Alveolar and maxillary sinus volumetric quantification after sinus lift, bone graft, and implant placement using cone-beam computed tomography: A retrospective study

Abstract

Background:

Tooth loss in the posterior maxilla frequently leads to alveolar ridge resorption and maxillary sinus pneumatization, compromising implant placement and often requiring sinus lift (SL) procedures. This study evaluated volumetric changes in the alveolar ridge and maxillary sinus using cone-beam computed tomography (CBCT) after SL, inorganic bovine bone grafting, and implant placement.

Materials and Methods:

A retrospective analysis was performed on 16 maxillary sinuses from 12 patients (6 female and 6 male; mean age: 55.8 years). CBCT scans were obtained at baseline (T0), postgraft evaluation before implant planning (T1), and postimplant healing (T2; mean follow-up 29 months). Alveolar ridge and sinus volumes were measured using ITK-SNAP software. The outcomes evaluated were alveolar ridge volume (mm³), maxillary sinus volume (mm³), percentage of bone gain (T1–T0), and graft resorption (T1–T2). Volumetric measurements at different time points were compared using analysis of variance; bone gain and resorption were compared using t-test, and clinical/demographic variables were assessed for associations. The significance level was P < 0.05.

Results:

A significant increase in alveolar ridge volume was observed at T1, followed by 11% resorption at T2 over 4 years, primarily in the cervical implant region. Maxillary sinus volume significantly decreased at T1 without subsequent re-pneumatization at T2. Sites with a volumetric gain exceeding 200% at T1 exhibited lower resorption rates at T2 (P = 0.036). Clinical and demographic variables had no association with bone gain nor resorption (P > 0.05).

Conclusion:

Bone gain and graft volume maintenance were primarily influenced by the extent of grafting, while patient-related variables showed no significant association.

INTRODUCTION

Tooth loss is a prevalent condition worldwide, requiring attention and treatment for both total edentulism and single-tooth loss.[1] In the upper posterior region, tooth loss often leads to alveolar bone resorption and pneumatization of the maxillary sinus,[2] complicating implant placement due to insufficient bone height.[3] Therefore, to enable rehabilitation with dental implants, various techniques, including Le Fort I osteotomy, onlay bone grafting, and sinus lift (SL), are employed alongside diverse graft materials such as autogenous, allogeneic, xenogenic, and alloplastic materials.[4,5]

Diagnosis and treatment planning for SL and bone grafting include clinical and imaging evaluations. While radiographs provide lower radiation doses, they offer limited two-dimensional assessments of three-dimensional structures. Cone-beam computed tomography (CBCT) is the preferred imaging modality for planning oral rehabilitation with osseointegrated implants and SL surgery due to its superior spatial resolution and capability to assess hard tissue and graft material.[6,7]

CBCT’s high spatial resolution allows detailed evaluation of bone and graft material, making it a valuable tool for understanding graft resorption and new bone formation.[5,8] In a systematic review, Shanbhag et al.[8] found that autogenous bone grafts may resorb by up to 45% over 6 months to 2 years, whereas inorganic bovine bone grafts exhibit resorption rates of 18%–23%. Although graft resorption and new bone formation are expected, they generally do not compromise implant stability or long-term survival.[8] Nevertheless, CBCT is not the preferred imaging modality for routine implant follow-up,[6,7] even though the evaluation of bone and graft stability adjacent to implants after functional load is crucial.[9,10] CBCT is particularly useful for assessing volumetric changes post-SL, providing insights beyond linear measurements offered by radiographs. It has primarily been used to evaluate graft volume and resorption rates, but studies exploring maxillary sinus volume changes are limited.[11,12,13] This aspect is increasingly relevant as sinus volume stability may influence long-term outcomes of grafting and implant placement.

The growing use of CBCT in dental practice has the potential to contribute to diagnosing, planning, and monitoring rehabilitations involving SL and implants. While previous studies have predominantly focused on graft volume changes or linear dimensional assessments, the combined longitudinal evaluation of alveolar ridge augmentation and maxillary sinus volumetric behavior following implant placement remains insufficiently explored. A comprehensive understanding of these simultaneous volumetric changes may provide deeper insight into graft stability, sinus adaptation, and long-term rehabilitation outcomes.

Therefore, the present retrospective study aimed to evaluate volumetric changes in the alveolar ridge and maxillary sinus using CBCT after lateral window SL, inorganic bovine bone grafting, and implant placement, as well as to investigate possible associations with clinical and demographic variables.

