Dental inlay. Advantages, Types and Materials
Dental inlay is a crown filling made in the dental laboratory.
Known as an indirect filling, a dental inlay is the traditional method of restoring teeth, but due to the growing variety of filling materials available, it is not often used in dental surgeries, often opting for glass ionomers or light-curing composites because of their lower price and shorter fabrication time. When the occlusal surface of the tooth has suffered damage and the ordinary filling is not adequate, a dental inlay offers the possibility of restoring severe loss of substance to the tooth.
What, in fact, is a dental inlay?
Dental inlays can be of several types: inlays, onlays and pinlays. The inlay is a piece of reconstruction, which can restore 1-2 walls of a tooth, one lateral interdental and one occlusal. It is made in the laboratory, from materials that provide the same strength as the dental tissue and the same thermal expansion with it, optionally – with the same color and appearance as the tooth to which it is applied. A dental inlay is larger than a regular filling but smaller than a dental crown. It is applied and cemented into the pre-cleaned cavity. It is similar to a filling but is positioned between the cusps of the tooth.
Unlike an inlay, an onlay also restores a lateral, vestibular or oral wall of the tooth, thus covering 2-3 to a maximum of 4 of the 5 walls of the tooth. Its high strength makes it the last resort before a vital tooth is covered with a dental crown.
An onlay is larger than an inlay and covers more tooth cusps, known for this reason as a partial crown. In this way, it covers more of the occlusal surface of the tooth, but not all of it, as dental crowns do.
The pinlay is an inlay on devital teeth, however, which has all the elements of the onlay with the addition of one or more root elements.
With dental inlays we preserve and restore the contact points of the tooth with neighboring teeth much better than with classical fillings, protect the interdental papilla from masticatory pressures, restore the physiognomy and functionality of the tooth.
They are necessary in cases such as:
- teeth with proximal (interdental) caries with destruction of more than 1mm
- proximal cavities with difficult access for composite fillings
- missing or difficult to create contact points
- mirror caries (on two neighboring teeth) on vital teeth
- papilla affected by masticatory forces that needs to be restored
- destruction of up to 60% of the crown of a vital tooth.
We can use a dental inlay in most situations where fillings can be made, when teeth have suffered damage through decay or fracture and the damage caused is not extensive enough to require capping with a dental crown.
Usually, a dental inlay is preferred when the loss of dental tissue is great and the doctor wishes to protect the remaining dental tissues.
Any dental inlay can be made of ceramic, various alloys (CrNi, CrCo) or Zirconium. (see video below)
Because it can be made from materials that mimic the natural color of the tooth, inlays and onlays are preferred by patients to replace unsightly fillings in order to achieve a more natural look.
Zirconia is the material of choice in cosmetic dentistry because of its natural aesthetic appearance and its many qualities: it is durable, resistant (superior to ceramic), biocompatible and identical to natural tooth structures.
The differences between a metal dental inlay and a Zirconium dental inlay are in the realization of the aesthetic criteria. The differences between ceramic and zirconia are in the degree of strength, the latter being far better than ceramic.
It should be noted that in patients with low caries activity (few cavities) and good oral hygiene, a Zirconia dental inlay can have a longevity of even 25 – 40 years. The type of material used affects the following factors: aesthetics, strength, durability and cost.
Types of dental inlays:
Depending on the fabrication technique and application method, inlays can be of two types:
- Direct – these are made in the dental office and fitted during a single dental visit
- Indirect – they are made in the dental laboratory and require at least two visits to complete the restoration.
The type chosen depends on the integrity of the tooth structure (how much of the tooth affected by the caries process remains) and the desired appearance of the procedure.
How many sessions does an inlay require?
For a direct inlay, only one session is required (the dental cabinet must have its own laboratory to be able to process the inlays on the spot).
At least two treatment sessions are required to obtain an indirect inlay. In the first session, the dentist prepares the cavity and takes the impression, which is sent to the laboratory. The technician molds the model received and creates the inlay.
The second session aims to cement the inlay.
A dental inlay can come loose if the cement is eroded or combines with saliva when it is applied. Inlays made of composite resins or porcelain can crack if certain factors put too much pressure on the teeth.
The longevity of the dental inlay depends on the material from which it is made, the strength and stability of the treated tooth, the occlusal surface being restored and the patient’s cooperation in maintaining proper oral hygiene and having regular examinations.
A dental inlay is a better alternative to glass ionomer, composite or amalgam fillings.
