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Biomedical subjects

Arndt Klocke

Publications and source records attributed to Arndt Klocke.

At least 19 recordsLinked to original sources
PubMed2007

CO2 laser-induced zonation in dental enamel: a Raman and IR microspectroscopic study.

The gradient of structural alteration and molecular exchange across CO(2) laser-irradiated areas in dental enamel was analyzed by Raman and attenuated total reflectance infrared microspectroscopy. The type and the degree of structural changes in morphologically distinguishable zones within the laser spot vary depending on the laser-irradiation parameters--power (1 and 3 W), treatment time (5 and 10 s), and operational mode (super pulse and continuous wave). Using higher power, irrespective of the operation mode, the enamel tissue ablates and a crater is formed. The prevalent phase at the bottom of the crater is dehydrated O(2) (2-)-bearing apatite, that is, the fundamental framework topology is preserved. Additional nonapatite calcium phosphate phases are located mainly at the slope of the laser crater. No structural transformation of mineral component was detected aside the crater rim, only a CO(3)-CO(2) exchange, which decays with the radial distance. A lower-power laser irradiation slightly roughens the enamel surface and the structural modification of enamel apatite is considerably weaker for continuous wave than for super pulse mode. Prolonged low-power laser treatment results in recrystallization, and thus structural recovering of apatite might be of clinical relevance for enamel surface treatments.

Apatites↗
PubMed2006

Magnetic forces on orthodontic wires in high field magnetic resonance imaging (MRI) at 3 tesla.

BACKGROUND: In a previous investigation we reported on magnetic forces in the static magnetic field of a 1.5 Tesla MRI system. The aim of the present investigation was to assess forces on orthodontic wires in a high field strength MRI system at 3 Tesla. MATERIALS AND METHODS: Thirty-two different orthodontic wires (21 archwires, eight ligature wires and three retainer wires) were investigated in a 3 Tesla high field strength MRI system (Intera, Philips Medical Systems, Best, The Netherlands). Translational forces were measured by the deflection angle test (ASTM F2052-02), and rotational forces assessed on a 5-point qualitative scale. RESULTS AND CONCLUSION: Translational forces ranged between 43.5 mN and 136.1 mN for retainer wires and between 0.6 mN (Noninium) and 208.4 mN (Orthos Stainless Steel) for steel archwires. Translational forces were up to 53.8 times as high as gravitational forces for retainer wires and up to 54.5 times as high for steel archwires, associated with marked rotational forces for the most part. Archwires manufactured from nickel-titanium, titanium-molybdenum and cobalt-chromium and different ligature wires showed no or negligible forces in the magnetic field. Carefully ligated wires should not present a risk due to translational and rotational forces in the high field MRI system at 3 Tesla.

Alloys↗
PubMed2006

Effect of debonding force direction on orthodontic shear bond strength.

INTRODUCTION: The aim of this study was to determine the influence of debonding force direction in shear bond strength testing of orthodontic brackets in vitro. METHODS: One hundred fifty extracted bovine permanent mandibular incisors were randomly divided into 5 groups of 30 specimens each. Before bonding with a composite adhesive, enamel surfaces were etched with 37% phosphoric acid for 30 seconds. Teeth were bonded with mesh-based stainless steel orthodontic brackets. Shear bond strength was measured with a universal testing machine. Debonding forces were directed either parallel to the bracket base (group B), toward the enamel surface (group A: 15 degrees), or away from the enamel surface (group C: 15 degrees; group D: 30 degrees; group E: 45 degrees). RESULTS: Shear bond strength measurements were as follows: 22.90 (SD, 1.72) MPa (group A), 17.90 (SD, 2.63) MPa (group B), 12.99 (SD, 1.71) MPa (group C), 7.93 (SD, 1.14) MPa (group D), and 6.65 (SD, 1.14) MPa (group E). Analysis of variance indicated that shear bond strengths were significantly different between the groups investigated. Mean adhesive remnant index scores ranged between 1.60 in group B and 2.13 in group D. CONCLUSIONS: Shear bond strength measurements were significantly influenced by the direction of the debonding force, indicating the need for control and standardization of this testing parameter in orthodontic shear bond strength testing.

Adhesives↗
PubMed2005

Application of synchrotron-radiation-based computer microtomography (SRICT) to selected biominerals: embryonic snails, statoliths of medusae, and human teeth.

