GC EUROPE Fujivest Super User Manual

Focus Edition from GC

Phosphate

Bonded

Investments

for C&B techniques

Table of contents

Introduction 3

Guidelines for optimal use of phosphate bonded investments for Crown & Bridge techniques 5

Preparation before investing

2 Expansion and investing 12

3 Heating up / Burnout procedures 18

4 Casting 23

5 Effects of the main factors inﬂuencing the casting results 25

6 The GC Europe range of Phosphate bonded investments for C&B techniques 26

7 Related products 27

Troubleshooting Phosphate Bonded Investments for C&B techniques 29

1 Investment sets too quickly 30

2 Investment sets too slow 31

3 Differences in Investment texture (too thin or too thick, not consistent) 31

4 Rough casting surfaces (pits, nodules and porosities) 32

5 Investment cracking (ﬁns on the castings, miscasting ….) 34

6 Incomplete castings & rounded cervical edges 36

7 Inaccurate ﬁt of casting objects 37

Instructions for use for implantology 39

Optimal ﬁt, a simple step by step procedure 49

Clinical Cases 59

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Introduction

Dear Customer,

Thank you very much for selecting GC Europe’s Phosphate Bonded Investment material for your crown and bridge technique. You have purchased high quality products which have been speciﬁcally designed to produce consistently accurate castings and meet the production requirements of the modern dental laboratory.

For more information on GC products please visit our website www.gceurope.com

The construction of high quality crown and bridge restorations is dependant both on precise workmanship and a clear understanding of the processing instructions of the various materials involved in the dental casting process.

The aim of this document is to help you understand our products in more detail and provide useful information that will help you to avoid mistakes and potential problems in the future, by identifying the optimal techniques for their use and by analysing the various problems that can occur if ‘best practice’ is not followed.

Whilst we have tried to be as comprehensive as possible no guide can cover every eventuality, so should you require further any assistance please do not hesitate to contact your local GC representative.

Guidelines for

optimal use

of phosphate bonded investments for

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Crown & Bridge techniques

This chapter will help you understand our Phosphate Bonded Investments for C&B techniques in more detail and provide useful information that will help you to avoid mistakes and potential problems in the future, by identifying the optimal techniques for their use and by analysing the various problems that can occur if ‘best practice’ is not followed.

1 Preparation before investing

1.1 Instruction for Use

When working with our investments it is imperative that the ‘Instructions For Use’ are consulted from the outset as they offer you a clear summary of each working stage, based both on the results of comprehensive laboratory testing, carried out by the GC Europe Research and Development Department in combination with an extensive range of casting trials.

Each investment type has its own speciﬁc characteristics that should be taken into account to guarantee consistently accurate results.

Each package of GC investment contains multilingual ‘Instructions for Use’ and it is important that you use the latest version included with your material as this information is under a process of continual review.

The latest instructions for use are always available at the download section of our website www.gceurope.com.

1.2 Storage

When used on a regular basis the powder and liquid may be stored at normal room temperature (21-23°C), this is also the optimal working temperature. However for longer term or bulk storage a slightly lower temperature is preferable (please also see point 2.3).

The storage environment must be dry to avoid the risk of exposing the powder to humidity (this is particularly important once a package has been opened) which will cause it to react in an unpredictably fast manner.

It is important that the liquid is never stored below 5˚C as once it has frozen it can no longer be used and must be discarded. Pay particular attention to winter deliveries, if debris or crystals are present in the liquid, it must never be used!

The bottles should always be kept tightly sealed and away from direct sunlight to avoid problems caused by evaporation.

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1.3 Working temperature

The working temperature of the investment powder and liquid are critical factors in determining the setting time, expansion, surface roughness and consequently the ﬁnal ﬁt of the castings. The optimal working temperature of both powder & liquid is 21-23°C, this must be considered if either the room temperature is lower than this or the materials have been stored at a lower temperature.

