JADA Continuing Education
Clinical performance evaluation of a packable posterior composite in bulk-cured restorations
David C. Sarrett, DMD, MS,
Carol N. Brooks, DDS and
Jennifer T. Rose, DDS
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ABSTRACT
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Background. The authors evaluated the clinical performance of Prodigy Condensable (Kerr, Orange, Calif.) composite placed and cured in increments up to 5 millimeters thick.
Methods. The authors placed 57 Class II restorations in 32 patients in composite increments up to 5 mm thick. Using this technique, they placed the majority of restorations in one increment and then carved the occlusal and proximal anatomy before light curing. The authors evaluated the restorations at three, six, 12, 24 and 36 months.
Results. No restorations required replacement; however, 11 developed a defect requiring repair or continued observation. Of these 11, nine restorations developed defects on the margins of the restorations and two developed secondary caries. The Kaplan-Meier estimate of probability that a restoration would develop a defect during 36 months that would require immediate repair was 0.13. Postoperative sensitivity was not significantly different from preoperative sensitivity.
Conclusions. The authors found that no restorations required replacement and no increased postoperative sensitivity occurred.
Clinical Implications. The authors suggest that this composite material can be placed in a single increment up to 5 mm thick for Class II restorations.
Key Words: Dental restorations; resin-based composite; light curing; posterior restorations
Resin-based composites with viscosity higher than that of previous materials were introduced in the late 1990s to market to dentists who wanted to use a tooth-colored posterior restorative material that handled more like dental amalgam.1 A clinical challenge in placing Class II composite restorations is creating anatomically correct proximal contours and contact with adjacent teeth. Unlike amalgam, composite cannot be condensed to increase its density. Attempting to pack composite as a method of achieving adaptation of a matrix band to the adjacent tooth generally is not effective because the material will not increase in density and viscosity during placement. Without an increase in density, the material cannot resist the pressure applied by the matrix band, and the matrix band will return to its original shape; this may result in an open proximal contact when the matrix band is removed. So-called "packable" or "condensable" ("condensable" being a misleading term because the material’s density does not increase) composite materials have a noticeable stiffness that may allow them to be placed the same way as dental amalgam is placed.
A potential drawback to these stiffer materials is their limited ability to adapt to internal cavity wall surfaces and to cavity margins. The presence of postoperative sensitivity indirectly may indicate poor ability of the dentin adhesive combined with the restorative material to adapt to internal walls and seal the dentinal tubules. It also is known that fracture is a common reason for failure of posterior composite restorations.2 Packable composites do not have substantially better mechanical properties than do hybrid composites1,3 and would not be expected to perform better clinically in this respect. Because the packing technique can introduce air bubbles into a composite restoration made of such restorations may have a greater potential to fracture than may restorations made of hybrid composite materials. Sarrett4 provided a more complete review of the clinical challenges associated with posterior composite restorations.
Lopes and colleagues5 evaluated two packable posterior composites and found after two years that six to 12 percent of restorations had some margin adaptation defects and five to 11 percent showed margin discoloration. Two of 74 restorations had margin adaptation defects that required operative intervention. The other parameters evaluated showed acceptable clinical performance at two years.
Ernst and colleagues6 evaluated one packable composite and found that 79 percent of the studied restorations were acceptable at three years, and 16 percent of the restorations had margin adaptation defects that required intervention. They found secondary caries in 3.5 percent of the restorations, and margin discoloration in 28 percent. The material tested by Ernst and colleagues6 no longer is available in the formulation they tested.
In a review of 24 clinical studies of posterior composites, Brunthaler and colleagues2 found only two studies that listed margin defects as a main reason for failure; one of these studies involved packable composites. These authors analyzed all types of restoration failure and found no differences in the failure rate for packable composites compared with the rates of other composite materials in the 24 studies reviewed; however, the studies of packable composites were all three years or less in duration compared with studies of the other composite materials, which were as long as 17 years.
