Shlomo Matalon

Rigidity of major connectors when subjected to bending and torsion forces

Rigidity tests were performed on maxillary major connectors of different designs and mandibular major connectors of the lingual bar-type with different cross-sectional shapes and thicknesses. Each major connector was clamped on one side while the other side was subjected to bending, torsion, and bending under torsion forces. Deformation was measured with a micrometer microscope. The most rigid maxillary major connector was the design incorporating the anterior-posterior palatal bar. The most flexible was the U-shaped palatal bar. The full pear-shaped lingual bar (4 x 4 mm) was the most rigid of the major connectors. Among the more conventional lingual bars, the semielliptical bar (3.75 X 1.75 mm) was the most rigid, and the narrow semielliptical bar (4 x 1.5 mm) was the most flexible.

The Effect of Dentin on the Pulp Tissue Dissolution Capacity of Sodium Hypochlorite and Calcium Hydroxide

INTRODUCTION Sodium hypochlorite (NaOCl) and calcium hydroxide (Ca[OH]2) have tissue dissolution capacity. The aim of this study was to evaluate the potential effect of dentin on their tissue dissolution capacity in a novel dentin model. METHODS Dentin models were prepared from 25 freshly extracted human molar teeth; the crowns were separated from the roots, and a rectangular inner shape was prepared. Pulp tissue samples adjusted to similar weights of 6.5 ± 0.2 mg were randomly divided into 6 groups: NaOCl groups in test tubes or dentin models for 1 hour, Ca(OH)2 groups in test tubes or dentin models for 1 week, and control groups saline in test tubes or dentin models for 1 week. The final weights after the experimental period were checked and compared with the initial weights. The differences were statistically analyzed. RESULTS The tissue dissolution capacity of Ca(OH)2 was affected by the presence of dentin. Similarly, NaOCl lost its effect on the pulp tissue after incubation in dentin. Comparison between all test groups showed highly significant differences (P < .001). CONCLUSIONS Dentin has a detrimental effect on the ability of NaOCl and Ca(OH)2 to dissolve pulp tissue. The dentin model appears to be an efficient tool for the study of interactions between local endodontic medicaments, dentin, and pulp tissue.

Retention and marginal leakage of provisional crowns cemented with provisional cements enriched with chlorhexidine diacetate

STATEMENT OF PROBLEM Provisional crowns cemented with provisional luting agents are susceptible to washout, marginal leakage, and secondary caries when placed for a prolonged period. PURPOSE The purpose of this study was to examine the effect of incorporating chlorhexidine diacetate (antibacterial agent) into provisional cements on retention and marginal leakage of provisional crowns in vitro. MATERIAL AND METHODS Provisional crowns of acrylic resin (Duralay) were fabricated for 12 intact human molars with rounded-shoulder preparations. The 12 provisional crowns were luted individually with Temp Bond, Temp Bond NE, and Freegenol provisional cements with and without incorporation of chlorhexidine diacetate (CHDA) salt. Each test group included the same 12 specimens. Specimens with no luting agent served as the control (n=12). Specimens were thermal cycled 100 times (5 degrees C and 55 degrees C) with a 10-second dwell time, stored in 100% humidity at 37 degrees C for 6 days, and then immersed in a 0.5% basic fuchsin at 37 degrees C for 6 hours. Seven days after cementation, removal test of the crowns (tensile retention test) was conducted with a universal testing machine at a crosshead speed of 5 mm/min. Marginal leakage was assessed with a 5-level dye penetration scale. Results of the retention test were subjected to a 2-way ANOVA with repeated measures. A Bonferroni test was used to compare the means. Marginal leakage data were subjected to a nonparametric Wilcoxon signed ranks test. All hypothesis testing was conducted at the 95% level of confidence. RESULTS Retention of provisional crowns cemented with Freegenol enriched with CHDA increased 3-fold to an average level of 80.9 N. However, incorporation of CHDA into Temp Bond or Temp Bond NE did not affect retention. CHDA incorporated into the cements had no significant effect on the marginal leakage of all the tested cements. CONCLUSIONS The addition of CHDA increased retention of Freegenol and had no significant effect on the marginal leakage of the tested cements.

