The Postoperative Sensitivity of Fixed Partial Dentures Cemented With Self-Adhesive Resin Cements

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The postoperative sensitivity of fixed partial dentures cemented with self-adhesive resin cements A clinical study Diaa El-Din Saad, BDS, MSc; Osama Atta, BDS, MSc, PhD; Omar El-Mowafy, BDS, PhD, FADM

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Background. The authors investigated the postcementation sensitivity associated with selfadhesive resin cements used with fixed partial denN C U U tures (FPDs). A ING ED 4 RT Methods. The authors recruited 20 patients who ICLE needed posterior porcelain-fused-to-metal FPDs and divided them randomly into three groups. They prepared 50 abutments, then cemented FPDs with one of two self-adhesive resin cements (Breeze SelfAdhesive Resin Cement, Pentron Clinical Technologies, Wallingford, Conn., and RelyX Unicem Self-Adhesive Universal Resin Cement, 3M ESPE, Seefeld, Germany) or an etch-and-rinse resin cement (RelyX ARC Adhesive Resin Cement, 3M ESPE, St. Paul, Minn.). The authors measured participants’ tooth sensitivity to cold water, air blast and biting at 24 hours and at two, six and 12 weeks after FPD cementation by using a continuous visual analog scale (VAS). Data were analyzed statistically by means of the Mann-Whitney test. Results. For cold tests, the highest VAS scores occurred 24 hours after cementation. The mean VAS scores associated with RelyX ARC were significantly higher than those associated with Breeze and RelyX Unicem (P < .001) at all test intervals. The mean cold-test VAS scores associated with Breeze and RelyX Unicem were not significantly different (P > .05). With all cements, sensitivity to cold decreased significantly after two to six weeks; however, with RelyX ARC, VAS scores stayed above the 30 percent level even after 12 weeks. The biting sensitivity associated with RelyX ARC was significantly higher than that associated with Breeze and RelyX Unicem (P < .001), and it remained above the 20 percent level even after 12 weeks. Those with Breeze-cemented FPDs had no sensitivity to biting, whereas those with RelyX Unicem–cemented FPDs had a mean biting sensitivity value of less than 5 percent at two weeks only. Conclusions and Clinical Implications. Breeze and RelyX Unicem were associated with significantly lower postoperative tooth sensitivity values than was RelyX ARC. With Breeze and RelyX Unicem, postoperative tooth sensitivity disappeared after two to six weeks; however, with RelyX ARC it remained even after 12 weeks. Clinicians may use self-adhesive resin cements, and benefit from their bonding potential, without fear of patients’ developing tooth sensitivity. Key Words. Dental abutment; dental sensitivity; resin cements; dental bridgework. JADA 2010;141(12):1459-1466.

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Dr. Saad is an assistant lecturer and doctoral candidate, Department of Fixed Prosthodontics, Faculty of Dentistry, Suez Canal University, Ismailia, Egypt. Dr. Atta is a professor and the head, Department of Fixed Prosthodontics, Faculty of Dentistry, Suez Canal University, Ismailia, Egypt. Dr. El-Mowafy is a professor in restorative dentistry, Department of Clinical Sciences, Faculty of Dentistry, University of Toronto, 124 Edward Street, Toronto, Ontario M5G 1G6, Canada, e-mail “oel.mowafy@ utoronto.ca”. Address reprint requests to Dr. El-Mowafy.

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he introduction of selfadhesive resin cements with the advent of a more simplified cementing technique is considered a leap forward in prosthodontics therapy. These cements are manufactured in such a way so that they etch, prime and bond to dentin without the need to use separate agents for each of these steps. However, clinical evaluation reports about these materials are scarce. The potential for postcementation sensitivity is one of the clinical conditions that practitioners need to consider when dealing with these cements. Indeed, in a survey of dentists with a total of 466 valid responses, more than 50 percent of the respondents listed the luting agent as a “very important” factor in reducing sensitivity.1 More than two decades ago, when the use of glass ionomer for cementation of crowns and fixed partial dentures (FPDs) first was suggested,2 some clinical professionals were concerned that it could cause postoperative sensitivity. However, through properly designed research studies,

