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PubMed1995

A comparison of tissue reactions to Ketac-Fil and amalgam.

The objective of this study was to compare the bone tissue reactions of Ketac-Fil to the most commonly used retrograde filling material, amalgam, in a rat model. Forty-eight Harlan rats were divided into three groups: amalgam, Ketac-Fil, and controls. Following anesthesia, the right lower incisor was extracted from each animal. A 3-mm long x 1-mm diameter polyethylene tube filled with amalgam or Ketac-Fil was implanted in the extraction site. The animals were killed at 14, 42, and 90 days; and the mandibles were dissected en block and processed histologically. The inflammatory reaction was assessed by the number of plasma cells, lymphocytes, polymorphonuclear neutrophils, giant cells, and osteoclasts within 100 microns of the implant. Bone formation was determined as either present or absent in the same area. There was no statistically significant bone apposition within 100 microns of the Ketac material, and there was a statistically significant increase in inflammation in the amalgam group. This study indicates that both Ketac-Fil and amalgam are relatively biocompatible, and provides support for clinical usage tests of Ketac-Fil as a retrograde filling material.

Alveolar Process↗
PubMedDate not supplied

Criteria for implant selection: surgical and prosthetic considerations.

With the availability of osseointegrated implants in an assortment of diameters as well as lengths, the implant selection process has become more complex. To expand treatment options and optimize outcome, implant selection should be guided by a number of surgical considerations and prosthetic requirements specific to each implant site. Small diameter implants are appropriate in areas of narrow ridge dimension or where prosthetic space is limited. Wide diameter implants are well suited to posterior regions with poorer bone quality and restricted vertical height. They provide a higher degree of implant-to-bone contact, increased stability, reduced screw stress, and an improved emergence profile. The learning objective of this article is to discuss these considerations and to outline the implant selection criteria.

Alveolar Bone Loss↗
PubMed1992

Effect of stannous fluoride and tetracycline on periodontal repair after delayed tooth replantation in dogs.

Previous studies have indicated that inflammatory resorption and ankylosis, which are frequent sequela after delayed tooth replantation, can be greatly reduced by treating the root surface with 1% solutions of stannous fluoride and tetracycline. However, the SnF2 conditioning leaves a long-standing inflammatory reaction in the periodontal ligament. To examine whether a more dilute SnF2 solution would reduce postoperative inflammation without jeopardizing any beneficial effects, anterior teeth in three young adult beagles were extracted and allowed to air-dry for 45 min. They were then immersed in 0.1% SnF2 for 5 min, rinsed in saline, immersed in 1% doxycycline HCl for 5 min, rinsed, and replanted. Control teeth were air-dried and replanted without further treatment. Block biopsies were harvested after 4 wk of healing and processed for histometric analysis. In experimental teeth, 85% of the root surface area showed normal healing, compared to 33% in control teeth. Conversely, resorption and ankylosis were more frequent in controls than in experimental teeth. A persisting inflammatory reaction either adjacent to or at a distance from the root surface was seen in limited areas in both experimental and control teeth. Compared to preceding studies, the findings indicate that reducing the strength of the SnF2 solution from 1% to 0.1% may result in less persistent inflammation, at the cost, however, of less complete prevention of inflammatory resorption and ankylosis.

Alveolar Process↗
PubMed1993

Surfactant treatment effects on alveolar type II cell morphology in rabbit lungs.

