Risk assessment of inferior alveolar nerve injury for immediate implant placement in the posterior mandible: A virtual implant placement study

Objectives

To investigate the prevalence and morphological parameters of lingual concavity, and whether these factors are related to a higher risk of inferior alveolar nerve (IAN) injury when performing an immediate implant surgery in posterior mandible region.

Methods

The CBCT images from 237 subjects (1008 teeth) were analysed the shape of the mandibles (C, P, U type), dimensional parameters of lingual concavity (angle, height, depth), and its relation to inferior alveolar canal (IAC) (A, B, C zone), RAC (distance from root apex to IAC) and probability of IAN injury. Multiple logistic regression modelling to determine the odds ratio of variables that made an important contribution to the probability of IAN injury and to adjust for confounding variables.

Results

The U type ridge (46.7%) and the most concave point located at C zone (48.8%) are most prevalent in this region. The mandibular second molar presents highest risk for IAN injury than other tooth type (p < 0.001), which were 3.82 times to occur IAN injury than the mandibular second premolar. The concave point located at A zone and B zone were 7.82 and 3.52 times than C zone to have IAN damage, respectively. The probability of IAN injury will reduce 26% for every 1 mm increase in RAC (p < 0.001).

Conclusions

The tooth type, morphological features of lingual concavities, and RAC are associated with risks of IAN injury during immediate implant placement.

Clinical significance

Pre-surgical mapping of the IAC and identification of its proximity relative to the lingual concavity in the posterior mandible regions may avoid unpleasant complications, specifically when performing immediate implant procedures.     

Forsus矫治恒牙期安氏Ⅱ类错(牙合)下颌后缩的牙弓及基骨弓宽度的变化

目的应用Forsus治疗已过生长发育高峰期安氏Ⅱ类错（牙合）下颌后缩恒牙期患者,探讨其牙弓及基骨弓宽度的变化。方法临床选择45例（男20例,女25例）恒牙期安氏Ⅱ类错（牙合）下颌后缩患者,年龄15-16．5岁。戴用Forsus矫治器前后制取牙颌模型,测量牙弓及基骨弓宽度。用Spss15．0统计软件对治疗前后的测量结果进行配对t检验。结果戴用Forsus矫治器前后牙弓及基骨弓宽度均增加。结论Forsus矫治器可用于牙弓狭窄患者的扩弓治疗,但扩弓后的远期疗效和稳定性还有待进一步研究。     

Biologic width changes around loaded implants inserted in different levels in relation to crestal bone: histometric evaluation in canine mandible

Objectives: The aim of the present study was to evaluate histometric changes around dental implants inserted at different levels in relation to the crestal bone, under different loading conditions. Material and methods: Thirty‐six implants were inserted in the edentulous mandible of six mongrel dogs. Each implant was assigned to an experimental group according to the distance from the top of the implant to the crestal bone: Bone Level (at the crestal bone level), Minus 1 (1 mm below the crestal bone) or Minus 2 group (2 mm below the crestal bone). Each hemimandible was submitted to a loading protocol: conventional or immediate restoration. After 90 days, the animals were killed. Specimens were processed, and measurements were performed concerning the length of soft and hard peri‐implant tissues. Data were analyzed using ANOVA and Student's t test (α=5%). Results: Among conventionally restored sites, the distance from the most coronal position of soft tissue margin (PSTM) and first bone–implant contact (fBIC) was greater for Minus 2 than for Bone Level and Minus 1 sites (P=0.03), but significant differences were not observed among immediately restored sites. Differences among groups were not observed concerning the PSTM, and the distance from the implant–abutment junction to fBIC. Greater amounts of lateral bone loss were observed for conventionally than for immediately restored sites (P=0.006). Conclusions: These findings suggest that the apical positioning of the top of the implant may not jeopardize the position of soft peri‐implant tissues, and that immediate restoration can be beneficial to minimize lateral bone loss. Further studies are suggested to evaluate the clinical significance of these results in longer healing periods.     

