The influence of implant number and attachment type on maximum bite force of mandibular overdentures: a retrospective study

doi: 10.1111/j.1741‐2358.2010.00421.x
The influence of implant number and attachment type on maximum bite force of mandibular overdentures: a retrospective study Aim: Assessment of the influence of such factors as attachment type, number of implants, gender and age of patients on maximum bite force (MBF). Material and methods: Sixty‐two edentulous patients (32 females, 30 males; aged 64.03 ± 10.07 years, range 42–90 years) with mandibular implant overdentures with various attachment types were included in the study and their MBFs were recorded. The results were evaluated statistically at a significance level of p < 0.05. Results: The MBF in male patients was found to be statistically significantly (p < 0.05) higher than in female patients. No statistically significant differences (p > 0.05) were found with respect to age groups, attachment types and number of implants supporting the mandibular overdentures. Conclusion: Within the limitations of this study, it is concluded that independent of the number applied, dental implants increase MBF in edentulous patients. While males show higher bite force, patient age and attachment type seem not to play an important role.     

The effect of attachment type and implant number on satisfaction and quality of life of mandibular implant-retained overdenture wearers

doi: 10.1111/j.1741‐2358.2011.00531.x The effect of attachment type and implant number on satisfaction and quality of life of mandibular implant‐retained overdenture wearers Objective: The aim of this study was to compare the quality of life and patient satisfaction outcomes of two attachment systems in mandibular overdentures with different numbers of supporting implants. Materials and methods: Sixty‐two edentulous patients with either splinted or single attachments in mandibular implant overdentures with different numbers of supporting interforaminal implants were investigated for patient satisfaction and quality of life in this retrospective study. Comparisons between groups were perceived by the Mann–Whitney U test. Relations among the parameters were investigated by Spearman’s rho correlation analysis. The results were evaluated statistically at a significance level of p < 0.05. Results: No statistically significant association is found between visual analogue scales scores and attachment type as well as implant number (p > 0.05), whereas Oral Health Impact Profile (OHIP)‐14 total scores for patients with 4‐implant‐supported bars were significantly lower than all the other attachment types (p < 0.05). Additionally, a negative (rate = 32.2%), statistically significant association between period of edentulism and total OHIP‐14 scores was detected (p < 0.05). Conclusions: A mandibular implant‐retained overdenture supported with four implants and bar attachments shows the highest ‘quality of life’ score and patient satisfaction is not influenced by the number of implants or attachment type.     

Influence of connection type on the biomechanical behavior of distal extension mandibular removable partial dentures supported by implants and natural teeth

Few studies are performed to evaluate the influence of connection type on the stress distribution of distal extension mandibular removable partial dentures (RPDs) supported by both implants and natural teeth. In this study, five three-dimensional finite element models were prepared to simulate mandibular bilateral partially edentulous arches. Four were RPDs supported by both implants and natural teeth, and the other one was RPDs supported only by natural teeth. The maximum equivalent (EQV) stress values of bone around implants, the abutments, and the mucosa displacements of the related supporting structures were measured. It was found that a non-rigid telescopic coping was more favorable to protect the implant than a rigid telescopic coping. Compared with other connection types, the easy resilient attachment (ERA) system seemed to be effective to associate implant without complications. However, the results obtained in the present study should be cautiously interpreted in the clinic.     

Elders with implant overdentures: a 22-year clinical report

doi: 10.1111/j.1741‐2358.2012.00628.x Elders with implant overdentures: a 22‐year clinical report Objective: To report on the long‐term survival and prosthodontic maintenance of two edentulous adults with mandibular overdentures supported by hydroxyapatite (HA)‐coated implants. Background: Mandibular implant overdentures are a successful treatment option with positive impact on the quality of life of elderly edentulous adults. Long‐term survival of the implants requires continued rigorous prosthodontic maintenance. Clinical report: Two elderly edentulous adults with mandibular overdentures supported by 2 HA‐coated implants were presented for prosthodontic rehabilitation after 22 years of placement. The implants were osseo‐integrated and surviving at presentation based on accepted criteria. The mandibular implant overdentures suffered recurrent loss of retention and stability. Prosthodontic treatment involving the replacement of defective attachment systems and construction of new sets of mandibular implant overdentures opposing complete maxillary dentures is presented. Conclusion: The long‐term survival of mandibular 2‐implant overdentures requires continued prosthodontic maintenance. A conservative approach in the rehabilitation of two older edentulous adults with mandibular 2‐implant overdentures was described including proper selection of attachment systems.     

