Inlays and onlays
| Inlays and onlays | |
|---|---|
| ICD-9-CM | 23.3 |
| MeSH | D007284 |
In dentistry, inlays and onlays are a form of indirect restoration. This means they are made outside of the mouth as a single, solid piece, that fits the specific size and shape of the cavity[1]. The restoration is then cemented in place in the mouth. This is an alternative to a direct restoration, made out of composite, amalgam or glass ionomer, that is built up within the mouth.
Inlays and onlays are used in molars or premolars, when the tooth has experienced too much damage to support a basic filling, but not so much damage that a crown is necessary. The key comparison between them is the amount and part of the tooth that they cover. An inlay will incorporate the pits and fissures of a tooth, mainly encompassing the chewing surface between the cusps. Whereas an onlay will involve one or more cusps being covered. If all cusps and the entire surface of the tooth is covered this is then known as a crown[1].
Historically inlays and onlays will have been made from gold and this material is still commonly used today. Alternative materials such as porcelain were first described being used for inlays back in 1857[2]. Due to its tooth like colour, porcelain provides better aesthetic value for the patient. In more recent years, inlays and onlays have been made out of ceramic materials. In 1985, the first ceramic inlay created by a chair-side CAD-CAM device was used for a patient[2]. More recently, in 2000, the CEREC 3® was introduced. This allows for inlays and onlays to be created and fitted all within one appointment[2]. Furthermore, no impression taking is needed due to the 3D scanning capabilities of the machine.
Inlays
Sometimes, a tooth is planned to be restored with an intracoronal restoration, but the decay or fracture is so extensive that a direct restoration, such as amalgam or composite, would compromise the structural integrity of the restored tooth or provide substandard opposition to occlusal (i.e., biting) forces. In such situations, an indirect gold or porcelain inlay restoration may be indicated.
Comparison of inlays and direct fillings
When an inlay is used, the tooth-to-restoration margin may be finished and polished to a very fine line of contact to minimize recurrent decay. Opposed to this, direct composite filling pastes shrink a few percent in volume during hardening. This can lead to shrinkage stress and rarely to marginal gaps and failure. Although improvements of the composite resins could be achieved in the last years, solid inlays do exclude this problem.[3] Another advantage of inlays over direct fillings is that there is almost no limitations in the choice of material. While inlays might be ten times the price of direct restorations, it is often expected that inlays are superior in terms of resistance to occlusal forces, protection against recurrent decay, precision of fabrication, marginal integrity, proper contouring for gingival (tissue) health, and ease of cleansing offers. However, this might be only the case for gold. While short term studies come to inconsistent conclusions, a respectable number of long-term studies detect no significantly lower failure rates of ceramic [4] or composite [5] inlays compared to composite direct fillings. Another study detected an increased survival time of composite resin inlays but it was rated to not necessarily justify their bigger effort and price. [6]
Onlays
When decay or fracture incorporate areas of a tooth that make amalgam or composite restorations inadequate, such as cuspal fracture or remaining tooth structure that undermines perimeter walls of a tooth, an onlay might be indicated[7]. Similar to an inlay, an onlay is an indirect restoration which incorporates a cusp or cusps by covering or onlaying the missing cusps. All of the benefits of an inlay are present in the onlay restoration. The onlay allows for conservation of tooth structure when the only alternative is to totally eliminate cusps and perimeter walls for restoration with a crown. Just as inlays, onlays are fabricated outside of the mouth and are typically made out of gold or porcelain. Gold restorations have been around for many years and have an excellent track record. In recent years, newer types of porcelains have been developed that seem to rival the longevity of gold. If the onlay or inlay is made in a dental laboratory, a temporary is fabricated while the restoration is custom-made for the patient. A return visit is then required to fit the final prosthesis. Inlays and onlays may also be fabricated out of porcelain and delivered the same day utilizing techniques and technologies relating to CAD/CAM dentistry.[8][9]
A systemic review found that the most common cause of onlay failure is ceramic fracture, followed by ceramic de-bonding from the tooth structure, and the occurrence of secondary caries which is seen as a discolouration at the margins of the restoration. High failure rates were associated with teeth that had previous root canal treatment, and with patients who exhibit para-functional habits such as bruxism , or teeth clenching. [10]
Indications
Inlays/onlays are indicated when teeth are weakened and extensively restored. There are no obvious contrast between the two.
Inlays are usually indicated when there has been repeated breach in the integrity of a direct filling as metal inlays are more superior in strength.[11][12] It is also indicated when placement of direct restoration may be challenging to achieve satisfactory parameters (shape, margin, occlusion).[12] They are usually reserved for larger cavities as tooth conservation is paramount in current practice and small cavities can be restored with direct composites instead.
