POST-OPERATIVE TOOTH HYPERSENSITIVITY WITH DIFFERENT RESTORATIVE MATERIALS. A LITERATURE REVIEW

Abstract

The purpose of this paper is to review the incidence of postoperative hypersensitivity with different restorative materials and to propose some techniques to manage and prevent its occurrence. 2.AMALGAM RESTORATIONS Tooth sensitivity after a new amalgam restoration is always predictable. Some factors contribute to the postoperative sensitivity under amalgam restorations, such as cavity depth, type of alloy and use of bases and liners. Since the number of dentinal tubules per mm2 is higher in deeper than shallower cavities, it could be expected that such deep restorations will exhibit higher sensitivity then the more shallow ones. [20] tested the clinical performance of self-etch and total-etch bonding systems for teeth restoration with posterior dental composite restorations. Two-step self-etch adhesives (Clearfil SE, Kuraray) succeeded in reducing postoperative sensitivity, especially when adding an extra step of etching at enamel margins with phosphoric acid, to improve the marginal seal in Class V restorations [25].

Headnote

Abstract

Postoperative hypersensitivity is described as a sensation of pain in a tooth or teeth trigerred with with sensitivity to hot, cold, and sweet stimuli or mastication one week or more post-restoration. While pain during clenching suggests restoration in hyperocclusion, pain during chewing is regarded as postoperative hypersensitivity associated with polymerization shrinkage and gaps between dentin and the fluid filled restoration, which causes tooth hypersensitivity as the fluid slips down the dentin tubules during mastication. Postoperative hypersensitivity is one of the most frequent complaints in dentistry medicine. A handful of research reports have documented postoperative hypersensitivity with amalgam, tooth-colored, composite resin, luting cements and indirect restoration materials. The present review paper aims at mapping the recent evidence on the incidence of postoperative hypersensitivity with different restorative materials, and further discusses, in the light of latest literature, the prevention and management of postoperative hypersensitivity.

Keywords: postoperative, tooth hypersensitivity, restorative materials, prevention, management.

1.INTRODUCTION

One of the most frustrating situations is when the patient complains of tooth sensitivity following a dental procedure. This discomfort rises during chewing on the new restoration, or when this is subjected to thermal stimuli (usually cold). Unfortunately, pain may persist for one week or up to two years after the initial placement of the restoration.

Many theories tried to explain the causes of postoperative hypersensitivity. One of the most frequently accepted ones is the hydrodynamic theory by Brännström, elaborated in 1984, which states that the fluid flow within the dentinal tubule can elicit a painful stimulus [1]. Cold causes a rapid increase in this flow which may be interpreted as pain by the patient when a gap between the prepared tooth and the restoration exposing dentin occurs. As dentin comes near the pulp, tubule density and diameter increase permeability [2]. This will increase both the volume and flow of the pulpal fluid with a cold stimulus. The resistance to such fluid movement is proportional to dentin thickness or tubular length, which may explain why deeper restorations are associated with more sensitivity problems.

The second theory is that sensitivity is the result of a direct thermal shock to the pulp via temperature changes transferred from the oral cavity through the restorative material, especially when the remaining dentin thickness is thin [3]. Protection can be achieved with a low thermal diffusing base of adequate thickness under the metallic restorations or materials that exhibit higher rates of temperature transfer [4]. Other causes for such an excessive heat during tooth preparation could be: no use of water-air coolant [5], desiccation of dentin [6], excessive use of laser procedure [7] and toxicity of the material used [8].

The purpose of this paper is to review the incidence of postoperative hypersensitivity with different restorative materials and to propose some techniques to manage and prevent its occurrence.

2.AMALGAM RESTORATIONS

Tooth sensitivity after a new amalgam restoration is always predictable. A fresh amalgam restoration is unable to produce corrosion products immediately, to seal the gap between the prepared tooth and the restoration. Short-term pain is explained by the hydrodynamic theory [1] and by the presence of bacteria which cause pulpal inflammation [9]. The products of corrosion gradually reduce postoperative hypersensitivity, which might take several months [10]. Some factors contribute to the postoperative sensitivity under amalgam restorations, such as cavity depth, type of alloy and use of bases and liners.

