Investigation of a Novel PLGA/CaP Scaffold in the Healing of Tooth Extraction Sockets to Alveolar Bone Preservation in Humans Ana Claudia Araujo-Pires, DDS, MSc, PhD;*† Vanessa Cristina Mendes, DDS, MSc, PhD;†‡ Osny Ferreira-Junior, DDS, MSc, PhD;* Paulo Sérgio Perri Carvalho, DDS, MSc, PhD;*§ Limin Guan, MASc;† John Edward Davies, DDS, MSc, PhD†‡
ABSTRACT Background: It is expected that 40% to 60% of initial alveolar bone volume will be lost up to 6 months after tooth extraction. OsteoScafTM (TRT, Toronto, ON, Canada) (poly (DL-lactide-co-glycololide/calcium phosphate [PLGA/CaP] scaffold) is a novel bone substitute material and represents a promising alternative for maintaining alveolar bone integrity in this clinical scenario. Purpose: Here it was hypothesized that OsteoScaf would reduce alveolar bone lost after tooth extraction in patient, acting as a clot-retention device. Material and Methods: A total of 10 patients (32 sockets) were included in the study, of which 16 sockets were grafted with OsteoScaf and 16 were used as control (coagulum alone). Cone beam computed tomography (CBCT) was performed both immediately following extraction and also at 120 days postoperatively, at which time biopsy samples were also harvested for histological analyses. Results: Quantitative analysis of CBCT showed less bone resorption in the OsteoScaf groups, being 10.5% to 14.4% less bone lost in the center of the socket, 15.4% in the buccal region, and 12.6% in the palatal. Qualitative histological analysis showed new bone tissue in direct apposition to the scaffold – demonstrating its osteoconductive nature. Conclusion: OsteoScaf diminished the expected bone lost during the postextraction remodeling of the alveolar bone ridge at 120 days postextraction. KEY WORDS: alveolar bone remodeling, biomaterials, bone regeneration, bone substitutes, bone tissue engineering, CBCT imaging, clinical study, extraction socket, histological analysis, micro-CT
INTRODUCTION One of the biggest obstacles to overcome in dental implant surgery is to find sufficient height and width of alveolar bone to receive the implant.1,2 The aesthetic and functional success of prostheses, both conventional noninvasive and implant-supported, depend on the presence of sufficient healthy bone volume.2,3 Preserving alveolar bone architecture during socket healing is challenging. The process of alveolar healing after tooth extraction is associated with a catabolic remodeling of the residual alveolar ridge, which can result in considerable loss of bone.4 Indeed, it has been shown that 40% to 60% of the initial alveolar bone volume will be lost up to 12 months after tooth extraction.5–9 In fact, the alveolar process is rapidly
*School of Dentistry, Stomatology and Oral Surgery Bauru, University of São Paulo, Bauru, São Paulo, Brazil; †Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada; ‡Dental Research Institute, Faculty of Dentistry, University of Toronto, Toronto, ON, Canada; §Surgery and Integrated Clinic, São Paulo State University, Araçatuba, São Paulo, Brazil Corresponding Author: Professor John Edward Davies, Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College Street, Toronto, ON M5S 3G9, Canada; e-mail: davies@ ecf.utoronto.ca Disclosure: All the authors declare no conflict of interest. © 2015 Wiley Periodicals, Inc. DOI 10.1111/cid.12326
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reduced in the first 6 months, but slower resorption continues throughout life4,10–12 and is responsible for a significant change in jaw structure.8,9,13 Specifically, vertical ridge height is lost and is most pronounced on the buccal wall;5–12,14,15 this relocates the alveolar ridge to a more palatal/lingual position.12 The main etiology of the residual ridge reabsorption after tooth extraction is believed to be atrophy,5,12,13,16–19 and it is well known that alveolar bone integrity is closely linked to the presence of teeth.12,13,16–19 Socket preservation should be considered at the time of tooth extraction and can reduce, or eliminate, the need for future ridge augmentation.6,20,21 Among the various techniques indicated to preserve alveolar bone, the use of autologous bone graft is known as the “gold standard” because it represents a physiologically optimized combination of the three elements considered essential for the bone regenerative therapy: osteoconductivity, osteoinductivity, and osteogenic cells. Moreover, immunologic rejection and disease transmission are absent using autologous bone. However, this procedure has disadvantages such as donor site morbidity, prolonged pain, infection risk, limited availability, and the possibility of cosmetic defects.22–27 Thus, considerable efforts have been made to develop alternatives to autologous bone grafting, resulting in a wide range of biomaterials for bone regenera-
tion, such as cement particles of calcium phosphate, bioactive glass, inorganic bone, polymers, and demineralized bone matrix. However, despite the widespread use of commercial bone substitutes, an ideal bone filler material has not yet been developed. In this context, OsteoScaf™ (TRT, Toronto, ON, Canada) is a poly (DL-lactide-co-glycololide/calcium phosphate)-based (PLGA/CaP) totally biodegradable macroporous composite scaffold that represents a promising alternative for maintaining alveolar bone integrity. OsteoScaf has an architecture and interconnecting macroporosity similar to that of human trabecular bone (Figure 1). OsteoScaf can be used as a biomaterial alone, as a carrier for cells or a threephase drug delivery device.28,29 Due to the highly interconnected macroporosity ranging from 81% to 91% and an ability to wick up blood, this biomaterial acts as both a clot-retention device and an osteoconductive support for host bone growth,28 do not being necessary. OsteoScaf, which has been fully described elsewhere,30,31 comprises PLGA, and two osteoclastresorbable calcium phosphate phases, one as internal particles and the other as a surface coating.29,32 We report herein the first clinical study to employ this material for alveolar ridge preservation after tooth extraction. We hypothesized that OsteoScaf would reduce alveolar bone lost in patients by acting as a clot-retention device.
Figure 1 OsteoScaf™ has an architecture and interconnecting macroporosity similar to that of human trabecular bone. A, OsteoScaf with large pores (L = 850∼1,180 μm). B, OsteoScaf with small pores (S = 355∼595 μm). C, A MicroCT image of a sagittal cut (5 μm thick) from a harvested sample. The region of interest (ROI) is delimited for analysis, which corresponded to the center of the tooth socket. MicroCT = micro-computed tomography.