Synchrotron-radiation-based computer microtomography (SRmicroCT) was applied to three biomineralised objects First, embryonic snails of the freshwater snail Biomphalaria glabrata, second, rhopalia (complex sense organs) of the medusa Aurelia aurita, and third, human teeth. The high absorption contrast between the soft tissue and mineralised tissues, i.e. the shell in the first case (consisting of calcium carbonate) and the statoliths in the second case (consisting of calcium sulphate hemihydrate), makes this method ideal for the study of biomineralised tissues. The objects can be non-destructively studied on a micrometre scale, and quantitative parameters like the thickness of a forming a snail shell or statolith crystal sizes can be obtained on a length scale of 1-2 mum. Using SRmicroCT, the dentin-enamel border can be clearly identified in X-ray dense teeth.

Animals↗
PubMed2005

Magnetic field interactions of orthodontic wires during magnetic resonance imaging (MRI) at 1.5 Tesla.

BACKGROUND: Orthodontic appliances pose a potential risk during magnetic resonance imaging (MRI) due to forces on metallic objects within the static magnetic field of MRI systems. The aim of the present investigation was to measure forces on orthodontic wires caused by the static magnetic field of a 1.5-Tesla MRI system, and to assess the safety hazards associated with these forces. MATERIALS AND METHODS: Thirty-two different orthodontic wires (21 arch wires, eight ligature wires and three retainer wires) were investigated in a 1.5-Tesla MRI system (Magnetom Symphony, Siemens Medical Solutions, Erlangen, Germany). The translational forces were measured using the deflection angle test (ASTM F2052-02); rotational forces were assessed on a 5-point qualitative scale. RESULTS AND CONCLUSION: All retainer wires and the steel arch wires (the Noninium arch wire being the exception) were subjected to considerable rotational and translational forces within the MRI system's magnetic field. Translational forces were from 9.1- to 27.6-times as high as gravitational forces on these objects. Steel ligature wires and arch wires made of cobalt chromium, titanium molybdenum, nickel-titanium, and brass alloys showed no or negligible forces within the magnetic field. The translational and rotational forces within the MRI magnetic field should pose no risk to carefully-ligated arch wires. Steel retainer wire bonds should be checked to ensure secure attachment prior to an MRI investigation.

Biocompatible Materials↗
PubMed2005

Influence of cross-head speed in orthodontic bond strength testing.

OBJECTIVE: The aim of this study was to investigate the influence of cross-head speed on debonding force of orthodontic brackets. METHODS: One hundred and twenty extracted permanent bovine mandibular incisors were randomly divided into 4 groups of 30 specimens each. Teeth were bonded with stainless steel orthodontic brackets. Enamel surfaces were etched with 37% phosphoric acid for 30 seconds and bonded with a composite adhesive. Debonding force measurements were performed with a universal testing machine Zwicki Z 2.5 (Zwick, Germany). Cross-head speeds of the four groups were: 0.1 mm s-1 (group A), 0.5 mm s-1 (group B), 1.0 mm s-1 (group C), 5.0 mm s-1 (group D). RESULTS: Mean debonding force measurements were as follows: 215.35 (39.09) N (group A), 231.79 (48.62) N (group B), 236.64 (39.26) N (group C), 224.95 (34.67) N (group D). Analysis of variance indicated that there were no significant differences in debonding forces between the groups investigated. The adhesive remnant index showed a median value of 2.0 for all groups. SIGNIFICANCE: Cross-head speed variation between 0.1 and 5 mm min-1 does not seem to influence debonding force measurements or failure mode of brackets bonded to enamel with a composite adhesive.

Acid Etching, Dental↗
PubMed2005

Influence of force location in orthodontic shear bond strength testing.

OBJECTIVE: The purpose of the present study was to analyze the influence of debonding force location in shear bond strength testing of orthodontic brackets in vitro. METHODS: Ninety extracted permanent bovine mandibular incisors were randomly divided into 3 groups of 30 specimens each. Teeth were bonded with stainless steel orthodontic brackets. Enamel surfaces were etched with 37% phosphoric acid for 30s and bonded with a composite adhesive. Debonding force measurements were performed with a universal testing machine. Location of the debonding force was: bracket base (group A), ligature groove (group B), occlusal bracket wings (group C). RESULTS: Mean shear bond strength measurements were as follows: 22.70(4.23)MPa (group A), 11.52(2.74)MPa (group B), 9.44(2.96)MPa (group C). Analysis of variance indicated that there were significant differences in shear bond strength. Post-hoc Tukey tests showed that bond strength measurements of group A were significantly different from those of groups B and C. The adhesive remnant index also showed significant differences and ranged from a mean of 1.53 in group A to a mean of 2.10 in group C. SIGNIFICANCE: Debonding force location had a significant influence on shear bond strength measurements and bond failure pattern, indicating that this parameter needs to be taken into consideration for interstudy comparison of in vitro results.