Onlays are indicated when there is a need to protect weakened tooth structure without additional removal of tooth tissue unlike a crown, eg restoring teeth after root canal treatment to give cuspal coverage. It can also be used if there is minimal contour of remaining coronal tooth tissue with little retention. [12]
Fabrication Methods
There are a few methods of fabricating inlays and onlays, depending on the restorative material used.
Indirect restorative technique
The first common step is always to take an impression of the tooth preparation – either by scanning it using an intraoral scanner or by taking a conventional impression using polyvinyl siloxane.[13]
| Type of Restorative Material | Examples of System Available on Market[15] | Fabrication Method |
|---|---|---|
| Feldspathic porcelain | Lost wax technique | |
| Leucite reinforced porcelain | IPS Empress 2 / IPS e.max by Ivoclar Vivadent |
|
| Alumina core porcelain[16] | InCeram by Vita Zahnfabrik- Germany | Slip-casting technique |
| Lithium disilicate porcelain | Duceram Plus by Dentsply Degussa |
|
The details of the fabrication methods are as follows:
- CAD-CAM
- Lost wax technique
Sometimes, inlay wax is packed into the tooth preparation in the mouth to adapt the shape of the cavity. This is known as the direct wax technique using type 2 inlay-type waxes.[17]
Inlay wax is chosen due to its brittleness – it breaks upon removal from undercut of a cavity, either on the die or in the mouth. In this case, this is a beneficial character as it helps us to identify the presence of an undercut which then can be removed.[17]
- Slip casting technique
This method is only applicable to sintered alumina core porcelain. Firstly, a sub-structure made of alumina powder and modelling fluid is built on the special die. The die is then sintered by firing with the sub-structure, causing the fluid to be absorbed by the die and the alumina powder become more tightly packed.[18]
Following sintering, the outer surface of the sub-structure is painted with lanthanum aluminosilicate glass powder. The sub-structure is porous and therefore allows infiltration of the glass powder when fired again.[19]
Further strengthening of the material can be done by applying zirconium oxide.[20]
Direct Restorative Technique[21]
By using this technique, an impression of the tooth preparation is not required. Instead, the tooth preparation is coated with a layer of separating material such as glycerin first. Then, a composite restoration is built up directly on the preparation, allowing it to take the shape of the cavity. The restoration is then light-cured in the tooth before being removed from the tooth to be further light-cured.
Prior to cementation of the restoration onto the prepared the tooth, the layer of separating materials needs to be removed to ensure effective bonding between the tooth and the restoration.
This technique is only applicable when composite is used as the restorative material. Inlays and onlays made from ceramic or metal alloy require laboratory work and therefore can only be fabricated using indirect restorative techniques as mentioned in the previous section.
Survival Rates
A study done by Rippe et al has shown that ceramic inlays produced by the different methods, via indirect restorative techniques aforementioned, have similar longevity.[22]
References
- ^ a b "Filling vs Inlay vs Onlay vs Crown: What's the difference and which is the right one for you?". Dr. Jennifer Dean at Rancho Santa Fe Cosmetic & Family Dentistry. Retrieved 2018-10-25.
- ^ a b c "Publications | Pierre Fauchard Academy". www.fauchard.org. Retrieved 2018-10-25.
- ^ Schneider et al.: Shrinkage Stresses Generated during Resin-Composite Applications: A Review; (2010); J Dent Biomech; vol. 1 no. 1 131630
doi:10.4061/2010/131630
- ^ Clinical evaluation of ceramic inlays compared to composite restorations.; (2009); RT Lange, P Pfeiffer; Oper Dent. May-Jun;34(3):263-72. doi:10.2341/08-95
- ^ Pallesen, U; Qvist, V. "Composite resin fillings and inlays. An 11-year evaluation. (2003)". Clin Oral Invest. 7: 71–79. doi:10.1007/s00784-003-0201-z.
- ^ Dijken, JWV Van (2000). "Direct resin composite inlays/onlays: an 11 year follow-up". J Dent. 28 (5): 299–306. doi:10.1016/s0300-5712(00)00010-5. PMID 10785294.
- ^ "Inlay-Onlay en composite". Le courrier du dentiste. November 2012. Retrieved February 2018.
{{cite web}}: Check date values in:|access-date=(help) - ^ Masek R, Tsotsos S (October 2002). "Ultimate accuracy with correlation". Int J Comput Dent. 5 (4): 295–303. PMID 12736941.
- ^ Masek R (January 2003). "Designing in 3D—a more visual approach to Cerec correlation". Int J Comput Dent. 6 (1): 75–82. PMID 12838591.
- ^ "Longevity of ceramic onlays: A systematic review". BDJ. 224 (10): 787–787. 2018-05-25. doi:10.1038/sj.bdj.2018.414. ISSN 0007-0610.
