Tooth Stabilization Of The Periodontally Compromised Dentition With Fiber Reinforced Adhesive Composite Resin

by Howard E. Strassler, DMD, FADM, FAGD

For those patients with moderate to severe periodontal disease, tooth mobility can contribute to discomfort when eating and decreased masticatory and occlusal function. Clinical management of the hyper-mobile tooth can pose challenges, foremost, in determining etiology, whether related to existing periodontal attachment

loss, or genuine trauma due to occlusion. Occlusal trauma and mobility in the periodontally compromised dentition contributes to a worsening periodontal prognosis. 1-4 Tooth mobility, however, can be controlled and managed with splinting therapy. 5-7 There exists much evidence to support the use of tooth stabilization via splinting to improve the periodontal prognosis. 1,3,4,6-10 Splinting of teeth is a long-term commitment by clinician and patient. Also, regenerative procedures using membranes and bone are far more predictable if tooth movement is eliminated prior to use of a barrier membrane. 11,12 In cases with mobility that cannot be

eliminated by selective coronoplasty alone, splinting should be considered as an adjunct to provide additional tooth stability during the surgical and healing phases of guided tissue regeneration and guided bone regeneration to enhance stabilization.

Tarnow and Fletcher described the indications and contraindications for splinting periodontally involved teeth. 13 The rationale to splint teeth should take into consideration the degree of periodontal compromise in the dentition, as characterized by amount of radiographic bone loss and/or measured tooth mobility. The literature describes the following scenarios in which periodontal splinting may form a component of treatment:

• Primary occlusal trauma;

• Secondary occlusal trauma;

• Progressive mobility, migration, and pain on function.

Primary occlusal trauma is defined as injury resulting from excessive occlusal forces applied to a tooth or teeth with normal periodontal support, while secondary occlusal trauma is injury resulting from normal occlusal forces applied to a tooth or teeth with inadequate periodontal support. Identification of progressive mo-

www.oralhealthjournal.com bility requires repeated observation of clinical mobility over a period of months, or perhaps weeks.

Over the years there have been different restorative approaches used for splinting teeth. Before the advent of adhesive restorative dentistry the optimal choice for splinting teeth was the use of full coverage cast restorations. Each tooth to be splinted was prepared for a crown; the end goal was to fabricate a multiple-unit restoration to be placed on these contiguous involved teeth. 6,14 The advantage of this technique was that the teeth could be stabilized with an acrylic resin provisional restoration during periodontal therapy. At the completion of active periodontal therapy the definitive cast restoration was fabricated and completed. A perceived disadvantage of this treatment option was that all teeth in the splint were prepared and restored with full coverage restorations. Further, this restorative commitment in a short period at times did not allow for careful evaluation of individual tooth periodontal prognosis. In some cases teeth joined to the cast porcelain-metal splint developed a hopeless prognosis and needed to be extracted. Consequently, the only course of treatment was re-fabrication of the porcelain-metal fixed partial denture splint.

The clinical success of adhesive bonded composite resin to etched enamel provided additional solutions to splinting teeth. One modification was the use of a cast metal lingual splint that was surface treated and placed with a resin bonded adhesive technique for splint retention. 15,16 These restorations still required all the steps for the fabrication of a cast restoration, including multiple patient visits. Conservative splint ing completed in a single visit has been documented in the iterature. Teeth have been physically stabilized with twisted wire or ligature followed by an application of resin over the splinting material. 7 Metal and nylon mesh, embedded in resin, has been proposed. 17 Posterior teeth have been stabilized by use of intra-coronal preparations in the occlusal and proximal surfaces of teeth, or into existing amalgam restorations; cast bars or thick wires are placed into these channels and enclosed with resins. 18,19 Clinical failures of these approaches were common because of loading stresses placed on the splint during normal and para-function. 7,20 Frequently, repairs of splint fractures involve the placement of additional resin over the reinforcement material resulting in overbulked restorative surfaces. These overcontoured restorations lead to hygienic difficulties and food and plaque retention. 7,21

Composite resins by their chemical nature are brittle materials. In function when supporting pontics or stabilizing mobile teeth, cracks within the connector areas lead to outright fracture. 22-25 In order to fulfill both periodontal and restorative needs, a new class of bondable reinforcement ribbons and fibers were developed that could be used to place a thin but strong composite resin-based splint. Both glass fibers and polyethylene fibers are being used in fiber reinforcement materials. Glass fibers are treated with a silane chemical coupling agent to allow dental resins to chemically adhere to the glass fiber strands. To improve bond-ability of resin to ultra high weight polyethylene (UHMWPE) fibers, these synthetic fibers are plasma surface treated to achieve a high level of interfacial adhesion. Research with fiber reinforced composite resins has demonstrated that both glass and UHWMPE fiber reinforcement materials give an increase in flexural strength and flexural modulus of composite resins. 22-28

