Influence of the internal anatomy on the leakage of root canals filled with thermoplastic technique.

OBJECTIVES: The aim of this paper is to evaluate the influence of the internal anatomy on the leakage of root canals filled with the thermoplastic technique. MATERIALS AND METHODS: The upper central incisors (UCI) and mesial roots of the lower molars (MRLM) (n = 12 each) were tested regarding leakage using the gas-enhanced permeation test (GEPT) after root filling. The quality of the root fillings was assessed using micro-computed tomography (µCT) by superimposing scans before and after treatment to calculate unfilled volume. The calculated void volume was compared between the groups and correlated to the measured leakage values. Data were analyzed using t test and Pearson's correlation tests (p < 0.05). RESULTS: The mean void volume did not differ between UCI and MRLM (13.7 ± 6.2% vs. 14.2 ± 6.8%, respectively). However, significantly more leakage was evident in the MRLM (p < 0.001). While the leakage correlated highly to the void volume in the MRLM group (R 2 = 0.981, p < 0.001), no correlation was found in UCI (R 2 = 0.467, p = 0.126). CONCLUSION: MRLM showed higher leakage values, which correlated to the void volume in the root canal fillings. CLINICAL RELEVANCE: Care should always be taken while doing root canal treatments, but attention to teeth with known/expected complex root canal anatomy should be considered.

A longitudinal study of changes in psychosocial well-being during orthognathic treatment.

The aim was to evaluate changes in the psychosocial well-being of orthognathic surgery patients (n=22) during treatment and to compare results with those of adults not requiring orthognathic treatment (n=22). Patient data were collected before treatment (T0), after the first orthodontic examination (T1), three times during treatment (T2-T4), and 1 year after surgery (T5). In this article, only data corresponding to patient stage T5 are reported for the control subjects. Participants filled in a structured diary and the modified version of the Secord and Jourard body image questionnaire, the Orthognathic Quality of Life Questionnaire, the Rosenberg Self-Esteem Scale, and the Acceptance and Action Questionnaire II. Moreover, patients filled in the Symptom Checklist-90. After the placement of orthodontic appliances (T2), orthognathic quality of life, self-esteem, and psychological flexibility were lower and psychiatric symptoms increased. Improvements were observed from T2 to T5 in orthognathic quality of life, body image, self-esteem, psychological flexibility, and psychiatric symptoms. Treatment resulted in improvements from T0 to T5 in orthognathic quality of life, body image, and psychiatric symptoms. At T5, patient psychosocial well-being was comparable to or even better than that of control subjects. Orthognathic treatment seems to support psychological well-being, but the range of individual variation is wide.

The effect of adenoidectomy on occlusal development and nasal cavity volume in children with recurrent middle ear infection.

OBJECTIVES: The aim of the study was to examine the effect of adenoidectomy on occlusal/dentoalveolar development and nasal cavity volume in children who underwent tympanostomy tube insertion with or without adenoidectomy due to recurrent episodes of middle ear infection. METHODS: This prospective controlled study consisted of two randomly allocated treatment groups of children, younger than 2 years, who had underwent more than 3-5 events of middle ear infection during the last 6 months or 4-6 events during the last year. At the mean age of 17 months tympanostomy tube placement without adenoidectomy (Group I, n=63) tympanostomy tube placement with adenoidectomy (Group II, n=74) was performed. At the age of 5 years 41 children of the original Group I (14 females, 27 males, mean age 5.2 yrs, SD 0.17) and 59 children of the original Group II (17 females, 42 males, mean age 5.2 yrs, SD 0.18) participated in the re-examination, which included clinical orthodontic examination defining morphological and functional craniofacial status and occlusal bite index to measure upper dental arch dimensions. Acoustic rhinometry and anterior rhinomanometry was made by otorhinolaryngologist at the same day. RESULTS: No statistically significant differences were found between the groups in the frequencies of morphological or functional characteristics or upper dental arch measurements or in the minimal cross-sectional areas or inspiratory nasal airway resistance measurements. CONCLUSION: Combining adenoidectomy with tympanostomy tube insertion in the treatment of recurrent middle ear infection at an early age (under the age of 2 years) does not seem to make any difference in occlusal development in primary dentition at the age of 5 years as compared to tympanostomy tube insertion only. Since adenoid size was not evaluated, the findings do not allow interpretation that hypertrophic adenoids should not be removed in children with continuous mouth breathing or sleep disordered breathing.

