Local effect of titanium implant corrosion: an experimental study in rats.

The aim of this study was to evaluate histologically the biological effect of pitting corrosion and to contribute clinically relevant data on the permanence of titanium metal structures used in osteosynthesis in the body. Commercially pure titanium laminar implants (control) and commercially pure titanium laminar implants with pitting corrosion (experimental) were implanted in the tibiae of rats. At 14 days post-implantation the animals were killed. The tibiae were resected, fixed, radiographed and processed for embedding in methyl methacrylate. Percentage of bone-implant contact and peri-implant bone volume were evaluated. The histological study of the titanium implants submitted to pitting corrosion showed scarce bone-implant contact, it was only present in the areas with no pitting and/or surface alterations. There was a statistically significant lower percentage of bone-implant contact in the experimental group (6%+/-4) than in the control group (26%+/-6) (p<0.001). Products of corrosion in the peri-implant bed, especially around the blood vessels and areas of bone marrow in the metal-tissue interface, were observed. The microchemical analysis of corrosion products revealed the presence of titanium. The adverse local effects caused by pitting corrosion suggest that titanium plates and grids should be used with caution as permanent fixation structures.

A radiographic, histological, and histometric study of endodontic materials.

Silicone tubes filled with CRCS, a calcium hydroxide-based cement, were implanted at two different localizations in the right tibias of white male Wistar rats. A similar number of solid silicone rods were implanted in the left tibias of the same animals and were used as inert controls. Fifteen days after implantation the bone tissue reactions to these materials were evaluated by means of radiographic, histological, and histometric methods. The radiographic and histometric analysis of the tissues around the deep end of the implants showed that the amount of reactional bone formation in contact with CRCS was significantly lower than that observed in contact with the controls (p less than 0.01). Also, the cell counts obtained from the tissues in contact with CRCS were significantly less than those obtained from the controls (p less than 0.01). This methodology appears to be a refined procedure for analyzing the possible toxic effects of endodontic materials in bone tissues. However, we feel that more extensive experiments will be necessary before predicting the long-term results which could be obtained from this experimental model.

A histomorphometric study of tissue interface by laminar implant test in rats.

Study of the implant-tissue interface is one of the fundamental issues in implantology, both odontologic and orthopedic. The characteristics of this interface will influence the success or failure of an implant. The aim of the present study was to evaluate histomorphometrically the capacity of different metals to osseointegrate employing laminar implants of zirconium, titanium, aluminum, and zirconium coated with diamond-like carbon. The experimental model herein allowed for the quantitative evaluation of the tissue-implant interface for different metals. The implants were placed in the tibiae of Wistar rats under anesthesia and allowed to remain in situ for a 30-day period. The interfaces of the zirconium and diamond-like coated zirconium implants exhibited better responses than the interface of titanium implants. Aluminum produced a local toxic effect, evidenced by osteoid formation.

Malignant schwannoma of the gingiva.

A case of malignant schwannoma on the buccal-attached gingiva in the right mandible is described. There was no evidence of multiple neurofibromatosis and the tumor was totally excised. Numerous closely-packed spindle-shaped cells showing marked mitotic activity were seen. The recognizable pattern of neurilemmoma could be observed focally in a small area of the tumor. At two years follow-up, the patient has remained symptom-free with no signs of metastasis.

Ethane 1-hydroxy-1, 1-diphosphonate (EHDP) counteracts the inhibitory effect of uranyl nitrate on bone formation.

The beneficial effect of ethane 1-hydroxy-1, 1-diphosphonate (EHDP) in restoring the inhibition of bone formation in cases of acute uranium intoxication is presented. Bone formation was studied histomorphometrically in a model of alveolar bone healing. After tooth extraction, 40 rats were divided into 4 groups that received (1) no further treatment, (2) 10 daily intraperitoneal injections of 7.5 mg/kg of body weight of EHDP, (3) an intraperitoneal injection of 2.0 mg/kg of body weight of uranyl nitrate, and (4) the same treatment as was provided rats in groups 2 and 3. The results showed that the healing of bone did not occur in exposed animals, whereas healing in EHDP-treated exposed animals did not differ from that of nonexposed controls. This effect might result from a blocking and/or competitive action of EHDP and/or the stimulation that EHDP elicits at the doses and in the administration period studied.

Bone healing under experimental anemia in rats.

