Effects of food hardness on temporomandibular joint osteoarthritis: Qualitative and quantitative micro-CT analysis of rats in vivo.

BACKGROUND: Temporomandibular joint osteoarthritis (TMJ-OA) is a degenerative joint disease in which quantitative analysis based on magnetic resonance image (MRI) or cone-beam computed tomography (CBCT) remains limited. Moreover, the long-term effects of soft food on the adaptive condylar remodeling process in TMJ-OA remain unclear. This study aimed to assess the effects of food hardness on adaptive condylar remodeling in a healthy TMJ, TMJ-OA, and controlled TMJ-OA. METHODS: Complete Freund's adjuvant (CFA) was used for TMJ-OA induction and Link-N (LN) for TMJ repair. Eighteen mature rats were randomly divided into six groups: (1) control/normal diet (Ctrl-N); (2) control/soft diet (Ctrl-S); (3) TMJ-OA/normal diet (CFA-N); (4) TMJ-OA/soft diet (CFA-S); (5) Link-N-controlled TMJ-OA/normal diet (LN-N); and (6) Link-N-controlled TMJ-OA/soft diet (LN-S). Micro-CT was performed 14, 21, and 28 days after CFA injection to analyze the bone volume, bone volume fraction (BVF), bone mineral density (BMD), and trabecular bone number and thickness (Tb.N, Tb.Th). MRI and histological imaging were performed to support the analysis. RESULTS: Under CFA treatment, the BVF and BMD decreased significantly (p < 0.01) and later recovered to normal. However, more significant improvements occurred in normal-diet groups than soft-diet groups. Additionally, bone volume changes were more predictable in the normal-diet groups than in the soft-diet groups. The normal-diet groups presented a significant decrease and increase in the Tb.N and Tb.Th, respectively (p < 0.05), while the Tb.N and Tb.Th in the soft-diet groups remained largely unchanged. Furthermore, a significantly higher frequency of irregularities on the condylar articular surface was found in the soft-diet groups. CONCLUSIONS: Compared with a soft diet, a normal diet may be beneficial for preserving condyle articular surface and directing bone remodeling in TMJ-OA rats.

A systematic review and meta-analysis of the surgical outcomes in patients with osteochondroma of mandibular condyle.

Many options exist in the diagnosis and management of condylar osteochondroma. The purpose of this study was to provide a congregate information concerning treatment of the osteochondroma involving the mandibular condyle. The search was conducted in PubMed, Google Scholar, Semantic Scholar, and Cochrane database until February 2022. Twenty-seven studies were included for the final review. The review included 439 patients who underwent surgical management for mandibular condylar osteochondroma. The position of osteochondroma was mentioned in 13 studies. Preauricular, retromandibular, endaural, submandibular, transzygomatic, and intraoral approaches were used for approaching the tumor. Surgical techniques included resection, conservative condylectomy, and total condylectomy. Concomitant orthognathic surgery was performed along with tumor resection in 19 studies. In the entire review, the recurrence rate was 0.22% (1/439). The results of the meta-analysis showed that 2 studies reported significant malocclusion events after surgical therapy. Total joint replacement after tumor resection has a higher improvement in maximal mouth opening (8 mm) compared with vertical ramus osteotomy and no reconstruction groups, which have similar improvements (6 mm). The mainstay of treatment of osteochondroma is surgical excision either as condylectomy or conservative condylectomy. Among the various reconstruction modalities, total joint replacement showed better improvement in mouth opening. Adjunct procedures like orthodontic and orthognathic surgery have an important role in holistic management of severe cases. The treating surgeon must choose the surgical procedures in a pragmatic way.

Differential effects of high-physiological oestrogen on the degeneration of mandibular condylar cartilage and subchondral bone.

The striking predilection of temporomandibular disorders (TMD) in women, especially during gonad-intact puberty or reproductive years, indicates that oestrogen plays an important role in the progression of TMD, but the underlying mechanism remains unclear. In this study, unilateral anterior crossbite (UAC) was used to create temporomandibular joint osteoarthritis (TMJ OA) models in rats, while 17ß-estradiol (E2) injections were applied to mimic patients with high-physiological levels of oestrogen. Micro-CT scanning, histological staining and real-time PCR assays were preformed to observe the degenerative changes in the mandibular condylar cartilage and subchondral bone. The results showed that obvious degradation was found in the condylar cartilage and subchondral bone of rats with UAC procedure, including decreased cartilage thickness, loss of extracellular matrix, increased apoptotic chondrocytes and expression of pro-inflammatory and catabolic factors, decreased bone mineral density and increased osteoclast activity. E2 supplements aggravated the condylar cartilage degradation but reversed the abnormal bone resorption in the subchondral bone induced by UAC. Our results revealed that high-physiological oestrogen plays a destructive role in condylar cartilage but a protective role in subchondral bone at the early stage of TMJ OA. These dual and distinct effects should be given serious consideration in future OA treatments.

