Cartilage changes link retrognathic mandibular growth to TMJ disc displacement in a rabbit model.

Recent experimental research demonstrated that non-reducing temporomandibular joint (TMJ) disc displacement in growing rabbits impaired mandibular growth. TMJ disc displacement is also shown to induce histological changes of the condylar cartilage. The authors hypothesized that the severity of these changes would correlate to the magnitude of mandibular growth. Bilateral non-reducing TMJ disc displacement was surgically created in 10 growing New Zealand White rabbits. Ten additional rabbits constituted a sham operated control group. Aided by tantalum implants, growth was cephalometrically determined for each mandibular side during a period equivalent to childhood and adolescence in man. At the end of the growth period, histologically classified cartilage features were correlated with the assessed ipsilateral mandibular growth. Non-reducing displacement of the TMJ disc during the growth period induced histological reactions of the condylar cartilage in the rabbit model. The severity of cartilage changes was inversely correlated to the magnitude and the direction of mandibular growth, which resulted in a retrognathic growth pattern.

Quality difference in craniofacial pain of cardiac vs. dental origin.

Craniofacial pain, whether odontogenic or caused by cardiac ischemia, is commonly referred to the same locations, posing a diagnostic challenge. We hypothesized that the validity of pain characteristics would be high in assessment of differential diagnosis. Pain quality, intensity, and gender characteristics were assessed for referred craniofacial pain from dental (n = 359) vs. cardiac (n = 115) origin. The pain descriptors "pressure" and "burning" were statistically associated with pain from cardiac origin, while "throbbing" and "aching" indicated an odontogenic cause. No gender differences were found. These data should now be added to those craniofacial pain characteristics already known to point to acute cardiac disease rather than dental pathology, i.e., pain provocation/aggravation by physical activity, pain relief at rest, and bilateralism. To initiate prompt and appropriate treatment, dental and medical clinicians as well as the public should be alert to those clinical characteristics of craniofacial pain of cardiac origin.

Bilateral TMJ disk displacement induces mandibular retrognathia.

Unilateral non-reducing TMJ disk displacement has been shown to retard mandibular growth on the ipsilateral side, with facial asymmetry a sequela. We hypothesized that bilateral affliction would impair mandibular growth bilaterally, generating mandibular retrognathia. Non-reducing TMJ disk displacement was surgically created in 10 growing New Zealand White rabbits. Ten additional rabbits served as a sham-operated control group. Facial growth was followed in serial cephalograms, with tantalum implants, during a period corresponding to childhood and adolescence in man. The results verified that bilateral non-reducing TMJ disk displacement retarded mandibular growth bilaterally, the extent corresponding to mandibular retrognathia in man. Maxillary growth was also retarded, but to a lesser degree. Growth impairment fluctuated over time, the most striking retardation occurring during periods of general growth acceleration. This should be taken into consideration when orthodontic treatment, aimed at stimulating mandibular growth, is initiated in adolescent individuals with non-reducing TMJ disk displacement.

Virtual reality for simulation of radiographic projections: validation of projection geometry.

OBJECTIVE: To develop a software for virtual reality (VR) simulation of X-ray images based on perspective projections through a patient model derived from data from a CT examination and to evaluate the accuracy in the projection geometry obtained by the software. METHODS: A VR software was developed on a personal computer, with models of a patient, an X-ray machine and a detector. The model of the patient was derived from data from a CT examination of a dry skull. Simulated radiographic images of the patient model could be rendered as perspective projections based on the relative positions between the models. The projection geometry of the software was validated by developing an artificial CT data set containing high attenuation points as objects to be imaged. The accuracy in projection geometry was evaluated in a systematic way. The distances between two dots, representing the projected test points in the simulated radiographic images, were measured. They were compared with theoretical calculations of the corresponding distances using traditional mathematical tools. RESULTS: The difference between the simulated and calculated projected distances never exceeded 0.5 mm. The error in simulated projected distances was in most cases within 1%. No systematic errors were revealed. CONCLUSION: The software, developed for personal computers, can produce simulated X-ray images with high geometric accuracy based on perspective projections through a CT data set. The software can be used for simulation of radiographic examinations.

Snoring, sleep apnoea and swallowing dysfunction: a videoradiographic study.

