Thorkild Karring

Guided tissue regeneration combined with a deproteinized bovine bone mineral (Bio‐Oss®) in the treatment of intrabony periodontal defects: 6‐year results from a randomized‐controlled clinical trial

AIM To present the 6-year results of a randomized-controlled clinical trial evaluating guided tissue regeneration (GTR) combined with or without deproteinized bovine bone mineral (DBBM) in intrabony defects. MATERIAL & METHODS In each of 45 patients, one defect was treated with GTR combined with DBBM hydrated in saline (DBBM-) or gentamicin sulphate (DBBM+) or with GTR alone. Clinical parameters were recorded pre-surgery, at 1 and 6 years postsurgery. RESULTS Thirty-six patients/33 teeth were available for the 6-year control. Statistically significant clinical improvements were observed for all treatments. Clinical attachment level (CAL) gain averaged 2.5 mm (DBBM-), 4.1 mm (DBBM+), and 3.0 mm (GTR) at 1 year postsurgery, and remained stable over 5 additional years (2.3, 4.1, and 2.7 mm, respectively). Treatment did not appear to influence residual probing depths (PDs) or CAL gains at 6 years postsurgery, or the extent of PD and CAL change from 1 to 6 years, and did not associate with sites losing CAL during follow-up. No association of grafting with sites showing CAL gain >or=4 mm at the 1- or 6-year control was observed. CONCLUSION The improvements in periodontal conditions obtained after GTR treatment with or without the adjunct use of DBBM can be preserved on a long-term basis.

Bone and suture regeneration in calvarial defects by e-PTFE-membranes and demineralized bone matrix and the impact on calvarial growth: An experimental study in the rat

The aim of this study was to evaluate the effect of: guided tissue regeneration (GTR) alone, implantation of demineralized bone matrix (DBM) alone, and of the combined treatment on the healing of craniectomy defects involving the sagittal cranial suture, and to examine subsequent calvarial growth. Sixty four-week-old rats were used in the study. These animals were randomly assigned to five groups (A-E) of 12 animals. In four groups (A-D), a calvarial defect (5.0 mm) involving the sagittal suture was produced in each animal. Group A: The defect was left untreated. Group B: DBM was implanted into the defect. Group C: The cerebral and the galeal aspect of the defect was covered with an e-PTFE membrane. Group D: The defect was treated with the double membrane technique combined with implantation of DBM. Group E: The animals were sham-operated, no defect was created. In all groups, two gutta-percha points were placed to indicate the lateral borders of the parietal bones. Histological analysis 4 months following surgery showed that the untreated cranial defects (A) had healed with fibrous connective tissue in the midportion of the defect. The DBM grafted defects (B) healed either completely with bone containing DBM particles or partially with bone and connective tissue. The defects (D) treated with DBM combined with GTR healed completely with bone, while the defects (C) treated with membranes alone healed with bone but a suture-like tissue similar to the normal sagittal suture of the sham-operated controls (E) was always present in the midportion of the defect. Cephalometric radiography demonstrated that the membrane-treated (C) and the sham-operated animals (E) exhibited similar coronal growth of the cranial vault following treatment. Craniometric measurements on chemically defleshed specimens showed that sham-operated and membrane-treated animals presented significantly more biparietal width than the animals treated with DBM alone or DBM combined with GTR (P < 0.05). The results demonstrated that predictable osseous healing including the formation of a sagittal suture can be accomplished in craniectomy defects by GTR, and undisturbed cranial growth reestablished. The treatment of the defects with DBM alone or DBM combined with GTR resulted in craniosynostosis and reduced cranial growth.

Healing of fenestration-type defects following treatment with guided tissue regeneration or enamel matrix proteins

Abstract The aim of the present study was to evaluate histologically in monkeys the healing in acute fenestration-type defects following treatment with guided tissue regeneration (GTR) or enamel matrix proteins (EMD). Standardized ”critical size” fenestration-type defects were produced surgically at the vestibular aspect of teeth 13, 23, 33, 43 in three monkeys (Macaca fascicularis). The vestibular bone plates were removed and the root surfaces were debrided by means of hand instruments in order to completely remove the root cementum. Following root conditioning with ethylenediaminetetraacetate (EDTA), the defects were treated using one of the following therapies: (1) GTR, (2) EMD, or (3) control (coronally repositioned flaps). After 5 months the animals were killed and perfused with 10% buffered formalin for fixation. Specimens containing the defects and surrounding tissues were dissected free, decalcified in EDTA, and embedded in paraffin. Eight-micrometer-thick step serial histological sections were cut in a vestibulo-oral direction, stained with hematoxylin and eosin or oxone-aldehyde-fuchsin-Halmi, and subsequently examined under the light microscope. The results showed that, in the defects treated with GTR, a new connective tissue attachment (i.e., new cementum with inserting collagen fibers) and new bone formation had consistently occurred, whereas, in the defects treated with EMD or with coronally repositioned flaps, new attachment and new bone reformed to a varying extent. The quality of the cementum did not differ after EMD, GTR, or flap surgery. It was concluded that GTR treatment with bioresorbable membranes seems to predictably promote new attachment and new bone formation, whereas the application of EDTA or EMD may also enhance periodontal healing to a certain extent. Further studies with higher numbers of animals and defects are needed in order to definitely clarify the effect of root surface conditioning with EDTA and EMD on periodontal healing.