Analysis of Variance↗
PubMed2004

Custom base preaging in indirect bonding.

This in vitro evaluation analyzed the influence of custom base composite age on bond strength in indirect bonding. One hundred fifty permanent bovine mandibular incisors were randomly divided into 10 groups of 15 specimens each. Stainless steel brackets were bonded to the teeth using the Thomas indirect bonding technique using two different custom base composite-sealant combinations: (1) chemically cured Phase II composite and chemically cured Custom I.Q. sealant, and (2) light-cured Transbond XT composite and chemically cured Sondhi Rapid Set sealant. The composite custom bases were preaged for 24 hours and for seven, 15, 30, and 100 days. Shear bond strength tests for the two composite-sealant combinations showed no significant differences. Preaging of the custom base composite up to 30 days did not affect shear bond strength, and mean bond strength values exceeded 15 MPa in these groups. However, bond strength measurements for groups with a custom composite base aged for a longer interval (100 days) before sealant polymerization were significantly lower. On the basis of the results of this study, clinicians can safely use custom base composites aged up to 30 days when using the Thomas indirect bonding technique.

Adhesiveness↗
PubMed2004

Effect of time on bond strength in indirect bonding.

The purpose of this in vitro investigation was to determine the influence of a reduced time interval before debonding on shear bond strength of stainless steel brackets bonded with a custom base indirect technique. A total of 135 bovine permanent mandibular incisors was randomly divided into nine groups of 15 specimens each. Three base composite-sealant combinations were investigated: (1) Phase II base composite, Custom I.Q. sealant, (2) Phase II base composite, Maximum Cure sealant, and (3) Transbond XT base composite, Sondhi Rapid Set sealant. Shear bond strength was measured for three different debonding time intervals: (1) time of transfer tray removal as recommended by the manufacturer, (2) 30 minutes after bonding of the sealant, and (3) 24 hours after bonding of the sealant. For groups bonded with Maximum Cure or Sondhi Rapid Set sealants, no influence of debonding time on shear bond strength was found. The Custom I.Q. sealant groups showed significantly lower bond strength measurements when debonded at the recommended tray removal time, and the Weibull analysis indicated a higher risk of bond failure at clinically relevant levels of stress. All base composite-sealant combinations showed acceptable bond strength at 30 minutes and 24 hours after bonding of the sealant.

Analysis of Variance↗
PubMed2003

Plasma arc curing of ceramic brackets: an evaluation of shear bond strength and debonding characteristics.

The aim of this in vitro investigation was to evaluate bond strength and debonding characteristics when a xenon plasma arc curing light is used to bond polycrystalline and monocrystalline ceramic brackets. Brackets were bonded to 240 extracted bovine mandibular incisors with a composite adhesive. Curing intervals of 1, 3, and 6 seconds were chosen for curing with the plasma arc light, and the control group was cured at 10 seconds per bracket with a conventional halogen light. Debonding was performed on a universal testing machine and according to the bracket manufacturers' recommendations. Both the polycrystalline and the monocrystalline brackets consistently debonded at the bracket-adhesive interface, regardless of debonding method, curing interval, or curing light. No enamel fractures were observed after debonding. Bracket fractures were rare and did not affect debonding. Bond strength was significantly higher for the monocrystalline brackets (P <.0001): mean shear bond strength ranged between 9.68 +/- 2.17 MPa (plasma arc curing light, 1 sec curing interval) and 10.73 +/- 3.22 MPa (halogen light, 10 sec curing interval) for the polycrystalline brackets and between 19.85 +/- 2.97 MPa (plasma arc curing light, 1 sec curing interval) and 22.94 +/- 3.20 MPa (plasma arc curing light, 3 sec curing interval) for the monocrystalline brackets. Significant differences were also found for the curing methods used (P =.047). A curing interval of 3 seconds with the plasma arc curing light is recommended for both polycrystalline and monocrystalline ceramic brackets.

Analysis of Variance↗
PubMed2003

In vitro investigation of indirect bonding with a hydrophilic primer.

