Biomedical subjects
Publications and source records attributed to J C Maltha.
Root resorption after orthodontic treatment occurs frequently. The biologic process of tooth movement and root resorption is described. Furthermore, attention is given to the frequency and severity of root resorption, diagnostics and aspects of the orthodontic treatment which aggravate root resorption. Displacement of teeth with resorptions that already exist or with deviating rootforms is riskfull.
The present study compared the dentoalveolar development in beagle dogs after palatal repair according to the partially split flap technique and the von Langenbeck method. It was concluded that palatal surgery according to the partially split flap technique resulted in significantly wider transverse distances of the maxillary dental arch than after the von Langenbeck procedure and that its final outcome closely resembled that of the control group.
The role of intercuspation of the teeth in transverse maxillary growth and dental arch development was investigated radiographically with the aid of implants in Macaca fascicularis monkeys. Fourteen animals were randomly allocated to a control group (n = 7) and an experimental group (n = 7) and were followed from 29 to 100 weeks of age. Intercuspation was eliminated in the experimental group by grinding the canines and molar cusps in both dental arches as soon as possible after emergence. Maxillary occlusal radiographs were taken at regular intervals. Linear and angular analyses of skeletal changes revealed that midpalatal sutural growth seems to be independent of intercuspation. The developing dental arch, however, showed a significantly greater increase in width in certain areas in the experimental group than in the control group. Most findings support the hypothesis that the width of the maxillary dental arch is guided by the width of the mandible through the intercuspation of the posterior teeth.
This article reports on the histologic findings from a larger study that was designed to investigate whether the attachment of scar tissue to underlying bone, which is normally found after palatal surgery, can be prevented by using biodegradable poly-(L-lactic) acid membranes. Von Langenbeck's procedure was simulated in 12-week-old beagle dogs without clefts. In one group normal wound healing was allowed. In two groups, membranes were inserted immediately after surgery or 3 weeks thereafter. Sham and control groups were also included. Histologic evaluation was carried out at regular intervals. Reports have been published on other aspects, such as clinical wound healing, contraction and maxillary arch development in beagle dogs following this treatment. After direct implantation of membranes, wound healing was retarded. Disintegration of the membranes started soon after implantation and remaining particles were surrounded by a fibroblastic sheath and a fibrous capsule. At sites where membrane particles persisted, attachment of the scar tissue to the underlying bone by Sharpey's fibers was prevented.
The connection of scar tissue to palatal bone by Sharpey's fibers, after cleft palate surgery, might lead to maxillary growth inhibition. The aim of this study, in beagle dogs, was to investigate the possibility of preventing the development of Sharpey's fibers by means of a modified surgical technique. In group 1, palatal repair according to von Langenbeck, was simulated. In group 2, palatal surgery was performed using a new partially split flap technique. The palates were histologically evaluated 12 weeks after surgery and compared with a control group. In group 1, the scar tissue was firmly attached to bundle bone by means of Sharpey's fibers. In group 2 and in the control group, this kind of attachment was not found; the bone was of the lamellar type. The partially split flap technique had led to the development of vaguely demarcated scar tissue and it had prevented, to a large extent, development of Sharpey's fibers.
Palatal soft-tissue expansion might be appropriate for use in cleft palate surgery. Seventy-five cats were divided into four different experimental groups and one control group. Intraoral tissue expansion was started at the age of 14 weeks in normal or scarred mucoperiosteum. The experiment lasted until 24 weeks of age. Serial standardized lateral cephalograms from each animal were digitized, and the results were statistically analyzed. The results indicate that the effects are independent of the presence of scarred tissue, that sagittal growth is impaired by tissue expansion, and that the tissue expander induced resorption of palatal bone.
The attachment of 10 different Treponema denticola strains to monolayers of 4 types of epithelial cells derived from rat palatal epithelium, guinea pig ear, human buccal epithelium and human corneal epithelium was screened microscopically. Most T. denticola strains were able to attach to all four types of epithelial cells. The T. denticola strains seemed to attach better to epithelial cells derived from primary cultured material. The T. denticola strains showed different degrees of attachment. Scanning electron microscopy studies revealed that the attachment of T. denticola was not only tip-associated but occurred also at random points in close contact with microvilli of the epithelial cells. Attached spirochetes were non-uniformly distributed over the monolayers, indicating the presence of receptive subpopulations of epithelial cells in the monolayers.
