Evaluation of peri-implant bone defects on cone-beam computed tomography and the diagnostic accuracy of detecting these defects on panoramic images.

Purpose: This study was conducted to identify the typical sites and patterns of peri-implant bone defects on cone-beam computed tomography (CBCT) images, as well as to evaluate the detectability of the identified bone defects on panoramic images. Materials and Methods: The study population included 114 patients with a total of 367 implant fixtures. CBCT images were used to assess the presence or absence of bone defects around each implant fixture at the mesial, distal, buccal, and lingual sites. Based on the number of defect sites, the presentations of the peri-implant bone defects were categorized into 3 patterns: 1 site, 2 or 3 sites, and circumferential bone defects. Two observers independently evaluated the presence or absence of bone defects on panoramic images. The bone defect detection rate on these images was evaluated using receiver operating characteristic analysis. Results: Of the 367 implants studied, 167 (45.5%) had at least 1 site with a confirmed bone defect. The most common type of defect was circumferential, affecting 107 of the 167 implants (64.1%). Implants were most frequently placed in the mandibular molar region. The prevalence of bone defects was greatest in the maxillary premolar and mandibular molar regions. The highest kappa value was associated with the mandibular premolar region. Conclusion: The typical bone defect pattern observed was a circumferential defect surrounding the implant. The detection rate was generally higher in the molar region than in the anterior region. However, the capacity to detect partial bone defects using panoramic imaging was determined to be poor.

CBCT Images to an STL Model: Exploring the "Critical Factors" to Binarization Thresholds in STL Data Creation.

In-house fabrication of three-dimensional (3D) models for medical use has become easier in recent years. Cone beam computed tomography (CBCT) images are increasingly used as source data for fabricating osseous 3D models. The creation of a 3D CAD model begins with the segmentation of hard and soft tissues of the DICOM images and the creation of an STL model; however, it can be difficult to determine the binarization threshold in CBCT images. In this study, how the different CBCT scanning and imaging conditions of two different CBCT scanners affect the determination of the binarization threshold was evaluated. The key to efficient STL creation through voxel intensity distribution analysis was then explored. It was found that determination of the binarization threshold is easy for image datasets with a large number of voxels, sharp peak shapes, and narrow intensity distributions. Although the intensity distribution of voxels varied greatly among the image datasets, it was difficult to find correlations between different X-ray tube currents or image reconstruction filters that explained the differences. The objective observation of voxel intensity distribution may contribute to the determination of the binarization threshold for 3D model creation.

Three-dimensional structure of the facial canal and related blood vessels and nerves in the temporal bone.

PURPOSE: There are only limited anatomical data on nerves, veins, and arteries in the temporal bone. More detailed anatomical data are required to improve planning of treatments targeting the temporal bone region. Herein, we performed a detailed analysis of the facial canal (FC) and the related carotid artery and vein. METHODS: We examined the bony structure of the middle ear and FC, jugular foramen, and carotid canal in 30 Japanese elderly donor cadavers. Three-dimensional reconstruction of the canal structure was achieved using cone beam computed tomography, while macroscopic and histological analyses were also performed. RESULTS: The FC form was classified as either straight (28%) or bent (72%). There were significant differences in the diameter of the FC and the distance between the internal jugular vein, other FC branches, and the FC. Principal component analysis (PCA) was performed for the FC using 29 factors. Two principal components significantly explained 30.9% (component 1, 18.6%; component 2, 12.3%) of the FC. Histological observation showed numerous ganglion cells and shrunken neurons in the geniculate ganglion of the facial nerve of elderly samples. CONCLUSION: FC diameter is an important contributor to the relationship between the FC and the jugular foramen. The FC and the internal jugular vein are located close to each other, which is useful information for the trans-canal surgery of the otology. Furthermore, the geniculate ganglion contains numerous ganglion cells and shrunken neurons, which may affect the FC structure during bone matrix remodeling with aging.

Usefulness of preoperative computed tomography findings for airway management in patients with acute odontogenic infection: a retrospective study.

