Brånemark System® Wide Platform Implants for Single Molar Replacement: Clinical Evaluation of Prospective and Retrospective Materials

BACKGROUND

The use of oral implants for single tooth replacement has become a predictable treatment modality. As single tooth loss is most common in posterior areas of the jaws, the use of the protocol is of specific interest in those regions. New implant designs aimed at this purpose have also been introduced.

PURPOSE

The aim of the study was to present the outcomes for wide diameter implant treatment when being used in posterior areas of the jaws.

MATERIALS AND METHODS

This paper presents the 3-year results of a prospective multicenter study (three clinics; n = 38 implants) and the 1-year results from a retrospective multicenter study (two clinics; n = 20 implants) on wide diameter implants for single molar replacement. Based on the hypothesis that dense bone in posterior mandibles would benefit from careful surgery and longer remodeling time, the influences of surgical technique and healing time on implant success and bone resorption were particularly addressed.

RESULTS

The outcome demonstrated a good predictability for Brånemark System Wide Platform implants, at least short term, when used as single molar support (prospective group cumulative success rate [CSR] = 92% after 3 years; retrospective group CSR = 95% after 1 year). The increased mechanical strength of the wide platform implant/abutment complex also turned out to be important for mechanical stability.

CONCLUSIONS

The study indicated that it was important to carefully perform surgery in posterior mandibles in order to preserve and optimally use the existing dense bone. It was suggested that from bone healing and remodeling aspects, posterior mandibles may be more demanding to handle than corresponding areas of maxillae.

Correlation between translation efficiency and outcome of combination therapy in chronic hepatitis C genotype 3

Combination therapy with interferon-alpha (IFN-alpha) and ribavirin (RBV) in chronic hepatitis C demonstrates the best responses against hepatitis C virus (HCV) of genotype 3. Still, it has proven to be ineffective in 20-30% of patients infected with this genotype. In the present study, we analysed the translation efficiency mediated by the internal ribosome entry site (IRES) region in HCV genotype 3 genomes isolated from sustained responders (SR) and non-responders (NR), assuming that this may influence the outcome of treatment. Pretreatment isolates of genotype 3 from 22 individuals (15 SR, seven NR) were selected for such analyses. The IRES region [nucleotide (nt) 1-407] was cloned into a dual luciferase vector and IRES activity assessed following transfection into various cell lines. Low relative translation efficiency was observed for IRES elements derived from SR patients, whereas those of NR patients showed significantly greater translation efficiency (29.7 +/- 13 vs 69.4 +/- 22; P < 0.01). Subsequently, the effect of IFN-alpha plus RBV on IRES-driven translation in vitro was determined. A greater suppressive effect was observed on IRES activity isolated from seven SR patients, when compared with seven NR patients. In conclusion, IRES efficiency in vitro correlated with treatment response for HCV genotype 3. Further studies are warranted to investigate whether IRES efficiency in vitro, or sequence motifs associated with IRES efficiency, will be worthwhile to explore as prognostic tools for other HCV genotypes in the treatment of chronic HCV infection.

The implant-supported telescopic prosthesis: a biomechanical analysis

This in vitro project investigated load transfer through screw-retained telescopic prostheses. Three Brånemark System implants incorporating strain gauges were embedded in an aluminum block. Telescopic prostheses that included 1 mesial and 1 distal cantilever were fabricated over 1 central EsthetiCone and 2 Ti-Adapt abutments. The buffering capacity of the cement in a combined screw-retained/cemented prosthesis was studied. The degree of misfit of the prostheses could be adjusted by applying shims of various thicknesses under the EsthetiCone. Load distribution was measured while a 50-N load was applied in turn over each implant and each cantilever. The results showed that tightening the central prosthetic screw widened the load distribution. The cement accommodated misfits between the layers of the telescope, significantly reducing bending moments on some supporting implants. The system exhibited a degree of tolerance to misfit and can provide a versatile prosthodontic option.