Finite element analysis of implant-supported prosthesis with pontic and cantilever in the posterior maxilla

The aim of this study was to evaluate the influence of pontic and cantilever designs (mesial and distal) on 3-unit implant-retained prosthesis at maxillary posterior region verifying stress and strain distributions on bone tissue (cortical and trabecular bones) and stress distribution in abutments, implants and fixation screws, under axial and oblique loadings, by 3D finite element analysis. Each model was composed of a bone block presenting right first premolar to the first molar, with three or two external hexagon implants (4.0 × 10 mm), supporting a 3-unit splinted dental fixed dental prosthesis with the variations: M1 – three implants supporting splinted crowns; M2 – two implants supporting prosthesis with central pontic; M3 – two implants supporting prosthesis with mesial cantilever; M4 – two implants supporting prosthesis with distal cantilever. The applied forces were 400 N axial and 200 N oblique. The von Mises criteria was used to evaluate abutments, implants and fixation screws and maximum principal stress and microstrain criteria were used to evaluate the bone tissue. The decrease of the number of implants caused an unfavorable biomechanical behavior for all structures (M2, M3, M4). For two implant-supported prostheses, the use of the central pontic (M2) showed stress and strain distributions more favorable in the analyzed structures. The use of cantilever showed unfavorable biomechanical behavior (M3 and M4), mainly for distal cantilever (M4). The use of three implants presented lower values of stress and strain on the analyzed structures. Among two implant-supported prostheses, prostheses with cantilever showed unfavorable biomechanical behavior in the analyzed structures, especially for distal cantilever.     

Evaluation of bone remodeling around single dental implants of different lengths: a mechanobiological numerical simulation and validation using clinical data

Algorithmic models have been proposed to explain adaptive behavior of bone to loading; however, these models have not been applied to explain the biomechanics of short dental implants. Purpose of present study was to simulate bone remodeling around single implants of different lengths using mechanoregulatory tissue differentiation model derived from the Stanford theory, using finite elements analysis (FEA) and to validate the theoretical prediction with the clinical findings of crestal bone loss. Loading cycles were applied on 7-, 10-, or 13-mm-long dental implants to simulate daily mastication and bone remodeling was assessed by changes in the strain energy density of bone after a 3, 6, and 12 months of function. Moreover, clinical findings of marginal bone loss in 45 patients rehabilitated with same implant designs used in the simulation (n = 15) were computed to validate the theoretical results. FEA analysis showed that although the bone density values reduced over time in the cortical bone for all groups, bone remodeling was independent of implant length. Clinical data showed a similar pattern of bone resorption compared with the data generated from mathematical analyses, independent of implant length. The results of this study showed that the mechanoregulatory tissue model could be employed in monitoring the morphological changes in bone that is subjected to biomechanical loads. In addition, the implant length did not influence the bone remodeling around single dental implants during the first year of loading.     

Effect of electromagnetic field on bone regeneration around dental implants after immediate placement in the dog mandible: a pilot study

doi: 10.1111/j.1741‐2358.2011.00525.x Effect of electromagnetic field on bone regeneration around dental implants after immediate placement in the dog mandible: a pilot study Background: Accelerating bone healing around dental implants can reduce the long‐term period between the insertion of implants and functional rehabilitation. Objective: This in vivo study evaluated the effect of a constant electromagnetic field (CEF) on bone healing around dental implants in dogs. Materials and methods: Eight dental implants were placed immediately after extraction of the first pre‐molar and molar teeth on the mandible of two male dogs and divided into experimental (CEF) and control groups. A CEF at magnetic intensity of 0.8 mT with a pulse width of 25 μs and frequency of 1.5 MHz was applied on the implants for 20 min per day for 2 weeks. Result and conclusion: After qualitative histological analysis, a small quantity of newly formed bone was observed in the gap between the implant surface and alveolar bone in both groups.     

