Abstract
Objectives
Aim of the present prospective controlled clinical study was to compare the clinical performances of two different cementation procedures to lute IPS Empress inlays and onlays.
Methods
Eighty-three IPS Empress restorations (70 class-II inlays, 13 onlays/47 premolars, 36 molars) were placed in 30 patients (19 females/11 males, mean age = 39 years). Two cementation procedures were tested: group 1: forty-three restorations were luted with a self-adhesive resin cement (RelyX Unicem, RX, 3M ESPE); group 2: forty restorations were luted with an etch-and-rinse multistep adhesive (Syntac Classic, Ivoclar-Vivadent) and Variolink II low (SV, Ivoclar-Vivadent). All restorations were evaluated after 2 weeks (baseline = 1st recall = R1, n = 83), 6 months (R2, n = 83), 1 year (R3, n = 82), and 2 years (R4, n = 82) by two independent blinded calibrated examiners using modified USPHS criteria.
Results
From R1 to R4, one failure occurred in the SV group (at R2) due to marginal enamel chipping. After 2 years of clinical service (R4), better marginal and tooth integrity ( p < 0.05) was found in group 2 (SV) compared to the use of the self-adhesive cement (RX, group 1), while no differences were found for all remaining investigated criteria ( p > 0.05). The absence of enamel in proximal boxes (10% with no enamel and 51% of the restorations with less than 0.5 mm enamel width at the bottom of the proximal box) did not affect marginal performance ( p > 0.05).
Significance
The self-adhesive resin cement RelyX Unicem showed clinical outcomes similar to a conventional multi-step cementation procedure after 2 years of clinical service for most of the tested criteria.
1
Introduction
The technique sensitivity of multi-step adhesive systems used in association with resin-based cements along with different operator skills represents a fundamental problem for standardization and long-term clinical success of adhesive indirect restorations . Indeed in vitro and in vivo studies showed that adhesive luting is very technique sensitive procedure . Bonding to both tooth hard tissues (enamel and dentin) and to the internal surfaces of the ceramic indirect restoration is a challenging process and many imperfections may occur in the bonding process. Therefore, in order to reduce technique sensitivity simplified adhesive systems like one-step self-etch adhesives or even self-adhesive resin-cements were proposed .
The first introduced and most-evaluated self-adhesive luting cement is RelyX Unicem (RX, 3M ESPE, St. Paul, MN, USA). Since its commercial launch, several in vitro studies have been carried out to investigate its adhesive and mechanical properties as well as its biocompatibility .
Bonding to dentin with RX showed promising results even comparable to multi-step etch-and-rinse adhesives in combination with resin based cements when RX was used in the dual cure mode . Conversely adhesion to enamel with a self-adhesive cement was repeatedly reported to be less effective if compared to an etch-and-rinse approach . Due to the importance of bonding for long time success of adhesively luted ceramic restorations , reduced enamel bonding may represent an important limitation for the material. On the other hand, due to its chemical composition RX tends to have a higher moisture tolerance compared to the more technique sensitive etch-and-rinse approaches .
In the current literature only few controlled prospective clinical long-term investigations using RX to lute ceramic inlays and onlays have been published , and none comparing RX with the so-called gold-standard cementation procedure involving the use of an etch-and-rinse adhesive in combination with a resin-based cement.
Therefore, the null hypothesis tested in the present study was that there would be no difference between the clinical outcome of a self-adhesive dual-cure resin cement (RX) and a multi-step system etch-and-rinse adhesive/resin-based cement for luting IPS Empress inlays and onlays in vivo over a time period up to 2 years.
2
Materials and methods
Thirty patients (19 female, 11 male; age range: 23–64 years, mean age: 39 years) were selected for this study fulfilling the inclusion criteria reported in Table 1 . The study was performed according to EN 540 (Clinical investigation of medical devices for human subjects, European Committee for Standardization), to CONSORT statement and to previously established and published protocols .
| (1) No pain symptoms at the tooth to be restored |
| (2) Rubber dam application possible |
| (3) No further treatment needed in other posterior teeth |
| (4) Moderate level of oral hygiene |
| (5) Absence of any periodontal and pulpal disease |
| (6) Adult patients between 18 and 65 years |
| (7) No cavities, being close to the pulp |
All subjects were treated at the Dental Clinic 1, University of Erlangen-Nuremberg, Germany, by one clinician (assistant professor) being experienced in placing ceramic inlays and onlays. The study was approved by the Ethics Committee (University Clinic Erlangen, Germany). All patients were required to give written informed consents before starting the study and agreed to participate in a recall program of 4 years, consisting of two appointments in the first year and then one appointment per year.
Eighty-three IPS-Empress inlays (two surfaces = 31, three surfaces = 39, Ivoclar-Vivadent, Schaan, Principality of Liechtenstein) and onlays ( n = 13) were placed. Thirty-four IPS-Empress restorations were placed in maxillary premolars, 14 in maxillary molars, 13 in mandibular premolars and 22 in mandibular molars. Each patient received a maximum of two restorations per group in a split-mouth-design. Group 1: forty-three inlays/onlays were luted with RX; group 2: forty inlays/onlays were luted with Syntac/Variolink II low viscosity (SV, Ivoclar-Vivadent).