Relationship between the cranial base and the mandible in artificially deformed skulls.

OBJECTIVES: There is controversy regarding the relationship between mandibular position and alterations of the cranial base that provoke a more anterior location of the glenoid fossa. Artificially deformed skulls display marked alterations of the cranial base. This study evaluates mandibular changes as function of the morphology of the cranial base in these skulls. MATERIAL AND METHODS: A geometric morphometric study was performed on lateral cephalometric X-rays of three groups of skulls: 32 with anteroposterior deformity, 17 with circumferential deformity and 39 with no apparent deformity. RESULTS: In artificially deformed skulls, the cranial base was deformed causing the mandibular condyle to be in a more anterior position. There was a complete remodelling of the mandible involving narrowing and elongation of the mandibular ramus, rotation of the corpus of the mandible and increased vertical height of the symphysis. Forward displacement did not occur. Integration between mandible and cranial base is not altered by deformation of the skull. CONCLUSIONS: Deformity of the cranial vault exerts an influence on the mandible, supporting the theory of modular units in complete integration. This also supports the theory that mandibular prognathism is a multifactorial result and not a direct effect of displacement of the cranial base.

Analysis of MRI findings in minimum invasive treatment for habitual temporomandibular joint dislocation by autologous blood injection around the temporomandibular joint capsule.

The aim of this study was to investigate magnetic resonance imaging (MRI) findings following autologous blood injection (ABI) for habitual temporomandibular joint (TMJ) dislocation. MRI was performed one hour and four and twelve weeks after ABI, revealing three types of significant findings. The first type was similar to hematoma and/or joint effusion in the articular capsule of the TMJ (type I). The second showed sporadic and diffuse T2 emphasis around the TMJ capsule (type II). The third involved a decreased range of condyle movement compared to before ABI (type III). Furthermore, we analyzed the three types of significant MRI findings. At one hour after ABI, type I was Grade 0 in 0 of 14 patients, Grade 1 in 8, Grade 2 in 2, and Grade 3 in 4. Type II was seen in 9 of the 14 cases and type III in 8. After twelve weeks, all cases of type I were Grade 0, no type II cases were evident, and type III was seen in 11 cases. Injecting autologous blood into surrounding TMJ tissues is an important factor in ABI. Minimally invasive treatment for habitual TMJ dislocation using ABI around the TMJ capsule appears to represent a very effective and safe treatment.

Histopathologic evaluation of autologous blood injection to the temporomandibular joint.

PURPOSE: Chronic recurrent temporomandibular joint dislocation is treated by surgical and nonsurgical techniques described in the literature. However, these techniques have some complications noted in the literature. Recently, the autologous blood injection in temporomandibular joint technique has been applied to treat chronic temporomandibular joint dislocation. However, to date, there has been no study that describes the histopathologic effects of autologous blood injection within the literature. The aim of this study was to evaluate the histopathologic effects of autologous blood injection in rabbit temporomandibular joints. METHODS: Eight New Zealand white rabbits underwent bilateral autologous blood injection. After the injection, mandibles were fixed by orthodontic brackets and elastics for 24 hours. One rabbit was included in the control group. After 1-month follow-up period, the animals were killed. Temporomandibular joints were dissected and sent to histological examination. RESULTS: Only fibrin accumulations were seen in the tissue samples. There was no evidence of degeneration in the joint cartilage, and a fibrous bed was not formed in the injected regions. CONCLUSIONS: Although the procedure has successful results in the literature, a fibrous bed that is supposed to be the outcome of the treatment was not seen in the tissue samples. According to this study, therefore, the autologous blood injection does not change the structure of temporomandibular joint in rabbits.

Association between condylar morphology and changes in bony microstructure and sub-synovial inflammation in experimental temporomandibular joint arthritis.

