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Statement of problem Although the concept of angulated dental implants has been used for the rehabilitation of the completely edentulous maxilla, its use has yet to be validated with narrow-diameter implants. Proper estimation of narrow-diameter implant dimensions and angulations is essential for the correct use of these implants. Purpose The purpose of this 3D finite element analysis study was to compare the stress levels and distributions of 2 narrow-diameter angled implant arrangements supporting a maxillary fixed complete prosthesis. Material and methods Two commercially available narrow-diameter implants (3.5×11.5 mm, Unitite Prime; 2.9×11.5 mm, Unitite Slim) were compared for their performances under axial and oblique loading (masticatory force: 100 N) in simulated situations of all-on-4 treatment (2 parallel anterior implants perpendicular to the bone crest and 2 posterior implants angled at 30 degrees). An edentulous maxilla model generated from computed tomography and a prosthesis parametric computer-aided design (CAD) model were combined with computational models of implants and prosthetic components to represent implant-supported maxillary fixed complete prostheses. A condition of complete osseointegration was assumed. Peri-implant bone was analyzed by the Mohr-Coulomb criterion. Implants, abutments, and screws were analyzed by the von Mises criterion, and frameworks by the Rankine criterion. Results The 3.5-mm model showed higher axial load values for peri-implant bone, implants, and abutments than the 2.9-mm model. As for oblique load, values were higher for right-sided peri-implant bone, implants, abutments, and frameworks in the 3.5-mm model than in the 2.9-mm model. The 3.5-mm model had a 16% lower risk of peri-implant bone loss for the axial load and 4% for the oblique load. Conclusions The biomechanical behavior of an angled 2.9-mm implant was comparable with that of a 3.5-mm implant for an all-on-4 prosthesis. However, despite a lower risk of peri-implant bone loss, the 3.5-mm model had higher peak stress on implants and abutments than the 2.9-mm model.

Objective To evaluate healing time before loading, areas compression and tension and location of insertion on mini-implant stability. Design Six minipigs were used. Each animal received 3 mini-implants in each quadrant: 1 mini-implant was used as an unloaded control (G1, n = 24); the other 2 were loaded with 150 g-force at three time intervals (G2: immediate loading, G3: after 15 days and G4: after 30 days), with 16 mini-implant in each experimental group. After 120 days, tissue blocks of the areas of interest were harvested. Clinical analysis (exact Fisher test) determined the survival rate. Histological analysis (Kontron KS 300™, Zeiss) quantified the fractional bone-to-implant contact (%BIC) and bone area (%BA) at each healing time point, areas of interest, and insertion site (ANOVA and t tests for dependent and independent samples). Results The mini-implant survival rates were G1: 71%, G2: 50%, G3: 75% and G4: 63%, with no statistical differences between them. The groups presented similar %BIC and %BA. There were no differences between the compression and tension sides or maxillary and mandibular insertion sites. Conclusions These results suggest that low-intensity immediate or early orthodontic loading does not affect mini-implant stability, because similar histomorphometric results were observed for all the groups, with partial osseointegration of the mini-implants present.

The aim of this study was to evaluate the long-term success rate of immediate occlusal loading of extrasinus zygomatic implants after an 8-year follow-up. From 62 patients who needed implant treatment in 2003, 25 patients who presented with maxillary atrophy met the inclusion criteria and agreed to participate in the study. All patients received fixed dentures under immediate occlusal loading supported by extrasinus zygomatic implants associated with anterior standard implants. No bone grafting procedures were performed. During the 8-year follow-up period, 21 patients underwent clinical evaluation and radiographic examinations every 6 months. This study conforms to the STROBE guidelines regarding prospective cohort studies. 40 extrasinus zygomatic and 74 anterior standard implants were evaluated. All patients were clinically free of signs and symptoms of sinus disturbance at all follow-up appointments. After 8 years, the success rates of extrasinus zygomatic implants, standard anterior implants and definitive prostheses were 97.5%, 95.9% and 95.2%, respectively. Within the limits of this study, immediate occlusal loading of extrasinus zygomatic implants presents a predictable treatment option for the atrophic maxilla.

For implant-supported prostheses, passive fit is critical for the success of rehabilitation, especially when alternative materials are used.The purpose of this study was to compare interfacial fit of implant-supported prostheses cast in titanium to those cast in gold alloy.Five 3-unit fixed partial dentures were fabricated in gold alloy (Degudent U) as 1-piece castings, and 5 others were similarly cast in commercially pure titanium (Grade 1). The interfacial gaps between the prostheses and the abutments were evaluated with an optical microscope, before and after electroerosion. Readings were made with both screws tightened (10 N.cm torque), and with only 1 side tightened, so as to also evaluate the passive fit of the prostheses. Data were compared statistically by 2-way analysis of variance and the post hoc Tukey multiple range test (alpha=.05).Before electroerosion, the interfacial gaps for the 1-piece prostheses were significantly smaller (P.001) in the gold alloy group when the screws were tightened (Au=12.6 +/- 3.0 microm, compared to Ti=30.1 +/- 6.4 microm). When the side opposite the tightened side was analyzed, there was no significant difference between the gold alloy and titanium groups (Au=69.2 +/- 24.9 microm and Ti=94.2 +/- 39.6 microm). The electroerosion procedure significantly (P.001) reduced the gaps at the interfaces for both groups under all conditions. Comparison between groups after electroerosion did not present significant differences when the side opposite the tightened side was analyzed, but the gold alloy group showed better fit when the tightened side was analyzed (12.8 +/- 1.4 microm for gold alloy; 29.6 +/- 4.4 microm for titanium) and when both screws were tightened (5.4 +/- 2.3 microm for gold alloy; 16.1 +/- 5.5 microm for titanium).Cast titanium prostheses, despite showing larger interfacial gaps between the prosthesis and abutment than those obtained with gold alloy, had improved fit after being subjected to electroerosion.

T he conservative concept of Class II amalgam restorations suggests that the resistance and retention forms of the cavity preparation should be independent of each other. The convergence of the buccal and lingual walls toward the occlusal surface provides sufficient retention against displacement of the occlusal and proximal portions of the restoration. However, to ensure retention in the proximal portion, regardless of the occlusal dovetail, additional retention must be provided to resist proximal displacement and increase the strength of the Class II amalgam restoration.‘~s Repeated compressive stress applied to the proximal portion may cause its displacement or fracture because of the narrow isthmus of the dovetail69 7 The concept suggested by Markley” recommends eliminating the occlusal portion in the absence of occlusal caries. This view was recently supported by Almquist et al.9 Many authors agree that additional proximal retention is a basic principle toward a more conservative Class II amalgam cavity preparation.10-‘4 They also agree that the dovetail is of paramount importance. There are three designs for retention at the axiobuccal and axiolingual line angles: (1) an angular area from the axiogingivobuccal and axiogingivolingual point angles to a narrow vertex just apical to the axiopulpal line angle,“‘, 12S2o (2) a cone-shaped vertical groove which diverges toward the occlusal surface; the greater diameter is located at the level of the occlusal dentinoenamel junction, while the minor diameter is located close to the axiogingivobuccal and axiogingivolingual point angles,6’ ‘3 21-24 and (3) a cylindrical groove made with a straight fissure bur for deciduous teeth.25-28