Defect Height Research Articles

Periodontal Repair in Dogs: Healing in Experimentally Created Chronic Periodontal Defects

A need exists for well-defined animal models to objectively evaluate surgical principles and a possible role for biochemical wound conditioning and biomaterials in promoting periodontal regeneration. To test an existing model for its usefulness in quantitative evaluation of periodontal wound healing, large supraalveolar periodontal defects were surgically created around the mandibular premolars (P2, P3, P4) in left or right jaw quadrants in 5 beagle dogs. The defects were exposed to the oral environment for 6 months and were then subjected to reconstructive flap surgery (chronic defects). Healing in these defects was compared to healing following reconstructive surgery in similar contralateral defects which had not been exposed to plaque and calculus (acute defects). The animals were sacrificed after a 4-week healing period and tissue blocks including teeth and surrounding structures were processed for histometric analysis. Mean defect height (+/- s.d.) for chronic and acute defects amounted to 4.6 +/- 0.3 and 4.4 +/- 0.4 mm, respectively. Mean connective tissue repair to the root surface in chronic defects amounted to 62% (range 49% to 74%) of the defect height. Mean connective tissue repair in the acute defects exceeded 94% of the defect height in 4 of the dogs, but amounted to only 48% in 1 dog. Regeneration of alveolar bone and cementum was limited under both experimental conditions. Root resorption was frequently encountered, whereas ankylosis was seen in only few teeth. This study indicates that healing may vary not only as a result of controlled experimental variables, but also due to differences in biological response between dogs or to fortuitous traumatic factors.(ABSTRACT TRUNCATED AT 250 WORDS)

Periodontal Repair in Dogs: Effect of Root Surface Treatment With Stannous Fluoride or Citric Acid on Root Resorption

This study evaluated healing, with emphasis on root resorption, following root surface treatment with 1% aqueous stannous fluoride (SnF2), saturated citric acid (CA), or saline control (C) in conjunction with periodontal flap surgery. Supraalveolar periodontal defects were surgically created and immediately treated in the mandibular premolars in 6 beagle dogs. The defect height approximated 5 to 6 mm from the reduced alveolar bone to the cemento-enamel junction. Root treatments were rotated between experimental teeth within jaw quadrants and duplicated in left and right quadrants in the dogs. Flaps were raised to cover most of the crowns of the teeth and sutured. The dogs were sacrificed 12 weeks after surgery and tissue blocks with teeth and adjacent structures were processed for histometric analysis. SnF2-treated teeth healed with significantly longer junctional epithelium, less connective tissue repair to the root surface, and less bone regeneration than CA and C-treated teeth. New cementum formation was limited in all treatment groups. Root resorption was observed in almost all teeth exhibiting connective tissue repair, however to a lesser amount and not as frequent in SnF2 treated teeth due to limited connective tissue repair. No differences were found in amount and frequency of root resorption in CA and C-treated teeth. An inhibitory effect on root resorption of SnF2 could not be disclosed in this experiment, however, it may be concluded that CA treatment of the root surface in conjunction with reconstructive periodontal flap surgery does not seem to enhance root resorption.

Periodontal repair in dogs Healing patterns in large circumferential periodontal defects

This report describes the healing patterns of large circumferential periodontal defects in the beagle dog. Approximately 5 mm large periodontal defects were created around the mandibular premolars (P2, P3 and P4) in 13 animals. The root surfaces were then instrumented to remove all cementum and the wounds immediately closed by replacing and suturing the flaps just coronal to the cemento-enamel junction. Block biopsies were harvested after 4 weeks. Most of the surgically denuded root surface healed with connective tissue repair. Cementum formation and regeneration of alveolar bone was limited and averaged approximately 30% and 20%, respectively, of the defect height. Almost all teeth exhibited root resorption. Ankylosis was observed in 1/3 of the teeth. There was no difference in the healing response between the 3 premolars or their buccal and lingual surfaces. The range of healing responses indicates that a biological potential exists which makes this model useful for testing the effect of various root and wound conditioners in (1) enhancing cementum formation on the root surface, (2) increasing regeneration of alveolar bone and (3) preventing aberrant healing events such as root resorption and ankylosis. Conversely, whether such agents may compromise wound healing and result in reduced connective tissue repair may concomitantly be tested.

