Jörg Müller, MDT, CEO of Aesthetic-Press

The first thing you hear of from some colleagues is usually: Why should I press when I’m much faster with the layering technique?

Answer: It is important to appreciate the system and not be influenced by the question of whether to press or layer. Putting design and esthetics to one side, results are better distinguished through press technology, providing a more controllable, predictable planning. Wax-ups correspond exactly to pressed work.


Regarding the question of pressing or not pressing, a few points should be appreciated. It’s not enough to just analyze the time factor. You must also take other criteria into account. What’s important is the system concept, and not to ask if you should press or layer.

Check out this video with images for each step of the press 

 It always starts with an optimal design to each case, which is determined by a wax-up. This is the stage in dentistry where the technician can determine solutions for improved esthetics and function.


For anterior restorations, this wax-up is used for consultations together with the patient, to discuss the new look and represent to the patient what they can expect. Useful for the posterior region, the patient can be shown the problems in malocclusion which have negative influences; new occlusal functional correction is appreciated.

 The framework design is a necessary requirement for restoration success and stability. To avoid chipping of the ceramic, whether a metal or Zirconium-dioxide framework, it is recommended to have an even ceramic layer covering. An anatomically reduced framework is optimal, which can be done manually in wax, after being transferred by using a wax injector.

 In today’s increasing digital dentistry, good CAD/CAM systems are capable of scanning wax-ups, and then mill the desired anatomically reduced zirconia framework. (Figs. 1-3)


 Here is yet another important factor to bear in mind: An even, precise ceramic layer results in greater shade nuance depth!

 Pressing procedures provide better heat conduction. Because of the poor thermal conductivity of zirconium dioxide, it is understood from a study at the University of Aachen that porosity occurs in pontic areas when firing a layered crown.


 Layering technique firing processes are completed in about 15 to 17 minutes. During a pressing procedure, it is at least 60 to 90 minutes per frame to reach the final temperature, and at least 20 to 30 minutes for muffle cooling, which is much less invasive.

 As dental technicians, we are subject to natural variations which change the quality of our work. Everybody has good days and days when it does not work out really well. This can lead to significant variability in results. Likewise, there may be deviations in the shape of the work, such as when a technician creates the wax-up and then a few weeks later another technician manufactures the final restoration. All of these factors do not ensure quality in the sense of standards.


 If a case has been planned and the treatment plan is presented to the patient, you should of course comply with what was promised by the wax-up and what the patient expects.

Press technology costs relatively little time and material expense, and a very precise homogenous result can be achieved. Since the over-pressing framework is in line with the wax-up, the parameters result in the work corresponding with the planning, which is easily reproduced.

 Gentle firing reduces the risk of porosity. Putting aside shape and esthetics determinations separately, will allow the working stages easier to control


The press technique has proven to me over many years a guarantee for constant quality (Figs. 4-5). Cases can be prepared much easier and less stressful. This type of technique is simply more fun to work with-good humor for me provides a better lifestyle in the lab!   

Before receiving his degree as a master technician in 1993, Jörg Muller was trained in Jan Langner’s Dental Laboratory in Schwäbisch-Gmünd, where he specialized in tooth morphology in function and esthetics. In 1993, Jörg opened his first dental laboratory in Düsseldorf while concurrently teaching courses for dental technicians in posterior wax-up, the function of the TMJ and ceramics. In 1999, Jörg moved to San Francisco and established a high-end laboratory in downtown San Francisco. While working closely with his dentists and patients, he developed the Aesthetic Press System. In 2005, Jörg founded Aesthetic-Press LLC and developed a system to standardize a workflow for consistent and reproducible high-end restorations for every technician to use on a day-to-day basis.

This article originally appeared in the March issue of Dental Lab Products. 

Articles

Bench Mastery: To press, or not to press? [VIDEO]

While many different spruing instructions available for use state that there are rules users “must comply” to regarding spruing techniques, this may not actually always be the case.

According to my experience some of the complied rules regarding spruing objects are good, but not absolutely necessary.

With this article I will use products from 

 (Düsseldorf, Germany) to illustrate how  some of the “rules” applied when spruing objects are not absolutely necessary.

When spruing objects, there are basically the following parameters, which should be considered and discussed:


	Figures 1 and 2 show examples of the press result from the long sprues, which may 

well be longer than expected. Thus the length of sprues during pressing, using pink ingots 

 are several centimeters long. Also subsequent pressing of the white portions illustrate the dynamic possibilities.

After years of experience, I choose to use 0.3 cm to  3 cm sprue length to obtain these possibilities.
	 


	To put it in a nut shell, the diameter here should be 3 mm.

One can say that there is no compulsory fixed angle rule. Figure 1 pressed in pink ceramic illustrates the sprues going up and down rapping around the object, justifying the particularly good pressing properties of the AP-pressed ceramic that make difficult 

In general, one can maintain the length of the sprues as short as possible for minimal material usage. Even though there is no minimal sprue length required, I connect with a safety distance of 2 mm onto the edge. This avoids excessive heat in cuspal regions, which can cause cracks.

