Postoperative Hypersensitivity in Class I Resin-based Composite Restorations in General Practice: Interim Results

Gary S. Berkowitz, DDS; Allan J. Horowitz, DMD; Fredrick A. Curro, DMD, PhD; Ronald G. Craig, DMD, PhD; Jonathan A. Ship, DMD; Donald Vena; Van P. Thompson, DDS, PhD

Postoperative hypersensitivity (POH) can be defined as pain in a tooth associated with mastication or through contact with hot, cold, sweet, or sour stimuli 1 week or more posttreatment. Pain associated with clenching, which may indicate a restoration in hyperocclusion, is typically excluded from definitions of POH.

A 2006 survey of the authors’ practice-based research network (PEARL [Practitioners Engaged in Applied Research and Learning]) revealed that POH following posterior resin-based composite (RBC) restorations is a common concern among its member practitioner-investigators (PIs). The POH literature is sparse, however, and the few relevant published studies make it difficult to draw firm conclusions. Most research studies that address POH have small sample sizes and are typically associated with evaluation of a particular bonding agent or RBC formulation. Moreover, variables of interest differ from study to study as do methods of measurement. The inconsistencies and singularly examined factors in POH research thus limit understanding both of the overall problem and the influences and elements that may be key risk factors in the general practice setting.

To help improve understanding of this phenomenon, the PEARL Network undertook an observational study among its membership to investigate the effectiveness of a range of techniques and materials in preventing or ameliorating postoperative hypersensitivity in Class I resin-based composite restorations for shallow carious lesions in dentin.

A protocol describing overall study conduct and a manual detailing study procedures were developed by the PEARL Network Executive Management Team in conjunction with the PEARL Executive Committee (including PEARL PIs), representatives of the National Institute of Dental and Craniofacial Research, the EMMES Corporation (PEARL’s data coordinating center), and a panel of extramural consultants. The authors’ research presents preliminary 1-week results for a projected 3-month follow-up study that, as of this writing, continues to enroll participants.

Materials and Methods

Eligibility criteria included clinical diagnosis of one or more unrestored permanent posterior teeth with occlusal carious lesions judged on radiograph to be no more than one-half the distance from the dentinoenamel junction to the pulp (visibility of the lesion on the radiograph was not required but was recorded as visible, equivocal, or invisible in each instance). Not more than one tooth per quadrant was allowed nor more than two teeth per participant. Eligibility also required that each tooth of interest be in occlusion with a natural tooth, free of evidence of pulpitis (no report of lingering pain associated with any stimulus), and not periodontally involved (mobility < 2 and no evidence of gingival inflammation). In keeping with the standards of study conduct in a practice-based research network, any case selected had to be one for which the practitioner would normally apply his or her standard of care, which was, in this instance, use of a resin-based composite. Beyond that, each dentist was expected to employ his or her routine methods for restoration. Use of the following was recorded: desensitizing agent, antimicrobial agent, liner, dentin-bonding agent, flowable or other composite, and composite placement method (layering or bulk cure).

Baseline preoperative hypersensitivity in each participant’s tooth or teeth was established via a paper-based (11-point, 0 to 10) visual analog scale (VAS) questionnaire that collected the history of reactions to cold, hot, and sweet stimuli as well as chewing and clenching; clenching was included to determine whether hyperocclusion might be responsible for tooth hypersensitivity. Simultaneously, participants completed a 14-item oral health-related quality-of-life (OHRQoL) questionnaire, a modified version of the Oral Health Index Profile-14 (OHIP-14) that has been widely used elsewhere.^1-5 It recorded such information as difficulty in pronunciation and the need for diet modifications because of the person’s affected tooth or teeth.

Cavity preparation was initiated, and upon enamel removal, dentin caries activity was ranked according to a modification of Kidd’s dentin caries classification system:^6,7

• 1 = Soft, serous
• 2 = Soft, dry
• 3 = Soft, dry, granular
• 4 = Leathery
• 5 = Firm but discolored

On completion of the preparation, cavity depth, width, and length were recorded,⁸ as well as the extent of caries dentin removal (“all removed” or “some carious dentin left locally”). In addition, the details of dentin treatment, disinfection, desensitizing agent, liner, bonding agent, and resin-based composite used were recorded. Participants were advised to contact their dentists if they experienced any level of POH.