A texture analysis method for MR images of airway dilator muscles: a feasibility study.

OBJECTIVES: Airway dilator muscles play an important role in the analysis of breathing-related symptoms, such as obstructive sleep apnoea. Texture analysis (TA) provides a new non-invasive method for analysing airway dilator muscles. In this study, we propose a TA methodology for airway dilator muscles and prove the robustness of this method. METHODS: 15 orthognathic surgery patients underwent 3-T MRI. Computerized TA was performed on 20 regions of interest (ROIs) in the patients' airway dilator muscles. 53 texture parameters were calculated for all ROIs. The robustness of the TA method was analysed by altering the locations, sizes and shapes of the ROIs. RESULTS: Our study shows that there is significant difference in TA results as the size or shape of ROI changes. The change of location of the ROI inside the studied muscle does not affect the TA results. CONCLUSIONS: The TA method is valid for airway dilator muscles. We propose a methodology in which the number of co-occurrence parameters is reduced by using mean values from four different directions (0°, 45°, 90° and 135°) with pixel spacing of 1 pixel.

Upper airway changes in Pierre Robin sequence from childhood to adulthood.

OBJECTIVES: To investigate pharyngeal airway changes in patients with Pierre Robin sequence (PRS) longitudinally from childhood to adulthood. SETTING AND SAMPLE POPULATION: Cleft Lip and Palate Unit, Clinic of Orthodontics, University of Zurich. Twenty-four patients born between 1970 and 1990 with non-syndromic PRS. MATERIALS AND METHODS: Lateral cephalograms at age 5 (T1), 10 (T2), 15 (T3) and 20 (T4) years were available. Variables describing pharyngeal airway dimensions, soft palate morphology, tongue and hyoid position, skeletal morphology and head posture were assessed. RESULTS: A significant increase in nasopharyngeal depth was found over the entire observation period (T1 10.7 to T4 19.1 mm, p < 0.001), especially between T2 and T3 (change 3.8 mm, p < 0.001), and was mainly due to adenoid recession (r = -0.75, p < 0.001; variation explained by 56%). Increase in velopharyngeal depth mainly took place between T3 and T4 (change 2.3 mm, p < 0.01). It was due to more anterior tongue posture (r = 0.65, p < 0.001; 42.5% of variation explained), in turn allowing the soft palate to take a more vertical position (r = -0.52, p < 0.001). Increase in oropharyngeal depth was associated with head extension and anterior mandibular positioning (36% of variation explained). However, significance was not reached (T1 8.3 to T4 9.8 mm, p > 0.05). CONCLUSIONS: Upper airway dimensions in children with PRS improve with time, except for the oropharyngeal airway. Despite large interindividual variation, the mean remained in the lower reaches of normality described in other studies. Thus, further research should investigate the prevalence of obstructive sleep apnoea in adults with PRS.

Accuracy of linear intraoral measurements using cone beam CT and multidetector CT: a tale of two CTs.

