Anatomic considerations for immediate implant placement in the mandibular posterior region –A systematic review and meta-analysis

Abstract

Objectives

To review anatomical considerations for immediate implant placement in the mandibular posterior region using Cone Beam Computed Tomography (CBCT).

Materials and Methods

A systematic electronic literature search was conducted independently by two reviewers across PubMed, Web of Science, ProQuest, Scopus and Cochrane databases, supplemented by a manual search, to identify eligible clinical studies published from 2006 up to October 2024. Studies evaluating anatomical parameters relevant to implant placement were included.

Results

From 1,151 records,12 studies met the inclusion criteria, involving 1,834 patients who received immediate implants in the mandibular posterior region. The meta-analysis showed that the mean distance between the root apex and the inferior alveolar canal was 5.14 mm for premolars, 6.32 mm for first molars, and 4.65 mm for second molars. Undercut ridge morphology was most prevalent at the second molar site (73%), posing a higher risk for lingual plate perforation.

Conclusions

Immediate implant placement in the mandibular posterior region requires careful anatomical assessment, with particular attention to the distance from the inferior alveolar canal and the potential risk of lingual plate perforation, to optimize treatment outcomes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-025-06861-y.

Introduction

Dental implants are now considered as a reliable treatment option for replacing missing teeth both aesthetically and functionally [1]. Immediate dental implant placement (IIP) in a newly extracted tooth site has attracted attention since it was first described (more than 30 years ago) [2]. Reducing the duration, cost and complications of treatment and reducing the number of surgeries are the main advantages of this treatment method [3]. Although IIP has been successful [4], as a procedure it has high technical sensitivity and requires careful planning and choosing the right case to ensure the success of the implant and the final aesthetic results [5]. The indications for immediate implant placement typically include sites with intact socket walls, absence of acute infection, and sufficient bone volume for achieving primary stability. Factors influencing success include patient-related aspects such as systemic health, bone quality, and site-specific anatomy, as well as surgical expertise and implant design [6]. In dentistry, the extraction of mandibular molar teeth is a common phenomenon due to the failure of endodontics treatments, caries or vertical root fracture, and in this case, IIP can be considered [7].

The mandibular molar area is a challenging place for implant placement due to the inferior alveolar canal (IAC) and the concavity of the submandibular fossa, because it can lead to nerve damage and temporary or permanent paresthesia, lingual plate perforation (LPP) and sublingual or submandibular hematomas, accompanied by hemorrhage or infection [8–10].

To achieve initial stability, we need at least 4 mm of native bone to ensure survival of the immediate implant [11].However, the average distance between apex of first and second mandibular molar to inferior alveolar nerve (IAN) is most frequently 1.51 and 3.43 mm [8]. In the region of the first molar of the mandible, it is suggested that at least 2 mm distance should be between the IAN and the implant when placing the implant to ensure that the nerve is not damaged [12].

If LPP occurs in the mandibular molar area and under the mylohyoid muscle at a horizontal distance of about 2 mm from the mandibular second molar, it can cause damage to peri-mandibular vessels and may lead to hemorrhaging [13]. If LPP occurs above the mylohyoid ridge, which is generally the lingual nerve is located there, it can lead to nerve injury [14].

The use of cone beam computed tomography (CBCT) provides a precise tool for measuring bone surface, planning for implants, position of anatomical structures, and evaluating alveolar bone changes after implant placement in the mandible [15]. Many studies have evaluated the efficacy and safety of IIP, the risk of LPP and perforation of the mandibular canal (MCP) and injury to the inferior alveolar nerve associated with posterior mandibular anatomy using CBCT images [16, 17]. Now, a few research has been done on anatomical considerations during IIP in the posterior region of the mandible with the help of CBCT.

While immediate implant placement in the posterior mandible offers clear clinical advantages, its success relies heavily on thorough evaluation of anatomical limitations. Although previous reviews have addressed this topic, the growing number of CBCT-based studies and ongoing debates surrounding anatomical safety zones highlight the need for an updated synthesis. This review aims to consolidate recent evidence, explore underreported variables, and provide clinically applicable guidance. By systematically evaluating bone morphology, neurovascular anatomy, and other critical parameters, it seeks to support safer and more predictable implant planning.

