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Biomedical subjects

L Laurell

Publications and source records attributed to L Laurell.

At least 19 recordsLinked to original sources
PubMed1995

The influence of the design of two different bioresorbable barriers on the results of guided tissue regeneration therapy. An intra-individual comparative study in the monkey.

The aim of the present study was to compare two bioresorbable barriers to evaluate whether differences in design influence the result of guided tissue regeneration (GTR) therapy. Twenty-four (24) plaque exposed, recession type defects in 4 monkeys were treated. Contralateral defects were randomized for test or control treatment. During a healing period of 6 weeks, gingival recession resulting in device exposure occurred at 3 test and 10 control sites. One control barrier was exfoliated. Histologically, 9 of the 12 test barriers were completely integrated with the surrounding tissues. At 3 test sites, epithelium had migrated apically outside the barrier to a level not exceeding one-third of the height of the device. Seven of the 11 control barriers were enclosed by dentogingival epithelium. The adjacent connective tissue exhibited local inflammatory cell infiltrates (ICT). At the remaining 4 control sites, the epithelial downgrowth as well as the adjacent ICT areas were limited to the coronal 1/3 of the device. New attachment; i.e., new cementum with inserting collagen fibers, averaged 2.2 mm and 0.8 mm at the test and control sites respectively (P < 0.01). Based on the results of the present study, it was concluded that a bioresorbable GTR device, designed to prevent epithelial downgrowth along the barrier surface, has a higher potential to promote new attachment formation than a device which does not have this property.

Animals↗
PubMed1994

Guided tissue regeneration using a bioresorbable matrix barrier.

Bioresorbable barrier material, used in guided tissue regeneration, changes the conventional two-stage surgery to a single-step procedure. This article presents a general surgical protocol for application of a bioresorbable matrix barrier (Guidor AB, Huddinge, Sweden). Three case reports are used to illustrate the surgical treatment of a Class II furcation defect, an intrabony defect, and a recession type defect. The learning objective of this article is to enhance the knowledge of surgical procedures and bioresorbable barrier membranes available.

Adult↗
PubMed1992

Influence of occlusion on posterior cantilevers.

The incorporation of posterior two-unit cantilevers in fixed prosthodontics is generally discouraged because of the assumption that large posterior chewing and biting forces might jeopardize the prosthesis and the abutment teeth. This investigation was performed to study (1) the distribution of chewing and closing forces in dentitions with cross-arch bilateral posterior two-unit cantilever fixed partial dentures and (2) the influence of different occlusal arrangements on the magnitude of these forces along the cantilever segments. Six patients were included in the study. Axially directed closing and chewing forces were measured with miniature transducers bilaterally mounted in pontic units anteriorly and in each of the four cantilever units. In ideal occlusion, occlusal forces decreased considerably along the cantilever segments in the distal direction. Infraoccluding the distal cantilever unit by 80 microns had little influence on the magnitude of the initially small local force in this region, whereas an 80 microns high primary occlusal contact considerably increased the local force over the distal cantilever unit. The clinical implications of the results are discussed.

Acrylic Resins↗
PubMed1992

Frequency distribution of individuals aged 20-70 years according to severity of periodontal disease experience in 1973 and 1983.

The aim of this study was to compare changes in periodontal status of a Swedish population over a 10-year period expressed as frequency distributions of individuals according to severity of periodontal disease experience. The study involved 600 randomly selected individuals evenly distributed into age groups 20, 30, 40, 50, 60 and 70 years, examined in 1973 and another randomly selected group of 597 individuals similarly age distributed and examined in 1983. Based on clinical data and full mouth intraoral radiographs all individuals were classified into 5 groups according to severity of periodontal disease experience. In 1983, 23% of the individuals were classified as having healthy periodontal tissues, group 1, compared to 8% in 1973. The changes were most pronounced in the age groups 20 and 30 years, among whom 58% and 35%, respectively, were registered as having healthy periodontium in 1983. The prevalence of individuals with gingivitis without signs of lowered periodontal bone level, group 2, was 22% in 1983 compared to 41% in 1973. In all, 49% of the dentate population in 1973 and 45% in 1983 showed no marginal alveolar bone loss. Moderate periodontal bone loss, group 3, was found in 41% of the population in 1983 compared to 47% in 1973. Among 30-, 40-, and 50-year-olds, there were more, and among 60- and 70-year-olds, fewer individuals in this group in 1983 compared to 1973. 96% of the dentate population were classified as belonging to groups 1, 2 or 3 in 1973 compared to 86% in 1983.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Long-term prognosis of extensive polyunit cantilevered fixed partial dentures.

