Conditions for success in guided bone regeneration: retrospective study on 376 implant sites

Exposure of Barriers Used in GBR: Rate, Timing, Management, And Its Effect on Grafted Bone. A Retrospective Analysis

The purpose of this study is to compare exposure rate of three different barrier types after a guided-bone regenerationprocedure, as well as to compare the percentage grafted bone dimensional loss with and without exposed barriers. Patient records from September 2007 to May 2015 were reviewed to identify subjects that had received bone graft and then implant placement procedure after the graft is completely healed. The subjects were divided into 3 groups: 1) resorbable barrier 2) non-resorbable barrier, and 3) titanium-mesh barrier. Incidences of barrier exposure were recorded.  Cone-beam computed tomography images before treatment (T0), right after grafting (T1), and after healing (T2) were used to determine percentage grafted bone dimensional loss (%) and quantitative grafted bone remained (mm 2 ). Three cross-sectioned areas, at 1mm apart, of preplanned implant positions at the grafted site were measured on cone-beam computed tomography to calculate for grafted bone remained and grafted bone dimensional change. The exposure rate of all guided bone regeneration was 36.9%. Exposure rate of resorbable barrier (23.3%) is significantly lower than Titanium mesh (68.9%) and Non-resorbable (72.7%) (Chi-Square, P < .001).  The result from this study revealed that barrier types have significant effect on exposure rate. There was also a significant different in grafted bone dimensional loss in sites with barrier exposure (58.3%) and sites with no barrier exposure (44.1%) during the healing period (Mann-Whitney U, P = .008).

Effects of Impacted Lower Third Molar Extraction on Periodontal Tissue of the Adjacent Second Molar

The extraction of impacted lower third molars (ILTM) is one of the most common procedures in oral-maxillofacial surgery. Being adjacent to lower second molars, most impacted lower third molars often lead to distal periodontal defects of adjacent second molars. Several symptoms may occur after extraction, such as periodontal pocket formation, loss of attachment, alveolar bone loss and even looseness of second molar resulting in extraction. The distal periodontal defects of second molars are affected by many factors, including periodontal conditions, age, impacted type of third molars, and intraoperative operations. At present, several studies have suggested that dentists can reduce the risk of periodontal defects of the second molar after ILTM extraction through preoperative evaluation, reasonable selection of flap design, extraction instruments and suture type, and necessary postoperative interventions. This review summarizes the research progress on the influence factors, interventions methods and some limitations of distal periodontal defects of adjacent second molar after extraction of impacted mandibular third molars, with the aim of opening up future directions for studying effects of ILTM extraction on periodontal tissue of the adjacent second molar.

Changes in mucogingival junction after an apically positioned flap with collagen matrix at sites with or without previous guided bone regeneration: A prospective comparative cohort study

AIM

To assess changes in the position of the mucogingival junction (MGJ) after an apically positioned flap (APF) with collagen matrix performed at sites with or without previous guided bone regeneration (GBR).

MATERIALS AND METHODS

Dental implants were placed with or without GBR (group GBR or non-GBR) depending on the available ridge width in 30 patients with a limited width of keratinized mucosa (MGJ placed more coronally than the expected prosthetic margin). An apically positioned flap with collagen matrix was performed in both groups. Changes in the position of the MGJ from the day of an apically positioned flap up to 1, 3, and 12 months thereafter were assessed on digital scans (primary endpoint). Secondary endpoints were the width and thickness of the keratinized mucosa, and the position of the mucosal margin.

RESULTS

The position of the MGJ changed significantly from baseline to the first month, by 5.25 ± 2.10 and 4.40 ± 1.41 mm in groups GBR and non-GBR, respectively. Thereafter, the position remained stable in both groups up to 1 year (changes from baseline of 5.46 ± 2.28 and 4.58 ± 1.92 mm, respectively; p = .34). The position of the mucosal margin did not differ between groups GBR and non-GBR (-1.57 ± 2.04 and -1.75 ± 2.08 mm, respectively; p = .84), nor did the width of the keratinized mucosa (1.20 ± 1.03 and 0.99 ± 0.66 mm, p = .91) or its thickness (1.28 ± 0.44 and 1.40 ± 0.78 mm, p = .87).

