Local and Systemic Effects of Cyclosporine A on the Severity of Gingival Overgrowth in Post-Transplant Renal Patients

Background:

Cyclosporine A (CsA) is a potent immunosuppressant widely used to prevent renal post transplantation rejection. Gingival overgrowth (GO) is among various side effects of the long-term administration of CsA. Up to 90% of the patients under CsA therapy has been reported to develop CsA-induced GO.

Objectives:

The aim of the present prospective pilot study is to determine the local and systemic effects of Cyclosporine A (CsA) on the severity of gingival overgrowth and its relationship with periodontal parameters in post-transplant renal patients

Methods:

Twenty post-transplant renal patients, 12 females and 8 males, presenting gingival overgrowth were selected from Rizk Hospital’s clinic in Beirut. Patient’s CsA plaque levels were evaluated when CsA is administered by syrup and capsules mode. Periodontal parameters including gingival overgrowth, papillary bleeding, plaque and gingival indices were assessed for all patients.

Results:

Plaque concentration CsA levels, when administered in syrup mode, affected significantly the severity of gingival overgrowth as opposed to the administration by capsule mode. Significant correlations between severity of gingival overgrowth on one hand and plaque index, gingival index, and papillary bleeding index on the other hand were only observed in the Capsule group but not in the syrup group. A significant relationship was established between the severity of gingival overgrowth and all periodontal parameters (gingival, papillary and plaque).

Conclusion:

The present study underlines CsA dental plaque local effect, as a co-factor, in the development of gingival overgrowth. Cyclosporine plaque accumulation acts as a reservoir in the gingival inflammation and the periodontal indices seem to be the most accurate parameters associated with gingival overgrowth severity. Plaque CsA concentrations could be considered as a risk factor for inflammation and gingival overgrowth depending on CsA delivery mode in renal transplant patients.

Evaluation of the Papillary Gingival Vasculature in Smokers and Nonsmokers with Chronic Periodontitis: A Clinical In Vivo Study

Aim:

Cigarette smoking has been recognized as an important risk factor in periodontal diseases. One of the suggested mechanisms behind this association is that nicotine alters the microcirculation and causes vasoconstriction and reduced blood flow through the periodontal tissues. Scarce information is currently available relative to the microvascular alterations associated with smoking and the distribution of capillaries through the various areas of the gingival tissues. The aims of this study were to assess, in human interproximal gingival biopsies, the number and diameter of gingival capillaries in periodontally affected smokers and nonsmokers using the CD34 immunohistochemical staining method. The pattern of distribution of vessels in the different areas of the gingival tissues was also assessed.

Materials and Methods:

Systemically healthy patients with moderate chronic periodontitis and ranging in age between 30 and 60 years were recruited for the study from the patient population attending the Periodontology Department of the Faculty of Dental Medicine at the Lebanese University of Beirut. The patients were selected to have a group of 10 patients (Group SP) of smokers (>10 cigarettes/day for the last 10 years) and a second group (Group NP) consisting of nonsmoking periodontally affected patients. Three to four weeks following initial preparation, one interproximal gingival biopsy was obtained from each patient. Immunohistochemical staining with CD34 mouse monoclonal antibody was used to identify the endothelial cells of the blood vessels within each sample. Twelve biopsy samples (five in Group NP and seven in Group SP) were chosen for the measurement of the number and diameter of vessels in three regions of the connective tissue of the biopsy under a blinded protocol.

Results:

In the two groups, the quantitative distribution of small, medium, and large vessels followed a similar trend with the number of small vessels being significantly greater than both medium and large vessels. Small vessels prevailed in the peripheral regions, whereas large vessels were more abundant in the deeper connective tissue areas. The total number of vessels seemed unaffected by chronic cigarette smoking in both groups in the entire biopsy area and in the separate connective tissue regions. Quantitative alteration in the total number of gingival capillaries was not observed in chronic smokers. A redistribution of small and large vessels in the superficial and deeper connective tissue areas of the gingival papilla was noted as a result of smoking in periodontal patients.

Conclusion:

The quantitative distribution of small, medium, and large vessels follows a similar trend with the content in small vessels being significantly more important than both medium and large vessels. Smoking and periodontitis result in a redistribution of small and large vessels in the superficial and deeper connective tissue areas of the gingival papilla compared to nonsmoking periodontal patients. The significance and clinical implications of such rearrangement of vasculature within the gingival tissue need to be further investigated.

Fit Accuracy of Pressed and Milled Lithium Disilicate Inlays Fabricated From Conventional Impressions or a Laboratory-Based Digital Workflow

PURPOSE

The impact of material on the adaptation of lithium disilicate inlays is poorly documented. This in vitro study aims at comparing the fit accuracy of pressed and milled inlays obtained from conventional impression and laboratory-based computer-aided design and computer-aided manufacturing.

MATERIAL AND METHODS

A typodont molar was prepared for a mesio-occlusal ceramic inlay. The stone die generated from one conventional impression was scanned once using a laboratory scanner and the same design was used to produce 15 pressed lithium disilicate inlays from milled wax patterns (group CIDW), and 15 inlays from lithium disilicate blanks (group CICAD) with a 5-axis milling machine. Marginal and internal discrepancies were measured using the replica technique. Mixed-model ANOVA was applied to assess differences according to material and gap location at P⟨0.05.

RESULTS

Material and discrepancy location had a significant effect on fit measurements. Group CIDW showed significantly smaller marginal (37.4 μm) and internal (69.2 μm) discrepancies than group CICAD (59.6 μm and 93.7 μm respectively). Marginal discrepancies were significantly smaller than internal discrepancies within both groups.

CONCLUSIONS

Pressed inlays generated from conventional impression and milled wax patterns yielded better fit accuracy than milled inlays obtained from conventional impression and subtractive manufacturing.

Sterilization and Biologic Monitoring in Private Dental Clinics in Lebanon

AIM

The aim of the present study was to evaluate sterilization practices and effectiveness in the Lebanese private dental sector and identify potential factors contributing to sterilization failure.

MATERIALS AND METHODS

A 13-item questionnaire consisting of four demographic/professional questions and nine questions related to sterilization practices along with self-contained biologic indicators (SCBIs) were delivered to a representative sample of Lebanese private offices. Univariate statistics and bivariate analyses were performed to compare sterilization failure rates according to demographic, professional, and sterilization-related conditions.

RESULTS

Out of the 560 dentists contacted, 205 dentists returned the completed questionnaires and undamaged processed SCBIs. The tested autoclaves (n = 134) were mostly dynamic air removal (69.4%) and had a mean age of 10.5 ± 6.9 years. The dry heat ovens (n = 71) were all static air and had 12.9 ± 8.1 years. The dental assistants performed the routine sterilization procedures in nearly 62% of the practices and sterilization cycles were run 4 to 6 times per week in 75% of the offices. Correct temperature/time ratios were applied in 97% of the autoclaves and 80.3% of the ovens. Few dental practices reported having preventive maintenance (17.9% for the autoclaves and 14.1% for the ovens). Routine monitoring of sterilizer efficacy was infrequently performed and was mostly conducted using physical indicators. Sterilization failure rate was higher for the ovens (16.9%) than for the autoclaves (7.5%). Incorrect temperature/time ratio was the main significant factor associated with sterilization failures.

