Jan Gottlow

Healing of bone defects by guided tissue regeneration.

In this study we describe a principle for the accomplishment of bone regeneration based on the hypothesis that different cellular components in the tissue have varying rates of migration into a wound area during healing. By a mechanical hindrance, using a membrane technique, fibroblasts and other soft connective-tissue cells are prevented from entering the bone defect so that the presumably slower-migrating cells with osteogenic potential are allowed to repopulate the defect. Defects of standard size were created bilaterally through the man-dibular angles of rats. On one side of the jaw the defect was covered with Teflon membranes, whereas the defect on the other side served as control. Histologic analysis after healing demonstrated that on the test (membrane) side, half the number of animals showed complete bone healing after 3 weeks and all animals showed complete healing after 6 weeks. Little or no sign of healing was evident on the control side even after an observation period of 22 weeks.

Healing of Maxillary and Mandibular Bone Defects Using a Membrane Technique: An Experimental Study in Monkeys

Cyst-like cavities in the jaw bone often heal incompletely owing to ingrowth of connective tissue, thus preventing osteogenesis from occurring. In the present study, a new membrane technique has been utilized in an attempt to improve bone healing. By means of an inert, porous membrane, placed in close contact with the bone surface, a secluded space is created which can only be repopulated by cells from the adjacent bone. Thus, osteogenesis is able to occur without interference from other tissue types. Through-and-through bone defects were produced bilaterally (1) in edentulous areas of monkey (n = 5) mandibles, and (2) in conjunction with apicectomy of the lateral maxillary incisors, also in monkeys (n = 7). On one side, the defects were covered buccally as well as lingually/palatally with expanded PTFE membranes, whereas the defects on the other side served as controls (no membrane). In the mandible, complete bone healing was seen at all test sites after a healing period of 3 months. On the control side, 3 experimental sites showed bone discontinuity with a transosseous core of connective tissue, whereas some bone healing had occurred lingually at 2 sites, but with massive soft tissue ingrowth from the buccal side. In the maxillary periapical defects, all the membrane-covered defects had healed with bone closure after 3 months but with a minute portion of connective tissue, probably derived from the periodontal ligament, around the tooth apices. None of the control defects (no membrane) healed spontaneously, but all were filled with connective tissue to varying degrees.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of a new titanium-zirconium dental implant: a biomechanical and histological comparative study in the mini pig.

BACKGROUND Titanium zirconium alloy with 13-17% zirconium (TiZr1317) shows significantly better mechanical attributes than pure Ti with respect to elongation and fatigue strength. This material may be suitable for thin implants and implant components exposed to high mechanical constraints. PURPOSE The aim of this study was to test the hypothesis that TiZr1317 and Ti implants show comparable osseointegration and stability. MATERIALS AND METHODS The mandibular premolars (P1, P2, P3) and the first molar (M1) in 12 adult miniature pigs were extracted 3 months prior to the study. Six specially designed implants made from Ti (commercially pure, Grade 4) or TiZr1317 (Roxolid®, Institut Straumann AG, Basel, Switzerland) with a hydrophilic sandblasted and acid-etched (SLActive, Institut Straumann AG, Basel, Switzerland) surface were placed in each mandible; three standard implants modified for evaluation of removal torque (RT) in one side and three bone-chamber implants for histologic observations in the contralateral side. RT tests were performed after 4 weeks when also the bone chamber implants and surrounding tissue were biopsied for histologic analyses in ground sections. RESULTS The RT results indicated significantly higher stability (p=0.013) for TiZr1317 (230.9±22.4Ncm) than for Ti implants (204.7±24.0Ncm). The histology showed similar osteoconductive properties for both implant types. Histomorphometric measurements showed a statistically significant higher (p=0.023) bone area within the chamber for the TiZr1317 implants (45.5±13.2%) than did the Ti implants (40.2±15.2%). No difference was observed concerning the bone to implant contact between the groups with 72.3±20.5% for Ti and 70.2±17.3% for TiZr1317 implants. CONCLUSION It is concluded that the TiZr1317 implant with a hydrophilic sandblasted and acid-etched surface showed similar or even stronger bone tissue responses than the Ti control implant.

An Experimental Comparison of Two Different Clinically Used Implant Designs and Surfaces

BACKGROUND Various designs of dental implants representing different geometries and surface technologies are commercially available and clinically used in patients. However, data with regard to bone tissue responses and stability for comparison of their biologic performances are rare. PURPOSE The aim of the present experimental investigation was to compare the bone tissue responses and implant stability between two commonly used dental implants representing different geometries and surface characteristics. MATERIALS AND METHODS A total of 90 dental implants (4.3 mm in diameter, 10 mm long) with an oxidized surface (Replace Select Tapered, TiUnite, Nobel Biocare AB, Gothenburg, Sweden) (OX) and 90 implants (4.1 mm in diameter, 10 mm total length) with a hydrophilic sand-blasted and acid etched surface (Standard Plus, SLActive, Institut Straumann AG, Basel, Switzerland) (HSBA) were placed in the distal femur (n = 1) and tibia (n = 2) of 30 rabbits. The implants were analyzed with implant stability quotient (ISQ) measurements, removal torque (RTQ) and histomorphometry (bone-implant contact, BIC) after 10 days, 3, and 6 weeks. Moreover, RTQ values were corrected for differences in surface area by calculating the shear strength for each implant. RESULTS RTQ and ISQ measurements showed an increase with time for both implant types. A significantly higher RTQ value was observed for the HSBA implant at 3 weeks (p = .05). A lower ISQ value was seen for HSBA than for OX implants at placement in the tibia (p < 0.001). HSBA implants showed higher shear strength values than OX implants after 3 weeks (p < .001), and 6 weeks (p < .01). The morphometric measurements showed significantly higher BIC for HSBA implants after 10 days (p < .01), similar values after 3 weeks and significantly higher BIC for OX implants after 6 weeks (p < .001). CONCLUSIONS Both HSBA and OX implants were well integrated in bone and showed firm and increased stability from placement to after 6 weeks of healing. The HSBA implant showed more BIC after 10 days and the OX implant more BIC after 6 weeks of healing. The HSBA implant showed significantly higher shear strength after 3 and 6 weeks and higher RTQ values after 3 weeks than the OX implant. The results may be due to differences in surface roughness and hydrophilic properties.

