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. 2024 Aug 21;35(12):1568–1584. doi: 10.1111/clr.14344

Alveolar ridge preservation in posterior maxillary teeth for reduction in the potential need for sinus floor elevation procedures: A pilot study

Lisetta Lam 1, Saso Ivanovski 1,2, Ryan S B Lee 1,2,✉
PMCID: PMC11629457  PMID: 39165113

Abstract

Objectives

To investigate the effects of alveolar ridge preservation (ARP) on ridge height, sinus pneumatization and the potential need for lateral sinus augmentation following extraction in the posterior maxilla.

Materials and Methods

This randomized controlled pilot study included 28 patients requiring extraction in the posterior maxilla with bone height between 6 and 8 mm. The sites were randomly allocated to either unassisted socket healing (Control), ARP with deproteinized bovine bone mineral (DBBM) (Test 1), or collagen‐stabilized DBBM (Test 2) groups. Pre‐ and post‐operative CTs at 4 months were taken to determine changes in ridge heights, sinus volume, and the need for sinus floor elevation (SFE) procedures for cases where the residual mid‐ridge height was < 5 mm. Site‐level analyses for changes in vertical ridge dimensions and sinus volume pre‐ and post‐extraction/ARP were conducted using paired t‐tests. Differences in mean changes in vertical ridge dimensions and sinus volume between the groups were determined using one‐way ANOVA.

Results

Significantly greater mean mid‐ridge height reduction occurred in the control group (−2.7 ± 0.9 mm) compared to Test 1 (0.9 ± 3.7 mm) and Test 2 (1.0 ± 2.8 mm) groups (p < .05). No significant changes in mean mid‐ridge height were found in either test groups. Volumetric analysis showed a significantly greater increase in sinus volume in the control group (0.7 ± 0.7 cm3) compared to Test 1 (n = 3, −0.7 ± 0.8 cm3) group (p = .03). 89% of patients in the control group would require lateral window SFE  compared to Test 1 (42.8%) and Test 2 (40%) groups.

Conclusion

ARP was effective in attenuating height changes in the middle of the ridge and may reduce sinus pneumatization following extraction in the posterior maxilla. This could potentially decrease the need for more invasive sinus augmentation procedures.

Keywords: alveolar ridge preservation, alveolar ridge resorption, Bio‐Oss, Bio‐Oss collagen, extraction, maxillary sinus augmentation, maxillary sinus pneumatization, socket grafting

1. INTRODUCTION

Implant surgery is challenging in the posterior maxilla primarily due to the inherent lack of bone volume, especially in the vertical dimension (de Souza Nunes et al., 2013; Lekholm & Zarb, 1985). The residual vertical ridge dimensions following tooth extraction in this region are thought to result from two biological processes: resorption of the alveolar bone, and pneumatization of the maxillary sinus (Sharan & Madjar, 2008; Tan et al., 2012).

The cause of sinus pneumatization in adults after posterior tooth extraction, also referred to as the fourth expansion of the maxillary sinus, has been attributed to disuse atrophy due to the decrease of functional forces transferred to the bone after tooth loss, causing a shift in the remodeling process toward bone resorption (Sharan & Madjar, 2008). A significantly greater risk of developing sinus pneumatization has been associated with extraction of molars compared to premolars (Sharan & Madjar, 2006, 2008), second molars compared to first molars, multiple extractions of adjacent teeth and extraction of teeth with roots protruding into the sinus cavity (Choi et al., 2020; Jung et al., 2009; Sharan & Madjar, 2006).

Maxillary sinus pneumatization accounts for up to 46% of the variation in ridge height following tooth loss (Farina et al., 2011). The combined result of alveolar bone resorption and sinus penumatization can lead to significant reduction in ridge dimensions for implant placement (Tan et al., 2012). Consequently, additional sinus floor elevation (SFE) procedures, either via transalveolar or lateral approach, are often necessary to increase vertical dimension of the alveolar ridge prior to implant placement (Alayan et al., 2016; Tan et al., 2008). The selection of SFE technique and placement approach depends critically on the residual bone height, sinus floor anatomy and the possibility of achieving implant primary stability (de Souza Nunes et al., 2013; Pjetursson et al., 2008; Pjetursson & Lang, 2014; Summers, 1998; Thoma et al., 2015). A transalveolar sinus lift is usually recommended when the residual alveolar bone height is more than 5 mm; the lateral window sinus lift is suggested when the bone height is less than 5 mm.

Alternatively, short (<8 mm) implants may be an alternative option to longer implants placed in conjunction with sinus grafting for patients with a limited ridge height in the posterior maxilla, given that recent randomized controlled trials (RCTs) have reported similar 10‐year implant survival rates, reduced patient morbidity and lower costs associated with shorter implants (Fan et al., 2017; Sahrmann et al., 2023; Thoma et al., 2017, 2024). Zygomatic implants have also been used as a treatment option for patients with severely resorbed maxillae. However, long term clinical studies on survival and success of these implants and associated complications are sparse (Varghese et al., 2021).

Alveolar ridge preservation (ARP) is considered a valid treatment modality in the posterior maxilla, as it can significantly reduce the post‐extraction resorptive changes in ridge dimension (Choi et al., 2020; Park et al., 2020). Recent clinical studies have reported that ARP in the posterior maxilla can maintain vertical ridge dimensions by minimizing sinus pneumatization and alveolar bone resorption compared to unassisted socket healing, thus reducing the need for sinus augmentation (Cha et al., 2019; Jung et al., 2018; Levi et al., 2017; Park et al., 2020; Rasperini et al., 2010). Park et al. (2020) also demonstrated that lateral window SFE approach was performed significantly less at the APR sites (8.3%) than non‐ARP sites (37.2%) in patients that required sinus augmentations, thus reducing costs and the risk of complications and patient morbidity.

A key limitation of these previous studies is the use of linear measurements from 2D plain radiographs, which may be affected by magnification, distortions and superimpositions, potentially resulting in inaccurate measurements of a three dimensional structure like the maxillary sinus (Levi et al., 2017; Sharan & Madjar, 2008). Recent studies have instead used 3D imaging, such as cone beam CT, to quantify changes in sinus floor position and allow for accurate measurement of alveolar ridge dimensions (Choi et al., 2020; Park et al., 2020).

