Abstract
The aim of this study was to measure changes in buccal alveolar crestal bone levels after immediate placement and loading of dental implants with Morse taper prosthetic abutments after tooth extraction. This study followed the STROBE guidelines regarding prospective cohort studies. The sample comprised 12 patients with a mean age of 45 years, in whom a central or upper lateral incisor was indicated for extraction. Prior to extraction, computed tomography (CT) analysis was carried out to assess the presence of the buccal bone crest. CT scans were performed at 24 h and at 6 months after immediate implant placement and immediate loading. The distance from the most apical point of the implant platform to the buccal bone crest was assessed at the two time points. The buccal bone crest height was evaluated at three points in the mesio-distal direction: (1) the centre point of the alveolus, (2) 1 mm mesial to the centre point, and (3) 1 mm distal to the centre point. The values obtained were subjected to statistical analysis, comparing the distances from the bone crest to the implant platform for the two time points. After 6 months there was a statistically significant, non-uniform reduction in height at the level of the crest of the buccal bone in the cervical direction. It is concluded that the buccal bone crest of the immediate implants that replaced the maxillary incisors underwent apical resorption when subjected to immediate loading.
After tooth extraction, the physiological healing process of the alveolar bone is accompanied by changes in the surrounding soft and hard tissues. This event often compromises the aesthetics of the region due to the loss of bone volume in the vertical and horizontal directions. In order to select the best time to install an implant, it is essential to understand the events that occur after extraction, such as the resorption of alveolar bone in the absence of a load stimulus.
The placement of implants immediately after tooth extraction has been used in order to minimize alveolar resorption and maintain the periodontal architecture. However, there are reports that immediate implant placement with non-functional loading is not effective in preventing alveolar bone resorption.
Several factors are associated with the resorption of the alveolar bone crest in immediate implants with immediate loading, such as the thickness of the wall of the buccal bone, the defect type (circumferential or not), thickness of the gingiva, and the size of the existing space between the implant and the wall of the alveolus.
More recently, the validity of the technique of installing dental implants immediately after extraction has been demonstrated at sites with small peri-implant defects that do not require the use of grafting techniques or regenerative procedures. Some authors consider that when the space between the wall of the alveolus and the surface of the implant is ≤2.0 mm, there is no need for filling with a connective tissue graft or guided bone regeneration procedures.
During the osseointegration period, the absence of occlusal forces and excursive movements is considered necessary to achieve high success rates with dental implants used in oral rehabilitation therapy.
The purpose of this study was to evaluate the behaviour of the alveolar bone crest and the buccal surface of implants installed immediately after extraction with Morse taper type prosthetic connections. The hypothesis was that immediate Morse taper type implants in the alveoli of incisors with immediate loading could prevent the resorption of the buccal bone in the apical direction after dental extraction. The specific objective was to measure the distance of the buccal bone crest to the implant platform immediately after placement and after 6 months using computed tomography (CT) images.
Materials and methods
This prospective study analyzed the height of the buccal alveolar bone crest at 6 months after tooth extraction and immediate placement of implants with immediate loading. The study population consisted of all patients who attended the study institution between the years 2009 and 2010 with an indication for extraction of a central or lateral upper incisor, in whom immediate placement of an implant was possible. This study followed the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines regarding prospective cohort studies. The research project was approved by the university ethics committee (Pontifical Catholic University, Curitiba, Paraná, Brazil).
For inclusion in the study, patients had to meet the following criteria: age between 18 and 70 years, good oral hygiene, requirement for the extraction of a central or lateral upper incisor (with the presence of adjacent natural teeth), a keratinized gingival band between 3 and 5 mm wide, presence of a buccal bone plate, and at least 5 mm of bone tissue between the dental apex and the nasal cavity (observed in peri-apical radiographs, to enable primary stability of the implant). Patients with uncompensated systemic diseases or psychosomatic disorders, smokers, and patients with bruxism, non-occlusion of the posterior teeth, untreated periodontal disease, active infections in the area of surgery, or the presence of acute peri-apical lesions, were excluded from the study.
