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Radiopacity of light-cured posterior composite resins
RESEAR CH
REPORT S
Radiographic images of teeth and restorations were used to evaluate the radiopacity of 11 light-cured posterior composite resins. The radiopacity of these composite resins provided enough variation on radiographs so that clinicians distinguished the images of the restoration from adjacent tooth structure.
Radiopacity of light-cured posterior composite resins Clark M. Stanford, DDS P. L. Fan, PhD Charles M. Schoenfeld, DDS, PhD
Ray Knoeppel John W. Stanford, PhD
adiopacity is desirable in restorative materials as it allows radiographic distinction of existing restorations and recurrent caries. 1 Radiographic distinction is vital when evaluating contours, overhangs and major voids in restorations, and also serves an important role in detecting aspirated restora· tions. 1' 2 Subjective analyses of radiopacity in composite resins have been reported.3- 6 The degree of radiopacity in composite resins adequate for clinical radiographic evaluations has not been established. To distinguish the composite resin restoration from tooth structure, significant differences are needed in the radiopacity of the composite resin, enamel, and den· tin. The radiopacity of enamel and dentin sections 2.5·mm thick was reported by Abou-Tabl and others 7 as equivalent to 4.0 and 2.5 mm of aluminum, respectively. Cook 8 reported that the percentage of radiopacity in enamel and dentin, in relation to aluminum, was 150 and 83, respectively. Williams and Billington 9 reported that 1-mm thick sections of enamel have an aluminum equivalent of 2.1 mm and of dentin, 1 mm. The radiopacity of 2.5-mm thick composite resin samples ranged from 1.0-to-5.7 mm alum10 inum equivalent. 7 Orner and others compared 2.5-mm composite resin samples with a 2.5-mm section of a permanent molar and reported that 12 composite resins were more radiopaque than dentin. Ferreira 11 placed a composite resin, an amalgam, and seven glass ionomer materials in standard occlusal cavities; evaluated the radiographic densities; and concluded that three of the glass ionomer materials were insufficiently radiopaque. Ferreira 12 also reported the radiographic densities of nine posterior composite res-
in s in Class I cavi ty preparations. Goshima 13 reported the optical densities on radiographs of step wedges of composite resins and aluminum, and compared radiographs of Class II cavities restored separately with amalgam and composite resins. However, a systematic evaluation using both optical density and aluminum equivalent considerations has not been reported. Also the interference caused by the variability of remaining tooth structure when comparing radiopacity has not been eliminated. The purpose of this study was to measure the radiopacity of currently available light-cured posterior composite resin samples in terms of aluminum-equivalent values and to evaluate the ability of human observers to distinguish from tooth structure a Class I restoration of these composite resins, using radiographs of the restorations in the same tooth.
R
722 • JADA, Vol. ll5, November 1987
Fig I • Regions A, B, and C used in optical density measurements and human observer evaluations. Region A, comparison of the restoration, enamel, and dentin. Region B, comparison of the restoration, and mostly dentin. Region C, comparison of the restoration and enamel.
Methods and materials Eleven light-cured posterior composite resins were included in this study: Bisfil 1, Estilux Posterior, Ful-Fil, Heliomolar, Herculite, Luma-bis Posterior, Marathon One, Occlusin, P-30, Sinter Fil, and Status. Enamel and dentin sections from extracted human teeth were also included in this evaluation. For each type of composite resin, three samples of four different thicknesses (about 1.5, 2.5, 5, and 7 mm) were prepared. The samples were polymerized using a curing lamp (Coe). Enamel and dentin section thicknesses ranged from about 1.0 to 1.8 mm. Each sample thickness was measured using a micrometer. The thickness values were used in linear regression calculations. A radiograph was made of each sample using Eastman Kodak Ektaspeed E film. Exposures were at 70 kVp, 10 rnA, and 0.25 seconds (GE Model 1000 X-ray machine.) The films were developed in a Philips model 810 automatic processor. For each radiograph, an aluminum step wedge (1 to 4 mm) and a 4-mm thick lead specimen were used as internal standards with each sample exposure. The optical density of each radiographic image was measured using a MacBeth TD-504 film analyzer with a 2-mm orifice. Two readings were taken on each step wedge area and the lead specimen area. Three readings were taken for each sample area. The readings were corrected for inherent film fog as measured by the reading for the lead specimen image. The reading at an area without a sample was also obtained to provide an optical density for zero sample thickness. Linear regression calculation using the
RESEARCH
restoration and tooth structure at regions A, B, and C. T he evaluations were classi fied as whether the restoration, when compared with the adjacent tooth struc ture, appeared to be less, about the same, or more radiopaque. Majority decisions classified the relative radiopacity of the composition to adjacent tooth structure.
