Biomechanical aspects of oral implants

Abstract: The method used by the working group was an iterative process based upon a structured review of the relevant literature by a group of rapporteurs. The review papers were circulated to the members of the group before the conference and formed the basis for subsequent discussions. Each paper was subject to detailed collective analysis and subsequently modified on the basis of the panel's discussions and referenced to additional relevant literature where appropriate. The group assessed the levels of evidence for the statements made in the supporting documentation and recognized that it was necessary to adopt a compromise between acceptance of the lowest level, resulting in the largest body of material, and the highest level, which, in some cases, produced little evidence. While this approach does not represent endorsement of lower evidence levels per se , it was designed to provide conclusions of clinical utility within the existing knowledge base. The consensus statements were prepared after a detailed consideration of the papers submitted to the workshop by the working group. The papers were scrutinized, amended and approved by the group. The basis of each paper is described in the section on 'search strategy' and defines the parameters within which the consensus statements were prepared.     

State of the art in oral implants

Abstract. Uncontrolled oral implant devices are still being widely used. The documentation of most oral implant systems is poorly backed up or not followed up for an adequate time period. Success rates are being quoted without reference to any defined success criteria. Frequently used oral implant designs such as the Core-Vent, IMZ and Calcitek hydroxyapatite coated implants are in neither case supported by any adequate clinical reports from minimally 5-years of follow-up. Other implant systems such as the ITI, some subperiosteal designs and the Tubingen implant demonstrate well-controlled and acceptable 5-year data but are not followed up in a sufficient number or have demonstrated less good results in the 10-year evaluation. The Small transosteal staple has been adequately reported for more than 10 years of follow-up, whereas the Branemark implant is the only endosseous design that has demonstrated acceptable 15-year success rates.     

种植失败原因探析及再种植处理的体会

目的　分析种植义齿失败原因,探讨再种植手术技巧。方法　 1998年1月—2010年1月623例种植修复病例中,失败病例31例,共计52枚种植体。从脱落时间、部位和术中、术后并发症等方面分析失败原因;并对失败病例进行再种植及疗效评估。结果　 52例脱落种植体,85%（44枚）发生于上部结构修复前,上颌第一磨牙种植体脱落率远高于其他牙位;上颌窦穿通和牙槽骨壁侧穿是种植手术失败的主要并发症。失败病例的再种植时间为3～6个月,2枚种植体脱落后进行第3次种植手术并仍获得临床成功。结论　 骨整合作用是种植义齿存活的关键因素,它受全身和局部因素的影响,前者主要为骨质疏松所致的骨密度降低,后者包括局部病变（牙周病）和局部解剖条件限制,即上颌窦和下牙槽神经所致的骨量不足,种植失败后再种植仍能取得首次种植同样的疗效。     

Survival of NobelDirect implants: an analysis of 550 consecutively placed implants at 18 different clinical centers

Background: A recently introduced implant, the NobelDirect (Nobel Biocare AB, Göteborg, Sweden), has previously been documented with substantial bone resorption in a large number of operated cases. PurposeL The aim of this study was to evaluate the failure rate of NobelDirect implants in a retrospective multicenter survey. Materials and Methods: A total of 550 NobelDirect implants consecutively placed in over 269 patients at 18 centers were evaluated with regard to failure rate after an average follow‐up of about 1 year. Results: The overall failure percentage was 10.9% (59 failures). The 58 implants not loaded directly showed only one failure (1.7%) versus 58 failures (11.8%) of those implants that were loaded directly. A chemical x‐ray photoelectron spectroscopy analysis of an implant from the original batch showed up to 3.5% silicon at parts of the implants. A retrieval analysis of one implant removed at 2 years after placement demonstrated bone resorption down to the level of the fifth thread. Conclusions: It is concluded that the NobelDirect implant, if placed with a punch procedure, ground down in situ, and loaded directly, shows an unusually high failure rate at 1 year.     

