The clinical benefit of alveolar ridge preservation in the posterior maxilla: a systematic review and meta-analysis

Abstract

This study aimed to collectively synthesize the available evidence on the effect of alveolar ridge preservation at the posterior maxilla in reducing maxillary sinus pneumatization after tooth extraction, and the necessity of sinus floor augmentation during implant placement. Database search, along with additional screening in the grey literature were conducted, to find clinical studies where ridge preservation was performed in the posterior maxilla, and was compared with normal healing. Eleven studies were included, with 185 and 203 sites for the test and control groups, respectively. Ridge preservation significantly decreased sinus pneumatization (SMD = − 0.88, 95% CI − 1.19 to − 0.58, p-value < 0.00001) and reduced the need for additional sinus floor augmentation when placing dental implants (OR = 0.18, 95% CI 0.09 to 0.36, p-value < 0.00001). Moreover, ridge height was significantly greater (SMD = 1.33, 95% CI 0.58 to 2.09, p-value = 0.0005), while ridge width did not show a statistical significance, compared to spontaneous healing (p-value = 0.053). Therefore, alveolar ridge preservation in the posterior maxilla decreases sinus pneumatization, as well as the need for sinus floor augmentation at the time of implant placement, along with its general benefits in preserving bone volume. Nevertheless, future comparisons are still needed, considering the small number of studies available.

Introduction

The loss of alveolar bone structure following tooth extraction is an absolute outcome^1–3. This phenomenon is more evident in the posterior region of the maxilla, which undergoes alveolar bone resorption that is further exacerbated by additional factors, namely the quality of bone and sinus pneumatization^4,5. The latter has been related to certain considerations, such as genetics, the force of air pressure inside the sinus, and previous surgical procedures in the area. This generally leads to more bone resorption, compared with other regions of the jaw^6,7.

Alveolar ridge preservation is a well-established procedure that has been proposed to limit the event of bone resorption following tooth extraction. Several reports have shown its benefit in reducing ridge resorption and maintaining acceptable bone volume⁸. Studies have indicated that no material or technique is superior to another and all methods lead to somewhat similar outcomes^9–13.

With respect to the posterior area of the maxilla, various investigations have been performed to evaluate whether ridge preservation decreases sinus pneumatization and the need for additional sinus floor augmentation at the time of implant placement, compared to normal healing, in addition to its main advantage of preserving alveolar ridge dimensions^4,7,14. However, these reports were based on a small number of cases, thus, not being able to present conclusive results, i.e., some studies demonstrated the efficacy of ridge preservation in reducing sinus pneumatization and further sinus procedures at the time of implant insertion¹⁵, while others did not show a significant benefit⁷. Additionally, previous systematic reviews focused on the posterior area overall (i.e., maxilla and mandible) to evaluate whether ridge preservation reduces the need for additional augmentation^16,17. This does not provide sufficient insight, considering the major difference in the nature of this procedure between the two jaws (basic guided bone regeneration in the mandible versus sinus floor augmentation in the maxilla). Moreover, several recent reports concerning the maxillary posterior region have been published, which raises interest in further investigating this aspect^7,14,15,18.

Therefore, the aim of this systematic review and meta-analysis was to collectively synthesize and evaluate the available evidence on the effect of ridge preservation in limiting the pneumatization of maxillary sinus after tooth extraction and the decreasing the necessity of further sinus floor augmentation during implant placement, in order to obtain more conclusive results, and provide considerations that support clinical practice.

Methods

This investigation was registered in the PROSPERO database (CRD42024590227) and performed following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement¹⁹.

In order to develop a robust search strategy and include suitable studies based on relevant criteria, the PICO protocol was implemented.

Population (P): patients with posterior maxillary teeth indicated for extraction.

Intervention (I): alveolar ridge preservation.

Comparator (C): normal/clot healing.

Outcome (O): primary outcomes: sinus pneumatization and the need for additional augmentation at the time of implant placement. secondary outcomes: alveolar ridge volumetric changes (height and width) at the final follow-up.

Therefore, the formulated search question was:

In patients having posterior maxillary teeth indicated for extraction (P), what is the clinical benefit of alveolar ridge preservation (I) in reducing maxillary sinus pneumatization, as well as the need for additional sinus floor augmentation at the time of implant placement (O), compared to spontaneous healing (C)?

