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Biomedical subjects

J A von Fraunhofer

Publications and source records attributed to J A von Fraunhofer.

At least 19 recordsLinked to original sources
PubMed2004

Effect of a dental unit waterline treatment solution on composite-dentin shear bond strengths.

OBJECTIVE: The control of biofilm and effluent contamination of dental unit water lines (DUWL) includes additions of antimicrobial solutions, as well as automatic dosing units. There are, however, varying reports on the effects of such agents on the bond strength of restorative dental materials and, particularly, between these agents and dental hard tissues. METHODOLOGY: The possible effects of an antimicrobial DUWL treatment solution on the adhesion of composite resin to dentin was evaluated by shear bond strength (SBS) testing. A total of 20 caries-free human molar and premolar teeth were used as the test substrates. The teeth were divided into two sets of 10 teeth which, after appropriate cleaning with water and pumice, were embedded horizontally in dental die stone. The buccal surface of each tooth was ground flat to a 17 microns finish using water-lubricated SiC paper. The teeth were then etched for 15 seconds with 37% H3PO4 and rinsed with either water (control) or a proprietary DUWL treatment (ICX) solution. Thereafter, the teeth were lightly blown dry with clean dry air, and the dentin conditioned with Prime & Bond NT for 20 seconds. The excess solvent was then removed by gentle air drying for 5 seconds, and the conditioner cured with visible light for 10 seconds. A cylinder of composite was placed on the conditioned surface and cured. A second group of 20 caries-free human molar and premolar teeth were used as test substrates to evaluate the effect of the ICX DUWL treatment solution on a different dentin priming system (OptiBond Solo Plus). The teeth in the second group were divided into two sets and after a 15 second etch with 37% H3PO4, were rinsed with water (control) or the proprietary ICX DUWL treatment solution. Thereafter, the teeth were lightly blown dry with clean, dry air and the dentin conditioned with OptiBond Solo for 20 seconds. The excess solvent was then removed by gentle air drying for 5 seconds, and the conditioner cured with visible light for 10 seconds. A cylinder of composite was placed on the conditioned surface and cured. Shear bond strength testing was performed with a universal test machine at the default cross-head speed of 0.1 mm/min. A set of teeth, sectioned, mounted and etched as above but rinsed with a 0.01% mineral oil/water mix prior to conditioning and bonding, was used as the negative control. A separate corrosion testing was performed by immersing brass coupons in water and ICX for 31 days and measuring the weight loss. The brass coupons were bright-dipped, electroless nickel-plated and bright nickel electroplated. RESULTS: The bonding studies indicated that the DUWL treatment solution applied to a cut and etched dentin surface prior to conditioning and bonding with an adhesive system has no effect (p > 0.05) on bond strength for either group of specimens, compared to water. Negative control specimens were found to have minimal bond strengths. The corrosion study indicated no difference in the behavior of the test specimens in ICX compared to those in water, although differences were noted between the different surface finishes applied to the brass substrate. CONCLUSION: The findings of this study demonstrate that exposure of an etched dentin surface to a water-based DUWL treatment mixture has no adverse effects on subsequent adhesion strength. Minimal corrosive attack was noted in the ICX solution and water for brass coupons provided with three different surface finishes.

Analysis of Variance↗
PubMed2004

The role of cavity preparation and conditioning in the leakage of restorations.

PURPOSE: Restoration microleakage is thought to be determined by the method and location of cavity preparation, enamel etching, and dentin conditioning, as well as the restorative material. This study compared the microleakage of composite restorations placed in preparations cut with carbide and diamond burs and those treated with different bonding/conditioning agents. MATERIALS AND METHODS: Class V preparations (3 x 2 x 2 mm) were cut wholly in enamel or in enamel and cementum in 100 human premolars. Twenty teeth were prepared with carbide burs and the preparations etched and conditioned with Prime&Bond NT but not restored. A second set of 20 teeth had enamel-only preparations cut with carbides (n = 10) or diamonds (n = 10), and the preparations etched, conditioned (Prime&Bond NT) and restored with Prisma TPH. The other 60 teeth were divided into 3 groups of 20 teeth each with enamel-only (n = 10) or enamel/cementum preparations (n = 10). The 3 groups of teeth were conditioned with Optibond Solo, Clearfil SE Bond or Prompt-L-Pop prior to restoration with Prisma TPH. Two mm of root was resected from all teeth, pulpal tissue removed, and insulated copper wires inserted via the root canals to contact with the pulp chamber roof before the tooth-wire interfaces and root surfaces were sealed. The teeth were immersed in 0.9% NaCl and leakage assessed over 30 d by iR drop across a resistor in series with a DC source and stainless-steel counter electrode. RESULTS: Differences (p < 0.05) in leakage were found for enamel preparations cut with carbides and diamonds, and the relationship of leakage vs time was linear. Enamel/cementum preparations showed greater leakage, and the relationship of leakage vs time was sigmoidal. Conditioned-only preparations showed the same leakage as those conditioned and restored, while preparation leakage varied with the conditioning agent. CONCLUSION: Cavity preparation location, method of cutting, and the conditioning agent markedly affect leakage behavior.