At 6 to 7 days posttreatment, participants completed POH, VAS, and OHRQoL questionnaires and were reminded to report to the dentist any development of POH. Patient anonymity was ensured by submitting the reports through a secured web site or mailing them (with only a number identification) to the PEARL clinical coordinating center (EMMES Corporation, Rockville, MD).

Statistical Analysis

Descriptive statistics, including frequencies and percentages, were generated for variables of interest. For this analysis, appreciable hypersensitivity (AH) was defined as a VAS value of 3 or higher. Pearson correlation coefficients between sensitivity while chewing and sensitivity while clenching at baseline and at 1 week were obtained, and chi-square tests examined the relationship between baseline AH and active caries ranking, as well as between baseline AH and lesion visibility on radiographs.

For this interim analysis, multiple teeth in a given participant were treated as independent cases.

Results

Thirty-eight PEARL PIs enrolled 504 patients (target enrollment: 610). The median age was 25 years (range 10 to 59) with 24% ≤18, 43% 19 to 30, and 33% > 30 years of age; 39% were male, 61% female. Of the 565 teeth represented, 88.3% were molars and 11.7% premolars; 55.7% were in lower quadrants. Among teeth with baseline sensitivity data, 54.6% of teeth (293 of 537) were reported to have some hypersensitivity, defined as a score of > 0 on any VAS item; this proportion is 52.6% of teeth (283 of 538) if clenching is excluded. Teeth with AH (any score of ≥ 3) at baseline comprised 31.1% of teeth (167 of 537), or 29% (156 of 538) after excluding clenching (Figure 1). At baseline, AH to cold was the most prevalent report (42%), followed by sweets (32%), clenching (21%), heat (19%), and chewing (19%); at 1 week posttreatment, the proportions were 40% for cold, 27% for chewing, 25% for sweets, 25% for clenching, and 22% for heat (Figure 2). Pearson correlation coefficients between hypersensitivity while chewing and hypersensitivity with clenching at baseline and 1 week were significant (0.56 and 0.63, respectively).

At 1 week postoperative, 52.4% of teeth (215 of 410) left to follow-up had hypersensitivity and 26.1% (107 of 410) had AH (Figure 1). Among teeth with baseline AH, the proportion with AH at 1 week posttreatment was reduced to 50.9% (58 of 114). Among teeth with no baseline AH, 16% (46 of 287) had AH at 1 week (Figure 3). Neither baseline nor 1-week AH was correlated with either cavity depth or volume. Baseline AH was not associated with active caries ranking (< 3 on the dentin caries classification scale; chi-square test: P = .30). If inactive caries are equated with the highest three rankings on the dentin caries classification scale (in which the distribution was “3 = soft, dry, granular” [18.8%], “4 = leathery” [19.3%], and “5 = firm but discolored” [25.8%]), then active caries was present in only 36.1% of teeth (196 of 543).

These findings were analyzed for the influence of cofactors; however, no relationship was found between 1-week maximal hypersensitivity and, for example, cavity volume or depth, liner use, dentin-bonding agent use, and patient age or other demographics. Nor was maximal hypersensitivity at baseline different between the antimicrobial subgroup and teeth with no antimicrobial treatment, further suggesting that these populations are similar in all respects other than level of 1-week AH. Caution in interpretation is nevertheless advised with regard to the effect of antimicrobial agents, as the numbers of these results are small and possible variations in the details of application and removal have yet to be determined.

One cofactor that correlated with preoperative AH was the radiographic appearance of the lesion. Among teeth with lesions visible on the radiograph, 40.4% (76 of 188) had preoperative AH as compared to 24.2% (16 of 66) whose radiographs were judged equivocal and 26.6% (54 of 203) in which a lesion was not visible (P < .01). Among teeth without POH at baseline, it was observed that those treated with an antimicrobial were more likely to report AH at week 1 than those not receiving an antimicrobial. Further analyses of this possible relationship are being conducted.

