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     

利塞膦酸钠对骨质疏松大鼠牙槽骨Bcl-2、BAX表达的影响

目的: 观察利塞膦酸钠对骨质疏松大鼠下颌牙槽骨显微结构、抗凋亡因子Bcl-2、凋亡因子BAX表达以及骨细胞凋亡的影响。方法: 30只6月龄雌性SD大鼠,随机分为3 组（每组10只）,即Sham组（假手术组）、OVX组（接受双侧卵巢切除术）和RIS组（接受双侧卵巢切除术,然后给予利塞膦酸钠）;造模3个月后,取各组大鼠下颌骨进行micro-CT扫描,并通过TUNEL染色以及Bcl-2、BAX免疫组织化学染色检测下颌骨骨细胞的凋亡。采用SPSS 13.0软件包对组间数据进行比较。结果: 与Sham组相比,OVX组牙槽骨丧失和骨细胞凋亡明显增多;RIS组与OVX组相比,骨细胞凋亡显著减少,BV/TV显著增加,Bcl-2 表达增加,Bcl-2/BAX比值增加（P<0.05）。结论: 利塞磷酸钠增加下颌牙槽骨中Bcl-2的表达和Bcl-2/BAX的比值,部分逆转去卵巢骨质疏松大鼠的牙槽骨丧失,减少下颌骨骨细胞凋亡。     

羟基磷灰石人工骨微粒植入牙槽窝的临床应用研究

目的 :研究拔牙后即刻植入羟基磷灰石微粒人工骨预防术后并发症及牙槽骨吸收的临床疗效。方法 :3 1例患者拔牙后牙槽窝内即刻植入羟基磷灰石微粒人工骨 ,术后对患者拔牙创出血、干槽症、牙槽嵴高度等项进行观察并于术后、术后 4周、12周复诊进行临床及X线片检查。结果 :3 1例患者创口愈合良好 ,术后无出血、无干槽症发生 ,X线片见牙槽窝内羟基磷灰石存在 ,牙槽高度恢复良好。结论 :拔牙创内即刻植入羟基磷灰石人工骨不影响创口愈合 ,能很好地维持牙槽嵴高度 ,为人工义齿的修复创造条件     

Effects of a single intravaneous dose of zoledronic acid on bone healing following tooth extraction in ovariectomized rabbits

ObjectiveThe present study is aimed to investigate the effects of administering a single intravenous dose of zoledronic acid (ZA) on bone healing following tooth extraction in ovariectomized rabbits.Materials and methodsFemale, New Zealand rabbits were randomly divided into three groups including Control, ovariectomy + saline (OVX) and ovariectomy + zoledronic acid group (ZOL). Bilateral ovariectomy was performed to the rabbits in OVX and ZOL groups under general anesthesia. Control group underwent sham surgery. Eight weeks later, mandibular right incisors of all animals were extracted under general anesthesia. Before the procedure, Control and OVX groups were given saline and 0.1 mg/kg ZA was administered to ZOL group intravenously. All animals were sacrificed after 12 weeks.ResultsThe findings of histopathological and biochemical evaluations reflected insignificant differences among study groups in vascular endothelial growth factor (VEGF), increases in osteoclasts, ossification, vascularization and mononuclear cell infiltration measures (p > 0.05). In contrast, bone morphogenic protein 2 (BMP-2), tumor necrosis factor alpha (TNF-α) and organization of the extraction wound differed significantly between groups (p < 0.05)ConclusionThe potential beneficial effects of ZA administration on the wound healing process following tooth extraction were demonstrated via serum TNF-α, BMP-2 and VEGF levels in an osteoporotic model in ovariectomized rabbits.     

拔牙后牙槽骨愈合速度及骨密度变化的横向研究

目的：探讨性别差异对拔牙创牙槽骨愈合速度的影响。方法：采用双能Ｘ线吸收法测量不同年龄组的男性、女性拔牙后的牙槽骨骨密度。结果：３５～５４岁之间,男性与女性之间牙槽骨骨密度值无显著差异,而牙槽骨愈合速度有一定差异;５５～６４岁年组男性牙槽骨骨密度值高于女性。结论：年龄、性别对牙槽骨骨密度变化有显著影响,随着年龄的增长,男性牙槽骨愈合速度高于女性。     

