Root proximity and stability of orthodontic anchor screws

Abstract

This study aimed to investigate a causal relationship between the stability of orthodontic anchor screws (screws) and the degree of their proximity to the root (root proximity) using mobility test device (Periotest) and cone-beam computed tomography (CBCT). In total, 165 (diameter 1.6 mm; length 8 mm) screws in 58 patients (average age, 24.4 ± 8.5 years) were evaluated. After screw placement, CBCT was used for diagnostic imaging of the area around the site. Root proximity was evaluated and categorized into three groups: A, no contact; B, single contact; and C, multi-contact. The Periotest value was used to assess screw stability. The screw failure rate according to root proximity significantly differed between categories A and C. In addition, failure rate significantly differed between mandibular screws with and without root contact. Periotest values in categories A and C were significantly higher in the mandible than in the maxilla. Mandibular screws had greater mobility than maxillar screws, even when the screw avoided root contact. The lower stability of mandibular screws with root contact might be related to their greater mobility. (J Oral Sci 56, 59-65, 2014)

Risk factors for failure of orthodontic mini-screws placed in the median palate

“…The Periotest device was developed to measure mechanical retention between bone and dental implants. Using PTVs obtained after placement, Shigeeda (28) found that mini-screws had greater mobility, which can result in failure regardless of root proximity. Inaba (23) reported a strong correlation between screw-bone contact state and PTV and concluded that PTV was an appropriate index of screw stability.…”

Effects of tooth root contact on the stability of orthodontic anchor screws in the maxilla: Comparison between self-drilling and self-tapping methods

“…Screws that contacted the tooth root were removed and defined as failures when the patient experienced clinical manifestations such as pain and discomfort or when there was mobility of the screw. According to Shigeeda,27 screws that contacted the tooth root without root injury were not considered failures and were kept under observation.…”

Optimal implantation site of orthodontic micro-screws in the mandibular anterior region based on CBCT

“…Furthermore, if the micro-screws are too close to the root, they will cause loosening and shedding, resulting in failure of the implantation surgery and damage to other important anatomical structures due to incorrect positioning. Therefore, the micro-screw should be positioned in the central area between the two roots to ensure the continuity and stability of the anchor [21][22][23] . In clinical practice, it is necessary to consider the proper safety range of both the alveolar bone and the soft tissue.…”