Roland Frankenberger

Marginal quality of flowable 4-mm base vs. conventionally layered resin composite

OBJECTIVE This study evaluated marginal integrity of bonded posterior resin composite fillings to enamel and dentine with and without 4mm flowable base, before and after thermo-mechanical loading (TML). METHODS 80 MOD cavities with one proximal box beneath the CEJ were prepared in extracted human third molars. Direct resin composite restorations (SDR with CeramX mono, Tetric EvoCeram, Filtek Supreme XT, and Venus Diamond or the respective resin composites alone) were bonded with system immanent adhesives XP Bond, Xeno V, Syntac, Adper Prompt L-Pop, and iBond self-etch. Before and after thermomechanical loading (100,000×50N, 2500 thermocycles between 5 and 55°C), marginal gaps were analysed using SEM of epoxy resin replicas. Results were analysed with Kruskal-Wallis and Mann-Whitney U-tests (p<0.05). After thermomechanical loading, specimens were cut longitudinally in order to investigate internal dentine adaptation by epoxy replicas under a SEM (200× magnification). RESULTS In enamel, high percentages of gap-free margins were initially identified for all adhesives. After TML, etch-and-rinse adhesives performed better than self-etch adhesives (p<0.05). Also in dentine, initially high percentages of gap-free margins were found for all adhesives. After TML, etch-and-rinse adhesives again performed better than self-etch adhesives for both marginal and internal adaptation (p<0.05). The presence of a 4mm layer of SDR had no negative influence on results in any group (p>0.05). CONCLUSIONS SDR as 4mm bulk fill dentine replacement showed an good performance with the material combinations under investigation.

Is Adhesive Cementation of Endodontic Posts Necessary

Recently, the appropriate, durable bond of adhesive systems and composite resin cements to retain endodontic posts was challenged. The question arises whether it would be possible to place glass fiber posts in a less technique sensitive conventional nonadhesive approach. The influence of nonadhesive, self-adhesive, and etch-and-rinse systems on load capability of postendodontic restorations was studied. Human maxillary central incisors were divided into 4 groups (n = 10). Teeth were endodontically treated and restored by using glass fiber posts luted with different cements/composite resin combinations: (1) RelyX Unicem (3M ESPE, Seefeld, Germany)/Clearfil Core (Kuraray Europe, Duesseldorf, Germany), (2) RelyX Unicem/LuxaCore, (3) zinc phosphate cement/Clearfil, and (4) LuxaCore (DMG, Hamburg, Germany)/Clearfil. A 2 mm-ferrule preparation was performed. All specimens received adhesively luted all-ceramic crowns and were exposed to thermal cycling and mechanical loading before subsequent static loading. Significant differences between the experimental groups regarding load capability and fracture patterns were observed. The conventional non-adhesive post cementation is less reliable to withstand simulated functional forces compared to adhesive approaches.

The anti-adherence activity and bactericidal effect of microparticulate silver additives in composite resin materials.

OBJECTIVE Resin composite materials tend to accumulate microorganisms and dental plaque, which in turn may induce secondary caries around adhesive restorations. The aim of the present in vitro study was to evaluate the antibacterial activity of a resin composite material loaded with silver microparticles against Streptococcus mutans. DESIGN Circular specimens (10.0mm in diameter) of a resin composite matrix loaded with two different concentrations of a silver additive (Comp0.3: 0.3%; Comp0.6: 0.6%) and one unloaded reference composite matrix (Comp0: 0%) were made. Surface roughness R(a) was assessed by perthometer measurements and hydrophobicity according to water contact angles was determined by computerized image analysis. The specimens were incubated in a S. mutans suspension (1h, 37 degrees C) and adhering streptococci were quantified by using a biofluorescence assay (Alamar blue/Resazurin). Additionally, the viability of adhering bacteria was assessed by live/dead cell labelling in combination with fluorescence microscopy. RESULTS Statistically significant differences between the median water contact angles of Comp0 (66.3 degrees ), Comp0.3 (76.7 degrees ), and Comp0.6 (89.4 degrees ) were observed (p<0.001). A three- to fourfold higher amount of adhering S. mutans was found on reference Comp0 (12,093relative fluorescence units) than on Comp0.3 (4258rfu) and Comp0.6 (3292) (p<0.001 for both). Significantly higher percentages of dead cells than on Comp0 (0.5%) were found on Comp0.3 (6.1%) and on Comp0.6 (10.1%) (p<0.001 for both). CONCLUSIONS The addition of microparticulate silver to a resin composite material increased the surface hydrophobicity and reduced the number of adhering streptococci. Simultaneously it increased the percentage of dead and inactive cells on the composite surface. Thus, silver additives seem to demonstrate anti-adherence activity as well as a bactericidal effect.