The buccal bone plate of the incisors was assessed by CT at three time points: pre-surgery ( T 0 ), 24 h after surgery ( T 1 ), and 6 months postoperatively ( T 2 ). The goal of the preoperative CT was to locate the buccal bone plate. A tomographic guide, which consisted of a metal point located in the most central area of the tooth alveolus in the mesio-distal direction, was made for each patient in order to locate the same region in the CT sections at the different times evaluated. The tomographic guide was made using a plaster model that was obtained using an impression of the teeth with irreversible hydrocolloid. An auto-polymerized acrylic resin guide was built using the plaster model and adjusted on the coronal surface of the maxillary front teeth. This structure supported the wire in order to direct the CT sections ( Fig. 1 ).
All CT scans were carried out in the same radiology clinic using the same apparatus, and by the same technician. During all of the CT examinations, the patients used an autostatic lip retractor (Arcflex; FGM Dental Products, Joinville, SP, Brazil). The soft tissues were retracted in order to avoid the superimposition of images of the lips, tongue, and cheek. CT scans were done with an i-CAT scanner (Imaging Sciences International, LLC, Hatfield, PA, USA) and the images were acquired using i-CAT software. The scan of the maxilla took 40 s (scan size of 6 cm × 17 cm × 7 cm). CT sections 1.0 mm in thickness were obtained.
After the first CT scan had been done and the presence of the buccal bone plate of the incisor in the section located by the metal point was confirmed, the patient was referred to the clinic for tooth extraction and implant placement ( Fig. 2 ).
Surgical and prosthetic procedure
The selected patients were treated with 1 g amoxicillin (Ranbaxy Laboratories Ltd, India) and 4 mg dexamethasone (Decadron; Aché Laboratórios Farmacêuticos S.A., Brazil), 1 h before surgery. Antisepsis, both extraoral (4% chlorhexidine gluconate, Riohex; Rioquímica, Brazil) and intraoral (0.12% chlorhexidine gluconate, Perioplak; Reymer, Brazil), was carried out. Next, local terminal anaesthesia was achieved using mepivacaine (2% mepivacaine hydrochloride) with 1:200,000 epinephrine (Mepiadre 100 DFL; Biodental Produtos Dentarios Ltda, Brazil).
The extraction was carried out without elevation of a mucoperiosteal flap, and the utmost care was taken to avoid damaging the alveolar crest. To achieve this, a ‘Bivers’ type scalpel (Neodent, Curitiba, Paraná, Brazil) was used on the mesial, distal, and lingual walls of the tooth, in order to penetrate the periodontal ligament and separate the tooth from the alveolar bone. After luxation of the tooth, number 150 forceps were used for tooth removal. The cavity was inspected carefully in order to verify the integrity of the buccal wall.
Subsequently, the osteotomy preparation was carried out through the wall of the alveolar process, using drills of increasing diameter, prior to installation of the implant. The implant was positioned palatally so that a cemented crown could be used ( Fig. 3 ). The implant used was of the Morse tapered cone platform type (Morse taper, Alvin; Neodent), with a diameter of 3.5 mm or 4.3 mm and a length of 13.0 mm.
The initial stability of the implant was at least 45 N·cm, measured by a surgical ratchet with a manual torque meter (Neodent). The platforms of the implants were located 1.0–2.0 mm below the buccal bone crest level. The spaces between the walls of the alveoli and the surfaces of the implants were ≤2.0 mm, measured using a calliper (ICB, Brazil), and filled only with blood clot.
Next, 3.3-mm diameter abutments were installed with a retention of 6.0 mm (intermediate 2.5 mm or 3.5 mm of height). This same intermediate was used for the preparation of the final prosthetic crown. One hour after the implant installation, an acrylic provisional crown Trilux (Vipi ® , Pirassununga, São Paulo, Brazil) was cemented onto the abutment (Temp-Bond; Kerr Corporation, Orange, CA, USA). The crowns were free of contact in centric occlusion and excursive movements, but had proximal contacts. The provisional restoration was lower than the buccal original tooth in order to avoid labial pressure and facilitate the adaptation of the tomographic guide.