CONCLUSION

The present study demonstrated a relatively high rate of sterilization failures in the Lebanese private dental sector and identified the human error in setting sterilization cycle parameters as the predominant cause of failure. These findings should prompt actions toward increasing knowledge of the sterilization processes and their monitoring among dental professionals and improving the quality control of sterilization through collaborative efforts among health authorities, dental schools, and associations.

CLINICAL SIGNIFICANCE

This study presents the first published data relative to sterilization practices and effectiveness in private Lebanese dental offices and provides a rationale to implement biologic monitoring protocols in Lebanon as long practiced in developed countries.

Canal Straightening Following Overinstrumentation with Three Nickel-Titanium Rotary Instruments

AIM

The aim of the present in vitro study to compare canal straightening following shaping of curved canals with three types of new generation nickel-titanium (NiTi) rotary instruments-ProTaper Next (PTN)®, BT RaCe (BTR)®, and WaveOne Gold (WOG)®- and three different levels of protrusion beyond the major apical foramen.

MATERIALS AND METHODS

Forty-five extracted human maxillary and mandibular molars with at least one curved canal were distributed in three comparable groups of 15 canals each. The canals were instrumented to the major foramen and then overinstrumented with the final file 0.5 mm, 1 mm, and 1.5 mm beyond the foramen using PTN (Group PTN = 15), BTR (Group BTR = 15), and WOG (Group WOG = 15). Standardized pre- and post-instrumentation radiographs of the root canal were obtained for all groups using digital intraoral radiographs coupled with software. Differences in the degree of curvature were regarded as straightening and canal curvature was evaluated based on Schneider technique using the AmScope software for measurements and compared between groups and levels of instrumentation applying Mixed-model ANOVA. Significance was set at 0.05.

RESULTS

Canal curvature tended to gradually straighten out as the level of instrumentation increased in all three groups without statistically significant difference among the groups (P = 0.826).

CONCLUSION

Overinstrumentation in curved canals resulted in straightening of the canal curvature.

Immediate vs conventional loading of variable-thread tapered implants supporting three- to four-unit fixed partial dentures in the posterior maxilla: 1-year interim results of a split-mouth randomised controlled trial

PURPOSE

To compare the outcome of immediately loaded and one-stage conventionally loaded variable-thread tapered implants in the posterior maxilla.

MATERIALS AND METHODS

This study was designed as a split-mouth randomised controlled trial. Twenty-six patients missing teeth bilaterally in the posterior maxilla received three to four implants in each of the posterior sextants. Bone quality was recorded based on Misch criteria (D1-D4) and insertion torque values were measured using a manual wrench. The implants on one side were immediately loaded with a temporary resin fixed partial denture on definitive multi-unit abutments. The implants in the contralateral side received definitive multi-unit abutments according to the one-stage unloaded protocol. Three to 3.5 months following implant placement, the implants were restored with metal-ceramic fixed prostheses. Outcome measures were implant and prosthesis failure rates, complications, and peri-implant bone level changes at 1 year following delivery of the definitive prostheses.

RESULTS

Two patients dropped out prior to the delivery of definitive prostheses. Four implants supporting a four-unit immediately loaded prosthesis failed in one patient, 3 months following delivery of the definitive prostheses. None of the conventionally loaded implants or prostheses failed. There were no significant differences in the proportions of implant and prosthesis failures (difference = 4.2%; 95% CI -4.2 to 12.6%; P = 0.999). In the immediately loaded group, four early prosthetic complications occurred during the provisionalization phase (three small resin chippings and one prosthetic screw loosening). No other complications were reported. The difference in the rate of complications between the two interventions was not statistically significant (difference = 16.7%; 95% CI -1.2% to 35.6%; P = 0.125). The 1-year peri-implant marginal bone level changes were evaluated in 23 patients (77 immediately loaded and 76 conventionally loaded implants). On average, patients lost 0.42 mm at the immediately loaded and 0.46 mm at the conventionally loaded implants, the difference being statistically not significant (difference = 0.044 mm; 95% CI -0.27 to 0.18 mm; P = 0.701).

CONCLUSIONS

Immediate loading of 3- to 4-unit fixed partial prostheses supported by variable-thread implants in the posterior maxilla can yield good and similar 1-year results to one-stage conventionally loaded implants.

Relative Translucency of a Multilayered Ultratranslucent Zirconia Material

AIM

The aim of this study was to compare the translucency parameter (TP) of ultratranslucent multilayered (UTML) zirconia according to thickness and layer level.

MATERIALS AND METHODS

Rectangles of UTML zirconia with four layers [dentin layer (DEL), first transitional layer (FTL), second transitional layer (STL), and enamel layer (ENL)] and four different thicknesses (0.4, 0.6, 0.8, and 1 mm) were milled from blanks. Digital images were taken in a dark studio against white and black backgrounds under simulated daylight illumination and international commission on illumination (CIE) Lab* color values recorded using Photoshop Creative Cloud software. The TP was computed and compared according to thickness and layer level using analysis of variance (ANOVA) followed by Bonferroni post hoc analysis for multiple comparisons. Significance was set at p < 0.05.

RESULTS

In each thickness, TP values were similar between any two layers. The significant effect of thickness on the TP was observed only in the first two layers. In the DEL, translucency was significantly greater at 0.4 mm than all other thicknesses. In the FTL, differences were significant between 0.4 and 0.8 mm and between 0.4 and 1 mm.

CONCLUSION

The investigated zirconia does not seem to show gradational changes in relative translucency from dentin to enamel levels regardless of the thickness used. Thickness affected the TP only in the first two layers with better translu-cency at 0.4 mm.

CLINICAL SIGNIFICANCE

Since relative translucency does not seem to be significantly different between layers, clinicians can modify the apicocoronal positioning of the UTML layers within the restoration according to the desired Chroma without any implications on the clinically perceived translucency. While the thickness of 0.4 mm may be suggested for anterior esthetic veneers because of its higher translucency, the other thicknesses of 0.6 to 1 mm can be used to mask colored abutments in full contour restorations.

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 Tukey's 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.

CO2 Laser-Mediated Apically Positioned Flap in Areas Lacking Keratinized Gingiva

BACKGROUND AND OBJECTIVES

Autogenous gingival grafts are considered the "gold standard" for gingival augmentation, however they require a second surgical site for graft harvesting. Apically positioned flaps (APFs) represent an alternative method in soft tissue augmentation procedures. Limited information is available relative to the effectiveness of laser-mediated APF in augmenting keratinized gingiva (KG). The aim of this paper is to evaluate soft tissues changes following APF using CO2 laser in mandibular incisors with minimal KG and high labial frenum attachment.

MATERIALS AND METHODS

A total of 20 patients with minimal amount of KG (< 2 mm) on the labial aspect of one mandibular incisor and high buccal frenum insertion were selected for treatment. Only 19 completed the last follow-up visit. An APF consisting of a single superficial horizontal incision just coronal to the mucogingival junction using CO2 laser, elevation of a split-thickness flap, and suturing of the flap to the periosteum in an apical position was performed. The apico-coronal height of KG was measured at baseline, and at 3, 6 and 12 months postoperatively.