OBJECTIVES: The aim was to compare the accuracy of linear bone measurements of cone beam CT (CBCT) with multidetector CT (MDCT) and validate intraoral soft-tissue measurements in CBCT. METHODS: Comparable views of CBCT and MDCT were obtained from eight intact cadaveric heads. The anatomical positions of the gingival margin and the buccal alveolar bone ridge were determined. Image measurements (CBCT/MDCT) were performed upon multiplanar reformatted data sets and compared with the anatomical measurements; the number of non-assessable sites (NASs) was evaluated. RESULTS: Radiological measurements were accurate with a mean difference from anatomical measurements of 0.14 mm (CBCT) and 0.23 mm (MDCT). These differences were statistically not significant, but the limits of agreement for bone measurements were broader in MDCT (-1.35 mm; 1.82 mm) than in CBCT (-0.93 mm; 1.21 mm). The limits of agreement for soft-tissue measurements in CBCT were smaller (-0.77 mm; 1.07 mm), indicating a slightly higher accuracy. More NASs occurred in MDCT (14.5%) than in CBCT (8.3%). CONCLUSIONS: CBCT is slightly more reliable for linear measurements than MDCT and less affected by metal artefacts. CBCT accuracy of linear intraoral soft-tissue measurements is similar to the accuracy of bone measurements.

Stability, adaptation and growth following distraction osteogenesis in the craniofacial region.

The objective of the study was to provide a comprehensive review of the literature describing research done on the stability, adaptation and growth of craniofacial structures following distraction osteogenesis (DO). The design of the study was a literature review of clinical and experimental studies using electronic search with several keywords. Despite immediate normalization of craniofacial relationships after DO, post-distraction mandibular and midface stability and growth is variable in the long-term based on the initial condition. Unpredictable and/or unstable outcomes after DO can arise mainly from three main sources: 1) true relapse, 2) return to original morphology and 3) defective growth. Despite the biologic and clinical feasibility of DO in the craniofacial region, relapse, compromised adaptation, and defective post-distraction growth can lead to variable clinical outcomes. When important structures for the mandibular forward and downward displacement are rudimentary or missing in syndromic patients, DO can not 'correct' the condition and post-distraction growth will be defective. Non-syndromic patients have a better potential to respond favourably to DO.

Hemimandibular elongation: treatment and long-term follow-up.

OBJECTIVE: To study long-term changes in the mandibular asymmetry of patients with hemimandibular elongation (HE) treated with two-phase surgical orthodontic approach. DESIGN: Descriptive clinical study. SETTING AND SAMPLE POPULATION: Private practice setting. Seven (six females) out of 47 diagnosed and treated patients for severe mandibular asymmetry were included with the following criteria: diagnosis of HE based on clinical, radiological and single photon emission computed tomography bone scintigraphic studies, good quality orthopantomograms (OPT) available at six time-points, two-phase surgical treatment (high condylectomy, HC, and orthognathic surgery, OS) and measurements of maximal mouth opening (MMO) available. METHOD: Mandibular ramus height and corpus length were measured on OPTs at six time-points. Ratios between the affected/non-affected sides were calculated. RESULTS: All patients had progression of mandibular asymmetry before any operation, which finding together with the scintigraphy resulted to the decision to perform HC. Thereafter ramus and corpus asymmetry decreased compared with the initial measurements. After OS, stable symmetry of corpuses and alignment of skeletal and dental midlines were obtained. MMO reduced on average 50% after HC, regained 20% after OS and recovered almost totally at the last follow-up. CONCLUSIONS: High condylectomy to stop excessive growth and OS to correct facial asymmetry is considered successful and necessary treatment for patients with HE. MMO can well recover after surgical traumas. Orthodontists should consider mandibular asymmetry as abnormal and need for surgical treatment if asymmetry is progressive and the ratio between affected/non-affected sides approaches 10%.

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.

Fatigue resistance of removable orthodontic appliance reinforced with glass fibre weave.

The aim of this study was to measure the fatigue resistance of fibre-reinforced composite (FRC) reinforced polymeric parts of a removable orthodontic appliance beside the clasp. The effect of quantity and position of FRC-reinforcement were investigated. In addition, the influence of water storage on the fatigue properties was determined. The test specimens for eight groups (n=6) were manufactured from autopolymerizing acrylic resin. Polymethylmethacrylate pre-impregnated woven glass fibre was used as reinforcement of acrylic resin specimens at the region of steel wire clasp. The test specimens of the control group were not reinforced. In the second group, the test specimens were reinforced with one fibre layer (thickness: 0.06 mm) on the tension side, and in the third and fourth group with two fibre layers. Fatigue resistance was measured by applying repeated bending force to the clasp. The highest fatigue resistance values were achieved when the test specimens were fibre-reinforced with two fibre layers. The lowest fatigue resistance values resulted when the test specimens were not reinforced (P=0.046, anova). Water storage had a tendency to decrease the fatigue resistance in all fibre reinforced test specimen groups. The results suggest that use of the woven polymer pre-impregnated glass FRC-reinforcement increases the fracture resistance of orthodontic appliance made of acrylic polymer.