If the ambient working temperature is below 20°C, the following problems can occur:

- A delay in setting time

- Uncontrollable expansion values

- A reduced surface quality, meaning a rougher surface of the casting object

- A higher risk of crack formation leading to possible miscasting

Likewise if the ambient working temperature is higher than 21-23°C the following factors must be considered:

- An increase in temperature of liquid and/or powder decreases the working time and accelerates setting

- The working time at 23°C is approximately 9 min, whilst at 24°C it will be approximately 8 min as for each 1°C increase in working temperature the working time decreases by +/- 1 min

- If the temperature of the powder and liquid cannot be optimised a slight reduction in the mixing time may help increase the working time

The use of a temperature controlled refrigerator set at 21-23°C is highly recommended for the storage of the investment powder, liquid and mixing vessels, as this completely eliminates the risk of seasonal temperature differences.

1.4 Preparations before investing

1.4.1 Modeling

- Die Separator

Use a high quality type 4 dental stone such as GC Fujirock EP for optimal accuracy and wear resistance. GC Multi Sep is an ideal wax separator, leaving no oily residue on the die stone surface.

- Modeling materials

The correct positioning of the wax/resin patterns is important in order to ensure sufﬁcient thickness of investment material around the objects to withstand the casting forces and provide sufﬁcient expansion. The highest point of the pattern structure should be 5-10 mm lower than top of the ring and at least 5 mm away from the axial wall of investment ring.

- Resin modeling materials

1.4.2 Ring sizes

GC Pattern Resin LS makes an excellent choice, offering a high degree of accuracy in combination with optimal burnout properties which leave no residues. It is always advisable to cover the pattern resin with a layer of wax to allow for its expansion during the burnout process. For single crowns, the investing and burnout procedures can be performed in the usual manner, however for larger amounts of pattern resin it is advisable to hold the temperature at 250°C (482°F) for 1 hour, before rising to the ﬁnal burn out temperature or follow the step heating schedule according to the ‘Instructions for Use.’

The rigid nature of the pattern resin material means that the initial setting expansion can be restricted, which may result in a tight casting. This problem can be solved by the adoption of a slightly higher ratio of investment liquid/distilled water.

The majority of GC Europe investment materials can be utilised for both the ring and ringless techniques, using either the quick or step heating technique as detailed in the particular ‘Instructions for Use.’ In most instances GC Europe investments can be used with all ring sizes from X1 to X9 for the casting ring technique (metal ring with liner) and sizes from X1 to X6 for the ringless technique.

The choice of ring size depends on the size and type of work, however to get consistently accurate casting results it is advisable to take a uniform approach. This is best achieved by always selecting the same size/type of investment ring for the same size/type of work. In general terms ring sizes X3 & X6 provide consistently accurate and reproducible results due to the optimal volume of investment material that is used.

When using the X1 type ring tighter castings may be produced, this is caused by the smaller amount of material producing a smaller setting expansion; this is related to the exothermic reaction during setting. Conversely ring sizes above X6 tend to produce a less stable expansion values and an increased risk of cracking.

1.4.3 Ring types

Various sizes and types of casting ring are available, all created with the same goal of producing a refractory investment mould which can be heated to eliminate the pattern material and ﬁlled with molten alloy.

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When using the metal casting ring technique it is advisable to use a high quality casting liner such as GC New Casting Liner. This enables the investment material to expand during setting and provide the optimal buffer to achieve consistently accurate castings and reduce any risk of cracking (please see section 1.4.4).

When using the ringless technique, it is best to use a soft type of silicone ring former to allow the optimal setting reaction and expansion to occur. This type of ring former also has the advantage of being sufﬁciently ﬂexible to be easily removed from the investment material after the initial set without the need for excessive or damaging removal forces.

Using the more rigid type of plastic ring former can impede the setting reaction as they tend to be poor insulators, allowing the heat from the exothermic reaction to be dissipated far too quickly. The rigidity of the plastic also means that these formers need to be removed very quickly after the initial set, as they allow for very little expansion. This creates the further problem that ‘weak’ investment may be placed under too much stress if this is done at a too early stage, resulting in cracks or distortion.

1.4.4 Liner for metal ring types

When using a metal casting ring type, it is advisable to use a high quality casting ring liner such as GC New Casting Liner which is approximately 1 mm thick. This enables the investment material to expand during setting and provides the optimal buffer to achieve accurate castings and reduce the risk of cracking.

