Influence of tooth surface roughness and type of cement on retention of complete cast crowns

STATEMENT OF PROBLEM

Bond strength of luting cements to dentin is a critical consideration for success of cast restorations.

PURPOSE OF STUDY

This study determined the relationship between surface characteristics of teeth prepared for complete cast crowns and retention of respective cemented restorations.

MATERIAL AND METHODS

Ninety artificial crowns were cast for standardized complete crown tooth preparations accomplished with the use of a milling machine on extracted human teeth. Diamond, tungsten carbide finishing, and cross-cut carbide burs of similar shape were used. The crowns in each group were randomly subdivided into three subgroups of 10 for the three luting cements selected for this study: zinc phosphate cement (Fleck's), glass ionomer cement (Ketac-Cem), and adhesive resin cement (Panavia-EX). Retention was evaluated by measuring the tensile load required to dislodge the artificial crowns from tooth preparations with an Instron testing machine.

RESULTS

Analysis of forces with parametric analysis of variance and Tukey's Studentized Range (HSD) disclosed a statistically significant difference for both luting cement and finishing burs (p < 0.001). A statistically significant interaction effect (p < 0.001) was also found. The greatest retention value (372.9 N) was for tooth preparations refined with carbide burs and cemented with Panavia-EX cement. However, the least retention value (201.6 N) was for tooth preparations completed with finishing burs and luted with zinc phosphate cement.

CONCLUSIONS

Significant differences were found among all three cements for finishing burs. However, there was a difference only between Panavia-EX cement and the other two cements for tungsten carbide burs. For diamond rotary instruments, zinc phosphate cement was significantly different from glass ionomer and Panavia-EX cements.

The orthodontic-periodontal connection in implant site development

Implant-supported restorations have become an established treatment modality, well accepted by patients and clinicians. Regaining function is now routinely expected, and the focus of patient demand has shifted to aesthetics. Aesthetic restoration of the partially edentulous anterior maxilla can be particularly challenging. The learning objective of this article is to present a comprehensive multidisciplinary treatment protocol, developed to establish a foundation for optimal aesthetics in implant therapy, with emphasis on the role of orthodontics in the enhancement of deficient components. Periodontal orthodontics is used to increase the vertical osseous dimension and preserve papillae; restorative orthodontics optimizes the site through manipulation of supragingival restorative space. Two clinical cases are utilized to illustrate the principles and implementation of this protocol.

Oral terbutaline after parenteral tocolysis: a randomized, double-blind, placebo-controlled trial

OBJECTIVE

Our purpose was to determine whether oral terbutaline, used after successful intravenous tocolysis, will prolong pregnancy and prevent recurrent preterm labor.

STUDY DESIGN

After successful intravenous tocolysis, 203 women with preterm labor at 24 weeks' to 34 weeks 6 days' gestation were randomized to terbutaline (5 mg orally, every 4 hours) or placebo until 37 weeks' gestation. Women with recurrent preterm labor were treated with intravenous magnesium sulfate; if tocolysis was successful, they continued with the initial study medication. The primary outcome was the percentage delivered of their infants within 1 week of beginning oral tocolytic therapy. Latency, recurrent preterm labor, and maternal and neonatal outcomes were also assessed.

RESULTS

Pregnancy outcome data were available in 200 women. There were no differences seen between the two groups in the incidence of delivery at 1 week (18% vs 24%, 95% confidence interval 0.44 to 1.29). In addition, there were no differences regarding median latency, mean gestational age at delivery, or the incidence of recurrent preterm labor (20% vs 16%, 95% confidence interval 0.64 to 2.71). Post hoc evaluation of 96 women enrolled before 32 weeks' gestation suggested pregnancy prolongation with maintenance oral terbutaline (p < 0.01).

CONCLUSIONS

Maintenance oral terbutaline therapy initiated at 24 weeks' to 34 weeks 6 days' gestation after successful parenteral tocolysis is not associated with pregnancy prolongation or a reduction in the incidence of recurrent preterm labor.

Immediate loading of bilaterally splinted titanium root-form implants in fixed prosthodontics--a technique reexamined: two case reports

A load-free healing period has been advocated as a prerequisite to achieving osseointegration. This article reports two cases in which immediate loading of a specially designated additional, or "expendable," set of titanium root-form implants was successfully utilized to support provisional fixed restorations in the maxilla and the mandible. This immediate-loading protocol is suggested as a reliable adjunctive therapeutic modality for offering implant patients access to fixed interim restorations during the healing phase of the primary fixtures. Another advantage of this approach is that it provides protection from potential transmucosal overload of the primary implants as well as any sites undergoing osseous regenerative procedures.

Maternal morbidity and mortality in 442 pregnancies with hemolysis, elevated liver enzymes, and low platelets (HELLP syndrome)

OBJECTIVE

Our purpose was to describe the incidence and effects of serious obstetric complications on maternal outcome in pregnancies complicated by HELLP syndrome.