Surface Antibacterial Properties of Compomers

Aim: This was to evaluate the antibacterial properties of four different compomers, using direct contact test (DCT) and agar diffusion test (ADT). Compomers (Polyacid Modified Composite Resin) form a group of dental restorative materials which were developed in order to improve conventional glass-ionomer and are widely used by paediatric dentists in the primary dentition. Microorganisms captured under restorations or penetrating through the micro-gap at the tooth-restoration interface are the cause of secondary caries and pulpal pathology. Methods: For the DCT, 8 samples of Freedom (SDI), F2000 (3M-ESPE), Dyract AP (Dentsply) and Hytac Hplitip (3M-ESPE) were placed on the sidewalls of wells in 96 microtiter plate. After polymerization, freshly grown streptococcus mutans cells (1×106) were placed on the surface of each sample for one hour at 37°C, fresh media was then added to each well and bacterial growth was followed for 16 hours by temperature controlled spectrophotometer. Similarly prepared samples were aged in phosphate buffered saline for 1 or 7 days and the DCT was repeated. The ADT was performed by placing samples in uniform wells punched in agar plates. Results: In the DCT, freshly polymerized samples of F2000 showed the most potent antibacterial properties, while those of Hytac Hplitip showed moderate antibacterial phenomena. Dyract AP and Freedom did not show any antibacterial activity relative to the control. None of the four aged materials showed antibacterial activity in the DCT after 1 or 7 days. In the ADT the halo in the bacterial lawn was measured after 48 hours and only F2000 demonstrated an inhibition zone of 2.15±0.3 mm. Statistics: Two way ANOVA indicated a significant difference in the growth rate of bacteria placed both on the different compomers (P<0.001) and in different tested time points (P<0.001). Conclusion: None of the compomers tested provided significant long term antibacterial activity.

Effect of implant insertion and loading protocol on long-term stability and crestal bone loss: A comparative study

STATEMENT OF PROBLEM Different insertion and loading protocols have been used to implement implant therapy; the consequences of these methods are unclear. PURPOSE The purpose of this retrospective study was to compare the long-term outcomes of different implant insertion and loading protocols on crestal bone loss. MATERIAL AND METHODS This was a nonrandomized retrospective study investigating data of patients in a private practice. Data were collected by an independent Tel Aviv University group from the patient records of a general practitioners private practice. A total of 1688 implants were inserted in 343 patients whose records met the inclusion criteria, that is, 1317 immediately placed implants (IP group), 310 early placed implants (EP group) placed 6 to 8 weeks after implant placement, and 61 delayed placement implants (DP group) placed 4 to 6 months after extraction. The groups were also divided by implant loading method, giving 1203 immediately loaded implants (IL group), 273 early loaded implants (EL group) loaded within 4 to 10 weeks after implant placement, and 212 delayed loading implants (DL group) loaded within 3 to 6 months. Mixed model analysis was used to account for the different number of implants for each patient. RESULTS The average follow-up time was 107 months, with a cumulative implant survival rate of 95.6% and an average crestal bone loss of 2.03 mm. No statistical differences (P>.05) were found among the insertion or loading protocols. However, additional statistical analysis showed the influence of implant type on marginal bone loss (P<.05). CONCLUSIONS The 3-implant insertion and loading protocols exhibited minimal crestal bone loss and a high survival rate.

An in vitro assessment of circumferential grooves on the retention of cement-retained implant-supported crowns

STATEMENT OF PROBLEM Crowns cemented on short implant abutments may have insufficient retention. PURPOSE The purpose of this study was to evaluate the effect of circumferential grooves on the retention of cemented cast copings on implant abutments. MATERIAL AND METHODS Sixty similarly-shaped implant abutments were divided into 4 groups (n=15): without grooves, with 1 groove, with 2 grooves, and with 3 grooves. Fifteen identical NiCr cast copings were prepared to fit all 60 abutments. The castings were cemented to each group of abutments with a noneugenol provisional cement (Tempbond NE) and a zinc phosphate cement (Harvard). After thermal cycling and storage for 6 days in a water bath, retention tests were conducted with a tensile testing machine (Instron) (5 mm/min) and retentive forces were recorded. Data were subjected to 1 way-ANOVA, Tukeys (HSD) test, and repeated measures ANOVA (α=.05). RESULTS For the noneugenol temporary cement, group retention values were increased according to the number of grooves (P<.001). For the zinc phosphate cement, the first groove increased the retention by approximately 60% (P<.001). The retentive values were higher for the zinc phosphate cement than the provisional cement. The influence of the grooves depended on the type of cement used (P<.001). Cement remnants were found primarily on the castings for provisional cement and for the plain abutments cemented with zinc phosphate cement. Remnants were found primarily on the abutments for the grooved abutments cemented with zinc phosphate cement. CONCLUSIONS The addition of circumferential grooves to implant abutments increased the retention of cement-retained castings. For zinc phosphate cement, 1 groove was as effective as several, whereas for the provisional cement, the retention increased gradually with additional grooves.

One Piece Immediately Loaded Implants Versus 1 Piece or 2 Pieces Delayed: 3 Years Outcome.

