Assessing the effect of multibracket appliance treatment on tooth color by using electronic measurement.

BACKGROUND: The purpose of this study was to investigate how tooth color is affected by multibracket appliance (MBA) treatment. METHODS: The color of teeth #14 to #24 of 15 patients with MBA was measured on body and gingival tooth segments using the spectrophotometer Shade Inspector™. Colors of both segments were recorded before start of MBA treatment (baseline T0), end of MBA treatment (T1; 2 years ±0.3), and 3 months after T1 (T2). A 2D color system and a 3D system served as reference systems. Multilevel models were used to analyze color change within segments and to compare the difference in color change between segments (treatment effect). RESULTS: 2D system. Changes within tooth segments from T0 to T2 were at worst 2.0 units (ΔE in the gingival segment), which is less than the threshold of 2.7 units for a clinically meaningful difference. Confidence intervals for the treatment effect indicated no clinically important differences in color change between body and gingival segments. 3D system. Changes within tooth segments from T0 to T2 were at worst 2.3 units (ΔE in the body segment), which is less than the threshold of 2.7 units for a clinically meaningful difference. Confidence intervals for the treatment effect indicated no clinically important differences in color change between body and gingival segments. Thus, MBA treatment did not lead to clinically relevant changes in tooth color. CONCLUSION: Within the limitation of this study the MBA treatment can be seen as a safe method with respect to tooth color.

Shear bond strength of different retainer wires and bonding adhesives in consideration of the pretreatment process.

INTRODUCTION: We aimed to compare the shear bond strength (SBS) of three different retainer wires and three different bonding adhesives in consideration of the pretreatment process of enamel surface sandblasting. METHODS: 400 extracted bovine incisors were divided into 10 groups of 20 paired specimens each. 10 specimens of each group were pretreated by enamel sandblasting. The retainer wires Bond-A-Braid™, GAC-Wildcat®-Twistflex and everStick®ORTHO were bonded to the teeth with the adhesives Transbond™-LR, Tetric-EvoFlow™ and Stick®FLOW and then debonded measuring the SBS. RESULTS: While sandblasting generally increased SBS for all tested combinations, the retainer wires bonded with Transbond™-LR showed the highest SBS both with and without prior sandblasting. Significantly lower SBS were found for Tetric-EvoFlow™ that were comparable to those for everStick®ORTHO. CONCLUSIONS: Pretreatment of enamel surfaces by sandblasting increased the SBS of all retainer-wires. Transbond™-LR showed the best results compared to Tetric-EvoFlow™ and everStick®ORTHO, while all combinations used provided sufficient bonding strengths for clinical use.

Correlation of condylar kinematics in children with gender, facial type and weight.

OBJECTIVE: The aim of the study has been to describe the normal range of mandibular movements and condylar kinematics in children as well as to test the null hypothesis that these variables are not associated with gender, facial type and weight. MATERIALS AND METHODS: The sample was comprised of 92 healthy children (7.2-10.6 years old) and 40 adult controls (18-34.7 years old). Examinations included the maximal mouth opening capacity and laterotrusion to the right and to the left. The condylar path inclination angle was calculated at 3mm and 5mm protrusion of the mandible. Kinematic variables were registered using the ultrasonic JMA system. RESULTS: Maximal mouth opening capacity averaged 46.73 mm for the children and 53.53 mm for the adults. The mean values of the lateral movements were 9.36 mm to the right and 9.62 mm to the left for the boys, and 9.91 mm and 9.68 mm for the girls, respectively. Mean condylar path inclination in the children was 36.5° (right) and 36.2° (left) at 3mm of protrusive movement, and 34.3° (right) and 34.0° (left) at 5mm of protrusive movement. Associations of the kinematic variables with gender, weight, or facial type were insignificant. CONCLUSION: Younger school children have not yet reached the maximum mouth-opening capacity. Correlation analysis suggests some weak, but insignificant associations of gender, facial type and weight with mouth opening, laterotrusion and the condylar path inclination angle. The null hypothesis was not rejected.

An Investigation about the Influence of Bleaching on Shear Bond Strength of Orthodontic Brackets and on Enamel Colour.