The aim of this retrospective study was to elucidate the long-term prognoses of extensive fixed partial dentures including unilateral or bilateral polyunit cantilevers in patients with healthy but reduced periodontal support. Following periodontal therapy 36 cross-arch fixed partial dentures with two or more cantilever units unilaterally or bilaterally were fitted in 34 patients. In the prosthodontic design, special attention was given to the retention to long parallel preparations, to the dimensions of the framework, and to the occlusal design. After completion of therapy, the patients were enrolled in a regular maintenance care program and followed up for a period of 5 to 12 years. During this follow-up period one abutment tooth was fractured in one patient. One fixed partial denture with extremely reduced periodontal support was lost as a result of complete periodontal breakdown from occlusal trauma. For 33 fixed partial dentures, neither periodontal nor technical complications occurred.

Dental Abutments↗
PubMed1990

Periodontal healing after scaling and root planing with the Kavo Sonicflex and Titan-S sonic scalers.

Several types of air turbine scalers have recently been introduced as alternatives to hand instruments and ultrasonic devices in periodontal therapy. Whereas differences in scaling and root planing efficiencies have been demonstrated in vitro between different types of sonic scalers (Lie & Leknes 1985), periodontal healing after instrumentation with the Titan-S sonic scaler, Cavitron ultra sonic scalers and hand instruments has shown to be similar (Gellini et al. 1986, Loos et al. 1987, Laurell & Pettersson 1988). This split mouth designed study compared periodontal healing expressed as reduction in number of sites with probing depths of 4 mm or deeper and bleeding on probing following scaling and root planing with the Sonicflex and the Titan-S sonic scalers. Fifteen patients with moderately advanced periodontitis participated in the study. In each patient one side of the dentition was treated with the Sonicflex and the other with the Titan-S sonic scalers. Reexaminations performed three and seven months after treatment showed significant and similar reductions in number of sites with probing depths of greater than or equal to 4 mm and bleeding scores for the two sides.

Adult↗
PubMed1990

Occlusal interferences and cantilever joint stress in implant-supported prostheses occluding with complete dentures.

Naturally occurring closing and chewing forces were measured in dentitions with mandibular fixture-supported bilateral distal two-unit cantilever fixed prostheses occluding with complete dentures, and the vertical bending stress in the cantilever joint of the preferred chewing side was assessed. Occlusal forces were measured using eight miniature strain gauge transducers bilaterally and symmetrically mounted in complete dentures. Occlusal forces over the entire prosthesis were registered in basic (habitual) occlusion and with a 100-microns-high premature occlusal contact on the second cantilever unit. Closing and chewing forces increased distally. The premature occlusal contact did not significantly influence the total forces over the entire dentition but increased the local forces over the second cantilever unit. The group mean maximal vertical bending stress for closing forces reached the fatigue limit for unhardened type III dental gold alloy in basic occlusion. Although the interfered occlusion resulted in a significant redistribution of forces and significantly altered the stress contributions from each cantilever unit, maximal vertical bending stress in the cantilever joint was not significantly influenced. During chewing, the fatigue limit was not reached in basic or in interfered occlusion.

Adult↗
PubMed1989

General oral status in adults with rheumatoid arthritis.

The oral status of an adult population of 204 patients with rheumatoid arthritis (RA) was compared with that of an age and sex-matched random sample of non-rheumatic subjects. The percentage of edentulous subjects, number of existing teeth in dentate subjects, prevalence, and quality of fixed and removable prostheses and prevalence of disorders of the stomatognathic system was recorded. The percentage of edentulousness among RA-patients was 17% and among non-RA subjects 19%. Number of remaining teeth was equal. 75% of removable partial and 62% of complete dentures among RA-patients were considered unsatisfactory compared to 25% and 56% respectively among non-RA subjects. Disorders related to the TMJ occurred much more frequently among RA-patients than among non-RA subjects. It is suggested that thorough stomatognathic examination and TMJ-prophylaxis be included in the overall care of RA-patients.