RESULTS

Uneventful healing was observed in all patients and an increase in KG of 2-3 mm was obtained. Most patients rated the procedure and the postoperative course as non painful.

CONCLUSIONS

CO2 laser-assisted APF procedure is a minimally invasive treatment modality associated with reduced risk of bleeding and predictable increase in the height of KG.

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. Pearson's 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 C₂ cannot adequately replace C₂ blood 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.

Craniofacial characteristics in the sagittal dimension: A cephalometric study in Lebanese young adults

OBJECTIVES

The purpose of this study was to assess the sagittal cephalometric characteristics of young adult Lebanese individuals and assess gender-related differences.

MATERIALS AND METHODS

Conventional lateral cephalograms were obtained from 117 subjects. Eight linear/angular measurements combining sagittal parameters selected form McNamara and Steiner analyses were recorded. Paired t-test was applied to evaluate differences between genders and skeletal classes.

RESULTS

Males showed significantly greater maxillary and mandibular length than females. ANB was larger in females with no significant differences in SNA values indicating that Lebanese females tend to have a more convex profile than their male counterparts. Subjects with skeletal Class III tended to have a retrognathic maxilla rather than a prognathic mandible.

CONCLUSIONS

Sexual dimorphism is evident in young Lebanese adults relative to linear skeletal dimensions regardless of the skeletal class. Skeletal determinants of Class III malocclusions may be different from those of other population groups.

Foramen Changes following Over Instrumentation of Curved Canals with Three Engine-Driven Instruments: An In Vitro Study

INTRODUCTION

The present in vitro study aimed to evaluate and compare the changes in shape and surface area of the major foramen following shaping of curved canals with three new generation NiTi engine-driven instruments naming ProTaper Next, BT RaCe and WaveOne Gold- with 3 different levels of protrusion beyond the major apical foramen.

METHODS AND MATERIALS

A total of 45 extracted human molars with at least one curved canal were distributed in 3 comparable groups of 15 that were instrumented using either ProTaper Next (PTN), BT RaCe (BTR) or WaveOne Gold (WOG). The canals were instrumented to the major foramen and then over instrumented with the final file 0.5 mm, 1 mm and 1.5 mm beyond the foramen. Standardized pre- and post-instrumentation photographs of the foramen were obtained for all groups using a stereomicroscope. Foramen shape and surface area were evaluated using the AmScope software for measurements and compared between groups and levels of instrumentation applying binary conditional logistic regression and repeated measures ANOVA. The level of significance was set at 0.05.

RESULTS

Foramen shape tended to gradually change from circular to oval as the level of instrumentation increased in all groups. The original foramen shape in WOG group remained better than other groups. Foramen surface areas increased in all groups with Group BTR demonstrating significantly greater values than the other 2 groups.

CONCLUSION

Over instrumentation resulted in apical enlargement and ovalization in all 3 groups but with different patterns. These differences can be attributed to the final file size, design characteristics and kinematics of the 3 systems.

Evaluation of gold-machined UCLA-type abutments and CAD/CAM titanium abutments with hexagonal external connection and with internal connection

PURPOSE

The purpose of this study was to assess the precision at the implant interface of gold-machined UCLA-type abutments and computer-assisted design and manufacture (CAD/CAM) titanium abutments with both external-hexagonal connection and internal-hexagonal connection.

MATERIALS AND METHODS

Fifteen gold-machined UCLA-type abutments with external-hexagonal connection, 15 gold-machined UCLA-type abutments with internal-hexagonal connection, 15 CAD/CAM titanium abutments with external-hexagonal connection, and 15 CAD/CAM titanium abutments with internal-hexagonal connection were produced. The rotational freedom of all the abutments was assessed to detect the precision of fit of each abutment on the top of the implant platform. Measurements of rotational freedom were compared among groups. The quantitative differences among groups were assessed using 1-way analysis of variance (alpha = .05).

RESULTS

Significant differences relative to rotational freedom were not found among the 4 groups (P > .19).

CONCLUSION

Both types of abutments (gold-machined UCLA-type and CAD/CAM titanium) consistently showed 1 degree of rotational freedom between the implant and abutment in both cases of external-hexagonal connection and internal-hexagonal connection.

Applicability of the dimodent equation of sex prediction in a Lebanese population sample

BACKGROUND

Sexual dimorphism represents a group of morphologic characteristics that differentiate a male from a female. Among these dimorphic traits, tooth size has been evaluated in various populations for its interest in anthropologic and forensic applications. Recent studies have shown that dental dimorphism is population-specific and that the most dimorphic tooth is the mandibular canine. In addition to the dimension of single teeth in dimorphic dental assessment, dimorphism has been evaluated, using equation of prediction, applying various dimensions of one or more teeth or indices.

PURPOSE

The objective of this preliminary study was to evaluate the applicability of the Dimodent predictive equation in sex determination in a sample of Lebanese young individuals.

MATERIALS AND METHODS

Mesiodistal widths of the mandibular canine and lateral incisor were measured from dental casts of the permanent teeth of 60 Lebanese University dental students (30 males and 30 females), aged 18-25 years. The sex-predictive equation of Fronty was applied to calculate the percentage of accurately-diagnosed sexes.

RESULTS

Accuracy of sex prediction ranged from 63.3% for males and 90% for females. Overall, the Dimodent equation enabled a correct sex determination in 76.7% of the cases. When compared to the accuracy obtained with this equation in a French population sample, the accuracy was significantly different (Z=3.1225).

CONCLUSIONS

This research supports earlier studies that sexual dimorphism is population specific. The difficulty or lack of dimorphism seems to originate from male subjects. Further investigations should include the preparation of population-specific prediction tables and testing their accuracy in a larger sample with a strongly-established Lebanese background.

A 4-Year Prospective Study to Assess Peri-Implant Hard and Soft Tissues Adjacent to Titanium Versus Gold-Alloy Abutments in Cemented Single Implant Crowns

PURPOSE

The purpose of this prospective clinical study was to compare titanium and gold-alloy abutments when used with cemented, implant-supported single-tooth crowns. For 4 years following prosthodontic rehabilitation, these abutments were evaluated with respect to peri-implant marginal bone levels and peri-implant soft tissue parameters.

MATERIALS AND METHODS

During the years 1998 to 2000, 20 patients were selected from a patient population receiving treatment in the Implantology Department at the University of Padova, Italy. They all presented with single-tooth bilateral edentulous sites in the premolar/molar region with adequate bone width, similar bone height on each side, and an occlusal scheme that allowed for the establishment of identical occlusal cusp/fossa contacts on each side. Each subject received two identical implants (one in each edentulous site). One was randomly selected to be restored with a titanium abutment and a cemented implant-supported single-tooth crown, and the other was restored with a gold-alloy abutment and a cemented implant-supported single tooth crown. Data on peri-implant marginal bone levels and soft tissue parameters were collected for 4 years after abutment and crown insertion placement and analyzed to determine whether there was a significant (p< .001) difference with respect to the type of abutments (titanium vs. gold alloy) used.

RESULTS

All subjects completed the study. All 40 implants survived, resulting in a cumulative implant success rate of 100%. Statistical analysis revealed no significant differences between the two groups with respect to peri-implant marginal bone levels and soft tissue parameters.