The aim of this in vitro investigation was to evaluate bond strength for a custom base indirect bonding technique using a hydrophilic primer on moisture-contaminated tooth surfaces. Stainless steel brackets were bonded to 100 permanent bovine incisors using a light-cured custom base composite adhesive, a chemically cured sealant, and the hydrophilic primer Transbond MIP (3M-Unitek, Monrovia, Calif). Five groups (A-E) of 20 teeth each were formed according to the time of contamination (before or after application of the primer) and the type of contaminant (distilled water or saliva): A, control group with no contamination; B, contamination with saliva before application of the primer; C, contamination with water before application of the primer; D, contamination with saliva before and after application of the primer; and E, contamination with water before and after application of the primer. Mean bond strength for the group without contamination (A) was 15.07 +/- 4.14 MPa and was not significantly different from bond strengths for groups B (14.91 +/- 3.99 MPa) and C (16.12 +/- 3.67 MPa), in which contamination occurred before application of the hydrophilic primer. Average bond strength in group D was 11.92 +/- 4.76 MPa. The lowest mean bond strength was measured for group E (9.85 +/- 3.77 MPa) and was significantly lower than for groups A, B, and C. Contamination after primer application resulted in an increased risk of bond failure at clinically relevant levels of stress.

Adhesives↗
PubMed2003

In vitro evaluation of a moisture-active adhesive for indirect bonding.

The aim of this in vitro investigation was to evaluate bond strength for a cyanoacrylate adhesive in combination with an indirect bonding technique. Eighty bovine permanent mandibular incisors were randomly divided into four groups of 20 teeth each. The influence of two factors on shear bond strength was investigated: (1) type of adhesive (Smartbond cyanoacrylate, Sondhi Rapid Set composite sealant) and (2) time of debonding (30 minutes and 24 hours after bonding). Stainless steel mesh-based brackets were used. Although, bond strength was not significantly different for the two debonding time periods, significantly lower bond strength measurements were found for the cyanoacrylate adhesive (P < .001). The mean bond strength for the cyanoacrylate adhesive group was 5.44 +/- 1.65 MPa for debonding 30 minutes and 6.92 +/- 1.48 MPa for debonding 24 hours after the bonding procedure vs 16.16 +/- 5.25 MPa and 14.98 +/- 2.85 MPa for the composite adhesive groups debonded at 30 minutes and 24 hours, respectively. The Weibull analysis indicated that there was an increased risk of bond failure at clinically relevant levels of stress for indirect bonding with the cyanoacrylate adhesive.

Adhesives↗
PubMed2003

Bond strength with custom base indirect bonding techniques.

Different types of adhesives for indirect bonding techniques have been introduced recently. But there is limited information regarding bond strength with these new materials. In this in vitro investigation, stainless steel brackets were bonded to 100 permanent bovine incisors using the Thomas technique, the modified Thomas technique, and light-cured direct bonding for a control group. The following five groups of 20 teeth each were formed: (1) modified Thomas technique with thermally cured base composite (Therma Cure) and chemically cured sealant (Maximum Cure), (2) Thomas technique with thermally cured base composite (Therma Cure) and chemically cured sealant (Custom I Q), (3) Thomas technique with light-cured base composite (Transbond XT) and chemically cured sealant (Sondhi Rapid Set), (4) modified Thomas technique with chemically cured base adhesive (Phase II) and chemically cured sealant (Maximum Cure), and (5) control group directly bonded with light-cured adhesive (Transbond XT). Mean bond strengths in groups 3, 4, and 5 were 14.99 +/- 2.85, 15.41 +/- 3.21, and 13.88 +/- 2.33 MPa, respectively, and these groups were not significantly different from each other. Groups 1 (mean bond strength 7.28 +/- 4.88 MPa) and 2 (mean bond strength 7.07 +/- 4.11 MPa) showed significantly lower bond strengths than groups 3, 4, and 5 and a higher probability of bond failure. Both the original (group 2) and the modified (group 1) Thomas technique were able to achieve bond strengths comparable to the light-cured direct bonded control group.

Acrylic Resins↗
PubMed2002

Enamel conditioning for orthodontic bonding with a single-step bonding agent.

AIM: In-vitro evaluation of an alternative method to the conventional acid etch technique. MATERIAL AND METHOD: 240 human anterior and posterior teeth were divided into 16 groups of 15 teeth each. Group variables were: tooth type, enamel conditioning technique (Prompt L-Pop((R)): 3M Espe, Seefeld, Germany, or 37% phosphoric acid and bonding), adhesive (Transbond trade mark XT: 3M Unitek, Monrovia, CA, USA and ENlight((R)): Ormco, Orange, CA, USA), and testing procedure (shear and tensile bond strength). Upper lateral incisors and premolar brackets (Mini-Diamond((R)): Ormco, Orange, CA, USA) were used. Intergroup differences were analyzed by an analysis of variance. The enamel surface and the failure mode of debonded specimens were investigated with light and scanning electron microscopy. RESULTS: Despite a tendency towards a higher bond strength after phosphoric acid conditioning, no statistically significant differences were found between the enamel conditioning methods. Statistically significant differences were recorded for the different adhesives: bond strength with Transbond trade mark XT was higher than with Enlight((R)). CONCLUSION: The single-step bonding agent sems to provide an acceptable bond strength between adhesive and enamel. No enamel fractures were detected. In vivo studies will be conducted to investigate the clinical performance of the new material.

