Jonathan C. Meiers

Effect of Fatigue Testing on Core Integrity and Post Microleakage of Teeth Restored with Different Post Systems

The purpose of this study was to evaluate a new nondestructive test system, which could test concurrently fatigue and microleakage. Fifty, single-rooted teeth were restored with one of the following posts systems and a composite core: titanium ParaPost cemented with zinc phosphate cement; CosmoPost; C-Post; Esthetic C-Post; and FibreKor post, all cemented with resin cement. Samples were embedded and placed in a positioning jig. They were impacted at 45 degrees to the long axis of the tooth with a force of 55 N at a frequency of 3 Hz for a total of 100,000 impacts. After 60,000 impacts, samples were thermocycled. Core integrity and post microleakage were evaluated periodically throughout the 100,000 impacts. Samples showed no detectable displacement of any of the cores, but the metallic group showed a statistically significant increase in microleakage (p < 0.05) at the conclusion of the study compared with the nonmetallic groups.

Seating accuracy and fracture strength of vented and nonvented ceramic crowns luted with three cements

Methods to facilitate the seating of artificial crowns can improve the gingival margins and ensure longevity. This study examined the effects of venting and different luting agents on the seating accuracy and compressive strength of Dicor ceramic crowns. Vented and unaltered anterior restorations were tested using zinc phosphate cement (ZnPO4), glass ionomer, and composite resin cement. Rexillium metal dies of a tooth preparation of a maxillary canine were provided and standardized crowns were fabricated. The artificial crowns were evaluated for adaptation of the finish line before and after cementation, then were compressively loaded to failure. Under the conditions of this study, neither the design of the artificial crown nor the luting agent had a significant effect on the compressive strength. Composite resinous cement appeared to enhance seating of the crown, whereas ZnPO4 cement inhibited seating.

Measurement of hydrostatic pressures during simulated post cementation

Tooth sensitivity and fracture after cementation of posts for endodontically treated teeth have been a problem. This investigation developed an in vitro method of measuring intraradicular hydrostatic pressures created during simulated post cementation. The testing apparatus consisted of a pressure transducer and brush recorder connected to precision milled post spaces in a Plexiglas block. Cast post and cores were fabricated and cemented with three different luting agents: resinous cement, glass ionomer cement, and zinc phosphate cement. Mean hydrostatic pressures (psi) recorded during post cementation were zinc phosphate cement, 22.67; resinous cement, 19.77; and glass ionomer cement, 17.66. Zinc phosphate cement created substantially greater hydrostatic pressures than either the resinous or glass ionomer cements. This in vitro system was capable of discriminating intraradicular hydrostatic pressures among different classes of luting agents.

Chairside Fabricated Fiber-reinforced Fixed Partial Denture

In this issue of the Journal, the case report by Garoushi et al illustrates an exciting technique for fixed tooth replacement that can be done chairside using a new class of dental material, fiber-reinforced composite. This approach provides the patient with a cost effective treatment alternative that a clinician can choose to augment the traditional fixed prosthodontic approaches of porcelain fused to metal or all ceramic fixed partial dentures. The technique utilizes skills and materials most clinicians are familiar with – resin composite restorative materials and acid etch techniques. The beauty of this approach is the minimal to no abutment tooth loss in the placement of the bridge. This also allows the patient to consider other treatment options in the future -such as an implant. The success of this approach relies on the ability of the clinician to properly construct the framework for the bridge using strips of fiber-reinforced composite. The manipulation of the FRC material and the framework design are variables that must be correctly done to provide the basis for a successful chairside bridge. These skills need to be mastered by the clinician and once these skills are mastered, this approach has the potential to provide the patient with long term results. Our FRC research group at the University of Connecticut School of Dental Medicine has been placing chairside FRC bridges for about nine years with great success. We have developed a technique that uses a pre-fabricated FRC framework that eliminates the need for the clinician to piece together a framework before developing the pontic tooth [1–8]. We have applied this approach for all areas of the mouth, incisor, canine, premolar and molar. The problems we have seen with this technique usually revolve around the particulate resin composite used for fabricating the pontic shape. These are primarily are in the area of cohesive bulk fracture of part of the pontic or lust of luster and high gloss of the surface. The strength of the FRC attachment to the abutment teeth and the framework itself is rarely where these bridges develop problems. As improvements in particulate resin composite technology develop, this technique has the potential for even more impressive results. Clinicians should consider this as one of their treatment alternatives when considering fixed tooth replacement.