16. Lovdahl PE, Nicholls JI. Pin retained amalgam cores vs. cast-gold dowel-cores.J PROSTHETDENT1977;38:507-14.
11. Standlee JP, Caputo AA, Collard E, Pollack E. Analysis of stress distribution by endodontic posts. Oral Surg Oral Med Oral Pathol 1972;33:953-60. 12. Davy DT, Dilley GL, Krejci RF. Determination of stress patterns in root-filled teeth incorporating various dowel designs. 3 Dent Res 1981;60:1301-10. 13. Black GV. Descriptive anatomy of the human teeth. Philadelphia: Willmington Dental Manufacturing Co., 1890:16-21. 14. Steiner CC. The use of Cephalometrics as an aid to planning and assessing orthodontic treatment. Am J Orthod 1960;46:721-35. 15. Caputo AA, Standlee JP. Pins and posts: why, when, and how. Dent Clin North Am 1976;20:299-311.
Cement luting platinum foil J. G. Wall,
thickness MS,a M. H. Reisbick,
The Ohio State University
College of Dentistry,
Contributing author J. M. S. Clancy, DDS, MS, Assistant Professor, The University of Iowa, College of Dentistry, Iowa City, Iowa
beneath DMD, Columbus,
DR.JEFFREY SRYTHER COLLEGEOFDENTISTRY UNIVERSITYOFIOWA IOWACITY, IA 52242
MS,b and K. G. Espeleta,
Porcelain laminate veneers were made using a platinum foil matrix and were subsequently cemented to mandibular anterior Cymel teeth. Cement film thickness was measured in six predetermined locations. Repeated measures analysis of variance and single degree of freedom contrasts delineated a significant difference between marginal openings at the incisal edge where foil is folded and in four of the other vertical areas (132 versus 74.1 ym). Marginal cement film thickness of veneers made on platinum foil is less than that reported for veneers made on a refractory investment. (J PROSTHET DENT 1992;68:448-50.)
he marginal integrity of complete porcelain restorations, such as the inlay or crown, has been questioned because of unavoidable errors that result from porcelain firing shrinkage.l The benchmark for this statement is the fact that cement film thickness is frequently evaluated by American Dental Association (ADA) specification standards that suggest that an acceptable film thickness for precision restorations is 50.025 mm.2 Accordingly, porcelain laminate veneers are often considered to have relatively large marginal openings-a concern of most clinicians. Sorensen et a1.3 compared marginal openings between veneers made on platinum foils and those made on refractory casts and found that those made on foil were significantly smaller. Since both fabrication methods are popular and useful, the one that minimizes marginal openings (all else being equal) would be the method of choice. The purpose of this investigation was to measure the
Presented at the Carl 0. Boucher Prosthodontic Conference. aAssistant Professor, Section of Restorative and Prosthetic Dentistry. bprofessor and Chairperson, Section of Restorative and Prosthetic Dentistry. CPredoctoral student. 10/l/39133
luting space under porcelain laminate veneers that were fabricated on platinum foils and that were cemented to typical tooth preparations on Cymel mandibular incisors (Columbia Dentoform Corp., Long Island City, N.Y.). Of special interest were the marginal gaps where the foils had more than one thickness as a result of conventional folds (tinners joints).
Nine mandibular central incisor teeth were identically prepared with a pantographic milling device to receive porcelain laminate veneer restorations made from a highleucite porcelain (Optec VP, Jeneric Gold Co., Wallingford, Conn.). Tooth undercuts were blocked out with modeling plastic before adapting platinum foil (0.001 inch thick). Complete tooth coverage with platinum foil produced more predictably visual marginal fits than mere facial coverage. Proximal foil joints could be kept lingual to the margins; however, there was always a double thickness of foil at the lingual incisal edge and on proximal incisal corners. After adaptation and burnishing, the foils were removed, air abraded at 40 psi with aluminum oxide, and cleansed with water. The high-leucite porcelain was applied in three body bakes and a glaze. Shade Al body porcelain was used for the first two bakes and white enamel was used for the third
space data in six measured locations
Sample size Minimum (mm) Maximum (mm) Mean (mm) Variance (mm) Standard deviation
9 0.045 0.335 0.132 0.008 0.088
9 0.025 0.078 0.048 0.000 0.016
0.026 0.086 0.056 0.001 0.023
0.046 0.150 0.082 0.001 0.034
0.041 0.160 0.073 0.001 0.037
0.049 0.155 0.079 0.001 0.031
Error 2 Error
Epoxy Potting Medium 1
0.046 0.002 0.004
8 1 8
0.040 0.006 0.002 0.000
SS,Sum ofsquares;MS, meansquare.
