Die Aufhellung verfärbter Zähne mithilfe von Bleaching stellt eine minimalinvasive und wirkungsvolle Methode dar, um ästhetische Verbesserungen ohne Substanzverlust zu erreichen. Insbesondere das interne Bleichen wie die „Walking bleach“-Technik bietet bei devitalen Zähnen eine effektive Möglichkeit, selbst intensive Verfärbungen aufzuhellen, die von subgingival durchscheinen. Vor einer prothetischen Versorgung kann das Bleichen als Vorbehandlung die Basis für ein ästhetisches Gesamtbild schaffen und somit den Erfolg und die Langlebigkeit der Restaurationen unterstützen. Für den langfristigen Behandlungserfolg sind bei internen Bleichmaßnahmen sorgfältige endodontische Maßnahmen entscheidend. Eine suffiziente Wurzelfüllung und ein dichter zervikaler Verschluss minimieren das Risiko zervikaler Resorptionen, während sich durch eine regelmäßige Nachsorge mögliche Komplikationen (vor allem bei Traumazähnen) frühzeitig erkennen lassen. Durch die Kombination von präprothetischem Bleichen und gezielten prothetischen Maßnahmen kann ein ästhetisch optimales Ergebnis erzielt werden, das den individuellen Bedürfnissen der Patient/-innen gerecht wird. Manuskripteingang: 13.01.2025, Manuskriptannahme: 05.02.2025 Keywords: Frontzahnästhetik, Zahnverfärbung, Bleaching, Vorbehandlung, Zahnaufhellung

Durch die wachsende Nachfrage nach monolithischen Zirkonoxid-Restaurationen wächst der Anspruch an die Veredelungstechniken. Die stetige Weiterentwicklung des Gerüstmaterials schafft neue Möglichkeiten der Finalisierung. So lassen sich sowohl einige Vorteile als auch neue Herausforderungen durch das Mikrolayering-System beobachten. Die Datenlage ist derzeit noch begrenzt und ein Vergleich der verschiedenen Massen hat noch nicht stattgefunden. Eine Einteilung hinsichtlich verfahrenstechnischer und werkstoffkundlicher Aspekte verschafft einen Überblick. Keywords: Mikrolayering, Minimalverblendung, Beschichtung, Veredelung, Zirkonoxid

Aim: To evaluate the fracture load and type of failure of two different monolithic restorative materials bonded to standardized titanium bases and fabricated by two different procedures regarding the bonding interface. Materials and methods: All screw-retained implant crown specimens (n = 40), subjected to fatigue by thermomechanical loading, differed in the restorative material (lithium disilicate [LDS] or polymer-infiltrated ceramic network [PICN], referred to as ‘hybrid ceramic’ [HYC]) and the interface type between the restorative material and the titanium base abutment (prefabricated ex-factory or produced during a CAM-milling procedure). This resulted in the following groups (n = 10/group): 1) LDS-M: lithium disilicate crown with a CAM-milled interface; 2) LDS-P: lithium disilicate crown with a prefabricated interface; 3) HYC-M: PICN crown with a CAM-milled interface; and 4) HYC-P: PICN crown with a prefabricated interface. Aged specimens underwent static fracture load testing. The load (N) at which the initial crack occurred was denoted as Finitial, and the maximal load (N) at which the restorations fractured as Fmax. All specimens were examined under a stereomicroscope to determine the failure mode. Results: The median Finitial values were 180 N for LDS-M, 343 N for LDS-P, 340 N for HYC-M, and 190 N for HYC-P. The median Fmax values were 1822 N for LDS-M, 2039 N for LDS-P, 1454 N for HYC-M, and 1581 N for HYC-P. The intergroup differences were significant for Finitial (KW: P = 0.0042) and for Fmax (KW: P = 0.0010). The failure types also showed differences between the restorative groups. Conclusions: The choice of restorative material had a stronger influence on the fracture load than the abutment interface workflow. Lithium disilicate showed the highest load for initial crack appearance (Finitial) and for complete fracture of the restoration (Fmax). Keywords: lithium disilicate, dental materials, polymer-infiltrated ceramic network, thermomechanical aging, fracture load, failure mode, prosthetic dentistry, restorative material, abutment interface

Purpose: To evaluate the minimum ceramic thickness needed to increase the lightness by one value by means of glass-ceramic restorations, as perceived by dental technicians, dentists, and laypersons. Materials and Methods: A total of 15 assessment pairs (= reference and test sample) were formed using glass-ceramic blocks in four different colors. Each assessment pair was comprised of two underground blocks differing by one value of lightness. On top of the underground blocks, glass-ceramic platelets were cemented in 5 different thicknesses (0.1 to 0.5 mm) in the same color as the reference. Dental technicians, dentists, and laypersons (n = 41/group) were asked to determine the presence of a color difference between the two samples under standardized light conditions. The threshold ceramic thickness was defined as the thickness at which ≥ 50% of the evaluators were not able to perceive a difference within an assessment pair. The thresholds were analyzed, and groups were compared by applying chi-square test (P < .05). Results: The majority of dentists and dental technicians (> 50%) detected a lightness difference between test and reference samples up to a ceramic thickness of 0.5 mm. The majority of laypersons (≥ 50%) did not perceive lightness differences with ceramic thicknesses of 0.5 mm. If separated by the different color changes, the threshold ceramic thickness started at 0.4 mm and varied within the groups of evaluators and the lightness of the assessed color. Conclusions: A considerable number of evaluators perceived a lightness difference when minimally invasive ceramic restorations of 0.5-mm thickness were applied. The threshold ceramic thickness, however, was reduced when the lightness of the substrate was lower.

