Index

1 Introduction........................................................................................................................ 2
Outline of universal shade composite resin and development history of “A·UNO”............................. 2

2 Basic knowledge of composite resins for dental fillings...... 4
2.1 What is composite resin?........................................................................................................................ 4
2.2 Reaction Mechanism of Photo-radical Polymerization Reaction by Photosensitizers..... 5
2.3 Initiating Reaction and Light Irradiator............................................................................................. 6
2.4 Technological Development of Composite Resin......................................................................... 8

3 Concept of A･UNO....................................................................................................... 9
3.1 Overview of "Camouflage Effect", a unique color matching technology............................. 9
3.2 What is color?........................................................................................................................................... 10
3.3 Structure of Eye and Light.................................................................................................................. 11
3.4 Intensity Difference and Visibility..................................................................................................... 12
3.5 YAMAKIN's Golden Ratio of Transparency, Shielding Property and Intensity.................. 14
3.6 Cavity filling using A･UNO................................................................................................................. 16
3.7 Two Types Can Be Chosen According to Clinical Scenes and Doctor’s Preferences....... 18
3.8 Higher Functionality through Maximum Utilization of Filler Technology......................... 20

COLUMN Derivation of the product name "A･UNO“................................................ 21

4 Characteristics of A･UNO................................................................................... 22
4.1 Handleability............................................................................................................................................ 22
4.2 Mechanical Properties.......................................................................................................................... 23
4.3 Fluoride sustained release property............................................................................................... 25
4.4 Biological Safety..................................................................................................................................... 28

5 Clinical cases of A･UNO....................................................................................... 30
6 Conclusion......................................................................................................................... 34

1

Introduction

Outline of universal shade composite resin and development history of “A•UNO”
Direct composite resin has been used in a variety of cases and also satisfies patients' requests for white teeth
since the idea of MI (Minimal Intervention) treatment has recently gained popularity. Direct composite
resin is used not only for the treatment of small caries on the tooth surface layer but also for the restorationof molars. Therefore, it requires high strength to withstand occlusion. In addition, direct composite resin
exhibits a number of all-around exceptional qualities such as durability, workability, color tone, and fluoride
release property. In particular, good rheology (formability and fluidity) is needed to avoid posing a workability
challenge for doctors. And fluoride release property is proposed for the prevention of secondary caries and it
is believed that the sustained release and recharge property can be effective.
Furthermore, in recent years, the ability to easily reproduce the color of natural teeth has become desirable.
Therefore, universal shade type direct composite resins are attracting a great deal of attention, as they save thetrouble of shade selections and make it easy to control inventory.
Universal shade type direct composite resin is a product with a different color tone design from conventional
direct composite resins1). As Figures 1-1 and 1-2 show, conventional direct composite resins come in arange of different shades, such as A1, A2, A3, etc., in order to match the color of each tooth substances. The
universal shade type, on the other hand, is designed to be used with only one shade and not require shade
taking or shade selection for any of the basic shades (16 colors).
In addition to the chameleon effect demonstrated by adjusting light transmission and light diffusivity, whichis also applied to our conventional product "TMR-Z Fill 10.", in order to develop a universal shade typedirect composite resin, YAMAKIN CO., LTD. (hereinafter referred to as YAMAKIN) has optimized thebalance of transparency, shielding property, and saturation using our unique color-matching technology, andfocused on color tone design so that many cases can be covered simply with a single color. YAMAKIN hasleveraged its filler technology, which has evolved through the development of resin products to date, and its
unique color-matching technology to create a new composite resin product, "A·UNO", which maintains both
fluoride release and strength while being suitable for a wide variety of cases.
Based on the concept of easily reproducing a wide range of natural tooth color tones in a shade-free manner,
this product has been developed in consideration of the required strength and workability. In this technicalreport, "A·UNO" is introduced from various viewpoints. We hope that this product will be of interest to you
and that you will make use of it as an aid in your future dental treatment.
Leader, Organic Materials Development Section Doctor (Engineering) Yusuke Mizuta
Chief Researcher, Laboratory of Bioscience and Safety Dr. Miki Hayashi
Specially Appointed Chief Researcher Doctor (Engineering) Takahiro Kato
Chief Researcher Dr. Masatoshi Yamazoe
Supervisor Yamakin Doctoral Association

What is the YAMAKIN Ph.D. Group?
This is a group of experts in various specialized fields who bring together their knowledge, experience andtechnical expertise to act as a prime motivator in the continuous generation of innovation.

2

Multiple shades required

Conventional directcomposite resin

A1

Universal shade type directcomposite resin

A2

A3

A3.5

A4

B1

D4

Shade
Free

One syringe can cover 16 shades !

Figure 1-1 Summary of Universal Shade-type Direct Composite Resin (Shade Free)







Conventional directcomposite resin
Shade Taking

Shade Selection

Filling after adhesive
treatment
Shade taking andshade selection
processes can beomitted!

Universal shade type directcomposite resin

Shortenthechair time

Filling after adhesive
treatment

Figure 1-2 Summary of Universal Shade Type Composite Resin (Shorten Chair Time)

About the definitions of the terms "Universal type" and "Universal shade type"The word "Universal" has a wide range of meaning, such as “general purpose” or “for everyone”. In the dental field, "Universal" isoften used to refer to bonding materials and cements that are applicable to various materials without the need to change thebonding or cement depending on the materials. Also, since there were two types of direct composite resins, one for anterior
teeth and the other for molars, depending on strength and esthetics, the term "Universal type" in composite resins was used
to refer to a general-purpose type of resin that is superior in both strength and esthetics and can be used for both anterior
teeth and molars. With the development of the "Flow type" which has good flowability and filling workability for cavities, the"Universal type" now generally refers to a type with a high filler content and a clay-like paste before curing.
As mentioned above, the versatility of direct composite resins has further evolved in recent years, with the development of
products collectively known as "Universal shade type direct composite resins" meaning that they “cover a wide range of shadesof tooth substances with one shade”. Thus, "Universal" is used with multiple meanings in direct composite resins. Therefore, thedefinitions of "Universal type" and "Universal shade type" in this report are defined as follows.

“Universal type”
Direct composite resin with a high filler content and excellent formability in the form of a paste (distinguished from the flow type).

“Universal shade type”
A single shade of composite resin that can be used for a wide range of shades of tooth substances.

3

2

Basic knowledge of composite resins for dental fillings

2.1 What is composite resin?
Direct composite resins are organic-inorganic composites and consist of monomers such as matrices as
their organic component and fillers such as silica glass as their inorganic component. Monomers are organic
materials that have the property of changing into polymers through polymerization curing. In composite resins,
crosslinkable methallylate monomer mixtures are often used because of their superior strength and biologicalsafety. The nature of polymerization, which transforms flowable monomers into solid polymers, is an important
property that is related to the workability, color tones, and durability of composite resin restorations.
In other words, while the monomer can be freely shaped before polymerization, it serves to provide highstrength that allows it to be used on occlusal surfaces after polymerization.
Figure 2-1-1 shows Urethane Dimethacrylate (UDMA), Bisphenol A Diglycidyl Methacrylate (Bis-GMA),
and Triethylene Glycol Dimethacrylate (TEGDMA), which are widely used as resin-based restorations fordental applications. Various other monomers are also used, and properties such as viscosity, transparency,
and polymerization shrinkage of resin pastes can be adjusted by mixing several monomers with different
properties.
O
O

O

N
H

O

O

H
N

O

O

O
UDMA

HO
O

OH
O

O

O

O
O

Bis-GMAOOOO3TEGDMA

Figure 2-1-1 Examples of Monomers Used in Dental Resin-based Restorations
The inorganic filler is made of silica, alumina, or zirconia in particulate form, which is filled into the monomer
to form an uncured composite resin. Filler filling can impart mechanical strength, such as flexural strengthand hardness, to the properties of the matrix. Various types of fillers are used, including inorganic fillers
with sizes ranging from submicron to several microns, nano-sized colloidal silica, and organic and inorganic
composite fillers made by filling monomers with nano-fillers in advance, polymerizing and curing, and thenpulverizing the resulting substance. By changing the components and shapes used in inorganic fillers, therange of functions can be expanded, such as improving polishability and workability, and imparting fluoride
sustained release properties. In addition, the operation of the paste is adjusted by using a combination of thesefillers (Figure 2-1-2).