BACKGROUND: In juvenile idiopathic arthritis involvement of the temporomandibular joints (TMJs) is often associated with mandibular growth deviations. The relation between the growth deviations and severity of the inflammation, condylar shape, the micro-architecture, and the quality of the bone has not previously been investigated. This paper studies the effect on the bony structures in mandibular condylar development in rabbits with antigen-induced arthritis. METHODS: Included were 42 juvenile rabbits with ovalbumin-induced arthritis of the TMJs treated with intraarticular saline, intraarticular etanercept or subcutaneous etanercept. A TMJ from each animal was scanned using micro-computed tomography and structural parameters were calculated. Three-dimensional reconstructions of the mandibular condyle were scored blindly as normal or abnormal. TMJs were stratified for condylar morphology and were evaluated against data on trabecular structural parameters, inflammation, degree of mineralization, overall mandibular growth, and mineral apposition rate. RESULTS: Abnormal morphology were seen in 15/32 animals available for data analysis. Erosions were an uncommon finding. Abnormal morphology was strongly related to the degree of inflammation. The trabecular separation was larger in group with abnormal morphology than in the group with normal morphology. Abnormal condylar morphology was not associated with overall mandibular growth. No differences were observed in mineral apposition rate. No differences in structural parameters were seen according to treatment modality. CONCLUSION: We showed that severe inflammation in the TMJs during mandibular development was associated with morphological changes in the mandibular condyle. These changes were predominantly seen at the macro-morphological level and only very few differences were structural.

A clinical, MRI, and EMG analysis comparing the efficacy of twin blocks and flat occlusal splints in the management of disc displacements with reduction.

Internal derangement of the temporomandibular joint (TMJ) is characterized by an abnormal disc-condyle relationship. Of all the various treatment modalities used in the management of disc displacements, flat occlusal and anterior repositioning splints are the most commonly used. Myofunctional appliances (such as bite-jumping appliances) are also advocated to treat anterior disc displacements. The present study compares the efficacy of twin blocks with conventional flat occlusal splints in patients with anterior disc displacement with reduction using clinical examination, MRI, and EMG. The sample consisted of 20 subjects between 12 and 20 years of age, who were randomly divided into two groups of 10 patients each: Group 1 was treated with twin blocks, while group 2 was treated using maxillary flat occlusal splints. The twin block is more effective in relieving joint pain, diminishing joint dysfunction, reducing joint clicking, and eliminating muscle tenderness in patients with anterior disc displacement with reduction as compared to the occlusal splint.

Spatial orientation in bone samples and Young's modulus.

Bone mass is the most important determinant of the mechanical strength of bones, and spatial structure is the second. In general, the spatial structure and mechanical properties of bones such as the breaking strength are direction dependent. The mean intercept length (MIL) and line frequency deviation (LFD) are two methods for quantifying directional aspects of the spatial structure of bone. Young's modulus is commonly used to describe the stiffness of bone, which is also a direction-dependent mechanical property. The aim of this article is to investigate the relation between MIL and LFD on one hand and Young's modulus on the other. From 11 human mandibular condyles, 44 samples were taken and scanned with high-resolution computer tomography equipment (micro-CT). For each sample the MIL and LFD were determined in 72602 directions distributed evenly in 3D space. In the same directions Young's modulus was determined by means of the stiffness tensor that had been determined for each sample by finite element analysis. To investigate the relation between the MIL and LFD on one hand and Young's modulus on the other, multiple regression was used. On average the MIL accounted for 69% of the variance in Young's modulus in the 44 samples and the LFD accounted for 72%. The average percentage of variance accounted for increased to 80% when the MIL was combined with the LFD to predict Young's modulus. Obviously MIL and LFD to some extent are complementary with respect to predicting Young's modulus. It is known that directional plots of the MIL tend to be ellipses or ellipsoids. It is speculated that ellipsoids are not always sufficient to describe Young's modulus of a bone sample and that the LFD partly compensates for this.

Relationship between TNF-alpha and TUNEL-positive chondrocytes in antigen-induced arthritis of the rabbit temporomandibular joint.

