TP Orthodontics Research Articles

Orthodontic bonding to porcelain: A comparison of bonding systems

Statement of problem. Direct bonding of orthodontic brackets to porcelain surfaces has been plagued by failure. Purpose. The purpose of this study was to compare the bond strengths of several different bonding systems when bonding orthodontic brackets to porcelain-fused-to-metal surfaces. Material and methods. Fifty natural glazed feldspathic porcelain-fused-to-noble metal disks 6 mm in diameter and 3 mm in height (1 mm metal and 2 mm porcelain) were fabricated and divided into 5 groups of 10. A different bonding system (GC America Fuji LC, American Ortho Spectrum, 3M Transbond, TP Orthodontics Python, and Kerr Herculite) was assigned to each group, and 50 identical orthodontic brackets were bonded (with the above mentioned systems) to each disk according to each manufacturer's instructions. Each system except TP Orthodontics Python conditioned with phosphoric acid (35% to 37.5%) and all systems were primed with silane before bonding. The specimens were subjected to gradual shear forces up to 123 N in a universal testing machine (Instron Corp, Canton, Mass.) until fracture. The shear bond strength of the bonding systems between the porcelain surface and the bracket was measured in megapascals (MPa). Failures were observed via a Zeiss optical microscope (10×); Tukey's HSD Test and analysis of variance were used to determine significance between the bonding systems at P<.05 level of significance. Results. Failure of all of specimens was adhesive between the porcelain surface and the bonding agents. On the basis of a current literature review, bonding systems were categorized as clinically acceptable if they had a shear bond strength of 6 to 8 MPa. The 3M Transbond Bonding System, American Orthodontics Spectrum Bonding System, and GC America Fuji Ortho LC Bonding System performed within this clinically acceptable range (6 to 8 MPa), whereas Kerr Herculite Bonding System and TP Orthodontics Python Bonding System did not (2 to 4 MPa). The bond strengths of GC America Fuji Ortho LC, 3M Transbond, and American Orthodontics Spectrum were significantly greater (mean = 2.3 times) than TP Orthodontics Python or Kerr Herculite bonding systems. Conclusion. Within the limitations of this study, the results reaffirm the regimen of conditioning with phosphoric acid and priming with silane before bonding orthodontic brackets to feldspathic porcelain fused to noble metal. All products indicated for this purpose may not achieve satisfactory bond strengths; however, because they do not all include the critical steps of conditioning with phosphoric acid and priming with silane. The 3M Transbond Bonding System, American Orthodontics Spectrum Bonding System, and GC America Fuji Ortho LC Bonding System performed within the clinically acceptable range (6 to 8 MPa), whereas Kerr Herculite Bonding System and TP Orthodontics Python Bonding System did not (2 to 4 MPa). (J Prosthet Dent 2003;89:66-69.)

The relationship between acid-etch patterns and bond survival in vivo

The aim of this study was to investigate the relationship between acid-etch quality and bond survival in vivo. The subjects were 29 orthodontic patients. High-resolution silicone impressions were taken of the buccal tooth surfaces after etching for 30 seconds with 37% phosphoric acid. The impressions were replicated in epoxy resin and examined under high magnification in a scanning electron microscope. A 4-point classification system and histometric techniques were used to evaluate etch patterns on the enamel surfaces where orthodontic brackets were to be bonded. After impressions were made, all teeth (including first molars) were bonded with 0.022-in Andrews' prescription brackets (“A” Company, San Diego, Calif) and Right-On composite (TP Orthodontics, Leeds, England). The first date of bond failure for each tooth was recorded; it varied from 1 to 806 days. An ideal etch pattern was found on less than 5% of the orthodontic bonding area; type C pattern (pitted enamel surface) occupied the greatest area. Overall, the failure rate was 55.8% over 26 months; the greatest failure rate occurred in first molars. Multiple regression analysis revealed a positive and statistically significant relationship between the area occupied by ideal etch type and the length of survival of the bond (P < .001). (Am J Orthod Dentofacial Orthop 2002;121:502-9)

