Joseph Nissan

Accuracy of three polyvinyl siloxane putty-wash impression techniques***

STATEMENT OF PROBLEM There is much discussion in the dental literature concerning the effect of the impression technique on the accuracy of cast restorations. PURPOSE This study assessed the accuracy of 3 putty-wash impression techniques using the same impression material (polyvinyl siloxane) in a laboratory model. MATERIAL AND METHODS The 3 putty-wash impression techniques used were (1) 1-step (putty and wash impression materials used simultaneously); (2) 2-step with 2-mm relief (putty first as a preliminary impression to create 2-mm wash space with prefabricated copings. In the second step, the wash stage was carried out); and (3) 2-step technique with a polyethylene spacer (plastic spacer used with the putty impression first and then the wash stage). For each technique, 15 impressions were made of a stainless steel master model that contained 3 complete crown abutment preparations, which were used as the positive control. Accuracy was assessed by measuring 6 dimensions (intraabutment and interabutment) on stone dies poured from impressions of the master model. RESULTS One-way analysis of variance showed statistically significant differences among the 3 putty-wash impression techniques, for all intraabutment and interabutment measurements (P <.001). Overall discrepancies of the 2-step technique with 2-mm relief putty-wash impression technique were significantly smaller than that in the 1-step and polyethylene putty-wash impression techniques. CONCLUSION The polyvinyl siloxane 2-step, 2-mm, relief putty-wash impression technique was the most accurate for fabricating stone dies.

Assessment of the resistance to fracture of endodontically treated molars restored with amalgam

STATEMENT OF PROBLEM Controversy exists concerning the preferred type of final restoration of endodontically treated molars regarding their resistance to fracture under occlusal load. PURPOSE The aim of this study was to assess the resistance to fracture of endodontically treated molars with various degrees of tooth structure loss restored with amalgam under simulated occlusal load. MATERIAL AND METHODS . The study teeth consisted of 90 noncarious, nonrestored molars stored in physiological saline solution. The teeth were endodontically treated and randomly divided into 9 experimental groups of 10 specimens each with various degrees of tooth loss, ranging from a conservative endodontic access to removal of all cusps. All teeth were restored with a standardized technique to their original contour with amalgam. Each specimen was mounted onto a specialized jig for loading at the central fossa at a 30-degree angle to the long tooth axis. The resistance to fracture, under continuous compressive force at a cross-head speed of 2 mm/minute, was applied by a universal testing machine and was recorded. One-way analysis of variance with Scheffé contrast was used to statistically compare the differences between the groups at significance level P<.05. RESULTS One-way analysis of variance showed that the group with a conservative endodontic access (1137.6 +/- 311.6 N) and the group with removal of all cusps (1261.4 +/- 195.1 N) presented a significantly higher resistance to fracture when compared with the other groups (P<.05). There was no significant difference in resistance to fracture under the simulated load between the other 7 groups, which ranged from 655.8 +/- 229.4 to 906.3 +/- 168.1 N (P>.05). CONCLUSION Within the limitations of this study, the endodontically treated molars with a conservative endodontic access or after removal of all cusps that were restored to their original contour with amalgam presented the highest resistance to fracture under a simulated occlusal load.

Characteristics of Early Versus Late Implant Failure: A Retrospective Study

PURPOSE Implant failures can be divided into early and late according to the timing of failure. The purpose of this study was to characterize and compare both types. PATIENTS AND METHODS A retrospective cohort study was conducted in 194 patients (98 men and 96 women) who presented after dental implant failures during a 6-year period (2000 to 2006). The patient served as the unit of analysis. A history of at least 1 failed and removed dental implant served as the inclusion criterion. Patients were excluded from this study whenever their files had missing data. The collected data included a patients characteristics, failure characteristics, and the anatomic status of the alveolar ridge after failure. RESULTS Late failures were associated with moderate to severe bone loss, a larger number of failed implants per patient, a higher incidence in men, and mostly in posterior areas. Early failures were associated with minimal bone loss, occurred more in women, at a younger age, and in most cases the implants were intended to support single crowns. CONCLUSIONS Meticulous follow-up is needed to reveal and treat failing or ailing implants. Once established as hopeless, they should be removed as soon as possible to prevent further bone loss.

Clinical Effectiveness of Implant-Supported Removable Partial Dentures-A Review of the Literature and Retrospective Case Evaluation

PURPOSE To review the published data on the treatment outcomes of restoring the partially edentulous patient with implant-supported removable partial dentures (ISRPDs) and describe the concept of ISRPDs and the clinical guidelines for placing implants for ISRPDs, and evaluate case series results. MATERIALS AND METHODS For the review, a literature search was performed using the PubMed and Ovid databases. Reports in English from 1969 to 2008 were considered. Also, 35 patients have had their dentition restored with ISRPDs supported by 67 implants. These patients were evaluated in terms of implant and teeth survival. RESULTS The data from the published reports and the presented case series suggest that the incorporation of dental implants into removable partial dentures could be an optional treatment plan for the partially edentulous patient to improve function and patient satisfaction. CONCLUSIONS ISRPDs provide patients with stable, long-term predictable prostheses. This treatment alternative should be considered whenever fixed restorations are not a valid option. Strict maintenance and a follow-up protocol are recommended to obtain satisfactory results. Longitudinal clinical studies are required for evaluation of ISRPDs.

