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Biomedical subjects

W M Jenkins

Publications and source records attributed to W M Jenkins.

At least 19 recordsLinked to original sources
PubMed2001

The reasons for extraction of permanent teeth in Scotland: a 15-year follow-up study.

AIMS: Although Scotland has the highest proportion of edentulous adults in the UK, the frequency of edentulousness has fallen by 21% during the last 20 years. This study, carried out in 1999, was designed to establish whether the reasons for tooth loss have also changed since 1984 when they were last determined. METHODS: The Scottish Dental Practice Board provided the names of every fourth dentist on its list among which 425 general dental practitioners were identified. They were asked to record permanent tooth extractions for 1 week, specifying the age, sex and dental attendance of patients who underwent extractions and the reasons for these extractions. 352 dentists took part: a response rate of 82.8%. RESULTS: The study confirmed that there has been a reduction in the number of extractions between 1984 and 1999: there were 25% fewer teeth extracted per patient and 30% fewer per dentist per week. From 0-20 years of age, orthodontics has replaced caries as the commonest reason for extraction and in all age groups over 20 years, caries has become the commonest reason in contrast to 1984 when periodontal disease was the principal reason in patients over 40 years old. CONCLUSIONS: Caries and its sequelae remain the most important cause of tooth loss throughout adult life in Scotland and, therefore, caries prevention and maintenance of restorations are of great importance at all ages.

Adolescent↗
PubMed2001

The reasons for the extraction of various tooth types in Scotland: a 15-year follow up.

OBJECTIVES: The aim of this survey was to investigate the reasons for extraction of the various tooth types in Scotland. This study replicated one which was undertaken 15 years earlier. A further aim, therefore, was to identify any changes in the frequency of extraction of each tooth type in the 15 years between the two studies. METHODS: The names of every fourth dentist on the list of the Scottish Dental Practice Board were obtained. Four hundred and twenty-five general dental practitioners were asked to record permanent tooth extractions for 1 week. Data requested for each extraction were: the patient's age, gender and dental attendance pattern, the type of tooth removed and the reason for the extraction. RESULTS: Three hundred and fifty-two dentists participated (a response rate of 82.8%). There were 25% fewer teeth extracted per patient and 30% fewer per dentist than in the 1984 study. In 1999, more teeth of most types were extracted from regular attenders whereas, in 1984, more teeth of all types were extracted from irregular attenders. Premolars and first and second molars were the tooth types most frequently extracted in both surveys. In 1999 premolars were the teeth most commonly removed below 21 years of age, accounting for 57.5% of extractions in this age range. Molars accounted for 33.8% of extractions in this age range compared with 52% in 1984. Overall, caries was found to be the principal reason for loss of all tooth types apart from lower incisors which were extracted mainly for periodontal reasons. However, below 21 years, 84.5% of premolar extractions were performed for orthodontic purposes. CONCLUSIONS: Over the last 15 years, the overall number of extractions has reduced and the proportion of extractions from regular attenders has increased. Proportionately more premolars and fewer molars were extracted from under-21-year-olds. This observation can be explained by an increase in orthodontic extractions or a decline in extractions for caries in this age group. However, when extractions from the population as a whole are considered, caries and its sequelae remains the principal reason for loss of all tooth types other than lower incisors which are extracted mainly for periodontal reasons.

Adolescent↗
PubMed2000

Effect of subgingival scaling during supportive therapy.

BACKGROUND, AIMS: This prospective study was designed to investigate the rôle of root débridement at 3 month intervals for patients with periodontitis whose disease had persisted following the completion of conventional periodontal treatment. METHODS: 39 maintenance patients with at least 4 pockets at least 4 mm deep were assigned to coronal scaling (CS) and subgingival scaling (SS) groups. Probing depths (PD), bleeding on probing (BOP) and relative attachment levels (RAL) were recorded at all eligible sites at baseline and 3, 6, 9 and 12 months later. Plaque index scores were recorded at the 12-month visit. At every visit, following data collection, both groups received a coronal scaling and the SS group, in addition, received a thorough subgingival débridement. In the CS group, subgingival débridement was performed only for 'loser' sites which inhibited loss of attachment > or = 2 mm relative to baseline values. Due to low compliance, only 31 patients completed the study. Thus, data analyses were carried out for 130 sites in 17 CS group patients and 146 sites in 14 SS group patients. RESULTS: During the course of the study, 21 loser sites were identified in each group, but the difference in proportion of loser sites between groups was not significant. Furthermore, although there was a trend toward PD reduction in both groups throughout the study, mean PD, RAL and BOP values were not significantly different from baseline values at any time point, and there were no significant differences between groups with respect to these variables. Mean plaque scores measured at the 12-month visit revealed no significant differences between groups. CONCLUSION: These findings call into question the value of performing repeated subgingival scaling at 3-month intervals for patients with persistent disease.