Various types of graft materials have been utilized for ridge preservation, such as autogenous bone (Becker et al., 1994), demineralized or mineralized freeze‐dried bone allografts (Frank Feuille et al., 2003; Froum et al., 2002), deproteinized bovine bone mineral (DBBM) xenografts (Araújo, Silva, Mendonça, et al., 2015), alloplastic polymers (Serino et al., 2003), and bioactive glasses (Darby et al., 2009; Froum et al., 2002). More recent studies have primarily used a combination of xenografts and collagen membranes due to their availability and long‐term evidence of clinical success (Araújo, Silva, Misawa, et al., 2015; Stumbras et al., 2019). These studies have reported consistent benefits of using xenografts for ARP in terms of minimizing the extent of alveolar bone resorption and dimensional ridge changes in both anterior and posterior sites (Jung et al., 2018; Lim et al., 2019; Lombardi et al., 2018).

It was hypothesized that ARP at the time of extraction would minimize vertical ridge resorption and sinus pneumatization, maintaining sufficient vertical ridge height such that lateral window sinus augmentation could be avoided for implant placement. Therefore, the objective of this prospective, randomized controlled pilot study is to test whether ARP using DBBM xenografts, either as particulate or a block (stabilized in 10% porcine type 1 collagen matrix), can reduce changes in vertical ridge height, sinus pneumatization and the need for sinus augmentation in the posterior maxilla, compared to unassisted socket healing.

2. MATERIALS AND METHODS

2.1. Study design and population

This is a prospective, randomized controlled pilot study was conducted at two university clinics (Griffith University, Australia and the University of Queensland, Australia) and a private practice (ACTRN registration number: ACTRN12619000125123). The recruitment phase started in February 2017 and ended in November 2019 (Figure 1). The research protocol was approved by the Griffith University Human Research Ethics Committee (GU Ref No. 2016/923) and the Royal Brisbane & Women's Hospital Human Research Ethics Committee (HREC/18/QRBW/98). The project complies with the provisions contained in the National Statement on Ethical Conduct in Research Involving Humans and the recognized standards have been followed (Declaration of Helsinki; US Federal Policy for the Protection of Human Subjects; or European Medicines Agency Guidelines for Good Clinical Practice). This trial was conducted and presented in compliance with the CONSORT guidelines/checklist.

FIGURE 1.

FIGURE 1

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CONSORT flowchart of treatment sequence and data collection, including number of teeth (site level) included in each step.

2.2. Inclusion criteria

Individuals attending the clinics requiring extractions of maxillary molars and second premolars were invited to participate in the study based on the eligibility criteria. An information sheet describing the aim and methodology of the study was provided to all eligible participants. Informed consent was obtained from all participants who agreed to partake in the study. Additionally, all participants received professional oral hygiene care and instructions to minimize any infective complication prior to the extraction appointment.

The following inclusion criteria were applied:

  1. 20 years of age or over.

  2. Extraction of maxillary second premolars, first molars and/or second molars.

  3. Pre‐extraction alveolar bone height of 6–8 mm from alveolar bone crest to maxillary sinus floor as measured on the CT scan.

  4. All indications for extraction (periodontal, orthodontic, endodontic and restorative).

  5. Individuals with chronic periodontitis were initially treated and subsequently enrolled in a supportive maintenance program prior to recruitment into the study.

2.3. Exclusion criteria

The following exclusion criteria were applied:

  1. Pre‐extraction alveolar bone height <5 mm or >8 mm or if more than 50% of the buccal bone wall is missing or damaged after extraction.

  2. Uncontrolled or untreated periodontal disease.

  3. Any systemic medical condition which is a contraindication for dentoalveolar surgery or interferes with normal wound healing.

  4. Currently pregnancy or lactation at the time of recruitment.

  5. History of smoking, alcoholism, or chronic drug abuse.

  6. History of malignancy, radiotherapy, or chemotherapy for a malignancy in the past 5 years.

  7. Taking long‐term steroids, bisphosphonates, chemotherapeutic or require antibiotic prophylaxis.

  8. Significant soft tissue thickening, sinus opacification or pathology in the sinus of interest.

  9. Extraction of upper third molars only.

  10. Inability to consent to participation in the study and/or to accept the proposed treatment plan.

2.4. Randomization

Following subject enrolment, treatments were randomly allocated at site level at the time of extraction into either the control group or two ARP (Figure 1). Alveolar ridge preservation treatments were randomly assigned via computer‐generated numbers. Group allocation was concealed in an opaque envelope, which was opened immediately after extraction.

  1. Test 1 (n = 10) received extraction and ARP with DBBM in particulate form (Geistlich Bio‐Oss® large granules 1‐2 mm, Geistlich Pharma AG, Wolhusen, Switzerland) and a double layer of native bilayer collagen membrane (NBCM; Bio‐Gide®, Geistlich Pharma AG).

  2. Test 2 (n = 11) received extraction and ARP with DBBM in a block form that is stabilized in 10% porcine type 1 collagen matrix (DBBM‐C; Geistlich Bio‐Oss® Collagen, Geistlich Pharma AG) and a double layer of NBCM.

  3. Control (n = 10) had extraction without ARP.

Thirty participants were clinically and radiographically assessed for study eligibility. Four participants did not meet the eligibility criteria and were excluded. Twenty‐six participants requiring one or multiple tooth extractions in the posterior maxilla met the inclusion criteria. The demographic data of the participants included in the final analysis is presented in Table 1.

TABLE 1.

Demographic data of the included participants by treatment groups.

Control Test 1 Test 2
Patient level
Total (no. of participants) 9 c 6 a , b 10 a
Gender
Female 4 2 4
Male 5 4 6
Age (mean years ± SD) 59.1 ± 13.1 62.2 ± 11.5 65.5 ± 13.3
Age groups
<60 years 6 3 1
≥60 years 3 3 9
Type of extraction
Single tooth 8 5 10
Multiple adjacent extractions 1 1 0
Mean treatment time (minutes ± SD) 36.9 ± 14.4 51.9 ± 13.7 55.3 ± 7.1
Mean time (months ± SD) between extraction and CT scan 4.6 ± 0.9 4.5 ± 1.1 4.1 ± 0.4
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a

Two patients had split mouth treatment: extraction on one side in test group 1 and extraction on the other side in test group 2.

b

One patient had two adjacent teeth (15 and 16) extracted on the one side and one tooth (26) extracted on the other side.

c

One patient had two adjacent teeth (26 and 27) extracted on the same side.

