The mandibular implant-retained overdenture could improve masticatory function compared to the conventional complete denture. However, increased forces exerted by the overdenture could increase residual ridge resorption of the maxillary anterior and mandibular posterior areas. The aim of this study was to compare the effect of the mandibular implant-retained overdenture using two or four dental implants, or the conventional complete denture on resorption of the residual ridge of the maxillary anterior and mandibular posterior areas over a period of 10 years. In total, 120 patients, 30 patients treated with an overdenture on two implants (two-implant group), 30 patients with an overdenture on four implants (four-implant group) and 60 patients treated with a conventional full denture (conventional group), participated in this study. On panoramic radiographs, made before and 10 years after treatment, proportional area measurements were applied to determine changes in bone height. After 10 years, a statistically significant amount of bone resorption had occurred in the anterior maxilla in the two-implant group and in the four-implant group. A significant amount of bone resorption had occurred in the posterior mandible in all three groups. There were no statistically significant differences between the groups in both areas. Patients presented large individual differences. It is concluded that patients rehabilitated with implant-retained mandibular overdentures are not subjected to more residual ridge resorption in the anterior maxilla when compared to patients wearing a conventional full denture. Regarding the mandibular posterior residual ridge, resorption was irrespective of wearing an implant-retained mandibular overdenture or a conventional mandibular denture.

Tymstra N, Raghoebar GM, Vissink A, Den Hartog L, Stellingsma K, Meijer HJA: Treatment outcome of two adjacent implant crowns with different implant platform designs in the aesthetic zone: a 1‐year randomized clinical trial. J Clin Periodontol 2011; 38: 74–85. doi: 10.1111/j.1600‐051X.2010.01638.x Abstract Aim: To evaluate the peri‐implant tissues in patients with two adjacent implant crowns in the aesthetic zone, treated with either two adjacent implants with a scalloped platform or with a flat platform. Material and methods: Forty patients were randomly allocated to: (1) a “scalloped implant group”: 20 patients treated with two adjacent implants with a scalloped platform, and (2) a “flat implant group”: 20 patients treated with two adjacent implants with a flat platform. Clinical and radiographic examinations were performed during a 1‐year follow‐up period to assess hard and soft tissue changes. Results: The scalloped implant group showed significantly more marginal bone loss (scalloped: 2.7±1.4 mm, flat: 0.9±0.8 mm) and more inter‐implant bone crest loss (scalloped: 1.8±1.4, flat: 1.0±0.9 mm) than the flat implant group. There was no significant difference between the groups with regard to the papilla index and patients' satisfaction. Conclusion: After 1 year of function, there was more bone loss around scalloped implants than around flat implants. With regard to the presence of papilla, there were no differences between the groups. With both applied implant designs, it is difficult to establish a predictable and harmonious aesthetic result, especially regarding the peri‐implant mucosa. Patients were very satisfied with the aesthetic outcome of the adjacent implants irrespective of the treatment concept applied.

For anterior tooth replacements, implants with a scalloped neck showed more marginal bone loss and less favourable clinical outcome compared with implants with a 1.5 mm smooth neck or implants with a rough neck.