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Crestal bone level changes and survival of immediately placed extra-wide diameter implants in posterior molar sites: A prospective clinical study
*Corresponding author: Katherine Sue Hanser, Department of Surgical Sciences and Community Care, Southern Illinois University School of Dental Medicine, Alton, United States of America. kathans@siue.edu
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Received: ,
Accepted: ,
How to cite this article: Hanser KS, Miley DD, Blackwell RL, Duncan RC, Omran-Alfaitouri M. Crestal bone level changes and survival of immediately placed extra-wide diameter implants in posterior molar sites: A prospective clinical study. J Adv Dental Pract Res. 2026;5:17-22. doi: 10.25259/JADPR_25_2026
Abstract
Objectives:
To evaluate crestal bone level changes and survival of immediately placed extra-wide diameter implants in posterior molar sites.
Material and Methods:
This prospective clinical study included 30 patients requiring molar extraction and implant placement, with 28 patients completing follow-up. A total of 29 implants were placed immediately following atraumatic extraction and positioned subcrestally. Crestal bone levels were measured radiographically at placement and at a minimum of 1-year post-restoration using calibrated ImageJ analysis.
Results:
The mean crestal bone level was 1.28 mm at placement and 0.46 mm at follow-up, with a mean change of 0.82 mm (95% confidence intervals: 0.34–1.29 mm). This difference was statistically significant (p = 0.001). Despite this change, crestal bone levels remained coronal to the implant platform at follow-up. One implant failure occurred, resulting in a survival rate of 96.5%.
Conclusion:
Immediate placement of extra-wide diameter implants in posterior molar sites demonstrated high survival rates and maintenance of crestal bone levels above the implant platform, suggesting this approach is a predictable treatment option.
Keywords
Crestal bone level
Dental implants
Immediate implant placement
Posterior molar
Wide diameter implants
INTRODUCTION
Tooth loss remains a common consequence of oral disease, most frequently resulting from advanced dental caries, periodontal disease, trauma, or failure of previous dental treatment. Partial and complete edentulism are associated with significant functional, esthetic, and psychosocial consequences, including impaired mastication, altered speech, and diminished oral health–related quality of life. Previous studies have demonstrated that the loss of even a single tooth may negatively affect dietary habits, self-perception, and patient satisfaction, highlighting the importance of timely and predictable tooth replacement therapies.[1,2]
Dental endosseous implants have become a highly predictable treatment modality for the replacement of missing teeth. Numerous studies have demonstrated favorable long-term outcomes for implant-supported prostheses in both partially and completely edentulous patients.[2] In addition to restoring dentition, implant therapy has been shown to improve oral health–related quality of life by reestablishing masticatory function, esthetics, and patient confidence.[2,3] Despite these high success rates, implant outcomes remain influenced by local anatomic factors, particularly the quantity and quality of available alveolar bone at the implant site.[3,4]
Posterior molar regions present unique clinical challenges due to anatomical constraints, including limited vertical bone height, proximity to vital structures, and increased occlusal loading. In these situations, the use of shorter implants is often required to accommodate anatomic limitations while avoiding additional surgical procedures such as sinus augmentation or nerve repositioning. To compensate for reduced implant length, increasing implant diameter has been proposed as a method to enhance bone-to-implant contact, improve primary stability, and increase resistance to occlusal forces.[5,6]
Wide-diameter implants were historically used primarily as rescue implants following failure of standard-diameter implants and were initially associated with higher failure rates.[7] However, more recent studies suggest that advancements in implant macro design and surface characteristics have resulted in improved clinical outcomes for wide and extra-wide diameter implants, particularly in posterior regions.[6,8] For this study, wide diameter implants were defined as implants with a diameter of ≥4.5 mm, and extra-wide diameter implants were defined as those ≥6.0 mm. Immediate implant placement following tooth extraction offers several potential advantages, including reduced treatment time, preservation of alveolar bone, and elimination of additional surgical procedures. In addition, reducing the duration of edentulism may help restore function and patient comfort more rapidly. However, concerns remain regarding crestal bone stability and long-term outcomes, particularly when implants are placed in molar extraction sites.