骨组织对不同处理的种植体表面早期反应的分析研究

目的 比较骨组织对两种不同处理的种植体表面早期反应的不同.方法 种植体分为喷砂、双重酸处理组(A组)和喷砂、双重酸、双氧水、热处理组(B组),然后随机植入兔子股骨远心末端,2、4、8周后制作带种植体的骨组织样品,采用带能谱分析的扫描电镜观察分析.结果 植入2周后在两组种植体表面均见到有机骨基质层,4～8周时B组种植体表面新生骨组织比A组附着多,EDX分析显示富含钙磷.结论 两组种植体表面在植入早期骨反应大致相同,均在表面形成有机骨基质层,但B组种植体表面比A组种植体表面在植入后期更能促进新骨形成.     

Radiographic study of periosteal new bone formation in osteomyelitis of the mandible

A total of 1008 cases with osteomyelitis of the mandible underwent radiological examinations at the department of Oral Radiology, Osaka Dental University Hospital from 1979 to 1988. Osteomyelitis with periosteal new bone formation was observed in 114 out of the 1008 cases (11.3%). The radiographic patterns of the periosteal new bone formation were grouped into 3 types: solid, laminated and one-layer. Sixty-seven of the 114 cases (58.8%) were of the solid type, 23 cases (20.2%) were the laminated type and 24 cases (21.0%) were the one-layer type. The average age in the solid type was 30.8 years, 23.8 years in the laminated type and 38.0 years in the one-layer type. Concerning the sites of periosteal new bone formation 94 out of 114 cases (82.5%) were in the mandibular body and 20 (17.5%) in the ascending ramus of the mandible. The extent of the periosteal new bone formation was far larger among the young. This was particularly remarkable in the ascending ramus of the mandible. These findings were proved to correlate with the age, the clinical symptoms, the route of infection and the condition of eruption in the lower molars.     

下颌后牙区不同时机游离龈移植的效果对比

目的对不同时机的游离龈移植术（FGG）增加下颌后牙区种植体周颊侧角化龈的临床效果进行评价。 方法选择2018年10月至2020年10月就诊于东莞健力口腔医院修复种植科下颌后牙区单牙缺失角化牙龈不足的患者（宽度为2 ~ 4 mm）共40例,将纳入的40例患者进行编号,以随机数字表法抽取20例为实验组,其余20例为对照组。实验组种植Ⅰ期手术时放置愈合基台同期行FGG。对照组种植Ⅰ期手术潜入式愈合,3个月Ⅱ期手术时放置愈合基台同期行FGG。术后观察移植物的存活情况,测量术前牙槽嵴顶剩余角化龈宽度,测量颊侧FGG后即刻、移植术后2个月、戴牙后即刻和戴牙后6个月的颊侧角化龈宽度,使用SPSS 20.0软件对移植物存活率、颊侧不同时间点角化龈宽度等进行统计分析,采用配对t检验进行比较,以P<0.05认为差异有统计学意义。 结果两组手术均获得成功,伤口正常愈合,组织瓣均存活。术前实验组和对照组牙槽嵴顶余留角化龈宽度分别为（2.9 ± 0.3）和（3.0 ± 0.3）mm,差异无统计学意义。实验组和对照组术后即刻种植体颊侧龈缘中点角化龈宽度分别为（4.9 ± 0.5）和（4.9 ± 0.5）mm,差异无统计学意义（t = 0.2,P = 0.8）。实验组和对照组术后2个月颊侧龈缘中点角化龈宽度分别为（4.2 ± 0.4）和（4.5 ± 0.4）mm,差异有统计学意义（t = -2.9,P<0.05）。实验组和对照组戴牙当天种植体颊侧龈缘中点角化龈宽度为（3.2± 0.4）和（3.7± 0.5）mm,差异有统计学意义（t = -2.6,P<0.05）。实验组和对照组戴牙后6个月种植体颊侧龈缘中点角化龈宽度为（3.1 ± 0.4）和（3.5 ± 0.3）mm,差异有统计学意义（t = -3.7,P<0.05）。 结论当下颌后牙区剩余角化龈为2 ~ 4 mm时,FGG在种植Ⅰ期手术同期及Ⅱ期手术同期均能获得较好的增加角化龈的效果。相比于种植Ⅰ期手术同期进行FGG,Ⅱ期手术同期FGG能获得更好的颊侧角化龈的宽度,但会增加手术次数。     

