Changes in rabbit jaw-muscle activity parameters in response to reduced masticatory load.

Mechanical food properties influence the neuromuscular activity of jaw-closing muscles during mastication. It is, however, unknown how the activity profiles of the jaw muscles are influenced by long-term alterations in masticatory load. In order to elucidate the effect of reduced masticatory load on the daily habitual activity profiles of three functionally different jaw muscles, the electromyograms of the masseter, temporalis and digastric muscles were recorded telemetrically in 16 male rabbits between seven and 20 weeks of age. Starting at eight weeks of age the experimental animals were fed significantly softer pellets than the control animals. Daily muscle activity was quantified by the relative duration of muscle use (duty time), burst number and burst length in relation to multiple activity levels. The daily duty time and burst number of the masseter muscle were significantly lower in the experimental group than in the control group at 5% and 10% of the maximum activity during the two weeks following the change in food hardness. By contrast, altered food hardness did not significantly influence the activity characteristics of the temporalis and digastric muscles. The findings suggest that a reduction in masticatory load decreases the neuromuscular activity of the jaw-closing muscles that are primarily responsible for force generation during mastication. This decrease is most pronounced in the weeks immediately following the change in food hardness and is limited to the activity levels that reflect muscle contractions during chewing. These findings support the conclusion that the masticatory system manifests few diet-specific long-term changes in the activity profiles of jaw muscles.

Perceptions of Dutch orthodontic patients and their parents on oral health-related quality of life.

OBJECTIVE: To test the hypotheses that 1) there is no difference between orthodontic patients' and their parents' reports of patients' oral health-related quality of life, and 2) there are no gender differences. MATERIALS AND METHODS: The sample consisted of 182 orthodontic patients (age range, 8-15) and their parents. Respondents were required to complete the Child Oral Health Impact Profile (COHIP). Items were divided into five different subscales, and scores on all subscales were compared between and within groups. Also, scores on six additional items regarding treatment expectations and global health perception were compared. Two hypotheses were tested: first, that no differences between parents and patients would be detected, and second, that no differences between boys and girls would be found. RESULTS: The first hypothesis could not be rejected. Only a few minor differences between parents and patients were found. The second hypothesis was rejected. Differences between boys and girls were found on the subscales Emotional Well-Being and Peer Interaction, indicating that girls experience more effects of oral health on their quality of life than do boys. CONCLUSIONS: Parents' reports on their children's oral health-related qualities of life were in agreement with reports of the orthodontic patients. This suggests that parents are suitable alternatives to their children in surveys measuring oral health-related quality of life.

[Do primary care physicians acting as gatekeepers really improve health outcomes and decrease costs? A systematic review of the concept gatekeeping]. / Macht der Hausarzt als Lotse die Gesundheitsversorgung wirklich besser und billiger? Ein systematischer Review zum Konzept Gatekeeping.

AIM: The aim of this systematic review was to analyse the effects of gatekeeping where primary care physicians (PCP) control access to specialist care. METHODS: Literature search in Medline, EMBASE, Cochrane Library, and a hand search were carried out. INCLUSION CRITERIA: (1) intervention: gatekeeping by PCP compared to free access to specialist care; (2) outcomes: health outcomes, health related quality of life, quality of care, utilization of care, costs, satisfaction of patients and providers; (3) design: RCT, quasi-random. CT, CBA, cohort and case control studies, ITS. Data extraction and assessment was done by two independent reviewers according to Cochrane EPOC-Group and USTFCPS. RESULTS: 24 included studies (1989-2007) were as follows: 1 RCT, 2 quasi-randomised CT, 3 prospective, and 12 retrospective cohort studies, 4 CBA, and 2 ITS. 67% of the studies analysed data from the USA, the remaining from CH, UK, DK and NL. Studies had relevant limitations concerning the quality of execution and publication. Overall 13 of 24 studies reported a positive and two a negative effect of gatekeeping compared to open access models; nine showed no differences. The results varied according to outcome parameters. CONCLUSIONS: International evidence on effects of gatekeeping is limited by the low internal validity of studies and applicability to other contexts. It suggests that gatekeeping by PCP decreases utilization of specialist care and health care costs. Based on very few studies health outcomes and patient quality of life in gatekeeping models might be comparable with those in open access models. Evidence is inconsistent or not available concerning the quality of care, patient or provider satisfaction.