Fatigue behaviour of different dentin adhesives

Abstract The aim of this in vitro study was to compare quasistatic and cyclic fatigue dentin bond strength of modern adhesive systems representing different generations. One hundred and fifty cavities were made in discs of freshly extracted human third molars and filled with direct resin composite restorations. Dentin adhesives of different generations (SY = Syntac Classic, multi-step system with self-etching primer; SE = Syntac Classic with additional phosphoric acid etching prior to application of the self-etching primer; SB = Scotchbond Multi-Purpose Plus, multi-step system with total etching; PE = Prime&Bond 2.1, single-step system with and without [PB] total etching) were used in combination with one hybrid composite. After 21 days of storage, 10 specimens for each adhesive system were subjected to thermocycling (1150 cycles) for 24 h and were afterwards debonded in a push-out test. Another 20 specimens were tested with cyclic fatigue according to the staircase method with 5000 cycles for each specimen. Static and cyclic push-out bond strengths, respectively, for each group were (MPa): SY 16.9±0.9 and 14.2±1.7, SE 17.5±1.8 and 14.8±3.4, SB 18.5±1.7 and 13.9±2.1, PB 14.6±2.2 and 7.2±2.4, PE 13.4±2.2 and 6.8±1.8. Both quasistatic and dynamic bond strengths revealed better values for the multi-step systems (P<0.05). All adhesive systems tested revealed a significant fatigue behaviour which was more pronounced for the one-bottle system with a decrease of about 50% independent of additional dentin etching.

IPS Empress inlays and onlays after four years — a clinical study

OBJECTIVE Ceramic inlays are used as esthetic alternatives to amalgam and other metallic materials for the restoration of badly damaged teeth. However, only limited clinical data are available regarding adhesive inlays and onlays with proximal margins located in dentine. In a prospective, controlled clinical study, the performance of IPS Empress inlays and onlays with cuspal replacements and margins below the amelocemental junction was examined. MATERIALS AND METHODS Ninety-six IPS Empress fillings were placed in 34 patients by six clinicians. The restorations were luted with four different composite systems. The dentin bonding system Syntac Classic was used in addition to the acid-etch-technique. At baseline and after 6 months, one, two and four years after placement the restorations were assessed by two calibrated investigators using modified USPHS codes and criteria. A representative sample of the restorations was investigated by scanning electron microscopy to evaluate wear. RESULTS Seven of the 96 restorations investigated had to be replaced (failure rate 7%; Kaplan-Meier). Four inlays had suffered cohesive bulk fractures and three teeth required endodontic treatment. After four years in clinical service, significant deterioration (Friedman 2-way Anova; p < 0.05) was found to have occurred in the marginal adaptation of the remaining restorations. Seventy-nine percent of the surviving restorations exhibited marginal deficiencies, independent of the luting composite. Neither the absence of enamel margins, nor cuspal replacement significantly affected the adhesion or marginal quality of the restorations. CONCLUSION After four years, extensive IPS Empress inlays and onlays bonded with the dentin bonding system Syntac Classic were found to have a 7% failure rate with 79% of the remaining restorations having marginal deficiencies.