The effects of exogenous surfactant administration on alveolar type II cells and the lung parenchyma were examined in adult rabbits. Natural surfactant was instilled into the left lobe of New Zealand White rabbits while the right lobe served as the control. Four hours post-instillation, the lungs were fixed by vascular perfusion. Surfactant instillation did not change alveolar type II cell size but was associated with a significant reduction in the volume fraction of lamellar bodies in type II cells (20.4% in control lobes compared with 11.9% in surfactant-treated lobes). The size distribution of lamellar body profiles was different in surfactant-treated lobes compared with control lobes, with a significant decrease in lamellar bodies > 0.8 microns in diameter and a twofold increase in lamellar bodies 0.2-0.4 microns in diameter. Composite body profile number was also increased by 87% (P < 0.05) after instillation of surfactant compared with control. Saline instillation decreased lamellar body volume fraction in type II cells but three times less than surfactant instillation. These observations are consistent with a strong stimulus for secretion of endogenous surfactant 4 h after surfactant instillation in normal adult rabbit lungs, whereas the increase in composite bodies is consistent with new lamellar body formation, probably from both de novo synthesized and exogenous natural rabbit surfactant. These observations confirm that the secretory and synthetic processes of alveolar type II cells are significantly affected by exogenous surfactant instillation.

Animals↗
PubMed2006

Analysis of bone-implant interaction phenomena by using a numerical approach.

OBJECTIVES: The purpose of the present work is to investigate the interaction phenomena occurring between endosseus dental implants and peri-implant bone tissue. MATERIAL AND METHODS: Detailed finite element models are adopted in order to analyze the actual behavior of bone-implant system depending on implant and anatomical site configuration and loading conditions. Different types of titanium dental implants are considered. Implant finite element models are obtained through a reverse engineering procedure and adopting specific software for the reconstruction of geometrical configuration. Anatomical sites are modeled starting from computerized tomography data, according to specific image processing procedures. RESULTS: Occlusal static forces are applied to the implants and their effects on the bone-implant interface region are evaluated. The influence of several parameters, such as morphometry of anatomical site or loading condition, on the biomechanical response of bone-implant system is considered. CONCLUSIONS: The evaluation of the biomechanical response of implant-bone compound necessarily requires the adoption of accurate numerical models, accounting for the complex geometry of threaded implants, as well as of the anatomy of the patients to be able to provide for reliable results pertaining to stress/strain path on peri-implant bone tissue.

Alveolar Process↗
PubMed1988

Automated classification of periodontal disease using bitewing radiographs.

The feasibility of applying a prototype, computer-based pattern recognition system to the objective classification of periodontal disease using dental radiographs was tested. Twenty-nine observer-classified bitewing radiographs, representing seven individuals with varying grades of periodontal disease, were selected. The radiographs were digitized using a computer-controlled TV camera. Mathematical features of these radiographs were interactively extracted using a digital image processing system (International Imaging Systems Model 75 and System/575). The features extracted from these radiographs included the brightness levels of cortical and trabecular bone and ratios of bone-loss to linear-crown height. Twenty-eight mathematically defined features (variables) were determined for each radiograph. Stepwise linear discriminant analysis used these features to classify subjects based on the presence and extent of periodontal disease. This pattern recognition system was able to grade periodontal disease in our test series with percentages of correct classifications ranging from 78.8% to 91%. This technology is particularly applicable to the development of morbidity and activity indices for periodontal diseases.

Alveolar Process↗
PubMed1979

The Merkel cell in the labial ridge epidermis of the anuran tadpole. II. Electron microscope observations on the appearance and differentiation of the Merkel cell.

The appearance and cytodifferentiation of the Merkel cell were studied electron microscopically using the developing labial ridges of Rana japonica. The most primitive Merkel cell was identified with specific cored granules with an average diameter of about 90 nm. Such a primitive Merkel cell was found in the basal layer of the primitive labial ridge epithelium. As the primitive labial ridge continued to mature, the primitive Merkel cell accumulated an increased number of the specific granules, developed digital shaped cytoplasmic processes and came into contact with nerve fibers. When the labial ridge was sufficiently developed the cell showed typical morphological features of the mature Merkel cell except for a small accumulation of tonofilament-like structures and glycogen particles. It was also observed that the position of the Merkel cell in the epithelium changed from the basel layer to the third basal layer during development. On the other hand, it was difficult to find the Merkel cell in the mesenchymal layer of the developing labial ridges. From the results, it was suggested that the cytodifferentiation of the Merkel cell in the labial ridge of an anuran tadpole occurs within the epithelium.

