Risk Assessment Before Extraction for Immediate Implant Placement in the Posterior Mandible: A Computerized Tomographic Scan Study

Background: Controversy exists in treatment planning relative to the attempt of saving a tooth with unfavorable prognosis or extracting it and placing an immediate or delayed implant. Preextraction radiographic assessments of teeth are traditionally performed using two‐dimensional periapical and panoramic radiographs. These can reveal bone loss around a tooth, but have limited use in assessing implant risk before tooth extraction. Three‐dimensional radiographs or cone‐beam (CB) or computerized tomographic (CT) scans are often taken after tooth extraction and socket healing to assess the healed ridge as a potential implant site. However, when treatment planning for an immediate implant in the posterior mandible, a CT scan taken before tooth extraction can be of value in assessing the available bone and anatomy of the area. This allows the clinician and patient to consider alternative options, such as treating and maintaining the tooth or using a delayed implant protocol, when the site presents a high risk for immediate implant placement (IIP). The purpose of the present study is to assess the prevalence of sites associated with the mandibular second premolar, mandibular first molar, and mandibular second molar teeth that present high risk for IIP using a preextraction CT scan to assess the available apical bone and the anatomy of the posterior mandible in the area of the anticipated extraction site. Methods: One hundred consecutive CT scans were obtained and screened from the New York University College of Dentistry, Office of Quality Assurance–Approved Implant Dentistry Database. Forty‐one of these CT scans were further assessed because they included the presence of ≥2 of the following tooth types: mandibular second premolars, mandibular first molars, and mandibular second molars. Measurements were obtained on the axial sections of the selected teeth to evaluate the amount of bone available apical to the root apices to determine the frequency of sites where an IIP protocol presented a high risk for inferior alveolar nerve injury or lingual plate perforation. Results: Of the 135 teeth assessed from 41 CT scans, 65% of the mandibular second premolars, 53% of the mandibular first molars, and 73% of mandibular second molars had <6 mm of bone available for IIP, presenting high risk for inferior alveolar nerve injury. Of the sites in which the inferior alveolar canal did not limit available bone for IIP, 7% of the second premolars, 9% of the first molars, and 31% of the second molars presented high risk for lingual plate perforation. Conclusions: Preextraction CT scans may present a useful diagnostic aid to assess the risk of inferior alveolar nerve injury and lingual plate perforation for IIP in the posterior mandible. This information may be used for assessing risk when deciding whether to retain a questionable tooth or replace it with an implant with either an IIP or delayed protocol.     

Decoronation of an ankylosed permanent incisor: alveolar ridge preservation and rehabilitation by an implant supported porcelain crown

Abstract –  Replacement resorption and ankylosis are frequently diagnosed following severe dental trauma. The complications that may develop as a result of ankylosis of a permanent incisor in children and adolescent include: esthetic compromise, orthodontic complications because of: arch irregularity; lack of mesial drift; tilting of adjacent teeth, arch length loss and local arrest of alveolar ridge growth. To avoid such complications, an ankylosed tooth should be removed before the changes become so pronounced that they compromise future prosthetic treatment. The purpose of this article was to present a case of preservation of the alveolar ridge for implant rehabilitation by utilizing decoronation for the treatment of a young permanent central incisor. An implant was inserted, without any bone augmentation procedures, followed by prosthetic porcelain crown rehabilitation. We conclude that treatment of an ankylosed young permanent incisor by decoronation may maintain the alveolar bone ridge width, height and continuity, and facilitate future rehabilitation with minimal, if any, ridge augmentation procedures.     

