Working Models or Impressions

Working Models & Dental Impressions for Dental Professionals

We encourage you to experience the seamless process of transforming your patients’ smiles by sending us your dental impressions or work models. At Ohlendorf Appliance Laboratory, we understand the pivotal role that accurate dental impressions or work models play in providing top-notch orthodontic care. Rest assured that every impression you send is handled with the utmost precision and care to facilitate the creation of impeccable custom appliances and models. Partner with us today, and let’s work together towards achieving the perfect fit and function that will leave your patients smiling with confidence.

As a committed lab serving all 50 states from our central location in St. Louis, MO, our mission is to provide dentists and orthodontists with the finest appliances available.

Why Choose Ohelndorf?

High-Quality Standards:

Our dedication to excellence ensures every model we create is precise and meets the highest quality standards.

Advanced Technology:

Leveraging 3D printing in orthodontics, we bring to you the most accurate dental and orthodontic models for your patients.

Nationwide Service:

We conveniently serve practices across the entire country, ensuring that wherever you are, you can access our specialized services.

Personalized Support:

Our Technical Support Specialists are always available to assist you with appliance designs, treatment options, and any questions you might have.

How to Send Us Dental Impressions or Working Models

For Appliances:

To ensure the best fit for appliances, please send working models poured in yellow ortho stone. Alternatively, you can send PVS impressions with an additional fee for pouring. Avoid sending wet alginate impressions to prevent distortion.

For Traditional Display Models

For creating display models, we accept wet alginate or PVS impressions. If sending wet impressions, ensure they are packaged in a wet paper towel and placed in a zip lock bag. You can also send working models for duplication with an additional fee.

For Digital Study Models:

Our digital study model service requires working models for scanning. There is no need for special trimming; we will generate virtual bases for a traditional model appearance. Impressions require an additional fee for conversion into working models, as we are currently unable to scan them directly.


Construction Bites
Proper construction bites are very important and can drastically affect the way an appliance fits. The type of material that you use is not as important. You can use any type of material that you are comfortable with. Wax bites work just fine for us to use to fabricate the appliance. You can send us whatever type of bite material that you are comfortable using. We have no preference.
Fixed Appliances

When you send in a case for a fixed appliance, we prefer that you send in a set of upper and lower models.
You can send in prefitted bands if you want to or allow us to supply the bands for you.

Often times the opposing model is not needed, but in some cases it makes a big difference. The opposing model allows us to fabricate an appliance that fits great the first time and is closely adapted for that particular patient. We always have your patients comfort in mind when we fabricate your appliances. The more information we have, the better we can make the appliance.

If your fixed appliance requires bands, you have a couple different options:

1. We supply the bands for you.

About 75% of the cases that we receive are sent without prefitted bands and we supply them. You do not need to place separators when you take the initial impression for the appliance. Simply take the impression with the arch as it is. When we receive the model, we will trim it and fit the correct size band for that tooth. We will fabricate the appliance with the band seated in the ideal position. Before you seat the appliance, you will need to separate the teeth to make sure you can seat the band correctly.

2. You send prefitted bands with the models.

Some doctors prefer to size their own bands and send them with the models. Please do not pour the bands up in the model. Just pour up the impression and send the bands loose in a plastic bag. When we receive the case, we will trim the model and place the band in the correct position before we make the appliance. We have determined that we can fabricate a better fitting appliance this way. It is also easier on your staff and saves them time.

Perio Protect

Perio Protect is one of the most popular services that we provide. These appliances must fit extremely well in order for the medication to be delivered correctly. Since the fit is so important, we need very accurate working models that capture all the teeth and soft tissue areas. It is important that the impression includes the tissue at least 4mm below the gingival margin.

We prefer that you send us working models poured in yellow ortho stone for us to fabricate the Perio Protect Trays. The models cannot have any air bubbles or holes on the tooth surfaces. A tight seal can only be achieved with an accurate model. Therefore, it is always best to have each cast poured up and inspected by the doctor for bubbles or distortion before the patient is released. This simple precaution can save you the expense and inconvenience of calling a patient back for a new impression.

Alginate has been shown to be the best impression material to use for Perio Protect Trays. Kromopan is the recommended alginate. PVS impressions can be used, but they are not necessary. If you would like information about taking alginate impressions and pouring models, we have an excellent Practice Building Bulletin under our Educational Information section on our Home Page.

Shipping Models
Whenever you ship us case, it is important that everything is wrapped properly. The working models should be wrapped separately. Everything should fit tightly in the box, so there is no room for items to slide around. Construction bites should also be wrapped separately. Do not put them on the models and wrap everything together as one unit. Everything should be wrapped separately.If you are sending Alginate impressions for display models, please wrap them in a wet paper towel and put them in a ziplock bag.

We can provide you with packing material if you need it. We can send you boxes and also send some wrapping material as well. Just let us know what you need.

Don’t forget to include the Prescription sheet in the box and be sure to put your return address on the mailing label.

Turnaround Time

All of the following time estimates are working days and do not include weekends:

Sending the case from your office to our Laboratory: 1-3 days

Time in lab for the Appliance to be fabricated: 4-5 days

Time in lab for Orthodontic Records Package: 5-6 days

Sending the case from our Laboratory to your office: 1-3 days

If you have already scheduled the patient’s appointment, let us know. We will do everything that we can to get the case back to you to meet that appointment. If we can’t, we will contact you and let you know that we may have a problem getting the case back to you on time.

Shipping Instructions

In order to send us a case we provide Postage Free Mailing Labels. All you need to do is place the label on the outside of the box and give it to the postman or drop it in a mail box. You do not need to weigh it or place any stamps on it. As long as the label has our St. Louis address on it, we will receive it in the Midwest. If you would like to use UPS instead of the Post Office, just let us know. We can also send you some pre-printed Ground UPS labels for you to use.

