Pre-restorative crown lengthening surgery: influence of restorative treatment timing on clinical outcomes-a pilot study.

OBJECTIVES: Aim of this study was to assess the influence of restorative treatment timing on the periodontal, patient and operator-reported outcomes following crown lengthening surgery (CLS). MATERIALS AND METHODS: Eighteen study participants requiring CLS were divided into two groups based on prosthetic rehabilitation timing (6 or 14 weeks postoperatively). Clinical parameters were recorded around treated and neighboring teeth before and after surgery, 6 and 14 weeks postoperatively, at prosthesis delivery, and three and six months after. Soft tissue and radiographic bone changes were evaluated. Patients assessed their perception of the procedure by means of a questionnaire. The final treatment outcome was rated by both patients and prosthodontists. RESULTS: CLS resulted in statistically significant and stable apical displacement of the gingival margin, at both treated and adjacent sites. Plaque and bleeding scores remained low throughout. No statistically significant differences were observed between groups for any clinical or radiographic parameter examined. Healing was uneventful and treatment outcome was satisfying for both patients and prosthodontists, without statistically significant differences between groups. CONCLUSIONS: The present study has been characterized as pilot, because it was not possible to reach the sample size indicated by the a priori power analysis. CLS is an effective pre-prosthetic procedure as long as it is performed under a certain surgical protocol which predicts for at least a 3 mm distance between bone crest and the flap margin at suturing. Within the limitations of this study, six weeks after surgery may be an adequate healing time for the onset of prosthetic restoration. CLINICAL RELEVANCE: Crown lengthening surgery is commonly performed in daily clinical practice with the aim to restore teeth with short clinical crowns. Based on periodontal, patient and operator-reported criteria, 6 weeks after CLS may be adequate healing time before the onset of prosthetic restoration. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT03947658, 13/05/2019, retrospectively registered.

Micro-Computed Tomographic Evaluation of Canal Transportation and Centering Ability of 4 Heat-Treated Nickel-Titanium Systems.

INTRODUCTION: This study aimed to evaluate and compare canal transportation and centering ability of 4 different root canal preparation systems produced with thermal treatments by means of micro-computed tomographic imaging. METHODS: Eighty mesial canals of human extracted mandibular molars were selected based on similar morphologic parameters and were randomly assigned to 4 experimental groups (n = 20) according to the canal instrumentation technique: HyFlex CM (HCM [Coltène-Whaledent, Allstätten, Switzerland]), HyFlex EDM (HEDM [Coltène-Whaledent]), WaveOne Gold (WOG [Dentsply Sirona, Ballaigues, Switzerland]), and OneCurve (OC [Micro-Mega, Besancon, France]). The specimens were scanned before and after root canal preparation using X-ray micro-computed tomographic imaging at a resolution of 19.9 µm. Apical transportation and centering ability were then analyzed at 3 different levels: 3 mm, 5 mm, and 7 mm from the apex, representing the apical, midroot, and coronal thirds of the root, respectively. One-way analysis of variance and Kruskal-Wallis tests were used to statistically compare the groups. The significance level was set at 5%. RESULTS: HCM caused less canal transportation than WOG at the 3-mm level in both the buccal and lingual canals (P < .05). Also, HCM resulted in less canal transportation than WOG and OC at the 7-mm level regarding lingual canals. No statistically significant differences were recorded between the groups when the mean centering ratios were compared. CONCLUSIONS: The 4 evaluated systems safely prepared root canals causing minimal canal transportation and producing relatively centered preparations. In terms of canal transportation, HCM performed better than WOG at the apical level and better than WOG and OC at the coronal level.

Crestal bone resorption after the application of two periodontal surgical techniques: a randomized, controlled clinical trial.

AIM: To radiographically assess, by means of digital subtraction radiography, crestal bone loss following two periodontal surgical techniques, over a period of 6 months. MATERIAL AND METHODS: A total of 30 chronic periodontitis patients participated in this randomized controlled clinical trial and were separated into two groups. Modified Widman flap was applied in the control group and apically positioned flap, without intervention to the bone, in the experimental group. Clinical measurements (plaque index, gingival bleeding index, probing pocket depth and clinical attachment level) were recorded at baseline, 6 weeks, 3 and 6 months after surgery. Digital radiographs were taken at baseline, 1, 3, 6 weeks, 3 and 6 months after surgical treatment and subtracted digitally in pairs. RESULTS: Both groups showed statistically significant improvement of clinical parameters. Statistically significant differences between the two groups were observed only in probing pocket depth (PPD) at 6 weeks interval, where the test group showed more reduction (smallest statistically significant differences observed, SSSDO = 0.64). Both groups showed the same rate of crestal bone resorption. CONCLUSIONS: Bone resorption of the alveolar crest is a phenomenon that is observed as a consequence of periodontal surgical treatment without significant differences between the two techniques. Furthermore, both surgical techniques lead to satisfactory clinical results, indicating that bone removal during periodontal surgical treatment is not always necessary.

A new methodology for the comparative study of the root canal instrumentation techniques based on digital radiographic image processing and analysis.

OBJECTIVE: The objective of this study was to evaluate the utility of digital image processing and analysis procedures for the study and comparison of the efficiency of 2 root canal instrumentation techniques. STUDY DESIGN: Forty mandibular incisors with a single canal were randomly divided into 2 groups of 20 teeth. A step-back technique was followed for the instrumentation of the root canals of Group 1 teeth using hand stainless steel Hedström files (Dentsply Maillefer, Switzerland), while a crown-down technique using ProFile engine-driven nickel-titanium instruments (Dentsply Maillefer) was followed for the instrumentation of the Group 2 root canals. Radiographs of each tooth were taken in bucco-lingual and mesio-distal projections, both before and after instrumentation, under constant conditions and by using a direct digital intraoral radiography system. The postoperative radiographs were digitally subtracted from their respective preoperative radiographs. A contrast enhancement process was applied to the resultant digital subtractive images. The enlargement of the root canals created by each instrumentation technique regarding the apical 6 mm was assessed through the application of region segmentation and area measurement processes. RESULTS: Using this methodology no significant difference between the 2 preparation techniques was found in terms of configuration and enlargement of the root canals. CONCLUSIONS: The application of this methodology provided the ability to (1) visualize dentin lost during root canal instrumentation, (2) simultaneously compare root canal morphology before and after instrumentation, and (3) quantitatively evaluate the enlargement of the root canal area induced by each of the instrumentation techniques.