Analysis of marginal bone loss and implant stability quotient by resonance frequency analysis in different osteointegrated implant systems. Randomized prospective clinical trial

Background: The aim of the present prospective clinical study is to compare the stability of the implant-bone interface by the ISQ quotient and marginal bone loss (MBL) rate during one year of follow-up in four system implants with the same surface and different design. Material and Methods: Prospective randomized clinical trial of 21 patients in which four implant systems with the same surface and different design were placed. Patients were treated by the same operator following a similar surgical protocol with submerged technique. The second surgery to perform the prosthesis was performed at 3 months. All patients went to their review at 6 months and a year. A periapical radiograph for crestal bone analysis and an Implant stability quotient by resonance frequency analysis (ISQ) analysis were taken at baseline and the reviews. Results: No statistically significant differences were found in the Implant stability quotient by resonance frequency analysis and Marginal Bone Loss in the four types of implants. The ISQ increased from the moment of insertion of the implant until the revision to the year, showing an increase of the stability implant, being this increasing less between the 6 months and the year. Conclusions: Differences in the design of the four implants tested in this study did not show statistically significant differences in any of the variables studied, so the implant design does not influence implant stability and marginal bone loss in the first year after placement

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Influência do agente cimentante e desajuste interno na adaptação marginal de coroas em resina nanocerâmica / Influence of the cement agent and internal mismatch in the marginal adaptation of nanoceramic resins crowns

A adaptação marginal é um dos requisitos fundamentais para a longevidade e o sucesso das restaurações. O objetivo desse estudo foi avaliar a influência do desajuste interno associado à diferentes agentes cimentantes na desadaptação marginal de coroas em resina nanocerâmica (Lava Ultimate 3M ESPE) confeccionadas pelo sistema CAD-CAM. A partir do escaneamento de um preparo de coroa total em um pré-molar, foram obtidos 36 modelos em metal. Esses foram divididos em seis grupos de acordo com o desajuste interno (70 µm ou 100 µm) e o cimento (Fosfato de zinco- SS White, Cimento de ionômero de vidro- Ketac Cem 3M/ESPE e Cimento resinoso- Relyx Ultimate 3M/ESPE). Após escaneamento de todos os modelos as coroas foram confeccionadas a partir da fresagem de blocos de resina nanocerâmica (Lava Ultimate 3M/ESPE). Com auxílio de microscópio óptico comparador (40X) foram medidas as desadaptações marginais prévia e posteriormente à cimentação, sendo considerados 8 pontos ao longo do término em todas as faces do corpo de prova. Os valores obtidos após serem submetidos aos testes two-way anova e teste t, demonstraram que as coroas confeccionadas com desajuste interno de 70 µm apresentam desadaptação marginal inferior estatisticamente significante às coroas com desajuste interno de 100 µm. Para o desajuste interno de 70 µm o grupo do cimento fosfato de zinco apresentou o menor gap marginal, sendo que este valor não foi estatisticamente diferente em relação ao grupo do Ketac Cem. Ainda com esse desajuste, o grupo do Ketac Cem não apresentou diferença estatística significante em relação ao grupo do Relyx Ultimate, no entanto esse último promoveu "gap" marginal estatisticamente maior em relação ao grupo do cimento fosfato de zinco. Para o desajuste interno de 100 µm não houve diferença estatisticamente significante no "gap" marginal entre os três cimentos avaliados. O presente estudo demonstrou através da metodologia utilizada, que a menor desadaptação marginal observada nas restaurações de Lava Ultimate, foi proveniente do desajuste interno de 70 µm. Neste grupo os cimentos de fosfato de zinco e de ionômero de vidro demonstraram melhor comportamento comparado ao cimento resinoso, embora o cimento de ionômero de vidro numericamente, mas não estatisticamente tenha apresentado resultado inferior ao do fosfato de zinco

