/ Clin Periodontal 1996: 23: 971-973 Printed iti Denmark . Alt rights' reserve
Copyright C Munksgaard l'>96
!SS\ 0303-6979
Short Communication
Dimension of the periimplant mucosa
T. Berglundh and J. Lindhe Department of Periodontology, Goteborg University, Sweden
Biological width revisited Berglundh T. Lindhe J: Dimension of the periimplant mucosa. Biological width revisited. J Ctin Periodontol 1996: 23: 971-973. © Munksgaard, 1996. Abstract. The objective of the present study was to determine the dimension of the mucosal-impiant attachment at sites with insufficient width of the ridge mucosa, 5 beagle dogs were used. Extractions of ail mandibuiar premoiars were performed and 3 months later, 3 fixtures of the Branemark System® were installed in each side. Foiiowing 3 months of healing, abutment connection was carried out. On the right or ieft side of Ihe mandibie, abutment connection was performed according to the Branemark System® manual ~ (control side). On the contralateral side (test side), an incision not extending through the periosteum was made at the crest of the ridge. The soft tissue was dissected and a critical amount of connective tissue on the inside of the flap was excised. The periosteum was subsequently incised, abutment connection performed, and the trimmed flaps sutured. The sutures were removed after 10 days. After a 6-month period of plaque controi, the animals were sacrificed, biopsies sampled and processed for light microscopy. The length of the junctional epitheiium varied within a rather narrowrange; 2.i mm (control side) and 2.0 mm (test side). The height of the suprabony connective tissue in this model varied between 1.3i0.3 mm (test side) and l,8±0,4 mm (control side). At sites where the ridge mucosa prior to abutment connection was made thin (S2 mm), wound heaiing consistentiy inciuded bone resorption. This implies that a certain minimum width of the periimplant mucosa may be required, and that bone resorption may take place to allow a stable soft tissue attachment to form.
In a series of studies from our laboratory the structure and function of the keratinized, non-mobile gingiva and the corresponding periimplant mucosa were examined in the beagle dog modei (Berglundh et al. 1991, 1992, 1994, Ericsson et al. 1992), The 2 tissues were found to have many features in common. Thus, both soft tissues included a junctionai epithelium that was about 2 mm in "apico-coronal" direction and was separated from the bone crest by a zone of connective tissue attachment > i mm high. The fibers within the supraaiveolar tissue at the tooth site originated from the aceliular, extrinsic fiber cementum on the root surface, while the majority of the fibers at the iinpla.nt sites occurred in
an avascular compartment and were apparently anchored in the periosteum of the bone crest. In a recent experiment in the dog (Abrahamsson et a], 1996), it was observed that the mucosal barrier that formed following successful 1- and 2- stage implant installations had similar composition, i.e. it was comprised of one zone of junctional epithelium and one zone of connective tissue. Furthermore, it was detected that at sites where the mucosa of the edentuious ridge was thin, (i) angular bone defects occurred at the marginal border of the implants, and (ii) the dimension of the mucosal attachment to the implant was similar to that of sites with a thick mucosa. This feature of the implant - tissue interface was
Key words: periiimplant mucosa; attachment; histometry; bioiogical width Accepted for publication 4 January 1996
characteristic for both 1- and 2- stage implant systems. Abrahamsson et ai. (1996) suggested that a certain width of the periimpiant mucosa is required to enable a proper epithelial-connective tissue attachment, and if this soft tissue dimension is not satisfied, "bone resorption will occur to ensure" the establishment of attachment with a appropriate "biological width"". The objective of the present study was to further test this hypothesis.
