Long-term survival of structurally compromised tooth preserved with crown lengthening procedure and restorative treatment: A pilot retrospective analysis

Comparison of the biomechanical effects of the post-core crown, endocrown and inlay crown after deep margin elevation and its clinical significance

BACKGROUND

The purpose of this in vitro study was to compare and evaluate the stress distribution of maxillary first premolar residual crowns restored with post-core crowns, endocrowns and inlay crowns after deep margin elevation, to explore the fitting restoration for residual crowns using finite element analysis.

METHODS

A healthy complete right maxillary first premolar from a male adult was scanned by cone beam computed tomography (CBCT). The finite element model of the tooth was established by reverse engineering software such as Mimics, Geomagic and Hypermesh. On this basis, the residual crown model after deep margin elevation was made, and the experimental group models were divided into three groups, those restored with post core crowns, endocrowns and inlay crowns. Vertical and oblique static loads were applied to the experimental models to simulate the force on the tooth during mastication (the loading position was located in the central fossa of the occipital surface, and the load was 100 N) using Abaqus software.

RESULTS

The peak value and distribution of von Mises stress in each part of the experimental model were observed. After deep margin elevation, the peak dentin von Mises stresses were lower than the tensile strength of normal dentin in the post-core crown, endocrown, and inlay crown groups; the lowest stress results were found in the post-core crown group for the dentin, restoration, enamel, and deep margin elevation (DME) layers under vertical and oblique loading. In terms of stress distribution clouds, the peak stresses in the dentin tissue were located in the apical 1/3 of the root after postcore crown restorations for both loads, while stress concentrations were evident in the cervical and root areas after endocrown and inlay crown restorations; regardless of the load and restoration method, the corresponding stress concentration areas appeared at the junction of the DME and dentin tissue at the loading site of the restorations; CONCLUSIONS: Post-core crowns, endocrowns and inlay crowns can be used to restore residual crowns after deep margin elevation, and post-core crowns can better protect the residual tooth tissue.

Survival analysis of teeth following clinical crown lengthening and crown insertion procedures up to 14 years: A retrospective cohort study

BACKGROUND

The purpose of this study was to conduct survival analysis of teeth following clinical crown lengthening procedures (CLPs) and crown insertions via a retrospective cohort study.

METHODS

Patient- and tooth-related data were collected from 268 participants who received CLPs from 2009 to 2015. The Kaplan-Meier curve and the log-rank tests were used to estimate the probability of survival and compare the survival probabilities among different variables. A Cox multivariate proportional hazard regression model was used to investigate the collective effects of root canal treatment (RCT) and the types of opposing dentition.

RESULTS

The rate of tooth loss was 21.6% during the observation period from 1 to 14 years, with 58 teeth extracted. The most attributable reason for tooth extraction was coronal tooth fracture, followed by endodontic failure such as root fracture. The survival probability was 0.87 at 5 years and 0.7 at 10 years. No significant differences in the survival probabilities were found among different providers and locations, the presence of a post, and the types of crowns. The hazard ratio for tooth loss was 6.3, 95% confidence interval (CI) [2.6 to 20.9] in the teeth with RCT (p < 0.001) and 2.4, 95% CI [1.1 to 4.8] in the teeth occluding implant-retained prostheses (p = 0.016).

CONCLUSIONS

Tooth loss following CLPs and crown insertions appeared least among the teeth without RCT when occluding natural teeth, while tooth loss was most among the teeth with RCT when occluding implants.

Digital resources for surgical and restorative treatment of excessive gingival display in one session

OBJECTIVE

This article aims to showcase the implementation of a digital workflow in addressing a case of multifactorial excessive gingival display in a patient with high esthetic demands, incorporating both surgical and restorative interventions in a single session.

CLINICAL CONSIDERATIONS

A 28-year-old female patient presented with excessive gingival display, attributed to a combination of short teeth due to altered passive eruption, lip hyperactivity, and a sub-nasal depression that lodged the upper lip during spontaneous smiling. The multidisciplinary treatment strategy encompassed surgical crown lengthening, the placement of a biovolume in the maxillary concavity, and the rehabilitation of the six anterior teeth with direct composite resin, all done in a single session. Smilecloud Biometrics was used to digitally plan the smile, and the final wax-up/mock-up was approved by the patient prior to any irreversible procedure. A digital planning center (GuiderLab) enabled the materialization of the virtual planning and the printing of the periodontal surgical guide, the biovolume, and the resin layering guides for the restorative technique.

CONCLUSIONS

Adopting a digital workflow in multidisciplinary cases with excessive gingival display leads to predictable and more expedited outcomes, ensuring a favorable result between soft and hard tissues.

CLINICAL SIGNIFICANCE

Excessive gingival display is a condition with multifactorial etiologies, including dentoalveolar, periodontal, skeletal, or muscular origins, or a combination of these factors. The diagnoses of altered passive eruption and a hypermobile upper lip are common in daily clinical practice and can be successfully managed through surgical crown lengthening and filling of the maxillary concavity, respectively. To achieve the desired outcome, restorative procedures often complement these surgical interventions.

Success rate of fractured teeth receiving modified crown lengthening surgery and restorations

BACKGROUND

Whether to preserve a structurally compromised tooth or remove it is a dilemma often encountered by clinicians. The aim of this study was to assess the long-term success rate of fractured teeth preserved by modified crown lengthening surgery and restorations.

METHODS

Thirty-nine patients with a total of 45 fractured teeth who had received modified crown lengthening surgery were recruited and examined. Numbers of teeth lost were recorded, and the criteria for successful teeth were defined. Kaplan-Meier estimator was used to determine the success rate. Possible risk factors were compared between successful and unsuccessful groups by a Cox regression analysis to explore the potential predictors of failure with a significant level at α = 0.05.

RESULTS

The mean ± SD of success time without considering variants was 6.2 ± 0.6 years (95% CI 5.1-7.7). The mean survival rates ± SD at 1.0-, 2.0-, 3.0-, 5.0-, 7.0-, and 9.0-year intervals was 97.8 ± 2.2%, 92.2 ± 4.4%, 72.8 ± 7.9%, 68.2 ± 8.6%, 60.7 ± 10.5%, and 40.4 ± 13.6%, respectively. Failure cases in teeth with poor plaque control and step-shaped fracture margin were significantly more than those with good plaque control and knife-shaped fracture margin (HR = 7.237, p = 0.011; HR = 15.399, p = 0.006; respectively).

CONCLUSIONS

Fractured teeth treated with modified crown lengthening surgery are anticipated to have a high clinical success rate for 6.2 ± 0.6 years. Plaque control and fracture morphology appeared to be significantly associated with the success of the multidisciplinary treatment approach.