Patients were prescribed 500 mg of amoxicillin every 8 h for 7 days, 100 mg of nimesulide (Eurofarma, São Paulo, Brazil) every 12 h for 2 days, and 500 mg of analgesics (Dipyrone 500mg, Novalgina ® , Sanofi-Aventis Pharmaceuticals Ltd. Suzano, São Paulo, Brazil) every 6 h, in case of pain. Furthermore, 0.12% chlorhexidine digluconate (Perioplak) mouth rinse was prescribed once per day during the first week, starting 24 h after surgery. Patients were also advised to carry out physiotherapy care with ice and to restrict their diet to liquid and paste-type foods postoperatively.
A CT scan of the area was done at a maximum of 24 h ( T 1 ) ( Fig. 4 ) and at 6 months ( T 2 ) ( Fig. 5 ) after surgery.
Analysis of the CT sections
Three radiologists in the same clinic analyzed the images in order to determine the most apical point in the bone crest level. The distance from the crest to the implant platform was calculated using the images to evaluate possible alterations. In order to achieve this, a straight line was drawn in the direction of the long axis of the implant ( R 1 ) and another straight line tangent to the implant platform ( R 2 ) and perpendicular to the first. The distance between the apex crest point and the straight line was then measured ( R 2 ) ( Fig. 6 ).
Upon installation of the implant ( T 1 ), which was 1.0–2.0 mm below the bone crest, this distance to the crest ( R 2 ) was recorded as a positive value. At T 2 , if the crest of the bone had moved towards the apex line ( R 2 ), the distance had a negative value. The measurements of each patient were taken on three CT sections: central (coincident with the metal point of the guide), one that was located 1 mm away from the central point mesially, and another that was 1 mm away from the central point distally. The data were recorded and subsequently analyzed and compared between the observation periods.
Statistical analysis
To compare the cervical–apical distance between T 1 and T 2 , the Student’s t -test for dependent samples was used. For the comparison between locations (centre, mesial, and distal), analysis of variance (ANOVA) was used. P -values <0.05 were considered statistically significant. The data were organized into an Excel spreadsheet and analyzed using Statistica v. 8.0 software.
Results
The sample consisted of 12 patients, six females and six males, aged between 26 and 65 years (mean age 45 years). The results of the measurements according to the observation period ( T 1 and T 2 ) are shown in Tables 1 and 2 .
| Patient | Centre | 1 mm mesial | 1 mm distal |
|---|---|---|---|
| 1 | 2.04 | 2.28 | 2.21 |
| 2 | 1.46 | 1.55 | 1.17 |
| 3 | 1.84 | 2.01 | 1.61 |
| 4 | 1.41 | 1.61 | 1.89 |
| 5 | 0 | 0 | 0 |
| 6 | 1.17 | 0.63 | 1.79 |
| 7 | 2.24 | 2.51 | 2.68 |
| 8 | 1 | 0.45 | 1.7 |
| 9 | 1.61 | 1.72 | 1.34 |
| 10 | 1.56 | 1.84 | 0.72 |
| 11 | 2.06 | 2.33 | 2.16 |
| 12 | 1.52 | 1.89 | 1.89 |
| Patient | Centre | 1 mm mesial | 1 mm distal |
|---|---|---|---|
| 1 | −7.8 | 0 | −11.11 |
| 2 | −0.4 | 0 | 0 |
| 3 | −6.6 | −3.16 | −4.6 |
| 4 | −1.28 | 0 | −1.44 |
| 5 | 0 | 0 | 0 |
| 6 | −0.57 | 0 | 0.85 |
| 7 | 1.61 | 2.05 | 1.41 |
| 8 | 0 | 0 | 0 |
| 9 | 1.34 | 1.34 | 1.61 |
| 10 | 0 | 0 | −0.85 |
| 11 | −6.11 | −6 | −6.9 |
| 12 | 1.34 | 1.44 | 1.52 |
All of the results for the cervical–apical distances are described using the mean, median, minimum, and maximum values and standard deviations in Fig. 7 .