Randomization was performed at site (tooth) level at the time of extraction. As a result, two patients received split mouth treatment: one side in Test 1 and the other side in Test 2. The CONSORT flowchart for randomized controlled clinical trial is presented at site level in Figure 1. All sites in Test 1 and control group received the assigned treatments without any intraoperative complications. One site in Test 2 had to be excluded due to fracture of the buccal wall during extraction and hence ridge preservation could not be performed. At the 4‐month review, two sites in Test 1 were excluded from the final analysis as the participants dropped out of the study. Reasons for dropout were medically related (pregnancy and commenced chemotherapy). There were no significant postoperative complications in terms of facial swelling, wound infection, or loss of graft material.

The characteristics of the extraction sites by treatment group included in the final analysis are presented in Table 2.

TABLE 2.

Characteristics of the extraction sites by treatment group.

Control Test 1 Test 2
Tooth level
Total (no. of teeth) 10 8 10
Type of extraction
2nd premolar 1 3 0
1st molars 7 4 7
2nd molars 2 1 3
Single tooth extractions 8 6 10
Multiple adjacent extractions 2 2 0
Reason for extraction
Caries 2 4 2
Endodontic failure 3 2 1
Root fracture 0 1 3
Coronal fracture 1 0 3
Periapical lesion 3 1 1
Periodontal abscess 1 0 0
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2.5. Outcome variables

2.5.1. Primary outcome

Change (linear measurement) in mid‐ridge height 4 months after extraction with or without ARP.

2.5.2. Secondary outcomes

Change in sinus volume 4 months after extraction with or without ARP. (i.e. degree of pneumatization following the extraction).

Need for lateral window sinus augmentation, based on residual ridge height <5 mm.

2.6. Treatment procedure

The following demographic and clinical parameters were recorded: age, gender, number, and location of the teeth present in posterior maxilla, number, and location of the tooth or teeth to be extracted and reasons for extraction.

2.6.1. Imaging protocol

Participants had CT scans before (t0) and 4 months (t4) after extraction/ARP. The image acquisition settings were developed in consultation with a specialist Dento‐Maxillofacial Radiologist, with the aim of using a low radiation dose protocol to minimize dose exposure while achieving clear imaging quality for measurements.

The imaging protocol was standardized to include the occlusal plane of the maxilla teeth and the whole maxillary sinus. The mid‐sagittal plane was to be perpendicular to the horizontal plane using vertical and horizontal alignment beams as recommended by the manufacturer. All CT scans were performed with the occlusal plane approximately parallel with the primary X‐ray beam during acquisition and with no gantry tilt. The occlusal plane was used as the reference plane for subsequent image reconstruction.

2.6.2. Surgical procedures

After a pre‐procedural rinse with 0.2% chlorhexidine mouth rinse and administration of local anesthesia with 4% articaine plus epinephrine (1:100,000), tooth extraction was performed by two of the investigators (L.L. and S.I.) with the minimally traumatic procedure to preserve the buccal bone plate and the surrounding soft and hard tissues. For multi‐rooted teeth, roots were sectioned and removed separately to minimize damage to the bony cortex and inter‐radicular bone. In all cases, extraction was performed without elevating a mucoperiosteal flap.

The socket was carefully debrided and irrigated with sterile saline. The integrity of the buccal cortex was inspected visually under magnification with a probe. Participants were excluded if there was fracture of the buccal bone plate that prevented ridge preservation to be performed. The participants were then randomly assigned to one of test groups according to an opaque, concealed, continuously numbered randomization envelope. Sockets in Test 1 were grafted with DBBM granules (particle size 1–2 mm) firmly and incrementally compacted into the socket (Cho et al., 2017). In Test 2, DBBM‐C blocks were placed into the sockets. To ensure the sockets were filled to the apical region, each root‐alveolus of multi‐rooted teeth was filled individually. Sufficient material was placed until the graft materials were about 1 mm above the alveolar crest. In all test sites, no attempt to obtain primary closure was made. The graft materials were completely covered by a double layer of NBCM with the marginal soft tissue of the sockets slightly undermined to receive the membrane without mobilization of the soft tissue to achieve primary closure. Using a 4/0 non‐resorbable, monofilament polypropylene suture (Prolene®, Ethicon), a ‘hidden‐X’ suture technique was used (Park et al., 2016). In control sites, sockets were left open for spontaneous healing.

Intra‐operative complications and adverse events during extraction and ARP procedures, such as buccal bone fracture, need for surgical extractions, oro‐antral communication, and intra‐operative bleeding requiring intervention, were recorded.

A postoperative regimen of amoxicillin 500 mg three times daily for 7 days (or 150 mg clindamycin four times daily for 7 days if the patient was allergic to penicillin) was prescribed, as was paracetamol 500 mg and ibuprofen 2 mg, to be taken as required, for 7 days. Participants were instructed to avoid rinsing and spitting for the first 24 h. After that, participants were advised to use 0.2% chlorhexidine mouthwash for rinsing twice daily and to avoid brushing directly on the surgical site until complete gingival closure occurred. Participants were also advised to avoid chewing on the operated side and to maintain a soft diet for 2 weeks. Both oral and written postoperative care instructions were given. No removable appliances were used, and the sockets were left to heal undisturbed.

2.6.3. Evaluations after surgery

All participants were reviewed at 2 weeks and at 4 months, with any postoperative complications such as wound dehiscence, loose graft material, wound infection, extra‐oral bruising, oedema or other signs of morbidity recorded. In the test groups, sutures were removed after 2 weeks. All participants were reviewed at 4 months (t4) clinically and a postoperative CT scan was taken ridge height and sinus volume analysis.

2.7. Radiographic analysis

All Digital Imaging and Communications in Medicine (DICOM) CT scans data were imported into a 3D dental implant planning software (Simplant Pro 18.0 Dentsply Implants NV, Research Campus 103500 Hasslet Belgium). All data sets were allocated a code number so the identity of the participants was masked to the operator. The same operator performed all data set reconstruction and measurements. The examiner was blinded to the nature of the treatment group (i.e., Test 1 or Test 2); however, it was not possible to mask the test groups from the control group on the post‐extraction scans due to the presence of the grafting material.