A study evaluating the use of a flowable composite before placement of the packable composite found no differences in survival rates of restorations placed with or without a flowable composite layer between the adhesive and the packable composite.7 The overall survival rate after two years was 94 percent. The reasons for failure were margin adaptation defects, secondary caries, fracture and degradation of surface finish. Three of 116 (3 percent) restorations fractured. Ernst and colleagues6 reported a 9 percent fracture rate of a packable composite over three years, with 60 percent of the fractures being in molar restorations. Loguercio and colleagues8 evaluated four packable composites over one year and reported marginal ridge fractures in 1 percent of restorations made with the same brand of material as studied by Ernst and colleagues.6 Loguercio and colleagues8 observed no fractures for the remaining three packable composites they studied; however, restorations made with a nonpackable composite in that study showed that 28 percent of the restorations developed small fractures. Overall, two of the three packable composites in this study had acceptable clinical performance after one year. Three other studies9–11 evaluated one of the materials found acceptable by Loguercio and colleagues8 and found 94 to 100 percent survival over 12 to 24 months. One of these three studies10 reported 6 percent and another11 reported 3 percent fracture of restorations made with this same packable composite.
Brunthaler and colleagues2 found that five of the 24 studies they reviewed reported postoperative pain as a reason for failure; two of those five studies found postoperative pain to be the primary reason for failure. In the two studies in which postoperative pain was the main reason for failure, one was a study of direct composite inlay placement and the other was a study of ultraviolet–light-cured materials. Ernst and colleagues6 reported a 4.8 percent rate of replacement of packable composite restorations over three years owing to postoperative sensitivity. Loguercio and colleagues8 and Türkün and colleagues10 reported no problems with postoperative sensitivity, whereas subjects in the study by Yip and colleagues11 had sensitivity in 9 percent of the restorations made with a packable composite versus in 3 percent of the restorations made with a nonpackable material.
The American Dental Association Acceptance Program Guidelines: Resin-Based Composites for Posterior Restorations12 include designations of Type A and B materials. The guidelines suggest the unrestricted use of Type A materials in restoring posterior teeth, including for cuspal replacement. For acceptance as a Type A material, the ADA requires 18-month clinical data from studies that include at least 30 Class I and II restorations of a buccal and/or lingual surface. Failure rates must be no greater than 5 percent in terms of margin integrity and secondary caries and no greater than 10 percent in terms of margin discoloration and bulk color. The ADA also requires evidence that there were no bulk fractures and no restoration loss. Type A materials also must meet a series of laboratory test standards. For Type B materials suggested for use in Class I and II restorations, only the laboratory testing is required. Thus, it is difficult to compare the results from previous clinical studies of packable composites with the current ADA guidelines for Type B materials to determine acceptable clinical outcomes. It appears that a restoration replacement rate of greater than 10 to 15 percent after 18 to 36 months is clinically unacceptable. The most common defects that require replacement are secondary caries, bulk fracture or total restoration loss, or unresolved postoperative sensitivity. One further complication is how to handle composite restoration defects that can be repaired easily to ensure that the restoration continues to serve the patient well for years. There are no current standards or guidelines regarding an acceptable repair rate.
The most common defects that require restoration replacement are secondary caries, bulk fracture or total restoration loss, or unresolved postoperative sensitivity.
We evaluated the clinical performance of Prodigy Condensable (Kerr, Orange, Calif.) composite. The manufacturer’s directions indicate that increments up to 5 millimeters may be placed and cured, and that sculpting of the restoration may be completed before curing. We included these two components in the protocol for placing the restorations. We were keenly interested in clinical signs of undercured composite and polymerization shrinkage; these signs included bulk composite fracture or loss of restorations, postoperative pain and cuspal fractures.
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MATERIALS AND METHODS
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We placed a total of 57 Class II restorations in 32 patients in teeth with opposing natural occlusion. One of the authors (DCS) placed all restorations in the Advanced Education in General Dentistry (AEGD) clinic at Virginia Commonwealth University (VCU) School of Dentistry, Richmond. AEGD residents administered anesthetic, placed rubber dams and prepared some cavities; however, one faculty member with more than 20 years of experience (again, DCS) completed all cavity preparations and placed the composite restorations. We used rubber dam isolation in all cases, usually after the majority of cavity preparation was completed. The occlusal portion of the cavity was at least 2 mm deep and the axial wall was prepared so that it extended into dentin. Proximal contact was broken on the majority of teeth with a minimum of 0.5 mm extension from adjacent teeth in facial, gingival and lingual locations. We rounded line angles by using no. 330 and round burs for cavity preparation and caries removal.
