A simple method to fabricate stabilized record bases: a modified approach using casting wax for the borders.

Retention and stability of a record base is often compromised in the mouth because of blockout procedures performed before adapting a record base material on a definitive cast. This article presents a technique of fabricating a stable and retentive record base, in which a definitive cast does not receive a blockout procedure so that the record base engages the facial undercuts in the cast by means of a green coloured inlay casting wax.

Congenital neuroblastoma presenting as profound neonatal metabolic acidosis with systemic hypertension: Case report.

BACKGROUND: Clinical collapse in the newborn most often occurs secondary to sepsis, delivery complications, congenital cardiac defects, or inborn errors of metabolism. We report on a neonate with respiratory, cardiac, and hepatic failure, with disproportionate metabolic acidosis and systemic hypertension, found to be caused by a congenital neuroblastoma. CASE DESCRIPTION: A term infant presented to our Level IV NICU via emergent transport at 12 hours of life with clinical and laboratory findings consistent with respiratory, cardiac, and hepatic failure. Typical workup for sepsis and cardiac etiology was unrevealing. The infant was noted to have systemic hypertension despite prolonged capillary refill. A profound metabolic acidosis led the primary team to pursue a genetics consult. In the course of the workup for disorders of metabolism, a urine organic acids panel revealed an elevated HVA (homovanillic acid) and VMA (vanillylmandelic acid), the metabolites of the neurotransmitters epinephrine, norepinephrine and dopamine. Subsequent abdominal ultrasound and chest/abdomen CT revealed a large heterogeneous mass with internal vascular flow and scattered calcifications arising from the medial limb of the left adrenal gland, consistent with neuroblastoma. CONCLUSION: Although rare, neuroblastomas can present clinically in the perinatal period in a manner requiring immediate life-saving intervention. Providers should consider the diagnosis in the setting of a newborn with a sepsis-like syndrome or profound metabolic acidosis presenting along with systemic hypertension without clear underlying etiology.

Fracture surface characterization of clinically failed all-ceramic crowns.

The goal of this study was to establish a protocol for the retrieval and fractographic analysis of failed restorations, and to compare the fracture surface features of clinically failed ceramic restorations and with those of controlled laboratory test specimens fabricated from the same materials. Ten fractured Dicor crowns and 12 fractured Cerestore crows were retrieved and analyzed. Optical microscopy of the failed crowns revealed that the critical segments of nine of the 10 (90%) Dicor crowns and nine of the 12 (75%) Cerestore crowns were acceptable for fractographic analysis. Twelve disks of each material were fabricated as controls and fractured by bi-axial flexure for analysis of the similarities and/or differences between the fractographic features of fractured clinical crowns and the disks. Each of the 10 Dicor crowns was observed to fail along the internal surface. For 78% of the Cerestore crowns, failure initiation occurred at the porcelain/core interface or inside the core material. Critical flaw sizes of the failed Dicor crowns ranged from 127 to 272 microns. Failure stresses of the Dicor crowns, estimated by fractographic techniques and fracture mechanics relationships, ranged from 65 to 94 MPa. Estimated failure stresses for two of the Cerestore crowns which had failure initiation sites in the porcelain layer were 15 and 68 MPa. It is concluded that the fracture initiation sites of dental ceramics are controlled primarily by the location and size of the critical flaw, and not by specimen thickness.

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.

Postmortem histologic evaluation of mandibular titanium and maxillary hydroxyapatite-coated implants from 1 patient.

Postmortem examination of human specimens is an extremely important aspect of evaluating the relative compatibility and long-term success of endosseous implant surfaces. The bone-implant interface of 5 commercially pure titanium screw-type mandibular implants after 85 months of service and 2 hydroxyapatite- (HA) coated maxillary implants after 38 months of service were examined. All implants were stable at the time of the patient's death. The mandibular implants had an average of 65% contact with bone and the maxillary implants had an average of 47% contact. The HA coating had separated from the maxillary implants in some areas and was free within surrounding connective tissue or surrounded by invaginating sulcular epithelium. The arrangement and pattern of bone contact appeared different between HA-coated and titanium implant surfaces.

The efficacy of a counter-rotational powered toothbrush in the maintenance of endosseous dental implants.