Clinical evaluations of bonded fiber reinforced composite resins restorations for both splinting and for fixed partial dentures have been successful. 29-32 There have been a number of investigations comparing the physical properties and durability of different fiber reinforcement materials. Studies focusing on degradation of the fiber-composite in ter face have described a variety of behaviors that contribute to failure. Bouillaguet et. al. investigated the hydrothermal and mechanical stresses that degrade the fiber-composite interface in the glass fiber reinforced splinting. 33 Loss of mechanical properties was due to loss of interfacial bond strength between the glass and resin phases. Glass fiber pullout was noted when breaking specimens after water storage. Failures were attributed to both a degradation at the resin and glass interface combined with hydrolytic degradation of the glass as well. The degradation of the glass fiber-resin interface is due to the hydrolysis of the silanated bond of glass with glass fibers exhibited pullout and the glass fibers broke as well. 24 In UHM WPE lock-stitch leno-weave ribbon fiber reinforced (Ribbond) specimens, composite cracking was observed but the beam remained intact. Of interest, the UHMWPE bi-axial braid and leno-weave reinforced specimens do not fail through rupture-rather resin. 24 In flexural strength tests, the failure mode of the fiber reinforced beam is different between unidirectional glass fibers and UHMWPE with a lock-stitch lenoweave (Ribbond). Unidirectional glass fibers and unreinforced composite specimens had catastrophic fracture. The unidirectional there was a deflection and bending of the beam. 24 This mode of bending is evidence of high levels of strain energy absorbed by the specimens and a greater toughness Currently, there are two types of UHMWPE fiber reinforcement materials. Ribbond is a UHMWPE lock-stitch, lenoweave fiber ribbon that has a weave configuration that holds its shape during manipulation. 17, 21-

24 Connect (Ke
rr) is an open biaxial braided UHMWPE ribbon that is dimensionally unstable during manipulation and the fiber ribbon unravels when cut. 21,22 An additional advantage of the UHMWPE is the tight weave that allows the ribbon to maintain a structural integrity through minimizing weave and fabric shifting within the composite. This results in a multidirectional reinforcement to restorative polymeric resins which acts as a “crack stopper.” 23,24,32,34,35 Both UHM WPE and glass fiber composite reinforcement materials provide composite resins with equivalent physical property enhancement. Often, fiber material choice is based upon the clinical scenario, taking into account width of the available fiber material product, and the ease of clinical manage- ment and manipulation. 17,21,22 The following case report describe the use of a fiber-reinforced composite resin splint placed to stabilize a moderate to severely periodontally compromised dentition.

CASE REPORT

Periodontal splint fabricated with a fiber reinforcement ribbon using an adhesive light cure composite resin The patient presented with the chief complaint of discomfort while functioning on the mandibular anterior teeth. (Fig. 1) Radio graphically, the mandibular incisors had approximately 40% bone loss (Fig. 2) with a grade 2 mobility. The patient was referred for splinting by the treating periodontist. With consultation with the periodontist, a treatment plan of a directly placed ribbon reinforced composite resin bonded splint to extend from canine to canine was decided upon. The advantage of the directly bonded splint is that it is a single-visit procedure. Before the restorative visit to place the splint the teeth were scaled and root planed to assure all calculus and stain were removed from the teeth. The teeth were isolated for the clinical procedure with a dental dam. Besides

providing for a high degree of isolation, the dental dam for patients with exposed root surfaces and root sensitivity acts as a barrier to air, water, and air-water spray during the splinting procedure, many times making the use of local anesthesia unnecessary. The teeth were cleaned on the facial and lingual surfaces using a prophylaxis cup with a non-fluoridated pumice paste. The teeth were thoroughly rinsed and dried. The interproximal surfaces of the teeth were cleaned and prepared with a medium grit gapped diamond finishing strip (Gateway Vision strips, Brasseler, Savannah, GA) In some cases when the teeth have spaces a diamond abrasive on a handpiece can be used to clean the interproximal surfaces. To minimize bulk on the esthetic facial surface interproximally, a thin, round-end, chamfer diamond (Revelation, #854-016, SS White, Lakewood, NJ) was used to barrel into the interproximal areas (Fig. 3).