Since the number of dentinal tubules per mm2 is higher in deeper than shallower cavities, it could be expected that such deep restorations will exhibit higher sensitivity then the more shallow ones. Histologically, there are pulpal reactions to the materials when decreasing the remaining dentin thickness. A study of Wegehaupt et al. [11] showed no correlation between cavity depth and postoperative hypersensitivity. The type of alloy used also affects the incidence of postoperative hypersensitivity. The spherical alloy has higher microleakage and therefore, compared to admix high copper alloys, it may result in higher postoperative hypersensitivity [12].

The use of liners and bases under amalgam restorations has been introduced to reduce postoperative sensitivity and to provide thermal insulation. A recent study from Pakistan, elaborated by Rana and colleagues, evidenced a significant difference between dentin adhesive liner and copal varnish, the dentin adhesive liner being superior in reducing postoperative hypersensitivity [13]. Similar findings were also reported by Saba et al, who compared copal varnish and dental adhesive liners [14]. Bonding amalgam with a 4-methacryloxyethyl trimellitate anhydride bonding agent (Amalgambond) was found to decrease significantly the microleakage of amalgam restorations, compared to unlined and copal varnish liners. This was explained by the ability of the 4-META monomer to infiltrate the peritubular dentin, forming a hybrid layer responsible for improving bond strength, enhancing the seal, decreasing microleakage and therefore decreasing postoperative hypersensitivity [15]. In a recently published systematic review, bonded and nonbonded amalgam restorations showed no significant difference in postoperative sensitivity [16]. On the other hand, a 3-year randomized clinical trial performed by Kemaloglu et al. communicated that composite restorations were more competent in decreasing postoperative sensitivity, compared with amalgam restorations [17].

3.TOOTH-COLORED RESTORATIVE MATERIALS

In recent years, there is a high demand for aesthetic restorations, which resulted in the production of new tooth-colored materials, to enhance not only the aesthetics of these materials but also their function and durability. Unfortunately, one of the major drawbacks of resin composites restorations is postoperative hypersensitivity.

3.1. Adhesive System

The most remarkable feature of resin restorations is the strength of their bonding to tooth surfaces. More recently developed adhesive systems have enabled higher bond strength to be realized in fewer clinical steps and shorter treatment time. Etching of dentin with phosphoric acid removes the smear layer, including the smear plugs on the prepared cavity walls, and opens the end of dentinal tubules [18]. Failure to completely seal these tubules may result in dentin fluid movement and ingress of microorganisms into the dentinal tubules, resulting in postoperative hypersensitivity.

Total-etch technique involves the removal of smear layer by etching the enamel and dentin surface with 30-40% phosphoric acid before the application of the adhesive material. Self-etchant adhesives do not require a separate etchant step and do not remove completely the smear layer. They are composed of acidic functional monomers, mainly phosphoric acid esters with a pH of 1-2. These etchants do not etch enamel to the level obtained with phosphoric acid [19].

Some clinical studies focused on the postoperative hypersensitivity caused by dental adhesives. Many of them hypothesized that selfetch systems are better in preventingpostoperative hypersensitivity, since they remove completely the smear layer. Amin et al. [20] tested the clinical performance of self-etch and total-etch bonding systems for teeth restoration with posterior dental composite restorations. They concluded an excellent performance of these materials in terms of reducing postoperative sensitivity from day 1 to day 7. On the other hand, Unemori et al. [21] found out that the incidence of postoperative sensitivity in deep cavities was higher in totaletch than in self-etch adhesives. Also, (Fluoro Bond, Liner Bond II, Mac-Bond II) when placed in deep cavities, the self-etchant adhesives performed comparably as in the cavities restored with liners/ bases for pulpal protection.

The clinical performance of two-step and onestep self-etching was investigated by several authors as to the postoperative sensitivity of Class V resin restorations. Both adhesive systems performed very well at intervals of 1, 2, 3 and 5 years [22, 23]. However, the two-step system exhibits slightly better retention than the onestep system [24].