Adult↗
PubMed2000

Rate of loss of irradiated polyglactin 910 (Vicryl Rapide) from the mouth: a prospective study.

We aimed to find out how long irradiated polyglactin 910 (Vicryl Rapide) remained in the oral tissues and to investigate the effect of chlorhexidine mouthwash on absorption time and bacterial growth on sutures. Twenty-one volunteers each had two Vicryl Rapide sutures placed intraorally under local anaesthesia. Ten of these subjects used chlorhexidine mouthwash twice daily. After 7 days, one suture was removed to be cultured for aerobic and anaerobic bacteria. The other was monitored for time from insertion to loss. The median survival value was 3 days (range 1-13). The median number of days to suture loss was less in the chlorhexidine group (3, range 1-11) than in the control group (4, range 1-13) but this was not significant. There were no significant differences in aerobic and anaerobic counts between the two groups. Vicryl Rapide may be useful for intraoral use.

Adult↗
PubMed1998

Speech modifications algorithms used for training language learning-impaired children.

In this paper, the details of processing algorithms used in a training program with language learning-impaired children (LLI's) are described. The training program utilized computer games, speech/language training exercises, books-on-tape and educational CD-ROM's. Speech tracks in these materials were processed using these algorithms. During a four week training period, recognition of both processed and normal speech in these children continually increased to near age-appropriate levels. We conclude that this form of processed speech is subject to profound perceptual learning effects and exhibits widespread generalization to normal speech. This form of learning and generalization contributes to the rehabilitation of temporal processing deficits and language comprehension in this subject population.

Algorithms↗
PubMed1997

A primate model for studying focal dystonia and repetitive strain injury: effects on the primary somatosensory cortex.

BACKGROUND AND PURPOSE: Job-related repetitive strain injuries (RSIs) are increasing, and current treatment strategies often fail to return injured people to work. This study documented the neural consequences of using two different movement strategies for active, repetitive hand closing and opening. METHODS: Two owl monkeys were trained for 20 weeks to repetitively close a handpiece against an 80-g force (3-400 trials per day, training at 80%-90% accuracy). One monkey used a highly articulated hand-squeezing strategy, and the other monkey used a proximal arm-pulling strategy. Changes in motor performance were analyzed, and the electrophysiological maps of the hand representation on the trained primary sensory cortex (area 3b) were compared with those of untrained control animals and the untrained sides of the trained monkeys. RESULTS: The monkey using the articulated hand-squeezing strategy showed motor deterioration and dedifferentiation of the normally sharply segregated areas of the hand representation in area 3b. Mild degradation of the hand representation was measured in the monkey using the proximal arm-pulling strategy, but there was no motor dysfunction. CONCLUSION AND DISCUSSION: Attended, highly articulated, repetitive finger squeezing degrades the hand representation and interferes with motor control. A proximal, more variable repetitive strategy minimized the sensory degradation and preserved motor control. Restoring the hand representation may be a critical part of treatment for patients with chronic RSI and focal hand dystonia.

Animals↗
PubMed1996

Use-dependent alterations of movement representations in primary motor cortex of adult squirrel monkeys.

