Synthesis of CAD/CAM, robotics and biomaterial implant fabrication: single-step reconstruction in computer-aided frontotemporal bone resection

The preoperative manufacturing of individual skull implants, developed by an interdisciplinary research group at Ruhr-University Bochum, is based on the use of titanium as the most common material for implants at present. Using the existing technology for materials that can be milled or moulded, customized implants may be manufactured as well. The goal of the study was to examine biodegradable materials and to evaluate the practicability of intraoperative instrument navigation and robotics. Data acquisition of an adult sheep's head was performed with helical computer tomography (CT). The data were transferred onto a computer aided design/computer aided manufacturing system (CAD/CAM system), and two complex defects in the frontotemporal skull were designed. Standard individual titanium implants were milled for both of the defects. Additionally, for one of the defects a resection template, as well as a mould for the biodegradable poly(D,L-lactide) (PDLLA) implant, were fabricated by the CAD/CAM system. A surgeon carried out the first bone resection (#1) for the prefabricated titanium implant using the resection template and an oscillating saw. The robot system St?ubli RX90CR, modified for clinical use, carried out the other resection (#2). Both titanium implants and the PDLLA implant were inserted in their respective defects to compare the precision of their fit. A critical comparison of both implant materials and both resection types shows that fabrication of a PDLLA implant and robot resection are already possible. At present, the titanium implant and resection using a template are more convincing due to the higher precision and practicability.     

Experimental computer-assisted alloplastic sandwich augmentation of the atrophic mandible

Purpose: This study evaluated the effectiveness of a technique that combined computer-aided surgery with alloplastic augmentation and implant-borne prosthodontic rehabilitation of the atrophic mandible.Materials and Methods: Computed tomographic (CT) data from an atrophic cadaver mandible were transferred to a computer-aided design (CAD) system that prepared an anterior sandwich osteotomy. The cranial segment was moved upward and backward to provide an ideal alveolar relationship, and the geometry of the intermediate space was used to design a titanium implant. Furthermore, a surgical template was derived for the osteotomies, and insertion of dental implants was planned to stabilize both the transposed bone and the intermediate implant on the bony base. An identical implant for augmentation was also fabricated from poly-D,L-lactide in a mold as a possible resorbable carrier for osteoinductive proteins.Results: The experimental surgery was successfully performed with maximum precision on the dried mandible. The fabrication of an implant made out of poly-D,L-lactide for the same purpose was also possible.Conclusions: This preliminary experiment showed that it is possible to use CAD/computer-aided manufacturing (CAM) technology to prepare a prefabricated template and a corresponding titanium implant for mandibular augmentation with a high degree of exactness. Dental implants could be planned and integrated in this procedure as well. The fabrication of a mold using this method also provided the opportunity to give a complex shape to possible carriers of osteoinductive substances.     

Individual prostheses and resection templates for mandibular resection and reconstruction

This new technique uses helical computed tomography data and computer-aided design and manufacturing for preoperative fabrication of individual mandibular prostheses together with corresponding resection templates. Coherent 3D geometries for computer-based models are the basis for the construction of prostheses and provide data for a computerized numerical control fabrication. Fixation plates are fabricated with the titanium prostheses. The identical data of these plates are used for the computer-aided design and manufacturing of resection templates, which guide an oscillating saw in a precisely determined resection plane. This plane again is identical with the prostheses' margins for mandibular body replacement. The use of this technique in four patients is reported on: after temporary insertion of the templates for resection and after resection, the prostheses were stabilized with the same screws in the same screw-holes where the templates had been. Resection and reconstruction were thus highly precise, safe and fast and primarily led to excellent aesthetic and functional results. Wound-healing depends on a safe soft-tissue reconstruction over these large prostheses. Coverage with flaps seems obligatory. In spite of the superior technical aspects, the clinical long-term results of this new technique were poor.     