4

Micron-sized irregularly shaped
inorganic filler from 1 to 10 μm,
spherical nano-fillers from 10 to
100 nmSubmicron-sized spherical inorganic
fillers from 200-300 nm, organic andinorganic composite fillers from
20-30 µm containing 200-300 nm
submicron fillers

Micron-sized spherical inorganic
fillers from 0.5 to 1 µm, organicand inorganic composite fillers
from 10 to 50 µm containing
10~30 nm nano-filler

Figure 2-1-2 Schematic Diagram of Filler Filling
As shown above, though each monomer and inorganic filler plays an important role, sufficient strength anddurability cannot be obtained unless they are firmly bonded at the interface. This is because fractures andbreaks in composite materials occur at the interface between the matrix and the filler. Basically, the monomers
are lipophilic, and the surfaces of inorganic fillers are hydrophilic. Therefore they do not have a high affinity

for each other. The method used to solve this problem is surface treatment with a silane coupling agent. The
surface of inorganic filler treated with a silane coupling agent is modified to become lipophilic and have ahigh affinity for monomers. In addition, silane coupling agents have radical-polymerizable groups in theirmolecules. Therefore they have the ability to react simultaneously during the polymerization of monomers.
As a result, high filler content of inorganic fillers is possible, and after polymerization curing, they are firmly
bonded and integrated with the polymer matrix, contributing greatly to the high strength and high durabilityof composite resins. As described above, monomers, inorganic fillers, and their interfaces must fulfill theirrespective roles sufficiently for composite resins to meet the required performance as dental materials.

2.2 Reaction Mechanism of Photo-radical Polymerization Reaction by Photosensitizers
To obtain a polymer from a monomer, a specific reaction called a polymerization reaction is required.
Polymerization reactions are classified into chain reactions and sequential reactions. In chain reactions, whena polymerization active species is generated from a monomer, it immediately reacts with another monomer,
followed by a rapid reaction to another monomer (Figure 2-2-1). As a result, the monomer is instantaneouslytransformed into a mixture of a high molecular weight polymer and an unpolymerized monomer by a chain
reaction. On the other hand, sequential reactions require a certain amount of time for the polymer to reach ahigh molecular weight because of the slow consumption of monomers. In the case of monomers with multiple
polymerizable groups in the molecule (crosslinkable monomers), the polymer forms a network structure(crosslinked structure) through polymerization, and as polymerization progresses and the density of thepolymer network structure increases, the resulting substance exhibits high solvent resistance (i.e., it does notdissolve even in solvents), and stable strength in the oral cavity for a long time.

(Short Time)

Before reaction (Monomer)

Mixture of polymer (insoluble) andunreacted monomer

Figure 2-2-1 Chain Reaction (Radical Polymerization)

5

Initiation+

2
Initiating radical
Propagation

Monomer

Shortest propagating
radicalnPropagating radical

Termination

2(Recoupling)

Or
－H +

(Disproportionation)

Chain transfer

Propagating radical

Chain transfer
agent

Deactivation

Reinitiating radical

Figure 2-2-2 Four Elementary Reactions in Radical Polymerization(Initiation, Propagation, Termination, and Chain Transfer)
When the composite resin is irradiated with light, radical polymerization of the monomer occurs and apolymer is formed and cured. This radical polymerization usually does not proceed with the monomer
alone, but uses an initiator, that is a thermal sensitizer for polymerization by heating or a photosensitizer forpolymerization by light irradiation. Most composite resins are polymerized and cured by light irradiation
using photosensitizers such as Camphorquinone (CQ) and accelerators such as tertiary amines. Radical
polymerization consists of four types of elementary reactions: Initiation, Propagation, Termination, andChain Transfer, as shown in Figure 2-2-2. In the case of photoirradiation polymerization, the photosensitizer
generates an initiating radical upon light irradiation, and the addition of the initiating radical to the monomer
generates a propagating radical. These two types of reactions form the Initiation. During Propagation,
propagating radicals repeatedly add themselves to the monomer one after the other, growing to a highmolecular weight. At Termination, recombination or bimolecular disproportionation of propagating radicals
renders the propagating radicals inactive, and a single or bimolecular polymer chain is formed.

2.3 Initiating Reaction and Light Irradiator
Radical polymerization of composite resins is initiated by light irradiation from a light irradiator, but
the light used for initiation must be light that is absorbed by the photosensitizer. CQ is widely used as aphotoinitiator for photoinitiating polymerization of dental materials, and is excited by light irradiation inthis wavelength region because it shows an absorption maximum at around 470 nm. Photoexcited CQ draws
hydrogen from hydrogen donors such as tertiary amines to form initiating radicals. Visible light irradiationof CQ/amine initiators produces two types of radicals, but CQH· does not add to monomers due to its large
steric hindrance. On the other hand, R "CH(•)N(R)(R2') causes addition to the monomer and becomes theinitiating radical (Figure 2-3-1).

6

R
O
CQ

O

N CH2R"+

RG
Tertiary amine

O
Visible lightirradiationOR
N CH2R"
RG

Exciplex(Excited-state complexes)

O
Electron transfer

M
O

R
+N
RG

R

OH
CH2R"

N CHR"

H+ abstractionO
CQH(inactive)

RG
Initiating radical

Figure 2-3-1 Radical Formation from Camphorquinone/
Tertiary Amine Initiator System by Visible Light Irradiation

In other words, resin materials that use CQ as a photosensitizer polymerize and cure when irradiated withlight at a wavelength of around 470 nm. The polymerization rate and the physical properties of the polymer

produced (dental material after curing) differ depending on the intensity of the irradiated light. Light-curing
material must be irradiated with light of the appropriate wavelength and intensity . If not appropriate, theinitiation reaction may not proceed sufficiently, resulting in insufficient polymerization, and the material
after polymerization may not exhibit its original properties. Currently, light irradiators with various lightsources and light intensity are commercially available. Light sources include Halogen lamps, plasma lamps,
and LED lamps, but in recent years, LED light irradiators have become the mainstream. In addition, LED
light irradiators with maximum irradiance (Table 2-3-1) are now available to shorten the curing time of resinmaterials, and the irradiation time that can be set is also becoming shorter. In addition, products equippedwith not only blue LED (about 470 nm) but also purple LED (about 40 nm) are now available for use
in glazing material and whitening. Each product has a wide variety of characteristics, and light exposuremust be applied for the appropriate amount of light and time for the composite resin used. In many cases,
IFU indicate that LED lamps can reduce irradiation time by half when compared to halogen lamps andLED lamps. This is because LED lamps can irradiate light of 470 nm, the excitation wavelength of CQ,
to a more limited extent than halogen lamps, and can achieve a sufficient polymerization rate even with ashort irradiation time. The development of such light sources has also contributed to the efficiency of dental
treatment.

7

Table 2-3-1 Examples of Commercial Light Illuminator (LED)
Effective
wavelength
range (nm)Maximum
irradiance(mW/cm2)

Penguin α

380 ~ 415
440 ~ 480

2400

SellerYAMAKIN CO., LTD./
PIERCE CORP.
PIERCE CORP.

Ultradent Products, INC.

Product Name

Delight ortho

420 ~ 490

2700

VALO LED Curing Light395 ~ 480

3200

VALO Cordless

395 ~ 480

3200

VALO GRAND LED Curing Light395 ~ 480

3200

VALO GRAND Cordless

395 ~ 480

3200

VALO Ortho

395 ~ 480

3200

VALO Ortho Cordless

395 ~ 480

3200

J. MORITA MFG. CORP.

PenCure 2000

405 ~ 460

2000

GC CORP.

SlimLight

390 ~ 480

2000

Hakusui Trading CO., LTD.

miniLED Ⅲ

420 ~ 480

2200

Bluephase N G4

385 ~ 515

2000

SHOFU INC.

Ivoclar Vivadent, INC.