Horizontal alteration of anterior alveolar ridge after immediate implant placement: A retrospective cone beam computed tomography analysis

PURPOSEThe aim of this study was to evaluate the labio-lingual alterations of the alveolar bone where the implant was placed immediately after tooth extraction.MATERIALS AND METHODSImplants were placed immediately after tooth extraction on anterior alveolar ridges in the maxilla and mandible. The pin-guide system was used to help determine the location and path of implants during the surgical process. The horizontal distance from implants to the outer border of alveolar bone was measured at the rim and middle of the implants in the cone beam computed tomography images. The alteration of alveolar bone was evaluated comparing the horizontal distances measured immediately after surgery and 3 months after surgery.RESULTSThe results show that more resorption occurred towards the labial bone than the lingual bone in the maxilla. A similar amount of labial and lingual bone resorption was observed in the mandible.CONCLUSIONConsidering the horizontal alteration of alveolar bone, labio-lingual positioning of the implant towards the lingual bone in the maxilla and at the center of the alveolar ridge in the mandible is recommended when it is placed immediately after tooth extraction.     

根形骨块onlay移植治疗上颌前牙种植术所需的牙槽骨骨量不足

目的:研究根形骨块移植治疗上颌骨前部骨量不足的效果。方法:通过对7例患者前牙区的26个牙位进行根形植骨术,重建牙槽骨的形态后植入种植体,术后随访时间平均10个月。结果:重建的牙槽骨唇侧丰满,骨面根形逼真,种植体无松动,无脱落,唇侧牙龈无退缩。结论:根形植骨术是治疗上颌多颗前牙缺失伴水平向骨量不足的有效手段。     

前牙骨缺损环状骨移植同期植入种植体近期疗效观察

目的探讨临床应用环状骨移植同期植入种植体修复前牙区骨缺损的效果。方法 7例前牙区严重骨吸收患者,在颏部或者上颌骨取环状骨,将种植体旋入环状骨,再将种植体连同环状骨一起同期植入已制备好的种植窝内。植入共12颗种植体。种植术后半年行上部结构修复。完成修复后随访3～12个月。结果 6例10颗种植体成功完成上部结构修复。1例失败,该患者1颗种植体环状骨少量暴露,磨除少量环状骨后愈合良好,另1颗种植体因环状骨暴露,去除环状骨后螺纹暴露过多而被取出后重新植入种植体。结论应用环状骨作为前牙区骨增量手段,效果肯定,可同期植入种植体。     

Reconstruction of the severely resorbed atrophic edentulous ridge of the maxilla and mandible for implant rehabilitation: report of a case

We describe a case with a severely resorbed atrophic edentulous ridge in both the maxilla and mandible. The maxilla was reconstructed using a sinus-lifting procedure and onlay bone graft. The mandible was reconstructed by anterior osteotomy with an interpositional sandwich iliac bone graft at the symphysis area, subperiosteally with iliac bone chips mixed with hydroxylapatite bilaterally at the posterior atrophic ridge, and vestibuloplasty with a split thickness skin graft (STSG). After full-mouth implant rehabilitation, a 5-year follow-up of this case shows a satisfactory result.     

Multidisciplinary approach to a nonsyndromic oligodontia patient using advanced surgical techniques

Treatment of a woman suffering from oligodontia and multiple diastemata with insufficient alveolar ridges in both the maxilla and mandible is described in this clinical report. The total number of missing teeth was 11 (excluding the wisdom teeth). The treatment strategy consisted of an interdisciplinary team approach of orthodontic, surgical, and prosthodontic phases. Sinus floor augmentation, alveolar ridge augmentation via vertical alveolar distraction, and lateral augmentation with ramus graft procedures were performed after fixed orthodontic treatment and prior to dental implant placement. Oral rehabilitation of the patient was completed with the placement of fixed prostheses in the maxillary and mandibular posterior edentulous areas. Early dental intervention improved the patient's appearance and minimized the onset of emotional and psychosocial problems.     