CONCLUSION

Apically positioned flap combined with a collagen matrix results in a more apical position of the MGJ at sites with or without GBR. Following a coronal shift during the first month after the apical positioning of the flap, the level of the MGJ remained stable.

Barrier membranes: More than the barrier effect?

AIM

To review the knowledge on the mechanisms controlling membrane-host interactions in guided bone regeneration (GBR) and investigate the possible role of GBR membranes as bioactive compartments in addition to their established role as barriers.

MATERIALS AND METHODS

A narrative review was utilized based on in vitro, in vivo and available clinical studies on the cellular and molecular mechanisms underlying GBR and the possible bioactive role of membranes.

RESULTS

Emerging data demonstrate that the membrane contributes bioactively to the regeneration of underlying defects. The cellular and molecular activities in the membrane are intimately linked to the promoted bone regeneration in the underlying defect. Along with the native bioactivity of GBR membranes, incorporating growth factors and cells in membranes or with graft materials may augment the regenerative processes in underlying defects.

CONCLUSION

In parallel with its barrier function, the membrane plays an active role in hosting and modulating the molecular activities of the membrane-associated cells during GBR. The biological events in the membrane are linked to the bone regenerative and remodelling processes in the underlying defect. Furthermore, the bone-promoting environments in the two compartments can likely be boosted by strategies targeting both material aspects of the membrane and host tissue responses.

Effect of membrane exposure on guided bone regeneration: A systematic review and meta-analysis

AIMS

This review aimed at investigating the effect of membrane exposure on guided bone regeneration (GBR) outcomes at peri-implant sites and edentulous ridges.

MATERIAL AND METHODS

Electronic and manual literature searches were conducted by two independent reviewers using four databases, including MEDLINE, EMBASE, Web of Science, and Cochrane Central Register of Controlled Trials, for articles up to February 2017. Articles were included if they were human clinical trials or case series reporting outcomes of GBR procedures with and without membrane exposure. A random-effects meta-analysis was conducted, and the weighted mean difference (WMD) between the two groups and 95% confidence interval (CI) were reported.

RESULTS

Overall, eight articles were included in the quantitative analysis. The WMD of the horizontal bone gain at edentulous ridges was -76.24% (95% CI = -137.52% to -14.97%, p = .01) between sites with membrane exposure and without exposure. In addition, the WMD of the dehiscence reduction at peri-implant sites was -27.27% (95% CI of -45.87% to -8.68%, p = .004). Both analyses showed significantly favorable outcomes at the sites without membrane exposure.

CONCLUSION

Based on the findings of this study, membrane exposure after GBR procedures has a significant detrimental influence on the outcome of bone augmentation. For the edentulous ridges, the sites without membrane exposure achieved 74% more horizontal bone gain than the sites with exposure. For peri-implant dehiscence defects, the sites without membrane exposure had 27% more defect reduction than the sites with exposure.

Expanding soft tissue with Osmed tissue expanders in the goat maxilla

OBJECTIVES

soft tissue limitations are encountered in implant dentistry, due to the loss of alveolar bone. The aim of this study is to compare the outcome of soft tissue preparation using Osmed self-inflating soft tissue expanders with different in situ times in two implantation techniques.

MATERIAL AND METHODS

Osmed self-inflating soft tissue expanders were implanted in goats using a tunnel approach and a flap approach. The animals were sacrificed after 1h (controls) and 40 days (treated). A tattoo technique for stereographic measurements was used to look for soft tissue surface gain. Histological and histomorphometric analyses were performed to quantify and compare the changes in soft tissue volume and bone volume after 1h and 40 days of implantation.

RESULTS

after 40 days, the expansion was visible and none of the goats had shown any inflammation. The space between the soft tissue and the bone was filled by the completely expanded expander and surrounding connective tissue. Between the test groups and the control groups, there was no histological difference in the structure of the soft tissue.

CONCLUSIONS

all the tissue expanders expanded to their maximum size (2.8 times) and were a reliable product for creating a space between soft tissue and bone. The overlying soft tissue remained in excellent shape. There was no difference in the soft tissue volume and the bone volume between the tunnel and the flap approach after 40 days.

