Abstract
Objective
Evaluate the peri-implant status on the long-term (1–9 years) of patients treated with immediately-loaded full-arch prostheses in a private practice.
Methods
A retrospective cohort study was carried out in patients consecutively treated with immediately loaded full-arch restorations supported with a minimum of 4 implants (Replace ® Tapered, Nobel Biocare AB) and Multi-Unit conical abutments (MUA ® , Nobel Biocare AB) with a follow-up of over 12 months after placement of the final prosthesis.
Results
A total of 378 implants were placed in 56 patients. Forty upper and 32 lower arches were restored, and 16 patients received bimaxillary rehabilitation. The mean duration of follow-up was 50 months, and the implant and patient peri-implantitis prevalences were 14.3% and 50%, respectively. Mucositis affected 56.9% of the implants and 50% of the patients. The survival rate was 96.4% by patient, but reached 99.5% in the implant-based analysis, and the success rate was 95.5% for implants and 80.4% for patients.
Conclusions
Immediately-loaded full-arch restorations have an acceptable outcome after 1–9 years of follow-up. However, the incidence of peri-implant diseases is high, and further research is needed to confirm whether these may compromise the predictability of the prostheses over the long-term.
Clinical significance
After a mean follow-up of 50 months, the incidence of mucositis and peri-implantitis affected the 96.4% and 50% of patients, respectively. However, these results were reduced almost by half when the threshold of bleeding on probing and peri-implant bone loss applied was less strict.
1
Introduction
Implant-supported restorations are a highly predictable treatment option for edentulism. Implantology has become more demanding, and some protocols such as immediate loading and postextraction implants have been developed to allow fast establishment of function and esthetics. Some studies have demonstrated a high satisfaction level compared to the conventional loading protocol . On the other hand, the presence of peri-implant diseases is a genuine concern that may hamper the long-term predictability of dental implants.
A study published by Mir-Mari et al. assessed the prevalence of peri-implant diseases in private practice. The proportion of patients with peri-implantitis ranged from 12% to 22%, while the mucositis rate was 39%. However, these authors underscored that the prevalence of peri-implant diseases was much higher in patients with four or more implants.
There are well-known risk factors for the development of mucositis and peri-implantitis . Some studies have recommended the placement of an abutment in order to reduce marginal bone loss . Furthermore, placing the definitive abutment at the time of implant placement seems to reduce soft and hard tissue changes, at least within the first 6 months, compared to healing abutments . Thus, an immediate loading protocol involving a conventional intermediate abutment may have advantages when compared to other protocols in terms of tissue remodeling, long-term health and predictability of the results.
The aim of the present study was to evaluate the clinical outcome and prevalence of peri-implant diseases in patients treated with immediately-loaded full-arches after a follow-up period ranging from 12 months to 9 years in a private practice.
2
Materials and methods
This study has been carried out according to the STROBE (The Strengthening the Reporting of Observational Studies in Epidemiology) guidelines . A retrospective cohort study comprising adult patients consecutively treated between June 2006 and December 2014 in a private practice with immediately loaded full-arch restorations supported by a minimum of four implants (Replace ® Tapered, Nobel Biocare AB) and Multi-Unit straight or angled conical abutments (MUA ® , Nobel Biocare AB) was carried out. All patients signed an informed consent, and the study protocol was approved by the ethical review board of the Dental Hospital of the University of Barcelona (Protocol number 2014-28). The Declaration of Helsinki guidelines were followed throughout the trial.
2.1
Treatment protocol
Panoramic X-rays and computed tomography scans were first performed to adequately plan treatment. The surgical procedure was done under conscious sedation and local anesthesia. Once the teeth were extracted, a minimum of 4 and a maximum of 6 implants were placed in each arch. Immediate loading of the implants was carried out when the insertion torque was higher than 35 Ncm. Conical prosthetic abutments were connected (straight with a torque of 35 Ncm and angled with 15 Ncm), and soft tissue augmentation techniques such as connective tissue grafting were applied when necessary. In post-extraction defects around immediately-placed implants, when the remaining bone around the fixtures was thin (<1.5 mm) or when bone defects were present, autologous bone chips collected from a tuberosity or retromolar area and/or xenografts (BioOss ® , Geistlich Biomaterials, Wolhusen, Switzerland) were used along with a resorbable bovine collagen membrane (BioGide ® , Geistlich Biomaterials, Wolhusen, Switzerland). Once the open-tray impression copings were placed, the wound was closed with 4/0 (Supramid ® , SMI AG, Belgium) or 5/0 polyglycolic reabsorbable sutures (Resotex ® , Resorba, Wundversorgung GmbH & Co., Nürnberg, Germany), and an impression with polyether (Impregum-Penta ® , 3 M Espe, MN, USA) was obtained. The dental technician manufactured a screw retained acrylic full-arch provisional prosthesis. A 1.2 mm in width metal ligature was used inside to reinforce the structure, and an ovoid pontics design was adopted. A no cantilevers and reduced thickness principle was applied in order to avoid discomfort to the patient and to facilitate proper oral hygiene. The distal implants were placed in the second premolar or first molar areas leading to 10 or 12 unit prostheses (without cantilevers). These prostheses were provided to the patient within 6–48 h after surgery and the prosthetic screws were inserted at a 15 Ncm torque. The sutures were removed after 7–10 days, and the patients were followed-up on until 90 days. At this time, the provisional prostheses were removed to check osseointegration. After delivering and adapting the definitive prosthesis, made of either metal-ceramic or metal-resin materials, the patients were all enrolled in a peri-implant maintenance program. This protocol has been described more thoroughly in a previous report .