不同垂直骨面型成人上下颌后牙区皮质骨密度测量研究

目的探讨不同垂直骨面型成人上下颌后牙区微螺钉种植体（MSI）常植入部位的皮质骨密度,为临床成功植入MSI提供参考。 方法采用整群抽样的方法从2015年1月至2018年12月广州市花都区妇幼保健院（胡忠医院）口腔正畸科就诊并拍摄锥形束CT（CBCT）的20 ~ 40岁成人患者中抽取57例患者,其中高角组患者20例、均角组患者22例和低角组患者15例。应用Ez3D-i软件重建上下颌骨三维模型,测量上下颌骨12个牙根间部位（距离牙槽嵴顶4 mm处）皮质骨密度（HU值）,运用单因素方差分析（ANOVA）比较3组各测量部位皮质骨密度均数的差异。 结果3组间上下颌后牙区颊侧多数测量部位皮质骨密度差异有统计学意义（P<0.001）,其中高角组最小。上颌腭侧多数测量部位差异无统计学意义。各组中相同牙位上颌后牙区颊侧、腭侧、以及下颌颊侧皮质骨密度差异有统计学意义（P<0.001）,其中上颌腭侧最小,下颌颊侧最大。 结论成人上下颌后牙区颊侧皮质骨密度受垂直骨面型影响,高角成人在上颌后牙区颊侧植入MSI需谨慎;上颌后牙区腭侧皮质骨密度几乎不受垂直骨面型影响,但骨密度低,植入MSI时也需谨慎。     

Micro-leakage at the implant-abutment interface with different tightening torques in vitro

Objectives

This study evaluated the microleakage at the implant/abutment interface of external hexagon (EH) implants and abutments with different amounts of bacteria and tightening torques.

Material and Methods

A bacterial suspension was prepared to inoculate the implants. The first phase of this study used nine EH implants and abutments that were divided into three groups with different amounts of bacterial suspension (n=3): V0.5: 0.5 µL; V1.0: 1.0 µL e V1.5: 1.5 µL, and tightened to the manufacturer''s recommended torque. The second phase of this experiment used 27 assemblies that were similar to those used in the first phase. These samples were inoculated with 0.5 µL of bacterial suspension and divided into three groups (n=9). T10: 10 Ncm; T20: 20 Ncm and T32: 32 Ncm. The samples were evaluated according to the turbidity of the broth every 24 hours for 14 days, and the bacteria viability was tested after that period. The statistical evaluation was conducted by Kruskal-Wallis testing (p<.05).

Results

During the first phase, groups V1.0 and V1.5 was presented with bacterial contamination in all samples after 24 h. During the second phase, two samples from group T10 and one from T20 presented positive results for bacterial contamination. Different amounts of bacterial solution led to overflow and contamination during the first 24 h of the experiment. The tightening torques did not statistically affect the microleakage in the assemblies. However, the group that was tightened to 32 Ncm torque did not show any bacterial contamination.

Conclusion

After 14 days of experimentation, the bacteria were proven to remain viable inside the implant internal cavity.     

钛网成形自体颗粒骨修复下颌骨缺损并同期种植的实验研究

目的 观察犬钛网成形自体颗粒骨移植修复下颌骨节段性缺损并同期植入钛种植体后的骨愈合和骨结合情况.方法 5只Beagle犬,一侧下颌骨制备长40 mm的节段性缺损;钛网成形修复下颌骨缺损.将切除后的下颌骨和自体髂骨剪成直径约2mm颗粒,骨皮质、骨松质体积比3∶1混合,紧密充填在钛网内,将2枚纯钛种植体埋置于颗粒骨内,术后6个月处死动物.用下颌骨X线片、组织学切片、扫描电镜以及能谱分析观察钛网内颗粒骨愈合以及种植体骨结合的情况.结果 钛网成形自体颗粒骨移植重建后的下颌骨外形满意,功能正常、颗粒骨成骨良好、结构优良,未见明显骨吸收.同期植入的种植体能够与周围骨组织形成良好的骨结合,并有促进邻近骨组织结构优化的趋势.结论 钛网成形自体颗粒骨移植是一种修复下颌骨节段性缺损的好方法,当修复后下颌骨形态良好、骨质优良、骨量充足时可以同期植入种植体.     