MATERIALS AND METHODS

Ethical aspects

The research protocol of this study was approved by the Institution Research Ethics Committee (protocol number CAAE44943321.3.0000.5346) and was conducted in accordance with the World Medical Association Declaration of Helsinki. This study was developed according to STROBE guidelines.

Sample

A retrospective study was conducted using all CBCT images from patients who underwent SL surgery, inorganic bone grafting, and delayed implant placement between 2015 and 2021. The exams were requested for diagnosis, planning, and monitoring of bone grafting and dental implant procedures and were stored at the Dental Radiology sector of the institution.

Patients were eligible for inclusion if they had undergone lateral window SL with inorganic bovine bone grafting in the posterior maxilla, received delayed implant placement in the grafted region, and had three CBCT examinations available corresponding to evaluation of the residual ridge (T0), postgraft evaluation before implant planning (T1), and postimplant healing (T2). In addition, complete clinical and demographic records had to be available in the institutional database to allow comprehensive data collection. CBCT images with acquisition errors, which did not present the entire graft region or whose patient did not have all treatment stages documented in the medical record registered in the institution files, were excluded. Due to the strict inclusion criteria requiring three CBCT examinations over an extended follow-up period, only a limited number of cases were eligible for analysis. Consequently, the study sample represents a convenience sample comprising all patients who met the eligibility criteria within the defined timeframe.

Image acquisition

All CBCT exams were performed on the Orthopantomograph OP300 equipment (Instrumentarium Dental, Tuusula, Finland). The patient positioning followed the manufacturer’s recommendations: patient with midsagittal plane perpendicular to the ground and the occlusal plane parallel to the ground, aligned in the region of interest (ROI) (posterior maxilla). The acquisition parameters used were 3.24 mAs, 110 kVp, 20 s, 6 cm × 8 cm field of view (FOV), and 0.2 mm voxel. The same acquisition protocol was used in all clinical evaluation stages. Three CBCT scans were analyzed for each selected case: diagnosis and surgical planning of SL and graft (T0), evaluation of the graft after SL and surgical planning of the dental implant (T1), and longitudinal evaluation of the dental implant (T2).

Clinical procedures

All surgical procedures were performed by the same professional, specialist in implantology, after careful physical, clinical, and imaging evaluation of the patient. All patients presented a residual bone height <5 mm (evaluated in the cross-sectional image from CBCT).

SL was performed using the lateral window SL technique. Under local anesthesia, a full-thickness mucoperiosteal flap was elevated to expose the buccal cortex of the maxillary sinus. An oval-shaped window was created with a straight handpiece and a #6 round-shaped diamond bur with abundant irrigation using 0.9% saline solution. The sinus membrane was exposed and gently dissected with curettes (Neodent, Curitiba, Brazil). The buccal bone was then displaced medially and superiorly, elevating the floor of the maxillary sinus. The space created was filled exclusively using inorganic bone graft (Bio-oss; Geistlich, Wolhusen, Switzerland) in a sufficient quantity to reach a height of 10–12 mm, aiming for the subsequent placement of a 10 mm implant, with its apex completely covered by grafting material. A collagen membrane (Bio-Gide; Geistlich, Wolhusen, Switzerland) was placed over the buccal window to prevent graft migration and soft-tissue invasion. The soft-tissue flap was replaced with tension-free sutures (Nylon 4-0). The suture was removed after 14 days. Patients were prescribed Amoxicillin (875 mg), twice daily, from 3 days before surgery to 4 days after surgery, Flancox (400 mg) twice daily, for 5 days, Dipyrone (1 g), up to 4 times daily, and told to rinse with chlorhexidine 0.12% twice a day for 1 week.

After the healing process and a second CBCT examination (T1), Cone Morse or Gran Morse dental implants, all conical (Neodent, Curitiba, Brazil), were planned and inserted in the grafted region. The sequence of drilling and torque for implant placement followed the protocol as recommended by the manufacturer. The implant platform was always placed at the alveolar crest. The implants were left unloaded and covered by soft tissue, with no immediate functional load. Suture was performed (Nylon 4-0). Patients were prescribed Amoxicillin (2 g) 1 h before surgery, Flancox (400 mg), twice a day, for 5 days, Dipyrone (1 g), up to 4 times a day, and told to rinse with chlorhexidine 0.12% twice a day for 1 week.

