Effect of two different primers on the shear bond strength of metallic brackets to zirconia ceramic.

BACKGROUND: In view of the increasing demand of adult orthodontics for esthetic purposes, adult treatment with brackets has become an important issue. One essential factor for the quality of such treatment is bracket bonding on ceramics. For testing the adhesive bond between the bracket and the ceramic surface it is important to consider the static or cyclic loading that goes along with it. METHODS: Metallic Brackets were adhesively fixed on zirconia ceramic blocks in a simulated leveling phase using two different primers (Monobond S and Monobond Etch & Prime). Half of the metallic brackets were activated using a 0.14-nickel titanium wire, while the other half remained non-activated. Shear bond testing (SBT) was performed after thermocycling. Furthermore the Adhesive Remnant Index (ARI) was analyzed. RESULTS: SBT resulted in significantly higher shear bond values when Monobond Etch & Prime was used compared to the use of Monobond S. Activation of the brackets did not show different results in comparison to the non-activated brackets. The ARI did not indicate cement remnants on the ceramic surface, regardless of the primer and the activation status. CONCLUSIONS: The use of Monobond Etch & Prime has great potential for the bonding of brackets on dental zirconia ceramics.

Long-term outcomes of mandibular kinematics following class II malocclusion therapy with removable functional appliance therapy.

OBJECTIVE: To evaluate mandibular kinematics in class I adults following class II therapy with removable functional appliances (RFAs) during the growth period in comparison with orthodontically untreated class I and II individuals. METHODS: Condylar (CRoM) and incisal range of motion (InRoM), velocity during opening and closing, and the mandibular rotation angle were recorded using an ultrasound-based jaw-tracking system in 36 test patients (mean age = 28.03 ± 6.58 years). RESULTS: Significant group effects were found for CRoM towards the posterior in the right joint (p = 0.002) and InRoM towards the anterior (p = 0.043). The post hoc Tukey test indicates a significantly longer CRoM (posterior) for the right condyle in class II (p = 0.003) and RFA individuals (p = 0.023). DISCUSSION: The kinematic data imply greater dentoalveolar effects due to RFA therapy than adaptive remodeling of the temporomandibular joint. The class I relationship in the RFA group following treatment indicates stable long-term outcomes.

An in vitro comparative assessment of different enamel contaminants during bracket bonding.

In orthodontics, adhesive failures can occur because of saliva contamination during bonding. However, most in vitro studies concerning bond strength of saliva-contaminated enamel disregard the influence of temperature changes in a wet environment. The aim of the present study was to compare the influence of saliva, blood and etching gel remnant contamination on shear bond strength (SBS) after thermocycling. After etching of extracted human third molars (n = 80), a conventional primer (Transbond XT) and a moisture-insensitive primer (Transbond MIP) were evaluated using the adhesive, Transbond XT, under dry conditions and after contamination with saliva, blood and etching gel remnants. To simulate temperature changes and the moisture of saliva in the oral cavity, all samples were thermocycled (6,000 x 5 degrees C/55 degrees C) in a mastication device before SBS testing. A Mann-Whitney U test was used to determine statistical differences. Under dry conditions Transbond XT and Transbond MIP showed no significant difference in SBS. However, clinically unacceptable (P = 0.005) bond strength was observed using Transbond XT after saliva and blood contamination. In wet conditions only Transbond MIP showed sufficient bond strength. If contamination during bonding is expected, a hydrophilic primer should be used. Under dry conditions hydrophilic or hydrophobic primers could be applied. Blood contamination seems to be a more serious problem for bond strength than saliva or etching gel contamination.

A comparative evaluation of bracket bonding with 1-, 2-, and 3-component adhesive systems.