Distribution of insulin-like growth factor-I mRNA in the mandibular condyle and rib cartilage of the rat during growth.

This study makes a molecular biological comparison of primary and secondary cartilage at an early phase of postnatal development. The distribution of insulin-like growth factor-I (IGF-I) mRNA expression in the mandibular condyle and rib cartilage of 1-28-day-old rats was examined after in situ hybridisation using an oligo probe cocktail for IGF-I mRNA. In the condyle, expression was localised to a narrow strip under the articular layer where the cells are undifferentiated. Essentially, no differences were found in IGF-I synthesis within three samples from the same age group or between different age groups. In rib cartilage, IGF-I mRNA was localised within the germinative, proliferative and early hypertrophic cell layers in 1-28-day-old rats. Again, there were no differences in expression among animals of the same age or as a function of age. This pattern of IGF-I mRNA expression indicates that IGF-I synthesis during growth of the mandibular condylar cartilage is different from that of costal cartilage. The findings shed light on the problem of overgrowth often associated with the use of costochondral grafts to replace defective mandibular condyles.

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.

Induced leukemia and antineoplastic agent carmustine cause permanent changes in craniofacial growth of immature rats.

OBJECTIVES: The purpose of the present study was to investigate the possible effects of untreated terminal leukemia on craniofacial growth (Study I), and also the effects of the antineoplastic agent carmustine on craniofacial growth in both leukemic and healthy rats (Study II). MATERIAL: A total of 367 inbred Piebald variegated rats was used. METHOD: Transmission of leukemic cells was carried out intraperitoneally at 30 days of age, and without treatment (Study I), the rats reached the terminal phase within 17 +/- 1 days. Rats with induced leukemia was cured with 10 mg/kg carmustine (BCNU) given on days 6 and 13 following cell transmission (Study II), the rats remaining in remission until they were killed at 100 days of age. Final weight was recorded and 12 craniofacial dimensions and tibial length were measured with a digital sliding caliper. RESULTS: The results showed that the effect of untreated terminal rat leukemia (Study I) on craniofacial growth differed between the genders. Male rats showed clearly reduced dimensions of facial structures and also retarded general body growth, whereas females showed differences mainly in general body growth. The effect of cured leukemia (Study II) as such was minor, while BCNU had a strong and permanent reducing effect on both craniofacial and general body growth in both genders. CONCLUSION: We suggest that the results in Study I came both from a direct effect of leukemia and an indirect effect of untreated terminal leukemia through malnutrition. The alkylating agent BCNU seemed to be the main cause of permanent craniofacial and general growth retardation in Study II.

Distribution of fibroblast growth factors (FGFR-1 and -3) and platelet-derived growth factor receptors (PDGFR) in the rat mandibular condyle during growth.

