Influence of Cavity Margin Design and Restorative Material on Marginal Quality and Seal of Extended Class II Resin Composite Restorations In Vitro.

PURPOSE: To investigate the influence of three cavity designs on the marginal seal of large Class II cavities restored with low-shrinkage resin composite limited to the enamel. MATERIALS AND METHODS: One hundred twenty (120) intact human molars were randomly divided into 12 groups, with three different cavity designs: 1. undermined enamel, 2. box-shaped, and 3. proximal bevel. The teeth were restored with 1. an extra-low shrinkage (ELS) composite free of diluent monomers, 2. microhybrid composite (Herculite XRV), 3. nanohybrid composite (Filtek Supreme XTE), and 4. silorane-based composite (Filtek Silorane). After artificial aging by thermocycling and storage in physiological saline, epoxy resin replicas were prepared. To determine the integrity of the restorations' approximal margins, two methods were sequentially employed: 1. replicas were made of the 120 specimens and examined using SEM, and 2. the same 120 specimens were immersed in AgNO3 solution, and the dye penetration depth was observed with a light microscope. Statistical analysis was performed using the Kruskal-Wallis and the Dunn-Bonferroni tests. RESULTS: After bevel preparation, SEM observations showed that restorations did not exhibit a higher percentage of continuous margin (SEM-analysis; p>0.05), but more leakage was found than with the other cavity designs (p<0.05). The lowest percentage of continuous margin was observed in ELS restorations (p<0.05). More fractured margins were observed in the undermined enamel cavity design groups (p<0.05). CONCLUSION: Bevel preparation failed to improve margin quality in large Class II composite restorations and is no longer recommended. However, undermined enamel should be removed to prevent enamel fractures.

Laboratory-made composite resin restorations in children and adolescents with hypoplasia or hypomineralization of teeth.

Management of children and adolescents with qualitative or quantitative defects of enamel or dentin are often impeded by patient compliance, rare prevalence of disease, lack of evidence, and cost. The aim for all patients in this case series was to develop a suitable treatment strategy that required little chair time and was applicable to several conditions. Thirty-four laboratory-made composite resin restorations were placed in differently affected permanent posterior teeth of eight young patients. The ages of the patients ranged from 6 to 15 years. All restorations were adhesively inserted with the etch-and-rinse technique and are still in situ. The longevity of the restorations at present is 2 to 48 months. This treatment method allowed relatively comfortable treatment for children and adolescents who required extensive dental treatment. The outcome has been favorable with good patient compliance, brief chair time, and functional and esthetic restorations.

Treatment of a crown-root fracture with concomitant root fracture.

The aim of this case report was to present a treatment strategy for severely injured teeth in children and adolescents by using periodontal surgery and adhesive techniques. A 16-year-old boy presented after a severe bicycle accident. A radiograph revealed a root fracture with connective tissue healing and displacement. Clinically, a crown-root fracture as well as an uncomplicated crown fracture of the same fragment was obvious. The root canal was prepared and filled with gutta-percha to the fracture line. A full periodontal flap was performed, and the crown-root fragment was adhesively fixed. The flap was tightly apposed, and the missing mesial edge of the tooth was restored with composite resin. A control radiograph showed a neatly fixed coronal fragment and sufficient root canal filling. The amount of work required proved to be acceptable for both patient and clinician--even if an implantation might have to be considered when the patient is full-grown--because of the longevity of the procedure.

Influence of matrix systems on proximal contact tightness of 2- and 3-surface posterior composite restorations in vivo.

OBJECTIVES: To investigate the influence of cavity preparation (MO/DO/MOD) and type of matrix system on proximal contact tightness of direct posterior composite restorations. MATERIALS AND METHODS: 85 patients in need of a two- or three surface Class II direct composite restoration were randomly divided into two treatment groups. Group 1 was treated with a sectional matrix system combined with a separation ring (Palodent); Group 2 was treated with a circumferential matrix system in combination with a retainer (Tofflemire). Proximal contact tightness was recorded before treatment and directly after finishing the restoration. RESULTS: For the two-surface cavities use of the separation ring resulted in a statistically significantly tighter proximal contacts at both the mesial and distal site (MO: 2.51±0.81 N; DO: 2.82±1.14 N) compared to the use of the circumferential (MO: -1.08±1.04 N; DO: -0.22±0.87 N) (p=0.01). Regarding the three-surface (MOD) cavities no statistically significant differences were found between the mesial and distal site, nor was there an effect of the used matrix system. No statistically significant influence of cavity design (mesially/distally) was recorded for all cavities (MO, DO and MOD). CONCLUSIONS: Use of the sectional matrix system in two-surface Class II cavities resulted in statistically significantly tighter proximal contacts than the use of the circumferential matrix system. For the three-surface no statistically significant differences in contact tightness were found between the different matrix systems. Location of the cavity (mesially or distally) did not show to have any statistically significant effect on the obtained proximal contact tightness.

