Three-Dimensional Guided Zygomatic Implant Placement after Maxillectomy

Zygomatic implants are used in patients with maxillary defects to improve the retention and stability of obturator prostheses, thereby securing good oral function. Prosthetic-driven placement of zygomatic implants is even difficult for experienced surgeons, and with a free-hand approach, deviation from the preplanned implant positions is inevitable, thereby impeding immediate implant-retained obturation. A novel, digitalized workflow of surgical planning was used in 10 patients. Maxillectomy was performed with 3D-printed cutting, and drill guides were used for subsequent placement of zygomatic implants with immediate placement of implant-retained obturator prosthesis. The outcome parameters were the accuracy of implant positioning and the prosthetic fit of the obturator prosthesis in this one-stage procedure. Zygomatic implants (n = 28) were placed with good accuracy (mean deviation 1.73 ± 0.57 mm and 2.97 ± 1.38° 3D angle deviation), and in all cases, the obturator prosthesis fitted as pre-operatively planned. The 3D accuracy of the abutment positions was 1.58 ± 1.66 mm. The accuracy of the abutment position in the occlusal plane was 2.21 ± 1.33 mm, with a height accuracy of 1.32 ± 1.57 mm. This feasibility study shows that the application of these novel designed 3D-printed surgical guides results in predictable zygomatic implant placement and provides the possibility of immediate prosthetic rehabilitation in head and neck oncology patients after maxillectomy

Novel finite element-based plate design for bridging mandibular defects:Reducing mechanical failure

Introduction: When the application of a free vascularised flap is not possible, a segmental mandibular defect is often reconstructed using a conventional reconstruction plate. Mechanical failure of such reconstructions is mostly caused by plate fracture and screw pull-out. This study aims to develop a reliable, mechanically superior, yet slender patient-specific reconstruction plate that reduces failure due to these causes. Patients and Methods: Eight patients were included in the study. Indications were as follows: fractured reconstruction plate (2), loosened screws (1) and primary reconstruction of a mandibular continuity defect (5). Failed conventional reconstructions were studied using finite element analysis (FEA). A 3D virtual surgical plan (3D-VSP) with a novel patient-specific (PS) titanium plate was developed for each patient. Postoperative CBCT scanning was performed to validate reconstruction accuracy. Results: All PS plates were placed accurately according to the 3D-VSP. Mean 3D screw entry point deviation was 1.54 mm (SD: 0.85, R: 0.10–3.19), and mean screw angular deviation was 5.76° (SD: 3.27, R: 1.26–16.62). FEA indicated decreased stress and screw pull-out inducing forces. No mechanical failures appeared (mean follow-up: 16 months, R: 7–29). Conclusion: Reconstructing mandibular continuity defects with bookshelf-reconstruction plates with FEA underpinning the design seems to reduce the risk of screw pull-out and plate fractures

Prefabricated fibula free flaps in reconstruction of maxillofacial defects:Two cases of transplanting a fractured fibula

BACKGROUND: The two-staged prefabricated vascularized fibula free flap is used in maxillofacial reconstruction. We describe the possible cause and management of two cases of fibula fracture after implant placement.METHODS: The patients were treated with two-stage reconstruction with a prefabricated vascularized fibula free flap. Six dental implants were placed in both fibulas. Fibula fractures occurred during the osseointegration period before the second procedure. The reconstruction was continued as planned.RESULTS: Both fibulas fractured in the distal segment, possibly due to a thinner cortex more distally. Harvesting of a fractured fibula flap is more difficult than normally due to callus formation and fibrosis. Both transplants became fully functional with extended healing and additional surgery.CONCLUSION: The fracture apparently did not compromise the vascularisation of the fibula and proved still sufficient for successful harvest and transfer of the flap. The patient should be made aware that additional corrective surgery may be indicated.</p

Prefabricated fibula free flaps in reconstruction of maxillofacial defects:Two cases of transplanting a fractured fibula

BACKGROUND: The two-staged prefabricated vascularized fibula free flap is used in maxillofacial reconstruction. We describe the possible cause and management of two cases of fibula fracture after implant placement.METHODS: The patients were treated with two-stage reconstruction with a prefabricated vascularized fibula free flap. Six dental implants were placed in both fibulas. Fibula fractures occurred during the osseointegration period before the second procedure. The reconstruction was continued as planned.RESULTS: Both fibulas fractured in the distal segment, possibly due to a thinner cortex more distally. Harvesting of a fractured fibula flap is more difficult than normally due to callus formation and fibrosis. Both transplants became fully functional with extended healing and additional surgery.CONCLUSION: The fracture apparently did not compromise the vascularisation of the fibula and proved still sufficient for successful harvest and transfer of the flap. The patient should be made aware that additional corrective surgery may be indicated.</p

In vivo quantification of photosensitizer concentration using fluorescence differential path-length spectroscopy:influence of photosensitizer formulation and tissue location

In vivo measurement of photosensitizer concentrations may optimize clinical photodynamic therapy (PDT). Fluorescence differential path-length spectroscopy (FDPS) is a non-invasive optical technique that has been shown to accurately quantify the concentration of Foscan (R) in rat liver. As a next step towards clinical translation, the effect of two liposomal formulations of mTHPC, Fospeg (R) and Foslip (R), on FDPS response was investigated. Furthermore, FDPS was evaluated in target organs for head-and-neck PDT. Fifty-four healthy rats were intravenously injected with one of the three formulations of mTHPC at 0.15 mgkg(-1). FDPS was performed on liver, tongue, and lip. The mTHPC concentrations estimated using FDPS were correlated with the results of the subsequent harvested and chemically extracted organs. An excellent goodness of fit (R-2) between FDPS and extraction was found for all formulations in the liver (R-2 = 0.79). A much lower R-2 between FDPS and extraction was found in lip (R-2 = 0.46) and tongue (R-2 = 0.10). The lower performance in lip and in particular tongue was mainly attributed to the more layered anatomical structure, which influences scattering properties and photosensitizer distribution. (C) 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.JBO. 17.6.067001

