Short term bone healing in calcium deficiency osteopenia and disuse osteopenia: experimental studies in adult rats

Adult male Sprague-Dawley rats (average weight 530–540 g) were studied in two different series. In series I, studying disuse osteopenia, the experimental rats had all maxillary molars extracted on one side. After 16 wk they had their mandibular first molar of the corresponding side extracted and were followed for another 4 wk. In series II, studying calcium deficiency osteopenia, the experimental rats were given a low calcium diet for 16 wk and at this time had their mandibular first molars extracted. Both disuse and calcium deficiency caused osteopenia, which did not seem to impair the healing process after tooth extraction in the short term. One puzzling finding in the disuse series (I) was that the alveolar height at the extraction site was higher in the experimental than in the control group 4 wk after extraction.     

miRNA-21在口腔鳞癌患者唾液中的表达及意义

目的:探讨miRNA-21在口腔鳞癌患者唾液上清中的表达及其临床意义。方法:以2012-01—2015-06期间,新余市人民医院口腔科收治的64例口腔鳞癌患者及25例健康对照人群为研究对象,收集唾液标本,采用实时定量聚合酶链反应技术,检测唾液标本中miRNA-21表达情况,并分析其与口腔鳞癌临床病理学特征之间的联系。结果:口腔鳞癌患者唾液上清液中miRNA-21的表达水平(2.75±0.94)显著高于健康对照组(0.78±0.45,P<0.01)。相关性分析结果显示,唾液上清液中miRNA-21表达水平与口腔鳞癌细胞分化程度(P<0.01)及淋巴结转移状态(P<0.05)显著相关。受试者工作特征曲线分析结果显示,唾液上清液中miRNA-21表达水平,评价口腔鳞癌细胞分化程度的敏感性和特异性为89.5%和66.7%。结论:口腔鳞癌患者唾液上清液中miRNA-21的表达上调,可能与口腔鳞癌的发生发展有关,唾液中miRNA-21可作为评价口腔鳞癌细胞分化的辅助指标。     

骨组织工程支架材料充填下颌阻生智牙拔牙窝的临床效果

目的:探讨下颌阻生智牙拔除后,用骨组织工程支架材料充填拔牙窝,修复第二磨牙远中牙槽骨高度的临床效果。方法:13例患者在阻生智牙拔除后,即刻植入组织工程骨微粒(小牛无机松质骨Bio-oss、倍骼生PerioGlasfi)于牙槽窝内,术后定期随访,并从临床和X线影像检查比较术后1、12周时,第二磨牙远中牙龈附着水平和牙槽嵴高度的变化。采用SPSS10.0软件包对数据进行配对样本t检验。结果:所有患者术后未出现并发症,术后12周时,第二磨牙远中牙槽嵴高度显著降低(P<0.05)。结论:下颌阻生智牙拔除术后即刻植入组织工程骨支架材料,有利于保持第二磨牙远中牙槽嵴的高度。     

Effects of lithium on extraction socket healing in rats assessed with micro-computed tomography

Abstract

Objective. Lithium is an activator of β-catenin signaling and β-catenin plays an important role in regulating bone formation and remodeling. The purpose of this study was to investigate the effects of lithium on bone repair in tooth extraction sockets in rats. Material and methods. Twenty male Wistar rats were subjected to maxillary left second molar extraction. The animals received a daily injection of lithium chloride (LiCl) or the same dose of sodium chloride (NaCl) starting 7 days before tooth extraction until sacrifice 14 days after extraction. Rats were randomly divided into: (1) a pre-treated group that received LiCl injection from 7 days before to 3 days after tooth extraction; (2) a post-treated group that received LiCl injection starting 4 days after tooth extraction; (3) a continuously treated group that received LiCl injection for the entire 21 days; and (4) a control group that received NaCl injection only. The volume of new bone and the bone density in the extraction socket were quantified by micro-computed tomography. Results. The percentage of new bone formation in the extraction socket was as follows: 63.2 ± 13.4% (pre-treated group), 53.9 ± 9.8% (post-treated), 23.8 ± 8.0% (continuously treated) and 37.5 ± 4.2% (control). The difference in percentage was statistically significant between each pair of groups. Pre- and post-treated groups also showed a significant increase in the density of new bone. Conclusions. Lithium enhances bone repair in extraction sockets when delivered before or after tooth extraction. Tooth extraction during lithium treatment may impair bone healing.     