All of our cases are returned to you Ground UPS. Since we are centrally located in St. Louis, the shipping time is greatly reduced over other laboratories located in different parts of the country.

If you need a mailing label or prescription sheet, you can download them from this website. It is available on this page.

Models vs Impressions

When you send us a case for us to fabricate an appliance, we prefer you send us working models poured in yellow ortho stone or Digital Scans. We do not guarantee the fit of the appliances if you send in wet alginate impressions. They may distort no matter what brand you use.

If you would like us to fabricate your Display Models, we prefer you send wet alginate impressions or PVS impressions. If you send wet dental impressions, please wrap them in a wet paper towel and send them in a zip lock bag. There may be a small amount of distortion, but it will not affect the way the display models look. You can send working models, but there is an additional charge to duplicate them to make the Display Models.

Our newest service is Digital Study Models. When you send in a case, we prefer that you send working models. You do not need to trim them in any special way. After we scan the models, we will build virtual bases on them, so they look just like the Traditional Display Models. At this point we cannot scan impressions. If you send impressions there is an additional charge to pour them up into working models.

Prescription Forms

One of the most basic things that we need to fabricate an appliance is a properly filled out Prescription Sheet. Some basic information will go a long way to helping us get the exact appliance that you are looking for and be able to return it back to your office in the quickest possible time frame.

Please fill out the Prescription Sheet with as much detail as possible. This includes the patient’s age. The age of the patient can affect the design of the appliance particularly when it comes to which teeth to clasp and the types of clasps to use.

Another important section to fill out is the “Date Wanted.” Please indicate the date you need the case back in your office. If the patient is already scheduled, you may want to request it back 1-2 days before the appointment to make sure that you receive it in plenty of time. If for some reason we are unable to meet the date you requested, one of our staff members will call your office immediately to let you know.

If you ever have a question about the name of an appliance or the type of appliance to use, give us a call or we can call you. Just mark off “Phone Doctor Concerning Case.” When we receive the case, one of our technicians will contact you and answer any question you may have. We welcome your phone calls, and are available to help you to make sure you get what you need and ask for.

If you know the Appliance Number from our book “The Principles of Appliance Therapy” be sure to indicate it on the Prescription Sheet. We will make your appliance exactly like it is pictured in the text book. We have tried to list many of our most popular appliances on our Prescription Sheets. If you do not see the one that you are looking for, just check off “Other” and write us a note about the appliance you want. If we have any questions, we will be sure to call you.

We have a variety of Prescription Sheets for the appliances we fabricate and services that we offer. If you need more of them, please contact us, and we will get some out to you right away.

Removable Appliance

When you send in a case for a removable appliance, we prefer that you send in upper and lower working models and a bite. The bite should be taken in the patient’s normal occlusion. This will help us prevent any occlusal interferences when we are fabricating the appliance. We can check to make sure that the patient isn’t biting on the wires. It is also helpful to let us know if the patient will be losing any deciduous teeth in the next couple of months. The loss of the teeth can affect the design of the appliance. We don’t want to clasp a tooth that will be lost next month. This reduces retention and can affect the fit of the appliance.If you want occlucal coverage or an anterior bite plane, we will need to send a specific bite. The bite should reflect the vertical that you want and the mandibular position you want to achieve. We have an excellent technical bulletin on how to take these types of bites. It will show you the steps to take, so the appliance will fit without having to adjust the acrylic when you seat the appliance. Look for it under the Educational Information Tab on the home page.


For information about our appliances, please click here to visit our Appliance Instructions page.

Repairs and Remakes

Our appliances are fabricated with the highest quality materials that are available. Occasionally an appliance may break and need to be repaired or does not fit properly.

If an appliance breaks, and you want it repaired, please send back as much of the broken appliance as possible. We will also need a working model. Do not pour up the broken appliance in the model. Please send it separately in a plastic bag. The working models will help us make sure that the repaired appliance will fit properly when we return it to you. Any appliance that you send in for us to repair will be turned around in 24 hours. We will rush it through our lab and make sure that we get it back to you as soon as possible.

Sometimes an appliance may not fit when you go and seat it. If this happens, please return the appliance along with a new working model. Please do not pour up the appliance in the model. It is also helpful to write us a note about why it did not fit. This will help us pin point the problem and improve the fit of the remade appliance.

Traditional Orthodontic Records

Our Traditional Orthodontic Records Package consists of a set of Acrylic Finished Display Models and a Hand Traced Cephalometric Analysis.

You have a couple of different options that you can choose to send us the x-ray.

1. If you are taking film x-rays, just send us the x-ray. You can mail it in an envelope separately from the impressions. If you do, indicate that you are sending it separately, and we will match up everything at the lab when we receive it. We do have boxes that will hold the x-ray and the impressions. If you need one, just let us know that you need some “Ceph Boxes” and we will get them right out to you.

2. If you are taking digital x-rays, you have a couple different options. You can email the x-ray to us at, save the x-ray to a disk and mail it to us, or you can print the x-ray and mail the print out to us. We do not have a preference how you send it to us. Whatever works best for you and your staff is great.

In order for us to fabricate the Acrylic Finished Display Models we prefer you send us impressions. You can send wet impressions, but you will need to wrap them in a wet paper towel and place them in a zip lock bag. We are not making any appliances from these impressions, so if there is any distortion, it will not affect look of the models. You can send PVS impressions if you are concerned about alginate impressions. You can send working models, but there is an additional charge to turn them into impressions so we can make the Display Models. Please include a bite taken in the patient’s normal occlusion, so we can get the models to articulate in the patient’s true bite.

If you would like more information about what to send, check out our video on this topic in our Video Library.