Effects of alendronate on bone healing after tooth extraction in rats

Oral Diseases (2010) 16 , 674–685 Objectives: Tooth extraction has been identified as an important risk factor for bisphosphonate‐induced osteonecrosis of the jaw. Therefore, the main goal of this study was to determine the effects of alendronate on healing of the extraction socket and on interdental alveolar bone after tooth extraction in rats. Materials and methods: Animals were injected subcutaneously with vehicle or alendronate for 3–4 weeks before the first mandibular molar was extracted and these treatments were continued during post‐extraction periods of 10, 21, 35 and 70 days. Mandibles were processed to evaluate healing of the extraction socket and adjacent alveolar bone by assessing bone formation, bone resorption and vascularity by histomorphometric techniques. Results: Alendronate decreased new woven bone formation, blood vessel area, perimeter and number in the extraction socket at 10 days postextraction, but not at later time points. Furthermore, alendronate‐treated rats had increased interdental alveolar bone volume and height only at 10 days postextraction. In addition, a 2.5‐fold increase in the percentage of empty osteocyte lacunae was found in alveolar bone of alendronate‐treated rats only at 10 days postextraction. Conclusions: Alendronate transiently decreases bone formation and vascularity in the extraction socket and delays the removal of interdental alveolar bone after tooth extraction in rats.     

Histomorphometric evaluation of the effect of systemic and topical ozone on alveolar bone healing following tooth extraction in rats

The aim of this study was to investigate the effects of systemic and topical ozone applications on alveolar bone healing following tooth extraction. One hundred and twelve male Wistar rats were divided into eight groups of 14 rats each; seven groups were experimental (A–G) and one formed the control group (K). The experimental groups were further divided into two sub-groups, with seven rats in each – sacrificed on days 14 and 28 (subgroups 1 and 2). The maxillary right central incisors were extracted under general anaesthesia following the administration of local anaesthesia. After sacrifice, semi-serial histological sections were prepared, and mineralized and trabecular bone and osteoid and osteoblast surfaces were measured. Measurements of the trabecular bone showed statistically higher values in the groups treated with systemic ozone (D₂: 50.01 ± 2.12; E₂: 49.03 ± 3.03; F₂: 48.76 ± 2.61; G₂: 50.24 ± 3.37) than in the groups that underwent topical ozone administration (A₂: 46.01 ± 3.07; B₂: 46.79 ± 3.09; C₂: 47.07 ± 2.12; P = 0.030 (G₂–A₂, G₂–B₂, G₂–C₂)). Within the limitations of the current study, it may be concluded that postoperative long-term systemic ozone application can accelerate alveolar bone healing following extraction. However, additional studies are required to clarify the effects of the different ozone applications on new bone formation.     

大鼠正畸牙移动过程中转化生长因子β1在牙槽骨中的表达

目的：观察大鼠正畸牙移动过程中转化生长因子β1（TGF－β1）在牙槽骨中的表达变化,探讨TGF－β在正畸牙槽骨改建中的作用。方法：建立大鼠正畸牙移动模型,用免疫组织化学方法检测牙槽骨中TGF－β1的表达。结果：对照组正常牙槽骨组织TGF－β1呈弱阳性表达。实验组压力侧和张力侧牙槽骨组织TGF－β1阳性表达增强。牙齿移动5d组和7d组,压力侧破骨细胞和张力侧成骨细胞TGF－β1均呈阳性表达。结论：TGF－β1作为局部调控因子可能参与了正畸牙槽骨改建过程。     

Effects of ovariectomy on turnover of alveolar bone in the healed extraction socket in rat edentulous mandible

Objective

The number of patients with postmenopausal osteoporosis receiving dental implants because of edentulism is increasing. Since osseointegration around implants requires formation and maintenance of new bone, knowledge of how ovariectomy (OVX) affects turnover of mandibular and maxillary bone is required. In the present study, we investigated the effects of OVX on turnover of alveolar bone in the healed extraction socket of the rat left mandibular incisor.

Methods

The molars and the incisor on left side in 6-month-old Sprague–Dawley female rats (n = 38) were extracted and left to heal for 4 months. Animals were then ovariectomized and killed at the time of OVX (baseline) (n = 4), 6 weeks (n = 10), 6 months (n = 12) and 9 months (n = 12) post-OVX. Changes in bone mass and bone turnover were assessed using static and dynamic histomorphometric parameters.

Results

Bone turnover was increased by ovariectomy (OVX) as reflected by increased static parameters of bone formation and resorption. The changes in dynamic parameters were not statistically significant. Cancellous bone volume/total volume (%) in the post-OVX group decreased more than that in the control group.

Conclusions

Our results suggest that OVX increases the turnover of alveolar bone in the healed extraction socket of rat mandibular incisor, resulting in a decrease of cancellous bone volume with time.     