Micro Tech. CORP.
Forest-one CO.,LTD.
Dentaltechnika KFT.
Apixia CORP.
Dentrade KFT.

B.S.A. Sakurai CO., LTD
WSPT japan LLC.

Bluephase 20i

385 ~ 515

2000

Bluephase Style 20i

385 ~ 515

2000

Bluephase PowerCure

385 ~ 515

3000

LEDEX turbo WL-090

440 ~ 480

2400

LEDEX WL-090

440 ~ 480

3200

FUSION5420 ~ 490

4000

NOBLESS

430 ~ 490

3000

NOBLESS A

385 ~ 515

3000

LITEX 696 Turbo

440 ~ 490

2500

D-LUX LED

420 ~ 490

2400

D-LUX Pen

385 ~ 430
440 ~ 515

2300

X Light

430 ~ 480

2500

X Light PLUS

385 ~ 515

3200

HABILETE

385 ~ 515

2300

2.4 Technological Development of Composite ResinAt the time of development, composite resins were only clay-like pastes that were built up with a spatula,but many composite resins on the market today are available in a flow type, which can be injected directly
into cavities using a syringe, and to facilitate filling of deep cavities, various viscosities have been developedfor each product, ranging from those with very high flowability (high flow) to those with low flowability(low flow) that can also be shaped with septa and other tools. There have been remarkable technologicaldevelopments in composite resins, such as flow-type composite resins with high strength that can be used on
molar occlusal surfaces, and bulk-type composite resins that exhibit a curing depth of 4.0 mm with a single
light irradiation. In recent years, Universal shade type composite resins, which do not require shade selection,
have attracted particular attention. This type not only easily reproduces the color tone of natural teeth, butalso reduces inventory loss, which may contribute to the Sustainable Development Goals (SDGs). The color
matching technology of the Universal shade type composite resin "A·UNO" will be covered in the following
chapter.

8

3Concept of A･UNO

3.1 Overview of "Camouflage Effect", a unique color matching technology

Camouflage EffectPursuing a balance between
light diffusivity andlight transmission

YAMAKIN’ s optimization oftransparency, shielding property
and intensity

Chameleon EffectGolden BalanceIntegration of technologies
Figure 3-1-1 Unique Color Matching Technology "Camouflage Effect”

As shown in Figure 3-1-1, the "Camouflage
Incident light
Reflected lighteffect" used in "A·UNO" combines two
major color matching techniques. The first is"Pursuing a balance between light diffusivity
and light transmission”. Light incident on"A·UNO" is scattered by its light diffusivity
and reaches the surrounding tooth substances.
Through the process of scattering, the filling
Figure 3-1-2 Pursuing A Balance Between
area becomes blurred and appears to blend
Light Diffusivity and Light Transmission
in with the color of the surrounding tooth(Chameleon Effect)
substances (Figure 3-1-2). In addition, the lightreflected from "A·UNO" is diffused into the surrounding tooth substances as mentioned above. Therefore,
the color of "A·UNO" is blended with the surrounding tooth substances. This ability to transmit light while
diffusing it is the fundamental technology of A·UNO's color compatibility. This property, also known as thechameleon effect, is also applied to our conventional product, "TMR-Z Fill 10."
As shown in Figures 3-1-3 and 3-1-4, "A·UNO" can blend well with cavity models of different shades.
A1

A3

A4

Before Filling

After Filling

Figure 3-1-3 Apply A • UNO on A1, A3 and A4 shade cavity models

9

A1

A2

A3

A3.5

A4

B1

B2

B3

B4

C1

C2

C3

C4

D2

D3

D4

Filled in part

Figure 3-1-4 Artificial tooth filled with "A • UNO" in 16 shades

Transparency

YAMAKIN’s
Golden Ratio

Shielding
Property

Intensity

Figure 3-1-5 YAMAKIN’s Golden Ratio of Transparency, Shielding Property and Intensity

Another technology is the "YAMAKIN's Golden Ratio of Transparency, Shielding Property and Intensity"
shown in Figure 3-1-5. Through repeated trial and error regarding transparency, shielding property, andintensity, we were able to find a design that reduced the influence of the base color tone and made it possible
to reduce the difference in brightness between the resin filling part and the tooth substances.
The details of this technique are described in 3.5. This unique technology allows "A·UNO" to not only matcha wide range of tooth color tones, but also to perform well in a wide range of cavity conditions which areassumed clinical practice.
These two technologies were combined to create "A·UNO", featuring the "Camouflage Effect", a unique color
matching technology developed by YAMAKIN. Next, basic information about color is presented, followed bya detailed explanation of the color matching properties of A·UNO.

3.2 What is color?
The three colors of blue, red, and green in the YAMAKIN's logo represent respectively the "sea and sky,""sun" and "trees" of Kochi Prefecture, the development and manufacturing base. This design represents thecompany's commitment to delivering products with excellent quality based on innovative ideas in a richnatural environment. It is also used as a company badge (Figure 3-2-1).

Figure 3-2-1 YAMAKIN's Logo

10

Interestingly, while blue, red, and green are the three primary colors of light, there are significant differences in
the mechanisms by which humans feel the "blue of the sky," the "green of trees," and the “red of the sun”. The
blue of the sky is caused by the scattering of light in the atmosphere at wavelengths that are perceived as blueby the human eye , and the colors of grass and leaves are caused by the reflection of light at wavelengths thatappears green to the human eye. The red color of the sun follows the image and culture of Japanese people (thecolor of sunsets and the Japanese flag), and is originally white, almost yellow, while in Europe and the UnitedStates, it is painted yellow, and there are regional differences2).
In his book "OPTIKS" published in 1704, physicist Isaac Newton stated the famous phrase “The rays are
not colored” 3). In other words, light itself has no color, but the sensation of "color" is generated only whenlight enters the eye and is transmitted to the cerebrum, and light itself is only a trigger for generating suchsensation. In the following sections, the physiology of the human visual system and color vision will be briefly
discussed, and the "Camouflage Effect," a color matching technology for "A·UNO" will be explained indetail.

3.3 Structure of Eye and Light
The structure of the human eye is similar to that of a camera. It includes an "iris", which is a control that
adjusts the amount of light, a "crystalline lens", which acts as a lens to adjust focus, a "retina", which accepts
light and projects an image, and neurocytes that transmit visual information to the brain. The most importantpart in the eye that receives light is the retina (Figure 3-3-1) 2, 4-8).
Crystalline lensRetinaFovea

Optic nerve
CorneaIris

Corpus vitreum

Figure 3-3-1 Structure of the Human Eye
The retina is neural tissue, with neat layers of cells. The outermost layer of the retina is composed of jet black
pigment cells that prevent the reflection of light, and photosensitive cells, which sense light directly, are locatedjust inside the pigment cells. These photosensitive cells are a type of neuron that has been transmuted to besensitive to light, and there are cones and rods. (Figure 3-3-2) The name of cone is said to derive from cone
shape and the name of rod is said to derive from the rod-like shape of the outer segments. There are three typesof photosensitive proteins in the cones, which respectively react most sensitively to blue, green, and red lights.
Since we perceive final light by combining blue, green, and red information, we humans recognize all colors
from purple to crimson using only three cones for blue, green, and red. On the other hand, rods have only
one type of photosensitive protein (called rhodopsin, made of vitamin A), which cannot distinguish between
different wavelengths but is very sensitive and can perceive even weak light sensitively 2, 5-8).

11

Rod

Red cone Green cone Blue conescotopiabrightness

brightness

Red/ Yellow/
Green Blue

Figure 3-3-2 Photosensitive Cells
These photosensitive cells are distributed in the outer layers of the retina, with approximately 6.5 to 7 million
cones and 115 to 120 million rods 2, 8). In addition, the central retina, which corresponds to the exact center ofthe visual field and is the most important area of the retina for the development of vision, is called the central
retinal fovea. Only the cones are present in high density in the central retinal fovea, and there are no rods.
Visual acuity is particularly high only in this region, and is considered weak outside the central fovea. For
example, when we gaze at something, we use only the central retinal fovea. On the other hand, the rods are
distributed throughout the retina except for the central fovea, and their sensitivity to light is said to be several
hundred times higher than that of the cones.
When sufficient brightness is available, the cones are mainly active, and vision at this time is called photopic
vision (or cone vision). Conversely, vision in which brightness is insufficient and only the rods are active iscalled scotopic vision (or rod vision). For example, a red or yellow flower may seem brighter than a green leaf
during the daytime, but at dusk, the green leaf may seem brighter. This is due to the different wavelength
sensitivity of the cones and rods. In clinical dentistry, it is believed that humans perceive color mainly by thecones, because sufficient brightness is provided by the clinic lighting 2, 5-8).

