Biomedical subjects

R A Howell

Publications and source records attributed to R A Howell.

At least 19 recordsLinked to original sources

PubMed1996

Prosthetic rehabilitation of the atrophic maxilla using pre-implant surgery and endosseous implants.

Pre-implant surgery was carried out in 20 patients with advanced atrophy of the edentulous maxilla, using autogenous bone grafts. Endosseous implants were placed after the initial healing period and these were used to retain removable overdentures. Patients were observed for up to 5 years with 15 of the 105 implants placed being lost and two remaining as sleepers. The resulting implant success rate was 84%. Three patients had to return to conventional dentures while the remaining 17 expressed a high degree of satisfaction with their implant retained prostheses. Pre-implant surgery successfully extends the scope for implant therapy by providing sufficient bone for implant placement. The survival rate of implants in these cases appears promising up to 3 years, although further data is required to confirm the effectiveness of this treatment in the long term. Implant retained overdentures are able to successfully restore both oral function and facial form. The rehabilitation of the atrophic, edentulous maxilla remains difficult and complex, even when using pre-implant surgery and implant retained prostheses.

Adult↗

PubMed1996

Familial temporal lobe epilepsy: a common disorder identified in twins.

We describe a new syndrome of familial temporal lobe epilepsy in 38 individuals from 13 unrelated white families. The disorder was first identified in 5 concordant monozygotic twin pairs as part of a large-scale twin study of epilepsy. When idiopathic partial epilepsy syndromes were excluded, the 5 pairs accounted for 23% of monozygotic pairs with partial epilepsies, and 38% of monozygotic pairs with partial epilepsy and no known etiology. Seizure onset for twin and nontwin subjects usually occurred during adolescence or early adult life. Seizure types were simple partial seizures with psychic or autonomic symptoms, infrequent complex partial seizures, and rare secondarily generalized seizures. Electroencephalograms revealed sparse focal temporal interictal epileptiform discharges in 22% of subjects. Magnetic resonance images appeared normal. Nine affected family members (24%) had not been diagnosed prior to the study. Pedigree analysis suggested autosomal dominant inheritance with age-dependent penetrance. The estimated segregation ratio was 0.3, indicating an overall penetrance of 60% assuming autosomal dominant inheritance. The mild and often subtle nature of the symptoms in some family members may account for lack of prior recognition of this common familial partial epilepsy. This disorder has similarities to the El mouse, a genetic model of temporal lobe epilepsy with a major gene on mouse chromosome 9, which is homologous with a region on human chromosome 3.

Adolescent↗

PubMed1996

Suggestion of a major gene for familial febrile convulsions mapping to 8q13-21.

Febrile convulsions affect 2 to 5% of all children under the age of 5 years. These convulsions probably have a variety of causes, but a genetic component has long been recognised. A large and remarkable family is described in which febrile convulsions appear to result from autosomal dominant inheritance at a single major locus. A gene for febrile convulsions was excluded from regions of previously mapped epilepsy genes and extension of exclusion mapping, using microsatellite markers, to the entire genome implied that a locus on chromosome 8q13-21 may be involved. Linkage analysis of markers on chromosome 8 gave a multipoint lod score of 3.40, maximised over different values of penetrance and phenocopy rate, for linkage between the gene for febrile convulsions and the region flanked by markers D8S553 and D8S279. This lod score was calculated assuming the disease has a penetrance of 60% and a phenocopy rate of 3%. Although there was no indication of linkage other than to markers on chromosome 8, linkage remains suggestive rather than significant because of the maximisation procedure applied. The support for linkage involving a major gene, as opposed to an alternative hypothesis of a complex inheritance pattern, relied upon the assumption of low penetrance.

Adolescent↗

PubMed1995

Prosthetic management of the atrophic mandible using endosseous implants and overdentures: a six year review.