PLGA/CaP Scaffold to Alveolar Bone Preservation
MATERIALS AND METHODS This clinical study had institutional review board approval by Ethical Committee to Human Research of Bauru Dental School, University of São Paulo. All surgical procedures and patient follow-ups were performed at the University of São Paulo, while the histology and all analyses were conducted at University of Toronto. Clinical Test Model OsteoScaf was custom made according to the protocol previously established (Lickorish and colleagues29), in cylinders of 3 mm diameter and 10 mm length, and of two different porosities: 355∼595 μm (SMALL – S) and 850∼1,180 μm (LARGE – L) (Figure 1). Ten patients, in need of at least two anterior maxillary tooth extractions and delayed implant placement, were selected by panoramic radiography to receive either OsteoScaf lithomorph cylinders or extraction alone (CONTROL – C). The exclusion criteria were patients who were: (1) 218 year of age; (2) current or previous smokers; (3) current or previous drug/alcohol addicts; (4) currently pregnant or expecting to be; or who had (5) a medical condition or were taking medication associated with compromising bone healing; (6) psychiatric disorders; (7) parafunctional habits; (8) or the presence of any suppurating infection in desired area. The main inclusion criterion on tooth socket selection was that the extraction socket exhibited a four-wall configuration with a height of at least 10 mm. Overall, 32 tooth sockets were used in this study, 16 in the test group and 16 in the C-group, contralateral to one another. In total, eight OsteoScaf S and eight L were used, as described below. The test sockets were numbered 1 to 16 and the porosities of the OsteoScaf (S and L) were blindly distributed among the patients. Surgical Procedures The surgical procedures were performed at two time points: (1) tooth extraction; and (2) sample harvesting at the time of implant placement. Tooth Extraction. After administration of local anesthesia, the teeth in question were atraumatically extracted, following flap elevation. The sockets were curetted to remove any granulation tissue. The sockets were then 2 mm drilled in the apical region with a
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2 mm twist drill (2 × 13 mm implant drill, Kit Master Conect, Conexão Sistema de Protéses, Ltda, São Paulo, Brazil) under saline irrigation, for scaffold anchorage. The test and C-sites were contralateral to one another, and the sockets were randomly assigned to either test or control groups by the flip of a coin. Two titanium mini-screws 2 × 4 mm (Conexão Sistema de Próteses, Ltda.) were used to provide reference guide points. One screw was placed on the maxillary alveolar bone near to the test site and the other close to the correspondent control, each 10 mm from the alveolar bone crest – a well-known nonresorbable area. Nonresorbable 4.0 nylon vertical mattress sutures (ETHILON™, Johnson & Johnson, São Paulo, SP, Brazil) were used to close the soft tissues. Immediately following extraction, cone beam computed tomography (CBCT) (i-CAT® Cone Beam 3-D Imaging System, Imaging Sciences International, Hatfield, PA, USA) was performed. Patients were allowed to wear a total prosthesis to substitute the function of the missing teeth. The prosthesis was made with transparent acrylic resin, making it possible to check any undesirable pressure/trauma on/to the operated areas. Follow-ups were arranged 48 hours, 7 days (suture removal), 15 days, 30 days, and 120 days postoperative (PO). At the last follow-up, a second CBCT was performed. Sample Harvesting. One hundred twenty days after the OsteoScaf placement, the anterior superior alveolar ridge in question was surgically exposed to receive dental implants. Bone samples were harvested in the socket’s core with a 2.75 mm trephine bur (Conexão Sistema de Próteses, Ltda.). The bone biopsies were stored in 10% phosphate-buffered formalin prior to histologic processing. Micro-Computed Tomography (MicroCT) The bone biopsy specimens were scanned using a micro-computed tomography system (MicroCT40, Scanco, Zurich, Switzerland) at 85 kV and 77 μA. After image reconstruction, two-dimensional images representing sagittal cuts (5 μm thick) of the harvested samples were used to select the region of interest (ROI) for analysis, which corresponded to the center of the tooth socket (Figure 1C). The quantification of bone formation (bone volume/total volume, or BV) as well as trabecular number (Tb.N), thickness (Tb.Th), and
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separation (Tb.Sp) were possible by determining the gray-level distribution at specific thresholds for human bone. CBCT Imaging Study The CBCT images were acquired by iCAT® (Cone Beam 3-D Imaging System, Imaging Sciences International, Hatfield, PA, USA) and converted in DICOM (digital imaging communications in medicine) to export to the MicroCT Scanco System, to permit two-dimensional and three-dimensional analyses. A comparison between baseline images and scans acquired 120 days after was performed for each patient on a socket-to-socket basis. Changes in socket height and thickness were evaluated. Linear Measurements. In order to take measurements reflecting the socket height, a reference point Y was created by intersecting the horizontal plane of the mini-
screw (dashed red line) with the extension of the palatal bony wall line of the socket, named PBL (Figure 2, A and B). From Y, three measurements were taken: (1) Dpalatal = line segment YP , or Y to the more occlusal point of the PBL – P; (2) Dbuccal = line segment YV , or Y to the more occlusal point of the buccal wall – V; (3) Dcenter = line segment YC , or Y to the more occlusal point of the bisectrix of the angle formed by Dpalatal and Dbuccal – C (Figure 2, C and D). The aforementioned eight measurements (three socket heights and five socket thicknesses) were performed in the three image slices from the CBCT that were determined to be in the center of the socket. For measurements of the socket width, five measurements were taken (T1, T2, T3, T4, T5) to represent the distance between the palatal and the buccal wall. The separation between each measurement was 2 mm (Figure 3, A and B).
Figure 2 Measurement of loss of bone height from CBCT sagittal images of the upper alveolar ridge: (A) and (C) baseline, immediate postoperative; (B) and (D) 120 days PO. Dashed red line = horizontal plane marked by the screw. Blue line = palatal bony wall line of the socket (PBL); Y = point of intersection between the screw line and PBL; P = most occlusal point of the PBL; V = the most occlusal point of the buccal wall; C = most occlusal point of the bisectrix of the angle formed by Dpalatal and Dbuccal; YP = Dpalatal; YC = Dcenter; YV = Dbuccal. CBCT = cone beam computed tomography; PO = postoperative.
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Figure 3 Bone width and socket area measurements on CBCT images. A, Baseline (immediate postoperative [PO]). B, 120 days PO. The widths T1, T2, T3, T4, T5 are parallel and are 2 mm apart; (C) baseline socket area, and (D) at 120 days PO. Yellow space = palatal area; red space = buccal area; green line = bisectrix of the angle between the palatal bony wall line of the socket (PBL) and the buccal bony wall line (BBL); Dashed red line = horizontal plane marked by the screw. CBCT = cone beam computed tomography.
Area Measurements. Area measurements were also calculated for buccal, palatal, and total areas. The total area was defined by the screw line, PBL, the occlusal limit, and the buccal bony wall line (BBL). The palatal area was defined by the PBL, the occlusal limit, the screw line, and the bisectrix line (bisectrix of the angle between the BBL and the PBL). The buccal area was defined by the BBL, the occlusal limit, the screw line, and the bisectrix line (Figure 3, C and D). Three image slices for each tooth socket were measured. The buccal and the palatal areas were calculated in the CBCTs at baseline and at 120 days PO (Figure 3, C and D). All measurement steps were performed three times by the same examiner, blind, with at least a 1 month interval between each measurement. Calculating the Bone Lost. All measurements at 120 days PO were subtracted from those of the baseline to allow calculation of the bone lost following extraction. The
measurements were converted to bone lost percentage (the proportion of bone that was lost at 120 days PO compared with baseline). Statistical Analysis We used repeated measure ANOVA to investigate the significance of variation among three measurements, difference among three groups at each time point and comparing baseline and 120 days PO within each group. All comparisons were adjusted for repeated measures (using random effect regression models) and multiple comparisons were taken into account using Bonferroni corrections. Afterward, we matched controls with S and L groups, and calculated the difference between matched pairs. Then we used paired “t”tests to examine the significance of the difference for S and L groups. In fact, we matched C and L, and C and S groups, and respectively compared them. p < .05 was considered statistically significant.
