Positional Trueness with Different Titanium Base Bonding Techniques for Single Implant Crowns: In Vitro Evaluation of Model-Free Workflow Versus Additively Manufactured Models.

OBJECTIVES: To compare the positional trueness of implant-crown bonding to titanium bases (Ti-bases) using different bonding protocols. MATERIALS AND METHODS: A nonprecious alloy model with a single implant at the mandibular right first molar site was digitized, then a single implant crown was designed. The crown was milled, adhesively cemented on a Ti-base, and screw-retained on the implant in the master model to obtain a reference scan. Forty PMMA implant crowns were subtractively manufactured and allocated to one of four study groups (n = 10 crowns per group) based on the bonding protocol on Ti-bases: Group 1 = modelfree bonding; Group 2 = bonding on the master model (control); Group 3 = bonding on a model from an industrial-grade 3D printer (Prodways); Group 4 = bonding on a model from a conventional 3D printer (Asiga). To assess the positional trueness of crowns, the scans of crowns when on the model were superimposed over the reference scan. Median distance and angular deviations were analyzed using Kruskal-Wallis and Mann- Whitney tests (α = .05). Mesial and distal contacts of crowns were assessed by two independent clinicians. RESULTS: The control group (Group 2) resulted in the smallest distance deviations (0.30 ± 0.03 mm) compared to model-free (0.35 ± 0.02 mm; P = .002; Group 1) and conventional 3D printer (0.37 ± 0.01 mm; P = .001; Group 4) workflows. Buccolingual (P = .002) and mesiodistal (P = .01) angular deviations were higher in the conventional 3D printer group than in the control group (P = .002). Proximal contact assessments did not show any differences among groups. CONCLUSIONS: While bonding crowns to Ti-bases on a master model created with an industrial-grade 3D printer resulted in the highest positional trueness, model-free workflows had a similar positional trueness to those manufactured with a conventional 3D printer.

[Sustainable dentistry - Part II: Sustainable workplace and waste management]. / Die nachhaltige Zahnmedizin. Teil 2: Nachhaltigkeit am Arbeitsplatz und in der Abfallreduktion.

This second and final part of the publication on the topic of sustainability in dental practices deals with the so-called workplace management, which describes the work processes and the consumption of energy and materials in the practice itself. Waste management is also addressed, which discusses the path of resources from the practice to disposal and recycling. Finally, an example from materials research is presented using implants.

[Sustainable dentistry - Part I: Sustainability and pre-workplace management]. / Die nachhaltige Zahnmedizin ­ Teil 1: Nachhaltigkeit im Umfeld von Zahnarztpraxen.

Sustainability in dental practices is playing an increasingly important role. External and internal factors have an influence on the emissions of a practice. The external factors include the domains of politics, science, and education. It is eminent that the discussion on the environmental impact in healthcare finds its way into these three domains, as it lays the foundation for behavioural change and thus paves the way for a greener future. The internal factors include practice operations, supply chain, employees, and patients. Overall, the topic of sustainability is hardly prevalent in the dental workplace. This first article of a two-part series highlights how sustainability in dentists' practices and work is influenced by many environmental factors which, taken together, can affect the interplay between the environment and dentistry.