The marginal adaptation is one of the basic requirements for the longevity and success of restorations. The aim of this study was to evaluate the influence of the internal imbalances associated with different luting agents on marginal leakage of crowns Nanoceramic resin ( Lava Ultimate 3M ESPE) made by CAD-CAM system. From the scanning of a full crown preparation in a pre molar were obtained 36 metal models. These were divided into six groups according to the internal imbalances ( 70 or 100 micrometres) and cement (SS White Zinc phosphate, glass ionomer cemet Ketac Cem 3M/ Espe and resinous cement Relyx Ultimate 3M / Espe). After scanning all models crowns were made from milling Nanoceramic resin blocks (Lava Ultimate 3M / Espe). With the aid of optical comparator microscope (40X) were measured prior marginal mismatches and after the cementation, being considered 8 points along the end in all specimen faces. The values were submitted to ANOVA two-way test and t test. Results showded that crowns made with internal imbalances of 70 uM show statistically significant lower marginal leakage to the crows with internal imbalances of 100 micrometres. For the internal imbalances 70 uM zinc phosphate cement group showed the lowest "gap" marginal, and this figure does not show a statistically significant difference compared to Ketac Cem gropu. Even with this misfit, Ketac Cem group showed no statistically significant difference in relation to Relyx Ultimate group, though the latter showed a statistically significant difference compared to zinc phosphate cement group. For the internal imbalances of 100 micrometres there was no statistically significant difference in the "gap" marginal among the three cements. This study demostrated through the methodology used, the lower marginal leakage oberved in Lava Ultimate restorations, was from the inner misfit 70 micrometers...

A microstrain comparison of passively fitting screw-retained and cemented titanium frameworks.

STATEMENT OF PROBLEM: An imprecise fit between frameworks and supporting dental implants in loaded protocols increases the strain transferred to the periimplant bone, which may impair healing or generate microgaps. PURPOSE: The purpose of this study was to investigate the microstrain between premachined 1-piece screw-retained frameworks (group STF) and screw-retained frameworks fabricated by cementing titanium cylinders to the prefabricated framework (group CTF). This procedure was developed to correct the misfit between frameworks and loaded implants. MATERIAL AND METHODS: Four internal hexagon cylindrical implants were placed 10 mm apart in a polyurethane block by using the surgical guides of the corresponding implant system. Previously fabricated titanium frameworks (n=10) were divided into 2 groups. In group STF, prefabricated machined frameworks were used (n=5), and, in group CTF, the frameworks were fabricated by using a passive fit procedure, which was developed to correct the misfit between the cast titanium frameworks and supporting dental implants (n=5). Both groups were screw-retained under torque control (10 Ncm). Six strain gauges were placed on the upper surface of the polyurethane block, and 3 strain measurements were recorded for each framework. Data were analyzed with the Student t test (α=.05). RESULTS: The mean microstrain values between the framework and the implants were significantly higher for group STF (2517 mε) than for group CTF (844 mε) (P<.05). CONCLUSIONS: Complete-arch implant frameworks designed for load application and fabricated by using the passive fit procedure decreased the strain between the frameworks and implants more than 1 piece prefabricated machined frameworks.

Effect of cyclic loading on the vertical microgap of long-span zirconia frameworks supported by 4 or 6 implants.

