Sinus Augmentation Procedures Research Articles

A New Method to Evaluate Volumetric Changes in Sinus Augmentation Procedure

In sinus augmentation procedure, the assessment of volume changes of grafted materials is important both in the clinical practice and in dental research to evaluate the features of filling materials. In this study, we assessed the repeatability of a new method proposed to evaluate volumetric changes following sinus lift augmentation procedure. In 10 patients, maxillary sinus augmentation procedure with simultaneous implant placement was performed. Maxillary cone beam computer tomographies were taken 1 week after surgery (T1) and 6 months after surgery (T2). At each evaluation the gap inside the implant between the fixture and the bottom of the screw was used as reference point (Rp), and a standardized volume of interest (VOI) centered on the Rp was selected. Masks were chosen to select the graft and bone tissue within the VOI; the volume at T1, T2, and the difference of volume between T1 and T2 were computed. Expert and non-expert operators performed the analysis. Method errors were computed. The error of the method was 1% for both intra-operator and inter-operator measurements. Tissue contraction at T2 was 19 ± 4% of the total initial volume. The standardization of the method allows to obtain repeatable measurements.

Maxillary sinus augmentation procedures through equine-derived biomaterial or calvaria autologous bone: immunohistochemical evaluation of OPG/RANKL in humans

Autologous bone is considered the gold standard for bone regeneration, even if different heterologous bone substitutes have been proposed to overcome the limits related to its use. The aim of this study was to analyze and to compare the molecular events switched on by autologous or heterologous bone graft insertion, focusing on TGFβ1 expression and OPG/RANKL ratio, to analyze resorption process, and estimating graft vascularization, new bone tissue deposition and its mineralization, through VEGF, BSP and SPARC expression evaluation, respectively. Patients needing pre-prosthetic rehabilitation of the posterior maxilla were treated using an equine-derived biomaterial (Group 1) or calvaria autologous bone (Group 2), according to the morphology of the bone defect. Bone graft integration was evaluated on bone samples obtained from the treated areas at the moment of dental implant insertion, by morphological and immunohistochemical analyses for TGFβ1, OPG, RANKL, VEGF, BSP, and SPARC expression. Morpho - logical analysis shows the presence of biomaterial residual granules in Group 1, in parallel to a good integration between graft and host tissue. Moderate TGFβ1 expression is seen in both Group 1 and Group 2. OPG/RANKL ratio appears higher in Group 1; VEGF expression appears very strong in Group 1 and strong in Group 2, while BSP and SPARC expression results weak in Group 1 and moderate in Group 2. Our results reveal the good integration between both types of graft and the host tissue, even though autologous graft seems to produce a faster regenerative process, as evidenced by the different expression of the investigated molecules. According to these observations, the clinical use of heterologous particulate equine-derived biomaterial may ensure long-term predictability of implantprosthetic rehabilitation, comparable to that obtained with autologous bone graft.

Morphological evidences of Bio‐Oss® colonization by CD44‐positive cells

Our objectives were to examine vascular and cellular colonization in anorganic bovine bone (ABB) after 6months of healing in human maxillary sinus augmentation grafts. Fifty unilateral maxillary sinus augmentation procedures were performed on 50 consecutive patients. Bone cores were obtained through the implant receptor sites 6months later and evaluated with morphological image analysis and immunohistochemical techniques. Image analysis revealed a mean of 35.44±16% vital bone, 31.66±15% non-mineralized tissue, and 32.72±25% remnant ABB particles. In our patients, neovascularization in 46.3% of cases was demonstrated within ABB particles 6months after sinus floor augmentation surgery. Neovascularization of ABB particles was inversely related to age, directly to osteoclast number per mm², and not influenced by habits or disease. CD44-positive cells colonization was found in 74% of cases. An important correlation was found regarding CD44 expression and number of vessel in ABB particles (r=0.624 P<0.001, Pearson). Osteopontin expression was detected on the interstitial boundary of bone with ABB particles and within the osteocyte lacunae and bone canaliculi and was relationship with presence of CD44-positive cells inside ABB particles (r=0.388, P=0.046, Pearson). In conclusion, images compatible with osteone colonized by osteocytes CD44 positive and neovascularization in ABB particles were observed after 6months of graft maturation. These biologic events have not previously been morphologically and immunohistochemically documented.