Search strategy

Database search was carried out in MEDLINE/PubMed, Cochrane Central Register of Controlled Trials (CENTRAL), as well as Scopus. No restrictions, such as article language or the date of publication, were applied during the search process. A combination of MeSH terms and free keywords was used to find potential studies to be included. The set of keywords was (“ridge preservation” OR “socket preservation” OR “socket grafting”) AND (“maxilla” OR “maxillary” OR “molar”).

An additional search stage was done in the grey literature (Google Scholar), aiming to find more articles if available. The date of ending the overall literature search phase was May 20, 2025.

Study selection

Investigations selected for this systematic review and meta-analysis were (1) clinical studies (prospective and retrospective), where (2) alveolar ridge preservation was done in the posterior maxillary region, and (3) was compared to spontaneous healing, (4) focusing on the outcomes of sinus pneumatization, the need for additional sinus augmentation when placing implants, as well as the changes in alveolar ridge dimensions, (5) after a minimum of a 3-month follow-up period. Investigations that evaluated soft tissue changes only were excluded from this systematic review.

The literature search was performed independently by 2 reviewers (B.M, S.J). Disagreements concerning the inclusion of identified studies were overcome by discussion or seeking a third reviewer’s (A.P) opinion. To navigate and select suitable studies, Rayyan website (Rayyan, Qatar Computing Research Institute, Qatar Foundation) was utilized²⁰. Screening through the references of the included studies was done also, attempting to find more potential studies to be added.

Data extraction

The data items compiled from the included studies were study design, sample size, extracted teeth, reasons for tooth extraction, baseline ridge dimensions (height and width), material used for ridge preservation, material for graft coverage (i.e., site closure), length of follow-up, and the outcomes of interest; sinus membrane pneumatization, need for additional sinus floor augmentation when placing dental implants, as well as ridge height and width changes compared to the baseline. Additional information related to the main outcomes were also extracted, represented by the method of measuring sinus pneumatization, and the minimum length of implants inserted in the grafted sites.

Risk of bias and quality assessment

The risk of bias in the randomized clinical trials (RCTs) was assessed with the revised Cochrane risk-of-bias tool for randomized trials (RoB 2)²¹. This tool includes five aspects or domains to evaluate, bias arising from the randomization process, bias due to deviations from intended interventions, bias due to missing outcome data, bias in measurement of the outcome, and bias in selection of the reported result. The level of bias for each study was determined based on the questions in the excel tool of RoB2.

Regarding the controlled clinical trials (CCTs), the Risk of Bias in Non-randomized Studies – of Interventions (ROBINS-I) tool was utilized²². This tool has 3 main aspects (pre-intervention, at intervention, post-intervention), divided into 7 domains to criticize. Each study was reported as having a low, moderate, or serious risk of bias.

The figure of the risk of bias in the included prospective clinical trials was created with the Risk of Bias Visualization Tool (robvis)²³.

As for the retrospective studies, the Newcastle–Ottawa Scale (NOS) was implemented, which criticizes studies in relation to three aspects: selection of the sample, comparability of the groups, and assessment of the outcomes. A maximum of 9 points is given, based on certain considerations. Studies were judged to be of a good quality if they achieved a score of 7 or higher.

Data synthesis

Means and standard deviations (SD) of sinus pneumatization, as well as alveolar ridge width and height were collected from the included studies undergoing the meta-analysis. Ridge width at the closest point to the alveolar crest (1 mm below the crest, based on the included studies) was selected as the representative value of this outcome. For studies that did not report the height change in the center of the socket but presented the mean change in the buccal and palatal aspects, the combined mean and the pooled standard deviations were calculated using Cohen’s formula for the pooled standard deviation²⁴, in order to obtain a similar format to the other investigations. Moreover, for trials that had two ridge preservation/control groups with a different sample size for each^14,15, the data from the two relevant groups (i.e., means and SDs) were combined and used in the meta-analysis²⁵. The number of cases needing additional sinus procedures at the time of implant placement was also extracted from the included studies to undergo meta-analysis.

Considering the different methods of measuring the continuous data, the related outcomes were analyzed using the standardized mean difference (SMD) with the 95% confidence interval (CI). As for the dichotomous data, they were pooled and presented as Odds ratio (OR) with the 95% CI. The extent of heterogeneity in the included studies under each of the outcomes was evaluated with the Chi² test and I² static, where I² values of 25%, 50%, and 75% were considered to be low, moderate, and high heterogeneity, respectively²⁶. When I² values of 50% or higher were seen, the random-effect model was applied, in order to reduce the possible bias arising from methodological differences between the analyzed studies. If no evidence of significant heterogeneity was noted, the fixed-effects model was used.