Fluoride release from new light-cured orthodontic bonding agents

The purpose of this study was to compare the rates of fluoride release with time from 1 nonfluoridated and 3 fluoride-containing orthodontic bonding materials in distilled water and artificial saliva. Materials tested were Assure (Reliance Orthodontic Products, Itasca, Ill), Fuji Ortho LC (GC, Tokyo, Japan), Python (TP Orthodontics, LaPorte, Ind), and Transbond XT (3M Dental Products, Monrovia, Calif). Ten specimens of each material type were stored in distilled water, and 10 of each type were stored in artificial saliva at 37°C. Fluoride release was measured with an ion-specific electrode. Readings were taken periodically for a total time period of 6 months. At day 1, Assure released the most fluoride into distilled water (66.2 μg/cm2) and into artificial saliva (65.8 μg/cm2), followed by Fuji Ortho LC (25.9 μg/cm2; 18.8 μg/cm2), Python (6.3 μg/cm2; 4.2 μg/cm2), and Transbond (0.1 μg/cm2; 0.1 μg/cm2). The fluoride release rates were highest during the first days of testing, declining to lower but more stable levels. At the end of 6 months, Fuji Ortho LC released the most fluoride (3.8 μg/cm2; 3.5 μg/cm2) followed by Assure (3.1 μg/cm2; 2.8 μg/cm2), Python (2.6 μg/cm2; 1.7 μg/cm2), and Transbond (0.1 μg/cm2; 0.1 μg/cm2). The type of storage medium did not dramatically affect fluoride release. The second part of the study, undertaken after a year of sample storage, tested the 20 samples of Assure for a further 2-week period, after exposure to running and still distilled water. Although fluoride release rates declined with time, they were still higher than the 1.5 μg/cm2 level that is referenced as inhibiting decalcification of enamel in a clinical environment. Release rates were similar in running and still water at all time points. Throughout the 6-month period, all 3 fluoride-containing materials had rates of fluoride release that could theoretically inhibit decalcification of enamel. (Am J Orthod Dentofacial Orthop 2001;120:392-7)

The “tip-edge” torquing mechanism: A mathematical validation

The Tip-Edge (TP Orthodontics, LaPorte, Ind) bracket is unique among orthodontic brackets because it can be used in combination with rectangular archwire to torque teeth, not through activation of the archwire itself but through the action of auxiliary springs that are active in the tip plane. The purpose of this report is to describe the way in which a tipping couple generates a secondary torquing couple and the resulting path traced by the root apex and to express those actions mathematically. The magnitude of forces applied by the auxiliary spring to the tooth apex is calculated on the basis of an experiment. (Am J Orthod Dentofacial Orthop 2001;119:632-9)

The effect of food simulants on enamel-composite bond strength.

The effect of food simulants upon the enamel-composite bond strength of two orthodontic adhesive composites was studied. Thirty extracted premolars were used in each experimental group. Orthodontic brackets were bonded with either Transbond (3M Unitek) or Right-On (TP orthodontics) and were then exposed to either distilled water (control), 8 per cent ethanol (aqueous food), 50 per cent ethanol (alcoholic food), buffered lactic acid pH4 (acidic food), or corn oil (fatty food) for 12 weeks. Bond strength and Adhesive Remnant Index was recorded. It was found that 50 per cent ethanol had a significant effect upon the bond strength of both Transbond and Right-On. Right-On was affected to a greater extent. The clinical significance of this finding is that alcoholic mouth rinses, and alcohol-containing foods and drinks may be a causative factor in bond failure. However, the use of an alcoholic mouthrinse late in treatment may aid bracket removal. This potential use requires more research. Refereed Scientific Paper

Comparison of the debonding characteristics of two innovative ceramic bracket designs

Two new ceramic brackets—one designed with a metal-lined arch wire slot and the other with an epoxy resin base—have been recently introduced. The new brackets are thought to combine the esthetic advantages of ceramics and the functional advantages of debonding metal brackets. The purpose of this study was to compare the following: 1) the shear bond strength of the 2 brackets, and 2) the bond failure location when the brackets are debonded with pliers. Sixty-one Clarity (3M Unitek) collapsible ceramic brackets and 66 MXi (TP Orthodontics, Inc) brackets were bonded to the teeth with the same bonding system. The Zwick Universal Test Machine (Zwick Gm bH & Co) was used to determine the shear bond strength force levels needed to debond the brackets. The appropriate pliers also were used to debond both types of brackets to determine the mode of bond failure that will be encountered clinically. After debonding, all the teeth and brackets were examined with 10× magnification. Any adhesive that remained after the bracket removal was assessed according to the Adhesive Remnant Index. The findings indicated that the shear bond strength of the Clarity ceramic brackets was significantly greater than that of the MXi ceramic brackets. However, both brackets exhibited forces that were adequate for clinical use. The Adhesive Remnant Index scores for both the shear test and the plier debonding indicated a similar bond failure pattern when the 2 ceramic brackets were compared with each other. This suggests that, when these brackets are debonded with the Weingart (Ormco) and ETM (Ormco) pliers, there was a greater tendency for most of the adhesive to remain on the enamel surface. In conclusion, the most efficient method to debond the MXi ceramic bracket is by placing the blades of the ETM 346 pliers between the bracket base and the enamel surface. On the other hand, the most efficient method of debonding the Clarity bracket is by using the Weingart pliers and applying pressure to the tiewings. When the 2 ceramic brackets were debonded as recommended here, most of the residual adhesive remained on the enamel surface, a pattern similar to the one observed previously with metal brackets. The failure at the bracket-adhesive interface decreases the probability of enamel damage but necessitates the removal of more residual adhesive after debonding. (Am J Orthod Dentofacial Orthop 1999;116:86-92)

