Non-Cochrane · prognostic · PM42321706
Association between impacted third molars and external root resorption on adjacent second molars based on cone-beam computed tomography: a systematic review and meta-analysis.
Liu Wenxuan, Liang Ailin, Zhou Yanling, et al. · BMC oral health · 2026 · PubMed · doi:10.1186/s12903-026-08820-7
Findings
21 findings
| Population | ||||
|---|---|---|---|---|
| Patients with impacted third molars (iM3s) and adjacent second molars (M2s) assessed by CBCT | iM3 present (overall) | None (single-group prevalence) | Prevalence of external root resorption (ERR) on adjacent M2s Single CBCT assessment · Dental imaging studies using CBCT · Overall | Pooled prevalence (%) 31 [26, 36] GRADE not reported 26 studies · 8188 participants |
| Patients with impacted third molars (iM3s) and adjacent second molars (M2s) assessed by CBCT | Male patients | Female patients | Prevalence of external root resorption (ERR) on adjacent M2s Single CBCT assessment · Dental imaging studies using CBCT · Sex: male | Pooled prevalence (%) 32 [23, 41] GRADE not reported 11 studies |
| Patients with impacted third molars (iM3s) and adjacent second molars (M2s) assessed by CBCT | Female patients | Male patients | Prevalence of external root resorption (ERR) on adjacent M2s Single CBCT assessment · Dental imaging studies using CBCT · Sex: female | Pooled prevalence (%) 34 [26, 42] GRADE not reported 11 studies |
| Patients with impacted third molars (iM3s) and adjacent second molars (M2s) assessed by CBCT | Age 26 to 35 years | Other categories of the same factor | Prevalence of external root resorption (ERR) on adjacent M2s Single CBCT assessment · Dental imaging studies using CBCT · Age: 26 to 35 years | Pooled prevalence (%) 25.93 [16.67, 37.89] GRADE not reported 7 studies |
| Patients with impacted third molars (iM3s) and adjacent second molars (M2s) assessed by CBCT | Age >= 36 years | Other categories of the same factor | Prevalence of external root resorption (ERR) on adjacent M2s Single CBCT assessment · Dental imaging studies using CBCT · Age: >= 36 years | Pooled prevalence (%) 21.88 [12.28, 35.48] GRADE not reported 7 studies |
| Patients with impacted third molars (iM3s) and adjacent second molars (M2s) assessed by CBCT | Age <= 25 years | Other categories of the same factor | Prevalence of external root resorption (ERR) on adjacent M2s Single CBCT assessment · Dental imaging studies using CBCT · Age: <= 25 years | Pooled prevalence (%) 20.63 [11.5, 32.89] GRADE not reported 7 studies |
| Patients with impacted third molars (iM3s) and adjacent second molars (M2s) assessed by CBCT | Mandibular iM3s | Maxillary iM3s | Prevalence of severe ERR on adjacent M2s Single CBCT assessment · Dental imaging studies using CBCT · Arch position: mandible | Pooled prevalence (%) 3.85 [1.96, 7.41] GRADE not reported 10 studies |
| Patients with impacted third molars (iM3s) and adjacent second molars (M2s) assessed by CBCT | Maxillary iM3s | Mandibular iM3s | Prevalence of external root resorption (ERR) on adjacent M2s Single CBCT assessment · Dental imaging studies using CBCT · Arch position: maxilla | Pooled prevalence (%) 28.57 [20, 38.27] GRADE not reported 14 studies |
| Patients with impacted third molars (iM3s) and adjacent second molars (M2s) assessed by CBCT | Maxillary iM3s | Mandibular iM3s | Prevalence of severe ERR on adjacent M2s Single CBCT assessment · Dental imaging studies using CBCT · Arch position: maxilla | Pooled prevalence (%) 6.54 [2.91, 10.71] GRADE not reported 8 studies |
| Patients with impacted third molars (iM3s) and adjacent second molars (M2s) assessed by CBCT | Mandibular iM3s | Maxillary iM3s | Prevalence of external root resorption (ERR) on adjacent M2s Single CBCT assessment · Dental imaging studies using CBCT · Arch position: mandible | Pooled prevalence (%) 31.51 [26.47, 37.5] GRADE not reported 18 studies |