Alternative Knochenersatzmaterialien zur präoperativen Fertigung individueller CAD/CAM-Schädelimplantate

Background. The preoperative manufacturing of individual skull implants using computer aided design (CAD) and computer aided manufacturing (CAM) is based on the use of titanium, although the use of other materials is also potentially possible. The use of other materials. The use of poly(D,L-lactide) (PDLLA) as an implant material was investigated using an adult, formalin fixed sheep's head with a complex frontolateral defect. A standard individual titanium implant as well as a resection template made of aluminium were milled in order to allow bone resection and reconstruction within one operation. A mould was made of Teflon for the fabrication of the PDLLA implant using carbon dioxide at high pressure. This procedure allowed a critical comparison to be made of both implant materials and showed that the production of a biodegradable PDLLA implant is possible. At present the titanium implant is superior to the PDLLA implant, as PDLLA settled with slightly larger dimensions than the mould, although the structure itself was exact. Discussion. The goal of the present research is the fabrication of a functionally graded material made of polylactide, polyglycolide, calcium phosphate and osteoinductive proteins using existing technology, which will meet all of the requirements for stability, resorption kinetics, biocompatibility, radiotranslucence and osteogenic potency of an ideal implant material.     

The use of cranial resection templates with 3D virtual planning and PEEK patient-specific implants: A 3 year follow-up

Purpose

The aim of this study was to evaluate the accuracy of resection templates in cranioplasties in order to facilitate a one-stage resection and cranial reconstruction. Patients and methods: In three cases, cranial resections were combined with direct reconstructions using the principles of computer-aided design, manufacturing, and surgery. The precision of the resection template was evaluated through a distance map, comparing the planned and final result.

One-step primary reconstruction for complex craniofacial resection with PEEK custom-made implants

PurposeReconstruction of large craniofacial defects has largely improved since custom-made implants have been developed in the past decade. For large lesions in fronto-orbital region (such as osteomeningioma), we applied a simple and reliable protocol to perform optimal primary reconstruction with PEEK (polyetheretherketone) specific implant at the same time of the resection.Material and methodsOur protocol is based on virtual preoperative surgery with a planned bone resection that allows engineering of a specific implant to accurately fit to the defect during the surgery. Thus tumour removal and optimal immediate reconstruction are performed easily in a single-step procedure. The use of navigation is required to perform accurate resection according to the planning. We report our experience in five patients requiring complex orbito-frontal reconstruction.ResultsPlanned resection was always achieved with accurate placement of the implant. Optimal orbital reconstruction is allowed and permits exophthalmos correction and orbital contour symmetry. No major complication was observed.ConclusionWe provide a simple one-step technique to reconstruct the orbit while achieving symmetric cosmetic and functional results, reducing operative time and avoiding donor site morbidity.     

快速成形术在下颌骨缺损修复中的应用进展

快速成形术(rapid prototyping technology,RP)是一种能够形成固体形状的新型现代制造技术。在骨缺损修复领域,通过与骨移植、个体化钛支架植入以及组织工程技术相结合,RP发挥着越来越重要的作用,并发展成为一门新的学科——计算机辅助外科。近年来,越来越多的学者将RP技术应用于制作出具有特定孔隙率和特定内部结构的个体化支架材料,以此来促进组织工程化骨的构建,取得了一定成果。作者结合当前骨移植等方法,就该技术用于下颌骨缺损修复的进展情况作一综述。     

Computer-aided Design/Computer-aided Manufacturing–guided Endodontic Surgery: Guided Osteotomy and Apex Localization in a Mandibular Molar with a Thick Buccal Bone Plate