This study was undertaken to document plastic changes in the functional topography of primary motor cortex (M1) that are generated in motor skill learning in the normal, intact primate. Intracortical microstimulation mapping techniques were used to derive detailed maps of the representation of movements in the distal forelimb zone of M1 of squirrel monkeys, before and after behavioral training on two different tasks that differentially encouraged specific sets of forelimb movements. After training on a small-object retrieval task, which required skilled use of the digits, their evoked-movement digit representations expanded, whereas their evoked-movement wrist/forearm representational zones contracted. These changes were progressive and reversible. In a second motor skill exercise, a monkey pronated and supinated the forearm in a key (eyebolt)-turning task. In this case, the representation of the forearm expanded, whereas the digit representational zones contracted. These results show that M1 is alterable by use throughout the life of an animal. These studies also revealed that after digit training there was an areal expansion of dual-response representations, that is, cortical sectors over which stimulation produced movements about two or more joints. Movement combinations that were used more frequently after training were selectively magnified in their cortical representations. This close correspondence between changes in behavioral performance and electrophysiologically defined motor representations indicates that a neurophysiological correlate of a motor skill resides in M1 for at least several days after acquisition. The finding that cocontracting muscles in the behavior come to be represented together in the cortex argues that, as in sensory cortices, temporal correlations drive emergent changes in distributed motor cortex representations.

Animals↗
PubMed1996

Temporal processing deficits of language-learning impaired children ameliorated by training.

Children with language-based learning impairments (LLIs) have major deficits in their recognition of some rapidly successive phonetic elements and nonspeech sound stimuli. In the current study, LLI children were engaged in adaptive training exercises mounted as computer "games" designed to drive improvements in their "temporal processing" skills. With 8 to 16 hours of training during a 20-day period, LLI children improved markedly in their abilities to recognize brief and fast sequences of nonspeech and speech stimuli.

Child↗
PubMed1996

Language comprehension in language-learning impaired children improved with acoustically modified speech.

A speech processing algorithm was developed to create more salient versions of the rapidly changing elements in the acoustic waveform of speech that have been shown to be deficiently processed by language-learning impaired (LLI) children. LLI children received extensive daily training, over a 4-week period, with listening exercises in which all speech was translated into this synthetic form. They also received daily training with computer "games" designed to adaptively drive improvements in temporal processing thresholds. Significant improvements in speech discrimination and language comprehension abilities were demonstrated in two independent groups of LLI children.

Algorithms↗
PubMed1996

Experience-induced plasticity of cutaneous maps in the primary somatosensory cortex of adult monkeys and rats.

In a first study, the representations of skin surfaces of the hand in the primary somatosensory cortex, area 3b, were reconstructed in owl monkeys and squirrel monkeys trained to pick up food pellets from small, shallow wells, a task which required skilled use of the digits. Training sessions included limited manual exercise over a total period of a few hours of practice. From an early clumsy performance in which many retrieval attempts were required for each successful pellet retrieval, the monkeys exhibited a gradual improvement. Typically, the animals used various combinations of digits before developing a successful retrieval strategy. As the behavior came to be stereotyped, monkeys consistently engaged surfaces of the distal phalanges of one or two digits in the palpation and capture of food pellets from the smallest wells. Microelectrode mapping of the hand surfaces revealed that the glabrous skin of the fingertips predominantly involved in the dexterity task was represented over topographically expanded cortical sectors. Furthermore, cutaneous receptive fields which covered the most frequently stimulated digital tip surfaces were less than half as large as were those representing the corresponding surfaces of control digits. In a second series of experiments, Long-Evans rats were assigned to environments promoting differential tactile experience (standard, enriched, and impoverished) for 80 to 115 days from the time of weaning. A fourth group of young adult rat experienced a severe restriction of forepaw exploratory movement for either 7 or 15 days. Cortical maps derived in the primary somatosensory cortex showed that environmental enrichment induced a substantial enlargement of the cutaneous forepaw representation, and improved its spatial resolution (smaller glabrous receptive fields). In contrast, tactile impoverishment resulted in a degradation of the forepaw representation that was characterized by larger cutaneous receptive fields and the emergence of non-cutaneous responses. Cortical maps derived in the hemispheres contralateral to the immobilized forelimb exhibited a severe decrease of about 50% in the overall areal extent of the cutaneous representation of the forepaw, which resulted from the invasion of topographically organized cortical zones of non-cutaneous responses, and numerous discontinuities in the representation of contiguous skin territories. The size and the spatial arrangement of the cutaneous receptive fields were not significantly modified by the immobilization of the contralateral forelimb. Similar results were obtained regardless of whether the forelimb restriction lasted 7 or 15 days. These two studies corroborate the view that representational constructs are permanently reshaped by novel experiences through dynamic competitive processes. These studies also support the notion that subject-environment interactions play a crucial role in the maintenance of basic organizational features of somatosensory representations.