Discussion

There are few studies with which to compare the present investigation, which focuses on short-term POH in Class I resin-based composite restorations of carious lesions that extend no more than halfway through the dentin toward the pulp, using state-of-the-art materials and techniques. Perdigao et al⁹ compared a self-etch to a total-etch adhesive system in Class I and Class II restorations by measuring responses to air and cold using a VAS as well as times to response. The authors reported no significant changes from baseline to periods up to 6 months in measurements for either system. In a subsequent study by the same group using the identical measurements but addressing only Class II restorations,¹⁰ a significant reduction was found in severity of cold response, as well as a significantly longer time to cold response at 2 weeks postrestoration. In these latter findings, however, no allowance was made for some of the large, open lesions restored or for the thermal conductivity of the many amalgam restorations replaced. Moreover, while participants reported mean sensitivity responses ranging from 1.5 to 3, the fact that overall responses were in the range 0 to 10 for both air and cold stimulus suggests at least some patients experienced a noxious stimulus. It bears mentioning that sensitivity on mastication was reported as 0 in both studies.

More recently, Casselli and Martins¹¹ employed a split-mouth design to compare a total-etch to a self-etch system (neither using liners) in 104 Class I restorations placed by a single clinician. At 7 days postoperative, 71% of the restorations were rated 0 on a 11-point VAS for sensitivity, 17% were 1.1 to 2, 2% were rated 2.1 to 3, and 4% were rated > 3 (one rated 4 and one 5.1). At 6 months posttreatment, only 1% (1) of the restorations were rated in the range 1.1 to 2 and 2% (2) in the range 2.1 to 3 for sensitivity. No significant difference was found between bonding agents.

In all these studies, participants reported their perceptions directly to the treating clinician, raising the question of whether their responses can be considered forthright.

Reports of longer-term outcomes testify to the persistence of POH and the long-term implications of POH regardless of occurrence. One representative study of 148 RBC restorations (mixed Class I and Class II) found that POH requiring restoration replacement occurred in 4% (5 of 140 patients) during 2 years.¹² It was not reported whether the hypersensitivity in these restorations developed spontaneously or gradually.

The most comprehensive study of POH outcomes to date is a multicenter clinical trial involving 1101 restorations treated using a calcium hydroxide (CaOH) liner, a single bonding agent, and a single resin-based composite.¹³ The authors concluded that at 5 years: (1) restorations with POH were more likely to fail than restorations without POH; (2) restorations with POH in large cavities were more likely to fail than restorations in small cavities; and (3) regardless of cavity size, restorations were more likely to fail if POH occurred within the first recall (1 month after placement).

As this summary suggests, POH is often a secondary focus of studies that primarily examine restorative material and placement techniques and, thus, measurement approaches have not been uniform. Because of the complexity involved in studying the underlying trigger(s) of POH and predicting its occurrence, sophistication and standardization of measurement have not evolved.

In the present study, the investigators did not expect that 31% of teeth would have AH pretreatment. Caries, unless extensive, is generally considered to be a “silent” disease, and the lesions included in this study were limited to no more than half the dentin depth. Frank caries with visibly open enamel was reported only in a few instances. Indeed, 30% of lesions were either not evident or equivocal on radiograph but diagnosed clinically. There was a positive correlation between caries diagnosed radiographically and AH. However, despite the lack of correlation between cavity depth following preparation and baseline, maximal hypersensitivity was unanticipated.

Although AH appears to have been significantly reduced by placement of a restoration (AH to no AH) (Figure 3), it should be noted that 16% of no-baseline AH teeth reported to have AH at week 1. As can be seen in Figure 1, the percentage of teeth with AH was reduced by only 5% from baseline to week 1 (31% to 26%) and the percentage of teeth reporting any hypersensitivity was changed only from 55% to 52%.