equivalent values for 2-mm thick samples, composite resins that were not more radi opaque than enamel were Heliomolar, Luma-bis Posterior, P-30, Sinter Fil, and Status. Radiographs of the unfilled preparation and of the Class I cavity prep aratio n restored with composite resins are shown in F ig u re 3. D ifferences can be d is tinguished in the radiographic images of the composite restorations. A histogram detailing differences in optical densities and the corresponding observer evalua tions is shown in Figure 4. H igh optical density differences between restoration and surrounding tooth structure correlate with consensus among observers. When com posite resins were compared with mostly d e n tin , region B show ed the clearest radiographic distinctions.
Results
Fig 2 ■ Linear regression lines for alum inum
T he linear regression plots of the loga rithm of optical density at 70 kV(p) and sample thickness for alum inum and a composite resin are shown in Figure 2. The linear correlation (r2) values were greater than 0.98 except for Status (0.93), enamel (0.85), and dentin (0.93). The alum inum equivalent for 1-mm and 2mm thick composite resins, enamel, and dentin are shown in Table 1. All poste rior composite resins used in this study were more radiopaque than dentin but not necessarily more radiopaque than enamel. On the basis of the alum inum
REPORTS
Discussion
All composite resins in this study were more radiopaque than dentin, but all were
and a com posite resin for obtaining alum inum equivalent for 1-mm and 2-mm samples.
Table 1
logarithm of corrected optical density and sample thickness was performed for each composite resin, as well as for enamel, dentin, and alum inum . The alum inum equivalent for 1-mm and 2-mm thickness for the composite resins, enamel, and dentin were obtained from the correspond ing linear regression calculations. A Class I cavity preparation was made on the occlusal surface of an extracted hum an second molar. The same tooth and cavity preparation was used for all composite resins. The tooth was mounted for reproducibility of focal spot object and object-to-film distances during radi ographic procedures. Radiographs were made of the tooth without restoration and with the cavity restored with each of the composite res ins. T he composite resins, however, were not polymerized so that they could be removed after the radiographic procedure without affecting the cavity preparation. T he cavity was cleaned with alcohol before the next com posite resin was placed. T his enabled the same tooth and cavity preparation to be used with each composite resin, and provided a constant configuration for radiographic evaluation. Optical density readings were made at each of the areas w ithin the restoration and the tooth structure regions (Fig 1). Five practitioners subjectively evaluated each radiograph for contrast between the
■ Aluminum equivalent (mm) of composite resins, enamel, and dentin.
Bisfil 1 E stilu x Posterior F ul-Fil H elio m o lar H erculite L u m a-b is Posterior M arath o n O n e O cclusin P-30 Sin ter Fil S tatus E nam el D en tin A lu m in u m
1-mm sam ple
2-m m sam ple
1.82 2.16 2.47 1.93 1.95 1.72 2.00 2.52 1.77 1.65 1.93 2.22 0.79 1.00
3.88 4.20 4.97 3.64 4.64 3.58 4.32 5.77 3.47 2.70 3.64 3.84 1.82 2.00
F ig 3 ■ Posterior com posite resins in the same m andibular m olar Class I preparation. T he unfilled preparation is also show n as a baseline for comparison. From top to bottom: unfilled preparation, Sinter Fil, P-30, Luma-bis Posterior, H eliom olar, Status, B isfil 1, Estilux Posterior, Marathon One, Herculite, Ful-Fil, Occlusin.
