Minimal invasive microscopic tooth preparation in esthetic restoration: a specialist consensus.

By removing a part of the structure, the tooth preparation provides restorative space, bonding surface, and finish line for various restorations on abutment. Preparation technique plays critical role in achieving the optimal result of tooth preparation. With successful application of microscope in endodontics for >30 years, there is a full expectation of microscopic dentistry. However, as relatively little progress has been made in the application of microscopic dentistry in prosthodontics, the following assumptions have been proposed: Is it suitable to choose the tooth preparation technique under the naked eye in the microscopic vision? Is there a more accurate preparation technology intended for the microscope? To obtain long-term stable therapeutic effects, is it much easier to achieve maximum tooth preservation and retinal protection and maintain periodontal tissue and oral function health under microscopic vision? Whether the microscopic prosthodontics is a gimmick or a breakthrough in obtaining an ideal tooth preparation should be resolved in microscopic tooth preparation. This article attempts to illustrate the concept, core elements, and indications of microscopic minimally invasive tooth preparation, physiological basis of dental pulp, periodontium and functions involved in tool preparation, position ergonomics and visual basis for dentists, comparison of tooth preparation by naked eyes and a microscope, and comparison of different designs of microscopic minimally invasive tooth preparation techniques. Furthermore, a clinical protocol for microscopic minimally invasive tooth preparation based on target restorative space guide plate has been put forward and new insights on the quantity and shape of microscopic minimally invasive tooth preparation has been provided.

Prospective observation of CAD/CAM titanium-ceramic-fixed partial dentures: 3-year follow-up.

PURPOSE: There is lack of knowledge about the clinical performance of computer-aided design/computer-aided manufacturing (CAD/CAM) titanium-ceramic-fixed partial dentures (FPDs). The purpose of this study was to evaluate CAD/CAM titanium-ceramic FPDs after 3 years in function. MATERIALS AND METHODS: Thirty-one FPDs were fabricated for 23 patients. The Ti frameworks were completely fabricated using CAD/CAM technology, and the low-fusing porcelain was veneered. After confirming there were no mechanical or biological complications, the FPDs were cemented using zinc phosphate cement. The patients were recalled at 12, 24, and 36 months after cementation to examine for the presence of any mechanical complications, such as fractures of the veneering porcelain or the supportive framework, or biological complications, including caries, gingivitis, or periodontitis. The periodontal condition was measured using probing depth (PD), bleeding on probing (BOP), and plaque index (PI). Success and survival rates were estimated using the Kaplan-Meier analysis. RESULTS: There were four cohesive and three adhesive porcelain fractures, but no framework fractured. The Kaplan-Meier cumulative success rate of the CAD/CAM titanium-ceramic crown with regard to mechanical complications was 76.4%, and the cumulative survival rate was 96.8% after 3 years of use. One patient developed caries, but the condition was not associated with marginal discrepancy. No other biological complications were reported. The periodontal parameters demonstrated a tendency that slightly increased up to 24 months and was maintained by 36 months. At the end of the follow-up, PD was 2.86 mm, percentile of surface with BOP was 23.5, and PI was 0.45. CONCLUSION: The CAD/CAM titanium-ceramic FPDs survived in the mouths of patients without major complications for 3 years, although the risk of porcelain fracture appeared to be relatively high.

Influence of sterilization on the retention properties of magnetic attachments for dental implants.