Any dental inlay has the following advantages:
- Superior marginal adaptation (biocompatibility with gum tissue)
- Perfect restoration of the anatomical shape of the tooth through laboratory modelling
- Perfect restoration of interdental contact points (maximum tightness compared to a composite filling)
- Unlike amalgam and even metal fillings, inlays do not stain the tooth
- Wear resistance superior to any type of filling
- High aesthetics of Zirconia inlays (natural look)
- Does not require long adaptation times, does not create discomfort (the natural feeling is established from the start)
- The color obtained does not change, as is often the case when restoring teeth with composite materials
- In some cases, depending on the cement used, a dental inlay can provide protection for the dental tissues remaining after caries removal (stimulates neodentinogenesis)
- By perfectly restoring the outline of the tooth, the inlay contributes to the maintenance of gum health
- Contributes to the elimination of dental sensitivity
- Causes little or no abrasion on the antagonists
- Prevent tooth loss
- Teeth can be more easily cleaned and maintained in terms of oral hygiene
- Strengthen tooth structure (approximately 75%)
- Minimal risk of secondary caries (due to optimal marginal closure)
- Unlike precious metal fillings, no dental calculus shrinks or expands (significantly) with temperature changes, which weakens the tooth and can cause cracking or fracture
- A dental inlay can last up to 40 years (due to the strength of the materials and manufacturing method)
- The strength of dental inlays is superior and the hardness close to that of the tooth
- Optimal restorability: an onlay can restore 3-4 fifths of the tooth crown.
- One of the greatest benefits in saving treated teeth is the avoidance of extensive dental restoration procedures (crowns, bridges, dental implants).
- Increased dental sacrifice compared to that required to apply a traditional filling, either amalgam, glass ionomer or composite materials
- On devital teeth the inlay can act as a wedge, fracturing the tooth
- Due to the greater hardness of the teeth than natural teeth, it will erode the antagonist tooth over time
- The high price of this type of filling is mainly due to the cost of fabricating the inlay/onlay in the dental laboratory
- Classic fillings (cheaper)
- Another alternative is the dental crown (more expensive)
Prior to the procedure, a local anesthetic is given or a sedative is administered to the patient to help them relax during the procedure.
The decayed tissue is removed, after which the tooth surface is properly prepared.
Direct inlays: After preparing the tooth, a composite material is applied to shape the cavity that has just been cleaned.
Then the inlay is removed and hardened in a special furnace. Under this the shape is again placed in the appropriate place and cemented by the dentist and then sanded and polished to achieve a natural appearance.
Indirect inlays: Unlike those that are set and cemented on the same day, indirect inlays involve two sessions. In the first session, the decay is removed and a cast of the treated tooth and the adjacent teeth is made, and the tooth receives a temporary filling.
The cast includes at least the treated tooth, its neighboring teeth and the opposing tooth (to ensure correct occlusion).
In the second session, after removing the temporary filling and cleaning the tooth, the laboratory processed inlay will be fitted according to the dental impression.
After polishing, the final adjustments are made so that the new restoration is completely and naturally integrated into the dental assembly and does not generate a poor or incorrect occlusion.
Once the procedure is complete, the patient can return to his or her normal activities, experiencing only slight sensitivity in the treated area.
Arguments for choosing dental inlays:
- Any dental inlay is much easier to clean and maintain than regular dental crowns or fillings.
- These, if properly fitted, provide an effective treatment to prevent secondary decay.
- They integrate perfectly into the harmony of the oral cavity. They are fixed so well and naturally that they will ensure the longest lasting and most aesthetic dental restorations.
- They are ideal for repairing cavities between teeth.
Usually, fillings made of composite or other material are used to fill small cavities, while crowns are used when the decay is deeper or if there is substantial hard tissue destruction.
However, there may be situations where a filling is not enough and a crown is too large to protect the tooth.
Dental inlays and onlays are what many dentists will use when the cavity created falls between the 2 situations described above. They are larger than composite fillings, but not as invasive as a dental crown, which involves preparing the teeth by removing hard tooth structures to a greater extent.
In their basic definitions, an inlay covers cavities created in the areas between cusps.
An onlay will not only fill cavities in these spaces, but may cover a larger area, including cusps.
It works similarly to crowns, but does not cover the entire surface of the tooth.
Both are made of the same materials and perform the same function, but they restore different areas of the tooth to protect them properly when there is tooth decay.
One of the main benefits of inlays and onlays is how durable and resilient they can be. You can expect an inlay to last between 5 and 30 years.
Your dentist cannot guarantee an exact time due to a variety of factors. Some may experience more wear and tear than others and, if left uncared for, may deteriorate sooner than expected.
One of the most important factors is how well the patient performs their dental hygiene after the inlays are placed.
This means brushing twice a day, flossing every day and following the recommendations given by your dentist.
It is also a good idea to check the stability and integrity of the restorations regularly. Along with proper hygiene, patients should also reduce wear on inlays and onlays by avoiding hard, sticky foods that can damage the material. In addition, bruxism should be treated by wearing mouthguards at night.
In the past, onlays were made only of gold, but nowadays more and more patients are asking for an inlay that is not visible. Making ceramic/porcelain restorations allows a better fit to the tooth, thus improving its strength and providing a proper marginal seal.
Inlays and onlays are generally better than fillings in that they can cover a larger cavity and are more durable.
Inlays adapt much better to the shape of the cavity and provide a better seal, because an impression is used to make the restoration. The advantage of composite fillings is that they are quicker to apply, whereas an inlay requires at least 2 sessions. The cost is also lower for fillings.
Your dentist will determine what type of restoration you need based on your clinical situation and explain all the details you need, so don’t hesitate to go for a check-up when necessary.