We studied the nature of attachment of Treponema denticola ATCC 33520 to a microscopically distinct population of rounded rat palatal epithelial cells. The motility of the freshly harvested spirochetes appeared not be a prerequisite for attachment. Treatment of T. denticola ATCC 3350 with proteinase-K, heat, glutaraldehyde, formaldehyde and periodate oxidation decreased the attachment to the rounded rat palatal epithelial cells, indicating the involvement of protein and carbohydrate moieties. Trypsin treatment had no effect on the attachment. The attachment of T. denticola ATCC 33520 was decreased after treatment with native non-immune rabbit serum, native polyclonal rabbit serum, D-mannose, N-acetyl-D-galactosamine and sialic acid. The results indicate that the attachment of T. denticola ATCC 33520 to rounded rat palatal epithelial cells is mediated by trypsin-resistant adhesin(s) of protein and carbohydrate nature, with affinity for D-mannose, N-acetyl-D-galactosamine and sialic acid.
In the present study an assay for the attachment of T. denticola to epithelial cells is described. An indirect immunohistochemical staining method, using two native polyclonal antisera, revealed dark-brown coloured spirochetes attached to rat palatal epithelial cell (RPE) monolayers. In addition, two morphologically distinct populations of RPE cells could be distinguished in the monolayers when using phase contrast microscopy. One minor population consisted of isolated rounded RPE cells that were lying on top of a confluent monolayer of flattened RPE cells. The rounded RPE cells were more receptive for the attachment of T. denticola than the flattened cells. The rounded RPE cells were evenly distributed over the monolayer, but the attachment of spirochetes to the rounded cells was greater at the edge than in the centre of the monolayers. The percentage of rounded RPE cells with attached spirochetes depended on the incubation time (optimum 6 h), temperature (optimum 37 degrees C) and pH (optimum 7.0). It is speculated that the attachment of T. denticola is a physical/chemical process of yet unknown nature and that differences in the number of microvilli and/or the amount of available receptors, between the two morphologically distinct cell types, accounts for the differences in the numbers of attached spirochetes.
The effect of implantation of poly-(L-lactic) acid membranes after palatal surgery on dentoalveolar development was investigated. Beagle dogs were randomly assigned to four experimental groups and a control group. In the experimental groups, a soft tissue defect was created in the medial region of the palate by excising a standardized elliptical mucoperiosteal flap at 12 weeks of age. This defect was closed according to the Von Langenbeck technique, leaving two areas of denuded bone. Poly-(L-lactic) acid membranes were implanted on the denuded bony areas either directly or 3 weeks after surgery. Group L and LS served as sham groups. Dental casts were made at regular intervals until 25 weeks of age, and maxillary arch dimensions were studied. Dental arch dimensions in the deciduous dentition of the experimental groups were not markedly disturbed, but after transition of teeth, mainly transversal maxillary arch dimensions in the premolar region were reduced. It was concluded that implantation of poly-(L-lactic) acid membranes after palatal surgery in Beagle dogs did not prevent iatrogenic disturbances of dentoalveolar development under conditions used in this study.
The effect of implantation of poly-(L-lactic) acid membranes on wound healing and wound contraction after palatal surgery was investigated macroscopically in beagle dogs. Thirty beagle dogs were randomly assigned to two experimental groups (group L and LM; both n = 12) and a control group (group C; n = 6). At 12 weeks of age, a soft-tissue defect was created in the median region of the palate by excising a standardized elliptical mucoperiosteal flap. This defect was closed according to the Von Langenbeck technique, leaving two areas of denuded bone. Immediately after surgery, poly-(L-lactic) acid membranes were implanted on the denuded bony areas in the animals of the LM group. In the L group, no poly-(L-lactic) acid membrane was used. Tattoo points were placed in the mucoperiosteum on opposite wound margins in all groups to quantify wound contraction. Standardized intraoral photographs were taken at regular intervals. Wound surface areas and weekly increments of the distance between the tattoo points were calculated. Clinical wound healing was significantly retarded in animals of the LM group. Wound contraction was comparable in both experimental groups and was restricted to the first 2 weeks after surgery. Corresponding lateral migration of the tattoo points in the median region of the palate in these groups occurred in the first week after surgery, followed by wound contraction in the second week. Implantation of poly-(L-lactic) acid membranes following palatal wounding in beagle dogs had no beneficial short-term effects on wound healing and contraction.
At present no information is available about biological effects on oral tissues of the photocuring periodontal dressing Barricaid. This animal study examines histologically the tissue responses of surgical areas covered during 7 days with either Barricaid, the eugenol-containing dressing Ward's Wondrpak or the bionert control gel Carboxyl Methyl Cellulose. One group was studied immediately after the removal of the dressings; in the other group, further healing was permitted for another week. Results after 7 days indicate acute inflammatory reactions in the test areas without significant differences between the 2 periodontal dressing materials. The control areas showed to a lesser degree basically the same tissue response. In the 2nd week, generally all areas healed. After 14 days, no differences between test- and control sites could be detected. From a biological point of view, these findings suggest no contra-indication for application of this photocuring dressing material after periodontal surgery.
