Zeina Majzoub

Mandibular overdentures anchored to single implants: A five-year prospective study

STATEMENT OF PROBLEM It is unknown what minimum number of implants are required to satisfactorily support and retain a mandibular overdenture. PURPOSE The purpose of this study was to evaluate a treatment modality by using mandibular overdentures anchored to single implants in a geriatric patient population. MATERIAL AND METHODS Twenty-one patients with a mean age of 74.2 years were treated with single implants inserted at the mandibular midline according to the standard two-stage surgical technique. O-Ring or ball attachments were connected to the implants and served as overdenture anchorage. Implant success rate, improvement of oral comfort and function, condition of the peri-implant soft tissues, Periotest values, and the interproximal marginal bone level were evaluated for up to 5 years after delivery of the overdentures. RESULTS None of the implants were lost during the follow-up period. A mean marginal bone loss of 1.42 +/- 0.56 mm was noted at 60 months. Plaque Index was consistently high around the abutments at all reevaluation intervals but was associated with a low Gingival Index. Pocket Depth averaged 2.41 +/- 0.17 mm for the entire follow-up period. Remarkable improvement of oral comfort and function were evidenced with the overdenture treatment. CONCLUSION Rehabilitation with mandibular overdentures anchored to a single implant can be a therapeutic alternative for elderly patients experiencing discomfort and functional difficulties with conventional mandibular dentures.

In vitro comparison of master cast accuracy for single-tooth implant replacement.

STATEMENT OF PROBLEM The inaccuracy in transferring the position of the hexagonal head of a single implant to the working cast can result in a final single tooth crown, which clinically may present occlusal and/or interproximal contacts that are different from those contacts on the master cast obtained by the technician. PURPOSE This in vitro study evaluated the accuracy of the master casts obtained using square pick-up impression copings for single-tooth replacement. Copings used were (1) copings as sold by the manufacturer, and (2) copings modified by sandblasting and coating with impression adhesive their roughened surfaces before final impression procedures. MATERIAL AND METHODS A polymeric resin model with a standard single implant was used to simulate a clinical situation. A group of 20 impressions were made using nonmodified impression copings; a second group of 20 impressions were fabricated with modified copings. Master casts fabricated for both groups were analyzed to detect rotational position change of the hexagon on the implant replicas in the master casts in reference to the resin model. RESULTS The rotational position changes of the hexagon on implant replicas were significantly less variable in the master casts obtained with the modified impression copings than in the master casts achieved with the nonprepared copings. CONCLUSION Improved precision of the impression was achieved when the adhesive-coated copings were used.

Sexual dimorphism of mandibular angle in a Lebanese sample

Sexual dimorphism represents a group of morphologic characteristics that differentiate males from females. Craniofacial morphology and more specifically the mandibular angle have been evaluated for their interest in orthodontic, anthropologic and forensic applications. Currently, limited data are available relative to the significance of the mandibular angle in sex determination in various populations. The objective of this preliminary study is to evaluate the significance of the mandibular angle in sex determination in a sample of Lebanese young individuals. Lateral cephalometric radiographs were obtained from 83 young individuals (40 males and 43 females) aged between 17 and 26 years. No statistically significant differences were detected between both genders relative to the mean values of A1, A2 and A3 measured for each individual using the ramus plane intersected with the mandibular planes of Downs, Sassouni and Steiner, respectively. This study demonstrated no significant difference of the mandibular angle in sex determination in the young Lebanese population. Further investigations with a larger sample size and a strongly established Lebanese background should be conducted to test the applicability of the mandibular angle sexual dimorphism.

Evaluation of rotational freedom of In-Ceram ceramic blank abutments before and after infiltration.

Purpose:Laboratory processing of implant-supported prostheses may alter the surface of the abutment in contact with the corresponding surface and thus the interface fit. This study assessed changes in the rotational freedom (R) at the interface of 1 implant ceramic abutments before and after preparation and glass infiltration processes. Materials and Methods:The abutment R was assessed for 20 as-received In-Ceram Ceramic Blanks over synOcta abutments and after both preparation and infiltration procedures. Results:Compared with the as-received blanks, there was a statistically significant (P < 0.009) increase of 0.8 minutes in the R after preparation and glass infiltration processes. Conclusion:The results of this investigation suggest that, if all laboratory steps are observed carefully, changes at the abutment interface of Ceramic Blanks do not occur.

