Prophylaxis and antibiotic therapy in management protocols of patients treated with oral and intravenous bisphosphonates.

INTRODUCTION: Osteonecrosis of the jaw (MRONJ) linked to bisphosphonate treatment has specific characteristics that render its therapeutic management challenging for clinicians. Poor response to standard treatment makes it essential to take special precautions when treating this type of disease; therefore, antibiotic prophylaxis and/or antibiotic therapy have been proposed as effective and helpful tools in these situations. OBJECTIVES: This article seeks to assess published evidence in order to evaluate the different protocols used for antibiotic prophylaxis and/or antibiotic therapy in the general context of patients treated with bisphosphonates. MATERIAL AND METHODS: A literature review of the last 10 years was carried out in PubMed using the following keywords: "antibiotic prophylaxis and osteonecrosis," "bisphosphonates AND osteonecrosis AND dental management," "bisphosphonate AND osteonecrosis AND antibiotic prophylaxis AND oral surgery." A total of 188 articles were obtained, of which 18 were ultimately selected. RESULTS AND DISCUSSION: In patients treated with oral and intravenous bisphosphonates without chemotherapy-associated osteonecrosis of the jaw, antibiotic prophylaxis prior to oral surgery is an important tool to avoid osteonecrosis and promote healing of the affected area. If the patient previously exhibited chemotherapy-associated osteonecrosis after tooth extraction, antibiotic prophylaxis is indicated to prevent recurrent osteonecrosis and promote healing of the extraction site. If chemotherapy-associated osteonecrosis is already present, antibiotic therapy is a vital part of conservative management to reduce the symptomatology of MRONJ and keep it from worsening. Finally, a lack of clinical data and randomized controlled trials makes it difficult to choose the most appropriate protocol for the various clinical situations studied. Key words:Bisphosphonates, antibiotic prophylaxis, maxillary osteonecrosis, antibiotic treatment.

Analysis of different therapeutic protocols for osteonecrosis of the jaw associated with oral and intravenous bisphosphonates

INTRODUCTION: Chemotherapy-associated osteonecrosis of the jaw caused by bisphosphonates is an exposure of necrotic bone with more than eight weeks of evolution that is attributable to bisphosphonates and no prior radiation therapy. Its etiopathogenesis remains unknown, although there are two hypotheses that may explain it: the drug's mechanism of action, and the risk factors that can lead to osteonecrosis. There is a wide range of treatment options for managing chemotherapy-associated osteonecrosis of the jaw, from conservative treatments to surgical procedures of varying levels of invasiveness, which are sometimes supplemented with adjuvant therapies. OBJECTIVES: The objective of this article is to group the therapeutic options for osteonecrosis of the jaw (ONJ) into seven different protocols and to evaluate their effectiveness in relation to stage of ONJ. MATERIAL AND METHODS: A literature review was carried out in PubMed following the PRISMA criteria. A total of 47 were collected after compiling a series of variables that define ONJ, applied treatments, and the clinical results obtained. Results and DISCUSSION: The 47 articles selected have a low to average estimated risk of bias and are of moderate to good quality. According to the data obtained, Protocol 3 (conservative treatment, clinical and radiological followup, minimally invasive surgical treatment, and adjuvant therapies) is the most favorable approach for ONJ lesions caused by oral bisphosphonates. For lesions caused by intravenous bisphosphonates, Protocol 2 (conservative treatment, clinical and radiological follow-up, minimally invasive surgical treatment, and no adjuvant therapies) is the best approach. When comparing the different stages of ONJ, Protocol 1 (conservative treatment, clinical and radiological follow-up) promotes better healing of Stage 1 ONJ lesions caused by orally administered bisphosphonates, and Protocol 3 is recommended for Stage II. For ONJ lesions attributable to intravenous bisphosphonates, Protocol 7 (conservative treatment, clinical and radiological follow-up, and adjuvant therapies) provides the best results in Stage 0; in Stages I, II, and III, Protocol 1 gives better results

Transmigration of mandibular cuspids: review of published reports and description of nine new cases.

