Jacob Horwitz

Fracture of dental implants: literature review and report of a case.

Fracture of dental implants is a rare phenomenon with severe clinical results. In this article, the literature is reviewed and various causative factors that may lead to fracture are presented. Galvanic activity has not been mentioned before as a possible cause for implant fracture, yet, it can occur at the level of contact with the superstructure. This is illustrated by the case of a titanium implant restored with a nonprecious porcelain-fused-to-metal cemented crown that fractured 4 years after loading. The radiographs show alveolar bone resorption around the fixture. Metallurgical analysis of the implant indicated that the fracture was caused by metal fatigue and that the crown metal, a nickel-chromium-molybdenum alloy, exhibited corrosion. These findings suggest a new explanation for implant fractures; cytotoxic nickel ions, leaching from the base metal alloy may cause bone resorption. This in turn leads to increased mobility, facilitating washout of the luting cement. Contact of the base metal with titanium in the presence of oral fluids produces galvanic currents that hasten corrosion and leaching out of nickel ions, thus leading to further bone resorption. Loss of bone support allows lateral bending moments that cause metal fatigue, eventually leading to fracture. Therefore, good treatment planning and appropriate case selection might have prevented this fracture. Furthermore, the use of nonprecious metal alloy for the crown’s infrastructure had further contribution to the chain of events that led to the implant’s fracture.

Accuracy of a computerized tomography-guided template-assisted implant placement system: an in vitro study

OBJECTIVES To evaluate the accuracy of computer-assisted 3D planning and implant insertion using computerized tomography (CT). MATERIALS AND METHODS Nine implants were planned on pre-operative CTs of six resin models, which were acquired with radiographic templates, using a planning software (E implants). Each resin model contained three pre-existing control implants (C implants). Radiographic templates were converted into operative guides containing 4.8-mm-diameter titanium sleeves. A single set of insertable sleeves was used for consecutively drilling the six models, followed by implant insertion through the guide sleeves. Models were further divided into group A (the first three models) and group B (the last three models). Post-operative CTs were used to compare implant positions with pre-operative planned positions. Statistical analysis included the Mann-Whitney U test for E and C implants and the Wilcoxons signed ranks test for groups A and B. RESULTS The mean apex depth deviations for E and C implants [0.49 mm+/-0.36 standard deviation (SD) and 0.32 mm+/-0.21 SD, respectively], and the mean apex radial deviations (0.63 mm+/-0.38 SD and 0.49 mm+/-0.17 SD, respectively) were similar (P>0.05). The mean angulation deviations for E and C implants were 2.17+/-1.06 degrees SD and 1.33+/-0.69 degrees SD, P<0.05. E implant deviations of all the parameters in group A were significantly smaller than E implant deviations in group B. CONCLUSIONS Computer-assisted implant planning and insertion provides good accuracy. Deviations are mainly related to system and reproducibility errors. Multiple use of drills and titanium sleeves significantly reduces system accuracy.

Dental implants placed in previously failed sites: survival rate and factors affecting the outcome

OBJECTIVES The purpose of the present study was to evaluate the survival rate of dental implants in previously failed implant sites. In addition, factors that might affect the outcome of these redo procedures were also explored. MATERIAL AND METHODS Patients that had failed dental implants, which were replaced with the same implant type at the same site, were included. Data on the failed implants were collected. The same parameters, along with the interval between retrieval and re-implantation, were collected for the second set of implants. Descriptive statistics were used to describe the patients and implants. Life table analysis of these implants was tabulated for both implant sets. The effect of systemic, environmental and local factors on the survival of the redo dental implants was evaluated. RESULTS Fifty-six patients with a total of 79 redo implants were included in this study. Implants were followed for 7-78 months (mean 29.9+/-2). Thirteen implants failed that resulted in an overall survival rate of 83.5%. Successful implants had greater diameter (4.05+/-0.52 mm) than failed implants (3.72+/-0.56 mm); however, these differences were only marginal (P=0.06). Conversely, smoking habits, implants length and location, mode of placement and spontaneous exposure did not have a significant effect on the outcome of this procedure. CONCLUSION Redo of dental implants has a lesser survival rate compared with previous reports for implants in pristine sites. These results were not associated with most implant- and/or patient-related factors. Thus, a possible negative effect that is associated with the specific implants site might account for this phenomenon.

Treatment of osseous cleft palate defects : A preliminary evaluation of novel treatment modalities