INTRODUCTION: Today, 1- and 2-component adhesives are available for bracket bonding that could diminish the possibility of contamination during the bonding procedure and save the clinician chair-side time. Our aim in this study was to compare the shear bond strengths and the adhesive remnant index (ARI) scores of 1-, 2-, and 3-component adhesives after thermocycling. METHODS: Fifty stainless steel brackets (10 per adhesive group) were bonded to extracted third molars with 5 adhesives. Group 1 was a 1-component adhesive, RelyX Unicem (3M Espe, Seefeld, Germany). Group 2 was a 1-component adhesive, Maxcem (Kerr, Orange, Calif). Group 3 was a self-conditioning 2-component adhesive system, Multilink (Ivoclar-Vivadent, Schaan, Liechtenstein). Group 4 was a 2-component adhesive system, Transbond Plus primer (self-etching) and Transbond XT adhesive (3M Unitek, Monrovia, Calif). Group 5 (control group) was a conventional 3-component adhesive system consisting of an etchant, Transbond XT primer, and XT adhesive (3M Unitek). All samples were thermocycled (6000 x 5 degrees C/55 degrees C) in a mastication device before shear bond strength testing and evaluation with the ARI. RESULTS: No significant differences of shear bond strength between the 2- and 3-component adhesive systems were found. Significant decreases of shear bond strength were observed with 1-component adhesives, RelyX Unicem and Maxcem, compared with 2- and 3-component systems. The ARI scores indicated no significant differences between the groups. CONCLUSIONS: With enhanced shear bond strength, 1- component adhesives have the potential to compete successfully with 2- or 3-component adhesives.

In vitro colour stability of aesthetic brackets.

Contrary to their popularity in satisfying aesthetic demands, plastic brackets still present some problems because of their decreased hardness and wear resistance. A problem of plastic brackets is discolouration, due to ultraviolet (UV) light and food dyes. The aim of this study was to investigate the colour stability of aesthetic brackets during UV irradiation and exposure to food dyes. Four different polymer brackets were exposed in a Suntest CPS+ ageing device to a xenon lamp to simulate natural day light. Because most tooth-coloured bracket systems are used in adult treatment, red wine, coffee, and tea were chosen as food colourants. After 24 and 72 hours of exposure, colour measurements were performed by means of a spectrophotometer according to the CIE L*a*b* system and colour changes (DeltaE*) were computed. Statistical differences were investigated using three-way analysis of variance (ANOVA). With the exception of the Aesthetic-Line bracket, almost all investigated polymer brackets showed clinically unacceptable discolouration during in vitro exposure to colourants. Most of the brackets became yellower after UV light treatment. In spite of the short exposure period of 72 hours, almost all polymer brackets showed undesirable discolouration. These current in vitro findings indicate that even newly developed plastic brackets, consisting of composite materials or modern polymers (polyoxymethylene) may have clinically unacceptable colour stability in the long-term.

Esthetic brackets: the influence of filler level on color stability.

INTRODUCTION: An undesirable effect of plastic brackets is their discoloration after a short time in the oral cavity. The objective of this study was to investigate the influence of the filler level of plastic brackets on color stability after exposure to food dyes or ultraviolet (UV) light. METHODS: Three bracket groups were produced with silicon dioxide as the filler: an unfilled urethane-dimethacrylate (UDMA) bracket, a UDMA bracket with filler content of 35% by volume, and a UDMA bracket with filler level of 70% by volume. All brackets were exposed for 72 hours to UV light in an aging device with a xenon lamp to simulate natural daylight or to food dyes (cola or tea). Color measurements were made with a spectrophotometer according to the CIE L*a*b* system, and color changes (DeltaE*) were computed. RESULTS: Greater exogenous discoloration was observed by raising the filler level of UDMA brackets. Almost all investigated polymer brackets showed clinically acceptable color stability during in-vitro exposure to colorants. However, almost all brackets seemed more yellow after UV light treatment. CONCLUSIONS: Silicon-dioxide filler-reinforced UDMA brackets showed an obvious trend for increased exogenous discoloration when filler level was raised. Highly filled brackets were less susceptible to endogenous discoloration caused by UV light.

Influence of fibre and filler reinforcement of plastic brackets: an in vitro study.