A mandibular molar with a thick buccal bone plate is a challenging problem in endodontic surgery despite the increase in the success rate of endodontic surgery nowadays. This report describes the application of a surgical template to guide osteotomy and facilitate apex localization in a mandibular molar with a thick buccal bone plate. A 57-year-old woman visited the authors’ clinic for pain in tooth 19 and was diagnosed with symptomatic apical periodontitis in this previously treated tooth. Nonsurgical retreatment was performed; however, 2 years later, the patient reported pain in the same tooth. A periapical lesion was confirmed using cone-beam computed tomographic (CBCT) imaging, and endodontic surgery on the mesial root of tooth 19 was planned. After CBCT imaging and cast scan data were transferred to implant surgical planning software, the data were superimposed. In the superimposed model, an anchor pin was designed to target the mesial root apex of tooth 19. The surgical template was then printed using a 3-dimensional printer. Endodontic microsurgery included application of this printed surgical template. A computer-aided design/computer-aided manufacturing (CAD/CAM)-guided surgical template minimized the extent of osteotomy and enabled precise targeting of the apex in this case. There were no postoperative complications. A CAD/CAM-guided surgical template is useful in endodontic surgery for complicated cases.     

Guided flapless surgery with immediate loading for the high narrow ridge without grafting

Computer guided implant treatment allows implants and associated restorations to be precisely placed during the same procedure directly through the gingiva with reduced postoperative complications and surgical time. When bone height is adequate but very narrow, the virtual guided sleeve is often placed too deeply into the ridge crest interfering with the seating of the surgical template. This case report of a patient exhibiting very narrow residual ridges due to severe resorption describes a new computer guided procedure using a single surgical template maintaining bone height and immediate restoration without a mucoperiosteal flap. The success of this technique is the result of innovative modifications in the software as well as instrumentation. Modifications include planning a different implant length virtually to raise the position of guide sleeves, alteration of drilling sequences, modifications of the start drill, incorporation of osteotomes, and use of an alternative implant seating mount. The combination of these methods allows for deeper site preparation and implant seating beyond the default settings, without any crestal bone reduction. These modifications not only make the guided concept possible for the entire preparation and seating procedures, but also allow for the slight removal of bone that would interfere with the implant seating through the surgical template without a mucoperiosteal flap. This new approach to computer guided surgery maintains prosthetic precision in the fabrication of a provisional restoration prior to implantation with minimal delivery adjustments using prefabricated conical abutments when placing implants at differing levels into the high narrow ridge.     

CAD/CAM联合游离腓骨肌皮瓣修复双侧下颌骨大范围骨缺损

目的:探讨恢复双侧下颌骨大范围骨缺损的解剖外形、重建患者咬合功能的有效方法。方法:对病变累及双侧下颌骨、需进行(或已进行)节段性骨切除术的15例患者行术前CT扫描,提取扫描数据,采用CAD/CAM快速原型技术行数字化颅颌面骨三维重建和下颌骨实体模型打印。在实体模型上设计截骨区间和钛网外形,数控成型机冲压钛网,使预成钛网与缺损区下颌骨外形完全一致。切取腓骨肌皮瓣,血管化游离移植联合预成钛网植入完成下颌骨缺损的修复重建。结果:15例患者腓骨肌皮瓣全部存活,创口愈合良好,下颌骨解剖外形包括自然弧度、曲率和高度恢复满意,同期修复者手术前后容貌无明显变化。结论:CAD/CAM快速原型技术联合游离腓骨肌皮瓣移植修复双侧下颌骨大范围节段性骨缺损,不仅可以最大限度地重建下颌骨的自然外形,维持患者容貌,也为种植体植入及咬合功能重建创造了良好条件。     

Inter-implant papilla reconstruction by means of a titanium guide

To help reconstruct the osseous support for a missing interdental papilla between two adjacent dental implant, an inter-implant papillary template has been conceived and fabricated. This titanium housing or stent carries the bone grafting mixture to protect the process of osteogenesis during the healing period. It eliminates the need for harvesting bone from another area in the oral cavity. Because the placement of this titanium component is bone at the first stage of surgery (that is, at the implant placement stage), there is no need for another surgical invasive procedure. This article describes the shape, manipulation, and the handling of the inter-implant papillary template.     