The protocol for the reconstruction of the scans to ensure accurate and reproducible orientation and spatial alignment of the three planes was developed in consultation with an experienced oral and maxillofacial radiologist. A panoramic curve was drawn to bisect the maxillary alveolar ridge, at mid‐level between the sinus floor and bony crest on the axial plane. The coronal and sagittal planes were then positioned to place the tooth/extraction site in the middle of the ridge. Specifically, axial slices were assessed to identify the slice that displays the mid‐ridge parallel to the long axis of the tooth in the mesiodistal and transverse dimensions. The mid‐sagittal and the mid‐coronal bisecting lines were then identified on this axial slice (Figure 2). To perform the measurements, each extraction site was considered separately and evaluated in the coronal section corresponding to the center of the extraction/edentulous site.

FIGURE 2.

FIGURE 2

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Standardized method of reconstruction, orientation and spatial alignment of CT in axial, coronal and sagittal planes for ridge height measurements. (a) Pre‐extraction and (b) 4 months post‐extraction/ARP.

2.8. Outcome measurements

2.8.1. Ridge height measurements

Ridge heights (measured in mm) before (t0) and after extraction/ridge preservation (t4) were measured at the mid‐section of the alveolar ridge where both the coronal and sagittal planes intersect using the linear measurement tool (Figure 3):

  1. Pre‐extraction mid‐ridge height = distance from midpoint on the line connecting the buccal and palatal bone crest to the sinus floor.

  2. Post‐extraction mid‐ridge height = distance from midpoint of the edentulous ridge to the sinus floor.

  3. Pre‐extraction buccal‐bone height = distance from buccal bone crest to the horizontal line drawn through the sinus floor in a perpendicular manner.

  4. Post‐extraction buccal‐bone height = distance from the most coronal aspects on the buccal side of the ridge to the horizontal line drawn through the sinus floor in a perpendicular manner.

  5. Pre‐extraction palatal‐bone height = distance from palatal bone crest to the horizontal line drawn through the sinus floor in a perpendicular manner.

  6. Post‐extraction palatal‐bone height = distance from the most coronal aspects on the palatal side of the ridge to the horizontal line drawn through the sinus floor in a perpendicular manner.

FIGURE 3.

FIGURE 3

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Ridge height measurements: (a) pre‐extraction and (b) post‐extraction.

The difference between the post‐ and pre‐extraction ridge height measurements determined the change in ridge heights (t4 – t0) over 4 months.

2.8.2. Sinus volumetric measurement

Sinus volume was determined using a segmentation technique based on a previously established protocol (Alayan & Ivanovski, 2018). DICOM data was imported into the 3D dental implant planning platform Simplant Pro 17.0 (Dentsply Implants NV, Research Campus 103500 Hasslet Belgium). Accurate 3D volumetric analysis required the inclusion of all sinus boundaries within the scan and the absence of mucosal in either maxillary sinuses as well as any bone deformities (Alayan & Ivanovski, 2018). Data sets were excluded if significant sinus opacification or mucosal thickening prevented the ability to perform the masking or segmentation function in Simplant. A mask was initially created to highlight the air‐filled cavities, followed by the use of a segmentation tool to manually define the entire volume of the maxillary sinus cavity (Alayan & Ivanovski, 2018) (Figure 4). This allowed the software to automatically calculate the sinus volume in cubic centimetres. The difference between post‐ (t4) and pre‐extraction (t0) sinus volume determined the change in sinus volume (t4 – t0) over 4 months.

FIGURE 4.

FIGURE 4

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Calculation of the maxillary sinus volume using digital 3D reconstruction and segmentation on the CT scan. (a) Pre‐extraction and (b) Post‐extraction.

2.8.3. Requirement for sinus augmentation

The need for sinus augmentation procedures for placement of a standard‐length implant was determined at site level based on the residual mid‐ridge height after extraction (Table 3). Lateral sinus augmentation would be required when the residual mid‐ridge height was <5 mm. These criteria were based on recent RCTs using moderately rough surface implants comparing short (6 mm) versus longer implants in combination with SFE procedures (Avila‐Ortiz et al., 2012; Pjetursson & Lang, 2014; Schincaglia et al., 2015; Thoma et al., 2015). The implants that were encroaching ≤1 mm inside the sinus were considered to not require additional sinus augmentation (Pjetursson & Lang, 2014; Schincaglia et al., 2015; Thoma et al., 2015).

TABLE 3.

Criteria for determining need for sinus augmentation based on residual mid‐ridge height 4 months after extraction (t4).

Mid‐ridge height at t4 Criteria for sinus augmentation or short implant
<5 mm Lateral window sinus augmentation is required
≥5 mm Transalveolar sinus augmentation is required for placement of ≥8 mm implant or placement of 6 mm implant without additional augmentation procedure
≥8 mm Placement of a standard‐length implant (≥8 mm) without the need for sinus augmentation
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2.9. Statistical analysis and sample size calculations

Descriptive statistics (means, percentage change, and standard deviations) were produced for each group to summarize mid‐ridge, buccal, and palatal bone heights and sinus volume before (t0) and 4 months after extraction/ARP (t4) for each treatment group. The intragroup differences for mean changes in vertical ridge dimensions and sinus volume pre‐ and post‐extraction/ARP were determined by paired t‐test. For intergroup analysis, the mean changes in vertical ridge heights and sinus volume over 4 months were compared using either ordinary one‐way ANOVA or Kruskal–Wallis Friedman nonparametric one‐way ANOVA was performed using GraphPad Prism version 10.2.3.

Due to the nature of a pilot study, no sample size calculation a priori was performed. Intra‐examiner reliability for measurement of mid‐ridge height and sinus volume pre‐ and postoperative measurements for both control and treatment groups was calculated by repeating the measurement procedures over a 2‐week interval. Intra‐rater class correlation coefficient (ICC) was used to determine intra‐rater reliability for the following variables. ICC for pre‐extraction mid‐ridge height was 0.987 (0.960, 0.996), post‐extraction mid‐ridge height was 0.998 (0.995, 0.999), and sinus volume was 0.996 (0.984, 0.999).

3. RESULTS

3.1. Change in ridge height

The control group had significant reduction of 2.7 ± 0.9 mm in mean mid‐ridge height, or 39.7% of the baseline height, following extraction (p < .001, 95% CI −3.3, −2.0). Conversely, there was a mean increase of 0.9 ± 3.7 mm in the mid‐ridge height, or 15.3% of the baseline height, in Test 1, and a mean increase of 1.0 ± 2.8 mm in mid‐ridge height, or 18.5% of the baseline height, in Test 2 following extraction. These changes in groups that received grafting did not reach statistical significance (Table 4).

