Short strategic implants for mandibular removable partial dentures: One-year results from a pilot randomized crossover abutment type study

Abstract

Objectives: The present pilot study analyzed two abutment types (a retentive ball and a non-retentive dome) in implant-assisted removable partial dentures (IARPDs) on 6 mm short implants with respect to clinical, radiological, and patient-reported outcomes (PROs), during the first year.

Materials and methods: Two implants were placed bilaterally in mandibular molar sites, converting existing free-end removable partial dentures (RPDs) to IARPDs. Twelve subjects were randomized to initially receive either the dome (Group A, n = 6) or the ball abutment (Group B, n = 6). After eight weeks, the abutments were exchanged. After another 8 weeks, the participants were given the choice of one of the abutments. Mean values and standard deviations (SD) were calculated, and random-effect linear regression analyses were applied to analyze marginal bone level alterations and PROs (α < .05).

Results: Twelve participants were included in the study; however, one dropout occurred. Patient ratings increased significantly in both study groups. The majority of the participants (82%) ultimately chose the ball abutment. The implant survival rate was 100%, and the success rate was 90.9% twelve months after implant placement (mean peri-implant bone-loss: -1.2; SD: 0.6 mm) without a statistically significant difference between the study groups, in terms of clinical- and radiological outcomes.

Conclusion: Placing 6 mm short implants at mandibular molar sites of RPD wearers seems to be a viable treatment option, based on this investigation with a short-term follow-up. Although only minor differences between the two abutments were observed, patients seem to prefer the ball over the dome abutment.

Keywords: OHRQoL; Short implant; abutment; anchor; bone-remodeling; implant overdenture; strategic implant.

FIGURE 1

Schematic of the applied abutments: (a) the dome and (b) the ball abutment on short implants. For the dome attachment, less vertical space is required

FIGURE 2

Customized radiographic splint supported by anterior teeth, for standardized x‐ray recording. The rough surfaces of the splint on the x‐ray film holder and in the molar region were used for reproducible repositioning

FIGURE 3

Intraoral view and intaglio denture surface of a participant with the dome abutments (upper) and another participant with the ball abutments (lower)

FIGURE 4

Study flowchart, summarizing the randomization, clinical, and follow‐up procedures

FIGURE 5

Patient ratings: Mean values and 95% confidence intervals of changes in terms of denture stability, painfulness, chewing ability, and cleanability at 8 (evaluating the first abutment type) and 16 weeks (evaluating the second abutment type) after loading; a score of +10 being the maximum possible improvement in each period

FIGURE 6

X‐ray of an implant in the right molar site (a) at baseline with the healing abutment, (b) at the 6‐month follow‐up with the dome abutment, and (c) at the 12‐month follow‐up with the ball abutment. At the mesial aspect, a slight decrease in the MBL to the first implant thread can be observed. (SIC ace, 6.0 mm × 4.5 mm, SIC invent AG, Basel, CH)

FIGURE 7

Bland–Altman plot, demonstrating differences (y‐axis) of the individually determined MBLs (x‐axis) of the two reviewers. The limits of agreement ranged from −0.15 to 0.16 mm