Mandibular retromolar space in adults with different sagittal skeletal patterns: <i>Cone-beam computed tomography analysis</i>

Zhang, Fan; Zhang, Qi; Jiang, Yujun; Qin, Qianyi; Hu, Sheng; Guo, Jin

doi:10.2319/112021-854.1

Cited by 9 publications

(15 citation statements)

References 21 publications

(42 reference statements)

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“…Similarly, the comparison of the cortical bone thicknesses between different sites within the subgroups did not show statistically significant differences, except for the comparison within the hypo-subgroup at the M0 vs. M4 sites. Interestingly, descriptive statistics in the subgroups revealed greater cortical bone thicknesses in subjects with hypo-divergency, which aligns with the previous literature [4,23,[28][29][30]. This indicates the influence of facial morphology on mandibular cortical bone thickness [31].…”

Section: Discussionsupporting

confidence: 90%

Anatomical Bone Characteristics of the Buccal Step Insertion Site for Mini-Screw Placement in Orthodontic Treatment: A CBCT Study

Derton,

Bellocchio,

Ciancio

et al. 2024

Oral

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Background: To analyze the anatomical characteristics of a posterior area in the mandible localized distally to the second molars and extending in the vestibular direction toward the bony step, which we define as “buccal step”, in a patient with different skeletal patterns for mini-screw insertion. Methods: The sample included 85 CBCT (cone beam computed tomography) records selected from the digital archive. Analysis focused on the buccal step area. Sections were obtained in axial view using reference lines, and measurements of cortical and total bone were taken at specific points M0 (starting point, 6 mm apical from CEJc—cementoenamel junction crest), M2 (located 2 mm posterior to M0 in the apical direction), and M4 (positioned 4 mm posterior to M0 in the apical direction) in both directions. Six measurements were recorded for each scan root plane, assessing cortical and total bone depth. Results: The thickness of the bone increases toward the inside of the mouth at all tested sites (M0, M2, M4), which is good for placing mini-screws. Cortical bone thickness decreases toward the inside of the mouth, with no significant differences among the sites except for M0 vs. M4. People with a particular jaw shape (hypo-divergent) have a thicker cortical bone, indicating that facial structure affects bone thickness. Conclusions: The posterior buccal step insertion site has biomechanical advantages and reduces the risk of damaging roots during mini-screw insertions.

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Section: Discussionsupporting

confidence: 90%

Anatomical Bone Characteristics of the Buccal Step Insertion Site for Mini-Screw Placement in Orthodontic Treatment: A CBCT Study

Derton,

Bellocchio,

Ciancio

et al. 2024

Oral

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“…10 While Fan's study reported signi cantly larger RMS in Class III group compared to other groups. 11 This discrepancy may be due to the variation of samples used in these studies. Thus, distalizing the upper and lower dentition with TAD at the same time can be used to relieve the mild to moderate crowding and maintain the molar relationship in Class I patients.…”

Section: Discussionmentioning

confidence: 91%

“…A recent CBCT study which measured the RMS in normodivergent subjects with similar methods as ours also found shorter RMS in Class II group. 11 However, other studies reported that RMS was not related to the sagittal skeletal class but the vertical facial patterns 4,18 .This discrepancy may be due to the fact that vertical facial patterns have more prominent effect on the RMS compared to sagittal classes 18 . This result was well in line with previous two-dimensional study which suggested that skeletal classes were related to the morphology of the mandible, especially mandibular body length.…”

Section: Discussionmentioning

confidence: 96%

“…10 Fan's study suggested that Class III patients had a larger RMS than Class I and Class II patients at all four different planes, while another study found no signi cant difference in RMS between subjects with different skeletal classes. 4,11 Despite complex multifactorial mechanism of mandibular third molar(M3M) impaction, the short distance of RMS at crown level has long been recognized as a etiologic factor. 7,[12][13][14] The reduced RMS was attributable to the less resorption at the anterior border of the ramus, which has been correlated with vertical direction of condylar growth.…”