收集骨修复种植体周围骨缺损的效果评价

目的:测量aspeo12000骨收集器在牙种植术中收集的骨量,观察收集骨的组织学特点、成骨活性及即刻移植修复种植体周围骨缺损的临床效果。方法:分2组进行。第1组,15例健康牙种植患者,应用aspeo12000骨收集器收集18颗ITI种植窝制备时钻出的骨屑,测量收集骨的体积,并用t检验比较不同性别、不同部位之间是否存在差别;每一样本脱钙后常规包埋、HE染色,光镜下观察其形态结构,计算骨组织面积所占的比例。第2组:11例患者,植入16颗种植体时发生12处骨缺损,所有缺损应用收集骨即刻移植或收集骨与Bio-oss混合移植。结果:健康牙种植患者收集骨量在不同性别、不同部位之间无显著差异,制备1个种植体窝平均可获得0.93倍体积的“湿骨”。光镜下收集骨以骨组织为主,其面积约占94.2%。牙种植术后3～6个月,原缺损处局部形态饱满,二期手术时见缺损处已覆盖成熟骨质,移植骨成活良好。结论:应用骨收集器获得的收集骨即刻移植修复种植体周围小的骨缺损,是一种简单实用的方法。     

外科种植支抗在正畸、修复治疗中的应用评价

目的：对使用种植体作为支抗矫正错he畸形,并在此基础上修复牙列缺损的效果进行评价。方法：对Angle Ⅱ类牙he畸形,合并牙列缺损,无法常规使用磨牙或根本无磨牙作为支抗的14例患者．选用种植体植入颌骨．以此作为支抗矫正错he畸形,并存此基础上修复牙列缺损,结果：腭部植入的支抗种植体,种植体支持的后牙未见明显近中移位,前牙内收6～8mm。在颊部颧牙槽嵴处植入的支抗种植体,3例失败。5例成人Angle Ⅱ类Ⅰ、Ⅱ分类错he畸形．同时合并下颌Kennedy Ⅱ类牙列缺失的病例,至8～10个月正畸治疗基本结束,植入的牙种植体未发现移位：正畸效果明显,下前牙内收达约6～8mm、下前牙排齐、中线纠正,下前牙间隙关闭。再利用原牙种植体,重新制作种植修复体,修复缺牙,恢复牙列的完整性。结论：在缺乏支抗的正畸、修复病例的治疗中,使用种植体支抗是有效、可行的方法。     

自体颏部块状骨移植二期种植修复上颌前牙区骨量不足的临床研究

目的：探讨以颏部块状骨移植修复上颌前牙区骨量不足,二期行ITI种植术修复该区缺失牙的临床效果。方法：2009年7月~2012年5月间完成的上前牙区颏部块状骨移植后种植修复病例21例,平均年龄27.7岁（18～42岁）。单牙缺失14例,多牙缺失7例,共28枚种植体。结果：移植骨块愈合期平均6.3个月（4.5～10.0个月）,种植体骨结合期平均5.2个月（3.5～9.0个月）。1例术后创口开裂,经局部处理后为粘膜重新覆盖;3例术后出现下唇麻木、其中1例同时伴下前牙感觉异常,经治疗后3例下唇麻木症状消失,下前牙感觉异常症状改善。21例均完成最终修复,平均随访17.3个月（12～30个月）。植入的28枚种植体成功率达100％。结论：通过自体颏部块状骨移植改善上颌前牙区骨量不足,种植治疗能取得比较理想的效果。     

Age‐related new bone formation following the use of cancellous bone‐block allografts for reconstruction of atrophic alveolar ridges

Background

An age‐related decrease in the number of osteogenic progenitor cells may compromise bone augmentation.

Purpose

Histomorphometrical assessment of age‐related new bone formation, following atrophic alveolar ridge reconstruction, using cancellous bone‐block allografts.