Material and Methods 5 beagle dogs, about 1 year oid, were used. Extractions of all mandibular pre-
972
Berglundh & Lindhe
molars were performed. After 3 months of healing, fixtures of the Brftnemark System* (length: 7 mm, 0: 3,75 mm; Npbelpharma AB, Goteborg, Sweden) were installed according to methods described by Berglundh et al, (1991), Eaeh animal was fitted with 3 implants on each side of the mandible; in all 6 implants. Following a healing period of 3 months, abutment connection was carried out. On the right or the left side of the mandible, muco-periostal flaps were elevated, and abutment connection performed according to he Br4nemark System* manual - (control side). The flaps were sutured. On the contralateral side (test side), an incision not extending through the periosteum was made at the crest of the ridge. Using a blunt elevator, the soft tissue was dissected, and in order to obtain a thin ridge mucosa, a critical amount of connective tissue on the inside of the flap was excised. The periosteum was subsequently incised, abutment connection performed, and the trimmed flaps sutured. The sutures were removed after 10 days, A 6-month period of plaque control was initiated, This included daily cleaning with toothbrush and dentifrice. The animals were sacrificed with an overdose of Sodium-Pentothal and perfused through the bilateral carotid artery by a fixative (Karnowsky 1965), The mandibles were removed and placed in the fixative. Each implant region was dissected using a diamond saw (Exakt*, Kulzer, Germany), The tissue samples, comprising the implant and the surrounding soft and hard peri-implant tissues, were decalcified in EDTA and processed using a modification of the "fracture technique" (Thomsen & Ericson 1985) as described by Berglundh et al, (1994), Decalciflcation was performed in EDTA and dehydration performed in serial steps of alcohol concentrations, Secondary fixation in OSO< of the tissue samples was carried out and the units were finally embedded in EPON* (Schroeder 1969), Sections were produced from each tissue unit with the microtome set at 3 ^m. The sections were stained in PAS and toluidine blue (Schroeder 1969),
of the junctional epithelium; B: the marginal level of bone to implant contact; BC; the bone crest, i,e,, the most coronal portion of the periimplant bone; A/F: the abutment/fixture junction. The distances between the landmarks were determined in an Olympus® Research Stereo Macroscope connected to a PC (Compac*) equipped with an image system and a mouse cursor. Results and conclusion The vertical dimension of the periimplant mucosa (Fig, 1) in the control side, i,e,, the distance between the bone crest (BC) and the outer surface of the oral epithelium (PM), was on average 3,65 ±0,44 mm. The corresponding mucosa in the test jaw was in 4 out of 5 jaw quadrants thin, on the average 2,4±0.23 mm, while in 1 test quadrant, the periimplant soft tissue had adopted dimensions similar to those characterising the dimensions ofthe control sites (3,3 mm). The junctional epithelium of the periimplant mucosa at both the test and control side; of the mandible was consistently separated from the crestal
bone by a zone of collagen rich and cell poor connective tissue. The length of the junctional epithelium varied within a rather narrow range; 2,1 mm (control side) and 2,0 mm (test side). The height of the suprabony connective tissue (aJE-B) in this model varied between 1.3±O,3 (test side) and l,8±0,4 mm (control side). At sites where the ridge mucosa prior to abutment connection was made thin ( s 2 mm) and remained thin, wound healing consistently included bone resorption and the establishment of an angular bone defect (Fig, 1), This implies that a certain minimum width of the periimplant mucosa is required, and that bone resorption may take place to allow a proper soft tissue attachment to form. The present finding may in part explain the loss of alveolar bone that occurs during the 1st year following abutment connection and the subsequent loading of the implant system (Adell et al, 1981, Pilliar et al, 1991), It is suggested that once the implant is exposed to the oral environment and in function, a mucosal attachment of a certain minimum dimension is required to protect osseointegration.
HMetnttrle anitysla In each section, 5he following landmarks were identified and used for the linear measurements; PM: the marginal portion of the periimplant mucosa; • J E : the levei of the apical termination
Fig, I, Microphotograph of one test (TJ and one control (C) site. Note in the test side, the presence of an angular bone defect: PM: the marginal portion of the periimplant mucosa; «JE: the level of the apical termination of the junetional epithelium; A/F: the abutment/fixture junction, BC: the bone crest, i,e, the most coronal portion of the periimplant bone; B: the marginal level of bone to implant contact,
Dimension of the periimplant mucosa Zusammentassung Die Abmessung der periimplantSren Mukosa. OberprUfung hinsichtlieh eines biologisch gUnstigen Durchmessers Gegenstand der vorliegenden Studie war die Dimensionsbestimmung des implantiren Mukosaattachments in Regionen mit unzureichendem Durchmesser der Mukogingiva des Alveolarfortsatzes, Die Studie wurde an 5 Beagle Hunden vorgenommen, S£mtliche Unterkieferpramolaren wurden extrahiert. 3 Monate danach wurden in jede der beiden Kieferseiten 3 Fixturen des Implantatsystems nach Brinemark* inkorporiert. Das Aufbringen der DistanzhUlsen fand nach einer Einheilungsperiode von 3 Monaten statt. In der rechten oder der linken Unterkieferseite (in der KontroUseite) wurden die DistanzhUlsen nach den Anweisungen des Handbuchs ftlr das Br4nemark System* fixiert. An der kontralateralen Seite (Testseite) wurde vorerst ein Schnitt in den Alveolarkamm gelegt ohne die Knochenhaut zu perforieren. Das Weichgewebe wurde dargestellt und eine beachtliche Menge Bindegewebe an der Innenseite des Lappens exzidiert, AnschlieBend wurde das Periost inzidiert. Nach Aufbringen der Distanzhdlsen wurden die angepaBten Lappen mit Nahten fixiert. Die Nahte wurden nach 10 Tagsn entfernt, Nach einer Zeitspanne von 6 Monaten mit Plaquekontrolle, wurden die Tiere geopfert, Gewebeproben wurden entnommen und fto lichtmikroskopische Untersuchungen vorbereitet. Die L4nge des Saumepithels schwankte in ziemlich engen Grenzen: 2,1 mm (KontroUseite) und 2,0 mm (Testseite). Die HOhe des oberhalb des knOchernen Alveolarfortsatzes gelegenen Bindegewebes streute bei diesem Versuchsmodel! zwischen l,3±0.3 mm (Testseite) und l,8±0,4 mm (Kontrollseite), An den vor der Fixation der Distanzhttlsen dUnn gestalteten Stellen der Mukosa des Alveolarkamms ( s 2 mm) ging die Wundheilung durchweg mit Knochenresorption einher. Das bedeutet, dafl es einer gewissen Mindestbreite der periimplantaren Mukosa bedarf. Um die Bildung eines stabilen weichgeweblichen Attachments zu erlauben, kann es zur Resorption des alveolSren Knochens kommen.