The borders of the liner should be sealed with a thin layer of petroleum jelly. GC New Casting Liner is impervious to the absorption of liquid and should not be immersed in or moistened with water. If the border is not sealed, a wet liner used or an absorbent dry liner there is a risk that the powder/ liquid ratio of the mixture will be altered and consequently alter the expansion. Be sure that the entire inner surface of the metal ring is evenly covered with casting liner and that the liner is ﬂush with the upper rim of the metal ring, so that there is no direct contact between investment and metal ring. A badly ﬁtting ring liner leads to an uneven expansion and the risk of crack formation.

We therefore recommend the use of GC New Casting Liner, a dry casting liner made of ceramic ﬁbers

For X3 ring size = Use 1 layer of

GC New Casting Liner

For X6 ring size = Use 2 layers of

GC New Casting Liner

For X9 ring size = Use 2 layers of

GC New Casting Liner

As a liner needs to provide an optimal buffer to achieve accurate castings and reduce the risk of cracking it is important that it is of the correct thickness and does not absorb any water from the investment. Liners that absorb water are best avoided as they can remove moisture from the investment mixture whilst setting, thus compromising the ﬁnal result by either causing cracking or expansion in an unpredictable manner. Conversely if the liner is soaked there is a similar risk, but this time the problem is the dilution of the investment mixture.

Dry GC New Casting Liner & Competitor product

Competitor product

GC New Casting Liner

Competitor product, GC New Casting Liner liner absorbing water a dry casting liner

1.4.5 Wetting agents

A surface tension reducing agent is designed to allow the investment to ﬂow uniformly and smoothly over all areas of the pattern helping to eliminate casting bubbles; however please bear in mind the following:

- All GC investment materials have the optimal ﬂuidity and smooth consistency which eliminates the need for these agents.

- If these agents are used, it is very important to check that they are fully dry before pouring in the investment material as a wet residue of these agents may adversely react with the investment material, creating a rough mould and casting surface together with an increased risk of fracture.

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1.5 Powder / Liquid ratio

All of the phosphate bonded investment materials manufactured by GC Europe for the Crown and Bridgework technique share a common Powder/ Liquid ratio of 100 g to 22 ml (with the exception of GC Vest-G, please consult the ‘Instructions for Use’). In order to obtain consistently accurate castings the correct powder/liquid ratio must be used, as this ratio is the result of comprehensive laboratory development and batch testing.

Any alteration of the ratio is likely to result in less predictable expansion properties, inferior casting surface and an increased risk of mould fracture.

The use of an accurate electronic balance for weighing the powder together with a measuring cylinder or pipette for the liquid is highly recommended. It is also suggested that only distilled water is used when diluting the investment liquid.

Ringsize Powder Liquid

X1 60 g 13,2 ml

X3 150 g 33,0 ml

X6 300 g 66,0 ml

X9 420 g 92,4 ml

1.5.1 Atomized measuring equipment for

investments

Whilst as previously discussed in sections 1.3 &

1.5 the use of accurate measuring equipment and

a temperature controlled refrigerator should guarantee consistent results, an alternative method exists in the form of atomized measuring equipment. This combines an integrated cooling system with precise measuring technology to produce a consistently accurate temperature controlled ratio of water, investment liquid and investment powder to produce highly accurate mixing results and subsequent castings.

These devices need to be programmed with correct ratio and it should be noted that as the measuring of the liquids is done by weight for increased accuracy the precise input of the liquid density is a critical factor. The correct densities for GC Europe phosphate bonded investment liquids are listed in the table below.

Liquid Density

)

(g/cm

GC Fujivest II Liquid 1,25

GC Fujivest II Low Expansion Liquid 1,15

GC Fujivest Super Liquid 1,14

GC Fujivest Super High Expansion Liquid

GC Fujivest Platinum 1,14

GC Vest-G 1,19

GC Stellavest 1,23

GC Fujivest Premium 1,25

1,23

2 Expansion and investing

2.1.1 General rules about expansion levels

The expansion rate of phosphate bonded investment material may be adjusted by altering the ratio of expansion liquid to water, we can therefore state that:

- Pure liquid gives the maximum setting expansion, meaning the largest casting.