2.2
Data collection
The following data were registered: demographic parameters (age, gender, arch, smoking habit, history of periodontal disease and bruxism), treatment variables (implant placement protocol, implant angulation, abutment exposure, abutment height, prosthetic material, opposing dentition, compliance with the maintenance visits opposing dentition, time in function of the provisional prosthesis, time of follow-up, major mechanical complications – framework fracture and mobility of the prosthesis –) and outcome data (biological complications: mucositis, peri-implantitis). Clinical and radiographic evaluations were carried out to establish the peri-implant diagnosis. Small mechanical complications related with the final prosthesis (ceramic or resin fractures, initial cracks, tooth wear and prosthetic retention screw fractures) were not registered.
2.3
Clinical and radiographic evaluation
Between January 2015 and January 2016, all patients treated at least one year before were recalled for inclusion in the study. A panoramic X-ray was taken at that time.
One examiner performed the clinical assessments after disconnecting the prosthesis. The probing pocket depth (recording the highest value per implant) and the modified gingival index (mGI) and plaque index (mPI), according to Mombelli et al. , were evaluated. Then, two examiners independently analyzed the X-rays, comparing the last panoramic X-ray with the one taken at the time of delivery of the definitive prosthesis (i.e., once the remodeling phase had ended). The examiners were previously calibrated with 10 patients and yielded an interclass correlation coefficient (ICC) of 0.907. Each examiner measured the mesial and distal aspects of the implants, from the base of the abutment to the interproximal bone. The worst value for each implant was selected.
With regard to peri-implant diseases, the diagnostic criteria for mucositis were bleeding on probing, without suppuration and changes in crestal bone ≤1.5 mm. Peri-implantitis in turn was defined as bone loss >1.5 mm, with bleeding on probing and/or suppuration . Patients were classified according to the most demanding peri-implant diagnosis.
The implant success rate was calculated according to the criteria of Albrektsson et al. .
2.4
Statistical analysis
The SPSS version 22.0 statistical package (IBM Corp, Armonk, NY, USA) was used. A bivariate analysis was performed based on the chi-square test for dichotomic variables and the Student t -test for scale variables. A patient-based non-conditional logistic regression using periimplantitis was made. The binary outcome variable was peri-implantitis and the rest of the registered variables were entered as dependent variables. The significance level was set at 0.05.
2
Materials and methods
This study has been carried out according to the STROBE (The Strengthening the Reporting of Observational Studies in Epidemiology) guidelines . A retrospective cohort study comprising adult patients consecutively treated between June 2006 and December 2014 in a private practice with immediately loaded full-arch restorations supported by a minimum of four implants (Replace ® Tapered, Nobel Biocare AB) and Multi-Unit straight or angled conical abutments (MUA ® , Nobel Biocare AB) was carried out. All patients signed an informed consent, and the study protocol was approved by the ethical review board of the Dental Hospital of the University of Barcelona (Protocol number 2014-28). The Declaration of Helsinki guidelines were followed throughout the trial.
2.1
Treatment protocol
Panoramic X-rays and computed tomography scans were first performed to adequately plan treatment. The surgical procedure was done under conscious sedation and local anesthesia. Once the teeth were extracted, a minimum of 4 and a maximum of 6 implants were placed in each arch. Immediate loading of the implants was carried out when the insertion torque was higher than 35 Ncm. Conical prosthetic abutments were connected (straight with a torque of 35 Ncm and angled with 15 Ncm), and soft tissue augmentation techniques such as connective tissue grafting were applied when necessary. In post-extraction defects around immediately-placed implants, when the remaining bone around the fixtures was thin (<1.5 mm) or when bone defects were present, autologous bone chips collected from a tuberosity or retromolar area and/or xenografts (BioOss ® , Geistlich Biomaterials, Wolhusen, Switzerland) were used along with a resorbable bovine collagen membrane (BioGide ® , Geistlich Biomaterials, Wolhusen, Switzerland). Once the open-tray impression copings were placed, the wound was closed with 4/0 (Supramid ® , SMI AG, Belgium) or 5/0 polyglycolic reabsorbable sutures (Resotex ® , Resorba, Wundversorgung GmbH & Co., Nürnberg, Germany), and an impression with polyether (Impregum-Penta ® , 3 M Espe, MN, USA) was obtained. The dental technician manufactured a screw retained acrylic full-arch provisional prosthesis. A 1.2 mm in width metal ligature was used inside to reinforce the structure, and an ovoid pontics design was adopted. A no cantilevers and reduced thickness principle was applied in order to avoid discomfort to the patient and to facilitate proper oral hygiene. The distal implants were placed in the second premolar or first molar areas leading to 10 or 12 unit prostheses (without cantilevers). These prostheses were provided to the patient within 6–48 h after surgery and the prosthetic screws were inserted at a 15 Ncm torque. The sutures were removed after 7–10 days, and the patients were followed-up on until 90 days. At this time, the provisional prostheses were removed to check osseointegration. After delivering and adapting the definitive prosthesis, made of either metal-ceramic or metal-resin materials, the patients were all enrolled in a peri-implant maintenance program. This protocol has been described more thoroughly in a previous report .
