Robert K. Schenk

Enhanced Bone Apposition to a Chemically Modified SLA Titanium Surface

Increased surface roughness of dental implants has demonstrated greater bone apposition; however, the effect of modifying surface chemistry remains unknown. In the present study, we evaluated bone apposition to a modified sandblasted/acid-etched (modSLA) titanium surface, as compared with a standard SLA surface, during early stages of bone regeneration. Experimental implants were placed in miniature pigs, creating 2 circular bone defects. Test and control implants had the same topography, but differed in surface chemistry. We created the test surface by submerging the implant in an isotonic NaCl solution following acid-etching to avoid contamination with molecules from the atmosphere. Test implants demonstrated a significantly greater mean percentage of bone-implant contact as compared with controls at 2 (49.30 vs. 29.42%; p = 0.017) and 4 wks (81.91 vs. 66.57%; p = 0.011) of healing. At 8 wks, similar results were observed. It is concluded that the modSLA surface promoted enhanced bone apposition during early stages of bone regeneration.

Bone response to unloaded and loaded titanium implants with a sandblasted and acid-etched surface: A histometric study in the canine mandible

Many dental clinical implant studies have focused on the success of endosseous implants with a variety of surface characteristics. Most of the surface alterations have been aimed at achieving greater bone-to-implant contact as determined histometrically at the light microscopic level. A previous investigation in non-oral bone under short-term healing periods (3 and 6 weeks) indicated that a sandblasted and acid-etched titanium (SLA) implant had a greater bone-to-implant contact than did a comparably-shaped implant with a titanium plasma-sprayed (TPS) surface. In this canine mandible study, nonsubmerged implants with a SLA surface were compared to TPS-coated implants under loaded and nonloaded conditions for up to 15 months. Six foxhound dogs had 69 implants placed in an alternating pattern with six implants placed bilaterally in each dog. Gold crowns that mimicked the natural occlusion were fabricated for four dogs. Histometric analysis of bone contact with the implants was made for two dogs after 3 months of healing (unloaded group), 6 months of healing (3 months loaded), and after 15 months of healing (12 months loaded). The SLA implants had a significantly higher (p < 0.001) percentage of bone-to-implant contact than did the TPS implants after 3 months of healing (72.33 +/- 7.16 versus 52.15 +/- 9.19; mean +/- SD). After 3 months of loading (6 months of healing) no significant difference was found between the SLA and TPS surfaced implants (68.21 +/- 10.44 and 78.18 +/- 6.81, respectively). After 12 months of loading (15 months of healing) the SLA implants had a significantly greater percentage (p < 0.001) of bone-to-implant contact than did the TPS implants (71.68 +/- 6.64 and 58.88 +/- 4.62, respectively). No qualitative differences in bone tissue were observed between the two groups of implants nor was there any difference between the implants at the clinical level. These results are consistent with earlier studies on SLA implants and suggest that this surface promotes greater osseous contact at earlier time points compared to TPS-coated implants.

Lateral ridge augmentation using autografts and barrier membranes: a clinical study with 40 partially edentulous patients.

PURPOSE This study evaluated predictability and treatment outcome of the combined application of autografts and expanded-polytetrafluoroethylene (e-PTFE) membranes for lateral ridge augmentation in partially edentulous patients using a staged approach. MATERIALS AND METHODS Forty partially edentulous patients were consecutively treated. Emphasis was given to a lateral incision technique, perforation of the cortex to open the marrow cavity, stable placement of corticocancellous autografts and bone chips, precise adaptation of the e-PTFE membranes and stabilization with miniscrews, and a tension-free primary soft tissue closure. After 7 to 13 months, the sites were reopened for membrane removal and implant placement. RESULTS All but one patient showed complication-free soft tissue healing. After reopening, 38 patients exhibited excellent ridge augmentation, whereas two had compromised results, with soft tissue encapsulation of some bone chips. None of the applied block grafts showed clinical signs of resorption. Preaugmentation and postaugmentation measurements showed an enlargement of the crest width from a mean of 3.5 mm to 7.1 mm. This allowed the placement of nonsubmerged titanium implants in all 40 patients. CONCLUSIONS The current study demonstrates that the combined application of autografts and e-PTFE membranes is a predictable surgical procedure for lateral ridge augmentation that results in an enlargement of the alveolar crest in partially edentulous patients. The autografts support the membrane and activate bone formation with their osteoconductive and osteoinductive properties. The membrane acts as a physical barrier to nonosteogenic soft tissue cells, and protects the autografts against resorption during healing.