Acrylic Resins↗
PubMed2001

Effect of light source and time on the polymerization of resin cement through ceramic veneers.

PURPOSE: The purpose of this study was to evaluate the efficiency of 3 different light sources to polymerize a light curing resin cement beneath 3 types of porcelain veneer materials. MATERIALS AND METHODS: A conventional halogen light, a plasma arc light, and a high intensity halogen light were used to polymerize resin cement (Variolink II; Ivoclar North America Inc, Amherst, NY) through disks of veneer materials. Equal diameter and thickness disks of feldspathic porcelain (Ceramco II; Ceramco Inc, Burlington, NJ), pressable ceramic (IPS Empress; Ivoclar North America Inc), and aluminous porcelain (Vitadur Alpha; Vident Inc, Brea, CA) were used as an interface between the curing light tips and the light polymerized resin cement. The resin cement/veneer combinations were exposed to 4 different photopolymerization time protocols of 5 seconds, 10 seconds, 15 seconds, and 20 seconds for high intensity light units (Apollo 95E [Dental Medical Diagnostic Systems Inc, Westlake Village, CA] and Kreativ 2000 [Kreativ Inc, San Diego, CA]), and 20 seconds, 40 seconds, 60 seconds, and 80 seconds for conventional halogen light (Optilux; Demetron Research Inc, Danbury, CT). A surface hardness test (Knoop indenter) was used to determine the level of photopolymerization of the resin through the ceramic materials with each of the light sources. The data were analyzed by one-way analysis of variance and a post-hoc Scheffe test (p < .05). RESULTS: The data indicates that the Variolink II Knoop Hardness Number values vary with the light source, the veneer material, and the polymerization time. For a given light and veneer material, Knoop Hardness Number increases with longer polymerization times. The Kreativ light showed statistically significant differences (p < .05) between all test polymerization times. Use of this light required a polymerization time of greater than 20 seconds to reach maximum resin cement hardness. For samples polymerized with the Apollo light, there were statistically significant (p < .05) differences in surface hardness between samples polymerized at all times, except for the 15-second and 20-second times. Samples polymerized with the halogen light showed no statistically significant (p < .05) differences in hardness between polymerization times of 60 seconds and 80 seconds. CONCLUSIONS: High intensity curing lights achieve adequate polymerization of resin cements through veneers in a markedly shorter time period than the conventional halogen light. However, the data in this report indicate that a minimum exposure time of 15 seconds with the Kreativ light and 10 seconds with the Apollo 95E light should be used to polymerize the Variolink II resin, regardless of the composition of the veneer. Conventional halogen lights required a correspondingly greater polymerization time of 60 seconds.

Aluminum Oxide↗
PubMed2000

The effect of root canal preparation on microleakage within endodontically treated teeth: an in vitro study.

AIM: The purpose of this study was to evaluate the effects of smear layer and canal instrumentation on leakage in root-filled teeth. METHODOLOGY: Six groups (n = 12) of freshly extracted human canines and premolars with closed apices and single roots were used. Groups A, B, C, and D were instrumented with engine-driven rotary nickel-titanium MCXIM files and Groups E and F were instrumented with conventional stainless steel hand files. Groups A, C, and E were flushed with 3.0 mL of 17.0% REDTA to remove the smear layer prior to obturation. All teeth were flushed with 5.25% NaOCl, then obturated with AH-26 sealer and either the lateral condensation (Groups C-E) or thermomechanical compaction technique (Groups A and B). Copper wire was placed coronally in contact with the gutta-percha in each tooth and, after immersion in 0.9% NaCl solution, a 10 volt dc voltage was connected between each tooth and a stainless steel electrode. The current flow in the circuit was observed for 45 days. One way ANOVA and Duncan's Multiple Range Test were used to compare Groups A-F at time intervals of 10, 20, 30 and 45 days and identify statistically significant differences. RESULTS: Significantly less microleakage occurred when the smear layer was removed and when the canals were obturated with thermoplasticized gutta-percha. Canals instrumented with engine-driven NiTi files exhibited less leakage than hand-instrumented canals irrespective of obturation method. CONCLUSIONS: Smear layer removal is beneficial to root canal sealing. Obturation with thermoplasticized gutta-percha provides a superior seal whilst canal instrumentation with engine-driven NiTi files reduces the extent of microleakage in root canals.

