Tooth preparation for ceramic veneers: when less is more

Historically, preparations for ceramic veneers have varied from extremely aggressive to a minimal reduction or a lack of preparation. Today, we are moving toward minimally invasive dentistry with the philosophy that less is more. Less tooth reduction means more adhesion and clinical longevity. What must be considered when performing minimally invasive preparations is that in a significant number of cases the dental element will receive a veneer that will modify its final contour. This is quite common in cases of conoid teeth, diastemas or loss of dental structure by abrasion, erosion or attrition. The aim of this article is to present a step-by-step protocol to achieve conservative preparations for ceramic veneers, called the mock-up driven technique. This technique takes into account the final contour desired for the veneer, and results in considerably less invasive dental preparations.

The relationship between occlusal support and maxillary development: An animal study

Objective:

To test the hypothesis that maxillary development may be affected by occlusal support.

Materials and Methods:

The sample was composed by Wistar rats (5 weeks old) divided into three groups: Control (n = 10), extraction of mandibular molar teeth – left side (n = 10), extraction mandibular molar teeth – left and right sides (n = 10). The rats were sacrificed 8 weeks postextraction. Cone beam computed tomography scan images were taken for posterior measurement of maxillary length and width. Data were analyzed by one-way analysis of variance (Tukey test as post-hoc test).

Results:

Maxillary length was significantly shorter (P < 0.005) in both groups after tooth extraction. No difference was observed regarding maxillary width and body weight.

Conclusion:

Reduced occlusal support may impair the development of the maxilla in rats.

Changes in patient satisfaction and masticatory efficiency during adaptation to new dentures

Because adapting to new conventional dentures is highly variable, there is uncertainty as to how long dissatisfied patients should wait before choosing a treatment with dental implants. The authors investigated whether changes in patient satisfaction and masticatory efficiency may be observed between 3 and 6 months after the insertion of new conventional complete dentures. The study included 24 edentulous patients requiring new complete dentures. Masticatory efficiency and patient satisfaction were evaluated at 3 and 6 months post-insertion. Masticatory efficiency was evaluated through the colorimetric method, with the beads as the artificial test food. A method for quantifying overall satisfaction of complete-denture wearers was used. Subjects were asked to respond to questions with three-grade answers concerning 12 factors: chewing, tasting, speech, esthetics, pain, fit, retention, and comfort (maxillary and mandibular evaluations were done for each of the last four factors). The results of patient satisfaction and masticatory efficiency at 3 and 6 months post-insertion were compared using the paired-samples t test (α = 0.05). Significant reductions in mandibular pain (P less than 0.05) and improvements in mandibular fit (P less than 0.05) were observed at 6 months. No difference was found for patient overall satisfaction, chewing, tasting, speech, maxillary pain, esthetics, maxillary fit, retention, comfort, and masticatory efficiency. The authors concluded that reduction in pain and improvements in adaptation of the lower denture may be observed between 3 and 6 months after insertion of new conventional complete dentures. This period of adaptation should be considered before choosing a treatment with dental implants.

The influence of mandibular ridge anatomy on treatment outcome with conventional complete dentures

Since prognostic indicators are likely to take on increasing importance as a diagnostic tool for selection of patients for implant provision, this study investigated the influence of the shape and resiliency of the mandibular alveolar ridge on the retention and stability of conventional complete dentures. Ninety- three edentulous patients wearing both maxillary and mandibular conventional complete dentures composed the sample. Data were collected regarding shape and resiliencyof the mandibular residual ridge. Dentures were assessed for retention and stability using an objective and reproducible tool.The associations between the clinical characteristics of the mandibular alveolar ridge and denture retention and stability were analyzed using chi-square and Fisher exact tests (a = 0.05). A significant association between ridge shape and denture stability (p < 0.05) was found, while ridge resiliency was significantly associated to denture retention (p < 0.001). Based on the results, mandibular ridge shape and resiliency influenced the retention and stability of conventional complete dentures.

Bilateral balanced articulation: science or dogma?