Caries lesions after orthodontic treatment followed by quantitative light-induced fluorescence: a 2-year follow-up.

The aim of this study was to monitor, by means of quantitative light-induced fluorescence (QLF), the natural behaviour of white spot lesions detected immediately after orthodontic treatment and 2 years post-treatment. The buccal tooth surfaces of 51 subjects (>or=12 years), 24 males and 27 females, were examined with QLF for the presence of caries immediately after debonding (T0), and 6 weeks (T1), 6 months (T2), and 2 years (T3) thereafter. The fluorescence loss [Delta F (per cent)] and area [A (mm(2))] of any lesions were determined using dedicated software. The lesion development and influence of gender were determined by a general linear model (Friedman repeated-measures analysis and two-way repeated-measures analysis of variance). Using QLF, 370 carious surfaces were recorded at T0. During the study, 19 lesions were lost from QLF analysis of which 16 lesions (Delta F(0)=7.6-39.2 per cent) in two subjects were restored and three teeth with lesions were extracted or crowned. This resulted in 351 lesions that were included in this study with a median Delta F at T0 of 8.5 per cent (quartiles 6.6 per cent; 11.9 per cent). The lesions varied from incipient (Delta F<10 per cent, n=227) to advanced (Delta F>25 per cent, n=6). Overall, the lesions showed improvement between T0 and T2 (P<0.01) but no further significant improvement at T3. Thirty-five lesions became significantly worse after 2 years. The majority of lesions (n=171) were considered to be stable, and 145 lesions improved significantly of which only 10 lesions improved to such an extent that they disappeared. White spot lesions developed during orthodontic treatment have very limited ability to improve after appliance removal. Further research to investigate the potential of preventive measures to enhance lesion improvement is necessary.

Duty time of rabbit jaw muscles varies with the number of activity bursts.

The relative duration of muscle activity during a specified period (duty time) varies depending on activity level and time of the day. Since both the number and the length of activity bursts contribute to the duty time, it was hypothesized that these variables would show intra-day variations similar to those of the duty time. To test this, we determined duty times, burst numbers, and burst lengths per hour, in relation to multiple activity levels, in a 24-hour period of concurrent radio-telemetric long-term electromyograms of various rabbit jaw muscles. The marked intra-day variation of the burst number resembled that of the duty time in all muscles, and was in contrast to the relatively invariable mean burst length. Furthermore, the duty times were more highly correlated with the number than with the length of bursts at all activity levels. Thus, the variation of the duty time in rabbit jaw muscles is caused mainly by changes in burst numbers.

Morphological parameters as predictors of successful correction of Class III malocclusion.

The aim of the study was to assess pre-treatment cephalometric parameters and measurements of the size of the apical bases as predictors of successful orthodontic correction of Class III malocclusions. Pre- and post-treatment lateral cephalograms and study models of 80 completed Class III subjects were examined to obtain 23 cephalometric parameters taken mainly from the analyses of McNamara and Schwarz, and to measure the size of the apical bases. Success of occlusal correction was evaluated as the percentage change of peer assessment rating score during treatment, which was used as the dependent variable in multivariate statistical analyses testing the predictive value of the parameters assessed. No improvement in the Class III skeletal pattern occurred during treatment and the treatment effects were confined to dentoalveolar changes. With the exception of the percentage midfacial length/mandibular length ratio, the net sum of maxillary and mandibular length differences, the mandibular ramus height/mandibular body length ratio and the gonion angle, most cephalometric parameters of pre-treatment craniofacial morphology assessed were poor predictors of successful correction of Class III malocclusions. Assessment of the size relationship of the maxillary and mandibular apical bases was the strongest predictor of occlusal correction achieved and may serve as a valuable diagnostic addition in the prediction of successful treatment outcome.

Effects of mechanical stimulation on cell cycle duration in rat gingival fibroblast progenitor cells.

