Evaluation of arch forms depending on the angle classification.

It is generally accepted that each individual has his or her own dental arch form. However, during orthodontic treatment, industrially preshaped archwires are widely used. The resulting use of the same arch form for all malocclusions may compromise occlusal stability after orthodontic treatment. AIM: To determine the average dental arch form of a non-consulting Moroccan population depending on the Angle classification, after digitization of plaster models of the dental arches. MATERIAL AND METHODS: A sample of 50 dental students aged between 21 and 27 was selected. After digitization of the plaster models to produce a cloud of points, the barycentric method was applied to this representation, enabling all the arch shapes of each series to be superimposed with Photoshop CS 5 software (layer mode) and the average curves for each Angle class to be thereby determined. RESULTS: The average maxillary and mandibular arch forms were defined for each class: Class I: a normal maxillary form and an ovoid mandibular form; Class II: a tapered maxillary form and a narrow tapered mandibular form; Class III: narrow tapered forms for both upper and lower arches. Globally speaking, in this sample an ovoid mandibular arch form and a normal maxillary arch form are the dominant shapes. DISCUSSION AND CONCLUSION: The studied population exhibited specific arch form features. This study could serve as the basis for the choice and use of preformed archwires better-adapted to the needs of our patients.

Comparison of the efficacy of a conventional primer and a self-etching primer.

INTRODUCTION: In orthodontic practice, the bonding protocol makes use of a primer between the bracket and the enamel surface to create a reliable bond. In order to optimize the technique and reduce bonding time, a new group of primers has been introduced in orthodontics: the self-etching primers (SEP). The aim of this work was to compare their efficacy with that of a traditional primer. MATERIALS AND METHOD: This study is a single-center, single-blind, clinical trial using the SEP system on teeth 14 and 25 and the Ortho-Solo(®) system (traditional hydrophilic primer) on teeth 24 and 15 in the same patient. The study population was composed of 100 patients treated in a private orthodontic office in Casablanca. Recruitment for this sample included all patients treated orthodontically without extractions, possessing teeth that were considered healthy, with no occlusal interferences; on the other hand, all patients with mental or physical disabilities, those aged under 14 and those with poor orodental hygiene were excluded from the study. The Kaplan-Meier test was used to compare results. RESULTS: The bond failure rates for the two groups were 7.5% in the SEP group and 9% in the Ortho-Solo(®) group. The difference between these two adhesive systems was not statistically significant (P=0.34). Concerning the type of bond failure, the comparison again shows no statistically significant difference (P=0.44). In both systems, cohesive failures concerned only 2% of all the brackets bonded. DISCUSSION: The clinical trial was performed with a crossover design to avoid bias due to chewing patterns, a factor that is responsible for most of the failures noted in the study. The results of the studies by Miller and Buyukyilmaz, and some others, are in agreement with our results. However other in vivo and in vitro studies contradict our results, showing higher bond failure rates with the self-etching system. CONCLUSION: SEP is as effective as a traditional hydrophilic adhesive and, in addition, possesses advantages in terms of ergonomics and chair-time. The literature confirms the data of this clinical trial and recommends the use of SEP; the only remaining limitation is its high cost.