with DNA was added to and mixed with the products to produce fluorescence to verify retention of the experimental products. The teeth were submersed in a lactic acid solution for 32 days to create WSLs. All sample teeth were brushed twice daily with a non-fluoride toothpaste to evaluate retention of the experimental products. Photos were taken under fluorescence microscopy and white light at three time intervals. Demineralization was quantified utilizing computer software, and photos were analyzed to obtain values for percent surface area of demineralization and surface color change.

RESULTS

Percent surface area of WSL data, both under white light conditions and fluorometric analysis, revealed a significant difference between Pro Seal and Vanish XT when compared with the control group. No significant differences were found between Pro Seal and Vanish XT treated teeth. Fluorescence evaluation revealed that both experimental products were largely removed by 32 days of brushing and acid exposure.

CONCLUSION

Vanish XT is effective in preventing demineralization around orthodontic brackets. Its preventive efficacy is equivalent to that of Pro Seal.

Die Untersuchung fast-adiabatischer Stöße mit Spaltprodukten

Spaltprodukte wurden in Targets verschiedener Ordnungszahlen abgebremst. Die dabei auftretende Ionisation innerer Elektronenschalen wurde mit Hilfe der charakteristischen RÖNTGEN-Strahlung als Funktion der Energie der Spaltprodukte, der Masse der Spaltprodukte und der Ordnungszahl der Target-Atome gemessen. Ferner wurde eine Abhängigkeit der Energie der L-Strahlung der Spaltprodukte von der Ordnungszahl der Target-Atome gefunden.

Comparison of larval foraging behavior of Aedes albopictus and Aedes japonicus (Diptera: Culicidae)

Aedes albopictus (Skuse) (Diptera: Culicidae) invaded the United States in 1985 and spread rapidly across eastern North America, whereas Aedes japonicus (Theobald) invaded and became established in the United States more recently (1998). The two species may co-occur in container habitats, and they are of potential public health concern as arbovirus vectors. To evaluate ecological differences between Ae. albopictus and Ae.japonicus, we compared larval foraging behavior of these two species. Based on results from a previous competition experiment, we predicted that Ae. albopictus would be a more active forager than Ae. japonicus. However, Ae. japonicus exhibited greater foraging activity than Ae. albopictus in four of six food environments, including a "no food" control treatment. Our results, therefore, suggest that more active foraging does not connote superior competitive ability, and competitive interactions between these species may be mediated by factors other than feeding behavior.

Inbreeding depression in benign and stressful environments

Understanding the consequences of inbreeding has important implications for a wide variety of topics in population biology. Although it is often stated in the literature that the deleterious effects of inbreeding (inbreeding depression) are expected to be more pronounced under stressful than benign conditions, this issue remains unresolved and controversial. We review the current literature on the relationship between the magnitude of inbreeding depression and environmental stress and calculate haploid lethal equivalents expressed under relatively benign and stressful conditions based on data from 34 studies. Inbreeding depression increases under stress in 76% of cases, although this increase is only significant in 48% of the studies considered. Estimates of lethal equivalents are significantly greater under stressful (mean = 1.45, median = 1.02) than relatively benign (mean = 0.85, median = 0.61) conditions. This amounts to an approximately 69% increase in inbreeding depression in a stressful vs a benign environment. However, we find strong lineage effects to be ubiquitous among studies that examine inbreeding depression in multiple environments, and a prevalence of conditionally expressed deleterious effects within lineages that are uncorrelated across environments. These results have important implications for both evolutionary and conservation biology.

Measurement of a complete set of nuclides, cross sections, and kinetic energies in spallation of 238U 1A GeV with protons

Spallation residues and fission fragments from 1A GeV 238U projectiles irradiating a liquid hydrogen target were investigated by using the fragment separator at GSI for magnetic selection of reaction products including ray-tracing, energy-loss and time-of-flight techniques. The longitudinal-momentum spectra of identified fragments were analyzed, and evaporation residues and fission fragments could be separated. For 1385 nuclides, production cross sections down to values of 10 microb with a mean accuracy of 15%, velocities in the uranium rest frame and kinetic energies were determined. In the reaction all elements from uranium to nitrogen were found, each with a large number of isotopes.

