Assessing the position and bony support of mandibular incisors with cone-beam computed tomography
Baysal A, Ucar FI, Buyuk SK, Ozer T, Uysal T. Alveolar bone thickness and lower incisor position in skeletal Class I and Class II malocclusions assessed with cone-beam computed tomography. Korean J Orthod 2013;43:134-40
Correction of Class II malocclusions often requires forward movement of the mandibular dental arch; this can lead to excessive incisor proclination, causing instability and stress to the periodontium. The limit of incisor movement is dictated by the periodontal tissues and the anatomy of the symphysis. Several studies have found differences in bone thickness and morphology according to facial types. The aim of this study was to assess alveolar bone thickness and incisor position in Class I and Class II subjects with average-angle and high-angle growth patterns using cone-beam computed tomography. Cone-beam computed tomography records were collected from 41 Class I subjects and 38 Class II subjects, and further divided into high-angle and average-angle subgroups. The only difference observed between the Class I and Class II patients was that the Class I patients had greater labial alveolar bone thickness. When the authors compared the high-angle and the average-angle subgroups, the Class II average-angle group showed more mandibular incisor protrusion, more proclination, and higher lingual alveolar bone angles. The Class II high-angle group had root apices closer to the labial cortex and thinner spongious bone. These differences were not seen in the Class I subgroups. The position and movement of the mandibular incisors play a critical role in orthodontic treatment planning, and the limits of incisor movement should be considered before beginning treatment. Furthermore, clinicians should take into account the vertical growth pattern when planning treatment because the decreased thickness of cancellous bone in Class II high-angle patients limits the range of movement of their mandibular incisors.
Reviewed by Shane Hoelz
Gingival recession in orthodontically treated patients with bonded lingual retainer
Renkema AM, Fudalej PS, Renkema AA, Abbas F, Bronkhorst E, Katsaros C. Gingival labial recessions in orthodontically treated and untreated individuals: a case-control study. J Clin Periodontol 2013;40:631-7
This was a retrospective case-control study to evaluate the development of labial gingival recession 6 years after orthodontic treatment in patients with bonded lingual retainers, compared with untreated controls. One hundred orthodontically treated patients were selected from the Department of Orthodontics and Craniofacial Biology, Radboud University, Nijmegen Medical Centre, in The Netherlands, and 120 untreated subjects were selected from the Nittedal Growth Material, a longitudinal record from the University of Oslo in Norway. Dental models, consisting of a mixture of Angle Class malocclusions, were examined for both groups about ages 12, 15, 18, and 21 years, with pretreatment about age 12 and debond at age 15. The prevalence and number of gingival recessions were evaluated at each time point. The authors found an odds ratio of 4.48 ( P <0.001; 95% CI, 2.61-7.70) of developing gingival recession for the patients compared with the controls, and the mandibular incisors seemed to be relatively more vulnerable to gingival recession among the treated subjects. The authors acknowledged the limitation of the study to distinguish the effects of the active and retention phases of orthodontic treatment. In addition, the use of a different population as the control group and the use of a retrospective study with confounding variables (plaster model, diet, hygiene habit, and smoking) also affected the validity of the study. Even though the authors did not specify the type of orthodontic treatment performed, the finding is potentially relevant to orthodontists to be aware of long-term gingival recession when making clinical decisions to extract teeth, or buccally expand and alter the mandibular incisor angle.
Reviewed by Leon Su
Gingival recession in orthodontically treated patients with bonded lingual retainer
Renkema AM, Fudalej PS, Renkema AA, Abbas F, Bronkhorst E, Katsaros C. Gingival labial recessions in orthodontically treated and untreated individuals: a case-control study. J Clin Periodontol 2013;40:631-7
This was a retrospective case-control study to evaluate the development of labial gingival recession 6 years after orthodontic treatment in patients with bonded lingual retainers, compared with untreated controls. One hundred orthodontically treated patients were selected from the Department of Orthodontics and Craniofacial Biology, Radboud University, Nijmegen Medical Centre, in The Netherlands, and 120 untreated subjects were selected from the Nittedal Growth Material, a longitudinal record from the University of Oslo in Norway. Dental models, consisting of a mixture of Angle Class malocclusions, were examined for both groups about ages 12, 15, 18, and 21 years, with pretreatment about age 12 and debond at age 15. The prevalence and number of gingival recessions were evaluated at each time point. The authors found an odds ratio of 4.48 ( P <0.001; 95% CI, 2.61-7.70) of developing gingival recession for the patients compared with the controls, and the mandibular incisors seemed to be relatively more vulnerable to gingival recession among the treated subjects. The authors acknowledged the limitation of the study to distinguish the effects of the active and retention phases of orthodontic treatment. In addition, the use of a different population as the control group and the use of a retrospective study with confounding variables (plaster model, diet, hygiene habit, and smoking) also affected the validity of the study. Even though the authors did not specify the type of orthodontic treatment performed, the finding is potentially relevant to orthodontists to be aware of long-term gingival recession when making clinical decisions to extract teeth, or buccally expand and alter the mandibular incisor angle.
Reviewed by Leon Su
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