Radiographic Evaluation of Permanent Second Molar Substitution After Extraction of Permanent First Molar: Identifying Predictors for Spontaneous Space Closure

PURPOSE

The purpose of this study was to investigate pre-extraction variables associated with spontaneous space closure of the perma- nent second molar (PSM) following early extraction of the permanent first molar (PFM), and test an existing prediction model for the mandibular arch as the rates of spontaneous space closure are significantly lower in the mandible compared to the maxilla.

METHODS

Pre-extraction panoramic radiographs of 162 patients (138 maxillary and 168 mandibular quadrants) between five and 15 years old at the time of PFM extraction were evaluated. The prediction model was applied to the mandibular quadrants. Postextraction radiographic evaluation was used for outcome assessment, with success defined as the presence of a visible contact between the second premolar and PSM without marginal ridge discrepancy.

RESULTS

Success was observed in 82 percent of maxillary quadrants and 51 percent of mandibular quadrants. Maxillary PFM extraction between eight and 10 years or PSM Demirjian stage D or E demonstrated over 90 percent predictive probability for success. Mandibular PFM extraction at age eight years or PSM Demirjian stage D demonstrated 80 percent success. The prediction model did not add a more predictive value than chronological age or PSM Demirjian stage.

CONCLUSIONS

The prediction model was not validated in this study population. Chronological age and permanent second molar developmental stage were the primary predictors for successful substitution with the permanent second molar.

Retrieval of Prefabricated Zirconia Crowns with Er,Cr:YSGG Laser from Primary and Permanent Molars

(1) Background: Prefabricated zirconia crowns are used to restore teeth in children. The purpose of this study was to evaluate the removal of these crowns with the erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser; (2) Methods: A total of 12 primary and 12 permanent teeth were prepared and prefabricated zirconia crowns were passively fitted and cemented with two resin modified glass-ionomer (RMGI) cements. Surface areas of prepared teeth and crowns were calculated. Crowns were removed using two laser settings: 4.5 Watts, 15 Hertz, 20 water/20 air, and 5 Watts, 15 Hertz, 50 water/50 air. The retrieval time and temperature changes were tested recorded. Data were analyzed using ANOVA with Tukey’s adjusted post hoc pairwise comparison t-test; (3) Results: The average time for crown removal was: 3 min, 47.7 s for permanent; and 2 min 5 s for primary teeth. The mean temperature changes were 2.48 °C (SD = 1.43) for permanent; and 3.14 °C (SD = 1.88) for primary teeth. The time to debond was significantly positively correlated with tooth inner surface area and volume, outer crown volume, and the cement volume; (4) Conclusions: Use of the Er,Cr:YSGG laser is an effective, safe and non-invasive method to remove prefabricated zirconia crowns cemented with RMGI cements from permanent and primary teeth.

Utilization of and Dental Students' Perceived Benefits of an Urgent Care Clinic in a Dental School

The aims of this study were to describe patient utilization of an urgent care clinic (UCC) in a dental school for one year and to assess dental students' perceptions of the benefits of training in this clinic. Aggregate clinic data from July 3, 2017, through July 6, 2018, were used to determine number of patients, number of new patients, number of new patients who elected to transfer their primary dental care to the university, number who were seen for a follow-up, and service/clinic to which each patient was referred. Student evaluations were used to determine the benefits students perceived in their training in the UCC. Results showed that 1,674 patients were seen in the UCC during the study period. Of these, 67% were new patients, and 53% of these new patients opted to transfer their primary dental care to the university. An average of 7.03 patients were treated per day, and 2.48 new patients per day were generated for the predoctoral student clinic. The most common referrals were to oral surgery (37%), endodontics (30%), and the predoctoral dental clinic (28%). Among these patients, 39% scheduled follow-up appointments, and the attendance rate was 69%. About 80% of eligible students (40/50) completed the questionnaire, and many provided optional comments. Over 80% of the responding students responded favorably regarding the learning experiences and assessments during the UCC rotation. This study found that establishment of the UCC increased the pool of patients and provided students the necessary experiences in triaging and treating dental emergencies.