Biomimesis: A Bioengineering Concept Applied to Dentistry

INTRODUCTION
Biomimesis, a bioengineering concept that means mimicking natural biologic essence, is the key factor of all healers in restoring lost natural substance.
As dentists, today more than ever, we have the ability to repair, replace, and restore lost natural structure in such a way that biologic form, function, and appearance are restored, as well as masking the fact that there ever was a defect.
Direct composite resin systems provide ultraconservative, long-lasting solutions to many dental aesthetic problems.¹ Success with composite resin restorations depends on the combination of 3 factors: material selection, the type of adhesion used, and placement technique.² Simplification and speed are emphasized with most of the newer materials and the equipment available today.
Research has now produced self-adhering restorative composite resin systems that successfully bond to tooth structure, and that has eliminated the need for the separate use of etchants or bonding agents. Collectively, this category of self-adhering, light-cured, resin-based composite dental restoratives are designed for direct placement. They are indicated for all cavity classes in the anterior and posterior teeth alike. They have incorporated adhesion technology, which eliminates the additional steps of etching/priming/bonding otherwise necessary to bond a resin composite to dentin and enamel.
Other systems, like the nanofilled composites, produce all of the positive characteristics of the microfilled resins, including polishing and handling, along with the better physical properties of the microhybrid systems. The formulations of these composites have been designed to combine dentin color and enamel value in relationship to the natural tissue anatomy. These composite restorative systems not only simplify the replication of the optical properties of the natural tooth, but have similar physical and mechanical properties to that of tooth structure and can easily be combined with the self-adhesive systems for sensitivity elimination. Therefore, composite resins have become simpler to use. The resin systems that have been available to dentists for more than 40 years now are not the same anymore.

Before Image. Preoperative photo. Previously placed amalgam and composite, active caries, potholes, and cracks were evident.	After Image. The postoperative view reflects an ideal integration of composite to tooth structure.

CASE REPORT
Diagnosis and Treatment Planning
A 50-year-old patient presented with symptoms of severe sensitivity. Clinical evaluation and consultation revealed an old amalgam restoration (tooth No. 30), old composite (tooth No. 29), active caries (tooth No. 31), potholes, and visible cracks due to bruxism (Before Image). Pulp testing was done, revealing vital and healthy pulps.

Prerestorative Considerations
The following considerations were completed before any restorative treatment was initiated: First, prior to administering anesthesia and rubber dam isolation, the preoperative contact zone and excursive occlusal patterns were evaluated. Next, the shade of the tooth was determined. Shade selection must be accomplished prior to dental dam placement to prevent improper color matching as a result of dehydration and elevated values.³ When teeth dehydrate, air replaces the water between the enamel rods, changing the refractive index, which makes the enamel appear opaque and white.⁴
Before starting any restorative procedure, it is important (if physically permissive) to place a dental dam after anesthesia administration to achieve adequate field control and protect against contamination.⁵

Operative Treatment
Once the rubber dental dam (Hygenic [Coltène/Whaledent]) was placed, the first step was to remove the old amalgam in tooth No. 30, composite in tooth No. 29, and the decay in tooth No. 31 (Figure 1). The preparations were then scrubbed with a 2% chlorhexidine digluconate aqueous solution (BISCO). One can simply remove diseased tooth structure and be able to maintain (with confidence) the integrity of the natural enamel/dentin as much as possible. The Hawe SuperMat Matrix System (Kerr) was used to separate the cleaned preparations prior to bonding.

Figure 1. The rubber dam has been placed (Hygenic [Coltène/Whaledent]), and removal of amalgam, composite, and decay was accomplished.	Figure 2. Placement of Vertise Flow (Kerr) with the applicator tip after air-drying the cavity preparations.
Figure 3. The self-adhering flowable composite was brushed with moderate pressure onto the cavity floor for 15 to 20 seconds.	Figure 4. Light-curing with the Optilux 501 (Kerr) curing light.
Figure 5. The rest of the preparation was etched for 15 seconds with 35% phosphoric acid (Ultra-Etch [Ultradent Products]), then rinsed for 5 seconds and gently air-dried.	Figure 6. OptiBond Solo Plus (Kerr), a single-component adhesive, was applied for 20 seconds, air-thinned, and then light-cured.
Figure 7. Incremental placement of a nanohybrid composite resin (Premise [Kerr]). This was light-cured for 40 seconds.	Figure 8. Placement of the self adhering composite (Vertise Flow) into the shallow occlusal preparation, and as a sealant.
Figure 9. Adaptation of the self-adhering flowable composite to the enamel with the brush (provided in the kit). This was then light-cured for 20 seconds.	Figure 10. After the rubber dam was removed and the occlusal adjustment was completed, all teeth were easily polished with the Occlubrush (Kerr). The contacts were tested with unwaxed floss to ensure the removal of any remaining unwanted adhesive or sealant.