转化生长因子-β1基因治疗对种植体周骨质疏松的影响

目的探讨转化生长因子- β1（TGF- β1）基因治疗对种植体周围骨质疏松和骨缺损的影响。方法构建pCDNA3.1（+）- TGF- β1真核表达载体，转染大鼠骨髓间充质干细胞（BMSCs），并与聚乳酸- 羟基乙酸（PLGA）体外黏附。制备骨质疏松大鼠股骨植入钛种植体模型，将24只Wister大鼠随机分为实验组、对照组和空白对照组，实验组为在种植体周骨缺损处植入TGF- β1基因修饰BMSCs复合PLGA；对照组为BMSCs复合PLGA。术后第4和8周取标本行免疫组化和组织学分析，观察种植体周骨组织中TGF- β1的表达和组织学变化。结果术后第4周，实验组骨缺损区的TGF- β1表达较对照组和空白对照组明显；第8周实验组骨缺损区被新生骨充填，骨质较对照组和空白对照组明显改善。结论TGF- β1基因修饰BMSCs体内回植后，可在种植体周围骨组织内表达TGF- β1，并可以影响种植体周骨缺损的修复和骨质疏松状况。     

Alveolar bone formation at dental implant dehiscence defects following guided bone regeneration and xenogeneic freeze‐dried demineralized bone matrix

The present study evaluated rate and extent of alveolar bone formation in dental implant dehiscence defects following guided bone regeneration(GBR) and implantation of xenogeneic freeze‐dried demineralized bone matrix (xDBM). A total of 16 titanium plasma‐sprayed (TPS) and 16 hydroxyapatite‐coated (HA) titanium cylinder implants were inserted in 4 mongrel dogs following extraction of the mandibular premolar teeth. Four implant sites per jaw quadrant (2 TPS and 2 HA implant sites) were prepared into extraction sockets in each dog. Buccal alveolar bone was removed to create 3 x 5 mm dehiscence defects. Two jaw quadrants in separate animals received GBR, GBR+xDBM, xDBM (control), or gingival flap surgery alone (GFS; control). Thus, four conditions were available for each implant type (TPS or HA): GBR, GBR+xDBM; xDBM and GFS. The animals received fluorescent bone labels to allow observations of rate and extent of bone formation. Animals were sacrificed at 12 weeks postsurgery and block sections were harvested for histologic analysis. There were no apparent histologic differences between TPS and HA implant defects. GBR and GBR+xDBM resulted in almost complete bone closure of the dental implant dehiscence defect. Rate of bone formation appeared higher following GBR alone. Extent of bone formation appeared somewhat greater following GBR+xDBM; however, delayed. xDBM alone did not adequately resolve the bony defect. In conclusion, GBR results in rapid, clinically relevant bone closure of dental implant dehiscence defects. Adjunctive implantation of xDBM does not appear to significantly improve the healing response in the model used.     

计算机辅助设计（CAD）的种植手术导板的应用

目的：采用计算机辅助设计和制造种植手术的导板,较好地保证种植体植入在正确的位点和方向。方法：按照导板制做的数据要求,用CT扫描患者的上下颌骨,在获取颌骨数据后输入种植导板设计的软件中,并引导制造出患者颌骨的硅胶模型,在此模型上作出准确的种植手术导板并在手术中应用。结果：6例患者采用计算机辅助设计引导下制造的手术导板较好地完成了以修复为导向和最终获得良好位置的种植体的植入。结论：计算机辅助设计和制造种植手术的导板能在术前了解患者患者骨量,术中确定种植的位点、控制植入的方向、缩短了手术时间,具有很好的应用前景。     

Alveolar bone formation at dental implant dehiscence defects following guided bone regeneration and xenogeneic freeze-dried demineralized bone matrix.