Material and methods

Ninety‐three consecutive patients (58 females and 35 males) were referred for implant‐supported restoration of 122 severe atrophic alveolar ridges. Alveolar ridge deficiency locations were classified as anterior maxilla (n = 58), posterior maxilla (n= 32), and posterior mandible (n = 32). A bony deficiency of at least 3 mm horizontally and up to 3 mm vertically according to computerized tomography (CT) in the posterior mandible and anterior maxilla, served as inclusion criteria. In the posterior maxilla, a residual alveolar ridge up to 4 mm vertically according to CT served as inclusion criteria. Augmentation was performed by the use of cancellous bone‐block allografts. Bone biopsies (9‐month posterior maxilla, 4 months anterior maxilla and posterior mandible) of young (≤40 years) versus older (>40 years) patients were histomorphometrically evaluated.

Results

In the posterior maxilla, no statistically significant histomorphometric differences were noted. While at the anterior maxilla and posterior mandible, statistically significant more newly formed bone was found in young versus older individuals, respectively (38.6% vs 19.8%, P = 0.04 and 69% vs 31%, P = .05).

Conclusion

New bone formation following residual alveolar ridge bone grafting is age‐related. Longer bone consolidation and healing time may be recommended for older individuals.     

Augmentation in two stages of atrophic alveolar bone prior to dental rehabilitation: a case report

AIM: The aim of this report is to describe a significantly deficient case of alveolar bone that was managed by alveolar bone augmentation using a technique of distraction osteogensis and onlay bone grafting prior to dental implant placement. BACKGROUND: Injury to the teeth and alveolar ridge of the maxillary anterior region can cause a severe alveolar ridge deficiency resulting in ridge atrophy and maxillary retrognathism. The loss of these teeth and alveolar bone together with fibrotic scar formation can result in adverse changes of the interarch space, occlusal plane, arch relationship, and arch form which complicates rehabilitation and can compromise the esthetic outcome. While implant dentistry has become a new paradigm in oral reconstruction and replacement of missing teeth, ideal implant positioning can be compromised by inadequate alveolar bone in terms of bone height, width, and quality of the bone itself. Correction of osseous deficiencies with ridge augmentation allows ideal implant placement and creates a more natural soft tissue profile which influences crown anatomy and esthetics. REPORT: A 20-year-old female presented with a complaint of poor esthetics resulting from oral injuries incurred in a traffic accident six years previously. In addition to a mandibular parasymphyseal fracture, five maxillary anterior teeth and the most of the alveolar ridge were lost. Clinical examination revealed severe loss of bone in the maxillary anterior region, an absence of a labial sulcus, loss of upper lip support, and a slight over eruption of the mandibular anterior teeth. In preparation for dental implants a distraction osteogenesis surgical procedure was done to lengthen the height of the alveolar ridge. After a three-month healing period, the width of the residual ridge was found to be insufficient for implant placement. To correct this deficiency, a bone graft of a cortiocancellous block was harvested from the chin and fixed to the labial aspect of the ridge. To facilitate revascularization, small perforations were made in the cortical bone of the alveolar ridge at the recipient site before cancellous bone retrieved from the donor site was gently placed between the bone block and the ridge. The patient was then appropriately medicated and healing was uneventful. After three months, the width of the residual ridge was assessed to be adequate for endosseous implants. SUMMARY: The clinical result reported here has shown several procedures may be necessary for the rehabilitation of a trauma patient. Distraction osteogenesis per se may not always satisfactorily improve the anatomical alveolar anatomy but it has advantages over other methods of augmentation. It can improve the height and also expand the soft tissue for further bone grafting. Augmentation of the alveolar bone with an onlay bone graft often provides the desired gain of bone, allows for the ideal placement of dental implants, and improves any discrepancy between the upper and lower arches.     

Segmental osteotomy to reposition multiple osseointegrated dental implants in the anterior maxilla in a trauma patient

Abstract –  A 16-year-old young man had severe loss of alveolar bone and lost four teeth in the anterior maxilla because of traumatic injury in a traffic accident. To overcome the surgically compromised condition for implant rehabilitation, the deficient ridge was augmented by autogenous bone graft from the mandibular symphysis. The augmented ridge had much improvement in width but less in vertical height. Four implants were placed to gain initial osseointegration. Segmental osteotomy was performed to occlusally reposition the implants and bone for 5-mm in the anterior maxilla. After 2 years of clinical follow-up, the rehabilitation outcome is satisfactory and stable.     