To further validate the main results, subgroup analysis was performed, including prospective studies only. Since both randomized and non-randomized trials were included in this meta-analysis, an additional step was taken, where a design-adjusted approach was performed, in which the collective effect size from the non-randomized studies was first calculated, to decrease their magnitude on the main meta-analysis results. Then, these estimates of effect were pooled with the results of the randomized studies in additional meta-analyses^3,27. Moreover, another subgroup analysis was conducted, including investigations where ridge preservation was performed using the same grafting material and membrane, in order to confirm the validity of the main analyses, based on the most homogenous trials.

Sensitivity analysis was also carried out, first by excluding each of the included studies under one meta-analysis at a time, and then by removing studies with potential risk of bias, aiming to evaluate the robustness of the meta-analysis, and investigate whether certain studies had a significant influence on the outcomes^28,29.

P-values of < 0.05 represented a significant difference between the study and control groups. Forest plot for each meta-analysis was generated to illustrate the outcomes. All data were analyzed with the Review Manager software, version 5.4 (2020; The Nordic Cochrane Centre, The Cochrane Collaboration, Copenhagen, Denmark).

Certainty of evidence

The level of evidence was determined using the GRADE rating system³⁰, which sets the quality of evidence from each of the meta-analysis outcomes as “high”, “moderate”, “low”, or “very low” based on several important aspects (risk of bias, imprecision, inconsistency, indirectness). The table of the certainty of evidence was generated using the GRADEpro website³¹.

Results

Literature screening outcomes

The number of articles identified from the databases and the manual search was 1294. Following the stage of removing the duplicates and screening the titles and abstracts for relevant papers, 38 studies reached the full-text assessment phase. This process led to the exclusion of 27 investigations. Consequently, 11 publications were included in this systematic review and meta-analysis (Fig. 1)^{4,7,9,14,15,18,32–36}.

Fig. 1.

PRISMA flowchart of the search process.

Study characteristics

Table 1 presents the characteristics of the included studies.

Table 1.

Characteristics of the included studies.

Study	Design	Sample	Tooth extracted	Reason for tooth extraction	Baselines ridge height (mm)	Baseline ridge width (mm)	Material for ridge preservation	Graft coverage	Follow-up
Dai 2025	Retrospective case–control	Test: 9 Control: 29	Molars	Periodontitis	Test: 13.61 ± 2.9 Control: 14.54 ± 3.04	Test: 8.21 ± 2.04 Control: 7.40 ± 1.93	DBBM	Collagen membrane/Collagen sponge	6–9 months
Khoury 2024	CCT	Test: 31 Control: 22	Premolars, molars	–	Test: 11.78 ± 3.09 Control: 11.13 ± 2.12	–	DBBM	Collagen membrane	6 months
Lam 2024	RCT	Test 1: 8 Test 2: 10 Control: 10	Second premolar, molars	Caries, endodontic failure, root/coronal fracture, periapical lesion/abscess	Test 1: 5.9 ± 2.4 Test 2: 5.4 ± 2.2 Control: 6.8 ± 0.8	–	Test 1: DBBM particles Test 2: DBBM blocks	Collagen membrane	4 months
Khaddour 2024	Retrospective case–control	Test: 17 Control: 22	Molars	Caries, endodontic failure, periodontitis, fatigue fracture	Test: 13.61 ± 2.92 Control: 14.54 ± 3.04	Test: 8.21 ± 2.04 Control: 11.12 ± 1.46	A-PRF	Collagen sponge	3 months
Wei 2022	CCT	Test: 18 Control: 18	Molars	Periodontitis	Test: 4.09 ± 4.29 Control: 4.99 ± 4.53	Test: 5.60 ± 6.11 Control: 4.94 ± 5.22	DBBM	Collagen membrane + collagen sponge	6 months
Shuman 2021	RCT	Test: 12 Control: 12	Molars	–	Test: 9.36 ± 1.54 Control: 8.95 ± 1.51	–	DBBM	Platelet-rich fibrin	6 months
Lee 2020	RCT	Test 1: 10 Test 2: 10 Control: 8	Molars	–	–	–	Test 1: DBBM + EMD Test 2: DBBM	Collagen membrane	5 months
Cha 2019	RCT	Test: 20 Control: 19	Molars	Periodontitis, cracks, endodontic failure	Test: 7.60 ± 0.42 Control: 2.84 ± 0.45	Test: 9.89 ± 0.98 Control: 7.81 ± 0.86	DBBM	Collagen membrane	6 months
Lombardi 2018	CCT	Test: 13 Control: 13	First molars	–	Test: 8.34 ± 3.25 Control: 6.40 ± 1.64	Test: 11.27 ± 1.71 Control: 12.06 ± 2.46	Synthetic nano-hydroxyapatite	Hemostatic sponge	6 months
Levi 20,217	Retrospective case–control	Test: 21 Control: 42	Second premolar, molars	–	Test: 8.79 ± 4.18 Control: 9.86 ± 4.73	–	DBBM	NR	8 months
Rasperini 2010	RCT	Test: 6 Control: 8	Molars	Periodontitis	Test: 19.3 ± 3.3 Control: 20.25 ± 5.96	–	DBBM	Collagen membrane	6 months