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investigators proved that postoperative sensitivity caused by glass ionomer cement was not significantly different from that caused by zinc phosphate.2,3 Postoperative sensitivity rates reported in clinical studies in which investigators evaluated different types of restorations have varied widely. In a practice-based setting that involved 210 patients and the use of two glass ionomer–based cements for cementation of porcelain-fused-tometal (PFM) crowns, Hilton and colleagues4 reported that on a scale from 0 to 10, one-half of the patients experienced a mean postcementation sensitivity to temperature and biting of 0.52 and 0.23, respectively, whereas the other one-half experienced no sensitivity.4 In contrast, in a longterm study that involved 86 vital abutments and the use of two glass ionomer cements along with zinc phosphate cement, Jokstad and Mjör5 reported only five cases of postcementation sensitivity associated with the glass ionomer cements. In another study involving 99 vital teeth that either acted as abutments for FPDs or received inlay, onlay or crown restorations, no patient reported any postcementation sensitivity.6 Postoperative sensitivity may occur owing to a number of reasons. The type of cement used (zinc phosphate versus glass ionomer–based versus resin-based), the extent of tooth preparation, any inadequacy of provisional restorations, removal of the smear layer with a phosphoric acid etching agent and presence of occlusal discrepancies might be among the factors that lead to postoperative sensitivity.7-9 In light of this, we conducted a study to investigate postcementation sensitivity to cold water, air blast and biting in patients receiving FPDs cemented with new self-adhesive resin cements and compare it with that of patients receiving FPDs cemented with adhesive resin cement used in conjunction with a total-etch system. The null hypothesis was that there is no significant difference in postcementation sensitivity when any of these cements is used. METHODS, PARTICIPANTS AND MATERIALS

The protocol for this clinical study was approved by the institutional review board at Suez Canal University, Ismailia, Egypt. Participants. We considered for inclusion in the study patients who needed posterior FPDs to replace one missing tooth who sought treatment at the Faculty of Dentistry Clinics of Suez Canal 1460

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University. We used these specific inclusion criteria to recruit patients into the study: dgood health or presence of noncontributory medical condition(s); dabutment teeth located in the mandible and in normal occlusal relationship with the maxillary opposing dentition to permit us to conduct the test of sensitivity to biting; dabutment teeth that were vital, caries-free, restoration-free and nonsymptomatic; dcompletion of education equivalent to high school diploma level or higher, thus excluding any person who might find it difficult to deal with a visual analog scale (VAS) in scoring the degree of his or her dental sensitivity. We used the following exclusion criteria: dcurrent receipt of anti-inflammatory or analgesic drug therapy (as this may raise the pain threshold for tooth sensitivity artificially); dsupererupted or mesially tilted or drifted mandibular molar abutment teeth (we excluded patients with such teeth to avoid the need for additional reduction of dental tissues during tooth preparation, which may influence postoperative sensitivity); dhistory of periodontal surgery within the preceding three months, which could indicate that the patient had preexisting sensitivity; dpregnancy. We provided an oral explanation of the objectives of the study to patients who met the inclusion criteria. When they indicated their willingness to participate, we asked them to sign a consent form that explained the purpose and the nature of the study and showed them the schedule they would need to follow for recall appointments. All participants were female and their ages ranged from 30 to 40 years. Preoperative examination. We obtained preoperative bitewing and periapical radiographs of the abutment teeth to confirm the presence of adequate bony support and lack of any periapical lesions. Abutments were in normal occlusal relationship with natural opposing dentition. We determined sensitivity to cold (water and air) and biting for each abutment before beginning treatment. ABBREVIATION KEY. bis-GMA: Bisphenol Aglycidyl methacrylate. FPD: Fixed partial denture. HEMA: 2-hydroxyethyl methacrylate. PFM: Porcelain fused to metal. TEGDMA: Triethylene-glycol dimethacrylate. VAS: Visual analog scale.