Two-step self-etch adhesives (Clearfil SE, Kuraray) succeeded in reducing postoperative sensitivity, especially when adding an extra step of etching at enamel margins with phosphoric acid, to improve the marginal seal in Class V restorations [25]. They also performed better in reducing postoperative sensitivity after 30 days, compared to two-step etch-and-rinse adhesives (One-step Plus) [26].

In the battle of total-etch versus self-etch adhesives ability to reduce postoperative sensitivity, many clinical trials concluded that there were no significant difference, and that both were able to reduce sensitivity. [27-31]

Thickness of the adhesive layer might be also an important factor in the reduction of polymerization shrinkage. A thick adhesive layer may compensate for the polymerization shrinkage stresses due to its elastic properties, therefore it might reduce gap formation. In Class II restorations with beveled enamel margin, the thick adhesive layer will fill in this margin, causing a pooling phenomenon that may compromise the quality of the restoration. Arisu et al. [32] found out that self-etch adhesives, when subjected to occlusal load, tend to leak along the occlusal margins.

3.2. Composite Resins

Posterior teeth restored with resin composites have been known to exhibit postoperative sensitivity. Most patients described their sensitivity pain as sharp/ dull rather than hot/ cold [33]. The type, size and design of the cavity, materials properties and handling techniques, and operator skills may influence its incidence. When the new restoration is loaded by any opposing tooth or during mastication of solid food, deformation of the restoration margins and interfaces may result in dimensional gaps, which may cause pain, due to percolation of fluid in the dentinal tubules. The complexity of this phenomenon makes it difficult to point out the original cause.

Cavity depth seems to be one of the major factors contributing to postoperative sensitivity. As the depth of the cavity increase, the incidence of postoperative sensitivity was increased, as well. [34] Other authors found no significant difference in cavity depth as to sensitivity.[ll]

Research suggests that the remaining dentin thickness under cavity preparation should be at least 2 mm, to guarantee the protection of pulp [35]. Pulpal inflammatory response was found at less than 0.5 mm thickness [36]. Placing a liner and/or bases was studied in view of reducing postoperative sensitivity. Wegehaupt et al. [11] found that placing calcium hydroxide liner did not reduce sensitivity, whichever the liner used. Kaurani et al. [37] used many liners under Surefil packable resin composite in Class I and II restorations as total-etch adhesive (Prime & Bond NT, Dentsply), self-etch adhesive (Propt L-Pop, 3M ESPE), RMGIC (GC Fuji II LC, GC Corp) and a flowable poly-modified resin composite (Dyract Flow, Dentsply). After an evaluation period up to 90 days, the self-etchant showed least postoperative sensitivity. Using a polyacidmodified resin composite (Dyract) as a base (dentin substitute), coverage with resin composite (Prisma TPH) was tested clinically as closed sandwich technique in Class I restorations. After 6 years, only 1.16% of them showed postoperative hypersensitivity and, generally, such restorations exhibited good marginal adaptation and durability [38].

The clinical class of restoration may be involved in the presence of postoperative hypersensitivity. Briso et al. [39] found out that MOD Class II restorations exhibited more sensitivity that occlusal Class I restorations, concluding that the occurrence of sensitivity is correlated with the complexity of restoration. However, Auschill et al. [33] found no significant difference between Class I and II resin restorations and the incidence of postoperative hypersensitivity.

Gaps in relation to composite resins may be formulated when the bonded adhesive capacity is insufficient to resist the forces of polymerization shrinkage during composite curing [40]. Unfavorable configuration of the cavity as Class II restorations may increase the incidence of gap formation. Polymerization shrinkage forces also cause cuspal deformation and gap formation [41]. The presence of gaps, therefore, may induce postoperative sensitivity.

Regarding the polymerization mode, Al-Omari et al. [42] found out that the soft-start mode in LED curing units showed less polymerization shrinkage, as it allows flowing of the resin composite, thus decreasing the stresses caused by polymerization, while Deliperi et al. [43] suggested the use of pulse-curing mode in combination with flowable composite liner and oblique layering technique to reduce polymerization shrinkage. The oblique buccolingual layering technique results in less postoperative sensitivity, as stated by Deliperi et al. [43]. With this technique, the resin is best adapted to the walls of the cavity and is least affected by polymerization shrinkage, due to the decrease of the configuration factor.