We applied a metal matrix before initiating the bonding procedure. We placed the majority of restorations using a matrix system with a dead soft-sectional metal matrix, wedge and a Palodent BiTine (Dentsply International, York, Pa.) ring. When we placed practice restorations using a circumferential matrix and wedges for tooth separation, we did not routinely achieve satisfactory proximal contours and contacts. We used Optibond Solo (Kerr) adhesive system according to the directions supplied by the manufacturer. We applied light-cured glass ionomer base to only four cavities before placing the adhesive. We chose the appropriate shade of composite and placed the restoration in one increment when the thickness was 5 mm or less by injecting the material directly from the supplied unidose cartridges. Using this technique, less than 10 percent of restorations required more than one increment, and we created the majority of the final occlusal and proximal anatomy before light curing. We used a burnisher and amalgam carvers lubricated with Optiguard resin (Kerr). We first cured the restorations from the occlusal aspect for 40 seconds using an Optilux 501 light-curing unit (Kerr). After removing the matrix, we then cured the restorations for 40 seconds from each proximal wall of the restoration. For example, we cured a mesialocclusal restoration 40 seconds from the occlusal aspect, 40 seconds from the mesiobuccal aspect and 40 seconds from the mesiolingual aspect, for a total curing time of 120 seconds. We measured the curing light intensity just before curing each restoration with a Demetron radiometer (Kerr) to ensure that it always was at least 500 milliwatts per square centimeter. We performed occlusal adjustment with carbide burs, and we polished the restorations with diamond paste. We then etched and sealed the restorations, as well as 1 to 2 mm of surrounding enamel, with Optiguard resin.
Tables 1
through 4 provide descriptive data on the teeth restored and the materials used. The youngest patient was 21 years old, the oldest patient was 72 years old, and the median age was 33 years. About one-half of the patients were 20 to 39 years of age. Exclusion criteria for patient selection included pregnancy and serious chronic diseases that would not allow for routine restorative dentistry. Most of the patients were regular patients of the VCU School of Dentistry and included VCU students. None of the patients were considered to be at high risk of developing dental caries. All patients signed an informed consent form and this research was approved by the VCU Institutional Review Board.
We recalled the patients at three, six, 12, 24 and 36 months, and two of the authors (CNB and JTR) evaluated the restorations using modified U.S. Public Health Service (PHS) criteria4,13,14 based on the R, S, T, V scoring system. Table 5 (page 76) describes the definitions for the rating scale, and Sarrett4 fully described the details of each criterion. We examined 53 of the original 57 restorations at the three-month recall appointment, which was the baseline examination for the study. Before the first recall visit, the two examiners practiced using the criteria by examining patients with posterior composite restorations. During the practice sessions, they discussed differences in judgments to achieve a consensus evaluation. They recorded the data on a form that included a complete copy of the modified PHS criteria. The examiners did not have access to the data from their previous evaluations. They used a mirror, an explorer and magnification glasses to assess all clinical parameters, and the patients brushed their teeth before being examined.
At each recall visit, the examining authors evaluated surface appearance, color match, anatomical form (occlusal contours, proximal contact and retention), margin integrity (adaptation—tactile, adaptation—visual, discoloration and caries) and sensitivity. They measured tooth sensitivity before placing each restoration and at each recall visit. The patient rated his or her discomfort on a scale of 0 (no sensitivity) to 10 (the worst pain he or she had ever felt) after receiving a three-second blast of air to the restored tooth. At the first recall visit, we asked the patients if they had postoperative sensitivity during the first week after the placement of the restoration.
