• The Journal of Advanced Prosthodontics
• /
• v.10 no.4
• /
• pp.286-290
• /
• 2018

PURPOSE. Conventional resin-bonded fixed partial dentures (RBFPDs) are usually made with a two-retainer design. Unlike conventional RBFPDs, cantilever resin-bonded fixed partial dentures (Cantilever RBFPDs) are, for their part, made with a single-retainer design. The aim of this study was to compare the effect of tooth surface preparation on the bond strength of zirconia cantilever single-retainer RBFPDs. The objective is to evaluate the shear bond strength of these single-retainer RBFPDs bonded on 3 different amount of tooth surface preparation. MATERIALS AND METHODS. Thirty extracted bovine incisors were categorized to 3 groups (n=10), with different amounts of tooth surface preparations. Teeth were restored with single-retainer RBFPDs with different retainer surfaces: large retainer of $32mm^2$; medium retainer of $22mm^2$; no retainer and only a proximal connecting box of $12mm^2$. All RBFPDs were made of zirconia and were bonded using an adhesive system without adhesive capacity. Shear forces were applied to these restorations until debonding. RESULTS. Mean shear bond strength values for the groups I, II, and II were $2.39{\pm}0.53MPa$, $3.13{\pm}0.69MPa$, and $5.40{\pm}0.96MPa$, respectively. Statistical analyses were performed using a one-way ANOVA test with Bonferroni post-hoc test, at a significance level of 0.001. Failure modes were observed and showed a 100% adhesive fracture. CONCLUSION. It can be concluded that the preparation of large tooth surface preparation might be irrelevant. For zirconia single-retainer RBFPD, only the preparation of a proximal connecting box seems to be a reliable and minimally invasive approach. The differences are statistically significant.

• The Journal of the Korean dental association
• /
• v.21 no.5 s.168
• /
• pp.395-402
• /
• 1983

The purpose of this study was to apply the etched metal ceramometal retainer using a composite resin and acid-etch procedure with minimal tooth reduction of abutments for the replacement of one missing anterior or posterior tooth. Author obtained the following conclusions. 1. conservation of tooth structure and minimal chair time and patient expense were the primary advantages of etched metal retainer. 2. This fixed partial denture permitted good esthetic results. 3. This retainer was successfully applied for the replacement of one missing anterior or posterior tooth. 4. Proper retainer etching ws an important procedure. 5. Etched castings could be applied to periodontal splinting and post orthodontic fixation.

• The korean journal of orthodontics
• /
• v.46 no.1
• /
• pp.36-41
• /
• 2016

Objective: The aim of this study was to evaluate retention practices commonly employed by orthodontists. The objectives were to identify the types of retainer frequently used and to investigate the variations in retention practice. Methods: A total of 97 orthodontists were randomly selected, and a questionnaire consisting of 25 multiple-choice questions sent to them by mail. Upon receiving of the completed questionnaires, the data were statistically analyzed. Results: A total of 32 responses were received; among these, 59.4% of orthodontists' practiced is in a government setting and 40.6% were in private practice. A vacuum-formed retainer was the most commonly used removable retainer for both maxillary (46.9%) and mandibular (46.9%) arches, followed by a Hawley retainer (maxilla, 43.8%; mandible, 37.5%), and a fixed retainer (maxilla, 3.1%; mandible, 9.4%). Of the responding orthodontists, 78.1% prescribed full-time wear (more than 20 h per day) for a duration of 3-9 months for a maxillary arch, compared to 71.9% for the mandibular arch. Only 18.8% of the orthodontists prescribed part-time wear of the retainer for the maxillary arch, compared to 21.9% for the mandibular arch. The majority of orthodontists did not instruct their patients to stop wearing removable retainers (71.9%) or fixed retainers (66.8%) at any specific time and they preferred their patients to continue wearing retainers. Conclusions: Vacuum-formed retainers are the most commonly used retainers among orthodontists. The majority of orthodontists prescribed full-time wear for more than 20 h per day with a duration of 3-9 months and preferred indefinite use of the retainer.