Prosthetic rehabilitation was conducted after a minimum period of implant osseointegration of 6 months. The success of the procedure (absence of mobility, absence of symptoms, and absence of a radiolucent line between the implant and the bone tissue) was assessed by clinical and CBCT evaluation (T2).

Data collection

All CBCT images (T0, T1, and T2) were exported in DICOM format and evaluated by two trained and calibrated examiners. The training consisted of a meeting to define concepts and anatomic landmarks. Calibration consisted of the evaluation of nine exams, twice, with a 7-day interval. The intra- and interexaminer agreement, according to the Intraclass Correlation Coefficient (ICC), was >0.9.

Volumetric measurements at T0, T1, and T2 were obtained by segmenting the ROI on CBCT images using ITK-SNAP software (University of Pennsylvania, Philadelphia, PA, USA). At T0, the residual alveolar ridge volume was measured before SL surgery. At T1, volumetric assessment corresponded to the augmented area after graft healing and before implant placement. At T2, the grafted region was re-evaluated following implant placement and functional follow-up to determine volumetric maintenance and dimensional changes over time.

Volume assessment was performed as follows: first, the ROI, comprising the rehabilitated region and extending 20 mm from the alveolar crest into the maxillary sinus, was delimited in the sagittal plane. The sagittal plane was used for the mesiodistal definition of the interest area and the axial plane for the buccolingual delimitation [Figure 1]. After delimitation, the region was segmented from the total volume to calculate the volume (in mm³). The measurement of the maxillary sinus was performed with a semi-automatic tool, with manual refinement. Hard tissue measurement was performed with the manual segmentation tool. At T0, only the residual ridge was present for segmentation [Figure 2a]; at T1, the bone ridge and the graft material were segmented [Figure 2b]; finally, at T2, the bone ridge, the graft material, and the implant, when inserted into the bone tissue, were included in the segmentation [Figure 2c]. At T2, the implant platform was used as the reference point for ROI measurement. Sagittal sections (a–c) and volumetric segmentations of the maxillary sinus region (shown in red) and the ridge (shown in green) are illustrated in Figure 2 [at T0 (a/d), T1 (b/e), and T2 (c/f)].

Figure 1.

Region of interest defined in the sagittal (a); axial (b); and coronal (c) planes at baseline cone-beam computed tomography scan (T0)

Figure 2.

Sagittal sections (a-c) and corresponding three-dimensional volumetric segmentations (d-f) of the maxillary sinus region (red) and alveolar ridge (green) at T0 (a and d), T1 (b and e), and T2 (c and f)

The axial, coronal, and sagittal planes were adjusted and aligned based on the center of the implant’s long axis, assuring all three evaluated images would present the same region. The zoom and brightness-contrast tools were available to allow better identification of structures and delineation of cavities.

Clinical and demographic data were collected from the patients’ dental records. Demographic data included gender (female and male) and age (collected in years). Clinical data included systemic impairment (including smoking), history of periodontal disease, and presence of prosthetic rehabilitation in the implant. The dates when the graft, implant, and prosthesis procedures were performed were also registered, allowing the time elapsed evaluation since the treatments were carried out. The follow-up time was the time between the SL graft and the T2 CBCT scan, indicating the longitudinal follow-up of the patient. The prosthetic time, calculated only for those patients who had already experienced prosthetic rehabilitation and indicating the time during which the implant was under functional loading, was calculated between the prosthesis installation and the T2 CBCT scan.

Statistical analysis

The outcomes evaluated were alveolar ridge volume (mm³), maxillary sinus volume (mm³), percentage of bone gain (T1-T0), and graft resorption (T1-T2). Mean variations in bone gain at T1 and bone resorption at T2 were used as cut-off values to dichotomize these variables.

Data normality was assessed using the Kolmogorov–Smirnov test. Comparisons across time points were performed using repeated measures analysis of variance, followed by Bonferroni post hoc tests when appropriate. Associations between dichotomized outcomes and categorical variables were analyzed using the Chi-square test. Bone gain and resorption were compared according to clinical and demographic variables (gender, age, systemic impairment, periodontal disease, presence of dental prosthesis, and follow-up period) using the independent samples t-test.

Statistical analyses were performed using Microsoft Office Excel (Microsoft Corp., Redmond, WA, USA) and SPSS (SPSS Inc., Chicago, IL, USA). The level of statistical significance was set at P < 0.05.

