Research on implants and osseointegration.

Osseointegration was originally defined as a direct structural and functional connection between ordered living bone and the surface of a load-carrying implant. It is now said that an implant is regarded as osseointegrated when there is no progressive relative movement between the implant and the bone with which it is in direct contact. Although the term osseointegration was initially used with reference to titanium metallic implants, the concept is currently applied to all biomaterials that have the ability to osseointegrate. Biomaterials are closely related to the mechanism of osseointegration; these materials are designed to be implanted or incorporated into the living system with the aims to substitute for, or regenerate, tissues and tissue functions. Objective evaluation of the properties of the different biomaterials and of the factors that influence bone repair in general, and at the bone tissue-implant interface, is essential to the clinical success of an implant. The Biomaterials Laboratory of the Oral Pathology Department of the School of Dentistry at the University of Buenos Aires is devoted to the study and research of the properties and biological effects of biomaterials for dental implants and bone substitutes. This paper summarizes the research work resulting from over 25 years' experience in this field. It includes studies conducted at our laboratory on the local and systemic factors affecting the peri-implant bone healing process, using experimental models developed by our research team. The results of our research on corrosion, focusing on dental implants, as well as our experience in the evaluation of failed dental implants and bone biopsies obtained following maxillary sinus floor augmentation with bone substitutes, are also reported. Research on biomaterials and their interaction with the biological system is a continuing challenge in biomedicine, which aims to achieve optimal biocompatibility and thus contribute to patient health.

Efficacy of Core Needle Biopsy Technique for Jawbone Diseases.

Core needle biopsy (CNB) has been proven useful for diagnosing bone lesions, although it is not often used for jawbone lesions. The aim of this study was to evaluate the efficacy of the CNB method in a series of cases of intramaxillary lesions. CNB was performed on 85 patients with intraosseous lesions which were grouped according to radiographic appearance as: radiopaque lesions (RO, n=13), radiolucent lesions (RL, n=39) and mixed lesions with both radiolucent and radiopaque areas (RL-RO, n=33). The technique enabled us to obtain several tissue cylinders from each lesion (average 2.5 cylinders), which were processed following routine histopathological technique and H&E stain, plus special techniques when necessary. The histopathological analysis together with clinical data enabled accurate diagnosis (AD) in 81% of the cases and descriptive diagnosis (DD) in 14%. The material obtained in 5% of the cases was not appropriate for study (ND). The difference between successful (AD) and unsuccessful (DD+ND) CNB cases is statistically significant. The highest percentage of successful CBNs was for RO and RLRO lesions (85% and 100% respectively). RL lesions were more difficult because most of them were cystic lesions with fluid content.

La biopsia-punción ósea ( Core needle biopsy, CNB) es un procedimiento de probada utilidad en el diagnóstico de lesiones óseas. Sin embargo, no es una técnica de uso frecuente en las lesiones de los maxilares. La finalidad de este trabajo fue evaluar la eficacia del método de CNB en una serie de casos de lesiones intramaxilares. Se realizaron CNB en 85 pacientes con lesiones intraóseas, las cuales fueron agrupadas según su aspecto radiográfico en lesiones radiopacas ( RO, n=13), lesiones radiolucidas (RL, n=39) y lesiones mixtas con sectores radiolúcidos y radiopacos (RL-RO, n=33). La técnica permitió obtener varios cilindros de tejido de cada lesión ( promedio: 2.5 cilindros) los cuales fueron procesados según técnica histopatológica de rutina con tinción de H&E y técnicas especiales en los casos en que fueron necesarias. El análisis de los cuadros histopatológicos conjuntamente con los datos clínicos, permitió realizar un un diagnóstico de certeza (AD) en el 81% de los casos y un diagnostico descriptivo (DD) en el 14 % . En el 5% de los casos el material obtenido no fue adecuado para su estudio (ND) La diferencia entre los casos de CNB exitosa y no exitosa ( DD+ND) es estadisticamente significativa. El mayor porcentaje de CBN exitosas correspondió a las lesiones RO y RL-RO ( 85% y 100% respectivamente) Las lesiones RL presentaron mayor dificultad debido a que, en su mayoría, eran lesiones quísticas con contenido líquido.