Odontogenic infection is more likely to affect the airway and interfere with intubation than non-odontogenic causes. Although anesthesiologists predict the difficulty of intubation and determine the method, they may encounter unexpected cases of difficult intubation. An inappropriate intubation can cause airway obstruction due to bleeding and edema by damaging the pharynx and larynx. This study was performed to determine the most important imaging findings indicating preoperative selection of an appropriate intubation method. This retrospective study included 113 patients who underwent anti-inflammatory treatment for odontogenic infection. The patients were divided into two groups according to the intubation method: a Macintosh laryngoscope (45 patients) and others (video laryngoscope and fiberscope) (68 patients). The extent of inflammation in each causative tooth, the severity of inflammation (S1-4), and their influence on the airway were evaluated by computed tomography. The causative teeth were mandibular molars in more than 90%. As the severity of inflammation increased, anesthesiologists tended to choose intubation methods other than Macintosh laryngoscopy. In the most severe cases (S4), anesthesiologists significantly preferred other intubation methods (33 cases) over Macintosh laryngoscopy (9 cases). All patients with S4 showed inflammation in the parapharyngeal space, and the airway was affected in 41 patients. The mandibular molars were the causative teeth most likely to affect the airway and surrounding region. In addition to clinical findings, the presence or absence of inflammation that has spread to the parapharyngeal space on preoperative computed tomography was considered an important indicator of the difficulty of intubation.

A deep transfer learning approach for the detection and diagnosis of maxillary sinusitis on panoramic radiographs.

To investigate the use of transfer learning when applying a deep learning source model from one institution (institution A) to another institution (institution B) for creating effective models (target models) for the detection of maxillary sinuses and diagnosis of maxillary sinusitis on panoramic radiographs. In addition, to determine appropriate numbers of training data for the transfer learning. Source model was created using 350 panoramic radiographs from institution A as training data. Transfer learning was performed by adding 25, 50, 100, 150, or 225 panoramic radiographs as training data from institution B to the source model; this yielded the target models T25, T50, T100, T150 and T225. Each model was then evaluated using test data that comprised 40 images from institution A, 30 images from institution B. The performance indices (recall, precision and F1 score) for detecting the maxillary sinuses by the source model exceeded 0.98 when using test data A from institution A, but they deteriorated when using test data B from institution B. In the evaluation of target models using test data B, model T25 showed improved detection performance (recall of 0.967). The diagnostic performance of model T50 for maxillary sinusitis exceeded 0.9 in sensitivity. Transfer learning, which involves applying a small amount of data to the source model, yielded high performances in detecting the maxillary sinuses and diagnosing the maxillary sinusitis on panoramic radiographs. This study serves as a reference when adapting source models to other institutions.

Morphological Observations of the Bony Canal Structure of the Eustachian Tube in Elderly Human Cadavers With Cone-Beam Computed Tomography and Principal Component Analysis.

OBJECTIVE: Anatomical information regarding the eustachian tube (ET) is limited; therefore, more detailed analytical data on ET structure is needed when planning surgical treatments involving the temporal bone. METHODS: We examined the bony structure of the middle ear and ET in 30 Japanese donor cadavers (71-97 years old at the time of death) both macroscopically and with cone-beam computed tomography. Each ET was reconstructed in 3 dimensions, and the structure and correlations of ET element measurements, identified via principal component analysis, were analyzed. RESULTS: Delineation between bony and cartilaginous zones appeared unclear, and the space between ET cartilage and the carotid canal was narrow. We observed stenosis of the ET bony canal in 43.3% of the specimens (n = 30). In 50% of the specimens, the position of the ET bony canal was depressed at the pharyngeal orifice of the auditory side of the tube, and the middle region was a roundish structure. The lateral and central regions of the bony canal were related to the ET bony canal structure. CONCLUSION: The close proximity of the ET bony canal to the carotid canal is an important anatomical and morphological finding. Pre-surgical 3D modeling of the middle ear structure, or at a minimum, of the central region of the middle ear canal, may provide useful information for planning procedures that involve the ET.

Root canal sealers affect artifacts on cone-beam computed tomography images.