CONCLUSIONS

Within the limitations of this study, the results indicate that there was no evidence of different response with the peri-implant marginal bone and soft tissue when titanium or gold-alloy abutments were used in conjunction with the cemented, single-tooth implant restorations provided for this limited patient population. There was no evidence of different behavior of peri-implant marginal bone and of peri-implant soft tissue when titanium abutments or gold-alloy abutments were used for cemented single-tooth implant restorations in this limited patient population.

An in vitro evaluation of titanium, zirconia, and alumina procera abutments with hexagonal connection

PURPOSE

The purpose of this study was to assess the precision at the implant interface of titanium, zirconia, and alumina Procera abutments with a hexagonal connection for single-tooth restorations.

MATERIALS AND METHODS

Twenty Procera abutments were produced with commercially pure titanium, 20 with zirconia, and 20 with alumina using computer-assisted design and manufacture (CAD/CAM). The rotational freedom of the abutments was assessed to detect the precision of fit of each abutment on the top of the implant hexagon.

RESULTS

Significant differences relative to rotational freedom were found between groups: the titanium group and the zirconia group did not differ significantly, but both demonstrated significantly smaller mean rotational freedoms than the alumina group (P < .05). Rotational freedom was less than 3 degrees for all abutments.

CONCLUSIONS

The hexagonal misfit of the Procera abutment on the implant hexagon may be implicated in screw joint loosening. In the present study, all types of CAD/CAM Procera abutments consistently showed less than 3 degrees of rotational freedom in a situation where the abutment was connected to an implant by a hexagonal external connection.

Two patterns of histologic healing in an intrabony defect following treatment with enamel matrix derivative: a human case report

Human histologic evidence of periodontal regeneration following treatment of intrabony defects with enamel matrix derivative has yielded inconsistent results in recent case reports. A 46-year-old woman presenting one deep intrabony defect at the distal root of a mandibular first molar scheduled for extraction was selected for enamel matrix derivative therapy. During surgery, a notch was placed at the most apical level of calculus on the experimental root. Nine months postsurgery, a block section including the distal root and surrounding periodontal tissues was obtained and processed in a mesiodistal plane. Histologic analysis demonstrated two different patterns of healing along the proximal and furcal surfaces. Regeneration with new cellular cementum, bone, and periodontal ligament with functional fiber orientation was observed on the distal aspect of the root, whereas the furcal surface healed through ankylosis. This report underlines the biologic variability in wound healing following enamel matrix derivative therapy in periodontal intrabony defects and within the same defect. Host-specific intrinsic and/or extrinsic factors accounting for this variability remain to be investigated.

Master cast accuracy in single-tooth implant replacement cases: an in vitro comparison. A technical note

PURPOSE

This in vitro study evaluated the accuracy of master casts obtained by using (1) copings modified by sandblasting and coating their roughened surfaces with impression adhesive before final impression procedures and (2) gold machined UCLA abutments as impression copings in final impression procedures for single-tooth implant replacement cases.

MATERIALS 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 square impression copings sandblasted to roughen their external surfaces at a supragingival level and then coated with Impregum polyether adhesive; a second group of 20 impressions were made using gold machined UCLA abutments as impression copings. The castable part of the UCLA abutments was secured with resin to the gold machined section of the UCLA abutment to prevent movement of the castable part itself on the gold machined portion during the impression procedures; the castable portion of the UCLA was also coated with the Impregum polyether adhesive to improve the stability of the gold machined UCLA abutment inside the impression material. Master casts fabricated for both groups were analyzed to detect rotational position change of the hexagon on the implant replicas in the master casts with 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 using gold machined UCLA abutments as impression copings than in the master casts achieved with the roughened square impression copings.

DISCUSSION

Improved precision of the impression was achieved when the gold machined UCLA abutments were used as impression copings.

CONCLUSION

This report suggests that using gold machined UCLA abutments as impression copings in the final impression procedures can enable the clinician to achieve a more accurate orientation of the implant replicas in the laboratory master casts for single-tooth implant replacement cases.

An in vitro evaluation of ZiReal abutments with hexagonal connection: in original state and following abutment preparation

PURPOSE

Laboratory processing of implant-supported prostheses may alter the surface of the abutment in contact with the implant head, with potential repercussions for the interface fit. The purpose of this study was to assess changes at the implant interface of high-strength zirconia ceramic esthetic abutments with a hexagonal connection (ZiReal; 3i/Iimplant Innovations, Palm Beach Gardens, FL) following abutment preparation for single-tooth restorations.

MATERIALS AND METHODS

The depth (d) and width (w) of the titanium hexagonal portion of the abutment, the apical diameter of the abutment (D), and the rotational freedom (R) of the abutment were assessed for 20 ZiReal abutments prior to preparation (time 0) and following abutment preparation (time 1) to detect any eventual change of fit of the abutment on the top of the implant hexagon.

RESULTS

No significant differences relative to any study parameter (d, w, D, and R) were observed between time 0 and time 1 (P = .9542).

DISCUSSION AND CONCLUSIONS

The hexagonal misfit of the titanium machined ZiReal abutment on the implant hexagon may be implicated in screw joint loosening. The results of this report suggest that if all laboratory steps are carefully observed, changes at the implant/ZiReal abutment do not occur. The maintenance of the original features of the ZiReal abutment may reduce the risk of screw loosening.

An evaluation of impression techniques for multiple internal connection implant prostheses

STATEMENT OF PROBLEM

Movement of impression copings inside the impression material using an open-tray impression technique during clinical and laboratory phases may cause inaccuracy in transferring the 3-dimensional spatial orientation of implants intraorally to the definitive cast. Consequently the restoration may require corrective procedures.

PURPOSE

This in vitro study evaluated the accuracy of 3 different impression techniques using polyether impression material to obtain a precise definitive cast for a multi-unit implant restoration with multiple internal connection implants.

MATERIAL AND METHODS

A reference acrylic resin model with 4 internal connection implants (3i Implant Innovations) was fabricated. Forty-five medium-consistency polyether impressions (Impregum Penta) of this model were made with square impression copings using an open-tray technique. Three groups of 15 specimens each were made with different impression techniques: in the first group, nonmodified square impression copings were used (NM group); in the second group, square impression copings were used and joined together with autopolymerizing acrylic resin before the impression procedure (R [resin] group); and in the third group, square impression copings previously airborne-particle abraded and coated with the manufacturer-recommended impression adhesive were used (M [modified] group). Matching implant replicas were screwed into the square impression copings in the impressions. Impressions were poured with ADA type IV stone (New Fujirock). A single calibrated examiner blinded to the nature of the impression technique used examined all definitive casts to evaluate the positional accuracy (mum) of the implant replica heads using a profile projector (at original magnification x10). These measurements were compared to the measurements calculated on the reference resin model which served as control. Data were analyzed with a 1-way analysis of variance at alpha=.05, followed by the Student Newman-Keuls test (alpha=.05).

RESULTS

The data obtained with the profile projector revealed significant differences within the 3 impression techniques ( P <.001). The Student Newman-Keuls procedure disclosed significant differences between the groups, with group R casts being significantly more accurate than group NM and group M casts ( P =.05). The mean distance (+/-SD) between the posterior implants compared to the reference acrylic resin model was 18.17 mum (+/- 6.4) greater for group R casts, 41.27 mum (+/- 8.4) greater for group M casts, and 46.21 mum (+/- 8.9) greater for group NM casts. Distances between the anterior implants were also greater than those recorded on the reference model. The distance was 15.23 mum (+/- 5.9) greater on group R casts, 38.17 mum (+/- 8.3) greater on group M casts, and 43.23 mum (+/- 8.7) greater on group NM casts.

