Bernd Klaiber

Comparison of photo‐activation versus chemical or dual‐curing of resin‐based luting cements regarding flexural strength, modulus and surface hardness

This study investigated the efficiency of chemical activation of dual-cure resin-based luting cements as compared with light- and dual-curing. Curing was performed by (i) mixing base and catalyst without subsequent irradiation (chemical curing=CC), (ii) mixing base and catalyst with direct irradiation (dual-cure=DC) or with (iii) irradiation through 2.5 mm of leucite-reinforced glass-ceramics (IPS Empress, Ivoclar) (dual-cure through porcelain=DCtP), (iv) using only the base paste with direct irradiation (light-curing=LC) or with (v) irradiation through porcelain (light-curing through porcelain=LCtP). Specimens of four fine-hybrid DC resin composites and one self-cure hybrid resin composite (only CC) were prepared and tested after 24 h for flexural strength, modulus of elasticity (ISO 4049) and surface hardness (Vickers). For all materials and parameters, dual-curing produced higher values than LC, even when irradiation was performed through porcelain. Following self-curing without photo-activation, flexural strength was 68.9-85.9%, the modulus 59.2-94.5% and Vickers hardness 86.1-101.4% of the corresponding values obtained by dual-curing with direct irradiation. Light-curing through porcelain as compared with direct irradiation reduced the values for most parameters and materials. In contrast, dual-curing maintained flexural strength for all, the modulus for three and the hardness for one of the materials. The mechanical properties of the self-curing resin cement ranged between those of the DC materials.

Effect of storage media on microleakage of five dentin bonding agents

The objective of this study was to investigate the effect of different storage media on microleakage at the gingival margin of mixed Class V composite restorations. Human molars were either used immediately after extraction (control group) or after a 3-4 wk storage period in 1% chloramine, 70% ethanol, 10% formalin, or 0.1% thymol. Class V cavities with cervical margins in cementum or dentin were prepared and restored with a microfill composite using five different dentin bonding agents. After thermocycling (1440 x from 5 degrees C to 55 degrees C) and basic fuchsin staining, the depth of dye penetration at the gingival margins was determined and ranked on a scale of 0 to 4. Class V restorations in teeth stored in formalin showed significantly less microleakage (mean leakage score, MLS = 1.7) than restorations in freshly extracted teeth (control group; MLS = 3.1). Microleakage scores in teeth stored in chloramine (MLS = 2.7), ethanol (MLS = 3.0) or thymol (MLS = 3.2) were not significantly different from the microleakage scores in the control group. The improvement of in vitro efficacy of dentin bonding agents when using extracted teeth stored in formalin is probably a result of collagen cross-linking by formaldehyde. Since such an alteration of the dentin does not reflect the condition of the substrate in vivo, extracted teeth assigned for in vitro evaluation of dentin bonding agents should not be stored in formalin. In teeth stored in 1% chloramine, the sums of ranks and the rank orders of the dentin bonding agents were comparable to those in freshly extracted teeth.(ABSTRACT TRUNCATED AT 250 WORDS)

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 observers 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.

Working parameters of a sonic scaler influencing root substance removal in vitro

Abstract This study assessed defect depth and volume resulting from root instrumentation using a KaVo Sonicflex Lux 2000 L sonic scaler with a slim scaling tip (Perio-Tip no. 8) in vitro. Combinations of the following working parameters were analyzed: lateral forces of 0.5 N, 1 N, and 2 N; tip angulations of 0°, 45°, and 90°; and instrumentation time of 10 s, 20 s, 40 s, and 80 s. Defects were quantified using a three-dimensional optical laser scanner. Instrumentation time had an almost linear impact on defect depth and volume. Although lateral force (β-weight 0.55±0.062) had a greater influence on defect volume than tip angulation (β-weight 0.29±0.062), their effects on defect depth were similar (β-weight 0.43±0.052 and 0.50±0.052, respectively). The combination of force and angulation showed synergistic effects resulting in a wide range of defect depths (21.9±0.96 µm to 174±28.8 µm, at 40 s) and volumes (0.056±0.019 mm3 to 0.68±0.10 mm3 at 40 s). Severe root damage (>50 µm/40 s) did not occur at any combination of 0.5 N lateral force and/or 0° tip angulation. By adjusting lateral force and tip angulation, the efficacy of the assessed sonic scaler may be adapted to various clinical needs.

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.

