Alessandro Geminiani

The influence of veneering porcelain thickness of all-ceramic and metal ceramic crowns on failure resistance after cyclic loading

STATEMENT OF PROBLEM In some clinical situations, the length of either a prepared tooth or an implant abutment is shorter than ideal, and the thickness of a porcelain crown must be increased. Thickness of the coping and the veneering porcelain should be considered to prevent mechanical failure of the crown. PURPOSE The purpose of this study was to investigate the influence of veneering porcelain thickness for all-ceramic and metal ceramic crowns on failure resistance after cyclic loading. MATERIAL AND METHODS All-ceramic and metal ceramic crowns (n=20) were fabricated on an implant abutment (RN Solid Abutment) for the study. Two different framework designs with 2 different incisal thicknesses of veneering porcelain (2 mm and 4 mm) were used for each all-ceramic and metal ceramic crown system, resulting in 4 experimental groups (n=10) with identically shaped crowns. The all-ceramic crown consisted of alumina (Procera AllCeram) frameworks and veneering porcelain (Cerabien), while metal ceramic crowns were made of high noble metal (Leo) frameworks and veneering porcelain (IPS Classic). All crowns were cemented on the corresponding abutments using a resin cement (Panavia 21). They were subjected to 1000 cycles of thermal cycling (5 degrees C and 55 degrees C; 5-second dwell time). The crowns were tested with a custom-designed cyclic loading apparatus which delivered simultaneous unidirectional cyclic loading at 135 degrees, vertically, at an rpm of 250, with a load of 49 N. Each specimen was loaded for 1.2 x 106 cycles or until it failed. The specimens were thoroughly evaluated for cracks and/or bulk fracture with an optical stereomicroscope (x10) and assigned a score of success, survival, or failure. The specimens without bulk fracture after cyclic loading were loaded along the long axis of the tooth, on the incisal edge, in a universal testing machine at a crosshead speed of 1.5 mm/min, until fracture. Fishers exact test was used to compare the success and survival rate between the 2 different materials (alpha=.05). Two-way ANOVA was used to analyze data in terms of material, porcelain thickness, and interaction effect. Also, a 2-sample t test was performed to compare between 2 thicknesses within the same material (alpha=.05). RESULTS According to the Fishers exact test, the all-ceramic group showed significantly higher success (P=.003) and survival rates (P=.001) than the metal ceramic group. For the failure load, the 2-way ANOVA showed significant effects for material (P<.001) and porcelain thickness (P=.004), but not a significant interaction effect (P=.198). For the metal ceramic groups, crowns with a 2-mm porcelain thickness showed a significantly greater failure load than crowns with a 4-mm porcelain thickness (P=.004). However, all-ceramic groups did not show a significant difference between the 2 different thicknesses of veneering porcelain (P=.198). CONCLUSIONS The all-ceramic crowns showed significantly higher success and survival rates after cyclic loading, but lower failure loads than metal ceramic crowns. The thickness of the veneering porcelain affected the failure load of the metal ceramic crowns, but not that of the all-ceramic crowns.

Temperature increase during CO(2) and Er:YAG irradiation on implant surfaces.

Purpose:The purpose of this study was to evaluate the temperature gradient (&Dgr;T) generated by laser irradiation of an implant surface using a carbon dioxide (CO2) and an Erbium:yttrium aluminium garnet (Er:YAG) laser. Materials and Methods:A dental implant was irradiated with a CO2 and an Er:YAG lasers, with variable power settings. Temperature increase was measured in 2 locations of the implant surface: in the cervical area (&Dgr;Tc) and in the apical area (&Dgr;Ta). Results:The CO2 laser showed the following results: after 60 seconds of irradiation with continuous mode, &Dgr;Tc was 13.9°C and &Dgr;Ta was 12.5°C. The Er:YAG laser showed the following results: after 60 seconds of irradiation with continuous mode, the temperature rise &Dgr;Tc was 50.6°C and &Dgr;Ta was 38.6°C. The CO2 laser with continuous mode generated a temperature increase of 10°C after only 36 seconds. The Er:YAG laser with continuous mode produced a more rapid temperature increase and took only 10 seconds to reach the critical threshold. Conclusions:The irradiation of implant surfaces with CO2 and Er:YAG lasers may produce a temperature increase above the critical threshold (10°C) after 10 seconds of continuous irradiation.

Sonosurgery for atraumatic tooth extraction: A clinical report

The preservation of an intact labial plate during tooth extraction is a critical determinant of whether an immediate implant can be placed and is also an important predictor of the esthetic result. The purpose of this clinical report was to present a method for atraumatic tooth extraction by using an air-driven sonic instrument with specially designed inserts. This surgical technique provides the clinician with an efficient method for atraumatic tooth extraction and preservation of an intact labial plate.