We analyzed the modified PHS data by calculating percentages of restorations scored R, S, T or V for each clinical criterion.4 We performed 
2 analyses to compare the clinical criteria and analysis of variance with the mean postoperative sensitivity across all recall periods. We used the Kaplan-Meier method to estimate two functions for the probability that a restoration would require some continued observation or intervention over 36 months. One function was for the probability that a restoration would develop a T- or V-score defect; the second function was for the probability that a restoration would develop only a V-score defect. We used the first occurrence of a T or V score for each restoration to estimate the above probabilities. We used an alpha level of .05 for all statistical analyses.
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RESULTS
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At the six-, 12-, 24- and 36-month recall appointments, we evaluated 50, 43, 43 and 25 restorations, respectively (Table 6, pages 77 and 78). The percentage range of pre-molar restorations evaluated across the recall periods was 53 to 60 percent and of molar restorations was 40 to 47 percent. The percentage range of two-, three-and four-surface restorations evaluated across the recall periods were 64 to 72 percent, 24 to 33 percent, and 2 to 4 percent, respectively. The median age of the patients at each recall visit ranged from 28 (at the 12-month recall visit) to 45 (at the 36-month recall visit) years.
Table 6
presents the results in percentages of each score—R, S, T and V—for each criterion for all restorations we evaluated at each recall appointments. The 2 analyses of the data in Table 6 indicated that there was a significant difference in the criteria for surface. The surface appearance was rougher at six months than at the other recall points. There were no other significant differences in the other clinical criteria across all recall periods. A total of 19 restorations developed a T- or a V-score defect. Eight of these restorations scored T or V only because of proximal contacts’ not being tight; two other restorations also developed open contacts. Four of the open contacts were adjacent proximal restorations in the study. We determined from the patient’s history and the appearance of the proximal contours that wear of the material caused none of the open contacts. Seven of the 10 were caused by orthodontic treatment, two by changes in occlusion from other restorative procedures and one by unexplained factors. We attributed T- or V-score defects of 11 restorations to true issues related to the composite material. Of these 11 restorations, six developed only T-score defects caused by chipping of the material near margins. Five restorations developed a V-score defect, of which two were due to secondary caries and three were due to marginal defects.
The Kaplan-Meier analyses showed that for this composite, the probability that a restoration would develop a V-score defect by 36 months was 0.13 and the probability that a restoration would develop a T or V score was 0.24. We did not replace any restorations during the study for any reason, and we kept in the study any restorations that were repaired.
Seventy-three percent of patients reported no sensitivity during the first week after placement of restorations. The mean preoperative sensitivity caused by a three-second air blast was 0.35 with a standard deviation of 1.03. This was not statistically different from the mean sensitivity at three, six, 12, 24 or 36 months, which were 0.40 (± standard deviation 1.15), 0.50 (± 1.02), 0.51 (± 1.22), 0.30 (± 0.91) and 0.76 (± 1.36), respectively.
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DISCUSSION
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The number of patients we examined and restorations we evaluated at each recall visit decreased over time. This is a typical problem with these types of clinical studies, and it can lead to bias in the sample available for evaluation in the later years of the study. We experienced deviation of 8 percent or less in the tooth type and restored surfaces distributions between the baseline recall appointments and all other recall periods. This likely had limited impact on our results. The median age of patients at restoration placement was 33 years; the greatest deviation from this value was 45 years at the 36-month recall appointment. The range of median age at the other recall appointments was 28 to 35 years. The increased median age of patients at the 36-month recall visit may have introduced some bias in the 36-month results.
Surface appearance.
The percentage of R scores for surface appearance decreased from 81 percent at three months to 58 percent at six months and, ultimately, returned to 96 percent at 36 months (Table 6). This material maintained its viscosity during placement and shaping. Slumping that usually occurs when composite warms to mouth temperature did not prevent us from sculpting the anatomical contours before light curing. We believe the increase in surface roughness between three and six months was caused by the initial loss of the sealed surface, which exposed the carved surface. The carved surface had rough areas that were filled in by the sealer. The sealed surface initially appeared glossy and created an illusion of smoothness; however, the gloss wore off in the first six months. We observed a subsequent increase in the percentage of R scores, indicating a smoother surface appearance, which we believe was caused by a self-polishing effect of wear that resulted in smoothing out the rough areas left by our carving.
