eet of various incremental techniques on the aptation of class II composite resin restoratio Anthony H. L. Tjan, DrDent, DDS,a Brian H. Bergh, BS,b altd Carla Lidner, BA, MSb Loma Linda University, School of Dentistry, Loma Linda, Calif. The effects of various placement techniques on the formation of microgaps were compared at the gingival margins of class II composite resin restorations. Three incremental techniques (occlusogingival layering, oblique layering, and faciolingual layering) and two one-bulk techniques of placing composite resin were studied. In the first one-bulk placement technique the composite resin was photocured occlusally; in the second one-bulk technique the composite resin was irradiated from three directions; facial, lingual, and occlusal. None of the incremental placement techniques improved the adaptation at the gingival margin compared with a one-bulk technique irradiated occlusally. However, the one-bulk placement technique that was irradiated from three directions created a substantial marginal discrepancy. (J PROSTHET DENT 1992;67:62-6.)

osterior composite resins have several limitations; est of these has been the appreciable polymerization shrinkage, ranging from 1.67 % to 5.68% .lm6Several studies reported that significant tensile stresses developed during polymerization of composite resins, producing powerful forces that created separation at the composite resin/ tooth interface.7-g This problem is distinct for class II composite resin restorations because the margin of the proximal box may exhibit only minimal enamel. Contraction gaps are formed without specific measures to prevent the composite resin from separating from the weak dejltinal bond. These gaps can sponsor postoperative sensitivity and pulpal irritation.‘O$ I1 Measures such as incremental placement techniques,5-12 light-reflecting proximal wedges,13pl4 or dentinal bonding agents are recommended to resolve this problem. Yet many dentists have discovered that theoretical placement techniques are clinically impractical. The methods for class II composite resin placement must be assessedthat address both aspects: marginal adaptation and practical clinical application. This study compared the effects of various placement techniques on the formation of gingival microgaps of class II composite resin restorations. MATERIAL 00th

AND

METHODS

preparation

Standardized mesio-occlusal cavities were prepared in 25 freshly extracted intact human premolar teeth by use of a No. 245 carbide bur in a high-speed handpiece with air and

aProfessorand Director, Biomaterials Research,Department of Restorative Dentistry. bSeniordental student. lQ/1/29632

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Fig. 1. Various composite resin placement techniques: (1) one-bulk, (2) occlusogingival layering, (3) oblique layering, and (4) faciolingual layering. water spray. The margins of the preparations were extended apically so that the gingival margins were definitely in cementurn, and the gingival floor was 4 mm long and 1.5 mm wide. The depth of the proximal box was 5 mm, and the axiogingival line angle was rounded. The enamel cavosurface margins were bevelled approximately 0.5 to 1 mm long with a pointed diamond bur. The prepared teeth were mounted adjacent to other natural teeth to simulate intraoral conditions. Composite

resin

placement

Three incremental techniques including occlusogingival layering, oblique layering, and faciolingual layering were

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Fig. 2. Marginal gap was measured at five points: at approximate half distance of gingival/center margin and two points on both sides of center with 0.5 mm distance increments. Average of these five readings represented gap of specimen.

3. Bar graph depicts mean microgap values and standard deviation at gingival margins.

Fig.

Table

examined and two one-bulk techniques of placing the composite resin were reviewed (Fig. 1). In the first one-bulk placement technique, the composite resin was only photocured occlusally for 90 seconds with a light source (Optilux 400, Demetron Research Corp., Danbury, Conn.). In the second one-bulk technique, the composite resin was irradiated from three directions-facial, lingual, and occlusal-for 30 seconds in each direction. In the remaining three methods that used differing incremental techniques, each increment was irradiated for 30 seconds, so that each specimen received an equal curing time of 90 seconds. Five specimens were tested for each of the five methods. A clear matrix band and a reflective curing wedge (CureThru, ESPE-Premier Sales Corp., Norristown, Pa.) were used in all five techniques. The enamel cavosurface margins were acid-etched (Phosphoric acid etching gel, Batch No. 0039, ESPE-Premier) for 30 seconds, rinsed with water for 30 seconds, dried with filtered compressed air, coated with a bonding resin (Visio-Bond, Batch No. R076MD031688, ESPE-Premier), and irradiated for 20 seconds. A light-cured hybrid composite resin (Visio-Molar, Radiopaque, A3/D3, Batch No. R076MD031688, ESPEPremier) was used to restore the cavities. ~~a~~r~rne~t