BACKGROUND: Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate biotin nick end-labeling (TUNEL) staining is a widely accepted method for the detection of DNA fragmentation in nuclei of apoptotic cells. Tumor necrosis factor (TNF)-alpha is closely associated with changes in condylar cartilage and modulates apoptosis in various tissues including cartilage. The aim of this study was to investigate the relationship between apoptotic chondrocytes and TNF-alpha in a rabbit model of arthritis. METHOD: Unilateral temporomandibular joint (TMJ) arthritis was induced in 20 adult New Zealand White rabbits. From 1 day to 6 weeks after the induction of arthritis, immunohistochemical analysis for TNF-alpha and TUNEL was performed. RESULTS: In condylar cartilage, TNF-alpha-positive cells and TUNEL-positive cells were localized together. TNF-alpha-positive chondrocytes seemed to precede TUNEL-positive cells. CONCLUSIONS: The results of the present study suggest that TNF-alpha may be involved in apoptosis and/or apoptotic necrosis of chondrocytes as TMJ arthritis progresses from the acute to chronic stage.

The effect of irradiation and hyperbaric oxygenation (HBO) on extracellular matrix of the condylar cartilage after mandibular distraction osteogenesis in the rabbit.

The effects of irradiation and hyperbaric oxygenation (HBO) on the extracellular matrix of condylar cartilage after mandibular distraction were evaluated. Unilateral distraction was performed on 19 rabbits. Five study groups were included: control, low- and high-dose irradiation, and low- and high-dose irradiation groups with HBO. Additionally, four temporomandibular joints (TMJ) were used as control material. The high-dose irradiated animals were given in the TMJ 22.4 Gy/4 fractions irradiation (equivalent to 50 Gy/25 fractions). Low-dose irradiation group received a 2.2 Gy dosage. Two groups were also given preoperatively HBO 18 x 2.5ATA x 90 min. After a two-week distraction period (14 mm lengthening) and four-week consolidation period the TMJs were removed. Proteoglycan (PG) distribution of the extracellular matrix was evaluated using safranin O staining and collagen I and II using immunohistochemistry. The organization of fibrillar network was studied by polarized light microscopy. On the operated side of the control group and on the unoperated side in all, except for high-dose irradiated group, PG distribution and fibrillar network were normal appearing. In the irradiated groups, with or without HBO, the cartilaginous layer was partially or totally devoid of PG and the network structure was severely damaged. In conclusion, irradiation in conjunction with the pressure applied by distraction causes severe damage to extracellular matrix of condylar cartilage.

Bifid mandibular condyle: archaeological case report of a rare anomaly.

In this paper, an archaeological case of unilateral bifid mandibular condyle is presented. This uncommon anomaly is characterized by a division of the mandibular condylar head. In this case, the left condyle was divided into two articulating surfaces oriented mediolaterally; two articular facets on the anterior wall of the glenoid fossa for the double condyle were observed. The morphological and radiological analysis do not show any evidence of injuries or degenerative pathology. Taking into account the two main causes of bifid condyle suggested in the literature (traumatic and developmental), an embryopathy by teratogenic agents is proposed as a possible aetiology of the bifid condyle reported here.

Formation of a mandibular condyle in vitro by tissue engineering.

PURPOSE: Mandibular reconstructive procedures often produce significant donor site morbidity. Recently, the use of minimally invasive techniques has been reported for mandibular reconstruction with decreased morbidity at the primary operative site. To date, these techniques have not addressed the graft donor site. We hypothesize that tissue-engineering techniques may be used to fabricate bone and thereby eliminate donor site morbidity. METHODS: Porcine mesenchymal stem cells (pMSCs) were isolated from the bone marrow of 3 Yucatan minipigs and grown in standard culture flasks. When they became near-confluent, cells were detached and replated with the addition of osteogenic supplements. A model of a porcine mandibular condyle was made and used to fabricate porous polymer scaffolds from biodegradable poly DL-lactic-co-glycolic acid (PLGA). Differentiated osteoblasts were transferred to the PLGA scaffold and cultured for 6 weeks in a rotational oxygen-permeable bioreactor system. The cultured constructs, consisting of scaffold and cells, were evaluated by gross, radiologic, and histologic examinations. RESULTS: The engineered constructs were white and hard and had a shape that closely resembled that of the model condyle. Plain radiographs demonstrated that the radiodensity of the construct was between that of the normal condyle and that of control scaffolds. Histologically, bone was observed on the entire surface of the PLGA scaffolds with an average thickness of 0.03 mm. Bone was not observed in the control scaffolds. CONCLUSION: In this pilot study, autologous tissue-engineered bone constructs were successfully made by combining biodegradable polymers and pMSCs.

