Clinic meets research Vol.3
Cementation is a crucial step in the process of ensuring the retention, marginal seal and durability of indirect restorations. Cementing procedures are either adhesive or non-adhesive. Adhesive cementation involves the use of an agent to promote bonding of the restorative material to the substrate; it is a combination of adhesive chemical bonding and micromechanical interlocking. Non-adhesive cementation involves the use of a luting agent to fill the space between the restoration and the natural tooth and relies solely on micro-mechanical retention. The clinician must have a good understanding of metal alloys or ceramic type to determinate whether a restoration should be cemented adhesively or non-adhesively. Choosing and applying the appropriate surface treatment and cementation procedure will contribute to long-lasting restorations.
BONDING PROCEDURES IN INDIRECT POSTERIORS
CEMENTATION OF METAL RESTORATIONS
The cementation of metal or metal-ceramic restorations can be performed with conventional cements (zinc phosphate, glass ionomers, resin-modified glass ionomer) or with a chemical polymerization resin cement. In using chemical polymerization composite cements, base-metal alloys can increase adhesive bond to metal and metal-ceramic restorations due to the formation of a oxides layer capable of reacting with cement acid groups (1-2). Silanization of surfaces of silicate metal (Rocatec, 3M ESPE, St. Paul, Minnesota, USA; and Silicoater, Heraeus Kulzer, Hanau, Germany) can further improve the micromechanics interconnection and chemical covalent bonds (3). The adhesion that is reached is a micro-mechanical type and some surface treatment is generally required to increase the adhesive bond. However, the noble alloys offer a lower adhesion capacity compared to other materials, such as vile alloys.
CEMENTATION OF GLASS CERAMIC RESTORATION
This ceramic is highly esthetic, biocompatible and resistant to abrasion and compressive forces. It must be cemented to the prepared tooth adhesively to increase the restoration’s resistance to fracture (4). Non-adhesive cementation is not indicated for feldspathic ceramic (5). The clinician must condition the glass feldspathic ceramics before performing adhesive cementation. The clinician etches the ceramics’ internal surface with a solution of hydrofluoric acid (HF) 5% for approximately two minutes (6), to increase surface area, micromechanical retention and to clean surface for adhesive cementation. Then the surface must be silanized (5-6). Adhesive cementation to enamel or dentine requires the use of an adhesive system, followed by application of a resin cement (7). Adhesive systems can be either self-etching or total etching (8). Resin cements can be cured via light, chemicals or a dual process combining the two. Light-polymerized resins are recommended when the ceramic is thin and fairy translucent (9). Dual-polymerized resin cements are indicated when the ceramic is too thick or too opaque to allow the light transmission (5).
CEMENTATION OF ALUMINUM OXIDE CERAMICS
Adhesives protocols applied with success to the silica-based ceramics cannot be used for the aluminum oxide ceramics, because the etching with HF acid does not appear to increase the retention of resin cements (10). These ceramics can be cemented conventionally rather than adhesively. Long-term adhesion studies recommend blasting (with particles of Al2O3 from 30-50 µm at 2,8-3 atm) to roughen the surface for micromechanics adhesion (11-12). Coating the ceramic with tribochemical silica and air abrading of internal surface, followed by application of 10-methacryloyloxydecyl dihydrogen phosphate before using resin cement (chemical or dual cured resin cement ), improve the bond to this type of ceramic (13-14).
CEMENTATION OF ZIRCONIA CERAMICS
Zirconium oxide ceramics are characterized by the absence of glass in their composition. These ceramics possess high toughness and strength. Polycrystalline ceramics most often are cemented conventionally but can benefit from adhesive cementation. The use of low-pressure air abrasion with aluminum oxide particles or tribochemical silica application followed by application of an adhesion-promoting agent increase the bond-strength of resin cements (chemical or dual cured resin cement)(15).
It is imperative that the clinician achieve affective isolation to keep the field free of saliva and other contaminants when using adhesive cements (16). Field isolation in not required in the case of zinc-phosphate and glass-ionomer cementation, but it’s necessary the fluid and saliva control.
CEMENTATION OF COMPOSITES
The bond between composite restoration and resin cements is very high and allows to have good levels of adhesion. So we can reach a very good adhesion even with indirect restorations. To have it one of the most effective protocols is that one that provides sandblasting the inner surface of the restoration with aluminum oxide for about 10 seconds, silanization (possibly activation with hot air or in special ovens of the silane), drying , then the application of a layer of bonding resin and at the end the luting procedures with a resin material that could be a dual composite cement or composite photo – polymerizable (generally pre-heated in a special oven)(17-18).
New rubber dam isolation.
In a different clinical case the same procedures, I.D.S. and build up.
Sometimes we can perform posteriors in semi direct ways.
With indirects, in some cases we can use new flowable composites which are filled at 69-70% in weight, for bonding procedures, this can be useful to avoid the usage of special ovens to heat the composite( which is still the gold standard in bonding composite indirect restorations).
Composite overlays are always bonded under rubber dam. We can use transparent matrices instead of PTFE to control the excess.