The aim of the study was to investigate the effect of bleaching on the colouration of tooth enamel and shear bond strength of orthodontic ceramic brackets based upon current whitening practice. The bleaching and bonding techniques were performed on extracted bovine teeth for the investigation of their colorimetric spectrum and the adhesive bond strength on surface enamel. One group was designated as the control group with no pre-treatment. Another group was treated with a 45% hydrogen peroxide solution prior to bonding. The difference in colour was expressed as the Euclidian distance ΔE. The resulting shear bond strength was analyzed and evaluated by scores of Adhesion Remnant Index. Statistical analysis was performed using the Kruskall-Wallis and post-hoc test. The colorimetric analysis revealed statistically significant differences between original and bleached as well as bleached and debonded teeth setting off a blue colour shift. Furthermore, statistically there was no significant difference noted in bonding strength between non-treated surfaces and those treated with peroxide. It can be concluded that peroxide pre-treatment does result in colour differences of teeth. Bonding and debonding procedures seem to have no statistically significant influence on the enamel colour using current materials.

The influence of electron beam irradiation on colour stability and hardness of aesthetic brackets.

Electron beam irradiation can be used to improve the mechanical properties of polymers. The aim of this study was to investigate the influence of electron beam irradiation with an energy dose of 100 kGy on the mechanical properties and colour stability of conventional polymer brackets and experimental filled composite brackets. The conventional brackets tested were Aesthetik-Line, Brillant, and Envision. The experimental brackets contained urethane dimethacrylate, as a monomer matrix and functional silane-treated SiO(2) fillers with a filler content of either 10 (Exper 1) or 40 (Exper 2) vol per cent. The influence of electron beam post-curing on Vickers hardness (VH) of the polymer brackets was investigated. Additionally, a possible discolouration of the brackets after electron beam irradiation was determined according to the three-dimensional L* a* b* colour space. The irradiated brackets were compared with untreated control groups. Statistical analysis was performed using the Wilcoxon test. With the exception of Brillant brackets, all investigated brackets showed a significant enhancement of VH after electron beam post-curing. However, the brackets suffered a significant increase in discolouration. Aesthetik-Line brackets showed the highest discolouration, ΔE, and Exper 2 brackets the lowest ΔE values. The discolouration of the examined brackets differed significantly. These results demonstrate that the mechanical properties of polymer brackets could be modified by electron beam irradiation. Nevertheless, clinical use of electron beam post-curing might be restricted because of unacceptable colour changes.

The two main theories on dental bruxism.

Bruxism is characterized by non-functional contact of mandibular and maxillary teeth resulting in clenching or grating of teeth. Theories on factors causing bruxism are a matter of controversy in current literature. The dental profession has predominantly viewed peripheral local morphological disorders, such as malocclusion, as the cause of clenching and gnashing. This etiological model is based on the theory that occlusal maladjustment results in reduced masticatory muscle tone. In the absence of occlusal equilibration, motor neuron activity of masticatory muscles is triggered by periodontal receptors. The second theory assumes that central disturbances in the area of the basal ganglia are the main cause of bruxism. An imbalance in the circuit processing of the basal ganglia is supposed to be responsible for muscle hyperactivity during nocturnal dyskinesia such as bruxism. Some authors assume that bruxism constitutes sleep-related parafunctional activity (parasomnia). A recent model, which may explain the potential imbalance of the basal ganglia, is neuroplasticity. Neural plasticity is based on the ability of synapses to change the way they work. Activation of neural plasticity can change the relationship between inhibitory and excitatory neurons. It seems obvious that bruxism is not a symptom specific to just one disease. Many forms (and causes) of bruxism may exist simultaneously, as, for example, peripheral or central forms.

Strontium promotes cell proliferation and suppresses IL-6 expression in human PDL cells.

This study was designed to investigate the effect of strontium on human PDL cells in vitro. Strontium is used to treat osteoporosis because of its bone formation promoting effect on osteoblast cells. This investigation presents evidence that strontium promotes PDL cell proliferation. Simultaneously, strontium suppresses the expression of the inflammation-promoting cytokine IL-6. The observed effect of strontium on PDL cells supports its use it in guided dental tissue regeneration.

Effects of hypodontia on craniofacial structures and mandibular growth pattern.

INTRODUCTION: This study was performed to examine craniofacial structures in persons with hypodontia and to reveal any differences, that may occur, when agenetic teeth are only found in the maxilla, the mandible or in both jaws. The groups consistent of 50 children (33 girls, 17 boys) aged between 9 and 13.5 years were analyzed and assigned to three subgroups. Group 1 = upper jaw hypodontia. Group 2 = lower jaw hypodontia. Group 3 = hypodontia in both jaws. MATERIALS AND METHODS: Eleven angular and three index measurements from lateral encephalographs and two linear measurements from dental blaster casts were calculated. All data was statistically analyzed, parameters with p < 5% were investigated for each subgroup respectively. RESULTS: In comparison with standards the study group showed bimaxillary retrognathism and a reduction of the lower anterior facial height. Moreover both overbite and overjet significantly increased. Other values laid within the normal ranges. Evaluating results of the subgroups, differences in the means of SNA, SNB and overjet between the groups were observed.Analysis of the mandibular growth pattern revealed, that neither vertical nor horizontal patterns are dominant in hypodontia patients. CONCLUSIONS: In certain dentofacial parameters differences between persons with hypodontia and such with full dentition exist. According to our findings agenetic teeth may have a negative influence on the saggital development of a jaw and the lower face and may be responsible for increased overbites. This should receive attention in orthodontic treatment of hypodontia patients.