Objective To compare the use of autogenous iliac bone graft (ABG) alone with nonresorbable expanded polytetrafluoroethylene Gore-Tex TR membrane (GTM) and with ABG plus resorbable Resolut XT membrane barriers for the secondary closure of alveolar cleft defects. Study Design Fifteen patients aged 9 to 17 years with unilateral cleft palate were included in this study. All patients had primary closure of the soft tissues at infancy. Presurgical orthodontics and scaling preceded the surgery. The patients were randomized to one of three surgical treatment groups: (1) ABG, (2) GTM, or (3) autogenous bone plus resorbable membrane (ABM). Periapical radiographs were taken pretreatment and 2 to 6 years later and were used to measure changes in size (linear and area) of the osseous defect. Results Significant decreases were observed in mean initial defect width (9.8 to 6.7 mm; p = .0263), mean initial defect height (20.7 to 15.1 mm), and overall mean defect size (223.6 to 143.9 mm2). Greater improvement in mean defect width was observed for the ABM group (6.42 mm) compared with the ABG (1.22 mm) and GTM (1.38 mm) groups. The reduction in overall mean defect size was significantly greater in the ABM group (177 mm2) compared with the GTM (20.51 mm2) and ABG (41.69 mm2) groups. Conclusion Guided bone regeneration was found potentially useful for the treatment of osseous cleft palate defects. The combined approach yielded significantly greater defect fill. If further substantiated in larger independent studies, the adjunctive use of barrier membranes could improve the management of secondary closure of cleft palate defects.

Third attempt to place implants in sites where previous surgeries have failed.

BACKGROUND a lower survival rate for re-implantation in previously failed sites was reported. A third implant attempt in sites where previous implants have failed twice is rare; however, it may be necessary where other treatment alternatives are unacceptable. The aim of the present report is to explore the survival of implants placed three times at the same site. METHODS patients in whom a third attempt of implant placement at sites where two implants failed previously were evaluated. Medical history and smoking were recorded. The implant dimension, characteristics and survival were documented. The same implant and surgeon were involved in all three attempts. RESULTS fifteen third attempt implants in 12 patients were evaluated. The average age of the patients at first implantation was 48.8 ± 14.1 years. Six of the 15 second re-do implants have failed (60.0% survival rate). Smoking was reported by two patients. The implants that survived were followed for 44.1 ± 35 months (range 4-86). The mean implant length and diameter did not vary between attempts: the mean implant width/lengths were 3.6 ± 0.3/12.2 ± 1.4, 3.7 ± 0.3/12.6 ± 1.5 and 3.80 ± 0.3/12.4 ± 1.6 mm for the first, second and third attempts, respectively (p>0.05). CONCLUSIONS a third attempt to place implants in sites where two implants had failed previously results in significantly lower survival rates compared with similar procedures in pristine sites.

Diagnostic accuracy of cone beam computed tomography for dimensional linear measurements in the mandible.

PURPOSE To compare linear measurements made on cone beam computed tomography (CBCT) images to direct measurements in ex vivo porcine mandibles. MATERIALS AND METHODS Six cross-sectional planes were defined by gutta-percha-filled cavities in seven mandibles. The mandibles were scanned in a CBCT apparatus and later sectioned, using a band saw, through the gutta-percha markers. Next, four direct (DIR) linear measurements were performed for each section with a handheld digital caliper, using the gutta-percha markers as reference points. The corresponding radiographic (RAD) cross sections were then measured using dedicated software. A total of 168 sites were measured. Differences between RAD and DIR measurements [Δ (RAD - DIR)] were calculated for each pair individually. RESULTS Mean Δ (RAD - DIR) was -0.17 ± 0.53 mm (range, -1.42 to 1.09 mm). CBCT overestimated direct measurements at 36% of the sites; 8% of sites (95% confidence interval, 3.8% to 12.2%) showed errors between +0.5 and +1 mm, and 1.8% (95% confidence interval, -0.2% to 3.9%) showed errors greater than +1 mm. CONCLUSIONS Good correlation was found between CBCT and direct measurements. However, the significant percentage of sites with overestimation of at least 0.5 mm indicates a need for safety margins to be maintained when CBCT is used to plan surgical interventions such as dental implant therapy.

Variables affecting tooth survival and changes in probing depth: a long-term follow-up of periodontitis patients.

AIM To retrospectively assess tooth-survival rate and its association with patient and oral variables in periodontal office patients, followed up to 18 years. MATERIAL AND METHODS Patients in a private periodontal office whose files included initial examination (T0 ), reevaluation (TRe ) and ≥ 10 years after T0 (TF ) chartings, and received periodontal therapy and supportive periodontal therapy (SPT) after TRe were included. General health, plaque scores (PI), probing depth (PPD), bleeding on probing (BOP) at six points/tooth, tooth extractions, and SPT visits were extracted from patient files at T0 , TRe , and TF . Descriptive statistics and Cox regression analysis were performed. RESULTS Fifty patients (mean 26 ± 4 teeth/patient, 1301 teeth) fulfilled inclusion criteria. About 20 and 129 teeth respectively were extracted before/after TRe , 96 of them for periodontal causes. PPD>7 mm at TRe (HR = 17.7, 95%CI 8.6, 36.6), age above 60 years (HR = 3.3, 95%CI 1.5, 7.2), multi-rooted teeth (HR = 1.9, 95%CI 1.2, 3.1) and SPT<3 times/year (HR = 1.8, 95%CI 1.1, 2.9), were the best prognostic factors for tooth loss during follow-up. (p < 0.05, Cox regression analysis). A continuous, statistically significant reduction was observed in mean PPD among teeth that survived follow-up [4.3 ± 1.8 mm, 3.5 ± 1.4 mm, 3.2 ± 1.3 mm, at T0 , TRe , TF , respectively. (p < 0.001, Repeated-measures test)]. CONCLUSION Regular SPT was associated with low tooth-loss rates and continuous reductions in probing depth. PPD after initial therapy, age above 60, multi-rooted teeth and infrequent SPT were strong negative prognostic factors for long-term tooth survival among periodontal patients.

