Identification of Critical Amino Acid Residues of a Two-Component Sensor Protein for Signal Sensing in Porphyromonas gingivalis Fimbriation via Random Mutant Library Construction.

Porphyromonas gingivalis (Pg) utilizes FimA fimbriae to colonize the gingival sulcus and evade the host immune system. The biogenesis of all FimA-related components is positively regulated by the FimS-FimR two-component system, making the FimS sensory protein an attractive target for preventing Pg infection. However, the specific environmental signal received by FimS remains unknown. We constructed random Pg mutant libraries to identify critical amino acid residues for signal sensing by FimS. Optimized error-prone polymerase chain reaction (PCR) was used to introduce a limited number of random mutations in the periplasmic-domain-coding sequence of fimS, and expression vectors carrying various mutants were generated by inverse PCR. More than 500 transformants were obtained from the fimS-knockout Pg strain using the Escherichia coli-Pg conjugal transfer system, whereas only ~100 transformants were obtained using electroporation. Four and six transformant strains showed increased and decreased fimA expression, respectively. Six strains had single amino acid substitutions in the periplasmic domain, indicating critical residues for signal sensing by FimS. This newly developed strategy should be generally applicable and contribute to molecular genetics studies of Pg, including the elucidation of structure-function relationships of proteins of interest.

Effective approach for improving a gummy smile : Upward movement of the maxillary occlusal plane using midpalatal miniscrews and a modified transpalatal arch.

PURPOSE: Correction of a gummy smile by orthodontic treatment alone has recently become feasible with the use of miniscrews. However, the optimal treatment mechanics remain unclear. Here we cephalometrically evaluated jaw and tooth displacement in cases where a gummy smile was improved using a level anchorage system (LAS). METHODS: Sixteen patients underwent orthodontic treatment using an LAS consisting of a modified transpalatal arch and midpalatal miniscrews. Cephalometric pretreatment and posttreatment measurements were compared using the paired t­test to determine significant skeletal and dental changes. The Mann-Whitney U test was used for nonparametric data. Spearman's rank correlation coefficient was used to evaluate correlations between different variables and the vertical change in prosthion position which was used to indicate the amount of gingival exposure. RESULTS: The changes noted after treatment were intrusion of the maxillary first molars (P < 0.001) combined with only minor extrusion of the mandibular first molars. Suppressed extrusion of the mandibular first molars was significantly correlated with greater upward movement of the prosthion (r = 0.676, P < 0.01). Upward movement of the prosthion was also significantly correlated with intrusion of the maxillary and mandibular incisors, anterior upward movement of the maxillary occlusal plane, and an increase of the SNP angle. CONCLUSIONS: Treatment involving the combined use of miniscrews and a modified transpalatal arch resulted in intrusion of the maxillary first molars and maxillary incisors and consequently elevated the maxillary occlusal plane. The results of this study suggest that intruding the maxillary occlusal plane and minimizing mandibular molar extrusion were effective to induce autorotation of the mandible and to improve a gummy smile.

A case of skeletal maxillary protrusion with high angle and gummy smile treated with anchor screws.

This report discusses a case of a 20 year and 7-month-old female patient with a skeletal maxillary protrusion with gummy smile, crowding, and high angle due to horizontal protrusion of the maxillary anterior teeth. The gummy smile in this case was improved by an upward movement of the occlusal plane associated with maxillary molar intrusion and sufficient lingual movement while performing maxillary anterior teeth intrusion. Following treatment, it was stable even after 8 years of retention. Thus, it is important to ascertain the cause of gummy smile, and establish whether it is due to the vertical maxillary excess in the maxillary anterior teeth, or the horizontal protrusion of the maxillary anterior teeth.

Optimal sites for orthodontic anchor screw placement using panoramic images: risk of maxillary sinus perforation and contact with adjacent tooth roots during screw placement.

OBJECTIVES: This study investigated the safety of orthodontic anchor screw (OAS) placement by examining the morphology and degree of depression of the maxillary sinus adjacent to the alveolar bone between the maxillary molars. METHODS: We reviewed panoramic and CT imaging data of 25 patients. First, the morphology of the maxillary sinus adjacent to the alveolar bone between the maxillary molars on panoramic images was classified into three types: non-depressed sinus, funnel-like sinus depression, and sawtooth-like sinus depression. Then, the distance from the maxillary buccal bone to the maxillary sinus or to the maxillary lingual bone and the distance between the roots of the maxillary second premolar and first molar at heights of 5, 6.5, and 8 mm from the alveolar crest were measured on CT images and compared between the three sinus morphology groups. RESULTS: The sawtooth-like depression group had significantly smaller bone thickness than the other two groups, with mean thickness of < 4 mm at any height from the alveolar crest. The funnel-like depression and non-depression groups had mean bone thickness of > 8 mm at any height from the alveolar crest. CONCLUSIONS: Sawtooth-like sinus depression had increased risk of maxillary sinus perforation, suggesting that OAS placement in this region should be avoided. In contrast, OAS placement between 6.5 and 8 mm from the alveolar crest is advisable in patients with funnel-like sinus depression and at a site > 8 mm from the alveolar crest in those with a non-depressed sinus.

Insertion torque and Periotest values are important factors predicting outcome after orthodontic miniscrew placement.