CONCLUSION

Within the limitations of this study, improved accuracy of the definitive cast was achieved when the square impression copings joined together with autopolymerizing acrylic resin were used to make an impression of multiple internal connection implants.

Clinical evaluation of small-diameter implants in single-tooth and multiple-implant restorations: a 7-year retrospective study

PURPOSE

Placement of small-diameter implants often provides a solution to space-related problems in implant restoration. This 7-year retrospective study presents results from 192 small-diameter implants placed in 165 patients from 1992 to 1996.

MATERIALS AND METHODS

The dental records of each patient were reviewed. The implants, which were either 2.9 mm or 3.25 mm in diameter, were placed by 2 different surgeons. All prosthetic appliances were fabricated by the same prosthodontist. Ninety-four implants supported single-tooth cemented restorations; the remaining 98 implants supported cemented or screw-retained partial prostheses.

RESULTS

The total implant survival rate was 95.3%. Four implants were lost at second-stage surgery, and 5 more were lost after loading.

DISCUSSION

Small-diameter implants demonstrated a survival rate similar to those reported in previous studies of standard-size implants.

CONCLUSIONS

The results suggest that small-diameter implants can be successfully included in implant treatment. They may be preferable in cases where space is limited.

Endoscopic evaluation of the bone-added osteotome sinus floor elevation procedure

Sinus floor augmentation using the bone-added osteotome technique (BAOSFE) has been advocated as a predictable procedure when initial residual bone height is 4-6mm. In this report, 16 Osseotite implants were placed using the BAOSFE procedure in eight patients under endoscopic control. Intraoperative graft positioning, potential displacement of the graft material, Schneiderian membrane integrity and distension pattern were evaluated. A small-sized perforation of the sinus membrane was visualized during sinuscopic monitoring in two implant sites without significant loss of graft material confinement. Membrane vertical distension was restricted to the area surrounding the implant apices in four implant sites while a larger detachment of the membrane enfolding the implant tips, the in-between and circumferantial areas was observed in the remaining 12 sites. The two perforated sites demonstrated a localized vertical pattern of membrane distension limited to implant apices. None of the cases complicated by perforation showed clinical signs of ongoing sinus pathology throughout the follow-up period. This limited report suggests that: (1) the BAOSFE procedure in combination with implant placement yields various patterns of sinus membrane elevation; (2) potential membrane perforation may be expected when distension follows a localized vertical augmentation pattern; and (3) small membrane perforations during the BAOSFE procedure are compatible with clinically healthy postoperative sinus conditions.

Cemented versus screw-retained implant-supported single-tooth crowns: a 4-year prospective clinical study

PURPOSE

The purpose of this controlled prospective clinical study was to compare cemented and screw-retained implant-supported single-tooth crowns followed for 4 years following prosthetic rehabilitation with respect to peri-implant marginal bone levels, peri-implant soft tissue parameters, and prosthetic complications.

MATERIALS AND METHODS

Twelve consecutive patients were selected from a patient population attending the Implantology Department at the University of Padova. They all presented with single-tooth bilateral edentulous sites in the canine/premolar/molar region with adequate bone width, similar bone height at the implant sites, and an occlusal scheme that allowed for the establishment of identical occlusal cusp/fossa contacts. Each patient received 2 identical implants (1 in each edentulous site). One was randomly selected to be restored with a cemented implant-supported single-tooth crown, and the other was restored with a screw-retained implant-supported single-tooth crown. Data on peri-implant marginal bone levels and on soft tissue parameters were collected 4 years after implant placement and analyzed to determine whether there was a significant difference with respect to the method of retention (cemented versus screw-retained).

RESULTS

All patients completed the study. All 24 implants survived, resulting in a cumulative implant success rate of 100%. Statistical analysis revealed no significant differences between the 2 groups with respect to peri-implant marginal bone levels and soft tissue parameters.

DISCUSSION

The data obtained with this study suggested that the choice of cementation versus screw retention for single-tooth implant restorations is likely not based on clinical results but seems to be based primarily on the clinician's preference.

CONCLUSIONS

Within the limitations of this study, the results indicate that there was no evidence of different behavior of the peri-implant marginal bone and of the peri-implant soft tissue when cemented or screw-retained single-tooth implant restorations were provided for this patient population.

Healing of transplanted composite bone grafts-implants: a pilot animal study

This experimental pilot study was undertaken to evaluate healing of titanium implants transplanted with the surrounding bone into recipient osseous sites in the rabbit mandible. One short implant was inserted in the horizontal portion of the mandible in each of 10 New Zealand rabbits. Subsequently, and during the same session, the implant with 1.5-2.0 mm of bone circumferentially was removed using a trephine bur and immediately transplanted in a through-and-through hole prepared in the contralateral aspect of the mandible. Three months following the transplantation, the animals were sacrificed and the mandibles processed for histological evaluation. The healing pattern was assessed in relation to (1) bone bridging at the interface between the bone core and the surrounding recipient osseous tissue, (2) differences in bone density between the transplanted bone cylinder and the bone at the margins of the recipient site, and (3) bone-to-implant contact (BIC) at the interface. The transplanted graft-implant cores were integrated within the recipient sites in five out of the 10 specimens while the remaining five bone-implant cores showed fibrous encapsulation. Various patterns of resorption were observed within the peri-implant transplanted hard tissues. Percentage BIC ranged between 1% and 72% in the fibrous-encapsulated specimens and between 20% and 62% in the integrated transplants. Within the limits of this pilot study, the results suggest that immediate transplantation of endosseous implants with their surrounding bone into congruous recipient osseous sites cannot predictably yield graft-implant incorporation and osseointegration of the implants. This alternative surgical modality of immediately transplanting a composite bone graft-implant from highly cortical intraoral or extraoral sites to enhance bone quality and/or volume in implant recipient sites such as the maxillary sinus and tuberosity areas needs to be further investigated.

Evaluation of the accuracy of three techniques used for multiple implant abutment impressions

STATEMENT OF PROBLEM

Movement of pick-up type impression copings inside the impression material during clinical and laboratory phases may cause inaccuracy in transferring the spatial position of implants from the oral cavity to the master cast. As a consequence, the laboratory technician may fabricate a restoration that requires corrective procedures.

PURPOSE

This in vitro study evaluated the accuracy of 3 different impression techniques using polyether impression material to obtain a master cast for the fabrication of a prosthesis that would fit passively on multiple implants.