Lateral Sinus Augmentation: A Safer Technique

The posterior maxilla presents with a common problem clinically following tooth extraction or crestal bone loss resulting in loss of osseous height sufficient to place implants. Resorptive patterns in some patients along with sinus enlargement result in minimal bone that can accommodate implant placement. Maxillary sinus augmentation over the past 18 years with various bone graft materials has become routine treatment. Numerous studies have reported highly successful implant survival rates when placed into the augmented sinus. The most common complication of the lateral sinus elevation approach is typically tearing of the Schneiderian membrane which could allow for bacterial contamination or loose particles to gain access to the sinus cavity. A safer lateral window approach sinus augmentation procedure will be discussed using specialized safe cutting end drills with vertical stoppers for osseous window formation and subsequent membrane elevation.

Use of Plasma Rich in Growth Factor for Schneiderian Membrane Management During Maxillary Sinus Augmentation Procedure

The aim of this pilot study was to present a novel technique for the management of the Schneiderian membrane during maxillary sinus lift surgery using plasma rich in growth factors (PRGF). Eight maxillary sinuses were augmented in 8 patients. Two small perforations of the Schneiderian membrane occurred during the lifting procedure, which were solved using the PRGF clot before grafting the site with PRGF and anorganic bovine bone. With the exception of 1 patient who experienced pain following an acute sinus infection after 3 days of uneventful healing, the patients' postoperative quality of life was generally good. The most common complication (50% of cases) was hematoma, which disappeared after 1 week. Despite the limitations of this study concerning the sample size and the study design, the use of PRGF may be helpful in reducing complications following sinus lift surgery. More well-designed studies, with larger sample size, are needed to validate this protocol.

Anorganic Bovine-Derived Hydroxyapatite vs β-Tricalcium Phosphate in Sinus Augmentation: A Comparative Histomorphometric Study

The choice of augmentation material is a crucial factor in sinus augmentation surgery. Bovine-derived hydroxyapatite (BHA) and beta-tricalcium phosphate (β-TCP) have been used successfully in sinus augmentation procedures. Choosing one of these materials for sinus augmentation is still controversial. The aim of this clinical study was to compare the biological performance of the new BHA graft material and the well-known synthetic β-TCP material in the sinus augmentation procedure. The study consisted of 23 patients (12 male and 11 female) who were either edentulous or partially edentulous in the posterior maxilla and required implant placement. A total of 23 two-step sinus-grafting procedures were performed. BHA was used in 13 patients, and β-TCP was used in 10 patients. After an average of 6.5 months of healing, bone biopsies were taken from the grafted areas. Undecalcified sections were prepared for histomorphometric analysis. The mean new bone formation was 30.13% ± 3.45% in the BHA group and 21.09% ± 2.86% in the β-TCP group (P = .001). The mean percentage of residual graft particle area was 31.88% ± 6.05% and 34.05% ± 3.01% for the BHA group and β-TCP group, respectively (P = .047). The mean percentage of soft-tissue area was 37.99% ± 5.92% in the BHA group and 44.86% ± 4.28% in the β-TCP group (P = .011). Both graft materials demonstrated successful biocompatibility and osteoconductivity in the sinus augmentation procedure. However, BHA appears to be more efficient in osteoconduction when compared with β-TCP.

Predictive Factors for Maxillary Sinus Augmentation Outcomes

To determine the influence of different local and systemic factors on histologic, histomorphometric, and radiographic outcomes after maxillary sinus augmentation. Fifty-two sinus augmentation procedures were performed. Grafting material consisted of a mixture of anorganic bovine bone (ABB) and autogenous bone. After 6 months, bone core biopsies were harvested from implant sites for histologic and histomorphometric analyses. Data regarding age, gender, type of edentulism, alcohol consumption, smoking habits, and history of periodontal disease were recorded and statistically analyzed. Histomorphometric analyses revealed the presence of 35.75% ± 16.42% of vital bone, 40.56% ± 16.23% of nonmineralized tissue, and 23.69% ± 18.23% of residual ABB particles. Radiographic vertical bone resorption inversely correlated with residual ABB. A significant difference in bone resorption patterns was observed for completely edentulous patients and for those with a history of periodontitis. Tobacco and alcohol negatively influenced vital bone formation after sinus augmentation. Implant and prostheses survival after 2 years of functional loading was not directly affected by patient's individual habits. Certain patient-related variables such as history of periodontitis, type of edentulism, or smoking/drinking habits play an important role in bone graft maturation after maxillary sinus floor elevation.