For more than a hundred years, it has been supposed that canine guidance should be avoided in conventional complete dentures, since it would result in denture instability. Thus, bilateral balanced articulation has been held by many authors as fundamental for treatment success. However, randomized clinical trials have shown that balanced articulation is not as important as previously thought. The issue about which occlusal concept is the most appropriate for individual needs is clinically and economically relevant for both the dentist and dental technician. Therefore, the purpose of this study is to provide an evidence-based update on complete denture occlusion. Clinical Relevance: The issue about which occlusal concept is the most appropriate for individual needs is clinically and economically relevant.

Preheating impact on the degree of conversion and water sorption/solubility of selected single-bottle adhesive systems

OBJECTIVE

This study evaluated the degree of conversion (DC) and the water sorption/solubility of preheated single-bottle adhesive systems.

METHODS AND MATERIALS

Five adhesive systems were tested: Adper Easy One and Adper Single Bond 2 (3M ESPE), Excite and Tetric N-Bond (Ivoclar/Vivadent), and XP Bond (Dentsply/Caulk). After storage for two hours at 25°C or 60°C, 50 samples (n=5) were prepared for all adhesive systems and stored dry in lightproof containers at 37°C for 24 hours. Fourier transform infrared/attenuated total reflectance spectroscopy was used to evaluate the DC, and water sorption/solubility was measured by means of mass loss and gain after water storage. The data were analyzed by two-way analysis of variance followed by Tukey's test (p<0.05).

RESULTS

Preheated adhesive systems showed statistically significantly higher DC than those kept at 25°C. Except for XP Bond, preheated adhesive systems presented statistically significantly lower water sorption/solubility means.

CONCLUSIONS

Preheating improved the DC for all tested adhesive systems. Also, it promoted a decrease of water sorption/solubility, except for the XP Bond adhesive system.

Face-bow transfer in prosthodontics: a systematic review of the literature

An extensive search for randomised controlled clinical trials was accomplished to compare dental prostheses and occlusal splints constructed with or without face-bow transfer, and question whether face-bow transfer may present better clinical results than simpler approaches. Studies were identified by searching electronic databases (PubMed/MEDLINE, Latin American and Caribbean Literature on the Health Science, and Brazilian Bibliography of Dentistry). The keywords 'dental articulator', 'semi-adjustable articulator', 'face-bow', 'jaw relation record' and 'occlusal splint therapy' were used. The minimum inclusion requirements were (i) randomised controlled trials with patients of any age, (ii) comparison between dental prostheses or occlusal splints constructed with or without face-bow transfer and (iii) assessment of clinician's time, number of occlusal contacts, patient satisfaction or masticatory function. The search resulted in the identification of 8779 articles. Subsequently, 8763 articles were excluded on the basis of title and abstract. By the end of the search phase, eight randomised controlled trials were considered eligible. Current scientific evidence suggests that face-bow transfer is not imperative to achieve better clinical results in prosthodontics. Randomised clinical trials suggest that simpler approaches for the construction of complete dentures and occlusal splints may present acceptable results, while no clinical study has investigated its use in fixed and removable partial dentures.

Association between prosthetic factors and temporomandibular disorders in complete denture wearers

OBJECTIVE

The purpose of this study was to investigate the prevalence of temporomandibular disorders (TMD) in denture wearers and the association between prosthetic factors and this condition.

BACKGROUND

There is no consensus about the relationship between prosthetic factors and TMD among denture wearers.

MATERIALS AND METHODS

The sample was composed of 92 patients wearing both maxillary and mandibular complete dentures. The Research Diagnostic Criteria for TMD (RDC/TMD) were adopted for patient examination. Objective evaluation of denture quality was determined by analysis of retention and stability of mandibular denture, interocclusal distance, articulation and occlusion. Association between denture quality and TMD diagnosis was analysed using chi-square and Fisher's exact tests.

