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In der vorliegenden Dissertation wird ein innovativer Ansatz vorgestellt, Keramikkronen, Veneers und Keramikbrackets mittels Laserenergie unversehrt von der Zahnoberfläche zu entfernen, so dass diese nach erfolgreicher Behandlung wieder rezementiert werden können. Idealerweise würde in diesem Zuge lasergestützt auch der Befestigungszement minimalinvasiv entfernt werden können. Zur Wahl einer geeigneten Laserwellenlänge werden verschiedene gängige Dentalkeramiken zur Herstellung vollkeramischer Kronen oder Veneers auf Basis von Gerüst- und Schichtwerkstoffen oder monolithischer Blöcke im Bereich von 200-3000 nm spektroskopisch hinsichtlich deren Transmission, Remission und Absorption untersucht. Anhand von Modellen werden Experimente durchgeführt, keramische Kronen und Veneers mit dem Erbium-dotierter Yttrium-Aluminium-Granat-Laser (Er:YAG-Laser) vom Zahn abzulösen. Die Beurteilung der Wirksamkeit und Sicherheit der Ablösung wird licht- und rasterelektronenmikroskopisch sowie durch Farbeindringprüfung untersucht. Zur Entfernung von Befestigungszementresten auf Dentinflächen sowie Schmelzflächen von abgelösten Veneer- und Bracketversorgungen werden Laserverfahren überprüft und ebenso mikroskopisch untersucht. Auf Basis dieser Erkenntnisse erweisen sich Laser im Wellenlängenbereich zwischen 2500 und 3000 nm als besonders geeignet, so dass für die weitere Untersuchung der Er:YAG-Laser gewählt wird. Für Schmelz wird eine Ablationsschwelle von 2,5 J/cm² und für Dentin von 1,6 J/cm² ermittelt, um Zahnschäden zu vermeiden. Des Weiteren werden für das Laser-Debonding geeignete Laserparameter bestimmt, um Keramikrestaurationen, wie Kronen und Veneers, vom Zahn ablösen zu können. Beim Laser-Debondingprozess wird die Laserenergie von der Keramik transmittiert und vom Befestigungszement absorbiert. Der entstehende Verdampfungsdruck des Zements erzeugt einen Druckstoß, der die Keramik ablöst. Dieser Prozess benötigt zumeist nur wenige Pulse beziehungsweise Sekunden. Lichtmikroskopische Begutachtungen und Farbeindringprüfungen weisen nach, dass die Keramikrestaurationen durch die Lasereinwirkung nicht beschädigt werden und die Zahnsubstanz keine thermischen oder mechanischen Schäden erfährt. Um nach dem Laser-Debonding auf Zähnen verbliebene Zementrückstände zu entfernen, wird die Laser-Oberflächenreinigung unterhalb der Schmelz- beziehungsweise Dentin-Abtragsschwelle vergeblich versucht, da die Ablationsschwelle der untersuchten Befestigungszemente über diesen Schwellen liegt. Bei Laseranwendung oberhalb der Dentin- und Schmelz-Ablationsschwellen und Kombinationsverfahren mit Schallscaler oder Handinstrumenten sind Zementreste zwar abtragbar, jedoch nicht ohne dabei auch Zahnsubstanz abzutragen. Ein selektiver oder gründlicher Abtrag der Zementreste ist nicht möglich. Mittels des gepulsten Er:YAG-Lasers können Dentalkeramikrestaurationen für Kronen und Veneers zerstörungsfrei, schnell und ohne Beschädigung der Zahnsubstanz entfernt werden. Zur Entfernung von Zementresten erscheint die Laseranwendung neben der mangelnden Gründlichkeit und Selektivität insbesondere aus zeitlichen Gründen noch keine attraktive Alternative gegenüber der konventionellen Nutzung des Hartmetallfinierers zu sein, wobei auch bei Letzterem ein gelegentlicher Zahnhartsubstanzverlust stattfindet.

Objective: Bracket bonding has been a major advance in orthodontic treatment. However, the method of debonding can lead to diverse problems such as enamel fractures, enamel loss and enamel scratching. In this clinical investigation we aimed to evaluate the influence of wearing dental loupes on enamel damage during the debonding procedure. Material and Methods: 22 consecutive patients were randomly assigned in a split-mouth study to evaluate adhesive removal with and without the use of dental loupes (2.5×, LED headlight). Tooth replicas in epoxy resin were made from silicone impressions. Electron microscopic images (50× magnification) of 394 buccal enamel surfaces were evaluated according to an enamel damage index (EDI), line angle grooves (LAG) and composite residues (CR) on anterior teeth, premolars and molars. Results: The EDI revealed highly significant advantages for debonding with dental loupes, with which the EDI was significantly higher for molars, while still less than without dental loupes. We detected no differences between the tooth groups without dental loupes. We found significantly fewer LAG on anterior teeth debonded with dental loupes. CR were fewer in the dental loupes group, and we noted no significant differences between the tooth groups. Conclusions: Dental loupes affect the quality of the debonding procedure, resulting in less enamel damage and composite residue, as well as fewer LAG compared to the control group. We therefore strongly recommend the use of dental loupes in orthodontic debonding procedures

