Survival of various implant-supported prosthesis designs following 36 months of clinical function.

BACKGROUND: The use of endosseous dental implants to replace natural teeth lost to trauma, dental caries, or periodontal disease has become a predictable form of prosthetic treatment since gaining popularity in the early 1980s. While numerous clinical studies have focused on the survival of implants, few address the survival of different prosthesis designs. METHODS: Beginning in 1991, 882 prostheses supported by more than 2,900 implants (687 patients) were placed by the Department of Veterans Affairs Dental Implant Clinical Research Group (DICRG). These prostheses were divided into five research strata based on arch location. The recommended design for each stratum was: bar-supported overdenture (maxillary completely edentulous); screw-retained hybrid denture (mandibular completely edentulous); screw-retained fixed partial denture (mandibular and maxillary posterior partially edentulous); and cemented single crown (maxillary anterior single tooth). Alternative overdenture designs were utilized in the edentulous arches when the recommended prosthesis could not be fabricated. Prosthesis success rates for the research strata were calculated for an observation time of up to 36 months following prosthesis placement. RESULTS: Success rates for the maxillary edentulous stratum ranged from 94.6% for the bar-retained overdenture supported by five to six fixtures to 81.8% for the cap-retained overdenture. The mandibular edentulous strata produced success rates of 98.1% for the fixed hybrid prosthesis to 91.7% for the cap-retained prosthesis. Success rates for maxillary and mandibular posterior fixed partial dentures were 94.3% and 92.6%, respectively, while the maxillary anterior single-tooth prosthesis yielded a success rate of 98.1% for the 36-month observation period. CONCLUSIONS: The recommended prosthesis designs investigated in this study proved to be reliable, with encouraging success rates for an observation period of 36 months following placement.

Three-year post-placement survival of implants mobile at placement.

BACKGROUND: Although rigid fixation of endosseous implants at the time of placement is generally thought to be a prerequisite for successful osseointegration, the Dental implant Clinical Research Group (DICRG) of the Department of Veterans Affairs has reported on implants that integrated despite being mobile at placement. The present study examines the frequency of osseointegration and the 36-month post-placement survival of implants mobile at placement in a prospective, multicenter, longitudinal clinical study of more than 3,000 implants conducted by the DICRG. METHODS: A total of 3,111 implants of 6 different designs were placed in all jaw regions in more than 800 patients at 32 study centers. At the time of this report, 2,770 of these implants had been followed for 36 months post-placement. They included 89 implants that were mobile at placement. Data for demographic variables, implant coating, bone quality, incision type, bone augmentation, and antibiotic usage were recorded. An electronic hand-held probe was used to measure mobility at uncovering and at regular follow-up intervals. RESULTS: Eighty-nine of 2,770 inserted implants were mobile at placement. Results are reported for two periods: from placement to 36 months and from prosthetic loading to 36 months. The latter method eliminated early failures and resulted in substantially higher scores for both mobile implants at placement (95.9% survival from prosthetic loading to 36 months post-placement versus 79.8% from placement to 36 months) and implants not mobile at placement (98.4% versus 93.4%). Mobility at placement was significant to 3-year survival (P < 0.001). Hydroxyapatite (HA) coating improved the performance of implants mobile at placement (91.8% for HA-coated versus 53.6% for non-HA) and those not mobile at placement (97.2% for HA-coated versus 87.4% for non-HA). Radiographic findings suggested that crestal bone response around implants which were mobile versus immobile at placement was similar. CONCLUSIONS: Although implant stability at the time of placement is clearly desirable as seen in the superior 3-year survival of stable implants, it may not be an absolute prerequisite to osseointegration or to long-term survival. Several factors may influence the decision to remove or replace a mobile implant. HA-coating significantly improved the performance of both mobile and immobile implants at placement to 3 years post-placement (P < 0.001).

Variables affecting survival of single-tooth hydroxyapatite-coated implants in anterior maxillae at 3 years.