Electron-beam irradiation of polymer bracket materials.

INTRODUCTION: Electron-beam irradiation can be used to influence the properties of polymers. Electron beams cause cross-linking that enhances the molecular mass of the polymer; this leads to branched chains until, ultimately, a 3-dimensional network is formed. The aim of this study was to evaluate the effect of electron-beam irradiation on polymer bracket materials. METHODS: Since polymers are commonly used materials for brackets, polyoxymethylene, polycarbonate, and polyurethane were chosen for this study. The acceleration voltage of the electron-beam device was 10 MeV, and the energy dose was 100 kGy with an electron accelerator (BGS beta gamma service, Rhodotron, Bruchsal, Germany). Three-medium wear, fracture toughness, and Vickers hardness tests were performed. The irradiated samples were compared with untreated control groups. RESULTS: Polycarbonate and polyurethane bracket materials have enhanced fracture toughness and Vickers hardness after electron-beam irradiation of 100 kGy and 10 MeV. Polyoxymethylene bracket materials showed significantly lower fracture toughness values after irradiation compared with the untreated control group. Polyoxymethylene had the best mechanical properties, followed by polycarbonate and polyurethane. Almost the same effects could be measured during the 3-medium wear test. CONCLUSIONS: Electron-beam postcuring improved Vickers hardness and fracture toughness of polymers with lower mechanical properties (polycarbonate and polyurethane). Polyoxymethylene, with sufficient hardness and fracture toughness, could not be improved with electron-beam postcuring.

Effect of strontium on human Runx2+/- osteoblasts from a patient with cleidocranial dysplasia.

Strontium represents a new generation of anti-osteoporotic agents that exert anti-catabolic and anabolic effects on bone cells at once. We used strontium in vitro in order to examine its potential to stimulate bone marker transcription and hydroxyapatite formation on isolated Runx2(+/-) osteoblasts from a patient with cleidocranial dysplasia. This disease is evoked by heterozygous mutations of Runx2, an important transcription factor for osteoblast maturing and transcription of osteogenic genes, which results in insufficient gene dosage of Runx2. This genetic defect is responsible, for example, for patent fontanels, sometimes throughout the life, supernumerary teeth, and aplasia or hypoplasia of clavicles and mimics symptoms of hypophosphatasia. In this trial, we investigated the effect of strontium on gene expression of bone marker proteins, the formation of hydroxyapatite and the cell proliferation of strontium-treated Runx2(+/-)-osteoblasts. Unlike normal osteoblasts, gene expression of bone marker proteins was not affected in strontium-treated Runx2(+/-) osteoblasts, while improved hydroxyapatite formation was noted in the extracellular matrix. A WST-1 cell proliferation assay with strontium-treated Runx2(+/-)-osteoblasts showed that strontium induces cell proliferation and growth. This effect might be responsible for the improved mineralisation of the extracellular matrix of strontium-treated Runx2(+/-)-osteoblasts observed.

Evaluation of alternative polymer bracket materials.

INTRODUCTION: Polymer brackets still have some disadvantages because of decreased wear resistance and hardness. The aim of this study was to investigate the mechanical properties of alternative bracket polymers; urethane-dimethacrylate, high-density polyethylene, and an experimental bracket polymer (EBP) consisting of polyethylene and a copolymer were tested. Polycarbonate and polyoxymethylene brackets served as controls. METHODS: The mechanical properties of urethane-dimethacrylate, high-density polyethylene, EBP, polycarbonate, and polyoxymethylene bracket materials were evaluated after thermocycling (6000 x 5 degrees C-55 degrees C) in a mastication device before testing. Three medium-wear, fracture toughness, and Vickers hardness tests were performed. RESULTS: High-density polyethylene had the highest values of wear and the lowest values of fracture toughness and Vickers hardness. The urethane-dimethacrylate bracket material and the EBP had better mechanical properties than polycarbonate. The polyoxymethylene bracket material had the highest values of fracture toughness and Vickers hardness, and the lowest values of wear compared with the other investigated polymers. CONCLUSIONS: High-density polyethylene seems to be unsuitable as bracket material because it demonstrated excessive wear and insufficient fracture toughness. Polyoxymethylene had the best performance during mechanical testing.