The purpose of this study was to evaluate the appearance of artifacts by four types of root canal filling sealers on cone-beam computed tomography (CBCT) images. Thirty standardized tooth models were given the radiopacity equivalent to human teeth, and root canal preparation was performed using WaveOne Gold. Root canal filling by a single-point method was performed using WaveOne Gold gutta-percha points and four types of root canal sealers: AH Plus (AH), CANALS (CA), BioRoot RCS (BR), and MTA Fillapex (MTA). Samples were taken by periapical radiography at 60 kV and scanned by CBCT at three tube voltages (70, 85, and 100 kV). The gray-scale values (GVs) of the periapical radiographs were measured and the aluminum equivalents were calculated. On the CBCT axial images, the artifact and dentin area GVs were measured and the rate of change in the GV (RCGV) was calculated as follows: RCGV (%) = (dentin area GV - artifact GV)/dentin area GV × 100. High-density areas with artifacts on the CBCT images were also measured. On the periapical radiographs, the aluminum equivalent was largest for AH and smallest for MTA. On the CBCT images, AH showed the largest values for both RCGV and the high-density areas, while BR and MTA showed comparable values. Correlations were found between the radiopacity on the periapical radiographs and the degree of artifacts on the CBCT images. These findings suggest that the greater the contrast in the 2D image, the higher the artifacts in the 3D image.

DICOM segmentation and STL creation for 3D printing: a process and software package comparison for osseous anatomy.

BACKGROUND: Extracting and three-dimensional (3D) printing an organ in a region of interest in DICOM images typically calls for segmentation as a first step in support of 3D printing. The DICOM images are not exported to STL data immediately, but segmentation masks are exported to STL models. After primary and secondary processing, including noise removal and hole correction, the STL data can be 3D printed. The quality of the 3D model is directly related to the quality of the STL data. This study focuses and reports on the DICOM to STL segmentation performance for nine software packages. METHODS: Multidetector row CT scanning was performed on a dry human mandible with two 10-mm-diameter bearing balls as a phantom. The DICOM image file was then segmented and exported to an STL file using nine different commercial/open-source software packages. Once the STL models were created, the data (file) properties and the size and volume of each file were measured, and differences across the software packages were noted. Additionally, to evaluate differences between the shapes of the STL models by software package, each pair of STL models was superimposed, with the observed differences between their shapes characterized as the shape error. RESULTS: The data (file) size of the STL file and the number of triangles that constitute each STL model were different across all software packages, but no statistically significant differences were found across software packages. The created ball STL model expanded in the X-, Y-, and Z-axis directions, with the length in the Z-axis direction (body axis direction) being slightly longer than that in the other directions. The mean shape error between software packages of the mandibular STL model was 0.11 mm, but there was no statistically significant difference between them. CONCLUSIONS: Our results revealed that there are some differences between the software packages that perform the segmentation and STL creation of the DICOM image data. In particular, the features of each software package appeared in the fine and thin areas of the osseous structures. When using these software packages, it is necessary to understand the characteristics of each.

The use and performance of artificial intelligence applications in dental and maxillofacial radiology: A systematic review.

OBJECTIVES: To investigate the current clinical applications and diagnostic performance of artificial intelligence (AI) in dental and maxillofacial radiology (DMFR). METHODS: Studies using applications related to DMFR to develop or implement AI models were sought by searching five electronic databases and four selected core journals in the field of DMFR. The customized assessment criteria based on QUADAS-2 were adapted for quality analysis of the studies included. RESULTS: The initial electronic search yielded 1862 titles, and 50 studies were eventually included. Most studies focused on AI applications for an automated localization of cephalometric landmarks, diagnosis of osteoporosis, classification/segmentation of maxillofacial cysts and/or tumors, and identification of periodontitis/periapical disease. The performance of AI models varies among different algorithms. CONCLUSION: The AI models proposed in the studies included exhibited wide clinical applications in DMFR. Nevertheless, it is still necessary to further verify the reliability and applicability of the AI models prior to transferring these models into clinical practice.

Effect of resin composite filler on digital imaging fiber-optic transillumination.

Using a trans-illumination device that applies digital imaging fiber-optic transillumination (DIFOTI) technology, which involves the use of transmitted near-infrared laser light for inspection, the effect of composite resin (CR) restoration of a tooth on caries detection was evaluated. A cavity was formed in a tooth of the lower jaw cut from the specimen, experimental CRs with various filler rates were filled, and the influence of the filler on the obtained image was investigated. On the near-infrared images, the lightness differences between the CR-restored portion and the tooth portion were measured. The translucency parameter (TP) value and the correlation between the lightness differences and TP value of the CRs were investigated. The experimental results showed that the greater rate of macro-filler is, the lighter image and larger TP value. In other words, CR with hybrid filler to increase the TP value is less likely to affect caries detection by DIFOTI.