Barrier membranes used for ridge augmentation: is there an optimal pore size?

PURPOSE

To identify the optimal pore size of barrier membranes for successful alveolar ridge reconstruction procedures, to determine if cortical perforations have any effect on bone regeneration, and to reiterate that bone graft containment is an important parameter for successful regeneration.

MATERIALS AND METHODS

This was a prospective, randomized, controlled study performed on hound dogs. Corticocancellous tibial bone grafting was performed to the lateral border of the mandible and protected with barrier membranes (meshes). The experiment analyzed three different pore sized meshes, compared with controls without the mesh. Two meshes (macroporous and microporous) were made of titanium, and one was a resorbable mesh. Meshes were preformed into the shape of a cube with one face open. Each side of the cube measured approximately 10 mm. Cubes were open-faced on one side, to facilitate packing of the graft material. The dogs received bilateral ramus grafts. Cortical perforations were created on the left ramus of all the dogs and compared with the right side, which did not have perforations. The dogs were randomly divided into 3 groups and sacrificed at intervals of 1, 2, and 4 months. Before sacrifice, all dogs received 2 doses of tetracycline as a marker for new bone formation. Histomorphometry was performed by using Bioquant image-analysis software. Areas of new bone and soft tissue were measured. The rate of mineral apposition was also calculated. All values obtained via histomorphometry were statistically analyzed with a t test.

RESULTS

Thirty-one experimental sites were evaluated. The amount of new bone growth into the macroporous mesh was significantly higher than in the other groups. The mean area of new bone formation in large and small meshes was 66.26 +/- 13.78 mm(2) and 52.82 +/- 24.75 mm(2), respectively. In the resorbable mesh group, the mean area of new bone formed was 46.76 +/- 21.22 mm(2). The amount of new bone formed in the control group was 29.80 +/- 9.35 mm(2). There was no significant difference in amount of bone formation between left and right sides (P = .3172). Resorbable meshes had significant soft tissue ingrowth (23.47 mm(2)) compared with macroporous mesh (16.96 mm(2)) and microporous mesh (22.29 mm(2)). Controls had the least amount of soft tissue ingrowth (9.41 mm(2)). Mineral apposition rate was found to be higher in the resorbable group (2.41 microm/day), and the rate was lowest (1.09 microm/day) in the large pore mesh group.

CONCLUSION

Macroporous membranes facilitated greater bone regeneration compared with microporous and resorbable membranes. Macroporous mesh also prevented significant soft tissue ingrowth compared with other meshes. Containment of a bone graft is the most critical parameter in successful bone regeneration. Cortical perforations did not have any effect on the quantity of regenerated bone. Further research should be directed toward identifying a critical pore size and manufacturing a reliable mesh that would prevent excessive soft tissue ingrowth in ridge augmentation procedures.

Histologic and Histomorphometric Evaluation of Alveolar Ridge Augmentation Using Bone Grafts and Titanium Micromesh in Humans

BACKGROUND

Recently, the use of titanium micromesh for alveolar bone augmentation has drawn interest; however, only limited histologic data are available on the quality of the bone regenerated. Therefore, this study compared the use of 100% intraoral autogenous bone to a combination of intraoral autogenous bone (70%) and bovine porous bone mineral (BPBM) (30%) for alveolar ridge augmentation with titanium micromesh histologically and histomorphometrically.

METHODS

Twelve partially edentulous patients required alveolar bone augmentation before implant insertion because of ridge resorption. The defect sites, six in the maxilla and six in the mandible, were reconstructed with particulate autologous bone (control group, N = 6) or a mixture of autologous bone and BPBM (test group, N = 6) in combination with titanium micromesh. Core biopsies were taken from the defect sites 8 to 9 months after grafting at the time of implant insertion.

RESULTS

Newly formed compact bone with a well-organized lamellar pattern was identified in all specimens. In the samples taken from the test group, the BPBM particles were surrounded completely by newly formed bone with no signs of resorption. The mean total bone volume was 62.38% +/- 13.02% in the control group and 52.88% +/- 11.47% in the test group. The soft tissue volume was 37.61% +/- 13.02% and 29.96% +/- 12.58%, respectively, and the residual BPBM volume was 17.15% +/- 2.72% in the test group. No statistical difference was observed in the histologic parameters evaluated, irrespective of graft type and site (P >0.05).