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Prosthetic procedures. One of the authors (D.E.-D.S.) administered inferior alveolar nerve block anesthetic (Septanest-SP, Septodont, SaintMaur-des-Fossés, France) and prepared abutments to receive PFM retainers with an occlusal reduction of 1.5 millimeters and an axial reduction of 1.2 mm. To prepare the teeth, we used a high-speed handpiece (NSK, Kanuma, Japan) with diamond burs (TF-12, Mani, Tochigi, Japan) cooled with copious air-water spray. To maintain high cutting efficiency, we replaced the diamond burs after using them for two abutment preparations. We retracted gingival tissues with medicated and braided retraction cord (Stay-Put, Roeko, Langenau, Germany) to control bleeding and expose preparation margins. We made impressions by using an addition-silicone elastomeric impression material (Aquasil, Dentsply Caulk, Milford, Del.) in custom acrylic resin trays. We used a monophase technique. This required a medium-viscosity impression material to be mixed and placed in the custom tray, then a small portion of it to be loaded into a syringe and injected into the sulci around the preparations. We made provisional crowns (Protemp, 3M ESPE, Seefeld, Germany) by using vacuum-formed matrixes and cemented them with provisional cement (Dycal, Dentsply, York, Pa.). We used one laboratory for fabrication of all PFM prostheses. The laboratory technician used two layers of die spacer and fabricated prostheses with porcelain occlusal surfaces. At the cementation appointment, we administered inferior alveolar nerve block anesthetic, removed provisional crowns and cleaned abutments by using a slurry of pumice and rubber cup. We randomly assigned each participant to receive one of three resin cements: RelyX ARC Adhesive Resin Cement (3M ESPE, St. Paul, Minn.), used in conjunction with Scotchbond Etchant Gel (3M ESPE) and Adper Single Bond 2 adhesive (3M ESPE); selfadhesive resin cement RelyX Unicem SelfAdhesive Universal Resin Cement (3M ESPE, Seefeld, Germany); or self-adhesive resin cement Breeze Self-Adhesive Resin Cement (Pentron Clinical Technologies, Wallingford, Conn.). With each cement, we followed the manufacturer’s directions for cementation (Table 1). The mean time elapsed between tooth preparation and cementation of final FPDs was one week. Assessment of tooth sensitivity. In addition to preoperative assessments (baseline), one operator (D.E.-D.S.) evaluated tooth sensitivity

24 hours, two weeks, six weeks and 12 weeks after cementation. He evaluated and recorded the sensitivity of each abutment to cold water, air blast and biting at each visit. The criteria we adopted for hypersensitivity assessment were similar to those used by Johnson and colleagues.2 The operator assessed sensitivity to biting by having the participant bite firmly on the end of a cotton-tipped applicator applied at the central fossa of the abutment tooth. He asked participants to record their level of sensitivity by using a VAS ranging from 0 to 10, on which 0 represented “no sensitivity” and 10 “most sensitivity.” He then tested abutments for sensitivity to cold water and air blast. He fabricated a polyvinyl-siloxane stent for each tested abutment and used it to isolate the rest of the teeth in the same quadrant and expose only the abutment being tested. He mixed a polyvinyl-siloxane putty impression material (SwissTEC, Coltène/Whaledent, Altstätten, Switzerland) according to the manufacturer’s instructions and adapted it onto the teeth in the quadrant in a stone model, then opened a hole to expose the abutment of the FPD being tested. The operator irrigated the abutment tooth with 5 cubic centimeters of ice water through the hole in the stent for five seconds by means of a plastic syringe. He permitted the water to pool around the abutment and then evacuated the excess with a saliva ejector. The participant recorded her VAS score on paper. If at any stage a participant experienced severe pain, the operator terminated the test immediately. While maintaining the stent in place, the operator directed a stream of air onto the crown’s facial surface toward the margin by using an air-water syringe. At the end of each test, the participant recorded her VAS score for the degree of sensitivity she experienced. Postinsertion follow-up. The operator repeated chairside sensitivity testing at two, six and 12 weeks after cementation. At the 12-week visit, he obtained periapical radiographs of the abutments. Two examiners (one of whom was D.E.-D.S.) evaluated the pretreatment and 12week radiographs independently for prosthesis fit and periapical changes. Statistical analysis. A statistician analyzed the data by using the Mann-Whitney test at a 95 percent confidence interval (P < .05). RESULTS

A total of 50 mandibular posterior teeth (24 molars and 26 premolars) acted as abutments. JADA 141(12)

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TABLE 1

Resin cements: composition, classification and application procedures. CEMENT

MANUFACTURER

CLASSIFICATION

COMPOSITION

DELIVERY SYSTEM

APPLICATION PROCEDURE

Adper Single Bond 2 Adhesive

3M ESPE, St. Paul, Minn.