Frequency and type of incidentally detected radiodensities in the maxillary sinus: a retrospective analysis using cone beam computed tomography (CBCT).

OBJECTIVES: To evaluate the frequency, location, and characteristics of radiodensities in the maxillary sinus using cone beam computed tomography (CBCT). MATERIALS AND METHODS: All CBCT scans with a large field of view with both maxillary sinuses entirely visible were initially screened. Patients were included, if there was no suspicion of sinus pathology and no history of surgical intervention/trauma in the sinus region. The location and shape of the radiodensities were evaluated in axial, coronal, and sagittal CBCT views. The findings were correlated with age, gender, condition of the sinus mucosa, and status of the dentition. RESULTS: A total of 169 patients (338 maxillary sinuses) were included. Radiodensities were found in 35 sinuses (10.4%) of 28 patients (16.6%) with a mean age of 32.0 years. Most of the 35 affected sinuses had one radiodensity (19/54.2%). The radiodensities were typically located at the sinus floor (22/62.9%). Of the sinuses presenting with radiodensities, 17 (48.6%) were exhibiting reactive changes of the Schneiderian membrane. The presence of periodontal pathology was found to be associated with the presence of radiodensities. Age and sinus pathology were influencing factors on the shape of radiodensities, and the status of the dentition was an influencing factor on the number of lesions. CONCLUSIONS: One-sixth of the patients analyzed had incidentally diagnosed radiodensities in their maxillary sinuses. As almost 50% of the sinuses with radiodensities exhibited a form of chronic rhinosinusitis, the diagnosed ectopic calcifications may have formed as a result of mucosal changes of inflammatory origin. The presence of periodontal pathology was associated with a higher incidence of radiodensities. Nevertheless, this finding has to be interpreted with some caution due to the limited sample size available. CLINICAL RELEVANCE: Incidentally detected radiodensities in the maxillary sinus are not an infrequent finding in CBCT scans of asymptomatic patients, and are located typically on the sinus floor. Future studies are needed to assess the clinical significance of these findings especially with regard to planned surgical interventions in the posterior maxilla.

Deep-learning classification using convolutional neural network for evaluation of maxillary sinusitis on panoramic radiography.

OBJECTIVES: To apply a deep-learning system for diagnosis of maxillary sinusitis on panoramic radiography, and to clarify its diagnostic performance. METHODS: Training data for 400 healthy and 400 inflamed maxillary sinuses were enhanced to 6000 samples in each category by data augmentation. Image patches were input into a deep-learning system, the learning process was repeated for 200 epochs, and a learning model was created. Newly-prepared testing image patches from 60 healthy and 60 inflamed sinuses were input into the learning model, and the diagnostic performance was calculated. Receiver-operating characteristic (ROC) curves were drawn, and the area under the curve (AUC) values were obtained. The results were compared with those of two experienced radiologists and two dental residents. RESULTS: The diagnostic performance of the deep-learning system for maxillary sinusitis on panoramic radiographs was high, with accuracy of 87.5%, sensitivity of 86.7%, specificity of 88.3%, and AUC of 0.875. These values showed no significant differences compared with those of the radiologists and were higher than those of the dental residents. CONCLUSIONS: The diagnostic performance of the deep-learning system for maxillary sinusitis on panoramic radiographs was sufficiently high. Results from the deep-learning system are expected to provide diagnostic support for inexperienced dentists.

Analysis of the development of human foetal nasal turbinates using CBCT imaging.

PURPOSE: The morphological structure of the nasal cavity (NC) is important for endoscopic surgical treatment. The location of nasal turbinates, including the superior turbinate (ST), middle turbinate (MT) and inferior turbinate (IT), are well presented during the formation of the human NC in cone beam CT (CBCT) images. There is a complex relationship between the nasal sinuses, the maxillary sinus (MS), ethmoidal sinus and sphenoid sinus, during formation of the NC structure at the morphological level. There is a need to clearly define the relationships of these nasal elements at the ossification level, during development. METHODS: We investigated the three-dimensional construction of human foetal NC elements, including ST, MT, IT and vomer, using CBCT images from 16 weeks gestation (E16) to E31 (25 foetuses) and compared it to histochemical observations (E25). RESULTS: At the stage of ossification, the studied elements are elongated in the posterior region near the sphenoidal bone, showing that the locations of the ST, MT, and IT are important during formation of the NC. CBCT analysis revealed that the horizontal and vertical directions of nasal turbinates affect the formation of the human NC. CONCLUSION: The location and elongated development of the MT is one of the most important elements for NC formation. The relationship between the nasal sinus and nasal turbine at the level of ossification may provide useful information in clinical treatment of children.