Color.
Color matching and stability met ADA guidelines12 during the study period, with 91 percent of the restorations having R scores at 24 months and 80 percent of the restorations having R scores at 36 months with no T or V scores occurring at either time interval (Table 6).
Anatomical form.
Occlusal contours.
We also observed that 66 to 81 percent of the restorations scored R for anatomical form—occlusal contours. We believe this was caused mainly by our placement technique, which created the majority of the occlusal contour before curing the composite. This left some excess contour at the margins, resulting in 66 percent of the resotrations receiving an R rating at three months (Table 6). This excess wore during function and increased the score to 81 percent at 12 months. Subsequently, continued three-body wear caused by mastication resulted in some slightly undercontoured areas, and we observed that the percentage of restorations having R scores decreased to 68 percent at 36 months. The 2 percent of restorations that had T scores and 4 percent that had V scores at 24 and 36 months, respectively, for occlusal contours are within the ADA guidelines.12
Proximal contact.
We found that despite the material’s higher viscosity in comparison with that of nonpackable composite, we could not achieve satisfactory proximal contacts routinely by using only a metal circumferential matrix band and separation of the teeth with a wedge. We used a bitine ring and dead soft metal matrices for the majority of the teeth we restored (Table 4). We observed 10 restorations with open contacts over the 36 months, none of which we attributed to wear or other loss of composite material. Our study included dental students who decided to receive orthodontic treatment after restoration placement, resulting in seven of the open contacts. Despite this drawback to our study, the data from the other patients indicated that maintenance of proximal contact was satisfactory.
Retention.
An assessment of restoration retention evaluates partial and total restoration loss and bulk fracture of the composite. We found no restorations that were lost totally during the study; the percentage of R scores for retention was 98 percent and 96 percent, respectively, at 24 and 36 months (Table 6). The 4 percent failure (2 percent T scores and 2 percent V scores) at 24 months is well within the 5-percent-at-18-months limit specified in the ADA guidelines.12 The 4 percent T scores and 4 percent V scores for retention at 36 months were due to partial loss of material from two restorations. This rate of fracture is in the 3 to 9 percent range reported by others for packable composites6–8 and indicates that this material, cured in thicknesses up to 5 mm, was cured sufficiently to withstand occlusal forces. If the material did not cure adequately in the deeper area of the restorations, we would have expected to see bulk fractures into the poorly cured layer in the early months of the study.
Margin integrity.
Adaptation—tactile.
We evaluated marginal adaptation using an explorer to detect crevices and contour mismatches at the interface between the tooth and the composite. Our data in Table 6 show the baseline percentage of R scores for adaptation—tactile was 60 percent and then decreased to 48 percent at 36 months. As we did with occlusal contours, we detected excess composite at margins during the first year. This likely occurred because of the method we used, in which we shaped the majority of the occlusal anatomy with carvers before curing the composite. As wear from mastication occurred, the excess material at the margins disappeared and some areas of slight undercontour at the marginal resulted in the increase of percent S to 44 percent at 36 months. We speculate that the net result of these two mechanisms explains why we did not see any significant difference in marginal adaptation over time.
The ADA guidelines12 require margin integrity failures to be no more than 5 percent at 18 months for a Type A composite. At 12 months, 2 percent of restorations had a T-score defect for marginal adaptation; at 24 months, we observed some areas of crevice formation and marginal fractures that allowed penetration with an explorer, resulting in 9 percent (2 percent T and 7 percent V) of restorations requiring intervention. These data indicate that this material likely would meet the 18-month ADA standard and are in the range of 6 to 16 percent at 24 months reported in other studies for packable composites.5,6 The bulk curing method we used does not appear to have resulted in increased margin adaptation failures as might have been expected. At 24 months, two of the restorations with V-score defects in the same patient occurred at the buccogingival line angle of molar restorations. We decided to repair these areas and continue to follow the restorations. At 36 months, the repaired areas were intact and required no further treatment. The double dagger symbol next to the 36-month data for "adaptation—tactile" in Table 6 indicates that the data include the two repaired restorations. Composite restorations offer a distinct advantage over other materials: the option of repairing defects rather than replacing the entire restoration.