CONCLUSION

Within the limits of this study, BPBM (30%) in combination with autogenous bone (70%) did not yield a lower percentage of new bone formed compared to autogenous bone alone in ridge augmentation with titanium micromesh.

Healing of dehiscence-type defects in implants placed together with different barrier membranes: a comparative clinical study

OBJECTIVE

Premature exposure of membranes used in guided bone regeneration (GBR) results in decreased bone formation. The effect of an expanded polytetrafluoroethylene (e-PTFE) and two collagen membrane on bone healing of buccal dehiscence defects around implants in cases with and without premature membrane exposure was clinically evaluated.

METHODS

Three groups were established: Group OS (Ossix, n=73 implants, 41 patients), Group BG (Bio-Gide, n=53 implants, 28 patients) and Group GT (e-PTFE, Gore-Tex, n=34 implants, 17 patients). Defect height and width were measured at the time of implant placement and at second stage surgery. Surface area was calculated as half ellipses. When several implants were placed simultaneously, a mean of their defect width and height was calculated.

RESULTS

Mean percentage reduction of defect area (92.2+/-13.78% Group OS, 94.6+/-6.69% Group BG, and 97.3+/-4.91% Group GT) and height (81.6+/-23.19%, 85.4+/-12.26%, and 93.4+/-9.39% respectively) did not show statistically significant differences between groups. Differences between groups were not statistically significant for all parameters when cases without spontaneous membrane exposure were compared. However, differences were significant when spontaneous membrane exposure occurred. Mean percentage reduction of defect area among cases where membrane exposure occurred was 91.5+/-10.86% Group OS, 71.5+/-8.61% Group BG, and 73.7+/-13.97% Group GT. Mean percentage reduction of defect height among cases with membrane exposure was 76.4+/-18.28%, 53.4+/-9.86%, and 49.4+/-11.05%, respectively.

CONCLUSIONS

Premature exposure of membranes and subsequent and consequent exposure of implants results in impaired bone healing. Certain barrier membranes, as used in group OS, are apparently capable of supporting gingival healing even when prematurely exposed that could be advantageous in GBR procedures.

Guided bone regeneration to repair an osseous defect

The ultimate goal of orthodontic therapy is to establish functional and esthetic dental relationships in a balanced facial pattern. In patients with compromised periodontal support, the use of multidisciplinary treatment plans is essential in attaining these goals. This case report includes a thorough documentation of the orthodontic and periodontal treatments to demonstrate the effectiveness of guided bone regenerative procedures combined with a bone allograft to aid in correcting a dental malocclusion.

Histopathologic reaction of a calcium phosphate cement for alveolar ridge augmentation

The objective of the present study was to evaluate the feasibility of using a calcium phosphate cement (CPC) in the reconstruction of a defective alveolar ridge in conjunction with implant placement. The CPC consisted of an equimolar amount of tetracalcium phosphate and dicalcium phosphate anhydrous. At the beginning of the experiment, all mandibular premolar teeth of mature beagle dogs were extracted. After 1 month of healing, alveolar bone was reduced to make a space for a CPC block that was prefabricated from a CPC mixed with water at a powder/liquid ratio of 5 g/mL. After an additional month, 8-mm long hydroxyapatite-coated titanium implants were placed in such a way that the apical half was embedded into alveolar bone and the coronal half in the preformed CPC block. The dogs were sacrificed and biopsies were obtained at 1, 3, and 6 months after surgery. Sections that included implants were evaluated for integration of the CPC block to the alveolar bone and of the implant to the alveolar bone. Additional sections without the implants served as controls. The results obtained from this study show that the CPC ridge augmentation gradually is replaced by natural bone. Six months after surgery, histopathologic features of the augmentation area were quite similar to those of natural alveolar bone. The coronal half of the implants, previously surrounded by the CPC block, was firmly fixed by natural bone. Therefore, this method may be useful for increasing the height of the alveolar ridge.