YAMAMOTO PRECIOUS METAL CO., LTD.
OSAKA, JAPANThe Pursuit of International Standards inQuality and Safety

Yamamoto Precious Metal Co., Ltd.
Head Of f ice: 3-7 Sanadayama-cho Tennoji-ku Osaka 543-0015, Japan
Branch Of f ice: Tokyo, Osaka, Sendai, Nagoya, Fukuoka, JAPAN
Factory and R&D: Kochi, JAPAN
P: +81-6-6761-8338 F: +81-6-6761-0610
E: contact@yamakin-gold.co.jp

http://www.yamakin-gold.co.jp
INTERNATIONAL20130110

Pursuing Safety: Offering Safety and Peace of Mind…
Dental Materials have been developed with an eye to functionality over a long period oftime. However, is it enough that only functionality is called for, even though these materials
are to be used in our patients’ mouths?
Material dissolution caused by chewing and saliva expulsion has an incalculable effect on
the human body. Dental materials are, of course, classified as medical devices, and there
are guidelines regulated by the government.
However, our corporate mission is to transcend national guidelines and pursue safety at
global standards, offering long-standing Safety in terms of the human physique and toprovide safe, reliable, high-performance products. The pursuit of safety is the abiding
concern in our ongoing research and development.

Our Mission: Keywords for Safety

From Production Skills to Scientific Knowledge,
and onward to Fusion with Medical Science
Over the course of history, dental materials of various kinds have been used in multi-purpose ways, and newmaterials have constantly been researched and developed in order to achieve better quality and meet thedemand for new products. Treatment methods combining multiple materials have also become widely used.
On the other hand, the advance in sophistication of dental treatment has seen the demands placed on thematerials’ properties changing from their physical chemistry to their biological properties. There has been anotable increase in public interest in the area. This change has occurred along with the development of dental
materials and their associated treatment methods. Even if new materials are developed with excellent
properties, they must be strictly non-toxic.
It is absolutely vital to ensure the safety of dental materials, no matter whether they are used domestically oroverseas, and as a matter of course manufacturers must give priority to safety.
It is an undeniable fact that manufacturers have been prone to focus on mechanical properties such as
handling and strength in their R&D, without considering product development from a deeper medical
standpoint. This is a point which manufacturers need to fully understand.
By contrast, the research and development approach we propose constitutes a new system – more focused onsafety, and also with a fresh R&D stance which fuses scientific functionality and medical safety.
From this viewpoint, our mission is to provide the kind of safe, reliable, high-performance dental materials
that can accompany the future development of dental treatment to higher levels of sophistication.

2005: The Biological Science Safety Laboratory ofKochi Medical School, Kochi University,
Japan established2004: Collaboration with Medical Science
Department of Kochi University in Japan started

2003: Evaluation of Biological Safety

Collaboration in Biological Safety with theMedical Science Department of Kochi University, Japan–The Pursuit of Safety in Cell, Cell Structure, Genetic Engineering–

Biological Safety: the Pharmaceutical Affairs Law and theInternational Organization for Standardization–The Pursuit of Safety through ISO10993 “Biological Evaluation of Medical Devices” –2003: ISO9001 and ISO13985 Certifications
obtained
2000: ISO9002 Certification obtained

1995: Collaboration with a range of ResearchInstitutions in Japan
1995: R&D Center established

Quality Management ISO9001 ISO13485–Quality Management System for Global Standard Compliance –Dental Metallurgic Functionality, Organic Chemistry, Inorganic Chemistry,
Collaboration with Science and Engineering University Department etc.
–“The Fusion of Professional Skills and Know-how” –Hirohisa Yamamoto
Chairman and CEO of
Yamamoto Precious Metal Co., Ltd.
1

Dental Metallurgy

R&DISO9001/13485

ISO10993

Biogenetics

2Biological Safety I:

Biological Safety II:

the Pharmaceutical Affairs Law andInternational Organization for Standardization

the Pharmaceutical Affairs Law andInternational Organization for Standardization― Evaluation of Biological Safety through ISO10993 ―― Evaluation of Biological Safety through ISO10993 ―Keeping lab mice

What is required for the evaluation?

Mutagencity Test

Safety is absolutely required from medical devices in terms of their functionalmaterials. Safety is examined under The Pharmaceutical Affairs Law in Japan andISO 10993 globally; however, the evaluation method is different depending on theparts of devices to be used and also on use period. Here are some examples ofevaluations that we have implemented for biocompatibility in R&D:

Purpose of the Test
Some chemical substances react with human DNA and mutate DNA. A mutation may cause cancer
in general somatic cells; moreover, the mutation may affect its descendant cells. Therefore, it isimportant to examine whether the chemical constituents of raw materials in dental devices cause
mutations or not. The purpose of this test is to ascertain whether a test sample affects DNA or not.
Measuring a test sample

