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Biomedical subjects

L Laurell

Publications and source records attributed to L Laurell.

50 records · Page 3Linked to original sources
PubMed1986

Occlusal force pattern during chewing and biting in dentitions restored with fixed bridges of cross-arch extension. II. Unilateral posterior two-unit cantilevers.

The pattern of axially (perpendicular to the occlusal plane) directed occlusal forces developed during light tooth tapping in habitual occlusion, chewing, swallowing and maximal biting was studied in twelve subjects whose dentitions were periodontally treated and prosthetically restored with cross-arch bridges with unilateral posterior two-unit cantilevers. The measuring devices consisted of four strain-gauge transducers uniformly and bilaterally mounted in pontics of maxillary bridges to represent the posterior (end abutment and distal cantilever respectively) and anterior regions. Thus, the forces could be studied locally in various parts of the dentition simultaneously as well as totally over the entire dentition. The results demonstrated that the distal cantilever unit, on average, was subjected to forces about or less than half of those over the contralateral end abutment unit irrespective of the activity studied. Furthermore, the cantilever forces either equalled or were even significantly smaller than those of the anterior regions. All subjects preferred the end abutment side as the chewing side. When the cantilever side was used as the chewing side, which occurred most infrequently, the bolus was usually located in the anterior region. The mean total chewing force (about 50 N) was only about half of that found in a previous study of subjects supplied with cross-arch bridges with bilateral end abutments (Lundgren & Laurell, 1985). Furthermore, on average only 26% of the voluntary muscular capacity was used during chewing, compared with 37% in the 'bilateral end abutment group' referred to. The reasons for the comparably small forces over the distal cantilever unit and the lower muscular utilization during chewing in cross-bridges with unilateral posterior two-unit cantilevers as well as the implications of the findings for the dimension of such bridge constructions are discussed.

Adult↗
PubMed1986

Occlusal force pattern during chewing and biting in dentitions restored with fixed bridges of cross-arch extension. I. Bilateral end abutments.

The pattern of axially directed occlusal forces, i.e. magnitude, distribution, duration and frequency of occlusal forces perpendicular to the occlusal plane, was studied during chewing, swallowing and biting in twelve subjects whose dentitions were periodontally treated and prosthetically restored with fixed, cross-arch bridges whose periodontal support included bilateral end abutments. The measuring devices consisted of four strain gauge transducers bilaterally mounted into pontics of maxillary bridges to represent the posterior and anterior regions. The forces could thus be studied in various parts of as well as over the entire dentition simultaneously. All subjects exhibited a rhythmic chewing pattern with preference of one side as chewing side. Local chewing and biting forces were always larger in the posterior than in the anterior regions and largest in the posterior region of the preferred chewing side. The total chewing and swallowing forces were about 100 Newtons (N) whereas the total maximal bite force in habitual occlusion amounted to 320 N. On average 37% of the total maximal bite force in habitual occlusion was utilized during chewing (and swallowing). The capacity of the periodontal tissues on the preferred chewing side to withstand transient occlusal forces was utilized to an average of 25% during chewing and swallowing and to an average of 57% during biting with maximal strength in habitual occlusion. The mean duration of that part of the chewing cycle during which the teeth were subjected to occlusal forces was 240 ms. The duration of the occlusal forces during swallowing was about three times longer. It is concluded that the periodontal tissues can withstand transient occlusal forces which are much larger than those generally operating during chewing, swallowing and biting with maximal strength in habitual occlusion. However, when the bite force is concentrated to a limited area of the tooth-arch, its magnitude seems to be limited by feedback mechanisms evoked in the periodontal tissues of that region.

Adult↗
PubMed1986

Periodontal ligament areas and occlusal forces in dentitions restored with cross-arch unilateral posterior two-unit cantilever bridges.