Periodontal repair in dogs Effect of heparin treatment of the root surface

Studies on periodontal repair to denuded root surfaces have suggested that initial clot adhesion to the root surface may be important for the nature of subsequent healing. To study this hypothesis, circumferential periodontal defects, approximately 5 mm in vertical dimensions, were surgically created and immediately treated around the mandibular premolars in 4 beagle dogs. Prior to wound closure, the root surfaces were treated with either the anticoagulant heparin or with saline. Tissue blocks were obtained at sacrifice 4 weeks after surgery. Histometric analysis showed that connective tissue repair to the root surface averaged 50% of the defect height for heparin-treated teeth as compared to 95% for saline-treated teeth. Junctional epithelium amounted to an average of 33% of the defect height in heparin-treated teeth in contrast to 5% following saline treatment. It can be concluded that heparin treatment of the root surface compromises connective tissue repair, confirming clot adhesion as one prerequisite for connective tissue repair of periodontal defects.

Periodontal Repair in Dogs: Effect of Wound Stabilization on Healing

This study evaluated a biodegradable polylactic acid matrix as a wound stabilizing implant in reconstructive periodontal surgery. Supra-alveolar circumferential periodontal defects, 5 to 6 mm large, were surgically created around the mandibular premolars in 7 beagle dogs. The root surfaces in left and right jaw quadrants were treated with either heparin or saline. In this model, root surface treatment with heparin compromises periodontal repair and results in a long junctional epithelium and a reduced connective tissue repair to the root surface, whereas saline treatment results in almost complete connective tissue repair. Following heparin or saline treatment a polylactic acid implant was placed on 1 premolar in each quadrant. After 4 weeks of wound healing, the dogs were sacrificed and tissue blocks prepared for histometric analysis. Postoperatively, the implant became exposed and infected in 3 dogs and had to be removed. Therefore, the results reflect the 4 dogs in which healing progressed uneventfully. Connective tissue repair to the root surface in teeth treated with heparin averaged 82% of the defect height. Mean connective tissue repair in teeth treated with heparin and the implant was significantly greater and comprised approximately 99% of the defect height (P less than 0.05). Teeth treated with saline either with or without the implant also healed with almost complete connective tissue repair. The results support the importance of wound stabilization in periodontal wound healing. Development of biodegradable implant systems aimed at stabilizing and supporting the healing wound seems a desirable direction for future research in regenerative periodontal procedures.

Guided Tissue Regeneration Following Treatment of Recession‐Type Defects in the Monkey

Recent studies have demonstrated extensive amounts of new attachment formation following reconstructive surgery based on the biological principle of guided tissue regeneration (GTR). The aim of the present investigation was to evaluate the effect of using a polytetrafluorethylene (PTFE) membrane in GTR-treatment of recession-type defects and to examine the interrelationship between the PTFE membrane and surrounding periodontal tissues. Full-thickness flaps were raised around 24 maxillary premolar and molar teeth in 6 monkeys. The buccal alveolar bone was surgically removed to a level corresponding to the apical third of the roots. The exposed root surfaces were scaled and planed. In 12 teeth, PTFE membranes were adjusted to cover the exposed root surfaces from a level 1 to 2 mm apical to the CEJ, to a level 3 to 4 mm apical to the alveolar crest. The coronal border of the membranes was tightly adapted to the root surfaces by sling sutures. Twelve teeth served as control teeth without placement of membranes. The flaps were placed with the margin coronal to the CEJ and sutured. The animals were sacrificed after 3 months of healing and all experimental teeth were subjected to histological analysis. The membranes were found to be incorporated with the surrounding connective tissue, and the apical extension of the junctional epithelium terminated at the coronal border of the membranes. The amount of new attachment formation was on the average 74.3% of the defect height in the test teeth, which corresponded to 100% of the membrane covered root portion. Newly formed connective tissue attachment in the controls amounted to an average of 36.9% of the defect height.(ABSTRACT TRUNCATED AT 250 WORDS)

Periodontal Repair in Dogs: Effect of Saliva Contamination of the Root Surface

This study evaluated whether periodontal repair following reconstructive surgery may be compromised by saliva contamination of the root surfaces during the surgical procedure. Circumferential periodontal defects, 5 to 6 mm in vertical dimension, were surgically created in the mandibular premolars in 9 beagle dogs and immediately treated. The denuded root surfaces in left and right jaw quadrants in 4 dogs were treated with either filter sterilized saliva or saline, while in the remaining 5 dogs the root surfaces were treated with unfiltered saliva or saline. The wounds were closed and allowed to heal for 4 weeks. The dogs were sacrificed and tissue blocks prepared for histometric analysis. Results showed no difference between teeth treated with filtered or unfiltered saliva and the saline treated controls. Connective tissue repair to the root surfaces exceeded 70% of the defect height in all experimental groups. Regeneration of cementum and alveolar bone was limited and did not exceed 30% of the defect height. The results indicate that contamination of the root surface by saliva during the surgical procedure does not necessarily compromise connective tissue repair to the root surface.

