Screw Retention and Disease Prevention

The long-term success of dental implants is largely based on how they are placed. The implant type, crown, and abutment are finalized through analog and digital workflows well before surgery is ever performed. Each part mimics form and function of the teeth they replace. But what if we reframed our thinking and designed them to minimize peri-implant disease and its etiologies? These prostheses should also protect the integrity of the implant and supporting structures as they are used, modified, and replaced over time. Screw-retained and “screwmentable” restorations offer just that.

Role of Biocompatibility

Titanium forms a thin layer of dioxide as it’s inserted, which lends to its biocompatibility. Through frictional wear, micro-movement, and mechanical debridement, titanium ions are released into neighboring hard and soft tissues, making way for periopathogenic bacteria and dysbiosis.¹ Because no metal or alloy is ever totally inert, these particles create a localized, reactive, inflammatory front known as metallosis.² Rather than contribute to this pathology, screw-retained prostheses can be easily retrieved to facilitate repair and maintenance without damaging the implant body. In cases requiring surgical intervention, the implant restoration can be temporarily removed to provide better surgical access and regenerative outcomes.

Risk for Peri-Implant Breakdown

Today’s list of etiologies and risk factors for peri-implant breakdown is exhaustive. Open contacts have a now studied association with the hallmarks of such disease. In a retrospective study, 50% of implants were found to have at least one open contact over 10 years, especially along the mesial surface with associated pocketing, plaque, and inflammation.³ As the facial skeleton grows steadily until about age 20, bone “turns over” every 11 years via normal remodeling. As daily wear broadens interproximal contacts into contact areas, these spaces are created.⁴

Because of their retrievability, screw-retained prostheses can easily be redone. Restorative dentists should caution patients that they will eventually need at least one new implant restoration over their lifetime. They should also verify the appropriate contact tightness and inquire about food impaction and/or oral hygiene access as part of patient maintenance.

Most obviously, screw-retained prostheses forego the need for cement, which may lead to an unhealthy peri-implant sulcus. In fact, excess dental cement was associated with signs of peri-implant disease 81% of the time, and the majority of these sites returned to normal upon cement removal.⁵

The type of cement also matters. Increased red complex bacteria were associated with permanent cement materials.⁶ In a systematic review, deeper crown margins, splinted crowns, and multiple abutments were also related to a higher incidence of undetected cement.⁷ Care should therefore be taken to plan these cases with a screw-retained appliance whenever possible.

Conclusion

Regardless of the case’s complexity, the restoration should seat passively with proper torque control. High-strength esthetic materials, such as zirconia and hybrid ceramics, now exist to minimize the visibility of screw channels. This will continue to bridge the gap between the biomechanical advantages of screw-retained prostheses and the increasing esthetic demands of our patients. Taken together, a concerted effort should be made to place and restore implants in ways that minimize peri-implant disease and its sequalae from treatment onset.

References

1. Kotsakis GA, Olmedo DG. Peri-implantitis is not periodontitis: Scientific discoveries shed light on microbiome-biomaterial interactions that may determine disease phenotype. Periodontol 2000. 2021;86:231-240.
2. Wilson TG Jr. Bone loss around implants-is it metallosis? J Periodontol. 2021;92:181-185.
3. Gasser TJW, Papageorgiou SN, Eliades T, Hämmerle CHF, Thoma DS. Interproximal contact loss at implant sites: a retrospective clinical study with a 10-year follow-up. Clin Oral Implants Res. 2022;33:482-491.
4. Fudalej P, Kokich VG, Leroux B. Determining the cessation of vertical growth of the craniofacial structures to facilitate placement of single-tooth implants. Am J Orthod Dentofacial Orthop. 2007 Apr;131(4 Suppl):S59-67.
5. Wilson TG Jr. The positive relationship between excess cement and peri-implant disease: a prospective clinical endoscopic study. J Periodontol. 2009;80:1388-1392.
6. Linkevicius T, Puisys A, Vindasiute E, Linkeviciene L, Apse P. Does residual cement around implant-supported restorations cause peri-implant disease? A retrospective case analysis. Clin Oral Implants Res. 2013;24:1179-1184.
7. Staubli N, Walter C, Schmidt JC, Weiger R, Zitzmann NU. Excess cement and the risk of peri-implant disease — a systematic review. Clin Oral Implants Res. 2017;28:1278-1290.

From Decisions in Dentistry. April/May 2024; 10(3):8