Changes in the retention force of six prefabricated spherical and cylindrical attachments were examined in vitro under continuous loading. The testing machine permitted insertion-separation cycles to be tested under reproducible conditions while a calibrated measuring device determined the insertion and retention forces. At the beginning, during the so-called run-in period, all anchoring elements showed a very unstable behaviour characterized by a varying marked increase and subsequent decrease in the retention force. During the ensuing functional period, the retention force followed a more stable course. In this phase, the frictional attachments having lamellae for activation proved more stable than did the spring-loaded retention attachments. Furthermore, in two of five cylindrical anchors by Gerber, the spring broke. This provides support to the concept that prefabricated attachments should be constructed as robust elements composed of as few individual parts as possible. This would help to ensure that service and repairs remain at a minimum. Frictional attachments with lamellae for activation are to be preferred for use in matrices and patrices over attachments having spring-loaded retention.

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Aim. To evaluate the degree of correlation between a dental parameter of immediate clinical relevance (overjet) with skeletal (ANB angle) and dentoskeletal parameters such as the IMPA angle and upper incisor-bispinal angle. Materials and Methods. A sample of 42 subjects, all in complete permanent dentition and without a history of orthodontic treatment or systemic pathologies, was subdivided into 2 groups: group 1 consisted of 25 subjects with ANB angle 0°–4° (skeletal class I), and group 2 was made up of 17 subjects with ANB angle >4° (skeletal class II). Each subject underwent cone-beam computed tomography (CBCT). For each right and left CBCT, the following parameters were measured: (1) ANB, (2) OJ (overjet), (3) IMPA angle, and (4) upper incisor-bispinal angle (U1/ANS-PNS). Results. Analysis of the entire sample revealed that both right and left overjets were correlated in a statistically significant fashion (P < 0.001) with ANB. No correlation between overjet and IMPA emerged, while a weak correlation between overjet and the left U1-bispinal plane was ascertained. Conclusions. Overjet may be a reliable predictor of ANB, and to a lesser extent the U1-bispinal plane, particularly in skeletal class II.

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