In vitro age dependent response of macrophages to micro and nano titanium dioxide particles.

As a result of corrosion, microparticles (MP) and/or nanoparticles (NP) can be released from the metallic implants surface into the bioenvironment. The biological response to these particles depends not only on the physico-chemical properties of the particles but also on host factors, such as age. Macrophages have attracted wide concern in biomedicine. The aim of this investigation was to study the age related biological response of macrophages to TiO2 -MP and NP in vitro. Alveolar macrophages (AM) obtained from young and senescent rats were cultured and exposed to TiO2 -MP and NP. Cell metabolism, superoxide anion (O2 (-) ) and nitric oxide (NO) generation, and cytokine release (IL-6, TNFα, IL-10) were measured. Cell metabolism was not affected by particle exposure. O2 (-) and NO generation increased in a dose dependent manner. A marked increase on IL-6 release was found in the young-AM subpopulation exposed to TiO2 -MP. Conversely, both particle sizes induced a dose dependent release of TNFα in senescent-AM. Only the highest concentration of TiO2 -particles caused a significant increase in IL-10 release in AM-cultures. These observations lend strong support to the suggestion that cellular response of macrophages to TiO2 -particles is age dependent. The biological effect of the particles would seem to be more deleterious in the senescent age-group.

Impact through time of different sized titanium dioxide particles on biochemical and histopathological parameters.

Due to corrosion, a titanium implant surface can be a potential source for the release of micro (MPs) and nano-sized particles (NPs) into the biological environment. This work sought to evaluate the biokinetics of different sized titanium dioxide particles (TiO2 ) and their potential to cause cell damage. Wistar rats were intraperitoneally injected with 150 nm, 10 nm, or 5nm TiO2 particles. The presence of TiO2 particles was evaluated in histologic sections of the liver, lung, and kidney and in blood cells at 3 and 12 months. Ultrastructural analysis of liver and lung tissue was performed by TEM, deposit concentration in tissues was determined spectroscopically, and oxidative metabolism was assessed by determining oxidative membrane damage, generation of superoxide anion (O2(-)), and enzymatic and non-enzymatic antioxidants. TiO2 particles were observed inside mononuclear blood cells and in organ parenchyma at 3 and 12 months. TiO2 deposits were consistently larger in liver than in lung tissue. Alveolar macrophage O2(-) generation and average particle size correlated negatively (p < 0.05). NPs were more reactive and biopersistent in lung tissue than MPs. Antioxidant activity, particularly in the case of 5 nm particles, failed to compensate for membrane damage in liver cells; the damage was consistent with histological evidence of necrosis.

Exfoliative cytology and titanium dental implants: a pilot study.

BACKGROUND: Oral exfoliative cytology is a diagnostic method that involves the study of cells exfoliated from the oral mucosa. Ions/particles released from metallic implants can remain in the peri-implant milieu. The aim of the present study is to assess the presence of metal particles in cells exfoliated from peri-implant oral mucosa around titanium dental implants. METHODS: The study comprised 30 patients carrying titanium dental implants, who had neither a metallic prosthesis nor metal restorations in neighboring teeth. Individuals undergoing orthodontic therapy and those who had oral piercing were also excluded from the study. The study sample included patients with and without peri-implantitis. Cytologic samples of the peri-implant area were collected. Samples of the marginal gingiva on the contralateral side of the implant were taken from the same individuals to serve as control. Cytologic analysis was performed using light microscopy. Titanium concentration was determined using inductively coupled plasma-mass spectrophotometry. RESULTS: Metal-like particles were observed inside and outside epithelial cells and macrophages in cytologic smears of peri-implant mucosa of both patients with and without peri-implantitis. No particles were found in the control cytologic samples. The concentration of titanium was higher in the peri-implantitis group compared with the group without peri-implantitis; no traces of titanium were observed in controls. CONCLUSIONS: Regardless of an inflammatory response, ions/particles are released from the surface of the implant into the biologic milieu. Exfoliative cytology is a simple technique that may be used to detect metal particles in cells exfoliated from the peri-implant mucosa.

