THE USE OF FLOWABLE COMPOSITE RESIN INJECTION TECHNIQUE IN A CASE OF SEVERE TOOTH WEAR. A CASE REPORT

Headnote

Abstract

In the present case report, the use of the composite resin injection technique with flowable composite resin was described, aiming to rapidly restore functionality and aesthetics in a patient with severe dental wear. The used technique helped achieve an appropriate morphology, functionality and aesthetics within a reduced execution time. Initially, the teeth were clinically examined, then digital scanning was performed, on the basis of which the 3D wax up model was realized. The obtained model was impressed using a transparent silicone material, so that the silicone guide - on the basis of which the mock-up and, subsequently, the flowable resin injection technique were performed - was made. The results obtained by flowable composite resin injection and wax-up and mock-up techniques are highly satisfactory from an aesthetic, morphological and functional point of view, although the behavior over time should still be evaluated.

Keywords: composite resin, injection technique, aesthetics.

1. INTRODUCTION

Severe tooth wear is defined as a significant loss of tooth tissues with dentine exposure and destruction of more than one third of the clinical crown [1]. This pathological loss of tooth substance is characterized by pain, discomfort and impairment of functionality and aesthetics [2]. The use of bioadhesive materials is recommended for the treatment of these conditions. [1].

Indications for the use of composite resins as direct restorative materials have expanded, due to the constant advances made in their composition and physical, chemical and mechanical properties [3]. Improvements to composite resins relate to strength, aesthetics, and material handling [3,4].

The current philosophy in restorative dentistry is minimally invasive, aiming to remove as little healthy dental tissue as possible [5]. Restoration of the anterior teeth by using the direct technique is a laborious and challenging procedure that depends on the skills of the practitioner and the qualities of the chosen material [3]. In order to avoid the difficulties of this technique, many prefer to work together with a dental technician and to perform it through the indirect technique, which increases the costs and execution time of the work [3,6].

Over time, a lot of direct restoration techniques have been described, among which the "index technique" can be listed, a procedure based on the principle of using a transparent mold to transfer the anatomy from the wax-up model to the tooth surface using a preheated composite resin [7,8]. Another modern technique involves the use of dental veneers, which is disadvantageous as it implies preparation of dental structures and an increased price [9]. Another current technique is the "composite resin injection technique" which uses a reduced consistency composite resin as a flowable composite [3].

The injection technique was introduced with the aim of improving the aesthetics of temporary and permanent teeth or of obtaining temporary fixed prosthetics, benefiting from the advantage of an easier execution and lower cost [3]. The prior use of the mock-up technique facilitates treatment planning and previewing the future restoration, thus analyzing the impact on functionality, aesthetics, tooth position and alignment, phonetic contours [10] or vertical dimension of occlusion (VDO) [3].

Composite resin restoration should mimic the dental tissues it replaces, ensure color stability over time, maintain aesthetics and functionality [11]. The use of flowable composite resins in direct restorations is a relatively new technique, the reconstruction of anterior teeth being generally performed using conventional composite resins by the layering technique [1].

Flowable composite resins were initially indicated as sealants or as base restoration materials, due to the low loading of fillers, low wear resistance and color instability [12]. The goals of a sustainable restoration are to maintain functionality and aesthetics over time [11].

The latest developments in the field of direct restorative materials have led to the appearance of flowable resin options with a higher filler loading level, up to 70% by weight, so that low viscosity composite resins could be used in the "composite resin injection" technique, as well [13,14]. The literature presents a reduced number of case reports in which this technique was used, a follow-up over time of the behavior of these materials being recommended [11].

In the present case report, the use of composite resin injection technique with flowable composite resin was described, aiming to rapidly restore functionality and aesthetics in a patient with severe dental wear.

2. PRESENTATION OF THE CLINICAL CASE

Patient W.T. aged 57 had addressed a private dental office accusing a severe impairment of dental functionality and aesthetics (Fig/ 1). Anamnesis and clinical examination revealed the main cause of the dental condition - namely the association between citrus consumption and parafunctional behavior, i.e. bruxism. Several therapeutic options were presented to the patient, from which he chose the solution he considered the most advantageous in terms of execution time and finances, namely dental restoration by flowable composite resin injection, considered as the most suitable. Publication of this case report did not require any consent from the institution.

The images were recorded using a Canon EOS 250D camera (Canon Inc., Tokyo, Japan), each stage of the treatment being thus documented. Afterwards, the maxillary and mandibular arches were digitally scanned using a Medit 1700 scanner (Medit Corp. Seoul, Republic of Korea) and an Exocad Dental CAD software (Exocad, Darmstadt, Germany). The digital wax-up technique was performed on the 3D digital study model to prefigure the image of the future restorations on both upper and lower jaws (Figs. 2 and 3). The digital model was designed by a dental technician. Subsequently, the obtained 3D model was printed using a 3D Asiga MAX UV printer (Asiga Europe, Erfurt, Germany). A classical impression was performed to the 3D printed wax-up model using a GC Exaclear transparent silicone impression material (GC Corp., Tokyo, Japan), the future injection silicone guide thus resulting. Before the impression, the study model was immersed for 4-5 minutes in water for hydration, and the impression material was applied in a uniform layer of about 5 mm.

Initially, the mock-up technique was used to make the patient aware of the future restoration (Fig. 4). The mock-up was made with 3M Protemp 4 bis-acrylic composite provisional prosthetic material (3M ESPE, St. Paul, MN, USA) and was applied separately to each hemiarch.

