McKenna v Nationwide Corporate Services: When a Workplace Injury Destroyed a Worker’s Teeth

Citation: McKenna v Nationwide Corporate Services Pty Ltd NSWPIC 583 | Decided: 29 October 2025

A security guard was assaulted at work. His employer accepted the injury. Two years later, he needed full dentures. His employer refused to pay. The NSW Personal Injury Commission disagreed, and the decision has significant implications for how consequential conditions are treated under Australian workers compensation law.

This case is a reminder that workplace injury don’t always present the way employers expect. Sometimes the most expensive consequences show up months or years later, in parts of the body that seem completely unrelated to the original incident.

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Background: The Assault and Accepted Workplace Injury

Leslie McKenna, a 58-year-old security guard employed by Nationwide Corporate Services Pty Ltd, was assaulted while on duty on 7 January 2023. The assault caused multiple physical injuries and a primary psychological injury, including post-traumatic stress disorder (PTSD), anxiety, and depression.

The employer accepted liability for the accepted injury without dispute. What followed, however, became the subject of contested litigation before the NSW Personal Injury Commission (PIC).

McKenna’s treating psychiatrist noticed during a consultation in July 2024 that McKenna was constantly clenching his teeth and jaw. He was referred to a dentist. The findings were significant: severe bruxism, fractured teeth, heavy occlusal wear, and a dental condition that required full upper and lower dentures estimated at $7,803.

Nationwide Corporate Services declined to pay, issuing a liability denial in January 2025 and a further notice in March 2025.

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The Central Dispute: Bruxism as a Consequential Condition

The core legal question was whether McKenna’s bruxism (involuntary teeth grinding and clenching) was caused or materially contributed to by the accepted workplace injury, and whether the resulting dental treatment was therefore compensable under Section 60 of the Workers Compensation Act 1987 (NSW).

McKenna’s position was that bruxism developed after the assault as a direct consequence of three overlapping factors:

• PTSD and chronic psychological stress stemming from the workplace assault
• Lexapro (escitalopram), an antidepressant prescribed for his psychological condition that is known to cause bruxism as a side effect
• The ongoing psychological burden of the workers compensation claim process itself

Critically, McKenna had completed a dental history form just six months before the assault, in July 2022, which specifically recorded that he was not aware of grinding or clenching his teeth. That documentation became a pivotal piece of evidence.

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Medical Evidence

McKenna’s Expert Evidence

Dr Marios Argyou, the applicant’s independent dental expert, provided a detailed causal analysis linking the work-related psychological injury to the development of severe bruxism. His report documented:

• Enamel erosion and occlusal wear consistent with chronic bruxism
• Stress fractures in the tooth structure
• Increased tooth mobility
• Temporomandibular joint (TMJ) dysfunction

Dr Argyou concluded that PTSD, anxiety, depression, and the long-term use of antidepressants had directly contributed to xerostomia (dry mouth), progressive dental deterioration, and the need for prosthetic rehabilitation.

The treating dentist, Dr Juhi Krishnaswamy, supported this view. In reports dated September 2024 and February 2025, Dr Krishnaswamy confirmed that the bruxism was likely multi-factorial, involving general stress, PTSD, Lexapro as a contributing pharmacological cause, and possible airway issues. He noted that without treatment, the bruxism would continue to destroy McKenna’s remaining teeth, and that no viable alternative to dentures existed to restore functional oral health long term.

The Employer’s Expert Evidence

The respondent’s dental expert, Dr Georgios Sotiropoulos, attributed McKenna’s dental condition primarily to pre-existing chronic generalised advanced periodontal disease (Stage 3 to 4 periodontitis), poor oral hygiene, diet, and loss of posterior support.

Dr Sotiropoulos diagnosed only mild bruxism and expressed the view that the accepted workplace injury was unlikely to be the “main substantial contributing factor” to the dental condition, noting any exacerbation was “possibly minor, if any.”

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The Legal Framework: Section 60 and Material Contribution

Under Section 60 of the Workers Compensation Act 1987 (NSW), an employer is liable to pay the cost of medical or related treatment where it is reasonably necessary as a result of a work injury.

The key test applied by the Commission comes from two established authorities:

• Rose v Health Commission (NSW) NSWCC 2: treatment must alleviate the consequences of injury and should not be forborne by the worker
• Diab v NRMA Ltd: the work injury does not need to be the only or substantial cause of the need for treatment

The Commission also applied the causation principles from Murphy v Allity Management Services Pty Ltd and Kooragang Cement Pty Ltd v Bates, which establish that a commonsense evaluation of the causal chain is required. A condition can have multiple causes. The workplace injury only needs to have materially contributed to the need for treatment.

This is a meaningfully lower threshold than “substantial contributing factor,” which is the test Dr Sotiropoulos appeared to apply in his evidence.

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The Decision

Member Karen Garner found in McKenna’s favour.

She preferred the evidence of Dr Argyou over Dr Sotiropoulos, noting that Dr Argyou provided a comprehensive and detailed causal analysis that was consistent with the established legal test. She noted that Dr Sotiropoulos had effectively applied a higher causal threshold than the law requires.

The Commission determined:

• The accepted workplace injury materially contributed to the development of bruxism
• The bruxism caused progressive dental deterioration requiring dentures
• The proposed treatment was reasonably necessary as a result of the accepted injury
• The respondent was ordered to pay the costs of upper and lower dentures under Section 60

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What This Means for HSE Professionals

This case is significant for anyone managing workers compensation, incident response, or psychological injury prevention in the workplace.

Consequential conditions, meaning injuries or illnesses that develop as a result of an initial workplace injury, can be compensable even when other contributing factors exist. Employers and their insurers cannot simply point to a pre-existing condition or comorbidity and walk away from liability. The threshold is material contribution, not sole or dominant causation.

Several practical takeaways emerge:

• Psychological injuries have physical consequences. PTSD, anxiety, and depression can manifest as bruxism, gastrointestinal conditions, chronic pain, sleep disorders, and more. Treating these as isolated psychological events understates the true cost of the injury and the scope of potential liability.
• Medication side effects are part of the picture. Where a worker is prescribed medication to treat a compensable condition, and that medication causes a further physical condition, the causal chain can still lead back to the employer.
• Pre-injury documentation matters. The July 2022 dental history form noting no history of grinding was critical evidence. Employers and workers should be aware that baseline health records can determine disputes like this.
• Expert selection affects outcomes. The Commission preferred the applicant’s expert, in part, because Dr Sotiropoulos applied the wrong legal test. For insurers and employers, instructing medical experts with a clear understanding of the relevant legal threshold is essential.

For WHS managers and safety advisors, cases like this reinforce the importance of early intervention in psychological injury claims, robust return to work planning, and proactive claim management before consequential conditions compound liability.

Read the full decision: McKenna v Nationwide Corporate Services Pty Ltd NSWPIC 583