We have reviewed all documented cases of mandibular canine transmigration from 1951 (when to our knowledge the first case was published) to 2015, and retrospectively evaluated nine further sequential cases of transmigrating mandibular canines in one hospital by analysing relevant data, including patients' age and sex, presence of retained deciduous canines, radiographic changes, coexisting systemic diseases, and treatment. Transmigration of a mandibular canine is a rare anomaly of eruption, and extraction is the usual treatment. The nine new patients were aged from 16 -48 years, eight of the transmigrated canines were unilateral, and one patient had them bilaterally. They were all completely impacted. Four were retained primary teeth, and five exfoliated primary canines. Eight had no associated radiographic or clinical abnormalities, while one patient had an associated odontoma. Six mandibular canines were removed and three kept under observation. Early detection of transmigrated canines gives the opportunity to monitor their development, which may improve prognosis and treatment.

Actualización sobre la optimización de la estética en prótesis fija mediante el manejo tisula / Update on the optimisation of aesthetics in fixed protheses through tissue handling

Las restauraciones localizadas en la zona estética orofacial son un reto especialmente difícil cuando existe pérdida acusada del reborde residual. En este trabajo se revisan distintas opciones de tratamiento para mejorar la apariencia de los tejidos blandos en los tratamientos con prótesis fija convencional. Para ello se han seleccionado artículos científicos nacionales e internacionales publicados en los últimos diez años. Para la introducción de conceptos no se establece límite de antigüedad. Básicamente, los hallazgos obtenidos de la revisión bibliográfica pueden sintetizarse en lo siguiente: una vez realizada una correcta selección del caso, distintos tipos de tratamiento demostraron aportar resultados satisfactorios para la estética de los tejidos blandos en el tratamiento con prótesis fija convencional. En primer lugar, se proponen tratamientos destinados a modificar la esté- tica manteniendo los tejidos duros y blandos (pónticos ovoides, tratamientos ortodóncicos, técnicas de preservación alveolar, regeneración tisular guiada, injerto monocortical). En segundo lugar, se indican tratamientos quirúrgicos de tejidos duros (osteoplastia/ostectomía) y blandos (injertos de tejido blando, gingivoplastia/gingivectomía, distintos tipos de colgajo). Como última indicación, los materiales de restauración actuales permiten alcanzar resultados estéticos aceptables. En la actualidad, tanto los tratamientos quirúrgicos como los protésicos son considerados estrategias valiosas para realizar un adecuado manejo tisular. El injerto de tejido conectivo es el procedimiento quirúrgico más predecible en el tratamiento de las recesiones, mientras que los pónticos constituyen el procedimiento protésico de elección para obtener una estética apropiada del margen gingival (AU)

Restorations in the aesthetic orofacial zone are particularly challenging in presence of intense resorption of the residual ridge. In this paper various treatment options are reviewed focusing on the improvement of the appearance of the soft tissues combined with conventional fixed prostheses. A deep and rigorous selection of national and international scientific papers published in the last ten years has been made. No age limit was set to describe the key concepts. Basically, the findings that emerge from the literature review can be summarized as follows: once made a correct selection of the case, different types of treatments have been shown to provide satisfactory aesthetic of the soft tissues in combination with conventional fixed prostheses. Treatments that intend to modify the aesthetics preserving hard and soft tissues are proposed (i.e., ovoid pontics, orthodontic treatment, alveolar preservation techniques, guided tissue regeneration, monocortical graft). In addition, surgical treatments including hard tissue (osteoplasty / ostectomy) and soft tissue modification (i.e., soft tissue grafts, gingivoplasty / gingivectomy, various types of flap, etc.) are detailed. Nowadays, both prosthetic and surgical treatments are considered valuable strategies for adequate tissue handling. The connective tissue graft may be considered as the most predictable surgical procedure in the management of recessions, whereas pontics are the first choice for achieving suitable aesthetic results in shaping the gingival margin (AU)

Prospective double-blind clinical trial evaluating the effectiveness of Bromelain in the third molar extraction postoperative period