STATEMENT OF PROBLEM: Few studies have investigated the microgap of long-span complete-arch fixed dental prosthesis zirconia frameworks. PURPOSE: The purpose of this study was to evaluate the effects of cyclic loading on the vertical microgap of maxillary 12-unit prostheses supported by 4 implants and on 14-unit prostheses supported by 6 implants. MATERIAL AND METHODS: One-piece zirconia frameworks were fabricated with a computer-aided design/computer-aided manufacturing technique and divided into 2 groups (n=5): a group of 12-unit prostheses and a group of 14-unit prostheses. The vertical microgap between the frameworks and prosthetic abutments was measured with an optical microscope (80×) under 2 reading conditions. Condition 1 (1-screw test): 1A, the screw on implant 1 was tightened and readings were made on all implants; 1B, the screw was changed to implant 4 (implant 6 for the 14-unit group) and readings were made on all implants. Condition 2: the microgap was measured with all screws tightened before cyclic loading (2A). Specimens were submitted to 200 N underwater (37°C) cyclic loading at a 2-Hz frequency for 1×10(6) cycles. Microgap reading condition 2 was repeated after cyclic loading (2B). The data were submitted to a linear mixed-effects model for statistical comparison (α=.05). RESULTS: A lower (P<.05) vertical microgap (µm) was found for the 12-unit group (reading conditions: 1A, 47.93; 1B, 43.83; 2A, 11.77; and 2B, 11.25) compared to the 14-unit group (1A, 94.87; 1B, 112.56; 2A, 21.28; and 2B, 16.90). No differences were found when each group was compared before and after cyclic loading (P>.05). CONCLUSIONS: The vertical microgap was significantly reduced after tightening all the screws in the framework, possibly leading to a nonpassive situation. Longer-span frameworks showed an increased microgap. Cyclic loading had no influence on the vertical microgap within each group.

The evaluation of marginal gap with and without optical aids: clinicians versus technicians.

PURPOSE: This study investigated the reliability of visual assessment of marginal gaps in relation to the use of magnification and the operator's profession. MATERIALS AND METHODS: A titanium bar was notched, simulating 40 marginal gaps, and 35 operators performed a quantitative evaluation of the incisions. RESULTS: Visual examination was neither sensitive nor specific, as an extreme variability of data was recorded. The precision of readers improved with magnification aids only for clinicians; technicians were significantly more accurate in evaluating the incision's width. CONCLUSION: The visual examinations were inadequate to decide the clinical acceptability of a restoration with regard to its marginal fit.

Detection of proximal secondary caries at cervical class II-amalgam restoration margins in vitro.

OBJECTIVES: To compare the performance of LFpen (DIAGNOdent pen) with two different wedge-shaped tips to conventional bitewing radiography (BW) for detecting proximal secondary caries at the cervical margin of amalgam restorations in vitro. METHODS: Seventy-five molars with class II amalgam restorations were selected. Depending on the marginal filling extension, data was subdivided into a crown group (C), when the filling ended in enamel, and into a root group (R), when the filling ended beyond the cementum-enamel junction. Bayesian analysis including calculation of the area under the receiver operating curve (AUC) was performed. Furthermore, Spearman correlations between caries and cofactors, such as presence of plaque or stain, occlusal ditching, marginal gap size, filling overhangs, and shortfalls, were calculated. Additionally, for group R the correlation coefficient between LFpen measurements and lesion depth was calculated. Histology served as gold standard. RESULTS: In group C both at the D1 and D3 levels, LFpen with two different tips showed a better performance than bitewing radiography (AUC at D1: 0.83/0.79 (LFpen) and 0.63 (BW); at D3: 0.66/0.66 (LFpen) and 0.53 (BW)). In group R, the respective AUC values were 0.53/0.56 (LF) and 0.59 (BW). A significant medium correlation was observed for occlusal ditching and proximal caries. Stain accumulation at the restoration margins especially in combination with filling overhangs interfered with LFpen readings, resulting in false positive measurements. CONCLUSIONS: Compared to BW, LFpen enhances the detection of secondary caries lesions at the cervical margin of amalgam restorations that do not extend below the cementum-enamel junction.

Analysis of veneer failure of removable prosthodontics.

