Biomedical subjects

Ulrich Bismayer

Publications and source records attributed to Ulrich Bismayer.

5 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↗

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

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↗