The influence of cortical perforations and of space filling with peripheral blood on the kinetics of guided bone generation. A comparative histometric study in the rat

The aim of the present study was to evaluate the influence of cortical perforations and of peripheral blood addition in guided bone generation beyond the skeletal envelope in rats. A total of 30 isogenic adult rats were divided into 3 equal groups. In each rat, two hollow parallelipipedic titanium chambers were placed bilaterally on the calvaria after a periosteal skin flap was raised. While on the right sides (controls) the osseous surface was left intact and the chambers were empty, the cortical bone under the left-side chambers (test sites) was perforated with nine 0.8 mm-diameter holes (group I), or left intact but with the chambers filled with a clot of peripheral blood (group II). In group III, both procedures were combined in the test sites. The healing was assessed at 4, 8 and 16 weeks after surgery by histologic and computer-assisted histometric analysis. The results demonstrated a substantial augmentation of on average 141% (SD 18) of the skull's thickness after 16 weeks in the controls, indicating that a predictable bone formation can be achieved beneath completely occlusive barriers over a non-injured cortical layer. In all test groups, a significantly larger bone augmentation was observed after 16 weeks compared to the control sites 172.8% (SD 41.7) in group I (P < 0.05), 172.0% (SD 18.4) in group II (P < 0.05) and 221.5% (SD 42.3) in group III (P < 0.001), demonstrating that stimulating blood supply and bone forming cells access by cortical perforations and/or blood clot addition enhances de novo bone formation in this experimental model.     

Ten-year results of a prospective study using porous-surfaced dental implants and a mandibular overdenture

Background: Numerous investigators have used osseointegrated dental implants as retention for mandibular overdentures, but few have reported 10‐year outcomes or incorporated carefully standardized radiographs to document crestai bone loss. Purpose: The purpose of this study was to use a prospective clinical trial design to assess the performance of short sintered porous‐surfaced dental implants with a mandibular complete overdenture when all patients in the trial had undergone 10 years of continuous function. Materials and Methods: Fifty‐two fully edentulous patients, most with advanced alveolar ridge resorption, each received three free‐standing Endopore implants (7–10 mm in length, mean length, 8.7 mm; Innova Corporation, Toronto, ON, Canada) in the mandibular symphysis region. After 10 weeks of submerged healing, these implants were used to support an overdenture. Carefully standardized radiographs, using a customized stainless steel filmholder attached to each implant and the x‐ray tube, were collected at baseline, 3 months, 6 months, yearly to 5 years, and then again at 7 and 10 years. Results: Life table analysis revealed a 10‐year implant survival of 92.7% and a mean annual bone loss after year 1 of 0.03 mm. Conclusion: Short free‐standing dental implants with a sintered porous surface used for implant fixation are a predictable and effective means of retaining a mandibular overdenture in patients with advanced mandibular ridge resorption.     

Impact of cortical perforations of contiguous donor bone in a guided bone augmentation procedure: an experimental study in the rabbit skull

Background: It has been shown that bone can be augmented beyond the original skeletal envelope by using space‐making barriers. Further, it has been suggested that perforation of the contiguous donor bone enhances bone formation in guided bone augmentation procedures. Purpose: The goal of the present investigation was to evaluate whether perforations into the donor bone marrow through the cortical plate, located contiguous to an extracalvarial experimental space, influence bone generation into this space with regard to augmented bone tissue volume and bone density 3 months postoperatively. Materials and Methods: Two titanium cylinders, each with a titanium lid, were subcutaneously placed with their open ends facing the parietal bones of eight rabbits and secured with miniscrews. The cortical bone plate on the test side was perforated with seven evenly distributed holes, each with a diameter of 1.2 mm, using carbon‐steel burs. Together, these perforations corresponded to about one‐third of the total experimental bone area. The bone on the control side was left intact, and no bleeding occurred during the placement of the titanium lid. The perforation procedure (test side) resulted in various degrees of blood fill. After 3 months, the animals were sacrificed to obtain ground sections for histology and histomorphometry. Results: The cylinders were found to be partly filled with tissue containing slender bone trabeculae and marrow spaces in abundance. The bone consistently reached a higher level at the inner wall compared with the central part of the cylinders (p=.001). Hollow connections between the experimental space and the skull bone marrow were found in the contiguous outer cortical plate in four of the seven control sites. No statistically significant differences could be demonstrated between the perforated test sites and the control sites regarding augmented tissue volume (64.4 ± 18.9% vs. 64.9 ± 22.2%) or bone density, although there was a tendency toward denser bone in the test sites (21.5 ± 11.1%) versus control sites (14.7 ± 5.4%). There was no statistical difference regarding relative bone‐to‐titanium wall contact (27.4 ± 14.7% for test; 38.6 ± 25.9% for control). Thickness (height) and density of the skull bone vault were measured in the area beneath and lateral to the cylinders. No significant differences could be observed regarding these parameters between the test and control side. There were no correlations between thickness (height) or density of donor bone versus amount or density of augmented bone. The degree of immediate blood fill could not be shown to correlate with augmented tissue volume or augmented bone density. Conclusions: In the present model, as observed 3 months postoperatively, cortical perforations of contiguous donor bone or degree of immediate blood fill of an extracalvarial experimental space were not found to enhance augmented tissue volume beyond the skeletal envelope. Although there was a much higher mean value for bone density of augmented bone in the test sites, the large variations failed to show significant intergroup differences.     