3.4 Intensity Difference and Visibility
As mentioned above, light entering the eye from the external environment can be perceived as colors by thecones. It is said that the human eye can distinguish approximately 7.5 to 10 million colors, and in order tounderstand and utilize that many colors, it is necessary to organize and classify colors 9).
These colors can be roughly classified into chromatic colors such as red, yellow, green, and blue, andachromatic colors such as white, gray, and black. In addition, chromatic colors have independent attributes ofhue, intensity, and saturation (the three attributes of color), as shown in Figure 3-4-1. Hue is an attribute that
expresses the difference in color quality or shade, such as red, yellow, green, blue, etc. Intensity is an attributethat expresses the relative lightness, darkness and brightness of colors, and is determined by the reflectanceof an object's surface and other factors. Saturation is an attribute that expresses the intensity of shades andvividness of colors 10, 11).

12

Saturation

Brightness

Hue

Hue

Brightness

Saturation<Shades><Brightness of colors><Vividness of colors>

Figure 3-4-1 Three Attributes of Color (Hue, Brightness and Saturation)
In order to better understand how humans perceive colors, it is necessary to consider the interaction between
adjacent colors when multiple colors are juxtaposed (contrast phenomenon, Liebmann effect, etc.). For
example, in Figure 3-4-2, gray squares of the same intensity are lined up against background colors of different
lightness. In this case, the gray squares in the white area appear slightly darker and the gray squares in theblack area appear slightly whiter.

As a matter of fact, gray squares are all the same color

Darker background color
makes it seem brighter.

Lighter background color
makes it seem darker.

Figure 3-4-2 Color Appearance by Background Color(Those 3 gray squares are all the same color)
The figure above shows the brightness contrast among the contrast phenomena. In the case of universal shadedirect composite resin, the key point is how much the visibility (ease of recognition of the filling) can belowered when compared to the surrounding tooth substances. For example, on a black background, red andyellow are more easily recognized than blue and purple. Conversely, on a white background, blue and purple
are more easily recognized, showing the opposite trend from the case of a black background (Figure 3-4-3). In
other words, the difference in brightness between the background and the object is a factor that determines
visibility 10, 11).

13

Figure 3-4-3 Change in Color Visibility When Background Color Changes(corresponding illustrations top and bottom are the same color)
Furthermore, colors with small differences in brightness can give a calm impression to humans and appear to

blend well with each other, even if they are very different in hue. Conversely, if there is a great difference inbrightness, the contrast increases and visibility is enhanced (Figure 3-4-4). The above phenomenon, in whichadjacent colors have a great difference in hue but are close in brightness, causes the boundary to blend andbecome indistinct and difficult to see, and is known as the Liebmann effect 9-11). In the design of universal
shade direct composite resins, it is considered important to minimize the brightness difference from the tooth
substances so that the Liebmann effect is high.
When the difference in brightness is small

When the difference in brightness is great

the colors blend in overall

it causes a sense of discomfort only in blue color

Figure 3-4-4 Colors Perceived according to Brightness Differences(left: small differences, right: large differences)

3.5 YAMAKIN's Golden Ratio of Transparency, Shielding Property and Intensity
As mentioned above, brightness is the key for a material to blend in with the surrounding tooth substances.
Needless to say, the color design of the material itself is important, but considering that natural teeth aretranslucent materials, transparency and shielding property are also important. This is because the brightness ofthe direct composite resin will be greatly affected by the background color if it is a Class IV cavity where lightpasses through from the labial side to the lingual side or if it is a cavity with discoloration at the bottom of thecavity. Intensity, which has not been mentioned much up to this point, must also be taken into consideration
because it affects the tonal compatibility when the cavity is large.
In the following explanation of "Camouflage Effect", we break down the color matching technology of
A·UNO into the three components: ① Transparency, ② Shielding Property and ③ Intensity.

14

①Transparency
The transparency of direct composite resin should match the half-transparency of natural teeth, especially inthe restoration of Class IV cavities. For example, as shown in Figure 3-5-1, if the direct composite resin has
low transparency, the background color is excessively masked, making it difficult to reproduce the transparencyof the incisal area. On the contrary, if the transparency is too high, the direct composite resin filling is too
affected by the dark background color and is easily visible without blending with the surrounding tooth
substances. A·UNO is designed to be applied to Class IV cavities with optimal transparency close to that ofnatural teeth to reproduce natural color tones.
Transparency

Before filling(Class IV cavity)

Low

OptimalHigh

Difficult to reproduce
transparency of theincisal area

Natural color tone

Light penetrated too
much and the filledarea becomes dark.

Figure 3-5-1 Image of Cavity Filling of Direct Composite Resin with Different Transparencies② Shielding Property
As described above, A·UNO has a certain degree of transparency, allowing it to reflect the surrounding color
tone of the filling area while also reproducing of transparency at the incisal edge. However, there are casesthat cannot be handled simply by absorbing ambient light depending on transparency. For example, if there
is discoloration at the bottom of the fossa, this discoloration will be strongly reflected if the direct composite
resin has a low shielding property, whereas if the shielding property is too high, it will be hard for the fillingpart to blend well with the color of the surrounding tooth substances. A·UNO maintains transparency while
increasing turbidity, thereby shielding the discoloration at the bottom of the fossa optimally, and reproducing
a natural color tone.
Shielding Property

Before filling(discoloration on thebottom of the fossa)

Low

OptimalHigh

The filling part is affectedby the color tone of thebottom of the fossa toomuch and stands out.

Natural color reproduction

Filled parts are difficultto blend into the tooth
structure and stand out.

Figure 3-5-2 Images of Filled Cavities with Direct Composite Resins with Different Shielding15

③ Intensity
There are differences of width or thickness of the indirect composite resin depending on the size of thecavities. In the case of Universal shade direct composite resin, when the cavity is small, the color of the resin
itself has little effect on the color tone of the restoration even if its intensity (color depth) is low, because
the color tone of the surrounding tooth substances can be taken in. However, when the cavity is large, theintensity of the resin itself greatly affects the color tone of the restoration. In other words, if the intensityof the resin is low (pale color), the larger the cavity, the whiter and brighter the restoration appears, and thefilling area is more likely to appear white. Conversely, if the saturation of the resin is high (darker color),
the filling area appears darker. (Figure 3-5-3). In order to reduce the influence of the amount of filling on
the cavity, A·UNO is colored with a small amount of red and yellow pigments to minimize the change in
intensity and brightness with thickness, so that it blends well with cavities of different sizes.
Intensity

Before filling(deep cavity)

Low

OptimalHigh

Filling area becomeswhiter and stands out

Reproduction of natural
color tone

Filling area becomesdarker and stands out

Figure 3-5-3 Images of Cavity Filling with Direct Composite Resins of Different Intensity
As described above, A·UNO is designed to have high light transmission and light diffusivity so that thecolor tone of the surrounding tooth substances can be easily taken in. At the same time, it also has shielding
properties that are less affected by background color by increasing turbidity. Even when the amount of resin
filling is large, use coloring to add appropriate intensity to minimize the change in brightness. In other words,
A·UNO is a product that optimizes the balance between transparency, shielding property and intensity, basedon the concept of using a single color to suit as wide a range of cases as possible.

3.6 Cavity Filling Using A • UNO
1) Class IV cavity model
Because of its optimal transparency and shielding
properties, A·UNO can reproduce the naturalborder between the tooth substances whileshielding the background color, and can also
express the transparency of the incisal edge.
Figure 3-6-1 Class-IV Cavity: Cavity without Backing(Cavity Model : A2)

162) Case model with discoloration at thebottom of the fossa
The natural appearance is reproduced whileshielding the discolored area optimally.