RESULTS

A total of 12 patients and 16 maxillary sinuses were included in the analysis. Clinical, demographic, and tomographic characteristics of the sample are summarized in Table 1. All SL, grafting, and implant procedures were clinically successful, with no implant loss during the follow-up period. Seven out of 16 implants placed were rehabilitated with dental prosthesis and subjected to functional loading.

Table 1.

Demographic, clinical, and tomographic characteristics of the sample

Variable	Mean±SD (minimum–maximum)
Demographic and clinical variables (N=12), N (%)
Gender
Female	6 (50)
Male	6 (50)
Age (years)	55.8 (49–67)
Systemic impairment
Absent	8 (66.7)
Present	4 (33.3)
Periodontal disease
Absent	9 (75)
Present	3 (25)
Dental prosthesis (n=16)
Absent	9 (56.3)
Present	7 (43.8)
Tomographic variables (n=16)
Bone volume (mm3)
T0	457.53±293.40 (104.1–1232)
T1	1141.27±596.78 (546.7–2381)
T2	1019.32±563.14 (433–2137)
Sinus volume (mm3)
T0	1639.57±701.77 (460.2–3218)
T1	1080.90±451.53 (208–1907)
T2	1126.18±397.57 (380–1847)
Bone gain at T1 (mm3)	683.74±432.77 (298.4–1751.7)
Bone gain at T1 (%)	201.51±137.63 (50.57–458.54)
Bone resorption at T2 (mm3)	121.95±84.66 (9.5–319)
Bone resorption at T2 (%)	11.74±7.10 (1.03–21.30)
Implant follow-up (months)	29±19 (7–60)
Prosthetic follow-up (months) (n=7)	21±15 (3–43)

T0 – CBCT for diagnosis and surgical planning of SL graft; T1 – CBCT for graft evaluation after SL and dental implant surgical planning; T2 – CBCT for longitudinal evaluation of the dental implant and SL; SD – Standard deviation; CBCT – Cone-beam computed tomography; SL – Sinus lift; N – Number of patients; n – Number of grafts

The mean alveolar ridge volume increased from 457.53 mm³ (range: 104.1–1232) at T0 to 1141.27 mm³ (range: 546.7–2381) at T1, representing a mean volumetric gain of 200% (range: 50.57–458.54). During follow-up, the mean volume decreased to 1019.32 mm³ (range: 433–2137) at T2, corresponding to a mean absolute reduction of 121.95 mm³ (11%) [Table 1]. Repeated measures analysis confirmed a significant increase from T0 to T1 and a significant, though moderate, reduction from T1 to T2 [Table 2]. Despite this reduction, ridge volume at T2 remained substantially higher than baseline values.

Table 2.

Comparison of mean ridge and maxillary sinus volumes (mm³) at the evaluated time points

Variable	Volume			P
	T0	T1	T2
Bone volume	457.53A	1134.84B	1032.39C	<0.001
Sinus volume	1639.57A	1080.90B	1126.18B	<0.001

P value, repeated measures ANOVA followed by Bonferroni post-test; different letters indicate statistical difference between the groups. T0 – CBCT for diagnosis and surgical planning of SL graft; T1 – CBCT for graft evaluation after SL and dental implant surgical planning; T2 – CBCT for longitudinal evaluation of the dental implant; CBCT – Cone-beam computed tomography; SL – Sinus lift; ANOVA – Analysis of variance; P – Probability value

Maxillary sinus volume showed an opposite pattern compared with ridge volume. A significant reduction in sinus volume was observed after grafting, decreasing from 1639.57 mm³ at T0 to 1080.90 mm³ at T1. During follow-up, sinus volume remained stable (1126.18 mm³ at T2), with no evidence of sinus re-pneumatization over time.

Sites presenting volumetric gain >200% at T1 exhibited significantly lower graft resorption at T2 (P = 0.036) [Table 3], suggesting that the magnitude of initial augmentation may influence long-term volumetric stability.

Table 3.

Association between percentage bone gain at T1 and percentage graft resorption at T2 (n=16)

Percentage bone gain (T1–T0)	Percentage resorption (T1–T2)
	>11	<11
>200	1	6
<200	6	3
P	0.036

P value, Chi-square test. T0 – CBCT for diagnosis and surgical planning of SL graft; T1 – CBCT for graft evaluation after SL and dental implant surgical planning; T2 – CBCT for longitudinal evaluation of the dental implant; CBCT – Cone-beam computed tomography; SL – Sinus lift; P – Probability value; n – number

No statistically significant associations were identified between bone gain or graft resorption and clinical or demographic variables, including age, gender, systemic impairment, periodontal disease history, or follow-up period (P > 0.05) [Table 4].