BACKGROUND: The development and expanded use of endosseous dental implants over the last two decades have been remarkably rapid. It is, therefore, imperative that the dental profession closely monitor the performance of root-form implants used in a variety of applications. The Dental Implant Clinical Research Group (DICRG) was established in 1990 by the Department of Veterans Affairs as a forum for conducting prospective, multidisciplinary, multicentered studies in the field of implant dentistry. The DICRG comprised 30 VA medical centers and 2 dental schools at the time of this study. This paper reports on the survival of hydroxyapatite (HA)-coated grooved implants used to replace single missing teeth in anterior maxillae at 3 years post-implant placement. METHODS: During a 4-year accrual period, a total of 247 single-tooth implant restorations were placed in anterior maxillae. This paper focuses on the survival of 222 implants (149 patients) for which 3-year data were recorded for the period from placement. Survival was examined with respect to patient demographics and health status, implant location, surgical variables, and 2-week post-placement use of chlorhexidine digluconate (0.12%) rinses. Implant stability was recorded using a hand-held probe. Periodontal-type measures were recorded and evaluated, and all complications related to osseointegration were noted. Failure was defined as removal of the implant for any reason. RESULTS: Establishment and maintenance of osseointegration at 3 years post-placement was 97.3%. During this 3 year period, 6 implants were removed due to either failure to osseointegrate or loss of osseointegration. Implant length correlated positively with 3-year survival (P = 0.003, exact test). The use of preoperative antibiotics was nearly significant to implant survival (P = 0.051. Pearson chi-square). Mean stability values (PTVs) increased incrementally from -4.5 at uncovering to +1.1 at 36 months, indicating a decrease in stability of the bone-implant-prosthesis complex. The most common complication was related to inadequate available bone to fully house implants. CONCLUSIONS: Three-year post-placement survival data suggest that the use of HA-coated, grooved, endosseous implants to support maxillary anterior single-tooth replacements is a predictable and reliable procedure that can offer significant benefits. Longer implants demonstrated higher survival than shorter implants. The use of preoperative antibiotics was nearly significant to implant survival, and there was an increase in mean PTVs observed over the duration of the study. Further research is needed to assess stability of the hydroxyapatite-bone interface over time.

Factors affecting implant mobility at placement and integration of mobile implants at uncovering.

This study examined 1) factors that contributed to implant stability at placement and 2) the likelihood for an implant that was mobile at placement to osseointegrate. Eighty-one (3.1%) of 2,641 implants placed by the Dental Implant Clinical Research Group between 1991 and 1995 were found to be mobile at placement. Seventy-six (93.8%) of the 81 mobile implants were integrated at uncovering compared to 97.5% for the 2,560 immobile implants. Variables that influenced mobility at placement included patient age, implant design and material, anterior-posterior jaw location, bone density, and use of a bone tap. Hydroxyapatite (HA)-coated implants were slightly more likely to be mobile at placement (P = 0.324) than non-hydroxypatite (HA)-coated implants. Of the 54 HA-coated implants that were mobile at placement, all (100%) integrated, while only 17 (81.5%) of the 22 mobile non-HA-coated implants integrated (P = 0.003). Mean electronic mobility testing device values (PTVs) at uncovering for all implants mobile or immobile at placement that integrated were -2.9 and -3.6 respectively. PTVs for HA-coated implants that were mobile (-3.5 PTV) or immobile (-4.0 PTV) at placement differed by 0.5 PTV, whereas non-HA-coated implants exhibited a greater difference of 1.2 PTVs at uncovering. HA-coated implants, regardless of mobility at placement, integrated more frequently and exhibited greater stability than non HA-coated implants.

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.

A new angle on restoring anterior teeth with root-form implants: clinical report.

Root-form implants may be indicated for the replacement of missing anterior teeth. Occasionally fixtures are placed in a position inconsistent with proper tooth alignment. The new PreAngled Abutment (Dentsply/Implant Division, Encino, CA) addresses this problem and was used to successfully restore missing tooth numbers 7 and 8 for a patient that had two malpositioned implants.

The surgical template: a prescription for implant success.

The surgical template is utilized in the planning and execution of a successful implant rehabilitation. A method of template fabrication is presented which is useful for cases requiring precise root form fixture placement. Stents are fabricated using a duplicate denture or acrylic base and orthodontic wire, which is contoured to create the acceptable perimetric limits of fixture placement. This approach provides good visual access, operator flexibility, and template stability. The technique can be utilized for the edentulous and the partially edentulous arch.