OBJECTIVES: Snoring is associated with subclinical pharyngeal swallowing dysfunction, probably owing to vibration trauma to the pharyngeal tissues caused by snoring. Negative intrathoracic pressure during apnoea causes stretching of the velum and pharynx. The aim of this study was to investigate whether patients with severe sleep apnoea have an increased frequency of videoradiographically diagnosed subclinical pharyngeal swallowing dysfunction compared with snoring patients with or without mild sleep apnoea as well as with non-snoring controls. METHODS: Eighty consecutive patients referred for sleep apnoea recordings because of snoring were examined. Fourteen of these patients were excluded because they suffered from dysphagia. Fifteen non-snoring, non-dysphagic volunteers served as controls. Videoradiography was performed to examine the oral and pharyngeal swallowing function in patients and controls. Overnight sleep apnoea recordings were used to evaluate the apnoea-hypopnoea index (AHI). RESULTS: Pharyngeal swallowing dysfunction was observed in 34/66 (52%) of the snoring patients and in 1/15 (7%) of the non-snoring controls. Pharyngeal swallowing dysfunction was observed in 50% of patients with an AHI of >or=30, in 61% of patients with an AHI of 5-29 and in 43% of patients with an AHI of <5. There was no significant difference in the frequency of pharyngeal swallowing dysfunction between snoring patients with different AHIs. CONCLUSION: Snoring patients run an increased risk of developing subclinical pharyngeal swallowing dysfunction independent of concomitant sleep apnoea.

Swallowing dysfunction related to snoring: a videoradiographic study.

Biopsy studies of the soft palatal and oropharyngeal tissues in habitual snorers and patients suffering from obstructive sleep apnoea have shown signs of neurogenic lesions. These lesions might affect the pharyngeal swallowing function, which is dependent on adequate sensitivity. The objective of the present study was to test the hypothesis that snoring is associated with aberrant pharyngeal swallowing function. Forty-one consecutive patients without dysphagia, seeking medical attention because of heavy snoring and various degrees of daytime sleepiness, were prospectively selected. Fifteen non-snoring volunteers without dysphagia served as controls. Patients and volunteers were videoradiographically examined in lateral and posteroanterior views during the oral and pharyngeal phases of swallowing. The hypothesis was verified. Snoring patients demonstrated deviant pharyngeal swallowing function seven times more frequently than did the non-snoring volunteers. Deviant pharyngeal swallowing function was observed in 22 (54%) of the snorers compared with 1 (7%) of the non-snoring volunteers. Impaired bolus control with premature leakage of bolus into the pharynx and a delayed evocation of the swallowing reflex was the most common finding, followed by bolus residual in the pharynx and laryngeal penetration. The conclusion was that snoring is associated with subclinical pharyngeal swallowing dysfunction.

Validity of identification of gonion and antegonion in frontal cephalograms.

This study was designed to develop a method of transferring gonion from lateral to frontal cephalograms, and to use this method as gold standard when evaluating observer performance in identifying gonion in frontal cephalograms. Observer ability to identify antegonion was also evaluated. There was a range of 28 mm in the observers' identification of gonion and a statistically significant deviation from gold standard. The factors "observer" and "cephalogram," regarded as random effects in an ANOVA analysis, and their interaction, each influenced the result, P < .001. The deviation from the mean of all observations for antegonion ranged 8 mm with "cephalogram" having a statistically significant influence. The results suggest that neither gonion nor antegonion can be routinely used as valid landmarks in frontal cephalograms. Gonion can, however, be used if first identified in a lateral cephalogram and transferred to a paired frontal cephalogram aided by radiographic indicators combined with a bilateral scrutiny of projection geometry in different planes through gonion and indicator.

Deterioration of intraoral recognition of shapes after treatment of oral and pharyngeal cancer.

Thirty patients with diagnosed malignant tumors of the oral cavity or pharynx were tested in regards to intraoral shape recognition at 4 test occasions: before all treatment, after radiotherapy, 6 months after surgery, and 1 year after surgery. They were compared within groups as well as with a group of healthy reference individuals of the same age who underwent the same test procedure at a 2-month interval. The tumor itself did not influence the capability of shape recognition. The reference individuals demonstrated significantly better results on the second test occasion, which is known as a learning effect. Learning improvement was not seen in the patients whose second test occasions were after radiotherapy, implying an impediment amounting to the magnitude of the learning effect. At 6 months after surgery the patients' capabilities of shape recognition had deteriorated significantly with no difference between the oral cancer group and the pharyngeal cancer group. No spontaneous rehabilitation had taken place 1 year after surgery. The presence or absence of surgical lingual nerve damage did not influence the results. The nonoperated side does not compensate for the operated one. It is plausible that decreased oral sensory acuity in recognizing the shape of the bolus contributes to postoperative swallowing problems.