Analysis of Variance↗
PubMed2000

Evaluation of the slope of the articular eminence and the transverse angle of the glenoid fossa in an Anatolian population.

The purpose of this study was to compare a computer-aided method specially programmed for the measurement of the posterior angle of the articular eminence with formerly used methods, to investigate the angulation differences at different depths of slices, and to evaluate correlation with the transverse angulation. Three slices (central, medial, and lateral) at various depths of the glenoid fossa belonging to 64 dry skulls and two measurement methods were used in this study. The angulation of the articular eminence were measured and the transverse angle of each fossa calculated. No statistical difference was found between the articular eminence results of the two methods. According to the results, the one factor ANOVA central slice was found to be statistically steeper than the other two slices (p < 0.05) (central = 60.33 +/- 10.19, medial = 58.26 +/- 8.6, lateral 58.28 +/- 10.1). No correlation was found between the transverse angle of the inclination of the posterior slope angulation. It was concluded that the computer-aided method is more reliable and accurate and is much easier to use when compared to the manual method. An additional important finding of this study is that the inclination of the articular eminence should be evaluated at various depths of the temporomandibular joint.

Analysis of Variance↗
PubMed2000

Irrigation rates and handpieces used in prosthodontic and operative dentistry: results of a survey of North American dental school teaching.

PURPOSE: A data baseline on dental cutting methodologies was established by means of a survey of North American dental school teaching. MATERIALS AND METHODS: Sixty-four North American dental schools were surveyed regarding their recommendations on handpiece usage and coolant flow rates in fixed prosthodontics and operative dentistry. RESULTS: High-speed handpieces were the instruments of choice for tooth preparation in fixed prosthodontics. In operative procedures, recommendations for sole use of the high-speed, the low-speed, or both handpiece types were more uniform. CONCLUSIONS: North American dental schools advocate greater use of high-speed than low-speed handpieces. Although the use of high-speed handpieces predominate in schools in Canada and Puerto Rico, there is a proportionately higher use of low-speed handpieces than in US dental schools. Few (approximately 1 in 5) schools made recommendations on coolant flow rates during cutting procedures.

Canada↗
PubMed2000

Enhanced dental cutting through chemomechanical effects.

BACKGROUND: Previous studies have shown that certain surface-active agents--compounds that reduce interfacial tension--in a dental handpiece's irrigation water can enhance cutting rates, or CRs. This study evaluated these effects under test conditions simulating dental practice. METHODS: The authors used a self-contained cutting system with a digitally controlled handpiece speed, torque and water flow rate to cut machinable glass ceramic (Macor, Corning Inc.) with medium-grit diamond burs and cross-cut fissure carbide burs under a load of 147.5 grams and 22 milliliters per minute coolant flow rate using water with mouthwash (Scope, Procter & Gamble) additions. They used six burs for each irrigant mixture to make three 5-millimeter edge cuts through 13 mm of Macor; CRs were quantified as the time necessary to transect the Macor cutting substrate. RESULTS: Additions of small amounts of mouthwash to the coolant water accelerated the CR for both carbide and diamond burs. The CRs for carbide burs in millimeters per second were distilled water, 0.21; 1:2.5 mouthwash:distilled water mixture, 0.12; 1:5 mixture, 0.64; and 1:10 mixture, 0.66. The CR differences for the 1:5 and 1:10 mixtures were significant (P < .001). The CRs for diamond burs in millimeters per second were distilled water, 0.09; 1:1 mouthwash:distilled water mixture, 0.13; 1:2.5 mixture, 0.16; 1:5 mixture, 0.21; and 1:10 mixture, 0.18. When it came to the diamond burs, the CR differences between water and the mouthwash:distilled water mixtures were significant (P < .001). The authors found that the mouthwash additions ensured higher CRs compared with those for water alone over the entire cutting regimen; that is, while the CRs for both carbide and diamond burs dropped with prolonged cutting with water irrigation, the addition of mouthwash resulted in the burs' cutting faster and for longer than with water alone. CONCLUSION: Adding small amounts of mouthwash to the coolant water significantly enhanced cutting by diamond and carbide burs and maintained higher CRs with prolonged cutting. CLINICAL IMPLICATIONS: Making low additions of mouthwash (1:5 and 1:10 mouthwash:distilled water mixtures) to the handpiece irrigant system can lead to two- to threefold increase in the dental diamond and carbide bur cutting rate compared with that for water alone.