Tilting of posterior mandibular and maxillary implants for improved prosthesis support

Rehabilitation of atrophied edentulous arches with endosseous implants in the posterior regions is often associated with anatomic problems such as jaw shape and location of the mental loop, mandibular canal, and maxillary sinuses. The purpose of this investigation was to modify the method for implant placement in the posterior part of the jaws to extend fixed implant-connected prostheses further distally, and to reduce the length of cantilevers in complete-arch prostheses without transpositioning the mandibular nerve or performing bone grafting in the maxilla. Forty-seven consecutive patients were treated with implants (25 patients/36 mandibular implants, 22 patients/30 maxillary implants) placed in tilted positions. They were followed a mean of 40 months (mandibles) and 53 months (maxillae). In the mandible, implants close to the mental foramina were tilted posteriorly approximately 25 to 35 degrees. In the maxilla, the posterior implants were placed close to and parallel with the sinus walls and were titled anteriorly/posteriorly approximately 30 to 35 degrees. Patients gained a mean distance of 6.5 mm of prosthesis support in the mandible and 9.3 mm in the maxilla, as a result of implant tilting. There were no implant failures in mandibles. The cumulative success rates in the maxilla at 5 years were 98% for tilted implants and 93% for non-tilted implants. Paresthesias of the mental nerve were observed on 4 sides during the first 2 to 3 weeks after implant placement. Analysis of the load distribution in one mandibular case showed no significant difference between tilted and the non-tilted implants, and the improved prosthesis support was confirmed. Satisfactory medium-term results concerning osseointegration and significant extension of prosthesis support show that the method can be recommended. This technique may allow for longer implants to be placed with improved bone anchorage.

Effects of prenatal exposure to tributyltin and trihexyltin on behaviour in rats

The effects of prenatal administration of tributyltin (1 and 5 mg/kg) and trihexyltin (5 mg/kg) upon the development and behavioural repertoire of rats were studied. The dose levels were selected so as not to induce maternal toxicity. No consistent delay upon occurrence of various maturation markers of the organotin-treated offspring was seen. As adults the tributyltin-treated offspring showed considerable hyperactivity following the initial habituation whereas the trihexyltin-treated offspring showed hyperactivity to a lesser degree. In the spatial learning tasks applied, the radial arm maze and the circular swim maze, tributyltin-treated rats demonstrated a clearly retarded aquisition of the radial arm maze task whereas trihexyltin-treated rats performed as well as the control rats; no differences were obtained in the swim maze task. The tributyltin-treated offspring showed a drastic potentiation of d-amphetamine-induced hyperactivity, whereas trihexyltin treatment induced only a marginal increase.

Plant-derived neurotoxic amino acids (beta-N-oxalylamino-L-alanine and beta-N-methylamino-L-alanine): effects on central monoamine neurons

In the present study the subacute effects of beta-N-oxalylamino-L-alanine (BOAA) and beta-N-methylamino-L-alanine (BMAA) on CNS monoamine neurons in rats were investigated following intracisternal injections or local intracerebral administration into substantia nigra. In vitro effects of BOAA and BMAA on high-affinity synaptosomal uptake of dopamine (DA), noradrenaline (NA), and serotonin (5-HT) were also examined. Intracisternal administration of BMAA decreased NA levels in hypothalamus, whereas no effects were seen on DA or 5-HT levels. Following intranigral injections of BOAA, NA levels tended to decrease in several regions, whereas the DA levels and the levels of DA metabolites were unaffected in all regions analyzed. Loss of tyrosine hydroxylase (TH) immunoreactivity in the intranigral injection sites and the presence of TH-immunoreactive pyknotic neurons near the borders of the injection sites were observed following both BOAA and BMAA treatments. Furthermore, substance P-immunoreactive terminals in substantia nigra pars reticulata were also found to have disappeared within the lesioned area following either BOAA or BMAA injections. Incubations with both BOAA and BMAA (10(-5) M) reduced high-affinity [3H]NA uptake in cortical synaptosomes to 69% and 41% of controls, respectively, whereas the striatal high-affinity [3H]DA uptake and the cortical high-affinity [3H]5-HT uptake were unaffected by BOAA or BMAA. The results demonstrate that both BOAA and BMAA can affect central monoamine neurons, although the potency and specificity of these substances on monoamine neurons when administered acutely into cerebral tissue or liquor cerebri seem to be low. However, the in vitro studies indicate selective effects of both compounds on NA neurons in synaptosomal preparations.