Different types of resin composites may result in different sensitivity responses. Physical properties, such as filler size, type content, viscosity, modulus of elasticity may affect polymerization shrinkage. Recently, the introduction of new composite materials with better performance in reducing polymerization shrinkage may help reduce postoperative hypersensitivity. In a two-year clinical evaluation of Ormocer (Admira) and nanofill composite (Filtek Supreme), both materials succeeded in reducing postoperative hypersensitivity, with or without the use of flowable composite liners [44].

Nanocomposite (Filtek Supreme) and polyacid modified resin composite (Dyract eXtra) showed acceptable clinical performance in class V restorations after 2 years of clinical service with no postoperative sensitivity [45]. Highly filled resin composites (Tetric Ceram) performed very well along a 4-year clinical trial, when only 2.5% of the cases were observed with postoperative hypersensitivity [46]. The use of packable composites (Surefil and Filtek P 60) with self-etchant adhesives showed low sensitivity (5%) in a one-year clinical report [47]. Sarrett et al. [48] evaluated the application of packable composite (Prodigy condensable) in one bulk in Class II restorations and Optobond Solo etchant, and also the occurrence of postoperative sensitivity. They found no significant difference in pre- and postoperative hypersensitivity with the bulk technique.

Low shrinkage hybrid composites were introduced to solve the problems associated with polymerization shrinkage. A 5-year clinical study evaluated the clinical performance of a low shrinkage hybrid composite (Inten-S) and of a hybrid composite (Point 4) with total-etch adhesive system, both showing no incidence of postoperative sensitivity [49].

Mirohybrid composites were used as a liner under composite resins to improve adaptation by acting as an elastic, stress absorbing layer when subjected to polymerization shrinkage. Attar et al. [50] suggested the use of a flowable composite at the first gingival increment of Class II restorations with microhybrid or packable composites, to decrease gingival microleakage. Perdigao et al. [31] found no significant difference in the reduction of postoperative hypersensitivity with and without flowable composites liners.

4.LUTING CEMENTS AND INDIRECT RESTORATIONS

Postoperative hypersensitivity has been associated with cements and crown cementation since the introduction of zinc phosphate cement in the 19th century. Its reposts increased with the rise in the use of resin cement. When GIC and RMFIC were introduced, some claimed reduction of postoperative hypersensitivity. An ideal cement should be able to resist microleakage and seal the margins of the restoration, thus preventing sensitivity. Post-cementation hypersensitivity may also be caused by irritation provoked by cavity preparation, structure and quality of dentin, inflammation, and bacterial microleakage [51].

Chandrasekhar [52] explored in vivo postoperative hypersensitivity with a glass ionomer luting cement, zinc phosphate cement and resin-modified glass ionomer luting cement, finding that restorations cemented with resinmodified glass ionomer showed least postoperative hypersensitivity compared with others. In a randomized controlled trial performed by Shetty et al. [53], a self-adhesive resin cement was found to be superior to glass ionomer cement. Similarly, Prasad et al. [54] concluded that glass ionomer cement had high hypersensitivity, followed by low hypersensitivity with resin-modified glass ionomer cement and lowest with self-adhesive resin cements.

Due to the increased demand on colored tooth restorations, all ceramic crowns are largely used. Resin cements are used with these types of crowns, polymer crowns and some metal crowns requiring optimum retention [55]. Denner et al. compared the performance of an adhesive resin cement containing 4-META (Chemiace II) and a conventional GIC (Ketac-Cem) in terms of postoperative hypersensitivity. The incidence in both materials was similar, with a slight, insignificant increase in sensitivity in the first week after placing the resin cement. In both cements, sensitivity subsided after 24 months [56].

Fabianelli et al. [57] compared the incidence of postoperative sensitivity with Empress II porcelain inlays after luting them with a dualcure adhesive (Exicite DSC) and a self-curing resin cement (MultiLink). After 3 years, only one patient out of 40 presented with postoperative hypersensitivity in the first recall visit (1 week after placement), which indicated the good performance of the combination of those materials.

