Should I Use Screw-Retained or Cement-Retained for Dental Implant Restorations?

Implant-supported restorations require either a screw-retained or cement-retained retention method to secure the restoration to the abutment. Even though there is still controversy over which method is best, Shadid and Sadaqa reports there are advantages and disadvantages of each method of retention from different aspects. These different aspects include, “ease of fabrication and cost, esthetics, access, occlusion, retention, incidence of loss of retention, retrievability, clinical prosthesis fit, restriction of implant position, effect on peri-implant tissue health, provisionalization, immediate loading, impression procedures, porcelain fracture, and clinical performance”¹. The literature review also demonstrates there are certain clinical situations that prefer one method of retention over the other. The following will describe the different aspects that affect which method of retention is preferred over the other.

Ease of fabrication and cost

When it comes to cost, cement-retained restorations are usually the least expensive and easier to fabricate because of conventional laboratory and clinical prosthodontics techniques. Also, screw-retained restorations have extra components needed such as “plastic sleeves, laboratory fixation screws, and the fixation screws themselves”¹. However, the cost of retrievability needs to be considered when factoring in potential costs of damaging the cemented restorations if biologic or technical complications occur.

Esthetics

There have been debates on whether screw-retained restorations should be placed in an esthetic area, but with pre-angled and custom abutments the screw access channel can be changed from facial access to lingual access. When the dental implant is placed in the optimal position, predictable esthetics can be achieved with either screw- or cement-retained restorations¹.

Access

The authors argue cement-retained restorations rather than screw-retained offer easier access to the posterior of the mouth, but with new techniques it is now easier to place screw-retained restorations in the posterior of the mouth. Now with the angulated screw channel by Nobel Biocare, clinicians can easily retrieve posterior abutments with a low vertical clearance. With this angled ability, clinicians are able to change the direction of the esthetic outcome in an anterior tooth up to 25 degrees. This new technique means dental labs will be able to provide more restorative, esthetic options for clinicians.

Occlusion

Optimal and stable occlusal contacts can be found with cement-retained restorations because there are no occlusal screw access holes. Anterior guidance may be compromised when these screw access holes interfere with protrusive and lateral excursions¹.

Retention

The most important factor affecting implant prostheses longevity is security of retention. Several factors affect the retention of cement-retained restorations such as “taper of abutment, surface area and height, surface roughness, and type of cement”¹.

For screw-retained restorations, retention is achieved by fastening a screw and loss of retention is described as screw loosening. Factors that will affect the amount of retention include “insufficient clamping force, screw settling, biomechnical overload, off-axis centric forces (forces that are not directed along the long axis of the implant), implant components and prothesis misfit, differences in screw material and design, and finally hex height and implant diameter”¹.

Retrievability

Predictable retrievability can be achieved with screw-retained restorations without damaging the restoration—allowing for “prosthodontic components to be adjusted, screws to be refastened, and fractured components can be repaired with less time and at a lower cost than would be the case with cement-retained restorations”¹.

Clinical Prosthesis Fit

Substantial stress within the prosthesis, the implant, and surrounding bone may be created when there is not a precise fit between the crown and abutment in a screw-retained restoration. Some leading factors that affect the restoration fit depends on “accuracy preformed in the fabrication process such as impression technique, master cast accuracy, component tolerance, casting tolerance, and skill of the technician, while the type of retention does not play a role in transferring or compensating for inaccuracies of prosthesis fabrication”¹. However, screw-retained prostheses have been determined to produce tighter margins than cement-retained protheses.  

According to the review, many authors believe cement-retained prostheses are more likely to achieve a passive fit than a screw-retained one. But the review points out this increased passivity of cement-retained restorations “rests on the assumption that the cement could act as a shock absorber and reduce stress to bone and implant-abutment structure”¹. They also conclude cement-retained prostheses have the risk of bacteria colonization within the margins that may result in cement dissolution and gingival inflammation.

Effects on the Health of Peri-implant Tissue

Gingival inflammation was found to be an issue with cement-retained prosthesis because of the difficulty in removing the excess cement—especially when the prosthesis margin was greater than 3mm subgingivally. When excess cement is not removed completely, complications can arise such as peri-implant inflammation, soft tissue swelling, soreness, bleeding or exudation on probing, and resorption of peri-implant bone¹. According to Shadid and Sadaqa, these clinical situations can be solved by using either screw-retained restorations or custom abutments for cement restorations. They also found the gingival response to be better when using screw-retained crowns since no cement was used.

Provisionalization

When using provisional restorations, the review reports screw-retained provisional restorations are preferred over cement-retained restorations “because the screw can be used to seat the provisional restoration and to expand peri-implant mucosa”¹. Furthermore, they can be screwed into the master impression to send additional information to the technician about the contours¹. For cement-retained provisional restorations, the main disadvantage is the difficulty of removing excess cement and the risk of cement residues causing gingival inflammation.

Immediate Loading

Screw retention is the best choice for immediate loading because it eliminates the use of cement and the associated “difficulty in removing excess from the peri-implant area that may interfere with healing and implant integration”¹. Interestingly, it has been found the interface of machined implant components are superior to any cement margin that can be developed¹.

Porcelain Fracture

Porcelain fracture is most commonly seen in screw-retained restorations because the screw access hole disrupts the structural integrity of the porcelain.

Clinical Perfomance

Most of the studies reported that screw-retained restorations have more complications during follow-up periods, but the percentage of these complications was generally minimal and controllable¹.

Conclusions

The review concluded that certain situations may call for either screw retention or cement retention because there are certain advantages and disadvantages to both methods. Based on the review, they have demonstrated that “one type of restoration is more appropriate than the other in some clinical situations”¹.

About the organization

Since 1991, Iverson Dental laboratories has provided their clinicians with higher quality dental lab products and exceptional dental lab solutions to guarantee their clinicians' patients are fully content with their tailored restoration. Iverson dental labs strives to be a great dental resource for dentists by providing training on digital dentistry and new dental implant methods at their high-tech operatory and coaching facility. Iverson dental labs strongly believes in using high quality certified materials and authentic manufacturing elements to fabricate their dental restorations. Iverson also has a knowledgeable team of accredited dental technicians simply because clinical evidence has shown ample skills of the technician are critical for the prolonged success of a dental restoration.

Resources

1. Shadid, R., & Sadaqa, N. (2012). A Comparison Between Screw- and Cement-Retained Implant Prostheses. A Literature Review. Journal of Oral Implantology, 38(3), 298-307. doi:10.1563/aaid-joi-d-10-00146