Bone Screws

We stereotactically implanted two microdrives in each bird. The electrodes were positioned in NCL [anteroposterior (AP), +5.0; mediolateral (ML), –7.5; dorsoventral (DV), –1.5] and NIML (AP, +9.5; ML, –3.5; DV, –2.3) of the right hemisphere (Karten and Hodos, 1967 ). Coordinates for the regions were based on histologic studies on the localization of NCL (Waldmann and Güntürkün, 1993 (link); Herold et al., 2011 (link)) and NIML (Rehkämper et al., 1985 (link)). The birds were anesthetized using isoflurane and received meloxicam (2 mg/kg, i.m.) for analgesia. The skull was exposed, and small craniotomies were made over the target structures. Electrodes and microdrives were fixated with dental acrylic to small bone screws, one of which served as a ground for the recordings. After surgery, the birds received several days of recovery, with monitoring and analgesic treatment of butorphanol (1.5 ml/kg, i.m.). In one of the birds, the left hemisphere was also implanted with the same coordinates in a separate surgery.

This prospective study was carried out in the Department of Orthodontics and Dentofacial Orthopedics, A B Shetty Memorial Institute of Dental Sciences, Mangalore, India, to assess the failure rates and factors associated with failure of Infrazygomatic Crest Implants. Clearance for the study was obtained from the Institutional Ethics Committee. (Cert No: ABSM/EC/62/2018).
The study was carried out by taking a detailed case history, (age, gender, vertical skeletal pattern, medical history), photographic records, radiographs, and clinical examination of a total of 32 randomly selected. patients of south indian origin who required infrazygomatic implants bilaterally as the choice of anchorage conservation to retract their incisors. All selected subjects were required to take a PA Cephalogram after the implant placement. The age of the patients ranged from 18 to 33 with an average age of 25 years. The patient log was maintained which included the treatment mechanics, status of oral hygiene, stability of implants, time of loading of the implant, presence of inflammation and time of failure of implant. The angulation of implant was measured on a digital PA cephalogram using Nemoceph software.
Patients with incomplete logs/records, previous history of orthodontic treatment, and/or orthognathic treatment, and/or facial trauma were excluded from the study. Patients who were medically compromised (Diagnosed Syndromes/Congenital defects/Facial Deformities) were also excluded from the study. The patient details, clinical features, status of the implant, and treatment progress were examined from the treatment log and photographic images to evaluate independent and dependent variables. Bone screws used in the clinical setup were 12/14 mm in length and 2 mm in diameter. The bone screws used in the study were from S K Surgicals. All implants were made from Titanium (Grade 5). The specification number for the implant material was ASTM B 265 Gr.5 : 2015. The composition of elements of the alloy used were 0.015% of Carbon, 0.28% of Iron, 0.015% of Nitrogen, 4.05% of Vanadium, 6.02% of Aluminium and 89.62% of Titanium. All implants were placed by a senior orthodontic faculty from the same college who had years of experience placing over 500 bone screws. Mini-implant failure was the primary outcome. Failure was defined as loss of the mini-screw in less than 8 months after placement. Independent variables associated with clinical success of the mini implant were age, gender, mandibular plane angle, length of the implant, side on which it failed, occluso-gingival position, angle of placement, time till loading, method of force application, oral hygiene, inflammation around the implant and implant mobility. These variables were examined as predictors of implant failure (Table 1).Table 1

List of variables to be assessed.

Table 1

	CHARACTERISTICS
1	Age	<18 years
		≥18 years
2	Gender	Male
		Female
3	Length of the implant	12 mm
		14 mm
		All others
4	Side of implant failure	Left
		Right
5	Occluso-gingival Position	Upper attached gingiva
		Upper oral mucosa -low
		Upper oral mucosa -high
6	Angle of implant to the occlusal plane:
	Right	0°- 45°
		46°-90
	Left	0°- 45°
		46°-90
7	Time till loading	Immediate
		After two weeks
8	Oral hygiene	Good
		Fair
		Poor
9	Inflammation	Yes
		No
10	Mobility	Yes
		No
11	Mandibular plane angle	High angle
		Average angle
		Low angle