Stanford-O thers : RA D IO PA C ITY O F C O M PO S IT E RESINS ■ 723
RESEARCH
REPORTS
tion. No consensus on a minim al degree of radiopacity was reached.
Observer ratings on radiopacity Restoration versus tooth
Fig 4 ■ Observer eval uations and quantita
----------------- JfOA ------------------
tive m easurem ents of d iffe r e n c e s in r a d i op acity. Greater d is tinction between com
Same
posite resin and tooth
In fo rm a tio n a b o u t the m anufacturers of the p ro d ucts m entioned in this article may be available from the au th o rs. N either the au th o rs n o r the American D ental A ssociation has any com m ercial interest in the products m entioned.
structure is associated with higher differences in alum inum equiva lents.
not more radiopaque than enamel. The alum inum equivalent at 1-mm and 2-mm sample thicknesses showed some relative variations. For example, the alum inum equivalent values for 1-mm thick samples showed that Bisfil 1, Herculite and M ara thon One were less radiopaque than enamel but 2-mm samples were more radiopaque than enamel. T h is result m ight be attributable to data scattering and using the linear regression model. The values obtained, however, indicate a wide range in the radiopacity of lightcured posterior composite resins. T he results of this study correlate well with the previous work of Ferreira.12 Occlusin, for example, is highly radiopaque by comparison. Some composite resins, for example, Estilux Posterior, are similar to enamel in radiopacity. Sinter Fil had low radiopacity, whereas Ful-Fil and Occlusin had radiopacities higher than that of enamel. It has been suggested by Lutz and others14 that a posterior composite resin should not only match but exceed the radiopacity of enamel. T he use of a constant configuration in a single tooth for radiographic evaluation by hum an observers provided a consistent comparison for clinical radiographic eval uations. T he am ount of rem aining tooth structure and its radiographic contribu tion are constant for each radiographic image of the tooth with a composite resin restoration. Differences in radiographic images, therefore, are the result of the dif ferences in the radiopacity of the compos ite resin. There is, however, no consensus as to the degree of radiopacity preferred by the five practitioners acting as observers for radiographic evaluation. T h e ob servers’ ability to distinguish the restora tion from adjacent tooth structure was enhanced with increasing differences in the optical density of the two areas (Fig 4). In this study, optical density measure 724 ■ JADA, Vol. 115, N ovem ber 1987
ments were taken a small distance away from the restoration—tooth structure junc tion; however, the observers probably used the differences at the junction to make their evaluations. T he conclusions illus trate that optical density differences are used to indicate the relative magnitudes but not necessarily to indicate absolute definitive values. T he distinction of the restoration from adjacent tooth structure was more prom inently visible in regions where the radiographic image was com posed of more dentin. T his radiographic distinction correlates with the lower radi opacity of dentin as compared with the composite resins. The practitioner needs to consider the influence of cavity configuration and the remaining tooth structure when evaluat ing the radiographic image for interpreta tion. Radiographically, the am ount of enamel and dentin adjacent to, and super imposed on, the restoration also influence evaluation. The choice of a highly radi opaque composite resin decreases this influence. High radiopacity in the restor ative material, however, may also decrease the diagnostic inform ation on the radio graph in areas covered by the restoration. Conclusion
The radiopacity of light-cured posterior composite resins covered a wide range as measured in terms of alum inum equiva lents. These composite resins are more radiopaque than dentin, but not necessar ily more radiopaque than enamel. Clini cal evaluations of radiographic images of composite resin restorations in the same too th cavity p re p a ra tio n by hum an observers showed variations in distinguish ing the radiographic image of the restora tion and adjacent tooth structure. As expected, a higher radiopacity in the composite resin provided easier distinc
T h is project was su p p o rte d in p a rt by g ra n t DE 05761-07 from the N a tio n a l In s titu te of D ental Research, N ational Institutes of H ealth. T h e a u th o rs th a n k the 3M Co; Risco, Inc; L. D. C aulk Co; C entrix, Inc; Coe L aboratories; Den-M at C orp; H ealthco, Inc; K err/Sybron; Kulzer, Inc; T ele dyne Getz; and V ivadent USA for their d o n a tio n of m aterials used in this study. Dr. C. M. Stanford, a grad u ate student. U niversity of Iow a C ollege of D entistry, w as research assistant; Dr. Fan is associate secretary; Dr. Schoenfeld is assis ta n t secretary; Mr. K noeppel is research assistant; Dr. J o h n Stanford is secretary, C ouncil o n D ental M ate rials, Instrum ents, an d E q u ip m en t, A m erican D ental A ssociation, 211 E C h ic a g o Ave, C h ic ag o , 60611. Address requests for reprints to Dr. Fan.