BACKGROUND: Although most patients with implants have lost their natural teeth because of poor oral hygiene, limited data exist to guide practitioners in their recommendations of home-care regimens for their patients' endosseous dental implants and maintenance of peri-implant soft-tissue health. The authors conducted a study to compare the home-care effectiveness of a counter-rotational powered tooth-brush with that of conventional home-care regimens. METHODS: Before starting the six-year study, the authors trained 85 clinical investigators at 32 dental research centers across the United States in gathering periodontal data. Data for 2,966 implants were entered into a centralized database. Outcomes were derived from 24-month observations of a subset of the implants studied. RESULTS: Repeated-measures analysis of the toothbrushing methods used on 2,966 implants showed that the counter-rotational powered toothbrush removed plaque significantly better than manual methods (P < .0001 Wald statistic) from all implant surfaces and at all recall intervals up to 24 months. Similar results were demonstrated for the gingival index. CONCLUSIONS: The counter-rotational powered brush appears to be well-suited for home-care regimens aimed at maintaining optimal peri-implant soft-tissue health in patients with dental implants. CLINICAL IMPLICATIONS: The importance of maintaining the health of the peri-implant tissues is well-recognized by the dental profession. The counter-rotational powered toothbrush is an effective tool in meeting the oral hygiene challenges associated with implant prosthesis maintenance.

The ankylos endosseous dental implant: assessment of stability up to 18 months with the Periotest.

Osseointegration is an ongoing histometric process that may vary during clinical function. The implant must be stable at uncovering, which reflects the status of bone-implant interface. The physiology of bone healing associated with endosseous implants suggests that this process occurs between 8 and 12 months, and Periotest values (PTVs) tend to reflect changes in the stability of the bone-implant interface. Stability generally increases gradually from the time of uncovering to an optimal PTV that occurs at a point close to 12 months. This stable interface must remain intact for long-term clinical survival. Rapid development of this optimal PTV is highly desirable in order to prevent premature overloading of the bone-implant interface. The Ankylos implant is a new screw-type implant design in which the thread pitch and length vary to maximize trabecular bone contact. The purpose of this report is to evaluate to 18 months the stability (PTVs) of this implant design. More than 457 implants were placed and followed for a period of 18 months by the multicentered, multidisciplinary Ankylos Implant Clinical Research Group (AICRG). Implant stability (PTVs) was assessed using the Periotest at abutment connection and at 3, 6, 9, 12, and 18 months after uncovering. The Periotest values for all implants rapidly reached an optimal status between uncovering (-3.1 PTVs) and 3 months (-3.4 PTVs). This rapid increase in stability has not previously been reported for other implant designs. The mandibular arch was more negative (-3.8 PTVs) at uncovering as compared with the PTVs for the maxillary arch (-1.7 PTVs). Negative PTVs were recorded (1) as length and diameter increased, (2) as bone density increased, (3) in certain jaw regions, (4) as the number of implants/case increased, and (5) for implants stabile at placement. The Ankylos screw implant design produced rapid stabilization 3 months after uncovering.

A 48-month multicentric clinical investigation: implant design and survival.

This report is based on a total of 2,955 implants of 6 different designs, randomized and placed in 829 patients and followed for 48 months. Implant failure was defined as nonintegration at uncovering or removal due to mobility, persistent pain, infection, and evidence of radiographic bone loss. Failures were reported for 3 phases of treatment: implant placement to uncovering (phase 1), uncovering to loading (phase 2), and postloading (phase 3). Differences in survival were compared with Kaplan-Meier survival curves. The maxillary single tooth application resulted in 95.2% survival for the hydroxyapatite-coated grooved implants. In the maxillary completely edentulous application, survival of hydroxyapatite grooved and screw implants were considerably better compared with the titanium screw implants. The hydroxyapatite-coated cylinder had better survival than the titanium basket and screw designs in the mandibular completely edentulous application. The hydroxyapatite-coated cylinder and grooved implants in the maxillary posterior partially edentulous application had similar survival rates. The survival of the hydroxyapatite-coated cylinder exceeded that of the titanium basket in mandibular posterior partially edentulous applications. Analyses by phase of treatment indicated a pattern of early failure for nonhydroxyapatite-coated implants compared with hydroxyapatite-coated implants. The implant with the highest survival at all phases of treatment was the hydroxyapatite-coated press-fit cylinder. Two hydroxyapatite-coated implant designs performed well in the challenging posterior maxillary region.