OBJECTIVES: To elucidate the role of the fibroblast growth factors 1 and 3 (FGFR-1, -3) and the platelet derived growth factor (PDGFR) in the growth of the mandibular condylar cartilage in the rat. SETTING AND SAMPLE POPULATION: Institute of Dentistry and Department of Biostatistics, University of Turku, Turku, Finland. The material consisted of 1- to 21-day-old Long-Evans/Turku rats (total of 24 animals, three in each age group). DESIGN: An immunohistological in vivo study combined with histomorphometry and biostatistical analysis. EXPERIMENTAL VARIABLE: The animals were killed with an overdose of carbon dioxide and thereafter decapitated. Heads were fixed in 4% paraformaldehyde, decalcified in 12.5% ethylenediaminetetraacetic acid, cut sagittally into two halves and sectioned sagittally at 6 microns. In order to detect FGFR-1, -3 and PDGFR the sections were treated with H2O2/methanol (1:100), after which FGFR-1 and PDGFR monoclonal and FGFR-3 polyclonal antibodies were applied. The reaction products were visualized by using the Vectastain ABC Elite Kit using peroxidase substrate kit DAB as substrate. Negative and positive controls were also prepared. The sections were counterstained with hematoxylin. OUTCOME MEASURE: In order to measure the depth of the cell layer labeled with FGF-1, -3 and PDGF receptors, the condylar head was divided into four regions: anterior, superior, posterosuperior and posterior. The measurements were made perpendicular to the articular surface using a computerized image analysis system, the images being acquired by means of a microscope connected to a CCD camera. The mean of five equally distributed measurements of each region was used to indicate the depth of the cell layers secreting the receptors. Regression analysis was used to evaluate the association between the depth of the labeled cell layer in relation to total depth of the condylar head, as a function of age. RESULTS: Our results show that the depth of the cell layer labeled for FGFR-1, -3 and PDGFR increase significantly as a function of age in the mandibular condylar head of rats. CONCLUSION: Increase in the cell layer labeled for FGFR-1, -3 and PDGFR occurs during the stage when the articular function of the mandibular condyle intensifies. FGFR-1, -3 and PDGFR evidently have an important role in the growth regulation of the condylar cartilage during the most rapid growth period in the rat.

Craniofacial morphology in preschool children with sleep-related breathing disorder and hypertrophy of tonsils.

UNLABELLED: The purpose of this study was to examine craniofacial morphology, pharyngeal airway space and hyoid bone position in preschool children with sleep-related breathing disorder associated with hypertrophy of tonsils (SBDT). Thirty-eight preschool children, mean age 4.7 y, with SBDT and with an apnoea index (AI) of 0 < AI < 5, were divided into two groups. One consisted of 15 children with sleep-related breathing disorder (SBD) and more than 75% of the tonsils visible (GIII) and the other of 23 children with SBD and 25-75% of the tonsils visible (GII). The control group consisted of 31 children without ear, nose and throat disease and with GI (barely visible) tonsils. Compared with the controls, GIII children had a retrognathic mandible, a large posterior facial height, a large interincisal angle with retroclined lower incisors, a narrow pharyngeal airway space, an anterior tongue base position and a long soft palate. Compared with the controls, GII children had a large anterior lower facial height and a short nasal floor. However, like the controls, GII children did not have a retrognathic mandible. CONCLUSION: The findings show that children with SBDT display a characteristic facial appearance at an early age. Since the condition has an effect on growth, it needs to be prevented by controlling morphology and function at the preschool age.

Growth hormone and insulin-like growth factor I receptors in the temporomandibular joint of the rat.

While there are numerous investigations on hormonal control of long bone epiphyseal growth, corresponding knowledge is sparse concerning the condylar cartilage. We investigated the distribution of growth hormone (GH) and insulin-like growth factor I (IGF-I) receptors in the temporomandibular joint (TMJ), especially the condyle, and compared the findings with information of long bone epiphyseal plates. The localization of the receptors was examined in vivo by immunohistochemical methods in one- to 21-day-old rats. GH receptors were detected in various components of the TMJ, but not in the fibrous articular surface or in the cartilage layers of the condyle. IGF-I receptors were found in the fibrous articular surface of the condyle and particularly in the superior and posterosuperior regions of the condylar cartilage, the depth of the labeled cell layer increasing significantly with age. It is evident that the expression of GH and IGF-I receptors is area-specific in the TMJ. Early post-natal growth and development of the mandibular condylar cartilage seem to be IGF-I-dependent but not directly dependent on GH.

Associations between severity of clefting and maxillary growth in patients with unilateral cleft lip and palate treated with infant orthopedics.