Temporomandibular joint condyle changes after surgically induced non-reducing disk displacement in rabbits: a macroscopic and microscopic study.

Experimentally induced displacement of the temporomandibular joint (TMJ) disk has previously been shown to induce shortening of the mandibular ramus on the ipsilateral side. The aim of this investigation was to reveal whether this shortening develops due to primary influence on condyle growth or by secondary loss of condyle mass due to degenerative tissue breakdown. Disk displacement was created in the right TMJ in seven 3-month-old rabbits, the posterior disk attachment kept intact. Seven rabbits underwent surgical opening of the TMJ without disk intervention. Seven additional animals served as references. After a 3-month experimental period, the animals were sacrificed. Previous analysis revealed shortening of mandibular height and length caused by ipsilateral TMJ disk displacement. The condyles were examined macroscopically and by histologic sectioning or scanning electron microscopy. All condyles were covered with smooth articulating soft tissue and without visible signs of degenerative changes. Four condyles from joints with disk displacement demonstrated substantial regressive remodeling resulting in a change of condyle shape with forward/downward rotation of an enlarged articulating surface. It was concluded that TMJ disk displacement in a growing individual can induce reduction of mandibular height and length before a stage where visible osteoarthrotic changes develop. It implies a primary adverse effect on condyle growth.

Deterioration of intraoral hole size identification after treatment of oral and pharyngeal cancer.

Thirty-one patients with a diagnosed malignant tumour of the oral cavity or pharynx were tested in hole size identification on four test occasions: before all treatment, after radiotherapy and 6 months and 1 year after surgical treatment. They were compared within groups as well as with a group of healthy reference individuals of the same age who underwent the same test procedure at a 2 months' interval. The oral group did not decline in hole size identification after radiotherapy, but did after surgery. The deterioration was persistent 1 year after surgery. The pharyngeal group did not change performance in hole size identification after radiotherapy, nor after surgery. It is obvious that surgery of the oral structures causes the deterioration. No correlation with damage to the lingual nerve could be registered. The oral cavity reacts as one unit, despite sensory input from two sides. The non-operated side does not compensate for the operated side. It is plausible that decreased oral sensory acuity, in recognizing hole size of the bolus, contributes to postoperative swallowing problems.

Comparison between two types of pharyngeal flap with regard to configuration at rest and function and speech outcome.

OBJECTIVE: In management of hypernasality, wide pharyngeal flaps have been advocated when pharyngeal wall adduction is limited. Pharyngeal flaps merged into a transversely split velum (TS flaps) are reported to be wider than if the velum is split in the midline (MS flaps). The hypothesis to be tested was that TS flaps are wider than MS flaps and are more caudally based. DESIGN: In this prospective study, MS flaps were videoradiographically and nasopharyngoscopically compared with TS flaps at both rest and function. Pharyngoplasty was randomly performed by one of three surgeons and the radiographic examinations were carried out by one radiologist. The speech was assessed pre- and postoperatively. SETTING: The Stockholm Cleft Palate Team, Sweden, treated all patients. PATIENTS: After strict selection of the patients to avoid any uncontrolled impact on velopharyngeal sphincter function, 22 patients with limited pharyngeal adduction received TS flaps and 20 patients with good adduction received MS flaps. RESULTS: The data failed to show any difference in location of flap base and in flap width at rest. During function, TS flaps demonstrated statistically significant widening of the flap base. TS flaps, but not MS flaps, often had a bulge that appeared to assist velopharyngeal closure in some patients. Speech evaluation revealed that both flap types corrected velopharyngeal insufficiency equally well. CONCLUSIONS: TS flaps were not wider than MS flaps, and functional plasticity of the TS flap appeared essential for elimination of velopharyngeal insufficiency. Contribution of postoperative adaptation of the pharyngeal wall adduction remains to be clarified.

Adaptation of pharyngeal wall adduction after pharyngeal flap surgery.