Analysis of the pattern of the alveolar ridge remodelling following single tooth extraction

Introduction: Tooth extraction is followed by marked osseous changes of the residual alveolar ridge including severe bone alterations both in height and in width. However, such remodelling could jeopardize the subsequent implant insertion for two main reasons. Firstly, the absence of adequate bone levels makes implant placement impossible; secondly, aesthetic problems in the fabrication of implanto‐supported restoration could be caused by serious bone re‐absorption. Thus, it is of crucial importance that the dental surgeon knows how the alveolar crest changes when a single tooth has been removed. The aim of this study was to evaluate the pattern of alveolar crest remodelling observed in a single intercalated area of tooth extraction after at least a period of 6 months of healing, using standardized photos of model casts. Material and methods: Among the patients who were treated for a single intercalated tooth extraction during the last 2 years at the department of dentistry at Versilia Hospital, Lido di Camaiore (Lucca), Italy, we selected 50 patients. The amount of alveolar crest remodelling was assessed on standardized photos of study models. All measurement were recorded on an Excel sheet (Excel, Windows XP^®) and each value was multiplied by the enlargement index so that true values of re‐absorption could be obtained. Finally, we have calculated the percentage of amount of alveolar crest remodelling and shifting of alveolar crest. Results: We calculated the percentage of buccal remodelling and alveolar crest shift. The buccal re‐absorption was 19.4±9.4% at mesial point, 39.1±10.4% at midpoint and 20.3±10.7% at distal level. Moreover, the shift of the alveolar crest was 59.1±11.2% at mesial point, 64.8±10.5% at the midpoint and 56±12.5% at distal point. Conclusions: This study confirmed that buccal wall tends to re‐absorb after the extraction according to a specific pattern. Thus, the re‐absorption at the midpoint represent the double of bone loss at the distal and the mesial points. Furthermore, we have observed first how the alveolar crest shifts placing along the more lingual/palatal line which divides the original alveolar crest into three parts. To cite this article:
Covani U, Ricci M, Bozzolo G, Mangano F, Zini A, Barone A. Analysis of the pattern of the alveolar ridge remodelling following single tooth extraction.
Clin. Oral Impl. Res. 22 , 2011; 820–825
doi: 10.1111/j.1600‐0501.2010.02060.x     

Synthetic polymeric barrier membrane associated with blood coagulum,human allograft,or bovine bone substitute for ridge preservation: a randomized,controlled, clinical and histological trial

During the normal healing process, an extraction site may lose significant bone volume, making implant placement problematic. Quantitative evaluations of the amount of bone maintained by socket preservation with various materials are limited. The objective of this study was to evaluate, both clinically and histologically, the extent of alveolar bone preservation by blood coagulum (BC) and the potential additional benefits of bone allograft material (AL) versus the state-of-the-art bovine bone mineral (BB), covered by a polyethylene glycol (PEG) barrier, in extraction socket grafting procedures. Adult patients (n = 32) with single-rooted teeth indicated for extraction were treated (45 sites). After atraumatic extraction, the sockets were filled with BC, AL, or BB and covered with a synthetic PEG barrier membrane. Changes in bone height and width were measured clinically and the amount of bone formed and residual graft particles were measured histologically after 6 months. Changes in ridge width at 6 months were ?1.5 mm for AL versus ?2.5 mm for BB and ?2.3 mm for BC. New bone formation amounted to 47.8%, 33.3%, and 28.2% at BC-, AL-, and BB-treated sites, respectively. Using AL with the PEG barrier preserved the ridge width at 6 months better than BB or BC and resulted in similar amounts of bone histologically to BB.     