Conventional cement with totaletch adhesive

Ethanol, 2-hydroxyethyl methacrylate (HEMA), bisphenol A-glycidyl methacrylate (bis-GMA), methacrylate modified polycarboxylic acid copolymer, small amount of water, photo initiators

Liquid in bottle

• Clean the prepared teeth with pumice • Etch teeth for 15 seconds with acid etchant • Rinse etchant and dry without desiccation • Apply primer/adhesive and light cure • Dispense and mix cement with spatula • Apply cement into retainers and seat onto abutments • Have patient bite on wooden stick • Remove excess cement

Breeze SelfAdhesive Resin Cement

Pentron Clinical Technologies, Wallingford, Conn.

Self-adhesive resin cement

Mixture of bis-GMA, urethane dimethacrylate (UDMA), triethylene-glycol dimethacrylate (TEGDMA), HEMA and 4-methacryloxyethyl trimellitic anhydride (4-META) resins; silane-treated bariumborosilicate glasses, silica with initiators, stabilizers and ultraviolet absorbers; organic and/or inorganic pigments

Paste/paste doublebarreled tube with automatic mixing tip

• Clean prepared teeth with pumice • Dispense cement directly into retainers through mixing tip and seat fixed partial denture (FPD) onto abutments • Have patient bite on wooden stick • Remove excess cement

RelyX ARC Adhesive Resin Cement

3M ESPE, St. Paul, Minn.

Conventional cement with totaletch adhesive

Mixture of bis-GMA and TEGDMA resins; zirconia and silica fillers

Paste/paste doublebarreled tube with clicker dispenser

Same as for Adper Single Bond 2 Adhesive (above)

RelyX Unicem Self-Adhesive Universal Resin Cement

3M ESPE, Seefeld, Germany

Self-adhesive resin cement

Glass fillers, silica, calcium hydroxide, self-cured initiators, pigment, light-cured initiators (filler load 72 percent weight, particle size < 9.5 micrometers) Liquid: methacrylated phosphonic esters, dimethacrylates, acetate, stabilizers, self-cured and lightcured initiators

Capsule and applicator

• Clean prepared teeth with pumice • Activate capsule on the activator and then mix it in mechanical mixer • Apply cement through capsule applicator into the retainers and seat FPD onto abutments • Have patient bite on wooden stick • Remove excess cement

Scotchbond Etchant Gel

3M ESPE, St. Paul, Minn.

Conventional cement with totaletch adhesive

35 percent phosphoric acid, 50 to 60 percent water, 5 to 15 percent polyvinyl alcohol

Gel in syringe

Same as for Adper Single Bond 2 Adhesive (above)

Two participants received one three-unit FPD each; however, only one of the two retainers was cemented on a vital abutment, and the other had been treated endodontically. Six participants received two FPDs each, with a total of four retainers per participant. Twelve participants received one FPD each with two retainers per participant. The operator cemented 20 retainers with Breeze (11 premolars and nine molars), cemented 18 with RelyX Unicem (nine premolars and nine molars) and cemented 12 with RelyX 1462

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ARC (six premolars and six molars). Table 2 shows the participants’ VAS scores of different sensations (cold water, air blast and biting) at different test intervals for the three cements. RelyX ARC received significantly higher mean VAS scores than did RelyX Unicem and Breeze for the three tests at all test intervals (P < .05). Also, RelyX ARC received significantly higher mean VAS scores as compared with the pretreatment baseline score in the three tests, even after 12 weeks (P < .05).