This investigation was undertaken in order to analyse to what extent the magnitudes of chewing and biting forces in dentitions restored with cross-arch unilateral posterior two-unit cantilever bridges are correlated to the area of the periodontal tissue supporting the abutments. 12 subjects, whose dentitions were periodontally treated and prosthetically restored, participated in the study. The chewing and biting forces, simultaneously measured in various parts of, as well as over the entire dentition, were correlated to the periodontal ligament areas of the abutments supporting the bridge constructions. A strong positive correlation (r = 0.83; P less than 0.01) was found between the total remaining periodontal ligament area and the mean total chewing force. A positive correlation (r = 0.57; P = 0.05) was also found between the local remaining periodontal ligament area of the posterior end abutment tooth and the local chewing force in that region. No positive correlation was found between the amount of periodontal tissue support and the magnitude of the forces developed during biting with maximal strength in habitual occlusion either totally or locally, although there was a strong tendency (r = 0.54; 0.6 greater than P greater than 0.5) towards decreasing total maximal bite force with decreasing total remaining periodontal ligament area. A strong positive correlation (r = 0.74; P less than 0.01) was found on the end abutment side between the local remaining periodontal ligament area of the end abutment tooth and the local forces in that region during biting with maximal strength over a limited area at a time.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Oral health of individuals aged 3-80 years in Jönköping, Sweden in 1973 and 1983. I. A review of findings on dental care habits and knowledge of oral health.

The aim of the present study was to present data from dental care habits and knowledge of oral health in two cross-sectional studies carried out in 1973 and 1983. A random sample of approximately 1000 individuals evenly distributed in the age groups 3, 5, 10, 15, 20, 30, 40, 50, 60 and 70 years was studied for each of these two years. In the 1983-year examination 80 individuals 80 years of age were also included. All subjects were inhabitants of the community of Jönköping, Sweden. A questionnaire about dental care habits and knowledge was used in combination with a clinical and radiographical examination. The participants answered 23-101 questions. The same questions were raised in 1973 and 1983. For most age groups more then 80 per cent visited a dentist yearly in 1983. This yearly attendance was higher than that for 1973. In the 20-year-old group 14 per cent of the individuals received dental care in the PDS in 1973 compared to 63 per cent in 1983. The main reason to visit a dentist in 1973 was by the patient's own initiative while in 1983 the appointments were based on the dentist's initiative. The number of subjects that felt discomfort in connection with a visit to the dentist had decreased between 1973 and 1983. Knowledge about the etiology of caries had increased between 1973 and 1983 was not the case for gingivitis and periodontitis. An increase had occurred in toothbrushing frequency and the use of toothpicks and disclosing tablets but this between 1973 and 1983. In 1983, 98 to 93 per cent of the subjects in the age groups 10-30 years had been exposed to topical fluorides. The corresponding figure for 30-year-olds in 1973 was 1 per cent. It is obvious that during the period 1973 to 1983 there has been an increase in dental attendance, knowledge of dental diseases, oral health and the use of preventive measures.

Adolescent↗
PubMed1986

Oral health of individuals aged 3-80 years in Jönköping, Sweden, in 1973 and 1983. II. A review of clinical and radiographic findings.

The aim of this study was to present data from clinical and radiographic examinations on oral health in two cross-sectional studies carried out in 1973 and 1983. A random sample of approximately 1000 individuals, evenly distributed in the age groups 3, 5, 10, 15, 20, 30, 40, 50, 60 and 70 years was studied for each of these two years. In the 1983-year examination 80 individuals, 80 years of age, were also included. All subjects were inhabitants of the community of Jönköping, Sweden. The clinical and radiographic examination assessed edentulousness, removable dentures, number of teeth, caries, restorations and overhangs, gingival and periodontal status, oral hygiene and calculus, endodontic treatment and periapical status. A reduction in number of edentulous individuals by 25% was recorded between the two examinations. This was matched by an increase in the mean number of teeth, mainly of molars. The largest difference in mean number of teeth between the 1973 and 1983 examinations was found for the 70-year-olds. These were 8.5 and 11.8 teeth respectively. The younger age groups showed an increase in the proportion of individuals free from caries and restorations. In 1973 the caries-free proportions were 35% for 3-year-olds and 9% for 5-year-olds. In 1983 these values had improved to 70% and 29% respectively. Corresponding to this trend the number of decayed tooth surfaces was lower in 1983. Fewer filled tooth surfaces were present 1983 compared with 1973 for the age groups 10, 15, 20 and 30 years but higher for the age groups 5, 50 and 60 years and unchanged for the remaining groups. For the younger age groups the overall reduction in DFS was about 50% but this increased to 90% for buccal and lingual surfaces. Both secondary caries and overhanging restorations had decreased in the 1983 group for all ages. At least 75-86% of restorations were without overhangs in 1983 compared to 47-65% in 1973. Gingival health had improved over the 10-year period. Sites with plaque and calculus and gingival units exhibiting gingivitis had all decreased in frequency by 1983. Buccal surfaces showed the greatest improvement. The frequency of individuals with one or more periodontal pockets (greater than or equal to 4 mm) increased with age but was of the same distribution in 1983 as in 1973.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1985