Eventually there are situations in which bone resection (osteotomy and osteoplasty) is necessary in order to achieve a proper marginal seal, bringing the cervical margins at the right distance from the alveolar bone crest (3 mm, minimum 2 mm). We have to replace old crowns with new ones.
After sandblasting with aluminum oxide the inner surface of the restoration and etching it with 5% hydrofluoric acid for 20 seconds, the acid is rinsed and the overlays are put in alcool at 96% for 5 minutes to remove the precipitates. Then the silane is applied and the bonding too into the inner surface of the restorations. We bond the restorations and remove the excess.
We have to use dual cements when the restoration is not easily penetrable by the polymerization light. Among the dual cements those who do not self-polymerize in less than 6 minutes are preferred. This in order to reduce any problems caused by composite shrinkage.
We can use light-cured composites when the indirect restoration is easily crossable by the polymerization light and it is of adequate thickness (over 7-800 micron).
Finally we can use flowable composites when the restoration is easily crossable by the polymerization light but is very thin (less than 7-800 micron) (19-20-21).
1. Diaz-Arnold A, Keller JC, Wightman JP, Williams VD. Bond strength and surface characterization of Ni-Cr-Be alloy. Dent Mater 1996;12:58-63.
2. Almilhatti HJ, Giampaolo ET, Vergani CE, Machado AL, Pavarina AC, Betiol EA. Adhesive bonding of resin composite to varius Ni-Cr alloy surfaces using different metal conditioners and a surface modification system. J Prosthodont 2009;18:663-9.
3. Petrie CS, Eick JD, Williams K, Spencer P. A comparision of 3 alloy surface treatments for resin-bonded prostheses. J Prosthodont 2001;10:217-23.
4. Zidan O, Ferguson GC. The retention of complete crowns prepared with three different tapers and luted with four different cements. J Prosthet Dent 2003;89:565-71.
5. Blatz MB, Sadan A, Kern M. Resin-ceramic bonding: a review of literature. J Prosthet Dent 2003;89:268-74.
6. Blatz MB, Sadan A, Maltezos C, Blatz U,Mercante D, Burgess JO. In vitro durability of the resin bond to feldspathic ceramics. Am J Dent 2004;17:169-72.
7. Pospiech P. All-ceramic crowns: bonding or cementing? Clin Oral Investig 2002;6:189-97.
8. Perdigăo J. Dentin bonding variables related to the clinical situation and the substrate treatment. Dent Mater 2010;26:24-37.
9. Tripodakis AP, Kaitsas V, Putignano A, Eliades G, Gracis S, Blatz M. Proceedings of the 2011 Autumn Meeting of the EAED (Active Members’ Meeting)- Versailles, October 20-22nd, 2011. Eur J Esthet Dent 2012;7:186-241.
10. Al-Wahadni Am, Hussey DL, Grey N, Hatamieh MM. Fracture resistance of aluminium oxide and lithium disilicate-based crowns using different luting cements: an in vitro study. J Contemp Dent Prac 2009;73:240-9.
11. Blatz MB, Sadan A, Arch G, Lang B. In vitro evaluation of long-term bonding of Procera AllCeram alumina restorations with modified resin luting agent. J Prosthet Dent 2003;89:381-7.
12. Blatz MB, Oppes S, Chiche G, Holst S, Sadan A. Influence of cementation technique on fracture strength and leakage of alumina all-ceramic crowns after cyclic loading. Quintessence Int 2008;39:23-32.
13. Kern M, Thompson VP. Bonding to glass infilterd alumina ceramic: adhesive methods and their durability. J Prosthet Dent 1995;73:240-9
14. Valandro LF, Ozcan M, Bottino MC,Bottino MA, Scotti R, Bona AD. Bond strength of a resin cement to high-alumina and zirconia-reinforced ceramics: the effect of surface conditioning. J Adhes Dent 2006;8:175-81.
15. Lin J, Shinya A, Gomi H, Shinya A. Effect of self-adhesive resin cement and tribochemical treatment on bond strength to zirconia. Int J Oral Sci 2010;2:28-34.
16. Liebenberg WH. General field isolation and the cemenation of indirect restorations: Part I. J Dent Assoc S Afr 1994;49:349-53.
17.Valandro LF, Pelogia F, Galhano G, Bottino MA, Mallmann A. Surface conditioning of a composite used for inlay/onlay restorations: effect on muTBS to resin cement. J Adhes Dent. 2007 Dec;9(6): 495-8
18. D’Arcangelo C, Vanini L. Effect of three surface treatments on the adhesive properties of indirect composite restorations. J Adhes Dent. 2007 Jun;9(3):319-26.
19. Magne P. Composite resins and bonded porcelain: the postamalgam era? J Calif Dent Assoc. 2006 Feb; 34(2): 135-47.
20. Devoto W. Direct and Indirect Restorations in the Anterior Area: A Comparison Between the Procedures. QDT 2003: 127-138.
21. Magne P, Belser U. Bonded porcelain restorations. Quintessence Books,2002.