In vivo quantification of photosensitizer fluorescence in the skin-fold observation chamber using dual-wavelength excitation and NIR imaging

A major challenge in biomedical optics is the accurate quantification of in vivo fluorescence images. Fluorescence imaging is often used to determine the pharmacokinetics of photosensitizers used for photodynamic therapy. Often, however, this type of imaging does not take into account differences in and changes to tissue volume and optical properties of the tissue under interrogation. To address this problem, a ratiometric quantification method was developed and applied to monitor photosensitizer meso-tetra (hydroxyphenyl) chlorin (mTHPC) pharmacokinetics in the rat skin-fold observation chamber. The method employs a combination of dual-wavelength excitation and dualwavelength detection. Excitation and detection wavelengths were selected in the NIR region. One excitation wavelength was chosen to be at the Q band of mTHPC, whereas the second excitation wavelength was close to its absorption minimum. Two fluorescence emission bands were used; one at the secondary fluorescence maximum of mTHPC centered on 720 nm, and one in a region of tissue autofluorescence. The first excitation wavelength was used to excite the mTHPC and autofluorescence and the second to excite only autofluorescence, so that this could be subtracted. Subsequently, the autofluorescence-corrected mTHPC image was divided by the autofluorescence signal to correct for variations in tissue optical properties. This correction algorithm in principle results in a linear relation between the corrected fluorescence and photosensitizer concentration. The limitations of the presented method and comparison with previously published and validated techniques are discussed

The use of 3D virtual surgical planning and computer aided design in reconstruction of maxillary surgical defects

PURPOSE OF REVIEW: The present review describes the latest development of 3D virtual surgical planning (VSP) and computer aided design (CAD) for reconstruction of maxillary defects with an aim of fully prosthetic rehabilitation. The purpose is to give an overview of different methods that use CAD in maxillary reconstruction in patients with head and neck cancer.RECENT FINDINGS: 3D VSP enables preoperative planning of resection margins and osteotomies. The current 3D VSP workflow is expanded with multimodal imaging, merging decision supportive information. Development of more personalized implants is possible using CAD, individualized virtual muscle modelling and topology optimization. Meanwhile the translation of the 3D VSP towards surgery is improved by techniques like intraoperative imaging and augmented reality. Recent improvements of preoperative 3D VSP enables surgical reconstruction and/or prosthetic rehabilitation of the surgical defect in one combined procedure.SUMMARY: With the use of 3D VSP and CAD, ablation surgery, reconstructive surgery, and prosthetic rehabilitation can be planned preoperatively. Many reconstruction possibilities exist and a choice depends on patient characteristics, tumour location and experience of the surgeon. The overall objective in patients with maxillary defects is to follow a prosthetic-driven reconstruction with the aim to restore facial form, oral function, and do so in accordance with the individual needs of the patient.</p

The use of 3D virtual surgical planning and computer aided design in reconstruction of maxillary surgical defects

PURPOSE OF REVIEW: The present review describes the latest development of 3D virtual surgical planning (VSP) and computer aided design (CAD) for reconstruction of maxillary defects with an aim of fully prosthetic rehabilitation. The purpose is to give an overview of different methods that use CAD in maxillary reconstruction in patients with head and neck cancer. RECENT FINDINGS: 3D VSP enables preoperative planning of resection margins and osteotomies. The current 3D VSP workflow is expanded with multimodal imaging, merging decision supportive information. Development of more personalized implants is possible using CAD, individualized virtual muscle modelling and topology optimization. Meanwhile the translation of the 3D VSP towards surgery is improved by techniques like intraoperative imaging and augmented reality. Recent improvements of preoperative 3D VSP enables surgical reconstruction and/or prosthetic rehabilitation of the surgical defect in one combined procedure. SUMMARY: With the use of 3D VSP and CAD, ablation surgery, reconstructive surgery, and prosthetic rehabilitation can be planned preoperatively. Many reconstruction possibilities exist and a choice depends on patient characteristics, tumour location and experience of the surgeon. The overall objective in patients with maxillary defects is to follow a prosthetic-driven reconstruction with the aim to restore facial form, oral function, and do so in accordance with the individual needs of the patient

Prefabricated fibula free flaps in reconstruction of maxillofacial defects:Two cases of transplanting a fractured fibula

BACKGROUND: The two-staged prefabricated vascularized fibula free flap is used in maxillofacial reconstruction. We describe the possible cause and management of two cases of fibula fracture after implant placement.METHODS: The patients were treated with two-stage reconstruction with a prefabricated vascularized fibula free flap. Six dental implants were placed in both fibulas. Fibula fractures occurred during the osseointegration period before the second procedure. The reconstruction was continued as planned.RESULTS: Both fibulas fractured in the distal segment, possibly due to a thinner cortex more distally. Harvesting of a fractured fibula flap is more difficult than normally due to callus formation and fibrosis. Both transplants became fully functional with extended healing and additional surgery.CONCLUSION: The fracture apparently did not compromise the vascularisation of the fibula and proved still sufficient for successful harvest and transfer of the flap. The patient should be made aware that additional corrective surgery may be indicated.</p