Figure 3-6-2 Class I Cavity with Discoloration at the
Bottom of Fossa (Cavity Model: A3)

3) Case model with MTA cement in thebottom of fossa
After applying TMR-MTA cement Mielle (white)
to the bottom of fossa, A·UNO was filled in toreproduce a natural appearance while shielding thewhite color of the MTA cement.
Figure 3-6-3 Class I Cavity with MTA Cement at the
Bottom of the Cavity (Cavity Model: A3)

4) Class II cavity model vith adjacent metal
tooth
Thanks to the optimal shielding property andintensity of A·UNO, which reduces the influenceof the gray color of the metal and reproduces anatural tooth color tone without too much whitish
color, even in deep cavities.

Figure 3-6-4 Class II Cavity Deep Cavity with
Adjacent Metal Tooth (Cavity Model: A3)

So far, we have shown models of cases for which a single A·UNO syringe application is enough. However, insome cases, using only one A·UNO is esthetically difficult. For example, dark-colored aged teeth, whitenedbright teeth, etc. may be considered. In such cases, the use of a darker shade (such as A5 or OA5) or a white
shade (such as BW or OW) of TMR-Z Fill 10. as a base shade can provide a more esthetic restoration.
Also, care should also be taken in cases where the majority of the crown is formed using only one shade of
A·UNO. As explained in section 3.1, the Camouflage Effect of A·UNO assumes the presence of tooth color
in the surrounding area. Therefore, in cases where there is no tooth substance to serve as a base for color,
TMR-Z Fill 10. should be used as the base color of the crown.

173.7 Two Types Can Be Chosen According to Clinical Scenes and Doctor’s Preferences
There are two types of A·UNO lineup; Normal Type that changes color (transparency) before and after lightcuring, and St Type (Steady Transparent) that hardly changes color (transparency) at all.
Normal Type and St Type can be chosen depending on clinical cases or doctor’s preference (Table 3-7-1).
Table 3-7-1 Characteristics of Normal Type and St Type
Characteristics

Merit

Normal Type

Before curing, the transparency islower than that of the tooth
substances. Therefore, the fillingarea is highly visible.

・Because the boundary between the filling and tooth
substances is easy to see, the morphologicaltreatment process can be done easily.
・Transparency changes before and after curing.
Therefore, the completion of light curing can be
confirmed visually.

St Type

Almost no change in transparency
before and after curing.

・It is possible to imagine the color tone after treatment
at the time of filling.

Before Light Curing

After Light Curing

Normal Type
10 sec.

light irradiation
with 1200 mW/cm2

St Type(Cavity Model : A4)
See Figure 3-1-3 for cavity shape

Figure 3-7-1 Color Tone of Normal Type and St Type before and after Light Curing
The filler components and composition ratios are basically the same for the Normal Type and St Type.
Nevertheless, the reason for the large differences in color change behavior before and after curing is thatthe monomer components and their composition ratios described in Section 2.1 are unique. The important
physical property here is the refractive index. The refractive index is a physical quantity unique to amaterial that affects the speed of light in the material and is expressed as "the speed of light propagation
in a vacuum / the speed of light propagation in the material" 12). In organic-inorganic composite materials
such as composite resins, transparency is determined by the magnitude of the difference in refractive index
between the matrix as the organic component and the filler as the inorganic component. In other words, if
the refractive index difference between the matrix and filler is large, light scatters at the interface, resulting
in low transparency, and if the refractive index difference is small, transparency is high. There is a scientificexperiment called the "disappearing cup," in which a small glass cup is placed inside a larger glass cup, andwhen salad oil is poured into the glass cup, the smaller glass cup inside disappears. Since the refractive index
of glass and salad oil are almost the same, light is not scattered at the interface and becomes transparent,
making the small glass cup inside invisible.

18

In other words, to increase the transparency of the composite resin, it must be designed to have a close
refractive index to prevent light from scattering at the interface between the matrix and filler. In the caseof composite resins, it is necessary to design the material considering not only that, but also that when themonomer of the matrix is converted into a polymer by photopolymerization, the density increases due toshrinkage and the refractive index increases. Normal Type is designed so that the monomer refractive index islower than that of the filler before polymerization and the refractive index of the polymer after polymerization
is close to that of the filler. St Type is designed so that the refractive index of the filler is adjusted to be
between that of the monomer and polymer of the matrix, so that the difference in refractive index between
the matrix and filler before and after polymerization is stable and light transmission does not change before
and after polymerization.
MonomerLight irradiation

Polymer
Transmission rate

FillerRefractive Index

60%
Refractive Index of filler

60%

The closer to the blue line,
the higher the transparency.

60%

40%

Normal TypeSt TypeFigure 3-7-2 Image of the Refractive Index of Matrix-filler of Normal Type and St TypeLight
irradiation

Before curingLight
irradiation

After curing

Normal Type

Before curing

After curing

St TypeFigure 3-7-3 Color Tone Change before and after Light Curing of Normal Type and St Type19

3.8 Higher Functionality through Maximum Utilization of Filler Technology"KZR-CAD HR Block 2", a hybrid resin block for resin material for dental milling and machining launchedin September 2015, achieves both "strength" and "fluoride release", which were previously thought to bedifficult to achieve at the same time. This technology has also been applied to "iGOS", a direct composite
resin for dental restorative material launched in February 2016, and "TMR-Z Fill 10.", which is launched in
September 2018. By utilizing the filler technology developed by YAMAKIN to achieve both "strength" and"fluoride release", as well as by incorporating YAMAKIN's exclusive color-matching technology, the finishedproduct, A·UNO - a Universal Shade type composite resin, was launched in June 2022.

Table 3-8-1 Filler technologies utilized in A • UNO
ShapeFillerFunction

Actual use in
YAMAKIN's resin products

Ceramics Cluster Filler(C.C.F.)(2-8 μm)

Improved mechanical strength
Improved abrasion resistanceFormability
Improved polishability

・KZR-CAD HR Block series
・TWiNY・TMR-Z Fill 10.

Fluoride Sustained Release Filler(700 nm)

Fluoride sustained release property
Fluoride recharge property

・KZR-CAD HR Block series
・TMR-Z Fill 10.

Spherical Nano-Filler(20 nm)Improved mechanical strength
Improved handleability

・KZR-CAD HR Block series
・Luna-Wing
・TWiNY・TMR-Z Fill 10.

Spherical Nano-Filler(50 nm)Improved filling rate
Improved abrasion resistance―

As shown in Table 3-8-1, Ceramics Cluster Filler (C.C.F.), which are essential for improving mechanicalstrength and formability, are cluster fillers that primarily comprize particles (submicron fillers of 200-600 nm)
of silica-zirconia-alumina composite oxides synthesized by the sol-gel method, granulated to 2-8 µm by firingand milling, and having an uneven surface. Moreover, to improve mechanical strength and handleability, there
are Spherical Nano-Filler particles of about 20 nm, Fluoride Sustained Release Filler to provide fluoridereleasing and fluoride-recharging properties, and Spherical Nano-Filler particles of about 50 nm to improve
filler filling rate and abrasion resistance. Those fillers are used in combination according to the productconcept for each product.
A·UNO is the culmination of all the filler technologies that YAMAKIN has accumulated in its resin products
to date.

20

COLUMN

Derivation of the product name "A•UNO""A" means "one" in English and "UNO" means "one" in Italian and Spanish. In otherwords, the concept of covering 16 shades with "ONE shade" is incorporated into
the product name.
"Auno" in Japanese means "matching". This is from the fact that A•UNO matches
the color tone of the tooth substances. The development of this product started
as the "All A•UNO Project" based on the concept of matching all tooth colors.
However, in clinical practice, there were cases with very dark shades such as A5
shade, and pure white teeth that had been whitened, in addition to 16 shades.
Therefore, it was found that it would be difficult to match all natural tooth colors
with only one color. For that reason, The product name was decided as A•UNO.