The Influence of Verification Jig on Framework Fit for Nonsegmented Fixed Implant-Supported Complete Denture

PURPOSE The purpose of this retrospective study was to assess if there was a difference in the likelihood of achieving passive fit when an implant-supported full-arch prosthesis framework is fabricated with or without the aid of a verification jig. MATERIALS AND METHODS This investigation was approved by the University of Rochester Research Subject Review Board (protocol #RSRB00038482). Thirty edentulous patients, 49 to 73 years old (mean 61 years old), rehabilitated with a nonsegmented fixed implant-supported complete denture were included in the study. During the restorative process, final impressions were made using the pickup impression technique and elastomeric impression materials. For 16 patients, a verification jig was made (group J), while for the remaining 14 patients, a verification jig was not used (group NJ) and the framework was fabricated directly on the master cast. During the framework try-in appointment, the fit was assessed by clinical (Sheffield test) and radiographic inspection and recorded as passive or nonpassive. RESULTS When a verification jig was used (group J, n = 16), all frameworks exhibited clinically passive fit, while when a verification jig was not used (group NJ, n = 14), only two frameworks fit. This difference was statistically significant (p < .001). CONCLUSIONS Within the limitations of this retrospective study, the fabrication of a verification jig ensured clinically passive fit of metal frameworks in nonsegmented fixed implant-supported complete denture.

Bibliometrics Study on Authorship Trends in Periodontal Literature From 1995 to 2010

BACKGROUND Biomedical research has grown considerably in the last few decades, and the authorship characteristics of the dental literature as a whole and of its specialty fields has changed significantly. Unfortunately, the bibliometrics of the periodontal literature have not been thoroughly investigated. The aim of this study is to investigate the bibliometrics of periodontal literature, assessing the geographic origin, study design, and topics investigated in periodontal research published from 1995 to 2010. METHODS Articles published in periodontal journals during 1995 to 2010 were retrieved through hand search. Inclusion/exclusion criteria were applied. The following variables were extrapolated from each article: number of authors, study design, topic investigated, financial support, and geographic origin. The general linear model assessed the influence of independent variables on number of authors per article, and χ(2) test assessed the statistical difference of the variables over years 1995 to 2010. RESULTS A total of 2,260 articles were reviewed; 2,076 met the inclusion criteria. The number of authors per article increased (P <0.001) from 4.0 (1995) to 5.1 (2010). The proportion of articles published from North America and Europe decreased (P <0.001) from 84.3% (1995) to 58.6% (2010), whereas for Asia and South America the article proportion increased (P <0.001) from 13.8% (1995) to 40% (2010). Research targeting prevention and treatment of periodontal disease is decreasing (P <0.001) in favor of implant-related research. Governmental research funding is increasing (P <0.001). CONCLUSION Periodontal research significantly changed during the last 15 years.

A Comparative Study of the Incidence of Schneiderian Membrane Perforations during Maxillary Sinus Augmentation with a Sonic Oscillating Handpiece versus a Conventional Turbine Handpiece

BACKGROUND Sonic instruments may reduce perforation rates of the schneiderian membrane during lateral window sinus augmentation procedures. This study compares the incidence of membrane perforations using a sonic handpiece with an oscillating diamond insert versus a turbine handpiece with a conventional rotary diamond stone during lateral window sinus augmentation procedures. MATERIALS AND METHODS A retrospective chart analysis identified all lateral window sinus augmentation procedures done during a defined period. Among these procedures, those performed with a sonic handpiece and an oscillating diamond insert (experimental) and those performed with a conventional turbine and rotary diamond stone (conventional) were selected for this study. Reported occurrences of sinus membrane perforations during preparation of the osteotomy and elevation of the sinus membrane, as well as postoperative complications, were recorded and compared between treatment groups. RESULTS Ninety-three consecutive patients were identified for a total of 130 sinus augmentation procedures (51 conventional, 79 experimental). Schneiderian membrane perforations were noted during preparation of the lateral window osteotomy in 27.5% of the sinuses in the conventional group and 12.7% of sinuses in the experimental group. During membrane elevation, perforations were noted in 43.1% of the sinuses in the conventional group and 25.3% of sinuses in the experimental group. Both differences in perforation rates were statistically significant (p < .05). There was no statistically significant difference in postoperative complications. CONCLUSIONS In this study, the use of a sonic instrument to prepare the lateral window osteotomy during sinus elevation procedures resulted in a reduced perforation rate of the Schneiderian membrane compared with the conventional turbine instrument.

The incidence of membrane perforation during sinus floor elevation using sonic instruments: a series of 40 cases.

This study reports the incidence of complications and sinus membrane perforations when using sonic instruments to prepare the lateral window osteotomy for maxillary sinus augmentation. The charts of 33 consecutive patients (40 sinuses) were reviewed. Sinus membrane perforations were reported in 7 cases (17.5% of procedures), with 3 perforations occurring during preparation of the osteotomy window (7.5% of procedures). Postoperatively, 2 cases of sinus infection (5%) and 2 cases of flap dehiscence (5%) were recorded. This study demonstrates that elevation of the sinus floor with a combination of hand and sonic instruments is feasible and safe, with a limited incidence of complications.