While immediate implant placement and the use of wide-diameter implants have been independently investigated, limited prospective data exist evaluating the clinical performance of immediately placed extra-wide diameter implants in posterior molar sites, particularly with respect to crestal bone stability. Further investigation is therefore warranted to better understand the clinical outcomes associated with this treatment approach.
The purpose of this prospective clinical study is to evaluate crestal bone level changes and survival of immediately placed extra-wide diameter implants in posterior molar sites.
MATERIAL AND METHODS
Study design and ethical considerations
This prospective clinical study was conducted at the Southern Illinois University School of Dental Medicine, Alton, Illinois, USA. Ethical approval for the study was obtained from the Southern Illinois University Institutional Review Board (IRB approval number: 67, dated November 25, 2025). All procedures were performed in accordance with the ethical standards of the Institutional Research Committee and with the principles outlined in the Declaration of Helsinki of 1975, as revised in 2000.
Before participation, all patients were informed of the nature of the study and provided written informed consent. Patient anonymity and confidentiality were maintained throughout the study.
Participant selection
Patients presenting to the Southern Illinois University School of Dental Medicine clinics who required the extraction of posterior molar teeth and subsequent implant therapy were screened for eligibility. Screening included clinical examination and radiographic evaluation using cone-beam computed tomography (CBCT) imaging obtained with an Axeos CBCT unit (Dentsply Sirona, Charlotte, North Carolina, USA).
Inclusion criteria
Participants were eligible for inclusion if they met the following criteria:
Age ≥18 years
Presence of a molar tooth requiring extraction in the maxilla or mandible
Intact buccal plate following extraction
Adequate bone volume to permit immediate implant placement
Placement of at least one immediately placed implant
Primary implant stability with a minimum insertion torque of 35 Ncm.
Exclusion criteria
Patients were excluded if any of the following conditions were present:
History of radiation therapy to the head-and-neck region
Uncontrolled diabetes mellitus (Hemoglobin A1C ≥8.0)
Immunocompromising conditions or severe systemic disease
Heavy smoking (≥20 cigarettes/day)
Intravenous bisphosphonate therapy
Patients unable or unwilling to comply with study procedures.
Surgical protocol
All surgical procedures were performed under local anesthesia. Following atraumatic extraction of the molar tooth, the extraction socket was thoroughly debrided to remove granulomatous tissue and debris. Osteotomy preparation was completed according to the manufacturer’s surgical protocol for the implant system used, Southern ProMax dental implants (Southern Implants, Irene, Centurion, South Africa). Extra-wide diameter implants (≥6.0 mm) were placed immediately into the extraction socket and positioned at least 2 mm subcrestally to allow for an appropriate prosthetic emergence profile and anticipated crestal bone remodeling. Primary implant stability was confirmed with a minimum insertion torque of 35 Ncm.
When indicated, bone grafting material was used to fill residual gaps between the implant surface and the extraction socket walls using Straumann Allograft (Institut Straumann AG, Basel, Switzerland).
Following implant placement, a PEEK healing abutment (Southern Implants, Irene, Centurion, South Africa) was hand-tightened onto the implant. Post-operative CBCT imaging was obtained to confirm implant positioning and angulation.
Data collection and outcome measures
For each participant, demographic data and implant-related variables, including implant location, diameter, and length, were recorded.
Primary outcome measure
The primary outcome measure was crestal bone level changes. Radiographic measurements were obtained using CBCT images and analyzed with ImageJ software (National Institutes of Health, Bethesda, Maryland, USA), calibrated using the known implant length. Measurements were recorded at the mesial and distal aspects of each implant to provide standardized interproximal reference points for comparison between baseline and follow-up images. Buccal and lingual measurements were not included in the primary analysis to maintain consistency across implant sites and reduce variability related to socket morphology, implant angulation, and differences in cross-sectional image orientation.
Baseline measurements were obtained from radiographs taken at the time of implant placement [Figure 1]. These measurements were compared with follow-up radiographs obtained after delivery of the definitive restoration [Figure 2]. All post-operative radiographs were acquired a minimum of 1 year following implant placement and prosthetic restoration.
Because implants were placed in a subcrestal position, positive values indicated bone levels were maintained coronal to the implant platform, whereas negative values indicated remodeling placed crestal bone levels below the implant platform. Mesial and distal measurements were averaged to calculate the mean crestal bone level for each implant.