OBJECTIVES: To evaluate the anti-inflammatory and analgesic effect of Bromelain (pineapple extract) administered orally in the postoperative after extraction of impacted lower molars. Study DESIGN: This is a prospective, placebo-controlled, unicentric, double-blind study; the sample size was 34 patients. The pre and postoperative outcomes, evaluated on the third (D3) and eighth day (D8), included inflamtion, pain and oral aperture, as well as the need for analgesics. One group received Bromelain 150mg per day for three days and 100mg on days 4 to 7. The other group received placebo in the same dosage. All outcomes werrecorded quantitatively and analyzed with the Mann-Whitney U test for independent samples. RESULTS: Although there were no statistically significant differences between the treatment groups, a trend towards less inflammation and improved oral aperture was observed in the group that received Bromelain, compared to the group that received placebo. This trend can be attributed completely to random reasons, since there is no statistical difference in the results. CONCLUSIONS: Further studies are necessary to analyze different administration patterns and doses of Bromelain for the use in the postoperative of impacted third molars

Curricula for the teaching of complete dentures in Spanish and Portuguese dental schools

Objectives: Given the need to ensure that dentists are sufficiently skilled to offer the best possible care to their patients, this study aims to evaluate the teaching methods and clinical experience achieved by undergraduate dental students in Spain and Portugal as regards complete dentures. Study design: In February 2011, a questionnaire seeking information about the preclinical and clinical teaching of complete dentures was e-mailed to all Spanish and Portuguese dental schools with fully developed undergraduate degree dental programs. Results: A response rate of 82.6% was obtained. The distribution of lectures and hours spent at the laboratory and in clinical activities revealed that teaching complete dentures is eminently a practical issue, this being mostly performed by full-time prosthodontists. All surveyed schools teach the design of the record base, and most of them instruct students in the mounting of teeth in wax. Most schools (94.7%) used a semiadjustable articulator, alginate for primary impressions (73.7%) and elastomeric materials in border-molded custom trays for final impressions (68.4%). In most schools, within the clinical setting students work in pairs, the mean student/ professional staff member ratio being 2.3 ± 0.7. Most schools perform a competence-based assessment (83.3%), although innovative techniques such as problem-based learning are still rarely applied. On average, the students emplaced 1.8 ± 1.2 complete dentures during their clinical training, ranging from 0 to 4, although no clear trend was seen as regards the minimum number of dentures to be made for graduating. Conclusions: Variations in teaching programs and clinical experience concerning complete denture curricula among Spanish and Portuguese dental schools are evident, but all the schools base their teaching mainly on preclinical and clinical practice. However, the low number of dentures made by student per year seems insufficient to ensure clinical skills and cope with social needs (AU)

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Curricula for the teaching of complete dentures in Spanish and Portuguese dental schools.

OBJECTIVES: Given the need to ensure that dentists are sufficiently skilled to offer the best possible care to their patients, this study aims to evaluate the teaching methods and clinical experience achieved by undergraduate dental students in Spain and Portugal as regards complete dentures. STUDY DESIGN: In February 2011, a questionnaire seeking information about the preclinical and clinical teaching of complete dentures was e-mailed to all Spanish and Portuguese dental schools with fully developed undergraduate degree dental programs. RESULTS: A response rate of 82.6% was obtained. The distribution of lectures and hours spent at the laboratory and in clinical activities revealed that teaching complete dentures is eminently a practical issue, this being mostly performed by full-time prosthodontists. All surveyed schools teach the design of the record base, and most of them instruct students in the mounting of teeth in wax. Most schools (94.7%) used a semiadjustable articulator, alginate for primary impressions (73.7%) and elastomeric materials in border-molded custom trays for final impressions (68.4%). In most schools, within the clinical setting students work in pairs, the mean student/ professional staff member ratio being 2.3 ± 0.7. Most schools perform a competence-based assessment (83.3%), although innovative techniques such as problem-based learning are still rarely applied. On average, the students emplaced 1.8 ± 1.2 complete dentures during their clinical training, ranging from 0 to 4, although no clear trend was seen as regards the minimum number of dentures to be made for graduating. CONCLUSIONS: Variations in teaching programs and clinical experience concerning complete denture curricula among Spanish and Portuguese dental schools are evident, but all the schools base their teaching mainly on preclinical and clinical practice. However, the low number of dentures made by student per year seems insufficient to ensure clinical skills and cope with social needs.

