Potential for load-induced cervical stress concentration as a function of periodontal support

Saving teeth: Revisited. Esthetic improvement and long-term periodontal stability of a pathologic tooth migration case: An 84-month follow-up

INTRODUCTION

Advances in implant dentistry, often influence our clinical treatment planning and steer us as periodontists from our fundamental values of preserving teeth. Pathologic tooth migration (PTM) of maxillary anterior teeth is a common sequela of periodontitis in patients and results in significant esthetic and functional problems. Patients' growing concern about the esthetics of their teeth and their fears of losing teeth are often reasons for them to seek treatment. We commonly assign a hopeless prognosis to these pathologically migrated teeth because of the significant loss of periodontal support and go with the "safer" choice of replacing them with implants. The purpose of this case report is to present the long-term (7-year) periodontal stability of compromised teeth and to emphasize the successful outcomes achieved when orthodontics, non-surgical periodontal, and restorative treatments are combined.

METHODS AND RESULTS

A 38-year-old, otherwise healthy male with compromised function and esthetics, PTM, periodontal disease, and missing teeth presented to our clinic. Primary treatment objectives were to 1) eliminate the periodontal inflammation and 2) restore and stabilize the occlusion by employing non-surgical periodontal treatment, adult orthodontics, and prosthodontics. Following interdisciplinary treatment, clinical and radiographic re-evaluation revealed significant clinical attachment gain, reduction in tooth mobility, favorable esthetics, and better overall prognosis. At an 84-month follow-up, the patient was periodontally healthy and retained his natural dentition.

CONCLUSIONS

Interdisciplinary collaboration along with patient compliance may increase the longevity of periodontally compromised teeth and improve esthetics for periodontitis patients who suffer from PTM. Such long-term favorable outcomes reaffirm the value of classic periodontal treatment and the success of multidisciplinary treatment to save teeth as a viable alternative to the extraction of teeth and the placement of implant retained restorations.

Influence of cavity depth and restoration of non-carious cervical root lesions on strain distribution from various loading sites

Background

We aimed to investigate the load-induced strain variation in teeth with unrestored and resin-based composite restored non-carious cervical lesions (NCCLs).

Methods

Twelve extracted premolars were provided for measuring buccal-side root NCCLs. Strain gauges were fixed at four measuring sites of each tooth, two at the buccal surface and two at the lingual surface. NCCLs were prepared with occlusal margins at the cemento-enamel junction. A static 9-kg load was applied at seven occlusal loading points: buccal cusp tip (BC), inner inclination of the BC, lingual cusp tip (LC), inner inclination of the LC, center of the mesial marginal ridge or distal marginal ridge, and center of the central groove. The strain was detected at each site in teeth with NCCL depths of 0 (control), 0.5, 1.0, and 1.5 mm. Each NCCL was restored using an adhesive composite resin, and the strains were re-measured.

Results

The strains at the NCCL occlusal and gingival margins decreased with increasing defect depths, and the effect was significant when the depth of the defect was 1.5 mm. Loading on the buccal and lingual cusps induced prominent strain variation. The strains at all depth distribution recovered to nearly intact conditions when the NCCLs were restored.

Conclusions

NCCLs at 1.5 mm depth are detrimental, but they can be restored using resin composites.

Clinical significance

The existence of NCCLs should not be ignored. The depth of the NCCL may affect the progression of the lesion. Resin composite restoration is an appropriate method for preventing persistent NCCL deterioration.

A finite element study to determine the occurrence of abfraction and displacement due to various occlusal forces and with different alveolar bone height

Background:

Noncarious cervical lesions (NCCLs) are rarely described in the periodontal literature, perhaps because no direct link between NCCLs and periodontal lesions has been demonstrated.

Aim:

The aim of this study is to determine the stress and displacement produced in the tooth at different bone levels under different occlusal load using finite element model (FEM) study.

Materials and Methods:

Four FEMs of maxillary incisor were designed consisting of the tooth, pulp, periodontal ligament, and alveolar bone at the various level of bone height (25%, 50%, and 75%). Different occlusal load (5 kg, 15 kg, 24 kg, and 29 kg) at an angle of 50° to the long axis of the tooth was applied on the palatal surface at the level of middle third of the crown. All the models were assumed to be isotropic, linear and elastic, and the analysis was performed on a Pentium IV processor computer using the ANSYS software.

Results:

The maximum stress in the tooth was seen in the cervical region and to a greater extent at the apex for all models. The maximum tooth displacement for all the occlusal loads applied in this study was at the incisal edge with the minimum tooth displacement at the cervical third of the root which shifted apically with the reduction of alveolar bone support.

Conclusion:

The cumulative effect of increased stress and displacement at the cervical region of the tooth would result in abfraction as the age advances along with other wasting diseases.