RCT: randomized clinical trial, CCT: controlled clinical trial, DBBM: deproteinized bovine bone mineral, A-PRF: advanced platelet-rich fibrin, EMD: enamel matrix derivatives.

The included investigations were published between 2010 and 2025. Five studies were randomized clinical trials (RCTs)^{4,14,15,18,32}, three were controlled clinical trials (CCTs)^7,9,33, and three were retrospective case–control studies^34–36.

The total number of sites was 185 and 203 in the ridge-preservation and spontaneous-healing groups, respectively. The extracted teeth were molars in general in seven investigations^{4,15,18,32–35}, first molars only in one¹⁵, while three studies included patients with premolars and molars to be extracted^7,14,36. Six studies mentioned the reasons for tooth extraction. These encompassed periodontitis, endodontic failure, periapical lesions or abscess, as well as crown or root fracture^{4,14,15,33–35}.

Baseline ridge heigh ranged between 4.09–19.3 mm in the ridge preservation groups, and 2.84–20.25 in the control groups. One study did not report baselines ridge height³². Regarding ridge width at the baseline, it was presented in four trials, being 5.60–11.27 mm in the test groups, and 4.94–12.06 mm in the control groups.

The material used for ridge preservation was deproteinized bovine bone mineral (DBBM) in seven of the included studies^{4,7,14,15,18,32,33}. One of these had two tests groups, where enamel matrix derivative (EMD) was added to DBBM in one of the groups³². In one study, a synthetic nano-hydroxyapatite was used⁹.

The graft was covered with a collagen membrane in five studies^4,7,14,15,32, a collagen membrane with a collagen sponge in one³³, a hemostatic sponge in one⁹, and platelet-rich fibrin in one trial¹⁸.

The follow-up period was 3 months in one investigation³², 4 months in one¹⁴, five months in one³², 6 months in six^{4,9,15,18,33,35}, and 8 months in one publicationl³⁶. One study stated a range of 6–9 months of follow-up³⁴.

Outcomes of the included studies

Ridge height was reported in ten out of the eleven included studies^{4,7,9,14,15,18,32,33,35,36}. This ranged between a loss of 1.62 mm⁹ to a gain of 5.8 mm¹⁵ in the ridge preservation groups, while it was − 3.14 mm⁴ to + 5.64 mm¹⁵ in the control groups.

As for ridge width, this was − 5.27 mm⁴ to + 3.74 mm³³ in the test groups, whereas a loss of 1.58–4.13 mm^9,33 was noted in the normal-healing groups.

Regarding sinus pneumatization it was measured either from the alveolar crest area to the sinus floor^4,9, the center of the socket to the sinus floor³³, or from the sinus floor to its roof^18,36. This recorded an increase of 0.14–0.88 mm when the sites underwent ridge preservation^4,18. An increase of 0.59–2.02 mm was seen when areas left to heal spontaneously^18,33. One study measured sinus volume, documenting a decrease of 0.7 cm³ in sites grafted with DBBM particles, an increase of 0.1 cm³ in sockets receiving DBBM blocks, and a pneumatization of 0.7 cm³ in the control group¹⁴.

When the alveolar ridge was preserved, 33 sites needed additional sinus procedures at the time of implant placement, which was less compared to the control groups, with 68 sites that underwent sinus floor augmentation when placing implants. The minimum length of the implants placed was mentioned in five investigations, being 6 mm in two^7,14, and 8 mm in three trials^4,32,33.