Successful treatment of therapy-resistant pancreatic cholera with human leucocyte interferon

The pancreatic cholera syndrome is a serious and potentially fatal disease found in patients with endocrine pancreatic tumours and ganglioneuromas. Two patients with therapy-resistant pancreatic cholera syndrome were successfully treated with human leucocyte interferon given intramuscularly in a dose of 3 X 10(6)-6 X 10(6) IU per day. This produced a reduction in stool volume and plasma vasoactive intestinal polypeptide (VIP) within 3-5 days of the start of treatment. Tumour mass decreased in one of the patients after 3 months of treatment but some tumour tissue remained after 15 months' observation, although circulating concentrations of VIP are normal. The mechanisms of action of interferon are not known but a direct inhibition of tumour-cell hormone production and perhaps of tumour-cell proliferation might account for the rapid clinical response.

Development of a new inventory assessing memories of parental rearing behaviour

A new inventory (EMBU) to assess the own memories of parental rearing behaviour was constructed. EMBU is comprised of 81 questions grouped in 15 subscales and two additional questions referring to consistency and strictness of parental rearing behaviour to be answered in a four-step scale for the father and for the mother separately. The subscales cover rearing practices as for eexample overinvolment, affection, overprotectiveness, guilt engendering, rejection. 152 healthy subjects of both sexes (108 males and 44 females) completed the inventory. The item analysis showed that both parents attained similar scores in about half of the questions. Fathers scored higher in items referring to strictness, punishment and a low degree of involvement whereas mothers scored higher in items referring to involvement and affection. A principal component factor analysis permitted the hypothesized subscales to be identified. An analysis of the internal consistency of the subscales revealed a high frequency of significant internal correlations. A principal component factor analysis of the total scores of the 15 subscales allowed three main dimensions of rearing behaviour to be identified quite close to those reported in similar studies in the literature where other scales had been used.

Perceived parental behaviour and psychogenic needs

A new inventory aimed at the assessment of perceived parental rearing practices (EMBU) and an inventory aimed at assessing psychogenic needs (CMPS) were completed by 152 healthy subjects of both sexes (108 males and 44 females). The series was comprised of 73 conscripts, 57 medical students, 15 vocational therapy students and 7 staff personnel who were 17-46 years old. Several significant correlations were found between dimensions of parental rearing behaviour and personality characteristics, most of them being consistent with earlier findings by other authors. Although statistically significant, the correlation coefficients were mostly low, leaving a large amount of unexplained variance. The findings of this study support the general assumption that the perception of parental rearing practices is an important factor in the shaping of personality make-up but that other, still unexplored factors might have an even greater importance in the determination of habitual personality characteristics.

Interprofessional communicability and reliability of the Comprehensive Psychopathological Rating Scale (CPRS) as assessed by video-taped interviews

Five raters: two experienced psychiatrists, two psychologists (one acquainted with the use of the scale and one new to it) and an untrained social worker, participated in training sessions in the use of the CPRS. Videotaped interviews were used for assessing the level of inter-rater reliability and the communicability of the CPRS to unexperienced raters. As in previous studies, it was found that the CPRS is easily communicable and that a very satisfactory level of agreement among raters can be achieved.

The concentration of peroxidase in normal and adenomatous human thyroid tissue with special reference to patients with Pendred's syndrome

The peroxidase content in the thyroids from two patients with Pendred's syndrome (abnormal discharge of iodide from the thyroid after perchlorate administration, congenital deafness and sporadic goitre) was investigated and compared to the content in 11 patients with normal thyroids, 22 patients with adenomatous goitres and 12 patients with diffuse toxic goitres.

The results indicate that the peroxidase contents in the patients with Pendred's syndrome are not decreased as compared to normal or nodular thyroid tissue. The results are discussed with regard to the cause of an intrathyroidal iodide organification defect. It is suggested that patients with Pendred's syndrome may have a defective hydrogen peroxide producing system.