Influence of periodontal ligament simulation and splints on strains developing at the cervical area of a tooth crown

Many in vitro tooth models do not incorporate periodontal ligament (PDL) simulation. This study presents the influence of physiologically loaded occlusal splints on cervical strains in a model incorporating roots and PDL. Four sets (N = 10) of occlusal splints differing in material (hard/soft) and location (upper/lower) were prepared for first maxillary and mandibular anatomic molars. Two strain gauges were bonded to the buccal and lingual aspects of the lower molar. Teeth were embedded in acrylic resin with/without a PDL-simulating material. Force vs. strain data were acquired during loading and the maximal strains at 500 N were analyzed. When PDL was incorporated into the model without splints, buccal compressive strains were significantly decreased. Usage of a soft splint resulted in compressive strains on both tooth aspects. Usage of a hard splint on the lower tooth resulted in higher compressive strains on the lingual side compared with the buccal side, whereas usage of this splint on the upper tooth resulted in tensile strains on the lingual side. Bending towards the buccal side occurred when the splints were located on the upper tooth. Soft splints reduce buccal bending, but do not reduce cervical strains. Periodontal ligament stimulation materials should therefore be incorporated in models involving teeth.

Cementum Crack Formation by Repeated Loading In Vitro

BACKGROUND

In this study, the hypothesis was adopted that fatigue destruction may develop on the cementum of the root surface because of the repeated occlusal stresses loaded on the tooth as in the case of prolonged occlusal trauma. The purpose of this study is to clarify whether cemental fatigue destruction occurs when repeated stresses are loaded on the occlusal surface of a tooth.

METHODS

The teeth used were five human mandible premolars from individuals 14 to 22 years of age. The teeth were freshly extracted in orthodontic treatment. They were free of decay and fillings, and their roots were straight. One half of the root was embedded in cold curing acrylic resin, and a compressive load of 5.0 kgf was repeatedly applied along the tooth axis in water 1 million times with a speed of one time per second. Changes in the tooth surface were observed by taking photographs with a stereoscopic microscope and a digital camera after every 100,000 loadings. Cracks were dyed with 2% methylene blue solution, and crack areas were measured using gray-scaled and binary-processed photographs. Data were analyzed using image analysis software.

RESULTS

It was confirmed that cracks significantly developed on the buccal, mesial, and distal surfaces but not on the lingual surface; crack areas showed a tendency to significantly increase after 500,000 loadings; extension of the crack from the cemento-enamel junction to the root apex increased with time, and the average extension was 0.67 +/- 0.12 mm after 1 million loadings.

CONCLUSION

This study revealed that cementum cracks developed in the cervix by repeated loadings and extended toward the root apex with time, suggesting that repeated stresses by occlusion or strong stresses such as by bruxism may trigger the development of site-specific attachment loss, which is one of the potential factors inducing periodontal diseases.

Symmetry of non-carious cervical lesions in canines and premolars

OBJECTIVES

Clinically non-carious cervical lesions (NCCLs) are frequently seen. The aim of this study was to investigate the relationship between the shape and symmetry of NCCLs, wear of cuSPS and triangular ridge, and the curvature of the tooth root.

METHODS

One hundred and twenty-nine extracted human upper canine teeth and 274 extracted human upper premolar teeth with NCCLs were used in this study. The specimens were studied using photographs and three-dimensional scanning.

RESULTS

Asymmetric NCCL was observed in 69.0% of the canines and 44.5% of the premolars. Wear of cusp and lingual ridges was observed in 82.9% and 93.0% of the canines, respectively. Wear of the buccal cusp and buccal triangular ridge was observed in 85.4% and 89.8% of the premolars, respectively. On the other hand, the wear of lingual cusp and lingual triangular ridge was observed in 89.1% and 93.8% of the premolars, respectively. The curvature of the root was observed in 48.1% of the canines and 43.4% of the premolars.

CONCLUSIONS

There was no relationship between the symmetry of NCCLs, and the wear of cuSPS and triangular ridges for either canines or premolars. Although there was a relationship (p < 0.05) between the symmetry of NCCL and the curvature of the root in the canines, no relationship was observed between the symmetry of NCCL and the curvature of the root in the premolars.

Noncarious cervical lesions in adults: prevalence and occlusal aspects

BACKGROUND

The factors that induce the formation of noncarious lesions are not understood fully, particularly those that are related to occlusal aspects. The authors conducted a study to evaluate the prevalence of noncarious cervical lesions in adults and their association with occlusal aspects.

METHODS

The authors examined 70 people (35 men and 35 women) aged 25 to 45 years to determine the presence and type of noncarious cervical lesions, wear facets, tooth contacts in maximal intercuspal position, and lateral and protrusive movements. The assessment involved a questionnaire and clinical examination.

RESULTS

Among the teeth the authors evaluated, 17.23 percent had cervical lesions, 80.28 percent of which had wear facets (P < .01). The authors found a significant difference between the prevalence of noncarious lesions and the presence of wear facets (P = .0484).

CONCLUSIONS

The authors found that cervical lesions were related significantly to wear facets. These findings strengthen evidence for the role of occlusal forces as an etiologic factor for noncarious lesions.

CLINICAL IMPLICATIONS

The presence of wear facets should be considered in the treatment of noncarious cervical lesions.

