To choose between screw-retained or cement-retained crowns is a multifaceted decision that involves many components of consideration. This post will review the complex components that you should consider when choosing between the two.
The screw-retained crown contains both benefits and liabilities. The chief benefit is retrievability. You’re not only able to recover the crown, but you won’t experience damage upon removal if it becomes loose or fractured since it’s easily removable. You can also clean, replace the screw, and assess the surrounding tissue where need be. Most dentists consider an annual cleaning and screw replacement practical. The more time passes, the more important retrievability becomes.
To recuperate a crown or alter a screw for preservation, the restoration is detached, the cotton pellet is removed, and then the screw is accessed. When repair is completed, the screw is torqued, and then a new cotton pellet is implanted. To finish the process, composite or acrylic is used to close the opening.
In cement-retained crown cases, retrievability is not a huge disadvantage. Cemented crowns may be recovered if the right cement is used. Adding a water-soluble gel to the cement can ease the rescuing of the crown. Either way, although the screw-retained crown can be retrievable, removing a cement-retained crown can be a disputed task if durable cements are used.
“The screw-retained crown contains both benefits and liabilities. The chief benefit is retrievability.”
The Pros and Cons of Cement
Cement-retained implant-borne restorations can delivery many benefits, which include eliminating unaesthetic screw access holes and improved resistance to porcelain break. Standard crown & bridge measures can similarly be used in most circumstances. Nevertheless, extra cement left behind unintentionally is a key problem and can produce soft tissue damage, bone loss or extreme swelling.
Retention and Resistance
Various aspects that affect resistance and retention on natural tooth abutments on cement-retained crowns can also be functionable. The degree of taper, height, surface area and roughness of the abutment will all affect the resistance and retention of a cemented crown.
Six degrees is reported to be the ideal taper of opposing surfaces in natural tooth preparations. The direct effect on the taper of abutments is parallelism. If implants are not parallel they might require further tapering and preparation of abutments in order to permit an ideal path for insertion of the prosthesis.
A screw-retained prosthesis may be required when overtapered abutments lack appropriate retention for the cemented restoration. In order to prevent that while increasing retention for a cemented crown, you can indicate an irregular abutment surface or sturdier cement.
Another crucial factor for proper resistance and retention is abutment height. The longer the abutment walls are, the more surface area you’ll have which will make it more absorbent. The height will also play an important role in the resistance of tipping forces. You don’t want the tipping forces to dislodge the cemented restoration, so the length must be large enough to interfere with the arc of the casting, rotating a point on the margin from the opposite side of the restoration.An excellent option to correct the line of draw while producing retention and resistance is custom abutments.
You’ll need a minimum of 5 mm of abutment height to produce proper resistance and retention of cement-retained crowns. In other words, in cases where there is limited interarch space you’ll need screw-retained crowns for abutments that are shorter than 5mm
The key benefit of a screw-retained structure is the lower profile retention of the abutment scheme. These low-profile abutments offer a substantial gain application of bar-retained overdenture. The bar with lower height will generate greater thickness for acrylic to strengthen the restoration and creates more room for dentures.
When choosing between screw-retained and cement-retained crowns, esthetics will be a major influence. With anterior screw-retained crowns, the placement of the implant is lingual to permit the rise of the screw across the cingulum area.
Offset loading of the implant is a result of the rebuilding which is cantilevered facially from the implant body. A porcelain ridge lap, which is a result of lingual implant placement, can compromise hygiene. To eliminate the ridge lap and duplicate a more natural appearance, an angulated abutment is used for an anterior cemented restoration that is positioned under the incisal edge.
When it comes to posterior screw-retained restorations, the access hole will go out through the main fossa of the prosthetic tooth. Not only is this a cosmetic concession but an occlusal one as well. The cementable crown clearly has no entry cavity. Permitting the forces of occlusion to be dispersed along the axial inclination, congruent with the long axis of the tooth, is easier.
Implant-protective occlusal scheme that should be considered are:
Elimination of premature contacts
Timing of occlusal contacts
Surface area over which the occlusal forces are applied
Implant angle to occlusal load
Implant crown contour
Occlusal contact position
Dental professionals must assess restorative patients for parafunctional behaviors. Although model occlusal schemes exist in the restoration, extreme forces shaped by parafunction can over-load supportive bone around implants and result in catastrophe. If they do exist, modifications in the treatment plan will be necessary to compensate for these extreme forces, and an appliance to manage the harmful habit is suggested.
There are benefits and drawbacks to using a screw-retained vs. a cement-retained crown. To get the better of the pros and cons of each structure, innovative implant systems have been established that contain techniques that improve the link between the implant and abutment. These improvements have reduced the occurrence of screw loosening. Countless dental professionals would conclude that cement-retained crowns are greater for esthetics and obstruction. By the same token, many would conclude that screw-retained crowns are a requirement for several units that need retrievability. Individual viewpoint plays a major role, and only on a case-by-case scenario can you decide which crown is the better one to use.