Periodontal status of teeth with crown-root fractures: results two years after adhesive fragment reattachment.

AIM: This series of case reports evaluated the impact of adhesive crown-root fragment reattachment in periodontally healthy teeth suffering from crown-root fractures on various parameters of periodontal health over a time course of 2 years. MATERIAL AND METHODS: A total of 20 teeth with crown-root fractures in 18 periodontally healthy subjects were evaluated. After open-flap access, crown-root fragments were adhesively reattached to the root stub. In all cases, the vertical difference between the alveolar bone crest and the fracture line was

Influence of endodontic post type (glass fiber, quartz fiber or gold) and luting material on push-out bond strength to dentin in vitro.

OBJECTIVES: To determine the influence of post type and luting material on bond strength to dentin. METHODS: The root canals of extracted human upper central incisors were instrumented and post space was prepared using the respective drills for each post system. Glass fiber posts (Luscent Anchor, Dentatus [LA]) were luted using three dual-curing adhesive systems (Excite DSC/Variolink II, Vivadent [VL2]; EnaBond/EnaCem, Micerium [ENA]; Prime & Bond NT/Calibra, DentSply DeTrey [CAL]). A different brand of glass fiber post (EasyPost, DentSply Maillefer [EP]) and quartz fiber post (DT Light Post, VDW [DT]) were luted using CAL. Gold posts (Perma-dor, VDW) were luted either adhesively following tribo-chemical silicate coating (Rocatec, ESPE-Sil, 3M ESPE; CAL) or conventionally using glass ionomer cement (Ketac Cem, 3M ESPE). Three slices of 2mm height were cut perpendicular to the post from each restored root. Bond strength was determined by pushing out the post using a universal testing machine (/1449, Zwick). RESULTS: For all experimental groups combined, bond strength increased from the coronal to the apical section (Friedman test: P<0.001). Significant differences were observed among the fiber posts (DT/CAL>LA/CAL; Mann-Whitney U-test with Bonferroni-Holm adjustment: P<0.05; EP/CAL ranging in between) but not among luting materials (LA/VL2, LA/ENA, LA/CAL: n.s.). The gold posts were equivalent to DT/CAL with both luting procedures. SIGNIFICANCE: Selection of post type may be more important for bond strength than luting material. Bond strength of fiber posts was equivalent but not superior to adhesively or conventionally luted gold posts.

[Cavity micro-morphology following caries removal]. / Kavitätenmikromorphologie nach Kariesexkavation.

The objective of this research was to observe the effect of different caries removal techniques on human dentin topography. Thirty-six dentin samples of bisected carious human molars were treated with six different caries removal techniques, replicated and then examined by using a scanning electron microscope. The surfaces were observed before and after the smear layer removal at a magnification of 200- and 1000-fold. At a magnification of 200 the sono-abraded samples showed a significantly more undulated dentin topography than samples treated with other techniques. Using Carisolv hand instruments for caries removal resulted both at a magnification of 200 and 1000 in a significantly rougher, flakier and more fissured dentin surface texture compared to other techniques. Microcracks were observed in samples from all excavation methods but most frequently when treated with Carisolv hand instruments. The excavation process results in a dentin topography marked by smooth, flaky and fissured surface textures as well as by microcracks. The relative incidence in which these textures occur may indicate whether the removed dentin was rather cut or fractured.

Comparison of in vivo visual and computer-aided tooth shade determination.