Interface shear strength of titanium implants with a sandblasted and acid-etched surface: A biomechanical study in the maxilla of miniature pigs

The purpose of the present study was to evaluate the interface shear strength of unloaded titanium implants with a sandblasted and acid-etched (SLA) surface in the maxilla of miniature pigs. The two best documented surfaces in implant dentistry, the machined and the titanium plasma-sprayed (TPS) surfaces served as controls. After 4, 8, and 12 weeks of healing, removal torque testing was performed to evaluate the interface shear strength of each implant type. The results revealed statistically significant differences between the machined and the two rough titanium surfaces (p <.00001). The machined surface demonstrated mean removal torque values (RTV) between 0.13 and 0.26 Nm, whereas the RTV of the two rough surfaces ranged between 1.14 and 1.56 Nm. At 4 weeks of healing, the SLA implants yielded a higher mean RTV than the TPS implants (1.39 vs. 1. 14 Nm) without reaching statistical significance. At 8 and 12 weeks of healing, the two rough surfaces showed similar mean RTVs. The implant position also had a significant influence on removal torques for each implant type primarily owing to differences in density in the periimplant bone structure. It can be concluded that the interface shear strength of titanium implants is significantly influenced by their surface characteristics, since the machined titanium surface demonstrated significantly lower RTV in the maxilla of miniature pigs compared with the TPS and SLA surfaces.

Persistent Acute Inflammation at the Implant-Abutment Interface:

The inflammatory response adjacent to implants has not been well-investigated and may influence peri-implant tissue levels. The purpose of this study was to assess, histomorphometrically, (1) the timing of abutment connection and (2) the influence of a microgap. Three implant designs were placed in the mandibles of dogs. Two-piece implants were placed at the alveolar crest and abutments connected either at initial surgery (non-submerged) or three months later (submerged). The third implant was one-piece. Adjacent interstitial tissues were analyzed. Both two-piece implants resulted in a peak of inflammatory cells approximately 0.50 mm coronal to the microgap and consisted primarily of neutrophilic polymorphonuclear leukocytes. For one-piece implants, no such peak was observed. Also, significantly greater bone loss was observed for both two-piece implants compared with one-piece implants. In summary, the absence of an implant-abutment interface (microgap) at the bone crest was associated with reduced peri-implant inflammatory cell accumulation and minimal bone loss.

Peri-implant Inflammation Defined by the Implant-Abutment Interface

An implant-abutment interface at the alveolar bone crest is associated with sustained peri-implant inflammation; however, whether magnitude of inflammation is proportionally dependent upon interface position remains unknown. This study compared the distribution and density of inflammatory cells surrounding implants with a supracrestal, crestal, or subcrestal implant-abutment interface. All implants developed a similar pattern of peri-implant inflammation: neutrophilic polymorphonuclear leukocytes (neutrophils) maximally accumulated at or immediately coronal to the interface. However, peri-implant neutrophil accrual increased progressively as the implant-abutment interface depth increased, i.e., subcrestal interfaces promoted a significantly greater maximum density of neutrophils than did supracrestal interfaces (10,512 ± 691 vs. 2398 ± 1077 neutrophils/mm2). Moreover, inflammatory cell accumulation below the original bone crest was significantly correlated with bone loss. Thus, the implant-abutment interface dictates the intensity and location of peri-implant inflammatory cell accumulation, a potential contributing component in the extent of implant-associated alveolar bone loss.