The effects of anemia on different physiological parameters have been the object of permanent study. There are no studies in the literature on the effects of this disorder on the process on bone healing. The aim of the present study was to evaluate, histologically and histomorphometrically, the process of osteogenesis in the post-extraction alvcolus of the lower molar, and in the peri-implant environment of rats. Twenty male Wistar rats (body weight (b.w.): 60 +/- 7 g) were grouped into two experimental sets. The control group (n:10) was given 0.5 mL saline solution i.p. The anemic group (n:10) was injected with 6 mg/100 g of b.w. or 3 mg/100 g b.w. phenylhidrazine, a well known hemolytic agent. Under ketamine-xylazine anesthesia the rats were submitted to extraction of the first lower molars, and to implantation in the tibia in keeping with the "laminar test" procedure. Other parameters, i.e. body weight (b.w.), food intake (FI), hematocrit (Htc), and hemoglobinemia (Hb) were monitored every 48 hs. The results showed a reduction in b.w., FI, Htc and Hb in the experimental group. The histological and histomorphometrical data show that the condition of anemia affects osteogenesis quali-quantitatively in the post-extraction alveolus and peri-implant microenvironment. Both bone reparative situations showed that ostegenesis is "sensitive" to anemia and/or the associated conditions, causing a delay in bone healing.

Oral pathology in children. Frequency, distribution and clinical significance.

A statistical study of 1289 biopsies of children 0-15 years old, received at the Pathology Department, Dental Faculty, Buenos Aires University is presented. This number, represents 6.8% of the 18,966 biopsies received from 1960 to 1985. The histologic diagnosis were grouped into the following categories: 1) cysts, 2) tumour-like lesions, 3) inflammatory lesions, 4) neoplasms, 5) neck and head non-oral lesions, 6) dental anomalies and pulp diseases, 7) unclassified diagnosis. Cysts were the most frequent lesion (25.4%). 75% were localized in the jaws and 25% in soft tissue. Bone tumour-like lesions (20.1%) were less frequent than the soft tissue tumour-like lesions (79.9%). Inflammatory lesions and neoplasms in children, account for 15.7% and 10.2% of the lesions respectively. Eighty four percent of the neoplasms were benign and 16% were malignant. Odontogenic tumours constituted 49.6% of all the neoplasms studied. These results indicate the need to be constantly aware of the possible presence of these clinical and radiographic lesions to allow for early diagnosis and adequate treatment.

Chronodynamic evaluation of the stages of osseointegration in zirconium laminar implants.

Osteogenesis occurs throughout all stages in life, due to both bone turnover and reparative processes. Thus, osseointegration (OI) can be described as the final step in a cascade of processes involved in bone healing in relation to implants. Ten groups of 5 Wistar rats each (mean = 90 g b.w.) were used. Under ether anesthesia a zirconium laminar implant was placed in the tibia following the method previously described by our laboratory (Cabrini et al Imp Dent 2:264-7, 1993). The animals were killed at Ohs, and 1, 2, 3, 6, 7, 10, 12, 14, and 60 days post-implantation. Tibiae were resected, radiographed and processed for their embedding in methyl methacrylate. Three sections, perpendicular to the major axis of the tibia, were obtained per implant and histologic and histomorphometric studies were carried out. Volume occupied by blood clot, woven bone, percentage of OI and OI bone tissue thickness, were determined. Histologic and histomorphometric studies as function of time revealed: a) at 6 days the presence of non-osseointegrated woven bone around the device is evident increasing in volume from 7 to 10 days post-implantation, and disappearing from day 12 to 14., b) at 14 days after implantation lamellar bone formation on the surface of the zirconium implants (OI) is noticeable. Additional bone growth is observed after 60 days. This study enables quantification of peri-implant reparative process response in an unloaded, necrotic trabeculae free model showing, in the different phases of the osseointegration process, the role of the blood clot and of the appearance and disappearance of woven bone and the final stages of osseointegration. Further investigation will allow comparison of results obtained under the effect of local and/or systemic factors that might affect osseointegration.

Use of Zircalloy to induce bone regeneration. A 2-year follow-up study.

In a previous study we analyzed the behaviour of Zircalloy 4 particles employed in patients with significant loss of periodontal bone support which threatened the permanence in situ of the tooth. We herein present the results obtained after regular examination over a 2-year period of 6 patients submitted to this treatment. Our results reveal that all patients exhibited excellent gingivo-periodontal health with an increase in clinical insertion of 7 mm +/- 1 and a marked reduction in motility from 3 to 1. None of the cases featured added inflammation or expulsion of the implant material. In one of the cases it was possible to study the histology of the area by punch biopsy with a disposable needle (Sherwood-Medical). Analysis of the sample revealed the presence of bone tissue in intimate contact with implanted metallic particles of Zircalloy 4, producing osseointegration. This osseointegration would lead to filling of the periodontal bone defect. Macrophages loaded with metallic particles were found in the vicinity of particles which were not osseointegrated. These features may correspond to superficial areas related with soft tissue as observed in our study on alveolar filling in rats with the same type of particles.