The authors’ finding that 16% of teeth with no preoperative hypersensitivity were found to have AH at 1 week posttreatment was similarly unanticipated. As suggested earlier, this level of hypersensitivity may not be apparent in clinical settings if patients are reluctant to report it to their dentists unless it is severe. It is thus reasonable to speculate that hypersensitivity is underreported when patient outcomes are not solicited anonymously. The authors considered subtracting the number of participants with clenching AH from the analysis of the group with acquired AH (ie, those with 1-week posttreatment AH who had no baseline AH) because clenching AH may be related to the restoration being in hyperocclusion. However, given the baseline correlation (0.56) between clenching and chewing AH, hyperocclusion may not be a factor in the POH observed.

The finding that upon enamel removal only 36% of teeth had active caries suggests in many instances a caries risk management program rather than operative treatment is advised. This supports previous studies of early lesions^14,15 and argues for methods to describe and record the stages of the carious process in enamel, such as the International Caries Detection and Assessment System,¹⁶ given that many of these lesions were not visible or were equivocal on radiographs. The ability to monitor changes in lesion appearance becomes important in managing caries as a disease.

Regarding caries activity ranking, the modification of the Kidd classification to include an intermediate ranking (“3 = soft, dry, granular”) as a descriptor of inactive caries was based on the authors’ clinical experience, in which this state has been observed occasionally. The result that 18.8% of lesions were so ranked by PEARL PIs compared to 19.1% described as “leathery” was unexpected and will be further explored.

The limited numbers of the variety of treatments and materials used in this effectiveness study require that caution be exercised interpreting some of the results. For example, while antimicrobial treatment appears to be associated with a reduction in AH among baseline AH teeth, the opposite is true for no-baseline AH teeth. The use of an antimicrobial may be attributed to the dentist’s judgment based upon the depth of the preparation, appearance of the remaining dentin, or estimated caries activity upon opening the lesion. Still, the authors’ analysis of the results of using an antimicrobial suggests that the negative impact of these agents may be real, but further research is needed before recommending a change in clinical practice.

This study is unique not only in evaluating patients with regard to early caries and hypersensitivity but also in investigating several clinical variables linked with POH. Given the wide range of techniques employed by PEARL Network PIs following cavity preparation, the authors are not yet in a position to attempt to correlate POH with use of antimicrobials, liners, dentin bonding agents, or restorative techniques. It is worth noting that, irrespective of baseline hypersensitivity, patients in some dental practices reported that nearly 100% of teeth experienced AH following treatment, while those in other practices reported almost none. This reflects one of the strengths of conducting studies outside an academic environment: the ability of PIs to compare at the conclusion of the study their patient outcomes with the blinded outcomes of their fellow network members, which is an important aspect of participation in a practice-based research network.

It is hoped that, after completion of this study, the 4-week findings will provide guidance for future studies of POH, with the ability to positively impact the daily lives of patients. The authors are eager to review the final data to determine which, if any, of their preliminary results prove significant at longer term. Based on those findings, the PEARL Network anticipates conducting a randomized controlled trial to determine which methods and techniques are best for reducing or eliminating POH in resin-based composite restorations.

Acknowledgment

This study was supported by the National Institute of Dental and Craniofacial Research, National Institutes of Health, through grant UO1 DE016755 awarded to the New York University College of Dentistry.

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About the Authors

Gary S. Berkowitz, DDS
Practitioner Investigator,
PEARL Network,
New York University College of Dentistry,
New York, New York

Allan J. Horowitz, DMD;
Practitioner Investigator,
PEARL Network,
New York University College of Dentistry,
New York, New York

Fredrick A. Curro, DMD, PhD;
Executive Management Team,
PEARL Network,
New York University College of Dentistry,
New York, New York

Ronald G. Craig, DMD, PhD;
Executive Management Team,
PEARL Network,
New York University College of Dentistry,
New York, New York

Jonathan A. Ship, DMD;
(Deceased) Executive Management Team,
PEARL Network,
New York University College of Dentistry,
New York, New York

Donald Vena;
PEARL Coordinating Center Principal,
EMMES Corporation,
PEARL Coordinating Center,
Rockville, Maryland

Van P. Thompson, DDS, PhD
Executive Management Team,
PEARL Network,
New York University College of Dentistry,
New York, New York