Alveolar Process↗
PubMed1981

Associations between crestal lamina dura and periodontal status.

The purpose of the present study was to investigate associations between radiographic crestal lamina dura and the clinical periodontal status of the corresponding interdental area. The population consisted of 90 individuals (53 females and 37 males), ages 21 to 45 years (mean 31 years), who underwent a comprehensive periodontal examination. Buccal and lingual to the contact point at each interdental area four different clinical criteria were scored as being present or absent: (i) visual inflammation, (ii) bleeding after probing with 25 gm force, (iii) pocket depth greater than 3 mm after probing with 50 gm force, (iv) loss of connective tissue attachment. Bite-wing and full-mouth periapical radiographs were taken and processed using standardized techniques. Each interdental crestal area on the radiographs was examined and scored for presence or absence of an intact lamina dura. Statistical analyses were undertaken using correlated means to compare the presence or absence of lamina dura with the individual and simultaneous clinical criteria. No significant differences were obtained between any of the comparisons and, in addition, there was no correlation between lamina dura images on periapical and bite-wing radiographs. The results indicated that crestal lamina dura on radiographs did not appear to be related to the presence or absence of clinical inflammation, bleeding upon probing, periodontal pockets or loss of attachment.

Adult↗
PubMed1997

Failing hollow implants examined by light microscopy and image processing.

The purpose of this study was to evaluate the radiologic, histologic, and histometric findings of three failing hollow implants. On periapical radiographs, these implants showed vertical bone loss up to the hollow portion around the implant. Examination of the histologic sections disclosed that the hollow portions of all the implants were almost filled with bone tissue, although slight bone resorption and presence of granulation tissue infiltrated with inflammatory cells was observed coronal to the hollow portion. Histometric analysis disclosed that the average percent bone contact was 93.1% in case 1, 90.9% in case 2, and 84.3% in case 3 and the average percent bone filling was 42.1%, 50.5%, and 33.8%, respectively. Consequently, there seems to be some potential for successful treatment of these implants because the destructive changes were limited to the coronal aspects of the implant.

Alveolar Bone Loss↗
PubMed1985

The accuracy of clinical parameters in detecting periodontal disease activity.

A review of the literature shows that, currently, no reliable clinical parameter exists either to indicate existing disease activity or to predict future periodontal deterioration. The common clinical parameters used in practice merely assess gingival status or indicate that tissue destruction has occurred earlier (Fig 9). Although many clinicians mistakenly use them as indicators of ongoing destruction, these clinical findings have more value as educational and motivational tools. More sophisticated parameters (that is, antibody tests, and subtraction radiography) are being developed, and their accuracy in identifying disease activity is being tested. These parameters differ in their degrees of accuracy and reliability and, currently, are best suited for research purposes. Quantitative plaque assessments, once shown to have a correlation with incidence of periodontal disease in study populations, have been proved recently to be inaccurate in assessing periodontal disease activity when evaluating specific individuals and sites. Qualitative assessments are more reliable in determining areas that have suffered from specific periodontal disease processes, but their accuracy in identifying ongoing deterioration is questionable. Although it generally is agreed that bacterial plaque is the cause of periodontitis, no plaque assessment to date has been reliable consistently as an indicator of existing or impending periodontal disease activity. Plaque indexes can be used to educate and motivate patients in the removal of this most important etiologic agent. Clinical gingival assessments do not indicate existing or impending periodontal disease activity with loss of attachment and, therefore, are of little value in diagnosing periodontitis. Because gingival inflammation is an undesirable deviation from health, gingival indexes are valuable as a signal to the clinician to manage these patients more closely.(ABSTRACT TRUNCATED AT 250 WORDS)

Alveolar Process↗
PubMed1995

In situ hybridization shows Dmp1 (AG1) to be a developmentally regulated dentin-specific protein produced by mature odontoblasts.