Evaluation of the osteoconductive potential of bone substitutes embedded with schneiderian membrane‐ or maxillary bone marrow‐derived osteoprogenitor cells

Sinus augmentation procedures commonly employ osteoconductive scaffolding materials to stimulate and support bone formation. The aim of this study was to develop a simple screening methodology for the evaluation of the osteoconductive potential of various bone graft materials prior to clinical use. Materials tested were Bio-Oss, Bi-Ostetic, OraGraft, and ProOsteon. These Simple and composite bone substitutes were embedded with osteoprogenitor cells derived from either the human maxillary sinus schneiderian membrane (hMSSM) or from maxillary tuberosity bone marrow and then monitored both in vitro and in vivo. Cell adherence and proliferation was most pronounced in OraGraft, followed by ProOsteon. In vivo bone formation, within the bone graft, was also observed, with most marked results in OraGraft and ProOsteon grafts. The proposed osteoconductivity testing method proved simple, informative, and reliable for the purpose of screening candidate biomaterials for sinus lifting or sinus augmentation.

Bone Regeneration Using a Hollow Hydroxyapatite Space‐Maintaining Device for Maxillary Sinus Floor Augmentation – A Clinical Pilot Study

The mere lifting of the maxillary sinus membrane by implants protruding into the sinus cavity allows the establishment of a void space for blood clot and new bone formation. To evaluate bone formation by using a spherical, hollow, and perforated hydroxyapatite space-maintaining device (HSMD) in a two-stage sinus lift procedure where residual alveolar bone height was ≤2 mm. Spherical, hollow, and perforated HSMDs with a diameter of 12 mm were manufactured for this pilot study. Three patients with a residual bone height of 1-2 mm, as verified clinically and radiographically, and in need of a sinus augmentation procedure prior to implant installation were selected for the study. The HSMD and bone formation was evaluated by cone beam computerized tomography (CBCT) 6 months after augmentation procedure. Implants were installed 6 to 9 months after augmentation. The implant sites were prepared by a trephine drill to obtain a specimen of HSMD and bone for histological evaluation. After implant installation, the condition of the sinus membrane adjacent to the HSMD was evaluated endoscopically. After an additional 8 weeks, fixed partial prostheses were fabricated. Bone formation verified by CBCT was found around and inside the device in all three patients after 6 months. Despite the fact that residual bone before augmentation was ≤2 mm, 12-mm-long implants with diameter of 4.8 mm could be inserted with preservation of an intact and healthy sinus membrane verified endoscopically. Bone formation inside HSMDs was noted histologically in two out of three HSMDs. Implants were stable and without any marginal bone loss after 1 year of prosthetic loading. A spherical, hollow, and perforated HSMD used in sinus lift procedures can produce a void space for blood clot and new bone formation and subsequent implant installation.

Histomorphometric Analysis of Maxillary Sinus Augmentation Using an Alloplast Bone Substitute

To evaluate the regenerative potential of a fully synthesized homogenous hydroxyapatite:β-tricalcium phosphate 60:40 alloplast material in sinus lift procedures. Hydroxyapatite:β-tricalcium phosphate was used for sinus floor augmentation. After 9 months, 12 biopsies were taken from 12 patients. Routine histologic processing was performed and specimens were analyzed using a light microscope and a digital camera. Histologic evaluation showed 26.4% newly formed bone, 27.3% residual graft material, and 46.3% bone marrow. The osteoconductive index was 33.5%. Hydroxyapatite:β-tricalcium phosphate 60:40 alloplast material was found to be biocompatible and osteoconductive in maxillary sinus augmentation procedures.

