Correlation of the arch forms of male and female subjects with those of preformed rectangular nickel-titanium archwires.

Introduction: This investigation was carried out to correlate the normal arch forms of male and female subjects derived mathematically by the beta function with commercially available preformed rectangular nickel-titanium archwires.

Methods: The mathematical beta function was used to derive planar projections of natural archforms by using the spatial coordinates of the labial bracket interfacing surfaces in the maxillary and mandibular arches of both sexes. Graphic planar representations of corresponding bracket base spatial coordinates of archforms of 30 popular rectangular nickel-titanium archwire-bracket assemblies (derived through the same mathematical function) were superimposed on relevant maxillary and mandibular arches.

A comparison of marginal fit of glass infiltrated alumina copings fabricated using two different techniques and the effect of firing cycles over them.

Purpose: This study evaluated marginal fit of glass infiltrated alumina cores fabricated using two techniques and their marginal stability after firing cycles of veneering porcelain.

Materials And Methods: Fifteen standardized all-ceramic crowns were fabricated on a metal die using each technique: slip cast technique of VITA In-Ceram sprint Alumina (Group A as control) and plastic foil matrix technique of Turkom-Cera fused alumina core system (Group B). Copings were compared between groups and within groups at coping stage and after firing each layer of veneering porcelain.