Ira H. Orenstein

Distribution of Bone Quality in Patients Receiving Endosseous Dental Implants

Knowledge of the distribution of bone quality in the various jaw regions assists the clinician in dental implant treatment planning. Bone quality was assessed with radiographs and tactile sensation for 2,839 implants at the time of placement into four anatomic regions of the jaw. The Lekholm-Zarb classification system was used. Overall, bone quality types 1 and 4 were found much less frequently than types 2 and 3. Although variations in density existed in each region, quality 2 bone dominated the mandible, and quality 3 bone was more prevalent in the maxilla. For both anterior and posterior jaw regions, types 2 and 3 bone predominated. The anterior mandible had the densest bone, followed by the posterior mandible, anterior maxilla, and posterior maxilla.

AICRG, Part I: A 6-Year Multicentered, Multidisciplinary Clinical Study of a New and Innovative Implant Design

PROBLEM Repetitive microstrains, which occur at the bone-implant interface during function, can lead to implant loss. In an attempt to improve survival by directing the stresses during function away from the dense cortical bone and toward the resilient trabecular bone, the Ankylos implant was developed with a roughened, progressive thread and a smooth cervical collar. The highly polished collar reduces the stresses in areas of the crestal bone. A precisely machined Morse taper prevents rotation of the abutment on the implant and eliminates the microgap present in many 2-stage implant systems. Clinical studies of other implants at different clinical research centers have demonstrated varying degrees of survival. PURPOSE The purpose of this paper was (1) to assess the overall clinical survival of this new implant design and (2) to compare implant stability (ie, Periotest values [PTVs]) over time with other implants. METHOD The investigation represented a comprehensive, multicentered, international clinical study conducted over a period of 6 years. It was conducted under an Investigational Device Exemption (IDE) protocol that was reviewed and accepted in the United States by the Food and Drug Administration (FDA). Over 1500 implants were placed and restored, and follow-up data were gathered for a period of up to 3 to 5 years. RESULTS Over 44% of the clinical research centers reported no failures (100% survival). A total of 63% of the centers had none or only 1 failure during the study. One center reported 6 failures in 1 patient, which were not related to the implant design. Overall survival for implants in function for 3 to 5 years was 97.5%. Using failure criteria of earlier studies of other implants, 5-year survival was 98.3%. Higher handpiece speeds were associated with an increase in the number of failures. This new design produced a slightly more resilient trabecular bone-implant complex with a difference of about 1 PTV in all bone densities when compared with other implants. CONCLUSIONS The following conclusions can be made: (1) the implant design was effective under all clinical conditions; (2) no significant and unexpected complications or risk factors were evident; (3) survival was found to be excellent; and (4) this implant is well suited for use in the restoration of masticatory function and esthetics in patients with missing natural teeth.

AICRG, Part V: Factors influencing implant stability at placement and their influence on survival of Ankylos implants.

PROBLEM Several factors influence primary stabilization of dental implants at placement surgery. These include implant design, bone quality, implant jaw location, and the use of a bone tap. PURPOSE This report evaluates clinical data gathered by the Ankylos Implant Clinical Research Group (AICRG) to assess (1) the influence of several variables on primary stability and (2) the potential for an Ankylos implant (Friadent GmbH, Mannheim, Germany) that is mobile at placement to integrate and survive for at least 3 years of clinical function. METHODS The Ankylos implant is a roughened grade-2 titanium screw. A total of 1554 implants were placed in 478 patients. At both the time of placement and abutment connection, the implants were tested for evidence of clinical mobility by attempting to rotate or move the implant with an application of force. Survival was recorded from placement and up to 36 months following placement. RESULTS At placement, 2.8% were found to be mobile. In the maxillary posterior quadrant, 6.3% were clinically mobile. Implant mobility was frequent (12.2%) in jaw regions with poor-quality bone (BQ-4) or with short implants (8 mm = 8.3% mobile). Of the implants mobile at placement, 97.7% were stable at uncovering. The 3-year postplacement survival of initially mobile implants was 84.1% compared with 96.8% for implants not mobile at placement (chi2 test, P = .001). CONCLUSIONS The Ankylos implant predictably promoted primary stability during surgical placement. Poor bone quality, short implants, and maxillary posterior jaw locations were all associated with a slightly higher rate of mobility at placement. Primary implant stability, while highly desirable, is not absolutely necessary for achieving osseointegration of Ankylos

Bone density: Its influence on implant stability after uncovering

Primary implant stability and bone density are variables that have long been considered to be essential to achieving predictable osseointegration and long-term clinical survival. Although the dentist can control most factors associated with implant survival, bone density is the one factor that cannot be controlled. Measuring implant stability would assist in determining if an implant has integrated and is ready for the fabrication of the final prosthesis. Changes in implant stability in each type of Bone Quality (BQ-1, -2, -3, and -4), which may occur with time, have not been studied. Such information could help identify well-integrated implants and identify changes associated with impending implant failure. Several studies have used the Periotest instrument to study implant stability. Use of the Periotest implant stability will be studied during each phase of implant treatment for each bone density, and a range for clinically satisfactory integration will be suggested. Implant stability changes over time, and the changes are different for each bone density as the bone surrounding the nonhydroxyapatite implant becomes denser. This is clearly demonstrated in a postmortem histological specimen. The changes in implant stability (Periotest Values [PTVs]) are more apparent in BQ-1 and BQ-2 bone and less apparent in BQ-3 and BQ-4 bone. The Periotest is capable of providing valuable information concerning favorable or unfavorable changes in the bone-implant interface after uncovering. In addition, it can help identify when an implant is ready to be loaded. A new range of PTVs (-5 to -2) is suggested for monitoring the status of implants. Implants with PTVs more positive than -2 would indicate a bone-implant complex that may be marginal.