Animals↗
PubMed1996

Index of Oral Cleanliness (I.O.C.). A new oral hygiene index for use in clinical audit.

Although plaque control influences orthodontic treatment planning, treatment progress and outcome, current national orthodontic clinical audit software does not include an assessment of oral hygiene. This paper presents the development of the Index of Oral Cleanliness, a new simple rapid measure of oral hygiene, and describes its validation and reliability by comparison with the Silness and Loe plaque index in an unselected group of adolescents. It is concluded that the Index of Oral Cleanliness provides a valid quantitative method of scoring oral hygiene, with advantages for use in routine clinical practice.

Adolescent↗
PubMed1996

A primate genesis model of focal dystonia and repetitive strain injury: I. Learning-induced dedifferentiation of the representation of the hand in the primary somatosensory cortex in adult monkeys.

In this study we tested a neuroplasticity/learning origins hypothesis for repetitive strain injuries (RSIs), including occupationally induced focal dystonia. Repetitive movements produced in a specific form and in an appropriate behavioral context cause a degradation of the sensory feedback information controlling fine motor movements, resulting in the "learned" genesis of RSIs. Two adult New World owl monkeys were trained at a behavioral task that required them to maintain an attended grasp on a hand grip that repetitively and rapidly (20 msec) opened and closed over short distances. The monkeys completed 300 behavioral trials per day (1,100 to 3,000 movement events) with an accuracy of 80 to 90%. A movement control disorder was recorded in both monkeys. Training was continued until the performance accuracy dropped to below 50%. We subsequently conducted an electrophysiologic mapping study of the representations of the hand within the primary somatosensory (SI) cortical zone. The hand representation in the true primary somatosensory cortical field, SI area 3b, was found to be markedly degraded in these monkeys, as characterized by (1) a dedifferentiation of cortical representations of the skin of the hand manifested by receptive fields that were 10 to 20 times larger than normal, (2) the emergence of many receptive fields that covered the entire glabrous surface of individual digits or that extended across the surfaces of two or more digits, (3) a breakdown of the normally sharply segregated area 3b representations of volar glabrous and dorsal hairy skin of the hand, and (4) a breakdown of the local shifted-overlap receptive field topography of area 3b, with many digital receptive fields overlapping the fields of neurons sampled in cortical penetrations up to more than four times farther apart than normal. Thus, rapid, repetitive, highly stereotypic movements applied in a learning context can actively degrade cortical representations of sensory information guiding fine motor hand movements. This cortical plasticity/learning-based dedifferentiation of sensory feedback information from the hand contributes to the genesis of occupationally derived repetitive strain injuries, including focal dystonia of the hand. Successful treatment of patients with RSI will plausibly require learning-based restoration of differentiated representations of sensory feedback information from the hand.

Animals↗
PubMed1995

Remodelling of hand representation in adult cortex determined by timing of tactile stimulation.

The primate somatosensory cortex, which processes tactile stimuli, contains a topographic representation of the signals it receives, but the way in which such maps are maintained is poorly understood. Previous studies of cortical plasticity indicated that changes in cortical representation during learning arise largely as a result of hebbian synaptic change mechanisms. Here we show, using owl monkeys trained to respond to specific stimulus sequence events, that serial application of stimuli to the fingers results in changes to the neuronal response specificity and maps of the hand surfaces in the true primary somatosensory cortical field (S1 area 3b). In this representational remodelling stimuli applied asychronously to the fingers resulted in these fingers being integrated in their representation, whereas fingers to which stimuli were applied asynchronously were segregated in their representation. Ventroposterior thalamus response maps derived in these monkeys were not equivalently reorganized. This representational plasticity appears to be cortical in origin.

Animals↗
PubMed1994

Cervical marginal fit of proximal amalgam restorations.