TABLE 4.

Change in mid‐ridge height (mm) between t0 and t4 by treatment group.

Treatment groups No. of teeth Mid‐ridge height t0 (mean ± SD) Mid‐ridge height t4 (mean ± SD) Change in mid‐ridge height (mean ± SD) p Value 95% CI for mean difference % of height change
Control 10 6.8 ± 0.8 mm 4.2 ± 1.5 mm −2.7 ± 0.9 mm <0.001 −3.3, −2.0 −39.7
Test 1 8 5.9 ± 2.4 mm 6.8 ± 2.8 mm 0.9 ± 3.7 mm 0.534 −2.3, 4.0 15.3
Test 2 10 5.4 ± 2.2 mm 6.4 ± 2.7 mm 1.0 ± 2.8 mm 0.276 −1.0, 3.0 18.5
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Note: A negative value for the variable indicates a reduction in height measurement compared to pre‐operative value.

For changes in mean buccal ridge height, control group had a significant reduction of 2.7 ± 2.2 mm (p = .003, 95% CI −4.2, −1.2), or 39.7% of the baseline height, following extraction (Table 5). Similarly, Test 1 had a significant reduction of 2.5 ± 2.2 mm (p = .016, 95% CI −4.4, −0.6), or 35.7% of the baseline height. Test 2 had a significant reduction of 2.3 ± 1.7 mm (p = .002, 95% CI −3.6, −1.1), or 33.8% of the baseline height following extraction.

TABLE 5.

Change in buccal ridge height (mm) between t0 and t4 by treatment group.

Treatment groups No. of teeth Buccal ridge height t0 (mean ± SD) Buccal ridge height t4 (mean ± SD) Change in buccal ridge height (mean ± SD) p Value 95% CI for mean difference % of height change
Control 10 7.1 ± 1.4 mm 4.4 ± 1.8 mm −2.7 ± 2.1 mm 0.003 −4.2, −1.2 −38.0
Test 1 8 7.0 ± 1.7 mm 4.5 ± 3.0 mm −2.5 ± 2.3 mm 0.016 −4.4, −0.6 −35.7
Test 2 10 6.8 ± 2.3 mm 4.5 ± 2.3 mm −2.3 ± 1.7 mm 0.002 −3.6, −1.1 −33.8
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Note: A negative value for the variable indicates a reduction in height measurement compared to pre‐operative value.

For changes in mean palatal ridge height, the control group had a significant reduction of 2.1 ± 1.7 mm (p = .004, 95% CI −3.3, −0.9), or 35.0% of the baseline height, following extraction (Table 6). Similarly, Test 1 had a significant reduction of 1.6 ± 1.6 mm (p = .022, 95% CI −2.9, −0.3), or 24.2% of the baseline height. Test 2 had a significant reduction of 2.6 ± 1.7 mm (p < .001, 95% CI −3.8, −1.4), or 31.7% of the baseline height following extraction.

TABLE 6.

Change in palatal ridge height (mm) between t0 and t4 by treatment group.

Treatment groups No. of teeth Palatal ridge height t0 (mean ± SD) Palatal ridge height t4 (mean ± SD) Change in palatal ridge height (mean ± SD) p Value 95% CI for mean difference % of height change
Control 10 6.0 ± 1.3 mm 3.9 ± 1.7 mm −2.1 ± 1.7 mm 0.004 −3.3, −0.9 −35.0
Test 1 8 6.6 ± 2.1 mm 5.0 ± 2.5 mm −1.6 ± 1.6 mm 0.022 −2.9, −0.3 −24.2
Test 2 10 8.2 ± 2.5 mm 5.6 ± 2.9 mm −2.6 ± 1.7 mm <0.001 −3.8, −1.4 −31.7
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Note: A negative value for the variable indicates a reduction in height measurement compared to pre‐operative value.

Inter‐group analyses showed grafted sites in both test groups had significantly less change in mean mid‐ridge height compared to the control sites (Table 7 and Figure 5). However, there was no statistically significant difference in changes in mid‐ridge height between the sites grafted with DBBM and the sites grafted with DBBM‐C (p = .957, 95% CI −3.8, 3.6). There was also no significant difference in buccal and palatal ridge height changes between the grafted and control sites and between the two test groups (p > .05).

TABLE 7.

Statistical analyses on vertical ridge height changes between treatment groups.

Vertical ridge dimensions (mm) Intergroup comparison Mean difference (mm) Standard error difference p Value 95% CI
Change in mid‐ridge height Control vs Test 1 −3.9 1.311 0.022 −7.0, −0.8
Control vs Test 2 −3.7 0.887 0.002 −5.7, −1.7
Test 1 vs Test 2 −0.1 1.551 0.957 −3.8, 3.6
Change in buccal ridge height Control vs Test 1 −0.6 1.258 0.628 −3.6, 2.3
Control vs Test 2 −0.4 0.841 0.671 −2.3, 1.5
Test 1 vs Test 2 0.1 0.977 0.921 −2.2, 2.4
Change in palatal ridge height Control vs Test 1 −0.6 0.906 0.512 −2.8, 1.5
Control vs Test 2 0.5 0.567 0.410 −0.8, 1.8
Test 1 vs Test 2 1.0 0.443 0.059 0.0, 2.0
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FIGURE 5.

FIGURE 5

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Comparisons of vertical ridge height changes following extraction among treatment groups. (a) mid‐ridge, (b) buccal and (c) palatal. *p < 0.05 One‐way ANOVA.

3.2. Change in sinus volume

Twelve pairs of pre‐ and post‐extraction CT scans were available for sinus volume calculations and comparisons. Fourteen pairs of CT scans (five pairs in control group, three pairs in Test 1, and five pairs in Test 2) had to be excluded due to pathologic mucosal thickening or incomplete maxillary sinus inclusion in the field of view, which prevented accurate masking and segmentation.

Four pairs of sinuses in the control group were compared and showed a mean increase of 0.7 ± 0.7 cm3 in sinus volume after 4.4 ± 0.3 months following extraction. This represents an increase of 3.9% in sinus volume post‐extraction (Table 8).

TABLE 8.