OBJECTIVES: When used with dental implants advantages of the magnetic attachments include control of load transmitted to implants, improvements in stability, support and retention for the prosthesis, and the relative ease of prostheses fabrication. Clinically, the use of sterilized components is required, and this may be problematic as magnetic alloys are sensitive to temperature. The purpose of this study was to evaluate the influence of autoclave sterilization on the maximum retentive forces and characteristic curves for magnetic attachments recommended for use with dental implants. MATERIAL AND METHODS: Eleven SmCo and NeFeB implant magnetic attachments were evaluated as provided by the respective manufacturers. Implant magnetic abutment and the corresponding denture magnet (n=5 magnet pairs) were tested before and after standardized autoclave sterilization (10 min at 134 degrees C). Each magnet pair was tested 10 times in a calibrated universal testing machine using a non-magnetic test device (s=40 mm, v=20 mm/min). Results were recorded electronically and statistically analyzed using t-test and ANOVA (Welch and Brown-Forsythe test; P<0.05). RESULTS: After autoclave sterilization all magnetic pairs produced lower (though statistically insignificant) overall retention forces compared with the untreated pairs. After sterilization mean maximum retentive forces (SD) ranged from 5.65 (0.33) to 1.41 (0.07) N. The characteristic force-displacement curves of the tested magnetic systems showed differences among the single products. CONCLUSIONS: Autoclave sterilization caused a non-significant reduction in retentive force of 0.04-14.6% when compared with the unsterilized magnet pairs. There were differences between the tested magnetic pairs for both the initial breakaway forces and the characteristic force-displacement curves. Within the limitations of this study all tested magnetic attachments were sterilized in an autoclave without significant change of retention properties. Nevertheless magnetic implant abutments should be sterilized with caution to reduce the risk of alterations of the retention properties.

Corrosion of dental magnet attachments for removable prostheses on teeth and implants.

PURPOSE: For a long time, the use of magnets for the anchorage of dental prostheses failed due to lack of biocompatibility and the magnets' high susceptibility to corrosion in the mouth. These facts make encapsulation of the magnetic alloy with a corrosion-resistant, tight, and functionally firm sealing necessary. Due to different products and analysis methods, it is not feasible to compare the findings for contemporary products with the sparse and rather old test results in the literature. Therefore, the aim of this study was the standardized control and the comparison of the corrosion behavior of modern magnetic attachments for use on teeth and dental implants. MATERIALS AND METHODS: Thirty-seven components of magnetic attachments on implants and natural teeth from different alloys (NdFeB, SmCo, Ti, CrMoMnTiFe, etc.) as delivered by the manufacturers or fabricated according to their instructions were examined for their corrosion behavior using the statical immersion analysis (ISO 10271:2001). Four specimens of every product with the same design were used. An uncased SmCo magnet served as control. Analyses after 1, 4, 7, and 28 days of the storage in corrosion solution were made. The eluate was examined quantitatively on the alloy components of the respective component with the help of optical emission spectrometry (microg/cm(2)). The results were compared to the requirements of ISO standard 22674:2006. In addition, existing corrosion products were also defined in the solution after 28 days. The results were analyzed descriptively and statistically to determine possible significant differences (t-test and Mann-Whitney-Wilcoxon rank-sums test; p < 0.05). RESULTS: Dissolved metal ions could be found on all tested products. The release after 1 and 4 days was different for all specimens. In the group of implant abutments, the highest ion release after 7 days was found (all measurements microg/cm(2)): Fe (13.94, Magfit-IP-IDN dome type), Pd (1.53, Medical-anchor), Cr (1.32, Magfit-IP-IDN dome type), Ti (1.09, Magfit-IP-IDN abutment), Co (0.81, Medical-anchor), and B (0.6, Magfit-IP-IDN dome type). After 28 days, the analyzed ion release increased irregularly: Fe (173.58, Magfit-IP-IDN dome type), Pd (44.17, Medical-anchor), Cr (2.02, Magfit-IP-IDN dome type), Ti (2.11, Magfit-IP-IDN abutment), Co (26.13, Medical-anchor), B (1.77, Magfit-IP-IDN dome type), and Nd (79.18, Magfit-IP-IDN dome type). In the group of magnetic systems on natural teeth, the highest ion release after 7 days was found for Fe (4.81, Magfit DX 800 keeper), Cr (1.18, Magfit DX 800 keeper), Pd (0.21, Direct System Keeper), Ni (0.18, WR-Magnet S3 small), Co (0.12, Direct System Keeper), and Ti (0.09, Magna Cap - Mini). After 28 days, the analyzed ion release increased non-uniformly: Fe (31.92, Magfit DX 800 Keeper), Cr (6.65, Magfit DX 800 Keeper), Pd (18.19, Direct System Keeper), Ni (0.61, WR-Magnet S3 small), Co (10.94, Direct System Keeper), Ti (0.83, Magna Cap - Mini), and Pd (2.78, EFM Alloy). In contrast, the uncased control magnet showed an exponential release after 7 days of Sm ions (55.06) and Co-ions (86.83), after 28 days of Sm ions (603.91) and Co ions (950.56). The release of corrosion products of all tested products stayed significantly under the limit of 200 microg/cm(2) (ISO 22674:2006). In contrast, the non-encapsulated control magnet exceeded that limit significantly. CONCLUSION: The analysis of the corrosion behavior of modern magnetic attachments for use on teeth and dental implants according to ISO 10271:2001 showed that metal ions had dissolved on all specimens. In the case of one product, the magnet corroded. For this product, an improvement of the capsulation would be desirable. None of the products reached the limit specified in ISO 22674:2006. All products seem to be suitable for dental application. Further studies in regard to the specific biocompatibility and possible cytotoxic effects on mucosa and tissue would be desirable.