Differential Staining of Calcified Tissues in Plastic Embedded Microtome Sections by A Modification of Movat's Pentachrome Stain

Movats pentachrome I stain has been adapted and modified as a stain for undecalcified bone sections. After embedding in methyl methacrylate, this procedure yields consistently good results, with an excellent and colorful contrast between mineralized and unmineralized compartments of both cartilage and bone. In addition, osteoblasts, osteoclasts, and other cells and tissue components can easily be differentiated. The staining properties of the lacunar wall surrounding the osteocytes are considered to reflect various states of osteocytic activity. The method is especially useful for the study of bone growth and bone repair, and as a stain for conventional histomorphometry and computer-assisted image analysis in bone biopsies.

What is osteomalacia

A commonly accepted answer to this question given in many textbooks is ‘softness of bones caused by an increase in the relative amount of unmineralized bone matrix’. This definition is still valid, but only as long as the physical characteristics of a softening of bone are respected. The histological assessment of an increase in the relative amount of osteoid alone is not sufficient as a diagnostic criterion. This limitation became obvious when reliable staining procedures for the detection of osteoid in undecalcified sections were introduced. Based on his experience with such specimens, Frost1 proposed a distinction between ‘histological osteomalacia’ and what he called ‘dynamic osteomalacia’. According to his definition, histological osteomalacia characterizes bone with more osteoid seams than normal and therefore includes, besides such conditions where osteoid accumulates because of a mineralization delay, a variety of states with increased bone turnover such as thyrotoxicosis, hyperparathyroidism, Paget’s disease etc. Histological osteomalacia corresponds to ‘hyperosteoidosis’, a term used by Meunier and his group2, and with some restriction to ‘osteoidosis’ coined by Delling.3

A study of the fate of the buccal wall of extraction sockets of teeth with prominent roots

an evidence base to inform everyday practice, how remuneration systems may affect treatment modalities, and how the oral health assessment on determining recall intervals and clinical care pathways affect quality of life. It was heartening to see that, although they came from a variety of backgrounds and from groups which can be said to have potentially conflicting interests, those involved in the Faculty’s Delphi study reached a consensus view on research priorities in primary dental care relatively easily. In doing so, they reflected the consensus reached during the recent Delphi study on general (medical) practice management.13 As clinicians formed the largest interest group within the Delphi ‘consortium’, it was perhaps unsurprising that the first four priority areas that were identified came from the ‘clinical’ group of topics. However, they are all also of considerable importance to patients and those who commission the provision of oral healthcare. It was perhaps also unsurprising that the highest priority topic from the ‘patient’ group of topics was ‘evaluation of methods to improve access to NHS services and their cost-effectiveness’. The timing of the Delphi study was of importance. With the changes to the delivery of NHS pr imary dental care set out in Options for Change22 and the planned introduction of the new dentists’ contract it was felt by the participants that prospective research would be required to assess their impact on patient care. This approach supported a view held by many who believe that new arrangements for the delivery of healthcare, including the use of guidelines, should be vigorously tested before their adoption.23 It has also been suggested that the impact of any changes should be researched before their implementation in practice,24 something the present Government has singularly failed to do. Recently, the former Chief Dental Officer provided funds to help establish an Oral Health Research Unit at the University of Manchester. As previously highlighted, there is a need to engage all those with an interest when setting pr iorities for research. In the case of pr imary dental care, these include patients, practitioners and the commissioners of care. This point will be of great importance to the future success of the Unit and indeed to research initiatives developed by the Faculty and all other bodies.

Mode of thyrocalcitonin action in man

ConclusionsTCT exerts the same influence on blood Ca and P in man and in experimental animals. However only a limited fraction of Ca seems to be available for the rapid TCT-dependant homoeostatic control. Most likely this fraction can be located into the uncalcified osteoid, and TCT seems to accelerate mineral deposition thus filling a labile Ca pool. The net result is a decreased skeletal Ca binding capacity and a diminished responsiveness to TCT. After several days of TCT osteoclastic activity is not suppressed in man.