OBJECTIVE: The purpose of this investigation was to study lateral pharyngeal wall adduction relative to pharyngeal flaps of different widths. The hypothesis to be tested was that pharyngeal wall adduction does not increase postoperatively but may decrease due to the mechanical hindrance of a wide flap. DESIGN: In this prospective study, adaptation of lateral pharyngeal wall adduction during speech was studied relative to pharyngeal flaps of different widths utilizing videoradiography. Flap width was determined nasopharyngoscopically. SETTING: All patients were treated by the Stockholm Cleft Palate Team, Sweden. PATIENTS: Fifty-three patients were strictly selected by discarding conditions known to exert uncontrolled influence on velopharyngeal sphincter function. RESULTS: The results revealed a potential for adaptation of pharyngeal wall adduction to different flap widths. The magnitude and character (increase or decrease) of change in adduction was significantly correlated with the degree of preoperative adduction and with the width of the flap. In patients with limited preoperative adduction, pharyngeal wall activity increased, more in the presence of a narrow flap while less if the flap was wide. When preoperative adduction was pronounced, the postoperative activity decreased because of mechanical hindrance by the flap, and the degree of impediment was correlated to the width of the flap. CONCLUSION: A potential for increased lateral pharyngeal wall adduction after pharyngeal flap surgery was verified, but the result cannot be interpreted as generally applicable because of the strict selection of patients.

Validity of computed tomography in imaging thin walls of the temporal bone.

OBJECTIVES: To evaluate the validity of computed tomography (CT) for reproduction of the bone margins of the temporomandibular joint (TMJ). METHODS: Seven TMJ specimens were examined with a CT and then cryosectioned. The bone separating the TMJ from the middle cranial fossa, middle ear and external auditory canal was measured as the full width at half maximum (FWHM). Measurements were compared with the true thickness of the bone wall. RESULTS: There was good agreement when the bone walls were thicker than 1 mm: accuracy was influenced only by the angle of the bone wall to the scanning plane. Conversely, bone walls thinner than 1 mm were reproduced with a magnification that increased with decreasing bone thickness. The difference increased further as the inclination of the bone wall became greater. CONCLUSION: Measurements performed at FWHM are reliable within +/- 10% for bone walls more than approximately 1 mm thick which form an angle of less than 35 degrees to the perpendicular of the scanning plane. For bone walls thinner than 1 mm and for those thicker than 1 mm with an inclination exceeding approximately 35 degrees, partial volume effects result in a progressively increasing magnification of bone thickness.

Mandibular length and midline asymmetry after experimentally induced temporomandibular joint disk displacement in rabbits.

The purpose of the present investigation was to test the hypothesis that permanent disk displacement in the temporomandibular joint (TMJ) is one causal factor in the development of mandibular midline asymmetry. Unilateral, nonreducing disk displacement was therefore created in growing rabbits. The right TMJ in seven experimental animals was surgically opened, and the disk was anteriorly displaced with the posterior disk attachment kept intact above the condyle. The right TMJ in seven sham animals was surgically opened and closed without any disk manipulation. Seven additional rabbits served as reference animals. For identification of mandibular growth, tantalum implants were inserted into the mandibular body, and lateral cephalograms were exposed at the beginning and at the end of the experimental period. After the animals had been sacrificed, the mandibles were dissected and measurements were performed on the mandibular specimens. Axial radiographs of the mandibles were then exposed and measurements of mandibular length and midline shift were performed in the radiographs. The mandible in the experimental animals was consistently shorter on the disk displacement side resulting in a midline shift to the ipsilateral side. No mandibular asymmetry was observed in the sham and reference groups. The hypothesis was verified; disk displacement in the TMJ with an onset during the growth period can cause mandibular length and midline asymmetry in growing rabbits.

Prevalence of temporomandibular joint disk displacement in infants and young children.

OBJECTIVE: The purpose of this study was to determine the prevalence of temporomandibular joint disk displacement in infants and young children. STUDY DESIGN: Magnetic resonance images were obtained of the temporomandibular joints in 30 infants and young children ranging in age from 2 months to 5 years (median age, 3 years; mean age, 2.5 years). RESULTS: All joints had normal superior disk position. The computed 95% confidence interval was 0.00-0.06, which implies a minimal probability that disk displacement would occur in this age group. CONCLUSIONS: The result contradicts previous suggestions that temporomandibular joint disk displacement could represent a congenital normal anatomic variant.

Thickness of the articular soft tissue of the temporal component in temporomandibular joints with and without disk displacement.