Marginal and internal fit of pressed lithium disilicate inlays fabricated with milling, 3D printing, and conventional technologies

Statement of problem. The subtractive and additive computer‐aided design and computer‐aided manufacturing (CAD‐CAM) of lithium disilicate partial coverage restorations is poorly documented. Purpose. The purpose of this in vitro study was to compare the marginal and internal fit accuracy of lithium disilicate glass‐ceramic inlays fabricated with conventional, milled, and 3‐dimensional (3D) printed wax patterns. Material and methods. A dentoform mandibular first molar was prepared for a mesio‐occlusal ceramic inlay. Five groups of 15 inlays were obtained through conventional impression and manual wax pattern (group CICW); conventional impression, laboratory scanning of the stone die, CAD‐CAM milled wax blanks (group CIDW) or 3D printed wax patterns (group CI3DW); and scanning of the master preparation with intraoral scanner and CAD‐CAM milled (group DSDW) or 3D printed wax patterns (group DS3DW). The same design was used to produce the wax patterns in the last 4 groups. The replica technique was used to measure marginal and internal adaptation by using stereomicroscopy. Mixed‐model ANOVA was used to assess differences according to the groups and discrepancy location (&agr;=.05). Results. Group DSDW showed the smallest marginal discrepancy (24.3 &mgr;m) compared with those of groups CICW (45.1 &mgr;m), CIDW (33.7 &mgr;m), CI3DW (39.8 &mgr;m), and DS3DW (39.7 &mgr;m) (P<.001). No statistically significant differences were detected among groups CICW, CIDW, CI3DW, and DS3DW relative to the marginal discrepancy. The internal discrepancy was significantly larger than the marginal discrepancy within all groups (P<.001). Conclusions. Lithium disilicate glass‐ceramic inlays produced from digital scans and subtractive milling of wax patterns resulted in better marginal and internal fit accuracy than either conventional impression/fabrication or additive 3D manufacturing. Three‐dimensional printed wax patterns yielded fit values similar to those of the conventionally waxed inlays.

Effect of Simulated Mastication on the Retention of Locator Attachments for Implant-Supported Overdentures: An In Vitro Pilot Study

PURPOSE Limited information is currently available relative to the effect of masticatory loads on the retentive properties of Locator attachments. The aims of this in vitro study were to assess and compare the effect of simulated mastication on the retention of white, pink, and blue Locator inserts for overdentures retained by 2 implants. MATERIALS AND METHODS Thirty specimens simulating a nonanatomic edentulous flat ridge with two implants and an overdenture were divided into 3 groups according to the color of the fitted insert: transparent clear group (n = 10), pink group (n = 10), and blue group (n = 10). Retention forces were measured in an axial direction initially and after 100,000 cycles of simulated masticatory loads. One-way ANOVA followed by Tukeys post hoc tests were used to compare retention values and percentage retention loss between the 3 groups with significance set at p = 0.05. RESULTS The 3 groups presented significant differences in retention at baseline (9.95 ± 1.91 N, 15.43 ± 4.08 N, and 41.73 ± 9.29 N for the blue, pink, and clear groups, respectively) and after simulated mastication (6.37 ± 2.64 N, 14.00 ± 3.89 N, 38.20 ± 5.11 N for the blue, pink, and clear groups, respectively). Within the same group, cyclic loading did not significantly affect retention in the clear and pink groups, while the blue inserts showed a significant retention loss (-37%) after loading. CONCLUSIONS The results suggest that short-term simulated mastication affects the extra-light blue inserts but not the more-retentive inserts.

Could salivary cyclosporine dosage replace the whole blood cyclosporine measurements in renal transplant patients

Background: Cyclosporin (CsA) has been extensively used as the immunosuppressant of choice in renal transplantation. Currently available approaches to assess CsA levels, both in serum and blood, fail to accurately reflect the concentration of the pharmacologically active drug fraction. Free CsA levels in biological fluids (blood or saliva) have been advocated to play an important role. Traditional salivary CsA monitoring tests are based on available archaic salivary techniques that are nonspecific and require large amounts of saliva. The aim of this study was to assess salivary CsA correlation using a novel and more accurate technique and to correlate with CsA levels in blood. Material and Methods: Patients provided blood samples of 2 ml and 2 ml of unstimulated saliva on the same day 2 h after the morning CsA dose (C2). Whole blood levels of CsA were determined using the monoclonal fluorescent polarization immunoassay (FPIA) kit. The FPIA kit was adapted to salivary testing by using a novel extraction method developed and patented under the name of Middle East Research Institute (MERI). Wilcoxon signed rank test compared the differences in blood and salivary CsA. Pearsons correlation coefficient assessed the linear association between blood and salivary CsA concentrations. All analyses were performed using IBM-SPSS version 23 (IBM Corp, Armonk, NY, USA). Results: No significant correlation was observed between blood and salivary CsA levels. Conclusion: Salivary CsA concentrations at C2cannot adequately replace C2blood levels as an indicator of CsA bioavailability despite improved performance of monoclonal FPIA and application of the MERI technique. More studies may be warranted to design more reliable and less invasive procedures for therapeutic drug monitoring.