STUDY DESIGN

A prospective cohort study was performed on 442 pregnancies with HELLP syndrome managed at this center from August 1977 through July 1992.

RESULTS

Of 437 women who had 442 pregnancies with HELLP syndrome; 309 (70%) of the cases occurred ante partum and 133 (30%) post partum; 149 (11%) developed at < 27 weeks and 80 (18%) at term. Maternal mortality was 1.1% (five patients). Serious maternal morbidity included disseminated intravascular coagulation (21%), abruptio placentae (16%), acute renal failure (7.7%), pulmonary edema (6%), subcapsular liver hematoma (0.9%), and retinal detachment (0.9%). Fifty-five percent of patients required transfusions with blood or blood products, and 2% required laparotomies for major intraabdominal bleeding. Abruptio placentae was strongly correlated with the development of disseminated intravascular coagulation (p < 0.0001), acute renal failure (p < 0.001), and pulmonary edema (p < 0.01). Moreover, there was a strong association between pulmonary edema and acute renal failure (p < 0.0001). There were no differences in laboratory findings between HELLP syndrome before and after delivery; however, women with postpartum HELLP syndrome had significantly higher incidences of pulmonary edema and renal failure.

CONCLUSION

HELLP syndrome is associated with serious maternal morbidity, especially when it arises in the postpartum period.

The role of orthodontic extrusive remodeling in the enhancement of soft and hard tissue profiles prior to implant placement: a systematic approach to the management of extraction site defects

A classification scheme that systematizes the wide range of regenerative potential of common extraction site topographies is presented. Within this system, the parameters for immediate implant placement and preliminary ridge augmentation are discussed. In addition, a new adjunctive role for orthodontic extrusion is introduced. This approach is intended to manipulate "hopeless" teeth to modify their local defect environments, thereby enhancing the predictability of subsequent implant placement at those sites.

Levy-Reid hypothesis

The inconsistencies in the research findings looking to test for the Levy-Reid hypothesis on the relationship between hand posture and laterality have been accounted for in various ways. Some authors (Cohen, 1991; Weber and Bradshaw, 1981) have suggested that existing methodologies for experimentally establishing laterality of language functioning are unreliable. To overcome this constraint, we have taken Halsey, Blauenstein, Wilson, and Wills' (1980) suggestion of using cerebrovascular accident (CVA) patients in which laterality of expressive speech has been established incontrovertibly. We examined 74 CVA subjects assessing hand posture, handedness, and side of stroke. Our findings lend support for Levy-Reid, nevertheless further examination of the hypothesis using a cross-cultural sample underscores the impact education and culture have on hand posture.

Esthetic considerations in adult orthodontic treatment

The use of orthodontics to correct dental malocclusions and enhance the cosmetic appearance in the adult patient is evaluated. A review of the current literature highlights the latest materials and techniques in adult orthodontics. A categorization of the diagnostic variables involved and the therapeutic options available is presented. Alignment, sagittal, vertical, transverse, and soft-tissue discrepancies, as well as future considerations, are discussed.

Effectiveness of piracetam in cortical myoclonus

Twenty-one patients with disabling spontaneous, reflex, or action myoclonus due to various causes, who had shown apparent clinical improvement on introduction of piracetam, entered a placebo-controlled double-blind crossover trial of piracetam (2.4-16.8 g daily). All but one patient had electrophysiological evidence of cortical myoclonus. Patients were randomly allocated to a 14-day course of piracetam followed by identical placebo, or placebo followed by piracetam. Nineteen patients received piracetam/placebo in addition to their routine antimyoclonic treatment (carbamazepine, clonazepam, phenytoin, primidone, sodium valproate, or tryptophan plus isocarboxazid, alone or in combination) and two received piracetam/placebo as monotherapy. All patients were rated at the end of each treatment phase using stimulus sensitivity, motor, writing, functional disability, global assessment, and visual analogue scales. Ten of the 21 patients had to be rescued from the placebo phase of the trial because of a severe and intolerable exacerbation of their myoclonus. No patients required rescue from the piracetam phase of the double-blind trial. When the 21 patients were considered together, there was a significant improvement in motor, writing, functional disability, global assessment, and visual analogue scores during treatment with piracetam compared with placebo. The total rating score also improved significantly with piracetam, by a median of 22%. Piracetam, usually in combination with other antimyoclonic drugs, is a useful treatment for myoclonus of cortical origin.

Resolution of radiographic abnormalities with ursodeoxycholic acid therapy of primary sclerosing cholangitis

Ursodeoxycholic acid therapy has shown encouraging results in relieving symptoms and decreasing liver biochemical abnormalities in patients with primary sclerosing cholangitis. However, established biliary strictures are generally considered irreversible. A case of primary sclerosing cholangitis with extensive intrahepatic biliary as well as pancreatic duct strictures that resolved to near normal on ursodeoxycholic acid therapy is reported. The implications of these findings are discussed.

