Materials and methods

A retrospective cohort study was performed in order to address the proposed study aim. The study sample was derived from the population of patients treated with dental implants at the department of oral and maxillofacial surgery and the department of prosthodontics of the study institution between June 2007 and June 2012. Patient data and files from these two departments were examined in detail.

Patients who had undergone previous extraction of all remaining teeth and implant placement in both healed bone and at the extraction sites in the same procedure were eligible for inclusion. Patients were selected on the basis of inclusion and exclusion criteria.

Inclusion criteria were the following: age ≥18 years, systemically healthy, cooperative and likely to maintain good dental health, and adequate bone height for placement of implants with a minimum length of 7 mm. Teeth were extracted due to root fracture, root resorption, root perforation, a non-ideal crown–root ratio, or a peri-apical pathology.

Exclusion criteria were the following: presence of any local or systemic factors that might contraindicate oral surgery, poor oral hygiene, conditions that complicate wound healing such as uncontrolled diabetes, smoking (≥10 cigarettes a day), pregnancy, a history of drug or alcohol abuse, and an inability or unwillingness to return for follow-ups after occlusal loading.

This study was reviewed and approved by the regional ethics committee and adhered to the guidelines of the Declaration of Helsinki.

Surgical procedure

Preparations for surgery were performed according to standard protocols. A single experienced surgeon performed all operations. Surgical procedures were performed under local anaesthesia with intravenous sedation. A mucoperiosteal flap was elevated. Before implant placement, selected teeth were extracted carefully and multi-rooted teeth were sectioned to preserve the remaining bone; this was done on the day of surgery, within the same surgical procedure, by the same surgeon. Granulation tissue was eliminated and the implants were placed in the residual bone and in the extraction sockets, achieving primary stability. The longest and widest possible implants were installed in the residual crest and the extraction sockets in order to achieve an aesthetic profile and maximum vertical preservation ( Figs 1 and 2 ). If a gap occurred between the implant surface and the surrounding bone, a mixture of autogenous bone derived from the drilling of the implant beds and allogenic mineralized bone graft (Puros Allograft; Zimmer Dental Inc., Carlsbad, CA, USA) was inserted. In the case of an insufficient bone level in the posterior maxilla for implant placement, a lateral wall approach sinus augmentation procedure was performed and dental implants were subsequently installed. The mucoperiosteal flap was adapted and sutured with primary closure to allow healing.

Surgical view of implants installed in fresh extraction sites and in healed bone in the maxilla.

Surgical view of implants installed in fresh extraction sites and in healed bone in the mandible.

Following implant placement and suturing, all patients received antibiotic therapy (amoxicillin and clavulanic acid). Anti-inflammatory agents (naproxen sodium) and mouth rinse (chlorhexidine gluconate) were prescribed to all patients for 1 week. Sutures were removed 7 days after surgery.

The implants were left submerged for 3 months. Removable provisional prosthesis procedures were performed for those patients who were reluctant to be edentulous during this healing period. After the submerged healing period, patients were invited back for second-stage surgery. Following the re-entry procedure, the soft tissues were allowed to heal for at least another 2 weeks before impressions were taken. Definitive abutments were tightened using 35 N cm torque. Implant-supported fixed full-arch prostheses were then fitted for all patients ( Figs 3 and 4 ).

Final prostheses in the same patient.

View of the smile after delivery of the final prostheses in the same patient.

In line with the patient follow-up policy for patients receiving dental implants in the clinic, patients were examined at 3-month intervals for 6 months and then at 6-month intervals for 2 years. Radiographic follow-ups were performed for all patients before and after surgery, and all patients were evaluated at 6-month intervals for the first 2 years after loading ( Fig. 5 ).

Postoperative radiographic view of the same patient.

Based on the clinical and radiographic criteria described by Buser et al., each implant was classified as successful or as having failed. The implant was considered successful if the following parameters were absent: (1) persistent subjective complaints such as pain, foreign body sensation, and/or dysesthesia, (2) peri-implant infection with suppuration, (3) mobility, or (4) continuous radiolucency around the implant. Removed, lost, mobile, or fractured implants were regarded as implant failures.

Surgical procedure

Preparations for surgery were performed according to standard protocols. A single experienced surgeon performed all operations. Surgical procedures were performed under local anaesthesia with intravenous sedation. A mucoperiosteal flap was elevated. Before implant placement, selected teeth were extracted carefully and multi-rooted teeth were sectioned to preserve the remaining bone; this was done on the day of surgery, within the same surgical procedure, by the same surgeon. Granulation tissue was eliminated and the implants were placed in the residual bone and in the extraction sockets, achieving primary stability. The longest and widest possible implants were installed in the residual crest and the extraction sockets in order to achieve an aesthetic profile and maximum vertical preservation ( Figs 1 and 2 ). If a gap occurred between the implant surface and the surrounding bone, a mixture of autogenous bone derived from the drilling of the implant beds and allogenic mineralized bone graft (Puros Allograft; Zimmer Dental Inc., Carlsbad, CA, USA) was inserted. In the case of an insufficient bone level in the posterior maxilla for implant placement, a lateral wall approach sinus augmentation procedure was performed and dental implants were subsequently installed. The mucoperiosteal flap was adapted and sutured with primary closure to allow healing.

Surgical view of implants installed in fresh extraction sites and in healed bone in the maxilla.

Surgical view of implants installed in fresh extraction sites and in healed bone in the mandible.

Following implant placement and suturing, all patients received antibiotic therapy (amoxicillin and clavulanic acid). Anti-inflammatory agents (naproxen sodium) and mouth rinse (chlorhexidine gluconate) were prescribed to all patients for 1 week. Sutures were removed 7 days after surgery.

The implants were left submerged for 3 months. Removable provisional prosthesis procedures were performed for those patients who were reluctant to be edentulous during this healing period. After the submerged healing period, patients were invited back for second-stage surgery. Following the re-entry procedure, the soft tissues were allowed to heal for at least another 2 weeks before impressions were taken. Definitive abutments were tightened using 35 N cm torque. Implant-supported fixed full-arch prostheses were then fitted for all patients ( Figs 3 and 4 ).

Final prostheses in the same patient.

View of the smile after delivery of the final prostheses in the same patient.

In line with the patient follow-up policy for patients receiving dental implants in the clinic, patients were examined at 3-month intervals for 6 months and then at 6-month intervals for 2 years. Radiographic follow-ups were performed for all patients before and after surgery, and all patients were evaluated at 6-month intervals for the first 2 years after loading ( Fig. 5 ).

Postoperative radiographic view of the same patient.

Based on the clinical and radiographic criteria described by Buser et al., each implant was classified as successful or as having failed. The implant was considered successful if the following parameters were absent: (1) persistent subjective complaints such as pain, foreign body sensation, and/or dysesthesia, (2) peri-implant infection with suppuration, (3) mobility, or (4) continuous radiolucency around the implant. Removed, lost, mobile, or fractured implants were regarded as implant failures.

Statistical analysis

The statistical analysis was performed using SPSS version 13.0 software (SPSS Inc., Chicago, IL, USA). Fisher’s exact test was used to evaluate differences between success rates in immediate and non-immediate implants. The results were considered significant at P -values of less than 0.05.

The survival of immediate and non-immediate implants was investigated using the log rank test. Kaplan–Meier survival estimates were calculated. A separate log rank test was used to identify the effect of timing of implant installation on survival. A 5% type I error level was used to infer statistical significance.