5.VITAL TOOTH BLEACHING

Vital tooth bleaching as a treatment for discolored teeth includes different materials and methods of application [58]. However, tooth sensitivity is one of the unfavorable discomfort outcomes of this procedure. Office procedures can cause more pronounced discomfort than at-home bleaching. At-home bleaching procedure offers self-administration, high safety, less time in chair, less adverse effects and it is economic [59].

The severity of histological pulpal changes was observed as concentration of the bleaching agent was increased and heat was applied. Yu and Abbott [60] described that vasodilation and aspiration of odontoblast nuclei into the dentinal tubules and the increase of intra-pulpal pressure may result in a sensation of pain.

Nathanson and Parra [61] evaluated the effect of different hydrogen peroxide (HP) concentrations on different age groups. They found out that 30% HP did not differ from 35% HP in sensitivity, the younger groups developing higher sensitivity than older participants, due to wider pulp chambers.

In a clinical trial performed by Tay et al. [62], they used a desensitizing gel (5% nitrate potassium/ 2% sodium fluoride) before in-office bleaching with 35% HP, and noticed a decrease in postoperative sensitivity, with no effect on bleaching efficacy. On the other hand, Browning et al. [63] added a low percentage of potassium nitrate (0.5%) to 10%. Carbamide peroxide home bleaching did not significantly reduce postoperative sensitivity, compared to placebo, yet it decreased the number of days with sensitivity manifested, without reducing the efficacy of the bleaching agent. However, 3% potassium nitrate produced less tooth sensitivity than the control bleaching gel (10% carbamide peroxide only) during a 2-week at-home bleaching treatment with 10% carbamide peroxide bleaching gel containing also fluoride, without affecting the efficacy of the agent [64].

6.MANAGEMENT OF POSTOPERATIVE HYPERSENSITIVITY

Different approaches related to the control of dentinal sensitivity after tooth preparation have been extensively reported, namely mechanical abrasives and surface medications or surface coating, in order to occlude the sensitive dentinal tubules.

Anti-bacterial solutions are indicated after preparing the cavity in order to disinfect the remaining dentin. Once preparation completed, the presence of bacteria in the cavity will increase, as well as after restoration, if any microleakage occurs. Al-Omari et al. [65] suggested the use of cavity disinfectants, such as Chlorhexidine, before placing an amalgam restoration, in order to decrease postoperative sensitivity to cold stimulus. Sobral et al. [66] found that postoperative sensitivity resulting from Class II restorations using composite resin cannot be completely eliminated by the prior use of a dentinal desensitizer (35% hyclroxyethyl metacrylate/ 5% glutaraldehyde dentine desensitizer/Gluma Desensitizer) or of a cavity disinfectant (2% chlorhexidine-based cavity disinfectant / CavClean) after 7 days of clinical observation. Adding 4% potassium nitrate to the zinc oxide eugenol temporary cement reduced significantly the incidence and severity of pain after tooth crown preparation, in comparison to zinc oxide eugenol alone [67].

Many desensitizing agents introduced to the market claim to reduce dentinal hypersensitivity. Zaimoglu et al. [68] evaluated the smear layer with various desensitizing agents (varnish, Ca(OH)2, sodium fluoride) after tooth preparations to receive a PFM crown, and cemented with zinc ohosphate cement. This investigation indicated that the smear layer did not protect against zinc phosphate cement, and that cavity varnish prevented the formation of smear plugs.

Rajest et al. [69] investigated the effects of Novamin on hypersensitivity. Novamin is 5% calcium sodium phosphosilicate containing dentifrice. They analyzed 30 subjects with minimum two sensitive teeth, by the visual analogue scale of >3cm post air blast stimulation. Fifteen partcipants in each test and control cohort received Novamin toothpaste containing 5% calcium sodium phosphosilicate and Pepsodent toothpaste with no desensitizing compound, respectively. They were also exposed to cold water and air blast stimulation for examination of dentin hypersensitivity at the baseline, for six and eight weeks, via the visual analog scale. The findings suggested that 5% Novamin containing dentifrice statistically decreased dentin hypersensitivity within six and eight week, in comparison with the control group.