This study investigated the relationship between the adaptation, apical location and gap width of the cervical margin of proximal amalgam restorations. Three hundred and seventeen proximal cervical margins were studied in 243 extracted teeth. The restorations were categorized as 'flush fitting'; 'small overhang', or 'large overhang', based on examination with a Cross calculus probe. After trimming the overhangs to make the restorations flush with the tooth surface, the gap width was measured. In addition, the location of the cavity margin was measured relative to the amelocemental junction (ACJ), and the data were further grouped according to whether the restoration finished apical to the ACJ, less than 1.5 mm coronal to it, or more than 1.5 mm coronal to it. All measurements were made with a Reflex Microscope. Analysis of variance with the Scheffé multiple range test indicated that: the mean gap width of large overhanging restorations was significantly greater than that of small overhanging or flush fitting restorations (P < 0.001); the mean gap width of restorations which finished on the root surface was significantly greater than that of those restorations which finished on the enamel surface at more than 1.5 mm from the ACJ (P < 0.002); and large overhanging restorations were located further apically than small overhanging restorations which were, in turn, located further apically than flush fitting restorations (P < 0.0001). Furthermore, discriminant analysis indicated that the location of the cervical margin had more influence on gap width than the presence of an overhang (R2 = 3.6%; P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1992

Vibrissal roughness discrimination is barrelcortex-dependent.

We have investigated the contribution of the neocortical vibrissal representation within the posterior medial barrel subfield (PMBSF) to the high performance levels obtained by rats in a complex roughness discrimination task mediated by vibrissal inputs. Nine binocularly occluded rats were trained in a two-choice roughness discrimination until they obtained the 85% correct response criteria. Subsequently, the PMBSF was localized by electrophysiological recordings and bilaterally ablated. The locus and extent of the cortical lesions were confirmed by histological analysis after additional training and testing. There was no evidence of task retention after the cortical lesion and barrelless rats were unable to obtain prelesion discriminative performance levels when stimulation was restricted solely to vibrissal cues. After extensive postlesion training, four of these rats were allowed to palpate the discriminanda with their forepaws. Under these conditions rats rapidly reached the 85% correct criterion once again. The present results indicate that the PMBSF is essential for complex tactile discrimination when sensory information is obtained through the vibrissae by active palpation. This deficit is specific for the vibrissal system, the PMBSF is not essential to solve the same tactile discrimination task when the source of the somatosensory information is provided by other non-vibrissal cutaneous sensory receptors.

Animals↗
PubMed1992

Development of a computerized system for simultaneous visual discrimination in rats.

In order to automate a simultaneous visual discrimination system, a Sutherland jumping-stand box was modified by adding two lateral alleys which connect the feeder compartment with the starting box. By means of a digital interface, this modified box was connected to an Apple IIe PC. A group of rats (n = 8) was trained. All subjects learned. Advantages relevant to the apparatus design, as well as the benefits derived from the automated procedure are discussed.

Animals↗
PubMed1992

Progressive improvement in discriminative abilities in adult owl monkeys performing a tactile frequency discrimination task.

1. Adult owl monkeys were trained to detect a difference in the frequency of sequentially applied tactile stimuli presented to a constant, restricted location on the glabrous skin of a single finger. Psychophysical performance functions and thresholds were determined on daily sessions over a 3- to 20-wk-long training period. 2. Thresholds for the trained digit progressively decreased from a 6- to 8-Hz difference to a 2- to 3-Hz difference relative to a 20-Hz standard. These thresholds were similar to those described for macaques and humans determined by the use of a two-alternative forced-choice procedure. 3. Six of the seven studied monkeys showed a continuously progressive improvement in performance with training. Early in the training period, the performance improved at about the same rate for all frequencies. Later in the training period, the performance for frequencies much greater than the comparison frequency improved sooner than did the performances for frequencies more similar to the comparison frequency. This resulted in an increase of the slope of the psychometric function near threshold. In a single monkey, no clear later-component improvements were recorded. 4. Analyses of performances using the theory of signal detection revealed a progressive increase in the measure of d' for all frequencies above threshold. 5. Some improvements in performance were also recorded when stimuli were applied on an adjacent digit, which was trained for 2 or 3 sessions spaced throughout the course of training. However, thresholds on these digits were always greater than those on the trained digit. These findings suggest that there are local changes generated by this training at somatotopically restricted regions of the central somatosensory nervous system. 6. It is concluded that this training resulted in a genuine progressive improvement in temporal acuity specific to the trained skin. The initial rapid improvement was likely due to an improvement in the "strategy" or "cognitive" aspects of the task, whereas more gradual improvements in performance recorded throughout the training period were most probably due to somatotopically localized changes in the neural representations of the behaviorally relevant stimulus.

Animals↗