Susanne Reimann

Nickel concentration in the saliva of patients with nickel-titanium orthodontic appliances.

INTRODUCTION The purpose of this study was to examine whether nickel-titanium (Ni-Ti) archwires cause an increase of nickel concentration in the saliva of 18 orthodontic patients to estimate the possible risk of these archwires in patients who have nickel hypersensitivity. METHODS Saliva samples were collected before orthodontic treatment, after placement of the bands and brackets, 2 weeks later and before placing the Ni-Ti archwires, immediately after placing the Ni-Ti archwires, 4 weeks after placing the wires, and 8 weeks after placing the wires. RESULTS By using mass spectrometry, no statistically significant differences were found in the nickel concentrations in the samples taken without appliances, in those obtained 2 weeks after placement of the bands and brackets, and 4 and 8 weeks after placement of the archwires. Samples taken immediately after placement of the bands and brackets and the Ni-Ti archwires showed slight but significant increases in nickel concentration of 78 and 56 microg per liter, respectively, compared with the pretreatment value of 34 microg per liter. CONCLUSIONS Nickel leaching occurred after placement of the bands and brackets and after placement of the Ni-Ti archwires, associated with an increase of the nickel ion concentration in the patients saliva. This effect decreased within 10 weeks.

Numeric modeling of torque capabilities of self-ligating and conventional brackets

INTRODUCTION The purpose of this study was to investigate the torque capabilities of conventional and self-ligating brackets by using the finite element method. METHODS Three types of brackets were selected: self-ligating Hanson Speed (Strite Industries, Cambridge, Ontario, Canada) and Damon MX (Ormco, Glendora, Calif), and conventionally ligated Discovery (Dentaurum, Pforzheim, Germany). All brackets had a 0.022-in slot size. From the maxillary left incisor to the maxillary right canine, 4 brackets were included in the finite element models generated. Torque of 20 degrees was applied to the maxillary right incisor with 0.46 x 0.64 mm(2) (0.018 x 0.025 in) and 0.48 x 0.64 mm(2) (0.019 x 0.025 in) archwires. Three kinds of wire alloys were used: stainless steel, titanium molybdenum, and nickel titanium. For the conventional Discovery brackets, 2 types of ligation were modeled: elastic and stainless steel wire ligatures. The torque angle/torque moment characteristics in the simulated movement were calculated by using the MSC.Marc/Mentat 2005 FE software package (MSC Software Corporation, Santa Ana, Calif). RESULTS The torque angle/torque moment curves seemed to be dominated by the characteristics of the wire. The change of wire dimension increased the torque moments less than the change of wire alloy (125% increase for a 0.48 x 0.64 mm(2) instead of a 0.46 x 0.64 mm(2) stainless steel wire, and 220% for a 0.46 x 0.64 mm(2) stainless steel instead of a nickel-titanium wire). The combined change of the wire alloy and wire dimension resulted in a 600% increase for a 0.48 x 0.64 mm(2) stainless steel instead of a 0.46 x 0.64 mm(2) nickel-titanium wire.The play of the 0.46 x 0.64 mm(2) wires was about 9.0 degrees, and the play of the 0.48 x 0.64 mm(2) wires was about 7.5 degrees, with slightly more play for the Damon. The ligation effect of Discovery brackets with elastic and stainless steel ligatures could be compared with the behavior of the Damon. The Speed showed different behavior, with the lowest torquing moments and the smallest torque play. CONCLUSIONS Improving the adaptation of torque movements to the biomechanical reactions of the periodontium is best done by proper selection of both wire dimension and wire alloy. The effect of the bracket system is of minor importance, with the exception of brackets with an active clip (eg, Speed), which had the least play and the lowest torquing moments of all the wires.