Mean change in maxillary sinus volume at t0 and t4 by treatment groups.

Treatment groups Pairs of sinuses for comparisons Time (months) post‐ extraction (mean ± SD) Tooth sites Sinus volume t0 (cm3) Mean volume cm3 t0 (mean ± SD) Sinus volume t4 (cm3) Mean volume cm3 t4 (mean ± SD) Change in sinus volume (cm3) Mean change in volume cm3 (mean ± SD) p Value 95% CI for mean difference Percentage of volume change
Control 4 4.4 ± 0.3 26 & 27 17.5 18.0 ± 1.6 18.1 18.7 ± 2.3 0.7 0.7 ± 0.7 0.150 −0.4, 1.8 3.9%
26 20.1 21.8 1.7
16 18.0 18.4 0.4
16 16.4 16.4 0.0
Test 1 3 4.2 ± 0.9 26 20.5 19.2 ± 6.3 18.9 18.5 ± 6.1 −1.6 −0.7 ± 0.8 0.254 −2.7, 1.2 −3.7%
25 24.8 24.4 −0.4
17 12.4 12.3 −0.1
Test 2 5 4.0 ± 0.5 27 12.7 16.5 ± 4.0 12.6 16.7 ± 4.3 −0.2 0.1 ± 0.3 0.412 −0.3, 0.6 0.8%
26 14.5 14.7 0.3
26 16.1 16.1 0.1
26 16.1 16.0 −0.1
17 23.3 23.9 0.7
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Note: Negative value in the change in sinus volume indicates a reduction in sinus volume in the post‐extraction CT scan; a positive value indicates an increase in sinus volume in the post‐extraction CT scan; t0 = pre‐extraction, t4 = 4‐month post‐extraction.

Three pairs of CT scans were compared in Test 1 and showed a decrease of 0.7 ± 0.8 cm3 in sinus volume after 4.2 ± 0.9 months. This represents a reduction of 3.7% in sinus volume post‐extraction.

Five pairs of CT scans were compared in Test 2 and showed an increase of 0.1 ± 0.3 cm3 in sinus volume after 4.0 ± 0.5 months. This represents an increase of 0.8% in sinus volume post‐extraction. There was no significant difference in mean change in sinus volume pre‐ and post‐extraction within each group (Table 8).

When comparing changes in sinus volume between control and treatment groups, the control group showed significantly greater increase in sinus volume compared to Test 1 (p < .05, 95% CI 0.12, 2.67) (Table 9, Figure 6). There was no significant difference between control and Test 2 or between the two test groups.

TABLE 9.

Statistical analyses on sinus volume changes between treatment groups.

Intergroup comparisons Mean difference (cm3) Standard error difference Adjusted p value 95% CI
Control vs. Test 1 1.40 0.4562 0.03 0.12, 2.67
Control vs. Test 2 0.54 0.4007 0.40 −0.58, 1.66
Test 1 vs. Test 2 −0.86 0.4362 0.18 −2.08, 0.36
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FIGURE 6.

FIGURE 6

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Comparisons of sinus volume changes between control and treatment groups. *p < 0.05 Kruskal–Wallis test.

3.3. Requirement for sinus augmentation

Based on the criteria set for residual mid‐ridge height, 8 out of 9 patients (89%) in the control group required lateral window SFE for placement of a standard‐length implant (Table 10). In contrast, only three out of seven participants (42.8%) in Test 1, and 4 out of 10 participants (40%) in Test 2, required lateral window SFE. The remaining cases had sufficient residual ridge height to permit the placement of a standard‐length or a short (6 mm) implant without further vertical bone augmentations or placement of a standard‐length implant via transalveolar SFE approach.

TABLE 10.

Need for sinus augmentation based on residual mid‐ridge height.

Treatment group No. of tooth sites Tooth sites (mid‐ridge height at t4) Need for lateral SFE Treatment options
Control 10 26 (4.8 mm), 27 (5.2 mm) Yes Require lateral SFE
15 (3.5 mm) Yes Require lateral SFE
26 (3.8 mm) Yes Require lateral SFE
26 (3.1 mm) Yes Require lateral SFE
26 (1.7 mm) Yes Require lateral SFE
16 (4.7 mm) Yes Require lateral SFE
16 (2.8 mm) Yes Require lateral SFE
16 (5.0 mm) Yes Require lateral SFE
17 (6.9 mm) No 6 mm implant or 8 mm implant with transalveolar SFE
Test 1 8 16 (9.2 mm) No 8 mm implant
26 a (3.3 mm) Yes Require lateral SFE
16 a (2.9 mm), 15 a (7.0 mm) Yes (16 site) 15 site: 6 mm implant or 8 mm implant with transalveolar SFE
25 (8.8 mm) No 8 mm implant
17 b (8.1 mm) No 8 mm implant
15 (10.1 mm) No 8 mm implant
26 b (4.9 mm) Yes Require lateral SFE
Test 2 10 27 b (3.2 mm) Yes Require lateral SFE
27 (7.2 mm) No 6 mm implant or 8 mm implant with transalveolar SFE
26 (5.1 mm) No 6 mm implant or 8 mm implant with transalveolar SFE
26 (10.4 mm) No 8 mm implant
26 (9.4 mm) No 8 mm implant
26 (4.5 mm) Yes Require lateral SFE
17 (9.6 mm) No 8 mm implant
16 b (3.0 mm) Yes Require lateral SFE
16 (4.6 mm) Yes Require lateral SFE
26 (6.8 mm) No 6 mm implant or 8 mm implant with transalveolar SFE
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a

This patient has a single tooth (26) extraction on one side and multiple extractions (15 and 16) on the other side.

b

Patients that received split mouth treatment: one side in Test 1, the other side in Test 2.

4. DISCUSSION

Ridge dimensional changes in the posterior maxilla following extraction are the result of a combination of sinus pneumatization and alveolar bone resorption. With the use of current 3D imaging technology, this prospective study has demonstrated quantitatively that ARP in the posterior maxilla was able to maintain the vertical mid‐ridge dimension and reduce the sinus pneumatization process. A stringent inclusion criteria for pre‐extraction bone height of 6–8 mm was used to identify cases that would result in significant ridge resorption following extraction. This is clinically relevant in term of surgical planning to perform ARP at the time of extraction to reduce the frequency of ancillary guided bone regeneration (GBR) at implant placement.