A method for the quality control of osseointegration in endosseous implants.

Metallic dental and orthopedic implants are essential therapeutic tool. The biologic success of an implant involves intimate contact between the implant and vital bone tissue, an event which has been termed osseointegration. The aim of the present study was to study the biocompatibility and biomechanic properties of different implant materials. Zircalloy 4 metallic cones (1.8 mm base x 2 mm height) were implanted in the diaphysis of the tibiae of 6 Wistar rats (90 g body weight) under i.p. Ethyl Urethane anesthesia. The animals were killed 30 days postimplantation, the tibiae were resected, and radiographed. One side chosen at random was used for the biomechanical study; whereas the other implant of each animal was processed for embedding in methyl-methacrylate. The bond of the implanted material to bone tissue was monitored immediately after resecting the tibiae by applying an extraction force to the base of the cone via a device designed ad hoc connected to a testing machine. Histological and radiographic analyses revealed the presence of bone tissue in contact with the implant surface. A force of about 35 g was necessary to separate the implant from the bone tissue. The system proposed renders possible the study of biocompatibility in histologic terms and in terms capacity to bond to bone tissue and could be a valuable research tool and the basis for quality control of all types of material, metallic or otherwise, used in endosseous implants.

A quantitative method to evaluate corrosion products in tissues.

The use of odontological or orthopedic metal implants requires the availability of techniques to estimate tissue response to the corrosion processes. In previous experimental studies we showed the deposition of corrosion products not only locally (Olmedo et al., Implant Dent 2003; 12: 75-80) but also systemically (Olmedo et al., J Mater Sci: Mater in Medic 2002; 13: 793-796) in organs such as liver, spleen and lung. The aim of the present study was to propose a method to quantitatively assess the tissue deposits of the corrosion products of the materials used to manufacture implants. The samples (liver and lung) were embedded in paraffin, and the histological sections were submitted to thickness standardization. The quantitative evaluation of the deposits was performed in an MPM-800 (Carl Zeiss)* microscope. The light microscopy images were digitalized and then analyzed employing the DNA-IBAS-Kontron software that allows for the identification and evaluation of cells loaded with corrosion products (objective 20x). The following end-points were assessed: total field area, number of deposits of corrosion products, partial and total area of the deposits, and the ratio between volume of the deposits and tissue volume. The method proposed serves to quantitatively evaluate, at light microscopy level, the deposition of corrosion products in tissues.

Influence of age and gender on peri-implant osteogenesis. Age and gender on peri-implant osteogenesis.

Among the local and systemic factors affecting bone repair, great interest is focused on age and gender. The aim of this work was to perform a histomorphometric evaluation of peri-implant bone healing response in male and female rats aged 1 and 3 months. Forty Wistar rats were i.p. anesthetized with xylazine and ketamine. A c.p. Ti implant (Implant Vel, Buenos Aires-Argentina) was placed in the right tibia following the method described by Cabrini et al. (Implant Dent 1993; 2:264-267). Group I: (GI, n = 10) female rats aged 1 month; Group II: (GII, n = 10) female rats aged 3 months; Group III: (GIII, n = 10) male rats aged 1 month; Group IV: (GIV, n = 10) male rats aged 3 months. All the animals were killed by ether overdose 30 days post-implantation. The tibiae were resected, radiographed and embedded in methyl-methacrylate. Ground sections perpendicular to the longer axis of the tibia were obtained and stained with toluidine blue. Percentage of osseointegration and peri-implant bone tissue volume were evaluated. No differences in peri-implant bone tissue histology were observed among groups. No statistically significant differences in peri-implant bone volume and percentage of osseointegration were observed between GII (adult females) and GIV (adult males). Peri-implant bone volume and percentage of osseointegration were markedly greater in GIV (adult males) than in GIII (young males) (14 +/- 1 mm2 and 8 +/- 2 mm2) p < 0.01 and (49 +/- 6% and 24 +/- 9%) p < 0.01 respectively. Using this experimental model, differences in peri-implant osteogenesis (bone volume and percentage of osseointegration) associated to gender were only observed in the young rats, and differences associated to age were found between the groups of males.

An experimental model to study implant corrosion.