Effect of mini-implant length and diameter on primary stability under loading with two force levels

Mini-implants are widely utilized as anchorage units in orthodontic treatment. Nevertheless, there are factors that interfere with their clinical performance. The aim of this study was to examine the impact of length and diameter on the primary stability of two different types of orthodontic mini-implants loaded with two force levels. A total of 90 self-drilling mini-implants were inserted in bovine ribs in vitro, 62 of which were used in data analysis. The mini-implants were of two types, Aarhus (n=29) and Lomas (n=33), of two lengths (7 and 9 mm, n=26 and n=28, respectively), and of two diameters (1.5 and 2 mm, Lomas only, n=6 and n=8, respectively). A closed nickel-titanium (NiTi) coil spring was attached to each mini-implant. Half of the preparations were loaded with a low force of 0.5 N and the other half with a force of 2.5 N. Mini-implant deflections during force application were non-invasively registered using a three-dimensional (3D) laser-optical system. The results were analysed with analysis of variance for the effects of implant type, implant length, and force level, and with a t-test for the study of the effect of diameter in two different diameter variants of the same (Lomas) implant. In the low-force group, implant displacements were not statistically significant difference according to the investigated parameters. In the high-force group, the 9 mm long mini-implants displaced significantly less (10.5±7.5 μm) than the 7 mm long (22.3±11.3 μm, P<0.01) and the 2 mm wide significantly less (8.8±2.2 μm) than the 1.5 mm implants (21.9±1.5 μm, P<0.001). The force level at which significance occurred was 1 N. The rotation of the Lomas mini-implants in the form of tipping was significantly higher than that of the Aarhus mini-implants at all force levels. Implant length and diameter become statistically significant influencing parameters on implant stability only when a high force level is applied.

Force levels in complex tooth alignment with conventional and self-ligating brackets

INTRODUCTION The force applied to the teeth is a variable of orthodontic treatment that can be controlled. Poor control of the applied force can lead to adverse biologic effects as well as undesirable tooth movements. The selected archwire-bracket combination is a primary determining factor in the force level applied to a tooth during orthodontic treatment. The aim of this research was to use an experimental biomechanical setup to measure forces generated during complex orthodontic tooth movements with various archwire-bracket combinations. METHODS The materials consisted of 3 types of 0.022-in slot orthodontic brackets: (1) conventional brackets (Victory Series [3M Unitek, Monrovia, Calif] and Mini-Taurus [Rocky Mountain Orthodontics, Denver, Colo]), (2) self-ligating brackets (SmartClip [3M Unitek] and Time3 [American Orthodontics, Shegoygan, Wis]), and (3) a conventional low-friction bracket (Synergy [Rocky Mountain Orthodontics]); and 4 archwire types: (1) 0.012-in stainless steel (3M Unitek), (2) 0.0155-in coaxial (Advanced Orthodontics [Näpflein, Düsseldorf, Germany]), (3) 0.012-in Orthonol (Rocky Mountain Orthodontics), and (4) 0.012-in Thermalloy (Rocky Mountain Orthodontics). Stainless steel ligatures and elastomeric rings were used. The materials were used in different combinations in a simulated malocclusion that represented a maxillary central incisor displaced 2 mm gingivally (x-axis) and 2 mm labially (z-axis). RESULTS The lowest forces were measured when the brackets were combined with either the coaxial or the Thermalloy archwires; the forces ranged from 3.4 ± 0.2 to 0.7 ± 0.1 N in the x-axis direction, and from 4.5 ± 0.3 to 0.5 ± 0.1 N in the z-axis direction. The highest forces were measured in combination with stainless steel archwires; the forces ranged from 6.3 ± 0.3 to 3.0 ± 0.1 N in the x-axis direction, and from 6.3 ± 0.3 to 1.7 ± 0.1 N in the z-axis direction. CONCLUSIONS We recommend 0.0155-in coaxial and 0.012-in Thermalloy archwires for leveling and alignment. Elastomeric rings, when used with conventional brackets, increased the force applied to the teeth.

