From Full Coverage to Partial Coverage… Tooth INTEGRITY Preserved!
Masar Al-Sultani - BDS
Babylon University, College of Dentistry | Cosmetic Dentist at Moon Dental Clinics | Iraq - email@example.com
Masar Al-Sultani. From Full Coverage to Partial Coverage… Tooth INTEGRITY Preserved! Smile Dental Journal. 2022;17(2):20-2.
Preserving tooth structure has been for long the concern of most dentists; a full coverage crown is often needed in severely destructed teeth which in fact lead to further destruction of tooth structure. With the development of minimal invasive dentistry and the urge to preserve rather than to consume, along with the development of new bonding systems, mechanically retained full coverage crowns can be replaced with partial coverage onlays and overlays which depends completely on adhesion. In this article we have a case report about both onlay and overlay.
Partial coverage restorations, Adhesion, Overlay, Immediate dentin sealing, biomimetic dentistry.
Partial coverage restorations are a conservative treatment that minimizes the amount of tooth structure removed and defining the margin of the restoration at a supra-gingival level.
Such partial indirect restorations have become popular for reconstruction of large defects, allowing the conservation of the remnant intact tooth structure.1
A partial coverage restoration is very different from a full coverage restoration. For the cavity design, there is no exact preparation pattern in partial coverage restorations. The cavity design follows the defective area margins and the outline of any old restorations. The preparation must be carefully designed to cover the weak structure and with no undercut formation. The partial coverage restoration is fabricated to replace the destructed tooth structure so that the natural tooth structure is preserved. A full coverage crown, however, requires the core to be built up with restorative material to reconstruct the features of the tooth prior to removal of the circumferential tooth structure. The surrounding intact tooth structure is then removed to leave the restorative materials as the core to maintain the crown.2
Female patient 45 years old needs full rehabilitation as known from initial clinical examination, first the patient was sent for an OPG to minimize radiation exposure then treatment plan was made.
Figure 1 shows the initial situation; upper right first molar was heavily decayed with pulp involvement yet vital, upper second premolar has defective amalgam restoration, recurrent caries and a previous endodontic treatment that is under by 5mm. Upper first premolar has distal cavitation with pulp involvement.
All teeth were asymptomatic.
Figure 2 shows the upper second premolar after amalgam removal and caries excavation, immediate pre-endodontic dentin sealing (IPDS) and deep margin elevation (DME) was done (IPDS and DME was also done for upper first molar after access opening) then the old gutta-percha was removed completely.
IPDS should always be performed before RCT to prevent collagen damage caused by endodontic irrigants such as NAOCL.3
Figure 3; after caries removal, IPDS and RCT were done for upper first premolar which is then restored with direct composite restoration.
Obturation & Preparation
In figure 4, both upper second premolar and first molar were obturated and prepared for indirect restoration.
During the preparation all unsupported enamel should be removed, all cusps less than 3mm in endodonticaly treated teeth or less than 1.5mm in vital teeth measured from the cusp base should be reduced to ensure 1.5 overlap of ceramics (done for upper second premolar), proximal contact should be opened to allow for proper contour, undercuts can be removed “additively” by the application of IDS and composite resin.3
After preparation, sandblast was done for both, the pulp chamber then sealed with GIC to protect the sealer from the solvent in the adhesive primer,3 IDS performed and the teeth are now ready for impressions!
Double retraction cord size (00) was placed first to push the gingiva vertically, size (2) was placed after to push the gingiva in horizontal direction.
Two step impression were made using addition silicon, the first step is to insert a tray with putty body and a sheet of plastic wrap, with both retraction cords in place, after setting second step begins with the removal of the plastic wrap and light body injection in the tray at the same time one retraction cord is removed and the light body injected all over the teeth and we re- insert the impression. (Fig. 5)
Liquid dam was used to prevent proximal space closure and super-eruption of opposing teeth until cementation appointment. (Fig. 6)
Lithium dicilicate overlay for the premolar and Lithium dicilicate onlay for the molar.
After try-in, surface treatment was done to proceed with the cementation, as follows:
Etching with 5% HF acid for 20 seconds, rinsing and immersion in ultrasonic bath for 2 to 3 minutes (in distilled water or 90% ethanol), drying and application of silane solution (1-2 coats), air-drying and finally wetting with adhesive resin but without curing.3
Note that after drying the silane the surface shouldn’t look shiny, if it is shiny it means excessive material is used.3
Figure 8 shows absolute isolation with rubber dam for cementation.
Biobase was sandblasted with 50 microns aluminum oxide particles, etched and rinsed then adhesive resin applied (without curing, if cured it will occupy an additional space that may interfere with the seating of the prosthesis) heated composite at 68°C/155°F for 10 minutes is used for cementation, heating composite resin to reduce its viscosity and improve flow when seating porcelain restorations will increase the conversion of the monomer and reduce the required light exposure for photopolymerization. It will also improve the resin’s mechanical properties and wear resistance another advantage is that it demonstrates better adhesion to tooth substrate, better color stability and it is easier to handle because the operator has more time for excess removal prior to polymerization.4
After seating, all excess composite were removed using dental probe, dental floss and micro-brush.
Finally all surfaces were light cured. After high spots check, finishing and polishing. (Fig. 9)
It is the era of partial coverage restorations! No more posts, cores and crowns, it’s all about simplicity and preservation thanks to adhesion.
- Donovan, T.E. and Chee, Conservative Indirect Restorations for Posterior Teeth. Cast Versus Bonded Ceramic. Dental Clinics of North America. W.W. 1993;37:433-43.
- Wayakanon, K. Partially Coverage Restoration: An Esthetically Conservative Treatment for a Complex Cavity Restoration. Open Journal of Stomatology. 2017;7:234-41. doi: 10.4236/ojst.2017.74017.
- Pascal Magne, Urs C. Belser. Biomimetic Restorative Dentistry. 2nd Quintessence publishing USA. 2021: PP 409, 416, 396, 398.
- Timothy A. Hess, DDS, MAGD and Hai Zhang. Cementing Porcelain Restorations With a Warmed Composite Resin Containing a Rheological Modifier. Divisions in Dentistry. 2017;3(9):28–31.