Table 4.

Variation in bone gain (T1) and bone resorption (T2) considering clinical and demographic variables

Variable	Bone gain (mm3) (%) T1–T0	P	Bone resorption (mm3) (%) T1–T2	P
Gender
Female	595.77 (156.50)	0.20	97.61 (10.37)	0.46
Male	771.71 (246.52)		146.28 (13.11)
Age (years old)
<56	724.53 (198.66)	0.89	115.02 (10.28)	0.16
>56	561.37 (210.07)		142.72 (16.12)
Systemic impairment
Absent	771.64 (212.06)	0.66	119.07 (10.42)	0.28
Present	490.38 (178.29)		128.28 (14.65)
Periodontal disease
Absent	780.33 (179.11)	0.27	127.84 (10.18)	0.13
Present	393.97 (268.72)		104.27 (16.43)
Dental prosthesis
Absent			115.57 (8.90)	0.067
Present			130.15 (15.39)
Follow-up (months)
<29			115.38 (10.09)	0.24
>29			132.90 (14.49)

P value, t-test for independent samples. T0 – CBCT for diagnosis and surgical planning of SL graft; T1 – CBCT for graft evaluation after SL and dental implant surgical planning; T2 – CBCT for longitudinal evaluation of the dental implant; CBCT – Cone-beam computed tomography; SL – Sinus lift; P – Probability value; t – Statistic test

Although not statistically significant, implants subjected to functional loading demonstrated a tendency toward higher graft resorption (15.4%) compared with nonloaded implants (8.9%) (P = 0.067).

DISCUSSION

Implantology aims to rehabilitate patients by restoring function and esthetics and improving the quality of life. Tooth loss often leads to alveolar bone resorption and, in the posterior maxilla, pneumatization of the sinus floor,[2,14] hindering implant placement and leading to the need for bone grafts.[3] Longitudinal evaluation of graft behavior and volumetric maintenance after implant placement and prosthetic rehabilitation is essential to better understand long-term remodeling dynamics. Therefore, the present retrospective longitudinal study assessed volumetric changes in the alveolar ridge and maxillary sinus following lateral window SL with inorganic bovine bone grafting and delayed implant placement. The findings demonstrated a significant volumetric increase after graft healing and a reduction over 4 years following implant placement, predominantly affecting the cervical peri-implant region.

In agreement with previous studies,[15,16,17] SL and bone graft promoted alveolar ridge recovery, allowing the rehabilitation of patients with osseointegrated dental implants. However, most studies did not quantify bone gain. In the present study, grafting resulted in an approximate 200% volumetric gain, followed by an 11% reduction during follow-up. These findings suggest that the magnitude of initial augmentation may contribute to improved volumetric stability, possibly by compensating for early remodeling processes. Bone resorption rates reported in the literature range from 6.3% to 39.2% after 4–48 months post-SL.[13,14,15,16,18,19,20] The lower resorption (11%) observed here may be due to using the volume available for implant planning as a baseline. Klein et al.,[17] unlike previous studies, observed a 9.1% gain in bone volume when comparing the volume immediately after SL to 8 months of follow-up. In addition, the present study suggests that the residual ridge volume quantification might be an important measure for planning the graft material needed, as sites with volumetric variation over 200% showed less resorption. However, this finding should be interpreted cautiously due to the limited sample size and exploratory nature of the subgroup analysis.

In this study, bone augmentation was performed using the lateral window technique with inorganic bovine bone grafting and delayed implant placement, as the residual alveolar bone height was <5 mm. Despite the observed longitudinal bone resorption and volumetric reduction at T2, no implants were lost, and all prostheses remained functional during the 3- to 43-month follow-up, indicating clinical stability within the evaluated period. Factors such as SL technique, graft material, and implant timing may influence marginal implant and graft resorption. Sbordone et al.[21] reported greater cervical resorption with delayed implants regardless of graft type, whereas Mazzocco et al.[18] noted no significant difference in graft volume based on implant timing. Regarding the type of graft used, Sbordone et al.[15] verified less resorption for the block graft compared to the particulate grafts in a 6-year follow-up. In the present study, cervical resorption was moderate (reduction of 121.95 mm³ or 11%) compared with previously reported values.[15,19,20] Nevertheless, even moderate volumetric reduction in the cervical region may have meaningful clinical implications, as marginal bone stability is critical for maintaining peri-implant soft tissue support, preserving papillary architecture, and ensuring favorable biomechanical load distribution. Progressive cervical remodeling may compromise the biologic seal and long-term esthetic stability; therefore, potential early remodeling should be anticipated during graft planning, implant positioning, and prosthetic design to promote sustained peri-implant health.