Section: Introductionmentioning

confidence: 99%

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Comparison of the retromolar space in adults with different sagittal skeletal types and eruption patterns of the mandibular third-molar

Gao

Zhou

Chen

et al. 2022

Preprint

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Background: The retromolar space (RMS) has not been investigated in patients with different skeletal classes and third-molar eruption patterns. The objective of this study was to test the null hypothesis that there is no difference in the mandibular RMS among normodivergent subjects with different skeletal Classes and third-molar eruption patterns using cone-beam computed tomography (CBCT). Method: A total of 105 normodivergent patients (20-40years) were included in this study. Patients were categorized into Class Ⅰ, Ⅱ and Ⅲ groups based on ANB, and they were further categorized into third-molar impacted and erupted groups. The RMS was measured at four planes parallel to the occlusal plane along the cuspal and sagittal line. The RMS was compared among the three sagittal groups and between impacted and erupted groups. Results: The skeletal Class II group showed statistically smaller RMS (P<0.05). The RMS was larger in third-molar erupted group(P<0.05). The rates of root contact and third-molar impaction was significantly higher in Class II group. (P<0.05) Conclusions: The null hypothesis was rejected. Skeletal Class II patients have smaller RMS and higher rates of root contact and mandibular third-molars impaction. The presence of impacted mandibular third molars was observed to be associated with shorter RMS. As such, the RMS should be verified with CBCT before molar distalization, especially in patients with Skeletal Class II relation and third-molar impaction.

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“…For adult patients without growth potential, the limit for available distance is closer to the apical level 23 . Patients with Class III malocclusion have greater retro-molar space than Class II and Class I patients along the posterior line of occlusion 24,25 . Retro-molar distance showed a decreasing tendency as the mandibular plane angle increased 26 .…”

Section: Discussionmentioning

confidence: 95%

The effects of clear aligner to move mandibular first molar distally using finite element method.

Kang

Zhang

et al. 2023

Preprint

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Objectives To analyze the features of tooth movement with clear aligner(CA) under different starting point and attachment settings.Materials and methods A 3D finite element(FE) model was established including mandible, dentition, periodontal ligaments(PDLs), CA and horizontal rectangular attachment. The second molar was previously positioned 3.2mm distally. Three groups were created according to attachment setting: (1)no attachment, (2)attachment on the second molar, (3) attachment on the first molar. In each group, the starting point of the first molar was 0mm(SET1), 1mm(SET2), 2mm(SET3) and 3mm(SET4) to the premolar in turn. A distal moving distance of 0.2 mm was applied to the first molar.Results As the first molar got closer to the second molar, distal displacement of the first molar, mesial displacement of premolar and labial displacement of anterior teeth increased, while the mesial displacement of the second molar decreased. When the attachment was applied on the buccal surface of the first molar, the average displacement value reached the top for the first molar(6.79e− 2mm), premolar(2.72e− 2mm) and anterior teeth(2.59e− 2mm) in SET 4. The average displacement of the second molar reached the top(3.07e− 2mm) in SET1 when attachment was placed on the second molar.Conclusions The distal displacement of the first molar resulted in an opposite movement of other teeth in dentition without additional anchorage. The effect of mesial and labial movement increased except for the second molar when the first molar moved distally. The horizontal rectangular attachment placed on the first molar produced more distal movement of the first molar crown.

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Mandibular retromolar space in adults with different sagittal skeletal patterns: Cone-beam computed tomography analysis

Cited by 9 publications

References 21 publications

Anatomical Bone Characteristics of the Buccal Step Insertion Site for Mini-Screw Placement in Orthodontic Treatment: A CBCT Study

Anatomical Bone Characteristics of the Buccal Step Insertion Site for Mini-Screw Placement in Orthodontic Treatment: A CBCT Study

Comparison of the retromolar space in adults with different sagittal skeletal types and eruption patterns of the mandibular third-molar

The effects of clear aligner to move mandibular first molar distally using finite element method.

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