The aim of this study was to evaluate the performance of shade-determining devices. For the daily practitioner, it is essential to know whether modern computer-aided shade selection is reliable in everyday life. So the question of how the clinical usability of these machines could be rated has to be clarified. In the following, three actual devices available in the market were compared using a human observer's perception. The SpectroShade device (MHT Optic Research AG, 8155 Niederhasli, Switzerland), the ShadeVision device (X-Rite Co., Grandville, USA) and the Digital Shade Guide DSG4 (A. Rieth, 73614 Schorndorf, Germany) were assessed with respect to their agreement with the color perception of three examiners looking at 57 test persons (six teeth each for a total of 342). Shades were reported in Vita Classical shades. It could be demonstrated that every single human examiner showed a significantly higher agreement value (human group on average 40.2%) when compared with the remaining five methods than each computer-aided tooth shade determination device. The devices reached on average only a value of 28.6%, whereas the X-Rite ShadeVision showed a significant better result (33.2%) than the MHT SpectroShade and Rieth DSG4 (27.0 and 25.7%). Identical shade results given by all three methods of a group (group of three devices and three humans) were found to be rather low for the computer-aided devices (9.9%) compared with humans (36.7%). All six methods together agreed in 3.3% of the cases. It becomes evident that the methods-especially the computer-aided shade determination-are rather divided about the respective tooth color. Deficiencies of the instrumental as well as the visual detection become obvious. The best agreement level was performed by the human examiners. The best agreement of the evaluated devices was obtained-generally as well as among the human testers-by the X-Rite ShadeVision system, followed at a statistically significant distance by the MHT SpectroShade and the Rieth DSG4. The agreement among the examiner group was 52.9%, significantly better than that of each device compared to this group (31.3% on average). Color detection and its realization are very complex. As shown, in many cases, computer-aided color shade determination of natural teeth seems to not reflect human perception.

[Heat propagation in dentin during cavity preparation in vitro with oscillating instruments]. / Temperaturentwicklung im Dentin bei Kariesexkavation mit oszillierenden Instrumenten.

The purpose of this work was to study the temperature rise caused by preparation of human dentin using two different types of oscillating instruments. A newly designed tungsten carbide tip (Cariex TC, KaVo) and a diamond-coated tip (Cariex D, KaVo) in combination with an airscaler (Sonicflex 2003L, KaVo) and two different flow rates of two coolants were investigated. For both tips significant differences in temperature rise were found between cooling with waterspray or with Plakout Gel (Kerr, HaWe) and using no coolant. A flow of 7.3 ml water/min was found to be sufficient to avoid any critical temperature rise, an excavation of longer duration without coolant cannot be recommended. The use of water-based highly viscous substances over a defined period during the caries excavation process seems to be a viable alternative.

Effect of high intensity vs. soft-start halogen irradiation on light-cured resin-based composites. Part II: Hardness and solubility.

PURPOSE: To determine hardness and solubility of light-cured resin-based composites after high intensity vs. soft-start quartz tungsten halogen irradiation. METHODS: Knoop hardness of resin-based composite specimens was measured at 1.5 mm depth after dry storage for 24 hours at 37 degrees C so as to indirectly evaluate degree of cure. Solubility was determined gravimetrically by extraction of post-cured (24 hours, 37 degrees C) specimens in 50 wt% methanol for 72 hours. Four hybrid (Filtek Z250, Herculite, Solitaire 2, Tetric Ceram), an inhomogeneously filled hybrid (InTen-S) and a microfilled (Filtek A110, formerly Silux Plus) composite were cured using the quartz tungsten halogen units Astralis 10 and Optilux 501 in the high intensity (Astralis 10 High Power: 10 seconds @ 1300 mW/cm2; Optilux Boost: 10 seconds @ 1140 mW/cm2) or soft-start modes (Astralis 10 Pulse: increase to 700 mW/cm2 within 10 seconds, three periods of 2 seconds @ 1300 mW/cm2 alternating with two periods of 2 seconds @ 700 mW/cm2; Optilux Ramp: exponential increase within 10 seconds, followed by 10 seconds @ 1140mW/cm2). RESULTS: For the fast curing composites Z250, Tetric Ceram and InTen-S, equivalent hardness was observed after 10 seconds of high intensity and 20 seconds of soft-start irradiation. For the slower curing composites Herculite, Solitaire 2 and A110, the soft-start protocols produced higher hardness values. Regarding solubility however, the superiority of soft-start irradiation was also seen for Tetric Ceram and InTen-S. The lowest solubility was observed for InTen-S, followed by Z250, whereas Herculite and Solitaire 2 scored highest for this parameter.

