Gregory R. Parr

Titanium: The mystery metal of implant dentistry. Dental materials aspects

A number of important points concerning titanium and its alloys have been discussed. They are summarized as follows. Ti and its alloys, particularly the alpha-beta alloys, possess mechanical properties that make them ideal implant materials. Ti and its alloys oxidize readily in air. This surface oxide is extremely stable in the physiologic environment of the body. The stability and inertness of this surface oxide layer acts to protect Ti from corrosive breakdown when used in the body. The elimination of surface irregularities and contaminants is important when preparing a metal for implantation. Titanium can be coupled with equally passive metals in the body without causing galvanic corrosion.

Prosthodontic principles in the framework design of maxillary obturator prostheses

The Aramany classification system of postsurgical maxillectomy defects is a useful tool for teaching and developing obturator framework designs and enhancing communication among prosthodontists. This article describes a series of Aramany-obturator design templates and discusses the relevant considerations for each. In all situations, a quadrilateral or tripodal design is favored over a linear design because this allows a more favorable leverage design application that will aid in the support, stabilization, and retention of the prosthesis.

Ultrastructural analyses of the attachment (bonding) zone between bone and implanted biomaterials

This report presents transmission electron and high voltage transmission electron microscopic observations of bone and associated remodeling tissues directly interfacing with endosteal dental implants. Undecalcified interfacial tissues were serially sectioned from mandibular samples encasing 60 implants placed into 30 dogs. Two-dimensional ultrastructural analyses and three-dimensional stereology showed that osteogenesis adjacent to dental implants is a dynamic interaction of osseous cells and a collagenous fiber matrix. This study showed that the interfacial bone consists of a mineralized collagen fiber matrix associated with an inorganic (hydroxylapatite) matrix. This study suggested that an unmineralized collagen fiber matrix initially is laid down directly at the implant surface, and that this matrix then is mineralized. Osteoblasts interacted with this matrix, eventually becoming encased within developing lacunae during the remodeling process. This process formed the cellular (osteocyte) aspects of the developed bone. Osteocyte processes extended through canaliculi directly to the implant surface. Apparently, these processes also were entrapped within canaliculi during the mineralization events. At times, these processes paralleled the implant surface. The bone-implant interfacial zone was primarily fibrillar (both mineralized and unmineralized) in morphology, with an electron-dense, ruthenium positive deposition. This electron-dense material was approximately 20 to 50 nanometers in thickness, and only this thin layer separated the remodeled mineralized bone from the implant.

Soft tissue response to endosseous titanium oral implants

T he use of titanium for oral implants is rapidly gaining acceptance by the dental comniunity. The clinical success of titanium implants over long periods of time has been reported.‘, 2 Although there is impressive evidence in favor of titanium as the material of choice for certain types of dental implants, continued research is necessary to scientifically support the clinical results. This article reviews the nature of the soft tissue response to titanium implants.

Prosthodontic principles in surgical planning for maxillary and mandibular resection patients

Discussion between the surgeon and prosthodontist on surgical planning is important. It is necessary that they each be aware of the others problems. Only in this way can continuity be established between surgical and prosthetic procedures. This will provide a maximum level of treatment for the maxillofacial patients, thereby returning them to society most expeditiously.

Extending the longevity of temporary soft liners with a mono-poly coating

A method has been described that will reduce the incidence of fungal growth and increase the period of resiliency for temporary soft liners. The use of a monopoly coating procedure is limited to temporary soft liners only. The coating will not adhere to the more permanent soft liners such as Molloplast-B (Regneri & Co KG, Karlsruhe, West Germany). The coating, however, can be used on any conventional temporary soft liner with good results.

A light and electron microscopic comparison of osseointegration of six implant types.

This study compared six commercially available implants placed in an animal model for 5 months. Twelve of the implants were used for light microscopic analysis, and the remaining 12 were used for scanning electron microscopic analysis. With the exception of one implant, newly formed bone was evident in direct apposition to portions of all control implants. The light microscopic and scanning electron microscopic evaluations of the tissues surrounding the six commercially available implant types indicated that initial osseointegration is likely with all types. Implant design, material, and submergibility do not appear to be essential for initial osseointegration to occur as long as a biocompatible material is selected and the implant is placed using minimally traumatic surgical techniques.

The evolution of the obturator framework design

This brief overview of the progress and evolution of philosophies of obturator framework designs was accomplished by hand, as well as via Medline. It begins in 1530 ad with Ambrose Paré who described the first button-shaped sponge and metal obturator, and continues through the formation of the American Academy of Maxillofacial Prosthetics and the development of the specialty. It concludes with a simplified discussion of complex surgical-prosthetic coordination and the use of vascularized free flaps with osseointegrated dental implants.

Light microscopic and scanning electron microscopic retrieval analyses of implanted biomaterials retrieved from humans and experimental animals.

This paper reports analysis obtained from 200 implant cases retrieved from humans and submitted to the American Academy of Implant Dentistry Research Foundation, Medical College of Georgia implant retrieval center. The samples that were not decalcified were embedded in polymethylmethacrylate and examined with scanning electron microscopy and routine light, polarized, or Nomarski microscopy. Cases included both orthopedic and dental implants, as well as entire mandibles and portions of maxillae obtained at autopsy. A significant number of submitted implants had substantial amounts of adhered bone, which permitted evaluation of human bone remodeling to osseointegrated implants. These implants failed because of implant fracture. As was observed with animal studies, healthy bone supported these implants, with the bone containing an interdigitating canaliculi network that provided communication between interfacial osteocytes and osteocytes deeper within the remodeled osteonal and trabecular bone. Early dental implants containing a coating of beads showed a connective tissue interface, which corresponded to the bead surface of specific orthopedic implants that underwent some degree of micromovement. This is in contrast with the excellent response reported for successful contemporary beaded implants. Significant numbers of osseointegrated fractured hydroxyapatite (HA)-coated dental implants demonstrated the adequate serviceability of these implants before biomaterial fracture. In contrast, the HA coating was dissociated from retrieved orthopedic implants, leading to extensive cup loosening and case failure. This study, therefore, underscores the need for evaluation of failed human dental and orthopedic implants. Correlations can be drawn between human retrieval and experimental animal studies.

Retrieval analyses of implanted biomaterials: light microscopic and scanning electron microscopic analyses of implants retrieved from humans.

We report analyses obtained from 135 implant cases retrieved from humans and submitted to the American Academy of Implant Dentistry Research Foundation--Medical College of Georgia Implant Retrieval Center. The undecalcified samples were embedded in polymethyl-methacrylate and examined with scanning electron microscopy and with routine light via polarized or Nomarski microscopy. Cases included both orthopedic and dental implants as well as entire mandibles obtained at autopsy. Significant numbers of submitted implants had substantial amounts of adhered bone, which permitted evaluation of human bone remodeling to osseointegrated implants. These implants failed because of implant fracture. As has been observed in animal studies, an interdigitating canaliculi network provided communication between interfacial osteocytes and osteocytes deeper within the remodeled osteonal and trabecular bone. Significant numbers of osseointegrated fractured hydroxyapatite-coated dental implants demonstrated the adequate serviceability of these implants prior to biomaterial fracture. In contrast, the hydroxyapatite coating was dissociated from retrieved orthopedic implants, leading to extensive cup loosening and case failure. Caution is advised for the use of hydroxyapatite-coated acetabular implants. This study therefore underscores the need for evaluation of failed human dental and orthopedic implants. Correlations can be drawn between human retrieval and experimental animal studies.