Vertical misfit of laser-sintered and vacuum-cast implant-supported crown copings luted with definitive and temporary luting agents

Objectives. This study aimed to evaluate the vertical discrepancy of implant-supported crown structures constructed with vacuum-casting and Direct Metal Laser Sintering (DMLS) technologies, and luted with different cement types. Study Design. Crown copings were fabricated using: (1) direct metal laser sintered Co-Cr (LS); (2) vacuum-cast Co-Cr (CC); and (3) vacuum-cast Ti (CT). Frameworks were luted onto machined implant abutments under constant seating pressure. Each alloy group was randomly divided into 5 subgroups (n = 10 each) according to the cement system utilized: Subgroup 1 (KC) used resin-modified glass-ionomer Ketac Cem Plus; Subgroup 2 (PF) used Panavia F 2.0 dual-cure resin cement; Subgroup 3 (RXU) used RelyX Unicem 2 Automix self-adhesive dual-cure resin cement; Subgroup 4 (PIC) used acrylic/urethane-based temporary Premier Implant Cement; and Subgroup 5 (DT) used acrylic/urethane-based temporary DentoTemp cement. Vertical misfit was measured by scanning electron microscopy (SEM). Two-way ANOVA and Student-Newman-Keuls tests were run to investigate the effect of (..) (AU)

Teaching the placement of posterior resin-based composite restorations in Spanish dental schools

Objectives: In an area of esthetic dentistry such as posterior composites, in which new materials and techniques are being devolved continuously, it is important to confirm that dental students have a clear understanding of the basic principles of clinical application of this knowledge. Considering that the preparation of dental graduates in Spain may be of interest to competent dental authorities and employers with whom they can work worldwide, this study investigated the teaching of posterior composite restorations in Spanish dental schools. Study design: In late 2009⁄ early 2010, a questionnaire seeking information on the teaching of posterior composites was emailed to the professor responsible for teaching operative dentistry in each of the fifteen dental schools having complete undergraduate dental degree programmes in Spain. Results: The response rate was 100%. Most investigated topics did not show noteworthy differences depending on whether the schools were public or private. Variations were found among Spanish dental schools in both the amount and content of the teaching programmes concerning posterior composite restorations. Differences were recorded in the teaching of cavity design, contraindications to composite placement, indications for liners and bases, matrix and wedging techniques, composite and bonding systems, light curing and finishing procedures for composite restorations. More consistency was observed in teaching methods of moisture-control, indirect composites and amalgam bonding . Conclusions: As recommended in previously surveyed countries, efforts must be made to promote harmonization of dental curricula to make it easier for graduates to work elsewhere, and to ensure they meet the needs of their patients on entering independent practice (AU)

Resistance to bond degradation between dual-cure resin cements and pre-treated sintered CAD-CAM dental ceramics

Objective: To evaluate the bond stability of resin cements when luted to glass-reinforced alumina and zirconia CAD/CAM dental ceramics. Study design: Eighteen glass-infiltrated alumina and eighteen densely sintered zirconia blocks were randomly conditioned as follows: Group 1: No treatment; Group 2: Sandblasting (125 µm Al2O3-particles); and Group 3: Silica-coating (50 µm silica-modified Al2O3-particles). Composite samples were randomly bonded to the pretreated ceramic surfaces using different resin cements: Subgroup 1: Clearfil Esthetic Cement (CEC); Subgroup 2: RelyX Unicem (RXU); and Subgroup 3: Calibra (CAL). After 24 h, bonded specimens were cut into 1 ± 0.1 mm2 sticks. One-half of the beams were tested for microtensile bond strength (MTBS). The remaining one-half was immersed in 10 % NaOCl aqueous solution (NaOClaq) for 5 h before testing. The fracture pattern and morphology of the debonded surfaces were assessed with a field emission gun scanning electron microscope (FEG-SEM). A multiple ANOVA was conducted to analyze the contributions of ceramic composition, surface treatment, resin cement type, and chemical challenging to MTBS. The Tukey test was run for multiple comparisons (p < 0.05). Results: After 24 h, CEC luted to pre-treated zirconia achieved the highest MTBS. Using RXU, alumina and zirconia registered comparable MTBS. CAL failed prematurely, except when luted to sandblasted zirconia. After NaOClaq storage, CEC significantly lowered MTBS when luted to zirconia or alumina. RXU decreased MTBS only when bonded to silica-coated alumina. CAL recorded 100 % of pre-testing failures. Micromorphological alterations were evident after (..) (AU)

Teaching the placement of posterior resin-based composite restorations in Spanish dental schools.