Contribution of Orthodontic Load to Inflammationmediated Periodontal Destruction

AbstractAim:Orthodontic malpractice as well as hyperocclusal forces can aggravate periodontitis-induced destruction of tooth-supporting tissues, but the underlying mechanisms for the co-destructive effect of biomechanical loading are yet to be elucidated. This in-vitro study was performed to investigate whether biomechanical forces modulate the response of periodontal ligament (PDL) cells to inflammation.Materials and Methods:PDL cells (from six donors) grown on BioFlex® plates were treated with interleukin (IL) 1, which is increased at inflamed periodontal sites, and/or subjected to cyclic tensile strain (CTS) of low (3%) and high (20%) magnitudes for 1β and 6 d. The synthesis of proinflammatory mediators (IL1β, IL8, COX2), growth factors (IGF1, VEGF, TGFβ1), collagen type 1 (COL1) and osteogenic proteins (ALP, RUNX2) was analyzed by real-time PCR and ELISA. The wound fill rate was examined in an in-vitro wound healing assay. For statistical analyses, Student’s t-test and ANOVA were applied (p<0.05).Results:In general, the IL1β-induced expression of proinflammatory mediators was significantly enhanced by CTS on day 1 and significantly downregulated on day 6. CTS of high magnitude significantly inhibited the IGF1 synthesis but significantly upregulated VEGF under normal and inflammatory conditions. In general, CTS also downregulated the IL1β-induced COL1, ALP, and RUNX2 expression. From day 5 on, the lowest wound fill rate was observed in cells which were simultaneously exposed to inflammatory and biomechanical signals.Conclusion:These findings suggest that orthodontic and occlusal loading may contribute to periodontal destruction in periodontally-diseased patients through downregulation of matrix and osteogenic proteins but not via augmentation of periodontal inflammation.ZusammenfassungHintergrund und Ziel:Unsachgemäß durchgeführte kieferorthopädische Zahnbewegungen wie auch okklusale Überbelastungen können eine parodontitisinduzierte Destruktion des Parodontiums verstärken. Die zugrunde liegenden Mechanismen für den destruktionsverstärkenden Effekt der biomechanischen Belastung sind jedoch noch ungeklärt. In dieser In-vitro-Studie sollte untersucht werden, ob biomechanische Kräfte die Reaktion von parodontalen Ligament-(PDL-)Zellen auf Entzündungsreize modulieren.Material und Methodik:Auf BioFlex®-Platten kultivierte PDL-Zellen von sechs Patienten wurden mit Interleukin (IL) 1β, das an entzündeten parodontalen Stellen erhöht ist, inkubiert und/oder einer zyklischen Zugbelastung (CTS) niedriger (3%) und hoher (20%) Stärke für 1 und 6 Tage ausgesetzt. Die Synthese von proinflammatorischen Mediatoren (IL1β, IL8, COX2), Wachstumsfaktoren (IGF1, VEGF, TGFβ1), Kollagen Typ 1 (COL1) und osteogenen Proteinen (ALP, RUNX2) wurde mittels Real-Time-PCR und ELISA analysiert. Die Rate der Wundauffüllung wurde mit einem In-vitro-Wundheilungsassay untersucht. Für die statistische Auswertung kamen der Student’s t-Test und ANOVA zur Anwendung (p<0,05).Ergebnisse:Im Allgemeinen wurde die IL1β-induzierte Expression der proinflammatorischen Mediatoren durch CTS am Tag 1 signifikant verstärkt und am Tag 6 signifikant gehemmt. CTS hoher Stärke reduzierte signifikant die IGF1-Synthese, führte aber zu einer signifikanten Steigerung von VEGF unter normalen und entzündlichen Bedingungen. CTS hemmte im Allgemeinen auch die IL1β-induzierte Expression von COL1, ALP und RUNX2. Ab dem fünften Tag wurde die geringste Wundheilungsrate in den Kulturen beobachtet, die gleichzeitig entzündlichen und biomechanischen Signalen ausgesetzt waren.Schlussfolgerung:Diese Ergebnisse legen nahe, dass kieferorthopädische und okklusale Kräfte zur parodontalen Destruktion durch Herunterregulation extrazellulärer Matrixproteine und osteogener Differenzierungsmarker, jedoch nicht durch Verstärkung der parodontalen Entzündung bei Parodontitispatienten beitragen könnten.