Adult↗
PubMed1989

Periodontal conditions in adults with rheumatoid arthritis.

Periodontal conditions among an adult population of 161 dentate patients with rheumatoid arthritis (RA) were compared with those of an age and sex-matched random sample of non-rheumatic subjects. The number of teeth and prevalence of dental plaque, calculus, gingivitis, and deepened periodontal pockets were recorded. Alveolar bone breakdown and the distribution of subjects according to severity of periodontal disease were also registered. There was a tendency towards better periodontal conditions among RA-patients, severe periodontal breakdown occurring less frequently among RA-patients (12%) than among the controls (16%). The RA-patients had less plaque and calculus than the control group, a finding which could indicate a difference in periodontal care.

Adult↗
PubMed1989

Influence of number and distribution of occlusal cantilever contacts on closing and chewing forces in dentitions with implant-supported fixed prostheses occluding with complete dentures.

Axially directed closing and chewing forces were measured in patients with mandibular fixture-supported cross-arch bilateral posterior two-unit cantilever fixed prostheses occluding with maxillary complete dentures. Eight miniature strain-gauge transducers mounted in the maxillary denture enabled registration of local and total forces over the entire prosthetic restoration simultaneously. In "basic occlusion," with simultaneous occlusal contacts on all occluding units, closing and chewing forces were distally increasing. Infraoccluding the first cantilever unit bilaterally approximately 100 microns resulted in decreased total closing and chewing forces over the cantilever segments, but did not influence the leverage at the cantilever joint distal to the distal retainers. Infraoccluding the second cantilever units approximately 100 microns caused a pronounced reduction of both the total closing and chewing forces over the entire prosthetic restoration as well as over the cantilever segments, and also resulted in a marked (50%) decrease in the leverage at the cantilever joints. Causes of the force and leverage reductions and some clinical considerations are discussed.

Bite Force↗
PubMed1989

Occlusal force pattern in dentitions with mandibular implant-supported fixed cantilever prostheses occluded with complete dentures.

Naturally occurring axially directed closing and chewing forces were measured in ten patients with mandibular fixture-supported cross-arch prostheses occluding with maxillary complete dentures. The design of the mandibular constructions was characterized by bilateral posterior two-unit cantilevers. The forces were measured using eight miniature strain gauge transducers mounted in the maxillary denture and evenly distributed over the tooth arch. Forces were thus measured at four occlusal contact points over the fixture segment and over each of the four posterior cantilever units simultaneously, giving a detailed picture of the force distribution. The total forces developed during maximal closing in habitual occlusion and chewing were of the same magnitude as previously reported for patients with tooth-supported cross-arch fixed partial dentures occluding with natural teeth using the same method. Contradictory to previous findings, in dentitions with comparable tooth-supported cantilever constructions occluding with natural teeth, local closing and chewing forces increased bilaterally in the distal direction. On average, 70% of the forces were borne by the cantilevers and 30% by the fixture-supported segment of the prostheses.

Adult↗
PubMed1988

Distribution of occlusal forces along unilateral posterior two-unit cantilever segments in cross-arch fixed partial dentures.

Axially directed occlusal forces over unilateral posterior two-unit cantilever segments of cross-arch fixed partial dentures were measured during natural functioning by using built-in transducers, one in each cantilever unit. The mean local maximal occluding and maximal chewing forces were significantly larger over the first (124 N and 64 N) than over the second (21 N and 29 N) cantilever unit. The average intraindividual ratio between the forces over the first and second cantilever unit amounted to 12:1 for maximal occlusion and 3:1 for maximal chewing. Despite the smaller mean total maximal chewing (92 N) than mean total maximal occluding cantilever force (145 N), the resulting axially directed mean bending moments in the joint between the distal abutment crown and the cantilever segment did not differ significantly. This is explained by the larger mean maximal chewing (29 N) than mean maximal occluding (21 N) force over the second cantilever unit. This demonstrated that not only the magnitude of occluding and chewing forces over cantilever segments but also their distribution along the cantilevers is of importance for the magnitude of functional stress created in cantilever fixed prosthesis.

Bite Force↗
PubMed1988

Periodontal healing after treatment with either the Titan-S sonic scaler or hand instruments.