Rectangular wire and third-order torque: A new perspective

The Differential Straight Arch technique, more commonly known as "Tip-Edge" (TP Orthodontics Inc.), uses a modified edgewise type bracket to allow differential tooth movement. As bracketed teeth incline toward their finishing positions, the geometry of the arch wire slot causes the vertical slot dimension available to the arch wire to increase. Advantage has been taken of this facility, to evolve an entirely new torquing system for final finishing, during the root correction phase. Instead of increasing rectangular arch wire size to fit the arch wire slot, as with conventional edgewise brackets, the Tip-Edge method reduces the vertical arch wire slot dimension to achieve a precise, three-dimensional relationship to a full-sized rectangular arch wire. The active component is provided by auxiliary springs. The method, which awaits mathematical analysis, is described and illustrated with two case reports.

Bonded orthodontic retainers: The wire-composite interface

The bonded orthodontic retainer constructed from multistrand wire and composite is an efficient esthetic retainer, which can be maintained long-term. Clinical failures of bonded orthodontic retainers, most commonly at the wire/composite interface, have been reported. This in vitro investigation aimed to evaluate selected multistrand wires and composite materials that are available for use in the construction of bonded fixed retainers. An in vitro model was developed to simulate the forces encountered at the wire/composite interface. No significant difference was detected between different multistrand wire types and diameters with regard to retention in composite. Wires were placed in one of three groups according to surface characteristics identified with scanning electron microscopy. Increasing the thickness of composite overlying the wire increased the force required to detach the wire from the composite. Thickness of composite greater than 1.0 mm overlying the wire may give little clinical advantage. Greater force was required to detach the wire from Concise Orthodontic (3M Unitek) than any other composite tested. In vitro abrasion resistance testing found Heliosit Orthodontic (Vivadent) and Right On (TP Orthodontics, Inc.) to have poor abrasion resistance, whereas Concise Orthodontic and Transbond (3M Unitek) had abrasion resistance comparable with restorative composites. Clinical recommendations are made based on these findings. (Am J Orthod Dentofac Orthop 1997;111:67-74.)

Canine retraction: A comparison of two preadjusted bracket systems

Before the 1970s, Begg and Edgewise appliances were the most commonly used appliances in orthodontics. With the introduction of preadjusted appliances, many have made claims of superiority. These claims are often unsubstantiated, as few, if any, have ever been tested in a controlled, prospective in vivo study. The purpose of this study was to compare the time required to retract canine teeth by using two different preadjusted bracket systems (Tip-Edge, TP Orthodontics, LaPorte, Ind., versus A-Company straight wire, Johnson and Johnson, San Diego, Calif.) in a human sample. Anchorage loss as a result of this movement was also evaluated. A sample of 12 patients was randomly selected from the new patient pool at the postgraduate orthodontic clinic of Montefiore Medical Center. All patients required the removal of first premolars in one or both arches as a part of their orthodontic treatment. The rate of retraction and anchorage loss were evaluated. Paired t tests were performed separately for the rates of retraction and anchorage loss. The mean rates of retraction were 1.88 mm per 3-week period and 1.63 mm per 3-week period for the Tip-Edge and A-Company brackets, respectively. There was no statistically significant difference in the rates ( p > 0.05). The mean anchorage loss was 1.71 mm for the Tip-Edge bracket, and 2.33 mm for the straight wire bracket. The difference in the amount of anchorage loss was inconclusive as the sample size was too small (power was 10%). (Am J Orthod Dentofac Orthop 1996;110:191-6.)

Treatment mechanics in Class III open bite malocclusion with Tip Edge technique

Nonextraction treatment with nonorthognathic intervention for treatment of a skeletal Class III open bite malocclusion was performed. Light traction with effective uprighting of the lower dentition with Tip Edge brackets (TP Orthodontics, La Porte, Ind.) and anteriorly placed Class lIl elastics was the modus operandi. Class lIl elastics can prevent elongation of the upper molars and yet can cause the upper dentition to move forward. Ni-Ti wire with a reverse curve of Spee helped both the uprighting and depression of the mandibular molars. The present case was treated with the Kim philosophy 1,2 but employing tip Edge brackets. This combination was found to be very easy to manipulate and achieved good results in a very short period of time. (Am J Orthod Dentofac Orthop 1996;110:1-7.)