Marginal accuracy of combined tooth-implant-supported fixed dental prostheses after in vitro stress simulation.

OBJECTIVES: Caries, periodontal disease, and peri-implant inflammation caused by deficient marginal adaptation of fixed prostheses are reasons for clinical failure of combined tooth-implant-supported fixed dental prostheses (TISFDP). This in vitro study examined the marginal accuracy in TISFDP after simulated stress in an artificial oral environment. MATERIALS AND METHODS: Twelve three-unit TISFDPs were fabricated using a high noble alloy on models containing a human premolar with an artificial periodontium and an implant. Four three-unit tooth-supported prostheses (TSFDP) represented the control group. The experimental TISFDPs (four per group) were luted with three different cements: group 1, zinc phosphate; group 2, glass ionomer; group 3, self-adhesive resin. The specimens were mechanically loaded (1.2 million cycles/50 N) and thermally cycled (8000 cycles with 5/55 degrees C). The vertical marginal gap was measured before and after cementation, after chewing simulation and after thermal cycling by light microscopy (x 560). The results were subjected to statistical analysis (t-test/one-way analysis of variance/Bonferroni). RESULTS: Significant increase (P< or =0.05) in the marginal gap was found after cementation within the experimental TISFDPs (implants, 11.7-18.7 microm; teeth, 13.4-24.2 microm) and the control TSFDPs (28.5 microm). Comparison of groups 1 and 2 revealed significant differences for the teeth while comparison of the implants showed significant differences among all groups. Chewing simulation and thermal cycling caused statistically insignificant changes in the marginal gaps of the experimental as well as the control TSFDPs. CONCLUSION: The cementation of the TISFDPs with different luting materials caused a specific enlargement of the marginal gap in teeth and implants. Subsequent to simulated oral stress in an artificial oral environment, no significant changes of the marginal accuracy could be found.

Mechanical properties of magnetic attachments for removable prostheses on teeth and implants.