Analysis of Complications Following Augmentation With Cancellous Block Allografts

BACKGROUND Bone grafting may be associated with soft and hard tissue complications. Recipient site complications encountered using cancellous block allografts for ridge augmentation are analyzed. METHODS A total of 101 consecutive patients (62 females and 39 males; mean age 44 ± 17 years) were treated with implant-supported restoration of 137 severe atrophic alveolar ridges augmented with cancellous bone-block allografts. Alveolar ridge deficiency locations were classified as anterior maxilla (n = 58); posterior maxilla (n = 32 sinuses); posterior mandible (n = 32); and anterior mandible (n = 15). A total of 271 rough-surface implants were placed. Recipient site complications associated with block grafting (infection, membrane exposure, incision line opening, perforation of mucosa over the grafted bone, partial graft failure, total graft failure, and implant failure) were recorded. RESULTS Partial and total bone-block graft failure occurred in 10 (7%) and 11 (8%) of 137 augmented sites, respectively. Implant failure rate was 12 (4.4%) of 271. Soft tissue complications included membrane exposure (42 [30.7%] of 137); incision line opening (41 [30%] of 137); and perforation of the mucosa over the grafted bone (19 [14%] of 137). Infection of the grafted site occurred in 18 (13%) of 137 bone blocks. Alveolar ridge deficiency location had a statistically significant effect on the outcome of recipient site complications. More complications were noted in the mandible compared to the maxilla. Age and gender had no statistically significant effect. CONCLUSIONS Failures caused by complications were rarely noted in association with cancellous block grafting. The incidence of complications in the mandible was significantly higher. Soft tissue complications do not necessarily result in total loss of cancellous block allograft.

Efficacy of Cancellous Block Allograft Augmentation Prior to Implant Placement in the Posterior Atrophic Mandible

BACKGROUND The present study evaluated the outcome of ridge augmentation with cancellous freeze-dried block bone allografts in the posterior atrophic mandible followed by placement of dental implants. MATERIALS AND METHODS A bony deficiency of at least 3 mm, horizontally, vertically, or both, according to computerized tomography (CT) para-axial reconstruction served as inclusion criteria. Implants were inserted after a healing period of 6 months. Bone measurements were taken prior to bone augmentation, during implant placement, and at second-stage surgery. Marginal bone loss and crown-to-implant ratio were also measured. RESULTS Twenty-nine cancellous allogeneic bone blocks were placed in 21 patients. The mean follow-up was 37 months. Bone block survival rate was 79.3%. Mean horizontal and vertical bone gains were 5.6 and 4.3 mm, respectively. Mean buccal bone resorption was 0.5 mm at implant placement and 0.2 mm at second-stage surgery. A total of 85 implants were placed. Mean bone thickness buccal to the implant neck was 2.5 mm at implant placement and 2.3 mm at second-stage surgery. There was no evidence of vertical bone loss between implant placement and second-stage surgery. Implant survival rate was 95.3%. All patients received a fixed implant-supported prosthesis. At the last follow-up, the mean marginal bone loss was 0.5 mm. The mean crown-to-implant ratio was 0.96. CONCLUSION Implant placement in the posterior atrophic mandible following augmentation with cancellous freeze-dried bone block allografts may be regarded as a viable treatment alternative.

Cancellous Bone Block Allografts for the Augmentation of the Anterior Atrophic Maxilla

BACKGROUND Pre-implant augmentative surgery is a prerequisite in many cases in the anterior maxilla to achieve a stable, long-term esthetic final result. PURPOSE The aim of the present study was to evaluate the outcome of ridge augmentation with cancellous freeze-dried block bone allografts in the anterior atrophic maxilla followed by placement of dental implants. MATERIALS AND METHODS Thirty-one consecutive patients were included in the study. A bony deficiency of at least 3 mm horizontally and up to 3 mm vertically according to computerized tomography (CT) served as inclusion criteria. Sixty-three implants were inserted after a healing period of 6 months. Nineteen of sixty-three implants were immediately restored. Bone measurements were taken prior to bone augmentation, during implant placement, and at second-stage surgery. RESULTS Forty-six cancellous allogeneic bone blocks were used. The mean follow-up was 34 ± 16 months. Mean bone gain was 5 ± 0.5 mm horizontally, and 2 ± 0.5 mm vertically. Mean buccal bone resorption was 0.5 ± 0.5 mm at implant placement, and 0.2 ± 0.2 mm at second-stage surgery. Mean bone thickness buccal to the implant neck was 2.5 ± 0.5 mm at implant placement, and 2.3 ± 0.2 mm at second-stage surgery. There was no evidence of vertical bone loss between implant placement and second-stage surgery. Block and implant survival rates were 95.6 and 98%, respectively. All patients received a fixed implant-supported prosthesis. CONCLUSION Cancellous block allografts appear to hold promise for grafting the anterior atrophic maxilla.