Secondary outcome measures
Secondary outcome measures included implant survival and prosthetic complications.
Implant survival was defined as the implant remaining present and functional in the oral cavity at the time of evaluation. Prosthetic complications, including mechanical or restorative complications associated with the definitive restoration, were also recorded.
Statistical analysis
Statistical analysis was performed to evaluate changes in crestal bone levels between the time of implant placement and the follow-up evaluation. Because only one patient received two implants, implant-level analyses were performed. The potential effect of within-patient clusters was considered minimal due to the presence of only one participant with multiple implants. Descriptive statistics were calculated for baseline and follow-up bone crest–to–implant platform measurements, including means and ranges. Positive measurement values indicated that the crestal bone was maintained coronal to the implant platform, whereas negative values represented bone levels apical to the implant platform.
All radiographic measurements were performed by a single calibrated examiner. Agreement and repeatability between radiographic measurements were assessed using the Bland– Altman method for method comparison studies, which evaluates the differences between repeated measurements relative to their means and determines whether these differences fall within clinically acceptable limits.[9,10] This method allows assessment of measurement agreement and repeatability rather than simple statistical association. In this approach, the mean difference between measurements and the 95% limits of agreement are calculated, with the expectation that approximately 95% of measurement differences will fall within these limits.[11]
Before data analysis, a difference of 1.5 mm was considered clinically acceptable for measurement repeatability. The repeatability coefficient was calculated to determine the magnitude of change required to be 95% confident that an observed change represents a true biological difference rather than measurement variability.[11]
If the distribution of measurement differences was approximately normal, inferential statistical analysis was performed using a paired t-test to evaluate differences in crestal bone levels between baseline and follow-up measurements. The mean difference and 95% confidence intervals (CI) were calculated to estimate the magnitude of change in crestal bone levels over time. If the 95% CI included zero, no statistically significant difference between measurements would be assumed.[11]
Implant survival was calculated as the proportion of implants remaining present in the oral cavity at the time of follow-up evaluation. Statistical significance was set at p < 0.05. Statistical analyses were performed using R statistical software (R Foundation for Statistical Computing, Vienna, Austria).
RESULTS
A total of 30 patients were initially enrolled in the study. Two patients were lost to follow-up, leaving 28 patients for the final analysis. A total of 29 implants were evaluated because one participant received two immediately placed implants, while all remaining participants received a single implant. Implant diameters were distributed as follows: 6.0 mm (n = 1), 7.0 mm (n = 13), 8.0 mm (n = 14), and 9.0 mm (n = 1). All implants were either 9 mm or 11 mm in length. One implant failed during the observation period, resulting in an implant survival rate of 96.5%.
Radiographic measurements were obtained at the time of implant placement and at follow-up evaluation. The mean crestal bone level relative to the implant platform at implant placement was 1.28 mm (range −0.8–5.7 mm). At the follow-up evaluation, the mean crestal bone level was 0.46 mm (range −4.8–3.0 mm).
The mean change in crestal bone level between implant placement and follow-up evaluation was 0.82 mm. A paired t-test demonstrated a statistically significant difference between baseline and follow-up measurements (t = 3.42, df = 55, p = 0.001). The 95% CI for the mean difference ranged from 0.34 mm to 1.29 mm [Table 1].
| Measurement | Mean (mm) | Range (mm) |
|---|---|---|
| Crestal bone level at implant placement | 1.28 | −0.8–5.7 |
| Crestal bone level at follow-up | 0.46 | −4.8–3.0 |
| Mean change in crestal bone level | 0.82 | — |
Positive values indicate crestal bone levels maintained coronal to the implant platform
Because implants were intentionally placed subcrestally, positive values indicate crestal bone levels were maintained coronal to the implant platform, whereas negative values indicate bone levels below the implant platform. Although a statistically significant change in crestal bone level was observed, the mean bone level remained coronal to the implant platform at follow-up indicating maintenance of crestal bone relative to the implant platform.
No prosthetic complications were observed among the implants restored during the study period.
DISCUSSION
The present prospective clinical study evaluated crestal bone levels and survival of immediately placed extra-wide diameter implants in posterior molar extraction sites. The results demonstrated a high implant survival rate of 96.5%, with a mean change in crestal bone level of 0.82 mm between implant placement and follow-up evaluation.