A simple evaluation method for early detection of bisphosphonate-related osteonecrosis of the mandible using computed tomography

ObjectivesThe aim of this study was to establish a simple method for the early detection of bisphosphonate-related osteonecrosis of the jaw (BRONJ) using computed tomography (CT).Materials and methodsCT images of the mandible were obtained from a total of 20 patients with BRONJ and 20 control subjects. BRONJ was classified into 2 groups, with bone exposure (Stage 1–3 BRONJ) or without (Stage 0 BRONJ). In each patient, 15 transaxial CT images were selected and 30 configured regions of interest (ROI) were identified. The ANOVA test was applied to test the relationship between the severity of systemic risk factors.ResultsRegarding the local status of the mandible, significant differences were observed among the Stage 0 BRONJ, Stage 1–3 BRONJ, non-BRONJ and control groups in the cancellous bone CT radiodensity values, but there were no significant differences between the Stage 0 and Stage 1–3 BRONJ groups. In the cortical bone widths, significant differences were observed only between BRONJ and the controls.ConclusionsMeasuring cancellous bone CT radiodensity value has the potential to be a simple and quantitative method to detect the early stages of BRONJ.     

Effects of different abutment material and surgical insertion torque on the marginal adaptation of an internal conical interface: An in vitro study

PurposeTo evaluate the marginal adaptation at implant–abutment connection of an implant featuring a conical (45° taper) internal hexagonal abutment with a connection depth of 2.5 mm, comparing the performance of two identical abutments of different material (titanium grade-4 and Co-Cr-alloy).MethodsTwenty implants (3.75 mm × 15 mm) were connected to non-matching abutments (5.5 mm × 10 mm) of two different materials (titanium grade-4: n = 10; Co-Cr-alloy: n = 10). The specimens were separately embedded in epoxylite resin, inside copper cylinders, and submerged without covering the most coronal portion (5 mm) of the fixture. Five specimens per group were stressed simulating a surgical 100 Ncm insertion torque, while the others had no torque simulation. All specimens were subjected to a non-axial static load (100 N) in a universal testing machine, under an angle of 30° with respect to the implant axis. Once 100 N load was reached, low shrinkage self-curing resin was injected inside the cylinders, and load was maintained until complete resin polymerization. Specimens were cut and analyzed with optical and scanning-electron-microscope (SEM) to evaluate the marginal adaptation at the implant–abutment connection. Statistical analysis was performed using one-way ANOVA (p = 0.02).ResultsNone of the 20 samples failed. The implant–abutment connection was able to guarantee a good optical seal; SEM analysis confirmed the absence of microgaps.ConclusionsWithin the limits of this study (small sample size, limited time) the marginal adaptation of the implant–abutment connection was not affected by the abutment material nor by the application of surgical insertion torque.     

Biologic basis for interpositional autogenous bone grafts to the mandible

Interpositional autogenous bone grafting procedures were performed in the mandibles of 12 beagle dogs to assess cell survival within the graft and the superiorly repositioned alveolus, and to monitor the remodeling process. Histologic and radiologic results indicated that the grafts were well accepted and that new bone was rapidly laid down on their trabeculae. However, the osteocytes within the autografts generally did not survive. There was no evidence of necrosis of the superiorly displaced alveolus, nor any resorption of its surface cortex, and it rapidly united with the autograft and the mandible to produce a stable structure. This study confirms that the lingual pedicle of soft tissue is adequate to maintain the viability of the superiorly repositioned alveolus or segment and to allow rapid remodeling of the autogenous bone graft.     