Carbon↗
PubMed2000

Cutting efficiency of three diamond bur grit sizes.

BACKGROUND: Tooth preparation requires safe, efficient and rapid cutting, and diamond burs routinely are used for extracoronal preparation and gross tooth reduction. Coarser-grit diamond burs often are used for gross tooth reduction, with tooth surface finishes being sacrificed for the presumed greater cutting rates, or CRs, of the coarser diamond burs. The authors compared the CRs of medium-, coarse- and super-coarse-grit diamond burs. METHODS: The authors used a self-contained dental treatment system with digitally controlled handpiece speed, torque and water flow rate to cut a machinable glass ceramic cutting substrate with medium-, coarse- and super-coarse-grit diamond burs from the same manufacturer under a load of 147.5 grams (0.9 kilonewton at the bur tip) and a coolant flow rate of 22 milliliters per minute. They made three cuts through 13-millimeter bars of the cutting substrate with six diamond burs of each grit size. They determined CRs as the transection time per millimeter and analyzed CR data by one-way analysis of variance and post hoc Scheffé tests. RESULTS: The authors found no statistically significant difference in CR (P > .05) between the three diamond bur grit sizes for the first (13 mm) cuts. When they compared the three cuts (39 mm total cut length), they found no difference (P > .05) between CRs for coarse- and super-coarse-grit diamond burs, but they did find that the super-coarse-grit diamond burs cut faster than the medium-grit diamond burs (P < .01). CONCLUSION: Differences in CR for the three diamond bur grit sizes are due to the greater decrease in CR for the medium-grit diamond burs (50 percent) compared with the CRs of the coarse- and super-coarse-grit diamond burs (35 percent and 25 percent, respectively) over the total cutting period. CLINICAL IMPLICATIONS: Coarser-grit diamond burs may be useful for extensive gross tooth preparations, but dental professionals should be aware of the associated effects of the coarser grit on surface finish, heat generation and enamel damage.

Analysis of Variance↗
PubMed1999

Irrigating solution and pressure effects on tooth sectioning with surgical burs.

OBJECTIVE: The purpose of this study was to determine the influence of the applied load on the handpiece, type of cooling agent, and type of tooth on surgical tooth dissection with a tapered crosscut fissure bur. STUDY DESIGN: Cutting studies were performed at handpiece loadings of 295 and 590 g through use of an oral surgery straight handpiece, tapered crosscut fissure burs, and an established cutting regimen. Extracted molars were dissected under irrigation with water, 0.9% saline solution, and lactated Ringer's solution at constant flow rates of 15 and 25 mL/min. Cutting efficiencies were analyzed by 1-way analysis of variance and Scheffé tests. RESULTS: No difference in cutting efficiency was found at low loads under irrigation with water or saline solution, but under irrigation with lactated Ringer's solution, a higher cutting efficiency was found (P < .05). There was no difference in cutting efficiency for lactated Ringer's solution and saline solution at high loads, but both cut more efficiently than water (P < .01). CONCLUSIONS: Saline solution is a useful coolant/irrigant for the dissection of teeth under most conditions, but lactated Ringer's solution might be beneficial with respect to cutting efficiency when lower handpiece loads are required.

Analysis of Variance↗
PubMed1999

Dental cutting with diamond burs: heavy-handed or light-touch?