The two-year clinical performance of esthetic restorative materials in noncarious cervical lesions

BACKGROUND

Materials used in restoration of cervical lesions include resin-modified glass ionomer cements, polyacid-modified resin-based composites and resin-based composites. In this study, the authors evaluated the clinical performance of these materials over a two-year period.

METHODS

Thirty patients were enrolled in this study. The authors placed in these patients 130 restorations, 24 of which were Vitremer (3M Dental Products, St. Paul, Minn.), 38 were F2000 Compomer (3M Dental Products), 46 were Dyract AP (Dentsply DeTrey, Konstanz, Germany) and 22 were Valux Plus (3M Dental Products). Enamel margins were not beveled, and no mechanical retention was placed. Two independent, calibrated examiners evaluated the restorations baseline and at one and two years after placement using modified U.S. Public Health Service criteria.

RESULTS

Retention rates at the end of two years were 100 percent for Vitremer, 67 percent for F2000 Compomer, 68 percent for Dyract AP and 70 percent for Valux Plus. The retention rate of Vitremer was significantly higher than that of the others (P < .05). In other categories, however, Valux Plus had the most favorable performance (P < .05). No secondary caries was detected around any restoration.

CONCLUSION

Vitremer, with its high retention rate, seems to be the most appropriate material for restoration of noncarious cervical lesions, though it does not have the esthetic properties of resin-based composites. All materials used in this study were in need of improvements.

CLINICAL IMPLICATIONS

Resin-modified glass ionomer cement, polyacid-modified resin-based composite and resin-based composite behaved differently in the restoration of noncarious cervical lesions. Therefore, clinicians should take factors such as esthetic needs and localization into account in selecting materials for such restorations.

Attrition, abrasion, corrosion and abfraction revisited

OVERVIEW

The authors propose updated and revised nomenclature, definitions and classification for tooth surface lesions. Their objective is standardization, clarity and clinical utility for the dental practitioner. The article presents a schema of the pathodynamic mechanisms in the formation of tooth surface lesions--three basic physical and chemical mechanisms, their interactions and their dental manifestations.

CONCLUSIONS AND CLINICAL IMPLICATIONS

The use of precise definitions will assist the practitioner in determining the etiology of various tooth surface lesions. Understanding the pathodynamic mechanisms and their many possible interactions, as set forth in the schema, will enable the practitioner to make an accurate differential diagnosis and to provide effective prevention and treatment. It also will assist dentists in communicating more effectively with their colleagues as well as with their patients. In addition, the schema helps identify areas in which future research is indicated.

Analysis of etiologic factors and periodontal conditions involved with 309 abfractions

OBJECTIVES

Non-carious cervical lesions (NCCL), also termed abfractions, have long been thought to be produced by excessive brushing. Nearly 20 years ago an occlusal etiology was proffered (Lee & Eagle 1984). Controversy still exists concerning these two concepts. The present work was carried out to verify the occurrence of signs of excessive brushing or occlusal disturbances associated with abfractions.

MATERIAL AND METHODS

All first consultants were screened for the presence of abfractions during one trimester. NCCL were found in 61 patients who consequently received a thorough examination searching for clinical evidence of excessive brushing or occlusal disturbances. The presence of plaque, calculus, periodontitis, or mobility was also noted. Simple frequency and percentage were used to describe the occurrence of different clinical signs in association with the presence of abfractions.

RESULTS

Abfractions often exist in mouths presenting plaque (40.1%), calculus (41.7%), or periodontitis (20.4%). Ulceration of the gingiva is a rare finding (1.6%). However, subgingival apical limits were frequent (32.5%). NCCL coexist almost systematically with occlusal wear facets (94.5%). Lack of canine disclusion (77.2%) was also closely associated with the presence of abfractions. Conversely, mobility was seldom found (1.9%).

CONCLUSIONS

Clinical signs of excessive brushing were lacking, whereas signs of occlusal disturbance were very consistent with the presence of abfractions.

Noncarious cervical lesions and abfractions: a re-evaluation

BACKGROUND

The concept of abfraction is controversial. The authors present the fundamental basis of abfraction and review studies that describe the condition.

TYPES OF STUDIES REVIEWED

The authors used data on masticatory forces, enamel and dentin properties, as well as stress studies related to abfraction, for background information. They also analyzed the genesis of the abfraction theory, experimental evidence, case presentations, clinical investigations and restorative studies.

RESULTS

The theory of abfraction is based primarily on engineering analyses that demonstrate theoretical stress concentration at the cervical areas of teeth. While some recent stress studies support earlier findings, others have provided significant deviating information. Few controlled studies exist that demonstrate the relationship between occlusal loading and abfraction lesions. The role of occlusal loading in noncarious cervical lesions (as shown by clinical data) appears to be part of a multifactorial event that may not necessarily follow the proposed classic abfraction mechanism, and other mechanisms or factors may explain cervical restoration failure just as well.

CLINICAL IMPLICATIONS

There is little direct evidence supporting the theory of abfraction as the primary factor in the formation of noncarious cervical lesions. Controlled clinical trials are necessary to elucidate more fully the etiology of those lesions.