The lifespan and clinical durability of PFM crowns depends heavily on how well their contact surfaces are adjusted by clinicians because this procedure minimizes both material wear and technical problems [1]. Poor contact between teeth leads to an uneven dispersion of forces that causes fast deterioration of restorative materials while threatening the stability of dental prostheses [2]. The research on exact PFM crown occlusal adjustment continues extensively because these adjustments directly affect crown longevity and patient satisfaction levels [3].

Functional stability of prosthetic restorations depends heavily on proper alignment of dental occlusion. When malocclusion exists it leads to hyperwearing of restorative materials and disruption of periodontal structures and it can cause disorders of the temporomandibular joint [4]. Research evidence shows that adjusting the bite leads to superior load distribution which helps maintain the longevity of PFM restorations according to report [5]. Chipping or porcelain layer fracture occurs when occlusal discrepancies appear because of which both functional aesthetics suffer deterioration [6].

Wear of PFM crowns depends on three main factors which include opposing dentition and occlusal forces and material properties [7]. The wear resistance of PFM crowns surpasses specific ceramic restorations in terms of enamel abrasion [8]. The improper alignment between the teeth can boost ceramic surface wear which ultimately causes retention failure and carious tissue formation [9].

A retrospective study by Oh et al. highlighted the influence of occlusal adjustments on the long-term success of PFM crowns, demonstrating that adjusted crowns exhibited lower wear rates and reduced incidence of mechanical complications [10].  The current investigation explores how PFM crown performance and wear affects through an analysis of adjusted and unadjusted restorations. This research examines the dimensional connection between adjusted and unadjusted therapeutic tooth modifications while offering essential findings regarding clinical dentistry practices improvement.

Objective

The objective of this study was to evaluate the effects of occlusal adjustment on PFM crown wear and performance by comparing adjusted and non-adjusted restorations

This retrospective observational study was conducted at Department of Prosthodontics, Bangabandhu Sheikh Mujib Medical University (BSMMU) and beau-dent, Dhaka, Bangladesh from January 2009 to December 2009. This study included 40 patients who received porcelain fused-to metal (PMF) crowns, with or without occlusal adjustment.

Inclusion Criteria:

• Patients who received PFM crowns within the study period.
• Patients with complete treatment records.
• Patients who underwent occlusal adjustment or had non-adjusted crowns.

Exclusion Criteria: 

• Patients with a history of temporomandibular joint disorders.
• Patients with systemic conditions affecting occlusion.
• Incomplete or missing medical records.

Data collection: The study utilized patient records obtained from Bangabandhu Sheikh Mujib Medical University (BSMMU) and beau-dent, Dhaka, Bangladesh. The study obtained information about patient demographics alongside crown placement sites and adjustments made to the tooth surface along with achieved treatment results. The clinical assessments along with digital imaging provided measurements of wear. A specified questionnaire recorded patient satisfaction results. Follow-up visits revealed complications such as chipping and secondary caries development. A complete level of confidentiality protected the participants throughout the entire research period.

Statistical analysis: The statistical analysis was performed through SPSS software. Descriptive statistics, including mean, frequency, and percentage, were used to summarize findings. The study used independent t-tests to examine wear differences between groups along with chi-square tests for categorical data evaluation on complications and satisfaction rates. Results reaching a significance level below 0.05 proved to be statistically relevant. A p-value <0.05 was considered statistically significant.

Table 1: Patients baseline characteristics (n=40)

The patient demographic data shows that 35% of participants fell within the age range of 40-49 years while 27.5% were between 30-39 years. Males comprised 57.5% of the sample. Most dental crowns were placed in the upper jaw region (67.5%). Occlusal adjustment occurred for 50% of the participants. 

Table 2: Effects of occlusal adjustment (n=40)

Table 2 provides data about PFM crown wear patterns alongside performance results between adjusted and non-adjusted crown groups. The average wear measurement for adjusted crowns reached 121.5 µm while non-adjusted crowns experienced 162.5 µm of wear (p=0.04). The analysis showed adjusted crowns had lower chipping and fracture rates but this difference was not statistically significant. Patients in the adjusted group showed superior satisfaction rates at 90% when compared to the non-adjusted group at 70%. 

Table 3: Incidence of complications in PFM crowns (n=40)

This table highlights complications related to occlusal adjustment. Non-adjusted patients exhibited higher rates of tooth chippings (5% versus 20%) and loss of retention (0% versus 10%) as well as secondary caries (5% versus 15%) and periodontal complications (10% versus 25%) yet the differences between groups were not statistically significant. 

The current research investigated how tooth adjustment affects porcelain-fused-to-metal (PFM) crown wear together with their performance characteristics. Research outcomes showed that crowns receiving occlusal adjustment experienced lower wear manifestation with 121.5 μm compared to unadjusted crowns at 162.5 μm (p=0.04). Occlusal equilibration treatment during this study demonstrated similar findings to earlier studies which established its effectiveness at minimizing mechanical problems while extending prosthetic lifespans [11].

The research by Oh et al. indicated that unadjusted occlusal contacts result in more enamel and ceramic wear thus rendering the need for occlusal refinements critical for prosthetic rehabilitation [12]. Ceramic restorations without occlusal adjustment showed higher attrition rates with chipping when compared to restorations that received specific adjustment according to Al-Hiyasat et al. [13]. Our study results support the previous work because adjusted crowns showed lower rates of chipping (5% compared to 15%) and fractures (0% versus 10%) but these results remained statistically insignificant.