Radiographic and histologic evaluation of platelet-rich plasma and bovine-derived xenograft combination in bilateral sinus augmentation procedure

There is currently a great interest regarding the use of platelet-rich plasma (PRP) in combination with various bone graft materials in sinus lift procedures. The purpose of this study was to assess and compare the radiographic and histological results of sinus augmentation procedures following treatment with PRP/bovine-derived xenograft (BDX) vs. BDX/collagen membrane. Using a split mouth design, 10 patients, with ≤5 mm of residual alveolar bone in the vertical direction, were treated with PRP/BDX or BDX/collagen membrane. At 8 months after surgery, both graft materials led to a satisfactory increase in vertical dimensions of bone. Bone biopsies were taken from the augmented sites during the implant placement. Histological analysis demonstrated that majority of the trabecula contained orderly layered lamellar bone in the PRP/BDX group, whereas mainly woven bone with a haphazard arrangement of collagen fibers were noticed in the BDX /collagen membrane group. It can be concluded that both combinations resulted with a satisfactory bone height, but more prominent and mature bone formation was observed at sites treated with PRP/BDX.

Change in sinus membrane dimension following sinus floor elevation: a retrospective cohort study

To investigate: (1) the effect of the lateral window technique for maxillary sinus augmentation on sinus membrane thickness, and (2) to identify factors associated with the mean postoperative surgical space. This retrospective cohort study included 37 sinuses corresponding to 37 consecutive patients referred for maxillary sinus augmentation procedures aiming to increase with deproteinized bovine bone the surgical space for dental implant placement in the posterior maxilla. A total of 74 preoperative and postoperative computed tomography were analyzed with regard to the thickness of the sinus membrane. A linear regression model was used to explain the difference between the mean preoperative and postoperative surgical space No significant change in the membrane thickness was shown between pre and postoperative CT scans. The mean height of the graft was 12 mm (P < 0.001), resulting in a significant augmentation of the surgical space (P < 0.001). The multivariate analysis performed to identify variables associated with the postoperative surgical space shows that current smoking significantly reduces the chance to achieve the mean value of the surgical space normally expected in this type of surgical procedure (P = 0.02). No significant effect of complications, history of periodontal disease or ENT was found. Our findings suggest that: (1) sinus floor augmentation via a lateral approach with deproteinized bovine bone alone has no impact on the natural sinus physiology; and (2) that the mean postoperative surgical space may be affected by smoking.

Maxillary Sinus Augmentation Using Prehydrated Corticocancellous Porcine Bone: Hystomorphometric Evaluation after 6 Months

Insufficient alveolar bone height often prevents the placement of standard dental implants in the posterior part of edentulous maxilla. In order to increase adequately the vertical dimension of the reabsorbed alveolar process, a sinus lift procedure is often necessary. The aim of this study was to evaluate histologic results of a prehydrated corticocancellous porcine bone used in maxillary sinus augmentation. Patients (age 18-70 years) with a residual bone height requiring a maxillary sinus augmentation procedure to place dental implants were eligible for this study. All patients were treated with the same surgical technique consisting of sinus floor augmentation via a lateral approach. The space obtained by elevation of the mucosa wall was grafted with prehydrated and collagenated corticocancellous porcine bone. Biopsies were harvested 6 months after the augmentation procedures. Twenty-four patients were enrolled. The mean percentage of new formed bone was 43.9 ± 18.6% (range 7.5-100%), whereas the mean percentage of residual graft material was 14.2 ± 13.6% (range 0-41.9%). The new bone/residual graft material ratio in the maxillary sinuses was 3.1. The mean soft tissues percentage was 41.8 ± 22.7% (range 0-92.5%). The present study suggested that porcine bone showed excellent osteoconductive properties and could be used successfully for sinus augmentation. Moreover, the porcine bone showed a high percentage of reabsorption after 6 months; this might be because of the presence of collagen and the porosity of the graft material.

Anorganic bovine-derived hydroxyapatite versus β-tricalcium phosphate in sinus augmentation. A comparative histomorphometric study

Abstract AbstractIntroduction: The choice of augmentation material is a crucial factor in sinus augmentation surgery. Bovine-derived hydroxyapatite (BHA) and beta-tricalcium phosphate (β-TCP) have been used successfully in sinus augmentation procedures. Choosing one of these materials for sinus augmentation is still controversial. The aim of this clinical study was to compare the biological performance of the new BHA graft material and the well known synthetic β-TCP material in sinus augmentation procedure.Material and Methods: The study consisted of 23 patients (12 male and 11 female) who were either edentulous or partially edentulous in the posterior maxilla and required implant placement. A total of 23 two-step sinus grafting procedures were performed. BHA was used in 13 patients and β-TCP was used in 10 patients. After average of 6.5 months of healing bone biopsies were taken from the grafted areas. Undecalcified sections were prepared for histomorphometric analysis. Results: The mean new bone formation was 30.13±3.45% in BHA group and 21.09±2.86% in β-TCP group (p=0.001). The mean percentage of residual graft particle area was 31.88±6.05% and 34.05±3.01% for BHA group and β-TCP group, respectively (p=0.047). The mean percentage of soft tissue area was 37.99±5.92% in BHA group and 44.86±4.28% in β-TCP group (p=0.011).Conclusion: Both graft materials demonstrated successful biocompatibility and osteoconductivity in sinus augmentation procedure. However, BHA appears to be more efficient in osteoconduction when compared to β-TCP.

