Dental development in patients with hemifacial microsomia
Ongkosuwito EM, de Gijt P, Wattel E, Carels CE, Kuijpers-Jagtman AM. Dental development in hemifacial microsomia. J Dent Res 2010;89:1368-72
Few data are available describing the relationship and timing of dental and skeletal development in hemifacial microsomia (HFM), also referred to as oral-mandibular-auricular syndrome. The purposes of this study were to compare dental development between the affected and unaffected sides of the mandible in patients with HFM and to compare the HFM data from the patients with those of the controls. The authors hypothesized that the severity of adverse effects on dental development parallels the severity of the disturbance in mandibular development. Dental development was scored for the control children (n = 451) and in the affected and unaffected sides of the mandible for the patients with HFM (n = 84). The patients with HFM were grouped according to the Pruzansky/Kaban classification. Logistic functions were used to describe dental age over time for the HFM types. The results indicated that patients with more severe HFM (types IIb and III) have delayed dental development at young ages but experience “catch-up” development after age 5. Delay of tooth formation in patients with severe HFM indicates at least a partial relationship between dental and skeletal development in HFM. There was no significant asymmetry in dental development when both sides of the mandible were compared in patients with HFM. It is possible that delayed dental eruption can affect vertical development of the face and exaggerate mandibular deviation to the affected side. HFM stems from asymmetric development of structures originating from the first and second branchial arches. The mandibular teeth also originate from the first branchial arch, and it has been shown that skeletal and dental development rates are spatially and temporally related. The authors concluded that the greater disruption in dental development in patients with severe HFM supports the hypothesis that a disturbance in mandibular development affects dental development.
Reviewed by Daniel Cassarella
Rotation moments and implant stability
Cho YM, Cha JY, Hwang CJ. The effect of rotation moment on the stability of immediately loaded orthodontic miniscrews: a pilot study. Eur J Orthod 2010;32:614-9
Through broadened orthodontic implant use with wires or level arms, rotation moments have become important to the stability of miniscrews. The aim of this study was to evaluate the effect of rotation moment on the stability of immediately loaded miniscrews. Thirty-six miniscrews were plceed into the mandibular buccal alveolar bone of adult male beagle dogs. Immediately after placement, 24 screws were loaded with 1- and 2-Ncm nickel-titanium coil springs with either a clockwise or a counterclockwise rotation moment, and 12 screws were left unloaded. After 3 or 12 weeks, the animals were killed to prepare for the histomorphometric evaluations. Histomorphometry included measurement of bone-to-implant contact (BIC) and the ratio of bone volume to total volume (BV/TV). Three screws loaded with a 2-Ncm counterclockwise rotation moment were lost within 3 weeks, resulting in a 75% success rate compared with 100% for screws loaded with a clockwise rotation moment. The histomorphometric results showed significantly lower BIC for the counterclockwise group compared with the clockwise group. No BV/TV comparisons between the clockwise and counterclockwise groups were reported. Miniscrews have opened a new realm of orthodontics with treatment outcomes that were not previously possible with orthodontics alone. However, clinicians still experience high and variable failure rates with miniscrews. This study, with an animal model, is valuable in highlighting the magnitude and direction of the rotation moments that can influence miniscrew stability and suggests that a counterclockwise rotation moment is another possible risk factor for implant failure. Further evaluations of the effect of the rotation moment with larger samples, and varying force levels, loading times, implantation methods, and observation periods are needed.
Reviewed by Christine Hong
Rotation moments and implant stability
Cho YM, Cha JY, Hwang CJ. The effect of rotation moment on the stability of immediately loaded orthodontic miniscrews: a pilot study. Eur J Orthod 2010;32:614-9
Through broadened orthodontic implant use with wires or level arms, rotation moments have become important to the stability of miniscrews. The aim of this study was to evaluate the effect of rotation moment on the stability of immediately loaded miniscrews. Thirty-six miniscrews were plceed into the mandibular buccal alveolar bone of adult male beagle dogs. Immediately after placement, 24 screws were loaded with 1- and 2-Ncm nickel-titanium coil springs with either a clockwise or a counterclockwise rotation moment, and 12 screws were left unloaded. After 3 or 12 weeks, the animals were killed to prepare for the histomorphometric evaluations. Histomorphometry included measurement of bone-to-implant contact (BIC) and the ratio of bone volume to total volume (BV/TV). Three screws loaded with a 2-Ncm counterclockwise rotation moment were lost within 3 weeks, resulting in a 75% success rate compared with 100% for screws loaded with a clockwise rotation moment. The histomorphometric results showed significantly lower BIC for the counterclockwise group compared with the clockwise group. No BV/TV comparisons between the clockwise and counterclockwise groups were reported. Miniscrews have opened a new realm of orthodontics with treatment outcomes that were not previously possible with orthodontics alone. However, clinicians still experience high and variable failure rates with miniscrews. This study, with an animal model, is valuable in highlighting the magnitude and direction of the rotation moments that can influence miniscrew stability and suggests that a counterclockwise rotation moment is another possible risk factor for implant failure. Further evaluations of the effect of the rotation moment with larger samples, and varying force levels, loading times, implantation methods, and observation periods are needed.
Reviewed by Christine Hong
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