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PARTICIPANTS’ SCORE ON VISUAL ANALOG SCALE

TABLE 2 We found no statistical difference in mean Participants’ visual analog scale scores for cold water, VAS scores between air blast and biting tests at different intervals RelyX Unicem and for the three cements. Breeze for the three tests at the different TEST TYPE CEMENT* MEAN (STANDARD DEVIATION) SCORE, ACCORDING TO INTERVAL test intervals (P > .05). Pretreatment 24 Hours 2 Weeks 6 Weeks 12 Weeks (Baseline) For the cold test, both of these cements had Cold Water Breeze 0.3 (0.5) 4.8 (2.1)†‡ 2.2 (1.6)†‡ 0.8 (1.2)† 0 (0)† significantly higher ‡ ‡ ‡ RelyX ARC 1.0 (0.8) 7.8 (1.5) 6.0 (2.2) 3.5 (2.4) 3.0 (1.8)‡ mean VAS values as RelyX Unicem 1.0 (0.8) 3.7 (1.8)†‡ 2.3 (1.4)† 0.5 (0.5)† 0 (0)†‡ compared with the Air Blast Breeze 0 (0) 1.5 (1.0)†‡ 0.5 (0.8)† 0 (0)† 0 (0)† baseline values— ‡ ‡ ‡ RelyX ARC 0.8 (0.5) 7.0 (1.8) 4.5 (2.9) 3.5 (2.4) 3.0 (1.8)‡ P < .05 for RelyX RelyX Unicem 0.2 (0.4) 2.0 (2.4)† 0.8 (0.7)† 0 (0)† 0 (0)† Unicem and P < .001 † † † Biting Breeze 0 (0) 0 (0) 0 (0) 0 (0) 0 (0)† for Breeze. However, ‡ ‡ ‡ RelyX ARC 0 (0) 6.3 (1.7) 4.0 (3.4) 2.3 (2.2) 2.0 (2.2)‡ this significant differRelyX Unicem 0 (0) 0.2 (0.4)† 0 (0)† 0 (0)† 0 (0)† ence disappeared after two weeks for RelyX * Manufacturers are as follows: Breeze Self-Adhesive Resin Cement, Pentron Clinical Technologies, Wallingford, Conn.; RelyX ARC Adhesive Resin Cement, 3M ESPE, St. Paul, Minn.; RelyX Unicem Self-Adhesive Unicem and after six Universal Resin Cement, 3M ESPE, Seefeld, Germany. weeks for Breeze. † Denotes a statistically significant difference versus RelyX ARC mean within same sensation test (P < .05). ‡ Denotes a statistically significant difference versus pretreatment mean (P < .05). For the air blast test, RelyX Unicem had a mean VAS score at 10 24 hours that was not significantly different 9 ◆ Breeze from its pretreatment 8 ▲ RelyX ARC score (P > .05). The ▲ score for Breeze at 24 7 ■ RelyX Unicem hours was signifi6 ▲ cantly different from its score at baseline 5 ◆ (P < .001); however, after two weeks, the 4 ■ ▲ difference no longer ▲ 3 was significant (P > ◆ ■ .05). Neither of the 2 self-adhesive ■ ▲ 1 cements (RelyX ◆ ■ ◆ Unicem and Breeze) ■ ◆ 0 Pretreatment 24 Hours 2 Weeks 6 Weeks 12 Weeks was associated with sensitivity to biting TIME at any of the test intervals. Figures 1 Figure 1. Participants’ mean visual analog scale scores for sensitivity to cold water at different intervals for the three cements. Breeze Self-Adhesive Resin Cement is manufactured by Pentron Clinical Technologies, through 3 show Wallingford, Conn. RelyX ARC Adhesive Resin Cement is manufactured by 3M ESPE, St. Paul, Minn. RelyX graphic representaUnicem Self-Adhesive Universal Resin Cement is manufactured by 3M ESPE, Seefeld, Germany. tion of mean VAS scores obtained with the three cements in response abutments. However, during the three months’ to the three methods of sensitivity assessment. observation period, two abutments in which Assessment of the periapical radiographic RelyX ARC was used caused the participants perimages obtained before and after FPD insertion sistent pain, and they exhibited symptoms of irrerevealed proper fit of prostheses and lack of sigversible pulpitis that necessitated intervention nificant changes in the periapical zone of the with endodontic therapy.