OBJECTIVES: In an area of esthetic dentistry such as posterior composites, in which new materials and techniques are being devolved continuously, it is important to confirm that dental students have a clear understanding of the basic principles of clinical application of this knowledge. Considering that the preparation of dental graduates in Spain may be of interest to competent dental authorities and employers with whom they can work worldwide, this study investigated the teaching of posterior composite restorations in Spanish dental schools. STUDY DESIGN: In late 2009/ early 2010, a questionnaire seeking information on the teaching of posterior composites was emailed to the professor responsible for teaching operative dentistry in each of the fifteen dental schools having complete undergraduate dental degree programmes in Spain. RESULTS: The response rate was 100%. Most investigated topics did not show noteworthy differences depending on whether the schools were public or private. Variations were found among Spanish dental schools in both the amount and content of the teaching programmes concerning posterior composite restorations. Differences were recorded in the teaching of cavity design, contraindications to composite placement, indications for liners and bases, matrix and wedging techniques, composite and bonding systems, light curing and finishing procedures for composite restorations. More consistency was observed in teaching methods of moisture-control, indirect composites and amalgam bonding. CONCLUSIONS: As recommended in previous surveyed countries, efforts must be made to promote harmonization of dental curricula to make it easier for graduates to work elsewhere, and to ensure they meet the needs of their patients on entering independent practice.

Resistance to bond degradation between dual-cure resin cements and pre-treated sintered CAD-CAM dental ceramics.

OBJECTIVE: To evaluate the bond stability of resin cements when luted to glass-reinforced alumina and zirconia CAD/CAM dental ceramics. STUDY DESIGN: Eighteen glass-infiltrated alumina and eighteen densely sintered zirconia blocks were randomly conditioned as follows: Group 1: No treatment; Group 2: Sandblasting (125 µm Al2O3-particles); and Group 3: Silica-coating (50 µm silica-modified Al2O3-particles). Composite samples were randomly bonded to the pretreated ceramic surfaces using different resin cements: Subgroup 1: Clearfil Esthetic Cement (CEC); Subgroup 2: RelyX Unicem (RXU); and Subgroup 3: Calibra (CAL). After 24 h, bonded specimens were cut into 1 ± 0.1 mm² sticks. One-half of the beams were tested for microtensile bond strength (MTBS). The remaining one-half was immersed in 10 % NaOCl aqueous solution (NaOClaq) for 5 h before testing. The fracture pattern and morphology of the debonded surfaces were assessed with a field emission gun scanning electron microscope (FEG-SEM). A multiple ANOVA was conducted to analyze the contributions of ceramic composition, surface treatment, resin cement type, and chemical challenging to MTBS. The Tukey test was run for multiple comparisons (p < 0.05). RESULTS: After 24 h, CEC luted to pre-treated zirconia achieved the highest MTBS. Using RXU, alumina and zirconia registered comparable MTBS. CAL failed prematurely, except when luted to sandblasted zirconia. After NaOClaq storage, CEC significantly lowered MTBS when luted to zirconia or alumina. RXU decreased MTBS only when bonded to silica-coated alumina. CAL recorded 100 % of pre-testing failures. Micromorphological alterations were evident after NaOClaq immersion. CONCLUSIONS: Resin-ceramic interfacial longevity depended on cement selection rather than on surface pre-treatments. The MDP-containing and the self-adhesive resin cements were both suitable for luting CAD/CAM ceramics. Despite both cements being prone to degradation, RXU luted to zirconia or untreated or sandblasted alumina showed the most stable interfaces. CAL experimented spontaneous debonding in all tested groups.

Vertical misfit of laser-sintered and vacuum-cast implant-supported crown copings luted with definitive and temporary luting agents.