The influence of plasma arc vs. halogen standard or soft-start irradiation on polymerization shrinkage kinetics of polymer matrix composites.

OBJECTIVES: To determine polymerization shrinkage kinetics and hardness of photo-activated polymer matrix composites (PMC) after plasma arc vs. halogen standard or soft-start irradiation. METHODS: Polymerization shrinkage was measured using the 'deflecting disk technique', and Knoop hardness was measured at the bottom of 1.5 mm thick specimens stored for 24 h at 37 degrees C. The materials comprised one micro-filled (Silux Plus) and four fine hybrid PMC (Definite, Herculite XRV, Solitaire 2 and Z250). The irradiation protocols included halogen standard irradiation at three intensities (TriLight, ESPE), ramp curing (dito), step curing (HiLight, ESPE), pulse polymerization (VIP Light, BISCO) and plasma curing (Apollo 95E, DMDS; PAC Light, ADT). RESULTS: Standard halogen irradiation at reduced intensity delayed the start and slowed down the progression of shrinkage strain, but (except for Z250) as well produced lower hardness. Soft-start halogen curing produced similar kinetics but maintained hardness. Plasma arc irradiation resulted in an immediate start and a rapid progression of polymerization contraction, but produced low hardness values in Definite (cured by the ADT unit) and in Solitaire 2 (both units). Z250 featured the highest, Silux Plus the lowest maximum rate of contraction. Despite soft-start irradiation, contraction of Z250 progressed faster than that of Silux Plus with halogen standard irradiation at high intensity. CONCLUSIONS: Soft-start halogen irradiation protocols provide better chances for compensation of shrinkage stress by flow within PMC without compromising hardness and may contribute to a better marginal integrity of the restorations. Irradiation protocols should be individually adjusted to compensate for the different curing characteristics of PMC.

Influence of curing methods and materials on the marginal seal of class V composite restorations in vitro.

The study tests the hypothesis that soft-start irradiation improves, whereas, high intensity irradiation compromises the margin quality and marginal seal of Class V resin based composite [RBC] restorations. Box-shaped Class V cavities were prepared in extracted, human third molars with cervical margins located apical to the CEJ. Cavities were restored using a multi-step bonding agent (Optibond FL, Kerr), a thin layer of flowable resin composite and two increments of fine hybrid resin composite (Filtek Flow/Filtek Z250, 3M ESPE; Revolution f2/Herculite XRV, Kerr). Light irradiation was performed using either the standard (40 seconds) or the soft-start mode (40 seconds with exponential increase) of a quartz tungsten halogen or an LED curing light (Elipar Trilight, Elipar Freelight, 3M ESPE); for high intensity irradiation, a Plasma Are curing unit was used with three irradiations of three seconds (Apollo 95E, DMDS). After 30 days of water storage and thermal cycling (n = 2500, 5-55 degrees C), margin quality was assessed in the SEM using the replica technique and marginal seal was evaluated using dye penetration (AgNO3 50%). Few differences were observed between the light curing protocols. However, less leakage was observed in the case of the lower shrinking RBC Filtek Z250.

Effect of high intensity vs. soft-start halogen irradiation on light-cured resin-based composites. Part I. Temperature rise and polymerization shrinkage.