PURPOSE: The cutting efficiency of diamond dental burs using different handpiece loads was evaluated against simulated enamel, a machinable glass ceramic (Macor). MATERIALS AND METHODS: An ultra-high-speed dental handpiece was mounted in a frictionless bearing so that the pressure applied at the contact interface between the dental bur and the cutting substrate was controlled. One type of coarse- and two types of medium-grit diamond burs were studied. Handpiece loads of 44, 91.5, and 183 g were applied at the bur/Macor interface, and cutting efficiency was determined as the amount of Macor removed in ten 30-second-duration cuts that were 4 mm in length. The data were analyzed by one-way ANOVA and a post-hoc Scheffé test at an a priori alpha = 0.05. RESULTS: Cutting efficiency depended on both the diamond grit of the bur and the load applied to the handpiece. CONCLUSIONS: The pressure used by most dentists, about 100 g at the bur tip, appears to be optimal for medium-grit burs. If the pressure applied to the handpiece is markedly increased, there was no increase in cutting efficiency for medium-grit burs. In contrast, an increased handpiece pressure raises the cutting efficiency of coarse-grit burs but the effect of this enhanced rate of cutting on the pulpal tissues is uncertain. Cutting efficiency also appeared to be dependent on debris accumulation between the diamond chips.

Analysis of Variance↗
PubMed1999

Comparison of sectioning rates among carbide and diamond burs using three casting alloys.

PURPOSE: This study compared the sectioning rates of commercially available high noble, noble, and base metal casting alloys using two new cross-cut tungsten carbides specifically manufactured for alloy sectioning and two medium grit diamond burs. MATERIALS AND METHODS: Rectangular bars cast from a base metal alloy (Ni-Cr-Mo-Be), a noble alloy (Pd-Cu-Au), and a high noble alloy (Au-Ag-Cu-Pd) were sectioned under controlled conditions. Two types of cross-cut tungsten carbide and two types of medium grit diamond burs were tested using a high-speed handpiece under a coolant flow rate of 20 mL/min and an applied load at the bur tip of 0.9 N (91.5 g). Three 4-mm cuts were made through the alloy specimens using six burs of each type. The time required for Cuts 1, 2, and 3 was recorded, and sectioning rates in millimeters per minute were calculated as a relative measure of cutting efficiency. For each alloy, the total time required for the three cuts was analyzed using one-way analysis of variance (one-way ANOVA) and Scheffé tests (alpha = 0.05) to determine differences in sectioning rate among bur types. RESULTS: In general, mean sectioning rate for Cut 1 through Cut 3 decreased with longer use of the bur. Regarding total sectioning times, the carbide burs sectioned the base metal alloy significantly faster (P < .001) than the diamond burs. However, diamond burs sectioned the high noble alloy significantly faster (P < .001) than the carbide burs. Diamond burs also sectioned the noble alloy more quickly than the carbide burs, but the difference was not statistically significant. CONCLUSIONS: The cross-cut tungsten carbide burs should be used to section the base metal alloy but the medium grit diamond burs should be used to section the high noble alloy.

Analysis of Variance↗
PubMed1999

Dental burs--what bur for which application? A survey of dental schools.

PURPOSE: The purpose of this study was to survey North American dental schools regarding recommendations for rotary instrumentation for fixed prosthodontic and operative procedures at the predoctoral and postgraduate level. MATERIALS AND METHODS: A 25-question survey was sent to 64 North American dental schools, of which 15 questions specifically related to rotary instrument recommendations. One questionnaire was addressed to the individual at each school having administrative responsibility for teaching tooth preparation techniques. A high response rate was assured by follow-up telephone calls and faxes. The distributions of bur recommendations for both predoctoral and advanced prosthodontic programs were analyzed by chi-squared tests at an a priori alpha = 0.05. RESULTS: Completed surveys were received from 58 of 64 dental schools, a response rate > 90%. Medium grit burs predominate in predoctoral education for gross tooth reduction for fixed prosthodontics, whereas coarse grit burs predominate at the graduate level (p < .05). The use of the diamond bur alone predominates for axial wall refinement, whereas the use of carbide burs or carbide burs in combination with diamond burs prevails for marginal refinement (p < .05). In predoctoral operative dentistry, recommendations for cavity outline form were similar at all dental schools (p > .05) and were principally tungsten carbide (WC) burs. Carbide burs are the instrument of choice for internal walls, but the WC bur alone or in combination with diamond burs is preferred for refining composite margins (p < .05). CONCLUSIONS: There is a broad consensus within North American dental schools on rotary instrumentation used by dental students. There is a greater use of coarser grit burs for gross tooth reduction in fixed prosthodontics at the postgraduate than predoctoral level.

Chi-Square Distribution↗
PubMed1998

The effects of custom tray material on the accuracy of master casts.