MATERIAL AND METHODS

A machined metal model with 6 implants and abutments and a corresponding, passively fitting, matching metal template were fabricated. A total of 45 medium-consistency polyether impressions (Impregum Penta) of this model were made with pick-up type square impression copings. Three groups of 15 each were made with different impression techniques: in group 1, nonmodified square impression copings were used; in group 2, square impression copings were used and joined together with autopolymerizing acrylic resin before the impression procedure; and in group 3, square impression copings previously airborne particle-abraded and coated with the manufacturer-recommended impression adhesive were used. The matching metal template, which had been passively fit to the metal model so that it encountered no visually perceptible resistance or rocking on the abutments, was used as the control for evaluation of the accuracy of passive fit. A single calibrated and blinded examiner visually evaluated each cast. Positional accuracy of the abutments was numerically assessed with an optical scanner at original magnification x 10, which provided measurements to within 2 microm of the variations of the casts with respect to the horizontal distances between the 2 most posterior abutments and the 2 most anterior abutments. Data were analyzed with a 1-way analysis of variance at alpha=.05, followed by the Student Newman-Keuls method (P=.05).

RESULTS

Visual examination of the casts from group 1 revealed discrepancies between 1 or more abutments and the metal template. Visual analysis of the master casts from groups 2 and 3 revealed close alignment of the metal template on all 6 abutments. One-way analysis of variance analyzed the numerical data obtained with the optical scanner and revealed significant differences among the 3 impression techniques (P<.001). The Newman-Keuls procedure disclosed significant differences between the groups, with group 2 and 3 casts being significantly more accurate than group 1 casts (P=.05). The distance between abutments 1 and 6 compared to the standard metal model was 33.83 microm (SD +/- 5.4) greater on group 2 casts, 31.72 microm (SD +/- 4.6) greater on group 3 casts, and 78.16 microm (SD +/- 22.14) greater on group 1 casts. Distances between the most anterior abutments were also greater than those recorded on the metal model. The distance was 31.42 microm (SD +/- 7.6) greater on group 2 casts, 30.34 microm (SD +/- 6.4) greater on group 3 casts, and 67.91 microm (SD +/- 15.34) greater on group 1 casts.

CONCLUSION

Within the limitations of this study, improved accuracy of the master cast was achieved when the impression technique involved square impression copings joined together with autopolymerizing acrylic resin or square impression copings that had been airborne particle-abraded and adhesive-coated.

Maxillary sinus floor augmentation using bioactive glass granules and autogenous bone with simultaneous implant placement

This clinical study was undertaken to: 1) evaluate the use of bioactive glass Biogran combined with autogenous bone as grafting material for maxillary sinus augmentation with simultaneous implant placement using radiography and histology; and 2) document the short-term post-loading success of implants inserted in sinus cavities augmented with this material. Unilateral or bilateral sinus augmentation was performed in 12 patients with 3-5 mm of alveolar crestal bone height in the posterior maxilla prior to grafting. The sinuses were grafted with bioactive glass mixed in a 4:1 ratio with autogenous bone. Simultaneously, 2-3 threaded titanium implants were inserted into the augmented sinuses. Second stage surgery was carried out 9 to 12 months post implantation. At abutment connection, 10 core biopsy specimens were taken from different grafted sites and evaluated histologically. All 27 implants were clinically stable at second stage surgery. A mean increase in mineralized tissue height of 7.1 +/- 1.6 mm was evident when comparing the pre-surgical CT scans with those performed 9-12 months following the sinus augmentation procedure. Evaluation of the cores yielded a mean of 30.6 +/- 5.7% of bone tissue in the grafted sites. One implant failed during the prosthetic phase while the remaining 26 implants were stable 12 months post loading. This study suggests that Biogran/autogenous bone graft combination used in one-stage sinus augmentation yields sufficient quality and volume of mineralized tissue for predictable simultaneous implant placement in patients with 3-5 mm of bone height prior to grafting.

Comparison of 2 techniques of subepithelial connective tissue graft in the treatment of gingival recessions

BACKGROUND

The clinical outcome of connective tissue grafts in the treatment of gingival recessions has been documented in numerous studies. However, no attempt has been made to correlate the postoperative mucogingival changes with the surgical parameters. The present retrospective clinical study was undertaken to 1) evaluate root coverage and mucogingival changes 1 to 1.5 years following treatment of Miller's Class I and II recession defects using 2 variants of the subepithelial connective tissue graft (SCTG) procedure, and 2) assess the effect of the surgical parameters on the postoperative gingival width.

METHODS

Thirty-one recessions in 10 patients treated with the envelope technique (E) and 31 recessions in 11 patients treated with coronally positioned flap combined with connective tissue graft (CP) were retrospectively analyzed to evaluate: 1) percentage of root coverage obtained with the 2 procedures and variations in width of keratinized tissue (KT) 1 to 1.5 years postsurgery, and 2) the effect of the surgical parameters on the postoperative gingival width.

RESULTS

Results showed a mean root coverage percentage of 89.6 +/- 15% for the E group and 94.7 +/- 11.4% for the CP group; the difference between groups was statistically insignificant (P = 0.1388). Mean KT increased significantly from 1.4 +/- 1.1 mm presurgery to 4.5 +/- 1.1 mm postsurgery for the E group while a minor increase in KT was observed in the CP group (2 +/- 1.5 mm presurgery versus 2.7 +/- 1.6 mm postsurgery). For both treatment groups, the mean postsurgical width of keratinized tissue (POSTKT) was found to be mathematically correlated with the mean presurgical width of keratinized tissue (PREKT) and the corono-apical height of the graft that remained exposed (GE) coronal to the flap margin in the recipient site.

CONCLUSIONS

Treatment of human gingival recession defects by the 2 variants of SCTG resulted in significant recession reduction. When SCTG is grafted beneath alveolar mucosa using the combined technique (CP), transformation of the mucosa into keratinized tissue does not seem to occur, at least within 1 to 1.5 years postsurgery. The treatment outcome in terms of keratinized tissue width seems to be correlated with the presurgical gingival dimensions and the height of the graft that remains exposed at the end of the surgical procedure.

Histology of connective tissue graft. A case report

BACKGROUND

Few investigations can be found in the literature on the histological nature of the attachment of connective tissue grafts to root surfaces previously exposed by recession.

METHODS

In this case report, a 24-year-old patient was treated with a connective tissue graft combined with a partial-thickness coronally positioned flap for root coverage of Class I Miller recessions at the maxillary right and left canines and first premolars. The treated sites exhibited 83% and 100% root coverage on the right and left sides, respectively. Twelve months later, the case required extraction of all 4 first premolars for orthodontic reasons. Two conservative block sections including the maxillary first premolars with the buccal soft tissues were obtained and processed histologically in a bucco-palatal plane.

RESULTS

Histological analysis showed that healing occurred via a long junctional epithelium throughout the major portion of the previous recession site. Only minimal signs of new cementum-like tissue formation could be seen in the apical portion of the recession area coronal to the base of the instrumented root surface. No root resorption or ankylosis could be detected in any of the serial sections.

CONCLUSIONS

The findings of this case report outline the possible variations in the histological outcome of connective tissue grafts. These variations can be attributed to differences in size and shape of the recession defects and flap positioning at the end of surgery.

Measurement of the dimensions and abutment rotational freedom of gold-machined 3i UCLA-type abutments in the as-received condition, after casting with a noble metal alloy and porcelain firing

STATEMENT OF PROBLEM

Laboratory processing of implant-supported prostheses may alter the surface of the abutment in contact with the implant head and thus the interface fit.

PURPOSE

This study assessed changes at the implant interface of gold-machined UCLA abutments after casting and porcelain baking in the case of single-tooth restorations.