Immediate loading of Brånemark system TiUnite and machined-surface implants in the posterior mandible, part II: a randomized open-ended 9-year follow-up clinical trial.

PURPOSE To present clinical results with 9 years of follow-up of a protocol of immediately loaded implants with two different surfaces. MATERIALS AND METHODS A total of 44 patients received 66 Brånemark System TiUnite and 55 Brånemark machined implants, all immediately loaded. Control examinations were performed on the day of surgery and at 1-, 3-, and 9-year follow-up visits. RESULTS All implant sites had intact buccal and lingual bone walls. The prefabricated provisional restorations showed an excellent fit. Three TiUnite and 8 machined implants failed within 7 weeks of loading, resulting in a cumulative survival rate of 95.5% and 85.5% respectively after 9 years of load. The survival rate for implants in a partial prosthesis was 98.8% and 92.2% for single restorations in the TiUnite group, and 87.8% and 83.2%, respectively, for partial and single resorations in the control group. The marginal bone resorption in the first year was on average 0.9 mm in the TiUnite group and 1.0 mm in the machined group; at the third year it was 0.4 and 0.5 mm, respectively. On examination at 9 years, there was a general settlement of the bone, with a negligible further loss in height. CONCLUSIONS The unchanged survival rate and the low bone loss after 9 years confirm the feasibility of an immediate loading protocol in the mandible, which included flapless surgery. TiUnite implants obtained a 10% higher success rate compared with machined fixtures .

Mechanical Property Assessment of Bone Healing around a Titanium–Zirconium Alloy Dental Implant

BACKGROUND It has been reported that titanium-zirconium alloy with 13-17% zirconium (TiZr1317) implants show higher biomechanical stability and bone area percentage relative to commercially pure titanium (cpTi) grade 4 fixtures. PURPOSE This study aimed to determine whether the higher stability for TiZr1317 implants is associated with higher mechanical properties of remodeling bone in the areas around the implants. MATERIALS AND METHODS This study utilized 36 implants (n = 18: TiZr1317, n = 18: cpTi), which were placed in the healed ridges of the mandibular premolar and first molar of 12 mini pigs (n = 3 implants/animal). After 4 weeks in vivo, the samples were retrieved, and resin-embedded histologic sections of approximately 100 μm in thickness were prepared. In order to determine the nanomechanical properties, nanoindentation (n = 30 tests/specimen) was performed on the bone tissue of the sections under wet conditions with maximum load of 300 μN (loading rate: 60 μN/s). RESULTS The mean (± standard deviation) elastic modulus (E) and hardness (H) for the TiZr1317 group were 2.73 ± 0.50 GPa and 0.116 ± 0.017 GPa, respectively. For the cpTi group, values were 2.68 ± 0.51 GPa and 0.110 ± 0.017 GPa for E and H, respectively. Although slightly higher mechanical properties values were observed for the TiZr1317 implants relative to the cpTi for both elastic modulus and hardness, these differences were not significant (E = p > 0.75; H = p > 0.59). CONCLUSIONS The titanium-zirconium alloy used in this study presented similar degrees of nanomechanical properties to that of the cpTi implants.

An Experimental Evaluation of a New Craniofacial Implant Using the Rabbit Tibia Model: Part II. Biomechanical Findings

Hypothesis: This experimental study was undertaken to test the hypothesis that a new design of a craniofacial implant is more stable and shows faster integration than the currently used implant. Materials and Methods: A total of 60 newly designed Cochlear Baha titanium implants (test) and 60 of the current design (control) were placed in the tibiae of 30 adult loop-eared rabbits. The animals were euthanized after 5, 14, or 28 days. The stability of the implants was measured with Implant Stability Quotient measurements and removal torque (RTQ) tests. The Students t test for paired statistics were used for comparisons and a difference considered if p < 0.05. Results: The test implants showed a significantly higher RTQ at all time points and a steeper increase with time than the controls. The RTQ values were 19.0 (standard deviation [SD], 9.1) and 9.8 (SD, 5.6) Ncm for test and control implants, respectively, after 5 days; 27.6 (SD, 9.6) and 11.2 (SD, 3.9) Ncm after 14 days; and 43.3 (SD, 9.6) and 20.7 (SD, 14.1) Ncm after 28 days. Higher Implant Stability Quotient values were measured for the test implant at all time points. Calculations of shear stress to compensate for implant diameter revealed significantly higher values for test than for control implants after 14 and 28 days. Conclusion: It is concluded that the new craniofacial implant was more stable and showed a faster integration than the currently used implant. The data from the present study suggest that the new implant may be suitable for early loading protocols.