The choice of Ribbond THM Reinforcement Ribbon (Ribbond, Seattle, WA) for the splint was made. One problem with the fiber reinforcement materials that have been available, is their inherent thickness when embedded within composite resin in a splint. To overcome this problem, a lock-stitched cross-linked weave of thinner strands of polyethylene fibers, Ribbond THM Reinforcement Ribbon (Ribbond, Seattle, WA) was introduced. The thinner Ribbond still incorporates the ease of use of the original Ribbond ribbon’s lock stitch weave. Unlike braided fiber weaves that once cut to the desired length needed, have a tendency to unravel and not hold their dimensional shape, Ribbond will not unravel and will be dimensionally constant when embedded within composite materials. Another feature of the lock-stitch weave of the Ribbond is the tight weave allows the ribbon to maintain a structural integrity that imparts a multidirectional reinforcement to restorative polymeric resins that acts as a crack stopper. 34,35 Also, by changing the diameter of the polyethylene threads from a 215 denier thread to a 50% thinner 100 denier thread, the same width ribbon has more than twice the volume fraction of threads and when woven have more unidirectional orientation. With this increased volume fraction, there is a two and a

half times increase in flexural strength of composite resin when compared to no fiber reinforcement and a 15% increase compared to the original Ribbond ribbon. 23,24 The thinness of the Ribbond THM fiber ribbon requires no need for a channel preparation on the lingual surface to compensate for final thickness of the splint.

To measure out the length of fiber ribbon needed, a piece of dental floss was laid onto the facial surfaces of the teeth extending from the mesial of the left mandibular canine to the mesial of the right mandibular canine. The effective length of the final

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fiber ribbon was from the mid-lingual of the left canine to the mid-lingual of the right canine. Measuring on the greater length of the arch on the facial effectively gives you the length desired on the lingual surface. The plasma-treated fibers are susceptible to surface contamination. Therefore, when handling Ribbond® a clean cotton pliers must be used. Using the floss as a length template, a piece of 3mm wide Ribbond THM

was taken from its package using a cotton pliers and cut to an equal length with the Ribbond Scissors (Fig. 4). Some reinforcement ribbons require special scissors that the manufacturers provide with their products. Splint-It (Pentron, Wallingsford, CT) comes with a ceramic scissor while both Ribbond and Connect (Kerr, Orange, CA) because they are woven from polyethylene fibers have a special serrated scissor for cutting their products.

Once cut to length, the ribbon was wetted with an unfilled HEMA-free resin (Ribbond Resin, Ribbond, Seattle, WA) (Fig. 6). If a single component adhesive resin is used, it is recommended that the solvent within the resin be evaporated from the adhesive with a gentle air stream for ten seconds. Self-etch adhesives are contraindicated for use with fiber splinting. Once the ribbon fibers were wetted, they were blotted using a paper patient napkin to remove excess. Once wetted with resin the Ribbond can now be handled like any resin material. The ribbon was put aside and covered to keep light off it until it was placed on the teeth.

Currently there is not enough evidence to support the use of a self-etch adhesive for the placement of fiber reinforced composite resin splints. For this case an etch and rinse adhesive was used. The teeth were etched for 30 seconds with a 32% phosphoric acid gel being certain that etchant was placed on the lingual and facial surfaces and it flowed between all the teeth to be splinted (Fig. 7). The etchant was kept away from all exposed root surfaces to avoid increasing root sensitivity. The teeth were then rinsed with an air-water spray for 10 seconds and gently dried. The most distal tooth surfaces of mandibular right and left canines had inter-proximal matrix strips placed to maintain separation.

In the past, wedges were placed to minimize excess composite in the gingival interproximal embrasure areas. With wedges there is always the potential that highly mobile teeth could be splinted in a different position. Recently an innovative technique for minimizing excessive composite resin in these areas has been described. 36 The technique is the placement of a medium or heavy viscosity polysiloxane impression material using an impression syringe in these gingival embrasure areas. It is important that the impression material is placed after tooth etching, rinsing and drying to avoid the trapping of moisture that can occur if the technique is done earlier. This use of elastomeric impression material assures a passive placement of the blockout. For this case, a medium bodied fast setting polyvinyl siloxane im
pression material was syringed into the introproximal areas (Fig. 8).