Post‐extraction resorption in the maxillary molar and premolar regions, and the associated sinus pneumatization, has only been recently investigated qualitatively and quantitatively using 3D imaging techniques. Most previous studies investigating the effects of ARP on dimensional changes in the maxillary sinus are retrospective (Levi et al., 2017; Park et al., 2020; Sharan & Madjar, 2008; Thousand, 2015), and there are very few prospective clinical trials, evaluating the clinical efficacy of these procedures in the posterior maxilla (Cha et al., 2019; Choi et al., 2020). Furthermore, the effect of ARP on the extent of sinus pneumatization is unclear in the current literature and more prospective clinical studies are warranted.

4.1. Changes in the alveolar ridge height

Neither test groups showed significant change in postoperative mean mid‐ridge height, whereas the control group had significant mean reduction of 2.7 mm, that is, approximately 40% reduction from the baseline mid‐ridge height. Some of the test sites had an increase in the mid‐ridge mean height (ranging 0.1–2.4 mm) from the baseline, which could be attributed to the overfilling of grafting material coronal to the crestal bone. Although there were wide individual variations in the amount of post‐extraction ridge height changes, the current findings are consistent with other prospective studies demonstrating clinical benefits of ARP over unassisted socket healing in terms of ridge dimensional maintenance (Cha et al., 2019; Levi et al., 2017; Mercado et al., 2021; Rasperini et al., 2010; Wei et al., 2022). A recent clinical trial that focused on the posterior maxilla reported mean residual bone height at 6 months was significantly greater in the ARP group (7.30 mm [SD 6.36, 8.20]) compared to the control group (4.83 mm [SD 3.94, 5.76]) (Cha et al., 2019). Other clinical studies reported combined results of maxilla/mandible and anterior/posterior extraction sites, and demonstrated the benefit of ARP using xenografts in reducing the extent of dimensional changes as compared to unassisted socket healing (Cardaropoli et al., 2014; Kotsakis et al., 2014; Nevins et al., 2006; Sbordone et al., 2016).

There is wide variation in the magnitude of the clinical outcomes ranging from a gain of 0.7 mm to a reduction of 2.6 mm in the ridge heights, irrespective of the position of the extracted socket in the arch (Cardaropoli et al., 2014; Kotsakis et al., 2014; Mardas et al., 2011; Nevins et al., 2006; Vance et al., 2004). Radiological analysis (Cone beam CT) in other studies showed variations in the vertical bone level changes from gain of 1.2 mm (Jung et al., 2013) to resorption of <1.0 mm (Lambert et al., 2012) after 4–8 months following ARP procedures. However, high level of heterogeneity was present among clinical studies (Cha et al., 2019; Lombardi et al., 2018; Walker et al., 2017; Zhao et al., 2018), a fact acknowledged in recent systematic reviews (Avila‐Ortiz et al., 2019; Bassir et al., 2018; Troiano et al., 2018), and attributed to factors such as jaw and socket morphology, choice of biomaterials, surgical technique (e.g. flap reflection and type of closure), healing periods, and measurement methods.

Although ARP maintained the vertical bone height more efficiently for mid‐ridge implant placement in the posterior maxilla, it should be noted that ARP did not completely prevent horizontal resorption as there were significant reduction in both buccal and palatal ridge heights in both test groups. These results are in agreement with previous studies and additional GBR may still be required for contour augmentation at implant placement (Araújo, Silva, Mendonça, et al., 2015; Zhao et al., 2022).

4.2. Changes in the sinus volume

The current study evaluated the pre‐ and postoperative sinus volumetric changes by superimposing 3D images of sinus cavities (Alayan & Ivanovski, 2018). This allowed an accurate and reproducible quantification of sinus pneumatization following extraction and ARP. Since the maxillary sinus is a three‐dimensional air‐filled cavity, this study highlighted the volumetric change of the sinus cavity proper after extraction using 3D imaging, thus overcoming the inherit disadvantage of two‐dimensional linear measurements or perimeter tracing of the sinus (Alayan & Ivanovski, 2018).

Although Test 1 demonstrated statistically significant reduction in sinus pneumatization compared to that of the control group and Test 2 had minimal increase in sinus volume, sample size available for volumetric analyses were particularly small to determine the efficacy of ARP in the posterior maxilla. Furthermore, the clinical relevance of percentage of sinus volume change in evaluating the performance of ARP is yet to be established and future studies is needed.

It was not possible to directly compare the results of volumetric analysis in the present study with recent clinical studies due to differences in radiographic measurements. Cha et al. investigated the vertical distance between the reference point and the sinus floor at the center of the socket using the panoramic thin sections on the CBCT scan and found the ARP group showed only 0.14 mm of sinus pneumatization 6 months following extraction, compared to 1.16 mm in control group with unassisted socket healing (Cha et al., 2019). Similarly, Levi et al. reported significantly less sinus pneumatization in the ARP group compared to the control group by measuring dimensional changes of the sinus as circumferential outline and vertical distance between sinus roof and floor on 2D panoramic radiographs at 1 year follow‐up (Levi et al., 2017).

The difference in sinus volume change between the two test groups was not statistically significant. The comparative efficacy of DBBM and DBBM‐C for ARP in reducing sinus pneumatization warrants further investigation. A number of preclinical and clinical studies suggest application of a higher compressive force on particulate graft materials during socket preservation can facilitate the penetration of the graft material into the apical region of the socket, resulting in more bone formation at the coronal, middle, and apical thirds (Cho et al., 2017; Delgado‐Ruiz et al., 2018). The use of DBBM in ARP in posterior maxilla may allow for more graft particles to be in contact with the socket walls apical to the sinus floor, which may result in greater percentage of new bone formation and less apical displacement of the sinus floor. These parameters should be explored with histological analysis to identify the optimal technique and graft materials for ARP in the context of sinus pneumatization.

4.3. Requirement for sinus augmentation

The present study found that all but one of the control cases (89%) would require lateral window SFE for implant placement in the extraction sites, using residual mid‐ridge height of <5 mm as a cut‐off value. In contrast, 7 out of 17 patients (i.e., 41%) in the test groups would require a sinus augmentation. Most of the cases in the grafted groups would not require sinus augmentation for placement of a standard‐length (8 mm) implant or had sufficient ridge height to warrant a less invasive procedure (i.e., transalveolar SFE or short (<8 mm) implants).