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Histologic Processing
DISCUSSION
Bone samples were randomly chosen for light microscopy by either resin embedded undecalcified (Osteo-Bed™, Polysciences, Warrington, PA, USA) or paraffin-embedded decalcified preparations. The central slices from both histologic processing routes were stained with hematoxylin-eosin (HE) to permit qualitative evaluation.
We report herein the use OsteoScaf cylinders, of two different porosities, in the healing of tooth extraction sockets in patients (Figure 1). The numerical results obtained from CBCT measurements have clearly shown that OsteoScaf impaired the expected bone lost during the postextraction remodeling of the alveolar bone ridge at 120 days postextraction. Our findings are in contrast with those in the literature where ridge preservation did not prevent bone resorption after tooth removal,14,33,34 but do concur with some others where it was found that the use of the biomaterial strategies can maintain bone volume postextraction,2,14,15,35 although this may not be concomitant with preservation of alveolar ridge height as shown when using bioglass particulate.2 Indeed, although regenerative strategies for ridge preservation have been extensively proposed, alveolar ridge height maintenance was only shown when biomaterials, or bone allograft, were employed in conjunction with guided bone regeneration1,15,34,35 or growth factors.36,37 In the latter cases, when employed with a collagen membrane, bone morphogenetic protein 2 (BMP2) was shown to both maintain and restore lost36 buccal bone; while no change, compared with controls, was reported when BMP2 was employed with both demineralized bone powder and a collagen membrane.37 A comparison of this reported data remains challenging, as the different findings may be due to numerous factors: on the one hand, clot contraction can condense osteoconductive particulates; while on the other hand, different measurement methods5,12,38 and clinical assessments have been employed.2,5,14,15,33,37 In our study, we quantified the bone lost due to bone remodeling after tooth extraction by CBCT evaluation, and included controls in the same patients as the test groups with which they were compared. Thus, S and L groups were compared with their corresponding controls, which minimized the effect of the difference between groups due the individual characteristics of each patient. We also accounted for the differences in individual tooth sockets by expressing bone loss as a percentage value of the original rather than an absolute value, and this provided a more accurate interpretation of our results (Table 1). Interestingly, we found that the measurement Dcenter (Figure 4 and Table 1), for either L or S groups, demonstrates less bone resorption than
RESULTS The PO period was uneventful for all patients. MicroCT Study Results By MicroCT assessment, the Tb.Sp of the S test group was smaller than the control, which was the only statistically significant (p < .05) result of the MicroCT evaluation (Figure 4). The other parameters studied, BV, Tb.N, and Tb.Th, did not show statistically significant differences between test and control groups (Figure 4). CBCT Study Results Linear Measurement Results. Only the Dcenter measure presented a statistically significant difference (p < .05) in both L and S (Figure 4), being 14.4% and 10.5% less respectively when compared with the C group. Area Measurement Results. The buccal bone lost was more pronounced than the palatal bone lost, both in test and control groups (Figure 5). When test and control groups were compared, only the L group presented a statistically significant difference (p < .05) compared with the control group; the L group showed 15.4% and 12.6% less bone loss to buccal and palatal areas, respectively, than the control group (Figure 5). Histomorphology Qualitative analysis of the histologic slices (Figure 6) revealed that the test sites and controls showed a mononuclear inflammatory infiltrate permeating an intense fibroblastic and angioblastic proliferation in the region of the tooth socket repair at 120 days, together with the formation of new bone. In both test groups (L and S), fragments of the OsteoScaf persisted with surrounding multinucleated giant cells, suggesting the resorption of the material; while in neighboring areas, palisading osteoblasts elaborated bone matrix directly on the material surface.
PLGA/CaP Scaffold to Alveolar Bone Preservation
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Figure 4 Box plots for trabeculae separation (Tb.Sp), bone volume (BV), trabeculae number (Tb.N), trabeculae thickness (Tb.Th), from MicroCT scans of the bone core biopsies; and percentage of bone change during 120 days postextraction in the palatal wall (linear palatal = Dpalatal), center of the alveolar ridge (linear center = Dcenter), and in the buccal wall (linear buccal = Dbuccal) from CBCT images. The box stretches from 25th percentile to 75th percentile. The median is shown as a line across the box and the average is shown as a symbol inside the box. *Statistically significant differences (p < .05). CBCT = cone beam computed tomography.
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Figure 5 Chart of individualized percentage bone loss for each patient, in which each experimental site matched with its control. The “y” axis refers to patients while “x” axis represents the bone lost in percentage (%). The “y” axis labels refer to Patient (P); numbers 01 to 10 (patient identification); L = LARGE; S = SMALL OsteoScaf™ pore size. Only L group presented statistically significant difference (p < .05) compared with control.
controls. This was evidenced by the rounding of the alveolar ridge, rather than the expected knife-edge shape of the controls (Figure 7). We believe that the reason for this is that the OsteoScaf, being highly porous, but nevertheless a cylindrical lithomorph, retains the blood clot in the occlusal portion of the socket and minimizes the natural clot contraction that is normally seen during the
socket healing, as small volumes of clot are retained within the interstices of the scaffold, which is mechanically strong enough to withstand tissue shrinkage32 (Figure 8). It should be emphasized that tissue healing will not occur in a void, and can only occur through a transitory biological matrix; thus, clot retention in the occlusal region of the socket allows the regenerative
Figure 6 Trephine biopsies at 120 days, HE stain. A, Residual OsteoScaf™ (OS) has multinucleate giant cells (GC) on the left side and new bone formation (NB) on the right. B, Higher magnification of another bone contact area shows a palisaded arrangement of osteoblasts and some osteocytes (OC). Both (A) and (B) are decalcified preparations. (C) and undecalified preparation showing streaming fibrous tissue within the surrounding connective tissue matrix (CM) and also bone, with surface osteoblasts, juxtaposed to the residual OsteoScaf. HE = hematoxylin-eosin.