Delayed immediate implants: alveolar bone chamzes durinrr the healing period

Delaying the placement of immediate fixtures by 6–8 weeks after extraction of the natural dentition allows for the elimination of associated infective processes, the achievement of maximum osteoblastic activity that theoretically could help the osseointegration process and complete wound covering that simplifies the placement of grafts or membranes. This study examines the healing associated with 21 fixtures in 14 patients. The fixtures were placed into sockets 6–8 weeks after tooth extraction without the use of barrier membranes or bone substitutes. Measurements were taken immediately prior to fixture placement and 3–6 months later at the abutment placement. Alveolar bone height, the remaining socket depth and diameter and the depth to which a 3.75 mm fixture could be inserted into the socket were measured. After fixture placement the vertical and horizontal measurements from the cover screw to the surrounding alveolar bone and the distance from the cover screw to the CEJ of the adjacent tooth were recorded. All fixtures were integrated at exposure with 1 failure during the follow-up period. The distance from the cover screw to the buccal plate decreased by a mean of 2.17 mm. There was an increase in the mean vertical bone height at all 4 surfaces. When horizontal defects were present, the mean vertical distance decreased from 2.5±0.37 mm to 0.36±0.64 mm. When horizontal defects were absent, the mean vertical distance decreased from 3.86±0.58 mm to 0.48±0.25 mm. There was also a marked decrease in the horizontal distance between the bone margin and the surface of the fixture from 1.6±l.73 mm 1 to 0.02±0.02 mm. These results indicate a strong tendency for the defects to fill-in in the horizontal plane and for bone growth to occur in the vertical plane to the height of the cover screw. In conclusion the delayed immediate placement of fixtures has a good short-term prognosis with bone regeneration occurring around the defect without the use of barrier membranes or bone substitutes.     

Flapped versus flapless alveolar ridge preservation: a systematic review and meta-analysis

Alveolar ridge preservation (ARP) procedures can limit bone changes following tooth extraction. Flapped and flapless surgical approaches have been used for ARP; however, there is a lack of strong scientific evidence regarding their specific influences on the clinical outcomes of ARP. The aim of this systematic review and meta-analysis was to evaluate the effects of flapped and flapless surgical approaches on the dimensional changes of hard and soft tissues and patient-reported outcomes following ARP. Electronic databases were searched to identify randomized controlled trials (RCTs) that compared flapped ARP by means of a coronally advanced flap to flapless ARP where barrier membranes were left exposed. The risk of bias was assessed using the Cochrane Collaboration Risk of Bias tool. Data were analysed using a statistical software program. A total of 754 studies were identified, of which five studies with 149 extraction sockets in 128 participants were included. Overall, meta-analysis did not show any significant differences in the changes in ridge width or height between flapped and flapless ARP. The use of flapless ARP was associated with significantly less postoperative pain, thicker labial soft tissues, and marginally more favourable changes in width of the keratinized tissues compared to the flapped approach. The short-term hard tissue changes following ARP with a flapped or flapless approach are comparable. Postoperative pain and labial soft tissue changes are more favourable following ARP using a flapless approach. Further evidence from long-term RCTs is still required to substantiate the current findings.     

VDR deficiency affects alveolar bone and cementum apposition in mice

Objective

To compare the mineralisation density (MD), morphology and histology of alveolar bone and cementum amongst VDR +/+, VDR −/−, and VDR −/− groups supplemented with a diet TD 96348, containing 20% lactose, 2.0% calcium and 1.25% phosphorous.

Methods

Four groups of mice (6 mice/group) were identified by genotyping: VDR +/+ mice (VDR wild type), VDR −/− mice (VDR deficient), VDR −/− offsprings derived from VDR −/− parents receiving a supplemental diet (early rescued), and VDR −/− mice fed with a supplemental diet beginning at age one month (late rescued). All mice were sacrificed at age 70.5 days. Micro-CT was used to compare MD and morphology of alveolar bone and cementum. H–E and Toluidine blue staining was used to examine the ultrastructure of the alveolar bone and cementum at matched locations.

Results

In VDR −/− group, alveolar bone and cementum failed to mineralise normally. Early rescue increased MD of alveolar bone in VDR −/− mice with excessive alveolar bone formation, but which not observed in late rescue group. MD and morphology of cementum–dentine complex in both early and late rescue groups were comparable with VDR +/+ group when feeding with high-calcium rescue diet.

Conclusions

VDR affects alveolar bone mineralisation and formation systemically and locally. However, cementum apposition and mineralisation is mainly regulated by calcium concentrations in serum.