The Effect of Crown/Implant Ratio and Crown Height Space on Stress Distribution in Unsplinted Implant Supporting Restorations

PURPOSE To measure the transfer of axial and nonaxial load in unsplinted fixed implant supported restoration with varying crown to implant (C/I) ratios and crown height space (CHS). MATERIALS AND METHODS A photoelastic block model was constructed. Three holes were drilled vertically in a straight line in the mid axis of the photoelastic model at predetermined locations to lengths of 12 mm. Three implants were inserted into the model. Two strain gauges were cemented onto the neck of each implant on the buccal and lingual aspects, which provided a simultaneous direct reading of strain. Four groups of cement retained restorations with C/I ratios of 1:1; 1:1.5; 1:1.75, and 1:2 were used. CHS were 10, 15, 17.5, and 20 mm, respectively. Fifteen static loadings were carried out simultaneously with 20 kg weights via a custom-built loading apparatus at 0 and 30 degrees to the vertical axis. Descriptive analysis consisted of mean and standard deviation of microstrain values for each group. Groups were compared by the use of the 1-way parametric analysis of variance. A P value of less than .05 was considered statistically significant. RESULTS Occlusal force application at 30 degrees showed a statistically significant increase in both buccal (1,588 ± 150 vs 2,610.59 ± 150) and palatal (64.92 ± 7 vs 146.59 ± 15) microstrain values as C/I ratio increased from 1:1 to 1:1.5 (P < .001). Force application at 30 degrees in cases with C/I ratio of 1:1.75 and 1:2 resulted in fracture of the abutment screw followed by dislodgment of the crowns. Failures were noted at CHS >15 mm. CONCLUSIONS CHS is more significant than the C/I ratio in assessing biomechanical-related detrimental effects. Prosthetic failure occurred at CHS ≥ 15 mm.

Maxillary alveolar ridge reconstruction with monocortical fresh-frozen bone blocks: A clinical, histological and histomorphometric study

BACKGROUND This investigation is a clinical and histological assessment of fresh-frozen bone use in the reconstruction of maxillary alveolar ridges. The study evaluates the effectiveness of this material as a bone filler prior the placement of dental implants. PATIENTS AND METHODS Sixteen patients with atrophic maxillary ridges underwent maxillary reconstruction with fresh-frozen tibial human block grafts prior to implant placement. Sampling procedures were carried out 4, 6 and 9 months later when a bone core was removed from the grafts for histological and histomorphometric analysis. RESULTS Eighteen blocks were placed, and each patient received either 1 or 2 blocks. During the sampling procedures, all of the grafts were found to be firm in consistency, well-incorporated, and vascularized. A total of 34 implants were placed into the grafts with a minimum of 40-Newton-cm torque in all cases. The follow-up period ranged from 18 to 30 months. No implants were lost. The histological analysis revealed vital bone with mature and compact osseous tissue surrounded by marrow spaces. CONCLUSION Bone allografts can be used successfully as graft material for the treatment of maxillary ridge defects. This type of bone graft can be used safely in the areas of implant placement as a suitable alternative to autogenous grafts.

Late signs and symptoms of maxillary sinusitis after sinus augmentation

OBJECTIVES The aim of this study was to assess the incidence of late signs and symptoms of acute and chronic maxillary sinusitis after sinus augmentation and to correlate them with predisposing factors. STUDY DESIGN A total of 137 individuals (54 male and 83 female; 153 sinus augmentation procedures) were evaluated retrospectively for signs and symptoms of maxillary sinusitis, 12-80 months after surgery, using a questionnaire and clinical and radiographic examinations. RESULTS The incidence of acute and chronic sinusitis after sinus augmentation was low (<5%). History of preoperative sinusitis (P = .001) and sinuses with thick mucosa (P < .0001) were statistically significant factors correlated with late signs and symptoms of sinusitis. There was a slight correlation between chronic sinusitis and women (P = .079) or 2-stage procedures (P = .098). There was no statistical correlation to intraoperative complications, such as membrane perforation and excessive bleeding. CONCLUSIONS The occurrence of postoperative chronic sinusitis appears to be limited to patients with history of preoperative sinusitis and sinuses with thick mucosa, despite control of the disease before sinus augmentation. Intraoperative surgical complications have negligible effect. Patients presenting with preoperative sinusitis and sinuses with thick mucosa need to be informed of the increased risk. They require a close follow-up and prompt treatment in the event of signs and symptoms of sinusitis.