In the present study, the role of the periosteum in mandibular growth was investigated. The orientation of the superficial bony spicules of rabbit mandibles was determined on dry skulls after perfusion of the animals with an India ink solution. The spicular orientation in the ramus area appeared to be toward the condyle, rostrally toward the incisors, and caudally toward the angular region. The behavior, during growth, of the periosteum in the caudal mandibular half was studied by implantation of metal periosteal and bone markers. A series of cephalograms revealed the migration pattern of the periosteal markers, and by that the migration pattern of the periosteum. It can be concluded that both the pattern of the superficial bony spicules and the periosteal migration pattern suggest a possible influence of the periosteum on mandibular growth.
The effect of low level laser therapy on wound healing and wound contraction after palatal surgery in Beagle dogs of 12 weeks of age was investigated. A total of 30 Beagle dogs was used and assigned to a control group (Group C; n = 6) and two experimental groups (Group L; n = 12 and group LL; n = 12). In both experimental groups, Von Langenbeck's palatal repair was simulated. Then in the LL group the denuded bony areas were treated with low level laser therapy using a continuous Ga-As-A1 laser beam (830 nm) and energy output set at 30 mW. Per treatment a dosage of 1 J/cm2 wound surface area was used. Therapy was carried out three times a week with a total of ten treatments. Wound healing was observed clinically until wound healing was completed at 4 weeks p.o. and wound areas were measured at regular intervals on standardized intra-oral photographs. Wound contraction was measured as the increments of the distances between tattoo points on the opposite wound margins. No significant differences were found in the quality and rate of wound healing between the two experimental groups. The same held true for the increments of the distances between opposite tattoo points. It was concluded that macroscopically low level laser therapy under conditions used in this study did not have an influence on wound closure or wound contraction.
The response of maxillary tissues to mucoperiosteal manipulation at different ages was studied microscopically early after operation and at maturity. Thirty-two Beagles were divided into three experimental groups, a sham-operated group and a control group. At the age of 6, 16 or 25 weeks in the experimental groups an elliptical mucoperiosteal flap was excised in the midsagittal region of the palate, relaxation incisions were made and the mucoperiosteum was elevated and closed in the midline leaving two areas of denuded bone adjacent to the teeth. The animals were killed 1, 2 or 3 weeks after the operation or at the age of 37 weeks and serial sections of the jaw tissues were examined. Two weeks after the operation, scar had formed, its lack of elastic fibres indicating a more rigid type of tissue. The palatal bone showed rapid trabecular deposition. Cervico-palatal and apico-buccal bone resorption in the alveolar socket indicated medial tipping of the teeth. The different soft tissue composition persisted until maturity. In the areas where scar tissue had developed, attachment by means of Sharpey's fibres from the mucoperiosteum to the palatal bone was found at the age of 37 weeks. Thus the different mechanical properties of scar tissue adjacent to the teeth and its attachment to the palatal bone may influence the growth and development of dento-alveolar structures.
These structures were investigated with various histological stains and by polarization microscopy. The width of the periosteal layers was measured in nine ramal and condylar areas at five different ages (0, 2, 6, 12 and 30 weeks). The total periosteal width changed during growth, as did the absolute and relative thickness of its cellular and fibrous layers. The results suggest that in these areas periosteal tension may influence growth of the condylar cartilage, and that this may vary during growth.
The structure of the mandibular periosteum in rabbits of different ages has been studied by different histological staining techniques and polarization microscopy. The periosteum consisted of two layers. From the inner, cellular layer the functional state could be determined. A reproducible pattern of resorptive and depository areas was found on the bony surface. In the outer, fibrous periosteal layer, collagenous and elastin fibers were running in distinct directions. The masticatory muscles appeared to be attached directly endomysially or indirectly endomysially, via the perimysium or tendinous attachment. From the periosteal structures and the characteristics of muscular fiber attachments to the bone and periosteum, especially in the ramal and condylar areas, it could be concluded that a mechanical influence of the periosteum on condylar growth is very well possible, which will probably vary during life. The masticatory muscles seemed to be only of minor influence in condylar activity.
Transseptal fibers of the periodontal ligament are thought to play a role in relapse after orthodontic derotation. The aim of this study was to compare the location of the attachment site and the arrangement of the transseptal fibers in rotated emerged and non-rotated emerged teeth. In five dogs, unilaterally, the first upper premolars were replaced into a rotated position, before emergence. Histological evaluation showed that transseptal fibers developed in the experimental as well as in the control specimens. In all cases, transseptal fibers bridged the shortest distance between two adjacent teeth. It was concluded that the attachment site of the transseptal fibers was not determined by the tooth anatomy itself, but by the tooth position and its orientation in the dental arch during transseptal fiber development.