Dimension de ia muqueuse piri-implanlaire. Retour sur I'espace biologique La presente etude avait pour but de determiner les dimensions de I'attache muqueuse-implant dans des sites ou la largeur de la muqueuse du rebord 4tait insuffisante. Nous avons utilise 5 chiens Beagle, Toutes les piemolaires inferieures ont iti extraites, puis, 3 mois plus tard, 3 fixtures du Systeme Brinemark* ont eti mises en place de chaque c6ti, Apres 3 mois de cicatrisation, on a pratique la cormexion des piliers, Du c6ti droit ou gauche de la mandibule, la connexion des piliers a iii faite conformement au manuel du Systeme Brdnemark* (coli temoin=control), Du cote controlaterai (cote test), une incision ne traversant pas le perioste a ixi faite au niveau de la crete du rebord. Le tissu mou a ete dissdque et une quantite critique de tissu conjonctif a ete excisee de l'intirieur du lambeau, Le perioste a ensuite ete incise, la connexion des piliers effectute, et les lambeaux rectifies ont ete sutures, Les sutures ont ete enlevees apres 10 jours, Apres une periode de 6 mois avec elimination de la plaque, les animaux ont ete sacrifies; des echantillons ont ete preleves et prepares pour examen au microscope optique. La longueur de I'epithelium de jonction variait dans un intervaiie assez etroit; 2,1 mm (cote temoin) et 2,0 mm (cote test). La hauteur du tissu conjonctif supra-osseux variait dans oe modele entre 1.3±O,3 mm (cote test) et l,8±0,4 mm (c6t6 temoin), Dans les sites ou la muqueuse du rebord avait iti amincie ( £ 2 nun) avant la connexion du piiier, une resorption osseuse accompagnait toujours ia cicatrisation de la plaie, Ceci indique qu'une certaine largeur minimum de la muqueuse p6ri-implantaire est necessaire, et qu'une resorption osseuse peut prendre place pour permettre la formation d'une attache de tissu mou stable,
Adell, R,, Lekholm, U , Rockier, B, & Britiemark, P,L (1981) A 15-year study of osseointegrated implants in the treatment of the edentulous jaw International Journal of Oral Surgery 10, iHl-iie. Berglundh, T, Lindhe, J,, Ericsson, L, Marinello, CP,, Liljenberg, B, & Thomsen, P, (1991) The soft tissue barrier at implants and teeth. Clinical Oral Implants Research 2, 81-90, Berglundh, T, Lindhe, J,, Marinello, C.R, Ericsson, I. & Liljenberg, B, (1992) Soft tissue reactions to de novo plaque formation at implants and teeth. Clinical Orat Implants Research 3, 1-8, Berglundh, T, Lindhe, J,, Jonsson, K, & Ericsson, I. (1994) The topography of the vasctilar systems in the periodontal and peri-implant tissues in the dog. J Clin Periodontol 2\, 189-193, Ericsson, I,, Berglundh, T, Marinello, C P , Liljenberg, B. & Lindhe, J, (1992) Longstanding plaque and gingivitis at itnplants and teeth in the dog. Clinical Oral Implants Research 3, 99-103 Karnowsky, M, J, (1965) A formaldehydeglutaraldehyde fixative of high osmolarity for use in electron microscopy. Journal of Cell Biology V, 137A-138A, Pilliar, R,M,, Deporter, DA,, Watson, PA, & Valiquette, N, (1991) Dental implant design - effect on bone remodelling, Joumal of Biomedical Research 25, 467483. Schroeder, H,E, (1969) Ultrastructure of the junctional epithelium of the human gingiva, Acta Helvetica Odontologica 13, 6583, Thomsen, P , Ericson, L,E. (1985) Light and transmission electron microscopy used to study the tissue morphology close to implants, Biomaterials 6, 421-424,
Address:
Rafarancat Abrahamsson, I., Berglundh, T, WennstrOm, J, & Lindhe, J, (1996) The peri-implant hard and soft tissues at different implant systems, A comparative study in the dog. Clinical Oral Implants Research, in press.
973
Tord Berglundh Department of Periodontology GGteborg University Medicinaregatan 12 S-413 90 Geteborg Sweden