Connective tissue repair in circumferential periodontal defects in dogs following use of a biodegradable membrane

A biodegradable polylactic acid membrane was evaluated for its ability to enhance periodontal regeneration. In 8 Labrador dogs, circumferential defects were created around the maxillary 1st premolars. The defects were combination "1-wall vertical and horizontal". A membrane was adjusted to cover the defect on one side of the jaw, while the contralateral tooth served as control without membrane. After 3 months, healing was evaluated histologically. The results demonstrated that the amount of connective tissue repair with newly formed cementum approximated 50% of the defect height for both test and control groups. Thus, no advantage to the use of membrane was found, which is contradictory to the findings of our previous dog study using the same biodegradable membrane. The possible reasons for this difference in results are discussed relative to suggested mechanisms for membrane effects in periodontal regeneration.

The effect of spacing on Sitka spruce weevil damage to Sitka spruce

Tree diameter, height, form, and number of stem defects were recorded in 26-year-old plantations of Sitka spruce, Piceasitchensis (Bong.) Carr., established at three initial spacings (2.74 × 2.74, 3.66 × 3.66, and 4.57 × 4.57 m). These plantations were heavily attacked by the Sitka spruce weevil, Pissodesstrobi Peck, from an early age. Denser plantations sustained a lower intensity of attack than the more open plantations. Although the three spacings had similar average number of stem defects per tree, trees in the close spacing had a significantly higher frequency of trees of good form relative to the more open plantations. It was concluded that trees planted at close spacing had lower levels of weevil damage. As a management regime, it is recommended that Sitka spruce plantations be started at close spacing (2.74 × 2.74 m) and precommercially thinned at age 25. By this age trees will average about 19 cm in dbh and 12 m in height, thus ensuring a first log of good quality.

The approximal bone height and intrabony defects in young adults, related to the salivary buffering capacity and counts of Streptococcus mutans and lactobacilli

Using a computerized technique the bone height and prevalence of approximal periodontal intrabony defects were assessed on posterior bite-wing radiographs from 151 young adults. The results were related to the buffering capacity and counts of Streptococcus mutans and lactobacilli in whole stimulated saliva. The mean distance from the cement-enamel junction to the alveolar bone crest was greater in the high buffering group than in the low buffering group ( p < 0.05), and particularly in non-smokers ( p < 0.01). Intrabony defects were more common in the low buffering group ( p < 0.05) and in women ( p < 0.001).

Comparison of Decalcified Freeze–Dried Bone Allograft and Porous Particulate Hydroxyapatite in Human Periodontal Osseous Defects

The purpose of this study was to clinically compare the healing potential of the osteoinductive decalcified freeze-dried bone allograft (DFDBA) with an osteoconductive synthetic graft, particulate porous hydroxyapatite (HA). Six patients ranging in age from 28 to 52 (mean age 42.6) participated in this investigation. They were without significant systemic disorders and had advanced periodontitis with at least two comparable periodontal defects. Each patient received initial therapy consisting of oral hygiene instruction, scaling, root planing, and occlusal adjustment as indicated. Probing pocket depth, gingival recession, attachment levels, and bleeding on probing were recorded in the posthygiene phase of therapy. Alveolar crest height and depth of osseous defect were obtained at the time of surgery. The cemento-enamel junction was used as the fixed reference point. All measurements were repeated at the time of a 6-month reentry. There was no significant difference in any of the soft tissue measurements when DFDBA and HA were compared. However, both treatment modalities reduced pocket depth and demonstrated a gain in clinical attachment levels. There was 2.2 mm of bone repair with DFDBA and 2.1 mm with HA. These values corresponded to a percent defect fill of 61% for DFDBA and 53% for HA. These values were likewise not statistically different.