Table 2 summarizes the outcomes of the included studies.

Table 2.

Outcomes of the included studies.

Study	Method of measuring sinus pneumatization	Sinus floor change / pneumatization	Ridge height change (mm)	Ridge width change (mm)	Minimum implant length (mm)	Need for sinus floor augmentation at implant placement
Dai 2025	–	–	–	–	–	Test: 4/9 Control: 23/29
Khoury 2024	–	–	Test: 0.14 ± 2.94 Control: 0.17 ± 2.15	–	6	Test: 4/31 Control: 7/22
Lam 2024	Define the volume of the sinus with a segmentation tool to be calculated by the software (CT)	Sinus volume: Test 1 (3 sites): − 0.7 ± 0.8 cm3 Test 2 (5 sites): + 0.1 ± 0.3 cm3 Control (3 sites): + 0.7 ± 0.7 cm3	Test 1: + 0.9 ± 3.7 Test 2: + 1.0 ± 2.8 Control: − 2.7 ± 0.9	–	6	Test 1: 3/7 Test 2: 4/10 Control: 8/9
Khaddour 2024	–	–	Test: − 1.52 ± 0.76 Control: − 5.41 ± 1.93	Test: − 1.61 ± 0.96 Control: − 4.13 ± 1.16	–	–
Wei 2022	Vertical distance of sinus floor level to the center of the socket (CBCT)	Test: + 0.19 ± 0.45 mm Control: + 0.59 ± 0.63 mm	Test: + 5.11 ± 4.36 Control: + 2.55 ± 3.77	Test: + 3.74 ± 4.17 Control: − 1.58 ± 4.61	8	Test: 3/18 Control: 9/18
Shuman 2021	Distance from sinus floor to sinus roof (CBCT)	Test: + 0.88 ± 0.58 mm Control: + 2.02 ± 0.71 mm	Test: 0.94 ± 0.41 Control: 1.79 ± 0.41	–	–	–
Lee 2020	–	–	Test 1: Buccal − 0.61 ± 0.40 palatal − 0.69 ± 0.62 Test 2: Buccal − 0.90 ± 0.65 palatal − 0.60 ± 0.37 Control: Buccal − 1.30 ± 1.12 palatal − 0.98 ± 0.66	Test 1: − 1.44 ± 0.54 Test 2: − 1.42 ± 0.26 Control: − 2.36 ± 1.03	8	Test 1: 3/9 Test 2: 3/8 Control: 4/5
Cha 2019	Distance between reference line* and sinus floor, at the center of the socket (CBCT)	Test: + 0.14 ± 0.33 mm Control: + 1.16 ± 1.24 mm	Test: + 0.16 ± 1.59 Control: − 3.14 ± 1.99	Test: − 5.27 ± 3.26 Control: − 3.53 ± 3.77	8	Test 8/14 Control 14/14
Lombardi 2018	Mean of 4 measurements: from sinus floor to the apices of the roots and to the center of the socket (CBCT)	Test + 0.69 ± 0.48 mm Control + 1.04 ± 0.67 mm	Test: − 1.62 ± 0.49 Control: − 2.01 ± 0.84	Test: − 2.73 ± 1.68 Control: − 3.63 ± 2.24	–	Test 1/13 control: N/A
Levi 20,217	Distance from sinus floor to sinus roof (panoramic)	Test: + 0.30 ± 0.46 Control: + 1.30 ± 1.75	Test: − 0.32 ± 0.09 Control: − 1.26 ± 0.28	–	–	–
Rasperini 2010	–	–	Test: + 5.8 ± 2.4 Control: + 5.85 ± 3.57	–	NR**	Test: 1/6 Control: 3/8

*Line of the crest levels of the adjacent neighboring teeth.

**No information on implant length. However, 8 mm of vertical residual bone was considered as the minimum to place an implant.

Risk of bias and quality assessment

Three RCTs had a low risk of bias^4,14,15, while two were assessed as having some concerns^18,32, due to the unclear randomization process (Fig. 2A).

Fig. 2.

Risk of bias in each domain of the included randomized clinical trials (A), and controlled clinical trials (B).

As for the non-randomized studies, two showed low risk^9,33, whereas one investigation had a moderate risk of bias⁷. The main reason was the insufficient information on measuring and reporting the outcomes (Fig. 2B).