应用电子散斑干涉术对单端固定桥的受载分析

本文目的是对单端固定桥的运动及其受力状态进行试验性研究。采用电子散斑干涉术这一新的光学技术分别对下颌单端固定桥修复前后进行４种垂直加载测试,观察实时显示的散斑干涉条纹图,并测量相应牙槽骨处的离面位移。     

The effect of different attachment systems with implant‐retained overdentures on maximum bite force and EMG

doi: 10.1111/j.1741‐2358.2010.00389.x The effect of different attachment systems with implant‐retained overdentures on maximum bite force and EMG Objective: To compare the effect of different attachment systems with implant‐retained overdentures on maximum bite force and muscle activity using electromyography (EMG). Background: Denture retention and stability is of considerable interest in prosthetic dentistry. Materials and methods: Thirty‐five patients were examined: 15 edentulous patients treated with mandibular implant‐retained overdentures (MIRO) and maxillary dentures (MCD) (two implant‐ball attachment) (BC); 10 edentulous patients treated with MIRO and MCD (four implants‐bar attachments) (BRC); 10 patients with edentulous mandibular treated with MIRO and maxillary fixed partial dentures (MFPD) (two implant‐ball attachments) (BF). Before implant placement all patients received new dentures. After using these dentures for 3 months the maximum bite force and electrical activity of masseter muscle were measured. Two or four implants were then inserted into the intraforaminal region. After osseointegration periods, patients were treated with MIRO which duplicated their dentures and after three months the measurements were repeated. The data were collected and statistically analysed. Results: Muscle activity and chewing ability increased in the second period of measurements. Also chewing time was significantly decreased at the first measurements. The highest muscle activity was observed in the group of patients treated with group BF. Conclusion: The EMG values of the masseter muscle significantly increased when an implant attachments was used in the overdenture.     

Comparison of mandibular bone mineral density in osteoporotic, osteopenic and normal elderly edentulous subjects measured by the dual-energy X-ray absorptiometry technique

doi: 10.1111/j.1741‐2358.2012.00625.x Comparison of mandibular bone mineral density in osteoporotic, osteopenic and normal elderly edentulous subjects measured by the dual‐energy X‐ray absorptiometry technique Objective: The aim of this study was to compare the mandibular body bone mineral density according to bone mineral density status of spine and femur measured by dual‐energy X‐ray absorptiometry (DXA) technique in elderly edentulous individuals. Background: One of the factors that affect the survival rate of implants is bone mineral density (BMD) of the jaws. Materials and methods: Fifty edentulous elderly patients’ (27 women and 23 men) spine, femur and the mandibular body BMDs were measured using DXA technique. BMD scans of the AP lumbar spine (L2–L3) and femur were classified using World Health Organisation criteria for bone mass. Results: There was a statistically significant difference between the normal femur group’s–osteoporosis group’s mandibular body BMD (p = 0.001) and femoral osteopaenia group’s–osteoporosis group’s mandibular body BMD (p < 0.001). The femoral osteoporosis group’s mandibular body BMDs were lower than those of both the normal femoral and the femoral osteopaenia group subjects’. Conclusion: Classification of edentulous mandibles according to low and high bone mineral densities is a problem in implant dentistry. The results of this study demonstrated that femoral bone mineral density status may be used to provide preliminary information about the bone mineral density of the mandibular body region in elderly edentulous subjects.     

Relationships between bone mass and micro-architecture at the mandible and iliac bone in edentulous subjects: a dual X-ray absorptiometry, computerised tomography and microcomputed tomography study

doi: 10.1111/j.1741‐2358.2011.00527.x Relationships between bone mass and micro‐architecture at the mandible and iliac bone in edentulous subjects: a dual X‐ray absorptiometry, computerised tomography and microcomputed tomography study Objectives: To compare bone volume, bone mineral density, cortical thickness and bone micro‐architecture in a series of paired mandibular and iliac bone samples analysed by various imagery techniques to see whether relationships exist between the various techniques and between mandibular and iliac bone. Materials and methods: Bone samples from the mandible and ilium were harvested in 20 cadavers and analysed by dual energy X‐ray absorptiometry (DXA), computerised tomography (CT) on a conventional hospital machine and microCT. Results: Significant correlations were found between Hounsfield density obtained by CT, and bone mass determined by microCT but not with DXA values. Cortical thickness measurements were well correlated between CT and microCT. No relationships were found between mandibular and iliac bone, when considering mineral density, cortical thickness, bone volume or micro‐architecture. Conclusion: In clinical practice, CT remains the most appropriate routine means for bone qualitative and quantitative evaluation at the mandible. In this ex vivo study, these results confirm that mandibular bone status does not reflect the axial skeletal one and assist in the placement of implants with dental prostheses in old or osteoporotic patients.     