of the marginal

gap

The restored tooth was individually embedded in clear autopolymerizing acrylic resin (Orthocryl, Stratford-Cooksen, Newnan, Ga.) to form a rectangular base with the proximal portion of the restoration exposed and the gingival margin oriented horizontally to standardize its positioning under the microscope. The gingival margins were then levelled by careful grinding on the Handimet grinder (Buehler Ltd., Lake Bluff: Ill.) with Sic abrasive paper. The margins were then stained with red dye (Core Dye Check for Cerestore system, Ceramco, Inc., E. Windsor N.J.), and the descrepancies were recorded with a videoenhanced measuring microscope with a digital micrometer

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Microgaps at gingival margins (in Frn) One-bulk

Mean SD Coeff. of

technique

Incremental

technique

1

2

a

4

5

15 9 9 13 12 11.6 2.61 22.0

22 16 18 14 15 17.0 3.16 19.0

12 12 11 10 12 11.4 0.89 8.0

I.4 13 18 10 15 14.0 2.91 21.0

16 13 8 14 15 13.2 3.11 24.0

variation (% ) N = Five specimens for each method: 1, One-bulk technique irradiated from one direction; 2, one-bulk technique irradiated from three directions; 3, occlusogingival layering; 4, oblique layering; and 5, faciolingwl layering.

and image intensification on a high-resolution television screen (Mitutoyo, Tokyo, Japan). The measurements were recorded at five predetermined locations, and the values were averaged (Fig. 2). After all of the data were collected, the specimens were sectioned longitudinally through the center of the restoration mesiodistally with an Isomet lowspeed diamond saw (Buehler Ltd). This procedure allowed assessment of the microgaps at the axiogingival interfaces. A representative sample from each technique was photographed by scanning electron microscopy (Amray Inc., Bedford, Mass.) at ~200 and xl000 magnification. The data were analyzed by one-way analysis of variance (ANOVA), and Duncan’s multiple range test was calculated to determine the significance between group means at the p 0.05 level, using the statistical software (SPSS/PC+, SPSS, Inc., Chicago, Ill.). RESULTS The group means and standard deviations of the marginal gap measurements are listed in Table I and Fig. 3. The occlusogingival layering technique (group 3) produced the 63

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Fig. 4. Scanning electron micrographs of gingival margins at original magnification of xl000 (topside is composite resin). A, One-bulk technique irradiated from occlusal direction; B, occlusogingival layering technique; C, oblique layering technique; D, faciolingual layering technique, and E, one-bulk technique irradiated from three directions.

Table II.

Summary

of ANOVA

for marginal

gaps (in pm)

Source

DF

Sum of squares

Mean squares

F Ratio

F Prob

Between groups Within groups Total

4 20 24

102.9600 143.2000 246.1600

25.7400 7.1600

3.5950

0.0230

most consistent results with the least deviation. an analysis of the data revealed no statistically differences between groups 1,3,4, and 5 at p < onstrating uniformity within the groups (Tables Group 2, with the one-bulk placement technique

64

However, significant 0.05, demII and III). irradiated

from three surfaces, exhibited the largest marginal gap at p < 0.05. Fig. 4 demonstrates scanning electron micrographs of marginal gap formation at the gingival margins. For the axiogingival interface, the widest gaps were observed at the

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6. Overhang (arrow) of gingival margin due to water sorption at original magnification X200.

Fig.

5. Scanning electron micrograph of axiogingival interface demonstrating widest gaps at rounded axiolingual line angles at original magnification X200. Fig.

rounded axiolingual line angles that occlusally and gingivally (Fig. 5).

diminished

Table III. Summary p < 0.05 level

of Duncan multiple

range test at

both Group No.