MATERIAL AND METHODS

The depth (d) and width (w) of the hexagonal portion of the abutment, the apical diameter (D) of the abutment, and the abutment rotational freedom (R) were assessed for 30 gold-machined UCLA abutments before casting procedures (time 0), after casting with a noble metal alloy (time 1), and after the addition of porcelain (time 2) to detect any eventual fitting change in the abutments on the top of the implant hexagon.

RESULTS

No significant differences relative to all study parameters (d, w, D, and R) were observed between times 0, 1, and 2 (P=.576).

CONCLUSION

The results of this investigation suggest that, if all laboratory steps are observed carefully, changes at the implant interface of gold-machined UCLA abutments do not occur.

Removal torque and histomorphometric investigation of 4 different titanium surfaces: an experimental study in the rabbit tibia

This study presents a histomorphometric and biomechanical comparison of bone response to commercially pure titanium screws with 4 different types of surface topographies placed in the tibial metaphysis of 12 rabbits. Each rabbit had 4 implants placed, 2 in each tibia. The 4 surface topographies were a machined surface, a grit-blasted surface, a plasma-sprayed surface, and an acid-etched (Osseotite) surface. After a healing period of 5 weeks, histomorphometric and removal torque data revealed a significantly higher percentage of bone-to-implant contact and removal torque for acid-etched implants compared to machined, blasted, and plasma-sprayed implants. Within the limits of this short-term experimental study, the results indicated that micro-rough titanium surfaces obtained with acid-etching procedures achieved a 33% greater bone-to-implant contact over machined titanium surfaces with an abutment-type roughness and provided enhanced mechanical interlocking.

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.

Role of intramarrow penetration in osseous repair: a pilot study in the rabbit calvaria

BACKGROUND

The use of intramarrow penetration in combination with osseous reconstructive surgery has been recommended in various periodontal and oral surgical applications. The purpose of this pilot study was to evaluate the effect of intramarrow penetration on the rate of bone neogenesis in protected spaces created on the calvarial bone using occlusive titanium domes in 16 adult white rabbits.

METHODS

In each rabbit, 2 standardized circular 1 mm deep slits were prepared in the bone, one on each side of the midline using a trephine. Within the perimeter of one of the slits, the external cortical surface of the skull bone was mechanically perforated using a carbide round bur (experimental site), while the bone surface within the other slit (control site) was left intact. Subsequently, 2 prefabricated titanium domes with an inner diameter of 4.8 mm and an inner height of 3.0 mm were anchored in the prepared slits. The animals were divided into 4 groups of 4 rabbits each and were sacrificed at 10, 21, 42, and 60 days. The specimens were assessed for the percentage bone fill and density of the newly formed bone within the boundaries of the domes.

RESULTS

Histomorphometric analysis showed significantly increased bone neogenesis within the experimental domes at 10, 21, 42, and 60 days. A mean total area of 29% newly formed bone was demonstrated in the experimental sites at 21 days, while negligible bone formation (9%) occurred with the control domes at the same evaluation interval. Bone density was consistently higher in experimental domes at all healing intervals.

CONCLUSIONS

Within the limits of this study, the results demonstrate that intramarrow penetration accelerates initial bone neogenesis and results in increased bone fill and density, suggesting that its use can be beneficial in bone regenerative procedures.

Guided bone regeneration using demineralized laminar bone sheets versus GTAM membranes in the treatment of implant-associated defects. A clinical and histological study

This study was designed to compare the regenerative potential at dehisced implant sites of the resorbable demineralized laminar bone sheets and non resorbable GTAM membranes. Twenty-six standard screw-type fixtures showing buccal dehiscences in 7 patients were treated using the GBR principles and received either laminar bone sheets (experimental) or GTAM (control) membranes. Twelve experimental and 10 control sites were available for evaluation at second stage surgery carried out 8 months following implant placement. Height and maximum width of the dehiscence defects were measured at the time of implant insertion and at second-stage procedure. Mean percentage of defect fill was 75.17% in the experimental dehiscences versus 86.70% in the control defects. A statistically significant difference in the percentage of defect fill could not be evidenced between the two treatment modalities. Complete fill was observed in 25% of the experimental versus 70% of the control sites. A significant difference was found in the median Density Index with the GTAM group showing a consistency similar to bone in a larger number of sites. Histologically, material with the same staining features of bone was evidenced inside the GTAM membranes in 3 cases while newly-formed bone was present in all instances under the control GTAM barriers. In the laminar bone-treated sites, the membrane maintained its integrity in almost all cases. Newly formed bone was found underlying the membrane in cases with a Density Index of 5 with no evidence of bony tissue adhering to the laminar sheets.

Electrically charged GTAM membranes stimulate osteogenesis in rabbit calvarial defects

Bone neogenesis was studied in membrane-protected defects in a rabbit calvaria defect model using neutral, negatively, and positively charged titanium-reinforced GTAM membranes. Two standardized circular 8 mm wide and 1 mm deep defects were created in the calvaria of 36 rabbits leaving the inner cortex intact. The defects were subsequently covered with dome-shaped Ti-reinforced GTAM membranes stabilized with a titanium screw allowing the edges of the membranes to be closely approximated to the bone surface. The animals were divided into 6 groups of 6 rabbits each and were sacrificed at 5 days (Group 1), 10 days (Group 2), 3 weeks (Group 3), 5 weeks (Group 4), 10 weeks (Group 5), and 20 weeks (Group 6). The distribution of the 72 membranes according to charge yielded 4 positively charged, 4 negatively charged and 4 neutral domes in each group. Histomorphometric analysis showed a more rapid and increased bone neogenesis with the negatively charged domes. A mean total area of 27.95% of newly-formed bone was observed in the negatively charged membrane sites at 10 days while negligible bone formation occurred with the neutral and positively charged domes at the same evaluation interval. Over time, negatively charged membranes supported more new-bone formation than neutral membranes while positively charged membranes showed the least new bone. This work demonstrates that negative electrical stimulation accelerates and maintains bone neogenesis. These results also suggest the potential applications of negatively charged GTAM membranes in clinical settings.

Bone response to orthodontic loading of endosseous implants in the rabbit calvaria: early continuous distalizing forces

The purpose of this experimental study was to evaluate the effect of early orthodontic loading on the stability and bone-implant interface of titanium implants in a rabbit model. Twenty-four short threaded titanium fixtures were inserted in the calvarial mid-sagittal suture of 10 rabbits. Two weeks following insertion, 20 implants (test group) were subjected to continuous distalization forces of 150 g for a period of 8 weeks. The remaining four implants (control group) were left unloaded for the same follow-up interval. Clinically, all implants except for one test fixture were stable, and exhibited no mobility or displacement throughout the experimental loading period. Histologically, all stable implants were well-integrated into bone. No differences could be found between the pressure and tension surfaces of the test implants relative to bone quality and density within a range of 1000 microns from the fixture surface. Similarly, qualitative differences were not observed between the apical and coronal portions of test fixtures. Morphometrically, a mean percentage bone-to-implant contact of 76.00 +/- 18.73 per cent was found at the test pressure sides, 75.00 +/- 11.54 per cent at the test tension sides, and 68.00 +/- 15.55 per cent at the control unloaded surfaces. No statistically significant differences in the percentage of bone-to-metal contact length fraction were found between test pressure surfaces, test tension surfaces, and unloaded control surfaces. Marginal bone resorption around the implant collar or immediately beneath it was found in roughly the same percentage of analysed sites in the test and control fixtures. In contrast, slight bone apposition was demonstrated at the implant collar of the test pressure surfaces, while no apposition or resorption were observed in the test tension zones. This study suggests that short endosseous implants can be used as anchoring units for orthodontic tooth movement early in the post-insertion healing period.