The carious lesion on tooth 1.2 was treated by the minimal invasive technique using a conventional composite resin Fűtek Z250 (3M ESPE, St. Paul, MN, USA). The tooth surfaces were sandblasted using aluminum oxide of 50 microns, with an Aquacare sandblaster (Medivance Instruments Ltd., London, UK), then cleaned by brushing with a fluoride-free paste Proxyt RDA36 (Ivoclar Vivadent, Schaan, Lichtenstein), the retractor wire was applied, and the teeth were separately isolated with Teflon tape. 3M Unitek Etching Gel System Blue Tint phosphoric acid (3M ESPE, St. Paul, MN, USA) was applied for 30 seconds to all tooth surfaces using the total etch technique, then removed, the surfaces were dried, and a universal adhesive system Scotchbond Universal Plus (3M ESPE, St. Paul, MN, USA) was applied. The bonding system was lightcured for 20 seconds with a Bluephase curing light lamp (Ivoclar Vivadent, Schaan, Lichtenstein), according to manufacturer's recommendations.

A 69%wt filled GC G-aenial Universal Injectable flowable composite resin was used. The material was applied by composite resin injection through the perforations in the silicone guide and polymerized for 30 seconds on each of the surfaces through the thickness of the transparent guide. The same procedure was used for each tooth (Figs. 5-7). By the end of the light activation procedure, the guide was removed, after which a layer of glycerin gel was applied and polymerized for 30 seconds to avoid the formation of the inhibitedoxygen layer.

The last step consisted in finishing and polishing performed with fine-grained diamond burs, Arkansas stones, spiral Sof-Lex discs (3M ESPE, St. Paul, MN, USA) and abrasive strips for the interdental spaces (Figs. 8-10).

The patient was followed-up and the restoration was assessed after one year. The aspect after one year is presented in Figure 10.

3. DISCUSSION

A plethora of techniques have been described over time for the aesthetic, morphological and functional restoration of anterior teeth [3]. In the present study, restoration of a severe case of tooth wear was performed by using the flowable composite resin injection technique. The use of the transparent silicone guide has the role of helping replicate the functionality, morphology and aesthetics of the temporary or permanent teeth, without greatly involving the manual skills of the dental practitioner [11,12], while benefiting from a low price compared to indirect techniques [15]. A considerable disadvantage of this technique shown in the literature is given by the appearance of marginal defects and discolorations in a relatively short time interval of one year. [11,16].

Restorations on anterior teeth must benefit from color stability and durability over time [3], which requires obtaining of a smooth surface not prone to bacterial biofilm accumulation [17]. An average durability rate of composite resin restorations of 85% after 5 years has been reported [9].

The low consistency or flowable composite resins showed a good marginal adaptation to dental structures over time but, due to the reduced loading of the inorganic filler, it is prone to wear and to color modifications [18]. In order to overcome the above-mentioned disadvantages, the amount of filler loading increased to a percentage between 61 %-71 % by weight, and thus "injectable composite resins" appeared [1,11]. The resulted materials benefit from an increased resistance to flexure and wear compared to classic flowable resins, the injectable composite resins thus becoming suitable in several clinical situations [19]. In the present study, a G-aenial Universal Injectable flowable composite resin was used, a nanocomposite with filler particles of silicon dioxide and strontium glasses with sizes between 10-200 nm, which gives to it special aesthetic properties. However, several studies that evaluated the behavior of this material over time showed reduced color stability and the difficulty of obtaining a finished and polished surface [3]. Color instability can be based on the nature of the inorganic composition, the nanometric strontium particles having reduced hardness and a lower degree of attachment to the polymer matrix [20,21]. At the same time, another limitation of the material is given by the ratio between the organic matrix and the inorganic particles, which leads to an increase in polymerization shrinkage, compared to a conventional composite resin [3].

Along with the advantage of simple maneuverability, the composite resin injection technique can be associated with the mock-up technique to facilitate the patient a preview of the future restorations [22].

In the presented clinical case, the patient showed generalized severe wear caused by the association between a parafunctional behavior as bruxism and an increased citrus consumption. Tooth wear was classified using BEWE (Basic Erosion Wear Examination) classification [23]. The used phosphoric acid was applied by the total etching technique on both enamel and exposed dentine for 30 seconds, followed by the application of a universal adhesive. Before the application of the bonding system, the tooth surfaces were prepared by sandblasting using aluminum oxide particles of 50 pm. The low consistency composite resin was applied using the injection technique through perforations in the silicone guide and photoactivated for 30 seconds on each surface. The flowable composite facilitated a good marginal adaptation, while the existence of a low configuration factor (C factor) decreased the polymerization shrinkage and shrinkage stress [3,9,18].

Special attention to composite resin restorative treatments is given to the aesthetics, color adaptation and marginal integrity [24]. At the same time, the occlusion should be of real interest, given the dimensional changes of teeth [9]. In the present clinical case, restoration of severe tooth wear caused significant changes in the oral homeostasis, by increasing the vertical dimension of occlusion (VDO). These changes were shown to the patient by applying the provisional restoration, the half-arch mock-up. During restoration of the occlusion, special attention must be paid to the anterior and lateral guidance [9.25].

The longevity of composite resin restorations is dependent on the surface condition, so the finishing and polishing stage is very important. In our study, this stage was performed with finegrained diamond burs, Arkansas stones, Sof-Lex spiral discs and abrasive strips, similar to the techniques used by other authors [26,27].

Future studies could evaluate color stability, mechanical and wear resistance of the restorations resulted through the flowable composite resin injection technique.

4. CONCLUSIONS

The results obtained by flowable composite resin injection together with wax-up and mock-up techniques are highly satisfactory from an aesthetic, morphological and functional point of view, although the behavior over time should still be evaluated.

References

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