OBJECTIVES: This study aimed to evaluate the vertical discrepancy of implant-supported crown structures constructed with vacuum-casting and Direct Metal Laser Sintering (DMLS) technologies, and luted with different cement types. STUDY DESIGN: Crown copings were fabricated using: (1) direct metal laser sintered Co-Cr (LS); (2) vacuum-cast Co-Cr (CC); and (3) vacuum-cast Ti (CT). Frameworks were luted onto machined implant abutments under constant seating pressure. Each alloy group was randomly divided into 5 subgroups (n = 10 each) according to the cement system utilized: Subgroup 1 (KC) used resin-modified glass-ionomer Ketac Cem Plus; Subgroup 2 (PF) used Panavia F 2.0 dual-cure resin cement; Subgroup 3 (RXU) used RelyX Unicem 2 Automix self-adhesive dual-cure resin cement; Subgroup 4 (PIC) used acrylic/urethane-based temporary Premier Implant Cement; and Subgroup 5 (DT) used acrylic/urethane-based temporary DentoTemp cement. Vertical misfit was measured by scanning electron microscopy (SEM). Two-way ANOVA and Student-Newman-Keuls tests were run to investigate the effect of alloy/fabrication technique, and cement type on vertical misfit. The statistical significance was set at α = 0.05. RESULTS: The alloy/manufacturing technique and the luting cement affected the vertical discrepancy (p < 0.001). For each cement type, LS samples exhibited the best fit (p < 0.01) whereas CC and CT frames were statistically similar. Within each alloy group, PF and RXU provided comparably greater discrepancies than KC, PIC, and DT, which showed no differences. CONCLUSIONS: Laser sintering may be an alternative to vacuum-casting of base metals to obtain passive-fitting implant-supported crown copings. The best marginal adaptation corresponded to laser sintered structures luted with glass-ionomer KC, or temporary PIC or DT cements. The highest discrepancies were recorded for Co-Cr and Ti cast frameworks bonded with PF or RXU resinous agents. All groups were within the clinically acceptable misfit range.

Variations in teaching of removable partial dentures in Spanish dental schools

Objectives: Despite the increasing demand for implant-based treatments, removable partial dentures (RPDs)are frequently used in the oral rehabilitation of partially dentate patients. Furthermore, the Bologna Declaration Agreement (1999) promotes the freedom of movement both of students among dental schools and of graduates across the European Union (EU). Given that inconsistency in teaching among dental schools may lead to confusion,this study aimed to evaluate the status of teaching and clinical experience reached by undergraduate dental students in Spanish dental schools in relation to RPDs.Study design: A questionnaire seeking information on the preclinical and clinical teaching of RPDs was emailed to all Spanish dental schools (11 public, 4 private) with complete undergraduate degree dental programmes in November 2009. Descriptive statistical data analysis was performed.Results: A 100% response rate was obtained. The average duration of the preclinical course in Spain was 44 hours(38 hours in the public schools and 60.5 hours in the private schools). However, public schools reported a greater number of RPDs made per student prior to graduation, with an average of 3.4 acrylic (range: 1–20) and 3.4 cobaltchromium(range: 1–20) RPDs. The corresponding means for private schools were 1 acrylic (range: 0–2) and 2.3 cobalt-chromium (range: 1–4). One public school (9%) stated that they were teaching RPDs using Problem-Based-Learning.Conclusions: Similar to that noted in previously surveyed countries, variations in teaching programmes and clinical experience concerning RPDs achieved by Spanish dental students were evident. While diversity of teaching is often considered to be of benefit, dental students must be adequately trained to ensure that they meet the needs ofthe patients they will serve during their careers (AU)

Variations in teaching of removable partial dentures in Spanish dental schools.