Materials and methods

The methodology of this study was registered in the Open Science, under registration number 10.17605/OSF.IO/YBSU4 and is prepared in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and Cochrane Collaboration guidelines [18, 19].

The purpose of the present review was to assess the null hypothesis of IIP in mandibular molar area is safe. The focused question was: “During the IIP in the posterior region of the mandible, what are the significant anatomic considerations and which receiving region has greater risk of injury?”

Search strategy

An electronic search, with no time restrictions, was performed and was restricted to English articles in PubMed, Cochrane, Web of Science (WOS), ProQuest and Scopus, restricted from 2006 to October 2024. The following search model was accomplished using Boolean operators: ((immediate implant placement OR fresh socket implant* OR implant*) AND (mandibular posterior region OR molar region OR mandibular premolar OR anatomic consideration*) AND (CBCT analysis OR Cone-beam computed tomography)) in TITLE/SUBJECT/ABSTRACT based on the search strategy of each database (Table S1). Also, the reference part of the included studies (cross-referencing) was searched for possible further studies.

Selection criteria

Literature search was performed to detect clinical trial, cohort and cross-sectional studies. Exclusion criteria were case reports, case series, articles that did not use CBCT images and reviews. Studies providing data for CBCT analysis about anatomical consideration such as the relationship between IAN and the root apices, mandibular cross-sectional morphology, lingual undercut and risk of LLP for IIP in mandibular molar area were considered eligible at first analysis (Table S2).

Screening and selection of papers

After eliminating duplicates through both automated and manual methods, the titles and abstracts of the search results were initially reviewed by two independent authors (R.M. and Z.A.). Studies were eligible for full-text evaluation if they met the inclusion criteria during the initial analysis or if there was insufficient information in the title and abstract. Any disagreements between the authors were resolved through discussion. After a thorough assessment, studies were either included or excluded from the review.

Characteristics of outcome measures

Primary outcome measures

• The average distance between the root apices of the mandibular molars and the inferior alveolar canal is measured in millimeters, along with the percentage of subjects identified as being at high risk for inferior alveolar nerve injury.

Secondary outcome measures

• • Lingual undercut.

• • Mandibular cross-sectional morphology.

Quality assessment

Whereas all included articles are cross sectional studies; Quality assessment was performed by the Modified STROBE checklist. This checklist consists of 12 questions that cover several aspects of the methodology including sample size, study design, sampling method, population, data collection methods and tools, examining samples method, statistical analysis, aim of the study, way of reporting findings, and reporting findings based on objectives. Based on this checklist, each study was given a score from 0 to 12. If the score of a study is less than 8, it is removed from the systematic review. All articles were evaluated for inclusion in the evidence base by two trained referees and independently evaluated based on the inclusion criteria. A third reviewer was invited to re-evaluate disputed articles to resolve conflicts (Table S3).

Data extraction

The following data were extracted from the included studies for further investigations: First author, Year of publication, Country, Patient sex/age, Study design, Number of implants/patients, CBCT characteristics, Site, Race, mean distance between the root apices and the IAC, Mean distance between the roots and the outer lingual cortex.

Statistical analysis

Comprehensive meta-analysis (V3, Biostat) was used to conduct the meta-analysis. The pooled prevalence of C, P and U type of mandibular ridge morphology was calculated with 95% confidence intervals (CIs) using a random-effect model considering the observed heterogeneity [20]. The statistical heterogeneity within studies was quantified using I 2 statistics (I 2 = 0%−25%, no heterogeneity; I 2 = 25%−50%, moderate heterogeneity; I 2 = 50%−75%, large heterogeneity; and I 2 = 75%−100%, extreme heterogeneity) [21].

A separate meta-analysis was performed to evaluate the mean distance between the IAC and the root apex, reported with 95% CIs using the same random-effects model. Heterogeneity analysis was conducted as described above.