Bone quality in patients receiving endosseous dental implants

Die Qualitat von Knochen spielt eine wichtige Rolle im klinischen Langzeiterfolg von zahnarztlicher Implantatbehandlung. Mehrere Knochenklassifikationssysteme, die zum Groβteil auf anatomischer und histologiscner Information beruhen, wurden vorgeschlagen. Im Jahr 1991 begann die Dental Implant Clinical Research Group ein klinische Langzeitstudie in Zusammenarbeit mit dem Department of Veterans Affairs, um den Einfluβ von Implantatdesign, Anwendung, und Plazierungsort auf klinischen Langzeiterfolg und Alveolarkammhohe zu erforschen. Als Bestandteil dieser Untersuchung wurde die Qualitat des Knochens mittels Rontgenaufnahmen und taktiler Sensation wahrend der Implantatplazierung uber drei Jahre hin untersucht. Nach uber 1900 Untersuchungen zeigen die Resultate einen Bereich fur die Knochenqualitat in jeder anatomischen Region an. Der Unterkiefer ist generell dichter als der Oberkiefer. Der anteriore Unterkiefer hat den dichtesten Knochen, gefolgt von dem posterioren Unterkiefer, dem anterioren Oberkiefer, und dem posterioren Oberkiefer. Knochen mit der Qualitat 2 und 3 dominierte in allen anatomischen Regionen. Die Signifikanz unterschiedlicher Knochenqualitaten und wie sie die Behandlungsplanung und Prognose beeinflussen konnen wird La calidad del hueso juega un papel important en el exito a largo alcance en el tratamiento con implantes dentales. Diferentes clasificaciones de la calidad del hueso han sido presentadas, todas, basadas en la anatomia e histologia del area. En el 1991 el Dental Implant Research Group inicio un estudio longitudinal clinico con la cooperacion del Departamento de Asuntos al Veterano para investigar la influencia del diseno, aplicacion, posicion del implante, comportamiento clinico y la respuesta en el alto de la cresta alveolar. Como parte de la investigacion, la calidad del hueso fue evaluada usando radiografias y la sensacion tactilar al momento de la insercion de los implantes por un periodo de tres anos. Despues de 1900 evaluaciones, los resultados indicaron que hay un margen de calidad osea en cada una de las areas anatomicas evaluadas. El hueso en el area anterior tiende a ser mas denso que en el area posterior. La mandibula es mas densa que la maxila.Orenstein IH, Synan WJ, Truhlar RS, Morris HF, Ochi S, Dental Implant Clinical Research Group.

A technique for converting an existing denture into a cast metal-reinforced implant-retained overdenture

Prosthesis fracture is a common complication associated with implant-retained overdentures. A new overdenture can be strengthened by incorporating a cast metal reinforcement during processing. The authors describe a technique for converting an existing conventional nonreinforced serviceable denture into an overdenture that includes a cast metal reinforcement and its attachments.

Electronic Percussive Testing of the Stability of an Immediately Provisionalized Implant Placed Into a Fresh Extraction Socket: A Pilot Evaluation

It is important to achieve primary stabilization of dental implants that will be immediately loaded. Noninvasive devices that test the stability of immediately provisionalized implants placed into fresh extraction sockets are discussed. A titanium threaded implant was placed into a fresh extraction socket of a patients nonrestorable mandibular right canine. The implant received an interim restoration immediately following its placement. The stability of the bone-implant complex was evaluated from the day of implant insertion through day 246 using an electronic percussive testing instrument. During the first month the bone-implant complex became progressively less stable reaching a peak measured level of instability at 30 days postimplantation. This was followed by progressive stabilization first measured on day 46 as the implant continued to osseointegrate. These findings suggest that the bone-implant complex became less stable during the first month after implant placement and was followed by a period of progressive stabilization reflecting bone maturation around the implant. A search of the literature found similar results in a study of single-stage implants (not immediately provisionalized) using resonance frequency analysis. The known sequence of wound healing around dental implants is reviewed to explain the findings of this pilot evaluation. Studies that use noninvasive testing devices to assess implant stability at placement and during healing may provide information that can help to optimize implant treatment outcomes.

Use of transparent polyvinylsiloxane to replicate gingival peri-implant soft tissue.

The fabrication of an esthetic implant-supported restoration often necessitates consideration of the surrounding gingival architecture. Procedures for generating a definitive cast that accurately details the peri-implant soft tissue with a resilient material have been described. Currently used gingival replicating materials are usually pink and opaque, making it difficult or impossible for the dentist and laboratory technician to visually confirm complete seating of components subgingivally on laboratory analogs without altering the cast. This article describes a technique for fabricating a definitive cast using a transparent polyvinylsiloxane material to replicate the peri-implant gingiva.