Postloading behavior of regenerated tissues in GBR-treated implant sites

The objective of this study was to assess, using reentry procedures, the capacity of regenerated tissues in implant-associated defects to respond to occlusal loading. Two groups of patients treated with membrane-augmented osseointegrated implants were included in the study. In group A (7 patients), a total of 9 implant-associated defects, including 6 dehiscences and 3 immediate extraction sites, were prospectively followed up 6 months following prosthesis connection. In group B (3 patients), 4 dehiscence defects were retrospectively evaluated 5 years after prosthetic loading. All defects in both groups had an uneventful healing period beyond the 6 months following implant insertion and showed complete fill with bone-like hard tissues at abutment connection surgery. A second surgical reentry was carried out to evaluate the quantitative changes in the regenerated tissues at the membrane-treated sites; it was carried out 6 months following prosthesis connection in group A, and 5 years postloading in group B. At the second reentry procedure, the mean percentage of defect fill at the dehiscence sites was 82% +/- 12.8% in group A and 83% +/- 7.3% in group B. In the 3 immediate extraction sites in group A, the most apical bone-implant contact around the implant was consistently located at about 1 mm, relative to the coronal aspect of the implant shoulder, as evidenced both radiographically and during the second reentry. The trends noted in this investigation suggest that tissues regenerated in successfully treated implant-associated defects can be maintained in the short-term and long-term periods following prosthetic loading.

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.

Heat generation during implant site preparation: an in vitro study

Thermal changes elicited during drilling and tapping procedures used in site preparation for screw-shaped and cylindrical implants were measured in vitro in blocks of bovine cortical femur bone. Heat-sensitive thermocouples were placed in the bone specimens at 4- and 8-mm depths and at a constant distance from the periphery of the drilling site; this distance was preset for each type of bur used. Rotary cutting was performed with 10-mm-long twist drills (2- and 3-mm diameter) and triflute drills (3.3- and 4-mm diameter) running at 1,500 rpm with external irrigation. A special guide drill was used to ensure unidirectional continuous drilling with a load of 2,000 g. In addition, the effect of irrigation was evaluated during tapping procedures with 10-mm-long taps used at 20 rpm. The greatest temperature increase was observed with the 2-mm twist drill at both 4- and 8-mm depths. Significantly greater temperature increase was noted at the 8-mm depth versus the 4-mm depth with the twist drills. Such significant difference between temperature rise at the two different drilling depths was not observed with the triflute burs. The time interval required for the maximum temperature reached during rotary cutting to return to baseline values was two times longer for the 2-mm twist drill than for the 3.3-mm triflute bur at both drilling depths. No statistically significant differences could be found between the maximum temperatures generated when tapping was performed with and without irrigation at both 4- and 8-mm depths. It can be suggested that the geometry of triflute burs combines cutting efficacy with greater heat dissipation capabilities than twist drills at the drilling depths of 4 and 8 mm used in this study.

Clinical and radiographic findings following placement of single-tooth implants in young patients--case reports

Single-tooth implants were inserted in the maxillary anterior segments of three young patients aged 11.5 to 13 years. The patients were monitored for a period of 2.5 to 4.5 years. All implant-supported crowns ended up in an infraocclusion position relative to the adjacent teeth because of the continued vertical growth of the maxillary alveolar process. Between base-line examination and the date of recall, the distance from a fixed reference point located on the fixture to the crestal bone on the proximal surfaces of teeth adjacent to the implant sites increased up to 3 mm. Transverse growth changes were also observed. Although the prostheses could be removed and modified to compensate for the resulting soft and hard tissue changes, complications may occur altering the health of the mucogingival unit and the esthetic appearance of implant-supported restorations, and requiring further soft tissue correction procedures.

Quantitative analysis of periodontal defects in a skull model by subtraction radiography using a digital imaging device

This paper describes a quantitative study of periodontal defects produced in a skull model using subtraction images obtained with a digital imaging device, radiovisiography (RVG). Analysis using radiovisiography was compared to changes in weight and volume determined by physical measurements. Four types of periodontal defects were studied: 2-wall, 3-wall, crater, and furcation. All defects were fabricated on posterior teeth in alveolar bone and done with triplicate samples. Defects were made progressively larger in approximately 1 mm steps allowing examination of defects ranging from 1 mm to 5 mm. Radiographic images before and after each step were obtained with a radiovisiography system and subtracted. Changes in weight and defect volume were also recorded and compared to the results obtained after each step from the digital subtraction. For each defect type, a regression analysis was performed to compare changes in bone mass determined by weight with calculated bone loss determined by subtraction radiography or by volume measurements. When the calculated bone losses were compared to the true bone losses it was evident that the subtraction method frequently, but not always, underestimated the lesion sizes. For all lesions the average underestimation was 22%. The largest underestimation occurred with furcation lesions where the measured bone loss was underestimated on average by 67%. Two-walled lesions were underestimated by 30%, 3-wall lesions by 3%, and crater lesions were overestimated by 10%. Furthermore, the accuracy of each 1 mm step in bone loss varied considerably. At present, the imaging system is not sufficiently accurate to establish absolute determinations of the bone loss, but would be clinically useful in determining relative changes in bone loss or gain after treatment. In addition, caution must be taken in interpreting a given change in calculated bone loss, since considerable variation may result in either underestimation or overestimation of bone loss.

Tooth morphology following root resection procedures in maxillary first molars

The Disto-Buccal root is the most commonly resected root in maxillary molars. This root resection procedure results in a unique environment dictated by the contours of the remaining roots and the residual furcation between them. Tooth morphology was evaluated in 50 extracted maxillary first molars after disto-buccal root resection. The following measurements were studied: 1) The maximum concavity (D) on the distal aspect of the resected molar; 2) the minimum mesio-distal dimension (d) of tooth structure between the two remaining roots; 3) the width (s) of the residual interradicular septum; and 4) the distance (p) from the pulp chamber floor to the root separation on the distal aspect of the resected molar. The mean measurements were (D) = 2.47 mm, (d) = 3.67 mm, (s) = 3.33 mm and (p) = 2.70 mm. The value of (p) was equal to or less than 3 mm in 86% of the teeth; this means that the distance from the finish line to the interradicular osseous peak is less than 2.04 mm (average biologic width), if the finish line is placed on solid tooth structure about 1 mm below the pulp floor. Six percent of the resected molars had an overall topography easily amenable to periodontal maintenance and restorative procedures with (D) less than 2 mm, (d) greater than 3 mm, (s) greater than 3 mm, and (p) greater than 3 mm. Poor root anatomy of the remaining roots after removal of the disto-buccal root in maxillary first molars may be considered as a contraindication for root resection procedures. Unfortunately, this poor topography can be ascertained only during the surgery and after removal of the disto-buccal root.