In spite of their popularity in fulfilling aesthetic requirements, plastic brackets still present some disadvantages because of their low elastic modulus, decreased fracture toughness, and reduced wear resistance. Fibre-reinforced composites are well established in dentistry and consist of a polymer matrix in which reinforcing fibres are embedded. Stress is transferred from the polymer matrix to the fibres which present a high tensile strength. Hence, the mechanical properties of polymers could be improved. The purpose of this study was to compare fracture strength, fracture toughness and flexural strength of an experimental fibre-reinforced bracket material, an SiO(2) filler-reinforced bracket and an unfilled plastic bracket material (control group). Experimental brackets and specialized bars were manufactured. Tests were performed after thermal cycling (5 degrees C/55 degrees C) the samples in an artificial oral environment of a device to simulate mastication. Statistical evaluation was undertaken. The median, 25th and 75th percentiles were calculated and a Mann-Whitney U-test was performed. In this study two findings were obvious. (1) Filler reinforcement of plastic brackets improved fracture strength and fracture toughness in comparison with the unfilled bracket material. (2) Glass fibre reinforcement of orthodontic bracket materials resulted in the greatest enhancement of the mechanical properties in comparison with the other test groups. Therefore, the application of glass fibres in plastic brackets is a successful method to enhance fracture strength.

Influence of filler level on the bond strength of orthodontic adhesives.

OBJECTIVE: To evaluate the effect of different filler contents of orthodontic adhesives on shear bond strength and Adhesive Remnant Index (ARI). MATERIALS AND METHODS: Four experimental adhesive groups were created: group 1 was an unfilled urethane-dimethacrylate (UDMA) adhesive, group 2 consisted of UDMA and a filler content of 30 vol%, group 3 consisted of UDMA and a filler content of 50 vol%, and group 4 was manufactured with a filler level of 70 vol% in a UDMA matrix. The embedded filler was silicon dioxide. After etching and priming, stainless steel brackets were bonded to extracted human third molars (n = 60) with the experimental adhesives (15 teeth per group). After storage in distilled water for 72 hours, shear bond strength and ARI scores were evaluated. Kruskal-Wallis and post hoc test were performed for statistical analysis. RESULTS: Shear bond strength of UDMA-based adhesives depends on filler content. Higher adhesive filler levels reveal greater bond strength between enamel and stainless steel brackets. ARI scores showed no significant difference among the groups. However, higher filled adhesives (filler content 70 vol%) seem to present higher ARI scores. CONCLUSION: Highly filled UDMA adhesives offer greater bond strength than do lower filled or unfilled resins.

Acrylic removable appliances: comparative evaluation of different postpolymerization methods.

INTRODUCTION: In orthodontics, the polymeric part of removable orthodontic appliances could be a hazard for patients because high residual monomer contents can lead to allergic reactions. In addition, water uptake, color stability, and mechanical properties are influenced by the degree of conversion. The aim of this investigation was to evaluate the effectiveness of different postpolymerization methods on the properties of removable orthodontic appliance resins. METHODS: A total of 300 rectangular specimens (5 postpolymerization groups: 20 per group) were manufactured of Orthocryl (n = 100, Dentaurum, Ispringen, Germany), Palapress (n = 100, Heraeus-Kulzer, Wehrheim, Germany), and Pro Base Cold (n = 100, Ivoclar-Vivadent, Schaan, Liechtenstein). The first 2 postpolymerization groups were postcured in a stove (10 minutes at 40 degrees C or 80 degrees C). The third resin group was postcured in a microwave at 600W for 5 minutes, and the fourth polymer group was postcured in a microwave at 600W for 10 minutes. Twenty conventionally cured samples (cold-curing under pressure: water bath 40 degrees C, 25 minutes, 2.2 bar) were the control group. Water sorption, fracture toughness, and Vickers hardness were measured. RESULTS: Fracture toughness and Vickers hardness of the resins are slightly increased after curing. Heat as a secondary curing method decreases water uptake of resins used for removable orthodontic appliances. CONCLUSIONS: Heat postpolymerization appears to improve the properties of removable orthodontic appliance resins.