PURPOSE: To determine polymerization shrinkage kinetics and temperature rise of light-cured resin-based composites after high intensity vs. soft-start quartz tungsten halogen irradiation. METHODS: Shrinkage kinetics was evaluated using the "deflecting disk technique", modified for simultaneous measurement of temperature within the resin-based composite using a thermocouple. Additional irradiations after 60 and 65 minutes allowed the determination of temperature rises caused by radiation or by reaction heat. Four hybrids (Filtek Z250, Herculite, Solitaire 2, Tetric Ceram), an inhomogeneously filled hybrid (InTen-S) and a microfill (Filtek A110, formerly Silux Plus) were cured using the quartz tungsten halogen units Astralis 10 and Optilux 501 in the high intensity (A10 HiPo: 10 seconds at 1300 mW/cm2; OL Boost: 10 seconds at 1140 mW/cm2) or soft-start modes (A10 Pulse: increase to 700 mW/cm2 within 10 seconds, three periods of 2 seconds at 1300 mW/cm2 alternating with two periods of 2 seconds at 700 mW/cm2; OL Ramp: exponential increase within 10 seconds, followed by 10 seconds at 1140 mW/cm2). RESULTS: The soft-start protocols produced less contraction, and polymerization shrinkage started later and progressed slower (or: more slowly), compared to high intensity irradiation [correction]. The lowest shrinkage was observed for InTen-S, followed by Filtek Z250 and A110, whereas Solitaire 2, Herculite and Tetric Ceram scored highest for this parameter. Temperature rise was caused more or less equally by radiation and by reaction heat and reached values of up to 28.9 degrees C relative to a baseline of 37 degrees C. For some combinations of curing modes and resin-based composites, less heat was generated by the soft-start protocols and by Optilux 501.

Elution of leachable components from resin composites after plasma arc vs standard or soft-start halogen light irradiation.

OBJECTIVES: To determine the release of leachable components from resin based composites (RBC) after plasma arc vs. standard or soft-start halogen curing. METHODS: The tested RBC were the fine hybrids Herculite XRV (Kerr), Solitaire 2 (Kulzer) and Z250 (3M), the micro-fill Silux Plus (3M) and the polysiloxane-containing Definite (Degussa). The irradiation protocols included halogen standard irradiation at three different intensities (TriLight, ESPE), ramp curing (dito), step curing (HiLight, ESPE), pulse polymerization (VIP Light, BISCO) and plasma curing (Apollo 95E, DMDS; PAC Light, ADT). Initial solubility was determined applying RBC into simulated cavities (molds of 6mm inner diameter and 2mm height fabricated from pressed ceramics) and eluting 24h in demineralized water at 37 degrees C. Medium-term solubility was evaluated using plain RBC specimens of equivalent dimensions stored dark (37 degrees C, 24h) and extracted in 50% CH(3)OH (37 degrees C, 72 h). After drying the specimens to constant weight, solubility and sorption were determined gravimetrically. RESULTS: Medium-term solubility/sorption were higher than initial ones. Irradiation at reduced intensity increased solubility and sorption, whereas ramp curing, step curing and pulse polymerization (for most materials) maintained low values. Plasma arc curing worked well for Z250 and Herculite XRV, compared to medium or low intensity halogen irradiation for Silux Plus and Definite and produced moderately (PAC Light) or very (Apollo 95E) high solubility for Solitaire 2. CONCLUSIONS: Reducing irradiation intensity does and soft-start protocols do not compromise solubility and sorption. The efficiency of plasma arc curing depends markedly on the types of photo-initiators used.

Effect of irradiation type (LED or QTH) on photo-activated composite shrinkage strain kinetics, temperature rise, and hardness.

This study compares commercially available light-emitting diode (LED) lights with a quartz tungsten halogen (QTH) unit for photo-activating resin-based composites (RBC). Shrinkage strain kinetics and temperature within the RBC were measured simultaneously using the 'deflecting disc technique' and a thermocouple. Surface hardness (Knoop) at the bottom of 1.5-mm thick RBC specimens was measured 24 h after irradiation to indicate degree of cure. Irradiation was performed for 40 s using either the continuous or the ramp-curing mode of a QTH and a LED light (800 mW cm(-2) and 320 mW cm(-2), respectively) or the continuous mode of a lower intensity LED light (160 mW cm(-2)). For Herculite XRV and Filtek Z250 (both containing only camphoroquinone as a photo-initiator) the QTH and the stronger LED light produced similar hardness, while in the case of Definite (containing an additional photo-activator absorbing at lower wavelength) lower hardness was observed after LED irradiation. The temperature rise during polymerization and heating from radiation were lower with LED compared to QTH curing. The fastest increase of polymerization contraction was observed after QTH continuous irradiation, followed by the stronger and the weaker LED light in the continuous mode. Ramp curing decreased contraction speed even more. Shrinkage strain after 60 min was greater following QTH irradiation compared with both LED units (Herculite, Definite) or with the weaker LED light (Z250).