PLGA/CaP Scaffold to Alveolar Bone Preservation
TABLE 1 Linear Bone Loss Measurements Comparing the Proportion of Bone Lost in the Center of the Alveolar Socket – Dcenter, at 120 Days Postoperative Dcenter
Linear measure of the bone lost (mm) Proportion of the bone lost (%)
SMALL
LARGE
Control
1.29
1.62
2.68
10.8
14.7
25.2
properties inherent in the clot, such as platelet-derived cytokines and growth factors (PDGF), platelet factor 4 (PF-4), and transforming growth factor-beta (TGF-b); the stimulation of angiogenesis and the incursion of mesenchymal stromal cell (MSCs) as perivascular cells into the wound site, to contribute to wound healing in the occlusal portion of the wound,39,40 which would otherwise be devoid of any biologic matrix through which such healing could occur. Therefore, the rounded shape
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of the alveolar bone achieved at 120 days PO, which reflects that reported with BMP2/collagen outcomes, provides indirect evidence of such clot retention, as we have mentioned in previous translational studies.28,29 Regarding the amount of total bone lost, our study revealed that the L group showed statistically significantly less bone lost (28.7%) at 120 days PO, compared with the control (45.3%). The residual ridge resorption has been described in the literature as 40 to 60% during the first year;3,6–9 thus, the use of OsteoScaf L after tooth extraction showed a bone healing improvement and less catabolic remodeling. In addition, when we separated the vestibular area from the palatine to assess the bone lost, the results were consistent with the literature,5,12,14,15 revealing a greater amount of bone resorption in the buccal than the palatine region (Table 2). Morphometric analyses were completed on the bone biopsy using MicroCT. No significant differences were found in the trabecular bone structure parameters
Figure 7 CBCTs sagittal slices: (A) control baseline; (B) OsteoScaf™ L-baseline; (C) control at 120 days; (D) OsteoScaf L at 120 days PO. At 120 days, the control shows a knife edge-shaped alveolar architecture (C), while the socket grafted with OsteoScafT showed a rounder shape (D). CBCT = cone beam computed tomography; PO = postoperative.
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Figure 8 A, The blood clot that filled the dental socket after the tooth extraction suffers contraction during its maturation, resulting in shrinkage from the alveolar margin. B, OsteoScaf™ acts to retain the blood clot up to the alveolar margin. While clot shrinkage will still occur, the OsteoScaf™ minimizes shrinkage away from the alveolar margin although as illustrated here, and in the clinical photograph (C), those parts of the socket not filled with OsteoScaf will still exhibit shrinkage. Also, in (C), both SMALL (S) and LARGE (L) OsteoScaf cylinders have been employed. The latter is more rapidly filled with blood than the former.
BV, Tb.N, Tb.Th when comparing S, L with control groups. To our knowledge, only one other study has analyzed human postextraction socket cores with MicroCT, and it had similar results, where control and an experimental, using an osteoconductive allograft, presented the same trabecular bone pattern.33 However, in our study the Tb.Sp was significantly smaller in the S group than in the control group, probably due to the ingrowth template provided by the pore size of this material. TABLE 2 Proportion of Bone Lost at 120 Days Postoperative Buccal Area (%)
OsteoScaf™ SMALL OsteoScaf™ LARGE Control
40.8 38.9 54.3
Additionally, histological sections demonstrated that OsteoScaf is osteoconductive, that is, it provides a structural framework that allows the adhesion of preosteoblasts and osteoblasts that can then secrete de novo bone matrix on the scaffold surface, providing an interconnected structure through which new cells can migrate and can form new blood vessels. OsteoScaf, as previously reported,32 also abrogates the transition from acute to chronic inflammation, and thus minimizes the degree of the multinucleate giant cell response.
CONCLUSION
Palatal Area (%)
20.1 19.2 31.8
Our results show that both L and S OsteoScaf presented an advantage in reducing bone loss during postextraction alveolar ridge remodeling, although the large pore size format was better than the small.
PLGA/CaP Scaffold to Alveolar Bone Preservation
ACKNOWLEDGMENTS The authors would like to thank Rahim Moineddin for statistical analysis and research funding from CAPES (Brazil) and BoneTec Corporation (Canada). REFERENCES 1. Buser D, Dula K, Hirt HP, Schenk RK. Lateral ridge augmentation using autografts and barrier membranes: a clinical study with 40 partially edentulous patients. J Oral Maxillofac Surg 1996; 54:420–432. discussion 432–423. 2. Camargo PM, Lekovic V, Weinlaender M, et al. Influence of bioactive glass on changes in alveolar process dimensions after exodontia. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2000; 90:581–586. 3. Moya-Villaescusa MJ, Sanchez-Perez A. Measurement of ridge alterations following tooth removal: a radiographic study in humans. Clin Oral Implants Res 2010; 21:237– 242. 4. Jahangiri L, Devlin H, Ting K, Nishimura I. Current perspectives in residual ridge remodeling and its clinical implications: a review. J Prosthet Dent 1998; 80:224–237. 5. Schropp L, Wenzel A, Kostopoulos L, Karring T. Bone healing and soft tissue contour changes following singletooth extraction: a clinical and radiographic 12-month prospective study. Int J Periodontics Restorative Dent 2003; 23:313–323. 6. Wang HL, Kiyonobu K, Neiva RF. Socket augmentation: rationale and technique. Implant Dent 2004; 13:286–296. 7. Araujo MG, Lindhe J. Dimensional ridge alterations following tooth extraction. An experimental study in the dog. J Clin Periodontol 2005; 32:212–218. 8. Nair PN, Luder HU, Maspero FA, Fischer JH, Schug J. Biocompatibility of Beta-tricalcium phosphate root replicas in porcine tooth extraction sockets – a correlative histological, ultrastructural, and x-ray microanalytical pilot study. J Biomater Appl 2006; 20:307–324. 9. Araujo MG, Lindhe J. Ridge alterations following tooth extraction with and without flap elevation: an experimental study in the dog. Clin Oral Implants Res 2009; 20:545–549. 10. Carlsson GE, Thilander H, Hedegard B. Histologic changes in the upper alveolar process after extractions with or without insertion of an immediate full denture. Acta Odontol Scand 1967; 25:21–43. 11. Carlsson GE, Bergman B, Hedegard B. Changes in contour of the maxillary alveolar process under immediate dentures. A longitudinal clinical and x-ray cephalometric study covering 5 years. Acta Odontol Scand 1967; 25:45–75. 12. Pietrokovski J, Massler M. Alveolar ridge resorption following tooth extraction. J Prosthet Dent 1967; 17:21–27. 13. Atwood DA. Some clinical factors related to rate of resorption of residual ridges. J Prosthet Dent 1962; 12:441–450.
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tissue engineering: evolution of scaffold design. Biomaterials 2007; 28:1495–1502. Guan L, Davies JE. Preparation and characterization of a highly macroporous biodegradable composite tissue engineering scaffold. J Biomed Mater Res A 2004; 71:480– 487. Holy CE, Dang SM, Davies JE, Shoichet MS. In vitro degradation of a novel poly(lactide-co-glycolide) 75/25 foam. Biomaterials 1999; 20:1177–1185. Lickorish D, Chan J, Song J, Davies JE. An in-vivo model to interrogate the transition from acute to chronic inflammation. Eur Cell Mater 2004; 8:12–19. discussion 20. Brownfield LA, Weltman RL. Ridge preservation with or without an osteoinductive allograft: a clinical, radiographic, micro-computed tomography, and histologic study evaluating dimensional changes and new bone formation of the alveolar ridge. J Periodontol 2012; 83:581–589. Barone A, Aldini NN, Fini M, Giardino R, Calvo Guirado JL, Covani U. Xenograft versus extraction alone for ridge preservation after tooth removal: a clinical and histomorphometric study. J Periodontol 2008; 79:1370– 1377.