Begleitend zu der stetig steigenden Nachfrage nach monolithischen Zirkonoxid-Restaurationen, drängt die Methode der minimalen Verblendung und Bemalung zunehmend in den Vordergrund. Das sogenannte Mikrolayering oder die sogenannten 3-D-Massen gelten als Schlüsselbegriffe dieser Konzepte. Die momentane wissenschaftliche Datenlage zu diesen Systemen, bestehend aus Mal-, Textur- und Glasurmassen, ist unzureichend. Zahlreiche Anwenderbeispiele spiegeln positive Bewertungen hinsichtlich Ästhetik, Reproduzierbarkeit und Effizienz wider. Keywords: Mikrolayering, 3-D-Massen, Zirkonoxid, Pastenkeramik, Minimalschichtung

Wenn bei Patientinnen und Patienten restaurativer Bedarf besteht, so macht es aus biologischer Sicht Sinn, möglichst substanzschonend zu arbeiten. Nebst konventionellen Herstellungsverfahren stehen heute auch subtraktive und additive Verfahren für die Herstellung von minimal-invasiven Restaurationen zur Verfügung. Besonders im Zusammenhang mit minimal-invasiven dünnen Restaurationen zeigen subtraktive Fertigungstechniken ihre Limitationen. Die additive Fertigung von Keramiken für minimal-invasive Restaurationen birgt deshalb großes Potenzial. Erste In-vitro-Versuche liefern hoffnungsvolle Ergebnisse. Diese müssen jedoch noch weiter in vitro und später klinisch bestätigt werden. Keywords: additive Fertigung, minimal-invasive Restaurationen, Lithiumdisilikat, Passung, Belastbarkeit

Purpose: To measure the effect of simulated aging on stained resin-ceramic CAD/CAM materials regarding the durability of color and gloss. Materials and Methods: Test specimens (n = 15 per material) were prepared out of CAD/CAM ingots from two resin nanoceramics (Lava Ultimate [LVU], Cerasmart [CER]) and a polymerinfiltrated ceramic (ENA, VITA Enamic) stained with the manufacturer’s recommended staining kit using photopolymerization. Control specimens were made of feldspathic ceramic (VITA Mark II [VM2]) and stained by means of ceramic firing. Negative control specimens (n = 15) (no staining) were prepared for each group. Color and gloss measurements were performed before and after each aging cycle by means of mechanical abrasion with a toothbrush. Groups were compared using Kruskal-Wallis test and paired post hoc Conover test. Changes within a group were calculated using Wilcoxon signed-rank test (α = .05). Results: The color difference (ΔE) was statistically significant for all stained CAD/CAM materials after simulated aging: CER (P < .001, 95% CI: 2.96 to 3.69), LVU (P = .004, 95% CI: 1.09 to 1.46), ENA (P = .004, 95% CI: 0.20 to 0.42), and VM2 (P < .001, 95% CI: 0.29 to 1.08). Aging resulted in a statistically significant increase in gloss in the LVU group (P < 0.001, 95% CI: 13.78 to 17.29), whereas in the ENA (P < .001, 95% CI: 7.83 to 12.72), CER (P < .001, 95% CI: 2.69 to 8.44), and VM2 (P = .014, 95% CI: 0.22 to 1.87) groups, a significant decrease in gloss was noted. Conclusion: Color and gloss of stained resin-ceramic CAD/CAM materials changed significantly after aging by means of toothbrush abrasion in vitro.

Purpose: To investigate the effect of aging on the morphology of the interface between monolithic implant crowns and standardized titanium base abutments. Materials and Methods: Four groups of hybrid abutment crowns differing in restorative material (lithium disilicate [LD] or polymer-infiltrated ceramic network [PICN]) and in fabrication procedure of the interfacial zone for luting to a titanium abutment (milled during CAD/ CAM procedure [M] or prefabricated [P]) were formed: LDS-M, LDS-P, PICN-M, and PICN-P (n = 10 each). The morphology of the crown-abutment interface was examined before and after artificial aging using scanning electron microscopy. The total gap length per specimen was measured at both time points, and intergroup (Kruskal-Wallis [KW]) plus pairwise (Wilcoxon Mann-Whitney [WMW]) comparisons were performed (α = .05). Results: Before aging, statistically significant differences in gap length were identified among groups (KW: P = .0369) for PICN-P > LDS-P (WMW: P = .0496) and LDS-M > LDS-P (WMW: P = .0060). The effect of aging among the groups, expressed as an increment of total gap length, was 50% in LDS-M, 30% in LDS-P, 20% in PICN-M, and 30% in PICN-P. After aging, the statistically significant differences in gap length identified among groups (KW: P = .0048) were for PICN-P > LDS-P (WMW: P = .0134); LDS-M > PICN-M (WMW: P = .0204); PICN-P > PICN-M (WMW: P = .0486); and LDS-M > LDS-P (P = .0022). However, comparison of the difference in gap length from before to after aging among the groups was not statistically significant (KW: P = .3549). Conclusion: The cementation interfaces of CAD/CAM crowns on standardized titanium base abutments demonstrated a high percentage of gaps before and after thermomechanical loading. The composition of the restorative material and the nature of the interface influenced the interfacial gap dimension.