Parametric studies on the effect of defect characteristics on their detection and sizing by ultrasound

This paper describes the experimental results of the characterisation of the ultrasonic response produced by planar ‘diffusion welded’ defects, inspected with the pulse-echo technique with probes at angles of inclination of 45°, 60° and 70°. In particular, the amplitude and time locus curves for orthogonal scanning lines at the defect plane and passing through its middle have been determined. In general, a diffuse presence of effects linked to mode conversion phenomena of the ultrasonic wave incident on the defect was observed, which in many cases made interpretation of the results more complicated. For the embedded vertical defects (tilt angle equal to zero) it was possible to determine the curves giving the echo maximum amplitude as a function of the defect depth; these curves have a regular behaviour which follows the line of the DAC curve quite well. Even for surface defects which can be detected by the corner effect, one finds quite regular behaviour as a function of the various parameters (defect height, probe angle, tilt angle), while it is more complicated to interpret the results for the embedded inclined defects (tilt angle different from zero), probably because of the different contributions of the mode conversion phenomena in the individual cases.

Atom scattering from surfaces with isolated impurities: Calculations for hard wall and soft potentials

The angular intensity distribution for atom scattering from surfaces with isolated defects is calculated. For a two-dimensional model time-dependent wave packet calculations are carried out for potentials with different steepness and variable defect size and height. The influence of the potential softness is studied by comparison with results from a corresponding hard wall model. Within the hard wall model the Eikonal approximation (EA) and an improved Eikonal approximation (IEA) which accounts for double collision effects are tested against numerically exact results. While, in general, the EA works well only in the vicinity of the specular peak the IEA is quite accurate over the entire angular range. Finally, wave packet calculations are carried out for a model of a flat surface with isolated steps, fitted to represent a stepped Pt(111) surface. The results are compared to recent measurements of the incoherent elastic diffraction for this system. Basic measured features like a rainbow maximum and large angle interference oscillations are well reproduced by the calculations.

Destructive testing of defective weldments: Fracture mechanics predictions of failure loads and defect criticalities compared with experimental results

Thirty welded test plates containing discrete artificial defects were tested to destruction under controlled four point bending, and the failure loads recorded. The defect parameters, length, height and depth, were measured from the resulting fracture surfaces. Prior to destructive testing, the defective welds had been ultrasonically inspected, in two separate UT programmes, by a number of independent operators. Both actual and predicted defect sizes were used in conjunction with the Design Curve approach of British Standard PD 6493 to calculate failure stresses for each of the test plates. In addition, the Failure Assessment Diagram of the Central Electricity Generating Board (UK) R-6 document was used to establish defect criticality, of both the actual and the predicted defect parameters. The results obtained indicate that there appeared to be some tolerance in both assessment routes to the significant variability observed in the ultrasonic defect size predictions. However, precise predictions of failure stress levels and defect criticalities are only possible when defects are accurately sized.

Statistical aspects of defect evaluation using ultrasonics

The trend to use non-destructive testing, in particular ultrasonics, to provide quantitative information about weld defects for use in fracture mechanics calculations has highlighted the uncertainties surrounding measurements of defect size. Disquiet has been expressed concerning the degree of scatter which has been found to exist in ultrasonic measurements of both defect height and length, and how such scatter affects the ability to determine a fabrication's quality in relation to calculated fitness-for-purpose criteria. A statistical treatment of the scatter of ultrasonic defect size measurements, together with the other main factors which lead to a weld failure — thae chances that a defect exists and the likelihood that it is of critical size — shows that it is the occurence and severity of defects which have the major effect on weld integrity after inspection, not the accuracy of the ultrasonic measurements. Adequate weld quality is easily achieved without recourse to extremely high accuracy NDT if design and fabrication quality are good. It is very difficult to demonstrate fitness-for-purpose by the use of rigorous NDT if initial fabrication quality is poor.

Scattering Characteristics Of Optical Materials

In the visible and ultraviolet regions of the spectrum the dominant source of scattered light from optical components is surface scattering by microirregularities. They are typically only a few nanometers in height but cover the entire optically polished surface. Since microirregularity scattering is inversely proportional to the square of the wavelength, the dominant source of scattering in the infrared is often macroscopic defects such as scratches or digs. Pitting of the surface by sand or rain erosion also contributes to defect scattering. Dust particles and other particulates are a third important source of scattered light in the near infrared. When specifying the surface quality of optical components to be used in low scatter applications, at least the rms microroughness of the surface and the scratch/dig specification should be given. (An improved scratch standard would be most helpful here.) Better yet is a functional test of the scattering performance of the component. The most direct functional test is total integrated scatter. A prototype instrument utilizing a Coblentz sphere and a HeNe laser operating at 3.39 p.m, where the dominant source of scattering is scratches and other macro-scopic defects; at 1.15 p.m, where particulates such as dust may be important; and at 0.6328 pm, where microirregularity scattering dominates, has been constructed to perform this functional test. A simple theory allows us to extrapolate the results at these wavelengths to obtain a reasonably complete picture of the total integrated scattering behavior of the component at any wavelength. Additional data are required to understand the angular dependence of the scattered light since the angular dependence of scattered light is related to the slopes as well as the heights of the surface defects. Such data can be measured experimentally and analyzed to give a more complete picture of the surface than is obtainable from total integrated scattering measurements alone.