35. Iasella JM, Greenwell H, Miller RL, et al. Ridge preservation with freeze-dried bone allograft and a collagen membrane compared to extraction alone for implant site development: a clinical and histologic study in humans. J Periodontol 2003; 74:990–999. 36. Fiorellini JP, Howell TH, Cochran D, et al. Randomized study evaluating recombinant human bone morphogenetic protein-2 for extraction socket augmentation. J Periodontol 2005; 76:605–613. 37. Kim YJ, Lee JY, Kim JE, Park JC, Shin SW, Cho KS. Ridge preservation using demineralized bone matrix gel with recombinant human bone morphogenetic protein-2 after tooth extraction: a randomized controlled clinical trial. J Oral Maxillofac Surg 2014; 72:1281–1290. 38. Oghli AA, Steveling H. Ridge preservation following tooth extraction: a comparison between atraumatic extraction and socket seal surgery. Quintessence Int 2010; 41:605–609. 39. Davies JE. Understanding peri-implant endosseous healing. J Dent Educ 2003; 67:932–949. 40. Shiu HT, Goss B, Lutton C, Crawford R, Xiao Y. Formation of blood clot on biomaterial implants influences bone healing. Tissue Eng Part B Rev 2014; 20:697–712.
ABSTRACT Background: It is expected that 40% to 60% of initial alveolar bone volume will be lost up to 6 months after tooth extraction. OsteoScafTM (TRT, Toronto, ON, Canada) (poly (DL-lactide-co-glycololide/calcium phosphate [PLGA/CaP] scaffold) is a novel bone substitute material and represents a promising alternative for maintaining alveolar bone integrity in this clinical scenario. Purpose: Here it was hypothesized that OsteoScaf would reduce alveolar bone lost after tooth extraction in patient, acting as a clot-retention device. Material and Methods: A total of 10 patients (32 sockets) were included in the study, of which 16 sockets were grafted with OsteoScaf and 16 were used as control (coagulum alone). Cone beam computed tomography (CBCT) was performed both immediately following extraction and also at 120 days postoperatively, at which time biopsy samples were also harvested for histological analyses. Results: Quantitative analysis of CBCT showed less bone resorption in the OsteoScaf groups, being 10.5% to 14.4% less bone lost in the center of the socket, 15.4% in the buccal region, and 12.6% in the palatal. Qualitative histological analysis showed new bone tissue in direct apposition to the scaffold – demonstrating its osteoconductive nature. Conclusion: OsteoScaf diminished the expected bone lost during the postextraction remodeling of the alveolar bone ridge at 120 days postextraction. KEY WORDS: alveolar bone remodeling, biomaterials, bone regeneration, bone substitutes, bone tissue engineering, CBCT imaging, clinical study, extraction socket, histological analysis, micro-CT
INTRODUCTION One of the biggest obstacles to overcome in dental implant surgery is to find sufficient height and width of alveolar bone to receive the implant.1,2 The aesthetic and functional success of prostheses, both conventional noninvasive and implant-supported, depend on the presence of sufficient healthy bone volume.2,3 Preserving alveolar bone architecture during socket healing is challenging. The process of alveolar healing after tooth extraction is associated with a catabolic remodeling of the residual alveolar ridge, which can result in considerable loss of bone.4 Indeed, it has been shown that 40% to 60% of the initial alveolar bone volume will be lost up to 12 months after tooth extraction.5–9 In fact, the alveolar process is rapidly
*School of Dentistry, Stomatology and Oral Surgery Bauru, University of São Paulo, Bauru, São Paulo, Brazil; †Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada; ‡Dental Research Institute, Faculty of Dentistry, University of Toronto, Toronto, ON, Canada; §Surgery and Integrated Clinic, São Paulo State University, Araçatuba, São Paulo, Brazil Corresponding Author: Professor John Edward Davies, Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College Street, Toronto, ON M5S 3G9, Canada; e-mail: davies@ ecf.utoronto.ca Disclosure: All the authors declare no conflict of interest. © 2015 Wiley Periodicals, Inc. DOI 10.1111/cid.12326
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reduced in the first 6 months, but slower resorption continues throughout life4,10–12 and is responsible for a significant change in jaw structure.8,9,13 Specifically, vertical ridge height is lost and is most pronounced on the buccal wall;5–12,14,15 this relocates the alveolar ridge to a more palatal/lingual position.12 The main etiology of the residual ridge reabsorption after tooth extraction is believed to be atrophy,5,12,13,16–19 and it is well known that alveolar bone integrity is closely linked to the presence of teeth.12,13,16–19 Socket preservation should be considered at the time of tooth extraction and can reduce, or eliminate, the need for future ridge augmentation.6,20,21 Among the various techniques indicated to preserve alveolar bone, the use of autologous bone graft is known as the “gold standard” because it represents a physiologically optimized combination of the three elements considered essential for the bone regenerative therapy: osteoconductivity, osteoinductivity, and osteogenic cells. Moreover, immunologic rejection and disease transmission are absent using autologous bone. However, this procedure has disadvantages such as donor site morbidity, prolonged pain, infection risk, limited availability, and the possibility of cosmetic defects.22–27 Thus, considerable efforts have been made to develop alternatives to autologous bone grafting, resulting in a wide range of biomaterials for bone regenera-
tion, such as cement particles of calcium phosphate, bioactive glass, inorganic bone, polymers, and demineralized bone matrix. However, despite the widespread use of commercial bone substitutes, an ideal bone filler material has not yet been developed. In this context, OsteoScaf™ (TRT, Toronto, ON, Canada) is a poly (DL-lactide-co-glycololide/calcium phosphate)-based (PLGA/CaP) totally biodegradable macroporous composite scaffold that represents a promising alternative for maintaining alveolar bone integrity. OsteoScaf has an architecture and interconnecting macroporosity similar to that of human trabecular bone (Figure 1). OsteoScaf can be used as a biomaterial alone, as a carrier for cells or a threephase drug delivery device.28,29 Due to the highly interconnected macroporosity ranging from 81% to 91% and an ability to wick up blood, this biomaterial acts as both a clot-retention device and an osteoconductive support for host bone growth,28 do not being necessary. OsteoScaf, which has been fully described elsewhere,30,31 comprises PLGA, and two osteoclastresorbable calcium phosphate phases, one as internal particles and the other as a surface coating.29,32 We report herein the first clinical study to employ this material for alveolar ridge preservation after tooth extraction. We hypothesized that OsteoScaf would reduce alveolar bone lost in patients by acting as a clot-retention device.
Figure 1 OsteoScaf™ has an architecture and interconnecting macroporosity similar to that of human trabecular bone. A, OsteoScaf with large pores (L = 850∼1,180 μm). B, OsteoScaf with small pores (S = 355∼595 μm). C, A MicroCT image of a sagittal cut (5 μm thick) from a harvested sample. The region of interest (ROI) is delimited for analysis, which corresponded to the center of the tooth socket. MicroCT = micro-computed tomography.