Publication bias was assessed by funnel plot, Egger’s weighted regression, and Begg’s rank correlation method [22].

Results

Study selection

The initial search of the database resulted in 1151 publications: 541 from PubMed, 54 from Scopus, 436 from WOS, 58 from Cochrane, and 62 from ProQuest. After removing duplicates, 933 unique studies were retained, and one additional article was identified through manual searching. Following the screening of titles and abstracts, 21 articles were chosen for full-text evaluation. After reviewing these articles, 9 were excluded for not involving IIP (as detailed in Flowchart [Fig S1]). Thus, the final selection included 12 articles, consisting of 9 cross-sectional studies and 3 retrospective studies [17, 23–33]. These studies were chosen based on specific inclusion and exclusion criteria, focusing on the anatomical considerations for IIP in the mandibular posterior region. The kappa value for inter-reviewer agreement was 0.91. The primary parameters analyzed included the location of the IAC from various reference points, the risk of LLP, and the morphology of the mandibular ridge.

Characteristics of the included studies

Table S4 presents a detailed summary of the 12 included studies, outlining key characteristics such as study design (e.g., retrospective/prospective), sample size, age range, population demographics (including sex and race when reported), CBCT imaging parameters, and specific anatomical outcome measures relevant to immediate implant planning in the posterior mandible.

Risk of bias assessment

Assessing the risk of bias is crucial in ensuring the reliability and validity of findings in systematic reviews. In this study, the risk of bias in the included studies was evaluated using the Modified STROBE checklist, which includes 12 questions that address different aspects of study methodology, such as sample size, study design, sampling methods, data collection techniques, and statistical analysis.

Studies were scored on a scale from 0 to 12 based on their adherence to these criteria. A threshold score of 8 was set, with studies scoring below this threshold considered to have a high risk of bias and subsequently excluded from the review.

As shown in Table S3, all 12 included studies scored between 11 and 12, indicating consistently high methodological quality. The mean score was 11.416, reflecting strong adherence to scientific standards across studies. Common strengths included clear research questions, appropriate methodology, and sufficient supporting evidence. However, several studies did not clearly report the role of the researcher, which was the most frequently missing criterion. Overall, the included studies demonstrated low risk of bias, supporting the credibility of the review’s conclusions.

Qualitative and quantitative assessment

 Location of the inferior alveolar Canal (IAC)

The studies investigated the position of the IAC using various anatomical landmarks. The distance between the IAC and key reference points such as the root apex of mandibular second premolar (2PM), first molar (1 M), and second molar (2 M), the furcation of first and second molar, and the alveolar crest was measured.

• Findings: 8 studies investigated the mean distance from the IAC to the root apices of the 1 M and 2 M, and 2PM [23–25]28– [30, 32, 34]. The distance varied significantly across studies, which is shown in table S4.

• 2 studies evaluated the distance from furcation to IAC (IAC-F), one reported a mean distance of 14.14 + 2.57 and in 24% of the 1Ms, the IAC-F was < 10 mm [23]. Another Study reported 3% of 1Ms and 13.4% of 2Ms with less than 10 mm distance for IAC-F [28].

Table 1.

Root-to-Inferior alveolar Canal distances in mandibular teeth: summary of included studies