Crack formation of all-ceramic crowns dependent on different core build-up and luting materials

OBJECTIVES The aim of this in vitro study was to evaluate various core build-up and luting materials regarding their effect on crack formation of all-ceramic crowns. METHODS Fifty-six freshly extracted sound human third molars were prepared according to a standardized procedure obtaining a circular shoulder of 1.5 mm with all margins located in dentin. Sixty percent of the dentin volume were removed and restored with totally bonded build-up composite resins or resin-modified glass ionomer cements (RMGIC) or compomers. Cast IPS-Empress caps were manufactured and luted with the different materials. For each material group, the volumes of the core build-ups and of the luting cements were determined. The caps were examined for cracks after 1, 3, 6, 9 and 12 months storage in 0.9% saline solution at 37 degrees C. RESULTS The tested groups revealed no major differences in the percentage of the core build-ups and in the volume of the luting cements. After 12 months only the group with composite resin build-up and luting showed no crack formation. RMGIC/compomer build-up or RMGIC/compomer luting always resulted in cracking of the caps. CONCLUSIONS Within the limits of this study it can be concluded that the hygroscopic expansion of RMGIC/compomer materials led to failure of all-ceramic crowns, when the materials are used for both core build-up or adhesive bonding.

Long-term degradation of enamel and dentin bonds: 6-year results in vitro vs. in vivo

OBJECTIVES To evaluate marginal integrity of direct resin composite restorations before and after thermo-mechanical loading in vitro, and before and after 6 years of clinical service in a prospective clinical trial. METHODS For the in vitro part, MO cavities with the proximal box beneath the cemento-enamel junction were prepared in 32 extracted human third molars. The specimens were randomly assigned to four groups (n=8) and received bonded resin composite restorations (two groups each Grandio bonded with Solobond M and Tetric Ceram bonded with Syntac). Specimens were subjected to three different aging protocols: 6-year water storage (WS), thermo-mechanical loading (TML; 100,000×50N; 2500×+5/+55°C), and 6-year water storage plus thermo-mechanical loading (WS+TML). Initially and after aging, marginal qualities in enamel and dentin were evaluated using replicas at 200× magnification (SEM). For the in vivo part, 30 patients received 68 direct resin composite restorations of the same materials in a prospective clinical trial. Replicas of 11 selected subjects per group were assessed for marginal quality under a SEM at 200×. RESULTS in vitro, all initial results showed nearly 100% gap-free margins. For TML, percentages of gap-free margins dropped to 87-90% in enamel and to 58-66% in dentin (p<0.05). For WS, enamel margins still were at 97-99% whereas dentin margins exhibited 67-75% gap-free margins, and for WS+TML, enamel margins were at 85-87% and dentin margins at 42-52% gap-free margins. In vivo, gap-free enamel margins were reduced from initially 86-90% to 74-80% after 6 years of clinical service (p<0.05). Proximally exposed dentin margins were not recordable by impressions, however, clinically no considerable problems like recurrent caries or discolorations were detected. SIGNIFICANCE In vitro, hydrolytic degradation supports mechanical fatigue in dentin-composite bonds over time. In vivo, wear phenomena are superimposing marginal quality aspects. Gaps between enamel and resin composite did not play a major role.

Operator vs. material influence on clinical outcome of bonded ceramic inlays

OBJECTIVE The aim of the present study was to clinically evaluate the suitability of Definite Multibond and Definite ormocer resin composite for luting of Cergogold glass ceramic inlays in a two-center trial involving two dentists. METHODS Thirty-nine patients received 98 Cergogold inlays with at least one inlay luted with Definite Multibond/Definite (n=45) and at least one inlay luted with Syntac/Variolink Ultra (n=53) in a split mouth design. Treatments were carried out in two private practices by two operators (Operator A: n=38; Operator B: n=60). Forty-four cavities required caries profunda treatment, 23 cavities exhibited no enamel at the cervical margin. At baseline (2 months), and after 6, 14, 27, and 51 months of clinical service, the restorations were investigated according to modified USPHS criteria. RESULTS The drop-out rate was 3% after 4 years. After 48 months of clinical service, 21 restorations in 16 patients (9 luted with Definite, 12 with Variolink; 2 placed by operator A and 19 by operator B) had to be replaced due to inlay fracture (n=11), tooth fracture (n=4), hypersensitivities (n=3), or marginal gap formation (n=3). Seventy-seven inlays were in good condition (survival rate 89.9%, median survival time 4.2 years (95% confidence interval +/-0.25; survival analysis by Kaplan-Meier algorithm). Survival rate after 4 years was 97.4% for operator A, and 75.4% for operator B (p=0.002; Log Rank/Mantel-Cox) resulting in annual failure rates of 0.6% and 6.2%, respectively. The operators did not differently judge the clinical behaviour of the luting procedures (Mann-Whitney U-test, p>0.05). Independent of the operator and the used luting system, the following criteria significantly changed over time: color match, marginal integrity, tooth integrity, inlay integrity, sensitivity, hypersensitivity, and X-ray control (p<0.05; Friedman test). Significant differences between operators over the whole period were computed for the criteria marginal integrity, tooth integrity, and inlay integrity (p<0.05, Mann-Whitney test). Differences between luting materials were only present during single recalls. SIGNIFICANCES For luting of ceramic inlays, only slight differences between the two luting systems were detectable. The operator influence on clinical outcome was clearly proven.