A resin adhesive (Peak, Ultradent) was applied to the etched enamel surfaces including the interproximal surfaces and facial interproximal areas using a disposable brush. A medium viscosity hybrid composite resin in compules was dispensed onto the facial surfaces of all the interproximal areas of the teeth to be splinted. The facial surfaces were shaped to minimize excess and then light cured for 10 seconds with an LED curing light (Fig. 9). The purpose of this facial composite resin is to seal the interproximal areas against recurrent caries and to provide for a 180 wrap of composite resin to each of the splinted teeth. This will function as a crosssplint of each tooth to prevent tooth movement and breakage of the final splint. This step is important because once splinted, the interproximal surfaces of adjacent teeth can not be cleaned adequately. The composite resin was then placed onto the lingual surface from midcanine to midcanine. By placing the preloaded tube tip at right angles to the lingual surfaces of the teeth the composite resin can be applied

to the middle of the teeth where the splint will be placed (Fig. 10). The 3mm wide Ribbond THM ribbon was embedded into the composite resin starting at the canine moving around to the other canine using a gloved finger wetted with adhesive resin. The ribbon was further placed and adapted on the lingual and interproximal surfaces using a cotton pliers and burnisher (Fig. 11). Excess composite resin was removed before light curing. The lingual surfaces were then light cured for 20 seconds for each tooth to be certain the light penetrated the ribbon and composite resin for complete curing.

At this time the ribbon may be visible and not completely covered with an adequate thickness of composite resin. For this reason, a high strength, wear resistant, flowable composite resin (PermaFlo, Ultradent) was applied to smooth the irregular surfacing on the lingual and provide an even thickness of composite covering the ribbon (Fig. 12). The flowable composite resin on the lingual surface was light cured for an additional 10 seconds for each tooth. The polysiloxane impression material blockout was removed from the gingival embrasure areas (Fig. 13). There was very little finishing necessary for the gingival embrasure areas of the splint because of this blockout technique.

The composite resin was shaped, finished and polished to remove any excess bulk of restorative material and achieve an es thetic result. The lingual surfaces were finished and contoured with an egg-shaped finishing bur and polished with an aluminum oxide abrasive point. The rubber dam was removed and the splint was checked for occlusion and aesthetic appearance. Since the teeth are now joined together, it is important that the patient have demonstrated to them techniques and devices for cleaning the gingival embrasure areas. The completed splint provided tooth stabilization, increased function without bulk and fulfilled the patient’s aesthetic needs (Fig. 13).

CONCLUSION

Tooth mobility has been described as an important clinical parameter in predicting prognosis of periodontally compromised teeth. Tooth stabilization with splinting has been recommended for the periodontally compromised dentition for improved patient comfort and increased masticatory function. In the past directly placed adhesive splints using restorative resins with embedded wires, pins and meshes had been used successfully. 7 Unfortunately, these materials could only mechanically lock around the resin restorative and were not chemically integrated within the splint. The interface created between the composite resin or acrylic resin and wire, pins, or grid mesh had the potential of creating shear planes and stress concentrations that would lead to premature cracking of the composite and failure. If the splint fails, the clinical problems that can occur include traumatic occlusion, progression of periodontal disease, recurrent caries and patient discomfort. With the introduction of bondable, lock-stitch leno-weave polyethylene fiber ribbons (Rib bond), many of the problems with older types of reinforcement are solved. In a long term clinical evaluation of splinting over a period of 48-96 months using the original Rib bond Reinforcement Ribbon in fiber reinforced composite resins was highly successful. 32

This article described an innovative technique using a bondable, ribbon-splinting material for reinforcing dental resins. By combining the chemical adhesive and esthetic characteristics of composite resin with the strength enhancement of a thin-high modulus plasma treated, high modulus, reinforcing ribbon, dentists can provide patients with restorations and splints that will resist the load-bearing forces of occlusion and mastication. These fracture resistant restorations will be more durable than most alternative splinting materials of the past. OH

Howard E. Strassler is Professor and Director of Operative Dentistry, Department of Endodontics, Prosthodontics and Operative Den tistry, University of Maryland Dental School, Baltimore, MD. hstrassler@umaryland.edu

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Tooth mobility has been described as an important clinical parameter in predicting prognosis of periodontally compromised teeth.

———

Failures were attributed to both a degradation at the resin and glass interface combined with hydrolytic degradation of the glass as well

———

One problem with the fiber reinforcement materials that have been available, is their inherent thickness when embedded within composite resin in a splint

———

Currently there is not enough evidence to support the use of a self-etch adhesive for the placement of fiber reinforced composite resin splints

———

There was very little finishing necessary for the gingival embrasure areas of the splint because of this blockout technique