Acidic phosphorylated proteins are prominent constituents of the extracellular matrix of bone and dentin. It has been postulated that they may have important structural and regulatory roles in the process of tissue mineralization. Studies of a cDNA library, prepared from cells of the rat incisor odontoblast-pulp complex of 3 week old Sprague-Dawley rats, led to the identification of a serine-rich acidic protein, designated AG1, which appeared to be a dentin matrix component. In order to determine which cells of the odontoblast-pulp complex were responsible for the making of AG1, in situ hybridization was carried out using digoxigenin-labeled probes. The full length AG1 cDNA was subcloned into the pBluescript vector, which contains two strong promoters, T3 and T7. The sense and antisense complementary RNA (cRNA) hybridization probes were prepared by in vitro transcription using T3 and T7 polymerases in the presence of 11-dUTP. Incisor sections were obtained from rat embryos at days 16, and 20, and newborns at days 2 and 5. No AG1 mRNA was detected in the embryonic sections, but digoxigenin labeling was evident in odontoblasts secreting mineralizing dentin at postnatal days 2 and 5. Sense probes showed no hybridization. Pulp cells, Meckel's cartilage, and alveolar bone were free of hybridization with the antisense probe. Unexpectedly, a low level of digoxigenin staining was seen in the cytoplasm of secretory ameloblasts, but not in the preameloblasts, stratum intermedium or stellate reticulum of the enamel organ. These data show that AG1 expression is regulated developmentally and is restricted to secretory stage mature odontoblasts.

Alveolar Process↗
PubMed2004

Enamel matrix derivative and guided tissue regeneration in the treatment of dehiscence-type defects: a histomorphometric study in dogs.

BACKGROUND: The goal of this investigation was to histologically and histometrically evaluate the healing process of dehiscence-type defects treated by enamel matrix derivative (EMD) and/or guided tissue regeneration (GTR). METHODS: Seven mongrel dogs were used. Buccal osseous dehiscences were surgically created on the mesial roots of the mandibular third and fourth premolars. The defects were exposed to plaque accumulation for 3 months. After this period, the defects were randomly assigned to one of the treatments: open flap debridement (OFD), enamel matrix derivative (EMD), GTR with bioabsorbable membrane (GTR), and the combination of both procedures (EMD + GTR). After 4 months of healing, the dogs were sacrificed and the blocks were processed. The histometric parameters evaluated included gingival recession, epithelial length, connective tissue adaptation, new cementum, and new bone. RESULTS: A superior length of new cementum was observed in the sites treated by EMD (3.7 mm) and EMD + GTR (3.8 mm) in comparison with OFD (2.4 mm) (P < 0.05). No statistically significant differences were found in the remaining histometric parameters. CONCLUSIONS: Within the limits of this study, it can be concluded that EMD alone or in combination with GTR barriers may effectively promote new cementum formation. The combination of both therapies may not provide additional benefits.

Absorbable Implants↗
PubMed1998

Rapid canine retraction through distraction of the periodontal ligament.

The process of osteogenesis in the periodontal ligament during orthodontic tooth movement is similar to the osteogenesis in the midpalatal suture during rapid palatal expansion. A new concept of "distracting the periodontal ligament" is proposed to elicit rapid canine retraction in 3 weeks. It is called dental distraction. Fifteen orthodontic patients (26 canines, including 15 uppers and 11 lowers) who needed canine retraction and first premolar extraction were included. At the time of first premolar extraction, the interseptal bone distal to the canine was undermined with a bone bur, grooving vertically inside the extraction socket along the buccal and lingual sides and extending obliquely toward the socket base. Then, a tooth-borne, custom-made, intraoral distraction device was placed to distract the canine distally into the extraction space. It was activated 0.5 to 1.0 mm/day immediately after the extraction. The anchor units were the second premolar and first molar. Cephalometric and periapical x-rays were taken before and after the canine retraction. Both the upper and lower canines were distracted bodily 6.5 mm into the extraction space within 3 weeks. New alveolar bone was generated and remodeled rapidly in the mesial periodontal ligament of the canine during and after the distraction. It became mature and indistinguishable from the native alveolar bone 3 months after distraction. During the distraction, 73% of the first molars did not move mesially and 27% of them moved less than 0.5 mm mesially within 3 weeks. The radiographic examination revealed that apical or lateral surface root resorption of the canine was minimal. No periodontal defect or endodontic lesion was observed throughout and after distraction. We concluded that the periodontal ligament could be rapidly distracted without complications. The rapid orthodontic tooth movement through distracting the periodontal ligament cannot be emulated by current conventional orthodontic concepts and methods.

