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Biomedical subjects

Birte Melsen

Publications and source records attributed to Birte Melsen.

24 records · Page 2Linked to original sources
PubMed2003

Distal molar movement with Kloehn headgear: is it stable?

The aim of this study was to evaluate intramaxillary molar movement after 8 months of cervical traction and posttreatment displacement 7 years later. The total molar displacements in relation to stable intraosseous reference points were compared with those observed in an untreated control group that also had intraosseous reference indicators inserted. During the headgear period, the type of molar displacement could be predicted by the direction of the force system acting on the teeth. It was noted, however, that the variation in the vertical development was related more to each patient's growth pattern than to the force system applied. After cessation of the headgear, intramaxillary displacement of the molars was noted, and the total displacement of the molars did not differ from that of the untreated group. The indication for intramaxillary displacement of the molars by means of extraoral traction is therefore questioned.

Cephalometry↗
PubMed2003

The transfer of occlusal forces through the maxillary molars: a finite element study.

The morphology of the skeleton is known to reflect functional demand. A change in the intramaxillary position of molars can be expected to influence the transfer of occlusal forces to the facial skeleton. A finite element analysis allows us to simulate the displacement of a molar in relation to the well-defined morphology of the maxilla. Three 3-dimensional unilateral models of a maxilla from a skull with skeletal Class I and neutral molar relationships were produced based on CT-scan data. The maxillary first molar was localized so that the contour of the mesial root continued into the infrazygomatic crest. When the molar was loaded with occlusal forces, the stresses were transferred predominantly through the infrazygomatic crest. This changed when mesial and distal displacements of the molars were simulated. In the model with mesial molar displacement, a larger part of the bite forces were transferred through the anterior part of the maxilla, resulting in the buccal bone being loaded in compression. In the model with distal molar displacement, the posterior part of the maxilla was deformed through compression; this resulted in higher compensatory tensile stresses in the anterior part of the maxilla and at the zygomatic arch. This distribution of the occlusal forces might contribute to the posterior rotation often described as the orthopedic effect of extraoral traction.

Alveolar Process↗
PubMed2003

Does labial movement of lower incisors influence the level of the gingival margin? A case-control study of adult orthodontic patients.

It has been suggested that proclination of the lower incisors results in gingival recession. Proclination is, however, a valuable alternative to extraction especially when considering facial aesthetics in adult patients. The aim of this study was to evaluate the association between the extent of labial movement of the lower incisors and the prevalence and severity of gingival recession in orthodontically treated adult patients. A retrospective case-control study based on the analysis of study-casts and intra-oral slides of 300 adult patients was carried out. One hundred and fifty pairs matched by age and sex were selected using simple random sampling. Recordings of gingival recession were made using casts as well as intra-oral slides. Dental displacement was measured on casts comparing the measurements before and after treatment. The intra-oral slide recordings of gingival recession were more reliable than the cast recordings. Although the difference in prevalence of individuals with gingival recession among cases and controls was statistically significant (P < 0.001), no significant difference in the mean recession value could be found between cases and controls (P > 0.10). The mean value of the extent of recession of the four lower incisors amounted to 0.36 mm for treated subjects and 0.22 mm for the controls. This mean difference of 0.14 mm between members of a pair was not clinically relevant. Faced with the alternative between extraction and labial movement of lower incisors the present study indicates that the latter is a valuable alternative leading to no clinically relevant deterioration of the periodontium.

Adult↗
PubMed2003

Bone turnover rate in rats does not influence root resorption induced by orthodontic treatment.

The aim of this study was to determine, in a rat model, whether a state of high or low bone turnover had an effect on the rate and type of tooth movement and on the incidence of root resorption induced by orthodontic treatment. The maxillary left first molar was moved mesially for 21 days in 52 6-month-old Wistar rats. They were divided into three groups: group 1 (n = 19) with normal bone turnover, group 2 (n = 16) with high bone turnover, and group 3 (n = 17) with low bone turnover. The contralateral side was left untreated to act as a control. The different metabolic rates were created by inducing hyper- and hypothyroidism. The amount of tooth movement was measured using an electronic calliper and the location of the centre of rotation (CRot) was determined after microcomputer tomographic scanning and subsequent three-dimensional reconstruction. Histomorphometric evaluation of root resorption was performed on undecalcified 7 microm thick sections of the maxilla and the differences between treated and untreated sides were evaluated. The results showed that high bone turnover increased the amount of tooth movement compared with the normal or low bone turnover state. There was no statistical difference in the location of the CRot. The treated side presented more root resorption than the untreated side, but this difference was not influenced by the metabolic rates. On the contrary, the untreated side in the low bone turnover group showed more root resorption, suggesting that in subjects where a decreased bone turnover rate is expected, the risk of root resorption could be increased.

Analysis of Variance↗
PubMedDate not supplied

Microdamage in porcine alveolar bone due to functional and orthodontic loading.

Bone remodelling has been associated with microdamage. The aim of this study was to investigate the presence of microdamage in the alveolar bone and its potential role in the initiation of bone remodelling following the application of an orthodontic load. The three-dimensional morphology of the alveolar bone was investigated by means of high resolution micro-CT scanning. In 25, 3-month-old, male Danish land-race pigs, the alveolar bone around the lower right and left first molars was analysed. The right first molar was moved buccally with a force of 130 cN by means of a custom-made cantilever made of a TMA 0.017 x 0.025 inch wire. The left molar was left untreated. After 1, 2, 4, 7 and 15 days of treatment the regions containing the right and left molars were excised and en bloc stained in basic fuchsin and the presence of microdamage detected. Diffuse damage was present in the alveolar bone of both the treated and the untreated teeth on both sides. On the lingual sides, diffuse damage showed the same orientation as the periodontal fibres. Bone microcracks were also detected on both the treated and untreated teeth. On the buccal surfaces they where often observed in close proximity to scalloped resorption surfaces. After 1 day of treatment, the presence of microcracks on the buccal-treated side was particularly marked. To conclude, bone microdamage is present in porcine alveolar bone in form of both microcracks and diffuse damage, suggesting that microdamage-driven remodelling also occurs in the alveolar bone. The presence of bone microcracks in the direction of the orthodontic force at day 1 suggests that they could represent the first damage induced by the orthodontic load that has to be repaired.

Animals↗