Effective temporomandibular joint growth and chin position changes: Activator versus Herbst treatment. A cephalometric roentgenographic study.
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In 138 successfully treated Class II division 1 patients (40 Activator and 98 Herbst) effective temporomandibular joint (TMJ) growth changes (a summation of condylar remodelling, glenoid fossa remodelling, and condylar position changes within the fossa), and their influence on the position of the chin and the rotation of the mandible were analysed retrospectively. Lateral head films in habitual occlusion from before and after an average treatment period of 2.6 years for the Activator patients and 0.6 years for the Herbst patients were evaluated. Two different treatment changes were assessed: (1) overall growth changes and (2) treatment effects (overall growth changes minus age-related normal growth values: Bolton Standards). The comparison between the Activator and the Herbst group revealed larger effective TMJ and chin changes during Activator therapy due to the longer observation period (2.6 years versus 0.6 years). The treatment effects showed marked group differences for both the amount and direction of effective TMJ changes. The changes were vertical and slightly anterior in the Activator group, and predominantly posterior in the Herbst group. Concerning the chin changes, the treatment effects for the Herbst group exceeded those for the Activator group in both directions, caudally and anteriorly. The Activator group showed an anterior rotation and the Herbst group a slight posterior rotation of the mandible. The present investigation revealed that the effective TMJ and chin changes were increased by both Activator and Herbst treatment. However, the Herbst appliance renders more favourable sagittally orientated treatment effects in a much shorter period of time compared with the Activator. (+info)
Evaluation of the effects of functional orthopaedic treatment on temporomandibular joints with single-photon emission computerized tomography.
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The aims of this investigation were to evaluate the temporomandibular joints (TMJs) with single-photon emission computerized tomography (SPECT) in subjects treated with a mandibular advancement repositioning splint (MARS), and to compare the results with the total effect on dento-facial morphology. The study was undertaken on 17 Class II division 1 malocclusion subjects (nine males, eight females) with mandibular retrusion. Ten patients (five males, five females) formed the treatment group and seven (four males, three females) were used as the control. SPECT was performed only in the treatment group. Cephalometric evaluation showed significant increases in NAPog (P < 0.001) and SNB (P < 0.05) angles. Increased bone formation in theTMJs was analysed with the aid of pre- and post-treatment scintigraphic studies. The results indicate that new bone formation in the mandibular condyles seems to contribute to the increase in mandibular prognathism resulting from functional jaw orthopaedics. (+info)
Development of a non-radiographic cephalometric system.
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The purpose of the present study was to develop a three-dimensional (3D) non-radiographic cephalometric system based on Simon's three planes. In pursuit of cephalometry without irradiation of patients, readiness of data and simplicity of the system, a portable 3D computer-aided, contact-method cephalometric system, equipped with newly developed cephalometric software for chairside use, was developed. The feasibility of its clinical use was examined based on comparison of the measurements obtained with those from conventional radiographic cephalometry on a human dry skull, as well as on three living subjects. From a total of nine measurements, a statistically significant difference was seen in six measurements: FMPA, U1/FH, FMIA, ANB, IMPA, and A-Np for the dry skull; in four measurements: FPA, FMPA, U1/FH, and Pog-Np for subject A; in five measurements: FMPA, U1/FH, FMIA, AN/FH, and A-Np for subject B; and in seven measurements: FMA, FMPA, U1/FH, FMIA, ANB, IMPA, and AN/FH for subject C. A clinically significant difference was found only in one measurement, U1/FH for the dry skull, in four measurements FPA, FMPA, U1/FH, and Pog-Np for subject A, in one measurement AN/FH for subject B, and in three measurements U1/FH, FMIA, and AN/FH for subject C. While demonstrating workability as a chairside tool and whilst there is a need for further refinement in measurement accuracy, this newly developed cephalometric system shows potential applicability, not only in the clinic as an auxiliary to or as a substitute for existing radiographic cephalometry, but also outside the clinic as an epidemiological tool. (+info)
Angular photogrammetric analysis of the soft tissue facial profile.
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All medical specialties interested in improving facial appearance need to measure the face to quantify the desired facial changes. The purpose of this investigation was to obtain objective average measurements of the soft tissue facial profile to use them as a guide for aesthetic treatment goals. The analysis of the soft tissue facial profile from photographic records provides information on the morphology of the profile and its relationship with the underlying dentoskeletal tissues. In this investigation the soft tissue facial profile of a young adult European Caucasian population (212 individual, 50 males and 162 females, 18-20 years of age) was studied by means of standardized photographic records taken in the natural head position (NHP). Angular measurements were analysed digitally. Sexual dimorphism was found for several angles: nasofrontal (G-N-Prn: P < 0.01), vertical nasal (Cm-Sn/N-Prn: P < 0.01), nasal (N-Prn/TV: P < 0.01), nasal dorsum (N-Mn-Prn: P < 0.05), and mandibular contour (C-Me/G-Pg: P < 0.01). Wide individual variations in nasolabial and mentolabial angles were also observed. (+info)
Age-related changes in cardiac autonomic control during sleep.