Description

DISCUSSIQ Maximal contraction occurred when a one-bulk placement technique was used to restore cavities.15, l6 Incremental placement of composite resin may reduce, but did not eliminate, the marginal discrepancies resulting from polymerization shrinkage.14-Is This study suggested that the marginal gap was not eliminated by any one incremental composite resin placement methods. However, the incremental techniques ensured the complete polymerization of the composite resin. Layering techniques are recommended for restorations 3 to 4 mm in depth, because uncured materials are subjected to physical or chemical changes during aging.lg Another benefit of incremental placement is the reduction of the contractional stresses during polymerization of composite resins linked to cuspal displacementzO~ 21 or fracture.22 This displacement and/or lack of adaptation could be responsible for the proclivity to postoperative sensitivity in class II composite resin restorations. Donly et al.23 reported that composite resin placement and poly-

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Qcclusogingival layering One-bulk, irradiated from one direction Faciolingual layering

11.4 11.6

One-bulk, irradiated from Oblique layering three directions

17.0 I 14.0

13.2

Vertical lines connect means,which are not significant statistically.

merization in faciolingual increments produced substantially less cuspal deflection than “bulk polymerization” techniques. Further research is indicated to examine the influence of incremental placement techniques on cuspal displacement. Hygroscopic expansion of composite resin may eventually compensate for the interfacial gap from polymerization shrinkage.24,25 However, Davidson and Kemp-Scboltez5 also reported that previously debonded gingival margins of class V composite resin restoration expanded and caused

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an overhang. The same phenomenon was observed at the gingival margin of class II composite restorations after storage in water for several days in this in vitro study (Fig. 6). Bowen et alI5 reported that hygroscopic expansion was rarely sufficient to compensate completely for polymerization shrinkage. Another study confirmed that the contraction gaps of anterior composite resin restorations were closed within 28 days by the hygroscopic expansion, but all posterior composite resins recorded a residual gap.6 The diminished hygroscopic expansion of the posterior composite resins is hypothesized to be related to less organic material. (bysaed and Ruyterz6 reported that composite resins with the greatest quantity of filler particles exhibit the least water sorption and solubility after 3 months of exposure to water. There are conflicting reports regarding the effectiveness of dentinal bonding agents in preventing the formation of marginal gap. Several studies indicated that none of the commercial dentinal bonding agents were capable of restraining marginal contractional gaps.5l6,27-2g There is a steadily growing interest in posterior composite resin restorations, but despite the improvements in the roperties of composite resins, clinical and material limitations have restrict,ed their use as posterior restorations. The placement techniques are inordinately sensitive and clinically demanding. In addition, prudence must be exercised if the proximal cavity is extended beyond the cementoenamel junction because polymerization contractional gaps are unavoidable. A ranking for the ease of placement was that the one-bulk technique was the easiest, followed by the occlusogingival layering technique, the faciolingual layering technique, and finally the oblique layering technique. Thus, this study indicated that, despite a more rigid sequence of layering, the gingival marginal gap was not reduced. NCLUSTONS None of the incremental placement methods significantly improved adaptation at the gingival margins compared with the one-bulk technique irradiated from occlusal direction. However, the one-bulk placement method lightcured from the facial, lingual, and occlusal surfaces created a significantly greater marginal gap. A one-bulk placement technique is not recommended for class II composite resin restorations because of incomplete polymerization of the composite resins, especially in deep cavities.