There are various studies in the literature on bonding brackets to bleached teeth and on the effect of bleaching material on the color of compomers. The purpose of this study was to investigate changes in tooth color depending on the process of bonding - debonding and/or bleaching.Ninety crowns of lower bovine permanent incisors were divided into nine subgroups. Three bonding materials (chemical, light- and pressure-cured) and three bleaching materials (15% CP, 35% CP, or 38% HP) were applied to the teeth, whereby each tooth was divided into quarters: untreated, bleached only, bonded-debonded only, and bleached after a bonding-debonding procedure. The Easyshade spectrophotometer was used to determine CIELCh coordinates (lightness, color, and hue) three times for each area. The areas' differences in color were expressed as the Euclidian distance DeltaE. Four examiners (two orthodontists and two dentists) rated each tooth concerning color differences in the four areas. The data collected was subjected to the sign and Wilcoxon or the Kruskal-Wallis and Mann-Whitney U tests using the SPSS 12.0 program.Examiners found significant differences between those areas with and those without bleaching within each group of specimens (p0.05), but there were no differences concerning the bonding and debonding procedures (p0.05). Furthermore, digital tooth-shade measurements revealed no statistically-significant group-associated differences between those areas treated with bonding material and those not so treated, nor between bonded and debonded areas (p0.05). Nor did we observe any statistically-significant differences between bleached areas and those areas bleached after bonding and debonding procedures (p0.05).The processes of bonding and debonding alone do not seem to have any statistically-significant influence on the tooth color of bovine enamel using these testing materials, nor does the subsequent bleaching procedure.

Background: The removal of residual bonding resin with rotary instruments after bracket debonding may damage the enamel surface. Conventional carbide burs may scratch the enamel due to the shape and sharpness of their blades. Carbide Finishing Bur: A new carbide finishing bur with a slightly tapered shape, rounded tip and eight twisted blades has been developed. As a special feature the wedge angle of the blades has been enlarged to ca. 130–135° by means of an oblique ground chamfer (relief angle ca. 0–5°). The transition from head to shaft has been smoothed off with a safety chamfer. Overall, the cutting capacity has been reduced in the enamel, while the bur has remained sufficiently sharp within the adhesive resin. Prototype Testing: For prototype testing, incisor brackets were bonded in vitro to 70 human incisors according to the standard clinical technique and removed after 7 days. Residual bonding resin was removed with conventional carbide burs and with gradually modified prototypes of the new finishing instrument respectively. The resulting enamel surfaces were evaluated by scanning electron microscopy. The specimens were then treated with a polishing paste and evaluated again. Results: Conventional carbide burs remove not only residual bonding resin but also some enamel; scoring may occur. The newly developed finishing bur has been proven by morphological evaluation to be less aggressive in removing residual bonding resin after bracket debonding.

The aim of the study was to compare the shear bond strength of a fluoride-releasing composite resin adhesive (Light Bond, Reliance) and a light-cured resin-reinforced glass ionomer cement (Fuji Ortho LC, GC America) bonded to extracted teeth under different enamel surface conditions. Forty human premolars were divided at random into 4 groups of 10 specimens. Stainless steel brackets were attached to the enamel surface by 1 of the 4 protocols: 1. Fuji Ortho LC, moist non-etched enamel; 2. Fuji Ortho LC, moist etched (37% H3PO4); 3. Light Bond, dry etched (37% H3PO4); 4. Light Bond, dry etched (EtchPrime 3.0, Degussa). The teeth were stored in deionized water at 37 degrees C for 48 hours. Shear bond strengths was determined at a crosshead speed of 1 mm/min. The residual adhesive on the enamel surface was evaluated with the modified Adhesive Remnant Index (ARI). Analysis of variance (ANOVA) and Duncan's test were used to compare the 4 groups. Significance was predetermined at p = 0.05. Significant inter-group differences were found (p0.0001). The mean SBS (and SD), in MPa were: Group 1: 15.9 (4.7); Group 2: 20.3 (2.5); Group 3: 16.7 (2.6); Group 4: 11.7 (2.5). Glass ionomer cement without etching and composite with EtchPrime showed adhesive failures at the enamel and good enamel integrity after debonding. The other specimens showed mixed or adhesive fractures at the bracket failure sites. Glass ionomer used on wet tooth surfaces without etching shows a clinically acceptable bond strength with clean separation from the enamel after debonding.