1. C ouncil o n D ental M aterials, Instrum ents, and E quip m en t. T h e desirability of u sin g radiopaque plastics in dentistry: a status report. JAD A 102(3):347349, 1981. 2. M cA rthur, R ., an d T ay lo r, D. A d eterm ination of the m in im u m radiopacification necessary for radiog ra p h ic detection of a n a spirated o r sw allow ed object. O ral S urg O ral M ed O ral P a th o l 39(2):329-338, 1975. 3. Leinfelder, K.F., a n d R oberson, T . C linical eval u a tio n o f p o s te r io r c o m p o site re sin s. G e n D ent 31 (4):276-280, 1983. 4. O sborne, J ., an d o thers. In vivo com parison o f a com posite resin a n d its ra d io p a q u e counterpart. J P rosthet D ent 39(4):406-408, 1978. 5. O sborne, J ., an d G ale, E.N . A three year clinical assessm ent of a com posite resin a n d its radiopaque co unterpart. J P rosthet D en t 44(2);164-166, 1980. 6. Shey, Z., an d O p p e n h eim , M. A clinical evalua tio n of a rad io p aq u e m aterial in the restoration of anterior a n d posterior teeth. JADA 98(4):569-571,1979. 7. A bou-T abl, Z.M.; T id y , D.C.; an d Com be, E.C. R adiopacity of com posite restorative m aterials. Br D ent J 147(7): 187-188, 1979. 8. C ook, W.D. Investigation of the radiopacity of com posite restorative m aterials. A ust D ent J 26(2):105112, 1981. 9. W illiam s, J.A ., an d B illin g to n , R.W. A new technique for m easuring radiopacity of n a tu ra l tooth substance a n d re sto ra tiv e m ate ria ls. J D ent Res 65(4):513, abstract no. 230,1986. 10. O m er, O .E .; W ilson, N .H .; a n d W atts, D.C. T h e radiopacity of posterior com posite restoratives. J D ent Res 65(4):517, abstract no. 267, 1986. 11. Ferreira, M.R. R ad io g ra p h ic density of seven glass-ionom er m aterials. J D ent Res 65(4):620, abstract no. 26, 1986. 12. Ferreira, M R. R ad io g ra p h ic density of p oste rio r resins. J D ent Res 65(4):620, abstract no. 27,1986. 13. G oshim a, T . T h e ra d iopacity of com posite re storative m aterials. D entom axillofac R adiol 15(1):3740, 1986. 14. Lutz, F., a n d others. In vivo an d in vitro wear of po ten tial posterior com posites. J D ent Res 63(6): 914-920, 1984.
REPORT S
Radiographic images of teeth and restorations were used to evaluate the radiopacity of 11 light-cured posterior composite resins. The radiopacity of these composite resins provided enough variation on radiographs so that clinicians distinguished the images of the restoration from adjacent tooth structure.