PLGA/CaP Scaffold to Alveolar Bone Preservation
MATERIALS AND METHODS This clinical study had institutional review board approval by Ethical Committee to Human Research of Bauru Dental School, University of São Paulo. All surgical procedures and patient follow-ups were performed at the University of São Paulo, while the histology and all analyses were conducted at University of Toronto. Clinical Test Model OsteoScaf was custom made according to the protocol previously established (Lickorish and colleagues29), in cylinders of 3 mm diameter and 10 mm length, and of two different porosities: 355∼595 μm (SMALL – S) and 850∼1,180 μm (LARGE – L) (Figure 1). Ten patients, in need of at least two anterior maxillary tooth extractions and delayed implant placement, were selected by panoramic radiography to receive either OsteoScaf lithomorph cylinders or extraction alone (CONTROL – C). The exclusion criteria were patients who were: (1) 218 year of age; (2) current or previous smokers; (3) current or previous drug/alcohol addicts; (4) currently pregnant or expecting to be; or who had (5) a medical condition or were taking medication associated with compromising bone healing; (6) psychiatric disorders; (7) parafunctional habits; (8) or the presence of any suppurating infection in desired area. The main inclusion criterion on tooth socket selection was that the extraction socket exhibited a four-wall configuration with a height of at least 10 mm. Overall, 32 tooth sockets were used in this study, 16 in the test group and 16 in the C-group, contralateral to one another. In total, eight OsteoScaf S and eight L were used, as described below. The test sockets were numbered 1 to 16 and the porosities of the OsteoScaf (S and L) were blindly distributed among the patients. Surgical Procedures The surgical procedures were performed at two time points: (1) tooth extraction; and (2) sample harvesting at the time of implant placement. Tooth Extraction. After administration of local anesthesia, the teeth in question were atraumatically extracted, following flap elevation. The sockets were curetted to remove any granulation tissue. The sockets were then 2 mm drilled in the apical region with a
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2 mm twist drill (2 × 13 mm implant drill, Kit Master Conect, Conexão Sistema de Protéses, Ltda, São Paulo, Brazil) under saline irrigation, for scaffold anchorage. The test and C-sites were contralateral to one another, and the sockets were randomly assigned to either test or control groups by the flip of a coin. Two titanium mini-screws 2 × 4 mm (Conexão Sistema de Próteses, Ltda.) were used to provide reference guide points. One screw was placed on the maxillary alveolar bone near to the test site and the other close to the correspondent control, each 10 mm from the alveolar bone crest – a well-known nonresorbable area. Nonresorbable 4.0 nylon vertical mattress sutures (ETHILON™, Johnson & Johnson, São Paulo, SP, Brazil) were used to close the soft tissues. Immediately following extraction, cone beam computed tomography (CBCT) (i-CAT® Cone Beam 3-D Imaging System, Imaging Sciences International, Hatfield, PA, USA) was performed. Patients were allowed to wear a total prosthesis to substitute the function of the missing teeth. The prosthesis was made with transparent acrylic resin, making it possible to check any undesirable pressure/trauma on/to the operated areas. Follow-ups were arranged 48 hours, 7 days (suture removal), 15 days, 30 days, and 120 days postoperative (PO). At the last follow-up, a second CBCT was performed. Sample Harvesting. One hundred twenty days after the OsteoScaf placement, the anterior superior alveolar ridge in question was surgically exposed to receive dental implants. Bone samples were harvested in the socket’s core with a 2.75 mm trephine bur (Conexão Sistema de Próteses, Ltda.). The bone biopsies were stored in 10% phosphate-buffered formalin prior to histologic processing. Micro-Computed Tomography (MicroCT) The bone biopsy specimens were scanned using a micro-computed tomography system (MicroCT40, Scanco, Zurich, Switzerland) at 85 kV and 77 μA. After image reconstruction, two-dimensional images representing sagittal cuts (5 μm thick) of the harvested samples were used to select the region of interest (ROI) for analysis, which corresponded to the center of the tooth socket (Figure 1C). The quantification of bone formation (bone volume/total volume, or BV) as well as trabecular number (Tb.N), thickness (Tb.Th), and
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separation (Tb.Sp) were possible by determining the gray-level distribution at specific thresholds for human bone. CBCT Imaging Study The CBCT images were acquired by iCAT® (Cone Beam 3-D Imaging System, Imaging Sciences International, Hatfield, PA, USA) and converted in DICOM (digital imaging communications in medicine) to export to the MicroCT Scanco System, to permit two-dimensional and three-dimensional analyses. A comparison between baseline images and scans acquired 120 days after was performed for each patient on a socket-to-socket basis. Changes in socket height and thickness were evaluated. Linear Measurements. In order to take measurements reflecting the socket height, a reference point Y was created by intersecting the horizontal plane of the mini-
screw (dashed red line) with the extension of the palatal bony wall line of the socket, named PBL (Figure 2, A and B). From Y, three measurements were taken: (1) Dpalatal = line segment YP , or Y to the more occlusal point of the PBL – P; (2) Dbuccal = line segment YV , or Y to the more occlusal point of the buccal wall – V; (3) Dcenter = line segment YC , or Y to the more occlusal point of the bisectrix of the angle formed by Dpalatal and Dbuccal – C (Figure 2, C and D). The aforementioned eight measurements (three socket heights and five socket thicknesses) were performed in the three image slices from the CBCT that were determined to be in the center of the socket. For measurements of the socket width, five measurements were taken (T1, T2, T3, T4, T5) to represent the distance between the palatal and the buccal wall. The separation between each measurement was 2 mm (Figure 3, A and B).
Figure 2 Measurement of loss of bone height from CBCT sagittal images of the upper alveolar ridge: (A) and (C) baseline, immediate postoperative; (B) and (D) 120 days PO. Dashed red line = horizontal plane marked by the screw. Blue line = palatal bony wall line of the socket (PBL); Y = point of intersection between the screw line and PBL; P = most occlusal point of the PBL; V = the most occlusal point of the buccal wall; C = most occlusal point of the bisectrix of the angle formed by Dpalatal and Dbuccal; YP = Dpalatal; YC = Dcenter; YV = Dbuccal. CBCT = cone beam computed tomography; PO = postoperative.
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Figure 3 Bone width and socket area measurements on CBCT images. A, Baseline (immediate postoperative [PO]). B, 120 days PO. The widths T1, T2, T3, T4, T5 are parallel and are 2 mm apart; (C) baseline socket area, and (D) at 120 days PO. Yellow space = palatal area; red space = buccal area; green line = bisectrix of the angle between the palatal bony wall line of the socket (PBL) and the buccal bony wall line (BBL); Dashed red line = horizontal plane marked by the screw. CBCT = cone beam computed tomography.