| Patients with impacted third molars (iM3s) and adjacent second molars (M2s) assessed by CBCT | Horizontal iM3 inclination | Other categories of the same factor | Prevalence of external root resorption (ERR) on adjacent M2s Single CBCT assessment · Dental imaging studies using CBCT · Inclination: horizontal | Pooled prevalence (%) 45.05 [34.64, 56.14] GRADE not reported 19 studies |
| Patients with impacted third molars (iM3s) and adjacent second molars (M2s) assessed by CBCT | Transverse iM3 inclination | Other categories of the same factor | Prevalence of external root resorption (ERR) on adjacent M2s Single CBCT assessment · Dental imaging studies using CBCT · Inclination: transverse | Pooled prevalence (%) 33.77 [20.63, 49.49] GRADE not reported 9 studies |
| Patients with impacted third molars (iM3s) and adjacent second molars (M2s) assessed by CBCT | Mesioangular iM3 inclination | Other categories of the same factor | Prevalence of external root resorption (ERR) on adjacent M2s Single CBCT assessment · Dental imaging studies using CBCT · Inclination: mesioangular | Pooled prevalence (%) 41.86 [35.06, 49.24] GRADE not reported 19 studies |
| Patients with impacted third molars (iM3s) and adjacent second molars (M2s) assessed by CBCT | Vertical iM3 inclination | Other categories of the same factor | Prevalence of external root resorption (ERR) on adjacent M2s Single CBCT assessment · Dental imaging studies using CBCT · Inclination: vertical | Pooled prevalence (%) 14.53 [9.09, 22.48] GRADE not reported 19 studies |
| Patients with impacted third molars (iM3s) and adjacent second molars (M2s) assessed by CBCT | Distoangular iM3 inclination | Other categories of the same factor | Prevalence of external root resorption (ERR) on adjacent M2s Single CBCT assessment · Dental imaging studies using CBCT · Inclination: distoangular | Pooled prevalence (%) 23.08 [16.67, 31.03] GRADE not reported 17 studies |
| Patients with impacted third molars (iM3s) and adjacent second molars (M2s) assessed by CBCT | Pell and Gregory class B impaction | Other categories of the same factor | Prevalence of external root resorption (ERR) on adjacent M2s Single CBCT assessment · Dental imaging studies using CBCT · Impaction level: class B | Pooled prevalence (%) 30.56 [21.26, 41.86] GRADE not reported 11 studies |
| Patients with impacted third molars (iM3s) and adjacent second molars (M2s) assessed by CBCT | Pell and Gregory class C impaction | Other categories of the same factor | Prevalence of external root resorption (ERR) on adjacent M2s Single CBCT assessment · Dental imaging studies using CBCT · Impaction level: class C | Pooled prevalence (%) 42.53 [28.57, 54.95] GRADE not reported 11 studies |
| Patients with impacted third molars (iM3s) and adjacent second molars (M2s) assessed by CBCT | Pell and Gregory class A impaction | Other categories of the same factor | Prevalence of external root resorption (ERR) on adjacent M2s Single CBCT assessment · Dental imaging studies using CBCT · Impaction level: class A | Pooled prevalence (%) 24.24 [12.28, 42.86] GRADE not reported 10 studies |
| Patients with impacted third molars (iM3s) and adjacent second molars (M2s) assessed by CBCT | iM3 not in contact with M2 | iM3 in contact with M2 | Prevalence of external root resorption (ERR) on adjacent M2s Single CBCT assessment · Dental imaging studies using CBCT · Contact: noncontact group | Pooled prevalence (%) 2.91 [0.99, 9.09] GRADE not reported 6 studies |