作为GBR屏障膜的新型胶原膜的体内植入效果分析

［摘要］ 目的 探讨Ⅰ型胶原和矿化Ⅰ型胶原合成的胶原膜作为GBR屏障膜在动物体内植入后,诱导早期膜下成骨的能力。方法 实验于2013年10月—2014年3月在沈阳军区总医院动物实验中心完成。选取小型巴马猪双侧下颌骨,分别于下颌骨骨体处用牙科裂钻制备8 mm×8 mm全层骨缺损3个,分别应用实验胶原膜覆盖、Bio-gide@覆盖、无覆盖膜骨缺损区。术后1个月处死动物,在处死前1、2周分别肌肉注射四环素溶液与二甲酚橙溶液。固定样本后,制备硬组织切片。分别在荧光显微镜及光学显微镜下（甲苯胺蓝、亚甲基蓝-酸性品红染色）观测膜的降解程度及膜下新骨生成能力,评价材料膜下骨形成量和骨成熟程度。结果 实验组胶原膜具备良好的屏障作用,膜下新生骨矿化程度良好;骨小梁排列整齐,但新生骨量少于Bio-gide@覆盖组;无覆盖膜骨缺损区新生骨组织骨小梁排列混乱,新生骨量少。 结论 新型胶原膜在1个月时体内无明显降解,具备良好的膜下成骨能力,下一步需进行实验组胶原膜的改性,以增加胶原膜膜下成骨量。     

A randomized clinical trial comparing two mandibular implant overdenture designs: 3-year prosthetic outcomes using a six-field protocol

PURPOSE: This clinical trial tested the null hypothesis that there would be no difference in prosthetic maintenance for two-implant mandibular overdentures retained by either a bar-clip mechanism or ball attachments. Prosthetic outcomes are reported over 3 years using a six-field protocol. MATERIALS AND METHODS: One hundred edentulous participants received new maxillary complete dentures and a mandibular two-implant overdenture (IOD), with random assignment to either a bar and metal clip or two ball attachments (titanium alloy matrix and spring) for retention. Eighty-seven subjects were available for follow-up after 3 years. RESULTS: Almost three times as many bar-clip dentures (63%) were rated successful compared to the ball attachment design. Two percent of the participants in each group died over the course of the study, while 15% of the bar-clip and 8% of the ball IOD subjects were lost to follow-up. More than three times as many ball attachment IODs (60%) required retreatment in the form of excessive repairs, and twice as many of the ball attachment design (8%) required replacement. The ball attachment IOD was significantly more likely to require patrix tightening or matrix replacement, while the bar-clip design was more likely to require activation of the matrix. CONCLUSION: Using the criteria of a six-field protocol for implant overdenture outcomes, the bar-clip IOD was a significantly more successful prosthesis, requiring less maintenance than the titanium alloy matrix and spring ball attachment IOD employed in this study. The null hypothesis was therefore defeated.     

Guided bone regeneration in dental implant treatment using a bioabsorbable membrane

The aim of this study was to evaluate an osteopromotive technique, using a bioabsorbable membrane, for its ability to restitute bone over buccal fenes-tration and dehiscence defects following fixture installation. 11 patients requiring dental implant treatment and exhibiting sufficient vertical height of the maxilla and compromised bucco-palatal dimensions, as determined clinically and radiographically, were included in the study. 17 Brånemark® titanium fixtures were placed with buccal defects which were augmented by a bioabsorbable membrane, Resolut®. No complications were observed post-operatively. At 6-8 months, abutment connection was performed, and clinical evaluation of the healed defect area was made. The number of exposed buccal threads at fixture installation (median 8; range 2-19), and abutment connection (median 0; range 0-5), respectively, was compared. Out of the 17 fixtures; 14 exhibited complete coverage with bone, whereas 3 showed some remaining threads. A small punch biopsy taken at abutment connection in an area where the membrane had been placed showed a combination of dense connective tissue and bone. Radiographic evaluation of the marginal periimplant bone level is in progress and results to date show a median bone loss of 1.2 mm after a loading period of 4-6 months. Results show that fixture dehiscence and fenestrations, augmented with this bioabsorbable membrane, demonstrate a highly significant amount of new bone formation.     

