1 Use with caution in some situations.

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1 Issue How to obtain optimum results with ceramic inlays. There is now a comprehensive range of reports on the clinical performance of ceramic inlays over a period of 8 to 15+ years. This has enabled a profile to be built up on the procedures to follow to obtain optimum clinical results. This article identifies 5 of the key aspects. Examples of ceramic inlays. 1 Use with caution in some situations. In non-vital molar teeth >> Left: Longerterm studies have found that the longevity of ceramic inlays is affected if they are used in rootfilled teeth. For reasons that are not completely clear, ceramic inlays have not performed well in non-vital molar teeth. An 18-year study found that placing ceramic inlays on these teeth greatly reduced the chances of survival.this was so even though no excessive wear was detected nor was there any 1 evidence of parafunctional habits. These observations regarding the effect of tooth vitality on longevity were confirmed in a recent 15-year study where a more extensive coverage was done with ceramic s. Restorations on non-vital teeth failed more frequently than 2 those on vital teeth. Ceramic inlays are highly dependent on the quality of the dentine bond for retention. It appears that there is less water in the dentine of non-vital teeth and this may affect the quality of the bond from dentine-bonding agents over 3 a period of time. In MOD cavities in vital molar teeth >> Left: Longerterm studies have found reduced longevity of ceramic inlays if they are used in MOD cavities in molar teeth. In contrast to the situation with premolar teeth, the of MOD cavities in molar teeth has been found not to give a > predictable result. A number of long-term studies confirm that involving two approximal s in molars reduces the chances of ceramic inlay 4-7 survival. The reasons for this are not clear. It remains to be established whether it may be related to the rigidity of ceramic inlays and a disparity between this and that of the adjacent tooth structure under long-term cyclical loading. Top: Example of a ceramic inlay where the cavity preparation, inlay milling and inlay cementation were all performed in one visit using the Cerec System (Sirona). Bottom: Example of a ceramic inlay made from lithium disilicate (IPS e.max Press - Ivoclar Vivadent). The cavity preparation was carried out at one visit, the inlay fabricated in a laboratory and the inlay cemented at a subsequent appointment. Ceramic materials have a high compressive strength but low tensile and flexural strengths and low fracture toughness.

2 How to obtain optimum results with ceramic inlays. (cont) 1 Site selection: Where to use with caution. (cont) In patients with bruxism or clenching >> Cavity preparation features. rounded line angles Left: The use of ceramic inlays is contra-indicated for patients with bruxism or clenching habits. The life span of ceramic inlays has been found to be greatly reduced in patients with bruxism or clenching. The untoward effects of these parafunctional habits was particularly noticed in male patients. 1, 4, 8 tapered approximal box 2 Use specific cavity-preparation features. Adequate occlusal depth >> sloped cavity walls There are a number of areas where a cavity preparation for a ceramic inlay differs from a traditional inlay preparation. Dental ceramic materials are brittle with a relatively high compressive strength but low tensile and flexural strengths and low fracture toughness. 2 Therefore ceramic inlays need to be of adequate thickness and be well supported 9 by the underlying tooth structure. It is generally accepted that to limit flexure under loading, ceramic inlays need to be around 2 mm in thickness. 9 In terms of cavity preparation, the occlusal depth should be in the order of 2 mm overall. Areas of lesser depth may act as sites for fracture development. slope of degrees 2 mm flat gingival floor Increased slope of cavity walls >> Traditionally the recommended slope of cavity walls for gold inlays has been about 5 to 7 degrees. However, for ceramic inlays it is recommended that this be increased to 10 to 20 degrees. 9 Unlike a gold inlay, a ceramic inlay is unable to elastically deform if there are discrepancies of fit or 3 if the fit is too tight when it is seated in a cavity preparation. 9 Therefore to minimise any problems at the try-in and cementation stages, the cavity walls are made to diverge more than they would in a preparation for a gold inlay. The walls of a preparation are sloped between 10 and 20 degrees. There should be a uniform cavity depth of 2 mm and a flat gingival floor finishing at right angles to the outer enamel. Rounded line angles >> Sharp internal line angles can give rise to significant stress concentrations in the remaining tooth structure. Therefore all internal line angles, including the axio-pulpal line angle, are rounded to limit potential 9 areas for stress concentration. The approximal box should be tapered and all line angles rounded, including the axio-pulpal line angle.