Where deep penetration of caries was revealed (teeth Nos. 29 and 30), after its removal, the decision was made to line the preparation with a new self-adhering flowable restorative material (Vertise Flow [Kerr]) (Figure 2) which studies have shown significantly reduces (if not completely eliminates) postoperative sensitivity. This is primarily due to the lack of need for separate etching and bonding steps, which are often known to be the culprits for the “dreaded” postoperative sensitivity issue. This material incorporates the clinically proven OptiBond (Kerr) adhesive technology which directly bonds to dentin and enamel.
Vertise Flow was dispensed onto the preparation floor and then brushed for 20 seconds to obtain a thin layer of lining (Figure 3). It was cured for 20 seconds with a curing light (Optilux 501 [Kerr]) with output equal to or greater than 800 mW/cm² (Figure 4). With its ease of handling, nonslumping property, and excellent mechanical properties, it is an ideal choice for lining deep preparations in which postoperative sensitivity would have often been a problem in the past. However, as with all materials, it is important to follow the manufacturer’s recommendations exactly in order to achieve the expected results.⁶ I personally believe that is it also imperative in all chemistry-related procedures (placement of composite restorations, bonding, etc) to always use materials that have been designed, researched, and manufactured to work together in a single system, rather than mixing and matching different manufacturers’ systems hoping to achieve good results.
After the 2 restorations (Nos. 29 and 30) were lined and cured, an etching-bonding step sequence with a 35% phosphoric acid solution (Ultra-Etch [Ultradent Products]) (Figure 5) and with OptiBond Solo Plus (Kerr) (Figure 6) was implemented in order to place a nanohybrid composite (Premise [Kerr]). Incremental placement and curing (Optilux 501) of Premise Body composite and Premise Translucent composite (Kerr) was completed (Figure 7).
The Class I composite on tooth No. 31, and the sealant on tooth No. 28, were filled directly with Vertise Flow (Figure 8), again without etching or bonding. Then, the material was brushed with moderate pressure for even distribution (Figure 9). The rubber dam was removed and the patient was asked to perform closure without force, followed by centric, protrusive and lateral excursions. Any necessary equilibration was easily accomplished. Polishing was extremely simple with a composite finishing bur (Flame Carbide, Long, Ultra-Fine, 30-Bladed [Ultradent Products]), the Occlubrush (Kerr) and diamond polishing paste (Ultradent Products) (Figure 10).
At a prearranged 2-week post-op appointment, the patient reported no sensitivity. He was very happy with the aesthetic improvement evident in his dentition (After Image), but mainly with the comfort from not being sensitive anymore.

CLOSING COMMENTS
Placing composites has become easy, predictable, fast, aesthetic, and fun.
With a selection of improved biomaterials available now, the clinician is able to preserve, conserve, and reinforce tooth structure with more conservative preparation designs, which falls in line with the biomimetic principle. In the past, it was difficult to achieve the desired aesthetic results due to the limitations of the materials. Nowadays, the only constraint to achieving these desired results—from a biomimetic point of view—is the lack of desire of the practitioner to properly implement this new, wonderful, easy technology.
It is important to keep up with new materials and techniques available to us in order to improve treatment techniques and to achieve results that in the past we could only dream of. The delivery of predictable results continues to be an important objective in restorative dentistry.7

References

1. Winter R. Visualizing the natural dentition. J Esthet Dent. 1993;5:102-117.
2. Croll TP. Alternative methods for use of the rubber dam. Quintessence Int. 1985;16:387-392.
3. Hondrum SO. The longevity of resin-based composite restorations in posterior teeth. Gen Dent. 2000;48:398-404.
4. Bichacho N. The centripetal build-up for composite resin posterior restorations. Pract Periodontics Aesthet Dent. 1994;6:17-23.
5. Hickel R, Manhart J. Longevity of restorations in posterior teeth and reasons for failure. J Adhes Dent. 2001;3:45-64.
6. Terry DA, Leinfelder KE, Blatz MB. Achieving excellence using an advanced biomaterial: part 2. Dent Today. 2009;28:69-74.
7. Fahl N Jr, Denehy GE, Jackson RD. Protocol for predictable restoration of anterior teeth with composite resins. Pract Periodontics Aesthet Dent. 1995;7:13-21.

Dr. Cuevas is the head of The Institute of Esthetic Dentistry in San Antonio, Tex, where she also practices full-time general dentistry with an emphasis on cosmetic and restorative dentistry. She is a former assistant clinical professor at University of Texas Health Science Center at San Antonio, Department of Esthetics. She was a contributing editor for the Journal of Cosmetic Dentistry for more than 10 years and has published numerous articles in the field of aesthetic dentistry. She has lectured internationally on the topics of direct composite bonding, facial smile aesthetics, and indirect cosmetic restorations. She can be reached via e-mail at the address simona.dds@gmail.com.

Disclosure: Dr. Cuevas reports no conflicts of interest.