A functional approach to the TMJ disorders.

This manuscript describes our conservative approach to treatment of TMJ disorders. The method we use had been suggested by Rocabado - its aims are: joint distraction by the elimination of compression, restoration of physiologic articular rest, mobilization of the soft tissues, and whenever possible, to improve the condyle-disk-glenoid fossa relationship. To support these claims two clinical cases are presented where the non-invasive therapy was successful. The results obtained confirm the validity of this functional approach.

Effect of mandibular distraction osteogenesis on temporomandibular joint after previous irradiation and hyperbaric oxygenation.

The purpose was to evaluate the effect of mandibular distraction osteogenesis (DO) on condylar cartilage after radiotherapy and hyperbaric oxygenation (HBO). Unilateral DO was performed on low- and high-dose irradiated rabbits with or without accompanying HBO, and non-irradiated animals. High-dose irradiated animals were given irradiation in the temporomandibular joint (TMJ) equivalent to 50 Gy in 25 fractions. Low-dose irradiated rabbits received scattered irradiation of 10% of that of high-dose irradiated animals. After radiotherapy, some of the animals were given HBO 18 times at 2.5 ATA for 90 min/day. One month after completion of radiotherapy, distraction osteotomy with distractor placement was performed. After a latency period, distraction was started at the rate of 1 mm/day, continued for 2 weeks, and the regenerate was allowed to consolidate for 1 month. Condyles of non-operated rabbits served as controls. Histological changes were more evident on the distracted than on the non-distracted side. In distracted, non-irradiated animals, condylar cartilage changes were minor and probably clinically insignificant. In irradiated rabbits, condylar cartilage changes on the lengthened side were severe, and often cartilage was either totally or partially sealed off by bone. Condylar heads were morphologically deformed. Even low doses of irradiation resulted in notable changes on the operated side, and HBO did not prevent disadvantageous effects.

Regeneration ad integrum of the condyle head in a patient with temporomandibular disorders.

A 14-year-old who had suffered from a beta-hemolytic streptococcus infection presented with serious temporomandibular disorders, including a reabsorption of the condyle head on the right side, and reabsorption in the cavern of the left side. Her masticatory muscles were electronically deprogramed, achieving a mandibular position supported by a relaxed musculature. The patient's signs and symptoms subsequently disappeared. Study of the magnetic resonance image a year later clearly showed a regeneration ad integrum of the condyle head and a spontaneous reinsertion of the articular disk. The results suggest the need for use of electronic elements in order to treat patients with temporomandibular disorders effectively.

Effects of transforming growth factor-beta 1 and interleukin-1 alpha on matrix synthesis in osteoarthritic cartilage of the temporo-mandibular joint in aged mice.

Osteoarthritic lesions were observed in the mandibular condyle cartilage of mice aged 7 months and older. These lesions appeared as fibrillations along the articular surface and were accompanied by reduced extracellular matrix synthesis and chondrocyte proliferation. Explants of mandibular condyle cartilage were cultured in serum-free BGJb medium supplemented with ascorbic acid (300 micrograms/ml), penicillin (100 U/ml) and streptomycin (100 micrograms/ml) for up to 72 h. Cultures were further supplemented with either hTGF-beta 1 (0.1-5.0 ng/ml) or human IL-1 alpha (40 U/ml). [3H]thymidine (2 microCi/ml) and [35S]SO4 (10 microCi/ml) were added to the culture medium for the last 24 h of culture and incorporation into DNA and sulfated proteoglycans, respectively, studied. The results indicated that protein and DNA contents, [3H]thymidine and [35S]SO4 incorporation, as well as the specific activity of alkaline phosphatase, were increased by TGF-beta 1. Addition of 1.0 or 5.0 ng/ml hTGF-beta 1 to the cultures for 48 h, had the most stimulatory effect on matrix synthesis and cell proliferation, whereas 0.1 ng/ml hTGF-beta 1 appeared to be inhibitory when compared to controls. Increased [35S]SO4 labeling of chondrocyte clusters was observed by autoradiography in tissue sections from cultures treated with TGF-beta 1 (1.0 and 5.0 ng/ml). In contrast, IL-1 alpha exerted inhibitory effects on cell proliferation and matrix synthesis. However, it induced the activity of acid phosphatase in these cultures. The results of the present study show that IL-1 alpha had catabolic effect on his tissue, while TGF-beta 1 enhanced proliferation and induced synthetic activity of the cartilage cells. Such action by TGF-beta suggests the existance of a possible repair process in osteoarthritic cartilage of the temporo-mandibular joint of aged mice.