The clinical benefits of ARP in the posterior maxilla is to maximize bone availability (the combined effects of minimizing sinus pneumatization and ridge height resorption), thereby reducing the frequency of ancillary GBR at implant placement, complication rates and patient morbidity (Cha et al., 2019; Park et al., 2020; Rasperini et al., 2010; Wei et al., 2022). Park et al. demonstrated that although sinus augmentation procedures were performed at similar rates in both the ARP and control groups, the lateral approach was applied significantly more at unassisted socket healing sites (37.2%) than ARP sites (8.3%) (Park et al., 2020). Cha et al. also reported that implant placement without any additional sinus augmentation was performed in 42.9% of ARP cases, whereas 100% of cases in the control group required additional sinus augmentations (Cha et al., 2019).

Based on these findings, the utilization of ARP should be strategically considered during the treatment planning phase. The use of 3D imaging in pre‐extraction assessment is invaluable since the effectiveness of ARP will likely depend on the anatomical relationship between the tooth and sinus. As demonstrated in our results, there were cases in which ARP was not effective in maintaining the mid‐ridge height or minimizing sinus pneumatisation. These cases were usually associated with insufficient alveolar bone in the inter‐radicular area, divergent roots and/or inferior extension of the sinus floor into the inter‐radicular region. Previous studies have suggested that the clinical outcomes of alveolar ridge resorption and sinus pneumatization are likely to be influenced by the intimate relationship between tooth roots and the maxillary sinus floor, which would also determine the availability of intervening/inter‐radicular alveolar bone (Cavalcanti et al., 2018; Sharan & Madjar, 2008). Furthermore, other factors such as tooth sites (premolars vs molars), number of extractions, number of roots, apical alveolar bone height, presence of septa, pre‐existing sinus pathologies may also influence the outcomes of ARP. During the clinical decision‐making process, a number of factors needs to be considered as to when to apply ARP, such as ability to achieve primary stability in the restoratively driven position and proximity to the sinus are particularly relevant in the posterior maxilla (Tonetti et al., 2019). The type of implant placement protocol is also a relevant factor, since in some protocols such as Type 2 or early placement, the benefit of ARP appears to be limited (Strauss et al., 2024).

4.4. Limitations

This was a pilot study with a relatively small number of participants, primarily due to the stringent inclusion criteria used for pre‐extraction ridge height dimensions. There were also limitations to the recruitment process such as a change of study location from one university to another and length of the study subject to completion of post‐graduate training program. Although as many participants as possible were recruited, these factors limited sample size and participant follow‐up.

The wide confidence intervals indicated a large degree of individual variation. Several potential confounding factors, including uneven distribution of multiple adjacent extraction sites, dentate status in the posterior maxilla, and sinus mucosal thickening that excluded many of the scans from volumetric analysis, may have affected the results. Furthermore, age (Lim et al., 2019), type of extraction socket defect, and the vertical relationship between root apices and sinus floor are likely to affect the magnitude of pneumatization (Cha et al., 2019; Sharan & Madjar, 2006, 2008) and require further investigation in future studies.

While there was sufficient power to demonstrate statistically significant results for changes in mean mid‐ridge height between the control and both test groups, some analysis were underpowered because of limited sample size. A larger sample size (no. of extraction sites) based on the effect size observed would be required in future studies. Based on the data obtained from this pilot study, 1500 extraction sites per treatment group (i.e. 3000 sites total) are required to compare mean changes in buccal ridge height between the control and test groups to achieve a similar effect size (Cohen's d = 0.09) at 80% power and 5% significance. For sinus volume changes after extraction/ARP, 21 pairs of sinuses would be required to achieve a similar effect size (Cohen's d = 0.571) at 80% power and 5% significance. For comparison of mean changes in sinus volume between control and grafted group, 11 pairs of sinuses per group (i.e. 22 total) is required to achieve a similar effect size (Cohen's d = 0.4) at 80% power and 5% significance.

The requirement for sinus augmentation was assessed based on predetermined radiological criteria (Table 3). It would have been beneficial to confirm such procedures clinically during implant surgery. However, implant placement was elective in this study based on individual patient's preference. Further studies with sufficient samples should include implant outcome measures, histological outcomes via biopsies of osteotomy sites and patient‐reported outcomes.

5. CONCLUSION

Within the limits of the study, the findings support the efficacy of ARP in minimizing resorption in the middle of the ridge and may reduce sinus pneumatization following tooth extraction in the posterior maxilla. While some degree of resorptive change still occurs in the alveolar process, ARP could potentially decrease the need for more invasive sinus augmentation procedures, thus reducing treatment complexity and morbidity associated with implant placement.

AUTHOR CONTRIBUTIONS

Lisetta Lam: Writing – original draft; conceptualization; investigation; methodology; formal analysis. Saso Ivanovski: Conceptualization; investigation; methodology; supervision; writing – review and editing. Ryan S. B. Lee: Writing – review and editing; writing – original draft; conceptualization; investigation; methodology; supervision.

CONFLICT OF INTEREST STATEMENT

The authors declare no conflict of interest.

Supporting information

Appendix S1

CLR-35-1568-s001.doc (218.5KB, doc)

ACKNOWLEDGMENTS

Geistlich Pharma Australia for donating all the biomaterials used for the ridge preservation procedures in this study. Professor Paul Monsour and Dr. Raahib Dudhia for their guidance in developing the imaging protocol and Dr. Jamil Alayan for his work and training in sinus volume analysis. Dr. Kelly McGowen and Dr. Pingping Han for their statistical expertise and support. Open access publishing facilitated by The University of Queensland, as part of the Wiley ‐ The University of Queensland agreement via the Council of Australian University Librarians.

Lam, L. , Ivanovski, S. , & Lee, R. S. B. (2024). Alveolar ridge preservation in posterior maxillary teeth for reduction in the potential need for sinus floor elevation procedures: A pilot study. Clinical Oral Implants Research, 35, 1568–1584. 10.1111/clr.14344

Primary author is Lisetta Lam and Ryan Lee is the corresponding author of the manuscript.

The corresponding author is responsible for the overall research project and final approval of the manuscript.

ACTRN: ACTRN12619000125123.

DATA AVAILABILITY STATEMENT

Research data are not shared.

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Supplementary Materials

Appendix S1

CLR-35-1568-s001.doc (218.5KB, doc)

Data Availability Statement

Research data are not shared.

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