This material likely would meet the ADA standard for margin integrity failures and are in the range of 6 to 16 percent at 24 months reported in other studies for packable composites.
Adaptation—visual.
Margin integrity evaluated by the "adaptation—visual" criterion (Table 6) indicated higher values of percentage of restorations with R scores compared with values seen with an evaluation by the "adaptation—tactile" criterion. Our data illustrate the difficulty of seeing marginal changes because of the color and translucency match between the composite and enamel.
Discoloration.
We found no T- or V-score defects for margin discoloration and, thus, no failures for this criterion. The ADA guidelines12 require no more than 5 percent failures for margin discoloration at 18 months.
Caries.
We did not detect any secondary caries until the 24-month recall visit when one restoration (2 percent V in Table 6) had caries at a buccogingival line angle where the marginal was in dentin. We found one more case of secondary caries at the 36-month recall appointment in another patient resulting in a cumulative 8 percent V (Table 6). Our data are within the range of 3.5 to 13 percent failure owing to secondary caries in studies with observation periods up to five years2 and less than 5 percent at 18 months to meet the ADA guidelines.12
Postoperative sensitivity.
Brunthaler and colleagues2 reported failures due to postoperative sensitivity of 2 to 8 percent in five of the 24 studies they reviewed. These studies ranged in length from 1 to 17 years. The remaining 19 studies reported no postoperative sensitivity failures. Our data are similar in that no restorations failed because of postoperative sensitivity. We found that 73 percent of patients reported experiencing no postoperative sensitivity during the first week after placement of the restorations, and there were no significant differences in the sensitivity measured preoperatively versus postoperatively at all recalls periods. In our protocol, we cured the majority of restorations in bulk up to 5 mm in thickness, which likely created more polymerization contraction stresses in the teeth. It might be expected that this method would lead to problems with postoperative sensitivity; however, this was not the outcome. It is critical to note that we used a curing light with at least 500 mW/cm2 output and multiple curing cycles of 40 seconds, which are important factors in the results we obtained. Weaker curing lights, shorter curing times or both may not yield the same outcomes.
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CONCLUSION
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We evaluated the clinical performance of Prodigy Condensable composite when placed and cured in increments up to 5 mm thick in Class II restorations. No restorations required replacement; however, the probability over 36 months that a restoration developed a defect requiring an immediate repair was 0.13. The most frequent reason we observed for needing repair was defects on margins. Two restorations developed secondary caries after 24 months. We found no increase in the mean postoperative sensitivity compared with the mean preoperative sensitivity. On the basis of these limited results, we suggest that this composite material can be placed and cured as a single increment for most Class II restorations, and its performance should meet the ADA guidelines for posterior composites.
For this packable composite material, curing in bulk facilitates the placement of the material and prevents creating fins of material being packed between a cured layer and the matrix. Before light curing, anatomical shaping of the occlusal surface minimizes the need for carving with rotary instruments. We recommend that further research on the clinical outcomes of bulk-cured restorations be completed before any suggestion is made that this technique may be used with other composite materials.
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FOOTNOTES
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DISCLOSURE: This work was supported by a grant from Kerr (a subsidiary of Sybron Dental Specialties), Orange, Calif.
Dr. Sarrett is a professor of dentistry and the associate vice president for health sciences, Virginia Commonwealth University, 1012 E. Marshall St., PO Box 980549, Richmond, Va. 23298-0549, e-mail "dcsarrett{at}vcu.edu". Address reprint requests to Dr. Sarrett.
Dr. Brooks is an associate professor, School of Dentistry, Virginia Commonwealth University, Richmond.
Dr. Rose is a dentist in private practice, Richmond, Va.
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REFERENCES
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ABSTRACT
MATERIALS AND METHODS
