MRI of the temporo-mandibular joint: which sequence is best suited to assess the cortical bone of the mandibular condyle? A cadaveric study using micro-CT as the standard of reference

Objective: To determine the best suited sagittal MRI sequence out of a standard temporo-mandibular joint (TMJ) imaging protocol for the assessment of the cortical bone of the mandibular condyles of cadaveric specimens using micro-CT as the standard of reference. Methods: Sixteen TMJs in 8 human cadaveric heads (mean age, 81years) were examined by MRI. Upon all sagittal sequences, two observers measured the cortical bone thickness (CBT) of the anterior, superior and posterior portions of the mandibular condyles (i.e. objective analysis), and assessed for the presence of cortical bone thinning, erosions or surface irregularities as well as subcortical bone cysts and anterior osteophytes (i.e. subjective analysis). Micro-CT of the condyles was performed to serve as the standard of reference for statistical analysis. Results: Inter-observer agreements for objective (r = 0.83-0.99, P < 0.01) and subjective (κ = 0.67-0.88) analyses were very good. Mean CBT measurements were most accurate, and cortical bone thinning, erosions, surface irregularities and subcortical bone cysts were best depicted on the 3D fast spoiled gradient echo recalled sequence (3D FSPGR). Conclusion: The most reliable MRI sequence to assess the cortical bone of the mandibular condyles on sagittal imaging planes is the 3D FSPGR sequence. Key Points : • MRI may be used to assess the cortical bone of the TMJ. • Depiction of cortical bone is best on 3D FSPGR sequences. • MRI can assess treatment response in patients with TMJ abnormalitie

MRI of the temporo-mandibular joint: which sequence is best suited to assess the cortical bone of the mandibular condyle? A cadaveric study using micro-CT as the standard of reference

OBJECTIVE: To determine the best suited sagittal MRI sequence out of a standard temporo-mandibular joint (TMJ) imaging protocol for the assessment of the cortical bone of the mandibular condyles of cadaveric specimens using micro-CT as the standard of reference. METHODS: Sixteen TMJs in 8 human cadaveric heads (mean age, 81 years) were examined by MRI. Upon all sagittal sequences, two observers measured the cortical bone thickness (CBT) of the anterior, superior and posterior portions of the mandibular condyles (i.e. objective analysis), and assessed for the presence of cortical bone thinning, erosions or surface irregularities as well as subcortical bone cysts and anterior osteophytes (i.e. subjective analysis). Micro-CT of the condyles was performed to serve as the standard of reference for statistical analysis. RESULTS: Inter-observer agreements for objective (r = 0.83-0.99, P < 0.01) and subjective (κ = 0.67-0.88) analyses were very good. Mean CBT measurements were most accurate, and cortical bone thinning, erosions, surface irregularities and subcortical bone cysts were best depicted on the 3D fast spoiled gradient echo recalled sequence (3D FSPGR). CONCLUSION: The most reliable MRI sequence to assess the cortical bone of the mandibular condyles on sagittal imaging planes is the 3D FSPGR sequence. KEY POINTS: MRI may be used to assess the cortical bone of the TMJ. • Depiction of cortical bone is best on 3D FSPGR sequences. • MRI can assess treatment response in patients with TMJ abnormalities

Principles of cartilage tissue engineering in TMJ reconstruction

Diseases and defects of the temporomandibular joint (TMJ), compromising the cartilaginous layer of the condyle, impose a significant treatment challenge. Different regeneration approaches, especially surgical interventions at the TMJ's cartilage surface, are established treatment methods in maxillofacial surgery but fail to induce a regeneration ad integrum. Cartilage tissue engineering, in contrast, is a newly introduced treatment option in cartilage reconstruction strategies aimed to heal cartilaginous defects. Because cartilage has a limited capacity for intrinsic repair, and even minor lesions or injuries may lead to progressive damage, biological oriented approaches have gained special interest in cartilage therapy. Cell based cartilage regeneration is suggested to improve cartilage repair or reconstruction therapies. Autologous cell implantation, for example, is the first step as a clinically used cell based regeneration option. More advanced or complex therapeutical options (extracorporeal cartilage engineering, genetic engineering, both under evaluation in pre-clinical investigations) have not reached the level of clinical trials but may be approached in the near future. In order to understand cartilage tissue engineering as a new treatment option, an overview of the biological, engineering, and clinical challenges as well as the inherent constraints of the different treatment modalities are given in this paper

Pathogens and host immunity in the ancient human oral cavity.

Calcified dental plaque (dental calculus) preserves for millennia and entraps biomolecules from all domains of life and viruses. We report the first, to our knowledge, high-resolution taxonomic and protein functional characterization of the ancient oral microbiome and demonstrate that the oral cavity has long served as a reservoir for bacteria implicated in both local and systemic disease. We characterize (i) the ancient oral microbiome in a diseased state, (ii) 40 opportunistic pathogens, (iii) ancient human-associated putative antibiotic resistance genes, (iv) a genome reconstruction of the periodontal pathogen Tannerella forsythia, (v) 239 bacterial and 43 human proteins, allowing confirmation of a long-term association between host immune factors, 'red complex' pathogens and periodontal disease, and (vi) DNA sequences matching dietary sources. Directly datable and nearly ubiquitous, dental calculus permits the simultaneous investigation of pathogen activity, host immunity and diet, thereby extending direct investigation of common diseases into the human evolutionary past