- Diluting the liquid with water will result in the reduction of the setting expansion resulting in smaller castings.

Use only distilled water to dilute the expansion liquid and use only the correct expansion liquid designed for the investment powder that you are using, do not use other liquids.

2.1.2 Why is expansion needed?

Wax Modellation

invested

Setting Expansion

in Furnace

Thermal Expan-

sion in Furnace

The required concentration of the expansion liquid depends on various factors:

- Type of alloy

- Type of work (e.g. posts & inlays require less expansion)

- The ﬁt required

- Type of pattern material (see 1.4)

Comprehensive guidance is given in the “liquid dilution chart” in the ‘Instructions for Use’, which should enable you to ﬁnd the optimal expansion values for your individual requirement (see 2.1.4). It should also be noted that the expansion value is also inﬂuenced by the following factors:

- Storage & working temperature of the investment materials (see 1.2 & 1.3)

- Mixing time & paddle speed (see 2.2)

Investment with total Expansion

Casting

Cold Casting after

cooling down

Total expansion is needed to compensate for metal shrinkage during the cooling phase.

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2.1.3 Liquid dilution chart

The liquid dilution chart is designed to help produce the optimal expansion value for your individual castings and is based upon the type of alloy and size of ring used. This information is contained within the ‘Instructions for Use’ and is based on extensive laboratory testing in combination with a complete series of casting trials.For example here is the liquid dilution chart for GC Fujivest Premium.

Type of Alloy

High Precious > 70% Au

Semi Precious < 55% Au

Pd-base

Non-precious alloy

High Precious ceramic alloy

Semi Precious ceramic alloy

Pd-base ceramic alloy

Non-precious ceramic alloy

Liquid / Wa-

ter ratio %

50/50 6.6 ml/6.6 ml 9.9 ml/9.9 ml 16.5 ml/16.5 ml 33 ml/33 ml 42.2 ml/42.2 ml

60/40 8 ml/5.2 ml 11.8 ml/8 ml 20 ml/13 ml 40 ml/26 ml 55.4 ml/37 ml

NiCr 75/25 10 ml/3.2 ml 15 ml/4.8 ml 25 ml/8 ml 50 ml/16 ml 55.4 ml/37 ml

CoCr 100% 13.2 ml 19.8 ml 33 ml 66 ml 92.4 ml

55/45 7.3 ml/5.9 ml 11.8 ml/8 ml 18 ml/15 ml 36 ml/30 ml 55.4 ml/37 ml

60/40 8 ml/5.2 ml 11.8 ml/8 ml 20 ml/13 ml 40 ml/26 ml 55.4 ml/37 ml

NiCr 72/25 10 ml/3.2 ml 15 ml/4.8 ml 25 ml/8 ml 50 ml/16 ml 69,4 ml/23 ml

CoCr 100% 13.2 ml 19.8 ml 33 ml 66 ml 92.4 ml

X1 / 60 g 90 g X3 / 150 g X6 / 300 g X9 / 420 g

Ring size: Liquid / Water

However because the working methods and equipment can differ between individual dental laboratories (e.g. waxes, resins, casting liner, mixing equipment, etc.) it is possible that differing end-results may be obtained requiring slight changes to the stated ratios (see 2.1.4). All of the ﬁt tests have been carried out on castings using the quick heating method (20 min setting) and it should be noted that a longer setting time would increase the expansion.

2.1.4 Individual liquid dilution chart

Name

dental alloy

Ring type X1 Ring type X3 Ring type X6 Ring type X9

When trying new alloys, alloy manufacturers or investment materials we suggest that initially you use the correct ratio as stated in our ‘Instructions for Use’. It is then possible for you to judge whether this provides the correct expansion for your needs or a slight alteration of the dilution is needed.

We also provide a chart that can be used to indicate the alloy type, type of work and your personal choice of dilution ratio obtained following your personal casting experiences.

Here it is very important to consider the information given in sections 1.5 & 2.1.1.