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and females; therefore, our findings apply more appro9 ◆ Breeze priately to females. 8 Postcementation ▲ RelyX ARC sensitivity in some ▲ 7 ■ RelyX Unicem cases has been 6 attributed to acidetching of dentin, 5 which results in ▲ removal of the 4 ▲ smear layer and cre▲ 3 ates a passage by which bacteria can ■ 2 penetrate the pulp.10 ◆ 1 In addition, other ■ ▲ ◆ factors such as ■ ■ ■ ◆ ◆ ◆ 0 Pretreatment 24 Hours 2 Weeks 6 Weeks 12 Weeks excessive air drying of dentin during TIME cementation and inadequate water Figure 2. Participants’ mean visual analog scale scores for sensitivity to air blast at different intervals for the cooling during tooth three cements. Breeze Self-Adhesive Resin Cement is manufactured by Pentron Clinical Technologies, preparation have Wallingford, Conn. RelyX ARC Adhesive Resin Cement is manufactured by 3M ESPE, St. Paul, Minn. RelyX Unicem Self-Adhesive Universal Resin Cement is manufactured by 3M ESPE, Seefeld, Germany. been reported as being responsible for 10 causing pulpal reaction with subse9 ◆ Breeze quent postoperative 8 sensitivity.11,12 In ▲ RelyX ARC our study, all the 7 ■ RelyX Unicem abutments were pre▲ pared by one experi6 enced clinician 5 (D.E.-D.S.), who ▲ ensured that suffi4 cient water cooling 3 was maintained ▲ ▲ throughout the 2 preparation stage. 1 The fact that the ■ ▲ ■ ■ ■ ◆ ◆ ◆ ◆ ◆ ■ age range of the par24 Hours 2 Weeks 6 Weeks 12 Weeks 0 Pretreatment ticipants (30-40 years) was narrow TIME means that dentin maturity among Figure 3. Participants’ mean visual analog scale scores for sensitivity to biting at different intervals for the three cements. Breeze Self-Adhesive Resin Cement is manufactured by Pentron Clinical Technologies, abutments was Wallingford, Conn. RelyX ARC Adhesive Resin Cement is manufactured by 3M ESPE, St. Paul, Minn. RelyX within the same Unicem Self-Adhesive Universal Resin Cement is manufactured by 3M ESPE, Seefeld, Germany. range. DISCUSSION We used FPD abutments instead of single crowns because we designed this study to involve Although we had not intended to exclude male sound teeth that were free from caries and restoparticipants from this study, for some reason no rations. Under normal conditions, such teeth typimen were interested in taking part. Pain cally do not need crowns. Johnson and colleagues13 threshold and perception may vary between males

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reported in a clinical evaluation of postoperative sensitivity associated with posterior resin-based composite and amalgam restorations that there was no difference between molars and premolars in terms of response to cold stimuli; however, there was a difference between arches. They stated that unrestored molars and premolars in the maxillary arch were significantly more sensitive to cold than were their mandibular counterparts. That was the reason we selected only mandibular teeth for our study. The tests we used—cold water, air blast and biting—yielded similar results, albeit at varying levels. Air blast and cold water tests are similar in terms of the principle of their action, which basically is to cause a sudden drop in temperature. However, cold water testing resulted in mean VAS values higher than those resulting from air blast testing. We anticipated this, because cold water would be expected to cool the teeth more efficiently than would air. The biting test is different, because it does not affect the temperature of the teeth but rather transmits pressure to the abutments through the retainers. The duration of our study originally was limited to 12 weeks, because findings of a previous study indicated that the majority of symptoms of postoperative sensitivity after cementation of crowns and FPDs subside within one to three months.2 However, this was not the case with some participants in our study who had FPDs cemented with RelyX ARC, for whom more time was needed before sensitivity dissipated completely. Bonding of conventional resin cements to dentin is based on smear-layer removal or dissolution.14,15 Several steps typically are involved in the process, which may be technique sensitive. Selfadhesive resin cements simplify the cementing procedure, as they eliminate the need for using any agents. They consist of an organic matrix containing multifunctional phosphonic acid methacrylates that contribute to adhesion to dentin.16 The difference in postcementation sensitivity between the two self-adhesive resin cements and the conventional resin cement with total-etch adhesive could be attributed to the fact that with the total-etch adhesive, the smear layer was removed with the etchant, and the conditioning of the dentin with primer/adhesive occurred as a separate step after rinsing. Unavoidable errors that may take place during this process include overetching of dentin, inadequate rinsing of etchant, overdrying of dentin after rinsing and