Activator Appliances↗
PubMed2000

The origin and development of the upper lateral incisor and premaxilla in normal and cleft lip/palate monkeys induced with cyclophosphamide.

OBJECTIVE: Cleft lip/palate (CLP) is a common human congenital defect in which the maxillary lateral incisors are often absent, malformed, and malpositioned. The present study was designed to examine the origin of the upper primary lateral incisor relative to the medial nasal process (MNP) and maxillary process (MP) fusion area and to the premaxillary/maxillary (incisive) suture in monkeys. METHOD: Scanning electron microscopy, histology, skeletal staining, and drying techniques were used to study facial development in embryo and fetal monkey specimens. A teratogenic dose of cyclophosphamide was administered to pregnant monkeys prior to fusion of the MNP and MP and fetuses were examined for CLP. RESULTS: Formation of the anterior maxilla involved fusion of the MNP and MP at stages 14-18. At stages 18-20, the palatal portion of the MNP had formed the medial and lateral incisive mounds. By stage 22, the upper primary lateral incisor has formed within the MP, lateral to the MNP/MP fusion area and to the ossifying premaxilla. Ossification of the premaxilla begins in the MNP and subsequently spreads laterally across the MNP/MP fusion area into the MP. Accordingly, the lateral incisor undergoes a complex positional shift (mainly medial) relative to the incisive suture both prenatally and postnatally and is finally located medial to the suture. Examination of the cyclophosphamide-induced CLP fetuses showed that the lateral incisor is located lateral to the alveolar cleft and does not shift medial to the incisive suture. CONCLUSION: Understanding the origin of the lateral incisor (the tooth closest to the cleft) and the shift after its formation provides clues to high incidence of malformations and ectopia of this incisor in cleft patients.

Alveolar Process↗
PubMed1999

Iron overloading inhibits dentine mineralization.

The present study reveals the inhibitory effect of iron intoxication on the process of dentine mineralization. Wistar rats were injected intraperitoneally with iron dextran at 0.88 g/kg body weight per day for 10 days during the period of odontogenesis. An age-matched group was injected intraperitoneally with bisodium etidronate (EHBP) at 20 mg/kg body weight per day for 10 days. Another age-matched group was treated with similar amounts of saline intraperitoneally and considered as control. At the end of the experimental period the animals intoxicated with iron exhibited non-mineralized dentine and mineralized bone. The animals treated with EHBP showed non-mineralized dentine and bone. These findings would suggest the existence of different mineralization mechanisms for bone and dentine.

Alveolar Process↗
PubMed2001

Histology of connective tissue graft. A case report.

BACKGROUND: Few investigations can be found in the literature on the histological nature of the attachment of connective tissue grafts to root surfaces previously exposed by recession. METHODS: In this case report, a 24-year-old patient was treated with a connective tissue graft combined with a partial-thickness coronally positioned flap for root coverage of Class I Miller recessions at the maxillary right and left canines and first premolars. The treated sites exhibited 83% and 100% root coverage on the right and left sides, respectively. Twelve months later, the case required extraction of all 4 first premolars for orthodontic reasons. Two conservative block sections including the maxillary first premolars with the buccal soft tissues were obtained and processed histologically in a bucco-palatal plane. RESULTS: Histological analysis showed that healing occurred via a long junctional epithelium throughout the major portion of the previous recession site. Only minimal signs of new cementum-like tissue formation could be seen in the apical portion of the recession area coronal to the base of the instrumented root surface. No root resorption or ankylosis could be detected in any of the serial sections. CONCLUSIONS: The findings of this case report outline the possible variations in the histological outcome of connective tissue grafts. These variations can be attributed to differences in size and shape of the recession defects and flap positioning at the end of surgery.

