Third molar (M3) impaction is commonly observed in dental practice. While the causes of impaction are still not clearly understood, they appear to be multifactorial. Currently, an insufficient amount of space in the jaw distal to the second molar - the retromolar (RM) region - is considered to be the most significant of these putative risk factors. However, M3 eruption is not always guaranteed by space availability in the RM region, and other factors such as delayed M3 mineralization, tooth crown size, and dental arch size are suspected to increase impaction risk. Because studies have traditionally focused on mandibular M3s and been limited to two-dimensional (2D) radiographs, this study is the first to investigate the causes of M3 impaction in both jaws, using 3D imaging, with precision and accuracy not previously possible using standard 2D dental imaging modalities. This study tests the hypothesis that not only a reduced amount of space in the RM region is observed when M3 impaction is present but also delayed M3 mineralization, larger molar and premolar crowns, and shorter dental arches. Research ethics permission (BIO#11-202) was obtained to use existing retrospective cone beam computed tomography (CBCT) images of over 500 patients aged 8 to 24 years taken and curated at the College of Dentistry, University of Saskatchewan. Anatomical landmarks were defined and a proprietary software package, Xoran-CAT (Imaging Sciences International, Philadelphia, USA) was used to measure RM regions, molar and premolar crowns, and dental arch dimensions, as well as to score M3 mineralization status. Results were assessed using independent sample t-tests. When M3 impaction was present, both short RM regions and delayed M3 mineralization occurred in both jaws, indicating that both of these are risk factors for impaction. In the presence of M3 impaction, narrower dental arches were observed only in the maxilla, while larger premolar and molar crowns were seen only in the mandible. The observation of these last risk factors in distinct jaws when M3 impaction was present, suggests that these are secondary factors in the determination of the M3 impaction condition, and that standards of M3 impaction differ between upper and lower jaws.

El objetivo de este estudio fue evaluar los factores asociados a la impactación del tercer molar inferior en pacientes atendidos en una clínica universitaria de Chiclayo durante el año 2023. En este estudio se incluyó 120 participantes que contaban con al menos un tercer molar inferior impactado visible en una radiografía panorámica, donde se evaluó el grado de impactación según Pell & Gregory y el espacio retromolar; además, se tomó una muestra sanguínea donde se determinó el grupo sanguíneo y el nivel de fosfatasa alcalina en sangre. Los resultados mostraron una impactación de los niveles A (47.5%), B (40.8%) y C (11.7%), mayor prevalencia de impactación en el sexo femenino y no se encontró una correlación positiva entre la fosfatasa alcalina, grupo sanguíneo, espacio retromolar y la impactación del tercer molar mandibular. Se concluye que no existe relación entre la fosfatasa alcalina, el grupo sanguíneo, el espacio retromolar y la impactación del tercer molar inferior. / The objective of this study was to evaluate the factors associated with the impaction of the lower third molar in patients treated at a university clinic in Chiclayo during the year 2023. This study included 120 participants who had at least one impacted lower third molar visible in a panoramic radiograph, where the degree of impaction according to Pell & Gregory and the retromolar space were evaluated; In addition, a blood sample was taken where the blood group and the level of alkaline phosphatase in the blood were determined. The results showed an mpaction of levels A (47.5%), B (40.8%) and C (11.7%), a higher prevalence of impaction in the female sex and no positive correlation was found between alkaline phosphatase, blood group, space retromolar and impaction of the mandibular third molar. It is concluded that there is no relationship between alkaline phosphatase, blood group, retromolar space and impaction of the lower third molar.