The present study evaluated rate and extent of alveolar bone formation in dental implant dehiscence defects following guided bone regeneration (GBR) and implantation of xenogeneic freeze-dried demineralized bone matrix (xDBM). A total of 16 titanium plasma-sprayed (TPS) and 16 hydroxyapatite-coated (HA) titanium cylinder implants were inserted in 4 mongrel dogs following extraction of the mandibular premolar teeth. Four implant sites per jaw quadrant (2 TPS and 2 HA implant sites) were prepared into extraction sockets in each dog. Buccal alveolar bone was removed to create 3 x 5 mm dehiscence defects. Two jaw quadrants in separate animals received GBR, GBR + xDBM, xDBM (control), or gingival flap surgery alone (GFS; control). Thus, four conditions were available for each implant type (TPS or HA): GBR, GBR + xDBM; xDBM and GFS. The animals received fluorescent bone labels to allow observations of rate and extent of bone formation. Animals were sacrificed at 12 weeks postsurgery and block sections were harvested for histologic analysis. There were no apparent histologic differences between TPS and HA implant defects. GBR and GBR + xDBM resulted in almost complete bone closure of the dental implant dehiscence defect. Rate of bone formation appeared higher following GBR alone. Extent of bone formation appeared somewhat greater following GBR + xDBM; however, delayed. xDBM alone did not adequately resolve the bony defect. In conclusion, GBR results in rapid, clinically relevant bone closure of dental implant dehiscence defects. Adjunctive implantation of xDBM does not appear to significantly improve the healing response in the model used.     

Image data based reconstruction of the midface using a patient-specific implant in combination with a vascularized osteomyocutaneous scapular flap

BackgroundSecondary reconstructions in case of complex craniofacial defects of the midface, following radical tumour surgery, often require individualized surgical techniques. To achieve a satisfying functional and aesthetic outcome various anatomical aspects have to be considered such as the architecture of the bony structures as well as the very special shape of the orbit. Bone grafting is particularly challenging under these conditions, and one single graft type can hardly fulfil all anatomical demands.The presented method aims at combining a free microvascular bone graft and a preoperatively planned patient-specific alloplastic implant which takes into account all anatomic requirements as well as a functional rehabilitation including dental restoration.Case reportBy means of the described treatment approach, complex midfacial defects are reconstructed on the base of preoperative computer-assisted three-dimensional planning, a patient-specific prefabricated implant and a free vascularized bone transplant.A three-dimensional planning platform was used to create a mirror image of the unaffected contralateral side that was superimposed on the defect side referring to a virtual sagittal plane. The planned donor site of the scapula was then virtually matched into an ideal anatomic position considering all functional and aesthetical aspects, including a later implant based prosthodontic rehabilitation. By use of these virtual outlines, an individual titanium implant was manufactured to provide both for midfacial support and a graft fixture in a position, which was close to original. Intraoperative optical navigation was used to assess the accurate position of the implant with special regard to a correct reconstruction of the orbit. An implantologic rehabilitation could be achieved.ConclusionThe technique presented offers an ideal combination of a patient-specific alloplastic implant for the reconstruction of the very demanding orbital anatomy in combination with a scapular flap offering a sufficient bone stock for an implant based prosthodontic rehabilitation.     

Clinical application of stereolithographic surgical guides for implant placement: preliminary results