3 How to obtain optimum results with ceramic inlays. (cont) 3 Temporary stage: Watch for a complication. If using a resin-modified GIC base or a resin composite envelope >> Background: In situations where a ceramic inlay cavity is prepared at one visit and the inlay placed at another, it is necessary to use some form of in between. The use of cements or restorative materials containing eugenol is contraindicated. Eugenol suppresses the polymerisation of resins used in dentine-bonding agents and can adversely affect bond strength. Potential problem area: There are now a number of eugenol-free restorative materials that can be placed in a cavity and light cured. Example products include Luxatemp-Inlay (DMG), Fermit - N (Ivoclar Vivadent)) and DuoTEMP (Coltene Whaledent). Practitioners may not be aware that these materials contain a resin that can bond to the resin in light-cured materials, such as resin-modified GIC and resin composite. Resin-modified GIC is a commonly used base material and resin composite can be used to block > out undercuts and in the envelope technique. The consequences can be: Dislodgement of a resinmodified GIC base when the is removed. Temporary material bonding to resin composite that has been used to block out undercuts or in the envelope technique. Solution: To avoid the bonding to resincontaining materials, it has been suggested that a lubricant such as vaseline be used before placing the. However, at the cementing stage, complete removal of the smear layer left by the lubricant may prove difficult. A practical alternative would be to use a non-light curing restorative material product such as Cavit G (3M Espe). The material can be removed with a sharp probe. Potential problem with a resinmodified GIC base. light-cured resinmodified GIC base base removed with A light-cured restorative material may bond to a resin-modified GIC base and dislodge it when the is removed. Potential problems when undercuts blocked out or envelope technique used. undercut under wellsupported enamel undercut blocked out with resin composite or resinmodified GIC may bond to a layer of resin composite covering internal s of cavity may bond to If undercuts have been blocked out with resin composite or resin-modified GIC, the resin used in some restorative materials can bond to these materials. This can make the quite difficult to remove at a later stage. In the envelope technique resin composite is used to fill undercuts and cover all the internal dentine s of a cavity plus the entire gingival floor. Temporary restorative materials containing resin can bond to these s.

4 How to obtain optimum results with ceramic inlays. (cont) 4 Cementation: Maximise use of enamel areas. Separate etching of enamel margins >> With cavity preparations for ceramic inlays having reduced resistance and retention form, inlay retention is highly dependent on the quality of the bond between ceramic and tooth structure. The most reliable substrate to bond to is enamel and for this reason, all available enamel margins should be utilised. If using a 3-step resin cement, such as one of the products listed below, then a separate enameletching step is not required. An etching step with phosphoric acid is already an integral part of the > technique. However, if using one of the self-etching or self-adhesive types listed below, then selective etching of the enamel margins with phosphoric acid is indicated. 10 It is desirable to restrict the etchant to enamel because the over-etching of dentine can lead to reduced bond strengths. Selective etching of the enamel margins can provide enhanced retention if a self-etching or a selfadhesive resin cement is being used (see below). Selective etching of the enamel margins can help the bonding performance of materials like Panavia F 2.0 (far left) and RelyX Unicem (left). Resin cements where selective enamel etching is not required >> Variolink ll Ivoclar RelyX Arc 3M Espe Duolink Dual cement Calibra Comspan Ivoclar Dentsply Dentsply TwinLook NX3 Nexus C&B Cement Heraeus Kulzer Kerr Duo Cement Plus PermaFlo DC Coltene Whaledent Ultradent (Resin cements in the above category utilise three steps; (i) etching of the tooth with phosphoric acid (ii) application of a dentine-bonding agent and (iii) placement of the resin cement). Resin cements where selective enamel etching is indicated >> Self-etch type: Panavia F 2.0 Clearfil Esthetic and DC Bond Kuraray Kuraray (Resin cements of the self-etch type, shown on the left, utilise two steps; (i) application of a self-etching primer and (ii) placement of the resin cement). Self-adhesive type: RelyX Unicem MaxCem Elite SmartCem 2 BisCem 3M Espe Kerr Dental Dentsply Caulk G-Cem icem Set MonoCem GC Corp Heraeus Kulzer SDI Shofu (Self-adhesive resin cements, shown on the left, are one-step products where all the required constituents are combined).