7～12岁女性儿童的下颌头影测量的纵向变化研究

目的：研究混合牙列期的下颌生长发育的变化规律。方法：19名女性儿童中，10人从7岁开始，另9人从9岁开始，她们每年被拍摄头颅侧拉片1次，并连续观察4年。7～10岁组和9～12岁组分别作纵向研究。两个组9～10岁的重叠期，将它们的结果结合起来进行混合纵向分析，从而了解整个7～12岁的生长发育规律。采用SPSS8.0软件统计处理数据。结果：观察期内，下颌的水平深度继续增加，以下颌体的水平深度增加最为明显。下颌垂直高度也在继续增加，但增幅仅是水平深度增幅的一半。结论：在混合牙列期，面型基本正常的儿童的下颌水平深度增加要大于垂直高度的增加，这有利于矫正下颌长度不调。     

Validating of the pre-clinical mouse model for metastatic breast cancer to the mandible

Metastatic breast carcinoma has a great tendency to spread to the mandible. It is concomitantly associated with bone destruction, food intake disorder, and a poorer prognosis. Appropriate animal models need to be developed for a better understanding of the mechanisms underlying the metastatic process of breast cancer cells to mandible and to test the effects of potential lead compounds. Here, we assessed the metastasis model of intracardiac injection using luciferase-transfected metastatic breast cancer cells (MDA-MB-231^Luc+) by determining the incidences of metastasis, mCT images, and histopathological results. A high bioluminescence signal mainly detected mandibular lesions with less frequent distal femora and proximal tibiae lesions. Extensive mandibular bone destruction occurred in nude mice grafted with metastatic breast cancer cells. This type of animal model might be a useful tool in assessing therapeutic implications and the efficacy of anti-cancer drugs for osteolytic cancers.     

Anterior loop of the mental nerve in Saudi sample in Riyadh,KSA. A cone beam computerized tomography study

BackgroundThe portion of inferior alveolar nerve (IAN) existent anterior to the mental foramen, before parting the canal, is referred to as the anterior loop (AL) of the IAN. The presence of AL is important when placing the implant interforaminal area of the mandible. These anatomical discrepancies can be assessed by cone-beam CT (CBCT), for evaluating its position and exact location. The AL is classified into Types I, II and III. In Type I, Y-shaped anatomy; in Type II, anatomy is T-shaped; and in Type III, Y-shaped anatomy is seen, and the incisive branch is thicker as compared to the main branch.AimIn this study, we aim to analyse the prevalence of different types of AL of the IAN in Saudi sample population.Materials and MethodsThe present study is a retrospective analysis of 149 (86 female & 63 male) CBCT images of patients records from 2018 June to 2018 September in the department of implant dentistry, KSMC, Riyadh. The age range of the patients who participated in the study was 30–60 years. The mean age of female participants is 42.5 ± 5.8, for the male participants is 48.6 ± 11.4 years respectively.ResultsThe most frequent type of AL of mental nerve noticed on the right side was of type I (59.1%), followed by type II (27.5%) and type III (13.4%). The most frequent type of AL of mental nerve noticed on the left side was type I (61.7%), followed by type II (26.8%) and type III (11.4%).ConclusionThe results of the study encourage the usage of CBCT for planning implant treatment. We also suggest that it is obligatory for professionals to categorise the presence of AL and to measure them appropriately when planning for the procedures in the interforaminal region.     

Ultrasound to stimulate early bone formation in a distraction gap: a double blind randomised clinical pilot trial in the edentulous mandible

OBJECTIVE: In a double blind randomised clinical pilot trial, it was investigated whether low intensity pulsed ultrasound therapy stimulates early bone formation in a distraction gap created in a severely resorbed mandible. DESIGN: Eight patients underwent a mandibular vertical distraction over an average distance of 6.6+/-1.1mm. Ultrasound self-therapy or placebo therapy was started on the first day of distraction and continued daily until the implants were inserted. After 31+/-3.8 days of consolidation, the distraction device was removed, a transmandibular biopsy was taken, and two endosseous implants were inserted. RESULTS: All patients complied well with ultrasound therapy. During an average of 30.1+/-4.1 months follow-up, no complications did occur. Microradiographic examination of the biopsies revealed a comparable mean area of mineralised tissue in the distraction gap of 1.9+/-1.7mm(2) in the ultrasound treatment group and 1.9+/-1.3mm(2) in the placebo treatment group. Histological examination indicated that active woven bone was present within the distraction gap just adjacent to the osteotomy plane, with no apparent differences between the treatment groups. The lamellar bone formation outside the distraction gap appeared to have started as well. CONCLUSION: During a 31-day consolidation period, ultrasound treatment does not appear to stimulate bone formation in the severely resorbed vertical distracted mandible and it seems that this period is too short to evaluate properly if there is an effect. Therefore, a longer consolidation period has to be studied.     

