Assessment of infra‑zygomatic area for ideal placement of miniscrews: A systematic review and meta‑analysis

Abstract

Background: The infrazygomatic crest (IZC) is a commonly used extra‑alveolar site for orthodontic
miniscrew placement because of its favorable anatomical position and relatively dense cortical bone.
However, variations in bone thickness, insertion height, and angulation can influence the stability and
success of miniscrew placement. To systematically evaluate and synthesize the available evidence on
the infrazygomatic crest region to determine the most suitable site, insertion height, and angulation
for orthodontic miniscrew placement.
Materials and Methods: A systematic search was conducted across PubMed, Embase, Web of
Science, Scopus, the Cochrane Library, and grey literature sources including Google Scholar and
OpenGrey for studies published up to March 2023. Studies assessing cortical bone thickness and
anatomical characteristics of the IZC relevant to miniscrew placement were included. Thirteen
studies met the inclusion criteria for qualitative synthesis, and nine studies providing quantitative
data were included in the meta‑analysis. Mean values and standard deviations of bone thickness
and insertion height along the distobuccal root of the maxillary first molar at 70° angulation were
extracted. Forest plots were generated to compare findings across studies. Risk of bias was assessed
using the Quality Assessment of Measurement Accuracy Studies (QUAMAS) tool.
Results: Among the included studies, most reported adequate bone thickness in the region
buccal to the maxillary first molar. Meta‑analysis indicated that sufficient bone thickness is
generally observed when miniscrews are inserted at an angulation of approximately 60°–70°.
The optimal insertion height was commonly reported between 10 and 15 mm above the occlusal
plane, where greater cortical bone thickness was observed. Increasing insertion angulation
and decreasing insertion height were associated with improved bone engagement and primary
stability.
Conclusion: The current evidence suggests that the region buccal to the maxillary first molar
in the infrazygomatic crest is the most favorable site for orthodontic miniscrew placement. An
insertion angle of approximately 60°–70° and a height of 10–15 mm above the occlusal plane appear
to provide optimal bone thickness and stability.
Key Words: Bone thickness, cone beam computerized tomography, infrazygomatic crest,
mini‑implants, mini‑screw, temporary anchorage devices

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 Swapna Sreenivasagan: Pubmed,Google Scholar