Introduction: The need for increased bone availability in the posterior maxilla for placement of dental implants, led Tatum and Boyne, in the 80s, to describe the lateral access technique to regenerate the maxillary sinus. Later, Summers proposed a crestal access to regenerate the maxillary sinus, allowing to place implants in the same surgery. Currently, several authors suggest a crestal access whereby implants are placed without using biomaterials in locations with less than 4-5mm bone height, which are covered completely with bone spontaneously, where the implant apex itself maintains the sinus membrane elevated producing the "tent phenomenon". Objectives: The aim of the study was to evaluate bone formation obtained by implant placement using an osteotome and trephine technique and the survival rates in areas with an availability of less or equal to 5mm of bone. Material and methods: 32 implants were placed in locations of 5mm or less bone availability. Using a trephine, the site is prepared to a distance of 1 mm to the cortical sinus floor. After this, this part is fractured with an osteotome. Finally, the implant is placed. Standardized periapical radiographs, at 0, 6, 12 and 18 months for the measurement of newly formed bone were taken, and data of initial bone availability, sinus shape or Valsalva maneuver were related. Results: All 32 implants were successfully osseointegrated. The baseline mean bone availability was 3.69mm, with a range of 2 to 5mm. The mean achieved bone gain was 3.84mm. The Valsalva maneuver was positive In 8 cases, influencing bone formation, particularly in the distal implant apex. In all of the cases, spontaneous bone formation was observed, and this was stable over time. Discussion: The spontaneous bone formation observed in all cases, especially when the Valsalva maneuver is negative, simplifies the surgical approach to the maxillary sinus, avoiding regenerative techniques, and reducing the treatment time. The 100% implant survival rate coincides with other studies published in the literature. The mean bone gain of 3.89 mm is consistent with results from other studies. Palabras clave: Sinus floor elevation, without grafting, osteotomes, trephine