Prevalence and distribution of bone defects in moderate and advanced adult periodontitis

Abstract . The purpose of the present investigation was to evaluate the prevalence and distribution of different forms of bone defects using direct observation during periodontal surgery. 286 patients with moderate or advanced adult periodontitis diagnosed during clinical and radiographic examination provided a sample of 5476 teeth. After full thickness mucoperiosteal flaps were raised, osseous defects were explored and classified according to their morphology as interdental craters, hemisepta and infrabony defects with 1, 2, 3 or 4 osseous walls. 981 defects were detected; 533 were in the maxilla and 448 in the mandible (15.4% and 22.4%, respectively, of the teeth examined). The posterior mandibular segment had the highest % of teeth with defects (33.8%) followed by the posterior maxillary segment (19.9%). The proportions of teeth with defects in the anterior segments of both arches were similar. The comparison between maxilla and mandible showed a highly significant difference for the posterior segments ( p =0.00001) but no difference for the anterior segments ( p =0.88). The distribution of defects differed between the maxilla and the mandible, both for the posterior and anterior segments. Craters accounted for almost half the defects, being more prevalent in posterior segments, while hemisepta formed the lowest proportion. Anatomical variations in shape and the original morphology of the alveolar bone between the maxilla and the mandible and the anterior and posterior regions might have been the reason for the differences observed.     

Implant zones of the jaws: implant location and related success rate

The article demonstrates the factors of importance in the early and late failures of dental implants based on literature review. An implant location is one of many factors that can influence a success or failure of dental implants. The author identifies and describe four alveolar jaw regions--functional implant zones--with unique characteristics of anatomy, blood supply, pattern of bone resorption, bone quality and quantity, need for bone grafting and other supplemental surgical procedures, and a location-related implant success rate. The article discusses predisposing factors that can lead to early implant failures in different jaw zones. An implant location is investigated as one of these factors. A prior history of trauma to premaxillary region is described in the context of implant success in anterior maxilla. This zone is being referred by the author as the "traumatic zone." The challenges of mandibular posterior implant reconstruction are presented in the context of blood supply to the mandible. A deficiency of vascularization in this region, especially in elderly and edentulous patients, lead the author to refer to this zone as the "ischemic zone." The concept of relative ischemia of the posterior mandible that can develop with age and tooth loss is discussed. A thorough understanding of specifics of each functional implant zone should help to improve successes and prevent failures of dental implants.     

Augmentation of the narrow traumatized anterior alveolar ridge to facilitate dental implant placement

Abstract  – Traumatic tooth loss leads to alveolar resorption especially in sagittal direction. This can be due to avulsion of bone substance during the accident itself or due to resorption of the alveolar crest that takes place afterwards. Shortage of bone can prevent proper positioning of dental implants unless the volume of bone is increased before implantation. In the maxillary anterior area, this is also an esthetic problem. Several treatment modalities have been presented to augment the bone. This report reviews the latest literature on bone grafting, bone substitutes, guided bone regeneration, osteocompression and distraction which are potentially useful in the anterior maxilla. A special emphasis is paid to the versatility of using a crestal split osteotomy, by means of chisels and osteotomes to widen the narrow ridge. Three examples are illustrated showing onlay grafting, preservation of alveolar width with alloplastic coral material and lateral widening of a narrow maxillary alveolar ridge, using the crestal splitting technique.     