• The korean journal of orthodontics
• /
• v.40 no.5
• /
• pp.325-333
• /
• 2010

Objective: The aim of this study was to illustrate the circumferential comfortable retainer (CCR) as a removable maxillary retainer with good potential patient compliance and to evaluate the discomfort of the retainers including distorted speech, gagging sensation and appliance discomfort. Methods: Sixty-six orthodontic patients (male, 23; female, 43; mean age, $23.42{\pm}10.19$ years) who received orthodontic treatment with fixed orthodontic appliances were randomly assigned to two groups after debonding, a conventional wraparound retainer (CWR) group that fully covers the palate with an acrylic plate and a highly polished surface, and a circumferential comfortable retainer (CCR) group which has a horseshoe shaped base plate with three folds on the anterior region. A questionnaire that had a visual analog scale (VAS) which consists of a 100-mm horizontal line with 2 end-points labeled "no discomfort" on the left and "worst discomfort" on the right, with regard to distorted speech, gagging sensation and discomfort, was administered to patients after 4 weeks of retainer wear. The Mann-Whitney test was used to test the hypothesis that there was no difference between the two retainers. Results: Comparing distorted speech and discomfort, the CCR group significantly had lower values than the CWR group ($p$ < 0.05). Comparing gagging sensation, the CCR group had lower values than the CWR group but there were no statistically significant differences between groups ($p$ = 0.146). Conclusions: In conclusion, the results suggest that the circumferential comfortable retainer (CCR) might facilitate patient compliance and thereby improve the maintenance of the fixed orthodontic treatment outcome.

• Imaging Science in Dentistry
• /
• v.51 no.1
• /
• pp.63-71
• /
• 2021

Purpose: The aim of this study was to assess the artefacts of 12 fixed orthodontic appliances in magnetic resonance images obtained using 1.5-T and 3-T scanners, and to evaluate different imaging sequences designed to suppress metal artefacts. Materials and Methods: In vitro, study casts of 1 adult with normal occlusion were used. Twelve orthodontic appliances were attached to the study casts and scanned. Turbo spin echo (TSE), TSE with high readout bandwidth, and TSE with view angle tilting and slice encoding for metal artefact correction were used to suppress metal artefacts. Artefacts were measured. In vivo, 6 appliances were scanned: 1) conventional stainless-steel brackets; 2) nickelfree brackets; 3) titanium brackets; 4) a Herbst appliance; 5) a fixed retainer; and 6) a rapid maxillary expander. The maxilla, mandible, nasopharynx, tongue, temporomandibular joints, and cranial base/eye globes were assessed. Scores of 0, 1, 2, and 3 indicated no artefacts and minor, moderate, and major artefacts, respectively. Results: In vitro, titanium brackets and the fixed retainer created minor artefacts. In vivo, titanium brackets caused minor artefacts. Conventional stainless-steel and nickel free brackets, the fixed retainer, and the rapid maxillary expander caused major artefacts in the maxilla and mandible. Conventional stainless-steel and nickel-free brackets caused major artefacts in the eye globe (3-T). TSE with high readout bandwidth reduced image artefacts in both scanners. Conclusion: Titanium brackets, the Herbst appliance, and the fixed retainer caused minor artefacts in images of neurocranial structures(1.5-T and 3-T) when using TSE with high readout bandwidth.

• Journal of Periodontal and Implant Science
• /
• v.51 no.3
• /
• pp.163-178
• /
• 2021

Purpose: The aim of this study was to evaluate clinical factors affecting the longevity of fixed retainers and the influence of fixed retainers on periodontal health in periodontitis patients. Methods: In total, 52 patients with at least 2 years of follow-up after periodontal and orthodontic treatment were included in this study. After scaling and root planing, orthodontic treatment with fixed appliances or clear aligners was performed. Fixed retainers with twist-flex stainless steel wires were bonded to the palatal or lingual sides of anterior teeth. Changes in clinical parameters, including the plaque index, gingival index, calculus index (CI), probing pocket depth, and radiographic bone levels, were evaluated before bonding of fixed retainers and at a 12-month follow-up. Cumulative survival rates (CSRs) for retainer failure were evaluated according to sex, site, CI, stage of periodontitis, and the severity of the irregularity with the log-rank test and hazard ratios (HRs). Results: Twelve months after bonding of fixed retainers, improvements were observed in all clinical parameters except CI and radiographic bone gain. The overall CSR of the retainers with a CI <1 at the 12-month follow-up after bonding of fixed retainers was significantly higher than that of the retainers with a CI ≥1 at the 12-month follow-up (log-rank test; P<0.001). Patients with stage III (grade B or C) periodontitis had a higher multivariate HR for retainer failure (5.4; 95% confidence interval, 1.22-23.91; P=0.026) than patients with stage I (grade A or B) periodontitis. Conclusions: Although fixed retainers were bonded in periodontitis patients, periodontal health was well maintained if supportive periodontal treatment with repeated oral hygiene education was provided. Nonetheless, fixed retainer failure occurred more frequently in patients who had stage III (grade B or C) periodontitis or a CI ≥1 at 12-month follow-up after bonding of fixed retainers.