Acid Etching, Dental↗
PubMed2002

Skeletal Class II patterns in the primary dentition.

The aim of this longitudinal cephalometric study was to investigate early characteristics of favorable and unfavorable growth. Two groups of untreated subjects with skeletal Class II pattern were formed on the basis of an ANB angle at least 2.5 degrees above the individual norm, according to Järvinen, at age 5. The subjects were followed longitudinally until age 12. The favorable growth group (n = 13) consisted of subjects who exhibited a decrease in the individualized ANB angle of at least 1.5 degrees during follow-up. The unfavorable growth group (n = 10) was characterized by an increase in the individualized ANB angle during the growth period from 5 to 12 years. Early characteristics of unfavorable growth included increased mandibular plane angle (measured to the sella-nasion line and the palatal plane, P <.05), increased lower gonial angle (P <.05), and a decreased ratio of posterior-to-anterior face height (P <.05) [corrected]. At the longitudinal follow-up at age 12, the 2 groups showed significant differences in SNB (P <.01) and individualized ANB (P <.01). The improved sagittal jaw relationship in the favorable growth group was the result of changed mandibular position. Morphogenetic posterior rotation seems to occur early in patients with skeletal Class II pattern and unfavorable growth and might be part of an adaptive mechanism compensating for insufficient mandibular growth.

Cephalometry↗
PubMed2002

Role of cranial base flexure in developing sagittal jaw discrepancies.

The aim of this longitudinal cephalometric study was to investigate skeletal features in patients with small and large cranial base angles. Two groups of untreated subjects were formed on the basis of a small and large cranial base angle N-S-Ar at the age of 5 years: the large cranial base angle group (n = 22) consisted of subjects with an N-S-Ar angle larger than 125 degrees (mean, 128.1 degrees ), and the small cranial base angle group (n = 20) included subjects with an N-S-Ar angle of less than 120 degrees (mean, 117.6 degrees ). Cephalometric data of the 2 groups were analyzed at subject ages 5 and 12 years. At both ages, the groups showed significant differences of the variables SNA, SNB, individualized ANB, and Y axis. The unadjusted ANB angle and the angle of convexity N-A-Pg were not significantly different between the 2 groups. According to the individualized norm of the ANB angle, subjects with a large cranial base angle in the primary dentition demonstrated a skeletal Class II tendency both at the initial observation and at the longitudinal follow-up. On the basis of cephalometric variables at 12 years of age, it was possible to classify 88.1% of the initial large and small cranial base angle individuals, indicating a constancy of the skeletal pattern during the longitudinal follow-up. The relationship between cranial base flexure and skeletal pattern of the jaws seems to be established before the age of 5 years.

Cephalometry↗
PubMed2002

Plasma arc curing lights for orthodontic bonding.

Xenon plasma arc lights were introduced recently for light-cured orthodontic bonding. Compared with a conventional tungsten-quartz-halogen light source, these high-intensity lights promise a dramatic reduction in curing time. The purpose of this in vitro investigation was to evaluate bond strength with 2 commercially available plasma arc lights and reduced curing intervals. Brackets were bonded to 150 extracted human teeth (75 premolars, 75 incisors) with a composite adhesive. Intervals of 2 and 6 seconds were used for curing with the plasma arc lights; a control group was bonded with a halogen light source and 20 seconds of light exposure per bracket. Bond strength testing was performed with a universal testing machine. A substantial reduction in curing time was possible with both plasma arc units. Significantly lower bond strength values were found for premolar brackets bonded with plasma arc curing lights and the shortest curing interval of 2 seconds compared with the longer curing time of 6 seconds or the standard curing time with the halogen light. Although 2 seconds of curing might be adequate to achieve acceptable bond strength values for the incisors, the Weibull analysis indicated a higher probability of bond failure for premolar brackets in particular. Six seconds of curing time is recommended for bonding stainless steel brackets with xenon plasma arc light sources.

Analysis of Variance↗