BACKGROUND: The success of implant-supported restorations requires detailed treatment planning, which includes the construction of a surgical guide. Recently, computer-aided rapid prototyping has been developed to construct surgical guides in an attempt to improve the precision of implant placement. The aim of the present study was to evaluate the match between the positions and axes of the planned and placed implants when a stereolithographic surgical guide is employed. METHODS: Six surgical guides used in four patients (three women, one man; age from 23 to 65 years old) were included in the study and 21 implants were placed. A radiographic template was fabricated and computer-assisted tomography (CT) was performed. The virtual implants were placed in the resulting 3-dimensional image. Using a stereolithographic machine, liquid polymer was injected and laser-cured according to the CT image data with the planned implants, generating three surgical guides, with increasing tube diameters corresponding to each twist drill diameter (2.2, 3.2, and 4.0 mm), for each surgical area. During the implant operation, the surgical guide was placed on the jawbone and/or the teeth. After surgery, a new CT scan was taken. Software was used to fuse the images of planned and placed implants, and the locations and axes were compared. RESULTS: On average, the match between the planned and the placed implant axes was within 7.25 degrees +/- 2.67 degrees ; the differences in distance between the planned and placed positions at the implant shoulder were 1.45 +/- 1.42 mm, and 2.99 +/- 1.77 mm at the implant apex. In all patients, a greater distance was found between the planned and placed positions at the implant apex than at the implant head. CONCLUSIONS: Clinical data suggest that computer-aided rapid prototyping of surgical guides may be useful in implant placement. However, the technique requires improvement to provide better stability of the guide during the surgery, in cases of unilateral bone-supported and non-tooth-supported guides. Further clinical studies, using greater number of patients, are necessary to evaluate the real impact of the stereolithographic surgical guide on implant therapy.     

3D打印多孔钽种植体对骨整合影响的实验研究

目的 研究多孔钽及多孔钛种植体对骨整合的影响。方法 通过计算机辅助设计方法建模,采用3D打印技术制备两种微孔参数相同的多孔材料种植体：多孔钽及多孔钛。在24只新西兰大白兔双侧股骨外踝处建立骨缺损模型,每只动物左右侧缺损随机分组,分别用多孔钽（实验组）和多孔钛（对照组）种植体进行修复。种植体植入后2、4、8周取材,进行大体观察和亚甲基蓝-酸性品红染色,观测种植体和骨界面的骨整合情况,采用推出实验测试种植体-骨界面结合强度。 结果 术后2、4、8周,两组材料界面的新生骨组织逐渐增加,出现新生骨小梁并向材料孔隙内生长;两组的成骨情况及种植体-骨组织界面结合强度的差异无统计学意义（P>0.05）。结论 3D打印的多孔钽能与骨组织形成早期的生物结合,具有与多孔钛相当的骨整合能力。     

Possibilities and limitations of implant placement by virtual planning data and surgical guide templates

The use of computer-aided surgical systems for dental implant bed preparation and implant placement results in an average precision within 1 mm of implant position and within 5 degrees of deviation for implant inclination. The accuracy of axis and implant position is significantly more precise with the three-dimensional surgical guide than with the free-hand method. The three-dimensional assessment of the restorative goal (radiopaque simulation of prosthesis with scanning template) allows virtual planning of implants, which enables optimized positioning of implants with surgical guide templates in oral surgery. If there is a clear indication for three-dimensional diagnostics, it should always be checked whether the data can be used as planning data for a surgical guide template, otherwise the chance for guided surgery remains unused. Since uncertainties still exist despite the use of a drilling template, it is recommended that the minimum safety distance from adjacent structures be maintained. The successful use of surgical guide templates requires comprehensive knowledge of and experience in using three-dimensional information for the virtual planning of implant position.     

钛种植体-羟基磷灰石复合型植入体修复下颌骨缺损的动物实验

本研究采用钛种植体-羟基磷友石复合型植入体植入20只狗下颌骨牙缺失区．并对植入体与宿主骨结合的过程进行了X线、组织形态学观察和复合型植入体抗折强度测试。结果表明：术后12周．复合型植入体的抗折强度比植入体内前高；复合型植入体植入后用微型钛夹板固定组与宿主骨呈骨性结合；用骨膜复位缝合固定组与宿主骨呈纤维骨性结舍。钛种植体与羟基磷灰结合牢固．负荷条件下无松脱落。复合型植入体不干扰骨愈合过程。作者认为该种复合型植入体可用于颌骨缺损后的牙颌整复．但植入体植入后早期的稳定固定则十分重要。