A taper of between 10° and 20° is usually adequate and achievable. In reality this means a preparation that is as parallel as you can make it, without any undercuts.

Alginate is the most widely used of all the impression materials its is a hydrocolloid material made from seaweed. A hydrocolloid material is a gelatinous substance dispersed in water. It is described as being irreversible as it cannot return to a solution once set. Alginate also contains; Use a putty matrix of the ideal tooth shape and position (ideally from a wax-up) as a guide to keep you aware of what you are aiming for. Prepare from crown down Guided bone regeneration using titanium mesh with calcium phosphosilicate alloplast in the esthetic zone: A case report. Lanka M, Lahori M, Nagrath R, Sudan R., Int J Ultroson Piezoelect Bone Surg June 2014; 3(1): 19-24. All impression materials—polyvinyls, polyethers, polysulfides, and hydrocolloids—polymerize toward the rigid wall of the tray that has adhesive and/or perforations to retain the material. Unfortunately, the interproximal material has no tray, so it polymerizes toward its center (Figure 7). This explains why an impression of a perfectly round machined steel die produces an elliptical casting, which is observed regardless of the type or brand of material used.6 Polymerization shrinkage accounts for the 3-dimensional differences in dies made from impressions taken with the same material, but with different techniques—trays, dual-arch trays with sides, and sideless dual-arch trays. There is one material that is marketed specifically for use in the dual-arch quadrant metal tray (Inflex [CLINICIAN’S CHOICE]). Profeta AC, Prucher GM. Bioactive-glass in periodontal surgery and implant dentistry. Dent Mater J. 2015;34(5):559-571. doi: 10.4012/dmj.2014-233The most difficult aspect of a crown preparation is the interproximal margin. Therefore it makes sense to reduce the amount of preparation required in the area. Clinical and cone beam computed tomography comparison of NovaBone Dental Putty and PerioGlas in the treatment of mandibular class II furcations. Asmita, Gupta V, Bains VK, Singh GP, Jhingran R., Indian J Dent Res, 2014 25(2):166-73. Removal of a large radicular cyst and simultaneous ridge regeneration utilizing alloplastic CPS putty in combination with platelet rich fibrin (PRF): A case report. Kotsakis G, Chrepa V., JIACD Apr 2012; 4(2): 41-47. During this procedure, your healthcare provider dispenses a putty-like dental impression material into plastic or metal trays. Next, they’ll place the trays over your teeth. After a minute or two, the dental impression material sets and hardens. Finally, your healthcare provider removes the trays (and impression material) from your mouth. Results: Significant shrinkage of ImpregumTM PentaTM was 0.77 ± 0.17% in the control group, 0.42 ± 0.19% in the hypochlorite group and 0.52 ± 0.28% in the autoclave group. For ImprintTM 4 PentaTM Putty, the control group had a shrinkage of 0.42 ± 0.12%, the hypochlorite group 0.36 ± 0.09% and the autoclave group 0.59 ± 0.13%.

Use of the NovaBone augmentation material in the treatment of chronic periodontitis. Preliminary communication. Slezak R, Paulusova V., ACTA MEDICA (Hradec Kralove) 2013:56(4):157-161. Additionally an end-cutting only bur is brilliant for smoothing steps along the margin. Prosthodontips for an excellent crown preparation Prep for the crown you want, not the tooth you have The differences between impression materials, as outlined above, are the materials themselves and the purpose they are used for. Each of the materials has advantages and disadvantages, but they are each used for a different purpose and are effective and commonly used products in dentistry today. Comparative evaluation of bioactive synthetic novabone putty and calcified algae-derived porous hydroxyapatite bone grafts for the treatment of intrabony defects. Bembi NN, Bembi, S, Mago J, Baweja GK, Baweja PS. Int. J of Clin Pediatric Dent Oct-Dec 2016; 9(4):285-290.

Digital impressions

The powder is also divided into increments for base consistency, but this may include the division of one powder increment into yet smaller increments. Certain materials require more reduction than others. This is due to physical or optical properties. Margins should be smooth and continuous with no steps. This is difficult to achieve. I find that a fine grit bur (yellow or white) is very helpful in refining the margins. Preliminary impressions: Preliminary impressions are used for diagnostic purposes, or as the initial step in the process of fabrication (making) of different prostheses, including crowns and dentures. They’re often made at your initial office visit. They provide your dentist with a visual aid so they can plan your treatment.