The most important fundamental rule is to keep the sprues clean and smooth. Poorly unfinished waxed up areas increase the risk of investment embedding into the ceramic. Spruing angles can easily vary from 30- 90°.

The sprues should be placed at the edge of the main plunger channel stand. This enables the object to be in the warmer region of the muffle. Sprued objects in the middle of the plunger stand are more prone to a faulty pressing because the temperature in this area is cooler.

The distance of the crown to the mold bottom or the walls should be at least 0.75 cm (Fig. 3).


	This varies depending on the case, which can be direct single units, up to arched bar connected large span bridges.

For spruing large span bridges, we use bar connectors to reduce less connector length.
	Short sprues of 3 mm-gauge 8 lead to the cross connector, which also is a 3 mm diameter. The arched bar connector is waxed directly on the plunger stand. It is not to be treated the same way as casting processes, such as in a V shaped gradient (Fig. 4).

Fig. 4?One also can use arched bars to press.
	 


	In an implant-supported occlusal screwed bridge with small screw channels running through the crown, it is recommended, because of thin cervical regions, to use 2 pressing sprues per crown. Around 30 grams of press ceramic would be needed for this particular case. By using less sprues and less press material you increase the chances of failure.

For 14-unit bridges, if a technician goes with less material there is a much greater risk of ending up with  some flaws in the press result.

In this example (Fig. 5), the screw channels run right through the crowns. Thus, the crowns were incisally and lingually sprued (below the screw channels) and posterior region buccally and palatally.

Experience shows with large bridges that have been sprued only in palatall areas, that the last third of the buccal cervical wall regions of the two last molars did not fully press (Fig. 5 and 6).

Fig. 6?Another extreme example of thin single crown walls.

The pressing temperature can be raised by 20°C with such large objects. Ideally, the press time should  be set up to 20 minutes. The muffle should not be heated with speed process, and always must be placed in a cold burn out oven.
	
	Figure 7 shows a bridge with molars. In such a case you should make sure the molars are provided with two sprues.

One last tip, which can be improved here, is to donate sprues to the buccal cusps and not to the cusps in contact, preserving the intercuspal anatomy.

Fig. 7?Example of a bridge with molars: good clean spruing allows a good pressing result.


	Correct spruing justifies good homogeneous results in the press technology. Many believed rules as previously mentioned i.e. sprue angles, are rules that are not a compulsory necessity. Other spruing criteria when put into practice can provide a predictable and constant result.

		The Ingot Master Kit consists of 8 different ingot colors. The different color and opacities offer a range of ingots for the press and stain technique as well as the press and layering technique.

		The unique feature of the AP Press porcelain is that no glaze paste is needed to obtain a beautiful natural glaze. It is possible to re-press the ingots as well as to press on to, in case of a miss press.

How to use the Ingot Master Kit and correct spruing for optimal press technology results

Over the years, I have seen many restorations being modified and compromised due to poor planning from the start. Developing a plan, turning it into a protocol and then following every step precisely, will ensure a predictable and successful restoration.

 anterior restorations it is most important to start with a diagnostic wax up. This is a solid foundation for any case. All the critical points such as: length, proportions and anatomical details will be determined.

No technician wants to make changes-such as adding to the incisal edge-when it’s time to deliver a case. We feel great pleasure when the case just drops in and we meet the patient’s expectations. To make this a standard rather than playing a lottery game, we need to follow a step-by-step approach.
	First Step-the 

: Find the right functional elements, the right size, proportions, and horizontal and vertical dimensions, which are parameters that can be determined in the wax up.

For edentulous patients it has been common practice to set up denture teeth, because they are easy to place and quickly lead to a result. However, because those denture teeth are more generic rather than customized, it may lead to limits if the 

 needs to be modified. A more suitable solution, and equally as efficient, is the OccluMaster wax patterns by Aesthetic-Press. Because of their flexibility, these fully contoured posterior crowns help find the right occlusal dimensions in a very short time, while adjustments or functional elements can be easily done.

With the OccluMaster, a variety of occlusal concepts can be used and easily modified. The conventional P.K. Thomas anatomy can be found in our classic design, and the more advanced theories, like the Biomechanics taught by the renowned Michael Polz from Germany, can be found in the Premium morphology 

 offers a variety of advantages compared to its counterpart, metal. The very minimal porosity level of zirconia is far more biocompatible than any metal construction, not to mention the implications of soldering connections.

 is essential, which will be verified through a try in, in its frame stage. Any adjustments can be done chairside with light-cure materials. With a thorough milling procedure and controlled sintering process, the bar fits nicely to the implant.

 The bar is designed and milling is started using a 16 mm zirconia block. Four different burs are used to mill the bar on a 

). The abutment areas need to be milled very carefully.