OBJECTIVE: This retrospective study aimed to analyse the failure rate of the facings of double crown-retained dentures. MATERIALS AND METHODS: The clinical reports of 575 patients, who received double crown-retained removable dentures with a total of 1807 double crowns between 1984 and 2007, were included in the study. The 575 prostheses were attached to telescopic crowns using a friction fit (FF; n = 1999), conical crowns (CC; n = 61), or parallel-sided telescopic crowns with a clearance fit (CF; n = 315). Survival probabilities for the veneers were investigated using the Kaplan-Meier method; Cox regression analysis was carried out to determine the influence of the double crown used for retention, type of antagonist, and localisation. RESULTS: Veneer failure occurred in 7.0% of FF, 27.9% of CC, and 4.4% of CF. The risk of veneer failure was 2.3 times higher for CC than for FF (p = 0.042); no significant differences were found between CF and FF (p = 0.363). No significant influences on the localisation of the denture (p = 0.534) or the type of antagonist (p = 0.341) were found. CONCLUSION: CC-based double crowns have a higher risk of veneer failure than FF and CF, which may be due to high tensile stresses occurring in the cervical area of their outer copings.

Homogeneity of root canal fillings performed by undergraduate students with warm vertical and cold lateral techniques.

OBJECTIVES: The aim of this study was to determine radiographic and microscopic appearances of root canal fillings performed by undergraduate students using vertical and lateral compaction techniques. STUDY DESIGN: Thirty dental students were instructed how to fill curved simulated canals with gutta-percha and sealer using lateral and vertical compaction. Digital radiographs were taken in buccolingual and mesio-distal projections; radiographs were evaluated for homogeneity and root canal wall contact. Plastic blocks with simulated canals were sectioned and cross sections were assessed under a light microscope for voids. Probabilities were expressed as odds ratios (OR) with 95% confidence intervals (CI). RESULTS: Radiographs showed that the chances of obtaining a homogeneous root canal filling by using a vertical compaction technique were 3 times higher in the coronal canal third (OR 3.2; CI: 1.9, 5.3), the same in the middle third, and 2 times higher in the apical third (CI: 1.1, 2.4) than when using lateral compaction. Microscopic evaluation of the same canals revealed that the chances of obtaining a homogeneous root canal filling by vertical compaction were 3 times higher in the coronal canal third (CI: 1.6, 5.8), almost 3 times higher in the middle canal third (CI: 1.6, 4.7), and about 10 times higher in the apical canal third (OR 9.8; CI: 2.2, 43.4) than by lateral compaction. The chances of transporting filling material beyond the apex were almost 5 times higher (OR 4.6; CI: 2.8, 7.6) when using vertical rather than lateral compaction. CONCLUSION: Inexperienced students obtained more homogeneous root canal fillings with the vertical compaction method; however, the probability of overextruding filling material with this method was high.

Resin composite contours.

When placing posterior composite resin restorations, clinicians often struggle to achieve good contacts. Frequently contacts that are successful are only confined to the occlusal aspect of the proximal wall. A clinical technique is discussed which achieves the correct contour as well as tight contacts. The technique is also minimally invasive and highly aesthetic.

Effect of retorque on loosening torque of prosthetic screws under two levels of fit of implant-supported dentures.

This study evaluated the influence of retorque on loosening torque (Lt) of prosthetic screws in implant-supported dentures with different fit levels. Ten mandibular implant-supported dentures were fabricated and then 20 cast models were then prepared using prosthetic structures to create 2 fit levels: passive fit (Pf) and misfit (Mf). Two tightening techniques were also evaluated: initial torque only (T1); and initial torque and retorque after 10 min (T2). Gold or titanium screws were used, resulting in 4 groups to each one: Pf/T1, Pf/T2, Mf/T1, Mf/T2. The Lt was measured 24 h after the tightening torque using digital torque meter. Data were analyzed statistically by two-way ANOVA and Tukey's test (alpha=0.05), separately for each screw material. For titanium screws, no significant difference (p>0.05) was found between Pf/T1 and Pf/T2, or between Pf/T2 and Mf/T2. However, statistically significant difference (p<0.05) was found between Pf/T1 and Mf/T1, and between Mf/T1 and Mf/T2. Mf reduced the Lt using T1, while and T2 increased the Lt for Mf. Retorque and fit were shown to have no significant influence on the Lt of the gold screws. Retorque application made insignificant the misfit effect on the Lt of the titanium screws, suggesting that this procedure should be performed routinely during the screw tightening in multi-unit dentures.