Subcellular redistribution of NHERF1 in response to dehydroepiandrosterone (DHEA) administration in endometrial glands of Wistar rats.

To understand the regulation of Na(+)/H(+) exchanger regulatory factor (NHERF1) in polycystic ovarian syndrome, we studied the expression of NHERF1 in uterus of Wistar rats injected with (6 mg/kg) of dehydroepiandrosterone (DHEA) for 7 and 20 days. Immunohistochemistry analysis of NHERF1 showed a substantial shift in the intracellular localization of NHERF1 in endometrial glands and areas of luminal epithelium as early as 7 days of DHEA administration. The NHERF1 accumulated in the "Golgi apparatus area" virtually in all the glands in the 7-day protocol, and in the majority of the glands of 20-day protocol. In contrast, NHERF1 is expressed in the apical membrane and slightly in the cytoplasm of the control epithelium. The subcellular redistribution of NHERF1 could affect the sorting of proteins to the apical membrane and the organization of the apical compartment.

Oral mucosa tissue response to titanium cover screws.

BACKGROUND: Titanium is the most widely used metal in dental implantology. The release of particles from metal structures into the biologic milieu may be the result of electrochemical processes (corrosion) and/or mechanical disruption during insertion, abutment connection, or removal of failing implants. The aim of the present study is to evaluate tissue response of human oral mucosa adjacent to titanium cover screws. METHODS: One hundred fifty-three biopsies of the supra-implant oral mucosa adjacent to the cover screw of submerged dental implants were analyzed. Histologic studies were performed to analyze epithelial and connective tissue as well as the presence of metal particles, which were identified using microchemical analysis. Langerhans cells, macrophages, and T lymphocytes were studied using immunohistochemical techniques. The surface of the cover screws was evaluated by scanning electron microscopy (SEM). RESULTS: Forty-one percent of mucosa biopsies exhibited metal particles in different layers of the section thickness. Particle number and size varied greatly among specimens. Immunohistochemical study confirmed the presence of macrophages and T lymphocytes associated with the metal particles. Microchemical analysis revealed the presence of titanium in the particles. On SEM analysis, the surface of the screws exhibited depressions and irregularities. CONCLUSIONS: The biologic effects seen in the mucosa in contact with the cover screws might be associated with the presence of titanium or other elements, such as aluminum or vanadium. The potential long-term biologic effects of particles on soft tissues adjacent to metallic devices should be further investigated because these effects might affect the clinical outcome of the implant.

In vivo comparative biokinetics and biocompatibility of titanium and zirconium microparticles.

Titanium and zirconium are biomaterials that present a layer of titanium dioxide (TiO(2)) or zirconium dioxide (ZrO(2)). As a result of corrosion, microparticles can be released into the bioenvironment, and their effect on tissues is seemingly associated with differences in the physicochemical properties of these metals. The aim of this study was to perform a long-term evaluation of the distribution, destination, and potential risk of TiO(2) and ZrO(2) microparticles that might result from the corrosion process. Wistar rats were i.p. injected with an equal dose of either TiO(2) or ZrO(2) suspension. The following end-points were evaluated at 3, 6, and 18 months: (a) the presence of particles in blood cells and liver and lung tissue, (b) Ti and Zr deposit quantitation, (c) oxidant-antioxidant balance in tissues, and (d) O(2)(-) generation in alveolar macrophages. Ti and Zr particles were detected in blood mononuclear cells and in organ parenchyma. At equal doses and times postadministration, Ti content in organs was consistently higher than Zr content. Ti elicited a significant increase in O(2)(-) generation in the lung compared to Zr. The consumption of antioxidant enzymes was greater in the Ti than in the Zr group. The present study shows that the biokinetics of TiO(2) and ZrO(2) depends on particle size, shape, and/or crystal structure.

Expression of NHERF1 in colonic tumors induced by 1,2-dimethylhydrazine in rats is independent of plasma ovarian steroids.