Area Measurements. Area measurements were also calculated for buccal, palatal, and total areas. The total area was defined by the screw line, PBL, the occlusal limit, and the buccal bony wall line (BBL). The palatal area was defined by the PBL, the occlusal limit, the screw line, and the bisectrix line (bisectrix of the angle between the BBL and the PBL). The buccal area was defined by the BBL, the occlusal limit, the screw line, and the bisectrix line (Figure 3, C and D). Three image slices for each tooth socket were measured. The buccal and the palatal areas were calculated in the CBCTs at baseline and at 120 days PO (Figure 3, C and D). All measurement steps were performed three times by the same examiner, blind, with at least a 1 month interval between each measurement. Calculating the Bone Lost. All measurements at 120 days PO were subtracted from those of the baseline to allow calculation of the bone lost following extraction. The
measurements were converted to bone lost percentage (the proportion of bone that was lost at 120 days PO compared with baseline). Statistical Analysis We used repeated measure ANOVA to investigate the significance of variation among three measurements, difference among three groups at each time point and comparing baseline and 120 days PO within each group. All comparisons were adjusted for repeated measures (using random effect regression models) and multiple comparisons were taken into account using Bonferroni corrections. Afterward, we matched controls with S and L groups, and calculated the difference between matched pairs. Then we used paired “t”tests to examine the significance of the difference for S and L groups. In fact, we matched C and L, and C and S groups, and respectively compared them. p < .05 was considered statistically significant.
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Histologic Processing
DISCUSSION
Bone samples were randomly chosen for light microscopy by either resin embedded undecalcified (Osteo-Bed™, Polysciences, Warrington, PA, USA) or paraffin-embedded decalcified preparations. The central slices from both histologic processing routes were stained with hematoxylin-eosin (HE) to permit qualitative evaluation.
We report herein the use OsteoScaf cylinders, of two different porosities, in the healing of tooth extraction sockets in patients (Figure 1). The numerical results obtained from CBCT measurements have clearly shown that OsteoScaf impaired the expected bone lost during the postextraction remodeling of the alveolar bone ridge at 120 days postextraction. Our findings are in contrast with those in the literature where ridge preservation did not prevent bone resorption after tooth removal,14,33,34 but do concur with some others where it was found that the use of the biomaterial strategies can maintain bone volume postextraction,2,14,15,35 although this may not be concomitant with preservation of alveolar ridge height as shown when using bioglass particulate.2 Indeed, although regenerative strategies for ridge preservation have been extensively proposed, alveolar ridge height maintenance was only shown when biomaterials, or bone allograft, were employed in conjunction with guided bone regeneration1,15,34,35 or growth factors.36,37 In the latter cases, when employed with a collagen membrane, bone morphogenetic protein 2 (BMP2) was shown to both maintain and restore lost36 buccal bone; while no change, compared with controls, was reported when BMP2 was employed with both demineralized bone powder and a collagen membrane.37 A comparison of this reported data remains challenging, as the different findings may be due to numerous factors: on the one hand, clot contraction can condense osteoconductive particulates; while on the other hand, different measurement methods5,12,38 and clinical assessments have been employed.2,5,14,15,33,37 In our study, we quantified the bone lost due to bone remodeling after tooth extraction by CBCT evaluation, and included controls in the same patients as the test groups with which they were compared. Thus, S and L groups were compared with their corresponding controls, which minimized the effect of the difference between groups due the individual characteristics of each patient. We also accounted for the differences in individual tooth sockets by expressing bone loss as a percentage value of the original rather than an absolute value, and this provided a more accurate interpretation of our results (Table 1). Interestingly, we found that the measurement Dcenter (Figure 4 and Table 1), for either L or S groups, demonstrates less bone resorption than
RESULTS The PO period was uneventful for all patients. MicroCT Study Results By MicroCT assessment, the Tb.Sp of the S test group was smaller than the control, which was the only statistically significant (p < .05) result of the MicroCT evaluation (Figure 4). The other parameters studied, BV, Tb.N, and Tb.Th, did not show statistically significant differences between test and control groups (Figure 4). CBCT Study Results Linear Measurement Results. Only the Dcenter measure presented a statistically significant difference (p < .05) in both L and S (Figure 4), being 14.4% and 10.5% less respectively when compared with the C group. Area Measurement Results. The buccal bone lost was more pronounced than the palatal bone lost, both in test and control groups (Figure 5). When test and control groups were compared, only the L group presented a statistically significant difference (p < .05) compared with the control group; the L group showed 15.4% and 12.6% less bone loss to buccal and palatal areas, respectively, than the control group (Figure 5). Histomorphology Qualitative analysis of the histologic slices (Figure 6) revealed that the test sites and controls showed a mononuclear inflammatory infiltrate permeating an intense fibroblastic and angioblastic proliferation in the region of the tooth socket repair at 120 days, together with the formation of new bone. In both test groups (L and S), fragments of the OsteoScaf persisted with surrounding multinucleated giant cells, suggesting the resorption of the material; while in neighboring areas, palisading osteoblasts elaborated bone matrix directly on the material surface.
PLGA/CaP Scaffold to Alveolar Bone Preservation
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Figure 4 Box plots for trabeculae separation (Tb.Sp), bone volume (BV), trabeculae number (Tb.N), trabeculae thickness (Tb.Th), from MicroCT scans of the bone core biopsies; and percentage of bone change during 120 days postextraction in the palatal wall (linear palatal = Dpalatal), center of the alveolar ridge (linear center = Dcenter), and in the buccal wall (linear buccal = Dbuccal) from CBCT images. The box stretches from 25th percentile to 75th percentile. The median is shown as a line across the box and the average is shown as a symbol inside the box. *Statistically significant differences (p < .05). CBCT = cone beam computed tomography.
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Figure 5 Chart of individualized percentage bone loss for each patient, in which each experimental site matched with its control. The “y” axis refers to patients while “x” axis represents the bone lost in percentage (%). The “y” axis labels refer to Patient (P); numbers 01 to 10 (patient identification); L = LARGE; S = SMALL OsteoScaf™ pore size. Only L group presented statistically significant difference (p < .05) compared with control.
controls. This was evidenced by the rounding of the alveolar ridge, rather than the expected knife-edge shape of the controls (Figure 7). We believe that the reason for this is that the OsteoScaf, being highly porous, but nevertheless a cylindrical lithomorph, retains the blood clot in the occlusal portion of the socket and minimizes the natural clot contraction that is normally seen during the
socket healing, as small volumes of clot are retained within the interstices of the scaffold, which is mechanically strong enough to withstand tissue shrinkage32 (Figure 8). It should be emphasized that tissue healing will not occur in a void, and can only occur through a transitory biological matrix; thus, clot retention in the occlusal region of the socket allows the regenerative
Figure 6 Trephine biopsies at 120 days, HE stain. A, Residual OsteoScaf™ (OS) has multinucleate giant cells (GC) on the left side and new bone formation (NB) on the right. B, Higher magnification of another bone contact area shows a palisaded arrangement of osteoblasts and some osteocytes (OC). Both (A) and (B) are decalcified preparations. (C) and undecalified preparation showing streaming fibrous tissue within the surrounding connective tissue matrix (CM) and also bone, with surface osteoblasts, juxtaposed to the residual OsteoScaf. HE = hematoxylin-eosin.