body bake. Contours were adjusted with diamond burs in a low-speed handpiece, with periodic measuring to control axial thickness to 0.7 mm. Subsequent to contour correction, the veneers were cleaned with water in an ultrasonic bath, glazed, and defoiled. The tooth surface to receive the veneer and the resin side of the veneers were air abraded with 40 km aluminum oxide particles at 40 psi. The veneers were etched with a hydrofluoric acid substitute (Stripit, National Keystone Co., Philadelphia, Pa.) for 2.5 minutes. They were then cleansed in water for 10 minutes and silanated (Fusion, George Taub Products, Jersey City, N.J.). An unfilled, autocuring resin (Compspan, L. D. Caulk, Dentsply International, Inc., Milford, Del.) was painted in thin film on the porcelain and the tooth and an autocuring microfilled composite resin (Compspan, L. D. Caulk) was used as a luting agent. The veneers were vibrated into place and were held with hand pressure. Excess cement was removed before cure with a brush wet with unfilled resin.* The luted veneers were allowed to cure undisturbed for 15 minutes. Any excess luting agent was cleaned with a rubber point, and the veneers were polished with pumice. Nine luted porcelain laminate veneers were embedded in clear epoxy resin and sectioned midsagittally. Luting space of each specimen was measured at six predetermined and repeatedly locatable positions using a measuring microscope (E. Leitz, Inc., Rochleigh, N.J.) retrofitted with a digital indicator (Mitutoyo Mfg. Co., Tokyo, Japan). Digital measurements were sent to an interface device that permits microcomputer storage (Mitutoyo Mfg. Co.). Three measurements were made for each location (18 measurement per tooth). DP-1 represents the lingual marginal space and DP-6 represents the facial marginal space (Fig. 1). Statistical evaluations were made using the repeated
Fig. 1. Luting space measurement
measures analysis of variance and single degree of freedom polynomial contrasts. The hypothesis was that there would be a statistical difference in the areas where platinum foil is folded and those in which there is a single layer of platinum foil.
RESULTS The Greenhouse-Geisser Epsilon statistic produced a statistically significant difference between the nine measured locations 0, < 0.0001). There was a statistically significant difference between the film thickness at DP-1, where the foil is folded, and the four internal measurement areas (p = 0.029). Interestingly, there was not a statistically significant difference between the facial margin thickness (DP-6) and the four internal thickness measurements (p = 0.080). The data are given in greater detail in Tables I and II.
DISCUSSION Working with platinum foil is time-consuming and tedious. However, as stated by Rosenstiel et al.: if the shoulder margin is prepared at a go-degree angle to the preparation’s path of withdrawal and the thickness of foil is uniform, there will be (in theory) perfect marginal adaptation after foil removal. Marginal discrepancies found in this study were surprisingly small. Where there were no foil folds, the marginal discrepancy averaged 79 2 31 pm (DP6); this value reached an average of 132 + 88 pm where the foil was folded to produce the “tinners joint” (DP-1). These discrepancies were in excellent agreement with those reported in a previous study3 (74 t 53 pm, facial margin; 122 & 80 pm, lingual margin). Sorensen et aL3 also reported marginal discrepancies of 278 k 53 and 333 + 93 pm for margins of porcelain veneers fabricated on refractory dies. Therefore data from this present study corroborate the use of the foil technique for minimizing marginal discrepancies of the porcelain veneer restoration. Seemingly, platinum foil restricts porcelain margin shrinkage through some adherence phenomenon.
CONCLUSION This study corroborates the findings of Sorensen et a1.3 and further demonstrates that required folds in platinum foil substantially increase marginal discrepancies around luted porcelain veneers. However, these discrepancies are apparently smaller than those that are created when the porcelain veneer is fabricated on a refractory die. REFERENCES 1. Phillips RW. Skinner’s science of dental materials. 8th ed. Philadelphia: WB Saunders, 1982521. 2. American Dental Association. Dentists desk reference. 1st ed. Chicago, 1981:81.
An evaluation of smear layer agents a.fter tooth preparation Ali
3. Sorensen JA, Strutz D, Materdomini D, Torres TJ. Porcelain veneer marginal fidelity. Platinum foil vs refractory die technique [Abstract]. J Dent Res 1989;68:200. 4. Tay WM. Effects of some finishing techniques on cervical margins of porcelain laminates. Quintessence Int 1987;18:559. 5.. Rosenstiel SF, Land MF, Fnjimoto J. Complete ceramic crown fabrication, Contemporary fixed prosthodontics. St. Louis: CV Mosby, 1988:416. Reprint requests to: DR. J. GREGORY WALL THE OHIO STATE UNIVERSITY COLLEGE OF DENTISTRY 305 W. 12~~ AVE. COLUMBUS. OH 43210
with various DDS,
According to hydrodynamics, any agent blocking the dentinal tubules reduces the flow of fluids and diminishes hypersensitivity. The properties of the desensitizing agents that sponsor tubular occlusion and the barrier efficiency resulting from the interaction of the smear layer with test materials were examined with the scanning electron microscope and energy-dispersive x-ray microanalysis. Selected dentinal desensitizing was accomplished with burnishing procedures, cavity varnish, calcium hydroxide, and topical fluoride. Subjective evaluations were also recorded chnically after tooth preparation. This investigation indicated that the smear layer did not protect against zinc phosphate cement, and that cavity varnish prevented the formation of the smear plugs. The smear layer and plugs were basically composed of calcium and phosphorus, the major ingredients of dentin. (J PROSTHET DENT 1992;68:460-7.)
rfferent approaches related to the control of dentinal sensitivity after tooth preparation have been extensively reported, namely mechanical abrasives and surface medications.l-lo Despite these measures, sensitivity is encountered during cementation of castings, particularly in young people having numerous dentinal tubules with wide diameters. The coronal dentin of most young patients remains more sensitive to all external stimuli.lr Although the precise mechanism of pain transmission within the dentin is subject to speculation, there are currently three main theories. These are: (1) the direct nerve endings theory, (2) the odontoblast-receptor theory, and (3) the hydrodynamic theory.12vI3 The first theory suggested the existence of nerve endings in the dentin with a pulpal origin that can be directly stimaProfessor, Department bProfessor, Department 10/l/37847
of Prosthodontics. of Prosthodontics.
1. SEM of specimens in the control group. Age group 20 to 30 years. (Original magnification X2000.)