Regarding the retrospective studies, two obtained 8/9 points^35,36, whereas one gained 9 points³⁴. Therefore, the included publications demonstrated good overall quality (Supplementary File 1).

Data synthesis

Need for additional sinus floor augmentation at implant placement

Seven articles were included^{4,7,14,15,32,33,36}, with no heterogeneity among them (I² = 0%); therefore, the fixed-effect model was utilized. These trials had a total of 112 sites in the ridge preservation groups, and 105 in the normal-healing groups. The results of the meta-analysis revealed that significantly fewer sites needed additional sinus floor augmentation at the time of implant placement when the alveolar ridge was preserved (OR = 0.18, 95% CI 0.09 to 0.36, p-value < 0.00001) (Fig. 3A).

Fig. 3.

Forest plot of the results of the meta-analysis of the need for additional sinus augmentation. (A) Including all studies, (B) analysis of prospective studies, (C) adjusting for non-randomized trials, (D) analysis of studies with the same material and membrane used for the procedure.

The same was noted when analyzing prospective clinical trials only, adjusting for non-randomized studies, and for the meta-analysis of studies with the same graft material and membrane (DBBM + collagen membrane) (Fig. 3B–D).

Sensitivity analysis by excluding each study at a time, and studies with potential bias^7,32 led to the same outcome (highest p-value = 0.001, and p-value = 0.0002, respectively).

Sinus pneumatization

Six reports underwent the meta-analysis^{4,9,14,18,33,36}. The total number of sites was 92 and 107 for the test and control groups, respectively. No heterogeneity was recorded (I² = 0%). Meta-analysis of this outcome indicated less sinus pneumatization in the ridge preservation groups, with a notable statistical significance (SMD = − 0.88, 95% CI − 1.19 to − 0.58, p-value < 0.00001) (Fig. 4A).

Fig. 4.

Forest plot of the results of the meta-analysis of sinus pneumatization. (A) including all studies, (B) analysis of prospective studies, (C) adjusting for non-randomized trials, (D) analysis of studies with the same material and membrane used for the procedure.

A similar outcome was seen when including only prospective studies, adjusting for non-randomized trials, and analyzing studies with the same materials. (Fig. 4B–D).

Likewise, when conducting sensitivity analysis by excluding each trial at a time, as well as the investigation with possible bias¹⁸, the statistical significance remained (p-value < 0.0001 in both cases).

Ridge height

Ten studies were included in this meta-analysis^{4,7,9,14,15,18,32,33,35,36}, having 172 and 167 sites for the ridge preservation and normal healing groups, respectively. A high level of heterogeneity was noted (I² = 88%), thus the random-effect model was used. This meta-analysis showed significantly higher alveolar ridge height in the ridge preservation group (SMD = 1.33, 95% CI 0.58 to 2.09, p-value = 0.0005) (Fig. 5A).

Fig. 5.

Forest plot to demonstrate the results of the meta-analysis of ridge height. (A) including all studies, (B) analysis of prospective studies, (C) adjusting for non-randomized trials, (D) analysis of studies with the same material and membrane used for the procedure.

Subgroup analyses of prospective clinical trials only, adjusting for non-randomized studies, and of investigations using DBBM and collagen membrane resulted in a similar outcome (Fig. 5B–D).

The same results were recorded when removing each of the analyzed studies at a time (highest p-value = 0.006), and when excluding studies with a risk of bias^7,18,32 from the meta-analysis (p-value = 0.003).

Ridge width

Five investigations were analyzed^4,9,32,33,35, with 88 preserved sites and 80 sites left to heal spontaneously. High heterogeneity was seen (I² = 87%). The outcome of this meta-analysis showed no significant difference between the groups (SMD = 0.95, 95% CI − 0.02 to 1.91, p-value = 0.053) (Fig. 6A).

Fig. 6.

Forest plot to demonstrate results of the meta-analysis of ridge width. (A) including all studies, (B) analysis of prospective studies, (C) adjusting for non-randomized trials, (D) analysis of studies with the same material and membrane used for the procedure.

The same result was noted when analyzing prospective studies only, and adjusting for non-randomized trials, as well as in the analysis of studies using DBBM and collagen membrane (Fig. 6B–D).