Distance To Alveolar canal		Author	Year	Site	Result
	1	Bahaa Haj(24)	2021	5,6,7	The average root-to-alveolar canal (RAC) distance was measured at 7.6 ± 2.7 mm for the 1 M, 6.5 ± 3 mm for the 2PM, and 5.4 ± 3 mm for the second molar (2 M). The mean RAC distance for each root type ranged from 5.2 mm for the mesial root of the 2 M to 7.7 mm for the roots of the right 1 M.
	2	Padhye(23)	2020	6	The average distance from the IAN to the furcation (IAN-F) was 14.14 ± 2.57 mm. In 24% of the study population, the IAN-F distance was less than 10 mm. The mean distances from the IAN to the mesial roots and distal roots were 4.31 ± 1.06 mm and 4.61 ± 1.02 mm, respectively.
	3	Chrcanovic (25)	2016	5,6,7	The mean distance from the tooth apex to the inferior alveolar canal (DTC) was 3.76 ± 2.39 mm for the 2PM, 4.39 ± 2.58 mm for the 1 M, and 4.38 ± 2.45 mm for the 2 M. The DTC was greater for the first molar and progressively shorter for the second premolar and second molar. The percentages of teeth with a DTC of less than 6 mm were as follows: 75.4% for the right second premolar 2PM, 78.0% for the left 2PM, 70.3% for the right 1 M, 71.2% for the left 1 M, and 88.1% for both the right and left 2 M.
	4	J.Y. Ho (28)	2022	6,7	The 2 M was significantly closer to the IAC than the 1 M. A furcation-to-IAC distance of less than 10 mm was found in 3% of 1Ms and 13.4% of 2Ms. A mesial root apex-to-IAC distance of less than 2 mm was observed in 6.9% of 1Ms and 20% of 2Ms, while the distal root apex-to-IAC distance of less than 2 mm was found in 8.8% of 1Ms and 35% of 2Ms. On average, the mesial and distal root distances to the IAC for 2Ms were 3.78 ± 2.31 mm and 3.03 ± 2.24 mm, respectively.
	5	K. Rameswaran (32)	2021	3,4,5	The mean distance from the root apex to the nerve canal increased from the canine to the 1PM, but then decreased for the second premolar, reaching a distance like the canine. The overall mean root apex-to-nerve canal distances were: 4.10 ± 2.28 mm for the canine, 5.12 ± 2.86 mm for the 1PM, and 4.24 ± 2.46 mm for the 2PM.
	6	M.H.Lin (30)	2014	5,6,7	The mean RAC distances were 6.1 ± 2.7 mm for the 2PM, 7.0 ± 2.9 mm for the 1 M, and 4.3 ± 2.7 mm for the 2 M.
	7	Kovisto(29)	2011	5,6,7	The distal root of the 2 M had the shortest distance to the mandibular canal, averaging 1.42 mm, while the 2PM had the greatest distance, averaging 2.64 mm. In general, the roots of the 2 M were located closer to the mandibular canal than those of the 2PM or the 1 M.
	8	Zhan (33)	2023	4,5	In the mandibular premolars, 12.33% of first premolars and 20.33% of second premolars had a root apex-to-inferior alveolar nerve or mental foramen distance of less than 4 mm.

Correlation of gender/age/side and anatomic considerations

Gender

Findings: Six studies investigated the relationship between gender and anatomical factors that affect IIP [24, 25]27– [29, 31].

Chrcanovic et al. reported weak associations between sex and morphometric parameters [25]. In contrast, Yahya et al. found that female patients exhibited significantly shorter mean distances to the outer lingual cortex (DLC) and RAC compared to males, along with a higher risk of IAN injury during immediate implant placement IIP [24]. Similarly, Ho et al. observed that females had shorter distances from the interradicular septum crest and mesial root apex to the IAC, as well as reduced root cone heights in first and second molars. These findings suggest that female patients may be at greater risk of injury to the inferior alveolar neurovascular bundle when utilizing apical bone for primary implant stability [28]. Huang et al. found a difference in ridge morphology types (C, P, and U types) between sexes. However, no significant difference was observed between the sexes concerning the LPP [27]. Kovisto et al. observed that sex differences influence the proximity of the mandibular canal to root apices, with the canal being significantly closer to the mesial and distal roots of the mandibular second molar in female subjects over 49 years old compared to males of the same age group [29].

Age

Findings: Five studies examined the relationship between age and anatomical factors influencing IIP [24–26, 29, 31].

Yahya et al. reported that the RAC distance was significantly lower in patients under 40 compared to older patients [24]. Kovisto et al. generally observed that the distance between the mandibular canal and root apices increased with age [29]. Chrcanovic et al. identified a very weak to weak relationship between age and the distance to the DLC for most teeth [25]. Kong et al. observed no age-related differences in the angles formed by the tooth axis, alveolar bone axis, and basal bone axis [31]. Similarly, Chen et al. reported no, very weak, or weak correlations between age and parameters such as the distances from the implant surface to the buccal and lingual plates, as well as the cross-sectional morphology of the mandible [26].