Variations in the inclination of the condylar path in children and adults.

OBJECTIVE: To test the null hypothesis that there are no differences between children and adults in the condylar path inclination angle on the right and left sides. MATERIALS AND METHODS: A group of 80 children aged 6 to 10 years (subgroups I through V, according to chronologic age) was compared with an adult group with regard to the condylar path inclination angle (CPIA) on the right and left sides. The CPIA was measured using the ultrasonic JMA-System for registration. RESULTS: During development of the temporomandibular joint the condylar path inclination angle increased with age in the subgroups of children. A significant difference was found in the CPIA between the groups of adults and children. In the group with the oldest children (mean age: 10.3 years) the condylar path inclination angle had reached 81.87% on the right side and 78.85% on the left side compared with the adult group at a 5 mm protrusive path. In the pooled group of children the CPIA amounted to 73.08% on the right side and 72.13% on the left side compared with the values for the adults. No significant difference was found between the right and left CPIA in any group. CONCLUSION: The hypothesis is rejected. The CPIA on the right and left sides increased with age in the group of children and was significantly smaller in the group of children compared with the group of adults.

Effect of bracket base conditioning.

INTRODUCTION: The aim of this study was to compare the effect of a silicoating system, the influence of sandblasting, and the effect of a silane-coupling agent after sandblasting on the shear bond strength of stainless steel foil-mesh brackets. To simulate the oral environment, all specimens were thermocycled (6000 times at 5 degrees C and 55 degrees C) in a mastication device before testing. METHODS: Four bracket groups were tested: group 1 consisted of 20 metal brackets that were sandblasted on the base; group 2 contained 20 brackets that were sandblasted, and a silane-coupling agent was applied; in group 3, the surface of the base of 20 metal brackets was treated by using a tribochemical system; and group 4 was the control group. The brackets were bonded with a light-curing adhesive to extracted third molars, and the shear bond strength and the adhesive remnant index score were determined. The brackets of group 1 were reconditioned after debonding with sandblasting and tested again (group 5). RESULTS: Sandblasting and tribochemical treatment of brackets improved the shear bond strength of stainless steel brackets. Combined sandblasting and silane-coupling treatment offers no benefit of increased in-vitro strength. CONCLUSIONS: The bond of resins to tribochemically silicoated stainless steel brackets seems to be sufficient to strengthen the bond between the adhesive and the metal bracket. This treatment is mainly indicated for low-compliance patients or teeth that are difficult to bond.

The role of apoptosis in early embryonic development of the adenohypophysis in rats.

BACKGROUND: Apoptosis is involved in fundamental processes of life, like embryonic development, tissue homeostasis, or immune defense. Defects in apoptosis cause or contribute to developmental malformation, cancer, and degenerative disorders. METHODS: The developing adenohypophysis area of rat fetuses was studied at the embryonic stage 13.5 (gestational day) for apoptotic and proliferative cell activities using histological serial sections. RESULTS: A high cell proliferation rate was observed throughout the adenohypophysis. In contrast, apoptotic cells visualized by evidence of active caspase-3, were detected only in the basal epithelial cones as an introducing event for fusion and closure of the pharyngeal roof. CONCLUSION: We can clearly show an increasing number of apoptotic events only at the basic fusion sides of the adenohypophysis as well as in the opening region of this organ. Apoptotic destruction of epithelial cells at the basal cones of the adenohypophysis begins even before differentiation of the adenohypophyseal cells and their contact with the neurohypophysis. In early stages of development, thus, apoptotic activity of the adenohypophysis is restricted to the basal areas mentioned. In our test animals, the adenohypophysis develops after closure of the anterior neuroporus.

Bacterial adhesion of Streptococcus mutans to esthetic bracket materials.

INTRODUCTION: The formation of white spot lesions and enamel demineralization might be intensified by enhanced bacterial adhesion and formation of dental plaque on brackets. Our aim in this in-vitro study was to investigate the susceptibility of various plastic bracket materials to the adherence of Streptococcus mutans. METHODS: The esthetic bracket raw materials included in this study were polyoxymethylene, polycarbonate, high-density polyethylene, and an experimental polymer (90% polyethylene). Surface roughness was assessed by perthometer. S mutans suspension was incubated with test specimens and examined with fluorescence dye and an automated multi-detection reader. The oxidation-reduction fluorescence dye Alamar Blue/resazurin (0.007536 g per 10 mL distilled water) was used to determine the quantity of bacterial adhesion. RESULTS: The median values of fluorescence intensity varied between approximately 600 and 1600. The lowest fluorescence with median values below 700, indicating low bacterial adhesion, was found for polyoxymethylene (median of relative fluorescence intensity, 635). The highest relative fluorescence intensity, with median values of more than 1500, was for high-density polyethylene (1565). No statistical alteration of fluorescence intensity was measured between the polymeric bracket materials. CONCLUSIONS: The investigated polymeric bracket materials had no significant differences in the quantities of S mutans adhering to them. Regardless of the polymer, plastic bracket materials have similar bacterial colonization and plaque accumulation properties.