In vivo deterioration of proplast-teflon temporomandibular joint interpositional implants: a scanning electron microscopic and energy-dispersive X-ray analysis.

The surgical treatment of internal derangements of the temporomandibular joint (TMJ) often involves disc removal. Alloplastic interpositional implants for disc replacement have been widely used to avoid the development of osteoarthritic changes in the TMJ. This study reports the in vivo wear characteristics of Proplast-Teflon (Vitek Inc, Houston, TX) interpositional implants (PTIPI) in 12 patients who had their implants for 13 to 71 (mean 54.6 +/- 5.8 SEM) months. In all cases, changes in the condyle and fossa were found resulting from resorption and replacement of the articulating bone by granulomatous tissue. All implants showed significant signs of wear, such as thinning, cracks, and tears, and overt perforations were seen in five cases. Scanning electron microscopy (SEM) combined with energy-dispersive x-ray microanalysis (EDAX) showed numerous microfragments of the PTIPI in the peri-implant soft tissues. Microfragments were demonstrated by their aluminum content. In addition to the inflammatory foreign-body reaction, it is suggested that there also were toxic and hypersensitivity reactions to aluminum involved in the pathogenesis of the bone destruction.

Multicenter evaluation of temporomandibular joint Proplast-Teflon disk implant.

Seven oral and maxillofacial surgeons from all U.S. American Association of Oral and Maxillofacial Surgeons districts participated in a retrospective study of Proplast II Teflon interpositional implants that were placed after meniscectomy in 680 TMJs (465 patients) and followed from 6 to 76 months. At longest follow-up a relatively high number (85.9%) 584 of 680 implants were in place with an average weighted follow-up of nearly 32 months. Of these 584 joints, a very high number, 540, (92.4%) were asymptomatic, however, 224 asymptomatic and 25 symptomatic joints with the implants in place exhibited some degree of condyle resorption that included 45 with malocclusion. In the worst case scenario, if condylar resorption is indicative of a worn Proplast II Teflon interpositional implant, then 364 (54%) of the 680 implants may fail. Failure rates per year range from Vitek's reported 3% to an average 18% clinician report in the literature. Higher rates are reported by individual clinicians, and our recent in vitro wear tests of Proplast II Teflon interpositional implants suggest an in vivo service life of only 3 years. Because no one has reported follow-up beyond 5 years, the long term performance and survival of any of these implants is doubtful. Asymptomatic patients should be evaluated yearly with tomography, CT, or MRI. Symptomatic patients should be evaluated every 4 to 6 months. Implant removal should be recommended if occlusal changes or condyle/fossa articular bone changes are active past the time of expected remodeling from surgery. This report summarizes the success/failure incidence from the literature and makes recommendations on follow-up, removal, and repair surgery.

Growth of the skeletal units of the rat mandible in acute renal failure experimental model.

A study of the effect of acute renal failure (ARF) on the growth of the skeletal units of the mandible was performed. Male Wistar rats weighing 35-40 g were assigned to three groups. One of the groups received a basal choline-deficient diet ad libitum. A second group was pair-fed with the first one and was given a basal diet supplemented with 0.35 g choline chloride/100 g of diet. The third group was fed a basal diet plus 0.35 g choline chloride/100 g of diet ad libitum and used as the normal control. Body length, renal function parameters and measurements of the mandible were recorded at the end of a 12-day period on the different diets. Food intake and body weight were recorded every day. Plasma urea and creatinine concentrations markedly increased over the first 12 days of exposure to a choline-deficient diet. Significant increases in urine volume and significant depressions in urine osmolality were also observed. The average body weight and body length gains for rats given the choline-deficient diet were lower than those of control rats. There were no significant differences between the average body weight and body length of pair-fed and normal rats. All skeletal measurements of the mandible of the choline-deficient group differed significantly from those of the control group. These differences varied between 7% and 30%. The skeletal units of the mandible of the pair-fed group did not differ significantly from ad libitum controls. This study suggests that this rat model can be used for the investigation of the different alterations observed in uremia.(ABSTRACT TRUNCATED AT 250 WORDS)