Bone regeneration in sinus augmentation procedures with calcium sulphate. Microstructure and microanaytical investigations

The aim of this study was a histological and ultrastructural evaluation of the bone formed in human sinus augmentation procedures with calcium sulphate (CaS). Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were used to evaluate the relationship between CaS and newly-formed bone, while birefringence was used to evaluate the bone structure around the CaS particles by polarized light microscopy. Unstained sections were studied with an Axiovert 200 M using the fluorescence in reflected UV light to evaluate the interface between CaS and newly-formed bone. Twenty specimens retrieved from the sinus after a healing period of six months were studied. EDS analysis of six specimens showed that little sulphur remained and residual particles appeared to have transformed to calcium phosphate. Under polarized light a few biomaterial remnants were present in some areas and covered by mature bone. The relationship between residual particles and bone due to the different photon emission under UV light stimulation was observed under fluorescence microscopy. The present results confirm the high biocompatibility and rapid resorption rate of CaS. The mechanism of transformation of CaS to calcium phosphate, already demonstrated in animal studies, has been confirmed in the present human study.

Computed tomographic assessment of maxillary sinus wall thickness in edentulous patients

Posterior maxillary region is considered to be the most challenging area for dental implant placement. Lateral window opening is the gold standard procedure for maxillary sinus augmentation in this area. The purpose of this study is to evaluate lateral wall thickness of the maxillary sinus for sinus augmentation using computed tomography (CT) in edentulous patients. Computed tomography images of 302 patients were analysed. Using the maxillary sinus floor as the reference point in edentulous regions, lateral wall thickness was measured on CT scans. After drawing a tangent line at the lowest point of the sinus floor, another perpendicular line to the tangent line was drawn at the same point of the sinus floor. Thickness of the lateral wall of the maxillary sinus was measured using 10DR implant software at 3 (R1), 10 (R2) and 15 mm (R3) from the sinus floor. The mean thickness of the lateral wall of the maxillary sinus from the first premolar to second molar was 1·69 ± 0·71, 1·50 ± 0·72, 1·77 ± 0·78 and 1·89 ± 0·85 mm, respectively. The thickness differed significantly at the R2 and R3 points. Women had thinner lateral walls at the R1 and R2 points at the premolars than did men. At the R2 and R3 points at the second premolar, the mean thickness of smokers was larger than that of non-smokers. There were no significant differences on age or reasons for tooth loss. The changes in the thickness of the lateral wall at different reference points were observed, and CT examinations may help make lateral window without membrane perforation.

Allograft for Maxillary Sinus Floor Augmentation

The aim of this study is to demonstrate the clinical applicability and efficacy of an allograft for maxillary sinus augmentations in patients requiring placement of dental implants. Sixty consecutive patients underwent a total of 90 sinus augmentations. Twenty-nine were women and 31 men, with a mean age of 54 years. Twenty-six patients received a bilateral procedure and 34 unilateral. All cases were treated with the lateral wall technique. Allograft consisted of demineralized freeze-dried blocks in 6 cases, particulate in 82 cases, and a combination of both in 2 cases. In 30 patients, it was combined with platelet-rich plasma. A total of 84 implants were inserted. Bone samples of grafted areas were obtained in two patients for histological examination. Seventy-three implants were clinically successful at the reentry time. Eleven implants in seven patients were removed between 15 days and 6 months after their placement. Seven of these implants were replaced and received prostheses as well, for an overall postloading success rate of 95.2%. Follow-up for all patients after final restoration was between 12 and 96 months. Specimen's histological evaluation revealed bone formation and evidence of inflammatory infiltrate. Based on the findings of this study, it can be suggested that the use of the demineralized freeze-dried bone allograft from the Banco de Huesos y Tejidos Fundación Cosme y Damian for sinus augmentation is effective and constitutes a feasible therapeutic alternative for implant placement.