| Patients with impacted third molars (iM3s) and adjacent second molars (M2s) assessed by CBCT | iM3 in contact with M2 | iM3 not in contact with M2 | Prevalence of external root resorption (ERR) on adjacent M2s Single CBCT assessment · Dental imaging studies using CBCT · Contact: contact group | Pooled prevalence (%) 39.76 [25.93, 55.17] GRADE not reported 6 studies |
| Patients with impacted third molars (iM3s) assessed by CBCT | Location of iM3 contact on M2 root (apical third) | Contact with cervical or middle third of M2 root | Prevalence of ERR on adjacent second molars Single time point (CBCT assessment) · CBCT based studies of impacted third molars · Contact with apical third vs cervical or middle third Unresolved: the two extractors disagree on this row. | Prevalence of ERR significantly higher with contact at the apical third than at the cervical or middle third (p < 0.00001); 3 studies; pooled estimates in Fig. S11 not given in text GRADE not reported 3 studies |
Included primary studies 26
Open in Studies| Study | Year | Also included by | Outcomes it informs here | Trial data |
|---|---|---|---|---|
| Akkitap 2023 Can the Position of the Impacted Third Molars Be an Early Risk Indicator of Pathological Conditions? A Retrospective Cone-Beam Computed… PMID:37521325 | 2023 | this review only | not stated | not extracted yet |
| Baensch 2024 Prevalence and predictive parameters of external root resorption caused by retained wisdom teeth DOI:10.1007/s00784-024-05964-0 | 2024 | this review only | not stated | not extracted yet |
| Cui 2024 Relationship between the impacted mandibular third molar and adjacent second molar' external root resorption by cone-bean computed… PMID:37992149 | 2024 | this review only | not stated | not extracted yet |
| Gurses 2023 The effect of impacted third molars on second molar external root resorption, a cross-sectional cone beam computed tomography study. PMID:37823291 | 2023 | this review only | not stated | not extracted yet |
| Hermann 2019 Impact of CBCT on treatment decision related to surgical removal of impacted maxillary third molars: does CBCT change the surgical approach? DOI:10.1259/dmfr.20190209 | 2019 | this review only | not stated | not extracted yet |
| Kou 2025 A Prediction Model for External Root Resorption of the Second Molars Associated With Third Molars DOI:10.1016/j.identj.2024.09.031 | 2025 | this review only | not stated | not extracted yet |
| Lacerda-Santos 2023 matched by author and year (probable) | NR | this review only | not stated | not extracted yet |
| Li 2019 External root resorption in maxillary and mandibular second molars associated with impacted third molars: a cone-beam computed tomographic… DOI:10.1007/s00784-019-02859-3 | 2019 | this review only | not stated | not extracted yet |
| Lima 2024 Spatial Position and Anatomical Characteristics Associated with Impacted Third Molars Using a Map-Reading Strategy on Cone-Beam Computed… PMID:38337776 | 2024 | this review only | not stated | not extracted yet |
| Naik 2022 Frequency of Recommending Cone Beam Computed Tomography in Comparison to Panoramic Radiograph, While Diagnosing a Pathology/Status of… DOI:10.4103/jiaomr.jiaomr_156_21 | 2022 | this review only | not stated | not extracted yet |
| Oenning 2014 External Root Resorption of the Second Molar Associated With Third Molar Impaction: Comparison of Panoramic Radiography and Cone Beam… DOI:10.1016/j.joms.2014.03.023 | 2014 | this review only | not stated | not extracted yet |
| Oenning 2015 Mesial Inclination of Impacted Third Molars and Its Propensity to Stimulate External Root Resorption in Second Molars—A Cone-Beam Computed… DOI:10.1016/j.joms.2014.10.008 | 2015 | this review only | not stated | not extracted yet |