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Aging is commonly associated with decreased sleep quality and increased periodic breathing (PB) that can influence heart rate variability (HRV). Cardiac autonomic control, as inferred from HRV analysis, was determined, taking into account the sleep quality and breathing patterns. Two groups of 12 young (21.1 +/- 0.8 years) and 12 older (64.9 +/- 1.9 years) volunteers underwent electroencephalographic, cardiac, and respiratory recordings during one experimental night. Time and frequency domain indices of HRV were calculated in 5-min segments, together with electroencephalographic and respiratory power spectra. In the elderly, large R-R oscillations in the very-low frequency (VLF) range emerged, that reflected the frequency of PB observed in 18% of the sleep time. PB occurred more frequently during rapid eye movement sleep (REM) sleep and caused a significant (P < 0.02) increase in the standard deviation of normal R-R intervals (SDNN) and absolute low-frequency (LF) power. With normal respiratory patterns, SDNN, absolute VLF, LF, and high frequency (HF) power fell during each sleep stage (P < 0.01) compared with young subjects, with no significant sleep-stage dependent variations. An overall decrease (P < 0.01) in normalized HF/(LF + HF) was observed in the elderly, suggesting a predominant loss of parasympathetic activity which may be related to decreased slow-wave sleep duration. These results indicate that two distinct breathing features, implying different levels of autonomic drive to the heart, influence HRV in the elderly during sleep. The breathing pattern must be considered to correctly interpret HRV in the elderly. (+info)
Long-term effects of chin-cap therapy on the temporomandibular joints.
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It is commonly believed that upward/backward forces applied to the condyle by a chin-cap cause temporomandibular dysfunction (TMD). In the current study the long-term follow-up (2-11 years) of patients treated with a chin-cap was investigated regarding signs and symptoms of TMD. The treatment group consisted of 32 individuals who had a skeletal Class III malocclusion treated using chin-cap therapy (mean age 18.4 years). The two control groups contained 39 untreated subjects with skeletal Class III malocclusions (mean age 15.5 years) and 53 dental students (mean age 19.2 years) with acceptable normal occlusions. Functional examination of the subjects was carried out and those with at least one sign/symptom (clicking, pain, or deviation) were identified as the 'symptomatic' subgroup. The distribution of symptomatic individuals was 25 per cent in the treatment group, 23 per cent in the Class III malocclusion group, and 41.5 per cent in the normal group (dental students). In addition, the frequency of signs and symptoms of TMD in the symptomatic individuals was also investigated. There were no signs of crepitus in any subject, clicking was found in 50 per cent of the treatment group and pain in 54.5 per cent of the normal group. The results of this long-term follow-up indicate that chin-cap treatment is neither a risk factor nor a prevention for TMD. Age and stress factors should always be considered in the evaluation of TMD. (+info)
Geometric morphometric analysis of allometric variation in the mandibular morphology of the hominids of Atapuerca, Sima de los Huesos site.
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Allometry is an important factor of morphological integration that contributes to the organization of the phenotype and its variation. Variation in the allometric shape of the mandible is particularly important in hominid evolution because the mandible carries important taxonomic traits. Some of these traits are known to covary with size, particularly the retromolar space, symphyseal curvature, and position of the mental foramen. The mandible is a well studied system in the context of the evolutionary development of complex morphological structures because it is composed of different developmental units that are integrated within a single bone. In the present study, we investigated the allometric variation of two important developmental units that are separated by the inferior nerve (a branch of CN V3). We tested the null hypothesis that there would be no difference in allometric variation between the two components. Procrustes-based geometric morphometrics of 20 two-dimensional (2D) landmarks were analyzed by multivariate regressions of shape on size in samples from 121 humans, 48 chimpanzees, and 50 gorillas (all recent specimens), eight fossil hominids from Atapuerca, Sima de los Huesos (AT-SH), and 17 Neandertals. The findings show that in all of the examined species, there was significantly greater allometric variation in the supra-nerve unit than in the infra-nerve unit. The formation of the retromolar space exhibited an allometric relationship with the supra-nerve unit in all of the species studied. The formation of the chin-like morphology is an "apodynamic" feature of the infra-nerve unit in the AT-SH hominids. The results of this study support the hypothesis that allometry contributes to the organization of variation in complex morphological structures. (+info)
Unilateral posterior crossbite and chin deviation: is there a correlation?
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A retrospective study evaluating the clinical discernment of chin deviations in general, and especially in relation to unilateral posterior crossbite (UPXB), was carried out to determine whether (1) there is a correlation between UPXB and clinically discernible chin deviation, (2) there are differences between the judgement of professional dental observers and laymen, (3) visual assessment of chin deviation compares well with computer-assisted assessment and (4) how large a chin deviation should be before it is noticed. The experimental group consisted of 72 patients (30 males and 42 females, average age 14.5 years) with a UPXB. A control group of 72 subjects without a UPXB was matched for age and sex. In addition, one computer-designed face was added with chin deviations of 0, 2, 4, 6 and 8 mm to the left. The full-face slides of all subjects were shown twice, with an interval of 2 weeks, to an audience of seven orthodontists, ten dental students and five laymen judging by eye. A computer-assisted assessment was carried out by one observer, in order to create a standardized comparison to visual scoring. Inter-observer examination of visual scoring showed moderate agreement (kappa = 0.48). When comparing the computer-assisted and visual scores, the intra-class correlation coefficient (ICC) was 0.87. There were no major differences between professional observers and laymen, although the latter gave significantly more responses in the direction opposite to the crossbite. In 70.3 per cent (on average) of the subjects with a crossbite, a deviation in the same direction as the crossbite was noticed visually. The majority of the observers observed a chin deviation of at least 4 mm. (+info)