The absence of significant difference remained when excluding the study with potential bias³² (p-value = 0.47). In contrast, when removing each investigation at a time, the meta-analysis showed statistical significance (p-value = 0.0005) after excluding the study of Cha⁴, favoring the ridge preservation group.

Certainty of evidence

The level of evidence related to the outcome of sinus pneumatization, need for additional sinus augmentation, and alveolar ridge height was judged to be high. As for the evidence on ridge width, it was downgraded to be moderate. This was due to the inconsistency of the results from the analyzed investigations (Table 3).

Table 3.

Level of evidence according to the GRADE rating system.

Certainty assessment							Number of patients		Effect		Certainty	Importance
Number of studies	Study design	Risk of bias	Inconsistency	Indirectness	Imprecision	Other considerations	ridge preservation	normal healing	Relative (95% CI)	Absolute (95% CI)
Need for sinus floor augmentation at implant placement
6	4 RCTs 2 CCTs	not serious	not serious	not serious	not serious	none	27/107 (25.2%)	45/76 (59.2%)	OR 0.20 (0.08 to 0.38)	367 fewer per 1,000 (from 488 to 237 fewer)	⨁⨁⨁⨁High	CRITICAL
Sinus pneumatization
5	3 RCTs 2 CCTs	not serious	not serious	not serious	not serious	none	71	65	–	SMD − 1.01 SD lower (1.38 lower to 0.64 lower)	⨁⨁⨁⨁High	CRITICAL
Ridge height
7	4 RCTs 3 CCTs	not serious	not serious	not serious	not serious	none	122	91	–	SMD 0.72 SD higher (0.22 higher to 1.22 higher)	⨁⨁⨁⨁High	CRITICAL
Ridge width
4	2 RCTs 2 CCTs	not serious	seriousa	not serious	not serious	none	71	58	–	SMD 0.61 SD higher (0.27 lower to 1.49 higher)	⨁⨁⨁◯Moderatea	IMPORTANT

Note that the certainty of evidence was assessed based on the results of the meta-analyses of prospective studies only, to ensure more homogeneity.

CI: confidence interval; OR: odds ratio; SMD: standardized mean difference; RCT: randomized clinical trial; CCT: controlled clinical trial.

^aContradicting outcomes from the included studies.

Discussion

This systematic review and meta-analysis was carried out with the objective of investigating whether ridge preservation at the posterior maxillary region would reduce sinus pneumatization during the months following tooth extraction, as well as the need for further sinus procedures at the time of implant placement, in addition to its general advantage of limiting ridge resorption. Previous preliminary reports on this topic indicated a potential benefit of alveolar ridge preservation^4,14,15. Therefore, collectively synthesizing the available evidence to provide more robust and conclusive results would be of great value.

Ridge resorption following tooth loss manifests itself at the highest extent during the first 6 months^3,10. This will be more prominent on the horizontal aspect, with a reduction of 29–63%, than in the vertical dimension, which undergoes a reduction of 11–22%. It is noteworthy that most of this decrease in alveolar bone structure occurs during the first 3 months after tooth extraction³⁷. The outcomes of the current meta-analysis revealed that ridge preservation limited the vertical loss of alveolar bone in the posterior maxilla and was able to maintain acceptable volume at the time of the final follow-up. This was also in line with other studies on ridge preservation in the molar area overall^38–40. Therefore, this procedure would be recommended following the removal of posterior maxillary teeth. On the other hand, ridge width change was not significantly different, compared to spontaneous healing. The reason could be the low number of articles analyzed under this outcome. It is also important to keep in mind that the evidence on this outcome was downgraded, due to the inconsistency of the results from the analyzed investigations. This outcome was also not in agreement with what is reported in another systematic review¹⁶, which could be due to the inclusion of studies on the mandible and maxilla in that investigation. Conversely, when conducting sensitivity analysis and excluding the study of Cha⁴, the meta-analysis showed significantly less width loss when performing alveolar ridge preservation. This may have occurred by chance, considering the small number of studies, as mentioned previously. Taking these points into consideration, future clinical trials are encouraged, in order to explore this aspect and evaluate the benefit of ridge preservation in reducing ridge width change following tooth extraction.