Components of variance underlying fitness in a natural population of the great tit Parus major

Traits that are closely associated with fitness tend to have lower heritabilities (h2) than those that are not. This has been interpreted as evidence that natural selection tends to deplete genetic variation more rapidly for traits more closely associated with fitness (a corollary of Fisher's fundamental theorem), but Price and Schluter (1991) suggested the pattern might be due to higher residual variance in traits more closely related to fitness. The relationship between 10 different traits for females, seven traits for males, and overall fitness (lifetime recruitment) was quantified for great tits (Parus major) studied in their natural environment of Wytham Wood, England, using data collected over 39 years. Heritabilities and the coefficients of additive genetic and residual variance (CVA and CVR, respectively) were estimated using an "animal model." For both males and females, a trait's correlation (r) with fitness was negatively related to its h2 but positively related to its CVR. The CVA was not related to the trait's correlation with fitness in either sex. This is the third study using directly measured fitness in a wild population to show the important role of residual variation in determining the pattern of lower heritabilities for traits more closely related to fitness.

Geographic variation and the evolution of reproductive allocation in the pitcher-plant mosquito, Wyeomyia smithii

We measured the egg size of six geographic populations of the pitcher-plant mosquito, Wyeomyia smithii, from Florida (30 degrees N) to Ontario (49 degrees N). Populations from northern latitudes produced larger eggs than populations from southern latitudes. Egg size increased with increasing latitude more rapidly when larvae were reared under low rather than high density. One southern (30 degrees N) and one northern (49 degrees N) population of W. smithii that persisted through 10 generations of selection for increased persistence under conditions of chronic thermal- and nutrient-limiting stress (conditions similar to southern rather than northern habitats) produced smaller eggs more rapidly than unselected control lines. However, there were no differences in lifetime fecundity or fertility between control and selected lines. Thus, laboratory evolution in an environment representative of extreme southern latitudes caused evolutionary changes consistent with geographic patterns of egg size. These results implicate temperature as a selective factor influencing the geographic variation of egg size in W. smithii, and demonstrate a novel trade-off in reproductive allocation between egg size and egg maturation time.

Equivalent inbreeding depression under laboratory and field conditions in a tree-hole-breeding mosquito

Understanding the consequences of inbreeding has important implications for a wide variety of topics in population biology. However, most studies quantifying the effects of inbreeding are performed under artificial farm, greenhouse, laboratory or zoo conditions. Although several authors have argued that the deleterious effects of inbreeding (inbreeding depression) are likely to be more severe under natural field conditions than in artificial experimental environments, these arguments are usually speculative or based on indirect comparisons. We quantified the effects of inbreeding on fitness traits in a tree-hole-breeding mosquito Aedes geniculatus) under near-optimal laboratory conditions and in three natural tree holes. Our index of fitness (Ro) was lower in the field than in the laboratory and declined due to inbreeding in both However, environments, we found no significant interactions between inbreeding depression and environmental conditions. In both the field and laboratory a 10% increase in the inbreeding coefflicient (F) led to a 12-15) decline in fitness (Ro) These results suggest that inbreeding depression will not necessarily be more extreme under natural field conditions than in the laboratory.

Evaluation of expanded school mental health programs

Expanded school mental health programs provide a full range of mental health services (assessment, treatment, case management, prevention) to youth in regular and special education, and typically involve close collaboration between schools and community agencies. A major challenge for these programs is documenting that provided services are of high quality and leading to enhanced outcomes for the youth and schools served by them. Dimensions of school mental health evaluations and a step-by-step process for conducting them are presented, using the example of a well established program in Baltimore. Challenges to such evaluation and strategies for overcoming challenges are also presented.

Cross sections of spallation residues produced in 1A GeV 208Pb on proton reactions

Spallation residues produced in 1 GeV per nucleon 208Pb on proton reactions have been studied using the Fragment Separator facility at GSI. Isotopic production cross sections of elements from 61Pm to 82Pb have been measured down to 0.1 mb with a high accuracy. The recoil kinetic energies of the produced fragments were also determined. The obtained cross sections agree with most of the few existing gamma-spectroscopic data. The data are compared with different intranuclear-cascade and evaporation-fission models. Drastic deviations were found for a standard code used in technical applications.