OBJECTIVE: The purpose of this investigation was to test the hypothesis that temporomandibular joint disk displacement is associated with significant functional adaptive changes of the articular soft tissue of the articular eminence. STUDY DESIGN: Thirteen temporomandibular joint autopsy specimens with normal superior disk position and 12 with complete anterior disk displacement were cryosectioned, and sections were stained and photographed. At a magnification of x20 the soft tissue was measured (1) at the inflection point, (2) on the posterior slope, (3) at the apex, and (4) on the anterior slope of the articular eminence. RESULTS: Displacement of a deformed or nondeformed temporomandibular joint disk without perforation of the posterior disk attachment was associated with significantly increased thickness of the articulating soft tissue at the apex and on the posterior and anterior slopes of the articulating eminence. When disk displacement was associated with a perforation of the posterior disk attachment, the soft tissue was not significantly thicker than in joints with normal superior disk position. CONCLUSIONS: Increase in articulating soft tissue thickness is interpreted as an adaptive mechanism to maintain the condyle path and withstand excessive loading at interposition of the temporomandibular joint components. When the plasticity of the tissues is surpassed, the adaptation will be thwarted and replaced by tissue breakdown.

Persisting dysphagia after uvulopalatoplasty performed with steel scalpel.

OBJECTIVES/HYPOTHESIS: The aim of the present study was to determine the incidence of postoperative persisting dysphagia after uvulopalatoplasty performed with conventional steel scalpel (UPP) and to videoradiographically evaluate the oral and pharyngeal phases of swallowing in patients reporting persisting dysphagia. The hypothesis to be tested was that patients treated with UPP would demonstrate a lower incidence of persisting dysphagia than previously found after uvulopalatoplasty performed with laser technique (LUPP). STUDY DESIGN: Retrospective. METHODS: Sixty-eight of 76 consecutive patients treated with UPP answered a questionnaire concerning outcome and late complications after the operation. The patients who reported postoperative dysphagia were additionally interviewed at a minimum of 1 year postoperatively, and the oral and pharyngeal phases of swallowing were videoradiographically examined in those with persisting dysphagia. RESULTS: The incidence of persisting dysphagia after UPP was 29%. Videoradiographically 71% of the dysphagic patients showed a deviant pharyngeal swallowing pattern. CONCLUSION: The incidence of persisting dysphagia after UPP did not differ from that reported after laser uvulopalatoplasty. Dysphagia after UPP was mostly associated with videoradiographic signs of deviant pharyngeal swallowing function. Patients should be informed that there is a risk of developing dysphagia after uvulopalatoplasty.

Persistent dysphagia after laser uvulopalatoplasty: a videoradiographic study of pharyngeal function.

In a follow-up study of 79 patients two years after laser uvulopalatoplasty 21 (27%) reported persistent postoperative dysphagia, with aspiration symptoms in 22%. None of the patients had suffered from recurrent pneumonia. A total of 4% of the patients regretted the treatment because of their dysphagia problems. The objective of this study was to examine oral and pharyngeal function videoradiographically during swallowing in the patients with persistent dysphagia, to determine whether the subjective symptoms of dysphagia correlated with objective signs of pharyngeal dysfunction. Pharyngeal function during swallowing was deviant in 76% of the dysphagic patients. In 52% of the dysphagic patients premature leakage of bolus down to different levels of the pharynx, from the tongue base to sinus piriformis, was observed before the swallowing reflex was elicited. In the dysphagic patients substantial bolus retention was observed on the epiglottis or in the valleculae alter the propagation wave had passed (43%) as well as epiglottal dysmotility (24%). Of the dysphagic patients, 10% could not avoid aspiration during the examination. These findings could explain the symptoms reported by the patients.

Incidence of temporomandibular joint changes after whiplash trauma: a prospective study using MR imaging.

OBJECTIVE: The purpose of this study was to describe the incidence of temporomandibular joint (TMJ) changes after a well-defined whiplash trauma. SUBJECTS AND METHODS: Sixty consecutively admitted patients with symptoms in the neck after rear-end traffic collisions underwent MR imaging of the TMJs within 3-14 days after the collisions. Fifty-three healthy volunteers constituted a control group. RESULTS: No statistically significant differences were found between the 60 patients and the 53 volunteers regarding frequency, stage, grade, or direction of TMJ disk displacement or joint effusion. MR imaging revealed that 45% of the control group and 53% of the patient group had a displaced disk in one or both TMJs (p = .393). Disk displacement was seen in 35% of TMJs in the control group and 40% of TMJs in the patient group. Effusion was seen in 8% of TMJs in the control group and 6% of TMJs in the patient group. No signs of bleeding or edema in the soft tissues were observed. In 15% of the patients, mild clinical symptoms in the TMJ or masticatory muscles developed in association with the trauma; in one third of these patients the symptoms were transient. CONCLUSION: This prospective study does not show any significantly increased incidence of disk displacement, joint effusion, or any other injury to the TMJ after whiplash trauma that could be revealed by MR imaging.