Example :

Dental alloy

XYZ

6,6 ml Exp.Liq

6,6 ml H2O

16,5 ml Exp.Liq

16,5 ml H2O

33 ml Exp.Liq

33 ml H2O

46,2 ml Exp.Liq

46,2 ml H2O

2.2 Mixing of the investment

Tips for mixing:

In order to obtain a complete chemical reaction between the powder and the liquid, it is important to ensure that the components are mixed to a homogeneous consistency.

- Pre-mix powder and liquid thoroughly by hand with a spatula.

Be sure that all of the powder is completely

wetted by the liquid to produce a uniform mixture.

- Mix for 60 sec under vacuum (320-420 rpm).

Always use a clean mixing bowl and check

the vacuum level. An inadequate vacuum level leads to an inconsistent ﬁt and casting bubbles.

Insufﬁcient mixing produces rougher casting surfaces. Faster mixing (and or longer mixing) accelerates the set and decreases the working time and may also result in lower expansion values. Always check if the mixture is homogenous and smooth with no dry ‘lumps’ before pouring the investment. Over time it is possible for a residue of investment material to build up on the inner surfaces of the mixing bowl and this can reduce the expansion, so when switching to a new mixing bowl an increased expansion may sometimes be noticed.

- Use different mixing bowls for gypsum and for phosphate-bonded investments!

Gypsum contamination interferes with setting

of phosphate-bonded investments.

- For efﬁcient, homogeneous mixing, mix for only one ring at a time.

- Check the mixing and vacuum efﬁciency.

Do not rely on the indicated vacuum levels on

the mixing devises.

- Use calibrated equipment.

- Change worn paddles or mixing bowls.

- To keep the mixing bowl, mixing paddle and instruments clean:

Always clean them immediately after use eliminating all residues of investment material and store them in a clean plastic container (the GC Fujirock container makes an excellent choice) ﬁlled with water to help reduce the risk of a build up of sediment.

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2.3 Investing

2.3.1 Working time (see 1.3)

The working and pouring time for each investment material is stated in their individual ‘Instructions for Use,’ however it must be understood that this is calculated for material stored and used at normal room temperature of 21 - 23°C. Temperature variations will result in a longer (if cooler) or shorter (if warmer) working times.

2.3.2 Investing , ﬁlling the moulds

Invest using a thin stream of material and low frequency (gentle) vibration, once the ring is ﬁlled stop the vibration immediately and do not touch the investment until set. The optimised consistency of GC Europe’s phosphate bonded investments means that they possess excellent ﬂow properties rendering strong vibration unnecessary.

2.3.3 Investing under pressure

We do not recommend high pressure investing as this may lead to a delayed setting (especially when the compressed air temperature is low) which can result in a rough casting surface and increased risk of ﬁning on the cast objects.

2.4 Setting

2.4.1 Setting time

The optimal setting time prior to insertion in the furnace is normally 20 min, however please always check the most recent ‘Instructions for Use.’ The setting time is based on the material being stored and used at a room temperature of 21 - 23˚C, as said previously variations in this temperature may affect the setting time and expansion.

Best results are then normally obtained by placing the casting ring immediately into a preheated burnout furnace. Prior to putting the investment into the burnout furnace it is essential to make sure that it has fully set, as unset investment material is likely to cause casting defects such as distortion and/or rough surfaces.

Lengthening the setting time before putting the mould into the furnace is a technique often used when a lot of investing is done late in the day and the casting is to be undertaken the next morning, this is the so called “over night” burn-out technique. This longer setting period will usually work but can result in an over expansion, a reduction of surface smoothness and increased risk of cracking.

If the ﬁlled investment ring does need to be left for an extended period prior to burnout it is better to put it into a plastic container or bag which will help retain humidity within the investment material, it can be inserted into the burnout furnace and processed with the conventional step heating method.

2.4.2 Advise on variations in setting time

Setting times

Product Heating up schedule

Speed technique

GC Fujivest Platinum

GC Fujivest Premium

GC Fujivest Super

GC Fujivest II

GC Stellavest

GC Vest-G

Furnace at end temperature

Step heating technique