Thermal-induced residual stresses affect the lifetime of zirconia–veneer crowns

OBJECTIVES The purposes of this study were to investigate the effects of thermal residual stresses on the reliability and lifetime of zirconia-veneer crowns. METHODS One hundred and twenty eight second upper premolar zirconia-veneer crowns were manufactured for testing the initial strength (n=64) and under cyclic fatigue (n=64). Zirconia copings (YZ Cubes, VITA Zahnfabrik, CTE: alphac=10.5 ppm/°C) were milled using a Cerec3 InLab (Sirona) machine and sintered to a final thickness of 0.7 mm. Sixty-four copings were sandblasted with 105 μm alumina particles (15 s, 3 cm distance, 45° angle, 0.4 MPa pressure) in order to trigger a tetragonalmonoclinic transformation and to produce a rough surface. The copings were veneered using two different porcelains (VM9, VITA Zahnfabrik, CTE: alphaVM9=9.1 ppm/°C, Lava Ceram, 3M ESPE, CTE: alphaLava=10.2 ppm/°C) so to result in crowns with either high thermal mismatch (+1.4 ppm/°C with VM9) and low thermal mismatch (+0.3 ppm/°C with Lava Ceram). The porcelains were applied by the same operator and fired (VITA Vacumat 4000) according to the firing schedules defined by the manufacturers to a final thickness of 1.4mm (total crown thickness=2.1mm, core/veneer ratio=0.5). After the last glaze firing the crowns were cooled following a fast (600°C/min) or a slow (30°C/min) cooling protocol. The glazed crowns were submitted to a sliding-motion (0.7 mm lateral movement) cyclic fatigue in a chewing simulator (SD Mechatronik) under 20 kg (~200 N load) weight until failure (chipping) (n=16). The other half of the crowns were subjected to a compressive loading test in an universal testing machine (Instron model 4240) until failure at a cross-head speed of 0.75 mm/min (n=16). The failure probability for initial strength and cyclic fatigue was performed using a Weibull distribution approach at a scale factor of n=16. RESULTS The compressive strength test showed a low sensitivity to detect reliability variations regarding thermal stresses created within the veneer layer of tested crowns. For cyclic fatigue, slow cooling resulted in statistically higher cycles to failure only for the crowns that presented a high thermal mismatch between core and veneer (VM9 group). Comparisons between veneers with high or low thermal mismatches showed statistically higher sigma0 for Lava Ceram-veneered crowns only when the groups were fast-cooled. SIGNIFICANCE Minimizing the thermal residual stresses within the veneer through the use of a veneer with a closer CTE to the zirconia delays the failure of zirconia-veneer crowns. Slow-cooling increases the lifetime of crowns presenting large differences in CTE between the zirconia core and the veneering porcelain.

Antagonist Enamel Wears More Than Ceramic Inlays

Wear phenomena of ceramic inlays are not fully understood. The aim of the present study was to evaluate ceramic wear, antagonist enamel wear, and luting cement wear over 8 years. The two-fold null hypothesis was that there would be (1) no difference in wear behavior between ceramic and enamel, and (2) no influence of filler content of luting composites on composite wear. From 96 restorations, 36 Class II inlays from 16 participants were selected. For inlays with opposing enamel cusps (n = 17), replicas of inlays and enamel were scanned with a 3-D laser scanner. Luting gaps of inlays (n = 36) were analyzed with a profilometer, including 3-D data analysis. Ceramic and enamel wear increased between 4 and 8 years, with significantly higher values for enamel after 6 years (p < 0.05). Luting gap wear increased continuously up to 8 years (p < 0.05), with no influence of luting composites (p > 0.05) and location of teeth (p > 0.05).