Prospects for prosthetically guided implant rehabilitation at spontaneously healed molar sites.

Abstract

Objectives: This study was to evaluate the feasibility and treatment complexity (TC) for prosthetically-guided implants (PGI) after extraction and unassisted healing of first molar sites. Methods: A consecutive cohort of 106 subjects were recruited with 117 first molars (maxillary=49, mandibular=52) for extraction. Collected data at baseline included demographics, systemic conditions, smoking status, clinical parameters, reasons for extraction, CBCT and intraoral scanning (iOS). Atraumatic extractions were performed, and residual ridges were evaluated by CBCT and iOS following 6-month natural healing. Digital planning of PGI with 4.8/4.1mm diameter, 8mm long dental implant and the needs for bone augmentation (BA) were performed using CBCT and pre-extraction tooth position in iOS. Possibility of standard implant placement (STANDARD) and needs for simultaneous or staged BA were assessed. Results: Planning PGI placement was possible in majority of sites that completed follow-up (N=101). For a 4.8mm diameter implant, STANDARD was possible in 24.8% of the sites, 43.6% required BA for implant placement, 29.7% required staged BA, and 2% were impossible for planning. Marked difference occurred between maxillary sites (MAX) with mandibular sites (MAN) (p<0.001). Significantly more MAX required sinus lift procedures (p<0.05) and 49% of MAX required staged sinus augmentation for PGI. The use of 4.1 mm rather than 4.8 mm diameter implant did not significantly reduce the need for simultaneous or staged BA. Reasons for extraction was not associated with PGITC. Clinical attachment loss and sinus-root vertical relationship were good predictors for PGITC in MAN (p<0.05) and MAX (p<0.001) respectively. Conclusions: PGI planning at first molar residual ridges 6 months after unassisted healing is often possible. However, advanced simultaneous and staged lateral augmentation procedure and sinus augmentation are common. Pre-extraction clinical attachment loss and sinus-root vertical relationship are good predictors for the needs of staged BA prior to PGI placement in MAN and MAX.