The influence of mandibular implant-retained overdentures in masticatory efficiency

doi: 10.1111/j.1741‐2358.2011.00539.x The influence of mandibular implant‐retained overdentures in masticatory efficiency Objective: To evaluate the masticatory efficiency of patients rehabilitated with conventional dentures (CDs) or implant‐retained mandibular overdentures. Background: Despite the evident benefits of implants on mastication as assessed by subjective patient‐based outcomes, the extent of implant overdenture treatment effect on food comminution is not well established. Materials and methods: A randomised clinical trial was carried out with 29 completely edentulous patients divided into two groups. The first group was rehabilitated with a mandibular overdenture retained by two splinted implants with bar‐clip system, while the second group was rehabilitated with a mandibular CD. Both groups also were rehabilitated with maxillary CDs. Masticatory efficiency and patient satisfaction were assessed 3 months after denture insertion. Masticatory efficiency was evaluated through the colorimetric method with the beads as the artificial test‐food. Comparisons for masticatory efficiency and patient satisfaction were performed using Student’s t‐test (α = 0.05). Results: No significant statistical difference was found for masticatory efficiency (p = 0.198). Patient overall satisfaction was significantly higher for the mandibular overdenture (p < 0.001). In addition, mandibular overdenture patients were significantly more satisfied with chewing experience (p < 0.05) and retention of the lower denture (p < 0.005). Conclusion: The results of this study suggest that mandibular overdenture significantly improves chewing experience, although limited effect on masticatory efficiency has been observed.     

Extent and location of bone loss at dental implants in patients with peri-implantitis

Peri-implantitis is an infectious disease, which leads to loss of supporting bone around dental implants. To evaluate the extent and location of bone loss, 43 patients with peri-implantitis were examined. The bone loss was clinically measured at the time of dental surgery. Data revealed that 25% of subjects had bone loss associated with all their implants although the majority of the subjects had fewer than 50% of their implants affected by bone loss. A total number of 264 implants were examined and 131 of those had peri-implantitis associated bone loss. The pattern of bone loss at implants varied between and within subjects and location in the jaws. The highest proportion of implants with peri-implantitis was found in the upper jaw and within this group, at implants located in the incisor area of the upper jaw; the lowest was the canine area of the lower jaw. The highest proportion of implants that lost ≥ 2/3 of their bone support was found in the incisor area of the maxilla. We concluded that in the presence of peri-implant inflammation, bone quantity and characteristics may influence the progression of peri-implantitis bone loss at dental implants. We hypothesize that the ability of the bone to withstand occlusal forces will be altered as consequence of the loss of bone at the neck of the implants. To achieve an understanding of the local degradation of bone due to peri-implantitis, we need to analyze the microstructure of the bone as well the cellular biology of the peri-implant inflammation.     

富血小板纤维蛋白联合人工骨粉在口腔种植引导性骨再生中的临床应用价值

目的:探讨富血小板纤维蛋白(PRF)联合人工骨粉(Bio-Oss骨粉)在口腔种植引导性骨再生中的临床应用价值。方法:选取2017年6月到2018年6月期间在我院接受口腔种植引导性骨再生手术治疗的患者80例,根据随机数字表法分为对照组(40例)和研究组(40例),对照组采用Bio-Oss骨粉联合Bio-Gide生物膜进行干预,研究组采用Bio-Oss骨粉联合PRF进行干预。比较两组患者的组织愈合情况、出血指数、探诊深度、附着丧失、植体周围的骨密度、植骨高度、成骨厚度和术后并发症。结果:研究组的组织愈合优良率为95.00%,高于对照组的80.00%,差异有统计学意义(P0.05)。研究组患者的出血指数、探诊深度、附着丧失均低于对照组,种植体周围的骨密度、成骨厚度均明显大于对照组,植骨高度高于对照组,差异有统计学意义(P0.05)。两组患者的并发症发生率比较差异无统计学意义(P0.05)。结论:PRF联合Bio-Oss骨粉可有效增加种植区骨量和种植体周围的骨密度,促进骨缺损再生和组织愈合,且无明显的并发症,在口腔种植引导性骨再生中有较好的临床应用价值。     

