Introduction - Materials and methods.
S. I. Tobo n, J. A. Arismendi, M. L. Marin, A. L. Mesa & J. A.Valencia Departamento de Estudios Basicos Integrados, Facultad de Odontologia, Universidad de Antioquia. Medellin, Colombia.Introduction.
Most periapical radiolucent lesions heal uneventfully after endodontic treatment. However, some cases may require periradicular surgery in order to remove pathologic tissue from the periapical region and simultaneously eliminate any source of irritation that could not be removed by orthograde root canal treatment. With an adequate technique, surgery can address these issues, although it may be insufficient in some situations (Perlmutter et al.1988).
Regeneration of periapical bone defects constitutes a significant problem in periradicular surgery, since the proliferation of gingival connective tissue or the migration of the oral epithelium into such defects can occur and prevent the formation of normal trabecular bone (Dahlin et al.1988).
Several studies in humans and animals have evaluated the concept of guided tissue regeneration (GTR).This has led to the development of synthetic bone substitutes, bone grafts and membranes or barriers that allow the cellular re-growth of periodontal defects caused by pathosis or surgical trauma (Wang & MacNeil1998).
The principle of GTR used in periodontics has been applied in periradicular surgery with success by some clinicians who have reported an excellent recovery in cases that originally had a poor prognosis. This has helped to improve the predictability of periapical surgical procedures (Pecora et al.1995, Rankow & Krasner1996, Uchin 1996, Pecora et al. 1997).With these new techniques, the migration of cells of the gingival connective tissue or oral epithelium is prevented, allowing the cells of the periodontal ligament and trabecular bone to regenerate the lost tissue (Dahlin et al. 1988, Nyman 1991, Rankow & Krasner 1996, Uchin 1996, Pecora et al. 1997, Laurell & Gottlow1998, Aichelman-Reidy & Yukna 1998,Wang & MacNeil 1998).
The indications suggested for GTR in endodontic surgery are: through-and-through lesions that involve the integrity of both the buccal (labial) and palatal (lingual) alveolar cortical plates; chronic periapical lesions and combined endodontic-periodontic involvement, such as communication of periodontal pockets with periapical lesions, compromised bifurcation or trifurcation crests, and root perforation with alveolar crest bone loss (Pecora et al.1997).
The aim of this project was to investigate the efficacy of two bone regeneration techniques in periradicular surgery and their effect on the healing of periapical tissues. Materials and methods.
Twenty-eight patients were selected (10 men and 18 women), ages 14 through 74 (average 39.2 years), for a total of 30 surgical sites. The requirements for surgery were: previous root canal treatment and retreatment, post and crown inthe tooth, and failed previous surgery. Sixteen sites were in anterior teeth and 14 in premolar teeth; 23 were maxillary teeth and seven mandibular. Two patients had two surgical sites. The informed consent of all human subjects who participated in this study was obtained after the nature of the procedure and possible discomforts and risks were fully explained. Further more, the protocol was evaluated and approved by the Research Development Committee of the University of Antioquia for ethical considerations (CODI-Code 280-97).
Three groups were randomly established, eachwith10 surgical sites. Surgery was completed by one operator (SIT). Group A (control group) had periradicular surgery with a conventional technique (Fig.1). In group B (experimental group
- the patients had periradicular surgery with the addition of a nonbioabsorbable membrane of expanded polytetra fluoroethylene (e-PTFE) GoreTex1 Augmentation Gt4 submerged configuration (W.L. Gore & Associates, Flagstaff, AZ, USA) (Fig. 2). In group C (experimental group
- patients had periradicular surgery with a synthetic bioactive resorbable graft known as resorbable hydroxylapatite OsteoGen (Impladent Ltd, Holliswood, NY, USA) placed in the bony defect followed by the e-PTFE (GoreTex1) over the entire defect (Fig. 3).
Figure 1. Conventional technique (group A).
(a) Pre-operative radiograph of periapical lesion.(
b)Small bone defect on maxillary left second premolar following periradicular surgery root-end ?filled with amalgam.
(c) Histological section demonstrating granulomatous tissue obtained from original lesion.
(d) The same case12 months post-operative showing a persistent pariapical radiolucency.
(e) Unsatisfactory healing observed at re-entry surgery.
(f) Histological healing showing granulomatous tissue at 12 months.
Figure 2. A barrier technique case (group B).
(a) Maxillary central incisor witha periapical lesion.
(b) Large bone defect showing an apical pathosis with communication to the alveolar crest.
(c) Placement of membrane (e-PTFE) over the entire defect.
(d) Complete healing radiographically at one year.
(e) Membrane removal at re-entry surgery. A bone-like hard tissue covers the defect
(f) Histological healing showing formation of normal trabecular bone.
Figure 3. A barrier technique plus synthetic filling material (group C).
(a) Bone defect after debridement and root-end filling.
(b) Bioabsorbable hydroxylapatite placement.
(c) Membrane placement (e-PTFE) over the entire defect.
(d) Complete healingv12 months later.
(e) Apical healing with bone fill.
(f) Histological healing showing formation of normal trabecular bone.
The treatment protocol in all three groups was established in accordance with the following general scheme:
- medical-dental history, clinical evaluation and initial radiograph;
- surgical procedure, including mucoperiosteal flap reflection, osteotomy, periradicular curettage-enucleation, root-end resection with cylindrical surgical carbide finishing bur at high speed, cavity preparation with an inverted cone bur and root-end filling with zinc free silver alloy amalgam Nu-alloy (New Stetic, Medellin, Colombia), using a Messing syringe (Union Broach, Moyco, Ind., Emigsville, PA, USA).
In groups B and C, the membrane placement was extended 2-3 mm beyond the defect margins (Figs 2c and 3c), and in group C, the hydroxylapatite was placed until it was level with the peripheral margins of the bone defect (Fig. 3b). The sutures were removed between 7 and 10 days after the operation and then clinical and radiographic controls were performed every 3 months up to 12 months. Another surgical procedure was carried out in order to remove the membrane in the experimental groups and to take samples of tissue for histological evaluation from the periapical area of all patients with a 3i1 surgical bur (Implant Innovations, Palm Beach Gardens, FL, USA) of 2 mm in diameter and 2 mm in depth, at low-speed with water coolant.
The diagnostic and control radiographs were taken with the Rinn (XCP Instruments, Elgin, IL, USA) parallel technique and radiographic analysis compared the initial size of the lesion on the pre-operative film with the images on the follow up films. A Kodak Achromatic (Eastman Kodak Co., Rochester, NY, USA) 5x magnifying lens was used to measure the lesion area in mm and the percentage reduction on the final radiograph. These measurements and the qualitative changes generated in the apical rarefaction were used to assign each case to the categories of radiographic healing described by Rud et al. (1972).
The histological specimens were placed in 10% buffered formalin and then processed and stained with haematoxylin-eosin. The sections were observed with a light microscope Zeiss Axiolab (Carl Zeiss, Oberkochen, Germany) at10x and 40x magnification. Statistical analysis for the variable ‘size of the radiographic lesion’ was based on the Kruskal-Wallis test, with the purpose of establishing if there were any significant differences amongst the groups with a level of significance of 5% (P x 0.05). The initial and final evaluation within each group was performed using the Student’s t-test for paired samples. The data for ‘radiographic healing’ and ‘histologic healing’ were analysed based on the percentage distributions in order to produce a descriptive analysis.