2.2
Data collection
The following data were registered: demographic parameters (age, gender, arch, smoking habit, history of periodontal disease and bruxism), treatment variables (implant placement protocol, implant angulation, abutment exposure, abutment height, prosthetic material, opposing dentition, compliance with the maintenance visits opposing dentition, time in function of the provisional prosthesis, time of follow-up, major mechanical complications – framework fracture and mobility of the prosthesis –) and outcome data (biological complications: mucositis, peri-implantitis). Clinical and radiographic evaluations were carried out to establish the peri-implant diagnosis. Small mechanical complications related with the final prosthesis (ceramic or resin fractures, initial cracks, tooth wear and prosthetic retention screw fractures) were not registered.
2.3
Clinical and radiographic evaluation
Between January 2015 and January 2016, all patients treated at least one year before were recalled for inclusion in the study. A panoramic X-ray was taken at that time.
One examiner performed the clinical assessments after disconnecting the prosthesis. The probing pocket depth (recording the highest value per implant) and the modified gingival index (mGI) and plaque index (mPI), according to Mombelli et al. , were evaluated. Then, two examiners independently analyzed the X-rays, comparing the last panoramic X-ray with the one taken at the time of delivery of the definitive prosthesis (i.e., once the remodeling phase had ended). The examiners were previously calibrated with 10 patients and yielded an interclass correlation coefficient (ICC) of 0.907. Each examiner measured the mesial and distal aspects of the implants, from the base of the abutment to the interproximal bone. The worst value for each implant was selected.
With regard to peri-implant diseases, the diagnostic criteria for mucositis were bleeding on probing, without suppuration and changes in crestal bone ≤1.5 mm. Peri-implantitis in turn was defined as bone loss >1.5 mm, with bleeding on probing and/or suppuration . Patients were classified according to the most demanding peri-implant diagnosis.
The implant success rate was calculated according to the criteria of Albrektsson et al. .
2.4
Statistical analysis
The SPSS version 22.0 statistical package (IBM Corp, Armonk, NY, USA) was used. A bivariate analysis was performed based on the chi-square test for dichotomic variables and the Student t -test for scale variables. A patient-based non-conditional logistic regression using periimplantitis was made. The binary outcome variable was peri-implantitis and the rest of the registered variables were entered as dependent variables. The significance level was set at 0.05.
3
Results
A total of 56 patients were included (26 men and 30 women), with a mean age of 64 years (standard deviation (SD) = 11.1; range: 41–87). Since 16 patients received bimaxillary treatment, 72 arches were finally analyzed (40 upper and 32 lower). All patients had history of periodontal disease. The distribution of demographic and treatment variables can be seen in Table 1 .
| Demographic variables | ||
|---|---|---|
| Gender | Men | 26 (46.4%) |
| Women | 30 (53.6%) | |
| Smoking habit | Non-smoker | 41 (73.2%) |
| <10 cig/day | 0 | |
| ≥10 cig/day | 15 (26.8%) | |
| Bruxism | Yes | 22 (39.3%) |
| No | 34 (60.7%) | |
| Arch | Maxilla | 40 (55.6%) |
| Mandible | 32 (44.4%) | |
| Treatment variables | ||
| Implant placement protocol | Immediate | 133 (35.2%) |
| Delayed | 245 (64.8%) | |
| Implant angulation | Angled | 85 (22.5%) |
| Axial | 293 (77.5%) | |
| Abutment exposure | Yes | 57 (15%) |
| No | 321 (85%) | |
| Abutment height | 1 mm | 220 (58.2%) |
| ≥2 mm | 158 (41.8%) | |
| Prosthetic material | Metal-ceramic | 46 (63.9%) |
| Metal-resin | 26 (36.1%) | |
| Opposing dentition | Removable complete denture | 4 (5.6%) |
| Natural teeth | 28 (38.9%) | |
| Implant-supported full-arch | 40 (55.6%) | |
| Maintenance visits | Not regular | 27 (48.2%) |
| Regular | 29 (51.8%) | |
| Time wearing provisional prosthesis | 9.4 months (3–48) | |
| Time of follow-up | 50 months (12–108) | |
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