In normal embryonic fibroblasts, the Na(+)/H(+) exchanger regulator factor 1 (NHERF1) stabilizes E-cadherin/ß-catenin binding and the lack of NHERF1 expression promotes cell transformation thus acting as a tumor suppressor gene. We here tested the hypothesis that NHERF1 could act as a tumor suppressor gene in colon cancer as a mediator of estrogens' protective actions in colon carcinogenesis. We studied the expression and localization of NHERF1 and ß-catenin by immunohistochemistry in colonic tumors induced by 1,2 dimethylhidrazine (DMH) in Sprague-Dawley rats. One group of the rats treated with the carcinogen was ovariectomized (OVX) in the middle of the tumor induction, simulating a human menopausal condition. We observed a protective role of estrogens in colon cancer, as non-ovariectomized rats (DMH) had a reduced tumor area compared with the ovariectomized group (DMH + OVX; mean ± SE) 28.98 ± 4.65 vs. 67.58 ± 8.69 (p < 0.00380). Despite the lack of plasma estrogen stimulation, we found abundant expression of NHERF1 in colon tumors from ovariectomized rats. NHERF1 was mainly localized in the cytoplasm of the adenocarcinoma cells and lost the apical localization previously reported in normal colon tissue. We also detected expression of NHERF1 by western blot in the SW48, CACO-2, and HT29 colon cancer cell lines. Non-estrogenic factors in plasma or the tumor microenvironment may regulate NHERF1 expression in transformed colon epithelial cells. Further studies are required to understand the regulation of NHERF1 expression in colon cancer tissue.

Biochemical changes during goiter induction by methylmercaptoimidazol and inhibition by delta-iodolactone in rat.

BACKGROUND: We have demonstrated that the administration of delta-iodolactone (i.e., 5-iodo-delta lactone) of arachidonic acid (IL-delta), a mediator in thyroid autoregulation, prevents goiter induction by methylmercaptoimidazol (MMI) in rats. Other studies have shown that transforming growth factor beta-1 (TGF-beta1) mimics some of the actions of excess iodide, but its participation in autoregulation is disputed. The present studies were performed to test the hypotheses that IL-delta decreases thyroid growth by inhibition of cell proliferation and/or by stimulation of apoptosis due to oxidative stress, that TGF-beta is stimulated by an excess of iodide and by IL-delta, and that c-Myc and c-Fos expression are upregulated during goiter induction and downregulated during goiter inhibition. METHODS: Rats were treated with MMI alone or together with iodide or IL-delta. Thyroid weight, cell number, cell proliferation, apoptosis, and oxidative stress were determined. Proliferating cell nuclear antigen (PCNA), TGF-beta1, TGF-beta3, c-Myc, and c-Fos were measured by Western blot. RESULTS: MMI caused a progressive increase in thyroid weight accompanied by an increase in cell number, asymmetry of the ploidy histograms, and PCNA, c-Fos, and c-Myc expression. In addition, an early increase of apoptosis was observed. Peroxides as well as glutathione peroxidase and catalase activities were also increased in goitrous animals. The inhibitory action of IL-delta on goiter formation was accompanied by the inhibition of cell proliferation evidenced by a significant decrease in cell number, PCNA expression, and asymmetry of the ploidy histograms. A transient stimulation of apoptosis after 7 days of treatment was also observed. MMI administration stimulated TGF-beta1 but not TGF-beta3 synthesis. IL-delta alone caused a slight increase of TGF-beta3 but not TGF-beta1, whereas potassium iodide (KI) stimulated both isoforms and MMI reversed KI effect on TGF-beta1 expression but not on TGF-beta3. CONCLUSIONS: The goiter inhibitory action of IL-delta is due to the inhibition of cell proliferation and the transient stimulation of apoptosis. This latter action does not involve oxidative stress. TGF-beta1 does not play a role in the autoregulatory pathway mediated by IL-delta. Iodide stimulates TGF-beta3 without the need of being organified. These results suggest that there may be more than one pathway involved in the autoregulatory mechanism.

Osteoconductivity of strontium-doped bioactive glass particles: a histomorphometric study in rats.

