July 11, 2022
by Ross W. Nash, DDS; Tyler Wurmlinger, DDS
Innovative one-colour universal light-cured shade adaptive composites are trending, and it is essential to evaluate them from the perspectives of accurate clinical shade matching and saving of chairside time and effort. SpheriChrome (Oxford Scientific, Elmshorn, Germany) is based on an advanced shade-adaptive solution to colour matching based on the naturally occurring “universal structural colouration principle”.
Adaptive colour matching is based on structural colouration which is a naturally occurring result of the wave interference principle and can be seen in peacock feathers and soap bubble film. Structural colouration was first observed in 1665 by Robert Hooke. In 1892 Thomas Young explained it further with the wave interference principle. Structural colouration has been used commercially in photography and fashion. SpheriChrome was developed using the wave interference principle producing structural colour generation.
It has been designed for accurate shade-matching in all classes of dental restorations. “Structural colouration” is colour production by microscopically structured surfaces fine enough to interfere with visible light, sometimes in combination with pigments.1
Fillers of specific size and shape must be controlled in the generation of red-to-yellow colouration as ambient light passes through composite manufactured without dyes or pigments. The spherical fillers create a red-to-yellow that combines with the patient’s natural dentition, yielding a perfect match.
One composite with adaptive nano fillers offers multiple shades to match virtually all clinical situations, eliminating the need to individually shade match each restoration. This saves significant chair time and eliminates the concerns of variable ambient light, clinical error and metamerism.
Two separate recent studies addressed the colour adjusting principle CAP of resins utilizing differing compositions that permit the filling material to better reflect the natural tooth colour.
High CAP resins blend with surrounding enamel and dentin improving esthetics, simplifying shade matching and compensating for shade differences.2,3 This was confirmed by simply creating a restoration and placing it among artificial teeth of varying shades. SpheriChrome produced shade A2 colour when placed in a mouth with shade A2 teeth and the same restoration produced shade B2 when placed in a mouth with B2 teeth.
Many current composites utilize the addition of red and yellow dyes or pigments to simulate tooth colouration; thus, each practice must stock a considerable inventory of shades to adequately serve its patients. Structural colour SpheriChrome employs 200nm spherical fillers that refract ambient light and combine with the reflected colours of the patients’ remaining dentition to generate shade-matching Al to D4 red-to-yellow colouration without additional pigments or dyes.
A middle-aged female patient exhibited wear and occlusal carries in her mandibular left first and second molars. (Fig. 1) Minimal preparation with a small round diamond bur under rubber dam (Fig. 2) was followed by 10 seconds of phosphoric acid etching, thorough rinsing and gentle air drying. A 7th generation bonding agent was applied to the prepared areas and light-cured for ten seconds. SpheriChrome flowable was applied in several increments, each light-cured for twenty seconds. The composite was contoured with a carbide finishing bur and polished with a composite polishing brush. The final restorations before (Fig. 3) and after (Fig. 4) rubber dam removal.
The patient asked to have the central diastema (Fig. 5) closed for a more “normal looking” smile without orthodontic treatment. It was decided to directly veneer all four incisors with composite to establish correct proportionality. After minimal preparation with fine diamond burs, (Fig. 6) SpheriBlock was placed at the interproximal space between the central incisors. Regular SpheriChrome was layered over the entire facial surfaces of each tooth, providing the patient’s desired aesthetic result. (Fig. 7)
The chipping of the two central incisors (Fig. 8) offered minimal dentin exposure (Fig. 9). With minimal preparation and a slight bevel, SpheriChrome was added to restore the original tooth morphology. SpheriBlock was needed only at the mesial corner of the left central incisor, followed by layered SpheriChrome on the facial aspect and incisal edges. (Figs. 10 & 11) SpheriBlock is useful for masking for tooth discolouration or interdental/incisal show-through.
A mature patient wished to improve the appearance and alignment of her mandibular anteriors without orthodontics. (Fig. 12) She selected direct composite veneers on the basis of affordability.
Eight mandibular anteriors were recontoured to make room for approximately 0.5mm of composite. (Fig. 13) The lower left lateral was direct veneered with SpheriChrome, using the SpheriBlock only at the incisal. SpheriChrome was layered over the entire facial surface. (Fig. 14) The final result shows a fine gloss finish that matches the natural dentition, (Fig. 15) easily accomplished chairside as SpheriChrome polishes like a microfill, quickly and esthetically.
SpheriChrome’s flowability makes it easy to place. The Calset Thermal Unit composite warmer (Addent, Inc., Danbury CT) can readily adjust or modify the handling properties. (Figs. 16,17) The ability to change the viscosity and flow by warming can achieve excellent marginal adaptation.4
Rueggeberg (2003) indicated that the maximum intrapulpal temperature rise from the application of a 57.2˚C composite material was approximately 1.6˚C, well within the established pulpal tolerance of more than 10˚C. 5, 6, 7, 8 Further, the preheating insertion technique provided better adaptation to the cavity walls than those of the conventional and sonic insertion techniques.
In-house testing demonstrated that SpheriChrome has decreased surface roughness, (Graph 1) lower shrinkage, (Graph 2) and better flexural strength when compared to a competing product. A smoother restorative surface permits less biofilm to form, decreasing esthetic and maintenance problems.9,10,11 Lower shrinkage decreases the likelihood of microleakage and related marginal discolourations and secondary caries.12
Compressive strength is important but needs to be examined in perspective. (Graph 3) The generally accepted range of dentin compressive strength is 200-350 MPa; enamel 300-450MPa. The figures are greatly variable due to anatomical location, age, and method of testing. The ideal compressive strength of a restorative material should not be so high that it can damage the remining dentition during mastication. SpheriChrome’s compressive strength falls well within the acceptable range of value.13,14
SpheriChrome is a versatile composite that colour matches for most restorative applications. Available in the two most popular dispensing systems, syringes, and unit dose, SpheriChrome can be pre-warmed with the Addent Calset Thermal Unit or Compex dispenser. All of these features combine to make SpheriChrome one of the newest paradigms of the dental industry.
Oral Health welcomes this original article.
Additional pioneering books that discuss the theory of Structural colouration and Wave Interference studies and principles from history:
About the Author
Ross Nash maintains a private general practice in Huntersville, NC, where he focuses on cosmetic, aesthetic and full mouth rehabilitative treatment. He presents workshops and lectures nationally and internationally and has authored chapters in two clinical textbooks. He is the co-founder of the Nash Institute for Dental Learning in Huntersville and is a member and accredited fellow in the American Academy of Cosmetic Dentistry.
Tyler Wurmlinger is a practising dentist in Huntersville, NC. He earned his Doctorate of Dental Surgery at the University of Detroit Mercy in 2011. Since 2015, Dr. Wurmlinger has been practising dentistry in the greater Charlotte area, focusing on cosmetic dentistry. He is a member of The American Academy of Cosmetic Dentistry.