The Effect of Energy Densities on the Shear Bond Strength of Self-Adhering Flowable Composite to Er:YAG Pretreated Dentin

Objective. To investigate the shear bond strength of self-adhering flowable resin composite, to dentin, after exposing it to Er:YAG laser radiation, at different energy densities. Materials and Methods. Sixty freshly extracted human third molars were randomly divided into five groups (n = 12). In the control group, dentin was left unirradiated, whereas, in the other four groups, dentin was irradiated with Er:YAG laser in noncontact mode (MSP mode = 100 µs; 10 Hz; beam diameter: 1.3 mm; speed of 1 mm/second; air 6 mL/min; and water 4 mL/min), and respectively, with the following level of energy (50 mJ, 60 mJ, 80 mJ, and 100 mJ). Then, self-adhering flowable resin composite was bonded to all prepared dentin surfaces. Shear bond strength (SBS) was applied and fractured surfaces were examined using scanning electron microscopy. Results. SBS values showed significant differences in 60 mJ (P < 0.05) compared to other groups. Morphological evaluation revealed tags or plugs in dentinal tubules, especially when 60 mJ and 80 mJ were used. All four groups tended to leave more residues on the dentin surface, than the control group. Conclusion. Er:YAG dentin irradiation may enhance SBS of the self-adhering flowable resin composite when it is used at the appropriate low level of energy density.

Insertion Torque of Variable-Thread Tapered Implants in the Posterior Maxilla: A Clinical Study: Insertion Torque in Posterior Maxilla

PURPOSE Primary stability is a key factor for successful implant osseointegration, especially in poor bone quality and early/immediate loading. In the immediate loading protocol, insertion torque values (ITVs) have been suggested to be the most valid prognostic factor for osseointegration of maxillary implants. The objectives of this study were to: (1) evaluate ITVs achieved by a variable-thread tapered implant in the posterior maxilla; and (2) assess the impact of bone quality, implant dimensions, bicortical anchorage, and implant location on ITVs. MATERIALS AND METHODS Twenty-six adult, systemically healthy patients received 173 variable-thread tapered implants in maxillary premolar and molar healed edentulous sites with a minimum subsinus height of 8 mm. Implant sites were prepared using the bone-quality adjusted drilling sequence according to manufacturers recommendations. Bone quality was recorded subjectively during drilling based on Misch criteria (D1-D4), and ITVs were measured with a manual torque wrench. Univariate and multivariate analyses were performed at the 0.05 significance level. RESULTS First and second molar sites accounted for 46.8% of all implants. D4 bone was encountered in 61.3% of the sites. Most of the implants were 4.3 mm in diameter (59.5%), and lengths of 11.5 and 13 mm were most commonly used (75.2%). Approximately half of the implants were associated with apical cortical anchorage (51.4%). The overall mean ITV was 44.5 ± 23.0 Ncm, with 65.5 ± 15.6 Ncm, 55.5 ± 19.6 Ncm, and 36.6 ± 21.7 Ncm for D2, D3, and D4 bone, respectively. Bone quality and implant location significantly affected ITVs, while implant dimensions and apical cortical anchorage did not. CONCLUSIONS ITVs of variable-thread implants were significantly influenced by variations in bone quality and implant position in the posterior maxilla. Despite the influence of bone quality on primary stability, the mean ITVs attained with variable-thread tapered implants in poor bone quality were within the recommended range for immediate loading.

Comparison of fit accuracy of pressed lithium disilicate inlays fabricated from wax or resin patterns with conventional and CAD-CAM technologies

Statement of problem. The use of resin patterns to produce partial coverage restorations is poorly documented. Purpose. The purpose of this in vitro study was to compare the marginal and internal fit accuracy of lithium disilicate glass‐ceramic inlays obtained from wax or resin patterns and fabricated with digital and conventional techniques. Material and methods. A dentoform mandibular first molar was prepared for a mesio‐occlusal ceramic inlay. Six groups of 15 inlays were obtained by conventional impression and manual wax (group CICW) or resin patterns (group CICR); conventional impression, laboratory scanning of the stone die, CAD‐CAM milled wax (group CIDW), or polymethylmethacrylate (PMMA) blocks (group CIDR); and scanning of the master preparation with an intraoral scanner, CAD‐CAM milled wax (group DSDW), or PMMA blocks (DSDR). The same design was applied to produce the wax and PMMA patterns in the last 4 groups. The replica technique was used to measure marginal and internal fit under stereomicroscopy. Mixed‐model ANOVA was applied to assess differences according to the techniques, materials, and discrepancy location (&agr;=.05). Results. The results demonstrated significant effects of the technique (P<.001), material (P=.009), and discrepancy location (P<.001) on fit measurements. Marginal discrepancy was only affected by the technique (P<.001), with the digital approaches yielding the smallest marginal discrepancy (23.5 ±3.6 &mgr;m), followed by the conventional digital techniques (31.1 ±5.6 &mgr;m) and finally by the conventional (42.8 ±7.2 &mgr;m) techniques. Internal fit was significantly influenced only by the material with lower discrepancy in wax (75.2 ±9.0 &mgr;m) than in resin patterns (84.7 ±15.1 &mgr;m). The internal discrepancy was significantly larger than the marginal discrepancy in all groups (P<.001). Conclusions. Inlays generated from conventional wax and resin patterns tend to show higher marginal discrepancies than conventional digital and full digital patterns. Wax and resin materials yield similar marginal fit accuracies irrespective of the impression/manufacturing technique. Better internal fit was shown in wax than in resin patterns, regardless of the technique.