Cone-beam computed tomography and anatomical observations of normal variants in the mandible: variant dentists should recognize.

Many types of cone-beam computed tomography (CBCT) have recently been developed and are being used in many dental clinics. CBCT has significantly changed imaging diagnosis in dentistry by showing detailed structures in multiple dimensions with high spatial resolution. This allows dentists to confirm what cannot be recognized with conventional two-dimensional images, such as small neurovascular canals, the buccolingual location of structures/lesions, and the three-dimensional shapes of hard tissue structures. The aim of this study was to review the normal variants of detailed anatomical structures in relation with the mandibular canal by comparing the previous reports and anatomical evaluations. These structures are likely to be observed on CBCT images by dental practitioners prior to dental procedures involving the mandibular teeth and bone. Understanding the relationship of these structures is useful for dental practitioners and oral surgeons to reduce the possibility of causing damage and patient discomfort during dental procedures.

Clinical guidelines for dental cone-beam computed tomography.

Dental cone-beam computed tomography (CBCT) received regulatory approval in Japan in 2000 and has been widely used since being approved for coverage by the National Health Insurance system in 2012. This imaging technique allows dental practitioners to observe and diagnose lesions in the dental hard tissue in three dimensions (3D). When performing routine radiography, the examination must be justified, and optimal protection should be provided according to the ALARA (as low as reasonably achievable) principles laid down by the International Commission on Radiological Protection. Dental CBCT should be performed in such a way that the radiation exposure is minimized and the benefits to the patient are maximized. There is a growing demand for widespread access to cutting-edge health care through Japan's universal health insurance system. However, at the same time, people want our limited human, material, and financial resources to be used efficiently while providing safe health care at the least possible cost to society. Japan's aging population is expected to reach a peak in 2025, when most of the baby boomer generation will be aged 75 years or older. Comprehensive health care networks are needed to overcome these challenges. Against this background, we hope that this text will contribute to the nation's oral health by encouraging efficient use of dental CBCT.

CBCT imaging of the alveolar bone structure in maxilla of elderly donor cadavers and PCA analysis.

There is an important bone matrix with remodelling between dentate and edentulous samples of the human maxilla for bone metabolism. Cone beam computed tomography (CBCT) is useful for structural analysis of bone. The objective of this study was to investigate morphological data of donor cadavers in detail using CBCT imaging and principal component analysis (PCA). We analysed 38 donor cadavers using a CBCT apparatus. The analytical results defined differences in skull measurement parameters and dentate and edentulous levels using PCA. We observed cortical bone, trabecular bone, and the distance from the bottom of the maxillary sinus to the oral mucosa at a right angle to the palatal plane of the first molar region between dentate and edentulous samples of the human maxilla using CBCT imaging. In the dentate sample of the maxilla, component 1 was defined by negative contributions from gender (-0.84) and age (-0.54) to positive contributions such as cortical bone structure (CBS, 0.68) and trabecular bone structure (TBS, 0.50). There was a difference in CBS between dentate and edentulous human maxilla samples. This study of CBCT data provides useful basal information for planning dental implant surgery using PCA.

Morphological observation and CBCT of the bony canal structure of the groove and the location of blood vessels and nerves in the palatine of elderly human cadavers.

PURPOSE: The greater and lesser palatine nerves and vessels supply the hard and soft palates, and the roots of these vessels and nerves run through a bony structure. However, the arrangement of blood vessels in the maxilla requires attention during clinical treatments, but detailed morphological information about changes in the greater and lesser palatine arteries and nerves during aging is unavailable. We therefore need detailed investigations of the morphology of the donor cadaver palatine using cone-beam computed tomography (CBCT) and macroscopic observations. METHODS: We investigated 72 donor cadavers using macroscopic segmentation and CBCT. The results' analysis examined differences in skull measurement parameters and differences between dentate and edentulous cases. RESULTS: The greater palatine artery and nerve showed different macroscopic arrangements in dentate and edentulous cadavers. We also classified three types of bony structures of the nerve and vessel roots in the molar regions of the palatine using CBCT images: the shallow groove, deep groove, and flat groove. The deep groove is the deepest of the three and is remarkable in edentulous elderly cadavers. CONCLUSION: This study of macroscopic and CBCT data provides information useful for planning dental implant surgeries and autogenous bone harvesting.