Stability of implants and natural teeth as determined by the Periotest over 60 months of function.

Various methods for evaluating tooth mobility have been developed throughout the years, but their acceptance has been limited because of the subjectivity associated with their use. In recent years, the Periotest has been studied and used to evaluate the mobility of natural teeth and is claimed to b e potentially reliable in assessing the stability of the implant-bone interface. Few clinical implant studies have used natural teeth as controls to monitor changes in mobility associated with dental implants. The Dental Implant Clinical Research Group initiated a long-term clinical study in 1991 to assess the influence of design, application, and site of placement on clinical success and crestal bone height. As part of the study, Periotest values (PTVs) were recorded for 2,623 of the 2,998 implants placed and uncovered. For the statistical analysis, 2,623 implants were tested at second-stage surgery, with the number of implants tested varying at each follow-up visit. Data were collected from investigators at 32 study centers for periods ranging up to 60 months. A total of 975 natural teeth from 409 partially edentulous study subjects served as controls. FPVs on natural teeth and implants were combined, and the overall average Periotest values (OA-PTVs) were compared with values for individual subjects. The effect of implant and natural tooth locations on mobility were evaluated and compared with each other. The combined OA-PTV for all natural teeth was +1.8 and the OA-PTV for all implants was -3.4 PTVs. Compared with those in the maxillae, mandibular teeth and implants were found to be more stable Implants were found to be significantly more stable as compared with natural teeth. The recorded variations in PTVs for natural teeth and implants over the entire evaluation period were not found to be significantly different. This study developed the following conclusions: (1) implants were found to be significantly less mobile as compared with natural teeth for individual subjects; (2) the PTVs for natural teeth and implants did not exhibit significant variation over the evaluation period; (3) the Periotest can provide reproducible assessment of stability in a long-term clinical study; and (4) changes in PTVs may be helpful in evaluating improvement or degradation of the implant-bone complex.

A new implant designed to maximize contact with trabecular bone: survival to 18 months.

PROBLEM: A roughened, commercially pure titanium (CP-Ti) implant design has been developed that features a different length and pitch for each screw thread to direct functional stresses away from cortical bone and to the more resilient trabecular bone. Abutment-implant connection is made using a conical taper to provide a seal against invasion by microorganisms. PURPOSE: To assess short-term (18 months) clinical performance of this innovative implant design. METHODS: A total of 1,419 implants were placed in 313 patients to support 419 prostheses in a multidisciplinary, multicentered, prospective clinical study conducted by the Ankylos Implant Clinical Research Group (AICRG). More than 100 dentists at 32 centers in the United States, 1 in Korea, and 1 in Taiwan are involved in the study. Failure was defined as implant removal for any reason. The influence of mobility at placement, implant length and diameter, incision type, augmentation, crestal bone reduction, bone density, and the use of the operating room or dental clinic on survival were evaluated over 18 months. Crestal bone loss between placement and uncovering was also determined. RESULTS: Crestal bone loss ranged from 0.2 to 0.5 mm. The overall success rate from placement to 18 months was 96.6%. Implants mobile at placement failed more frequently (16.9%) compared with stable implants (3.1%). Wide-diameter implants and longer implants exhibited higher survival rates. Incision design and surgery location did not influence survival. Bone density was important to clinical survival.

Department of Veterans Affairs Cooperative Studies Project No. 242. Quantitative and qualitative evaluation of the marginal fit of cast ceramic, porcelain-shoulder, and cast metal full crown margins. Participants of CSP No. 147/242.

The primary objective of Veterans Administration Cooperative Studies Program No. 242 was to evaluate, in vitro and in vivo, the suitability of new dental materials and techniques used in making crowns and fixed partial dentures. Because inaccurate margins can lead to changes in the periodontal tissues and/or to recurrent caries, it is important to assess the accuracy of margins resulting from the use of new, improved materials or techniques. This segment of the project compared the marginal fit associated with the use of Dicor Crowns, Cerestore crowns, and porcelain-shoulder metal ceramic full coverage restorations using both quantitative and qualitative methods. Statistically significant differences were found among these materials following analysis of the quantitative data. The ranking in mean marginal opening from smallest to largest was: metal margins (27.5 microns), Dicor crowns (63.5 microns), porcelain shoulder restorations (66 microns), and Cerestore crowns (75 microns). The rank order based on the qualitative evaluation method was the same.