[Specificity of visual evoked potential alterations in Alzheimer's disease]

We have studied visual evoked potentials (VEP) in four groups: healthy young and aged subjects and aged patients suffering from depression or Alzheimer's disease (AD). In the flash modality, peak IV delay in AD patients as compared to aged controls corresponded to lengthened III-IV interlatency (IL). When AD and depressed patients were compared, peak IV delay in the former did not reach significance. Normal aging resulted in delayed peaks II and III, without IL modification. In the pattern reversal modality, no difference was observed between AD patients and aged, healthy or depressed controls. Aging delayed peaks P50 to P180. The abnormality exhibited by AD patients was specific to this group. However, the lack of significant difference between AD and depressed groups argues against the ability of VEP to differentiate those conditions.

Development and application of oligonucleotide probes for identification of Lactococcus lactis subsp. cremoris

Lactococcus lactis subsp. cremoris is of considerable interest to the dairy industry, which relies upon the few available strains for the manufacture of cheddar cheese free of fermented and fruity flavors. The subspecies cremoris differs from related subspecies by the lack of a few phenotypic traits. Our purpose was to identify unique rRNA sequences that could be used to discriminate L. lactis subsp. cremoris from related subspecies. The 16S rRNAs from 13 Lactococcus strains were partially sequenced by using reverse transcriptase to identify domains unique to L. lactis subsp. cremoris. All five strains of the subspecies cremoris had a unique base sequence in a hypervariable region located 70 to 100 bases from the 5' terminus. In this region, all L. lactis subsp. lactis biovar diacetylactis strains examined had a sequence identical to that of L. lactis subsp. lactis 7962, which was different from other strains of the subspecies lactis by only one nucleotide at position 90 (Escherichia coli 16S rRNA structural model) (J. Brosius, J. L. Palmer, J. P. Kennedy, and H. F. Noller, Proc. Natl. Acad. Sci. USA 75:4801-4805, 1978). Oligonucleotide probes specific for the genus Lactococcus (212RLa) and for the subspecies cremoris (68RCa) were synthesized and evaluated by hybridization to known rRNAs as well as fixed whole cells. Efficient and specific hybridization to the genus-specific probe was observed for the 13 Lactococcus strains tested. No hybridization was seen with the control species. All five strains of the subspecies cremoris hybridized to the subspecies-specific probe.

Quantitative EEG and neuropsychological effects of piracetam and of the association piracetam-lecithin in healthy volunteers

The electroencephalographic (EEG) and neuropsychological effects of single, oral doses or piracetam (800-6,400 mg) and of its association with lecithin (4,800 mg and 25 g, respectively) were investigated in two groups of healthy volunteers in placebo-controlled studies. The EEG was quantified by power spectral analysis; both parametric and nonparametric procedures were applied to process the EEG and neuropsychological data statistically. The drug plasma concentration was assessed (gas chromatography) in concomitance with the EEG and neuropsychological measurements. Piracetam was found to elicit systematic EEG effects, namely a decrease in the low-frequency components and an increase in the power of the 8.5- to 12.0-Hz and of the fast-frequency components. The EEG modifications were restricted to the anterior scalp areas; its detection by means of parametric statistics was conditioned by the relevant individual variability and was inferred resting upon a number of criteria (indication at nonparametric tests, topography, consistency across subjects, replicability, etc). The correlation between EEG changes and drug plasma concentration was ambiguous, and the compound was not found to be effective on any of the neuropsychological variables considered. The study exemplifies some of the methodological problems in quantitative pharmaco-EEG and emphasizes the relevance of topography and replication.

The efficiency of various solvents in the extraction of chemical mutagens from living tissues: a comparative study

The aim of this study is to find out the best solvent to be used in extraction of chemical pollutants from living organisms. Ethanol, benzene, chloroform, pentane, 1,4-dioxan, acetone, cyclohexane and ether were used in extraction of shrimp and clam samples collected from a Fahaheel site. The tissue extracts were tested for their mutagenic activity using E. coli and Salmonella on tester strains. The results revealed that ethanol was more efficient than other solvent in extraction of chemical mutagens concentrated in clams and shrimps.

[The treatment of the tumors by hyperthermia (author's transl)]

This paper is a review of the biological effects of hyperthermia and of their mechanisms. A great interest has been stimulated for the treatment of the tumors by hyperthermia alone or associated to chemo and radiotherapy. The clinical application needs an accurate control of the temperature which raises difficult technical problems.

Infection of intervertebral discs after operation

Infection of the intervertebral space is a rare complication of operation on the disc (Ford and Key 1955). It occurred in five cases in a series of 650 operations for lumbar disc protrusion done by two of the authors of this paper--an incidence of 0-8%. Symptoms began between seven and twelve days after operation. After initial relief of the original sciatic pain, the patients developed severe back pain and muscle cramps in the legs. Straight-leg raising became much more limited than before operation. The erythrocyte sedimentation rate was raised in all cases. The diagnosis was confirmed by rescreening the Myodil, when an indentation was seen opposite the intervertebral space from which the disc had been excised. Early removal of infected material from the disc space resulted in complete relief of pain and cure of the infection.