Genome analysis and clinical implications of the bacterial communities in early biofilm formation on dental implants restored with titanium or zirconia abutments

This cross-sectional study aimed to identify and quantify up to 42 target species colonizing the early biofilm of dental implants restored with titanium or zirconia abutments. A total of 720 samples from 20 healthy individuals were investigated. Biofilm samples were collected from the peri-implant sulci, inner parts of implants, abutment surfaces and prosthetic crowns over a functioning period of 30 days. Checkerboard DNA–DNA hybridization was used for microbial detection and quantitation. Clinical characteristics (probing depth, bleeding on probing, clinical attachment level and marginal bone loss) were also investigated during the monitoring period. Genome counts were low at the implant loading time point for both the abutment materials, and increased over time. Both the titanium and the zirconia groups presented similar microbial counts and diversity over time, and the microbiota was very similar to that colonizing the remaining teeth. Clinical findings were consistent with a healthy condition with no significant difference regarding marginal bone loss between the two materials.     

Evaluation of the double‐disk synergy test for New Delhi metallo‐β‐lactamase‐1 and other metallo‐β‐lactamase producing gram‐negative bacteria by using metal‐ethylenediaminetetraacetic acid complexes

New Delhi metallo‐β‐lactamase‐1 (NDM‐1), one of the metallo‐β‐lactamases (MBLs), has been identified from clinical isolates worldwide. Rapid detection of NDM‐1 producers is necessary to prevent their dissemination. Seven types of EDTA complexes were evaluated as MBL inhibitors in double‐disk synergy tests (DDSTs), resulting in detection of the first isolate of NDM‐1‐producing Escherichia coli (NDM‐1 Dok01) in Japan. NDM‐1 Dok01 was detected when EDTA magnesium disodium salt tetrahydrate (Mg‐EDTA), EDTA calcium disodium salt dihydrate, EDTA cobalt disodium salt tetrahydrate and EDTA copper disodium salt tetrahydrate were used as MBL inhibitors. The sensitivity and specificity of DDSTs using Mg‐EDTA for 75 MBL producers and 25 non‐MBL producers were 96.0% and 100%, respectively. These findings indicate that the DDST method using Mg‐EDTA can detect MBL‐producing strains, including NDM‐1 producers.     

Segmental mandibulectomy and immediate free fibula osteoseptocutaneous flap reconstruction with endosteal implants: an ideal treatment method for mandibular ameloblastoma

Thirteen patients with large ameloblastomas of the mandible underwent segmental mandibulectomy and immediate reconstruction, with simultaneous placement of osseointegrated implants. All patients received palatal mucosal grafts around the dental implants 6 to 10 months after surgical treatment and received implant-supported prostheses another 1 to 2 months later. There were five female and eight male patients, with a mean age of 32 years (range, 17 to 50 years). The mean length of the mandibular defect was 8.8 cm (range, 5 to 13 cm). All free fibula flap procedures were successful, with no reexplorations or partial flap losses. There was no clinical or radiographic evidence of failure during the osseointegration process for any implant. With functional occlusal loading, the marginal bone loss around the implants was less than 1.5 mm in a mean follow-up period of 40 months (range, 18 to 70 months). There were no recurrences during that time. The technique described allows improved access to the bone at the time of reconstruction, immediate assessment of alveolar ridge relationships, and accurate fixation of the implant-fibula construct. The advantages of this procedure include a reduced risk of recurrence with segmental resection, reliable mandibular reconstruction, and reduction of the number of surgical procedures, allowing full oral rehabilitation in a shorter time. It is concluded that segmental mandibulectomy and immediate vascularized fibula osteoseptocutaneous flap reconstruction, with simultaneous placement of osseointegrated implants, represent an ideal treatment method for large ameloblastomas of the mandible.     