PURPOSE: The accuracy of master cast reproduction by a polyvinylsiloxane impression material using two visible-light-curing resin and an autopolymerizing polymethyl methacrylate resin custom tray materials was investigated. MATERIALS AND METHODS: Custom trays were fabricated from a master cast that had three index points marked on both the inner and outer vestibules. Impressions were made of the master cast using Extrude and then poured in Die Keen Green stone. The distances between the reproduced index points were measured to +/- 0.01 mm with a traveling microscope and the algebraic norms calculated for each tray material. RESULTS: No differences (p > .05) were found in the dimensions of the inner index points, while the separations of the outer index points indicated that there were differences in the accuracy of reproduction (p < .01) by the three tray materials. The index points reproduced on the casts, compared with the master cast, were closer together for the Triad Blue trays than for the TruTray and Ontray impression trays. CONCLUSIONS: All three tray materials produced acceptable casts, but the greatest accuracy was achieved with TruTray, followed by Ontray. Triad Blue produced casts that were slightly smaller than the master. In practice, the small measured differences in cast dimensions may not have clinical significance.

Analysis of Variance↗
PubMed1997

Corrosion of orthodontic devices.

A brief overview of the theory of corrosion and the formation of galvanic couples is presented, followed by a discussion of the metals and alloys used in the fabrication of orthodontic appliances and devices. Attention is paid to the factors that contribute to establishment of corrosion cells in the mouth. Although oral corrosion generally does not cause significant destruction of metal, it can elicit in patients adverse physiological responses such as local irritation and metal hypersensitivity. There are indications that orthodontic treatment may lower the incidence of nickel hypersensitivity. Destructive attack on orthodontic appliances does occur, however, when certain types of denture cleanser are used to clean appliances that contain soldered joints.

Corrosion↗
PubMed1996

Assessing the cutting efficiency of dental diamond burs.

This study measured the cutting efficiencies of 15 types of roundend tapered conventional and disposable diamond burs. The results showed that disposable diamond burs had cutting efficiencies that were comparable to those of conventional (multiuse) diamond burs; their use should reduce the risk of clinical cross-infection.

Ceramics↗
PubMed1995

Frictional resistances using Teflon-coated ligatures with various bracket-archwire combinations.

Static frictional resistances were compared between Teflon-coated stainless steel and clear elastomeric ligatures used with various combinations of brackets and archwires. Stainless steel metal, polycrystalline ceramic and single crystal ceramic 0.022-inch slot brackets were used in combination with stainless steel and nickel titanium archwires, 0.018 inch and 0.016 x 0.022 inch. Friction was measured in the dry state at bracket-archwire angulations of 0, 5, 10, and 15 degrees. Moments induced by engagement of the archwires into the brackets were measured for each archwire type and bracket-archwire angulation. Teflon-coated ligatures produced less friction than elastomers for all bracket-archwire combinations. The ceramic brackets generally elicited greater frictional resistances than stainless steel brackets. Regarding both friction and control of tooth movement, these data suggest that sliding mechanics are best executed with stainless steel brackets and stainless steel archwires. Moreover, these data reveal the usefulness of Teflon-coated ligatures in minimizing the high friction of ceramic brackets when an esthetic appliance is imperative.

Aluminum Oxide↗
PubMed1994

Force delivery properties of colored elastomeric modules.

Elastomeric chains have been used by clinicians for some time to accomplish various treatment objectives. Recently, a number of manufacturers have added colored elastomeric chains to their inventories. The present study was designed to investigate the force delivery capabilities and dimensional stability of these new colored chains. Four different colors of short filament configuration produced by three manufacturers were examined. The force delivery capabilities of each chain were tested at 0 hours and, after storage at 37 degrees C in air, distilled water, and artificial saliva, at 1 hour, 4 hours, 24 hours, 1 week, 2 weeks, and 3 weeks. A universal testing machine was used to determine the amount of distraction necessary to generate 150 and 300 gf. Dimensional measurements were assessed initially and, after exposure to a simulated oral environment, at 1, 2, and 3 weeks. The data from the force delivery portion of the study were analyzed with a 4-factor factorial analysis of variance. The data compiled from the dimensional stability portion were subjected to a 3-factor factorial analysis of variance. Follow-up Bonferroni simultaneous t tests (family-wise a priori alpha p < 0.05) was used to determine statistical significance of the differences among sets of means. All colored elastomeric chains in the study appeared capable of initially generating force levels compatible with tooth movement. After 24 hours of storage in liquid, the amount of distraction needed to produce 150 and 300 gf substantially increased. The amount of increased need varied among manufacturers. All chains showed an increase in dimensional measurements after 1 week, with little change thereafter.

Analysis of Variance↗