LIDNER

3. Bandyopadhyay S. A study of the volumetric setting shrinkage of some dental materials. J Biomed Mater Res 1982;16:135-44. 4. Goldman M. Polymerization shrinkage of resin based restorative materials. Aust Dent J 1983;28:156-61. 5. Hansen EK. Effect of cavity depth and application techniqlue on marginal adaptation of resins in dentin cavities. J Dent Res 1986;65:131921. 6. Hansen EK, Asmussen E. Marginal adaptation of posterior resins: effect of dentin-bonding agent and hygroscopic expansion” Dent Mater 1989;5:122-6. I. Bowen RL, Nemoto K, Rapson JE. Adhesive bonding of various materials to hard tissues: forces developing in composite materials during hardening. J Am Dent Assoc 1953;106:475-7. 8. Asmussen E. Composite restorative resins: composite versus wall to wall polymerization contraction. Acta Odontol Stand 1975;33:337-44. 9. Jorgensen KD, Asmussen E, Shimokobe Ii. Enamel damage caused by contracting restorative resins. Stand J Dent Res 19’75;83:120-2. 10. Bergenholtz G, Cox CF, Loeske WJ, Syed SA. Bacterial leakage around dental restorations: its effect on the pulp. J Oral Path01 1982;11:439-50. 11. Br&mstroKm M. Communication between the oral cavity and the dental pulp associated with restorative treatment. Oper Dent 1984;9:57-65. 12. Lutz F, Krecji I, Oldenburg TR. Elimination of polymerization stresses at the margins of posterior composite resin restorations. A new restorative technique. Quintessence Int 1986;17:777-84. 13. Lutz F, Krecji I, Luescher B, et al. Improved proximal margin adaptation of Class II composite resin restoration by use of light-reflecting wedges. Quintessence Int 1956;17:659-64. 14. Pollack BF. Class II composites 1987 thoughts and techniques. Oral Health 1958;78:23-5. 15. Bowen RL, Rapson JE, Dickson G. Hardening shrinkage and hygroscopic expansion of composite resins. J Dent Res 1982;61:654-5. 16. McConnell RJ, Boksman L, Hunter JK, Gratton DR. The effect of restorative materials on the adaptation of two bases and a dentin bonding agent to internal cavity walls. Quintessence Inter 1986;17:703-10. 17. Crim GA, Chapman KW. Prevention of marginal leakage by four dentinal adhesives. Gen Dent 1986;34:235-6. 18 Podshadley AG, Gullett CE, Crim GA. Interface seal of incremental placement of visible light-cured composite resins. J PROSTHET DENT 1985;53:625-6. 19. Matsumoto H, Gres JE, Marker VA, Okabe T, Ferracane JL, Harvey

GA. Depth of cure of visible light-cured resin: clinical simulation. J PROSTHET DENT 1986;55:574-8. 20. McCullock A, Smith B. In vitro studies of cusp reinforcement with ad-

hesive restorative material. Br Dent J 1986;161:450-2. 21. Pearson GJ, Hegarty SM. Cusp movement of molar teeth with compos-

22

23.

24. 25. 26. 27. 25. 29.

1. DeGee AJ: Davidson CL, Smith AA. Modified dilatometer of continuous recording of volumetric polymerization shrinkage of composite restorative materials. J Dent 1981;9:36-42. 2. Baush JR, deLange K, Davidson CL, Peters A, deGee AJ. Clinical significance of polymerization shrinkage of composite resins. J PROSTHET

AiW

ite filling materials in conventional and modified MOD cavities. Br Dent J 1989;166:162-5. Wieckowski Jr 6, Joynt RB, Klockowski R, Davis EL. Effects of incremental versus bulk fill technique on resistance to cuspal fracture of teeth restored with posterior composites. J PROSTHET DENT 198S;60:283-7. Donly KJ, Wild TW, Bowen RL, Jensen ME. An in vitro investigation of the effects of glass inserts on the effective composite resin polymerization shrinkage. J Dent Res 1989;68:1234-7. Huang G, Soderholm K. An vitro investigation of the shear bond strength of Bondlite to dentin [Abstract]. J Dent Res 1987;66:239. Davidson CL, Kemp-Scholte CM. Shortcomings of composite resins in class V restorations. J Esthetic Dent 1959;1:1-4. 0ysaed H, Ruyter IE. Water sorption and filler characteristics of composites for use in posterior teeth. J Dent Res 1986;65:1315-5. Munksgaard EC, Hansen EK, Asmussen E. Effect of five adhesives on adaptation of resin in dentin cavities. Scald J Dent Res 1954;92:480-3. Jorgensen KD, Itoh K, Munksgaard EC, Asmussen E. Composite wallto-wall polymerization contraction in dentin cavities treated with various bonding agents. Stand J Dent Res 1985;93:276-9. Komatsu M, Finger W. Dentin bonding agents: correlation of early bond strength with margin gaps. Dent Mater 1986;2:257-62.

Reprint requests tot DR. ANTHONY H. L. TJAN SCHOOL OF DENTISTRY LOMA LINDA UNIVERSITY LOMA LINDA, CA 92350

DENT 1982;48:59-67.

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