RESULTS

37.4% of the patients presented TMD. Denture quality was not significantly associated with the presence of TMD: mandibular retention (p = 0.466); mandibular stability (p = 0.466); interocclusal distance (p = 0.328); centric relation (p = 0.175); and balanced occlusion (p = 0.56).

CONCLUSION

Within the scope of this case-controlled cross-sectional study, no robust association between prosthetic factors and TMD was found.

Evaluation of complete denture quality and masticatory efficiency in denture wearers

PURPOSE

This study aimed to investigate (1) the influence of complete denture quality and years of denture use on masticatory efficiency and (2) the relationship between complete denture quality and years of use.

MATERIALS AND METHODS

A cross-sectional study was conducted with 93 edentulous patients (mean age: 65.6 years) wearing both mandibular and maxillary dentures. Patients were classified into two categories according to years of denture use: ≤ 2 years and ≥ 5 years. Masticatory efficiency was evaluated via the colorimetric method with beads as the artificial test food. A reproducible method for objective evaluation of the technical quality of complete dentures was employed. The association between denture quality and years of denture use was analyzed using chi-square and Fisher exact tests. The results of masticatory efficiency testing were analyzed using two-way analysis of variance (with the Tukey post hoc test) in terms of years of denture use (≤ 2 years, ≥ 5 years) and denture quality (poor, average, good).

RESULTS

A significant relationship was found between denture quality and years of denture use (P < .05). Masticatory efficiency differed significantly (P < .05) between patients with ≤ 2 years of denture use (0.101 ± 0.076 absorbance) and ≥ 5 years of use (0.068 ± 0.076 absorbance). Masticatory efficiency was not influenced by denture quality.

CONCLUSIONS

Complete denture quality and masticatory efficiency significantly decreased over time. However, complete denture quality did not influence masticatory efficiency.

Complete denture occlusion: an evidence-based approach

PURPOSE

This study involved an extensive search for randomized controlled clinical trials comparing bilateral balanced and canine-guided dentures, and questioned whether a bilateral balanced occlusion is imperative for successful denture treatment.

MATERIALS AND METHODS

Studies were identified by searching electronic databases (PubMed/MEDLINE, ISI Web of Science, LILACS, and BBD). The keywords "denture" and "occlusion" were used. The minimum inclusion requirements were (1) randomized controlled trials with patients of any age wearing both maxillary and mandibular conventional complete dentures (CDs), (2) comparison between bilateral balanced and canine-guided dentures, and (3) assessment of masticatory function and/or patients' satisfaction.

RESULTS

The search resulted in the identification of 5166 articles. Subsequently, 5156 articles were excluded on the basis of title and abstract. By the end of the search phase, seven randomized controlled trials were considered eligible.

CONCLUSIONS

Current scientific evidence suggests that bilateral balanced occlusion is not imperative for successful treatment with conventional CDs in average patients. More studies are necessary to identify if specific clinical conditions may benefit from a balanced occlusion.

Altered mandibular growth under functional posterior displacement in rats

OBJECTIVE

To test the null hypothesis that there is no difference in mandibular growth between growing rats with posterior functional mandibular displacement and growing rats without functional mandibular displacement.

MATERIALS AND METHODS

Twenty female Wistar rats (5 weeks old) were randomized into two groups: (1) control and (2) mandible posterior displacement in the occluded condition induced by an occlusal guiding appliance. After 8 weeks all animals were sacrificed, cone beam computed tomography scan images of the heads were taken using the classic I-CAT, and acrylic rapid-prototyped templates of the mandibles were constructed. Mandibular length, ramus height, and intercondylar distance were measured. Mandibular length and ramus height were submitted to the two-way analysis of variance, while intercondylar distance was analyzed by nonpaired Student's t-test.

RESULTS

Mandibular length was bigger (P < .0001) in the control than in the experimental group, but no significant difference was found between the left and right sides (P  =  .9380). No significant differences were observed for ramus height and intercondylar distance.

CONCLUSIONS

The results of this study demonstrated that functional posterior displacement of the mandible in growing rats resulted in shorter mandibular length.