Department of Veterans Affairs Cooperative Studies Project number 147: level of examiner reliability over seven years.

In 1980 the Veterans Administration Cooperative Studies Program No. 147 initiated a multicenter, multidisciplinary clinical study to evaluate the use of alternative alloys for porcelain-fused-to-metal restorations. An investigation of interexaminer agreement was conducted after seven years utilizing three measures of reliability: percentage of exact agreement using a five-point scale, percentage of agreement using a dichotomous (satisfactory-unsatisfactory) scale, and [kappa], a statistic which is intended to measure agreement beyond what would be expected to occur by chance. Exact agreement on the five-point scale ranged from 77 to 99 percent. Percent agreement on the dichotomous scale was above 99 percent for all of the criteria. Kappa ranged from 0.56 to 0.91, indicating moderate to near perfect agreement among examiners. Reliability of the study evaluations reinforced the validity and significance of the findings.

Veterans Administration Cooperative Studies Project No. 147: association of metallic taste with metal ceramic alloys.

We examined patients to find out whether they noticed the prevalence of metallic taste and set out to determine the association of metallic taste with demographic, medical, and dental factors. Data were collected as part of a Veterans Administration Cooperative Study investigating the suitability of alternative metal ceramic alloys as substitutes for alloys that contain gold. Crowns and fixed partial dentures were made from control and alternative alloys for accepted volunteer patients. A month after placement of the restorations and at regularly scheduled recall appointments, the patients were asked if they tasted a metallic flavor. Of the 2023 times the question was asked, 101 positive responses were given by 68 patients (46 reported metallic flavor once, and 22 reported it more than once). Results indicated that youth, sensitivity to heat and cold, bruxism, grinding, and an increasing number of restorative units were significantly related to metallic taste. For any given visit, about 5% of the patients reported tasting a metallic flavor regardless of the type of alloy that was used in the restoration. Metallic taste does not appear to be a problem with alternative alloys.

Properties of cobalt-chromium metal ceramic alloys after heat treatment.

A comparison of mechanical properties of seven metal ceramic alloys in as-cast and heat-treated conditions resulted in significant differences. The alloys that were tested included seven cobalt-chromium metal ceramic alloys. Mechanical properties include strength, elongation, modulus of elasticity, and microhardness. Twenty-four tensile bars were cast for each alloy. Twelve of the 24 bars for each alloy were randomly selected for heat treatment with the Ceramco technique. Results indicated that the tested alloys had similar mechanical property values as a group in both the as-cast and the heat-treated conditions. The heat treatment had little effect on the cobalt-chromium alloys, although several did become significantly harder. In either condition, the cobalt-chromium alloys showed a high value of strength, a low percent of elongation, a high modulus of elasticity, and a high value of hardness. The high value of hardness and the low percent of elongation would make these alloys difficult to handle clinically.

Veterans Administration Cooperative Studies Project No. 147. Part II: A new assessment system for rating metal-ceramic crowns.

The rating system developed for this study combined ordinal and numerical scoring. The method involved the following: defining the critical criteria, defining the ordinal rating criteria for the assignment, assigning numerical scores for each individual criterion and totalling the scores for each restoration, adding an adjustment number, and scaling the results to the 0-to-10 range and rounding off to the nearest tenth. When tested on sample data gathered at the 12-month followup appointment, the new system elicited a finer discrimination of differences in the quality of the restorations. Although the system fully meets the needs of the specific project, it should not be considered an answer to the needs of all clinical investigations. It should be viewed as a different approach in the development of an acceptable clinical rating system.

Veterans Administration Cooperative Studies Project No. 147. Part I: A multidisciplinary, multicenter experimental design for the evaluation of alternative metal-ceramic alloys.

The factors necessary for a comprehensive multidisciplinary, multicenter clinical study have been incorporated into CSP No. 147. The experimental design provides the potential for multiple laboratory and clinical data comparisons of alternative alloys. The study incorporates clinical performance observations with dental and medical histories that permit many unique correlations. This potential demonstrates the comprehensiveness of the CSP No. 147 study design and its contributions to clinical dental research in the evaluation of restorative materials.