There is accumulating evidence that strontium (Sr)-containing bioceramics have positive effects on bone tissue repair. The aims of the present study were to evaluate the osteoconductivity of Sr-doped bioactive glass (BG) particles implanted in rat tibia bone marrow, and characterize the neoformed bone tissue by SEM-energy-dispersive X-ray microanalysis. Melt-derived BGs were prepared from a base 45S5 BG. Sr-doped glass (45S5.6Sr) was prepared using 6 wt % SrO as a substitute for the CaO. Histological analysis using undecalcified sections showed that new lamellar bone had formed along the surface of both 45S5 and 45S5.6Sr BG particles within 4 weeks. To evaluate osteoconductivity, affinity indices were calculated. At 30 days after implantation, 45S5 and 45S5.6Sr BGs had almost identical affinity indices (88% +/- 7% and 87% +/- 9%; p > 0.05). Strontium was not detected in the neoformed bone tissue surrounding 45S5.6Sr BG particles. These results indicate that 45S5.6Sr BG particles are osteoconductive when implanted inside the intramedullary canal of rat tibiae, and no alterations in bone mineralization, in terms of Ca/P ratio, were observed in the neoformed bone tissue around 45S5.6Sr BG particles.

Ploidy study in oral carcinomas: use of improved methodology to assess its clinical prognostic value.

OBJECTIVE: This study reports a ploidy analysis in oral squamous cell carcinomas (SCC) using methodologic adjustments to improve the accuracy of the measurements and derive numeric indices of aggressiveness of prognostic value. STUDY DESIGN: Sixty-seven SCC were assessed by DNA image cytometry in the areas of the histologic sections with most atypia. Five indices of aggressiveness were analyzed in relation to the clinical-pathologic data and evolution of the patients. RESULTS: The mean value of the index of deviation from the diploid value (2cDi) and malignancy index (Mi), taken as a cut-off value, defined 2 populations with statistically significant differences in survival. In patients with tumors in clinical stages III and IV (TNM classification), the Mi also exhibited prognostic value. CONCLUSIONS: The 2cDi and Mi can be used, under certain methodologic conditions, as an objective indicator of prognostic value of the degree of aggressiveness of oral SCC.

The issue of corrosion in dental implants: a review.

Pure titanium or titanium alloys, and to a lesser extent, zirconium, are metals that are often used in direct contact with host tissues. These metallic biomaterials are highly reactive, and on exposure to fluid media or air, quickly develop a layer of titanium dioxide (TiO2) or zirconium dioxide (ZrO2). This layer of dioxide forms a boundary at the interface between the biological medium and the metal structure, determining the degree of biocompatibility and the biological response of the implant. Corrosion is the deterioration a metal undergoes as a result of the surrounding medium (electrochemical attack), which causes the release of ions into the microenvironment. No metal or alloy is entirely inert in vivo. Corrosion phenomena at the interlace are particularly important in the evolution of both dental and orthopedic implants and one of the possible causes of implant failure after initial success. This paper comprises a review of literature and presents results of our laboratory experiments related to the study of corrosion, with special emphasis on dental implants. In situ degradation of a metallic implant is undesirable because it alters the structural integrity of the implant. The issue of corrosion is not limited to a local problem because the particles pmduced as a result could migrate to distant sites, whose evolution would require further studies.

Ploidy studies of pleomorphic adenomas and minor salivary gland carcinomas of the palate.

Ploidy studies of tumors are a diagnostic and prognostic aid. The aim of the present study was to evaluate the DNA content of palate aggressive pleomorphic adenomas (PA) and adenocarcinomas of the salivary glands. Twelve cases of salivary gland tumors of the palate were selected from the archives of the Oral Pathology Department, Faculty of Dentistry, University of Buenos Aires (1966-2001). Six cases corresponded to aggressive pleomorphic adenomas (PA) and the remaining six to adenocarcinomas (AD). Myxoid and epithelial areas of PA were evaluated. The epithelial areas of the most aggressive cases of PA exhibited a high DNA content. The myxoid areas of same cases of PA had a 2C ploidy level. The difference in ploidy values between the myxoid and epithelial areas of PA would suggest the presence of different cell populations. DNA content and the detection of aneuploidy would be prognostic aids in palate salivary gland carcinomas.

Biological response of tissues with macrophagic activity to titanium dioxide.