Variations in bone density at dental implant sites in different regions of the jawbone

Summary The survival rate of dental implants is markedly influenced by the quality of the bone into which they are placed. The purpose of this study was to determine the trabecular bone density at potential dental implant sites in different regions of the Chinese jawbone using computed tomography (CT) images. One hundred and fifty‐four potential implant sites (15 in the anterior mandible, 47 in the anterior maxilla, 55 in the posterior mandible, and 37 in the posterior maxilla) were selected from the jawbones of 62 humans. The data were subjected to statistical analysis to determine any correlation between bone density (in Hounsfield units, HU) and jawbone region using the Kruskal–Wallis test. The bone densities in the four regions decreased in the following order: anterior mandible (530 ± 161 HU, mean ± s.d.) ? anterior maxilla (516 ± 132 HU) > posterior mandible (359 ± 150 HU) ? posterior maxilla (332 ± 136 HU). The CT data demonstrate that trabecular bone density varies markedly with potential implant site in the anterior and posterior regions of the maxilla and mandible. These findings may provide the clinician with guidelines for dental implant surgical procedures (i.e., to determine whether a one‐stage or a two‐stage protocol is required).     

Full mouth implant rehabilitation of a patient with ectodermal dysplasia after orthognathic surgery, sinus and ridge augmentation: a clinical report

An 18-year-old male presented severe hypodontia due to hypohidrotic ectodermal dysplasia was treated with Le Fort I maxillary osteotomy with simultaneous sinus floor augmentation using the mixture of cortical autogenous bone graft harvested from iliac crest and organic Bio-Oss to position the maxilla in a right occlusal plane with respect to the mandible, and to construct adequate bone volume at posterior maxilla allowing proper implant placement. Due to the poor bone quality at other sites, ridge augmentation with onlay graft was done to construct adequate bone volume allowing proper implant placement, using tissue harvested from the iliac bone. Seven implants were placed in the maxilla and 7 implants were inserted in the mandible and screw-retained metal ceramic FPDs were fabricated. The two year follow up data showed that dental implants should be considered as a good treatment modality for patients with ectodermal dysplasia.     

Rapid orthodontic treatment after the ridge-splitting technique--a combined surgical-orthodontic approach for implant site development: case report

This article presents a clinical case of bilateral partial edentulism in the posterior mandible with severe horizontal and moderate vertical bone atrophy. A new technique using rapid orthodontics after ridge splitting is presented. The split-crest technique was carried out using piezosurgical instruments in the first molar and second premolar areas to widen the bone crest and open a channel for tooth movement. Immediately after, orthodontic appliances were used to move the first premolars distally and the second molars mesially into the surgical site. The rationale was to facilitate and accelerate orthodontic movement of the teeth, which is otherwise difficult in a cortical knife-edged ridge. The bone defect was filled with the alveolar bone of the adjacent teeth that were moved into the surgically opened path. Adequate bone volume for implant placement was generated in the first premolar area. Implants were then inserted, and the patient was rehabilitated.     

种植区牙槽骨密度的螺旋CT测量研究

目的：探讨螺旋CT对种植区牙槽骨密度测量的意义。方法：通过对30例上下颌种植区牙槽骨的螺旋CT扫描,在计算机工作站上三维重建、模拟种植,分别测量模拟种植体颈部、中部和根尖部牙槽骨的HU（hounsfield Unites）值,同时测量模拟种植体周围起支持作用的环状区域牙槽骨的HU值,并根据Lekholm和Zarb的分类法确定相对应区域的牙槽骨骨密度分类。结果：所有模拟种植体周围环状区域牙槽骨的平均骨密度为789±235HU,高于模拟种植体区牙槽骨的平均骨密度695±216HU（P〈0.01）,其中,下前牙环状区域牙槽骨平均骨密度最大,为1004±150HU,下颌后牙区为874±241HU,上颌前牙区为821±207HU,上颌后牙区为503±193HU。结论：螺旋CT扫描三维重建,测量模拟种植体周围起支持作用的环状区域牙槽骨密度,对种植前的评估和设计有着重要的指导意义。