# Wax Pattern Fabrication > Wax pattern fabrication in BDS Prosthodontics: inlay wax types, dipping and additive techniques, carving rules, distortion control and spruing. - Canonical URL: https://prepelephant.com/topics/bds/prosthodontics/wax-pattern-fabrication - Exam / course: BDS · Subject: Prosthodontics - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Wax Pattern Fabrication", PrepElephant, https://prepelephant.com/topics/bds/prosthodontics/wax-pattern-fabrication ## Direct answer A casting can never be better than the wax pattern it came from: the pattern dictates margins, contacts, occlusal anatomy and contour, and the metal inherits all of it — errors included. Inlay waxes are the material, classified as Type I for direct (intraoral) use and Type II for indirect use on the die, chosen because they carve cleanly without chipping, soften with gentle heat, and burn out of the investment leaving virtually no residue. Patterns are built by dipping dies into molten wax for uniform coping walls, by adding wax incrementally with heated instruments, or by full-contour waxing followed by cut-back where porcelain will veneer; then they are sprued and invested within the hour, because wax holds internal stresses that relax into distortion in a standing pattern. Margin adaptation, occlusal anatomy and prompt investing are the three disciplines on which everything else depends. ## What you must remember - **Wax types:** Type I inlay wax for direct intraoral patterns (softer, flows at mouth temperature); Type II for indirect patterns on the die — stiffer at room temperature, the routine laboratory choice. - **The cardinal property pair:** negligible residue on complete burnout, plus carving without flaking or chipping — the two requirements quoted in every materials answer. - **Dipping technique:** the lubricated die is dipped into molten wax to build a uniform coping wall in one or two immersions, giving thickness control (commonly around 0.5–1 mm per the design) no hand-adaptation matches. - **Additive technique:** wax added in small increments with a hot spatula, each addition fused into the last — cold carving refines, but never tears, the surface. - **Cut-back for metal-ceramic:** full contour is waxed, then approximately 1 mm circumferentially and 1.5–2 mm incisally or occlusally is removed for porcelain, leaving defined margins and connectors. - **Distortion is the enemy:** wax holds latent internal stresses from manipulation; store patterns cool, handle margins as little as possible, and invest promptly — commonly within 30–60 minutes of completion. - **Spruing rules:** sprue of adequate diameter (commonly 2.5–3 mm for single units), attached at the thickest part of the pattern on a non-functional cusp or lingual surface, as short as practical, with a reservoir for larger castings so solidification feeds the crown, not the sprue. ## Waxing a molar crown, start to sprue The die is sealed, lubricated and dipped twice in the wax pot, the first dip seated fully and rotated out cleanly to avoid folds; the resulting coping is checked for uniform thickness and thin spots patched with added wax. Occlusal anatomy is built cusp by cusp — marginal ridges first, then cusps with their ridges and fossae, wax added warm and carved cold, the anatomy checked against the opposing cast. Proximal contacts are overbuilt slightly and refined with articulating film; axial contours follow food-deflecting embrasure form. If this were a metal-ceramic crown, the next act is systematic cut-back — a millimetre off the axial walls, up to two off the incisal or occlusal table — converting full contour into subframework. The finished pattern is sprued at the thickest, least functional point, the sprue luted smoothly, and the whole assembly is invested without delay so tomorrow's casting matches today's pattern. ## Where students slip The classic slip is timing: waxing beautifully and investing the next morning, then wondering why the margin opened overnight — stress relaxation within the wax is the mechanism the viva wants named. The second is technique error at the margin: burnishing or pressing margin wax with a cold instrument, or repeatedly re-melting it, thinning it past reliability; the disciplined answer is a single clean flow of wax onto a warmed marginal area. The third is sprue placement on a functional cusp tip or across an embrasure, creating a casting with a fin or a ground-out contact; and the fourth, cut-back arithmetic — too little porcelain space (weak ceramic) or too much (thin metal) — separates recipe-followers from understanding. ## Frequently asked questions ### What distinguishes Type I from Type II inlay wax? Type I is formulated for direct intraoral use, softening at mouth temperature; Type II is the stiffer indirect wax used on dies at room temperature, the standard for laboratory patterns. ### Why must a wax pattern be invested promptly after completion? Manipulation locks internal stresses into the wax that relax over hours, distorting margins and contacts; investing within roughly 30–60 minutes captures the pattern as made. ### What are the rules for spruing a wax pattern? Sprue diameter commonly 2.5–3 mm, attached at the thickest part on a non-functional surface, kept short, oriented to allow metal flow and gas escape, with a reservoir added for larger patterns. ### How much wax is removed during cut-back for a metal-ceramic restoration? About 1 mm over axial surfaces and 1.5–2 mm at the incisal or occlusal areas — the space the porcelain veneer will occupy with its supporting metal intact. ### Which properties make inlay wax suitable for patterns? Clean carving without chipping, adequate flow when warmed, thermal and dimensional stability during handling, and essentially complete burnout leaving no residue in the mould.