There is a world-famous card game called "UNO", in which if a player forgets to
declare "UNO" when he or she has only one card in hand, he or she must draw
two cards from the rest of the cards when another player points out "Oh, youdidn’t say UNO!" The colors of UNO
cards are red, green, blue, and yellow,
which are also known as the four primarycolors. A•UNO has only Basic Shade, andthe name of this shade reflects our wish
that this shade is used as the basic colorOh,yyou didn’t sa

UNO!

for tooth substances.

21

4

Characteristics of A•UNO

4.1 Handleability1) Flowability
A·UNO is available in three types of pastes: Universal, which is less sticky and has excellent formability; Low
Flow, which has optimal viscosity and can be poured into the cavity without dripping; and Flow, which has
high fluidity and can flow into the cavity. The use of these types for different cases and on different filling sites
can shorten the working time.

15 min. after shaping (Horizontal)

Figure 4-1-1 Universal Type Paste Properties
Universal type adheres adequately to the tooth structure and prevents air bubbles from being entrapped
during filling, and is not sticky. Universal type also has excellent morphogenetic stability and does not drip
after applying, allowing for delicate filling work such as occlusal morphology (Figure 4-1-1).

10 seconds after
60 seconds after
having been taken out having been taken out(Horizontal)(Vertical/0.5g)

Figure 4-1-2 Low Flow Type Paste Properties
As shown in Figure 4-1-2, Low Flow type has optimal viscosity, displaying both fluidity and the ability toform a shape. This optimal viscosity is expected to allow the product to be used in a wider range of cases.

10 seconds after
60 seconds after
having been taken out having been taken out(Horizontal)(Vertical/0.5g)

Figure 4-1-3 Flow Type Paste Properties
As shown in Figure 4-1-3, the paste of Flow type flows and spreads quickly after having taken out, and thishigh fluidity allows it to easily flow into the cavity and quickly stick to the tooth substances. Suitable forfilling of small cavities and lining.

222) Polishability
Sufficiently polishing and smoothing the surface reduces the adhesion of plaque to direct composite resins. In
order to minimize the burden on the patient in composite resin restorations, polishing must be completed in ashort period of time.
A·UNO is designed to be easily polished despite its high filler content by maximizing the use of YAMAKIN'sfiller technology. In addition, the ratio of fine filler is higher than that of the existing composite resin TMR-Z
Fill 10., which makes it easier and quicker to obtain gloss (Figure 4-1-4).

AfterpolishTime (second)40

Beforepolish30

Shorten
15%

20
10
0

TMR-Z Fill 10.

Appearance of A•UNO crown
before and after polish

A•UNO

Time necessary for polish(Test method : In-House Test)
Polished resin surfaces equivalent to 5 mm diameter

Figure 4-1-4 Polishability Evaluation (Universal Basic)3) Improvement of syringes
In direct composite resin restorations, air bubbles in
the filled resin must be avoided because they cause
postoperative defects (reduced strength and esthetics).
Therefore, A·UNO investigated the cause of air bubbles
inside the syringe and improved the design of the syringe's
internal shape to significantly reduce the entrapping of air
bubbles (Figure 4-1-5).

Air bubbles

FormerNew

Reduced 97% of
Air bubbles

Figure 4-1-5 Improvement of Syringe Design

4.2 Mechanical Properties
1) Flexural strength
The flexural strength of A·UNO was evaluated by a three-point bending test in accordance with JIS T 6514 13).
A·UNO was filled into a 2 mm × 2 mm × 25 mm mold, light-cured, and prepared with water-resistant abrasive
paper to make test specimens. The specimens were stored in water at 37 °C for one day and then, measured using
a compact table-top tester. (EZ-Graph: Shimadzu Corporation). The thermal cycle test is used to evaluate thedurability of the material by alternately immersing the specimens in hot and cold water to promote material
degradation, utilizing the difference in thermal expansion coefficient of the constituent materials in the material.
This test is a model test assuming use in the oral cavity. In this test, the material was immersed at 4 °C and 60 °C
for 60 seconds each for 5,000 cycles, followed by a three-point bending test to confirm durability (Figure 4-2-1).
The flexural strength of A·UNO is equivalent or superior to that of our existing product, "TMR-Z FiIl 10."and the value after thermal cycling is improved. The surface treatment conditions (silane coupling agent andtreatment method) of the inorganic filler have been improved in A·UNO, and it is assumed that this has
improved the water resistance. The improved surface treatment conditions increased the filler filling ratio of
A·UNO by 3 to 4 %, from TMR-Z Fill 10. Universal (77 wt%) and Flow (67 wt%) to A·UNO Universal(81 wt%) and Flow (70 wt%). Universal and Flow types of A·UNO showed similar durability. Therefore, the23doctor can freely select the preferable paste type for the application case without considering the difference indurability.
(Reference Value)
Before thermal cycle test

Flexural Strength (MPa)200

After thermal cycle test 5,000 times

160
120
80
40
0

Universal

Low Flow

Flow

A•UNO

Universal

Flow

TMR-Z Fill 10.
(Test method: JIS T 6514)

Figure 4-2-1 Flexural Strength

2) Abrasion resistance
Dental restorations repeatedly come into contact with the opposing teeth through occlusion, causing abrasion
to the natural teeth and the restoration itself. If the amount of abrasion is too large, the occlusal balance will
be upset and the bite will be deteriorated. Therefore, abrasion resistance to the opposing teeth is an important
performance. Consequently, an opposing teeth test was conducted to evaluate abrasion resistance. The test
method was an impact abrasion test under 37 °C water, in which a model of an opposing teeth using a bovine
tooth was impacted with a load of 5.8 kgf against a pellet-shaped test specimen, and the cycle of moving themodel left and right by 1 mm was repeated 50,000 times (Figure 4-2-2). This test was conducted using bovine
tooth enamel (320 HV)15) with Vickers hardness close to that of natural human teeth (300-350 HV)14). As
shown in Figure 4-2-3, A·UNO has improved abrasion resistance compared to the existing product TMR-Z
FiIl 10. due to its dense and high filling of four types of inorganic fillers. Furthermore, the amount of abrasion
on the impact-worn counterparts was significantly lower than that of impact wear between bovine tooth
enamel, indicating that this material suppresses the risk of tooth abrasion on the occlusal parts.

Test Condition : Impact abrasion test
(Under 37°C water)
Load Weight : 5.8kgf
Frequency: 50,000 cycle
1 cycle: One impact and movementby 1mm to the left and right

Figure 4-2-2 Schematic Diagram of the Opposing Teeth Abrasion Test

24

(Reference Value)
Test Piece

Antagonist

Abrasion Depth (µm)

240
200
160
120
80
40
0

Universal

Low Flow

Flow

A•UNO

Universal

BovineEnamelTMR-Z Fill 10.

(Test Method : In-House Test)

Figure 4-2-3 Abrasion Test of Opposing Teeth

4.3 Fluoride sustained release property
1) The Amount of Fluoride Ion Release
Fluoride ions taken into the oral cavity are known to inhibit enamel demineralization, promote remineralizationand exhibit caries-preventive effects16-20). A·UNO contains fluoride sustained release fillers expecting these effects.
The fluoride sustained release property of A·UNO was evaluated as follows. A·UNO was filled into a mold with adiameter of 12 mm and a thickness of 0.5 mm, light cured by a light curing machine, and the surface of the cured
specimen was prepared with water-resistant abrasive paper. The prepared specimens were thoroughly rinsed under
running water and immersed in 15 mL of distilled water. After a predetermined period of time, the specimens
were removed and the fluoride ion concentration in the immersion water was measured with an ion meter (F-55:
HORIBA, Ltd.). The fluoride ion release per unit area was then calculated. The measurement results (Figure 4-31) show that A·UNO releases fluoride ions stably for more than 6 months.

Cumulative Fluoride Ion Release Amount(μg/cm2)(Reference Value)
A•UNO

45

Luna-Wing* (Without fluoride sustained release)

40
35
30
25
20
15
10
5
0
-10

40

90

140

190

240

Number of days
＊Light curing type indirect composite resin(Test Method : In-House Test)

Figure 4-3-1 Fluoride Sustained Release Property2) Fluoride recharge property
The fluoride sustained release filler used in A·UNO can recharge fluoride ions when brushing with a fluoridecontaining toothpaste. The following model experiments were conducted to verify this.