The research examined how patient satisfaction shifted through occlusal adjustment procedures. Patient satisfaction reached 90% among those who received occlusal adjustment treatment but only 70% satisfaction was reported by patients without adjustment treatment. According to Christensen patients achieve better comfort and reduced post-treatment complaints when their occlusal contacts are properly balanced [8]. Occlusal adjustment emerges as a crucial clinical step because it leads to enhanced functional results.

Research studies have demonstrated how occlusion affects prosthetic success rates. McAllister reported that occlusal misalignment contributes to higher failure rates in ceramic restorations due to excessive stress concentration [5]. Our research findings adopted the same view regarding retention loss (10% against 0%) and secondary caries (15% against 5%) in non-adjusted crowns although statistical significance was not established. According to Sailer et al. prosthetic survival depends on proper occlusion because improper tooth alignment produces periodontal issues along with prosthesis failures [14].

Occlusal material wear remains essential for conducting restorative dentistry procedures. The research of Ghazal et al. showed that feldspathic ceramics achieved meaningful wear decrease through exact occlusal modifications [15]. The results from our investigation confirm that specific adjustments to the biting surface decrease PFM crown deterioration which demonstrates that proper force management extends material viability. Research from Turp et al. showed that occlusal interferences lead to ongoing damage of prosthetic restorations so prevention through systematic occlusal refinement should enhance long-term success rates [9].

The data from this study supports the research of Olthoff et al. which showed that digital design combined with occlusal modifications in CAD/CAM restorations creates better wear resistance and improved functional adaptation [10]. Our research findings match the results which show that adjusted occlusal contacts reduced mechanical device issues and produced better patient satisfaction outcomes.

Occlusal adjustment enhances the durability, functionality and clinical success of PFM crowns by minimizing wear, reducing complications and improving patient satisfaction. These findings underscore the importance of precise occlusal refinements in restorative dentistry to optimize prosthetic outcomes and ensure the longevity and mechanical stability of dental restorations for superior patient care.

Limitations and recommendations                                                                               

The sample size was relatively small, which may limit the generalizability of the findings. Additionally, long-term follow-up is necessary to assess the sustained impact of occlusal modifications on the PFM crown performance.

Acknowledgment

I would like to express my sincere gratitude for the invaluable support and cooperation provided by the staff, participants, and my co-authors/colleagues who contributed to this study.

Financial support and sponsorship

No funding sources.

Conflicts of interest

There are no conflicts of interest.

1. Christensen GJ. Porcelain-fused-to-metal versus zirconia-based ceramic restorations, 2009. The Journal of the American Dental Association. 2009 Aug 1;140(8):1036-9.
2. Pilliar RM. Metallic biomaterials. Biomedical materials. 2009:41-81.
3. Wassell RW, Steele JG, Welsh G. Considerations when planning occlusal rehabilitation: a review of the literature. International dental journal. 1998 Dec;48(6):571-81.
4. Keough B. Occlusal considerations in periodontal prosthetics. International Journal of Periodontics & Restorative Dentistry. 1992 Oct 1;12(5).
5. McAllister BS. The rationale for the vented-crown technique and its application in today's dental practice. Operative Dentistry. 2008 Mar 1;33(2):116-20.
6. Ho HK. Replacement and modifications of anterior teeth: aesthetic considerations. Paediatric Dentistry and Orthodontics, Faculty of Dentistry, University of Hong Kong; 2000.
7. Yip KH, Smales RJ, Kaidonis JA. Differential wear of teeth and restorative materials: clinical implications. International Journal of Prosthodontics. 2004 May 1;17(3).
8. Christensen, G.J. Is occlusion becoming more confusing? A plea for simplicity. J. Am. Dent. Assoc. 2004, 135, 767–768.
9. Turp, J.C.; Greene, C.S.; Strub, J.R. Dental occlusion: A critical reflection on past, present and future concepts. J. Oral Rehabil. 2008, 35, 446–453.
10. Olthoff, L.; Meijer, I.; de Ruiter, W.; Bosman, F.; van der Zel, J. Effect of virtual articulator settings on occlusal morphology of CAD/CAM restorations. Int. J. Comput. Dent. 2007, 10, 171–185.
11. Shillingburg HT, Hobo S, Fisher DW. Preparation design and margin distortion in porcelain-fused-to-metal restorations. Journal of Prosthetic Dentistry. 2003 Jun 1;89(6):527-32.
12. Oh WS, DeLong R, Anusavice KJ. Factors affecting enamel and ceramic wear: a literature review. The Journal of prosthetic dentistry. 2002 Apr 1;87(4):451-9.
13. Al-Hiyasat AS, Saunders WP, Sharkey SW, Smith GM, Gilmour WH. Investigation of human enamel wear against four dental ceramics and gold. Journal of dentistry. 1998 Jul 1;26(5-6):487-95.
14. Sailer I, Feher A, Filser F, Lüthy H, Gauckler LJ, Schärer P, Hämmerle CH. Prospective clinical study of zirconia posterior fixed partial dentures: 3-year follow-up. Quintessence International. 2006 Oct 1;37(9).
15. Ghazal M, Hedderich J, Kern M. Wear of feldspathic ceramic, nano‐filled composite resin and acrylic resin artificial teeth when opposed to different antagonists. European Journal of Oral Sciences. 2008 Dec;116(6):585-92.