Survival rate of osseointegrated implants in atrophic maxillae grafted with calvarial bone: a retrospective study

Abstract

The aim of this study was to evaluate the clinical survival rate of osseointegrated implants placed in the atrophic maxilla that has been reconstructed by means of autogenous bone grafts harvested from a cranial calvarial site. Further, we sought to analyse the level of peri-implant bone after prosthetic rehabilitation and to determine subjective patient satisfaction with the treatment performed. This study conformed to the STROBE guidelines regarding retrospective studies. Twenty-five patients who had received osseointegrated implants with late loading in the reconstructed atrophic maxilla were included in the study. The survival rate and level of peri-implant bone loss were evaluated. A questionnaire related to the surgical and prosthetic procedures was completed. The observed implant survival rate was 92.35%. The mean bone loss recorded was 1.76 mm in the maxilla and 1.54 mm in the mandible. The results of the questionnaire indicated a high level of patient satisfaction, little surgical discomfort, and that the patients would recommend the procedure and would undergo the treatment again. From the results obtained, it is concluded that the cranial calvarial site is an excellent donor area; calvarial grafts provided stability and maintenance of bone volume over the course of up to 11 years.

The consequence of the absence of a tooth is continuous bone resorption. Depending on the period over which this occurs, it may become unfeasible to place implants in the edentulous region due to the absence of the minimum bone height and/or thickness required. The surgical procedure most often used for the reconstruction of these areas is bone grafting, for which materials of autogenous, homogeneous, heterogeneous, or synthetic origin may be applied. Material of autogenous origin is the only type that presents the biological property of osteogenicity. The scientific literature presents a wide variety of possible donor areas, both intraoral and extraoral. The latter include the cranial calvarium, fibula, iliac crest, rib, and tibia.

Among the possible extraoral donor areas, the most commonly used and studied is the iliac crest. This is characterized by corticomedullary bone with a predominance of the medullary portion, which has a good thickness. Its surgical advantages include better acceptance by the patient and a shorter surgical time, due to the possibility of simultaneously opening the receptor and donor areas. However, it leads to a higher rate of complications and morbidity, greater need for analgesics, greater susceptibility to infection, longer hospitalization time, greater postsurgical remodelling of the bone graft, and a higher failure of implants placed in these areas when compared with the calvarial cranial donor site, and also results in an external scar. With the iliac crest graft, postsurgical discomfort in the donor area lasting months or even years has been reported, in addition to pain on walking.

Another commonly used donor site is the cranial calvarium. This bone is of a membranous origin, formed of bones of the cortical and spongy types, with a predominance of the cortical portion. It presents rapid vascularization at the grafted site, which is a prerequisite for successful osteogenesis. There are many advantages to the choice of calvarial bone. This procedure presents a lower rate of complications and morbidity, a reduction in pain at the donor site, is less susceptible to infection, is subject to less resorption and postsurgical remodelling of the graft, involves a shorter hospitalization, and demonstrates higher success rates and better bone quality in comparison with the iliac crest graft; it also results in an imperceptible scar and does not affect respiration or walking.

The follow-up of clinical cases submitted to reconstructive surgery of the atrophic maxilla and mandible has become important in terms of evaluating patient satisfaction and the effectiveness of the procedure before undertaking the practice of extensive rehabilitations using bone grafts and implants. Within this context, the aim of the present study was to perform a retrospective evaluation of the success of implants placed in the atrophic maxilla reconstructed with autogenous bone obtained from the cranial calvarium, and to measure the patients’ personal satisfaction with their treatment from the initial surgical stage through to the conclusion of the rehabilitative stage.

Materials and methods

The STROBE guidelines (Strengthening the Reporting of Observational studies in Epidemiology) were followed for this retrospective study. The clinical records of 32 patients treated at the Continuing Education Nucleus (Nec-Odonto) post-graduate institution specializing in implant dentistry in Araçatuba, Brazil were retrieved from the database. All of these patients underwent reconstructive surgery by means of autogenous bone grafts harvested from the cranial calvarium with later placement of osseointegrated implants. Of these 32 patients, one could not be contacted at the address or using the telephone number provided in the clinical records, one patient was travelling in another country and had no return date, one patient was hospitalized, three patients did not respond to the telephone call or letter, and one patient had not yet completed the final prosthetic phase ( Fig. 1 ). Hence the study included a total of 25 patients.

Fig. 1
Flow diagram of patient selection for this study.

Twenty of the patients were women and five were men, and they ranged in age from 43 to 75 years (mean 57 years). These patients underwent the surgical and rehabilitative procedures during the years 1999–2011. The inclusion criteria used were: (1) Patients who were partially or completely edentulous in the maxilla and/or mandible, who presented severe atrophy in height and/or thickness making it impossible to perform rehabilitation with dental implants, those with significant deficiencies in residual bone below the nasal cavity and maxillary sinus, and those with the absence of teeth due to agenesis; these patients had to have undergone reconstructive surgery with autogenous bone harvested from the calvarial cranial site. (2) Patients whose treatment was completed with an implant-supported denture that had been in place for at least 6 months. (3) Patient agreement and the provision of a signed term of free and informed consent.

The exclusion criteria were the following: (1) Patients intellectually incapable of responding to the psychosocial evaluation questions about the rehabilitative treatment received. (2) Patients who did not complete the prosthetic rehabilitation.

All patients evaluated underwent bone reconstruction surgery by means of autogenous bone grafts harvested from the cranial calvarium. The surgeries were performed in a hospital environment, under general anaesthesia, with nasotracheal intubation, and all cases were indicated, planned, and carried out by the same multiprofessional team. All of the reconstructed maxillae were shown to be atrophied with a residual bone thickness of 1–2 mm and a residual bone height of ≤10 mm. The dimensions of the residual maxillary bone were compatible with Cawood and Howell classification IV for the anterior maxilla and classification VI for the posterior maxilla.