Chewing ability in patients restored with cross-arch fixed partial dentures.

The chewing ability of subjects with cross-arch fixed partial dentures was compared with that of subjects with complete healthy dentitions and complete-denture wearers. Chewing ability was expressed in terms of the number of chewing strokes, chewing time, chewing efficiency, and chewing performance. Almonds were used as the test food. In terms of chewing efficiency, that is, comminution in relation to time, subjects with cross-arch fixed partial dentures exhibited a chewing ability inferior to that of subjects with complete healthy dentition but superior to that of complete denture wearers. However, in terms of chewing performance, which describes the degree of pulverization before the time of swallow, chewing ability in subjects with cross-arch fixed partial dentures was almost as good as in subjects with complete, healthy dentitions and superior to that of complete denture wearers.

Dental Abutments↗
PubMed1985

Periodontal ligament areas and occlusal forces in dentitions restored with cross-arch bilateral end abutment bridges.

The aim of the present investigation was to find out to what extent the magnitudes of chewing and biting forces in dentitions restored with cross-arch bilateral end abutment bridges are correlated to the areas of the periodontal ligament supporting the abutment teeth. 12 subjects whose dentitions had been periodontally treated and prosthetically restored participated in the study. The chewing and biting forces were measured in various parts of as well as over the entire dentition simultaneously using 4 strain gauge transducers bilaterally placed in pontics of the posterior (first molar/second premolar) and anterior regions. Based on calculations of the periodontal ligament areas, a new periodontal support index, PSIL, is introduced. This index expresses the relation between the total remaining periodontal ligament area supporting the bridge abutments and total maximal periodontal ligament area if all teeth were preserved as abutments. It is compared with the index of Ante, PSIA, which expresses the relation between the total remaining periodontal ligament area of all abutments and the total maximal periodontal ligament area of all replaced teeth. Within the present group of subjects, PSIL varied from 10 to 44% and PSIA from 17 to 118%. Based on the results of the correlation analyses, it is suggested that in dentitions restored with cross-arch bilateral end abutment bridges, the magnitude of the chewing forces is positively correlated to the areas of the periodontal ligament supporting the bridge abutments, whereas the periodontal ligament areas have no influence on the comparatively larger biting forces. The relevance of the 2 periodontal support indices and the clinical implications of the results of the study are discussed.

Adult↗
PubMed1985

Occlusal forces and chewing ability in dentitions with cross-arch bridges.