Using a resin-based desensitizing agent as VivaSensTM was found to decrease the microleakage of amalgam restorations, possibly contributing to the reduction of postoperative sensitivity [70] while, in a clinical trial of 30 days, Adper Prompt L-pop showed reduction in postoperative sensitivity more than VivaSensTM and unbounded amalgam over all time intervals tested for 24 hrs, one week and one month posttreatment [71].

Johnson et al. [72] suggested that a resin-based sealer is not indicated after tooth preparation, when crowns are to be lured with zinc phosphate cement, because of a decreased crown retention stress, probably attributed to the reduced roughness of the prepared dentin. A resin sealer may be used successfully with the glass ionomer and modified-resin cements tested. Given short clinical crowns or a high angle of convergence, the modified-resin cement system may best retain the castings.

In a recent in vitro study, the abilty of two desensitizers (MS Coat, a self-curing resincontaining oxalate product, and Gluma Desensitizer, a glutaraldehyde/ HEMA-based agent without initiator) were tested to reduce sensitivity through decreasing the permeability of dentin. Both materials significantly reduced dentin permeability to virtually zero, in comparison with the control and albumin-soaked samples [73].

The use of laser was introduced to relive postoperative hypersensitivity. Lier et al. [74] tested the Nd:YAG laser against dentin hypersensitivity in a double-blind, controlled, split-mouth designed clinical trial and concluded that the effect of treatment of hypersensitive teeth with Nd:YAG laser is not different from placebo, apparently lasting for at least 16 weeks. Sipahi et al. tested the effect of different treatment modalities (Laser, Sodium Fluoride, Oxagel Oxalate, and Gluma Primer) and found that the laser treatment had a less negative effect on the retention of crowns luted with glass-ionomer cement. Omae et al. [75] investigated whether a desensitizing agent (GLUMA Desensitizer) containing glutaraldehyde and HEMA improves the bond strength and bonding durability of a self-etching primer adhesive to Er:YAGirradiated dentin. They found out that the application of GLUMA Desensitizer to Er:YAGirradiated dentin increases the bond strength and durability of the self-etching priming adhesive.

Gurbulak et al. [76] investigated the effects of different desensitizers (Systemp, Ivoclar; BisBlock, Bisco), a dentin adhesive (Prime Bond, Dentsply), on pulpal temperature rise during direct provisional restoration polymerization. An autopolymerizing methacrylate (Prevision, Heraeus Kulzer) and a light polymerizing composite (Revotek LC, GC) provisional restoration material were used in this study. The composite resin-based provisional material induced higher thermal changes than the methacrylate-based provisional one. Thickness of desensitizing agents adversely affected the thermal changes, however the desensitizers did not affect the intra-pulpal temperature, although the type of provisional material used may be effective.

Charakorn et al. [77] studied the effect of Ibuprofen (600 mg, PO single dose) on tooth sensitivity from in-office bleaching with 38% hydrogen peroxide, in a double-blind, randomized-controlled clinical trial and concluded that the use of an analgesic may help reduce tooth sensitivity during in-office bleaching only, but not after the treatment period.

Dentists commonly ask what to do about tooth sensitivity that occurs after cementation of a crown with resin. Unfortunately, after a crown has been cemented with resin and the tooth is sensitive, the clinician does not have many good choices. Christensen [55] prefers to wait for up to six weeks, to determine whether sensitivity resolves by itself. In many cases, it does. In some patients, pain only worsens and the crowns must be removed.

In general, preventing postoperative tooth sensitivity can be obtained by a proper cavity preparation, use of bur coolant, avoidance of excessive dentinal desiccation, use of tooth desensitizing solutions, flowable composites, high-viscosity bonding agents with multiple layers and a proper placement technique of the restoration, to avoid the development of any micro-gaps [78].

7.CONCLUSIONS

We found diverse reports on postoperative hypersensitivity with amalgam, tooth-colored, composite resin, luting cements and indirect restoration materials. However, data is still uncertain over the ideal restorative method. Mechanical abrasives and surface medications or surface coating to occlude the sensitive dentinal tubules are some of the recommended management stragtegies to control dentinal sensitivity. Further research works, especially well-designed randomized controlled trials, are required to explore and cement the impact of different restorative materials on postoperative hypersensitivity in dentistry medicine.

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