INTRODUCTION: Approximately 14% of orthodontic anchor screws (miniscrews) become dislodged regardless of the accuracy of placement. It is therefore important to investigate the factors causing dislodgement. We evaluated the stability of miniscrews after placement to identify factors influencing outcome in orthodontic treatment using miniscrews. METHODS: We investigated 120 miniscrews (Dual-top Auto Screw III; Jeil Medical, Seoul, Korea) (diameter, 1.4 mm; length, 6 mm) placed on the buccal or lingual side between the maxillary second premolar and the first molar in women. Patient age and rate and time of screw dislodgement were examined. Insertion torque values and Periotest (Tokyo Dental Industrial, Tokyo, Japan) measurements indicating horizontal and vertical mobility of the inserted screws were compared between groups with and without dislodgement (failure and success groups, respectively). RESULTS: Mean insertion torque values were 10.7 ± 1.9 N·cm and 8.5 ± 2.1 N·cm in the failure and success groups, respectively. Cortical bone thickness measurements (success group, 1.34 ± 0.35 mm; failure group, 0.99 ± 0.09 mm) were significantly higher, whereas Periotest values at placement (success group, horizontal, 4.9 ± 1.4; vertical, 4.7 ± 1.3; failure group, horizontal, 7.0 ± 0.8; vertical, 7.1 ± 0.9) were significantly lower in the success group than in the failure group. CONCLUSIONS: The Periotest value, together with insertion torque and cortical bone thickness, could serve as an index of initial stability for predicting the outcome of miniscrew placement.

Effectiveness of en-masse retraction using midpalatal miniscrews and a modified transpalatal arch: Treatment duration and dentoskeletal changes.

OBJECTIVE: The purpose of this study was to compare the treatment duration and dentoskeletal changes between two different anchorage systems used to treat maxillary dentoalveolar protrusion and to examine the effectiveness of en-masse retraction using two miniscrews placed in the midpalatal suture. METHODS: Fifty-seven patients (9 men, 48 women), who had undergone level anchorage system treatment at Aichi-Gakuin University Dental Hospital (Nagoya, Japan) were divided into two groups according to the method of maxillary posterior anchorage reinforcement: midpalatal miniscrews (25 patients, mean age 22 years) and conventional anchorage (32 patients, mean age 19 years). The en-masse retraction period, overall treatment duration, pre-treatment effective ANB angle, and change in the effective ANB angle were compared with an independent-samples t-test. RESULTS: Compared to the headgear group, the duration of en-masse retraction was longer by approximately 4 months in the miniscrew group (p < 0.001). However, we found no significant difference in the total treatment duration between the groups. Moreover, a greater change in the effective ANB angle was observed in patients treated with miniscrews than in those treated with the conventional method (p < 0.05). CONCLUSIONS: The level anchorage system treatment using miniscrews placed in the midpalatal area will allow orthodontists more time to control the anterior teeth during en-masse retraction, without increasing the total treatment duration. Furthermore, it achieves better dentoskeletal control than does the conventional anchorage method, thereby improving the quality of the treatment results.

Midpalatal miniscrews and high-pull headgear for anteroposterior and vertical anchorage control: cephalometric comparisons of treatment changes.

INTRODUCTION: Our aim was to evaluate which anchorage system is better suited for both anteroposterior and vertical anchorage control of maxillary posterior teeth. METHODS: Fifty-one subjects requiring maximum anchorage were divided into 2 groups according to maxillary posterior anchorage reinforcement: high-pull headgear, conventional transpalatal arch, and interarch elastics (n = 28); or modified transpalatal arch supported by 2 midpalatal miniscrews (n = 23). Bilateral maxillary first premolars were extracted in all patients. Pretreatment and posttreatment lateral cephalometric radiographs were superimposed to compare skeletal and dental changes between the groups. RESULTS: (1) The miniscrew group had less mesial movement of the maxillary first molars (0.85 vs 3.63 mm) and greater maxillary incisor retraction (6.87 vs 4.50 mm) than did the headgear group with the same treatment duration. (2) The maxillary molars were significantly intruded in the miniscrew group (1.30 mm), whereas they were extruded in the headgear group (0.71 mm). In the miniscrew group, intrusion of the maxillary molars resulted in a statistically significant decrease in the mandibular plane angle (0.80°). Patients using high-pull headgear showed no significant decrease in these measurements. CONCLUSIONS: In both the anteroposterior and vertical directions, a modified transpalatal arch supported by 2 midpalatal miniscrews provided more stable anchorage.

Accurate pre-surgical determination for self-drilling miniscrew implant placement using surgical guides and cone-beam computed tomography.

Miniscrew implants have proven to be effective in providing absolute orthodontic anchorage. However, as self-drilling miniscrew implants have become more popular, a problem has emerged, i.e. root contact, which can lead to perforation and other root injuries. To avoid possible root damage, a surgical guide was fabricated and cone-beam computed tomography (CBCT) was used to incorporate guide tubes drilled in accordance with the planned direction of the implants. Eighteen patients (5 males and 13 females; mean age 23.8 years; minimum 10.7, maximum 45.5) were included in the study. Forty-four self-drilling miniscrew implants (diameter 1.6, and length 8 mm) were placed in interradicular bone using a surgical guide procedure, the majority in the maxillary molar area. To determine the success rates, statistical analysis was undertaken using Fisher's exact probability test. CBCT images of post-surgical self-drilling miniscrew implant placement showed no root contact (0/44). However, based on CBCT evaluation, it was necessary to change the location or angle of 52.3 per cent (23/44) of the guide tubes prior to surgery in order to obtain optimal placement. If orthodontic force could be applied to the screw until completion of orthodontic treatment, screw anchorage was recorded as successful. The total success rate of all miniscrews was 90.9 per cent (40/44). Orthodontic self-drilling miniscrew implants must be inserted carefully, particularly in the case of blind placement, since even guide tubes made on casts frequently require repositioning to avoid the roots of the teeth. The use of surgical guides, fabricated using CBCT images, appears to be a promising technique for placement of orthodontic self-drilling miniscrew implants adjacent to the dental roots and maxillary sinuses.