Purpose:To compare time-dependent outcome of immediately loaded 1-piece (1P) implants with delayed loaded 1P and 2-piece (2P) implants. Materials and Methods:A cohort of 33 patients divided into 3 groups: group A, 13 patients, 49 immediately placed and loaded 1P implants; group B, 11 patients, immediately placed and delayed loaded 1P implants; and group C, 10 patients, 39 2P implants delayed placed and loaded in a two-stage procedure. Marginal bone loss (MBL) was analyzed using x-ray radiography every 6 months, 1 year, and 3 years. Results:A statistically significant mean MBL was observed between baseline, 6 months, 1 year, and 3 years in all groups. There was no statistical significant difference in MBL between immediate and delayed loaded 1P implants. MBL around mandibular implants was lower compared with maxillary implants. Conclusions:2P implants showed less MBL compared with 1P implants in both maxilla and mandible. There was no statistical difference in MBL between immediate and delayed loaded 1P implants. Immediate loaded implants show more MBL in maxilla.

Fluoride ion release and solubility of fluoride enriched interim cements

STATEMENT OF PROBLEM Interim and definitive restorations cemented with interim cements for a prolonged interval are susceptible to bacterial infiltration and caries formation. PURPOSE The purpose of this in vitro study was to evaluate the long-term fluoride release and solubility of aged ZnO-based interim cements enriched separately with 0.4% NaF and SnF2. MATERIAL AND METHODS Four different brands of cements (Tempbond, Tempbond NE, Procem, and Freegenol) were tested for fluoride release and solubility. For every test, 6 disk specimens of each cement with NaF and SnF2, and 6 with no fluoride enrichment (control) were fabricated, for a total of 72 specimens. The disks were incubated in deionized water. Fluoride ion release was recorded at 1, 7, 14, 21, 63, 91, and 182 days. Solubility was calculated as weight percent after 90 days of incubation. The data were analyzed by analysis of variance with repeated measures and the Tukey honestly significant difference post hoc test (P<.05). RESULTS Cements mixed with fluorides released fluoride ions for at least 182 days. Cements mixed with NaF released more fluoride ions than those mixed with SnF2 (P<.001). The cumulative release rates from all the tested cements mixed with either NaF or SnF2 were linear with respect to t(½) (r>.97), indicating a diffusion-controlled fluoride release. Cement and fluoride types were the main affecting factors in fluoride ion release. The addition of fluorides slightly increased the solubility of the cements. CONCLUSIONS Given their long-term sustained and diffusive controlled release, these fluorides, particularly NaF when mixed with ZnO-based interim cements, may be useful for caries prevention under provisionally cemented restorations.

One- and Two-Piece Implants Placed in the Same Patients: Clinical Outcomes After 5 Years of Function.

A retrospective evaluation of 24 subjects treated with one-piece (1P) (n = 34) and two-piece (2P) (n = 38) implants placed in contralateral mandibular premolar locations was conducted. Cumulative implant survival was 100% following a 5-year (range = 59.9-72.3 months; mean = 63.1 months) postrestoration monitoring period. Bone loss (P = .1952) and prosthetic complications (P = .3667) did not significantly differ between the two groups. Clinical efficacy was equivalent for both implant designs.

Collagen barrier membranes may accelerate bacterial growth in vitro: a potential clinical risk to regenerative procedures.

OBJECTIVES Evaluate the antibacterial properties of three commercial collagen membranes for guided bone regeneration (GBR). METHOD AND MATERIALS BioGide®, OsseoGuard®, and CopiOs® membranes were tested for antibacterial properties against Streptococcus sanguinis, Staphylococcus aureus, and Staphylococcus epidermidis using a direct contact test (DCT). Samples of each membrane, sized 5 × 2 mm, were fixed to the side wall of 6 wells in a 96-well microtiter plate. Bacterial suspension was placed on each sample. The plate was incubated at 37°C for 1 hour to allow suspension fluid evaporation. Fresh medium was added to each well and the plate was mixed. Non-contaminated membrane samples served as negative control. Bacterial growth was monitored spectrophotometrically at 650 nm for 24 hours. ANOVA and Tukeys comparison tests were used for the statistical analysis. RESULTS The presence of the membrane samples did not disrupt bacterial growth. However, the presence of OsseoGuard membrane accelerated bacterial growth rate of S sanguinis and S epidermidis as compared to the other two membranes and control samples (P < .001), and of S aureus as compared to the control alone (P < .001). CONCLUSIONS The tested collagen membranes have no antibacterial properties. However, OsseoGuard presents a significant bacterial growth enhancement effect with possible significant clinical implications on the success of regenerative procedures around teeth and implants.