Sides

Findings: One study evaluating the influence of contralateral side on anatomical factors relevant to IIP found no statistically significant differences [31].

Risk of lingual plate perforation

The risk of LLP during implant placement was assessed by several studies, assessing the ridge morphology, degree of concavity, and the height and depth of lingual concavity. Only some of these studies reported the actual risk of lingual perforation.

• Findings: Six studies investigated the risk of LLP during IIP in the posterior mandibular region, focusing on the relationship between LLP and both the morphology of the mandibular ridge and the implant placement site [17, 24, 26, 27, 31, 32].

The studies collectively emphasize a notable risk of LPP during IIP in the mandibular posterior region, particularly in U-type cross-sections and at more posterior sites. Sun et al. found that U-type cross-sections in 2 M sites, particularly with 4.8 mm implants, had the highest LPP incidence (22.2%) [17]. Yahya et al. reported considerable LPP risks of 70% in 1Ms and 76% in 2Ms, with high-risk rates of 18% and 44%, respectively [24]. Rameswaran et al. noted a general increase in LPP risk with larger implant diameters, though the overall incidence was low (1.2%) [32]. Chen et al. found that the risk of LPP was greater in the region of the mandibular second molar than in that of the first molar [26]. Huang et al. identified that LPPs was most observed at the second molar and with a U-type ridge and that LPP probability decreased by 34% for every 1 mm increase in RAC [27]. Kong et al. reported that the concave type, present in 11% of cases, posed the greatest challenge for implant placement due to the elevated risk of lingual perforation. This type required more careful consideration of the implant’s length, width, and direction [31].

Meta-analysis

Morphology of the mandibular ridge

The statistical analysis focused on synthesizing data on the morphology of the mandibular ridge based on Chen’s classification [14] into three groups: convergent (C), parallel (P), and undercut (U) (Figure S2). A meta-analysis was conducted using a random-effects model to integrate findings from multiple studies (Table S5).

Forest plots (Figs. 1, 2 and 3) and Funnel plots (Figure S3, S4 and S5) were generated to represent the event rates and their 95% confidence intervals (CIs) for each ridge type:

Fig. 1.

Forest plots for type-C ridge morphology (A), for type-P ridge morphology (B) and for type-U ridge morphology (C) in mandibular first molar

Fig. 2.

Forest plots for type-C ridge morphology (A), for type-P ridge morphology (B) and for type-U ridge morphology (C) in mandibular second molar

Fig. 3.

Forest plots for type-C ridge morphology (A), for type-P ridge morphology (B) and for type-U ridge morphology (C) in mandibular first and second molar

First molar site

• Convergent: 29.5% (95% CI: 20.1% − 41.1%) from 5 studies (df = 4, I² = 89.663).

• Parallel: 35% (95% CI: 20.8% − 52.6%) from 5 studies (df = 4, I² = 94.868).

• Undercut: 41.1% (95% CI: 27.6% − 56%) from 5 studies (df = 4, I² = 93.471).

Second molar site

• Convergent: 9.0% (95% CI: 4.0% − 18.9%) from 5 studies (df = 4, I² = 90.483).

• Parallel: 15.4% (95% CI: 8.6% − 26.1%) from 5 studies (df = 4, I² = 89.601).

• Undercut: 73% (95% CI: 62.5% − 81.4%) from 5 studies (df = 4, I² = 87.619).

Total event rate

• Convergent: 25% (95% CI: 17.9% − 33.7%) from 3 studies (df = 2, I² = 74.071).

• Parallel: 25.2% (95% CI: 17.5% − 34.9%) from 3 studies (df = 2, I² = 77.596).

• Undercut: 49.2% (95% CI: 40.3% − 58.2%) from 3 studies (df = 2, I² = 73.267).

These findings highlight significant variations in ridge morphology, with the undercut type being most prevalent, especially in the second molar site. This information is crucial for planning IIP to reduce complications.