Postnatal development, aging, and degeneration of the temporomandibular joint in humans, monkeys, and rats

http://babel.hathitrust.org/cgi/pt?id=mdp.39015038558022;view=2up;ui=fullscreen#page/n0/mode/2u

Resorption pattern and radiographic diagnosis of invasive cervical resorption

Summary The aim of this study was to evaluate, whether and how the histologic structure of invasive cervical resorption (external granulomas) affect their clinical radiographic diagnosis. For this purpose, nine more or less intact extracted teeth, of which intraoral radiographs were available, were processed for examination in the scanning electron (SEM) and light microscope. From some of the specimens non-decalcified ground sections were prepared and some were decalcified for preparation of histologic sections. Five teeth were scanned in an X-ray microtomography (microCT) device and digitally reconstructed in three dimensions. Three histologic characteristics, namely (1) the location and extension of the resorptive defect, (2) the size of the communication with the periodontium, and (3) the amount of mineralized substitution tissue formed in the lesion affected the radiographic diagnosis. At early and advanced stages, invasive cervical resorption had encircled the pulp cavities, however, without destroying the innermost dentin. Even if the dentinal wall adjacent to the pulp was histologically intact and thick, this important diagnostic feature frequently could not be recognized in conventional radiographs. Also, the communication between the resorptive lesion and the periodontium often was not visible radiographically, although it could always be identified in the microscopic evaluation, particularly at early stages when it proved to be very small. Invasive cervical resorption lesions containing large amounts of mineralized substitution tissue were difficult to recognize and, therefore, could easily be overseen. Thus, three features which are deemed essential for the differential diagnosis of invasive cervical resorption were not readily apparent in conventional radiographs. From these three features, the dentinal wall against the pulp cavity and the communication to the peri-odontium were, however, clearly visible in the microCT reconstructions

Tooth Agenesis

Tooth agenesis denotes a condition where teeth are missing due to a developmental failure. According to severity, this malformation can be subdivided into hypodontia, oligodontia and anodontia. With a frequency of 20–30%, tooth agenesis is the most prevalent dental dysplasia, but not all teeth are equally affected. Familial occurrence and concordance in twins indicate potential genetic causes. Thus far, mutations could be identified for the genes MSX1, PAX9 and AXIN2. All result in oligodontia. It is assumed that the defects cause haploinsufficiency, reducing the functional gene products below a critical level, which is required for normal odontogenesis. Both hypodontia and oligodontia can occur as an isolated dental malformation or in combination with defects in other organs, for example the skin and its appendages. Such syndromes can result from genetic defects affecting MSX1 and the EDA signalling pathway. In the case of isolated hypodontia, associations have been found with sequence variants of several genes

Factors affecting degeneration in human temporomandibular joints as assessed histologically.

The influence of sex, age, tooth loss, and articular disc position on temporomandibular joint (TMJ) degeneration was evaluated in specimens collected at autopsy from 15 women and 38 men ranging in age from 15 to 92 yr. The position of the articular discs was classified as normal or abnormal, tooth loss was both counted and categorized. Degenerative changes of the articular tissues were assessed histologically and quantified, taking into account both the severity of structural alterations and their extension along the articular surface. This was recorded separately in the condyle, disc, and temporal component, three latero-medial joint regions, and putative load-bearing and non-load-bearing surfaces. Analysis of covariance with repeated measures served for testing contributing factors. It showed that the effects of sex and the number of missing teeth were insignificant, whereas age up to about 55-60 yr and reduction of dental arch length proved to be the most important factors. Load-bearing seemed to play a significant role mainly at younger ages, and the effect of disc position was significant, when internal derangement was combined with reduction of dental arch length. Thus, rising severity of TMJ degenerative changes appears to be associated primarily with increasing age. In addition, it may also depend on mechanical factors, in particular loss of molar support and, to a minor degree, abnormal disc position

Biocompatibility of Beta-tricalcium phosphate root replicas in porcine tooth extraction sockets - a correlative histological, ultrastructural, and x-ray microanalytical pilot study.

This investigation studies porcine tissue response in tooth extraction sockets treated with root replicas made out of Beta-tricalcium phosphate (Beta-TCP; Beta-Ca(3)(PO(4))(2)) granules, molded and held together by thermal fusion of a thin film of polyglycolic-polylactic acid copolymer. Six left mandibular third incisors (n (1)/4 6) of experimental pigs are treated with the root replicas and four contralateral incisors are used as nontreated controls (n (1)/4 4). Two animals each were killed at 20, 40, and 60 weeks of observation periods. The mandibular jaw segments were prepared in toto for light microscopy by resin embedding and serial ground sectioning. Additionally, one Beta-TCP-treated socket at 60 weeks was thoroughly investigated by correlative light, electron microscopic and electron probe X-ray microanalysis to assess the bio-absorbability and host removal of the replica material from the implant site. The extraction wounds of the animals healed satisfactorily with very little histologically observable differences in the healing pattern of the test and control sites. The Beta-TCP was completely removed from extracellular sites, but at 60 weeks, remnants of it were found in the cytoplasm of multinucleated giant cells. The root replicas made out of Beta-TCP were biocompatible and bioabsorbable. Osseous healing occurred both in the test and control sockets, but the healing process was delayed due to the presence of Beta-TCP particles