Indirect inlays and onlays continue to be the most underdiagnosed and placed restorations in dentistry. An American Dental Association survey found that in 2005 to 2006, the average general practitioner placed 256 crowns to just 10 inlay or onlay restorations. Further, the average general practitioner placed 197 direct restorations that were 3+ surfaces.1 Most clinicians either fail to recognize when these restorations should be used, or are unfamiliar with the temporization process involved. All dental schools teach proper techniques for full-coverage crowns, but most fail to teach the techniques for inlays and onlays. This article will detail two examples of temporization techniques which can be used in general practice.
According to Jablonski’s Dictionary of Dentistry an inlay is a restoration made outside of the tooth to correspond with the form of the prepared cavity and then cemented into tooth.2 Sturdevant and colleagues clearly defined the onlay as “the treatment of choice for the restoration of a tooth that has been greatly weakened by caries or large, failing restorations with the facial and/or lingual tooth surfaces that have been relatively unaffected by disease or injury.”3 An onlay is a restoration that onlays or overlays cusps of the tooth, thereby lending strength to the restored tooth.2 Jackson defined inlays as the restoration type which “should be considered for areas of high functional stress so that the increased physical properties of the indirect material can be used to increase the longevity of the restoration.”4Indirect restorations also offer more control over proper contour, contact, and occlusion.5 Further, inlay and onlay restorations are indicated for teeth strongly predisposed to fracture, such as teeth that have the presence of a fracture line in the enamel or that is the proportional size of the pre-existing restoration.6
Indirect Temporization Technique
Indirect temporization is best utilized for quadrant dentistry of multiple units, or single large onlay is to be temporized. When preparing single or multiple units for inlay or onlay restorations (Figure 1), start by making a preoperative impression of the teeth to be treated with a triple or quadrant tray (Figure 2). After completion, the teeth can be prepared to the appropriate guidelines for the chosen final restoration material.
Figure 1 - Preoperative view of existing restorations on teeth Nos. 12 and 13, which will be prepared for a full-coverage crown and an inlay restoration, respectively.
Figure 2 - Triple tray preoperative impression of maxillary left quadrant.
In the author’s opinion, the guidelines for porcelain or laboratory-processed resin onlays should be: a minimum reduction of 1.5 mm in the proximal boxes, rounded internal line angles, butt-joint margins, and a minimum cuspal reduction of 2 mm. The proximal and occlusal walls should have a 6° to 8° taper. All undercuts should be removed. The same preparation guidelines should be used for inlays, except there should be no cuspal involvement.
After the units are prepared (Figure 3), indirect temporization can be accomplished with the use of the preoperative impression and a bis-acryl temporization material. Inject the bis-acrylic material into the preoperative impression (Figure 4) and place it into the patient’s mouth to set for 1 to 2 minutes. Then, remove the temporary from the impression (Figure 5), finish the temporary, check occlusion, polish the temporary, and cement it in place using a noneugenol temporary cement (Figure 6). For multiple units, it may be helpful to separate the temporaries into individual units, depending on the path of draw. This typically will offer the best coverage and protection of the preparations until the final restorations are seated. At the time the final restorations are ready to be placed, the bis-acrylic provisional can be removed with a hemostat or crown remover, as would be performed with a conventional full-coverage temporary crown.
Figure 3 - Teeth prepared for temporization.
Figure 4 - Bis-acrylic material in the preoperative impression.
Figure 5 - The temporaries after removal from the mouth.
Figure 6 - The temporaries after removal from the mouth.
Direct Temporization Technique
Direct temporization is recommended for inlays, or when the decision to restore a tooth with an inlay or onlay is made after initial preparation has occurred. This technique can be utilized for an onlay with a single cusp coverage, however; once a greater surface area is included in the preparation, the indirect technique works best because a temporary cement can be used. In this scenario, the tooth may have been prepared without a preliminary impression; however, for inlays, no preliminary impression is necessary with this technique (Figure 7).
After preparation and impression-making, wedges should be placed interproximally (Figure 8). In the author’s experience, Systemp.inlay/Systemp.onlay and Fermit-N (Ivoclar Vivadent Inc, Amherst, NY, www.ivoclarvivadent.us.com) work well for direct inlay temporization.
Place a desensitizing agent throughout the preparation, and air-dry thoroughly. Then, place the inlay temporary material of choice directly into the preparation. After initial condensing is completed, ask the patient to bite down and occlude into the uncured temporary material. Lubrication of the opposing tooth is helpful to prevent removal of the uncured material.
After initial sculpting (Figure 9), light-cure the temporary for 20 to 30 seconds. When fully set, adjust occlusal and proximal contacts with fluted carbide burs. Final polish can be accomplished with the traditional cones and cups used for direct composite polishing (Figure 10). At the final seating appointment, most temporization materials easily can be removed in a single piece with an explorer or spoon excavator.
Figure 7 - Preoperative view of the existing amalgam restoration on tooth No. 13, which will be prepared for an inlay restoration.
Figure 8 - Wedges placed around prepared tooth.
Figure 9 - Initial contour of direct temporary restoration on tooth No. 13.
Figure 10 - Direct temporary inlay after final finishing and polishing.
Conclusion
Inlay and onlay restorations can be a beneficial option to any restorative practice. Patients are better served with stronger restorations without the worry of the polymerization problems often seen with direct resin, the inconvenience of improper anatomy and contours often seen with direct restorations, or the unsightly appearance of amalgam. Dentists benefit by providing their patients high-quality restorations while increasing office production.
Figure 11 - Patient’s preoperative quadrant dentistry.
Figure 12 - Post-operative definitive restorations.
References
- American Dental Association Survey Center: 2005-2006 Survey of Dental Services Rendered
- Jablonski S. Jablonski’s Dictionary of Dentistry>. Malabar, Fla: Krieger Publishing Co; 1992.
- Sturdevant CM, Roberson TM, Heymann HO, et al. The Art and Science of Operative Dentistry. 3rd ed. St. Louis, Mo: Mosby; 1994.
- Jackson RD. Esthetic inlays and onlays: the coming of age. Autum Ceramic News. 2003;7:1-3.
- Radz G. Conservative treatment planning in the posterior quadrant: the use of traditional and modern restorative materials. Pract Proced Aesthet Dent. 2004;16:17-24.
- Bader JD, Shugars DA, Martin JA. Risk indicators for posterior tooth fracture. J Am Dent Assoc. 2004;135:883-893.
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