Radiopacity of light-cured posterior composite resins Clark M. Stanford, DDS P. L. Fan, PhD Charles M. Schoenfeld, DDS, PhD
Ray Knoeppel John W. Stanford, PhD
adiopacity is desirable in restorative materials as it allows radiographic distinction of existing restorations and recurrent caries. 1 Radiographic distinction is vital when evaluating contours, overhangs and major voids in restorations, and also serves an important role in detecting aspirated restora· tions. 1' 2 Subjective analyses of radiopacity in composite resins have been reported.3- 6 The degree of radiopacity in composite resins adequate for clinical radiographic evaluations has not been established. To distinguish the composite resin restoration from tooth structure, significant differences are needed in the radiopacity of the composite resin, enamel, and den· tin. The radiopacity of enamel and dentin sections 2.5·mm thick was reported by Abou-Tabl and others 7 as equivalent to 4.0 and 2.5 mm of aluminum, respectively. Cook 8 reported that the percentage of radiopacity in enamel and dentin, in relation to aluminum, was 150 and 83, respectively. Williams and Billington 9 reported that 1-mm thick sections of enamel have an aluminum equivalent of 2.1 mm and of dentin, 1 mm. The radiopacity of 2.5-mm thick composite resin samples ranged from 1.0-to-5.7 mm alum10 inum equivalent. 7 Orner and others compared 2.5-mm composite resin samples with a 2.5-mm section of a permanent molar and reported that 12 composite resins were more radiopaque than dentin. Ferreira 11 placed a composite resin, an amalgam, and seven glass ionomer materials in standard occlusal cavities; evaluated the radiographic densities; and concluded that three of the glass ionomer materials were insufficiently radiopaque. Ferreira 12 also reported the radiographic densities of nine posterior composite res-
in s in Class I cavi ty preparations. Goshima 13 reported the optical densities on radiographs of step wedges of composite resins and aluminum, and compared radiographs of Class II cavities restored separately with amalgam and composite resins. However, a systematic evaluation using both optical density and aluminum equivalent considerations has not been reported. Also the interference caused by the variability of remaining tooth structure when comparing radiopacity has not been eliminated. The purpose of this study was to measure the radiopacity of currently available light-cured posterior composite resin samples in terms of aluminum-equivalent values and to evaluate the ability of human observers to distinguish from tooth structure a Class I restoration of these composite resins, using radiographs of the restorations in the same tooth.
R
722 • JADA, Vol. ll5, November 1987
Fig I • Regions A, B, and C used in optical density measurements and human observer evaluations. Region A, comparison of the restoration, enamel, and dentin. Region B, comparison of the restoration, and mostly dentin. Region C, comparison of the restoration and enamel.
Methods and materials Eleven light-cured posterior composite resins were included in this study: Bisfil 1, Estilux Posterior, Ful-Fil, Heliomolar, Herculite, Luma-bis Posterior, Marathon One, Occlusin, P-30, Sinter Fil, and Status. Enamel and dentin sections from extracted human teeth were also included in this evaluation. For each type of composite resin, three samples of four different thicknesses (about 1.5, 2.5, 5, and 7 mm) were prepared. The samples were polymerized using a curing lamp (Coe). Enamel and dentin section thicknesses ranged from about 1.0 to 1.8 mm. Each sample thickness was measured using a micrometer. The thickness values were used in linear regression calculations. A radiograph was made of each sample using Eastman Kodak Ektaspeed E film. Exposures were at 70 kVp, 10 rnA, and 0.25 seconds (GE Model 1000 X-ray machine.) The films were developed in a Philips model 810 automatic processor. For each radiograph, an aluminum step wedge (1 to 4 mm) and a 4-mm thick lead specimen were used as internal standards with each sample exposure. The optical density of each radiographic image was measured using a MacBeth TD-504 film analyzer with a 2-mm orifice. Two readings were taken on each step wedge area and the lead specimen area. Three readings were taken for each sample area. The readings were corrected for inherent film fog as measured by the reading for the lead specimen image. The reading at an area without a sample was also obtained to provide an optical density for zero sample thickness. Linear regression calculation using the
RESEARCH
restoration and tooth structure at regions A, B, and C. T he evaluations were classi fied as whether the restoration, when compared with the adjacent tooth struc ture, appeared to be less, about the same, or more radiopaque. Majority decisions classified the relative radiopacity of the composition to adjacent tooth structure.
equivalent values for 2-mm thick samples, composite resins that were not more radi opaque than enamel were Heliomolar, Luma-bis Posterior, P-30, Sinter Fil, and Status. Radiographs of the unfilled preparation and of the Class I cavity prep aratio n restored with composite resins are shown in F ig u re 3. D ifferences can be d is tinguished in the radiographic images of the composite restorations. A histogram detailing differences in optical densities and the corresponding observer evalua tions is shown in Figure 4. H igh optical density differences between restoration and surrounding tooth structure correlate with consensus among observers. When com posite resins were compared with mostly d e n tin , region B show ed the clearest radiographic distinctions.