Observation of the temporal crest canal in the mandibular ramus by cone beam computed tomography and macroscopic study.

PURPOSE: The mandibular ramus is regarded as a relatively safe zone for a sagittal splitting osteotomy or for harvesting bone during implant treatment. The only important anatomical structure is the mandibular canal. The mandible has some anatomical variants that need to be recognized, such as a bifid mandibular canal, a retromolar canal, and rarely a temporal crest canal (TCC). In this study, cadaver mandibles were used to evaluate the TCC in the mandibular ramus using cone beam computed tomography (CBCT). METHODS: Altogether, 90 sites on 48 mandibles from Japanese cadavers were examined in this study. The CBCT volumetric images were acquired for areas of 79 mm[Formula: see text] 71 mm. Three-dimensional observation of the images was undertaken to estimate the frequency, position of the orifices, and canal continuity. The cadaver mandibles in which the TCCs were observed were dissected from the inner surface to confirm the contents. RESULTS: Five TCCs (5.6 %) were observed in 90 observation areas. At least one TCC was confirmed in four (8.3 %) of 48 mandibles. Two types of TCC were recognized. Dissection revealed that they contained neurovascular bundles. CONCLUSION: Three-dimensional diagnosis is essential prior to surgical procedures in the mandibular ramus because unexpected blood vessels may be present that may cause bleeding or complications during the surgery.

Observing the bony canal structure of the human maxillary sinus in Japanese cadavers using cone beam CT.

We observed the location of the posterior superior alveolar artery (PSAA) and nerve at the macroscopic level between the maxillary sinus (MS) and surrounding bone of the anterior region of the maxilla. This study was completed using cone beam computed tomography (CBCT) imaging of 19 human cadavers with 38 sides of Japanese origin (ranging in age from 59-94 years, mean 77.7 +/- 9.8 years) that were prepared for this study. The bony canal structure of the inner surface of the maxilla was clearly apparent in our results, and the bony canals were classified into three types according to the structure along the course of the PSAA: canal-like, ditch-shaped tunnel and fragmented, and the lest sides were undefined. Calcitonin gene-related peptide (CGRP)-positive fibers were identified along the PSAA in the bony canal of the maxilla by immunohistochemistry. The presence of the bony structure and CGRP-positive nerve fibers along the PSAA suggests that there is risk to the PSAA during surgery involving graft implant in the floor of the maxillary sinus.

Evaluation of the blood and nerve supply patterns in the molar region of the maxillary sinus in Japanese cadavers.

The maxillary sinus (MS) in the maxilla bone is located near the orbit, the nasal cavity and the oral cavity; however, the positioning of the constituent bones is complex. The posterior superior alveolar branches of the maxillary artery and nerve are distributed in the lateral wall of the MS. The courses of these blood vessels and nerves are restricted by the morphology of the craniofacial bones, and the landmarks used in dental implant treatment of these courses mainly run along the lateral wall of the MS. In this study, 19 human cadavers with 34 sides of Japanese origin (ranging in age from 59-94 years, mean 77.7 +/- 9.8 years) were prepared for measurement of the MS, the superior alveolar artery and the infraorbital artery using cone beam computed tomography (CBCT). The posterior superior alveolar artery (PSAA) of the lateral wall of the MS can be classified into one of three groups based on the supply pattern. In the greatest number of cadavers, the PSAA ran mainly to the lateral surface of the zone between the superior border of the alveolar foramen and the inferior border of the MS (53.0%, 18/34). In others, the PSAA ran to the zone between the infraorbital foramen and the superior border of the alveolar foramen (17.6%, 6/34); in a third group, the PSAA ran to the zone between the inferior border of the MS and the greater palatine foramen (23.5%, 8/34). The lest of two sides are spread out in this area (5.9%, 2/34). CBCT is the most accurate tool to evaluate important anatomical parameters, such as the distance of the blood supply, for the implant of grafts in the floor of the MS during surgical procedures.