The preparations for the IPS-Empress inlays/onlays were slightly divergent without beveled margins. Preparations were performed using 80 μm diamond burs (Inlay Prep-Set, Intensiv, Viganello-Lugano, Switzerland) and finished with 25 μm finishing diamonds. The minimum depth of the cavities was 1.5 mm with round angles, 2 mm at the isthmus and 1.5 mm below replaced cusps. No lining material was used. After preparation, full-arch impressions were taken using a polyvinyl-siloxane material (Dimension Garant H and Garant L, 3M ESPE).
The IPS-Empress inlays/onlays were manufactured at a commercial dental laboratory according to manufacturer’s instructions within 2 weeks after taking the impressions. After removal of the temporary restoration, the tooth surface was cleaned by temporary cement remnants with pumice slurry. After placing the rubber dam, the intraoral fit (maximum luting gap = 100 μm) was evaluated. Internal adjustments were performed using finishing diamonds under water irrigation. Proximal contacts were assessed using waxed dental floss and special contact gages (YS Contact Gage 50/100/150/200 μm, Amann Girrbach, Pforzheim, Germany). Thickness of the IPS-Empress inlays and onlays was recorded using a pair of tactile compasses (Schnelltaster, Kroeplin, Schluechtern, Germany) with an accuracy of 0.01 mm just before placement. The minimum thickness between deepest fissure and fitting surface, minimal width in the isthmus region for inlays, and the minimum thickness of the cuspal coverage in onlays were measured.
Sealed envelopes were prepared by study monitor for randomization of the cement and opened right before inlay placement. All inlays and onlays were luted adhesively under rubber dam. In group 1, RX was applied on a slightly moist tooth surface following manufactures’ instructions and without any other pre-treatment of tooth hard tissues. In group 2, SV was used in accordance with manufacturer’s instructions and without pre-curing the Heliobond (Ivoclar-Vivadent) layer. The internal surface of the restorations was etched with 4.5% hydrofluoric acid (IPS Ceramic etching gel) for 60 s, rinsed, and then silanized with Monobond S (Ivoclar-Vivadent) . After application of the silane coupling agent, the solvent was evaporated with compressed air. Only in the control group (SV) an unfilled resin (Heliobond, Ivoclar-Vivadent) was applied to the internal surface of the IPS-Empress inlays ( Table 2 ).
| Luting strategy | Tooth | Inlay/Onlay |
|---|---|---|
| Group 1: RelyX Unicem | Slightly moist tooth surface, no other pretreatment of tooth hard tissue | 4.5% hydrofluoric acid (IPS ceramic etching gel) for 60 s, rinsed thoroughly for 60 s, air dried for 10 s |
| Monobond S 60 s, gently air dried | ||
| Group 2: Syntac/Variolink II low | Etch with 35% phosphoric acid followed by water rinse. | 4.5% hydrofluoric acid (IPS ceramic etching gel) for 60 s, rinsed thoroughly for 60 s, air dried for 10 s |
| Remove excess water in accordance with the wet-bonding technique. | Monobond S 60 s, gently air dried | |
| Syntac primer 15 s, gently air dried | Heliobond uncured (cured after inlay placement) | |
| Syntac Adhesive 10 s, gently air dried | ||
| Heliobond uncured (cured together with Variolink) | ||
To prevent the formation of an oxygen inhibition layer, the luting composite was covered with glycerol gel before polymerization. Light curing from each side for 40 s (SV) or 20 s (RX) was done using a quartz-tungsten halogen light unit (PolyLux II, KaVo, Biberach, Germany). Irradiance levels of the light were monitored periodically to ensure at least 600 mW/cm 2 with a radiometer.
After curing, the luting areas were examined for defects and resin overhangs were removed. Rubber dam was removed and centric and eccentric occlusal contacts were adjusted using diamond finishing burs (Intensiv). Proximal polishing was done with interdental diamond and polishing strips. Final polishing was performed using felt discs (Dia-Finish E Filzscheiben, Renfert, Hilzingen, Germany) with diamond polishing paste (Brinell, Renfert). Potentially etched or ground enamel areas close to the restoration were covered with a fluoride gel (Elmex Gelee, GABA, Lörrach, Germany) for 60 s.
Recalls were performed at 2 weeks (baseline = R1), 6 months (R2), 1 year (R3) and 2 years (R4) after the cementation using modified United States Public Health Service (USPHS) criteria ( Table 3 ) by two calibrated blinded independent investigators using mirrors, magnifying eyeglasses, probes and bitewing radiographs (only at baseline recall). The following clinical parameters were examined:
- (1)
Surface roughness
- (2)
Color match
- (3)
Anatomic form
- (4)
Marginal integrity
- (5)
Integrity tooth
- (6)
Integrity inlay
- (7)
Proximal contact
- (8)
Changes in sensitivity
- (9)
Radiographic check
- (10)
Subjective satisfaction
| Modified criteria | Description | Analogous USPHS criteria |
|---|---|---|
| Excellent = alpha1 | Perfect | Alpha |
| Good = alpha2 | Slight deviations from ideal performance, correction possible without damage of tooth or restoration | Alpha |
| Sufficient | Few defects, correction impossible without damage of tooth or restoration. No negative effects expected | Bravo |
| Insufficient | Severe defects, prophylactic removal for prevention of severe failures | Charlie |
| Poor | Immediate replacement necessary | Delta |
All patients were asked a standardized questionnaire in order to investigate the occurrence and characteristics of post-operative sensitivity. The vitality of the restored teeth was tested at each recall by using CO 2 snow.