Effect of retorque on loosening torque of prosthetic screws under two levels of fit of implant-supported dentures

This study evaluated the influence of retorque on loosening torque (Lt) of prosthetic screws in implant-supported dentures with different fit levels. Ten mandibular implant-supported dentures were fabricated and then 20 cast models were then prepared using prosthetic structures to create 2 fit levels: passive fit (Pf) and misfit (Mf). Two tightening techniques were also evaluated: initial torque only (T1); and initial torque and retorque after 10 min (T2). Gold or titanium screws were used, resulting in 4 groups to each one: Pf/T1, Pf/T2, Mf/T1, Mf/T2. The Lt was measured 24 h after the tightening torque using digital torque meter. Data were analyzed statistically by two-way ANOVA and Tukey's test (α=0.05), separately for each screw material. For titanium screws, no significant difference (p>0.05) was found between Pf/T1 and Pf/T2, or between Pf/T2 and Mf/T2. However, statistically significant difference (p<0.05) was found between Pf/T1 and Mf/T1, and between Mf/T1 and Mf/T2. Mf reduced the Lt using T1, while and T2 increased the Lt for Mf. Retorque and fit were shown to have no significant influence on the Lt of the gold screws. Retorque application made insignificant the misfit effect on the Lt of the titanium screws, suggesting that this procedure should be performed routinely during the screw tightening in multi-unit dentures.

Este estudo avaliou a influência do retorque no Ta dos parafusos protéticos em próteses implantossuportadas com diferentes níveis de adaptação. Foram confeccionadas 10 próteses mandibulares implantossuportadas. Vinte modelos de gesso foram fabricados utilizando as estruturas protéticas para criar os 2 níveis de adaptação: adaptação passiva (AP) e desajuste (D). Foram avaliadas 2 técnicas de aperto do parafuso: inicial torque (T1); e inicial torque e retorque após 10 min (T2). Foram usados parafusos de ouro e titânio, resultando em 4 grupos para cada material do parafuso: AP/T1, AP/T2, D/T1, D/T2. O Ta foi mensurado 24 h após o torque de aperto utilizando torquímetro digital. Os resultados foram analisados pela ANOVA (2 fatores) e teste de Tukey (α=0,05), separadamente para cada material dos parafusos. Para os parafusos de titânio, não foi encontrada diferença estatística significante entre AP/T1 e AP/T2, ou AP/T2 e D/T2; porém, diferença significante foi encontrada entre AP/T1 e D/T1, ou D/T1 e D/T2. Onde, D reduziu a Ta utilizando T1; e T2 aumentou o Ta para D. Retorque e adaptação não apresentaram influência significante no Ta dos parafusos de ouro. A aplicação do retorque tornou insignificante o efeito do desajuste no Ta dos parafusos de titânio, sugerindo que este procedimento deveria ser usado rotineiramente durante os parafusos protéticos de titânio em próteses múltiplas.

Restoration margins in young adolescents: a clinical and radiographic study of Swiss Army recruits.