• The korean journal of orthodontics
• /
• v.39 no.6
• /
• pp.402-419
• /
• 2009

Successful treatment of the non-growing patient with an open bite of either dental skeletal pattern often presents a difficult challenge. The morphologic pattern in anterior open bite is characterized by longer vertical dimensions, an increase in development of the maxillary posterior dento-alveolar structure and a steep mandibular plane. In such cases, molar intrusion would be a good remedy for treatment. This article reports the successful treatment and retention of two anterior open-bite cases. We used orthodontic mini-implants for treatment and a circumferential retainer with posterior bite block or skeletal fixed retainer for retention. The diagnostic criteria and mechanics for appropriate treatment are discussed. Our results suggest that open bite can be reduced successfully with intrusion of molars using orthodontic mini-implants (OMI) without orthognathic surgery, and that circumferential retainer with posterior bite block and skeletal fixed retainer are effective for retention.

• The korean journal of orthodontics
• /
• v.47 no.3
• /
• pp.207-212
• /
• 2017

The popularity of clear overlay retainers (CORs) has increased recently because of their advantages such as better esthetics, cost effectiveness, easy fabrication, and good compliance. However, a deficiency in posterior occlusal settling is a reported limitation of CORs. The aim of this study was to evaluate the posterior occlusal contact changes in a new type of clear orthodontic retainer called Oral-treaper (OTP), which consists of three layers and has stronger mechanical characteristics than do conventional retainers. Three patients who completed fixed orthodontic treatment received OTP as a removable retainer. Cast models were fabricated after the removal of fixed appliances (T1) and after 4 to 11 months of using the retainers (T2). We evaluated all the cast models to compare the post-orthodontic settling pattern during the use of the OTPs. The depth of occlusal contacts was evaluated using color maps. The OTP did not prevent vertical settling in all patients but resulted in an improvement in posterior occlusal contact points.

• The korean journal of orthodontics
• /
• v.46 no.2
• /
• pp.104-110
• /
• 2016

Objective: Traditional retainers (both metal and fiber-reinforced composite [FRC]) have limitations, and a retainer made from more flexible ligature wires might be advantageous. We aimed to compare an experimental design with two traditional retainers. Methods: In this prospective preliminary clinical trial, 150 post-treatment patients were enrolled and randomly divided into three groups of 50 patients each to receive mandibular canine-to-canine retainers made of FRC, flexible spiral wire (FSW), and twisted wire (TW). The patients were monitored monthly. The time at which the first signs of breakage/debonding were detected was recorded. The success rates of the retainers were compared using chi-squared, Kaplan-Meier, and Cox proportional-hazard regression analyses (${\alpha}=0.05$). Results: In total, 42 patients in the FRC group, 41 in the FSW group, and 45 in the TW group completed the study. The 2-year failure rates were 35.7% in the FRC group, 26.8% in the FSW group, and 17.8% in the TW group. These rates differed insignificantly (chi-squared p = 0.167). According to the Kaplan-Meier analysis, failure occurred at 19.95 months in the FRC group, 21.37 months in the FSW group, and 22.36 months in the TW group. The differences between the survival rates in the three groups were not significant (Cox regression p = 0.146). Conclusions: Although the failure rate of the experimental retainer was two times lower than that of the FRC retainer, the difference was not statistically significant. The experimental TW retainer was successful, and larger studies are warranted to verify these results.

• The Journal of Korean Academy of Prosthodontics
• /
• v.41 no.1
• /
• pp.81-88
• /
• 2003

Resin-bonded bridge has been an alternative to conventional bridge, since resin-bonded bridge has many attractive advantages such as minimal tooth preparation, short chair time and low cost over conventional bridge. Unfortunately, however, it was reported that resin-bonded bridge showed high failure rate from debonding of retainer in spite of consecutive advances in preparation and materials. And it was shown that multiple abutments were more likely to fail. The majority of debonding failure was considered due to the mobility of the abutment during function. In this view, recently, modification in resin-bonded bridge design was tried. Single retainer, single pontic. 2-unit cantilevered resin-bonded bridge was applied to clinical performance and was shown as retentive or more retentive than fixed-fixed type resin-bonded bridge. This was consistent with the results of studies in 2-unit cantilevered resin-bonded bridges made with all ceramic, In-ceram. The purpose of this article was to overview principles of design and to analyze clinical results of 2-unit cantilevered resin-bonded bridge in comparison with the reports of fixed-fixed resin-bonded bridge.