Are Gingival Phenotype, Residual Ridge Height, and Membrane Thickness Critical for the Perforation of Maxillary Sinus?

Sinus membrane perforation is the most common complication of the sinus-augmentation procedure. Anatomic factors have been implicated in the risk of sinus membrane perforation (SMP) during sinus-lift surgery. However, there are no reports on the relationships among gingival phenotype (GP), residual ridge height (RRH), membrane thickness (MT), and perforation rate of the maxillary sinus. Therefore, the aim of this clinical study is to determine the associations among GP, RRH, MT, and SMP rate. Forty-four patients (64 sinus-lift procedures) were included in the study. Preoperative computed tomography scanning was performed to radiographically evaluate GP, RRH, and MT. The smallest RRH, highest MT, and gingival thickness values were recorded. These values were classified as follows: RRH, < or >3.5 mm; MT, < or >1 mm; and GP, <1.5 or >2 mm. Sinus-lift surgery was performed with a lateral window approach, and SMPs were detected at 11 sinus sites. Perforation size and locations were recorded, and the perforations were repaired with collagen membrane. One hundred seventy-six implants were placed immediately after augmentation procedure. Strong correlations of GP with RRH (r = 0.722, P = 0.001) and MT (r = 0.702, P = 0.001) were noted. Moderate correlations were found between RRH and MT (r = 0.596, P = 0.001) and between MT and SMP (r = 0.417, P = 0.001). Furthermore, mild correlations of SMP with RRH (r = 0.290, P = 0.020) and GP (r = 0.248, P = 0.04) were established. Four implants were lost, but no significant difference was found between implant failure and SMP. Within the limits of the study, it may be suggested that GP, RRH, and MT may be important factors for sinus perforation.

Use of Plasma Rich in Growth Factor for Schneiderian membrane management during maxillary sinus augmentation procedure.

The aim of this pilot study was to present a novel technique for the management of the Schneiderian membrane during maxillary sinus lift surgery using plasma rich in growth factors (PRGF). Eight maxillary sinuses were augmented in 8 patients. Two small perforations of the Schneiderian membrane occurred during the lifting procedure, which were solved using the PRGF clot before grafting the site with PRGF and anorganic bovine bone. With the exception of 1 patient who experienced pain following an acute sinus infection after 3 days of uneventful healing, the patients' postoperative quality of life was generally good. The most common complication (50% of cases) was hematoma, which disappeared after 1 week. Despite the limitations of this study concerning the sample size and the study design, the use of PRGF may be helpful in reducing complications following sinus lift surgery. More well-designed studies, with larger sample size, are needed to validate this protocol.

Slow Resorption of Anorganic Bovine Bone by Osteoclasts in Maxillary Sinus Augmentation

Different biomaterials have been suggested for guided bone regeneration (GBR). These might show the ideal properties to let a new bone formation in the grafted area. Among these ideal features, it is essential their controlled resorption in order to be replaced for new vital bone. Bovine bone has been used widely as a good biomaterial for GBR, however there is still an interesting controversy about its resorbable capacity. In this sense, the objective of this study was to examine the behavior of anorganic bovine bone (ABB) in long-term maxillary sinus graft healing and study its relationship with morphological and morphometrical variables. Seventeen maxillary sinus augmentation procedures were performed in patients. Bone cores were obtained from implant receptor sites at 6 months, 3 years, and 7 years of implant placement for histological, morphometric, and immunohistochemical (tartrate resistant acid phosphatase [TRAP]/cathepsin K/CD68) studies. The percentages of bone, ABB particles, connective tissue, osteocytes, and osteoblasts in maxillary sinus grafts were similar at 6 months, 3 years, and 7 years. A progressive and significant decrease was detected in osteoclasts (p = .05, Kruskal-Wallis test), TRAP and cathepsin K expression (p = .014 and p = .021, respectively), and osteoid lines (p = .038). According to these data, a decrease in osteoclasts over time may, partially, explain the ABB persistence observed in core biopsies. Further studies with more cases and different graft maturation times are required to elucidate the resorption rates and cell events underlying these phenomena.