Pneumatization of the sinus floor following tooth loss is well documented, but re-pneumatization post-SL requires further study.[12,13] To address this, the corresponding volume of the maxillary sinus was also calculated and compared in the three experimental times. This study observed a reduction in sinus volume postgrafting (T1) with maintenance over time (T2). Only one previous study also assessed the volume of the maxillary sinus after implant placement, verifying a reduction in sinus volume, possibly due to apical implant placement occupying previously ungrafted areas.[20] In the current study, all implants were placed within graft material. The absence of sinus re-pneumatization suggests that volumetric changes were predominantly localized at the cervical peri-implant region rather than reflecting instability of the grafted sinus floor.

Patient clinical and demographic factors influence treatment success and bone volume maintenance.[15,22] This study found no association between variables (e.g. gender, age, systemic conditions, and periodontal history) and bone gain or resorption. However, the observed pattern suggests resorption primarily occurs at the implant crest level, as maxillary sinus volume remained stable over time. This localized cervical reduction may be associated with functional loading, since implants subjected to prosthetic rehabilitation exhibited greater volumetric reduction compared to unloaded sites. Cervical bone remodeling is likely multifactorial, involving biologic width establishment, surgical and prosthetic manipulation, and stress concentration at the implant–abutment interface, with occlusal forces potentially contributing to adaptive bone remodeling in this region.[23] Although these associations did not reach statistical significance, possibly due to limited sample size, the findings highlight the importance of careful long-term monitoring of cervical volumetric alterations as potential early indicators of peri-implant tissue instability.

Implant timing should allow adequate biological maturation of the grafted tissue, especially in patients presenting systemic or behavioral risk factors that may affect bone metabolism and healing. Although smoking and systemic conditions were not statistically associated with volumetric changes in the present study, their known biological effect suggests that individualized healing intervals may be advisable. Furthermore, prosthetic design should aim to minimize biomechanical overload through appropriate occlusal schemes, controlled loading protocols, and optimized implant–abutment connections to reduce stress concentration in the cervical region. Together, these considerations may contribute to improved long-term peri-implant stability.

CBCT is a reliable method for volumetric assessment[24] widely used to quantify changes in grafted areas post-SL.[11,13,17,18,20,21,25] ITK-SNAP software enabled accurate manual segmentation, which is crucial for low-contrast regions, as CBCT does not provide Hounsfield units.[26] Thus, the segmentation of the alveolar ridge and the grafted area was performed using the manual segmentation, having the sagittal plane as reference. To mitigate bias, all exams were evaluated sequentially by the same calibrated examiner (ICC > 0.9). Although CBCT is not routinely indicated for implant follow-up,[7] its use in this study reflects real-world clinical conditions. To reduce the radiation exposure to the patient,[27] CBCT acquisitions were performed with a small FOV, which did not allow for the entire sinus to be present and demanded the use of a manual ROI selection. Another limitation inherent to this and other studies that measured bone graft adjacent to dental implants is the presence of metal artifacts in the tomographic image[2] that can jeopardize the delimitation of structures.

This study used a convenience sample from a dental center with no control over variables such as implant timing or prosthetic rehabilitation, as observed in prior research.[15,17,20,21,22] Nonetheless, the same professional performed all surgical and prosthetic procedures. Furthermore, CBCT scans were not performed immediately postgrafting but rather during implant planning, aligning with clinical practice after graft healing. The requirement of three CBCT examinations at distinct time points, combined with an extended follow-up period, substantially reduced case availability. Consequently, the limited sample size may have decreased the statistical power of the study and restricted subgroup analyses, particularly regarding potential associations between demographic or clinical variables and volumetric outcomes. Therefore, caution is warranted when generalizing these findings to broader populations. Besides, as a retrospective study, control over potential confounding variables such as implant timing, prosthetic design, and patient-related factors was limited. Further prospective, controlled studies with standardized postoperative imaging intervals and larger sample sizes are needed to confirm these results.

CONCLUSION

Within the limitations of this retrospective study, bone gain and graft volume maintenance were primarily influenced by the extent of grafting, while patient-related variables showed no significant association.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.