5 How to obtain optimum results with ceramic inlays. (cont) 5 Finishing: Avoid leaving potential fracture sites. Precautions when adjusting ceramic s >> If adjustments to an occlusal are required the complete removal of scratches and roughness is essential. If any such defects are left they can act as sites for crack propagation and bulk fracture. 1, 11 With ceramic inlays particular care is needed to ensure that the load on functional stops is equally shared between natural tooth structure and the occlusal of the inlay. A high functional stop on the inlay can lead to excessive forces during cyclical loading and increases the potential for bulk fracture. Making adjustments: If the inlay has not been prepared chairside, and if marked grinding has been carried out, the best > option is to return the inlay to the laboratory for re-polishing. For minor adjustments a standard sequence is as follows: 1. Use a fine grit (40 µm) diamond bur, under a copious water spray, for minor occlusal adjustments. 2. Follow up with diamondimpregnated silicon points, medium, fine and superfine (example product - Perla-Dia P5 Bullet Contra-angle kit CA8 [HP]). 3. Use a diamond polishing paste on a felt brush (an example kit is Diamond Twist SCL & SCO - Premier Dental). Aust. distributors: Perla-Dia P5 Bullet Contra-angle Kit - Argibond Tel: Diamond Twist SCL & SCO ( Premier Dental) from Gunz Dental. crack propagation unremoved scratch An unremoved scratch on a ceramic inlay (top) can act as a site for crack propagation (below). References: 1. Krämer N, Frankenberger R. Clinical performance of bonded leucite-reinforced glass ceramic inlays and onlays after eight years. Dent Mater. 2005;21: van Dijken JW, Hasselrot L. A prospective 15-year evaluation of extensive dentin-enamel-bonded pressed ceramic coverages. Dent Mater. 2010;26: Van Nieuwenhuysen JP, D'Hoore W, Carvalho J, Qvist V. Long-term evaluation of extensive s in permanent teeth. J Dent. 2003;31: Otto T, De Nisco S.Computer-aided direct ceramic s: a 10-year prospective clinical study of Cerec CAD/CAM inlays and onlays. Int J Prosthodont. 2002;15: Thordrup M, Isidor F, Hörsted-Bindslev P. A prospective clinical study of indirect and direct composite and ceramic inlays: ten-year results. Quintessence Int. 2006;37: Reiss B. Clinical results of Cerec inlays in a dental practice over a period of 18 years. Int J Comput Dent. 2006;9: Van Nieuwenhuysen JP, D'Hoore W, Carvalho J, Qvist V. Long-term evaluation of extensive s in permanent teeth. J Dent. 2003;31: Otto T, Schneider D. Long-term clinical results of chairside Cerec CAD/CAM inlays and onlays: a case series.int J Prosthodont. 2008;21: Thompson MC, Thompson KM, Swain M. The all-ceramic, inlay supported fixed partial denture. Part 1. Ceramic inlay preparation design: a literature review. Aust Dent J. 2010;55: De Munck J, Vargas M, Van Landuyt K, Hikita K, Lambrechts P, Van Meerbeek B. Bonding of an auto-adhesive luting material to enamel and dentin. Dent Mater. 2004;20: Boushell LW, Ritter AV. Ceramic inlays: a case presentation and lessons learned from the literature. J Esthet Restor Dent. 2009;21:77-87.