Maxillary sinus augmentation with a sonic handpiece for the osteotomy of the lateral window: A clinical report

Several techniques have been proposed to manage patients with insufficient bone height for implant placement in the posterior maxilla. The lateral approach to sinus elevation is a successful procedure, with percentages of success close to 100%. Unfortunately, a frequent complication encountered during sinus elevation procedure is perforation of the Schneiderian membrane. In this clinical report, the authors present the application of a diamond coated sonic tip and an air-driven sonic instrument, commonly used in prosthodontics for the preparation of the lateral window osteotomy during sinus augmentation procedures.

The influence of incisal veneering porcelain thickness of two metal ceramic crown systems on failure resistance after cyclic loading

STATEMENT OF PROBLEM In some clinical situations, the length of either a prepared tooth or an implant abutment is shorter than ideal, and the occlusal clearance to be restored by a porcelain crown is large. Incisal thickness of the coping and the veneering porcelain should be considered to prevent mechanical failure of the crown. PURPOSE The purpose of this study was to investigate the influence of incisal veneering porcelain thickness of metal ceramic systems on failure resistance after cyclic loading. MATERIAL AND METHODS With a standardized technique, 60 metal ceramic anterior crowns with 2 different incisal thicknesses of porcelain veneer (2.0 and 4.0 mm) and 2 different metal alloys (Pisces Plus (B), base metal, and Leo (N), high noble metal) were fabricated to fit a custom abutment and divided into 4 groups (B20, B40, N20, N40) (n=15). The crowns were then cemented using resin cement (PANAVIA 21) and thermal cycled and mechanically cycle loaded (49-N load) for 2,000,000 cycles. The specimens were evaluated for cracks and/or bulk fracture with an optical stereomicroscope (x10) and assigned a score of success, survival, or failure. The specimens without bulk fracture after cyclic loading were loaded along the long axis of the tooth, on the incisal edge, in a universal testing machine at a crosshead speed of 1.5 mm/min until fracture. The fracture strength value (N) was recorded. The exact logistic regression and Fishers exact test were used to study the effect of different alloys and porcelain incisal thicknesses on the success and survival rates after cycle loading. The forces at failure (fracture) of different groups were compared using the rank transform-based nonparametric 2-way ANOVA (alpha=.05). RESULTS According to exact logistic regression, crowns of the high noble alloy group showed significantly higher success rates (P=.002) than those of the base metal group after cyclic loading. The success rate of the crowns with 2 mm of incisal veneering porcelain was significantly higher (P<.001) than that of the crowns with 4 mm of incisal veneering porcelain. For crowns with a 4-mm incisal thickness, N40 showed a significantly higher success rate than B40 (P=.04, Fishers exact test). As for survival rate, the exact logistic regression indicated that neither metal type (P=.11) nor thickness (P=.60) had a significant effect. The 2-way ANOVA showed a significant effect of thickness (P=.001) and no significant effect of metal type (P=.08) on the failure load. CONCLUSIONS The high noble metal ceramic crowns demonstrated a significantly higher success rate after cyclic loading than the base metal ceramic crowns. Crowns with a porcelain incisal thickness of 2 mm showed, for both metal ceramic systems, a greater success rate than those with a 4-mm incisal thickness.

Clinical Evaluation of Immediate Loading of Electroeroded Screw-Retained Titanium Fixed Prostheses Supported by Tilted Implant: A Multicenter Retrospective Study

STATEMENT OF PROBLEM Immediate occlusal loading of dental implants in the edentulous mandible has proven to be an effective, reliable, and predictable treatment protocol. However, there is limited long-term data available in the literature, when an electroeroded definitive cast-titanium fixed prosthesis is used for this treatment protocol. PURPOSE The aim of this study was to evaluate the clinical effectiveness of dental implants (Astra Tech Dental, Mölndal, Sweden) in the edentulous mandible immediately loaded with an electroeroded cast-titanium screw-retained fixed prosthesis. MATERIALS AND METHODS Forty-five patients received five implants each in the interforaminal area. All the implants were inserted with torque up to 40 Ncm and the distal implants were distally tilted approximately 20 to 30 degrees to minimize the length of posterior cantilevers. Implants were loaded within 48 hours of placement with an acrylic resin-titanium screw-retained prosthesis fabricated by electroerosion. RESULTS Two of the 225 inserted implants failed after 3 and 16 months of healing, respectively, with a cumulative survival rate of 99.1% and a prosthetic survival rate of 97.8%. CONCLUSION Immediate loading of tilted dental implants inserted in the edentulous mandible with a screw-retained titanium definitive prosthesis fabricated with electrical discharge machining provide reliable and predictable results.