PURPOSE: The aim of the present study was to report the radiographical prevalence of overhanging fillings in a group of Swiss Army recruits in 2006 and to relate the dimensions of the overhangs to clinical parameters. MATERIALS AND METHODS: A total of 626 Swiss Army recruits were examined for their periodontal conditions, prevalence of caries, and stomatological and functional aspects of the masticatory system and halitosis. In particular, the present report deals with the presence or the absence of fillings, the presence or the absence of overhangs and their relation to clinical and radiographic parameters. RESULTS: A total of 16,198 interdental sites were evaluated on bitewing radiographs. Of these sites, 15,516 (95.8%) were sound and 682 (4.2%) were filled. Amalgam restorations were found in 94.1% and resin composite fillings in 5.9% of the sites. Of these 682 sites, 96 (14.1%) yielded overhanging margins of various sizes. This low prevalence of fillings represents not only a substantial reduction when compared with a similar Swiss Army study (Lang et al, 1988), but also an improvement in the quality of dental care delivery to young Swiss males. Plaque Index and Gingival Index increased statistically significantly with the presence of fillings, when compared with healthy non-filled sites. Clinical parameters that were significantly associated with the presence of overhangs included clinical attachment loss. Moreover, between 1985 and 2006 the prevalence of fillings was significantly reduced from 20.0% to 4.2% of all surfaces. Furthermore, the marginal fit of the fillings improved from 33.0% with overhangs to 14.1%. CONCLUSIONS: A significant improvement was observed in the periodontal and dental conditions of young Swiss males that was shown to have taken place within the previous two decades. From 1985 to 2006, the prevalence of fillings was reduced fourfold and that of overhanging margins twofold, documenting an improvement in the quality of restorative dentistry.

Optimization of the marginal gap of all-ceramic restorations and gold crowns by ultrasound activated, suspended Al2O3 powder.

PURPOSE: To evaluate if the use of ultrasound activated Al203 powder improved the fit especially of all-ceramic restorations. METHODS: 21 extracted teeth were prepared for 14 all-ceramic IPS Empress2 (IPS Empress2) restorations (four crowns, four partial crowns, two inlays, four veneers) and seven gold crowns (Degudent H). Each restoration was adjusted with a suspension of Al2O3 of 25 microm and 50 microm grit, respectively. The effect of the fitting adjustments was recorded with the silicone disclosing medium technique and measured at 11 points under the microscope in an interval of 0.4 mm. RESULTS: A significant (P < 0.001) improvement of the tight fit of all restorations by means of ultrasound activated Al2O3 powder was noticed. The approach of the restoration towards the prepared stump by the sonoerosive fitting correction was in the mean 201 +/- 60 microm in Empress2 restorations and 87 +/- 24 microm in gold crowns within a period of 10 minutes. SEM observation of the Empress2 specimens showed no microdamage after ultrasound machining.

Increasing the longevity of restorations by minimal intervention: a two-year clinical trial.

UNLABELLED: This investigation assessed the effectiveness of alternative treatments for the replacement of amalgam and resin-based composite restorations. Sixty-six patients (age 18 to 80 years, mean = 26.6) with 271 (amalgam [n = 193] and resin-based composite [n = 78]) defective restorations were randomly assigned to one of five different treatment groups: A) Repair (n = 27); B) Sealing of margins (n = 48); C) Refurbishing (n = 73); D) Replacement (n = 42) and E) Untreated (n = 81). USPHS/Ryge criteria were used to determine the quality of the restorations. Two calibrated examiners (Cohen's Kappa 0.74) assessed the restorations independently at the beginning of the study (baseline) and at two years after treatment using seven parameters from the USPHS/Ryge criteria (Marginal Adaptation, Anatomic Form, Roughness, Marginal Stain, Occlusal Contact, Secondary Caries and Luster). RESULTS: Two-hundred and fifty-six restorations (178 amalgam and 78 resin-based composite) were examined at the two-year recall exam. The sealing of marginal defects showed significant improvements in marginal adaptation (p < 0.05). Refurbishing of the defective restorations significantly improved anatomic form (p < 0.0001), luster (p < 0.016), marginal adaptation (p < 0.003) and roughness (p < 0.0001). The repair significantly improved anatomic form (p < 0.002) and marginal stain (p < 0.002). Replacement showed significant improvements for all parameters (p < 0.05). The Untreated group showed significant deterioration on marginal adaptation (p < 0.013). CONCLUSIONS: The two-year recall examination showed that sealant, repair and refurbishing treatments improved the clinical properties of defective amalgam and resin-based composite restorations by increasing the longevity of the restorations with minimal intervention.