WITHDRAWN: Variations of maximum mouth-opening capacity and condylar path length during growth period in children.

This article has been withdrawn consistent with Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). The Publisher apologizes for any inconvenience this may cause.

Experimental composite brackets: influence of filler level on the mechanical properties.

INTRODUCTION: Despite their popularity in satisfying esthetic demands, plastic brackets still have some disadvantages because of decreased wear resistance and hardness. Our aim in this study was to investigate the mechanical properties of an alternative bracket-polymer urethane-dimethacrylate (UDMA) reinforced by silicon dioxide fillers with several filler levels. METHODS: Three bracket groups were created: (1) unfilled UDMA, (2) UDMA with a filler content of 40% by volume, and (3) UDMA with a filler content of 70% by volume. Flexural strength, fracture force, and Vickers hardness of the bracket groups were tested. In addition, a 3-medium wear test was performed. RESULTS: The filler-reinforced brackets showed increased hardness, greater stiffness, and improved wear resistance compared with unfilled brackets. Higher filler concentrations in a polymer matrix result in greater stiffness of the polymer. Despite this, the filled composite brackets were not statistically more susceptible to fractures than the unfilled plastic brackets. CONCLUSIONS: Experimental UDMA brackets reinforced with silicon dioxide fillers showed an obvious trend for improved mechanical properties compared with unfilled UDMA brackets.

Expression of tropoelastin in human periodontal ligament fibroblasts after simulation of orthodontic force.

The ability of elastic fibers to respond to mechanical stimuli suggests that they play a central role in physiological adaptation to external stimuli including application of orthodontic force. The purpose of this study was to examine the effect of external pressure simulating orthodontic force on tropoelastin gene expression in cultured human periodontal ligament fibroblasts (hPDLF). External pressure simulation was achieved by centrifugation for 10, 30, 60, 90 and 120 min of hPDLF in a horizontal microplate rotor. Semi-quantitative RT-PCR analysis of tropoelastin mRNA was performed and beta-actin was used as an internal invariant control. While centrifugal force on mRNA levels of beta-actin showed almost no change, the mRNA levels of tropoelastin increased significantly to a peak level of more than four-fold after 30 min. Thereafter, at 60 min, the mRNA levels remained at more than three-fold. After 90 min, mRNA levels decreased to control levels. The finding that no changes in mRNA levels of beta-actin occurred during the first 90 min of centrifugation validates its use as an invariant control gene in such an experimental model. This study demonstrated that tropoelastin is expressed in hPDLF and that the pressure caused significant time-dependent upregulation of the tropoelastin gene. The responsiveness of the tropoelastin gene to force shows its possible clinical importance in orthodontic tooth movement. Further studies, however, are essential in order to learn whether the high expression of the gene in vitro will also be followed by corresponding protein synthesis and deposition in vivo in the extracellular matrix (ECM) of the periodontal ligament (PDL).

Evidence of intrafamilial variability of CBFA1/RUNX2 expression in cleidocranial dysplasia--a family study.

AIM: To investigate the phenotypical expression of an identical mutation of the CBFA1/RUNX2 gene within a family with cleidocranial dysplasia. PATIENTS AND METHOD: A five-member family underwent clinical examination. Two members, father and son, showed dissimilar symptoms of cleidocranial dysplasia. The two affected patients were examined for syndrome-typical symptoms, and the genotype was determined by molecular-genetic analysis. RESULTS: In both patients an identical missense mutation (G146R) in exon 2 of the CBFA1/RUNX2 gene was identified. In father and son the dental disturbances were similarly clearly expressed. However, the craniofacial skeleton of the son exhibited fewer dysostotic ossification features than that of the father. In the three clinically healthy family-members no mutation of the CBFA1/RUNX2 gene was found. CONCLUSION: In two patients with cleidocranial dysplasia an identical missense mutation in the CBFA1/RUNX2 gene leading to a divergent craniofacial phenotype was determined. The results indicate marked variability in the phenotypical expression of CBFA1/RUNX2 mutations.