Comparison between complete denture and implant‐retained overdenture: effect of different mucosa thickness and resiliency on stress distribution

Background: The effect of different mucosa characteristics on stress distribution of complete dentures and overdentures remains unknown. Objective: The aim of this study was to evaluate the effect of different mucosa thickness and resiliency on the stress distribution of complete dentures and implant‐retained overdentures using a two‐dimensional finite element analysis. Material and methods: Representative models of the edentulous mandible were constructed on AutoCAD software according to the groups’ characteristics. In group CD, a model of the edentulous mandible supporting a complete denture was obtained while in group IO, a model of edentulous mandible supporting an overdenture over two unsplinted implants with an o’ ring system was constructed. In each group, mucosa assumed three characteristics of thickness (1, 3 and 5 mm) corresponding to the resiliencies hard, resilient and soft respectively. Evaluation was performed on Ansys software with 100N vertical load applied on central incisor teeth. The principal stress was used as analysis criteria. Results: Group IO showed higher stress values than group CD regardless of mucosal thickness and resiliency. Stress decreased at the supporting tissues in both groups as the thickness and resiliency of mucosa increased. In relation to the supporting tissues, cortical bone showed the highest stress values. Conclusion: It was concluded that the use of an attachment system increases stress values and the thickness and resiliency of mucosa influence more on these values.     

An electronic device for accelerating bone formation in tissues surrounding a dental implant

A dental implant is a unique structure which can be used with a noninvasive method because it is inserted into the bone in part and extended extracorporally. This study presents an electronic device that is temporarily connected with the dental implant, and reports its effect on accelerating bone formation in the surrounding tissues in a canine mandibular model. A small sized and low power consumption biphasic electrical current (BEC) stimulator ASIC was developed and the surrounding tissue was exposed to continuous BEC stimulation for 7 days with the parameters of 20 µA/cm², 125 µs duration, and 100 pulses/s. After 2 (n = 5) and 5 weeks (n = 5), animals were sacrificed and the specimens were histomorphometrically evaluated. The newly formed bone area (BA) was 1.30 times (3 weeks, P < 0.05) and 1.35 times (5 weeks, P < 0.05) higher in the experimental group compared to the control group, respectively. Bone‐implant contact (BIC) in 3‐week specimens was 1.62 times (P < 0.05) greater in the experimental group, while there was no statistically significant difference in 5‐week specimens. Based on these results showing accelerated bone formation on and around the dental implant, it could be suggested that the latent time for osseointegration in dental implants can be reduced, and the success rate of implants in poor quality bone can be increased by using our device with BEC. Bioelectromagnetics 30:374–384, 2009. © 2009 Wiley‐Liss, Inc.     

利用共振频率分析牙种植体骨愈合期稳定性变化 与早期边缘骨吸收的关系

目的:利用共振频率测量仪(Osstell)连续监测骨愈合期种植体稳定性变化与早期边缘骨吸收的关系。方法:本研究于2010-2011年期间根据纳入及排除标准连续纳入32名成年男性患者作为实验对象共植入45枚Strauman种植体,每名患者选择一颗(4.8mm×10mm)种植体,共计32颗种植体,种植区位于下颌后牙(骨质均为Ⅱ或Ⅲ类骨)。利用共振频率分析仪(Osstell)测量种植体的稳定性,测量时间点为植入时以及术后第1,2,3,4,6,8,12周。另外,影像学分析测量32颗种植体12周时的边缘骨吸收;结果:本实验中所有种植体在12周均实现骨结合,并成功完成种植修复。通过重复性方差分析,见表1,在种植体植入时,初期稳定系数(ISQ)均值为(79.03±6.756)。术后一周,种植体稳定系数(ISQ)均值均呈下降趋势,至术后第2周时达到最低点,与植入时稳定性有统计学差异(P<0.05)。从术后第3周开始种植体稳定系数(ISQ)均值逐渐上升。其中,稳定系数(ISQ)均值在第6周时与第12周无统计学差异,已达到延期稳定期。32颗种植体在第12周的边缘骨吸收均值为(0.86±0.068mm),而在第12周的种植体的稳定系数均值与种植体植入时的稳定系数均值无统计学差异。结论:本实验通过共振频率测量仪(OsstellTM)连续监测,目前的结果认为种植体愈合期边缘骨吸收对种植体愈合期稳定性变化没有影响。