Corrosion phenomena would appear to play a decisive role in metallic implant long term behaviour. This study presents a method to correlate results obtained in "in vivo" and "in vitro" studies on materials used for metallic implants. Samples of titanium and copper immersed in saline solution (pH 7.4 and 5.2) were used for the "in vitro" study. Implants of these same materials were placed in rat tibiae following the method previously described by Cabrini et al. The animals were killed 14 days post-implantation, the tibiae were resected, radiographed and embedded in acrylic resin. Polarization curves revealed high corrosion in copper implants and low corrosion in titanium implants. It is important to point out that the titanium samples suffered slightly higher corrosion when immersed in a lower pH medium (pH 5.2), as in chronic inflammatory processes. A passive film was found on titanium samples as opposed to the strong corrosion observed in the copper implants. Microscopy revealed osseointegration around titanium implants and a severe inflammatory reaction with abscesses surrounding the copper implants. The method presented herein would allow to correlate "in vivo" and "in vitro" studies on corrosion in different implant materials and establish their relation with cell response.

Effect of bismuth subgallate (a hemostatic agent) on bone repair; a histologic, radiographic and histomorphometric study in rats.

Bismuth subgallate (BS) is a hemostatic agent used for soft tissue surgery in otorhinolaryngology and dermatology. Its effect on bone repair has not been studied. The present study undertook a quantitative and qualitative evaluation of post-extraction bone healing in the presence of BS. Under intraperitoneal anesthesia, forty male Wistar rats, 80+/-5g body weight, underwent the extraction of both lower first molars. BS was placed in the right post-extraction socket (group E) and the contralateral socket served as control (group C). The animals were killed in groups immediately, 7, 14 and 30 days post-extraction. The mandibles were resected, radiographed and processed for embedding in paraffin. The mesial socket was sectioned along the bucco-lingual axis and stained with hematoxylin-eosin. Total tissue volume and trabecular bone volume of the apical third of the sockets were determined histomorphometrically. At 14 and 30 days post-extraction, group E exhibited bone tissue that resembled that of group C. Histomorphometric analyses showed no statistically significant differences between groups C and E. Bismuth subgallate did not interfere with post-extraction bone healing. Further studies will analyze the effect of this hemostatic agent on bone repair in aniticoagulated rats.

Calcifying odontogenic cyst associated with odontoma: report of two cases.

The calcifying odontogenic cyst (COC) is a nonneoplastic lesion whose possible association with other odontogenic lesions such as odontoma has been considered improbable by some authors. This paper reports two cases of true odontoma found concurrently with the COC.

Histomorphometric study of peri-implant bone healing in the case of nerve injury: an experimental model in rats.

Causes of dental implant failure are of more than passing interest. Within the group of failures caused by iatrogenic factors, injury to the epineurium has been reported to cause the formation of peri-implant fibrous tissue (fibrointegration). The aim of this study was to perform a histomorphometric evaluation of the percentage of osseointegration of implants in contact with the epineurium. Twenty Wistar rats were used. The first lower molars were extracted under xylazine-ketamine anesthesia. A titanium screw implant (diameter, 0.75 mm; length, 2.26 mm) was placed. In the control group (n = 10), apical anchorage of the implant was performed. In the experimental group (n = 10), the apical portion of the implant was placed in contact with the epineurium of the lower mandibular nerve. All animals were killed by ether overdose 30 days after implantation. Radiographs were taken, and the samples were processed for embedding in acrylic resin. Ground sections were obtained along the vestibulo-lingual axis of the mesial alveolus that contained the implant and were stained with toluidine blue. The histologic analysis revealed the presence of bone tissue in the apical portion of the control group samples. In the experimental group, the implant was in contact with the epineurium. There were no statistically significant differences in the percentage of osseointegration between both groups (control group, 39% +/- 9%; experimental group, 38% +/- 10%). The results obtained with this experimental model show that the contact of the implant with the epineurium would not impair the process of osseointegration.

Alveolar wound healing and ridge remodeling after tooth extraction in the rat: a histologic, radiographic, and histometric study.

Healing of extraction wounds in rats was analyzed by histologic, radiographic and histometric methods at 0, 7, 14, 30, 60 days after tooth removal. Total alveolar volume, volume density of bone, percentage of bone formation, bone resorption areas, and height of both vestibular and lingual crests were analyzed. Total alveolar bone volume and bone density in the apical third increased from 0 to 60 days. Maximum bone formation was observed at 14 days, whereas the greatest bone resorption was observed seven days after extraction. The height of the lingual crest was lowest 14 days postextraction and then increased progressively to day 60.

Effect of calcitonin on alveolar wound healing.

The effect of calcitonin (CT) on alveolar wound healing was studied with histomorphometric methods. Wistar rats weighing 80-90 g were submitted to extraction of the three mandibular molars. Half of them were injected intraperitoneally with daily therapeutic doses of CT. The control group received no further treatment. All the rats were killed 14 days after the onset of the experiment. Bone healing was impaired in CT treated animals and involved a more intense bone remodeling activity. Bone resorptive areas were present both on the profiles of the newly formed bone and on the alveolar ridge surface. These results suggest that CT would accelerate the process of bone healing.