Short-term use of an exposed polypropylene barrier in the preservation of alveolar bone after extraction: randomized clinical trial

This study was performed to evaluate the short-term preservation of alveolar bone volume with or without a polypropylene barrier and exposure of the area after extractions. Thirty posterior tooth extraction sockets were distributed randomly to a control group (n = 15; extraction and suture) and a barrier group (n = 15; extraction, barrier, and suture). All sutures and barriers were removed 10 days postoperatively. Cone beam computed tomography scans taken with the aid of a tomographic guide were obtained preoperatively, immediately postoperative, and at 120 days postoperative. A visual analysis of the coronal sections of the alveolus was performed, and vertical loss in the mesial, distal, buccal, and lingual bone ridges and horizontal thickness were evaluated. The mean vertical loss after extraction did not differ significantly between the control and barrier groups (Student t-test: mesial P =  0.989, buccal P =  0.997, lingual/palatal P =  0.070, distal P =  0.107). The mean vertical loss at 120 days postoperative did not differ significantly between the control (0.65 mm) and barrier (0.52 mm) groups (P >  0.05), with an effect size of 0.13 mm. At 120 days, the barrier group presented a mean resorption in thickness (0.45 mm) that was significantly lower than that in the control group (0.76 mm) (P =  0.021), with an effect size of 0.31 mm. The polypropylene barrier reduced the horizontal resorption in sockets of posterior teeth after extraction.     

Radiographic study of alveolar bone height related to tooth and root length

In radiographs from 76 randomly selected periodontally healthy subjects, aged 18-22 yr, at the School of Dentistry in Stockholm, the alveolar bone height was evaluated and correlated to the root length as well as to the entire tooth length. The root lengths were also related to the entire tooth lengths. The mean tooth length was found to be 24.9 mm and the mean root length 65.7% of the mean tooth length. The correlation of alveolar bone height to the root length varied between 91.5% and 96.3% and the correlation to the entire tooth length between 54.0 and 65.7%.     

不同去势时间大鼠牙槽骨微结构变化的Micro-CT研究

目的： 观察不同去势时间大鼠牙槽骨微结构的改变,探讨去势时间对牙槽骨骨质疏松程度的影响。方法： 健康未孕雌性SD大鼠24只,随机分为去势组(OVX)与假手术组（sham）,每组各12只,分别在全麻下行双侧卵巢去势术与假手术。于术后3个月及6个月2个不同时间点分别处死每组大鼠各6只,取右侧上颌骨标本行Micro-CT扫描;观察去势3个月及6个月后大鼠上颌第一磨牙根分叉区牙槽骨微结构的改变。采用SPSS16.0软件包对数据进行统计学分析。结果： Micro-CT水平面、矢状面二维图像及三维重建均显示,去势3个月及6个月大鼠牙槽骨骨髓腔面积增加、骨小梁变细、部分发生断裂。骨结构参数分析显示,去势3个月及6个月后,大鼠牙槽骨骨密度（BMD）及骨体积分数（BV/TV）、骨小梁宽度（Tb.Th）均显著低于相应时间假手术大鼠（P<0.05）;去势6个月组较3个月组大鼠牙槽骨骨密度(BMD)、骨体积分数(BV/TV)、骨小梁宽度(Tb.Th)显著降低（P<0.05）。去势3个月及6个月大鼠骨小梁数目（Tb.N）及骨小梁分离度（Tb.Sp）显著高于相应假手术组（P<0.05）,且去势6个月组骨小梁数目(Tb.N)显著高于去势3个月组（P<0.05）。结论： 随着去势时间延长,大鼠牙槽骨骨量降低、骨小梁微结构破坏加剧,骨质疏松程度加重。     

Changes in alveolar bone structure during orthodontic tooth movement in adolescent and adult rats: A microcomputed tomography study

Background

Increasing number of adults are willing to seek orthodontic treatment, but treatment duration for them is commonly longer. Although there have been studies on molecular biological changes during tooth movement, few have focused on microstructural changes in alveolar bone.

Objective

This study aims to compare the microstructural changes in alveolar bone during orthodontic tooth movement in adolescent and adult rats.

Methods

25 6-week-old and 25 8-month-old male Sprague–Dawley (SD) rats were used to build orthodontic tooth-movement models. On Days 0, 1, 3, 7 and 14, the rats were sacrificed. Microcomputed tomography was used to evaluate tooth movement, alveolar crest height loss and microstructural parameters of alveolar bone (bone volume fraction, trabecular thickness, trabecular separation and trabecular number).

Results

Tooth movement in the adult group was slower than in the adolescent group. Alveolar bone crest height in adults was lower than it was in adolescents on Day 0. Under orthodontic force, the alveolar crest in both groups decreased and the degree of decrease are higher at early stage in adolescents. The microstructural parameters indicated that the alveolar bone was originally denser in the adult rats. With orthodontic force, it tended to be looser.

Conclusions

Under orthodontic force, changes in alveolar bone differ between adolescent and adult rats. Tooth movements in adults are slower, and the decrease in alveolar bone density are more severe.