| Orhan 2020 Evaluation of Mandibular Third Molar Region in a Turkish Population Using Cone-Beam Computed Tomography DOI:10.2174/1573405616666200103094611 | 2020 | this review only | not stated | not extracted yet |
| Sahin 2019 Structures Suggestive of Carotid Artery Calcifications and Their Prevalence on Digital Panoramic Radiographs Prevalence on Digital… DOI:10.14693/jdi.v26i1.1234 | 2019 | this review only | not stated | not extracted yet |
| Sakhdari 2021 Frequency and Severity of Second Molar External Root Resorption Due to the Adjacent Third Molar and Related Factors: A Cone-Beam Computed… DOI:10.18502/fid.v18i36.7561 | 2021 | this review only | not stated | not extracted yet |
| Schriber 2020 Risk factors for external root resorption of maxillary second molars due to impacted third molars as evaluated using cone beam computed… DOI:10.1016/j.ijom.2019.09.016 | 2020 | this review only | not stated | not extracted yet |
| Smailiene 2019 Relationship between the Position of Impacted Third Molars and External Root Resorption of Adjacent Second Molars: A Retrospective CBCT… PMID:31238599 | 2019 | this review only | not stated | not extracted yet |
| Suter 2019 Risk factors for root resorption of second molars associated with impacted mandibular third molars DOI:10.1016/j.ijom.2018.11.005 | 2019 | this review only | not stated | not extracted yet |
| Tassoker 2019 What Are the Risk Factors for External Root Resorption of Second Molars Associated With Impacted Third Molars? A Cone-Beam Computed… DOI:10.1016/j.joms.2018.08.023 | 2019 | this review only | not stated | not extracted yet |
| Tunc 2020 Evaluation of Risk Factors for External Root Resorption and Dental Caries of Second Molars Associated With Impacted Third Molars DOI:10.1016/j.joms.2020.04.041 | 2020 | this review only | not stated | not extracted yet |
| Velickovic 2019 Analysis of External Root Resorption of the Second Molar Associated with an Impaction of the Third Molar by the Application of CBCT DOI:10.2478/sjecr-2019-0053 | 2021 | this review only | not stated | not extracted yet |
| Wang 2017 External root resorption of the second molar associated with mesially and horizontally impacted mandibular third molar: evidence from cone… DOI:10.1007/s00784-016-1888-y | 2016 | this review only | not stated | not extracted yet |
| Yesiltepe 2022 Evaluation the relationship between the position and impaction level of the impacted maxillary third molar teeth and marginal bone loss,… DOI:10.1007/s11282-021-00554-2 | 2021 | this review only | not stated | not extracted yet |
| Zhang 2024 Full life cycle changes of low impacted mandibular third molar associated cystic lesions and adjacent tooth root resorption: a… DOI:10.1186/s12903-024-04248-z | 2024 | this review only | not stated | not extracted yet |
| Zhou 2023 DOI:10.13701/j.cnki.kqyxyj.2023.03.005 | NR | this review only | not stated | not extracted yet |
| Zou 2023 Is it necessary to remove bone-impacted teeth? A retrospective study DOI:10.1016/j.jormas.2022.10.003 | 2023 | this review only | not stated | not extracted yet |
Review question
| Element | Planned (methods) | Found (results) |
|---|---|---|
| Population | Patients with impacted third molars | 6285 patients with 10,344 iM3s (n=26 studies) |
| Intervention | Exposure: impacted third molars | Impacted third molars (maxillary and mandibular) |
| Comparison | Absence of iM3s or specific characteristics of iM3s | Other categories of iM3 characteristics (no control group of erupted M3s in most studies) |
| Outcomes | External root resorption (ERR) of adjacent second molars on CBCT | ERR prevalence and severity on adjacent M2s (8188 teeth pooled) |
| Study designs | Observational studies (cross-sectional) using CBCT | 26 cross-sectional studies |
| Timing | Not specified | Not specified |