Direct light transmittance through ceramic brackets

The objective of this study was to investigate the degree of direct light transmittance (%T) of various types of esthetic brackets and to correlate these values with their structure, morphologic factors, and composition. Eight types of brackets were used in the study; six brackets of each type were tested. An ultraviolet-visible spectroscopic direct transmission analysis was performed at 320 to 700 nm wavelength range. From each spectrum, the %T corresponded to the peak absorbance wavelength of the photoinitiator of the polymerization was recorded (468 nm). Recorded data were analyzed with one-way analysis of variance and Scheffe's test at α = 0.05 significance level. In addition, scanning electron microscope (SEM) images were used to reveal the structure and morphologic factors of the brackets tested. Highest %T values (Mean ± 1 SD) were obtained from a monocrystal type of bracket (Starfire [“A” Company, San Diego, Calif.] 35.02 ± 1.59%), followed by a polycrystalline (Fascination [Dentaurum, Pforzhein, Germany] 5.70 ± 1.41%) and a ceramic/polycarbonate base one (Ceramaflex [TP Orthodontics, Inc., La Porte, Ind.] 4.02 ± 0.96%). Also other brands presented the following data: Allure (GAC, Central Islip, N.Y.) 3.62 ± 0.5%; Transcend 2000 (Unitek/3M, Monrovia, Calif.) 2.62 ± 0.5%; Fascination (edgewise) (Dentaurum, Pforzhein, Germany) 1.97 ± 0.69%; Lumina (Ormco, Glendora, Calif.) 1.57 ± 0.5%; Signature (RMO, Denver, Colo.) 1.22 ± 0.5%. The results showed that the structure, morphologic factors, and composition of the brackets tested were found to affect direct light transmission significantly. Other clinical factors, such as diffuse transmittance, enamel reflectance or light directed about the edges of the bracket, might affect the polymerization and physical and biologic properties of any underlying light-cured adhesive resin as well. (A M J O RTHOD D ENTOFAC O RTHOP 1995;107:11-19.)

Employing Tip-Edge brackets on canines to simplify straight-wire mechanics

The straight-wire appliance was developed in part to reduce wire bending and therefore make treatment results more predictable. Because tip prescription is built into the bracket slots, teeth are held at their final crown angulations throughout treatment. Straight-wire brackets are used in an attempt to produce bodily tooth movement. However, teeth tend to tip when a force is applied. This tipping, especially when canines are retracted, can deflect the arch wire causing supereruption of the incisors with a resultant increase in anterior overbite and an open bite in the canine/premolar area. Placing Tip-Edge brackets (TP Orthodontics, Inc., LaPorte, Ind.) on canines and employing tipping and uprighting mechanics on these teeth can overcome these problems. Two cases are presented to illustrate this approach to treatment. (A M J O RTHOD D ENTOFAC O RTHOP 1994;106:341-50.)

Comparative evaluation of ceramic bracket base designs

Since the initial introduction of ceramic brackets, base designs have been modified to reduce tooth damage during debonding. The purpose of this study was to compare shear and tensile bond strengths and fracture sites of four second-generation ceramic brackets: Allure IV (A) (GAC International, Inc., Central Islip, N.Y.), Ceramaflex (C) (TP Orthodontics, Inc., LaPorte, Ind.), Intrigue (I) (Lancer Orthodontics, Carlsbad, Calif.), Transcend 2000 (T) (Unitek Corp., Monrovia, Calif.), and a foil-mesh base stainless steel bracket, DynaBond II (D) (Unitek Corp., Monrovia, Calif.). Twenty brackets of each type were bonded to 100 mandibular bovine incisor teeth with Concise bonding adhesive. The samples were thermocycled for 24 hours and the brackets were debonded with an Instron universal testing machine (Instron Corp., Canton, Mass.). A modified Transcend debonding instrument was used for tensile debonding, whereas a chisel was used for shear debonding. An analysis of variance was performed with a 0.05 level of confidence. Mean shear strengths (kg/cm2) necessary to debond were 174.0 (A), 71.0 (C), 189.0 (I), 228.0 (T), and 160.0 (D). Mean tensile strengths (kg/cm2) were 27.0 (A), 26.7 (C), 51.3 (I), 56.5 (T), and 48.6 (D). Fracture sites examined with a light microscope showed no enamel damage with any of the ceramic brackets. Intrigue was the only bracket to fracture and had 30% bracket fracture in the tensile mode and 20% bracket fracture in the shear mode. The percentage of fractures at the adhesive-bracket base interface for shear and tensile modes, respectively, were 80, 100 (A); 100, 90 (C); 10, 60 (I); 60, 90 (T); and 90, 80 (D).(ABSTRACT TRUNCATED AT 250 WORDS)