Cell-Free DNA Profile in Peri-Implant Skin Exudate of Craniofacial Implants with Various Degrees of Inflammation: A Pilot Study

Purpose: To profile human β-globin gene fragment lengths from cell-free DNA in peri-implant skin exudate of craniofacial implants with various degrees of soft tissue inflammation. Materials and Methods: Fifteen participants (30 implants) were recruited for this study. All participants were recalled for three consecutive visits at days 0, 14, and 28. During each visit, the soft tissue condition at the skin-abutment interface of each craniofacial implant was graded by Holgers score, and the implant stability quotient (ISQ) values of the implants were also measured. Peri-implant skin exudate specimens were collected and centrifuged to obtain cell-free DNA. Conventional polymerase chain reaction was used to assess DNA fragment lengths by amplifying five polymerase chain reaction amplicon sizes from 110-base pairs (bp) to 2-kilobase pairs (kbp) of human β-globin gene. The longest polymerase chain reaction amplicon size found in each specimen was then recorded. Results: No significant differences in the ISQ values of the implants (P > .05) were noted during the study period. In each recall visit, a correlation was observed between Holgers score and polymerase chain reaction amplicon sizes (P .001). A gradual decrease in both parameters was also noted following the treatment protocol (P .05). From the 90 exudate specimens obtained from all the observation visits, 1-kbp amplicon sizes were usually found in the group with Holgers score 1 (47 of 52 specimens); 2-kbp amplicon sizes were often found in the group with Holgers score 2 (22 of 32 specimens) and predominantly found in the group with Holgers score 3 (5 of 6 specimens). Conclusion: The 1-kbp amplicon sizes can serve as a marker for mild clinical inflammation of peri-implant skin. Similarly, 2-kbp amplicon sizes may be used as a prognostic marker for denoting greater cell destruction and inflammation, which indicate a greater risk of severe inflammation. However, further studies are required to support these findings. Keywords: cell-free DNA, craniofacial implant, DNA fragment lengths, Holgers score, peri-implant skin exudate