Avaliação in vitro da microinfiltração e adaptação marginal em restaurações classe V simulando lesões de abfração: estudo piloto / In vitro assessment of microleakage and marginal adaptation of class V restorations simulating abfraction lesions: a pilot study

Este estudo in vitro avaliou restaurações classe V, simulando lesões de abfração, quanto à microinfiltração e adaptação marginal. Vinte e quatro pré-molares superiores foram divididos em seis grupos(n=4), variando a combinação restauradora: G1=Ketac Molar Liquid/Ketac Molar Easymix, G2=Primer/Vitremer, G3=Adper Single Bond2/Durafill VS, G4=Adper Single Bond2/Z100, G5=Clearfil SE Bond/Durafill VS, G6=Clearfil SE Bond/Z100. Todos os dentes foram submetidos aos ensaios de ciclagem térmica(1000 ciclos/5º-55ºC), ciclagem mecânica (100.000 ciclos/8Kgf) e, em seguida, imersos em solução aquosade azul de metileno 0,5% (pH 7,2) por 4h. Os espécimes foram seccionados longitudinal e transversalmente, obtendo-se duas partes. A qualidade do selamento marginal foi avaliada através de dois métodos, um qualitativo, por meio de escores, e outro quantitativo, por análise morfométrica usando o software Imagelab 2000. Os resultados tratados pelos testes ANOVA a dois critérios e Tukey (5%) mostraram diferença estatística significativa (p < 0,05) em ambos os métodos, revelando menores valores de microinfiltração das restaurações para G1 e G2. Não houve diferença estatisticamente significante para a adaptação marginal em todos os grupos. Concluiu-se que os cimentos de ionômero de vidro convencional e modificado por resina são os mais indicados para restaurações em áreas de abfração quando comparados aos outros materiais testados.

Holographic detection of a tooth structure deformation after dental filling polymerization.

An experimental technique to reveal the effects of dental polymer contraction is established to choose the most appropriate polymerization technique. Tooth deformation following a dental filling polymerization is analyzed using double-exposure holographic interferometry. A caries-free, extracted human molar is mounted in dental gypsum and different cavity preparations and fillings are made on the same tooth. Dental composite fillings are polymerized by an LED light source especially designed for this purpose. Holographic interferograms are made for occlusal (class I), occlusomesial (class II), and mesioocclusodistal (class II MOD) cavities and fillings. Maximum intercuspal deformation ranges from 2 microm for the class I cavity to 14 mum for the MOD class cavity. A finite element method (FEM) is used to calculate von Mises stress on a simplified tooth model, based on experimental results. The stress varies between 50 and 100 MPa, depending on the cavity type.

Respuesta periodontal a la ubicación de los márgenes de las restauraciones protésicas / Periodontal response to the location of prosthetic restoration margins

El propósito de esta investigación es estudiar el efecto de la ubicación cervical de las restauraciones protésicas con coronas completas sobre la salud periodontal. Se realizaron 36 coronas, 11 con terminaciones a nivel de cresta gingival, 14 intracreviculares, 11 supragingivales, en 10 pacientes con necesidad de prótesis parcial fija. Se tomaron registros de índices de placa, índice gingival, gingivorragia, profundidad sondeable, nivel clínico de unión y retracción gingival durante dos años. En el primer año se hizo mantenimiento profesional estricto cada 4 meses, y durante el segundo año se realizó supervisión de la higiene bucal. En general, los datos clínicos mostraron coronas con poca inflamación gingival para las tres ubicaciones cervicales. Las ubicaciones se diferenciaron estadísticamente en los índices gingival y gingivorragia, siendo la terminación intracrevicular la de mayor inflamación. Se puede concluir que las terminaciones supra y a nivel de cresta gingival se comportan en forma similar y son más compatibles con la salud periodontal que las intracreviculares