25

A 15 mm diameter, 0.5 mm thick mold was filled with a resin material containing fluoride sustained releasefiller, which is also contained in A·UNO, and light cured. And the surface of specimen after light curing was
prepared with water-resistant abrasive paper. The specimens were immersed in 15 mL of distilled water for a
total of 48 hours to release fluoride ions to some extent. After fluoride ion release, the specimens were brushed
using a simple toothbrush abrasion tester based on ISO 14569-1 21). The specimens were fixed in fluoride
toothpaste liquid and brushed 500 times with a toothbrush at a load of 2.0 N and a sliding speed of 850 mm/
s. After brushing, the specimens were thoroughly rinsed under running water, and the amount of fluoride
ions released from the specimens was measured with an ion meter. Brushing and fluoride ion measurement
were performed four times in total. From the measured fluoride ion content, it was confirmed that brushingwith fluoride-containing dentifrice showed fluoride rechargeability (Figure 4-3-2). The amount of fluoride
ions released remained stable even after repeated recharging, suggesting that the fluoride rechargeability ishighly repeatable. In other words, if fluoride sustained release filler is used in direct composite resins that are
maintained in the oral cavity for several years or more, it can be expected to exhibit semi-permanent fluoride
release properties through regular brushing. On the other hand, no recharge behavior was observed in thesame experiment using a resin material without a fluoride sustained release filler, indicating that this property
is derived from the fluoride sustained release filler also used in A·UNO.
Direct composite resin with fluoride sustained release filler

Fluoride Ion Release Amount(μg/cm2)

1.0

Light curing type indirect composite resin without fluoride sustained release filler

0.8
0.6
0.4
0.2
0.0

1st
recharge

2nd
recharge

3rd
recharge

4th
recharge(Test Method : In-House Test)

Figure 4-3-2 Amount of Fluoride Ion Release during Brushing with Fluoride-containing Dentifrice

3) Effects on caries bacteria
Various caries-preventive functions of fluoride ions have been reported 22-24). As described supra, A·UNO
has long-term fluoride release property and recharging properties. In this section, the effects of A·UNO,
which has a low fluoride release rate, on Streptococcus mutans (hereafter referred to as "caries bacteria")
were examined using the propagation, adhesion, and acid production of the bacteria as indicators. Moldsof 12 mm in diameter and 1.0 mm in thickness were filled with Universal type of A·UNO, light cured bylight curing machine, and the surfaces were prepared with water-resistant abrasive paper to make specimens.
As a comparison, the existing product TMR-Z Fill 10. and Luna-Wing which is light curing type indirectcomposite resin without fluoride release property were used as control samples.

• Proliferative study
Resin extracts were prepared by adding 1 mL of BHI liquid medium per specimen and immersing thespecimens in the medium for 24 hours at 37 ºC. Caries bacteria were cultured in each resin extract, and theabsorbance at 590 nm was measured 24 hours after the start of culture. The higher the number of bacteria, themore turbid the culture medium becomes, which is reflected in the absorbance, and the absorbance decreases

26when propagation is inhibited. As shown in Figure 4-3-3, there was no decrease in absorbance for any of thelight curing type indirect composite resins which are without fluoride release property.
1.2

Absorbance (590 nm)

1
0.8
0.6
0.4
0.2
0

Luna-Wing*

A·UNO

TMR-Z Fill 10.
(Test Method : In-House Test)*Light curing type indirect composite resin

Figure 4-3-3 Propagation Test of Caries Bacteria• Adherence test
Caries bacteria were cultured aerobically in BHI liquid medium with sucrose for 24 hours at 37 °C on eachresin specimen. Washed with PBS (-), and then colored for 2 hours after the addition of test solution of
MicrobialViabilityAssayKit-WST (DOJINDO LABORATORIES) 25), and measured the absorbance of thereaction solution at 450 nm. In this test, orange-colored formazan was produced due to the caries bacteria
remaining on the specimen. Therefore, the smaller the number of bacteria adherence to the material, thepaler the orange coloration (lower absorbance). As shown in Figure 4-3-4, a large decrease in absorbance wasobserved for A·UNO, which has a higher fluoride release amount than the existing product, and TMR-Z Fill10., which is a existing product, unlike the light curing type indirect composite resin without fluoride release.
1
0.9

Absorbance (450 nm)

0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0

Luna-Wing**Light curing type indirect composite resin

A·UNO

TMR-Z Fill 10.
(Test Method : In-House Test)

Figure 4-3-4 Bacteria Adherence Test

• Lactic acid production test
The amount of lactic acid produced by caries bacteria was measured using the Lactate Assay Kit-WST(DOJINDO LABORATORIES). In this measurement method, lactate in the bacterial nutrient solution
is detected by absorbance measurement of WST formazan, which develops a color in accordance with theamount of lactate. If lactate production decreases, absorbance also decreases. Caries bacteria were cultured
in each resin extract, the culture medium was centrifuged, and the supernatant was collected. After adding
WST reagent to the supernatant, it was left to stand at 37 °C for 2 hours, and absorbance was measured at a27

wavelength of 450 nm. As shown in Figure 4-3-5, the absorbance of A·UNO and TMR-Z FiIl 10. was lower
than that of the control sample.

Absorbance (450 nm)

1.2
1
0.8
0.6
0.4
0.2
0

Luna-Wing**Light curing type indirect composite resin

A·UNO

TMR-Z Fill 10.
(Test Method : In-House Test)

Figure 4-3-5 Caries Bacteria Lactic Acid Production Test
Further validation of the above test results revealed that A·UNO and TMR-Z Fill 10. showed Enolase
inhibition. Since Enolase is an enzyme in the glycolytic system related to lactic acid production, inhibition of
Enolase in the bacteria is thought to have led to inhibition of lactic acid production 26).

4) Risks of fluoride ions
Fluoride has various properties related to the prevention of dental caries, but there are reports on therisks associated with fluoride occasionally. Excessive fluoride ingestion causes acute poisoning, while highconcentrations taken over a long period of time cause chronic poisoning. In Japan, the threshold for acutepoisoning has been set at 2 mg F/kg based on Baldwin's report27). Fluorosis is another symptom of chronic
poisoning. An epidemiological study by Dean et al. showed that fluorosis formation begins in areas where thefluoride concentration in drinking water exceeds 0.4 ppm, and that esthetically problematic fluorosis whichis medium degree or more occurs at around 2.0 ppm. The incidence of fluorosis is relatively low at fluoride
concentrations of around 1.0 ppm, and caries are also reported to be less common at this level 28).
In addition to the effects on the human body such as fluorosis, fluoride has been reported to cause corrosionof the pure titanium or titanium alloys used for dental implants. The details are discussed in the book
"Biocompatibility of dental materials"29). Fluoride-induced corrosion of titanium tends to occur under highfluoride concentrations, acidic conditions, and hypoxic conditions. However, the risk of fluoride-induced
corrosion of titanium prosthetics in the oral cavity is considered low because most fluoride products currently
in use are used in neutral environments, and saliva in the oral cavity buffers against low fluoride concentrations
and acidic environments. The daily fluoride ion release of A·UNO is 4.5 µg/cm2 (Universal type), which isvery low compared to the fluoride concentration in tooth coating agents and dentifrices, so the possibility oftitanium corrosion is considered to be extremely low.

