Fiber reinforced composite loop space maintainer: An alternative to the conventional band and loop.

The stainless steel band and loop appliance is the most commonly used fixed space maintainer in pediatric dentistry. But there are several disadvantages with this appliance such as the need for a cast or a working model, decalcification of the abutment tooth, loosening because of breakage or dissolution of the luting agent, tendency to get embedded in the soft tissue and the possibility of metal allergy. The purpose of this article is to present a simple, laboratory design of a "Fiber Reinforced Composite" (FRC) loop space maintainer and discuss the advantages over the traditional band and loop space maintainers.

Introduction

Premature loss of the primary teeth is a common occurrence in children. The safest way to prevent future malocclusions pertaining to early loss of a primary tooth is to place a space maintainer that is effective, durable and economical. Among the various space maintainers used in pediatric dentistry, band and loop is the most commonly used fixed space maintainer. However, the construction of band and loop requires three steps, it involves a clinician as well as a laboratory technician, and therefore it is expensive. With the advances in the technology and materials, there is a need to search for an alternative to overcome various disadvantages[1-5] of the band and loop space maintainer. Since the introduction of the acid-etch technique,[6] its area of application has increased rapidly and some types of direct bonded space maintainers have been tested clinically.[7-10] The purpose of this article is to present a simple, laboratory design of a “Fiber Reinforced Composite” (FRC) loop space maintainer and discuss the advantages over the traditional band and loop space maintainers.

Design and construction

The initial framework of FRC loop was constructed using a commercially available polyethylene fiber system (Ribbond, Inc., Seattle, WA, USA). Ribbond fiber of 40 mm length and 2 mm in breadth was wetted with unfilled adhesive resin (Adper™, Single Bond, 3M-ESPE, St. Paul, MN, USA) to formulate the loop, leaving 5 mm of fiber on each end for attachment to the abutment tooth [Figures 1 and 2]. A thin layer of restorative composite resin (Filtek Z 350, 3M-ESPE, St. Paul, MN, USA) was added to the outer portion of the fiber, leaving the 5 mm of fiber on each end to provide initial rigidity, handling and adaptability to the unetched middle third of the buccal and lingual surface of the mounted molar tooth in acrylic [Figures 3 and 4]. The assembly was then light cured for 40 seconds through its entire length. The loop was then detached from the tooth; restorative composite resin (Filtek Z 350, 3M-ESPE, USA) was added to the inner portion of the loop except the 5 mm of the fiber on each end and light cured for 40 seconds. The loop was finished and polished with finishing burs and soflex discs [Figure 5]. The buccal and lingual surfaces of the tooth were etched with phosphoric acid (Scotchbond™, 3M-ESPE, USA) for 15 s, rinsed with water, dried, and bonding agent (Adper™, Single Bond, 3M-ESPE, USA) was applied and cured for 40 seconds. The loop was finally attached to the tooth using restorative composite resin (Filtek Z 350, 3M-ESPE, USA) followed by finishing and polishing [Figure 6].

Figure 1

2-mm- ribbond fiber being utilized

Figure 2

Ribbond fiber being wetted with adhesive resin

Figure 3

Mounted teeth in acrylic to simulate the space

Figure 4

Wetted ribbond fiber being manipulated to form a loop

Figure 5

“FRC” loop after finishing and polishing

Figure 6

Finished “FRC” loop space maintainer

Discussion

The design presented in this article involves the use of FRC ribbon. Composites that are reinforced with polyethylene fibers or glass fibers can result in materials with enhanced mechanical properties,[1112] i.e. stiffness, strength, toughness and fatigueness. Fibers produce a load-enhancing effect on brittle composite materials by acting as the stress-bearing component and by crack-stopping or crack-deflecting mechanisms.[1213] Ramos et al.[14] demonstrated that composite test bars containing ribbond fibers had significantly higher fracture strength over non-reinforced test bars.

Although the design presented in this article matches with that of Gajanan et al.,[15] there is a huge difference in the technique of fabrication. The previous designs of FRC space maintainers[16-18] (FRCSM) are rigidly bonded to the teeth adjacent to the space, which may adversely influence the growth and development, exfoliation of primary teeth and the eruption of succedaneous teeth. Whereas the design presented in this article overcomes all the disadvantages of previous designs of FRCSM, thus simulating the conventional stainless steel band and loop space maintainer. Gajanan et al.[15] concluded that ribbond space maintainer as well as repaired ribbond space maintainer are comparable to the conventional band and loop in terms of physical strength. McDonald and Avery[19] suggested that the band and loop space maintainer should be removed once a year to inspect, clean and apply fluoride to the tooth. FRC loop space maintainer seems to eliminate these annual maintenance steps.

Hence, FRC loop space maintainer may be a clinically acceptable and expedient alternative to the conventional band and loop appliance, but further studies are needed to verify the success of these space maintainers over longer periods of observation time.