A Quantitative Analysis of the Epithelium-Connective Tissue Interface in Relation to Assessments of the Mitotic Index

This paper describes the individual variations in the length and area of the basement membrane and in the volume of the epithelium. The wide variations in the area of the basement membrane and the total epithelial cell population necessitates the introduction of a new method for calculating mitotic activity and turnover rate. A new mitotic index system is suggested.

Calvarial bone regeneration by a combination of natural anorganic bovine‐derived hydroxyapatite matrix coupled with a synthetic cell‐binding peptide (PepGen™): an experimental study in rats

OBJECTIVES The aim of this study was to evaluate histologically the effect of natural anorganic bovine-derived hydroxyapatite matrix (ABM) coupled with a synthetic cell-binding peptide on the healing of critical size calvarial defects in rats. MATERIAL AND METHODS Sixteen 4-month-old rats were used in the study. A 5 mm trephine defect was created in each parietal bone of every animal. One defect was left untreated (control) while the contralateral defect was treated with a natural ABM coupled with a synthetic cell-binding peptide (test). At 60 and 120 days post-operatively, groups of eight animals were sacrificed and 7-10-microm-thick decalcified sections were produced from both test and control sides. Three sections, 100 mum apart, representing the central area of each defect were selected for the histometric analysis. RESULTS Histological analysis showed limited bone formation in both control and test defects at both observation periods. The control defects healed with fibrous connective tissue occupying the midportion of the defect and minimal new bone formation at the periphery. In the test defects, the major part of the defect was occupied by graft particles embedded in connective tissue. After 60 days of healing the residual defects accounted up to 94.6% of the original defect dimensions in the control specimens and 90.6% in the test specimens. The differences between test and control defects were not statistically significant (P=0.06). After 120 days of healing, the residual defects accounted up 89.9% of the original defect dimensions in the control specimens and 85% in the test specimens. The difference was not statistically significant (P=0.33). CONCLUSION The ABM coupled with a synthetic cell-binding peptide failed to substantially promote new bone formation in rat calvarial defects.

Healing of Osseous Submucous Cleft Palates with Guided Bone Regeneration

The aim of this study was to develop an experimental model in rats of an osseous submucous cleft palate and to examine if bone regeneration can be achieved in such defects by the placement of membranes according to the principle of guided tissue regeneration (GTR). An osseous submucous cleft palate defect (5 mm x 2 mm) was created surgically in Wistar rats. Membranes of expanded polytetrafluoroethylene were placed so that they covered both the nasal and the palatal aspect of the defect before the palatal mucoperiosteal flap was repositioned and sutured. Histological analysis after seven weeks of healing showed that significantly more test animals (5/9) healed with newly formed bone and a suture-like tissue in the middle of the defects than controls treated without membranes (0/17). In specimens evaluated macroscopically after 12 weeks, the corresponding rates for the test group were 12/12 compared with 0/13. These observations indicate that an experimental model of an osseous submucous cleft palate can be established in rats, and that complete osseous healing and creation of a midpalatal suture-like tissue in the bony defect is favoured by the placement of membranes according to the principle of GTR.

Cantilevered fixed partial dentures in a geriatric population: Preliminary report

This study has shown that treatment with distally extending cantilever fixed partial dentures is a favorable alternative to treatment with removable partial dentures in elderly patients with reduced dentition. In patients with anterior teeth and one or two premolar teeth remaining in the mandible, sufficient occlusal stabilization for a maxillary complete denture was provided by a two- or three-unit cantilever fixed partial denture. A pronounced improvement in chewing function and stability of the maxillary denture was expressed, even by patients who were previously well adapted to wearing removable partial dentures.

PERIODONTAL REGENERATION AROUND NATURAL TEETH

1. Evidence is conclusive (Table 2) that periodontal regeneration in humans is possible following the use of bone grafts, guided tissue regeneration procedures, both without and in combination with bone grafts, and root demineralization procedures. 2. Clinically guided tissue regeneration procedures have demonstrated significant positive clinical change beyond that achieved with debridement alone in treating mandibular and maxillary (buccal only) Class II furcations. Similar data exist for intraosseous defects. Evidence suggests that the use of bone grafts or GTR procedures produce equal clinical benefit in treating intraosseous defects. Further research is necessary to evaluate GTR procedures compared to, or combined with, bone grafts in treating intraosseous defects. 3. Although there are some data suggesting hopeful results in Class II furcations, the clinical advantage of procedures combining present regenerative techniques remains to be demonstrated. Additional randomized controlled trials with sufficient power are needed to demonstrate the potential usefulness of these techniques. 4. Outcomes following regenerative attempts remain somewhat variable with differences in results between studies and individual subjects. Some of this variability is likely patient related in terms of compliance with plaque control and maintenance procedures, as well as personal habits; e.g., smoking. Variations in the defects selected for study may also affect predictability of outcomes along with other factors. 5. There is evidence to suggest that present regenerative techniques lead to significant amounts of regeneration at localized sites on specific teeth. However, if complete regeneration is to become a reality, additional stimuli to enhance the regenerative process are likely needed. Perhaps this will be accomplished in the future, with combined procedures that include appropriate polypeptide growth factors or tissue factors to provide additional stimulus.