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مقدمه: در سالیان اخیر ارتودنسی به سمت استفاده از تکنولوژی دیجیتال حرکت کرده است. هدف مطالعه حاضر، ارزیابی دقت اندازه‏گیری‏های سفالومتریک بدست آمده با نرم‏افزار تریسینگ سفالومتری در مقایسه با روش تریسینگ دستی جهت تعیین روش دقیق تر و مفیدتر بود. مواد و روش‏ها: در این مطالعه توصیفی-تحلیلی نمونه‏های مورد استفاده شامل تصاویر رادیوگرافی سفالومتری جانبی دیجیتال و معمولی 30 بیمار بود که با روشSandwich تهیه شدند. در این روش برای هر بیمار یک فیلم رادیوگرافی و یک تصویر دیجیتال همزمان به دست می‏آید. 15 لندمارک سفالومتریک و 10 اندازه‏گیری زاویه‏ای و خطی در هر دو روش دیجیتال و دستی محاسبه و مورد مقایسه قرار گرفتند. خطای اندازه‏گیری برای هر روش با تکرار تریسینگ 15 سفالومتری از بین 30 سفالومتری اولیه، با استفاده از ضریب همبستگی Pearson محاسبه شد. برای مقایسه دو روش از Paired t test استفاده گردید . یافته‏ها: نتایج بدست آمده نشان دادند که اختلاف بین دو روش برای اندازه‏گیری SNA و U1-L1 و Wit’s از لحاظ آماری معنی‏دار بودند (05/0P

Composite reins have recently become popular for posterior teeth restorations. Gap"nformation and subsequent microleakage are of the complications resulting from such restorations. One of the"ntechniques to overcome polymerization shrinkage of composite resins is sandwich technique (application of"nglass ionomer as a base beneath the composite resin). Since polymerization patterns in two types of composite"nresins (light cure and self cure) differ from each other, various effects on the bond strength between glass"nionomer and dentin are expected."nPurpose: The aim of this in vitro study was to evaluate the effects of self- cure and light- cure composite"nresins in sandwich technique on the bond strength of light cure glass ionomer and dentin."nMaterials and Methods: 40 extracted human premolars were selected and divided into four groups:"nGroup 1: Light cure glass ionomer of 1mm thickness was placed on dentin."nGroup 2: 1mm thickness of light cure glass ionomer plus a mass of self cure composite resin of 2mm"nthickness were placed."nGroup 3: 1mm thickness of light cure glass ionomer plus light cure composite resin as two separate 1mm layer"nwere placed."nGroup 4: 1mm thickness of light cure glass ionomer with 37% phosphoric acid etching followed by two"nseparate layers of light cure composite resin of 1 mm thickness were placed."nSEM was used to determine gap size ai Gl- dentin and Gi- composite interlaces. The findings were analyzed"nby ANOVA and t-student tests."nResults: Groups 1 and 2 showed no gap at Gl-dentm interface and also cracks were not observed in all these"nspecimens. In group 3, there was gap between light cure GI and light cure composite resin and cracks were"nseen in GI, too. Group 4 showed gap at both interfaces and more cracks were seen in GI. Groups I and 2"nshowed the least gap formation and group 4 showed the most. Statistically significant difference was found"nbetween groups 3, 4 and group 1 (control), 2."nConclusion: Base on this study, the application of self-cure composite resin on light cure GI showed no gap"nand crack formation on Gl-dentin and Gl-composite interfaces and GI itself. However, light cure composite"nresins and glass ionomer etching aggregated crack and gap formation.