The titanium dioxide layer is composed mainly of anatase and rutile. This layer is prone to break, releasing particles to the milieu. Therefore, corrosion may cause implant failure and body contamination. We have previously shown that commercial anatase-titanium dioxide (TiO(2)-anatase) is deposited in organs with macrophagic activity, transported in the blood by phagocytic-mononuclear cells, and induces an increase in the production of reactive oxygen species (ROS). In this study, we evaluated the effects of rutile-titanium dioxide (TiO(2)-rutile). Male Wistar rats were injected i.p. with a suspension of TiO(2)-rutile powder at a dose of 1.60 g/100 g b.w. Six months postinjection, the presence of Ti was assessed in serum, blood cells, liver, spleen, and lung. Titanium was found in phagocytic mononuclear cells, serum, and in the parenchyma of all the organs tested. TiO(2)-rutile generated a rise in the percentage of reactive cells, which was smaller than that observed when TiO(2)-anatase was employed in a previous study. Although TiO(2)-rutile provoked an augmentation of ROS, it failed to induce damage to membrane lipids, possibly due to an adaptive response. The present study reveals that TiO(2)-rutile is less bioreactive than TiO(2)-anatase.

Meta-analysis of the literature on 1946 cases of minor salivary gland tumors of the palate.

Minor salivary gland tumors are relatively rare and exhibit great diversity in terms of histopathology, localization, biological behavior and classification. The studies of significant case series report controversial data, mainly in terms of the proportion of benign versus malignant tumors and the relative frequency of histological types. Palate tumors are the most frequent, with an incidence of over 50%. The aim of the present study was to perform a meta-analysis to evaluate salivary gland tumors of the palate in terms of the proportion of malignant versus benign tumors, the frequency of the histological types and the data employed for statistical analysis. We analyzed a selection of international publications (1950-1999) of case series of minor salivary gland tumors of the palate, including our own series. The host institutions were classified into 3 categories: A) High Complexity Institutions (HCI), i.e. oncological reference centers and general hospitals that treat cancer patients; B) Medium Complexity Institutions (MCI); C) Low Complexity Institutions (LCI). Based on the main classifications, we joined categories and employed a simplified classification to analyze a total of 1835 cases in the literature and our own series of 111 cases (unpublish data). The results of the meta-analysis of the literature demonstrated that the data employed for statistical analysis depends on the type of host institution. The classification of institutions according to their level of complexity allowed for adequate interpretation of the previously published statistical data. Our interpretation of these studies suggests that the data on the percentage of malignant versus benign tumors and diversity of histological type must be obtained from series of low complexity institutions. LCI data are reliable whereas the HCI data are based on pre-selected cases, rendering the data unreliable.

Malignant fibrous histiocytoma associated with coxofemoral arthrodesis.

The discovery of biomaterials led to their use in the manufacture of implants for biomedical applications. In vivo, no metal or alloy is completely inert. The potential toxicity of some of the metals most frequently employed in the manufacture of orthopedic implants has been reported. Their carcinogenic potential has been evaluated in experimental animal models. However, few reports have discussed the potential development of malignant tumors associated with prosthetic structures in humans. The present study documents a case of intraosseous sarcoma that developed in the vicinity of a metallic prosthesis 43 months after a coxofemoral arthrodesis with metallic pins and screws. With this report the authors seek to contribute to the understanding of the potential toxicity and risks of using metallic implants. Since metallic implants employed in the rehabilitation of osteo-muscular-articular disorders usually remain in the organism for long periods of time, the need to monitor the metallic structures and the adjacent tissues is extremely relevant.

Effects of intraosseous implantation of silica-based bioactive glass particles on rat kidney under experimental renal failure.

The aim of the present study is to evaluate the effects of intraosseous implantation of silica-based bioactive glass (BG) particles on rat kidney under experimental renal failure. The animals are assigned to one of the two groups: renal failure (RF) and renal failure + bioactive glass (RF + BG). Particles of melt-derived 45S5 BG are implanted in the marrow of one tibia of each animal in the RF + BG group. The animals are killed 24 h and 14 days postimplantation. The RF + BG group exhibits a statistically significant increase in serum urea 24 h postimplantation. The tibiae of the RF + BG group are resected and embedded in methyl-methacrylate resin. Ground sections are analyzed by light microscopy and energy-dispersive X-ray (EDX) analysis. The presence of silicon, calcium, and phosphorus is evaluated in the BG particles. A 55% reduction in silicon content is observed at 14 days postimplantation as compared with that at 24 h.Light microscopy analysis reveals lesions in kidney parenchyma. Hyperplasia associated with nuclear vacuolization in the tubules and a marked thickening of the basal membrane are observed in the renal cortex of the RF + BG animals killed at 24 h postimplantation, but not in those at 14 days. The present results demonstrate reversible renal cell injury in rats exposed to intraosseous implantation of silica-based BG particles under experimental RF.