incomplete evaporation of solvent in primer/ adhesive. These errors may result in a discrepancy between the depth of dentin demineralization and the extent of resin infiltration.17 Such a discrepancy is unlikely to occur in the case of selfadhesive resin cements because both processes— removal of the smear layer and infiltration of the dentin surface with resin—occur simultaneously without rinsing or drying of dentin. Investigators conducting in vivo studies have hypothesized that resin components of primer are displaced outward after acid conditioning and application of a primer/bonding agent.18,19 The immediate outward movement of dentinal fluid that occurs during the etching of dentin creates an overwet surface onto which the primer/bonding agent is applied. This microscopic pooling of dentinal fluid on the occlusal and axial walls of the dentinal surfaces seems to interfere with the monomer conversion process. Furthermore, the temperature rise that can occur during photoactivation of the bonding agent creates an inward fluid shift, which can carry these residual monomers through the dentinal tubules toward the pulp.20 In vitro studies showed that uncured monomers released from resin-based materials have defined cytotoxic effects on cell cultures.21,22 In addition, a number of in vivo studies performed on human teeth demonstrated that leached resin components in direct contact with pulpal tissues may trigger a noticeable inflammatory response that is linked with tissue disorganization.18,19 In a histologic study of the human pulp’s response to resin cements, researchers noted that with RelyX Unicem, neither tag formation nor displacement of the cement components through dentin took place.23 The authors of that study speculated that the specific characteristics of this cement —namely, low solubility and the self-neutralizing mechanism that is activated during the setting reaction—may prevent further hydrolysis and release of components for diffusion through the dentinal tubules. Another important feature of self-adhesive resin cements is their reaction with the smear layer, which takes the form of alteration rather than total removal. This helps in preventing any migration of cement components toward the pulp and, hence, reduces the risk of pulpal reaction with subsequent postcementation hypersensitivity. Future research studies addressing the level and durability of bonding of these self-adhesive resin cements to dentin and their resistance to microleakage are warranted. JADA 141(12)

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CONCLUSIONS

The use of two self-adhesive resin cements, RelyX Unicem and Breeze, in the cementation of FPDs resulted in significantly less postcementation sensitivity than did the use of a resin cement that involved the use of a total-etch technique, RelyX ARC. There was no significant difference in the degree of postcementation sensitivity between the two self-adhesive resin cements. ■ Disclosure. None of the authors reported any disclosures. The authors thank Pentron Clinical Technologies, Wallingford, Conn., and 3M ESPE, St. Paul, Minn., for providing samples of the materials used in the study. 1. Rosenstiel SF, Rashid RG. Postcementation hypersensitivity: scientific data versus dentists’ perceptions. J Prosthodont 2003;12(2): 73-81. 2. Johnson GH, Powell LV, DeRouen TA. Evaluation and control of postcementation pulpal sensitivity: zinc phosphate and glass ionomer luting cements. JADA 1993;124(11):39-46. 3. Kern M, Kleimeier B, Schaller HG, Strub JR. Clinical comparison of postoperative sensitivity for a glass ionomer and a zinc phosphate luting cement. J Prosthet Dent 1996;75(2):159-162. 4. Hilton T, Hilton D, Randall R, Ferracane JL. A clinical comparison of two cements for levels of post-operative sensitivity in a practicebased setting. Oper Dent 2004;29(3):241-248. 5. Jokstad A, Mjör IA. Ten years’ clinical evaluation of three luting cements. J Dent 1996;24(5):309-315. 6. Yoneda S, Morigami M, Sugizaki J, and Yamada T. Short-term clinical evaluation of a resin-modified glass-ionomer luting cement. Quintessence Int 2005;36(1):49-53. 7. Dahl BL. Dentine/pulp reactions to full crown preparation procedures. J Oral Rehabil 1977;4(3):247-254. 8. Langeland K, Langeland LK. Pulp reactions to crown preparation, impression, temporary crown fixation and permenant cementation. J Prosthet Dent 1965;15:129-143.

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