## 2 Materials and Methods
### Miniscrew Insertion  
All miniscrews and implants were placed by the same clinician (R-V, A). The miniscrews used were low profile, self-tapping Optimus (Osteonic, Seoul, South Korea) Model O, of 1.6 mm diameter and 11 mm length, made from biocompatible TiAl6V4 titanium alloy. These miniscrews are designed with a flat hexagonal head, a mucosal protective collar, and smooth, polished transmucosal surface to avoid gingival inflammation, as well as an area of buttress thread to enhance pull-out strength. Miniscrew insertion was performed under local anesthetic at the host area. As these were self-tapping screws, it was not necessary to perform flap surgery to create access or to drill cortical bone tissue, as the screws were placed transmucosally with an electric counter-angle with torque limit (25 N) (NSK, Tochigi, Japan). The miniscrews were placed distal of the lower second molar in the middle of the bone crest in order to straighten the molar and gain the space required for endosseous implant placement to replace the missing first molar. The miniscrews used were 1.6 mm wide and 11 mm in length. At least 4.6 mm wide and more than 11 mm in length should be needed to use the miniscrew as a treatment option. The mesial inclination of the second molar is accompanied by the same inclination of the third molar, invading the prosthetic space of the first molar absent. To straighten the second molar and obtain enough space to replenish the first molar absent, the technique with miniscrews requires the extraction of the third molar inclined, favoring two objectives: obtain space for the placement of the miniscrew in the retromolar trigone and obtain the necessary space for the straightening of the second molar. All the third molars present were extracted for the straightening of the second molar. The miniscrew was placed so that the thread area was within the bone, while the transgingival portion and the head remained visible (Figure 1A,B). Figure 1: (**A**) Initial case with lack of available mesiodistal space for the replacement of the missing tooth. (**B**) Case after extraction of third molar and insertion of the miniscrew attached with an elastic chain to a mesial button of the tooth to upright. As soon as the screw was inserted, an extraoral radiograph was taken to check that insertion was carried out correctly. Ideally, this type of treatment should be performed on bone types I and II, including type III in some cases, but it would not be advisable in type IV for a fully trabecular bone. However, once the miniscrew is placed, its primary stability should be checked by applying the traction force to distal. A 0.12% chlorechidine gel (GUM, [PERSON]/Sunstar, Chicago, IL, USA) was applied as disinfect. No antibiotics or analgesics were prescribed. Immediately after miniscrew insertion and once the miniscrew load had started with the tensile forces, a mesial button (3M, St. Paul, MN, USA) was placed with an elastic chain (GC Orthodontics, Breckerfeld, Germany) surrounding the entire crown to straighten the tooth that would exert the necessary force to straighten the second molar. The button was cemented to the mesial surface of the inclined second molar. The inclined tooth was etched with 37% orthophosphoric acid etching gel (Total Etch, Ivoclar Vivadent, Amherst, NY, USA) for 30 s, and adhesive was applied to the dental enamel (Adhese Universal, Ivoclar Vivadent) and polymerized for 10 s (Bluephase G2 curing light, Ivoclar Vivadent). It was cemented using a flowable particulate filler composite (G-aenial Universal Injectable A2, GC America, Alsip, IL, USA) and light cured for 40 s. Once the button was cemented, an elastic chain was attached to the mesial button and to the miniscrew by the ends of the chain in order to upright the molar. The elastic chain was usually advanced a buttonhole every 15 days until maximum straightening and adequate prosthetic space were obtained (Figure 2). Occlusion forces should also be relieved (by using occlusal stops or by relieving the antagonist) during the treatment period.