This study analyses the damage done by three debonding procedures. Ceramic brackets (ORMCO) having a basic size of 12.3 mm2 were bonded with Concise Composite to 120 non-carious premolars extracted from adolescent patients and subsequently shorn off using a Zwick multipurpose testing device. In 90 teeth the brackets were removed once, in 60 twice, and in 30 three times. The shearing forces were measured electronically and evaluated statistically. In a separate experiment involving 30 teeth, the in-depth interlinkage (adhesive "pegs") were exposed by chemically dissolving the enamel. The enamel surfaces and adhesive matrix were analysed using scanning electron microscopy. Each repeat debonding was associated with a clear increase in the frequency and size of the enamel damage. This was, on average, 12% (in four teeth) at the first debonding, 17.4% (six teeth) at the second debonding, and 21.9% (nine teeth) at the third debonding, referred in each case to the exposed enamel surface after shearing off the bracket. The damage increasingly involved deeper regions within the enamel. The mean bonding force was 13.2 MPa at the first debonding, 16.1 MPa at the second debonding, and 15.5 MPa at the third. The differences are statistically significant (por = 0.05). It would appear that the increase in bonding force between the first and second bracket removal was due to a more pronounced adhesive matrix at the second bonding. The decrease in bonding force at the third debonding may be due to a structure of the enamel caused by the repeated debonding process.(ABSTRACT TRUNCATED AT 250 WORDS)

Two different methods of removing brackets, on the one side by torsion and on the other by bending, were compared for the purpose of analyzing the respective enamel lesions. Each test group consisted of 19 extracted human molars with metal brackets attached to the molars by means of the "concise etching technique". Bracket removal was standardized through the use of a Wolpert "Universalprüfmaschine TZZ 707" with modified torsion and bending mechanism. A scanning electron microscope was used to analyze the enamel surface. When using the torsion method, the mean extension of the enamel lesions was 48.3% of the adhesive free enamel surface. These lesions often reached into the deeper enamel layers and were mainly to be found on the broad side of the bonded area. On the other hand, when using the bending method, the enamel lesions were less frequent. They were mainly superficial and were confined almost exclusively to the pressure zones. The stress required to remove the brackets and the stress distribution were calculated on mechanical models and these results corresponded well with the enamel lesions observed on the molars. It can thus be concluded that the method of removing brackets is clinically relevant in relation to enamel lesions.

The aim of the present in-vitro study was to evaluate the changes in pulp temperature associated with thermal debonding of ceramic brackets using the Ceramic Debonding Unit (Dentaurum). In addition, several forms of false usage were simulated. Instead of thermoelements, the non-contact infrared thermography device SST/THETA 1000 (Heimann) was employed for the dynamic measurement of pulp temperature. Successful debonding after a single activation resulted in a maximal temperature change of 3 degrees C. These in vitro results indicate that the Ceramic Debonding Unit--properly applied--is gentle on the pulp tissue. If debonding fails, the increase in temperature is higher. The influence of differing bracket base morphologies and various resins on electrothermal debonding are discussed.

The mechanical debonding of ceramic brackets using special instruments involves the use of a degree of force that is damaging to the enamel. For this reason, the authors have developed the Ceramic Debonding Unit for the thermal debonding of ceramic brackets. The unit reduces the force necessary for debonding, without overheating the tooth. The present article explains the principle of the unit. The influence on the temperature increase in the pulpa of the mechanical torque applied during debonding, and the time taken for debonding was investigated in extracted teeth (lower central incisors). Tests on ceramic brackets made by various manufacturers showed that safe debonding is possible if the debonding time does not exceed 3 seconds at a torque of 100 Nnm. The temperature increase in the pulpa will not exceed 5 degrees C when the Ceramic Debonding Unit is used under these conditions, so that harmful overheating of healthy teeth does not occur.

To establish whether or not temporary cementing with zinc oxide-eugenol (ZOE) cement affects the bond strength of the subsequent zinc phosphate cement, 60 standardized metal blocks with cylindrical drill holes were produced. 50 specimens were coated with ZOE cement and subjected to different cleansing techniques (mechanical, with alcohol or organic solvent, soap, Al2O3) in groups of ten. After examination of the cleansed surfaces under the light microscope, amalgam cylinders manufactured according to a standardized procedure were cemented into the cavities using zinc phosphate cement and pressed out. Only the Al2O3 jet-cleaned surfaces were free of ZOE cement residues. With high statistical significance the knock-through test revealed lower bonding strength values for the specimens cleaned either with alcohol or organic solvents.

50 cemented crowns and three-unit-bridges of 34 patients were treated by piezo-electric ultrasound. 23 of 32 crowns were removed within 10 min, 14 of 18 bridges were removed within 15 min. Crowns and bridges could be taken off after an average time of 5 min or of 12 min of ultrasound treatment, respectively. To remove the restorations only few strokes with the Treymann crown remover were required. In most cases patients felt no or only slight pain during ultrasound treatment. Restoring metal or ceramic surfaces after ultrasound treatment required final firing of the ceramic and polishing of the metal surfaces.