One-year outcome of narrow diameter blasted implants for rehabilitation of maxillas with knife-edge resorption

Objectives: This study aimed at assessing the clinical outcome of narrow diameter implants in the treatment of knife‐edge edentulous maxillas of adequate bone height but inadequate width (class IV of Cawood and Howell). Material and methods: Twelve consecutive patients (eight women and four men, mean age 58 years) with class IV atrophic edentulous maxillas were included in the study. Seventy‐three microthreaded TiO₂‐blasted implants were placed and the resonance frequency measured. All the implants had a diameter of 3.5 mm. After 6 months of submerged healing, fixed implant‐supported prostheses were delivered to the patients and resonance frequency and radiographic examinations performed. After the first year of loading, the implant outcome was again evaluated clinically, radiographically and with resonance frequency analysis. Results: All the implants were followed up to 1 year of loading and their survival rate was 100%. Bone loss after 1 year of loading was (mean±SD) 0.30±0.13 mm. Stability values were (mean±SD) 63±5.8 ISQ at placement, 60±4.7 ISQ at the abutment connection and 61±5 ISQ after 1 year of loading. A significant difference resulted between placement and abutment connection values (P=0.03). Conclusions: According to the present study, narrow implants may be used to restore edentulous maxillas with atrophies of class IV of Cawood and Howell. When planning the treatment of edentulous maxillas with such a resorption pattern, this possibility has to be considered as an alternative to more demanding grafting techniques.     

Biomechanical aspects of oral implants. Consensus report of Working Group 1

The method used by the working group was an iterative process based upon a structured review of the relevant literature by a group of reporters. The review papers were circulated to the members of the group before the conference and formed the basis for subsequent discussions. Each paper was subject to detailed collective analysis and subsequently modified on the basis of the panel's discussions and referenced to additional relevant literature where appropriate. The group assessed the levels of evidence for the statements made in the supporting documentation and recognized that it was necessary to adopt a compromise between acceptance of the lowest level, resulting in the largest body of material, and the highest level, which, in some cases, produced little evidence. While this approach does not represent endorsement of lower evidence levels per se, it was designed to provide conclusions of clinical utility within the existing knowledge base. The consensus statements were prepared after a detailed consideration of the papers submitted to the workshop by the working group. The papers were scrutinized, amended and approved by the group. The basis of each paper is described in the section on 'search strategy' and defines the parameters within which the consensus statements were prepared.     

A 5-year prospective study of Astra single tooth implants

AIM: To evaluate the AstraTech Implant ST (Molndal, Sweden) for single tooth replacement clinically and radiographically after 5 years in function. SUBJECTS AND METHOD: Fifteen patients (age range 16 to 48) with missing maxillary anterior teeth (6 central incisors, 8 laterals, 1 bicuspid) had four 13 mm and eleven 15 mm single tooth implants provided. All patients were seen at 4- to 6-monthly intervals for oral hygiene maintenance. Periapical radiographs using Rinn holders and a long cone technique were taken at the crown insertion and after 1 year, 3 and 5 years. RESULTS: No implant losses were observed in 14 of the 15 patients available for evaluation. No abutment screw loosening or soft tissue problems were observed. At crown insertion the mean bone level was 0.46 +/- 0.55 to 0.48 +/- 0.56 mm apical to the top of the implant neck and there were no statistically significant changes in the radiographic bone level over the 5 years of the study (0.36 +/- 0.37 to 0.43 +/- 0.46 mm at year 5). One crown was recemented after 18 months in function and 1 crown was replaced because of a fracture to the porcelain incisal edge. CONCLUSION: The Astra Tech Implants ST were highly successful in single tooth replacement and bone levels during 5 years of function were stable.     