The distance between IAC and root apex

For the premolar teeth, the meta-analysis included data from 4 studies (Fig. 4, S6), yielding a pooled mean distance to the IAC of 5.146 mm (95% CI: 3.832 to 6.460 mm, p < 0.001) with significant heterogeneity (Q = 103.131, df = 3, p < 0.001, I² = 97.091%); for the first molar, the meta-analysis included data from 3 studies (Fig. 5, S7), yielding a pooled mean distance of 6.329 mm (95% CI: 4.477 to 8.182 mm, p < 0.001) with significant heterogeneity (Q = 101.432, df = 2, p < 0.001, I² = 98.028%). for the second molar, the meta-analysis included data 3 studies (Fig. 6, S8), yielding a pooled mean distance of 4.653 mm (95% CI: 4.057 to 5.249 mm, p < 0.001) with moderate heterogeneity (Q = 10.563, df = 2, p = 0.005, I² = 81.066%). Funnel plots for the premolar, first molar, and second molar analyses showed asymmetry, with all studies reporting positive mean distances (3.760–6.500 mm for premolars, and 4.390–7.600 mm for first molar, 4.300–5.400 mm for second molar) and standard errors between 0.3 and 0.95, suggesting potential publication bias where studies with smaller distances may have been underreported, though the small number of studies (n = 3–4 per tooth) limits reliability.

Fig. 4.

Forest plots for the distance between IAC and root apex of the 2PM

Fig. 5.

Forest plots for the distance between IAC and root apex of the 1 M

Fig. 6.

Forest plots for the distance between IAC and root apex of the 2 M

Discussion

The anatomical considerations outlined in this review are critical for the successful placement of immediate implants in the mandibular posterior region. The variability in the location of the IAC, the risk of LLP, and the morphology of the mandibular ridge must be carefully considered during surgical planning. The findings underscore the importance of individualized treatment planning and the use of advanced imaging techniques to minimize complications. CBCT provides high-resolution, cross-sectional images, making it highly effective for making linear measurements in the posterior regions of the mandible and maxilla, ensuring precise localization of vital anatomical structures.

Distance of the IAC from root apices and clinical implications

The proximity of the implant to the IAC is a critical consideration in IIP due to the risk of nerve injury. Our review found significant variability in the reported distances between the IAC and the root apices of mandibular molars. Pooled data revealed that the mean distance was greatest in the first molar region (6.32 mm), followed by the premolars (5.14 mm), and shortest in the second molar region (4.65 mm). These findings align with anatomical expectations, reinforcing the need for heightened caution during IIP in posterior sites—particularly near second molars, where the IAC is often closest.

Individual studies reported varying distances between the IAC and the apices of the first molar. Such variability may stem from differences in study populations, measurement techniques, and anatomical diversity. The observed heterogeneity, along with funnel plot asymmetry, also suggests potential publication bias, highlighting the necessity for further standardized, large-scale studies. Clinically, these measurements are vital for avoiding complications like nerve damage and paresthesia, emphasizing careful preoperative planning to ensure safe implant positioning.

Ridge morphology and implant placement

This review’s findings indicate significant variations in ridge morphology across different sites, with the undercut type being the most prevalent, especially in the second molar site. Specifically, the event rates for the undercut type were notably high: 41.1% on the first molar site and 73% on the second molar site. This prevalence underscores the importance of detailed pre-surgical planning and the use of advanced imaging techniques like CBCT to accurately assess the ridge morphology and minimize the risk of complications.

Risk of lingual plate perforation

The risk of LPP is a critical concern in the posterior mandibular region, particularly given the proximity to the inferior alveolar canal and the concavity of the submandibular fossa. Our review of the literature revealed that the risk of LPP is highest in U-type cross-sections and more posterior sites. For instance, Yahya et al. reported considerable LPP risks of 70% in first molars and 76% in second molars [24]. This highlights the necessity for clinicians to exercise caution and consider alternative techniques or adjunctive procedures to mitigate these risks.