Discolouration of orthodontic adhesives caused by food dyes and ultraviolet light.

Enamel discolouration after debonding of orthodontic attachments could occur because of irreversible penetration of resin tags into the enamel structure. Adhesives could discolour because of food dyes or ultraviolet irradiation. The aim of this study was to investigate the colour stability of adhesives during ultraviolet irradiation and exposure to food colourants. Four different adhesives were exposed in a Suntest CPS+ ageing device to a xenon lamp to simulate natural daylight (Transbond XT, Enlight, RelyX Unicem, and Meron Plus AC). Tomato ketchup, Coca Cola, and tea were chosen as the food colourants. After 72 hours of exposure, colour measurements were performed by means of a spectrophotometer according to the Commission Internationale de l'Eclairage L*a*b* system and colour changes (DeltaE*) were computed. Statistical differences were investigated using two-way analysis of variance (ANOVA) and Friedman test. Unsatisfactory colour stability after in vitro exposure to food colourants and ultraviolet light was observed for the conventional adhesive systems, Transbond XT and Enlight. RelyX Unicem showed the least colour change and the resin-reinforced glass-ionomer cement (GIC), Meron Plus AC, the greatest colour change. The investigated adhesives seem to be susceptible to both internal and external discolouration. These in vitro findings indicate that the tested conventional adhesive systems reveal unsatisfactory colour stability which should be improved to avoid enamel discolouration.

Bacterial adhesion of Streptococcus mutans to orthodontic adhesives with various filler-volume fractions.

INTRODUCTION: The aim of this in-vitro study was to investigate the effect of the filler-volume fraction of experimental composite adhesives on the bacterial adhesion of Streptococcus mutans. METHODS: Three experimental adhesive groups were created: an unfilled urethane-dimethacrylate (UDMA) adhesive, UDMA and a filler-volume fraction of 35%, and UDMA and a filler-volume fraction of 70%. The embedded filler was silicon dioxide. Additionally, 2 conventional orthodontic adhesives, Transbond XT (3M Unitek, Monrovia, Calif) and ConTec Duo (Dentaurum, Ispringen, Germany), were examined. S mutans suspensions were incubated with test specimens and examined with fluorescence dye and an automated multi-detection reader. Moreover, scanning electron micrographs were made to evaluate bacterial adhesion on substrata. RESULTS: The experimental adhesives consisting of UDMA and various filler-volume fractions of silicon dioxide showed no statistical difference in relative fluorescence intensities. Scanning electron micrographs demonstrated that greater bacterial colonization and more complex aggregates were found on adhesives with high relative fluorescence intensity. Relative fluorescence intensity values showed no correlation to the filler-volume fraction of the examined adhesives. CONCLUSIONS: The results indicate no relationship between the filler-volume fraction of UDMA-based orthodontic adhesives and the bacterial adhesion of S mutans.

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.

Outcomes of temporomandibular joint disorder therapy: observations over 13 years.

OBJECTIVE: To evaluate the outcome of temporomandibular joint (TMJ) disorder therapy with different kinds of splints. METHODS: One-hundred-and-twenty-nine patients with TMJ disorders and meeting the primary selection criterion of reporting pain in the TMJ region were clinically evaluated. Magnetic resonance imaging of the TMJ was performed at baseline 1993-94. A protrusion splint was used whenever joint clicking could be eliminated by protrusion. In the other cases, a pivot or a Michigan splint was inserted. Re-evaluation of the patients after 12 months included a clinical examination. After 5 and 13 years, all patients were examined by means of a questionnaire. RESULTS: Pain was significantly reduced in the case of more than two-thirds of the patients 1 year after the first consultation. After 5 and 13 years, the percentages of patients with reported pain had increased only slightly. However, the therapy did not reduce joint noises or mouth opening. The prevalence of joint noises was reduced to less than a quarter after 1 year, but during the next 13 years increased to the former level. Initially, one-third of the patients had mouth-opening reduction. This proportion dropped to one-third of these cases after 1 year, but increased to 40% after 13 years. CONCLUSIONS: Treatment using splints reduced pain in approximately two-thirds of the patients, but with no difference between the three types of splints used.

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.