A comparative evaluation of peri-implant soft and hard tissues between internal hexagonal and internal conical type of implant-abutment connection: A randomized controlled trial

AIM: To compare the effect of internal hexagonal and internal conical implant-abutment connection (IAC) on peri-implant hard and soft tissues. SETTINGS AND DESIGN: Parallel arm, randomized controlled trial. MATERIALS AND METHODS: A total of 44 participants requiring rehabilitation with single implant-supported crown in the posterior region were enrolled and randomly allocated to two groups (n = 22). Participants in Group 1 were rehabilitated with implants with internal hexagonal IAC while in Group 2 with implants having internal conical IAC. Following delayed loading protocol, implants were restored with single implant-supported crown and baseline data along with subsequent follow up data at 3rd, 6th, and 12th months after occlusal loading were recorded. STATISTICAL ANALYSIS USED: Data were analyzed using the Statistical Packages for Social Sciences (SPSS) version 29.0. Categorical variables were represented as counts/percentages, whereas continuous variables were denoted as mean ± standard deviation. Unpaired t-tests and Chi-square tests were used for group comparisons. RESULTS: At 12 months, crestal bone loss was lower in the internal conical group (0.78 ± 0.03 mm) than the internal hexagonal group (0.81 ± 0.02 mm; P < 0.001). Probing depth was consistently shallower in the internal conical group (3.17 ± 0.09 mm vs. 3.47 ± 0.17 mm; P < 0.001). Interleukin-1β levels were significantly lower in the internal conical group across all time points, with large effect sizes. CONCLUSION: Internal conical IAC showed lower inflammation, improved bone preservation, and shallower probing depths compared to internal hexagonal IAC. Despite small structural effect sizes, the inflammatory response indicated a meaningful biological advantage. Both IAC remain viable, with selection guided by patient-specific needs and long-term outcomes.