Influence of surgical and prosthetic techniques on marginal bone loss around titanium implants. Part I: immediate loading in fresh extraction sockets.

PURPOSE: Delayed placement of implant abutments has been associated with peri-implant marginal bone loss; however, long-term results obtained by modifying surgical and prosthetic techniques after implant placement are still lacking. This study aimed to evaluate the marginal bone loss around titanium implants placed in fresh extraction sockets using two loading protocols after a 5-year follow-up period. MATERIAL AND METHODS: A total of 36 patients received 40 titanium implants (Astra Tech) intended for single-tooth replacement. Implants were immediately placed into fresh extraction sockets using either a one-stage (immediate loading by placing an interim prosthesis into functional occlusion) or a two-stage prosthetic loading protocol (insertion of abutments after 8 weeks of healing time). Marginal bone levels relative to the implant reference point were evaluated at four time intervals using intraoral radiographs: at time of implant placement, and 1, 3, and 5 years after implant placement. Measurements were obtained from mesial and distal surfaces of each implant (α = 0.05). RESULTS: One-stage immediate implant placement into fresh extraction sockets resulted in a significant reduction in marginal bone loss (p < 0.002) compared to the traditional two-stage technique. Whereas mesial surfaces remained stable for the 5-year observation period, significant marginal bone loss was observed on distal surfaces of implants after cementation of interim prostheses (p < 0.007) and after 12 months (p < 0.034). CONCLUSIONS: Within the limitations of this study, immediate loading of implants placed into fresh extraction sockets reduced marginal bone loss and did not compromise the success rate of the restorations.

In vitro evaluation of the "replica technique" in the measurement of the fit of Procera crowns.

AIM: The objective of this study was to compare the film thickness of a light body polyvinylsiloxane addition silicone impression material using the "replica technique" (RT) to the film thickness resulting from the cementation of Procera copings. METHODS AND MATERIALS: Twenty Procera copings were fabricated on ten casts each having one central incisor and one premolar. The thickness of the light body was first measured using the RT; then on the same casts dies were cemented with glass-ionomer cement, sawed, and the film thickness of cement was measured. These two materials were expected to behave differently under stress according to their respective physical properties. RESULTS: The thickness of silicone material did not differ significantly from that of the glass-ionomer cement used in this experiment. Also, when the two groups of central incisors and premolars were taken separately, at three different areas (occlusal, axial, and cervical), no significant difference was found. Only when each surface (buccal, palatal, mesial, and distal) was compared separately at the cervical area, some significant differences between the two techniques was detected. CONCLUSION: Within the limitations of this study, the RT is an accurate and reliable technique that can simulate crown gap space after cementation. CLINICAL SIGNIFICANCE: The RT is reliable for evaluating cement thickness at the marginal and internal gaps of Procera AllCeram crowns during try-in sessions.