超音波斜角 B スコープ法による溶接欠陥の寸法評価

The estimation of the size of the artificial defects by the ultrasonic B-scope angle beam testing is investigated experimentally and the results obtained are summarized as follows. (1) The distributions and length of the weld defects in a joint can be recorded with single photograph by the ultrasonic B-scope angle beam testing. (2) The length of the planar defects and two dimensional defects can be estimated by the ultrasonic B-scope angle beam testing almost as well as the X-ray testing so far as adjusting previously the effects of the angle of beam spread. (3) The method to evaluate the shape of weld defects by the ultrasonic B-scope angle beam testing is examined and succeeded to some extent. (4) The height of weld defects can be estimated by the ultrasonic B-scope angle beam testing with some precision so far as adjusting previously the effects of the angle of beam spread (see, Fig.13).

超音波斜角探傷法による溶接欠陥の寸法評価

The estimation of the size of the model defects and the artificial weld defects by the ultrasonic angle beam testing is studied and the results obtained are summarized as follows, (1) As for the maximum resultant echoes reflected from the model defects, there is a difference of 15 dB between the upper and the lower range of the test results (see, Fig. -5). This is resulted from only the difference of the angle of inclination of the model defect to the surface of the test specimen. (2) As for the test results of the artificial defects, there is no relation between the defect length and the maximum resultant echo (see, Fig. -6), but there is a slight correlation between the defect height and the maximum resultant echo although the deviation of the test results is up to 14d (see, Fig. -7). (3) The results of the ultrasonic testing show considerable difference when tested from one side and from the other side of the weld bead even if the other test conditions remain the same (see, Table-3). (4) As for the estimation of the defect height the method of 6 dB attenuation is better than the method of the maximum resultant echo. (5) The method of 8-9 dB attenuation is applicable for the estimation of the length of the model defect, but 10 dB attenuation is preferable for the artificial defect since the shape of the tip of the defect is uncertain. (6) As for the defects of small size, attenuation methods are apt to overestimate the size of the defects.

Determination of the size of defects by the ultrasonic impulse echo method

Much to the detriment of ultrasonic testing and all attempts at standardization, it is not yet possible to compare the results from different kinds of equipment regarding the echo of a back wall or a small defect. In order to facilitate this, the relations between echo height, distance and size of circular disk defect are brought into simple and universally applicable forms. It is shown that the first back echo of a simple plate is the most convenient reference echo. With the help of a calibrated gain control as accessory to a usual flaw detector and a graphical representation of the formulae, an equivalent circular disk defect can be attributed to the actual defect. The influence of curved contact and back wall surfaces, and the application of the method for determining ultrasonic attenuation in thick specimens, is discussed.

Preliminary note on the spectral energy sensitivity of photographic materials

The ultimate goal of tissue engineering is to reproduce functional alveolar∖Periodontal complex. This study aimed to asses micro- and nano-formulated crystalline calcium sulfate as possible treatment of intrabony defect utilizing an autologous Platelet rich fibrin scaffold.and Methods: An experimental prospective split mouth design using eight healthy mongrel dog’s was conducted. After two months of extracting the first premolar, bilateral intrabony defects were created mesial to the mandibular second premolar. One side was grafted by nanocrystalline calcium sulfate, while, the opposite side was grafted with microcrystalline calcium sulfate graft. Dogs were randomly euthanized after one month (group I) and 3 months (group II). The primary outcomes were the histological changes of new bone formation in hematoxylin and eosin and Masson trichrome stains, while histomorphometric and radiographic analysis were the secondary outcome followed by statistical analysis (P value was set at .05).There was a significant increase in the percentage of bone formation in relation to defect height in nanocrystalline compared to microcrystalline form after one month and three months in both histological (p-values of <0.0001) and radiographic results (p-values of <0.0001).Nanocrystalline calcium sulfate presented a significant enhanced periodontal regeneration compared to the microcrystalline form.