Dimensional changes of the maxillary sinus following tooth extraction in the posterior maxilla with and without socket preservation

BACKGROUND Sinus pneumatization is commonly observed following tooth extraction in the posterior maxilla, however, the role of this pneumatization in the overall changes in the vertical bone height is not clear. PURPOSE To compare dimensional changes in the alveolar ridge and corresponding maxillary sinus following tooth extraction, with or without socket preservation. MATERIALS AND METHODS 42 patients underwent tooth extraction (control group) and 21 patients underwent tooth extraction with socket preservation using DBBM (study group). Panoramic radiographs, prior to and approximately 1 year post extractions were superimposed and matched using a fixed reference unit. The following measurements were performed in the midline of the tooth site: distance of the bone crest to the sinus floor; distance of the sinus floor to the sinus roof and the sagittal circumference of the maxillary. RESULTS The mean change in the distance from the sinus floor to the sinus roof pre and post operatively was 0.30 mm (±0.10 SE) in the study group and 1.30 mm (±0.27 SE) in the control group (P = .0221). The mean change in the distance from the bone crest to the sinus floor was 0.32 mm (±0.09 SE) in the study group and 1.26 mm (±0.28 SE) in the control group (P = .0019), and the mean change in the sinus sagittal circumference was 37.34 mm (±6.10 SE) and 125.95 mm (±15.60 SE), respectively (P = .0001). CONCLUSIONS Ridge preservation using bovine derived xenograft might reduce sinus pneumatization along with minimizing crestal bone resorption.

A comparative study on the use of digital panoramic and periapical radiographs to assess proximal bone height around dental implants.

OBJECTIVE The purpose of this study was to compare periapical radiographs (PA) and panoramic radiographs (PAN) in the measurement of proximal bone height around implants. METHOD AND MATERIALS Patients files that contained digital PAN and PA together with information on implant lengths and diameters were selected for this study. For each radiograph, the implant size served as reference for calibration. Proximal radiographic bone levels and the linear distance between the bone crest and implant shoulder were measured twice by one examiner. Paired t test was used to assess intra-examiner variability and differences between the two radiographic methods. Correlation was then assessed using Pearson correlation coefficient test. Significance level was determined at 5%. RESULTS For the PAN measurements, the median mesial distances from bone crest to implant shoulder were 0.53 and 0.56 mm (first and second sets, P = .53). Likewise, for distal measurements these readings were 0.92 and 0.86 mm respectively (P = .66). For PA measurements, the corresponding measurements were 0.33 and 0.44 mm (P = .48) and 0.99 and 0.99 mm (P = .42), respectively. When PAN and PA measurements were compared, no statistically significant differences were detected between the two radiographic modalities. A very high positive correlation (r > 0.91) was attained for the PAN - PA measurements (P < .0001). CONCLUSION PAN are potentially as reliable and reproducible as PA for the assessment of proximal bone height around dental implants.

The association between dental proximal restorations and periodontal disease: A retrospective 10-18 years longitudinal study.

OBJECTIVE Dental restorations may be plaque retentive. The aim of this study was to evaluate the long-term association between proximal restorations and the incidence and progression of periodontal disease in well-maintained patients. METHOD AND MATERIALS Probing pocket depths (PPD), bleeding on probing (BOP), and radiographic status of proximal restorations were retrospectively retrieved from files of patients attending a specialist periodontal office. Ill-fitting margins were recorded. The association between these parameters was evaluated at baseline examination (T0), after cause-related therapy (T1) and after ≥ 10 years from T0 (T2), during which supportive periodontal therapy (SPT) was administered, using descriptive statistics, ANOVA-Bonferroni, and chi-square analyses. RESULTS 1,301 teeth were examined. Mean PPD in unrestored surfaces was 3.7 ± 1.7 mm, 3.1 ± 1.3 mm, and 2.8 ± 1 mm at T0, T1, and T2, respectively. Deeper pockets were found in restored surfaces at those time points with PPD values of 4.4 ± 1.8 mm, 3.6 ± 1.4 mm, and 3.2 ± 1.1 mm, respectively (P < .001). Higher PPD values were found in restored surfaces exhibiting inadequate restorations when compared to restored surfaces with adequate restorations at all time points. These values were 4.9 ± 1.9 mm, 4.1 ± 1.5 mm, and 4 ± 1.7 mm vs 4.3 ± 1.8 mm, 3.6 ± 1.4 mm, and 3.1 ± 1.1 mm, respectively (P < .001). CONCLUSION The present study confirmed that restorations might be detrimental to periodontal health. A significant association between the presence of proximal restorations and the incidence of periodontal disease was observed. This association was more pronounced for inadequate restorations while becoming less significant over time in patients receiving routine SPT.