Here is the design of a clinical trial:

Official Title: Single-implant Overdentures Retained by the Novaloc Attachment System: Study Protocol for a Mixed Methods Randomized Cross-over Trial

Included conditions:
- Edentulous Mouth
- Edentulous Jaw

Study Armgroups:
- {'label': 'Novaloc, then Locator', 'type': 'EXPERIMENTAL', 'description': 'Participants will receive the Novaloc attachment on a single implant inserted in the mandibular midline. This attachment will be used for 3 months and then changed by the Locator attachment. The second attachment will be used for another 3-month period. Participants will keep preferred attachment for further 12 months', 'interventionNames': ['Device: Novaloc', 'Device: Locator']}
- {'label': 'Locator, then Novaloc', 'type': 'ACTIVE_COMPARATOR', 'description': 'Participants will receive the Locator attachment on a single implant inserted in the mandibular midline. This attachment will be used for 3 months and then changed by the Novaloc attachment. The second attachment will be used for another 3-month period. Participants will keep preferred attachment for further 12 months', 'interventionNames': ['Device: Novaloc', 'Device: Locator']}

Interventions:
- {'type': 'DEVICE', 'name': 'Novaloc', 'description': 'Attachment composed by a polyetheretherketone (PEEK) capsule and carbon-coated abutment. The yellow (medium) retentive component will be used', 'armGroupLabels': ['Locator, then Novaloc', 'Novaloc, then Locator']}
- {'type': 'DEVICE', 'name': 'Locator', 'description': 'Traditional cylindrical attachment (Locator system) with pink (medium) retentive components', 'armGroupLabels': ['Locator, then Novaloc', 'Novaloc, then Locator']}

Primary Outcomes:
- {'measure': 'Denture satisfaction', 'description': 'To be assessed by specific questionnaires', 'timeFrame': '18 months'}

Please estimate the sample size based on the assumption: 
A two-sided alpha of 0.01, a power of 90%, and a 20% dropout rate.
Sample size estimation
        Sample size for the quantitative phase was determined based on the primary outcome of this study (patient satisfaction). According to previous trials, a minimally important difference of 10Â mm was considered for the estimation [40], as well as a standard deviation of the difference in satisfaction of 7.5Â mm [41]. A two-sided alpha of 0.01 will be also considered to compensate for the number of secondary outcomes. Based on a power of 90%, this trial requires at least 21 participants [42]. An additional 20% will be added to the planned sample to compensate for possible dropouts, thus resulting in a total of 26 participants.