Tooth Borne Anchorage: A Comparative Analysis

Objective: The purpose of this study was to compare two anchorage modalities. Differential mass and differential moments were compared for their anchorage effectiveness in the sagittal and vertical dimensions. Class I patients with maximum anchorage requirements and treated with four first premolar extractions were selected. Background: Due to a severe combination of crowding, incisor proclination and protrusion, and procumbency of the lips, certain patients require extractions and maximum anchorage in orthodontic treatment.8 Two tooth borne anchorage modalities, differential mass and differential moments, have been shown to be able to achieve maximum anchorage requirements.5, 7 Methods: The available digital records of all patients (n=6478) treated within the Nova Southeastern University Department of Orthodontics and Dentofacial Orthopedics (NSU-DODO) clinic were searched to find all patients meeting the inclusion criteria. All patients that met the inclusion 6 criteria were selected and divided into the two groups, differential mass and differential moments, based on the tooth borne anchorage modality utilized during their treatment. Of the available records, 24 patients met the criteria for the differential mass group, while 10 patients met the criteria for the differential moments group. The pre-treatment and post-treatment cephalometric radiographs were traced and superimposed to evaluate the amount change of the upper and lower first molars in the sagittal and vertical dimensions during treatment. Results: The differential mass group, on average, showed less anchorage loss compared to the differential moments group, in the sagittal and vertical dimensions for the upper and lower first molars. The differential moments group, compared to the differential mass group, had smaller standard deviations and ranges in all dimensions in the lower molars and in the sagittal dimension for the upper molars. These differences were not found to be statistically significant. The statistical variance of the effect size showed that 65% of the variance in the lower arch and 64% of the variance in the upper arch were due to unknown circumstances. Conclusion: The null hypotheses, that both anchorage modalities would provide the same magnitude of anchorage, could not be rejected. This study was limited by many factors, including treatment by different residents, supervision by different clinical faculty members, unspecified initial treatment goals, and potential errors in measurement. This study is clinically relevant within the NSU-DODO clinic to show the results of completed treatments within the NSU-DODO clinic, and should be considered by the residents and faculty in the future treatment of patients with similar malocclusions.