Adult↗
PubMed1997

Effect of ovariectomy on the local residual ridge remodeling.

STATEMENT OF PROBLEM: Osteoporosis and edentulism are two disease processes that affect a large group of elderly people in the United States (24 and 25 million, respectively). These two diseases are independent of each other; however, they have several pathologic symptoms in common, such as reduction in bone mass. PURPOSE: The purpose of this study was to determine whether estrogen deficiency or its replacement therapy have any effect on the phenomenon of residual ridge remodeling. MATERIAL AND METHODS: Three animal groups were formed that consisted of six female Sprague-Dawley rats each. The two groups had ovariectomy and received either a vehicle solution or a daily dose (1.5 micrograms/day) of 17 beta-estradiol delivered through osmotic pumps. The control group underwent sham surgery and received a vehicle solution. Animals were pair fed throughout the experiment. Unilateral molar extraction was performed in the maxilla, which produced a suitable site for examination of histologic characteristics and molecular biologic analyses. At the 4-week postextraction period the bone remodeling activity was noted at the surface of the residual ridge in the control group. RESULTS: The ovariectomized group showed increased bone resorption activity, whereas the surface of the residual ridge alveolar bone of the ovariectomized and estrogen-treated group was covered by a layer of hyaline tissue. Poly(A)+ ribonucleic acid samples were isolated from the remodeling residual ridge tissues. Expression of alpha 2(I), alpha 1(II), alpha 1(IX), and alpha 2(X) collagens were examined by ribonucleic acid transfer dot blots. Compared with the control group, ovariectomized animals showed a reduction in bone formation with decreased expressions of type I and II collagens. In contrast, the estrogen-treatment group showed decreased formation of type I collagen with a much increased expression of type II collagen. Further examination of type II collagen formation on the ovariectomized and estrogen-treated group by means of in situ hybridization revealed the notable labeling by the type IIA collagen probe, which was associated with the surface tissue of the residual ridge alveolar bone. CONCLUSION: These findings suggest that estrogen deficiency and its replacement therapy seem to affect the activity of residual ridge bone remodeling at the molecular level.

Alveolar Process↗
PubMed1980

Conditions and pathological features of rapidly destructive, experimental periodontitis in dogs.

In order to analyze the conditions for rapidly destructive periodontitis and to describe the early histopathological changes and bone degradation, periodontitis lesions were produced in five male Beagle dogs, 8 to 12 months of age. Cotton floss ligatures were placed around the crowns of upper and lower third and fourth premolars for periods of 4, 7, 14, 21 days. The buccal gingival tissues, being slightly inflamed initially, were clinically scored for various symptoms of inflammation. Block biopsies of premorlars and the adjacent buccal periodontal tissues were taken and processed for light and electron microscopy. Depending on the ligature position in relation to the gingival margin (above, at, deep below) at the day of biopsy harvest, three groups of selected biopsies were formed, and randomly selected sections of these were used for various histometric measurements, for stereological estimation of the size and composition of the connective tissue infiltrate and the osteoclast density, and for general histopathological evaluation. The resulting data and observations implied that (1) onset and maintenance of this periodontitis lesion depend on subgingival ulceration, (2) rapid bone desstruction is the result of osteoclast activity stimulated by acute inflammation, and (3) bone degradation occurs independently of the loss of collagen fiber attachment and the apical migration of the junctional epithelium.

Alveolar Process↗