4.4 Biological Safety
When a dental material comes into contact with the human body, even slightly, a biological safety assessment
is required. A biological safety assessment is an evaluation of the risk of adverse effects on human health.
Marketing is authorized when a biological safety assessment demonstrates that there is no risk or that therisk is acceptable. The biological safety evaluation items to be considered for dental materials vary widely
depending on the characteristics of the dental material. As shown in Table 4-4-1, the classification is based on
the site of contact with the body (surface-contact medical devices, intra- and extra-corporeal contact medical
devices, and implantable devices) and the contact period (temporary contact, short to medium term contact,28

and long-term contact). Since A·UNO is used in the oral cavity, it is naturally a medical device that comes
into contact with humans. Biological safety evaluation is required, and the device falls into the category of"medical devices that connect the inside of the body to the outside of the body, long-term contact. "A·UNO"
is composed only of raw materials whose safety as a medical device has been confirmed through the necessary
biological safety evaluation.
All of the above biological tests were conducted in collaboration with the Department of Oral andMaxillofacial Surgery, Kochi Medical School, Kochi University, Japan.
Table 4-4-1 Endpoints to be addressed in a biological risk assessment for dental materials
Endpoints of biological evaluation
Degradation

Reproductive/developmental toxicity

Carcinogenicity

Genotoxicity

Hemocompatibility

Implantation effects

Chronic toxicity

Subchronic toxicity

Subacute toxicity

Acute systemic toxicity

Non-contact
medical devices

Material mediated pyrogenicity

Irritation or intracutaneous reactivity

Sensitization

Cytotoxicity

Physical and/or chemical information

Contact duration(accumulation)：A-limited(≦24h),
B-prolonged(>24h to 30 days),
C-Long term (>30
days)

None of the evaluations are required
E

E

E

×

E

E

E

C

×

E

E

E

×

E

E

E

A
B

×

E

E

E

E

E

C

×

E

E

E

E

E

×

E

E

E

E

E

B

×

E

E

E

E

E

E

C

×

E

E

E

E

E

E

A

×

E

E

E

E

E

B

×

E

E

E

E

E

E
E

Breached or Blood path, Tissue/bone/compromised
indirectdentinesurface

A

B

×

E

E

E

E

E

E

C

×

E

E

E

E

E

E

×

E

E

E

E

E

B

×

E

E

E

E

E

E
E

C

×

E

E

E

E

E

A

×

E

E

E

E

E

A
C

×

E

E

E

E

E

Tissue/bone

A

×

E

E

E

E

E

Blood

Implant medical device

Circulating
blood

Externally communicating medical device

Mucosalmembrane

Surface medical device

Intact skin

×

B

A

E
E

E

E

E
E

E

E

E

E

E

E

E

E

B

×

E

E

E

E

E

E

C

×

E

E

E

E

E

E

A

×

E

E

E

E

E

B

×

E

E

E

E

E

E

C

×

E

E

E

E

E

E

E
E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E
E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E

E means endpoints to be evaluated in the risk assessment (either through the use of existing data, additional endpoint-specific testing, or arationale for why assessment of the endpoint does not require an additional data set). If a medical device is manufactured from novel materials,
not previously used in medical device applications, and no toxicology data exists in the literature, additional endpoints beyond those marked“E” in this table should be considered. For particular medical devices, there is a possibility that it will be appropriate to include additional or fewer
endpoints than indicated.

29

5

Clinical cases of A･UNO
The following are examples of cases in which A·UNO was used. In the case of a median diastema with nobacking or having adjacent teeth made of metal, A·UNO can provide transparency at the incisal edge whileshielding the color of the backing and the bottom color of tooth, and reproduces a color tone that blends
well with the tooth substances. In large cavities with darker tones at the bottom of the fossa, A·UNO wasconfirmed to match the color tone of the surrounding tooth substances while shielding it optimally. For
more esthetic appearance, Nu:le Coat can be used to enhance the color tone reproduction of natural teeth
by characterization. A·UNO has also been confirmed to have excellent color compatibility in sealing accessholes. The clinical examples below are only a part of the process of direct composite resin restorations using
A·UNO. The electronic instructions for use should be referred to.

■ A case of repaired median diastema (Treated after whitening)
BeforeAfter

Photos provided by : Takeuchi Dental Clinic (Utazu-cho, Kagawa Prefecture, Japan); Dr. Kazutaka Takeuchi)■A case of repaired Class II cavity (bottom of fossa : TMR-MTA cement Mielle is applied)
BeforeAfter

Photos provided by : Takeuchi Dental Clinic (Utazu-cho, Kagawa Prefecture, Japan); Dr. Kazutaka Takeuchi)

30

■ A case of repaired Class I cavity(A large cavity with darker color of bottom of fossa)
BeforeAfter cavity preparation

After repairing

Photos provided by: Yamakita Dental Office (Konan City, Kochi prefecture, Japan);
Dr. Mayo Yamamoto31

■ A case of repaired Class I cavity (Characterized pit and fissure with Nu:le Coat)
BeforeAfter

Photos provided by : Takeuchi Dental Clinic (Utazu-cho, Kagawa Prefecture, Japan);
Dr. Kazutaka Takeuchi)■ A case of sealing an access hole (A crown with ceramic layering ona zirconia frame. Characterized pit and fissure with Nu:le Coat)
BeforeAfter

Photos provided by : Takeuchi Dental Clinic (Utazu-cho, Kagawa Prefecture, Japan);
Dr. Kazutaka Takeuchi)

32

Use with Existing Direct Composite Resins
As described in Section 3.6, for teeth with a shade darker than the general shade guide (A4), it is necessary
to use a existing direct composite resin such as A5 shade of TMR-Z Fill 10. First, the root surface of themaxillary right central incisor, shown below, was repaired only with TMR-Z Fill 10. Flow A5 shade because
the color intensity was very high. On the other hand, the incisal of maxillary right central incisor was repairedwith A·UNO, but the color matching was not sufficient, and the repaired area looked whitish. In this case, it
is considered that it is possible to reproduce the natural color tone by filling the dentin portion with a directcomposite resin with high color intensity before building up the enamel with A·UNO.
■ A case of repaired Class IV cavity which root caries(old age teeth) was repaired
BeforeRepaired with TMR-Z Fill 10. (A5) only

After

Repaired with A･UNO
Photos provided by : Takeuchi Dental Clinic (Utazu-cho, Kagawa Prefecture, Japan); Dr. Kazutaka Takeuchi)

33

6Conclusion
iGOS, a direct composite resin for dental filling with both "Strength" and "Sustained fluoride release", whichwere previously thought to be difficult to achieve simultaneously, was created as a result of YAMAKIN's
research and development. Building on the advantages of iGOS, YAMAKIN has developed TMR-Z Fill10., which has good handleability and color tone in clinical practice. However, YAMAKIN's research anddevelopment did not stop there, and by maximizing the use of filler technology to achieve both high strengthand fluoride release, as well as by incorporating the "Camouflage Effect", a color matching technology
developed by YAMAKIN, transparency, shielding property, and intensity were optimized, resulting in the new
Universal shade type direct composite resin A·UNO that blends with the surrounding color tones of a wide
range of cases with a single color.
We hope that this product, which is based on the concept of MI, will be used to improve patient satisfactionin the mission of preserving one’s own teeth with as few extractions and drill as possible. We will continue
to develop new products and services in the hopes that we can, even in tiny ways, make a contribution tocommunity healthcare.
The authors

Acknowledgments
We thank Professor Tetsuya Yamamoto of the Department of Oral and Maxillofacial Surgery, Kochi Medical
School, Kochi University, Japan, for his guidances on bacterial testing and advices on biological safety
evaluation, and Dr. Kazutaka Takeuchi of Takeuchi Dental Clinic and Dr. Mayo Yamamoto of Yamakita
Dental Office for providing clinical color evaluation and case photographs. We would also like to express our
gratitude to Dr. Kazutaka Takeuchi of Takeuchi Dental Clinic and Dr. Mayo Yamamoto of Yamakita Dental
Clinic for providing the clinical color evaluation and case photographs. Finally, we would like to express ourthanks and heartfelt gratitude to all parties involved in the editing of this publication.

34

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35

A • UNO Product Report

Basic Knowledge of Universal Shade Type Composite Resin and
YAMAKIN's unique color-matching technology, "Camouflage Effect".

Published on June 15, 2022, the 1st Edition
Published November 10, 2022, the 2nd Edition
Publisher: Shigenari Yamamoto
YAMAKIN CO., LTD.
Head Office: 1090-3 Kamibun, Kagami-cho, Konan-shi, Kochi, 781-5451, Japan
P: +81-887-55-0281
F: +81-887-55-0018
URL https://www.yamakin-global.com/

Unauthorized reproduction of this book is prohibited, with exceptions under copyright law.