Comparison of the long-term skeletal stability between a biodegradable and a titanium fixation system following BSSO advancement - a cohort study based on a multicenter randomised controlled trial.

Biodegradable fixation systems could reduce or eliminate the problems associated with removal of titanium plates. A multicenter randomised controlled trial (RCT) was performed in the Netherlands from December 2006-July 2009, and originally 230 injured and orthognathic patients were included. The patients were randomly assigned to either a titanium control group (KLS Martin) or to a biodegradable test group (Inion CPS). The aim of the present study was to compare the long-term skeletal stability of advancement bilateral sagittal split osteotomies (BSSO) of a biodegradable system and a titanium system. Only patients from the original RCT who were at least 18 years old and who had a BSSO advancement osteotomy were included. Those who had simultaneous Le Fort I osteotomy or genioplasty were excluded. Analysis of skeletal stability was made by digital tracing of lateral cephalograms. Long-term skeletal stability in BSSO advancement did not differ significantly between patients treated with biodegradable plates and screws and those treated with titanium plates and screws. Given the comparable amount of relapse, the general use of Inion CPS in the treatment of BSSO advancement should not be discouraged. On the basis of other properties a total picture of the clinical use can be obtained; the short-term stability, the intraoperative switches, the number of plates removed and cost-effectiveness. Trial registration of original RCT: http://www.controlled-trials.com; ISRCTN 44212338.

Long-term oral-appliance therapy in obstructive sleep apnea: a cephalometric study of craniofacial changes.

OBJECTIVES: The aim of this randomized controlled study was to cephalometrically assess possible changes in craniofacial morphology associated with long-term use of an adjustable oral-appliance compared with continuous positive airway pressure (CPAP) in patients with the obstructive sleep apnea/hypopnea syndrome (OSAHS). In addition, we wanted to study the relationship between these possible changes and the degree of mandibular protrusion associated with oral-appliance therapy. METHODS: Fifty-one patients were randomized to oral-appliance therapy and 52 patients to CPAP therapy. At baseline and after follow-up (2.3±0.2 years), a lateral cephalogram of all patients was made in maximum intercuspation to determine relevant cephalometric variables. Both baseline and follow-up cephalograms were traced digitally whereupon cephalometric variables were compared. Changes in craniofacial morphology between the oral-appliance- and CPAP group were evaluated with a linear regression analysis. RESULTS: Compared with CPAP, long-term use of an oral-appliance resulted in small but significant (dental) changes. Overbite and overjet decreased, 1.0 (±1.5)mm and 1.7 (±1.6)mm, respectively. Furthermore we found a retroclination (-2.0 (±2.8)°) of the upper incisors and a proclination (3.7 (±5.4)°) of the lower incisors. Moreover, the lower- and total anterior facial height increased significantly, 0.8 (±1.5)mm and 0.9 (±1.4)mm, respectively. No changes in skeletal variables were found. Linear regression analysis revealed that the decrease in overbite was associated with the mean mandibular protrusion during follow-up (B=-0.029, SE=0.014, p<0.05). CONCLUSIONS: Oral-appliance therapy should be considered as a life long treatment, and there is a risk of craniofacial changes to occur. Therefore, patients treated with an oral-appliance, need a thorough follow-up by a dentist or dental-specialist experienced in the field of dental sleep medicine.

Maintenance of a deep bite prior to surgical mandibular advancement.

Adult patients with a Class II skeletal base are often treated by a combined orthodontic and surgical approach. Advancement of the mandible, most often including a bilateral sagittal split osteotomy (BSSO), is preceded by orthodontic alignment and frequently the curve of Spee is levelled. When the chin is prominent, there is a risk of accentuating this as a result of surgery. An option to prevent this is to maintain a deep curve of Spee before surgical advancement. This will result in an opening rotation of the mandible during surgery and thus, a less prominent chin. The aim of this study was to compare, retrospectively, two orthodontic treatment approaches in patients treated by a BSSO. In one group (4 males, 20 females; mean age pre-surgery 29.3 years), the deep bite was maintained (deep bite group) while in the other (3 males, 10 females; mean age pre-surgery 27.1 years) the overbite was normal prior to surgery (level group). Lateral skull radiographs were taken before orthodontic treatment (T0), prior to surgery (T1), and at the end of treatment (T2). Differences between the groups as measured on lateral skull radiographs at T1 and T2 were analysed and quantified using an independent t-test. The results showed that soft tissue pogonion moved significantly further forward in the level than in the deep bite group (P < 0.05). Lower anterior face height and the cranial base-mandibular plane angle increased more in the deep bite than in the level group (P < 0.05 and P = 0.001, respectively). The maintenance of a deep bite prior to mandibular advancement surgery induces an opening rotation of the mandible reducing chin prominence and increasing lower anterior face height post-surgically.

Effects of a mandibular advancement device on the upper airway morphology: a cephalometric analysis.

The aims of this study were to assess changes in the upper airway morphology associated with an oral appliance in situ in patients suffering from the obstructive sleep apnoea-hypopnoea syndrome and to relate these changes to treatment response. Changes in upper airway morphology as a result of an oral appliance were assessed in 52 patients with obstructive sleep apnoea-hypopnoea syndrome by means of cephalometric analysis. Lateral cephalograms were taken at baseline and after 2-3 months of treatment. Baseline and follow-up cephalograms were traced twice and cephalometric variables were compared. The predictive value of changes in upper airway morphology for the treatment response was evaluated in univariate and multivariate regression analyses. Oral appliance therapy resulted in an increased posterior airway space at the level of the second vertebra, the uvular tip and the base of the tongue. The increase of the posterior airway space at the level of the second vertebra and the uvular tip were the best predictors for relative improvement of the apnoea-hypopnoea index. However, the predictive value for treatment response of these cephalometric upper airway changes should be interpreted with caution.

A comparison of the reproducibility of manual tracing and on-screen digitization for cephalometric profile variables.

The aim of this investigation was to analyse and compare the reproducibility of manual cephalometric tracings with on-screen digitization using a soft tissue analysis. A random sample of 20 lateral cephalometric radiographs, in the natural head posture, was selected. On-screen digitization using Viewbox 3.1.1.9 cephalometric software and manual tracing on a 1:1 printout of the image was carried out twice in different sessions 1 week apart. Differences were analysed using a repeated measurement analysis of variance with method, session, and method-session interaction as explaining variables. The differences were expressed as an absolute percentage of the overall mean. The findings of the present study indicate that the two measurement methods differ significantly for 11 variables (P = 0.001 to P = 0.042). The area around stomion was the least reproducible. Except for s-n(s)-unt, nasal protrusion, with the manual technique, all mean differences between sessions and between methods were less than 1 degree or 1 mm and were, on-screen, smaller for 13 variables compared with those traced manually. Absolute percentage differences of the overall mean were smaller for seven variables with the digital technique and three variables in the manual technique, while four manual variables and one on-screen variable exceeded 2 per cent of the overall mean. Although small significant differences were found, the clinical relevance remains questionable.