Systemic Toxicity Test

Confirming health conditions of mice

Purpose of the Test:
A wide range of substances produce toxicity by impacting the human body. Because of this, it isnecessary in advance to expect risk when medical devices come into close contact with the human body.
The purpose of the test is to analyze the quality and quantity of the toxicity in a subject by taking asolution (a test sample of raw material of chemical substances) from the mouth.
Summary of the Test
The test sample is orally administered in a single dose or multiple doses, and the subject’s reactions,such as changes in health condition and weight, are observed. If the test sample shows no reaction
during the observation period, there is deemed to be no toxicity; on the other hand, if there is toxicity,depression, notable weight reduction, or death may be observed. Assessment has generally been basedon the median lethal dose (LD50) value - an estimate of the dose of a test substance that kills 50% of
test animals. However, LD50 increasingly tends not to be used because it is actually possible todetermine whether there is toxicity or not by simply checking weight change; there are also concerns
from the animal welfare standpoint.

Setting culture medium

Summary of the Test
Mutated bacteria, with genes related to their amino acid metabolism which live only whereamino acid exists, such as histidine-dependent salmonella and tryptophan-dependent colon
bacillus, are used for the test. In cases where a test sample has an impact on the genes, thebacterial genes revert to normal (Reverse Mutation); the colony is then able to form even on aculture medium where there is not sufficient amino acid.
If the number of colonies increases to more than double as many as the negative control group,and confirms dose-dependency, we confirm the test sample as positive. In this case, thechemical substances used in the test cause cancer or have an impact on the genes.

Skin Sensitization Test

Configuring a test plate

Summary of the Test
A test sample is attached on the skin of a subject and left for 48 hours; a result is obtained byobserving how the skin changes over time. (This is generally called Skin Patch Test.) Reddeningof the skin is seen as a light symptom and scab or necrosis of the skin is seen as a severe
symptom. There are other irritation tests in addition to the skin sensitization test: Eye Irritation
Test for ocular tissue, Oral Mucosa Irritation Test for oral mucosa, and Vaginal Irritation Test forvaginal mucosa. Those tests are appropriately chosen depending on the method of use of therelevant medical devices. However, skin sensitization tests are not always sufficient for fullevaluation, because allergies are understood to be a still-developing contemporary medicalproblem, and they appear differently from individual to individual.

A test sample for skin sensitization test

Oral Mucosa Irritation Test
Observation of cells

Purpose of the Test
The test is performed to analyze whether or not the human body is at risk of being subject to
toxicity from material devices or their raw materials or chemical constituents thereof. It is
carried out by measuring how cultured cells react in terms of survival rate and reproduction
rate.

Observation of allergic reaction

Purpose of the Test
From a medical standpoint, the test is performed to analyze impact on oral mucosa frommedical devices, where the medical devices are used in the mouth.

Distribution of cultured cells

Observation of colonies

3

Observation of colony formation

Purpose of the Test
This test is performed to inspect if a test sample results in allergic contact dermatitis whendental devices come into contact with the human body, and also to evaluate the level of suchdermatitis.

In Vitro Cytotoxicity Test

Summary of the Test
Approximately 100 cultured cells are distributed on a test plate, a test sample is added, andincubation is performed for six days. The colonies will comprise the same number as the number ofcells in the original colony if the test sample is non-toxic. (For example, if 100 cultured cells aredistributed, a hundred colonies will form.) The smaller the number of colonies which form, thehigher toxicity the test sample has.
The colony-forming assay, in which the index is the number of colonies formed during cell
reproduction, is recommended by Japanese Ministry of Health, Labour and Welfare guidelines. For
medical devices, the method of processing cells with sample extract and the method of distributing
cells directly on a test sample are recommended, and these methods must be backed up by control
experiments.
In ISO 10993-5, both processing with sample extract and exposing test sample to cells directly orindirectly are stipulated. However, the agar overlay technique or direct contact method is generally
employed in western countries.

Developing enriched culture mediums in petri dishes

Summary of the Test
The entire medical device or the chemical constituents thereof are placed as a test sample into cheekpouches in a subject, and left for two weeks. Afterward, the pouches are observed histologically so as
to be able to predict how the use of the medical devices in question impacts the human body from a
medical standpoint. In normal cases, the tissue sequence will be regular; on the other hand, it will berandom in abnormal cases.

Tissue of the side of cheek pouch

Tissue of the bottom of cheek pouch

4Biological Safety

Collaboration with
External Organizations

Collaboration with Medical Science
Department of Kochi University in Japan― Biological Evaluation of Safety Based on Cell, Cell Structure,
Genetic Engineering ―To the Next Stage…

Observing cells under microscope

Industry-University Collaboration

It is of course mandatory for professionals involved in medical treatment to practiceproperly regulated Safety Evaluation; however, we always look for the “next stage”.
We are working on research and development from multiple aspects, such asallergies, carcinogenicity, the impact on our offspring, and those risks which cannot
be proven by a single evaluation.