 Once the bar is almost finished, the housing for the screws is 

 before sintering. The Eco milling machine provides the ability to mill the housing for the lateral screws, especially for constructions like this complex restoration 

. In addition, the bar can be milled either parallel or at a 2 degree angle. This will ensure that the over structure will fit nicely, and the friction will keep both parts together. The set screws will lock the construction in its final position. The 4 lateral screws carry the metal housing, which will be inserted once sintering is completed.

 the bar, the color liquids are added and the bar is sintered while still connected to the block to retain the precise shape during the sintering process 

 Cutting the connectors had to be done very carefully with water-cooling to avoid a fracturing of the bar. After fitting the bar, the zirconia was polished with the AP Diamond Polishing Paste, which has a high diamond content and gives the bar a perfect surface shine

 To cover the bar for the overstructure, the Rigid light-cure material was applied before the frame was put into the silicon matrix that was created from the original wax up 

 Maintaining the occlusion is a very critical point when duplicating a precise wax up. AnaxDent’s AnaxForm (

) is a special mold maker ideal for transferring the wax up into resin. This mold maker also can be used for a wax injector to re-inject the previous wax up.

 After milling the overstructure, the final details were milled after using the “drop the pin” technique. The milling bur is dropped approximately 0.75 mm, whereas the tester will stay in its original position 

. This technique will ensure the pressed porcelain has enough room for maximum stability and perfect light reflection

 Using the translucent Aesthetic-Press Zircon ingot will give you the optimum porcelain support. As Figure H illustrates, the Eco milling machine can be set to different angels to mill every corner of the restoration. After opening the set screws of the hinge, the milling plate can be adjusted as needed. The rotation of the 5 axes allows the placement of the lateral screws.

 The Gingiva, as well as the tooth colors, are applied carefully with a brush before the sintering process. The color liquids are needed to support the final color with the right chroma from within. For the experts, slight color nuances can be applied with a micro brush. A variation from violet, gray as well as a mild orange can be applied to bring some life into the zirconia structure 

 The pink porcelain will be pressed first. To accomplish this, the original wax up is re-injected onto the framework. The AP injection wax, with its specific properties, allows the occlusion and crowns to be removed with a simple cut of a scalpel at the red/white junction allowing the wax to be peeled off.

 The length of the sprues for pressing this porcelain were significantly longer than allowed in any textbook. For a successful press result, the restoration was supported by 4 sprues on the inside and 5 on the outside of this full arch zirconia framework 

 After investing the bridge for 15 minutes, bench set time was used before placing the ring into a cold burnout furnace. The program was set with a rising temperature of 17 degrees Celsius per minute. After reaching the final temperature of 850 degrees Celsius, a holding time of 60 minutes needs to be completed before placing the ring into the press furnace.

 The AP Feldspar ingots should not be preheated. Using 6 x 2.5 g ingots, the length of the plunger had to be shortened by 50% for the oven to close. The gingiva part was pressed with the Aesthetic-Press gingiva ingots. The press time was 20 minutes and the distance travelled was 21 mm. The 

 time describes the time used for the plunger to move the porcelain into the form.

Working with such a large amount of zirconia requires a lot of attention to a very slow rising temperature and cooling time. An extended cooling time was needed before carefully de-vesting this massive zirconia overstructure. After checking the fit of the upper construction with the model, the wax injection completed the missing layer of the clinical crown.

 Little adjustments were needed before the construction is ready to be re-invested for the second press cycle to press the white porcelain. Each tooth was connected with one sprue of gage 8 

. The reconstruction should be centered as much as possible to keep a balance of the porcelain during the cooling phase. This proves the point, that with the AP ingots, structures of any kind and size can be 

. The press temperature and thickness are the keys to success.

 With a precise wax up, only minimal corrections are needed to complete and glaze the construction 

. The ability to finalize the occlusion in wax makes such a large and complex case much easier to plan and manufacture. All the functional elements can be designed at the right place, more easily and more precisely than with a conventional build up technique in porcelain 

At the time when I developed the Aesthetic-Press System, I was looking for a system, which would help every technician simplify their work and make it more predictable at the same time 

. Working in my laboratory with my clients and technicians enabled me to develop this 

 and make it a success on a daily basis. This system is a great opportunity for every technician to bring high-end quality at an affordable price to their laboratory and even more importantly to make your work consistent for you and your technicians case by case.

After receiving his masters degree in 1993, Jörg Müller opened his dental laboratory in Düsseldorf, Germany. In 1999 he moved to San Francisco where he opened his second dental laboratory, European Dental, and developed the Aesthetic-Press System. Aesthetic-Press was founded in 2006 and now sells the AP System to many countries around the world. Müller is teaching technicians how to apply a proven system to streamline production and add a higher standard to their quality. The company’s motto is “Efficiency Through Simplicity.” Aesthetic-Press is not only selling a porcelain, but a completely integrated system that is unique in all its features. Aesthetic-Press has created a standard that ensures a reproducible and consistent high-end result, producing crowns and bridges that are amazingly beautiful.

Over the years, I have seen many restorations being modified and compromised due to poor planning from the start. Developing a plan, turning it into a protocol and then following every step precisely, will ensure a predictable and successful restoration. For aesthetic anterior restorations it is most important to start with a diagnostic wax up. This is a solid foundation for any case. All the critical points such as: length, proportions and anatomical details will be determined.