Recruitment and enrollment in a randomized clinical trial of mandibular two-implant overdenture

PURPOSE

The purpose of this study was to evaluate the effectiveness of a promotion campaign for subject recruitment and selection, and reasons of withdrawal from a prospective clinical trial of mandibular two-implant supported overdenture.

MATERIALS AND METHODS

The subjects of this study were participants in a randomized controlled clinical trial for investigating prognosis of implants and overdentures with attachments. Recruited subjects were classified by gender, age, and participation motives. Withdrawal rate of the participants before and after enrollment were evaluated.

RESULTS

177 patients were recruited and 51 patients were enrolled for the trial. Among them, 40 participants eventually took part in the trial. 116 subjects (65.5%) were recruited by advertisement and 61 (34.5%) were referred by patients of the hospital or local clinics. Regarding recruitment effectiveness, newspaper recruited the largest number of participants. With respect to referral patients, the proportion of our hospital patients was higher (37/61). Subjects in their 70s comprised the largest proportion (22/51). The male to female ratio was similar (25:26). Final withdrawal rate of all subjects were 74.0%. Among the reasons for withdrawal from enrollment (n=126) presence of remaining teeth and lack of motivation were the most common reasons.

CONCLUSION

To facilitate recruitment of clinical trial subjects and improve enrollment rate, it is important to obtain a sufficient number of researchers, perform promotion activity with diverse strategies, cooperate with local dentists, increase the research funding, and alleviate subjects'' fear against clinical trials by thorough consultation.     

Marginal bone loss adjacent to conventional and immediate loaded two implants supporting a ball-retained mandibular overdenture: a 3-year randomized clinical trial

Objectives: The aim of this study was to evaluate and compare marginal bone loss and clinical outcomes of conventionally and immediately loaded two implants supporting a ball‐retained mandibular overdenture. Materials and methods: Thirty six completely edentulous patients (22 males and 14 females) were randomly assigned into two groups. Each patient received two implants in the canine area of the mandible after a minimal flap reflection. Implants were loaded by mandibular overdentures either 3 months (conventional loading group) or the same day (immediate loading group) after implant placement. Ball attachments were used to retain all overdentures to the implants. Vertical and horizontal alveolar bone losses were evaluated in both groups 1 and 3 years after implant placement using multislice computed tomography, which allow evaluation of peri‐implant buccal and lingual alveolar bone. Plaque scores, gingival scores, probing depths and periotest values (PTVs) were evaluated at 4 months (baseline), 1 and 3 years after implant placement. Clinical and radiographic evaluations were performed at distal, labial, mesial and lingual peri‐implant sites. Results: After 3 years of follow‐up period, the immediate loading group recorded significant vertical bone loss at distal and labial sites than the conventional loading group and no significant differences in horizontal bone loss between groups were observed. Probing depth at distal and labial sites in the immediate loading group were higher than the conventional loading group, while plaque scores, gingival scores and PTVs showed no significant differences between the two groups. A low level of positive correlation between plaque scores, gingival scores, probing depths and vertical bone loss was noted. Conclusion: Immediately loaded two implants supporting a ball‐retained mandibular overdenture are associated with more marginal bone resorption and increased probing depths when compared with conventionally loaded implants after 3 years. The bone resorption and probing depths at distal and labial sites are significantly higher than those at mesial and lingual sites. Clinical outcomes do not differ significantly between loading protocols. To cite this article :
Elsyad MA, Al‐Mahdy YF, Fouad MM. Marginal bone loss adjacent to conventional and immediate loaded two implants supporting a ball‐retained mandibular overdenture: a 3‐year randomized clinical trial.
Clin. Oral Impl. Res. 23 , 23, 2012 496‐503.
doi: 10.1111/j.1600‐0501.2011.02173.x     

Bio-oss应用于种植牙唇侧骨缺损的锥形束CT研究

目的：???应用锥形束CT（CBCT）研究Bio-oss用于唇侧骨缺损种植牙的骨组织改建效果。方法???选择上前牙单颗牙唇侧骨缺损种植牙患者12例,种植体植入的同期应用Bio-oss骨粉行引导骨组织再生技术,保证唇侧具有2?mm以上骨厚度,术后6、12、24个月行CBCT检查,评价唇侧骨组织的厚度以及骨改建的情况。结果??术后6个月时, Bio-oss骨颗粒存在,与自体骨组织界限清晰,人工骨组织外形不规则;术后12个月时,人工骨颗粒与周边自体骨组织无明显分界,但整体呈高密度影像,无明显骨密质-骨松质界限,唇侧人工骨厚度降低35.12%;24个月时,人工骨与自体骨分界不清,形成明显的骨密质-骨松质界限,唇侧人工骨厚度降低36.73%。结论??Bio-oss人工骨在种植牙应用时骨组织量的改变主要发生在12个月内,唇侧人工骨厚度降低35.12%,24个月时可形成正常的骨密质-骨松质界限。     

Blood‐filled spaces with and without filler materials in guided bone regeneration. A comparative experimental study in the rabbit using bioresorbable membranes.