This paper presents the treatment results and experiences gained from a retrospective study of patients treated with the IMZ osseo-integrated implant system and mandibular overdentures. Patients experiencing problems wearing conventional dentures were assessed by the implant team and 65 cases were treated with 154 endosseous implants placed in the edentulous mandible. Two to four implants were placed in each case and in addition some patients have had augmentation of the mandible with hydroxyapatite. The definitive mandibular prostheses were supported by both implants and the residual ridges. A variety of retention systems were utilised, which included different types of bar and clip, stud attachments, and magnets. The patients have been followed up regularly and evaluated after periods of between one and six years. Six implants have failed over this time resulting in a success rate of over 96%. Most patients expressed a high degree of satisfaction with their new overdentures. There was, however, a considerable burden of maintenance care required for the patient group examined. The findings demonstrate that implant retained overdentures offer a highly effective means of oral rehabilitation for the atrophic mandible, restoring both oral function and facial form.

Adult↗

PubMed1995

Autosomal dominant rolandic epilepsy and speech dyspraxia: a new syndrome with anticipation.

We describe a family of 9 affected individuals in three generations with nocturnal oro-facio-brachial partial seizures, secondarily generalized partial seizures, and centro-temporal epileptiform discharges, associated with oral and speech dyspraxia and cognitive impairment. The speech disorder was prominent, but differed from that of Landau-Kleffner syndrome and of epilepsy with continuous spike and wave during slow-wave sleep. The electroclinical features of this new syndrome of autosomal dominant rolandic epilepsy resemble those of benign rolandic epilepsy, a common inherited epilepsy of childhood. This family shows clinical anticipation of the seizure disorder, the oral and speech dyspraxia, and cognitive dysfunction, suggesting that the genetic mechanism could be expansion of an unstable triplet repeat. Molecular studies on this syndrome, where the inheritance pattern is clear, could also be relevant to identifying a gene for benign rolandic epilepsy where anticipation does not occur and the mode of inheritance is uncertain.

Adult↗

PubMed1994

Phenotypic expression of benign familial neonatal convulsions linked to chromosome 20.

OBJECTIVES: To determine whether the syndrome of benign familial neonatal convulsions in a large family was linked to markers on chromosome 20q and to study the seizure patterns in affected individuals. DESIGN: A clinical and molecular biologic study of a single large family in which the probands were identical twins with benign familial neonatal convulsions. PATIENTS: Thirteen living affected family members and 27 living unaffected family members were evaluated. RESULTS: Multipoint linkage analysis with use of the chromosome 20q markers CMM6 and RMR6 gave a maximum lod score of 3.13 at theta = 0.063, indicating linkage in this family. Of the 13 affected members, 10 had known neonatal seizures. Four subjects had febrile seizures, of whom only two had known neonatal seizures. Two members had afebrile seizures later, one of whom had not previously suffered neonatal or febrile seizures. CONCLUSION: The phenotypic heterogeneity in this family, with an epilepsy syndrome determined by a single gene, was striking. This suggests that molecular genetic approaches to the common forms of idiopathic epilepsy, involving patients with clinically similar phenotypes from unrelated families, may be inappropriate.

Chromosomes, Human, Pair 20↗

PubMed1994

Interictal language fluency in temporal lobe epilepsy.

Mild language production difficulties, particularly in confrontation naming, have been documented previously in patients with left temporal lobe epilepsy (LTLE). These difficulties, however, do not seem to be reflected in the conversational speech of these patients. In order to compare speech fluency in patients with left and right temporal lobe epilepsy (RTLE) experimentally, we studied global pause-to-speech ratios in patients with unilateral temporal lobe epilepsy, using cases with primary generalized epilepsy (PGE) as controls. We hypothesized that left-sides cases would exhibit longer pause durations than right-sided cases. Speech samples were elicited by asking subjects to describe five different New Yorker cartoons, with three repetitions of each description. Phonation was converted to graphic output, and pauses between 200 ms and 4000 ms were summated and divided by total phonation time. This measure did not discriminate significantly between the groups, although the LTLE group tended to pause longer than the RTLE or PGE groups. Increased variability in pause duration in the LTLE group during cycle 1 suggested that some individuals with LTLE are vulnerable to disruption when planning demands are high. A post hoc correlational analysis showed that variation in fluency was primarily explained by orthographically-based lexical retrieval, suggesting that individual differences in fluency are related to limitations in a high-level capacity relevant to the production of speech. It is unlikely that such limitations are specific to LTLE.

Adult↗

PubMed1993

Twin birth is not a risk factor for seizures.