Additive manufacturing for microvascular reconstruction of the mandible in 20 patients

Objectives

The aim of this study was to evaluate the use of model mandibles made preoperatively by additive manufacturing, which were used to prebend reconstruction plates prior to mandibular resection and reconstruction with microvascular bony flaps.

Materials and methods

Computer Tomography (CT) or Cone Beam Tomography (CBT) scans acquired preoperatively were used to obtain DICOM data sets to produce a model of the mandible using rapid prototyping. This model was used as a template to prebend and then sterilize a 2.3 or 2.7 reconstruction plate, which was used to reconstruct the mandible with a microvascular bony flap. This technique was used in 20 consecutive patients who required mandibular resection and reconstruction because of a tumour or osteoradionecrosis.

Results

The prebent plate was used in all patients intraoperatively without the need for any further bending. The average time to bend a plate on a nonsterile model was 0.42 h (range 0.25-0.68 h). This is felt to represent the minimum amount of time saved during the operation.Additive manufacture of the mandible prior to resection and reconstruction with a microvascular flap is a useful technique which reduces the operating time.     

数字化导板在下颌骨良性病变截骨并保存下牙槽神经血管束中的应用：附1例报告

目的: 探讨数字化导板在保存下牙槽神经血管束的下颌骨良性病变治疗中的应用方法,并评价其应用效果。方法：下颌支骨化纤维瘤病1例,ProPlan CMF 1.3软件处理CT数据,标记患侧下牙槽神经管,并于其下方2 mm设计截骨线。制作相应数字化导板,指导术中截骨并分离神经;利用反求技术制作定位导板,定位预制的重建钛板。术后CT评价面部对称性与截骨的准确性,同时检测双侧颏部皮肤感觉、下颌牙牙髓活力,以评价神经功能。采用SPSS 17.0软件包对数据进行统计学分析。结果：应用导板截除病变彻底,术中完整剥离并保存下牙槽神经血管束。术后随访示面形对称,患侧下唇感觉存在,患侧下颌牙牙髓活力与健侧无显著差异。结论：数字化导板可帮助实现下颌骨良性病变的彻底切除、下牙槽神经血管束的保存和同期肋骨移植颌骨重建,是功能性外科的有力辅助工具。     

Evaluation of four different optimized magnetic-resonance-imaging sequences for visualization of dental and maxillo-mandibular structures at 3 T

ObjectivesThe purpose of this study was to evaluate four in-house optimized, non-contrast enhanced sequences for MRI-investigation of maxillo-mandibular and dental structures by use of 3 T.Methods12 volunteers with different dental status were examined by using a 3 T MRI with a 20-channel standard head-and-neck coil. All images performed were evaluated by using 3D-techniques, with different slice-thicknesses, in 3D T1- and T2-weighted sequences, as well as by using new techniques of image depictions. In addition phantom measurements were performed to estimate the extent of image artefacts caused by retainers and metal implants.ResultsMean age of the participants was 33 years (range, 25.5–62.75 years), and the sex ratio was 5 females to 7 males. We identified different techniques to improve osseous and dental structures, despite problems caused by dental implants, tooth crowns or braces.ConclusionThe sequences evaluated offered excellent visualization in 2D and 3D of osseous and dental structures. Anatomical, osseous and dental structures were described at their ROI, in relation to patients with dental and head and neck pathologies. The ability to detect and distinguish pathological processes as soon as possible in 3D with excellent image quality avoiding ionizing radiation remains a challenging domain.     

Impact of different placement depths on the crestal bone level of immediate versus delayed placed platform-switched implants

Purpose

The preservation of peri-implant bone is one requirement for long-term success of dental implants. The purpose of this study was to evaluate the impact of subcrestal placement on the crestal bone level of immediate versus delayed placed implants after loading.