Inlays and Onlays

Every day, our teeth are subjected to significant chemical and physical stress. Defects in teeth, caused by factors like cavities, should be promptly restored.

Inlays and Onlays are single-piece dental restorations designed to replace lost tooth structure. They do not differ in function but vary in shape and extent.

An Inlay is smaller in size and serves the inner part of the chewing surface. It is used when the tooth defect is relatively small.

An Onlay extends across the entire chewing surface of the tooth and is necessary when the defect is more extensive.

Every healthy tooth has an ideal anatomy to ensure optimal chewing, prevent food debris from getting stuck between teeth, and avoid overloading the jaw joints.

In various situations, repairing teeth with Inlays or Onlays is necessary:

Acid from certain bacterial strains can etch holes in the tooth. This defect should be anatomically repaired, and for larger cavities, Inlays and Onlays are recommended.

Amalgam fillings have adverse health effects and should be removed with effective protective measures. After removal, the missing tooth structure can be well replaced with Inlays or Onlays.

Occasionally, a part of the tooth may break off, especially in teeth that have been previously drilled or have cavities. The broken piece of the tooth can be restored with a high-quality Inlay or Onlay.

Patients with incorrect tooth contacts often compress their jaw joints and force them into an unnatural position. This leads to remodeling of the jaw joints and surrounding tissues, affecting the entire body. This condition can result in Temporomandibular Joint Disorder of the Joints (TMJ), significantly impacting the quality of life.

As a therapy, the impact of abnormal tooth contacts must be eliminated through a special TMJ splint (MAGO splint), allowing the jaw joints to regenerate slowly. After the completion of jaw joint regeneration, TMJ symptoms should completely disappear. To prevent the old bite from causing harm to the regenerated jaw joints, the correct anatomy of the teeth must be restored. This is achieved through a complete reconstruction of the chewing surfaces with Inlays, Onlays, and Veneers. This reconstruction can also be combined with orthodontics.

For simplicity, the term “Inlay” is used in the following part of the article, but it includes Onlays as well.

There are various materials used for the fabrication of inlays, each with its specific advantages and disadvantages that you should be aware of.

Ceramic inlays are also referred to as ceramic fillings and can be made from different types of ceramics.

Ceramic, as a material, is highly recommended in terms of biology, fit, durability, and aesthetics. It meets the requirements of high-quality aesthetic dentistry, allowing for the restoration of beautiful and anatomically correct teeth.

The precision and accuracy depend significantly on the type of ceramic and the manufacturing process.

Care must be taken during treatment and fabrication to maintain a minimum layer thickness to prevent later chipping and splintering.

With an experienced dental and dental technical team, ceramic can yield excellent results.

Gold has proven itself as a material for inlays over many decades in dentistry. Gold inlays are very precise and exhibit high durability.

However, gold has inferior aesthetic and health properties. The poor biocompatibility has been demonstrated in numerous samples and studies, including those by the IMD Institute for Medical Diagnostics Berlin.

These inlays are a combination of ceramic and gold, with the majority being ceramic and the inner layer facing the tooth made of gold. Galvano inlays generally show excellent fit and high durability. However, the subpar biological compatibility makes them not recommended.

Titanium is well-known in dental implants, being the most commonly used material in implantology.

Titanium inlays have good fit and high durability. However, many patients find issue with the unaesthetic metallic-gray color.

Similar to gold, there are various health concerns associated with titanium.

There are various materials that can be used for plastic inlays. Depending on the quality of the material and the manufacturing process, the results can vary significantly.

With correct production in the dental laboratory using high-quality material, plastic inlays can be an alternative to ceramic inlays.

However, plastic does not match the biology and stability of ceramics and plays a subordinate role in inlays.

As mentioned above, inlays are used to restore missing parts of a tooth, for example, after caries, in a single piece. This restores the tooth to its original anatomical shape.

If the caries is small, the defect can be replaced with a tooth filling made of plastic. This is often straightforward.

When the tooth defect is extensive, and anatomical reconstruction directly in the mouth is challenging, the inlay should be preferred. This allows the dental technician to optimally rebuild the ideal anatomy of the tooth. With a filling, there could be a risk that the contact with the adjacent tooth is too weak, allowing food residues to accumulate.

If you, as a patient, prefer the solution with the best compatibility and longest durability, you should opt for the ceramic inlay. Ceramic inlays are also ideal for aesthetic dentistry.

If the natural tooth crown is too severely damaged, it should be stabilized and restored with a ceramic crown. In such a case, a tooth filling or inlay would not be the right choice.

Therefore, the correct, individual choice of dental care is of great importance so that the stability and anatomy of the teeth can be ideally replicated. The dentist should always consider the biology of the material.

Inlays serve the function of replacing the missing tooth defect. To secure the missing piece, it is cemented or glued into the tooth.

There are various cements used in dentistry. These adhere to both the tooth and the inlay, ensuring a strong and definitive bond.

Common cements include glass ionomer cement, zinc oxide-phosphate cement (Harvard cement), or carboxylate cement. These have proven themselves over many decades and can be used for attachment depending on the material of the inlay.

Cements, in general, have high biological compatibility and low susceptibility to moisture during the placement of the restoration.

However, depending on the material, their stability may be lower than that of plastic adhesives.

Plastic adhesive is very similar in structure to the plastic used for plastic fillings. The adhesive is used along with a liquid bonding agent, creating a strong connection between the tooth, adhesive, and inlay.

This type of attachment is very strong and exhibits high stability.

Unfortunately, plastic adhesives contain many toxic and allergenic ingredients, compromising biological compatibility. Additionally, plastic adhesives are sensitive to moisture, which must be carefully considered during the placement of the inlay. Please refer to Environmental Dentistry for more information.

This is the classic procedure for providing patients with inlays.

First Appointment:

The impression is sent to the dental technician, who manufactures the inlays in the dental laboratory. The production takes approximately 7 days when using an external dental technology laboratory.

Second Appointment:

The two treatment appointments can be combined into a single day.

The first part of the treatment is conducted in the morning. Afterward, the patient has a few hours of break. During this time, the inlays can be manufactured either in the dental laboratory or using the CEREC system.

After the break, the second part of the treatment takes place.

This way, the inlays can be produced and placed on the same day.

Such a chairside treatment is only possible if the practice has its own dental laboratory or with the help of CEREC.

In an in-house dental laboratory, the dental technician can concentrate 100% on the patients of the dental practice. Consequently, lab-fabricated, highly precise inlays can be manufactured and placed on the same day.

Lab-fabricated inlays have the advantage of being ground with the highest accuracy. A 5-axis milling machine with super-fine 0.3mm wide cutters can produce optimal fit and precision.

As a result, inlays have an excellent fit, and the cement gap can be minimized.

CEREC stands for CEramic REConstruction. It is a procedure for dental practices to quickly and straightforwardly manufacture ceramic inlays.

Here too, the inlay treatment is completed in a single day.

The dentist takes a digital impression with an intraoral scanner, sends the information to a special milling machine that grinds the inlays from ceramic blocks.

This process is simple and also provides a very good result.

If you are considering getting an inlay and are not sure about your decision, please read the questions and answers on this topic.

The further information is intended to give you a better overview of the subject area.