The indication was made when the patient required an increased thickness and/or height of the ridge, and/or a unilateral or bilateral sinus lift. Panoramic radiographs and computed tomography examinations were used for planning. In the clinical–radiographic examination, the intraoral condition, state of conservation of the teeth, periodontal condition, presence of peri-apical lesions, and need for a provisional denture were evaluated; in addition, the patient’s psychological condition and acceptance of having the treatment performed were observed at this stage.

At all times, the graft from the calvarium was harvested by a neurosurgeon, who obtained surgical access by dermoperiosteal incision in the lateral region of the head using the lateral corner of the orbit as reference. The area of graft collection in the calvarium was the parietal bone. After the use of a trephine bur to determine the external cortical thickness, the oral and maxillofacial surgeon performed the osteotomies necessary for reconstruction of the area to be grafted, followed by removal of the graft blocks by means of chisels and a hammer. After obtaining the graft, the surgical reconstruction procedure was performed. Access to the atrophic maxilla was gained by a mucoperiosteal incision in the alveolar crest, with relaxing incisions in the midline and posterior region on the right and left sides. After detachment and exposure of the tissues, an osteotomy was performed in the anterior wall of the maxillary sinus, and then the sinus membrane was carefully detached. At all times, decorticalization was performed of the bone walls that were going to be constructed. After this, the bone blocks were modelled to the areas to be reconstructed, filling the maxillary sinus, or the maxillary sinuses, with particulated bone, in accordance with the initial indication and planning, and the bone blocks were fixed by means of cortical screws. As is the rule, each graft block was fixed with two cortical screws whenever possible. The goal of surgical reconstruction was to reconstruct the atrophic areas in which implants would later be placed, in accordance with the initial rehabilitation planning ( Fig. 2 ). Temporary implants were placed for retaining a removable denture without buccal flanges, where appropriate.

Fig. 2
Atrophic maxilla reconstructed with autogenous bone grafts harvested from the calvarium site (parietal bone).

The implants were placed at 6 months after the reconstructive surgery when the graft was to increase bone thickness, or at 8 months after surgery in cases in which there was sinus grafting. The implant placement surgery was performed under local anaesthesia, and the number and distribution of the implants were determined by the prosthetic planning. All implants placed were of external hexagon type, regular Brånemark standard platform of 4.1 mm, modified by dual acid etching surface (Conexão Sistemas de Prótese, São Paulo, Brazil), and ranged in length from 10.0 mm to 13.0 mm. The data relative to treatment, such as the date of each stage (reconstruction by means of graft, implant placement, and prosthetic completion), and data on graft complications and loss of implants were acquired from the clinical records of each patient.

During the postoperative period, the patients were monitored by means of monthly visits. Panoramic radiographs were taken preoperatively, immediately postoperative, at 6–8 months after the reconstruction procedure (the stage before implant placement), after implant placement, after prosthetic rehabilitation, and at postsurgical follow-up after the bone reconstruction period (condition in which the patients were found when they were invited to participate in this retrospective study).

This study was approved by the committee on human research of the study institution.

Clinical–radiographic evaluation

Evaluation of the success of implants was made by clinical–radiographic evaluation in accordance with the criteria for the evaluation of implant survival suggested by Chiapasco et al. : the absence of persistent pain or dysesthesia, absence of peri-implant infection with suppuration, absence of mobility, and absence of continuous peri-implant radiolucency. To obtain the data on peri-implant bone loss, panoramic radiographs were digitized. The measurements were obtained by means of the program CDR DICOM for Windows (Schick Technologies, Long Island City, NY, USA) and performed by a single investigator. Implant length, previously known, was measured using the calibration tool of the program. Thereafter, bone loss measurements were taken at the union between the implant platform and the abutment up to the first bone–implant contact in the mesial and distal region of each implant ( Fig. 3 ).

Fig. 3
Calibration and measurement made at the union between the implant platform and abutment up to the first bone–implant contact after calibrating the ruler.

Patients were divided into three groups by length of follow-up after the bone graft reconstruction. Group I comprised 16 subjects at 0–5 years post-surgical bone graft (13 maxilla only and three maxilla and mandible). Group II comprised five subjects at 6–10 years post-surgical bone graft (two maxilla only and three maxilla and mandible). Group III comprised four subjects at ≥11 years post-surgical bone graft (all maxilla only).

Subjective evaluation of personal satisfaction

All patients included in this study provided free and informed consent. Sixteen patients participated in this part of the analysis. Nine patients did not respond to the questionnaire as they were unable to attend the appointment on the day and at the time set for reasons of work, health, travel, or distance from the place where they lived. A questionnaire was prepared with questions covering embarrassment, difficulties, and dissatisfactions, in addition to questions evaluating the patient’s perception of the surgical procedure as regards cost, information received before surgery was performed, satisfaction with the implants, and whether they would recommend the procedure or would undergo the treatment again. With regard to prosthetic rehabilitation, questions were asked about aesthetics, phonetics, mastication, the comfort provided by the prosthetic rehabilitation, and the impact of treatment performed on their general health. The answers obtained were collected into four groups, as follows: group 1 – guidance, investment, and satisfaction with the professional and the work that was done; group 2 – surgical stage, complications, and pain; group 3 – would recommend the procedure to another person, or willing to undergo the treatment again; group 4 – restorative and aesthetic procedure, mastication, speech, sense of taste, and possible embarrassments.

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Jan 17, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Survival rate of osseointegrated implants in atrophic maxillae grafted with calvarial bone: a retrospective study
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