PURPOSE: Magnetic attachments on teeth and implants may be used to improve stability, support, and retention of removable prostheses. Various forms of magnetic attachments are available, divided according to the design, the mechanical properties of the attachments, and the clinical indication. Recently developed attachment systems are small and promise improved retentive capacity, while existing magnetic attachments continue to be technologically modified and improved. This investigation reviewed and compared maximum retentive forces and characteristic curves for magnetic attachments indicated for use as root anchors and on implants. MATERIALS AND METHODS: Twenty-four samarium-cobalt (SmCo) and neodym-iron-boron (NeFeB) magnetic attachments (12 tooth- and 12 implant-borne) were evaluated. Specimens were delivered by the manufacturers or fabricated according to their instructions. Five magnet pairs of each product and each combination were tested 10 times in a calibrated universal testing machine using a nonmagnetic test device (s = 40 mm, v = 20 mm/min). Results were recorded electronically and compared to manufacturers' details. RESULTS: Maximum retentive forces for root keepers ranged from 1.4 to 6.6 N. Maximum retentive forces for magnetic attachments on implants ranged from 0.7 to 5.8 N. After a distance of 0.1 mm, a complete reversed distribution of the different systems became obvious. The retentive force provided by the manufacturer was achieved in one implant abutment, with retentive force (as compared to those provided by the manufacturers) for root keepers ranging between 42.5% and 92.9% and for implant abutments between 43.0% and 99.4%. CONCLUSION: There were differences between magnetic attachments for both the initial retentive capabilities and the characteristic curves. Recently introduced products provided relatively high initial retentive forces despite their small size. The measured retentive forces and the manufacturer's information differed in the majority of magnetic systems evaluated.

Meta-analysis of treatment need for temporomandibular disorders in adult nonpatients.

AIMS: To determine the prevalence of treatment need for temporomandibular disorders in adult populations by meta-analysis of nonpatient studies and to investigate factors influencing temporomandibular disorder treatment-need estimates. METHODS: Population-based and nonpatient studies of adult subjects with temporomandibular disorders published in the English language prior to July 2006 were systematically reviewed. Electronic databases (MEDLINE, CINAHL, and Science Citation Index Expanded) were searched (n = 641). To combine data, fixed- and random-effects meta-regression models were used. Subgroup analyses were performed to assess factors influencing treatment need estimates. RESULTS: Of 676 articles identified, 17 (9,454 subjects) met the study criteria. The prevalence of treatment need for TMD in adults (95% confidence interval) was estimated to be 15.6% (10.0, 23.6) for the fixed effect model and 16.2% (11.2, 21.1) for the random-effects model. Criteria of estimating treatment need and place of study strongly influenced summary estimates of treatment need (P < .001). Need estimates derived from clinical TMD signs were higher than estimates based on subject-reported symptoms (P = .010). Estimates for younger subjects (19 to 45 years) were higher than for older subjects (46+ years; P = .013). CONCLUSION: The treatment need for TMD in the general adult population is substantial and varies according to definition, criteria, and age. Findings of this meta-analysis can be used for planning and allocating health-care resources.

Incisal tooth wear and self-reported TMD pain in children and adolescents.

PURPOSE: Incisal tooth wear may be a sign of long-term bruxing behavior. Bruxism is purported to be a risk factor for temporomandibular disorders (TMD). The aim of this population-based cross-sectional study was to determine if anterior tooth wear is associated with the self-report of TMD pain in children and adolescents. MATERIALS AND METHODS: In a population sample of 1,011 children and adolescents (mean age 13.1 years, range 10 to 18 years; female 52%; response rate 85%), TMD cases were defined as subjects reporting pain in the face, jaw muscles, and temporomandibular joint during the last month according to RDC/TMD. All other subjects were considered controls. Incisal tooth wear was assessed in the clinical examination using a 0 to 2 scale (no wear, enamel wear, dentin wear) for every anterior permanent tooth. The mean wear score for the individuals was categorized into 0, 0.01 to 0.20, 0.21 to 0.40, and 0.41+. A multiple logistic regression analysis, controlling for the effects of age and gender, analyzed the association between the categorized summary wear score and TMD. Specifically, the hypothesis of a trend between higher tooth wear scores and higher risk of TMD was tested. RESULTS: An odds ratio of 1.1 indicated, after adjusting for gender and age, no statistically significantly higher risk of TMD pain with higher tooth wear scores. CONCLUSION: Incisal tooth wear was not associated with self-reported TMD pain in 10- to 18-year-old subjects.