Results
Fig 2 ■ Linear regression lines for alum inum
T he linear regression plots of the loga rithm of optical density at 70 kV(p) and sample thickness for alum inum and a composite resin are shown in Figure 2. The linear correlation (r2) values were greater than 0.98 except for Status (0.93), enamel (0.85), and dentin (0.93). The alum inum equivalent for 1-mm and 2mm thick composite resins, enamel, and dentin are shown in Table 1. All poste rior composite resins used in this study were more radiopaque than dentin but not necessarily more radiopaque than enamel. On the basis of the alum inum
REPORTS
Discussion
All composite resins in this study were more radiopaque than dentin, but all were
and a com posite resin for obtaining alum inum equivalent for 1-mm and 2-mm samples.
Table 1
logarithm of corrected optical density and sample thickness was performed for each composite resin, as well as for enamel, dentin, and alum inum . The alum inum equivalent for 1-mm and 2-mm thickness for the composite resins, enamel, and dentin were obtained from the correspond ing linear regression calculations. A Class I cavity preparation was made on the occlusal surface of an extracted hum an second molar. The same tooth and cavity preparation was used for all composite resins. The tooth was mounted for reproducibility of focal spot object and object-to-film distances during radi ographic procedures. Radiographs were made of the tooth without restoration and with the cavity restored with each of the composite res ins. T he composite resins, however, were not polymerized so that they could be removed after the radiographic procedure without affecting the cavity preparation. T he cavity was cleaned with alcohol before the next com posite resin was placed. T his enabled the same tooth and cavity preparation to be used with each composite resin, and provided a constant configuration for radiographic evaluation. Optical density readings were made at each of the areas w ithin the restoration and the tooth structure regions (Fig 1). Five practitioners subjectively evaluated each radiograph for contrast between the
■ Aluminum equivalent (mm) of composite resins, enamel, and dentin.
Bisfil 1 E stilu x Posterior F ul-Fil H elio m o lar H erculite L u m a-b is Posterior M arath o n O n e O cclusin P-30 Sin ter Fil S tatus E nam el D en tin A lu m in u m
1-mm sam ple
2-m m sam ple
1.82 2.16 2.47 1.93 1.95 1.72 2.00 2.52 1.77 1.65 1.93 2.22 0.79 1.00
3.88 4.20 4.97 3.64 4.64 3.58 4.32 5.77 3.47 2.70 3.64 3.84 1.82 2.00
F ig 3 ■ Posterior com posite resins in the same m andibular m olar Class I preparation. T he unfilled preparation is also show n as a baseline for comparison. From top to bottom: unfilled preparation, Sinter Fil, P-30, Luma-bis Posterior, H eliom olar, Status, B isfil 1, Estilux Posterior, Marathon One, Herculite, Ful-Fil, Occlusin.
Stanford-O thers : RA D IO PA C ITY O F C O M PO S IT E RESINS ■ 723
RESEARCH
REPORTS
tion. No consensus on a minim al degree of radiopacity was reached.