Implications for clinical practice

The high prevalence of the undercut ridge type and the associated risks of LPP necessitate meticulous case selection and planning. Clinicians should be aware that the mean distance from the root apex to the IAC varies by tooth position—averaging 5.14 mm for second premolars, 6.32 mm for first molars, and 4.65 mm for second molars. A safety margin of at least 2 mm from the IAC is advisable during implant planning. The prevalence of undercut (U-type) ridge morphology—especially in the second molar region (73%)—further increases the risk of lingual plate perforation and must be assessed preoperatively via CBCT. Advanced imaging tools, such as CBCT, offer detailed anatomical visualization that can aid in evaluating bone volume and identifying vital structures, although further comparative studies are warranted to establish its definitive clinical superiority. Ensuring a safe distance from the IAC is paramount to avoid nerve damage. Furthermore, primary implant stability is significantly influenced by bone density and cortical thickness in the posterior mandible. Recent studies have demonstrated that higher bone density correlates with increased primary stability, emphasizing the need for thorough preoperative assessment of bone quality [35].

Limitations and future research

While our meta-analysis provides valuable insights, there are limitations to consider. The included studies varied in their methodologies and populations, which may contribute to the observed heterogeneity in results. Future research should aim to standardize assessment protocols and include larger, more diverse populations to enhance the generalizability of findings. CBCT-based measurements, though widely accepted, may be influenced by voxel size, beam hardening, or landmark identification errors; although cadaver studies generally support CBCT’s reliability, minor discrepancies may exist [36]. Future studies should also explore the role of interradicular septa in achieving primary stability during immediate implant placement in the posterior mandible, as they may offer additional support for implant anchorage [37]. Future studies should also develop and validate clinical protocols for immediate implant placement in posterior mandibular sites to minimize complications such as lingual plate perforation and guide appropriate management strategies when such risks are present. As the review focused on describing anatomical parameters, the ‘Comparison’ element of PICOS was not applicable and represents a limitation.

Conclusion

In conclusion, this systematic review and meta-analysis underscore the critical role of ridge morphology, neurovascular anatomy, and site-specific factors in determining the suitability of immediate implant placement (IIP) in the posterior mandibular region. The high prevalence of undercut ridges—especially in second molar sites—along with proximity to the inferior alveolar canal (mean distances: 5.14 mm for premolars, 6.32 mm for first molars, and 4.65 mm for second molars), and the elevated risk of lingual plate perforation, necessitate meticulous case selection and surgical planning. Incorporating advanced imaging techniques such as CBCT, along with a clear understanding of anatomical limitations and clinical indications, is essential to optimize outcomes and minimize complications.

Abbreviations

CBCT

Cone Beam Computed Tomography

IIP

Immediate dental implant placement

IAC

Inferior alveolar canal

LPP

Lingual plate perforation

IAN

Inferior alveolar nerve

WOS

Web of Science

MCP

Mandibular canal perforation

2PM

Second premolar

1M

First molar

2M

Second molar

IAC-F

Distance from furcation to IAC

IAN-F

Distance from furcation to IAN

DTC

Distance from the Tooth apex to the inferior alveolar Canal

RAC

Root-to-alveolar canal

DLC

Distance to the outer lingual cortex

C

Convergent

P

Parallel

U

Undercut

CI

Confidence interval

Authors' contributions

P.B: Original Draft Preparation, Writing – Review & Editing, SupervisionR.M: Methodology, Data Curation, Original Draft Preparation, Writing – Review & EditingM.A: Methodology, Original Draft Preparation, Writing – Review & EditingZ.A: Conceptualization, Methodology, Data Curation, Formal Analysis, Original Draft Preparation, Writing – Review & Editing.

Funding

Isfahan university of medical science with grant number: IR.MUI.DHMT.REC.1403.050.

Data availability

All data supporting the findings of this study are included in the supplementary files accompanying this article.

Declarations

Ethics approval and consent to participate

This study was conducted in accordance with ethical standards and received approval from Medical Ethics Committee, Faculty of Dentistry with reference number: IR.MUI.DHMT.REC.1403.050.

Not applicable.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.