The main aims of this thesis were 1) to study the pattern of axially directed occlusal forces developed during chewing and biting in dentitions restored with cross-arch bridges, 2) to find out to what extent these forces are influenced by the amount of periodontal tissue supporting the bridge abutments and 3) to study the chewing ability in subjects supplied with cross-arch bridges. For the purpose of aims 1 and 2 a method was developed which permits measurement of occlusal forces in various parts of as well as over the entire dentition simultaneously. The method is based on the use of strain-gauge transducers mounted into pontics or artificial teeth. Two groups, each comprising 12 subjects, were included in the studies of occlusal forces. In one group, the periodontal support included bilateral molar end abutments. In the other group, molar/premolar end abutments were unilaterally missing and replaced with posterior two-unit cantilevers. In each subject, four transducers were used, bilaterally distributed to represent the posterior and anterior regions and mounted so as to measure forces perpendicular to the occlusal plane. The occlusal forces were measured during 3 activities: 1) chewing and swallowing, 2) biting with maximal strength in habitual occlusion, expressing the voluntary capacity of the jaw-closing muscles, and 3) clenching between two antagonistic teeth, expressing the transient periodontal force withstanding capacity in that region. The amount of periodontal tissue supporting the bridge abutments was assessed from radiographs. The chewing ability was studied using a fractional sieving technique in principle according to Helkimo el al (1978) and was compared with the chewing ability of subjects with complete healthy dentitions and complete denture wearers. The mean total chewing force amounted to about 100 Newtons (N) in dentitions with cross-arch bilateral end abutment bridges, compared to about 50 N in dentitions with cross-arch unilateral posterior two-unit cantilever bridges (P less than 0.01). The mean maximal bite force in habitual occlusion amounted to 320 N and 264 N respectively (NS). In the presence of end abutments, the chewing and biting forces were significantly larger in the posterior than in the anterior regions. The local forces on the distal cantilever unit were, however, equal to or smaller than those in the anterior regions and much smaller than have been suggested in the literature.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1984

Occlusal forces in prosthetically restored dentitions: a methodological study.

The present paper describes a method developed to study occlusal forces in prosthetically restored dentitions. Using this method the magnitude, duration and frequency of the forces can be measured in various parts of the dentition simultaneously. The measurements are based on the use of strain gauge transducers of such dimensions that they can be mounted into artificial crowns, bridge-pontics or removable dentures, without interfering with the occlusion. The output signal of each transducer is linear for forces up to 300 N which corresponds to an amplitude (elastic deformation) of 20 microns. At least four transducers are used distributed over the tooth-arch to create bilateral and simultaneous contacts. They are mounted in a supraoccluding position of 20 microns in relation to non-transducer areas. This means that on jaw closure each transducer registers all the force transmitted to that part of the prosthetic construction represented by the transducer, provided there is no force leakage to non-transducer areas. The sum of these local forces constitutes the total force acting on the entire dentition at any given moment.

Bite Force↗
PubMed1984

A standardized programme for studying the occlusal force pattern during chewing and biting in prosthetically restored dentitions.

A recently described method for studying occlusal forces in prosthetically restored dentitions (Lundgren & Laurell, 1984) was applied in a standardized programme to elucidate the occlusal force pattern and the functional capability of a dentition during chewing and biting. The method is based on the use of strain gauge transducers mounted into preformed matrices evenly distributed over the tooth-arch. The programme was tested in a subject prosthetically restored with a fixed bridge of cross-arch design in the upper jaw, and with unsplinted teeth in the lower jaw. It involved chewing of (a) peanuts, (b) roast beef with potato salad, biting with maximal strength in habitual occlusion and biting over one limited contact area at a time. The magnitude of the occlusal forces developed during chewing and swallowing was well below all biting forces. The magnitude of the total force acting over the entire dentition when biting at maximal strength in habitual occlusion did not seem to be limited by reactions from the teeth or the periodontal tissues but, seemingly, by the capability of the jaw-closing muscles themselves. The magnitude of the local bite force over one limited contact area at a time was much smaller than that which the jaw-closing muscles were able to develop. This indicated that feedback mechanisms in the periodontal tissues and/or the temporo-mandibular joints were limiting factors for these forces. The programme will be applied to studies of dentitions supplied with prosthetic constructions of various design and with different distribution of periodontal support.

Bite Force↗
PubMed1983

The effect of different levels of polishing of amalgam restorations on the plaque retention and gingival inflammation.

This study was performed to elucidate the effect of different levels of polishing of amalgam restorations as part of the treatment of patients with gingivitis and/or incipient periodontitis on plaque retention and gingival inflammation. The results indicate that contouring of restorations and removal of marginal overhangs using diamond tips and conventional finishing burrs is sufficient to permit adequate tooth cleaning and that further polishing using rubber discs, rubber tips and polishing pastes does not result in further improvement of gingival health.

Adult↗