The effect of glass ionomer cement or composite resin bases on restoration of cuspal stiffness of endodontically treated premolars in vitro

Abstract The purpose of the present study was to decide whether composite resin or conventional glass ionomer cement should be preferred as a base material in endodontically treated premolars. Twelve extracted human maxillary premolars were mounted in a universal testing machine at a 35° angle. Cuspal stiffness was determined by applying a load of 75 N to the buccal cusp and recording the displacement of the cusp using inductive displacement transducers. In the same teeth, different cavity preparations and restorations were performed sequentially. Standard MOD cavities were enlarged to allow endodontic access. In addition, the cusps were undermined. Half of the teeth were restored to the level of the previous shallow cavities using conventional glass ionomer cement (Ketac Fil), in the rest of the teeth dentine bonding agent (Syntac) and composite resin (Tetric) were used instead. Finally, composite resin fillings (Tetric) were placed. All restorations were removed and the experiments were repeated twice. For each replication, the assignment of the base materials to the experimental groups was reversed, and ceramic inlays (Empress) were used as final restorations for the last replication. Improvement of cuspal stiffness achieved by conventional glass ionomer bases was very small, whereas composite resin bases increased cuspal stability by more than a factor of two. After placement of the final restorations, however, there was no longer a difference between teeth with different base materials. Nevertheless, composite resin bases might be preferred for two reasons. Firstly, deterioration of adhesive restorations will probably start at the cavosurface margins. The incidence of margin gaps, however, will not only compromise marginal seal but also the stabilizing effect of the restoration. In this situation, the resin base may still stabilize the tooth. Moreover, resin bases may reduce the risk of cusp fracture during the time between cavity preparation and the insertion of adhesive inlays.

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 <or=1 mm, i.e. violating the biological width. Subsequently, clinical attachment level (CAL), probing pocket depth (PPD), bleeding on probing (BoP) and gingival index (GI) scores were recorded at 6, 12 and 24 months postoperatively for the restored teeth as well as plaque index (PlI) and periodontal screening index (PSI) values for the whole dentition. RESULTS Two years after therapy, recorded CAL, PPD, BoP, GI, PlI and PSI scores revealed healthy periodontal conditions in 18 out of 20 treated teeth. Two teeth had suffered again from fragment fracture due to new traumata. CONCLUSIONS Adhesive fragment reattachment in periodontally healthy teeth affected by crown-root fractures had no detrimental impact on periodontal health over a time course of 2 years.

Clonal Infection with Actinobacillus actinomycetemcomitans Following Periodontal Therapy

Mechanical debridement results in a shift of the bacterial composition in the periodontal pocket on the species level. It is unknown, however, whether a clonal change within a species could lead to the emergence of strains with different levels of virulence. Therefore, in the present study, the genetic variability of Actinobacillus actinomycetemcomitans was assessed and strains identified which were associated with periodontal disease progression following periodontal therapy, i.e., refractory periodontitis. Twenty adult patients with untreated periodontitis and subgingival colonization of A. actinomycetemcomitans were randomly assigned to receive full-mouth scaling alone or scaling with an adjunctive antimicrobial therapy. Both groups received supportive periodontal therapy at 3, 6, 9, 12, 18, and 24 months. Subgingival plaque samples were taken at every visit; venous blood was obtained at 24 months only. A. actinomycetemcomitans isolates were typed by the RAPD method, and antibody reactivity against outer membrane proteins was assessed by immunoblot analysis. Eleven distinct RAPD patterns were found in 18 patients completing the study. All patients harbored only one A. actinomycetemcomitans genotype, and within each patient this genotype persisted throughout the 24-month observation period. No differences in the expression of antibody reactivity against outer membrane proteins were found between strains isolated at baseline and at 24 months. Three genotypes were associated with reduced survival rates of teeth without probing attachment loss of 2 mm or more. The results indicated that (i) most patients harbored only one A. actinomycetemcomitans genotype; (ii) the genotype persisted following therapy; and (iii) only some genotypes were associated with refractory periodontitis.

Shear bond strength to dentin by simulation of three-dimensional Class V cavity configuration

The purpose of this study was to investigate the effect of composite polymerization contraction on early shear bond strength of conventional and new dentin adhesives to dentin. The dentin adhesives selected for this study, i.e., Bondlite, Gluma, Prisma Universalbond, Scotchbond LC, Scotchbond 2, and XR Bonding, were tested in combination with Silux and in combination with their respective composites. The composite was applied to the treated dentin surface in cylindrical brass moulds of 4 mm diameter and 3 mm length. The configuration of cylindrical butt-joint Class V cavities was simulated by the coating of the insides of the brass moulds with silane in order that a chemical bond to the composite could be established. The results showed that shear bond strength to dentin was higher for XR Bonding and Scotchbond 2 compared with conventional phosphate ester-based dentin adhesives and Gluma. When XR Bonding or Scotchbond 2 was used, the obstruction of polymerization contraction had no effect on the bond strength to dentin. In contrast, the dentin adhesion of Scotchbond LC/Silux, Prisma Universalbond/Prisma Microfine, Bondlite/Herculite, and Gluma/Lumifor was adversely affected by the reduction of the unbonded composite surfaces. However, this effect was not observed when Prisma Universalbond, Bondlite, and Gluma were tested in combination with Silux. It can therefore be concluded that the effect of polymerization contraction on the bond strength to dentin depends not only on the dentin adhesive but also on the type of composite used.