- ^ Shillingburg, H. T., Sather, D. A., Wilson, E. L., Cain, J. R., Mitchell, D. L., Blanco, L. J. and Kessler, J. C. (2012). Fundamentals of fixed prosthodontics. Quintessence Publishing. ISBN 9780867154757.
{{cite book}}: CS1 maint: multiple names: authors list (link) - ^ a b c Ricketts, D. and Bartlett, D. (2011). Advanced Operative Dentistry. Elsevier. ISBN 9780702045660.
{{cite book}}: CS1 maint: multiple names: authors list (link) - ^ Pivetta Rippe, Marília; Monaco, Carlo; Missau, Taiane; Wandscher, Vinícius Felipe; Volpe, Lucia; Scotti, Roberto; Bottino, Marco Antonio; Valandro, Luiz Felipe (2018-08). "Survival rate and load to failure of premolars restored with inlays: An evaluation of different inlay fabrication methods". The Journal of Prosthetic Dentistry. doi:10.1016/j.prosdent.2018.03.019. ISSN 0022-3913.
{{cite journal}}: Check date values in:|date=(help) - ^ Hopp, Christa D.; Land, Martin F. (2013). "Considerations for ceramic inlays in posterior teeth: a review". Clinical, Cosmetic and Investigational Dentistry. 5: 21–32. doi:10.2147/CCIDE.S42016. ISSN 1179-1357. PMC 3666490. PMID 23750101.
{{cite journal}}: CS1 maint: PMC format (link) CS1 maint: unflagged free DOI (link) - ^ Santos, MJ; Mondelli, RFL; Navarro, MF; Francischone, CE; Rubo, JH; Santos, GC (2013-01). "Clinical Evaluation of Ceramic Inlays and Onlays Fabricated With Two Systems: Five-Year Follow-Up". Operative Dentistry. 38 (1): 3–11. doi:10.2341/12-039-c. ISSN 0361-7734.
{{cite journal}}: Check date values in:|date=(help) - ^ Diego, Alexandra Almeida; Santos, Claudinei dos; Landim, Karine Tenório; Elias, Carlos Nelson (2007-3). "Characterization of ceramic powders used in the inCeram systems to fixed dental Prosthesis". Materials Research. 10 (1): 47–51. doi:10.1590/S1516-14392007000100011. ISSN 1516-1439.
{{cite journal}}: Check date values in:|date=(help) - ^ a b F.), McCabe, J. F. (John (2008). Applied dental materials. Walls, Angus. (9th ed. ed.). Oxford, UK: Blackwell Pub. ISBN 9781405139618. OCLC 180080871.
{{cite book}}:|edition=has extra text (help)CS1 maint: multiple names: authors list (link) - ^ Diego, Alexandra Almeida; Santos, Claudinei dos; Landim, Karine Tenório; Elias, Carlos Nelson (2007-3). "Characterization of ceramic powders used in the inCeram systems to fixed dental Prosthesis". Materials Research. 10 (1): 47–51. doi:10.1590/S1516-14392007000100011. ISSN 1516-1439.
{{cite journal}}: Check date values in:|date=(help) - ^ Christine Niekrash, Dalia Giedrimienė, Jurgina Sakalauskienė, Alvydas Gleiznys, Eglė Ivanauskienė, Gaivilė Pileičikienė, Aušra Baltrušaitytė, Jonas Junevičius (2015). COMPOSITE AND CERAMIC RESTORATIONS - Handbook for students of odontology. Lithuanian University of Health Sciences Medical Academy: Lithuanian University of Health Sciences, Medical Academy. ISBN 978-9955-15-394-8.
{{cite book}}: CS1 maint: multiple names: authors list (link) - ^ F.), McCabe, J. F. (John (2008). Applied dental materials. Walls, Angus. (9th ed. ed.). Oxford, UK: Blackwell Pub. ISBN 9781405139618. OCLC 180080871.
{{cite book}}:|edition=has extra text (help)CS1 maint: multiple names: authors list (link) - ^ Phillips' science of dental materials. Anusavice, Kenneth J., Phillips, Ralph W. (11th ed ed.). St. Louis, Mo.: Saunders. 2003. ISBN 9781437725490. OCLC 606993019.
{{cite book}}:|edition=has extra text (help)CS1 maint: others (link) - ^ Pivetta Rippe, Marília; Monaco, Carlo; Missau, Taiane; Wandscher, Vinícius Felipe; Volpe, Lucia; Scotti, Roberto; Bottino, Marco Antonio; Valandro, Luiz Felipe (August 2018). "Survival rate and load to failure of premolars restored with inlays: An evaluation of different inlay fabrication methods". The Journal of Prosthetic Dentistry. doi:10.1016/j.prosdent.2018.03.019. ISSN 0022-3913.