The aim of the present study was to evaluate the effect of natural deproteinized bone mineral on the temporal and spatial pattern of bone formation in a guided bone regeneration model system while using a bioresorbable membrane device. A periosteal skin flap was raised uncovering the calvaria of 20 rabbits. A stiff hemispherical dome made of polylactic acid was placed onto the roughened calvaria and anchored by screws. Prior to placement, the dome was either filled with peripheral blood (control group, 8 rabbits) or with blood and OsteoGraf/N‐300 (test group, 12 rabbits). At 1 month, histologic sections revealed bone regeneration in both test and control domes to various degrees. In the test domes, bone height reached 78%(67–83) and bone volume was 11%(&17), while in the control domes, bone height was 45%(1467) and bone volume 6%(1‐I 1). At 2 months, bone height was unchanged in the test group at 70%(67–83) and bone volume had only slightly increased to 16%(1 l‐2 1). In the controls, height increased to 86%(60–100) and volume to 20%(9–27). Thus, in this model system, natural bone mineral fill contributed to accelerate initial bone neogenesis, while it did not contribute to increasing bone volume or bone height at later observation stages.     

Calvarial graft resorption index in the reconstruction of the maxillary sinus in patients with atrophic maxillas: a prospective clinical study

The objective of this study was to assess the resorption index of particulate calvarial grafts in maxillary sinuses of patients undergoing total reconstruction of an atrophic maxilla with residual alveolar bone that was less than, or equal to, 3 mm thick. Twenty-one maxillary sinus floor elevations were carried out using particulate calvarial grafts in 11 individuals with totally edentulous maxillas. All patients had computed tomography (CT) before (T0), and 48 hours (T1) and six months after surgery (T2). For each CT scan, linear measurements were taken of sections of the anterior, medial, and posterior regions of the maxillary sinus. There was a significant increase in the height of the maxillary sinus floor when T0 was compared with T1 (p = 0.001). There was a statistically significant reduction in all maxillary sinus measurements when T1 was compared with T2; the mean height reduction being 2.36 mm (16.87%) in the anterior region, 3.53 mm (22.47%) in the medial region, and 2.21 mm (22.78%) in the posterior region (p = 0.001). Mean resorption was 20.7%. Autogenous calvarial bone used alone is an option for graft material in pneumatised maxillary sinuses and in cases where there is limited alveolar bone.     

Effect of bovine bone and collagen membranes on healing of mandibular bone blocks: a prospective randomized controlled study

Aim: The aim of the present study was to evaluate if the use of deprotenized bovine bone mineral (DBBM) and collagen barrier membranes (CM) in combination with mandibular bone block grafts could reduce bone block graft resorption during healing. Methods: A prospective randomized controlled study has been designed. Twenty‐two ridges presenting horizontal alveolar deficiency (crest width <4 mm) and at least two adjacent missing teeth were included in the study. In the control group, one or multiple mandibular blocks were used to gain horizontal augmentation of the ridge. In the test group, DBBM granules were added at the periphery and over the graft. The reconstructions were covered by two layers of CM. Implants were placed 4 months after grafting. Direct measurements of crest width were performed before and immediately after bone augmentation, and immediately before implant placement. Results: Statistical analysis showed no significant differences in crest width between test and control groups at baseline and immediately after grafting. Mean augmentation at first surgery in the test group was 4.18 vs. 4.57 mm in the control group. Final gain obtained at the time of implant placement was 3.93 mm in the test and 3.67 mm in the control groups. The difference in mean graft resorption between test and control sites was statistically significant (0.25 mm in the test group vs. 0.89 mm in the control group, P=0.03). Complications seem to occur more often in the test group (complications recorded in three cases in the test group vs. one complication recorded in the control group). In all cases, implants could be placed in the planned sites and a total of 55 implants were placed (28 in the test group and 27 in the control group). All implants could be considered successfully integrated at the 24‐month follow‐up visit. Conclusion: The results from this study showed that the addition of bovine bone mineral and a CM around and over a mandibular bone block graft could minimize graft resorption during healing. On the other hand, the use of bone substitutes and barrier membranes in combination with block grafts increased the frequency of complications and the difficulty of their management. To cite this article:
Cordaro L, Torsello F, Morcavallo S, Mirisola di Torresanto V. Effect of bovine bone and collagen membranes on healing of mandibular bone blocks: a prospective randomized controlled study.
Clin. Oral Impl. Res. 22 , 2011; 1145–1150.
doi: 10.1111/j.1600‐0501.2010.02093.x