3D analyses of interface voids in root canals filled with different sealer materials in combination with warm gutta-percha technique

ObjectivesThe aim of the present study was to analyze the formation of voids and gaps in root canals obturated with different sealer materials in combination with warm gutta-percha vertical compaction technique by using BeeFill® 2in1.Materials and methodsTwenty-four single-rooted teeth were collected, and root canals were prepared by using rotary files. All teeth were randomly allocated into three groups. Each group was obturated by using the BeeFill® 2in1 system in combination with Sealapex (non-eugenol, calcium hydroxide polymeric root canal sealer; Kerr Sybron, USA), RoekoSeal (polydimethylsiloxane-based sealer; Roeko, Germany), or 2Seal (epoxy-amine resin-based sealer; VDW, Germany). Following preparation, all teeth were scanned with a micro-computed tomography (CT) scanner, and a three-dimensional reconstruction of the obturated root canals was performed to analyze the volume of interface voids and gaps in the obturated teeth.ResultsStatistical analysis demonstrated that the silicon-based sealer RoekoSeal induced significantly less voids and gaps than other tested materials. The amount of voids and gaps significantly was higher in the apical region.ConclusionsThese data indicate that none of the root canal-filled teeth were free of gaps. Teeth obturated with RoekoSeal demonstrated to have the highest quality in terms of voids and gaps formation in combination with the BeeFill® 2in1 obturation system.Clinical relevanceThese findings point to the potential benefit of micro-CT analyses for in vitro evaluation of root canal obturation systems and provide further information about sealer materials used in combination with a warm gutta-percha vertical compaction technique.

The leveling effectiveness of self-ligating and conventional brackets for complex tooth malalignments.