PLGA/CaP Scaffold to Alveolar Bone Preservation
TABLE 1 Linear Bone Loss Measurements Comparing the Proportion of Bone Lost in the Center of the Alveolar Socket – Dcenter, at 120 Days Postoperative Dcenter
Linear measure of the bone lost (mm) Proportion of the bone lost (%)
SMALL
LARGE
Control
1.29
1.62
2.68
10.8
14.7
25.2
properties inherent in the clot, such as platelet-derived cytokines and growth factors (PDGF), platelet factor 4 (PF-4), and transforming growth factor-beta (TGF-b); the stimulation of angiogenesis and the incursion of mesenchymal stromal cell (MSCs) as perivascular cells into the wound site, to contribute to wound healing in the occlusal portion of the wound,39,40 which would otherwise be devoid of any biologic matrix through which such healing could occur. Therefore, the rounded shape
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of the alveolar bone achieved at 120 days PO, which reflects that reported with BMP2/collagen outcomes, provides indirect evidence of such clot retention, as we have mentioned in previous translational studies.28,29 Regarding the amount of total bone lost, our study revealed that the L group showed statistically significantly less bone lost (28.7%) at 120 days PO, compared with the control (45.3%). The residual ridge resorption has been described in the literature as 40 to 60% during the first year;3,6–9 thus, the use of OsteoScaf L after tooth extraction showed a bone healing improvement and less catabolic remodeling. In addition, when we separated the vestibular area from the palatine to assess the bone lost, the results were consistent with the literature,5,12,14,15 revealing a greater amount of bone resorption in the buccal than the palatine region (Table 2). Morphometric analyses were completed on the bone biopsy using MicroCT. No significant differences were found in the trabecular bone structure parameters
Figure 7 CBCTs sagittal slices: (A) control baseline; (B) OsteoScaf™ L-baseline; (C) control at 120 days; (D) OsteoScaf L at 120 days PO. At 120 days, the control shows a knife edge-shaped alveolar architecture (C), while the socket grafted with OsteoScafT showed a rounder shape (D). CBCT = cone beam computed tomography; PO = postoperative.
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Figure 8 A, The blood clot that filled the dental socket after the tooth extraction suffers contraction during its maturation, resulting in shrinkage from the alveolar margin. B, OsteoScaf™ acts to retain the blood clot up to the alveolar margin. While clot shrinkage will still occur, the OsteoScaf™ minimizes shrinkage away from the alveolar margin although as illustrated here, and in the clinical photograph (C), those parts of the socket not filled with OsteoScaf will still exhibit shrinkage. Also, in (C), both SMALL (S) and LARGE (L) OsteoScaf cylinders have been employed. The latter is more rapidly filled with blood than the former.
BV, Tb.N, Tb.Th when comparing S, L with control groups. To our knowledge, only one other study has analyzed human postextraction socket cores with MicroCT, and it had similar results, where control and an experimental, using an osteoconductive allograft, presented the same trabecular bone pattern.33 However, in our study the Tb.Sp was significantly smaller in the S group than in the control group, probably due to the ingrowth template provided by the pore size of this material. TABLE 2 Proportion of Bone Lost at 120 Days Postoperative Buccal Area (%)
OsteoScaf™ SMALL OsteoScaf™ LARGE Control
40.8 38.9 54.3
Additionally, histological sections demonstrated that OsteoScaf is osteoconductive, that is, it provides a structural framework that allows the adhesion of preosteoblasts and osteoblasts that can then secrete de novo bone matrix on the scaffold surface, providing an interconnected structure through which new cells can migrate and can form new blood vessels. OsteoScaf, as previously reported,32 also abrogates the transition from acute to chronic inflammation, and thus minimizes the degree of the multinucleate giant cell response.
CONCLUSION
Palatal Area (%)
20.1 19.2 31.8
Our results show that both L and S OsteoScaf presented an advantage in reducing bone loss during postextraction alveolar ridge remodeling, although the large pore size format was better than the small.
PLGA/CaP Scaffold to Alveolar Bone Preservation
ACKNOWLEDGMENTS The authors would like to thank Rahim Moineddin for statistical analysis and research funding from CAPES (Brazil) and BoneTec Corporation (Canada). REFERENCES 1. Buser D, Dula K, Hirt HP, Schenk RK. Lateral ridge augmentation using autografts and barrier membranes: a clinical study with 40 partially edentulous patients. J Oral Maxillofac Surg 1996; 54:420–432. discussion 432–423. 2. Camargo PM, Lekovic V, Weinlaender M, et al. Influence of bioactive glass on changes in alveolar process dimensions after exodontia. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2000; 90:581–586. 3. Moya-Villaescusa MJ, Sanchez-Perez A. Measurement of ridge alterations following tooth removal: a radiographic study in humans. Clin Oral Implants Res 2010; 21:237– 242. 4. Jahangiri L, Devlin H, Ting K, Nishimura I. Current perspectives in residual ridge remodeling and its clinical implications: a review. J Prosthet Dent 1998; 80:224–237. 5. Schropp L, Wenzel A, Kostopoulos L, Karring T. Bone healing and soft tissue contour changes following singletooth extraction: a clinical and radiographic 12-month prospective study. Int J Periodontics Restorative Dent 2003; 23:313–323. 6. Wang HL, Kiyonobu K, Neiva RF. Socket augmentation: rationale and technique. Implant Dent 2004; 13:286–296. 7. Araujo MG, Lindhe J. Dimensional ridge alterations following tooth extraction. An experimental study in the dog. J Clin Periodontol 2005; 32:212–218. 8. Nair PN, Luder HU, Maspero FA, Fischer JH, Schug J. Biocompatibility of Beta-tricalcium phosphate root replicas in porcine tooth extraction sockets – a correlative histological, ultrastructural, and x-ray microanalytical pilot study. J Biomater Appl 2006; 20:307–324. 9. Araujo MG, Lindhe J. Ridge alterations following tooth extraction with and without flap elevation: an experimental study in the dog. Clin Oral Implants Res 2009; 20:545–549. 10. Carlsson GE, Thilander H, Hedegard B. Histologic changes in the upper alveolar process after extractions with or without insertion of an immediate full denture. Acta Odontol Scand 1967; 25:21–43. 11. Carlsson GE, Bergman B, Hedegard B. Changes in contour of the maxillary alveolar process under immediate dentures. A longitudinal clinical and x-ray cephalometric study covering 5 years. Acta Odontol Scand 1967; 25:45–75. 12. Pietrokovski J, Massler M. Alveolar ridge resorption following tooth extraction. J Prosthet Dent 1967; 17:21–27. 13. Atwood DA. Some clinical factors related to rate of resorption of residual ridges. J Prosthet Dent 1962; 12:441–450.
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