There is a belief that perinatal factors are a major cause of epilepsy. We studied a community-based sample of twins, a group with a marked excess of adverse perinatal events. The observed number of non-twin siblings with seizures did not differ from that predicted by the age-specific cumulative incidence rate of seizures (4.2% at age 10 years) in the twins. The types of epilepsies in the twins were largely benign and self-limited and not those associated with brain damage. Zygosity, birth order, and birth weight did not predict affected status. Within affected sibships, the frequency of seizures in co-twins of dizygotic probands (9%) was not different from the frequency in non-twin siblings (12%) but was much less than the frequency in co-twins of monozygotic probands (38%; p < 0.001), reflecting a major genetic component to certain epilepsies. These data show that twins do not have an increased risk of seizures and strongly suggest that perinatal factors have little bearing on the etiology of the common epilepsies in the community.

Adolescent↗

PubMed1991

Reconstructive preprosthetic surgery. I. Anatomical considerations.

When considering preprosthetic surgery of the edentulous jaws, it is important that the clinician fully understands the anatomical consequences of reduction of the residual ridges. Based on a classification of the edentulous jaws, changes in the relationship of the jaws to each other, in muscle relations and function, in the oral mucosa and in facial morphology have been measured relative to the stage of resorption of the edentulous jaws.

Humans↗

PubMed1991

Monitoring of Tübingen endosseous dental implants by glycosaminoglycans analysis of gingival crevicular fluid.

Glycosaminoglycans (GAG) in gingival crevicular fluid (GCF) samples were determined by cellulose acetate electrophoresis and densitometric scanning. Two GAG bands, hyaluronic acid and chondroitin-4-sulphate (C4S), were detected in GCF from implants, similar to the profile from teeth. High GCF volumes and GAG contents, notably C4S, may reflect postoperative alveolar bone responses, particularly resorption, at different stages of healing and function of successful implants. They may also indicate adverse tissue changes in failing implants. A comparison of crowned implants and matched teeth suggests that the periodontal ligament contributes to the GCF GAG profile. This may be a useful laboratory method of monitoring implants to detect adverse tissue responses at an early stage.

Adolescent↗

PubMed1989

The immediate or delayed replacement of teeth by permucosal intra-osseous implants: the Tübingen implant system. Part 2: Surgical and restorative techniques.

The previous paper emphasised the importance of case selection in determining success in the use of the Tübingen implant system. Adherence to strict clinical techniques has an equally important influence on implant success and failure. This paper describes the surgical and restorative techniques involved in the use of the Tübingen implant and comments on the authors' initial experiences with this system.

Aluminum Oxide↗

PubMed1989

The immediate or delayed replacement of teeth by permucosal intra-osseous implants: the Tübingen implant system. Part 1. Implant design, rationale for use and pre-operative assessment.

No single implant system is applicable to all clinical problems which may be treated with implants. Clinicians who wish to develop expertise in the field of dental implantology should decide which clinical situations they wish to treat with implants and then receive an appropriate level of instruction in the use of systems which have been shown, in refereed literature, to be successful in the treatment of such problems. The Tübingen implant system has been in clinical use for more than 13 years, following preliminary basic research and animal studies, and is supported by an extensive literature. It is applicable primarily to the immediate or delayed replacement of individual teeth which are subsequently to be restored with a post crown. It may also be used in other situations, such as in combination with bridge restorations. This is the first of two papers which describe in detail the range of applications, patient selection and assessment, and the surgical and restorative techniques involved in its use.

Adult↗

PubMed1988

A classification of the edentulous jaws.

A classification of the edentulous jaws has been developed based on a randomised cross-sectional study from a sample of 300 dried skulls. It was noted that whilst the shape of the basalar process of the mandible and maxilla remains relatively stable, changes in shape of the alveolar process is highly significant in both the vertical and horizontal axes. In general, the changes of shape of the alveolar process follows a predictable pattern. Such a classification serves to simplify description of the residual ridge and thereby assist communication between clinicians; aid selection of the appropriate surgical prosthodontic technique; offer an objective baseline from which to evaluate and compare different treatment methods; and help in deciding on interceptive techniques to preserve the alveolar process. An awareness of the pattern of resorption that takes place in various parts of the edentulous jaws, enables clinicians to anticipate and avert future problems.

Alveolar Process↗

PubMed1984