Background and Objective:The transfer of forces and moments between the bracket and archwire is decisive in the multi-band/bracket technique. New developments in bracket design and ligation method aim to optimize the transfer of forces and moments and improve leveling effectiveness. We thus aimed in this study to investigate whether leveling behavior is influenced by different bracket systems, or by the ligation method. The baseline situation for this examination was a complex tooth malalignment.Material and Methods:Using the orthodontic measurement and simulation system (OMSS), we tested the leveling effectiveness of nine self-ligating bracket systems made by various manufacturers (Forestadent-Quick®, in active and passive variants, Dentsply GAC In-Ovation®, adenta TIME®, Ormco Damon® 2 and Damon® 3MX, UP-Dental Opal-M™ and Opal™-2, Strite SPEED™) in the 0.022 inch slot system. A conventional bracket system (Dentaurum discovery®) was used for reference purposes. We also used a multistranded steel archwire (Ormco Tripleflex™, 0.44 mm round) and four nickel-titanium archwires of various diameters (Forestadent® BioStarter® 0.30 mm round, BioStarter® 0.40 mm round, Titanol® Low Force 0.40 × 0.40 mm2 and Titanol® Low Force 0.40 × 0.56 mm2). The leveling task consisted of correcting a complex malalignment (infraocclusion and vestibular displacement, each of 2 mm) of tooth 21. We analyzed the forces and torque movements that arose during the leveling phase.Results:The test of the ten bracket systems revealed no significant difference in terms of their leveling effectiveness. Both selfligating brackets and conventional brackets behaved similarly, and we observed roughly 80% of the infraocclusions to have been corrected. Vestibular displacement was corrected with all the bracket systems by as much as 100% or even more due to a developing torque movement. The influence of wire material and wire diameter became apparent in relation to existing forces durconvening the leveling stage; those factors’ influence was clearly greater than that of the ligation method.Conclusions:This study’s results demonstrate that bracket selection has a negligible influence on leveling effectiveness. Although self-ligating brackets are easier for the orthodontist to manipulate and provide patients with esthetic and wearing comfort advantages, they are not superior to conventional brackets in terms of their biomechanical characteristics.ZusammenfassungHintergrund und Ziel:In der Multiband-Bracket-Technik spielt die Übertragung von Kräften und Drehmomenten zwischen Bracket und Bogen eine entscheidende Rolle. Neuentwicklungen im Bracketdesign und in der Ligierungstechnik waren nicht nur darauf ausgerichtet, die Übertragung von Kräften und Drehmomenten zu optimieren, sondern auch eine bessere Nivellierungseffektivität zu erzielen. Im Rahmen dieser Studie wurde daher untersucht, ob das Nivellierungsverhalten durch verschiedene Bracketsysteme bzw. durch die Ligierungstechnik beeinflusst wird. Dabei stellte eine kombinierte Fehlstellung die Ausgangsposition dar.Material und Methodik:Mit Hilfe des Orthodontischen Messund Simulations-Systems (OMSS) wurden in der vorliegenden Arbeit neun selbstligierende Bracketsysteme im 0.022-Inch-Slotsystem von verschiedenen Herstellern (Forestadent-Quick®, in aktiver und passiver Variante, Dentsply GAC In-Ovation®, adenta TIME®, Ormco Damon® 2 und Damon® 3MX, UP-Dental Opal-M™ und Opal™-2, Strite SPEED™) auf ihre Nivellierungseffektivität untersucht. Ein konventionelles Bracketsystem (Dentaurum discovery®) diente als Referenzmaterial. Außerdem kamen ein geflochtener Stahldrahtbogen (Ormco Tripleflex™, 0,44 mm rund) und vier Nickel-Titan-Drahtbögen unterschiedlicher Querschnitte (Forestadent® BioStarter® 0,30 mm rund, BioStarter® 0,40 mm rund, Titanol® Low Force 0,40 × 0,40 mm2 und Titanol® Low Force 0,40 × 0,56 mm2) zum Einsatz. Die untersuchte Nivellierungsaufgabe bestand in der Korrektur einer kombinierten Fehlstellung (Infraokklusion und vestibuläre Verlagerung von jeweils 2 mm) am Zahn 21. Es wurden die in der Nivellierungsphase auftretenden Kräfte und die Torquebewegung analysiert.Ergebnisse:Die Untersuchung der zehn Bracketsysteme zeigte keine signifikanten Unterschiede im Hinblick auf ihre Nivellierungseffektivität. Sowohl selbstligierende Brackets als auch konventionelle Brackets verhielten sich ähnlich, und es waren Korrekturen der Infraokklusion von ca. 80% festzustellen. Die vestibuläre Verlagerung wurde bei allen Bracketsystemen um bis zu 100% oder sogar darüber hinaus korrigiert, was auf eine auftretende Torquebewegung zurückzuführen war. In Bezug auf die während der Nivellierungsphase auftretenden Kräfte wurde der Einfluss von Drahtmaterial und Drahtquerschnitt deutlich, der den Einfluss der Ligierungsmethode deutlich übertraf.Schlussfolgerungen:Die Ergebnisse der vorliegenden Untersuchung zeigen, dass die Bracketauswahl nur einen geringen Einfluss auf die Nivellierungseffektivität hat. Auch wenn selbstligierende Brackets Vorteile in der Handhabung für den Kieferorthopäden und in Bezug auf Ästhetik oder Tragekomfort für den Patienten bieten mögen, sind sie im Hinblick auf ihre biomechanischen Eigenschaften den konventionellen Brackets nicht überlegen.

Interactions of Enamel Matrix Derivative and Biomechanical Loading in Periodontal Regenerative Healing