自攻型微螺钉种植体支抗的临床应用研究

目的 研究自攻型微螺钉种植体作为磨牙强支抗的临床应用效果.方法 在30例采用自攻型微螺钉种植体作为磨牙支抗的临床病例中,选择6例已经结束治疗的患者进行分析.6例患者均为骨性Ⅱ类上颌前突患者,拔除上颌双侧第一前磨牙后采用上颌强支抗进行矫治.选择自攻型微螺钉种植体作为上颌支抗,以内收上颌前牙、关闭拔牙间隙.种植体植入部位为上颌第二前磨牙与第一磨牙牙根间的颊侧牙槽间隔,加力值为每侧1.47～1.96 N.对患者拔牙间隙关闭前后的头颅定位侧位片进行分析,测量前牙内收情况和磨牙支抗的变化.结果 6例患者共植入12枚微螺钉种植体,矫治后其上颌前突症状均得到明显改善,上颌切牙切缘平均内收6.06 mm,支抗磨牙平均前移0.44 mm,均获得了磨牙强支抗效果.治疗中,种植体保持稳定,种植体周围的软组织健康.结论 自攻型微螺钉种植体支抗是一种简便、有效的支抗形式,可以满足正畸临床治疗的需要.     

Current challenges in successful rehabilitation with oral implants

Very high survival/success rates have been reported for implant treatment, irrespective of the prosthetic type of reconstruction, be those full arcs, partial dentures, combined tooth implants or single crowns. However, survival/success is commonly reported in simple Cumulative Survival/Success Rate (CSR) tables only that may overestimate the true clinical outcome; furthermore, future challenges to clinical success may originate from too rapid launching of untested novelties or recommendations to apply too bold clinical procedures, potential problems that are summarised in the present paper.     

Clinical and radiographical features of submerged and nonsubmerged titanium implants

A clinical and radiographical study was performed to evaluate whether initial submergence of titanium fixtures is an obligate treatment measure for the establishment of proper bone anchorage when implants a.m. Brdnemark are used. The sample was comprised of 11 subjects with edentulous mandibles. A split-mouth design was employed; in the right mandibular quadrant a traditional 2-step procedure for fixture installation and abutment connection was utilized, while in the left quadrant a l-step procedure was carried out, i.e., fixtures were placed and abutments were connected in one and the same session. Three to 4 months after fixture installation, fixed bridgeworks were fabricated and rigidly connected to the implants. Clinical examinations (including probing pocket depth, bleeding on probing and implant stability test) were performed after 12 and 18 months. Radiographs were taken following insertion of the bridges and at the 12- and 18-month re-examinations. The probing pocket depth, the bleeding on probing, the implant stability and the radiographic deter-minations were similar for the 2 groups of treatment alternatives. This indicates that titanium fixtures a.m. Brinemark can be properly anchored (osseointegrated) in mandibular bone and successfully used for bridge retention also when a l-step procedure is used for implant installation.     

Resonance frequency analysis of implants subjected to immediate or early functional occlusal loading. Successful vs. failing implants

Objectives: The objective of this study was to analyze the development of implant stability by repeated resonance frequency analysis (RFA) measurements during 1 year in 23 patients treated according to an immediate/early‐loading protocol. The objective was also to evaluate the possible differences between failing and successful implants. Material and methods: Eighty‐one Brånemark System implants were placed in 23 patients for immediate/early‐occlusal loading in all jaw regions. Thirty of the implants were placed in extraction sockets and 62 were subjected to GBR procedures. Apart from clinical and radiographic examinations, the patients were followed with RFA at placement, prosthesis connection and after 1–3, 6 and 12 months. Statistical analyses were carried out to study the possible differences between implants that failed during the study period and implants that remained successful. Results: Nine implants failed (11.2%) during the 1 year of loading. RFA showed a distinct different pattern between the implants that remained stable and the implants that were lost. The implants that failed during the course of the study showed a significantly lower stability already after 1 month. Conclusion: Within the limitations of this study, it is concluded that failing implants show a continuous decrease of stability until failure. Low RFA levels after 1 and 2 months seem to indicate an increased risk for future failure. This information may be used to avoid implant failure in the future by unloading implants with decreasing degree of stability with time as diagnosed with the RFA technique.