Mandibular overdentures retained by 1 or 2 implants: a 5-year randomized clinical trial on implant stability and peri-implant outcomes.

AIM: This is a report of the 5-year results of a two-group parallel randomized clinical trial comparing longitudinal implant stability, and clinical and radiographic peri-implant outcomes of mandibular overdentures retained by one (1-IOD group) or two (2-IOD group) implants. METHODS: All participants received 4.1 mm diameter tissue-level implants (Straumann® Standard Plus - SLActive®, Institut Straumann AG), installed in the mandible midline (1-IOD; n = 23) or the lateral incisor-canine area bilaterally (2-IOD; n = 24), and loaded after 3 weeks. Implant Stability Quotient (ISQ) was measured using a resonance frequency device (Osstell® Mentor, Integration Diagnostics) at implant placement, after three weeks (loading), and at the 6-month, 1-, 3-, and 5-year follow-ups. Marginal bone loss and clinical implant outcomes (plaque, calculus, suppuration and bleeding) were assessed periodically up to 5 years after loading. RESULTS: Only minor changes in marginal bone level were observed after 5 years (mean = 0.37; SD = 0.44 mm), and satisfactory and stable peri-implant parameters were observed throughout the 5-year follow-up. No significant differences between groups were found. Overall, the mean primary implant stability was considered high (> 70) for the two groups (1-IOD = 78.1 ± 4.5; 2-IOD = 78.0 ± 5.8). No noticeable changes were observed between implant insertion and loading. A marked increase was observed from insertion to the 6-month follow-up - the mean difference for the 1-IOD group was + 5.5 ± 5.5 (Effect size = 1.00), while for the 2-IOD group, the mean difference was + 6.0 ± 5.6 (Effect size = 1.08). No relevant changes were observed throughout the follow-up periods up to 5 years. Linear mixed-effect model regression showed no influence of the bone-related variables (p > 0.05) and the number of implants (p = 0.087), and a significant effect of the time variable (p < 0.001). CONCLUSION: Satisfactory peri-implant outcomes and stable secondary stability suggest good clinical performance and successful long-term osseointegration of the implants for single and two-implant mandibular overdentures. Using a single implant to retain a mandibular overdenture does not seem to result in detrimental implant loading over the five years of overdenture use. CLINICAL RELEVANCE: This study corroborates the use of a single implant to retain a mandibular denture.

Is there a difference in the resonance frequency values obtained directly on the implants and abutments? / ¿Existe diferencia en la frecuencia de resonancia obtenida directamente en los implantes y pilares?

The aim was to evaluate the differences of implant stability quotient (ISQ) between implants with external hexagon and Morse taper connectors. The study had a split mouth design, composed by 10 patients who received hybrid protocol prosthesis. In total, 40 implants (3.75 x 13 mm) were installed: on the right side, 20 external hexagon, and on the left, 20 Morse taper. After two years in function, the stability test was applied by using the MRI machine Osstell ISQ directly on the implants and on the abutments. Considering the measurements made on the implants, there were differences between HE and CM mesial (p= 0.011), lingual (p= 0.003) and distal (p= 0.006). Considering the measurements made on the abutments, there were differences between HE and CM on the buccal (p= 0.020) and lingual (p= 0.004). The trend and higher values are for the CM group. The values for Morse taper implants were always higher in a statistically significant manner, when compared to the external hexagon.

El objetivo fue evaluar las diferencias del coeficiente de estabilidad de implantes comparando los de conexión de hexágono externo (HE) y cono morse (CM). El estudio tuvo un diseño de boca dividida, siendo compuesta por 10 pacientes que recibieron protocolos protésicos de tipo hibrido. En total, 40 implantes (3,75x13 mm) fueron instalados: en el lado derecho, 20 implantes de hexágono externo y en el lado izquierdo, 20 implantes de cono morse. Después de dos años en función, la prueba de estabilidad fue aplicada utilizando una maquina MRI, Ostell ISQ directamente sobre los implantes y pilares. Considerando las medidas en los implantes, hubo diferencias entre los implantes HE y CM en mesial (p= 0,011), lingual (p= 0,003) y distal (p= 0,006). Considerando las medidas en los pilares, hubo diferenciasentre HE y CM en el sector bucal (p= 0,020) y lingual (p= 0,004). Los valores mas altos se obtuvieron en CM; los valores de las conexión tipo cono morse presentaron mayor estabilidad al comparase con los implantes de conexión de hexágono externo.