BACKGROUND Although enamel matrix derivative (EMD) has been shown to promote periodontal regeneration, it is unknown whether the actions of EMD are modulated by occlusal loading. This in vitro study was performed to investigate whether biomechanical forces regulate the response of periodontal ligament (PDL) cells to EMD. METHODS Human PDL cells were treated with EMD in the presence and absence of cyclic tensile strain (CTS) of various magnitudes for ≤ 14 days. Synthesis of transforming growth factor (TGF)-β1, vascular endothelial growth factor (VEGF), growth factor receptors, collagen, and runt-related transcription factor 2- (RUNX2), cell numbers and adhesion, wound fill rate, and calcium accumulation were analyzed by real-time polymerase chain reaction, enzyme-linked immunosorbent assay, a wound healing assay, and alizarine red S staining. RESULTS Wound fill rate, cell numbers and adhesion, and expression of TGF-β1, VEGF, collagen, and RUNX2 were significantly increased by EMD. In the presence of CTS, the EMD-induced effects were significantly reduced. The inhibition of the EMD-upregulated VEGF expression by CTS was blocked by a specific inhibitor of nuclear factor-kappa B signaling. Moreover, CTS downregulated receptors for growth factors involved in the actions of EMD. CTS also antagonized significantly the EMD-induced calcium deposition. CONCLUSIONS These in vitro findings suggest that the beneficial actions of EMD on PDL cell functions critical for periodontal regeneration are jeopardized by biomechanical loading. Clinical studies should clarify whether protection of teeth against occlusal forces in the early healing stage may positively affect the outcome of regenerative therapy with EMD.

Development of a novel intraoral measurement device to determine the biomechanical characteristics of the human periodontal ligament

Periodontal diseases like gingivitis and periodontitis have damaging effects on the periodontium and commonly affect the mechanical properties of the periodontal ligament (PDL), which in the end might lead to loss of teeth. Monitoring tooth mobility and changes of the material properties of the PDL might help in early diagnosis of periodontal diseases and improve their prognosis. It was the aim of this study to develop a novel intraoral device to determine the biomechanical characteristics of the periodontal ligament. This includes the measurement of applied forces and resulting tooth displacement in order to investigate the biomechanical behaviour of the periodontium with varying loading protocols with respect to velocity and tooth displacement. The developed device uses a piezoelectric actuator to apply a displacement to a tooths crown, and the resulting force is measured by an integrated force sensor. To measure the tooth displacement independently and non-invasively, two magnets are fixed on the teeth. The change in the magnetic field caused by the movement of the magnets is measured by a total of 16 Hall sensors. The displacement of the tooth is calculated from the movement of the magnets. The device was tested in vitro on premolars of four porcine mandibular segments and in vivo on two volunteers. The teeth were loaded with varying activation curves. Comparing the force progression of different activation velocities, the forces decreased with decreasing velocity. Intensive testing demonstrated that the device fulfils all requirements. After acceptance of the ethical committee, further testing in clinical measurements is planned.

Regulatory effects of biomechanical strain on the insulin-like growth factor system in human periodontal cells

During mastication, dental trauma and functional dental habits the tissues that surround and support the teeth, i.e. the periodontium, are subject to complex biomechanical forces. The exact mechanisms mediating the anabolic and catabolic biomechanical effects on the periodontium are yet poorly understood. Therefore, the objective of this in-vitro study was to determine if continuous tensile strain (CTS) regulates the synthesis of components of the insulin-like growth factor (IGF) system in human periodontal ligament (PDL) cells. PDL cells from six donors were phenotyped, seeded on collagen type-I coated silicone membranes, and subjected to CTS of low (3%) or high (20%) magnitudes for 4 and 24 h. The gene expression of IGF1, IGF2, IGF1 receptor (IGF1R), insulin receptor substrate (IRS)1, and IGF-binding proteins (IGFBPs) was detected by real-time PCR. The protein synthesis was determined by immunoblotting. For statistical analysis, ANOVA and the Tukey test (p<0.05) were applied. When cells were subjected to low CTS for 4 h, the IGF1 expression was significantly increased, whereas high CTS or CTS applied for 24 h reduced the constitutive IGF1 synthesis. Although PDL cells also expressed IGF2, IGF1R, and IRS1, no significant differences for these molecules were found between stretched cells and controls. High CTS caused a significant upregulation of IGFBP1 and significant downregulation of IGFBP3 and IGFBP5 at 24 h. In conclusion, this in-vitro study suggests that biomechanical forces may regulate several components of the local IGF system in the human periodontium.