OBJECTIVE: The purpose of this study was to examine possible associations between severity of clefting in infants and maxillary growth in children with complete unilateral cleft lip and palate. DESIGN: This was a retrospective study of measurements made on infant maxillary study casts and maxillary cephalometric variables obtained at 5 to 6 years of follow-up. SETTING: The study was performed at the Institute of Reconstructive Plastic Surgery of New York University Medical Center, New York, New York. PATIENTS: Twenty-four consecutive nonsyndromic unilateral complete cleft lip and palate patients treated during the years 1987 to 1994. INTERVENTIONS: All the patients received uniform treatment (i.e., presurgical orthopedics followed by gingivoperiosteoplasty to close the alveolar cleft combined with repair of the lip and nose in a single stage at the age of 3 to 4 months). Closure of the palate was performed at the age of 12 to 14 months. RESULTS: Infant maxillary study cast measurements correlated in a statistically significant manner with maxillary cephalometric measurements at age 5 to 6 years. CONCLUSIONS: The results demonstrate the large variation in the severity of unilateral cleft lip and palate deformity at birth. Patients with large clefts and small arch circumference, arch length, or both demonstrated less favorable maxillary growth than those with small clefts and large arch circumference or arch length at birth.

Disturbances in craniofacial morphology in children treated for solid tumors.

Because of increased survival rates in childhood cancer, special interest has been focused on the side-effects of the therapy and the quality of life in long-term survivors. Our aim was to investigate craniofacial growth in children who had received different kinds of antineoplastic therapies for solid tumors. A total of 40 children treated in the Turku University Central Hospital were examined and divided into three different groups. Group 1 comprised 18 children treated for intracranial tumors with cranial irradiation (CRI) and chemotherapy (CT) including alkylating agents. Seven children out of 18 in this group received growth hormone (GH) therapy. In Group 2, 11 children with extracranial solid tumors also received multiagent CT including alkylating agents, but no CRI. Group 3 consisted of 11 children treated for Wilm's tumor with CT, which did not include alkylating agents or CRI. A total of 19 linear and four angular variables from the lateral cephalograms of the subjects were measured. Most deviations in craniofacial structures were found in children treated with combined CRI and multiagent CT. All disturbances were seen in the vertical measurements which were reduced when compared to the matched controls. It seems reasonable to assume that impaired growth following combined radio- and chemotherapy, as well as GH treatment, particularly affects cartilage-mediated growth. However, the deviations seen in the present study were fairly minor and did not usually require clinical consideration.

Collagen I and II mRNA distribution in the rat temporomandibular joint region during growth.

The distribution of type I and II collagen synthesis in the temporomandibular joint (TMJ) area of 1- to 28-day-old rats was studied after hybridization with probes to pro alpha1(I) and pro alpha1(II) collagen mRNA, and stain intensity through the various cartilaginous zones of the mandibular condyle and other areas of TMJ was assessed. The pro alpha(I) collagen mRNA was detected in the perichondrium/periosteum, in the fibrous and undifferentiated cell layers of the mandibular condyle, in the articular disc, and in all bone structures and muscles. The pro alpha1(II) collagen mRNA was found in the condylar cartilage and the articular fossa. Intensity in the condyle was highest in the chondroblastic layer and decreased towards the lower hypertrophic layer. In the condylar cartilage of the 21- to 28-day-old rats the chondroblastic cell zone was relatively narrow compared with the younger animals, whereas the reverse seems to be the case in the cartilage of the articular fossa. Changes in the pro alpha1(II) collagen mRNA were observed in the osseochondral junction area of the primary spongiosa, in that at the age of 5 days intense staining was found, whereas no staining was observed by 14 days. In the mineralizing zone, however, the majority of osteoblastic cells gave a positive signal with the pro alpha1(I) collagen probe. In conclusion, type II collagen synthesis of the mandibular condyle is restricted to its upper area. This differs from the long bone epiphyseal plate, where this type of collagen is produced virtually throughout the cartilage. Type II collagen synthesis of the fossal cartilage seems to increase as a function of age.