OBJECTIVES: Despite the increasing demand for implant-based treatments, removable partial dentures (RPDs) are frequently used in the oral rehabilitation of partially dentate patients. Furthermore, the Bologna Declaration Agreement (1999) promotes the freedom of movement both of students among dental schools and of graduates across the European Union (EU). Given that inconsistency in teaching among dental schools may lead to confusion, this study aimed to evaluate the status of teaching and clinical experience reached by undergraduate dental students in Spanish dental schools in relation to RPDs. STUDY DESIGN: A questionnaire seeking information on the preclinical and clinical teaching of RPDs was emailed to all Spanish dental schools (11 public, 4 private) with complete undergraduate degree dental programmes in November 2009. Descriptive statistical data analysis was performed. RESULTS: A 100% response rate was obtained. The average duration of the preclinical course in Spain was 44 hours (38 hours in the public schools and 60.5 hours in the private schools). However, public schools reported a greater number of RPDs made per student prior to graduation, with an average of 3.4 acrylic (range: 1-20) and 3.4 cobaltchromium (range: 1-20) RPDs. The corresponding means for private schools were 1 acrylic (range: 0-2) and 2.3 cobalt-chromium (range: 1-4). One public school (9%) stated that they were teaching RPDs using Problem-Based- Learning. CONCLUSIONS: Similar to that noted in previously surveyed countries, variations in teaching programmes and clinical experience concerning RPDs achieved by Spanish dental students were evident. While diversity of teaching is often considered to be of benefit, dental students must be adequately trained to ensure that they meet the needs of the patients they will serve during their careers.

Effect of alloy type and casting technique on the fracture strength of implant-cemented structures.

OBJECTIVES: To evaluate the influence of alloy type and casting procedure on the fracture strength (FS) of metallic frameworks for implant-supported fixed prostheses. STUDY DESIGN: Thirty three-unit structures for lower posterior bridges were waxed-up and randomly assigned to two groups (n=15) according to alloy type and casting technique: Group 1 (C): cobalt-chromium cast in a centrifugal machine (TS1, Degussa-Hüls); Group 2 (T): titanium cast in a pressure-differential device (Cyclarc II, Morita). Each structure was cemented onto two prefabricated abutments under a constant seating pressure. After 6 months of water aging, samples were loaded in a static universal testing machine (EFH/5/FR, Microtest) until fracture. Axial compressive loads were applied at the central fossa of the pontics. FS data were recorded and surface topography of the fractured connectors was SEM-analyzed. A Chi-Square test was performed to assess the dependence of pores on the alloy type and casting procedure. ANOVA and Student-Newman-Keuls (SNK) tests were run for FS comparisons (p <0.05). RESULTS: One third of the C structures showed pores inside the fractured connectors. T frameworks demonstrated higher FS than that of C specimens exhibiting pores (p=0.025). C samples containing no pores recorded the greatest mean FS (p <0.001). CONCLUSIONS: Fracture strength of metallic frameworks depended on the alloy type and casting procedure. Cobalt-chromium casts often registered pores inside the connectors, which strongly decreased the fracture resistance. An accurate casting of titanium with a pressure-differential system may result in the most predictable technique under the tested experimental conditions.

Influence of CAM vs. CAD/CAM scanning methods and finish line of tooth preparation in the vertical misfit of zirconia bridge structures.

PURPOSE: To evaluate the influence of CAD/CAM scanning method (wax-up digitization vs. direct scanning of tooth preparation) and finish line type (chamfer vs. shoulder) on the vertical fit of zirconia frameworks for three-unit posterior-lower bridges. METHODS: 30 sets of two stainless steel master dies were prepared with different marginal designs (chamfer and shoulder) around the contour of each abutment. Over these samples, 30 structures for three-unit posterior-lower bridges were made with Cercon Smart Ceramics CAD/CAM system (Dentsply). An optical laser digitized the wax patterns of 15 bridge structures, and 15 pairs of master dies were directly scanned for designing by computer the remaining half of frames. All zirconia milled structures were luted onto the metallic models with a special clamp made-up to maintain constant seating pressure. Vertical discrepancy around the margins was assessed under scanning electron microscopy (SEM). Misfit data was analyzed using two-way ANOVA and Tukey's test for multiple comparisons at a = 0.05. RESULTS: Vertical discrepancy of the wax-up/digitized bridge structures was significantly higher than that of the computer-designed frameworks (P < 0.0001). No statistically significant differences were found between the chamfer and shoulder vertical misfit values assessed around the metallic models margins (P = 0.55).