Are school based mental health services effective? Evidence from 36 inner city schools

In an effort to bridge the gap between service need and service utilization, an urban based, university-affiliated children's psychiatric outpatient clinic implemented a program which provides mental health services in inner city schools. Since impressions of school and mental health personnel affirmed the effectiveness of such services, an evaluation of this program was conducted, despite the difficulties inherent in implementing research in "naturalistic settings." A clinic sample of children (N = 220) was compared with a sample served in the urban schools (N = 256). The findings revealed that both sets of children showed improvement as indicated by the Children's Global Assessment Scale (C-GAS) and Global Assessment of Functioning Scale (GAF). The improvement was comparable, even though the school children were seen for a slightly shorter period of time (an average of 5 versus 8 months) but had an equally frequent level of service (3 sessions per month in each setting). This finding may have important implications for the managed care environment. These results indicate that school based mental health services show improvement comparable to the clinic-based services, and have the potential for bridging the gap between need and utilization by reaching disadvantaged children who would otherwise not have access to these services.

Collision or collaboration? School-based health services meet managed care

Describes interactions of for-profit managed-care organizations (MCOs) with not-for-profit school mental health programs that are affiliated with school-based health centers (SB-HCs). Discussion focuses on the developments and challenges that emerged between SBHCs and MCOs. While relations between MCOs and more traditional forms of mental health services (e.g., community mental health centers) are becoming established, such relations with SBHCs remain far from established. The example of the pathway Connecticut has taken in the continuing dialogue between SBHCs and MCOs is described in detail. Attention is given to the advocacy groups for child and adolescent mental health that were instrumental in convincing legislatures to enact safeguards to maintain SBHCs as providers of health and mental health care in the era of managed care. Challenges and recommendations are outlined to insure that the mental health needs of underserved, disadvantaged children are met through the provision of school-based mental health services.

Bridging the gap between service need and service utilization: a school-based mental health program

In an effort to bridge the gap between service need and service utilization, an urban based, university affiliated children's psychiatric outpatient clinic has implemented a program which provides mental health services in inner city schools. When compared with the central clinic populations (N = 304), the school sample (N = 44) was markedly socioeconomically disadvantaged, minority, and as psychiatrically impaired as the central clinic population. School based mental health services have the potential for bridging the gap between need and utilization by reaching disadvantaged children who would otherwise not have access to these services. Implications for such services are discussed.

Clinical, sociodemographic, and systems risk factors for attrition in a children's mental health clinic

Clinical, sociodemographic, and systems risk factors for attrition at a child guidance clinic were identified. All patients who completed the intake process were followed through various clinic phases. Lower socioeconomic status and low family cohesion predicted dropout. Dropouts and continuers were equally psychiatrically impaired. The Family Environment Scale was the only standardized measure that distinguished between dropouts and continuers.

Sociodemographic characteristics of dropouts from a child guidance clinic

OBJECTIVE

This study examined the characteristics of families who dropped out and families who maintained contact with a children's psychiatric outpatient clinic through various phases of intake and treatment.

METHODS

One year after intake, the authors examined the status of all patients (N = 555) who had sought treatment at an urban, university-affiliated children's psychiatric outpatient clinic over a two-year period and had completed the intake process. Factors associated with dropout were identified at four points in the clinic process: during intake, during evaluation, at completion of evaluation, and during treatment.

RESULTS

Urban residence, minority status, single-parent status, and Medicaid status were related to dropout at intake and during evaluation but not at subsequent clinic phases. Nonminority, two-parent, suburban families of higher socioeconomic status were more likely to drop out at the completion of the evaluation.

CONCLUSIONS

These results indicate that factors associated with attrition vary with the clinic phase. Further investigations of the clinical course of minority children and families involved with children's mental health services are necessary to understand the needs of this population and to design interventions such as increasing minority staff and providing training in multi-cultural competence.