Several types of air turbine scalers have recently been introduced as an alternative to ultrasonic equipment in periodontal therapy. The aim of this investigation was to compare clinical, periodontal healing after scaling with the Titan S air turbine scaler and hand instruments. Twelve patients referred to the School of Dental Hygiene, Jönköping, Sweden, for treatment of moderately advanced periodontitis participated in the study. After examination, diagnosis, treatment planning, and information, the teeth of the left and right quadrants were randomly assigned to Titan S or hand instruments scaling ("split mouth design"). The treatment was given by 6 dental hygiene students. Final re-examination was performed 3 months after instrumentation. After treatment, a marked improvement of periodontal conditions, expressed as number of tooth surfaces with plaque, number of sites with probing pocket depth greater than or equal to 4 mm and percentage of sites showing bleeding on probing to the bottom of the pocket, was obtained. No difference in results was observed when comparing Titan S and hand instrumentation. The time required for instrumentation was, however, shorter for Titan S than for hand instruments. Based on the results of this study, it may be concluded that, in patients with moderately advanced periodontitis, periodontal healing after scaling with the Titan S and hand instruments is comparable.

Adult↗
PubMed1988

Caries prevalence and distribution in individuals aged 20-80 years in Jönköping, Sweden, 1973 and 1983.

In 1973 an epidemiological study was performed in the community of Jönköping, Sweden. The study covered 1000 individuals, evenly distributed in the age groups 3, 5, 10, 15, 20, 30, 40, 50, 60 and 70 years. In 1983 a new cross-sectional study was carried out on the age-groups 3-80 years. The aim of the present study was to compare and analyse in detail caries prevalence and distribution in the age-groups 20-80 years at the examinations in 1973 and 1983. The subjects were examined clinically and radiographically regarding number of teeth, caries, restorations, etc. The mean number of teeth increased between 1973 and 1983, especially in the older age-groups. During the same period, the percentage of DFS decreased in the age-groups 20, 30 and 70 years, and was unchanged in the age-groups 40 to 60 years. There were only minor differences in DS in the respective age-group during the 10-year period. The distribution of subjects according to DFS showed that a large proportion of individuals in the age-groups 20 and 30 years had low DFS in 1983 as compared to 1973. For the age-group 40-years, the distribution was unchanged. For the 50, 60 and 70-year-olds, there was a change in distribution towards a larger proportion of individuals with high DFS values in 1983 as compared to 1973. The frequency distribution of individuals with primary and secondary carious lesions respectively was skewed, a small number of individuals having a high number of lesions in each age-group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Occlusal force pattern during mastication in dentitions with mandibular fixed partial dentures supported on osseointegrated implants.

The occlusal force pattern during chewing and biting was studied in eight edentulous patients whose dentitions had been restored with mandibular bilateral posterior two-unit cantilever fixed prostheses supported on osseointegrated titanium fixtures and occluding with complete maxillary dentures. The chewing pattern was comparable to that reported for subjects with complete healthy dentitions or with tooth-supported cross-arch fixed partial dentures. However, during chewing and swallowing the voluntary capacity of the jaw-closing muscles was used to a much greater extent. Contrary to reports for cantilevers in tooth-supported cross-arch unilateral posterior two-unit cantilever fixed partial dentures occluding with natural teeth, the posterior cantilever segments in the present fixture-supported cantilever prostheses occluding with complete dentures regularly exhibited the largest local forces. Despite this, material failures of this type of fixed prostheses are rare, as demonstrated in long-term follow-up studies.

Adult↗
PubMed1987

Histologic characteristics of clinically healthy gingiva in adolescents.

Gingival biopsies from healthy buccal gingival units in 10 young individuals (12-14 yr) were analyzed morphometrically. The connective tissue was generally characterized by a dense collagenous network, apart from a well defined zone subjacent to the smooth and noninfiltrated junctional epithelium. This zone, which constituted on average 10% of the connective tissue volume, was less dense than the remaining part of the connective tissue and devoid of well defined collagen fiber bundles. This zone could also harbor clusters of inflammatory cells, mainly mononuclear cells, surrounded by non-infiltrated collagen-poor connective tissue. In the noninfiltrated collagen-dense mid-portion of the gingival connective tissue small areas of infiltrates could be found, the composition of which resembled that of the infiltrated areas subjacent to the junctional epithelium.

Adolescent↗
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↗