The aim of this investigation was to estimate cell cycle duration in rat gingival fibroblast progenitor cells in steady-state control and during sustained mechanical stimulation. Elastics (0.15 mm thick) were inserted between maxillary M1 and M2 of 8 wk-old male rats which were labelled with H3-TdR and killed in groups of 6-7 animals together with equal-sized groups of labelled control animals at intervals between 1-168 h. Autoradiographs of consecutive mesio-distal sections were used to determine grain counts for H3-TdR-labelled cells in the connective tissue of the gingival papilla between M2 and M3. Median cell cycle times (MCC) were estimated from plots of mean and median grain counts against time. Under steady-state conditions, MCC for heavily-labelled and lightly-labelled paravascular cell populations and for labelled extravascular cells were 144, 76 and 50 h, respectively. Mechanical stimulation caused a significantly faster rate of reduction of total grain counts relative to controls in all three cell populations and a decline of estimated MCC to 115, 50 and 21 h in heavily labelled and lightly labelled paravascular cells and labelled extravascular cells, respectively. These findings indicate that mechanical stimulation induces faster progression of gingival fibroblast progenitor cells through the cell cycle.

Surgically assisted rapid palatal expansion. An acoustic rhinometric, morphometric and sonographic investigation.

This study aimed to evaluate the effect of surgically assisted rapid palatal expansion on the skeletal structures of the midface. Ten patients (mean age 28.5 years) were investigated by means of acoustic rhinometry, study model analysis and sonography before and after the procedure of surgically assisted rapid palatal expansion. The measurements revealed that surgically assisted rapid palatal expansion not only resulted in transverse expansion of the maxilla, providing dental arch space for lining up the teeth; the procedure also caused a substantial enlargement of the maxillary apical base and of the palatal vault, providing space for the tongue for correct swallowing and thus preventing relapse. There was a distinct subjective improvement in nasal breathing associated with enlargement of the nasal valve towards normal values and with an increase of nasal volume in all compartments. The measurements showed a marked influence of surgically assisted rapid palatal expansion on the skeletal structures of the midface. The significant widening can be demonstrated by non-invasive examination. Success of the osteotomy procedure can be readily monitored by sonographic examination of the expansion and the subsequent ossification, which allows individually adjusted retention periods and avoids frequent radiation exposure.

Reliability and validity of the Digigraph 100 in orthodontic diagnosis.

Cephalometric analyses of lateral cephalograms allow important statements to be made on diagnosis and treatment planning. Such radiographs should, however, be taken with a considerable reduction in radiation exposure. With the Digigraph 100 (Dolphin Imaging Systems Inc., USA) a cephalometric technique based on distance measurements of emitted sonic signals is now available. This study was aimed at determining the degree to which this procedure can cope with the requirements of reliability and validity in the field of orthodontics. For this purpose 50 volunteers were examined by conventional cephalometry with manual tracing of lateral cephalograms as well as by sonic cephalometry, with Jarabak analysis in both cases. In addition an option was available for reading lateral cephalograms into the Digigraph by means of a radiograph evaluation program. The 31 evaluated parameters were subjected to modified statistical analysis. Good reliability was recorded in the range between 0.96 and 0.99 for eleven sonic cephalometric measurements, whereas 26 values were between 0.69 and 0.95. The validity was significantly lower in comparison to radiocephalometry. In particular, measurements related to landmarks which were difficult to access or could be only indirectly determined, such as the sella point, the articulare point or the apices of the incisors, proved to be weak points of sonic cephalometry. The device is thus indicated rather in the field of communication with the patient or for intermediate examination without radiation exposure. Cephalometry without radiation exposure would represent decisive progress in orthodontic diagnostics. However, some developmental work on the processing software or even the development of a specific sonic cephalometry which deliberately dispenses with parameters that are difficult to record with this procedure is still needed.

Size discrepancy of apical bases and treatment success in angle Class III malocclusion.

The aim of this retrospective clinical study was to measure the apical bases and determine their size relationship in Class III malocclusion cases before and after orthodontic treatment, in order to evaluate their significance for the treatment success. Maxillary and mandibular apical bases were measured on study models of 104 Class III cases treated by conventional orthodontics, using a specifically constructed conveyance apparatus, and related to each other as an index. Treatment success was quantitatively assessed as the percentage change of PAR scores obtained from the pretreatment and posttreatment study models. Statistically significant relationships were disclosed between the measurements of the apical bases and several other evaluated parameters. The results obtained indicate a high prognostic value of the size relationship of the apical bases for the treatment success of Class III malocclusion.