Posterior molar regions present unique challenges for implant placement due to anatomical limitations, increased occlusal forces, and complex socket morphology following tooth extraction. Extra-wide diameter implants have been proposed as a potential solution in these situations because increasing implant diameter may enhance bone-to-implant contact and improve primary stability. Immediate implant placement offers additional advantages, including reduced treatment time, fewer surgical procedures, and decreased duration of edentulism for patients.
In the present study, implants were intentionally placed subcrestally which must be considered when interpreting crestal bone measurements. Although a mean change of 0.82 mm was observed between baseline and follow-up measurements, the mean crestal bone level at follow-up remained coronal to the implant platform. Because positive values represent bone maintained above the platform, this finding suggests that peri-implant bone support remained favorable despite the observed remodeling.
The statistically significant change in crestal bone levels likely reflects physiologic crestal bone remodeling commonly reported following implant placement and functional loading rather than pathological bone loss. Early crestal bone remodeling around dental implants has been widely described in the literature and is generally associated with the establishment of the peri-implant biologic width and adaptation of surrounding tissues.
The survival rate observed in this study is consistent with previously reported outcomes for wide and extra-wide diameter implants placed in posterior regions, which have demonstrated high survival rates for both prospective and retrospective analyses.[12,13] Increasing implant diameter may enhance primary stability and increase implant surface area, which may be particularly advantageous when implants are placed immediately into molar extraction sockets.
Several limitations of this study should be acknowledged. The sample size was relatively small, and two patients were lost to follow-up. In addition, the interval between implant placement and follow-up evaluation varied among participants, resulting in some restorations being in occlusal function longer than others at the time of radiographic evaluation. As crestal bone remodeling may occur over time following implant loading, this variability may have influenced the magnitude of bone level changes observed.
In addition, only mesial and distal crestal bone level measurements were included in the analysis. Although CBCT imaging permits three-dimensional assessment, buccal and lingual measurements were not evaluated in the present study, which may limit characterization of circumferential peri-implant bone changes.
Future studies with larger patient cohorts, standardized follow-up intervals, and longer observation periods are warranted to further evaluate the long-term performance of immediately placed extra-wide diameter implants in posterior molar sites.
No prosthetic complications were observed among the implants restored during the study period.
Clinical significance
While immediate placement of extra-wide diameter implants in posterior molar extraction sites demonstrated high survival rates and maintenance of crestal bone levels above the implant platform, suggesting that immediate placement of extra-wide diameter implants may represent a promising treatment option for carefully selected posterior molar sites, larger prospective studies are needed before definitive conclusions regarding predictability can be made.
CONCLUSION
Within the limitations of this prospective clinical study, immediate placement of extra-wide diameter implants in posterior molar extraction sites demonstrated favorable survival and maintenance of crestal bone levels relative to the implant platform. Although a mean crestal bone level change of 0.82 mm was observed, bone levels remained coronal to the implant platform, suggesting that the observed change likely represents physiologic remodeling rather than pathological bone loss.
Acknowledgments:
The authors would like to acknowledge the contributions of the clinical staff and support personnel who contributed to this study. The authors also acknowledge Southern Implants North America for the donation of the implants used.
Authors’ contributions:
KSH: Investigation, data curation, writing original draft, writing review & editing; DDM: Conceptualization, methodology, software, validation, formal analysis, investigation, data curation, writing review & editing, supervision; RLB: Conceptualization, methodology, writing review & editing, supervision, funding acquisition; RCD: Conceptualization, methodology, investigation, writing review & editing; MO: Conceptualization, methodology, investigation, writing - review & editing, supervision, project administration.
Ethical approval:
The research/study was approved by the Institutional Review Board at Southern Illinois University Edwardsville, number 67, dated 18th November 2025.
Declaration of patient consent:
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given consent for their clinical information to be reported in the journal. The patient understands that the patient’s names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Conflict of interest:
There is no conflict of interest.
Use of artificial intelligence (AI)-assisted technology for manuscript preparation:
The authors confirm that they have used artificial intelligence (AI)-assisted technology for grammatical editing, and formatting of the manuscript.
Financial support and sponsorship: Nil.
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