The posterior region of the upper jaw is susceptible to more vertical deficiency due to the pneumatization of the maxillary sinus, which is responsible for 46% of the variation in the height of the alveolar ridge after tooth extraction^4,14. The reason behind this phenomenon is still unclear, but could be related to the bone-remodeling process that inclines to be more of a resorptive pattern. This takes place due to the absence of physiological masticatory forces transferred to the bone through the tooth when it is present⁹. Previous research showed that sinus pneumatization is significant when second molars, or two or more adjacent posterior teeth are extracted⁴¹. Maxillary sinus pneumatization and the resultant height deficiency hinder proper implant placement. The current meta-analysis demonstrated that ridge preservation significantly reduced maxillary sinus pneumatization when it was compared to normal healing. Therefore, it could be utilized as a means to limit this event, until the region is ready for further rehabilitation. While the exact mechanism by which alveolar ridge preservation limits sinus pneumatization is not fully understood, it is suggested that following the extraction of posterior maxillary teeth, the absence of functional forces leads to bone remodeling, characterized by ridge resorption⁴². This process, often referred to as “disuse atrophy”, aligns with Wolff’s law, where bone adapts and remodels, because of the lack of mechanical stress^9,43. Consequently, the maxillary sinus may expand inferiorly. Moreover, a previous animal study noted that sinus pneumatization is an opportunistic process, taking place in areas where no structures inhibit this phenomenon. This indicates that maintaining alveolar bone structure by means of ridge preservation could physically impede sinus pneumatization⁴⁴. Nonetheless, future studies are still needed to gain deeper insights into this aspect.

Despite sinus floor augmentation procedures being effective in increasing the alveolar bone level and facilitating implant placement in the posterior maxilla,⁴⁵ this kind of surgery is always accompanied with potential complications, including sinus membrane perforation or postoperative infection⁷. Thus, reducing the need for sinus lift procedure, at least the lateral approach, would potentially decrease the overall complications following implant installation in the posterior maxilla, which may improve patients’ experience, as well as implant success and survival rates. As indicated by many of the included studies, and based on the outcomes of this meta-analysis, ridge preservation in the posterior maxilla decreased the need for additional sinus augmentation procedures at the time of implant placement. Consequently, implementing this step could help clinicians to simplify implant insertion and avoid complex procedures in a good portion of their cases. Nevertheless, it is noteworthy that the minimum length of implants placed in the augmented sites varied across the analyzed studies, with some placing longer implants (8 mm) than others (6 mm). In addition, several investigations did not report this aspect. Therefore, the results may have been different if shorter implants were considered in all investigations. As a result, the benefit of ridge preservation in eliminating the need for sinus floor augmentation, even when choosing short implants, should be further explored and confirmed in future studies.

Several materials and techniques have been proposed for alveolar ridge preservation. Although the current literature does not indicate the superiority of a certain graft or membrane^13,46, DBBM with collagen membrane have been used more frequently than other materials, which was also evident in the current systematic review. Therefore, to further validate the outcomes of this investigation, additional meta-analyses of studies that used DBBM covered by a collagen membrane were performed, in order to provide conclusions based on more homogenous clinical trials. The results remained consistent across all aspects, thus supporting the main outcomes on the efficacy of alveolar ridge preservation in the posterior maxillary region.

The strength of this study comes from collectively pooling the data from all the available studies on this topic, demonstrating the agreement in their results, and thus providing more robust conclusions with a good level of evidence. However, certain limitations should be kept in mind. The overall number of studies is still relatively small. Moreover, although gathering data from several investigations was done for each analysis, the number of cases remained low. As a result, future studies with a large number of cases and updated analyses when more clinical trials are available are essential, in order to further explore and confirm the conclusions drawn from the current systematic review.

Conclusions

Within the limitations of this study, it is concluded that alveolar ridge preservation in the posterior maxilla significantly decreases sinus pneumatization, as well as the need for sinus floor augmentation at the time of implant placement, along with its general benefits in preserving bone volume.

Author contributions

Conceptualization and Methodology: Basel Mahardawi and Nikos Mattheos; Formal analysis and investigation: Basel Mahardawi and Sirimanas Jiaranuchart; Writing—original draft preparation: Basel Mahardawi, Sirida Arunjaroensuk, and Nikos Mattheos; Writing—review and editing: Nikos Mattheos, Kanit Dhanesuan, and Atiphan Pimkhaokham; Supervision: Atiphan Pimkhaokham and Kanit Dhanesuan. All authors read and approved the final version of this submission.

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Competing interests

The authors declare no competing interests.

Supplementary Information

The online version contains supplementary material available at 10.1038/s41598-025-06261-w.