Meta-analysis of the literature on 1946 cases of minor salivary gland tumors of the palate

Minor salivary gland tumors are relatively rare and exhibit great diversity in terms of histopathology, localization, biological behavior and classification. The studies of significant case series report controversial data, mainly in terms of the proportion of benign versus malignant tumors and the relative frequency of histological types. Palate tumors are the most frequent, with an incidence of over 50%. The aim of the present study was to perform a meta-analysis to evaluate salivary gland tumors of the palate in terms of the proportion of malignant versus benign tumors, the frequency of the histological types and the data employed for statistical analysis. We analyzed a selection of international publications (1950-1999) of case series of minor salivary gland tumors of the palate, including our own series. The host institutions were classified into 3 categories: A) High Complexity Institutions (HCI), i.e. oncological reference centers and general hospitals that treat cancer patients; B) Medium Complexity Institutions (MCI); C) Low Complexity Institutions (LCI). Based on the main classifications, we joined categories and employed a simplified classification to analyze a total of 1835 cases in the literature and our own series of 111 cases (unpublish data). The results of the meta-analysis of the literature demonstrated that the data employed for statistical analysis depends on the type of host institution. The classification of institutions according to their level of complexity allowed for adequate interpretation of the previously published statistical data. Our interpretation of these studies suggests that the data on the percentage of malignant versus benign tumors and diversity of histological type must be obtained from series of low complexity institutions. LCI data are reliable whereas the HCI data are based on pre-selected cases, rendering the data unreliable.

Los tumores de glándulas salivales menores son relativamentepoco comunes, tienen una gran diversidad en cuanto a su clasificación,aspecto histopatológico, sitio anatómico delocalización y conducta clínica biológica.Las series de cierta importancia mundial presentan resultadoscontradictorios, principalmente con respecto a la proporciónde tumores benignos vs malignos y en relación a la frecuenciade los tipos histológicos. Siendo la localización palatina, en lamayoría de las series de tumores de glándulas salivales menoresanalizadas, la localización de mayor incidencia superandoen la mayoría el 50% de los casos. El objetivo de nuestro estudiofue analizar mediante un meta-análisis, dos aspectos delos tumores de glándulas salivales menores de paladar, la proporciónde tumores malignos vs tumores benignos, lafrecuencia de los tipos histológicos en esta localización y elorigen de la fuente estadística. Se realizó un meta-análisis dela literatura previamente seleccionada, de 29 series la literaturainternacional de tumores de glándulas salivales menores,publicadas desde 1950 hasta 1999 incluyendo nuestra serie.Las instituciones de donde provienen las series, se clasificaronen A) Instituciones de alta complejidad (I.AC): Centros de referencia de cáncer y hospitales generales con tratamiento oncológico. B)Instituciones de intermedia complejidad (I.CI.); C) Instituciones de Baja Complejidad (IBC) A partir de las principales clasificaciones usadas, se realizó una simplificación y unificación de las clasificaciones que fue aplicada en la sumatoria de 1835 casos de la literatura y nuestra serie de 111 casos. Los resultados del meta-análisis de la literatura, demostraron que los datos estadísticos de las series estudiadas, están en directa relación con el tipo de institución referente. La categorización de las instituciones según su complejidad permitió interpretar los datos estadísticos previamente publicados. Interpretamos que los porcentajes de tumores malignos vs benignos de paladar y la diversidad de tipo histológico debe ser obtenida a partir de series de I.BC, valores estadísticos que deberían tomarse como verdaderos. Los de I.AC tienen casos previamente seleccionados y nos son índices seguros de estas lesiones.