Observer ratings on radiopacity Restoration versus tooth
Fig 4 ■ Observer eval uations and quantita
----------------- JfOA ------------------
tive m easurem ents of d iffe r e n c e s in r a d i op acity. Greater d is tinction between com
Same
posite resin and tooth
In fo rm a tio n a b o u t the m anufacturers of the p ro d ucts m entioned in this article may be available from the au th o rs. N either the au th o rs n o r the American D ental A ssociation has any com m ercial interest in the products m entioned.
structure is associated with higher differences in alum inum equiva lents.
not more radiopaque than enamel. The alum inum equivalent at 1-mm and 2-mm sample thicknesses showed some relative variations. For example, the alum inum equivalent values for 1-mm thick samples showed that Bisfil 1, Herculite and M ara thon One were less radiopaque than enamel but 2-mm samples were more radiopaque than enamel. T h is result m ight be attributable to data scattering and using the linear regression model. The values obtained, however, indicate a wide range in the radiopacity of lightcured posterior composite resins. T he results of this study correlate well with the previous work of Ferreira.12 Occlusin, for example, is highly radiopaque by comparison. Some composite resins, for example, Estilux Posterior, are similar to enamel in radiopacity. Sinter Fil had low radiopacity, whereas Ful-Fil and Occlusin had radiopacities higher than that of enamel. It has been suggested by Lutz and others14 that a posterior composite resin should not only match but exceed the radiopacity of enamel. T he use of a constant configuration in a single tooth for radiographic evaluation by hum an observers provided a consistent comparison for clinical radiographic eval uations. T he am ount of rem aining tooth structure and its radiographic contribu tion are constant for each radiographic image of the tooth with a composite resin restoration. Differences in radiographic images, therefore, are the result of the dif ferences in the radiopacity of the compos ite resin. There is, however, no consensus as to the degree of radiopacity preferred by the five practitioners acting as observers for radiographic evaluation. T h e ob servers’ ability to distinguish the restora tion from adjacent tooth structure was enhanced with increasing differences in the optical density of the two areas (Fig 4). In this study, optical density measure 724 ■ JADA, Vol. 115, N ovem ber 1987
ments were taken a small distance away from the restoration—tooth structure junc tion; however, the observers probably used the differences at the junction to make their evaluations. T he conclusions illus trate that optical density differences are used to indicate the relative magnitudes but not necessarily to indicate absolute definitive values. T he distinction of the restoration from adjacent tooth structure was more prom inently visible in regions where the radiographic image was com posed of more dentin. T his radiographic distinction correlates with the lower radi opacity of dentin as compared with the composite resins. The practitioner needs to consider the influence of cavity configuration and the remaining tooth structure when evaluat ing the radiographic image for interpreta tion. Radiographically, the am ount of enamel and dentin adjacent to, and super imposed on, the restoration also influence evaluation. The choice of a highly radi opaque composite resin decreases this influence. High radiopacity in the restor ative material, however, may also decrease the diagnostic inform ation on the radio graph in areas covered by the restoration. Conclusion
The radiopacity of light-cured posterior composite resins covered a wide range as measured in terms of alum inum equiva lents. These composite resins are more radiopaque than dentin, but not necessar ily more radiopaque than enamel. Clini cal evaluations of radiographic images of composite resin restorations in the same too th cavity p re p a ra tio n by hum an observers showed variations in distinguish ing the radiographic image of the restora tion and adjacent tooth structure. As expected, a higher radiopacity in the composite resin provided easier distinc
T h is project was su p p o rte d in p a rt by g ra n t DE 05761-07 from the N a tio n a l In s titu te of D ental Research, N ational Institutes of H ealth. T h e a u th o rs th a n k the 3M Co; Risco, Inc; L. D. C aulk Co; C entrix, Inc; Coe L aboratories; Den-M at C orp; H ealthco, Inc; K err/Sybron; Kulzer, Inc; T ele dyne Getz; and V ivadent USA for their d o n a tio n of m aterials used in this study. Dr. C. M. Stanford, a grad u ate student. U niversity of Iow a C ollege of D entistry, w as research assistant; Dr. Fan is associate secretary; Dr. Schoenfeld is assis ta n t secretary; Mr. K noeppel is research assistant; Dr. J o h n Stanford is secretary, C ouncil o n D ental M ate rials, Instrum ents, an d E q u ip m en t, A m erican D ental A ssociation, 211 E C h ic a g o Ave, C h ic ag o , 60611. Address requests for reprints to Dr. Fan.
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