The clinician who had placed the restorations did not perform recall assessments. Acquired data were evaluated with SPSS for Windows V 18.0 (SPSS Inc., Chicago, USA). The statistical unit was one ceramic inlay/onlay. Due to the fact that the two groups did not exhibit normal data distribution (Kolmogorov–Smirnov test), non-parametric tests were used. Differences among the groups were analyzed pairwise with the Mann–Whitney U -test, differences over the time with the Friedman-test (level of significance p < 0.05).
2
Materials and methods
Thirty patients (19 female, 11 male; age range: 23–64 years, mean age: 39 years) were selected for this study fulfilling the inclusion criteria reported in Table 1 . The study was performed according to EN 540 (Clinical investigation of medical devices for human subjects, European Committee for Standardization), to CONSORT statement and to previously established and published protocols .
| (1) No pain symptoms at the tooth to be restored |
| (2) Rubber dam application possible |
| (3) No further treatment needed in other posterior teeth |
| (4) Moderate level of oral hygiene |
| (5) Absence of any periodontal and pulpal disease |
| (6) Adult patients between 18 and 65 years |
| (7) No cavities, being close to the pulp |
All subjects were treated at the Dental Clinic 1, University of Erlangen-Nuremberg, Germany, by one clinician (assistant professor) being experienced in placing ceramic inlays and onlays. The study was approved by the Ethics Committee (University Clinic Erlangen, Germany). All patients were required to give written informed consents before starting the study and agreed to participate in a recall program of 4 years, consisting of two appointments in the first year and then one appointment per year.
Eighty-three IPS-Empress inlays (two surfaces = 31, three surfaces = 39, Ivoclar-Vivadent, Schaan, Principality of Liechtenstein) and onlays ( n = 13) were placed. Thirty-four IPS-Empress restorations were placed in maxillary premolars, 14 in maxillary molars, 13 in mandibular premolars and 22 in mandibular molars. Each patient received a maximum of two restorations per group in a split-mouth-design. Group 1: forty-three inlays/onlays were luted with RX; group 2: forty inlays/onlays were luted with Syntac/Variolink II low viscosity (SV, Ivoclar-Vivadent).
The preparations for the IPS-Empress inlays/onlays were slightly divergent without beveled margins. Preparations were performed using 80 μm diamond burs (Inlay Prep-Set, Intensiv, Viganello-Lugano, Switzerland) and finished with 25 μm finishing diamonds. The minimum depth of the cavities was 1.5 mm with round angles, 2 mm at the isthmus and 1.5 mm below replaced cusps. No lining material was used. After preparation, full-arch impressions were taken using a polyvinyl-siloxane material (Dimension Garant H and Garant L, 3M ESPE).
The IPS-Empress inlays/onlays were manufactured at a commercial dental laboratory according to manufacturer’s instructions within 2 weeks after taking the impressions. After removal of the temporary restoration, the tooth surface was cleaned by temporary cement remnants with pumice slurry. After placing the rubber dam, the intraoral fit (maximum luting gap = 100 μm) was evaluated. Internal adjustments were performed using finishing diamonds under water irrigation. Proximal contacts were assessed using waxed dental floss and special contact gages (YS Contact Gage 50/100/150/200 μm, Amann Girrbach, Pforzheim, Germany). Thickness of the IPS-Empress inlays and onlays was recorded using a pair of tactile compasses (Schnelltaster, Kroeplin, Schluechtern, Germany) with an accuracy of 0.01 mm just before placement. The minimum thickness between deepest fissure and fitting surface, minimal width in the isthmus region for inlays, and the minimum thickness of the cuspal coverage in onlays were measured.
Sealed envelopes were prepared by study monitor for randomization of the cement and opened right before inlay placement. All inlays and onlays were luted adhesively under rubber dam. In group 1, RX was applied on a slightly moist tooth surface following manufactures’ instructions and without any other pre-treatment of tooth hard tissues. In group 2, SV was used in accordance with manufacturer’s instructions and without pre-curing the Heliobond (Ivoclar-Vivadent) layer. The internal surface of the restorations was etched with 4.5% hydrofluoric acid (IPS Ceramic etching gel) for 60 s, rinsed, and then silanized with Monobond S (Ivoclar-Vivadent) . After application of the silane coupling agent, the solvent was evaporated with compressed air. Only in the control group (SV) an unfilled resin (Heliobond, Ivoclar-Vivadent) was applied to the internal surface of the IPS-Empress inlays ( Table 2 ).