The Pursuit of Safety

Cell Growth Inhibition Test
Purpose of the Test:
The purpose of the test is to predict toxic presence in the living body by measuring the impact ofwhole medical devices or the chemical constituents thereof on the growth rate of cultured cells.
Summary of the Test
A test sample is placed on cultured cells and incubated for 48 hours. After the incubation, it ispossible to ascertain whether there is inhibitory action on the growth of cultured cells bycomparing the number of cells obtained when a test sample is added or not added. In normalcases, the growth speed is fixed. In abnormal cases, the growth speed is inhibited, or sometimes
the cells may be exterminated.

DNA Synthesis Test

Measuring test samples

Distribution of cultured cells

Purpose of the Test
When cells divide, they perform DNA synthesis. By examining DNA synthesis and its impact,
the test is performed to make a prediction of the toxicity of entire medical devices or thechemical constituents thereof in the human body.

Quality Management System

Summary of the Test
A test sample is added to cultured cells and incubated for 48 hours. Six hours before
completing the incubation, it is marked by adding a test liquid that will be incorporated into
the newly synthesized DNA. Afterward, it is possible to ascertain the impact on the DNA
synthesis of the test sample by measuring its beta-ray emissions and the synthetic quantity.

ISO 9001, ISO 13485,
and the CE marking certifications obtained

Cytotoxicity Test

Staining of cells

Purpose of the Test
The test is performed to predict if the human body is at risk of being subject to toxicity bymeasuring how many cells are damaged or have been exterminated after placing an entire
medical device or the chemical constituents thereof into cultured cells.
Summary of the Test
A test sample is placed on cultured cells marked by a radioactive substance, and incubated for
48 hours. After the incubation, it is possible to ascertain how much damage the cells havesustained by measuring the activity of the radioactive substance which was isolated from thesupernatant of the incubation.

DNA Fragmentation Test
Purpose of the Test
Electrophoresis is induced in the cell DNA, and the toxicity or lack thereof in the cell of a test
sample is observed. The test is performed to analyze whether the form of toxicity is apoptosisor necrosis when toxicity is found in the cell.
Summary of the Test
A test sample is added into cultured cells, and the cell DNA is removed after 48 hours ofincubation; electrophoresis is then induced to observe the movement pattern in order to obtaina result. If the cells survive, the DNA has not dissolved. For apoptosis cases, the DNA divides
in in a regular manner, and for necrosis cases, in an irregular manner.

Purpose of the Test
When cells are in normal condition, protein synthesis is performed by the action of DNA andRNA for purposes of cell division. Because of this, the test is performed to analyze if a test
sample has toxicity by measuring amount of protein synthesis after placing entire medical
devices or the chemical constituents thereof into cultured cells.
Summary of the Test
A test sample is added to cultured cells and incubated for 48 hours. The protein is then extracted
from the cells and the absorptivity is measured to determine the impact on protein synthesis.

Our Company has been continuously working on obtaining ISO certifications in order topurse international standards for quality and safety. As a first step, we obtained ISO 9002
certification in September, 2000. As a second step, in May, 2003, we obtained ISO 9001
and ISO 13485 certifications, and also the CE marking for our products in the EU. Whilecontinuing to obtain those international standards, we intend to move forward byoffering products and services, always thinking from the customers’ point of view.

− Terms and Definitions −DNA Fragmentation image

What is the ISO?

What is ISO 9001?

The ISO stipulates various kinds of standards, such as the “Company Standards(Manufacturer Standards)”used at the business level, “Organizational/IndustrialStandards,” “National Standards” used at the national level and “RegionalStandards” used in designated areas, for example in Europe. In addition to thesestandards, “International Standards” are used in common in all countries. TheISO (International Organization for Standardization) is the organization that
establishes such international standards.

ISO 9001 (Quality Management System) is an ISO standard designed tohelp organizations wishing to achieve the ISO standards ensure that they
can meet the relevant requirements in order to obtain good and/orimproved quality, and to publically demonstrate that they haveaccommodated to the standards. They receive certificate issued by thecertification body.

What is ISO 13485?

What is the CE Marking?

ISO 13485 (“Comprehensive Management System for the Design and
Manufacture of Medical Devices”) is an ISO standard, and it also is aquality management system just like ISO 9001. A fundamental difference,
however, is that ISO 13485 is applied only to medical devices. ISO 13485
is generally harmonized with ISO 9001 in terms of quality management
systems; ISO 13485 contains specific requirements for each medical
device and regulatory requirements concerning the pharmaceutical affairs
legislation of each country.

The CE marking means that the product conforms to essentialrequirements; it is a mandatory conformity mark for products placed on
the market in the EU. With the CE marking, the product can be provento comply with these requirements, and the mark is also obligatory forexport outside the EU.

Measuring the amount of cell

Protein Synthesis Test

5In 2005, The Biological Science Safety Laboratory wasestablished in the Department of Oral and Maxillofacial
Surgery, Kochi Medical School, Kochi University, Japan. We
are working on research and development from multiple
aspects, such as Cell Structure and Genetic Engineering, inaddition to performing general safety examinations(Dissolution Test, In Vitro Cytotoxicity Test).

Controlling temperature of culture media

6